The production of air ducts is a profitable business. They are needed in the construction of residential and commercial premises. Ducts are pipe-like structures 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?

Studying the assortment

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 centers, offices. Steel products have the following advantages:

• they are not susceptible to corrosion;
• cheaper than plastic ones;
• 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 will take a lot to produce them. Money. But they are in greatest demand. Therefore, experienced entrepreneurs say that it is better to start manufacturing ventilation ducts with this type.

We weigh the pros and cons

The main advantages can be highlighted:

• Profitability. Despite the fact that this business requires considerable 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 megacities, 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 will always be a client 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 earn an amount that will cover all initial expenses.

The disadvantages include:

• large investment investments;
• high level of competition.

Before opening own production, you need to assess the market situation in your region and conduct a competitor analysis. 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 and their rigidity. The owner of the enterprise decides what size and parameters of air ducts to produce, based on consumer demand.

Also, the main indicator of the type of manufactured product is installation. Thus, rectangular air ducts are less susceptible to this process 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 air ducts are more reliable ventilation structures. They are used for large cross-sectional areas. When difficult things are expected installation work in a building with an unusual design, rectangular ducts are also preferred.

Since it is unknown which types of products will be in higher demand in your region, 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, ruling form leaf;
• a machine that is responsible for supplying 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 are used (rolling), and for rectangular ones, machines that bend sheets and apply ribs are used.

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

Documents required to organize a business

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

In order to prepare documents for an individual entrepreneur, you need to pay a state fee, write an application, make copies of your TIN and passport, and then hand it all over to the tax inspector. The founders of an LLC need to additionally prepare the company’s statutory documents, resolve the issue of legal address and form an authorized capital (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 treatment can duct manufacturers choose?

If we're talking about about small volumes of production, then you can work under 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 large-scale production of air ducts and plan to enter into contracts with large companies, then you better work on a general basis. To organize internal and tax accounting in this situation, you need a qualified accountant, who must be paid a rather large salary. But a good specialist will always find legal ways to reduce the amount of tax payments, often exceeding the monetary reward for his work.

Air duct production technology

The production of air ducts takes place in several stages. Let's take a closer look at the production process of one of the types of round structures made of galvanized steel.

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

How much money do you need to start a business?

To organize this type of business, a large initial investment will be required. The main costs include:

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

If there is no money to create full-scale production, then you can start by manufacturing the parts needed for ventilation ducts. These include:

• plugs;
• bends;
• insets;
• nipples.

This will not require large expenses, since all these structures can be made from industrial waste and defective products. The machines for their production cost around 50 thousand rubles. Subsequently, you can expand your scope of activity and begin to manufacture air ducts of various types themselves.

To save money, you can hire unqualified personnel for the first time. Naturally, you need to care about the quality of the product, so it is worth considering the abilities of the employees.

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

This business is very profitable. This allows you to make large profits with relatively low initial costs. With established production, you can earn 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 within 6-12 months.

Manufacturing 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 burning out, but in this case you should not be afraid of it, because not a single room can do without ventilation.

Air duct production

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

Galvanized air ducts for ventilation are used in air exchange systems with a working environment with temperatures up to +80C (a short increase 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 not require additional protective coating, since the top zinc layer protects the metal from corrosion even in places where it is damaged (due to the steel-zinc galvanic couple, which forms an oxide film under the influence of atmospheric oxygen).

Stainless steel air ducts are designed to work with superheated air and aggressive gas-air mixtures. Working environment temperature - up to +500С (short-term increase to +700С is allowed). Steel in accordance with GOST 5632-72 (heat and corrosion resistant) is used as a blank material for the production of air ducts from stainless steel.

“Black” air ducts are made from low-carbon steel. The thickness of the workpiece is from 1.2 to 15 mm. “Black” air ducts for ventilation tolerate high temperatures and exposure to open flames well (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. Ventilation systems made of simple carbon steel are mainly in demand in production areas where excessive release of gases, dust, etc. is possible.

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

To install air ducts into a single main, various shaped components are used, which are conventionally divided into standard (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 their metal counterparts. Among the advantages of plastic air ducts, it is necessary to highlight the small specific gravity, ease of installation (no need for special tools and devices), reasonable price. But plastic air ducts are not suitable for moving chemically aggressive gas-air mixtures.

There are rigid, semi-rigid and flexible plastic air ducts. Rigid air ducts can be round or rectangular, while flexible and semi-rigid air ducts have only a round 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. We will tell you in the next article what is the reason for this popularity and how not to get lost in the diversity of the presented assortment.

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 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 model range, but also improves the aerodynamic characteristics of the line.
• Durability 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 active corrosion. The aesthetic appeal allows them not to be painted.

The disadvantages of galvanized steel include:

• Increased noise level, typical of any metal structure. However this problem allows you to solve either a well-thought-out wiring diagram that minimizes the number of bends and transitions, or sound insulation.
• Tendency to form and accumulate condensation. The solution is to insulate the pipeline.
• Susceptibility to deformation as a result of powerful mechanical stress caused by a strong impact, displacement or fall of the structure. Under normal operating conditions, such difficulties do not arise.

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

Types of galvanized air ducts

The variety of galvanized air ducts is due to a number of technical characteristics, which are endowed with products during the production process. So they highlight the following types products:

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

Rectangular and round

	Round steel duct	Rectangular steel air 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.	High-quality sound insulation is required.
Care requirements	High air speed prevents dirt and dust particles from settling in the pipeline.	Requires periodic cleaning of the pipeline.
Calculation data	The cross-sectional shape makes it difficult to calculate data on the area of ​​the structure.	The rectangular configuration makes calculations easier.
Installation	The products are lighter and do not require reinforced fastenings. Time saving and low labor costs.	The weight of the structure requires the installation of reliable fasteners.
Price	Cheaper by an average of 30%. Minimum costs for transportation, storage, installation and thermal insulation.	Due to its high aesthetics, there are no costs for masking and decorating the highway.

The advantage of rectangular air ducts lies in the configuration and diversity 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

Straight seam ones are made by bending a sheet of galvanized steel into a round or rectangular pipe. This technology makes the product cheaper, but it also limits its length, which increases the number of pipeline connecting elements.

Spiral-wound (spiral-lock or spiral-welded) air ducts are twisted from a thin metal strip. In this case, the seam runs 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 joint elements;
• increased speed of movement of the air mass, because the spiral shape creates additional rotation in a closed loop;
• reduced noise level.

However, the ribbing of the 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 pipeline reduces the quality of air exchange and entails an unreasonable increase in the power of pumping equipment, an increase in energy costs, and also leads to the accumulation of condensate inside the pipes.

There are 3 classes of air duct tightness:

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.

According to the coefficient of internal pressure (density) there are:

• N-models (normal pressure). Designed for ventilation and smoke removal systems for objects classified as fire hazard classes “B” and “D”. They do not require strong sealing, because allow a certain percentage of leakage. Rubber seals are usually used as a sealant.
• P-models (dense). Installed at facilities equipped with powerful pumping equipment and belonging to the category of fire and explosion hazards. They are characterized by 100% tightness of seam joints and the presence of a hermetically sealed lock at the junction of elements with each other.

Which is better and where is it used?

The protective layer of zinc resists the destructive 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. air conditioning;
3. aspiration (removal of small particles contained in the air);
4. smoke removal (removal of combustion products);
5. exhaust gas removal;
6. transportation of gas mixtures, air purifiers and humidifiers.

Even the organization of a regular hood in the kitchen is most often done through steel air ducts.

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

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

Elements of the ventilation system

A ventilation duct 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. go around ledges;
3. connect several circuits into a single network.

Bends and boxes

The main elements of the air 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 install without the appropriate elements. Such components are usually called shaped products.

These include:

• Adapters connecting circuits of different diameters - confusers and diffusers. The former narrow the highway, the latter widen it.
• Tees and collar inserts that ensure the adjacency of two highways to each other.
• Crosses used to intersect two perpendicular air flows.
• S-shaped adapters (canards) connecting two contours that do not coincide in axis and/or cross-section.
• Round nipples and couplings connecting two round boxes. The first ones are inserted inside, the second ones are put on top of the pipes.
• Plugs installed at the ends of the circuit.
• A roof umbrella that prevents precipitation from entering the ventilation shaft.
• Supply and exhaust grilles and other fittings.

Dimensions

GOST

1. GOST 14918-80 - air ducts made from steel sheets with a thickness of 0.5 to 1 mm by rolling and intended for transporting air with a humidity of no 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.

Weights and Diameters Size Chart

Production of galvanized air ducts

Galvanized air ducts are manufactured on special metalworking 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). Metal cutting occurs in automatic mode according to the parameters specified by the program.

• Parts with a round cross-section are processed by rollers, which set the workpiece to the required diameter, followed by rolling the longitudinal edge on a folding machine.
• Spiral-wound ones are made using a different technology: steel 137 mm wide is twisted in a spiral with the seam inward.

The use of high-quality galvanization does not allow the galvanized coating to peel off from the metal in places where the product is bent.

Technological standards require the use of metal of a certain sheet thickness for each type of section:

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 per 1 m². On average, the market cost of 1 m² of product is about 320 rubles. Installation work will cost an average of 700 rubles. for the same square meter.

Despite the wide presence of air ducts in online stores, it is still worth buying them directly from the manufacturer, who can provide each product with a quality certificate.

How to choose?

The operation of the air exhaust system (AWS) depends on how correctly its cross-sectional area is calculated.

S - Sectional area.

P - SVO performance.

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

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

• By volume of air required:

P - SVO performance.

A - Number of people in the room during an hour.

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

• By frequency of ventilation (ventilation):

P - SVO performance.

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

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

Shape and diameter

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

1. The smaller the diameter of the air duct, the higher the speed of movement 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 ducts provide faster air movement, are easier to install and are cheaper.
3. Rectangular ones are stronger and fit harmoniously into the design of any room.

Construction and rigidity

Depending on the specific application of the design, 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 manufactured in a standard type and insulated.

1. The design of insulated models includes a special insulating layer made of mineral fiber, polyurethane, foam elastomer, felt or other materials. They maintain the optimal air temperature inside the circuit, preventing the formation and freezing of condensation on the walls. In addition, the noise level is reduced.
2. The zinc coating can be single-sided or double-sided. Due to the formation of condensation inside the circuit, double-sided galvanizing is more practical, because protects the circuit from internal corrosion process.

Not long ago, aluminum-zinc-coated air 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

Methods for fixing air ducts depend on the configuration:

• with a round cross-section, coupling, bandage and nipple connections of elements are used;
• rectangular air ducts are fastened using latches and mounting angles.

Sometimes welding is used.

Rules for installing galvanized ventilation

The laying of ventilation ducts from thin-sheet galvanized steel takes place in stages.

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KGBOU NPO "PU No. 102"

WRITTEN EXAMINATION PAPER

Subject: Technologicalprocessair duct manufacturing

Nazarovo 2014

Introduction

Equipment for manual arc welding

Consumables

Labor protection instructions for electric welders

Individual protection means

Bibliography

Introduction

Welding is one of the leading technological processes of metal processing. The great advantages of welding have ensured its widespread use in the national economy. Welding is used to produce ships, turbines, boilers, aircraft, bridges, reactors and other necessary structures.

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

A 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 being welded, which leads to the establishment of an atomic bond in the boundary layer.

Welding metallurgy differs from other metallurgical processes in the high temperatures of the thermal cycle and the short lifetime of the weld pool in the liquid state, i.e. in a state accessible for metallurgical processing of 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 that changes in its properties are specific.

All welding methods can be divided into two main groups:

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

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

The most widely used method is arc welding, in which the heat source is an electric arc.

When making your own thesis I used electric arc welding with a consumable electrode.

Equipment for manual arc welding

Manual arc welding station

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

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

I note that the welder’s movement is allowed within the length of the cable used for welding. Usually this is no 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 process 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 occurs as follows. An alternating current with a frequency of 50 Hz is supplied to the network 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. This stage is the most important in the operation of a welding inverter, allowing it to achieve enormous advantages compared to other types of welding machines. Next, using transformer 4, the high-frequency alternating voltage is reduced to no-load values ​​(50-60V), and the currents are increased to the values ​​necessary for welding (100-200A). High-frequency rectifier 5 rectifies alternating current, which performs its useful work in the welding arc. By influencing the parameters of the frequency converter, they regulate the mode and form external characteristics source.

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

Control system using feedback generates ideal output characteristics for any electric welding method. 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 mains input current (A)
Welding current range
Load period (%)
Open circuit voltage (V)
No-load losses (W)
Power factor (cos?)
Insulation class
Protection class

Welding wires

Welding wires are used to connect the electrode holder and the workpiece being welded to 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, 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 supplying current to the electrode holder must be highly flexible to facilitate 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 for connection to power sources with a welding circuit voltage of up to 127 V AC with a frequency of 50 Hz or 220 V DC and can be used for work at temperatures environment from - 50 to 4 - 50° C. High flexibility of PRGDO welding wires is achieved by twisting the wire core from conductors of small cross-section and due to a thin sheath made of high-quality rubber.

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

where In is the rated welding current. A; c is the resistivity 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.

Electrical losses in a conductor are equal to the thermal losses of the conductor to the environment. As the length of the welding wire increases, the voltage drop in the welding circuit increases. Therefore, it is necessary to limit its length as much as possible. In cases where the welder services 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 must be increased. To increase the length, connectors with an insulated sheath or sections of wires with lugs connected by bolts, followed by insulation, are often used. For ease of operation, a short section (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. Recommended permissible current values ​​in the welding wire at PR = 60% are given in table. 4. For a different operating duration, the permissible current can be recalculated using formulas that take into account the operating duration of power supplies.

Table Permissible current values ​​in welding wires

Welding wire cross-section, mm2	Permissible welding current, A

Electrode holder

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

Consumables

OMA-2 electrodes are intended 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 electrodes

The coating is acid-cellulose.

Deposition rate - 8.0 g/A* h.

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

Electrode consumption per 1 kg of deposited metal is 1.7 kg.

Preparing metal for welding

Tenderloin

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

Marking

represents the application of a workpiece configuration to metal. Marking is carried out with an allowance. Allowance is the difference between the size of the workpiece and the finished size of the part. The allowance is removed during subsequent processing. For marking, marking tables or plates of the required sizes are used. Marking is carried out using various tools: steel meter, steel tape measure, metal ruler, scriber, center punch, compass, caliper, thicknesser, square, etc. To obtain a clearer outline of the workpiece, the metal surface is first painted over with white adhesive paint. When there are a large number of blanks or parts, markings are made using flat templates with allowance for subsequent processing. The outline of the part is traced with a scriber, and then punched along the entire length of the outline line with a step of 50-100 mm between the cores.

cutting

is carried out manually with oxygen torches along the intended contour line of the part or with special-purpose gas-cutting machines. Cutting on mechanical machines is more productive and has high quality cutting For mechanical straight cutting of sheet metal, press shears for longitudinal and transverse cutting are used. Stamping of blanks is carried out in a cold or hot state. Cold stamping is used for thin 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 the edges after oxygen cutting.

For stripping

For small parts, stationary installations with sanding wheels are used. Portable pneumatic or electric sanders are used to clean large parts.

Edit

parts and workpieces are processed on sheet-straightening rollers or manually on a plate with possible bending during oxygen cutting or cutting with mechanical shears. Straightening of thin sheet metal is carried out in a cold state on sheet-leveling rollers or presses. Straightening of thick sheet metal is done in a hot state by hand on straightening plates.

Preparation of edges

parts made of 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 performed on edge bending presses or special machines. Immediately before welding, additional cleaning of parts is carried out using mechanical or chemical methods. The most progressive way to clean parts is etching in solutions of acids or alkalis.

Bending

parts and blanks are produced on metal bending rollers, as a rule, for the manufacture of various cylindrical containers. The part takes the shape of a cylinder and is called a shell. Bending of 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 work, where parts are assembled into knots and adjusted to their location.

Selecting the manual arc welding mode

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

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

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

Table 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 no more than 4 mm, and with an electrode diameter larger 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 no more than 5 mm, ceiling seams - no more than 4 mm, regardless of the thickness of the metal being welded. When choosing the diameter of the electrode for welding corner and T-joints, the leg of the weld is taken into account. The diameter of the electrode at the weld leg is 3...5-3...4 mm, at the weld leg 6...8-4...5 mm.

The amount of 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 St = (40...60)d,

where I St is 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: Ist = (20 + 6d)d;

· for electrodes with a diameter of less than 3 mm: Ist = 30d,

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

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

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

Q = b n I st,

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

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

If the welding current is insufficient, the arc is unstable and there may be lack of penetration in the weld.

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.

St 3 GOST 8509-93

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

2. I took a sheet of galvanized sheet measuring 400 x 600 mm, 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 by 90 0, thereby making a square pipe.

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

Labor protection instructions for electric welders

1. GENERAL PROVISIONS.

1.1. Personnel who are at least 18 years old, who have undergone special training, have a certificate for the right to work, including electrical safety group III, and who have no contraindications due to health conditions, are allowed to perform manual electric welding work.

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

1.3. All new hires must undergo induction training at the labor safety service. The results are recorded in the logbook for introductory training on labor protection. After this, the HR department completes the final registration of the newly admitted employee and sends him to the place of work.

1.4. Every new hire must undergo initial training on labor safety in the workplace. All employees undergo repeated training at least twice every 6 months. The briefing is carried out by the head of the department. The results of the briefing are recorded in a journal.

1.5. Daily permission to work is issued in a work order - permission for hot work.

1.6. Upon entry to work and periodically at least once every 12 months, electric welders must undergo a knowledge test on occupational safety issues according to a program approved by the management of the enterprise.

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

1.8. In the course of daily production activities, an electric welder may be exposed to harmful and dangerous production factors:

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

Increased gas and dust levels in the air in the work area;

Increased levels of ultraviolet, visible and infrared radiation;

Increased air temperature in the working area and molten metal.

1.9. While working, electric welders must observe the rules of personal hygiene and wearing special clothing, special shoes, and using other personal protective equipment.

1.10. Workwear and other personal protective equipment are issued in accordance with the Standard Industry Standards.

1.11. Electric welders must not allow deviations from technological standards when carrying out work, know and comply with the requirements of this labor protection instruction, as well as the manufacturer’s instructions for the operation of equipment, accessories, and tools used in the work process.

1.12. The victim or an eyewitness to the accident must immediately notify the work manager of every production-related accident. The work manager must organize first aid for the victim, transport him to medical institution, inform the owner and the labor protection service about this. To investigate an accident, it is necessary to preserve the situation at the workplace and the condition of the equipment as they were at the time of the incident, unless this threatens the life and health of others and does not lead to an accident.

1.13. Electric welders must know how to provide first aid, how to transport a victim, know the location and contents of the first aid kit, and be able to use the equipment in the first aid kit.

1.14. Persons who violate labor safety instructions are subject to disciplinary and financial liability and an extraordinary test of knowledge about labor protection.

2. Safety requirements before starting work.

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

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

2.3. Receive a task to perform the work from the manager and a work permit to carry out the work.

2.4. Inspect and prepare necessary funds personal protection (when performing ceiling welding - asbestos or canvas oversleeves; when working lying down - warm bedding; when performing work in wet areas- dielectric gloves, galoshes or mats; 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 off wet or slippery floors;

Prepare tools, equipment and technological equipment necessary for performing the work;

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

Position the welding wires so that they are not subject to mechanical damage and high temperature, and do not come into contact with moisture;

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

The work site, as well as downstream areas, must be freed from flammable materials within a radius of at least 5 m, and from explosive materials and installations - at least 10 m.

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

2.7. When carrying out welding work in enclosed spaces or on the territory operating enterprise check compliance with fire and explosion safety and ventilation requirements in the work area.

2.8. An electric welder should not start work if the following safety requirements are violated:

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 housing, secondary winding, welded part and switch casing;

Insufficient lighting of workplaces and approaches to them;

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

Lack of exhaust ventilation when working in enclosed spaces.

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

3. Safety requirements while performing work.

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

3.2. Electric welding work at height should be performed from scaffolding or scaffolding with guardrails. It is prohibited to carry out work from ladders.

3.3. Welding must be carried out using two wires, one of which is connected to the electrode holder, and the other (reverse) to the part being welded. It is prohibited to use metal structures of buildings, technological equipment, sanitary pipes (water supply, electrical wire, etc.) as the return wire of the grounding network.

3.4. Welding wires must be connected by hot soldering, welding or using couplings with an insulating sheath. Connections must be insulated. Connecting welding wires by twisting is not allowed. Welding wires should be laid so that they cannot be damaged by machines and mechanisms.

3.5. Before welding, the electric welder must make sure that the edges of the product being welded and the adjacent area (20-30 mm) are cleaned of rust, slag, etc. When cleaning, you must use safety glasses.

The parts to be welded must be securely fastened before welding begins. 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 an energized electrode holder at the workplace; the welding machine must be turned off and the electrode holder secured to 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. Repair of the welding machine must be carried out by special personnel.

3.9. An electric welder is prohibited from:

Connect the welding wires by twisting;

Touch live parts with your hands;

Repair electric welding equipment;

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

Work at a permanent workplace without local suction turned on;

Look at the electric arc without protective equipment (mask, glasses, shields);

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

Cut and weld metal by weight;

Carry out welding work in a room where there are flammable substances and gases;

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

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

Heat the electrode on a grounded table or other objects.

4. Safety requirements after completion of work.

4.1. Turn off the electric welding machine.

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

4.3. Make sure there are no fires, and if there are any, fill with water.

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

4.5. Take off overalls and personal protective equipment and put them in a designated place.

5. Safety requirements in emergency situations.

5.1. If a fire occurs, notify the fire department by calling 01, the work manager and begin extinguishing.

5.2. In case of malfunction of the welding unit, welding wires, electrode holders, protective shield or helmet-mask, you must stop work and report it to the foreman or work manager. Operation can only be resumed after all faults have been corrected by appropriate personnel.

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

5.4. Work carried out outdoors must be stopped when it begins to rain or snow. Work can be resumed only after the rain or snow has stopped or a canopy has been installed over the place where the electric welder is working.

5.5. If you feel pain in your eyes or get burns, stop working immediately, notify the work supervisor, and seek medical help at the emergency room.

Individual protection means

Personal protective equipment is used in cases where work safety 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, bib overalls, jackets, trousers, suits, short fur coats, sheepskin coats, aprons, vests, arm ruffles);

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 glasses);

hearing protection equipment (anti-noise helmets, headphones, ear buds);

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 must be issued in accordance with the Model Industry Standards for the free issuance of special clothing, special footwear and other personal protective equipment to workers and employees, approved by the Resolution 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 for welders suits, jackets and trousers with protective properties “Tr”, providing protection from sparks and molten metal. In winter, special clothing with protective properties “Tn” is used, which provides protection from exposure to cold air (“Tn 30” - up to a temperature of -30 ° C).

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

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

Personal respiratory protection equipment is used in exceptional cases when ventilation means cannot ensure the maximum permissible concentrations of dust and gases in the worker’s breathing zone.

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

If the maximum permissible concentration of dust and gases is exceeded when working in confined and hard-to-reach rooms (containers), welders are provided with breathing equipment with a forced supply of clean air. Devices of this type include hose gas masks PSh-2-57 and RMP-62 or breathing machines ASM.

The air entering the breathing apparatus from the compressor must not contain droplets 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 and gas welders and gas cutters” 2007. Edited by G.G. Chernyshov.

5. V.S.Vinogradov “Electric arc welding” 2007

6. O.N.Kulikov, E.I.Rolin “Labor safety during welding work” 2007.

7. V.N.Volchenko “Welding and welded materials” 1991

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INTRODUCTION

Welding, along with casting and pressure processing, is the oldest technological operation mastered by man in Bronze Age while gaining experience 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 welding, which provided a fairly high quality of connection for those times, especially when working with ductile metals such as copper. With the advent of bronze (harder and less easily forged), foundry welding arose. During foundry welding, the edges of the parts to be joined were molded with a special earthen mixture and filled with heated liquid metal. This filler metal was fused to 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 humans increased, and therefore the scope and scope of welding expanded. New types of weapons are being created, means of protecting a warrior in battle are being improved, chain mail, helmets, and armor are appearing. For example, when making chain mail, more than 10 thousand metal rings had to be forged welded together. New casting technologies are being developed, and knowledge related to the heat treatment of steel and giving it different hardness and strength is gradually being acquired. Often this knowledge was obtained by chance and could not explain the essence of the processes taking place.

For example, a manuscript found in the temple of Balgona in Asia describes the process we know as steel tempering: “Heat the dagger until it glows like the morning sun in the desert, then cool it to the color of royal purple, burying the blade into the body a muscular slave. The slave's strength, turning into a dagger, gives him hardness." Nevertheless, despite the rather primitive knowledge, even before our era, swords and sabers were made that had unique properties and were called Damascus. To give the weapon high strength and hardness and at the same time provide plasticity, which prevented the sword from being fragile and breaking from blows, it was made in layers. 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 were impossible to obtain without the use of welding. Subsequently, in the Middle Ages, this technology began to be used to make highly efficient, self-sharpening plows and other tools.

Forge and foundry welding remained the main method of joining metals for a long time. 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 18th century. machine production, the need to create metal structures, steam engines, and various mechanisms has increased sharply. Known welding methods in many cases no longer meet the requirements, since the lack of powerful heat sources did not allow large structures to be evenly heated to the temperatures required for welding. The main method of obtaining permanent connections at this time was riveting.

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

At the same time, gas welding developed, in which a flame formed by the combustion of a flammable gas (for example, acetylene) mixed with oxygen was used to melt metal. IN late XIX V. this welding method was considered even more promising than arc welding, since it did not require powerful energy sources, and the flame, while melting 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 rail track joints. When thermites (a mixture of aluminum or magnesium with iron oxide) burn, 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 joints being welded.

An important stage in the development of arc welding was the work of the Swedish scientist O. Kelberg, who in 1907 proposed applying a coating to the metal electrode, which, decomposing during the burning of the arc, provided good protection of the molten metal from air and alloying it with the elements necessary for high-quality welding. After this invention, welding began to find increasing use in various industries. Of particular importance at this time were the works of the Russian scientist V.P. Vologdin, who created the first welding department at the Vladivostok Polytechnic Institute. In 1921 at Far East The first welding shop for ship repair was opened; 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, and a generator for the Dnieper Hydroelectric Station was manufactured by welding, which was half the weight of a riveted one. 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 Kyiv 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 famous 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 connection, and significantly simplify the work of the welder, turning him into an operator in control of the welding installation. This work of the institute received the State Prize in 1941. Automatic submerged arc welding played a huge role during the Great Patriotic War, for the first time in the world it became 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. In conditions of shortage of qualified welders during the war, an 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 metal of very large thickness (more than 1 m). An example of the use of electroslag welding is the production at the Novokramotorsk Machine-Building Plant, commissioned by France, of a press that can create a force of 65,000 tons. The press has a height equal to the height of a 12-story building, and its weight is twice the weight of the Eiffel Tower.

In the 50s last century, industry mastered the method of arc welding in a carbon dioxide environment, which 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 by 7.5 times, the fleet of welding equipment - by 3.5 times, and the output of welding engineers - by five times. Welding began to be used for the manufacture of almost all metal structures, machines and structures, completely replacing riveting. For example, normal a car has more than 5 thousand welded joints. The pipeline that supplies gas from Siberia to Europe is also a welded structure with more than 5 thousand kilometers of welds. Not a single high-rise building, television tower or nuclear reactor is made 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 high-quality joining of the smallest parts in microelectronics with a diameter and thickness of 0.01-0.1 mm. Quality is ensured by the sharp focusing of the monochromatic laser beam and the most precise dosage of welding time, which can last 10-6 seconds. The mastery of laser welding made it possible to create a whole series of new element base, which in turn made it possible to produce 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 assets. The electron beam allows you 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 sea vessels, oil production platforms, and submarines. Modern nuclear Submarine, having about 200 m and the height of a 12-story building, is a fully welded structure made of high-strength steels and titanium alloys.

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

Using welding, multi-ton BelAZ and MAZ vehicles, 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 operates under particularly difficult conditions. Subjected to direct influence of dynamic and vibration loads.

The fan housing consists of

Pos 1 Housing 1 piece

V =π*D*S*H = 3.14*60.5*0.8 = 151.98 cubic cm.

Q = ρ * V = 7.85 * 151.98 = 1193.01 g. = 1.19 kg

Pos 2 Flange 2 pcs.

fan welding deformation arc

V = π*(D out 2 - D inside 2)*s =3.14*(64.5 2 -60.5 2)*1 =1570 cubic meters cm

Q = ρ * V = 7.85 * 1570 = 12324.5 g. = 12.33 kg.

Pos 3 Ear 2 pcs

V = h + l + s =10*10*0.5 = 50 cubic meters. cm

Q = ρ * V = 7.85 * 50 = 392.5 g = 0.39 kg

Weld cross-sectional area

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

2 Justification of the material of the welded structure

Chemical composition of steel

Equivalent carbon content

Se = Cx + Cr

Cx - 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

Ср = 0.005 * S * Сх = 0.005 * 8 * 0.38 = 0.125

Preheat temperature

T p = 350 * = 350 * 0.25 = 126.2 degrees.

1.3 Specifications for the production of welded structures

The fan housing operates under particularly difficult conditions. Subjected to direct influence of dynamic and vibration loads.

4 Determination of 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 mass production, the type of production is characterized by the use of specialized assembly and welding fixtures; welding of units is carried out using 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 to 162 degrees and subsequent heat treatment are required.

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

1.6 Determination of welding modes

sv= h*100 / Kp

where: h - penetration depth

Kp - proportionality coefficient

c in =0.6*10*100/1.55 ​​= 387 A

Arc voltage

20 + 50* Isv* 10⁻³ / d⁰² V

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

Welding speed

V St = K n * I St / (ρ*F*100) m/hour =

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

where Kn is the deposition coefficient g/A*hour

ρ - metal density, accepted for carbon and low-alloy steels as 7.85 g/cm3;

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

7 Selection of welding materials

Steel 16G2AF can be welded using any types of welding using various types welding materials. Therefore, we use SV 08 G 2 S wire for welding. SV 08 G 2 S wire has good weldability, low emission of welding aerosols, and low price.

7.1 Consumption of welding materials

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

G e. pr. = 1.1 * M kg

M is the mass of deposited metal,

M = F * ρ * L*10 -3 kg

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

Electrode wire consumption

G e. pr. = 1.1 * M = 1.1 * 1.16 = 1.28 kg

Carbon dioxide consumption

G co2 = 1.5*G e. pr. = 1.5*1.28 = 1.92 kg

Electricity consumption

W = a* G e. pr. = 8*1.28 = 10.24 kW/hour

a = 5…8 kW * h/kg - specific electricity consumption per 1 kg of deposited metal

8 Selection of welding equipment, technological equipment, tools

MAGSTER WELDING SYSTEM

· Professional welding system with a remote 4-roller feed mechanism of famous Lincoln Electric quality at the price of the best Russian analogues.

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

· Successfully used for welding structural low-carbon and stainless steels, as well as for welding aluminum and its alloys.

· Step-by-step adjustment of welding voltage.

· Smooth adjustment of wire feed.

· Gas pre-purging.

· Thermal overload protection.

· Digital voltage indicator.

· High reliability and ease of operation.

· Synergetic welding process system - after loading the type of wire and diameter, the correspondence between the feed speed and voltage is automatically established using a microprocessor (for mod. 400,500).

· Multi-functional liquid crystal display - displaying 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 use).

· Supplied in ready-to-use kits and include: power source, feed mechanism with transport trolley, connecting cables 5 m, network cable 5 m, welding torch "MAGNUM" 4.5 m long, workpiece clamp.

· AGSTER 400 plus MAGSTER 500 w plus MAGSTER 501 w Maximum power consumption, network 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 FEEDING MECHANISM

· 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 burner. 20 kg. 20 kg. 20 kg.

9 Determination of technical standards for assembly and welding time

Calculation of technical standards for assembly and welding time of a unit.

		Parameter	Standard time min	Time min	Source
	Clean weld areas from oil, rust and other contaminants.		0.3 per 1 m of seam
	Install child position 2 into the device.	Child weight 12.33 kg
	Set child pos. 1 per child position 2
	Grab child pos. 1 to child pos. 3 to 3 potholders		0.09 1 catch
	Set child pos. 2 per child position 1	Child weight 12.33
	Grab child pos. 2 to child pos. 1 to 3 potholders		0.09 1 catch
	Install 2 children pos. 3 per child position 1	Child weight 0.39
	Grab 2 children pos. 3 to children pos. 1 to 4 potholders		0.09 1 catch
	Remove the assembly unit and place it on the welder’s table	Weight Sat. units 32.07 kg
		L seam = 1.9 m	1.72 min/m seam
	Weld the edges of part 1 to each other	L seam = 0.32 m	1.72 min/m seam
	Weld part 2 to part 1	L seam = 1.9 m	1.72 min/m seam
	Clean the weld from spatter.	Lzach = 4.12 m	0.4 min/m seam
	Control by worker, foreman
	Remove the assembly unit

Table 1

table 2

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

Assembly type	Weight of the part, assembly unit
fixer

Table 3

Time to tack

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

Time required to remove assembly units from the fixture and place them at the storage location

Basic time for welding 1 m seam

F - cross-sectional area of ​​the weld

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

a - deposition coefficient

a = 17.1 g/a* hour

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

10 Calculation of the amount of equipment and its load

Estimated amount of equipment

C p = = = 0.09

T gi - annual labor intensity of the operation, n-hour;

T gi = = = 308.4 n-hour

F d o - annual actual equipment operating fund

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

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

n - number of work shifts per day;

Kp - coefficient taking into account the time the equipment is under repair (Kp = 0.92-0.96).

Load factor

K z = = = 0.09

Ср - estimated amount of equipment;

Spr - accepted quantity of equipment Spr = 1

11 Calculation of the number of employees

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

Ch o.r. = = = 0.19

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

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

Kv - coefficient of fulfillment of production standards (Kv = 1.1-1.15)

Annual actual working time fund for one worker

F d r = (8*D p + 7*D s) * K nev = (8*246 + 7*7) * 0.88 = 1774.96 hours

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

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

12 Methods to combat welding deformations

The entire range of measures to combat deformations and stresses can be divided into three groups:

Activities that are implemented before welding;

Activities during the welding process;

Activities carried out after welding.

Measures to combat deformations applied before welding are implemented at the design stage of a welded structure and include the following activities.

Welding of a structure must have a minimum volume of deposited metal. Legs should not exceed the calculated values, butt seams should, if possible, be made without cutting edges, the number and length of seams should be the minimum permissible.

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 located as symmetrically as possible on the welded structure; it is not recommended to place the seams close to each other, to have a large number of intersecting seams, without the need to use asymmetrical cutting of edges. In structures with thin-walled elements, it is advisable to place seams on or near rigid elements.

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

Measures used during the welding process

Rational sequence of welding seams, 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 rigidity of the fasteners should be specified taking into account the metal being welded.

Preliminary deformation of welded parts.

Crimping or rolling of the weld, which is carried out immediately after welding. In this case, the zone of plastic shortening deformations undergoes plastic settlement along the thickness.

1.13 Selection of quality control methods

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

.) Control of preparation of parts for welding

It provides control over the processing of the front and back surfaces, as well as the end edges of the parts being welded.

The surfaces of the welded edges must be cleaned of 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 T-joints, the perpendicularity of the parts to be welded is controlled. When checking the quality of tacks, you should pay attention to the condition of the surface and the height of the tacks.

.) Monitoring the welding process includes visual observation of the process of metal melting and weld formation, monitoring the stability of mode parameters and equipment performance.

.) Inspection of welded joints. After welding, welded joints are usually inspected visually. The weld seam and the heat-affected zone are inspected. Usually inspection is carried out with the naked eye. When identifying surface defects smaller than 0.1 mm, optical devices are used, for example, a 4-7x magnification magnifying glass.

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 precautions, fire prevention and environmental protection

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 loss of ability to work, and in unfavorable circumstances - even to more severe consequences.

Electric current is dangerous for humans, and alternating current is more dangerous than direct current. Degree of danger of injury electric shock depends mainly on the conditions of inclusion of 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). The minimum calculated resistance of the human body is taken to be 1000 Ohms. There are two types of electric shock: electric shock and injury. An electric shock affects the nervous system and 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 tissue and blood vessels.

The light radiation of the arc, affecting 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 severe diseases (electroophthalmia, cataracts). The harmful effects of welding arc rays on the organs of vision affect the eyes at a distance of up to 10 m from the welding site.

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

Explosion hazard is caused by the use of oxygen, shielding gases, flammable gases and liquids during welding and cutting, the use of gas generators, cylinders with compressed gases, etc. Chemical compounds of acetylene with copper, silver and mercury are explosive. The danger is posed by backlash 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 required to prevent explosions.

Heat burns, bruises and wounds 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 due to the use of shields, masks and glasses with light-protective glasses.

Adverse meteorological conditions affect welders (cutters) - builders and installers for more than half of the year, since they have to work mainly outdoors.

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 flammable substances, wood, paper, fabrics and other flammable materials ignite at 250-400 ° C.

2. ELECTRICAL SAFETY MEASURES

It is necessary to reliably ground the housing of the welding machine or installation, the clamps of the secondary circuit of welding transformers that serve to connect the return wire, as well as the products and structures being welded.

2. It is prohibited to use ground loops, sanitary pipes, 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 the return wire of the welding circuit and only in cases where they are welded.)

4. Welding leads must be protected from damage. When laying welding wires and each time they move, do not damage the insulation; contact of wires with water, oil, steel ropes, hoses and pipelines with flammable gases and oxygen, with hot pipelines.

Flexible electrical wires for controlling the welding installation circuit, if they are of significant length, must be placed in rubber sleeves or in special flexible multi-link structures.

6. Only electrical personnel have the right to repair welding equipment. It is prohibited to repair welding equipment that is energized.

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

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

electric welding installations must be equipped with a device for automatically turning off the no-load voltage or limiting it to a voltage of 12V within no more than 0.5 s after stopping welding;

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

Welders should not be allowed to perform arc welding or cutting while wearing wet gloves, shoes or overalls.

9. Cabinets, consoles and frames of resistance welding machines, inside of which equipment with open live parts that are energized are located, must have a lock that ensures voltage relief when they are opened. Pedal start buttons of contact machines must be grounded and the reliability of the upper guard, which prevents inadvertent switching on, must be monitored.

10. In case of electric shock, you must:

urgently turn off the current using the nearest switch or separate the victim from live parts using dry materials at hand (pole, board, etc.) and then place him on a mat;

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

if the victim is unconscious and has no breathing, release him from constricting clothing, open his mouth, take measures against the tongue sticking and immediately begin artificial respiration, continuing it until a doctor arrives or normal breathing is restored.

3. PROTECTION AGAINST LIGHT RADIATION

To protect the welder’s eyes and face from the light radiation of the electric arc, masks or shields are used, into the viewing holes of which protective glass filters are inserted, absorbing ultraviolet rays and a significant part of light and infrared rays. Protect the light filter from the outside from splashes, drops of molten metal and other contaminants using the usual clear glass, installed in the viewing hole in front of the 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 an environment of protective inert gases (especially welding aluminum in argon), it is necessary to use a darker filter than when welding with an open arc at the same amperage.

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

2. To protect surrounding workers from the light radiation of the welding arc, portable shields or screens made of fireproof materials are used (in case of a non-permanent welder’s workplace and large products). In stationary conditions and with relatively small sizes of the 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 diffused reflection of light, and also to ensure good illumination of surrounding objects.

If your eyes are damaged by arc light radiation, you should immediately consult a doctor. If it is impossible to obtain a quick medical care Make eye lotions with a weak solution of baking soda or tea leaves.

Protection from harmful gas emissions and aerosols

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 in permanent places in shops or workshops (in cabins), it is necessary to use local ventilation with fixed side and bottom suction (welder's table). When welding and cutting products at fixed places in workshops or workshops, it is necessary to use local ventilation with an intake funnel attached to a flexible hose.

Ventilation should be performed by supply and exhaust with fresh air supplied to the welding areas and heated in cold weather.

When working in closed and semi-enclosed spaces (reservoirs, 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 welding (cutting) site or provide general ventilation. If it is impossible to carry out local or general ventilation, clean air is forced into the worker’s breathing zone in an amount of (1.7-2.2) 10-3 m3 per 1 s, using a specially designed mask or helmet for this purpose.

LITERATURE

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

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

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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