The production of air ducts is a profitable business. They are needed in the construction of residential and commercial premises. Air ducts are structures resembling pipes that distribute the flow of incoming and exhaust air. Ventilation pipes are also used for these purposes. The article will discuss air ducts made of galvanized steel and other materials.

How to start an air duct manufacturing business?

We study the range

There are several types of air ducts. They are:

• rigid and flexible;
• round or rectangular;
• steel (stainless or galvanized steel), plastic, aluminum, rubber, fabric (polyester), silicone, fiberglass;
• connecting (able to be fastened together using nipples or fasteners);
• fire retardant.

Manufacturing technology depends on the type of raw materials used in production.

Galvanized steel and aluminum are the materials with which the most labor-intensive of all production methods is carried out. ventilation ducts which are used in restaurants, schools, shopping malls, offices. Steel products have the following advantages:

• they are not susceptible to corrosion;
• cheaper than plastic;
• fire resistant;
• amenable to quick dismantling.

Flexible ducts for ventilation are more difficult to produce. They are installed in small buildings where it is necessary to remove harmful substances in the air. They also come in two shapes: round and rectangular. It takes a lot to produce them. Money. But they are in the highest demand. Therefore, experienced entrepreneurs say that it is better to start manufacturing ventilation ducts from this particular type.

Weigh the pros and cons

The main advantages can be identified:

• Yield. Despite the fact that this business requires a lot of investment, it brings great profits if developed in the right direction.
• High demand. No building is complete without air ducts. And every year, especially in metropolitan areas, more and more multi-storey buildings are being built. They are also needed by those who make repairs and change the communication system. Therefore, there is always a customer for air ducts.
• Year-round production. Since the business is not seasonal, management can sell goods to other regions.
• High payback. In a year, a skilled entrepreneur will be able to help out the amount that will cover all initial expenses.

The cons include:

• large investment investments;
• high level of competition.

Before opening own production, you need to assess the market situation in your region, conduct an analysis of competitors. This business is fraught with many features that can have a negative impact on the enterprise as a whole.

How to choose equipment for the production of air ducts?

The technical equipment of the plant is selected taking into account the area and cross-sectional shape of the pipes, their rigidity. Which air ducts to produce in terms of size and parameters is decided by the owner of the enterprise, based on consumer demand.

Also, the main indicator of the type of manufactured products is installation. So, rectangular ducts lend themselves to this process worse than round ones, which have another significant advantage. They are easier to produce due to the fact that they are connected using snap nipples.

But they also have disadvantages - quality. Rectangular ducts are more reliable ventilation structures. They are used for large cross-sectional areas. When Difficult Expectations installation work in a building with an unusual design, they also prefer rectangular ducts.

Since it is not known which types of products will be more in demand in your area, it is better to purchase two machines that can work with both rectangular and round structures.

Equipment for the production of air ducts:

• guillotine;
• machines that correct the shape of the sheet;
• a machine that is responsible for feeding raw materials to the main line;
• an apparatus capable of unwinding sheets made of metal from rolls;
• CNC system.

The equipment intended for the production of air ducts of various shapes does not differ much from each other. To create round structures, rollers (rolling) are used, and for rectangular structures, machines, bending sheets and applying ribs.

Machines for the manufacture of round air ducts will cost no less than 3 million rubles, and for rectangular ducts - 3.5-5 million rubles.

Documents required for organizing a business

Production of air ducts - direction commercial activities, does not require licenses or special permits. For legal work, it is enough to register as an individual entrepreneur or open an LLC. The first option is cheaper and easier in terms of preparing all the necessary papers. But serious companies that are interested in large volumes of finished products very rarely work with individual entrepreneurs. Another disadvantage is that in the event of bankruptcy, an entrepreneur (individual) may lose his personal property, and the founders of an LLC risk only the authorized capital and funds of the company.

In order to draw up IP documents, you need to pay a state fee, write an application, make copies of the TIN and passport, and then transfer all this to the tax inspector. The founders of an LLC need to additionally prepare the statutory documents of the company, resolve the issue with the legal address and form statutory fund(from 10 thousand rubles).

Regardless of the choice of legal form for your business, you need to choose a code that matches your activity. In this case, it is OKVED 28.1.

What tax regime can duct manufacturers choose?

If we are talking about small volumes of production, then you can work on a simplified regime, which provides for mandatory payments to the state in the amount of 6% of profits or 15% of gross income.

If you decide to organize a large-scale production of air ducts and plan to enter into contracts with large companies, then it is better for you to work on a common basis. In order to organize internal and tax accounting in this situation, a qualified accountant is needed, who must be paid a rather large salary. But a good specialist will always find legitimate ways to reduce the amount of tax payments, often exceeding the monetary reward for their work.

Air duct production technology

The production of air ducts takes place in several stages. Let us consider in more detail the production process of one of the types of round structures made of galvanized steel.

The entire production process is automated. The quality of finished products depends on the condition of the purchased machines.

How much money do you need to start a business?

Setting up this type of business requires a large initial investment. The main costs include:

• Purchase of equipment for the manufacture of air ducts of various shapes - 6-7 million rubles.
• Room rental - 50 thousand rubles.
• Salary - 50 thousand rubles.

If there are no funds to create a full-scale production, then you can start with the manufacture of parts needed for ventilation ducts. These include:

• plugs;
• bends;
• tie-ins;
• nipples.

This will not require large expenses, since all these structures can be made from industrial waste and defective products. Machine tools for their manufacture cost within 50 thousand rubles. Subsequently, you can expand the scope of activities and begin to manufacture various types of air ducts themselves.

To save money, you can hire unqualified staff for the first time. Naturally, you need to take care of the quality of the goods, so you should take into account the abilities of employees.

How much can you earn in the production of air ducts?

This business is very profitable. This allows you to get a large profit at a relatively low initial cost. With well-established production, you can get about 200-400 thousand rubles. per month, given that the market price for one meter of air duct varies between 300-600 rubles. The cost depends on the diameter of the pipe (outer).

With intensive work, the initial costs will pay off in 6-12 months.

The manufacture of air ducts is a great business idea for a novice entrepreneur who is looking for a field of activity in which he would like to realize himself. There is always a risk of burnout, but in this case you should not be afraid of this, because not a single room can do without ventilation.

Duct production

Box for ventilation and air conditioning systems are used in the construction of any duct systems. The material for their manufacture is selected depending on the actual operating conditions, the parameters of the working environment, and also on the purpose. For the manufacture of air ducts uses low-carbon steel, "galvanized" or "stainless steel", as well as various types of plastic.

Air ducts for ventilation made of "galvanized" are used in air exchange systems with a working environment with a temperature of up to + 80C (a short increase up to + 200C is possible) and humidity up to 60%. Air ducts made of galvanized steel can be used in areas with any climate in accordance with GOST 15150, subject to non-aggressive working environments (air and gas-air). Galvanized air ducts do without an additional protective coating, since the top zinc layer protects the metal from corrosion even in places of its damage (due to the steel-zinc galvanic pair, which forms an oxide film under the influence of atmospheric oxygen).

Air ducts made of stainless steel are designed to work with superheated air and aggressive gas-air mixtures. Working environment temperature - up to +500С (short-term increase up to +700С is allowed). As a procurement material for the production of stainless steel air ducts, steels are used according to GOST 5632-72 (heat and corrosion resistant).

"Black" air ducts are made from mild steel. Workpiece thickness - from 1.2 to 15 mm. "Black" air ducts for ventilation are well tolerated by high temperatures and exposure to open flames (they are slightly susceptible to deformation - the air ducts of the ventilation system will not depressurize, and the fire will not spread to neighboring rooms).

For aspiration systems and smoke removal, "black" ventilation ducts are the most right choice. Simple carbon steel ventilation systems are mainly in demand in production areas where excessive emission of gases, dust, etc. is possible.

Air ducts can be round or rectangular in cross section. The production of rectangular ducts is a classic of ventilation systems, but thanks to progressive technologies, the market is increasingly losing ground to round ducts, since they are more technologically advanced in manufacturing, have better aerodynamic characteristics and are easy to install. To date, the production of round air ducts is "gaining momentum", becoming more and more popular.

For the installation of air ducts in a single line, various shaped components are used, which are conventionally divided into typical (corners, turns, splitters, "ducks", transitions, etc.) and non-standard (adapters for ventilation grilles or reducers for air exchange systems).

Air ducts made of polymers (plastic) in some cases can be an excellent alternative to metal counterparts. Among the advantages of plastic air ducts, it is necessary to highlight a small specific gravity, ease of installation (no need for special tools and fixtures), reasonable price. But plastic air ducts are not suitable for moving chemically aggressive gas-air mixtures.

There are rigid, semi-rigid and flexible plastic ducts. Rigid air ducts can be round or rectangular, while flexible and semi-rigid air ducts are only round in cross section.

Good day!

No residential, office, retail, industrial or warehouse space today . And air ducts made of galvanized steel deservedly occupy a leading position among various ventilation ducts. About what this popularity is due to and how not to get lost in the variety of the presented assortment, we will tell in the next material.

Galvanized air ducts are the most common type of ventilation pipes. Which is easily explained.

Advantages of galvanizing:

• Light weight, due to which the installed structures create insignificant loads on the buildings. In addition, the lightness of the material facilitates the process of delivery to the installation site and engineering work.
• The flexibility of the material makes it possible to give the air duct elements any shape, which not only expands their range, but also improves the aerodynamic characteristics of the line.
• Strength and resistance to open fire and aggressive environments. This significantly expands the scope of use and increases the service life of ventilation pipes made of thin-sheet galvanized steel from 10 years or more.
• Low cost.

Galvanized ventilation ducts are easy to maintain. They do not require preliminary priming, since the metal is not subject to an active corrosion process. Aesthetic appeal allows them not to be painted.

The disadvantages of galvanized steel include:

• Increased noise level, characteristic of any metal structure. However, this problem can be solved either by a well-thought-out wiring scheme that minimizes the number of bends and transitions, or soundproofing.
• Tendency to form and accumulate condensate. As a solution - insulation of the pipeline.
• Susceptibility to deformation as a result of a powerful mechanical impact caused by a strong impact, displacement or fall of the structure. Under normal operating conditions, such difficulties do not arise.

The combination of quality, material cost and a variety of technologies that minimize the disadvantages makes galvanized pipelines the most popular types of air ducts used in the arrangement of ventilation mains.

Types of galvanized air ducts

The variety of galvanized air ducts is due to a number of specifications given to products during the manufacturing process. So the following types of products are distinguished:

1. Cross-sectional shape: rectangular or round.
2. By type of seam: welded and folded.
3. In the direction of the seam: spiral wound and straight seam.

Rectangular and round

	Round steel duct	Rectangular steel duct
Aerodynamics	Uniform air distribution and, as a result, improved aerodynamics.	High aerodynamic drag
Air mass movement speed	High.	Low. For large circuit sizes, forced air circulation is required.
Noise figure	Good noise-absorbing properties due to the absence of turbulence effect.	Requires good soundproofing.
care requirements	The high air velocity prevents dirt and dust particles from settling in the pipeline.	Requires periodic cleaning of the pipeline.
Estimated data	The shape of the section makes it difficult to calculate data on the area of ​​the structure.	The rectangular configuration makes calculations easier.
Installation	Products are lighter and do not require reinforced fasteners. Save time and low labor costs.	The severity of the structure requires the arrangement of reliable clamps.
Price	Cheaper by an average of 30%. Minimum costs for transportation, storage, installation and thermal insulation.	In view of the high aesthetics, there are no costs for masking and decorating the highway.

The advantage of rectangular air ducts lies in the configuration and variety of the model range, which allows you to adapt the ventilation circuit to the characteristics of any room without compromising the calculated cross-sectional area, playing with the width and height of the pipe.

Straight seam and spiral wound

Longitudinal welded pipes are made by bending a sheet of galvanized steel into a round or rectangular pipe. This technology reduces the cost of products, but it also limits its length, which increases the number of connecting elements of the pipeline.

Spiral-wound (spiral-lock or spiral-welded) air ducts are twisted from a thin metal tape. In this case, the seam goes in a spiral and plays the role of a stiffener, which increases the strength of the pipe, and when using the welding method, ensures its tightness.

Spiral-wound air ducts are characterized by:

• less weight;
• increased tightness;
• a small number of butt elements;
• increased speed of movement of the air mass, tk. the spiral shape creates additional rotation in a closed loop;
• reduced noise level.

However, the ribbed surface provokes the accumulation of dust inside the pipeline.

Tightness and density

Tightness and pressure are indicators that ultimately determine the efficiency and cost of the ventilation circuit. A leaky line reduces the quality of air exchange and entails an unreasonable increase in the capacity of pumping equipment, an increase in energy costs, and also leads to the accumulation of condensate inside the pipes.

There are 3 classes of tightness of air ducts:

1. A (low). Air permeability from 1.35 to 0.45 l/sec/m².
2. B (medium). Air permeability from 0.45 to 0.15 l/sec/m².
3. C (high). Air permeability less than 0.15 l/sec/m².

By the coefficient of internal pressure (density) distinguish:

• H-models (normal pressure). Designed for ventilation and smoke removal systems of objects belonging to the category of fire hazard class "B" and "G". Do not require strong sealing, tk. allow a certain percentage of leakage. Rubber seals are usually used as a sealant.
• P-models (dense). Are established on the objects equipped with powerful pumping equipment and belonging to the category of fire and explosion hazard. They are characterized by 100% tightness of seam joints and the presence of a hermetic lock at the junction of the elements with each other.

What is better and where is it used?

The protective layer of zinc resists the damaging effects of open air, moisture and ultraviolet radiation. Therefore, galvanized ventilation ducts are actively used both indoors and outdoors for arranging systems:

1. natural and forced ventilation,
2. conditioning;
3. aspiration (removal of small particles contained in the air);
4. smoke removal (removal of combustion products);
5. removal of exhaust gases;
6. transportation of gas mixtures, purifiers and air humidifiers.

Even the organization of a conventional hood in the kitchen is most often carried out by means of steel ducts.

When deciding on the use of one or another type of air duct, one should be guided by the features of the operation of the future design:

• Rectangular air ducts are used to save space in small predominantly residential or service premises (private houses, apartments or offices).
• For aspiration and transportation of harmful gases, round pipes with a welded seam are suitable, providing top speed air movement and complete tightness of the case.
• In industry, preference is given to round shapes, characterized by both the greatest efficiency and the lowest cost.

Elements of the ventilation system

The ventilation line is always a complex structure, consisting of numerous elements that allow:

1. change the direction of the contour depending on the configuration of the premises;
2. bypass ledges;
3. connect several circuits into a single network.

Branches and boxes

The main elements of the duct that determine its direction are ducts and bends. The former pave the path in a straight line, the latter change the contour geometry at an angle of 15⁰, 30⁰, 45⁰, 60⁰ or 90⁰.

Other shaped elements

Ventilation is a complex and extensive network of channels, which is problematic to mount without the appropriate elements. Such components are usually called shaped products.

These include:

• Adapters connecting circuits of various diameters to each other - confusers and diffusers. The former narrow the highway, the latter expand.
• Tees and collar tie-ins, ensuring the adjoining of two mains to each other.
• Crosses used to cross two perpendicular air currents.
• S-shaped adapters (ducks) connecting two circuits that do not match in axis and / or section.
• Round nipples and couplings connecting two round boxes. The first are inserted inside, the second are put on over the pipes.
• Plugs installed at the ends of the circuit.
• The umbrella is roof, preventing hit of an atmospheric precipitation in a ventilating shaft.
• Supply and exhaust grilles and other shaped parts.

Dimensions

GOST

1. GOST 14918-80 - air ducts made from steel sheet with a thickness of 0.5 to 1 mm by rolling and designed to transport air with a humidity of not more than 60% and a temperature of less than 80⁰C.
2. GOST 5632-72 - air ducts characterized by a high degree of tightness, resistance to corrosion and high temperatures (about 500⁰C) and designed to move hot air and chemical gases.

Size Chart Weights and Diameters

Production of galvanized air ducts

Galvanized air ducts are manufactured on special metal-working equipment from thin-sheet cold-rolled steel in accordance with the standards established by the state (SNIP 41-01-2003 and TU 4863-001-75263987-2006). Cutting of metal occurs in automatic mode according to the parameters set by the program.

• Circular sections are processed by rollers, which give the workpiece the required diameter, followed by rolling the longitudinal edge on a seam-rolling machine.
• Spiral-wound ones are made using a different technology: steel with a width of 137 mm is twisted in a spiral with a seam inward.

The use of high-quality galvanizing prevents the galvanized coating from peeling off the metal at the bending points of the product.

Technological standards prescribe for each type of section to use metal of a certain sheet thickness:

Average cost and where to buy

The cost of air ducts made of galvanized steel depends on the size of its cross section and the thickness of the metal. The price is calculated for 1 m². On average, the cost of 1 m² of a product on the market is about 320 rubles. Installation work will cost an average of 700 rubles. for the same square metre.

Despite the wide representation of air ducts in online stores, it is still worth buying them directly from the manufacturer, who is able to accompany each product with a quality certificate.

How to choose?

The operation of the air exhaust system (SVO) depends on how correctly the area of ​​\u200b\u200bits section is calculated.

S - Sectional area.

P - CBO performance.

v - The speed of movement of the air mass (for residential premises, an indicator of 3-4 m / s is used).

Determination of ventilation performance involves determining the amount of air required for a comfortable stay in the room. It is calculated in 2 ways:

• Air volume required:

P - CBO performance.

A - The number of people in the room during the hour.

n - Air consumption rate according to SNIP 41-01-2003 and MGSN 3.01.01.

• By the frequency of ventilation (ventilation):

P - CBO performance.

V - The volume of the room (with equal data, the entire room)

k - The ventilation rate established by the standards of SNIP 41-01-2003.

shape and diameter

The quality of air exchange, energy efficiency and design of the room depend on the selected configuration and the size of the air duct section. Therefore, the choice of air channels should be approached in detail:

1. The smaller the diameter of the duct, the higher the speed of the air mass. It is important to be guided by the principle of the "golden mean", because the higher the speed, the higher the noise level.
2. Round air ducts provide faster air movement, are easier to install and are cheaper.
3. Rectangular are stronger and harmoniously fit into the design of any room.

Construction and rigidity

Depending on the specifics of the design application, there are:

• rigid, semi-rigid or flexible;
• standard or thermally insulated;
• fire retardant.

The tighter the seams, the stronger the connection and longer period operation.

Material

Galvanized ventilation ducts are made of a standard type and insulated.

1. The design of insulated models provides a special insulating layer of mineral fiber, polyurethane, foam elastomer, felt or other materials. They maintain the optimum air temperature inside the circuit, preventing the formation and freezing of condensate on the walls. In addition, they reduce the noise level.
2. Zinc coating can be one-sided or two-sided. Due to the formation of condensate inside the circuit, double-sided galvanizing is more practical, because. protects the contour from the internal corrosion process.

Not so long ago, galvanized aluminum ducts appeared on the market, the coating of which is 95% zinc and 5% aluminum. They are characterized by greater ductility and improved anti-corrosion properties.

Fastening

Ways to fix the air ducts depend on the configuration:

• with a round section, coupling, bandage and nipple connection of elements are used;
• rectangular air ducts are fastened with latches and mounting brackets.

Sometimes welding is used.

Installation rules for galvanized ventilation

The laying of ventilation ducts from thin-sheet galvanized steel is carried out in stages.

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KGBOU NPO "PU No. 102"

WRITTEN EXAM WORK

Topic: Technologicalprocessduct manufacturing

Nazarovo, 2014

Introduction

Equipment for manual arc welding

Consumable

Labor protection instruction for electric welder

Personal protective equipment

Bibliography

Introduction

Welding is one of the leading technological processes of metal processing. The great advantages of welding ensured its widespread use in the national economy. With the help of welding, the production of ships, turbines, boilers, aircraft, bridges, reactors and other necessary structures is carried out.

Welding is a technological process for obtaining permanent joints by establishing interatomic bonds between the parts to be welded during their local or general heating, or plastic deformation, or the combined action of both.

The welded joint of metals characterizes the continuity of structures. To obtain a welded joint, it is necessary to carry out intermolecular adhesion between the parts to be welded, which leads to the establishment of an atomic bond in the boundary layer.

Welding metallurgy differs from other metallurgical processes by its high thermal cycle temperatures and short lifetime of the weld pool in the liquid state, i.e. in a condition available for metallurgical processing of the weld metal. In addition, the processes of crystallization of the weld pool, starting from the fusion boundary, and the formation of a heat-affected zone of metal changed in its properties are specific.

All welding methods can be divided into two main groups:

1. Pressure welding - contact, gas pressure - friction, cold - ultrasound,

2. Fusion welding - gas, thermite, electric arc, electroslag, electron beam, laser.

The most widespread place is occupied by arc welding, in which the heat source is an electric arc.

When making your thesis I used consumable electrode arc welding.

Equipment for manual arc welding

Post for manual arc welding

A welding station for manual arc welding is traditionally equipped with all devices, tools and materials that may be required during welding. It is mandatory to have a welding machine, which includes a power source, equipment for starting, wires for welding, electrode holders. In addition, it must be properly equipped and self workplace welder. Welding stations are both stationary and mobile (that is, those that can be transported to different sites).

The peculiarity of work at a stationary post is that structures that need to be welded are supplied to the welder's workplace. The welder, performing work, moves from seam to seam, while all the equipment is in one place.

I note that it is allowed to move the welder within the length of the cable used in welding. Usually it is not more than 30-40 meters. Let's make a reservation right away that longer wires are usually not used, as this leads to a significant voltage drop in the circuit. And this affects the entire welding process.

Welding inverter ARC-160 BRIMA

A device for converting direct current into alternating current. The figure below shows a simplified diagram of an inverter-type welding machine. welding technological metal

Rice. block diagram welding inverter: 1 - mains rectifier, 2 - mains filter, 3 - frequency converter (inverter), 4 - transformer, 5 - high-frequency rectifier, 6 - control unit.

The operation of the welding inverter is as follows. Alternating current with a frequency of 50 Hz is supplied to the mains rectifier 1. The rectified current is smoothed by filter 2 and converted (inverted) by module 3 into alternating current with a frequency of several tens of kHz. Frequencies of 100 kHz are currently being achieved. It is this stage that is the most important in the operation of the welding inverter, which allows to achieve huge advantages over other types of welding machines. Further, with the help of transformer 4, the high-frequency alternating voltage is reduced to idle values ​​(50-60V), and the currents are increased to the values ​​necessary for welding (100-200A). The high-frequency rectifier 5 rectifies the alternating current, which does its useful work in the welding arc. Influencing the parameters of the frequency converter, regulate the mode and form external characteristics source.

The processes of current transition from one state to another are controlled by the control unit 6. In modern devices, this work is performed by IGBT transistor modules, which are the most expensive elements of the welding inverter.

Control system using feedback forms ideal output characteristics for any method of electric welding. Thanks to high frequency, the weight and dimensions of the transformer are reduced significantly.

Specifications:

Supply voltage (V)
Mains frequency (Hz)
Power consumption (W)
Maximum input current of the network (A)
Welding current range
Load period (%)
Open circuit voltage (V)
No-load loss (W)
Power factor (cos?)
Insulation class
Protection class

Welding wires

Welding wires are used to connect the electrode holder and the workpiece to be welded with the power source. Wires with copper or aluminum conductors are used, the cross section of which corresponds to the rated welding current. Welding wires are equipped with a rubber insulating layer and in most cases with a rubber protective sheath.

Rice. 1 Cross-section of welding wires: a - PRGD type, b - APRGDO type, c - PRGDO type (with 4 auxiliary wires)

The welding wire carrying current to the electrode holder must be highly flexible in order to facilitate the manipulation of the electrode. For this purpose, flexible wires of the PRGD, PRGDO and APRGDO brands are used, manufactured in accordance with GOST 6731 - 68

Welding wires PRGD, PRGDO and APRGDO are designed to be connected to power sources with a welding circuit voltage of up to 127 V AC, frequency 50 Hz or 220 V DC and can be used for operation at an ambient temperature of - 50 to 4 - 50 ° C. The high flexibility of PRGDO welding wires is achieved by twisting the core of the wire from conductors of small cross section and due to a thin sheath of high-quality rubber.

The criteria for the allowable current in welding wires are the limiting temperature of the conductor and electrical losses, determined by the formula:

where Inom is the rated welding current. A; c - specific resistance of the conductor, equal to 0.0175 ohm mm21m for copper, 0.0283 ohm mm21m for aluminum; l - conductor length, m; F - cross-sectional area of ​​the conductor, mm2; Q - electrical losses, W.

The electrical losses in the conductor are equal to the thermal losses of the conductor to the environment. With an increase in the length of the welding wire, the voltage drop in the welding circuit increases. Therefore, it is necessary to limit its length as much as possible. In those cases where the welder serves a large area of ​​​​the production area and, therefore, needs a long wire, for economic reasons, the cross section of the welding wire in this case should be increased. To increase the length, connectors with an insulated sheath or pieces of wire with lugs connected by bolts are often used, followed by insulation. For convenience of work, a short segment (1.5 - 2 m) of reduced cross section and increased flexibility is left at the electrode holder (according to Table 2). The heating of this piece of wire according to GOST 6731 - 68 should not exceed 65 ° C at an ambient temperature of 20 ° C. The recommended allowable current values ​​in the welding wire at PR = 60% are given in Table. 4. For a different duration of operation, the allowable current can be recalculated using formulas that take into account the duration of the power supplies.

Table Permissible current values ​​in welding wires

Welding wire cross section, mm2	Permissible welding current, A

Holder for electrodes

Electrode holder TWIST 200 designed for reliable fixation and retention of the electrode and the supply of current to it during welding by the method. Electrically conductive parts are reliably isolated from accidental contact. Maximum welding current 200 A.

Consumable

OMA-2 electrodes are designed for welding structures made of thin sheets (thickness 1-3 mm) carbon steels with temporary resistance up to 410 MPa.

Welding in all spatial positions of the seam with alternating current and direct current of reverse polarity.

Characteristics of the electrodes

Coating - acid-cellulose.

Surfacing coefficient - 8.0 g/A*h.

Surfacing productivity (for a diameter of 3.0 mm) - 0.7 kg/h.

Consumption of electrodes per 1 kg of deposited metal - 1.7 kg.

Preparation of metal for welding

tenderloin

blanks from heavy and bulky pieces of sheet and profile products to facilitate the transportation of blanks and further operations for the manufacture of parts. The cut blanks are subjected to preliminary straightening and subsequent cleaning of the surface from dirt, rust and scale on shot blasting machines. Rolled products are straightened, as a rule, in a cold state on straightening machines or manually on straightening plates. Cutting blanks is carried out in most cases on cutting machines along the stops. The most common method of cutting low-carbon steels is gas-flame (oxygen) cutting. The manufacture of parts after pre-treatment is carried out by a number of sequential technological operations: marking, cutting, stamping, cleaning, straightening, edge preparation, flanging and bending of parts.

markup

is the application of a workpiece configuration to the metal. The markup is carried out with an allowance. The allowance is the difference between the size of the workpiece and the finished size of the part. The allowance is removed during subsequent processing. Marking tables or plates of the required dimensions are used for marking. The marking is carried out using various tools: a steel meter, a steel tape measure, a metal ruler, a scriber, a center punch, a compass, a caliper, a thickness gauge, a square, etc. To obtain a clearer outline of the workpiece, the metal surface is preliminarily painted over with white adhesive paint. With a large number of blanks or parts, the marking is carried out according to flat templates with an allowance for subsequent processing. The outline of the part is drawn with a scriber, and then they are punched along the entire length of the bypass line with a step of 50--100 mm between the cores.

cutting

is carried out by oxygen cutters along the intended line of the contour of the part manually or by gas-cutting machines for special purposes. Cutting on mechanical machines is more productive and has a high quality cut. For mechanical straight cutting of sheet metal, press shears are used for longitudinal and transverse cutting. Stamping of blanks is carried out in a cold or hot state. Cold stamping is used for sheet metal with a thickness of 6-8 mm. For metal with a thickness of 8-10 mm, hot stamping is used (with preheating). Metal cleaning is carried out to remove burrs from the edges of parts after stamping, as well as to remove scale and slag from the surface of edges after oxygen cutting.

For stripping

small parts use stationary installations with emery wheels. For cleaning large parts, portable pneumatic or electric grinders are used.

Edit

Parts and blanks are cut on straightening rollers or manually on a plate if they are possibly bent during oxygen cutting or cutting with mechanical scissors. Straightening of thin sheet metal is carried out in a cold state on sheet-straightening rollers or presses. Editing of thick sheet metal is carried out in a hot state manually on the correct plates.

Edge preparation

parts from low-carbon steel of large thickness are carried out by oxygen cutting or processing on planing or milling machines. Edge flanging is used for parts made of thin sheet metal for subsequent butt joints. This operation is carried out on bending presses or special machines. Immediately before welding, additional cleaning of parts is carried out by mechanical or chemical methods. The most progressive way of cleaning parts is etching in solutions of acids or alkalis.

bending

parts and blanks are produced on metal-bending rolls, as a rule, for the manufacture of various cylindrical containers. The part takes the form of a cylinder and is called a shell. Bending parts to obtain other geometric shapes is carried out on special machines or installations. However, it is not always possible to prepare metal for welding using industrial equipment, for example, in the conditions of construction and installation work, where parts are assembled into knots and adjusted in place.

Selecting the manual arc welding mode

The arc welding mode is a set of factors that ensure that a weld of good quality and specified dimensions is obtained. Such factors include the type and polarity of the welding current, its magnitude, type and brand of the electrode, its diameter, arc voltage, position of the seam in space, welding speed.

The type of welding current - direct or variable - and its polarity depends on the grade and thickness of the metal being welded; these data are given in tables with the characteristics of various brands of electrodes. The electrode type and brand can also be selected from these tables.

The electrode diameter, depending on the thickness of the parts to be welded, can be selected from the table. 2.

Table The value of the electrode diameter depending on the thickness of the metal being welded

When welding multilayer seams, the first seam is welded with an electrode with a diameter of not more than 4 mm, and with an electrode diameter greater than this, there may be a lack of penetration of the root of the seam.

The diameter of the electrode when welding vertical seams is not more than 5 mm, ceiling - not more than 4 mm, regardless of the thickness of the metal being welded. When choosing the electrode diameter for welding fillet and tee joints, the leg of the seam is taken into account. The diameter of the electrode at the leg of the seam is 3 ... 5-3 ... 4 mm, at the leg 6 ... 8-4 ... 5 mm.

The value of the welding current, depending on the diameter of the electrode, is printed on the packaging of the electrodes.

For welding in the lower position, the value of the welding current can be determined by the formula:

I sv \u003d (40 ... 60) d,

where I St - the value of the welding current, A; 40...60 -- coefficient depending on the type and diameter of the electrode; d -- electrode diameter, mm.

When welding structural steels:

For electrodes with a diameter of 3 ... 6 mm, the value of the welding current: I sv \u003d (20 + 6d) d;

For electrodes with a diameter of less than 3 mm: I St = 30d,

where I St - the value of the welding current, A; d -- electrode diameter, mm.

The value of the welding current depends both on the diameter of the electrode and on the length of its working part, the coating composition, and its position in the welding space.

The amount of metal deposited during welding depends on the value of the welding current:

Q \u003d b n I sv t,

where Q is the amount of deposited metal, g; b n - deposition coefficient, g / (A * h); I St - welding current, A; g - welding time, h.

But at a welding current that is unacceptable for a given electrode diameter, the electrode quickly overheats, which leads to a decrease in the quality of the weld and metal spatter.

With an insufficient value of the welding current, the arc is unstable, there may be lack of penetration in the seam.

The arc voltage varies in the range of 16...30 V.

Technological process

Galvanized sheet 600x400 mm

St 0.5 GOST 19904-90

Steel corner 20x20L= 1520 mm.; 190 mm - 8 pcs.

Article 3 GOST 8509-93

took a steel corner, cleaned the surface of dirt, marked it into 8 parts, as shown in Figure 1, cut it off along the marking line. I took 4 cut pieces and put them on the welder's table with the sides cut off at 45 0 as in Figure 1.2. Welded. I took the other 4 cut off parts and put them also on the welder's table with the sides cut off at 45 0 as in Figure 1.2. Welded.

2. I took a sheet of galvanized sheet 400 x 600 mm in size, cleaned the surface of dirt, marked the sheet as shown in Figure 2. In the places marked with a dotted line, I bent the sheet 90 0, thereby making a square pipe.

3. I took the welded structure from point 1 and substituted it to the end of the square pipe from point 2 as shown in Figure 3. I took the second welded structure from point 1 and attached it to the other end of the square pipe from point 2. Thus, we assembled and welded the “air duct” structure »

Labor protection instruction for electric welder

1. GENERAL PROVISIONS.

1.1. Electric welding manual work is allowed for personnel not younger than 18 years of age, who have undergone special training, have a certificate for the right to work, including electrical safety group III, and do not have contraindications for health reasons.

1.2. Electric welders must undergo a mandatory medical examination upon admission to work and periodic medical examinations at least once every 12 months.

1.3. All newly hired employees must undergo an introductory briefing at the labor protection service. The results are recorded in the registration log of the introductory briefing on labor protection. After that, the personnel department makes the final registration of the newly arriving employee and sends him to the place of work.

1.4. Each newly hired person must undergo an initial briefing on labor protection at the workplace. All employees are re-instructed at least twice every 6 months. Instruction is provided by the head of the department. The results of the briefing are recorded in the journal.

1.5. A daily permit to work is issued by an order - a permit for hot work.

1.6. When applying for a job and periodically at least once every 12 months, electric welders must pass a knowledge test on labor safety issues according to a program approved by the management of the enterprise.

1.7. In the process of performing work, electric welders are obliged to comply with the requirements of the internal labor regulations, work and rest regimes.

1.8. In the process of daily production activities, the electric welder may be affected by harmful and dangerous production factors:

Increased voltage in the electrical circuit, the closure of which can pass through the body of the worker;

Increased gas contamination and dustiness of the air in the working area;

Increased levels of ultraviolet, visible and infrared radiation;

Elevated air temperature in the working area and molten metal.

1.9. In the process of work, electric welders must observe the rules of personal hygiene and wearing special clothing, special shoes, and use other personal protective equipment.

1.10. Overalls and other personal protective equipment are issued in accordance with the Model Industry.

1.11. Electric welders should not allow deviations from technological standards during work, know and comply with the requirements of this labor protection instruction, as well as the instructions of manufacturers for the operation of equipment, tooling, and tools used in the process of work.

1.12. The victim or eyewitness of the accident is obliged to immediately notify the supervisor of each production-related accident. The work manager must organize first aid to the victim, deliver him to a medical institution, inform the owner and the labor protection service about this. To investigate an accident, it is necessary to maintain the workplace environment and the condition of the equipment as they were at the time of the accident, if this does not endanger the life and health of others and does not lead to an accident.

1.13. Electric welders must know the methods of providing first aid, methods of transporting the victim, know the location and contents of the first-aid kit, be able to use the means in the first-aid kit.

1.14. Persons who have violated the instructions on labor protection are subject to disciplinary, material liability, extraordinary testing of knowledge about labor protection.

2. Safety requirements before starting work.

2.1. Check the availability and serviceability of personal protective equipment, put it on, fasten the cuffs of the sleeves of the suit. In this case, the jacket should not be tucked into trousers, and trousers should be released over boots (felt boots).

2.2. Present to the work manager a certificate of knowledge of safe working methods.

2.3. Get a job assignment from the manager and a work permit for work.

2.4. Inspect and prepare the necessary personal protective equipment (when performing ceiling welding - asbestos or canvas sleeves; when working lying down - warm bedding; when working in wet rooms - dielectric gloves, galoshes or rugs; when welding or cutting non-ferrous metals and alloys - a hose gas mask ).

2.5. Inspect and prepare the workplace and approaches to it for compliance with safety requirements:

Remove all unnecessary items without cluttering the aisles;

Check the condition of the floor at the workplace, wipe wet or slippery floors;

Prepare tools, equipment and technological equipment necessary for the performance of work;

Make sure that the welding equipment is in good condition, that the welding installation is grounded and in good condition;

Arrange the welding wires so that they are not subjected to mechanical damage and high temperatures, and do not come into contact with moisture;

Make sure that flammable and explosive substances and combustible materials are not stored near the workplace.

The place of work, as well as the places below, must be freed from combustible materials within a radius of at least 5 m, from explosive materials and installations - at least 10 m.

2.6. Check the serviceability of a portable lamp with a voltage not higher than 12V.

2.7. When performing welding work indoors or on the territory operating enterprise check compliance with the requirements of fire and explosion safety and ventilation in the work area.

2.8. The electric welder should not start work in case of the following violations of safety requirements:

The absence or malfunction of the protective shield, welding wires, electrode holder, as well as personal protective equipment;

Absence or malfunction of grounding of the welding transformer case, secondary winding, welded part and knife switch casing;

Insufficient illumination of workplaces and approaches to them;

Lack of fencing of workplaces located at a height of 1.3 m or more, and equipped systems for accessing them in fire and explosive working conditions;

Lack of exhaust ventilation in case of work in enclosed spaces.

2. 9. Detected violations of safety requirements must be eliminated before the start of work, and if it is impossible to do this, the electric welder is obliged to report them to the manager.

3. Safety requirements during work.

3.1. When performing electric welding work outdoors (during rain or snowfall), a canopy must be installed above the workplace of the welder and the location of the welding machine.

3.2. Electric welding work at height should be carried out from scaffolding or scaffolding with fences. It is forbidden to work from ladders.

3.3. Welding should be carried out using two wires, one of which is connected to the electrode holder, and the other (reverse) - to the workpiece to be welded. It is forbidden to use metal structures of buildings, technological equipment, pipes of sanitary networks (water supply, electric wire, etc.) as a return wire of the grounding network.

3.4. Welding wires must be connected by hot soldering, welding or by means of connectors with an insulating sheath. Connection points must be insulated. Connection of welding wires by twisting is not allowed. Welding wires should be laid in such a way that they cannot be damaged by machines and mechanisms.

3.5. Before welding, the electric welder must make sure that the edges of the workpiece to be welded and the area adjacent to them (20-30 mm) are cleaned of rust, slag, etc. Protective goggles must be worn when cleaning.

The parts to be welded must be securely fastened prior to welding. When cutting structural elements, the electric welder is obliged to take measures against accidental falling of the cut elements.

3.6. During breaks in work, the electric welder is prohibited from leaving the electrode holder under voltage at the workplace, the welding machine must be turned off, and the electrode holder must be fixed on a special stand or suspension.

3.7. Connection and disconnection of welding machines must be carried out by special personnel through an individual switch.

3.8. Repairs to the welding machine must be carried out by specialized personnel.

3.9. The electrician is prohibited from:

Connect welding wires with a twist;

Touch live parts with your hands;

Repair electrical equipment;

Work with a shield or helmet that has cracks and cracks in the glass;

Work at a permanent workplace without local suction included;

Look at the electric arc without protective equipment (masks, goggles, shields);

Perform electric welding work outdoors without a canopy during rain and snowfall;

Cutting and welding metal on weight;

Perform welding work in a room where flammable substances and gases are located;

Perform welding work on vessels, pipelines and apparatus under pressure;

Use pipes, rails, etc. as a return wire. metal objects;

Warm up the electrode on a grounded table or other objects.

4. Safety requirements at the end of work.

4.1. Turn off the electric welder.

4.2. Tidy up the workplace, assemble the tools, wind the welding wires into coils and put away the places allotted for their storage.

4.3. Make sure that there are no foci of fire, if any, fill with water.

4.4. Report all violations of safety requirements that occurred during the performance of work to the foreman or work manager.

4.5. Remove overalls, personal protective equipment, put them in the designated place.

5. Safety requirements in emergency situations.

5.1. In the event of a fire, inform the fire brigade by phone 01, the head of the work and start extinguishing.

5.2. In the event of malfunctions of the welding unit, welding wires, electrode holders, protective shield or helmet-mask, it is necessary to stop work and inform the foreman or work manager about this. Operation can only be resumed after all faults have been rectified by the appropriate personnel.

5.3. In the event of gas contamination of the premises in the absence of exhaust ventilation, work must be suspended and the premises ventilated.

5.4. Outdoor work must be stopped with the onset of rain or snowfall. Work can be resumed only after the rain or snowfall has stopped or a canopy has been installed over the place of work of the electric welder.

5.5. If you feel pain in the eyes, get burns, immediately stop work, informing the work manager about this, and seek medical help at the emergency room.

Personal protective equipment

Personal protective equipment is used in cases where the safety of work cannot be ensured by the design of the equipment, organization production processes, architectural and planning solutions and means of collective protection.

Depending on the purpose, personal protective equipment is divided according to GOST 12.4.011 - 89 into the following classes:

special clothing (overalls, semi-overalls, jackets, trousers, suits, sheepskin coats, sheepskin coats, aprons, vests, armlets);

special footwear (boots, boots, galoshes, boots);

head protection (helmets, balaclavas, hats, berets);

respiratory protection equipment (gas masks, respirators);

face protection equipment (protective shields and masks);

eye protection (safety goggles);

hearing protection (anti-noise helmets, earmuffs, earmuffs);

safety devices (dielectric mats, hand grips, manipulators, knee pads, elbow pads, shoulder pads, safety belts);

hand protection (mittens, gloves);

protective dermatological products (pastes, creams, ointments, detergents).

Personal protective equipment should be issued in accordance with the Model Industry Standards for the Free Issue of Special Clothing, Special Footwear and Other Personal Protective Equipment to Workers and Employees, approved by the Decree of the Ministry of Labor and social development Russian Federation dated December 16, 1997 No. 63.

Special protective clothing in accordance with GOST 12.4.011-- 89 provides welders with suits, jackets and trousers with protective properties "Tr" that provide protection against sparks and molten metal. In winter, overalls with protective properties "Tn" are used, which provide protection from exposure to cold air ("Tn 30" - up to a temperature of -30 ° C).

In accordance with GOST 12.4.103 - 83, special footwear for welders in the warm season is leather boots with protective properties "Tr", having external metal socks and designed to protect the legs from thermal radiation, contact with heated surfaces, from scale, sparks and splashes of molten metal. In winter, felt boots are provided.

In areas (determined by the administration) where there is a risk of head injury, welders must wear safety helmets. For convenience in the work of welders, the use of helmets combined with a protective shield is recommended. During the simultaneous work of welders or metal cutters at different heights along the same vertical, along with the mandatory protection of the head with a helmet, enclosing devices (awnings, blind decks, etc.) must be provided to protect workers from falling splashes of metal, cinders, etc.

Individual respiratory protection equipment is used in exceptional cases when it is impossible to ensure the maximum permissible concentrations of dust and gases in the worker's breathing zone by means of ventilation.

If during welding the concentration of gases (ozone, carbon and nitrogen oxides) in the breathing zone does not exceed the maximum allowable, and the concentration of dust is higher than the allowable, then welders must be provided with dust respirators.

In case of exceeding the maximum permissible concentration of dust and gases when working in closed and hard-to-reach rooms (tanks), welders are provided with breathing devices with a forced supply of clean air. Devices of this type also include hose gas masks PSh-2-57 and RMP-62 or ASM breathing machines.

The air entering the breathing apparatus from the compressor must not contain drops of water, oil, dust, hydrocarbon vapors and carbon monoxide.

Bibliography

1. G.G. Chernyshov "Welding" 2004

2. V.I. Maslov "Welding work" 2002

3. V.M. Rybakov "Arc and gas welding" 1996

4. "Handbook of electric gas welder and gas cutter" 2007 Edited by G.G. Chernyshov.

5. V.S. Vinogradov "Electric arc welding" 2007.

6. O.N.Kulikov, E.I.Rolin "Labor protection in the production of welding work" 2007.

7. V.N. Volchenko "Welding and welded materials" 1991.

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INTRODUCTION

Welding, along with casting and pressure treatment, is the oldest technological operation mastered by man in bronze age during the acquisition of experience in working with metals. Its appearance is associated with the need to connect various parts in the manufacture of tools, military weapons, jewelry and other products.

The first method of welding was forge, which provided a fairly high quality connection for those times, especially when working with ductile metals such as copper. With the advent of bronze (harder and harder to forge), foundry welding arose. During foundry welding, the edges of the parts to be joined were molded with a special earthen mixture and poured with heated liquid metal. This filler metal was fused with the parts and solidified to form a seam. Such compounds have been found on bronze vessels preserved from the times of Ancient Greece and Ancient Rome.

With the advent of iron, the range of metal products used by man increased, so the scope and scope of welding expanded. New types of weapons are being created, the means of protecting a warrior in battle are being improved, chain mail, helmets, and armor are appearing. For example, in the manufacture of chain mail, more than 10 thousand metal rings had to be connected by forge welding. New casting technologies are being developed, knowledge is gradually being acquired related to the heat treatment of steel and giving it different hardness and strength. Often this knowledge was obtained by chance and could not explain the essence of the ongoing processes.

For example, in a manuscript found in the temple of Balgon in Asia, the process known to us as tempering steel is described as follows: “Heat the dagger until it glows like the morning sun in the desert, then cool it to the color of royal purple, sticking the blade into the body muscular slave. The strength of the slave, turning into a dagger, gives it hardness. " Nevertheless, despite the rather primitive knowledge, swords and sabers were made even before our era, which had unique properties and were called Damascus. In order to give the weapon high strength and hardness and at the same time provide plasticity that did not allow the sword to be fragile and break from blows, it was made layered. Alternately, in a certain sequence, hard layers of medium or high carbon steel and soft strips of low carbon steel or pure iron were welded together. The result was a weapon with new properties that cannot be obtained without the use of welding. Subsequently, in the Middle Ages, this technology began to be used for the manufacture of highly efficient, self-sharpening plows and other tools.

Forge and foundry welding for a long time remained the main method of joining metals. These methods fit well into the production technology of that time. The profession of a blacksmith-welder was very honorable and prestigious. However, with the development in the XVIII century. machine production, the need to create metal structures, steam engines, and various mechanisms has increased dramatically. Known welding methods in many cases ceased to meet the requirements, since the lack of powerful heat sources did not allow uniform heating of large structures to the temperatures required for welding. Riveting became the main method of obtaining permanent joints at that time.

The situation began to change at the beginning of the 20th century. after the creation of sources of electrical energy by the Italian physicist A. Volta. In 1802, the Russian scientist V.V. Petrov discovered the phenomenon of an electric arc and proved the possibility of using it to melt metal. In 1881 Russian inventor N.N. Benardos suggested using an electric arc burning between a carbon electrode and a metal part to melt its edges and connect it to another part. He called this method of joining metals "electrohephaestus" in honor of the ancient Greek blacksmith god. It became possible to connect metal structures of any size and various configurations with a strong welded seam. This is how electric arc welding appeared - an outstanding invention of the 19th century. It immediately found application in the most difficult industry at that time - steam locomotive building. Discovery of N.N. Bernardos in 1888 was improved by his contemporary N.G. Slavyanov, replacing the non-consumable carbon electrode with a consumable metal one. The inventor proposed the use of slag, which protected the weld from air, making it more dense and durable.

In parallel, gas welding developed, in which a flame was used to melt the metal, which was formed during the combustion of a combustible gas (for example, acetylene) mixed with oxygen. V late XIX v. this method of welding was considered even more promising than arc welding, since it did not require powerful sources of energy, and the flame, simultaneously with the melting of the metal, protected it from the surrounding air. This made it possible to get enough good quality welded joints. Around the same time, thermite welding began to be used to connect railroad joints. During the combustion of thermites (a mixture of aluminum or magnesium with iron oxide), pure iron is formed and a large amount of heat is released. A portion of thermite was burned in a refractory crucible, and the melt was poured into the gap between the welded joints.

An important stage in the development of arc welding was the work of the Swedish scientist O. Kelberg, who in 1907 proposed to apply a coating to a metal electrode, which, decomposing during arc burning, provided good protection of the molten metal from air and its alloying with the elements necessary for high-quality welding. After this invention, welding began to find more and more applications in various industries. Of particular importance at that time were the works of the Russian scientist V.P. Vologdin, who created the first department of welding at the Polytechnic Institute of Vladivostok. In 1921, the first welding workshop for the repair of ships was opened in the Far East, and in 1924, the largest bridge across the Amur River was repaired using welding. At the same time, tanks for storing oil with a capacity of 2000 tons were created, a generator for the Dneproges was manufactured by welding, which was twice as light as riveted. In 1926, the first All-Union Conference on Welding was held. In 1928, there were 1,200 arc welding units in the USSR.

In 1929, a welding laboratory was opened in Kiev at the Academy of Sciences of the Ukrainian SSR, which in 1934 was transformed into the Institute of Electric Welding. The institute was headed by a well-known scientist in the field of bridge construction, Professor E.O. Paton, after whom the institute was later named. One of the first major works Institute was the development in 1939 of automatic submerged arc welding. It made it possible to increase the productivity of the welding process by 6-8 times, improve the quality of the joint, significantly simplify the work of the welder, turning him into an operator for controlling the welding installation. This work of the Institute in 1941 received the State Prize. Automatic submerged arc welding played a huge role during the Great Patriotic War, for the first time in the world becoming the main method of joining armor plates up to 45 mm thick in the manufacture of the T34 tank and up to 120 mm in the manufacture of the IS-2 tank. With a shortage of qualified welders during the war, the increase in welding productivity through automation made it possible to short term significantly increase the production of tanks for the front.

A significant achievement of welding science and technology was the development in 1949 of a fundamentally new method of fusion welding, called electroslag welding. Electroslag welding plays a huge role in the development of heavy engineering, as it allows welding very thick metal (more than 1 m). An example of the use of electroslag welding is the manufacture of a press at the Novokramatorsky Mashinostroitelny Zavod commissioned by France, which can generate a force of 65,000 tons. The press has a height equal to the height of a 12-storey building, and its weight is twice the weight of the Eiffel Tower.

In the 50s. of the last century, industry has mastered the method of arc welding in a carbon dioxide environment, which in Lately is the most common welding method and is used in almost all machine-building enterprises.

Welding is actively developing in subsequent years. From 1965 to 1985, the volume of production of welded structures in the USSR increased 7.5 times, the stock of welding equipment - 3.5 times, the output of welding engineers - five times. Welding began to be used for the manufacture of almost all metal structures, machines and structures, completely replacing riveting. For example, the usual a car has more than 5 thousand welded joints. The pipeline, which supplies gas from Siberia to Europe, is also a welded structure with more than 5,000 kilometers of welds. Not a single high-rise building, TV tower or nuclear reactor is manufactured without welding.

In the 70-80s. new methods of welding and thermal cutting are being developed: electron beam, plasma, laser. These methods make a huge contribution to the development of various industries. For example, laser welding allows you to qualitatively connect the smallest parts in microelectronics with a diameter and thickness of 0.01-0.1 mm. The quality is ensured by the sharp focusing of the monochromatic laser beam and the finest dosage of the welding time, which can last from 10 to 6 seconds. Mastering] laser welding made it possible to create a whole series of new element base, which in turn made it possible to manufacture new generations of color televisions, computers, control and navigation systems. Electron-beam welding has become an indispensable technological process in the manufacture of supersonic aircraft and aerospace facilities. The electron beam makes it possible to weld metals up to 200 mm thick with minimal structural deformations and a small heat-affected zone. Welding is the main technological process in the manufacture of marine vessels, oil platforms, and submarines. Modern nuclear Submarine, with a height of about 200 m and a height of a 12-storey building, is a fully welded structure made of high-strength steels and titanium alloys.

Without welding, the current achievements in the space field would not have been possible. For example, final assembly missile system carried out in a welded assembly shop weighing about 60 thousand and 160 m high. The rocket containment system consists of welded towers and masts with a total weight of about 5 thousand tons. All critical structures on the launch pad are also welded. Some of them have to work in very difficult conditions. The impact of a powerful flame at the launch of a rocket takes on a welded flame separator weighing 650 tons, 12 m high. Complex welded structures are fuel storage tanks, a system for supplying it to tanks and the fuel tanks themselves. They must withstand enormous hypothermia. For example, a liquid oxygen tank has a capacity of over 300,000 liters. It is made with a double wall - from stainless and low carbon steel. The diameter of the outer sphere is 22 m. Tanks for liquid hydrogen are designed in a similar way. The pipeline for supplying liquid hydrogen is welded from nickel alloy, it is inside another aluminum alloy pipeline. The pipelines for supplying kerosene and superactive fuel are welded from stainless steel, and the pipeline for supplying oxygen is made of aluminum.

With the help of welding, multi-ton BelAZs and MAZs, tractors, trolleybuses, elevators, cranes, scrapers, refrigerators, televisions and other industrial products and consumer goods are manufactured.

1. TECHNOLOGICAL SECTION

1 Description of the welded structure and its purpose

The fan housing works in particularly harsh conditions. Subjected to direct impact of dynamic and vibration loads.

The fan housing is made up of

Pos 1 Body 1 pc

V \u003d π * D * S * H ​​\u003d 3.14 * 60.5 * 0.8 \u003d 151.98 cc.

Q \u003d ρ * V \u003d 7.85 * 151.98 \u003d 1193.01 gr. = 1.19 kg

Pos 2 Flange 2 pcs.

fan welding deformation arc

V \u003d π * (D out 2. - D int 2) * s \u003d 3.14 * (64.5 2 -60.5 2) * 1 \u003d 1570 cu. cm

Q \u003d ρ * V \u003d 7.85 * 1570 \u003d 12324.5 gr. = 12.33 kg.

Pos 3 Ear 2 pcs

V \u003d h + l + s \u003d 10 * 10 * 0.5 \u003d 50 cu. cm

Q \u003d ρ * V \u003d 7.85 * 50 \u003d 392.5 g \u003d 0.39 kg

Cross-sectional area of ​​the weld

t. sh. \u003d 0.5K² + 1.05K \u003d 0.5 * 6² +1.05 * 6 \u003d 24.3 sq mm

2 Weldment material justification

Chemical composition of steel

Equivalent carbon content

Ce \u003d Cx + Cp

Сх - chemical equivalent of carbon

Сх = С + Mn/9 + Cr/9 + Mo/12 = 0.16 +1.6/9 + 0.4/9 = 0.38

Ср - correction to carbon equivalent

Cp \u003d 0.005 * S * Cx \u003d 0.005 * 8 * 0.38 \u003d 0.125

Preheat temperature

T p \u003d 350 * \u003d 350 * 0.25 \u003d 126.2 degrees.

1.3 Specifications for the manufacture of welded structures

The fan housing works in particularly harsh conditions. Subjected to direct impact of dynamic and vibration loads.

4 Determining the type of production

The total weight of the spar is 32.07 kg. With a production program of 800 pcs, we select the serial type of production

In serial production, the type of production is characterized by the use of specialized assembly and welding fixtures, welding of units is carried out on stationary workers

5 Selection and justification of assembly and welding methods

This design is made of 16G2AF steel, which belongs to the group of well-welded steels. When welding, preheating up to 162 degrees and subsequent heat treatment is required.

Steel is welded by all types of welding. The thickness of the parts to be welded is 10 mm, which allows welding in a carbon dioxide environment with wire Sv 08 G2S

1.6 Determination of welding modes

sv \u003d h * 100 / Kp

where: h - penetration depth

Kp - coefficient of proportionality

c in \u003d 0.6 * 10 * 100 / 1.55 \u003d 387 A

Arc voltage

20 + 50* Ib* 10⁻³ / d⁰² V

20 + 50 *387 *10 ⁻³ / 1.6⁰² = 20 + 15.35 = 35.35 V

Welding speed

V sv \u003d K n * I sv / (ρ * F * 100) m / h =

1*387/7.85*24.3*100 = 34.6 m/h

where K n - surfacing coefficient g / A * h

ρ is the density of the metal, taken for carbon and low alloy steels, equal to 7.85 g/cm3;

F is the cross-sectional area of ​​the deposited metal. mm 2

7 Selection of welding consumables

Steel 16G2AF is welded by any type of welding using various kinds welding materials. Therefore, we use wire SV 08 G 2 S for welding. SV 08 G2S wire has good weldability, low emission of welding fumes, and low price.

7.1 Consumption of welding consumables

The consumption of electrode wire when welding in CO2 is determined by the formula

G e. pr. \u003d 1.1 * M kg

M - mass of deposited metal,

M = F * ρ * L * 10 -3 kg

M t. sh. \u003d 0.243 * 7.85 * 611.94 * 10 -3 \u003d 1.16 kg

Consumption of electrode wire

G e. pr. \u003d 1.1 * M \u003d 1.1 * 1.16 \u003d 1.28 kg

Consumption of carbon dioxide

G co2 \u003d 1.5 * G e. pr. \u003d 1.5 * 1.28 \u003d 1.92 kg

Electricity consumption

W \u003d a * G e. etc. \u003d 8 * 1.28 \u003d 10.24 kW / h

a \u003d 5 ... 8 kW * h / kg - specific energy consumption per 1 kg of deposited metal

8 Selection of welding equipment, technological equipment, tools

MAGSTER WELDING SYSTEM

· Professional welding system with the taken-out 4th roller giving mechanism of the well-known quality Lincoln Electric at the price of the best Russian analogues.

· Welding in shielding gases with solid and flux-cored wires.

· With success it is applied to welding of structural low-carbon and stainless steels, and also to welding of aluminum and its alloys.

· Step-by-step welding voltage adjustment.

· Smooth adjustment of giving of a wire.

· Gas pre-purging.

· Thermal overload protection.

· Digital voltage indicator.

· High reliability and easy operation.

· Synergic system of the welding process - after loading the type of wire and diameter, the feed rate and voltage are matched automatically by the microprocessor, (for mod. 400,500).

· Many functional liquid crystal display - displaying the parameters of the welding process (for mod. 400, 500).

· Water cooling system (for models with index W) .

· All models are equipped with a socket for connecting a gas heater (the heater is supplied separately).

· Designed in accordance with IEC 974-1. Protection class IP23 (outdoor operation).

· Supplied as ready-to-use kits and include: power source, feeder with transport trolley, connecting cables 5 m, mains cable 5 m, welding torch "MAGNUM" 4.5 m long, work clamp.

· AGSTER 400 plus MAGSTER 500 w plus MAGSTER 501 w Maximum power consumption, mains 380 V. 14.7 kW. 17 kW. 16 kW. 24 kW. 24 kW. Welding current at 35% duty cycle. 315 A. 400 A. 400 A. 500 A. 500 A. Welding current at 60% duty cycle. 250 A. 350 A. 350 A. 450 A. 450 A. Welding current at 100% duty cycle. 215 A. 270 A. 270 A. 350 A. 450 A. Output voltage. 19-47 V. 18-40 V. 18-40 V. 19-47 V. 19-47 V. Weight without cables. 88 kg 140 kg 140 kg 140 kg 140 kg

TECHNICAL PARAMETERS OF THE WIRE FEEDER

· Wire feed speed. 1-17 m/min 1-24 m/min 1-24 m/min 1-24 m/min 1-24 m/min Wire diameters. 0.6-1.2 mm 0.8-1.6 mm 0.8-1.6 mm 0.8-1.6 mm 0.8-1.6 mm Weight without torch. 20 kg. 20 kg. 20 kg.

9 Determination of technical standards for assembly and welding times

Calculation of technical norms of assembly time and assembly welding.

		Parameter	Time limit min	Time min	A source
	Clean the places for welding from oil, rust and other contaminants.		0.3 per 1 m of the seam
	Install child pos 2 in fixture.	Children's weight 12.33 kg
	Set children pos. 1 on det pos 2
	Grab det poses 1 to det poses 3 for 3 potholders		0.09 1 tack
	Set children pos. 2 on det pos 1	Children's weight 12.33
	Grab det poses 2 to det poses 1 for 3 potholders		0.09 1 tack
	Install 2 children pos. 3 on det pos 1	Children's weight 0.39
	Grab 2 det pos 3 to det pos 1 for 4 potholders		0.09 1 tack
	Remove the assembly unit and put it on the table of the welder	Sat weight units 32.07 kg
		L seam = 1.9 m	1.72 min / m seam
	Weld the edges of children pos 1 to each other	L seam = 0.32 m	1.72 min / m seam
	Weld child pos 2 to child pos 1	L seam = 1.9 m	1.72 min / m seam
	Clean the weld seam from spatter.	Lzach = 4.12 m	0.4 min/m seam
	Worker control, foreman
	Remove assembly unit

Table 1

table 2

Time to install parts (assembly units) when assembling metal structures for welding

Assembly view	Part weight, assembly unit
fixator

Table 3

Tack time

Thickness of metal or legs, mm	Tack length, mm	Time for one tack, min

Time to remove assembly units from the fixture and put them into storage

Basic time for welding 1 m. seam

F - cross-sectional area of ​​the weld

ρ - specific density of the deposited metal, g / cu. cm.

a - deposition coefficient

a \u003d 17.1 g / a * hour

That. t.sh = = 1.72 min / 1 m seam

10 Calculation of the amount of equipment and its loading

Estimated amount of equipment

C p = = = 0.09

T gi - the annual complexity of the operation, n-hour;

T gi = = = 308.4 n-hour

F d o - annual actual fund of equipment operation

F d o \u003d (8 * D p + 7 * D s) * n * K p \u003d (8 * 246 + 7 * 7) * 2 * 0.96 \u003d 3872.6 hours

D p, D s - the number of working days per year, respectively, with full duration and reduced;

n is the number of work shifts per day;

K p - coefficient taking into account the time the equipment is under repair (K p \u003d 0.92-0.96).

Load factor

K z = = = 0.09

Cp is the estimated amount of equipment;

Spr - accepted amount of equipment Spr = 1

11 Calculation of the number of employees

The number of main workers directly involved in the performance of technological operations is determined by the formula

Ch o.r. ===0.19

T g i - annual labor intensity, n-hour;

F d r - the annual actual fund of the working time of one worker, in hours;

K in - coefficient of performance of production standards (K in \u003d 1.1-1.15)

Annual effective fund of working time of one worker

F dr \u003d (8 * D p + 7 * D s) * K nev \u003d (8 * 246 + 7 * 7) * 0.88 \u003d 1774.96 hours

where D p, D s - the number of working days per year, respectively, with full duration and reduced;

K nev - absenteeism coefficient for good reasons (K nev = 0.88)

12 Methods for dealing with welding deformations

The whole complex of measures to combat deformations and stresses can be divided into three groups:

Activities that are implemented before welding;

Activities in the welding process;

Activities carried out after welding.

Deformation control measures applied before welding are implemented at the design stage of the welded structure and include the following measures.

Structural welding should have a minimum amount of deposited metal. The legs should not exceed the design values, butt welds should be made without cutting edges, if possible, the number and length of welds should be the minimum allowable.

It is necessary to use welding methods and modes that provide minimal heat input and a narrow heat-affected zone. In this regard, CO 2 welding is preferable to manual welding, and electron beam and laser welding is preferable to arc welding.

Welds should be as symmetrical as possible on the welded structure, it is not recommended to place welds close to each other, to have a large number of intersecting seams, without the need to use asymmetrical grooves. In structures with thin-walled elements, it is advisable to place the seams on rigid elements or near them.

In all cases where there is concern that undesirable deformations will occur, the design is carried out in such a way as to ensure the possibility of subsequent straightening.

Measures used in the welding process

Rational sequence of applying welds, on the structure and along the length.

When welding alloy steels and steels with a high carbon content, this can lead to the formation of cracks, so the stiffness of the fasteners must be assigned taking into account the metal being welded.

Preliminary deformation of welded parts.

Compression or rolling of the weld, which is carried out immediately after welding. In this case, the zone of plastic deformations of the shortening is subjected to plastic upsetting along the thickness.

1.13 Choice of quality control methods

The operational control system in welding production includes four operations: control of preparation, assembly, welding process and welded joints.

.) Control of the preparation of parts for welding

It provides for the control of the processing of the front and back surfaces, as well as the end edges of the parts to be welded.

The surfaces of the edges to be welded must be cleaned from dirt, preservative grease, rust and scale, to a width of 20 - 40 mm from the joint.

.) Assembly - installation of the parts to be welded in the appropriate position relative to each other when welding tee joints control the perpendicularity of the parts to be welded. When checking the quality of tacks, attention should be paid to the condition of the surface and the height of the tacks.

.) Welding process control includes visual observation of the process of metal melting and weld formation, control of the stability of the mode parameters and equipment performance.

.) Inspection of welded joints. After welding, welded joints are usually visually inspected. The weld and the heat-affected zone are subjected to inspection. Usually the control is carried out with the naked eye. When detecting surface defects less than 0.1 mm in size, optical devices are used, for example, a magnifier of 4-7 times magnification.

The main structural elements of welds are:

seam width

height of reinforcement and penetration;

smooth transition from reinforcement to base metal, etc.

1.14 Safety, fire prevention and environmental protection

The harmful effects of welding and thermal cutting on humans and industrial injuries when performing welding work, they are caused by various reasons and can lead to temporary disability, and in unfavorable circumstances - to more serious consequences.

Electric current is dangerous to humans, and alternating current is more dangerous than direct current. The degree of danger of damage electric shock depends mainly on the conditions for including a person in the circuit and the voltage in it, since the strength of the current flowing through the body is inversely proportional to the resistance (according to Ohm's law). For the minimum design resistance of the human body, 1000 ohms are taken. There are two types of electric shock: electric shock and trauma. Electric shock affects the nervous system, muscles chest and ventricles of the heart; paralysis of the respiratory centers and loss of consciousness are possible. Electrical injuries include burns to the skin, muscle tissues, and blood vessels.

The light radiation of the arc acting on unprotected organs of vision for 10-30 s within a radius of up to 1 m from the arc can cause severe pain, lacrimation and photophobia. Prolonged exposure to arc light under such conditions can lead to more serious diseases - (electrophthalmia, cataracts). The harmful effect of the rays of the welding arc on the organs of vision affects at a distance of up to 10 m from the place of welding.

Harmful substances (gases, vapors, aerosol) are released during welding as a result of physical and chemical processes that occur during the melting and evaporation of the metal being welded, components of electrode coatings and welding fluxes, as well as due to the recombination of gases under the action of high temperature welding heat sources. The air environment in the welding zone is polluted by welding aerosol, which consists mainly of oxides of the metals being welded (iron, manganese, chromium, zinc, lead, etc.), gaseous fluorine compounds, as well as carbon monoxide, nitrogen oxides and ozone. Prolonged exposure to welding aerosol can lead to occupational intoxication, the severity of which depends on the composition and concentration of harmful substances.

The explosion hazard is due to the use of oxygen, shielding gases, combustible gases and liquids in welding and cutting, the use of gas generators, compressed gas cylinders, etc. Chemical compounds of acetylene with copper, silver and mercury are explosive. The danger is backstroke in the gas network when working with low-pressure burners and cutters. When repairing used tanks and other containers for storing flammable liquids, special measures are necessary to prevent explosions.

Thermal burns, bruises and wounds are caused by high temperature sources of welding heat and significant heating of the metal during welding and cutting, as well as limited visibility of the surrounding space in connection with the production of work using shields, masks and goggles with light-protective glasses.

Unfavorable meteorological conditions affect welders (carvers) - builders and assemblers for more than half the time of the year, since they have to work mainly in the open air.

The increased fire hazard during welding and cutting is due to the fact that the melting point of metal and slag significantly exceeds 1000 ° C, and liquid combustible substances, wood, paper, fabrics and other flammable materials ignite at 250-400 ° C.

2. ELECTRICAL SAFETY PRECAUTIONS

It is necessary to reliably ground the body of the welding machine or installation, the clamps of the secondary circuit of welding transformers used to connect the return wire, as well as the products and structures to be welded.

2. It is forbidden to use ground loops, pipes of sanitary facilities, metal structures of buildings and technological equipment. (During construction or repair, metal structures and pipelines (without hot water or explosive atmosphere) can be used as a return wire of the welding circuit and only in cases where they are welded.)

4. It is necessary to protect the welding wires from damage. When laying welding wires and each time they are moved, prevent damage to the insulation; contact of wires with water, oil, steel ropes, sleeves (hoses) and pipelines with combustible gases and oxygen, with hot pipelines.

Flexible electric wires for controlling the scheme of the welding installation, with their considerable length, must be placed in rubber sleeves or in special flexible multi-link structures.

6. Only electrical personnel are entitled to repair welding equipment. Do not repair live welding equipment.

When welding in especially dangerous conditions (inside metal containers, boilers, vessels, pipelines, in tunnels, in closed or basements with high humidity, etc.):

welding equipment must be outside of these containers, vessels, etc.

electric welding installations must be equipped with a device for automatically switching off the open-circuit voltage or limiting it to a voltage of 12V for no more than 0.5 s after welding is stopped;

allocate a safety worker, who must be outside the tank, to monitor the safety of the welder. The welder is provided with a mounting belt with a rope, the end of which must be at least 2 m long in the hands of the insurer. Near the insurer there should be a device (knife switch, contactor) to turn off the mains voltage from the power source of the welding arc.

Do not allow welders to arc welding or cutting in wet gloves, shoes and overalls.

9. Cabinets, consoles and beds of contact welding machines, inside which there is equipment with open current-carrying parts under voltage, must have a lock that provides voltage relief when they are opened. Pedal start buttons of contact machines must be grounded and the reliability of the upper guard, which prevents involuntary switching on, must be monitored.

10. In case of electric shock, you must:

urgently turn off the current with the nearest switch or separate the victim from current-carrying parts using dry improvised materials (pole, board, etc.) and then put him on a litter;

immediately call for medical assistance, given that a delay of more than 5-6 minutes can lead to irreparable consequences;

if the victim is unconscious and does not breathe, release him from tight clothing, open his mouth, take measures against falling of the tongue and immediately begin artificial respiration, continuing it until the doctor arrives or normal breathing is restored.

3. PROTECTION AGAINST LIGHT RADIATION

To protect the eyes and face of the welder from the light radiation of an electric arc, masks or shields are used, into the viewing holes of which protective glass filters are inserted that absorb ultraviolet rays and a significant part of light and infrared rays. From splashes, drops of molten metal and other contaminants, the light filter is protected from the outside with ordinary clear glass installed in the viewing hole in front of the light filter.

Light filters for arc welding methods are selected depending on the type of welding work and the welding current, using the data in Table. 3. When welding in a shielding inert gas environment (especially when welding aluminum in argon), it is necessary to use a darker light filter than when welding with an open arc at the same current strength.

Table 3. Light filters for eye protection from arc radiation (OST 21-6-87)

2. To protect the surrounding workers from the light radiation of the welding arc, portable shields or screens made of fireproof materials are used (with a non-permanent workplace of the welder and large products). In stationary conditions and with relatively small sizes of welded products, welding is performed in special booths.

3. To reduce the contrast between the brightness of the arc light, the surface of the walls of the workshop (or cabins) and equipment, it is recommended to paint them in light colors with diffuse reflection of light, and also to ensure good illumination of the surrounding objects.

If the eyes are damaged by the light radiation of the arc, you should immediately consult a doctor. If it is not possible to obtain a fast medical care make lotions on the eyes with a weak solution of baking soda or tea leaves.

Protection against harmful gas emissions and aerosol

To protect the body of welders and cutters from harmful gases and aerosols released during the welding process, it is necessary to use local and general ventilation, supply clean air to the breathing zone, as well as low-toxic materials and processes (for example, use rutile-type coated electrodes, replace welding with coated electrodes for mechanized welding in carbon dioxide, etc.).

2. When welding and cutting small and medium-sized products at permanent places in workshops or workshops (in cabins), it is necessary to use local ventilation with fixed side and bottom suction (welder table). When welding and cutting products at fixed places in workshops or workshops, local ventilation with an intake funnel mounted on a flexible hose must be used.

Ventilation should be performed by supply and exhaust with the supply of fresh air to the welding areas and its heating in cold weather.

When working in closed and semi-closed spaces (tanks, tanks, pipes, compartments of sheet structures, etc.), it is necessary to use local suction on a flexible hose to extract harmful substances directly from the place of welding (cutting) or provide general ventilation. If it is impossible to carry out local or general ventilation, clean air is forcibly supplied to the breathing zone of the worker in the amount of (1.7-2.2) 10-3 m3 per 1 s, using a mask or helmet of a special design for this purpose.

LITERATURE

1. Kurkin S. A., Nikolaev G. A. Welded structures. - M.: Higher School, 1991. - 398s.

Belokon V.M. Production of welded structures. - Mogilev, 1998. - 139s.

Blinov A.N., Lyalin K.V. Welded structures - M .: - "Stroyizdat", 1990. - 352s

Maslov B.G. Vybornov A.P. production of welded structures -M: Publishing Center "Academy", 2010. - 288 p.

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