Description of the technological process of making galvanized air ducts. How to choose galvanized steel air ducts: dimensions, diameters, GOSTs and installation rules. Documents required to organize a business

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KGBOU NPO "PU No. 102"

WRITTEN EXAMINATION WORK

Topic: Technologicalprocessair duct manufacturing

nazarovo 2014

Introduction

Manual arc welding equipment

Consumable material

Labor protection instruction for electric welder

Individual protection means

Bibliography

Introduction

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

Welding is the technological process of obtaining permanent joints by establishing interatomic bonds between the parts to be welded during their local or general heating, or plastic deformation, or by the joint 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 high temperatures of the thermal cycle and a 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 metal of the heat-affected zone that have changed in its properties are specific.

All welding methods can be divided into two main groups:

1. Pressure welding - contact, gas-pressing - 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 an electric arc serves as a source of heat.

In the preparation of my thesis, I used consumable-electrode electric arc welding.

Manual arc welding equipment

Station 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. A welding machine is required, which includes a power source, starting equipment, wires for welding, electrode holders. In addition, the welder's workplace itself must be properly equipped. 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 fed to the welder's workplace. The welder, performing work, moves from seam to seam, while all the equipment is in one place.

Note that it is allowed for the welder to move within the length of the cable used for welding. Usually it 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 to alternating current. The figure below shows a simplified diagram of an inverter type welding machine. welding process metal

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

The work of the welding inverter is as follows. An 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 most important in the operation of a welding inverter, which makes it possible to achieve enormous advantages over other types of welding machines. Further, with the help of transformer 4, the high-frequency alternating voltage is reduced to no-load values \u200b\u200b(50-60V), and the currents increase to the values \u200b\u200brequired for welding (100-200A). The high-frequency rectifier 5 rectifies the alternating current, which performs its useful work in the welding arc. Influencing the parameters of the frequency converter, they regulate the mode and form the external characteristics of the 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 transistor IGBT modules, which are the most expensive elements of a welding inverter.

The feedback control system generates ideal output characteristics for any electric welding process. Due to the high frequency, the weight and dimensions of the transformer are significantly reduced.

Specifications:

Supply voltage (V)
Power supply 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 to the power source. Used wires with copper or aluminum conductors, the cross-section of which corresponds to the rated welding current. The welding leads are provided with a rubber insulating layer and, in most cases, with a rubber protective sheath.

Figure: 1 Section of welding wires: a - PRGD type, b - APRGDO type, c - PRGDO type (with 4 auxiliary wires)

The welding lead supplying current to the electrode holder must be highly flexible to facilitate handling 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 with a frequency of 50 Hz or 220 V DC and can be used for operation at an ambient temperature of - 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 by means of a thin sheath made of high-quality rubber.

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

where Inom is the rated welding current. AND; c - the specific resistance of the conductor, equal for copper to 0.0175 Ohm · mm21m, for aluminum - 0.0283 Ohm · mm21m; l - conductor length, m; F is the cross-sectional area of \u200b\u200bthe conductor, mm2; Q - electrical losses, W.

The electrical losses in the conductor are equal to the heat 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 serves a large section of the production area and, therefore, needs a long wire, for economic reasons, the cross-section of the welding wire must be increased in this case. To extend the length, connectors with an insulated sheath or sections of wires with lugs connected by bolts are often used, followed by insulation. For the 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). 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 \u200b\u200bin the welding wire at PR \u003d 60% are given in table. 4. With a different duration of operation, the permissible current can be recalculated using formulas that take into account the duration of the power supplies.

Table Permissible current values \u200b\u200bin welding leads

Section of the welding wire, mm2	Allowable welding current, A

Holder for electrodes

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

Consumable material

OMA-2 electrodes are designed for welding structures made of thin-sheet (1-3 mm thick) carbon steels with ultimate strength up to 410 MPa.

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

Characteristics of electrodes

Coating - acid-cellulose.

The deposition rate is 8.0 g / A * h.

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

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

Preparation of metal for welding

Tenderloin

blanks made from heavy and bulky pieces of sheet and profile rolled 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 in shot blasting machines. The straightening of rolled products, as a rule, is carried out in a cold state on straightening machines or manually on straightening plates. Cutting out of workpieces is carried out in most cases on cutting machines at stops. The most common method for cutting mild steels is flame (oxy-fuel) cutting. The production of parts after preliminary processing is carried out by a number of sequential technological operations: marking, cutting, stamping, cleaning, straightening, preparation of edges, flanging and bending of parts.

Markup

is the deposition of a workpiece configuration on the metal. The marking is carried out with an allowance. The allowance is the difference between the stock size and the finished size of the part. The allowance is removed during subsequent processing. For marking, marking tables or plates of the required dimensions are used. The marking is carried out using various tools: a steel meter, a steel tape measure, a metal ruler, a scribe, a center punch, a compass, a vernier caliper, a thickness gauge, a square, etc. To obtain a clearer outline of the workpiece, the metal surface is pre-painted with white glue paint. With a large number of blanks or parts, the marking is carried out using flat templates with an allowance for subsequent processing. The contour of the part is drawn with a scraper, and then it is punched along the entire length of the bypass line with a step of 50-100 mm between the cores.

Cutting

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

For stripping

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

Edit

parts and blanks are carried out on sheet-straightening rollers or manually on a plate with their possible bending during oxygen cutting or cutting on mechanical shears. The straightening of sheet metal is carried out in a cold state on sheet-straightening rollers or presses. The sheet metal is straightened hot by hand on straightening plates.

Edge preparation

parts made of low-carbon steel of large thickness are carried out by oxy-fuel cutting or processing on planing or milling machines. Flanging is used for thin sheet metal parts for subsequent butt joint. 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 acid or alkali solutions.

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 carry out the preparation of metal for welding using industrial equipment, for example, in the conditions of construction and installation work, where the parts are collected in bridles and adjusted in place.

Selecting MMA Mode

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

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

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

Table The size of the electrode diameter depending on the thickness of the welded metal

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 larger than this, the root of the seam may not be fusion-fired.

The diameter of the electrode when welding vertical seams is no more than 5 mm, overhead - no more than 4 mm, regardless of the thickness of the welded metal. When choosing the diameter of the electrode for welding fillet and T-joints, the leg of the seam is taken into account. The diameter of the electrode with the leg of the seam is 3 ... 5-3 ... 4 mm, with 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 sv - 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: Iw \u003d (20 + 6d) d;

For electrodes with a diameter of less than 3 mm: I sv \u003d 30d,

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

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

The amount of deposited metal 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 - surfacing coefficient, g / (A * h); I sv - welding current, A; g - welding time, h.

But with 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\u003d 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, 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 on. He took the other 4 cut parts and attached them also on the welder's table with the sides cut off at 45 0 as in Figure 1.2. Welded on.

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

3. He 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. He took the second welded structure from point 1 and attached it to the other end of the square pipe from point 2. Thus, the “air duct” structure was assembled and welded "

Labor protection instruction for electric welder

1. GENERAL PROVISIONS.

1.1. Electric welding manual work is allowed for personnel at least 18 years old, who have undergone special training, have a certificate for the right to work, including for the III group of electrical safety, and have no 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 newcomers to work must undergo induction training at the labor protection service. The results are recorded in the register of introductory briefing on labor protection. After that, the personnel department makes the final registration of the newly admitted employee and directs him to the place of work.

1.4. Every newly recruited person must undergo an initial briefing on labor protection at the workplace. All employees are re-instructed 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 the journal.

1.5. Daily admission to work is issued by an order - admission to hot work.

1.6. Upon admission to work and periodically at least once every 12 months, electric welders must pass a knowledge test on occupational safety issues according to the 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, harmful and hazardous production factors can act on an electric welder:

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

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

Increased levels of ultraviolet, visible and infrared radiation;

Increased 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 the wearing of special clothing, special shoes, and the use of other personal protective equipment.

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

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

1.12. The victim or eyewitness of the accident is obliged to immediately notify the supervisor of any industrial-related accident. The work manager must organize the first first aid to the victim, his delivery to the medical institution, inform the owner and the labor protection service about this. In order to investigate an accident, it is necessary to maintain the working environment and the condition of the equipment as they were at the time of the accident, if this does not threaten the life and health of others and does not lead to an accident.

1.13. Electric welders should know how to provide first aid, how to transport 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 brought to disciplinary, 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 cuffs of the suit sleeves. In this case, the jacket should not be tucked into the trousers, and the trousers should be released over the boots (felt boots).

2.2. Show the work supervisor a certificate of verification of knowledge of safe work methods.

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

2.4. Inspect and prepare the necessary personal protective equipment (when performing overhead welding - asbestos or tarpaulin oversleeves; when lying down - warm mats; when working in wet rooms - dielectric gloves, galoshes or rugs; when welding or cutting non-ferrous metals and alloys - a 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 passages;

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

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

Make sure that the welding equipment is in good working order, and that the grounding of the welding unit is in good condition

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

Make sure that no fire and explosive substances and flammable materials are stored near the workplace.

The place of work, as well as the places below, must be free 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 in closed rooms or on the territory of an operating enterprise, check the fulfillment of fire and explosion safety and ventilation requirements in the work area.

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

Absence or malfunction of a 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 illumination of workplaces and approaches to them;

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

Lack of exhaust ventilation when working in closed rooms.

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

3. Safety requirements during the performance of work.

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

3.2. Electric welding work at height must be carried out from scaffolding or fenced scaffolding. It is forbidden to carry out 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 part to be welded. It is forbidden to use metal structures of buildings, technological equipment, pipes of sanitary-technical networks (water supply, electricity, 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. The joints must be insulated. The connection of welding wires by twisting is not allowed. Welding wires should be laid so that they cannot damage machines and mechanisms.

3.5. Before welding, the electric welder must make sure that the edges of the work piece to be welded and the area adjacent to them (20-30 mm) are free of rust, slag, etc. Wear protective goggles when cleaning.

The parts to be welded must be securely fastened before welding. When cutting structural elements, the electric welder must 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. Connecting and disconnecting 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 electric welder is prohibited from:

Twist welding wires together;

Touching live parts with your hands;

Carry out repair of electric welding equipment;

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

Work at a permanent workplace without the included local suction;

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

To carry out electric welding works in the open air without a canopy during rain and snowfall;

Cut and weld metal by weight;

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

To carry out welding work on vessels, pipelines and apparatus under pressure;

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

Heat the electrode on a grounded table or other object.

4. Safety requirements at the end of work.

4.1. Switch off the electric welding machine.

4.2. Tidy up the workplace, assemble the tool, wind up the welding wires in coils and remove them from the places designated for their storage.

4.3. Make sure that there are no sources of ignition, if any, fill with water.

4.4. All violations of safety requirements that have taken place in the course of the work are reported to the foreman or the work supervisor.

4.5. Take off 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 work supervisor 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 the work supervisor about it. Work can be resumed only after all malfunctions have been eliminated 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 ventilated.

5.4. Open-air work should be stopped when it starts to rain or snow. Work can be resumed only after the rain or snow has stopped or a shed is installed over the place of work of the electric welder.

5.5. If you feel pain in the eyes, get burns, immediately stop work, notify the work manager, and seek medical help from the trauma center.

Individual protection means

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

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, short fur coats, sheepskin coats, aprons, vests, oversleeves);

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

head protection equipment (helmets, comforters, hats, berets);

respiratory protection equipment (gas masks, respirators);

face protection equipment (face shields and masks);

eye protection (goggles);

hearing protection (anti-noise helmets, headphones, earbuds);

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

hand protection (mittens, gloves);

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

Personal protective equipment must be issued in accordance with the Standard Industry Norms of Free Distribution of Special Clothing, Special Shoes and Other Personal Protective Equipment to Workers and Employees, approved by the Resolution of the Ministry of Labor and Social Development of the Russian Federation No. 63 dated December 16, 1997.

Special protective clothing in accordance with GOST 12.4.011-89 provides for welders suits, jackets and trousers with protective "Tr" properties, providing protection against sparks and molten metal. In winter, special clothing with protective properties "Тн" is used, which provides protection against the effects of cold air ("Тn 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", which have external metal socks and are designed to protect the feet from heat radiation, contact with heated surfaces, from scale, sparks and splashes of molten metal. In winter, felt boots are provided.

In areas (designated by the administration) where there is a risk of head injury, welders must wear protective 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 the mandatory protection of the head with a helmet, guarding devices (awnings, blank decks, etc.) must be provided to protect workers from falling metal splashes, cinders, etc.

Personal respiratory protection equipment is used in exceptional cases when it is impossible to ensure maximum permissible concentration of dust and gases in the breathing zone of the worker 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 permissible, and the concentration of dust is higher than the permissible, then the welders must be provided with anti-dust respirators.

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

The air entering the breathing apparatus from the compressor must be free of water droplets, oil, dust, hydrocarbon vapors and carbon monoxide.

Bibliography

1. GG Chernyshov "Welding business" 2004.

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

3. VM Rybakov "Arc and Gas Welding" 1996.

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

5. VS Vinogradov "Electric arc welding" 2007.

6. ON Kulikov, EI Rolin "Labor protection in the production of welding" 2007.

7. VN Volchenko "Welding and materials to be welded" 1991.

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Technologies for the production of rectangular air ducts

Air ducts of rectangular and square cross-section are often used for arranging ventilation systems and can be manufactured using either welding or soldering, or using a mechanical lock. The very technology for the production of rectangular air ducts is quite simple and consists of several stages:

First, a sheet of metal is cut according to the scan of the finished product;
Then the finished workpiece is bent on a plate bending machine until it is given the required shape;
Sealing of joints is carried out either using the folding lock technology, welding or soldering.

It should be noted that a mechanical lock is faster to manufacture and the manufacturing technology of such a joint is less laborious, its use leads to a slightly higher metal consumption. In addition, the joints of the air duct turn out to be leaky and can worsen the performance of the ventilation system with a significant length. However, with a small thickness of a metal sheet, and therefore a low cost of an air duct, such a lock can be considered optimal for the manufacture of air ducts for ventilation hoses of small and medium length.

With a small thickness of the sheet from which the air duct is made, soldering can be used to achieve complete tightness of the structure. If the metal thickness is from 1.5 mm or more, a welded joint of the seam can be used.

Circular air ducts can be manufactured in two ways:

By bending on rolling machines with subsequent seam welding or using a folded lock;
According to the technology of winding on a winding machine from a metal tape.

The rolling technology has almost the same features as the manufacture of rectangular air ducts. As for winding air ducts, the manufacturing process is simpler and does not require subsequent sealing. In addition, winding air ducts can be made of non-standard lengths, which allows you to optimize costs in the manufacture of non-standard ventilation systems.

INTRODUCTION

Welding, along with casting and forming, is the oldest technological operation mastered by man in the Bronze Age during his experience in working with metals. Its appearance is associated with the need to combine various parts in the manufacture of tools, military weapons, jewelry and other products.

The first welding method was forging, which provided a sufficiently high quality of the joint for those times, especially when working with ductile metals such as copper. With the advent of bronze (harder and worse forging), casting welding arose. During casting 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 fused with the parts and solidified to form a seam. Such compounds were found on bronze vessels that have survived from the times of Ancient Greece and Ancient Rome.

With the advent of iron, the nomenclature of metal products used by man has increased, therefore, the scope and scope of welding has expanded. New types of weapons are being created, the means of protecting a warrior in battle are being improved, chain mail, helmets, and armor appear. For example, in the manufacture of chain mail, more than 10 thousand metal rings had to be joined by forge welding. New casting technologies are developing, knowledge is gradually being acquired related to 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 processes taking place.

For example, in a manuscript found in the Temple of Balgon in Asia, the process known to us as steel hardening is described: “Heat the dagger until it shines like the morning sun in the desert, then cool it down to the color of royal purple, sticking the blade into the body a muscular slave. The strength of a slave, turning into a dagger, gives him firmness. " Nevertheless, despite the rather primitive knowledge, even before our era, swords and sabers were made that had unique properties and were called Damascus. In order to give the weapon high strength and hardness and at the same time provide plasticity, which did not allow the sword to be fragile and break from impacts, 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 connected by welding. The result was a weapon with new properties that cannot be obtained without welding. Subsequently, in the Middle Ages, this technology was applied to 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 with 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. The known welding methods in many cases ceased to meet the requirements, since the absence of powerful heat sources did not allow uniformly heating large structures to the temperatures required for welding. Riveting became the main method of obtaining permanent joints at this time.

The situation began to change at the beginning of the 20th century. after the creation of the Italian physicist A. Volta sources of electrical energy. In 1802 the Russian scientist V.V. Petrov discovered the phenomenon of an electric arc and proved the possibility of its use for melting 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 to another part. He named this method of joining metals "electrohephaestus" after the ancient Greek god-blacksmith. It has become 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. She immediately found application in the most complex industry at that time - steam locomotive construction. The 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 to use slag, which protected the weld from air, making it more dense and durable.

At the same time, gas welding was developing, in which the flame formed during the combustion of a combustible gas (for example, acetylene) mixed with oxygen was used to melt the metal. At the end of the XIX century. 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 obtain a sufficiently good quality of welded joints. Around the same time, thermite welding began to be used to join the joints of rail tracks. When termites (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 termite 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 to apply a coating on a metal electrode, which, decomposing during arc burning, provided good protection of the molten metal from air and its alloying with 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 Polytechnic Institute in Vladivostok. In 1921, the first welding shop for ship repair 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 being created, a generator for Dneproges was made by welding, which was two times lighter than a riveted one. In 1926 the first All-Union welding conference was held. In 1928 in the USSR, there were 1200 units for arc welding.

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 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 of the 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, to improve the quality of the joint, to significantly simplify the work of the welder, turning him into an operator to control the welding installation. This work of the institute was awarded 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 the conditions of a shortage of qualified welders during the war, an increase in welding productivity due to automation made it possible to significantly increase the production of tanks for the front in a short time.

A significant achievement of welding science and technology was the development in 1949 of a fundamentally new method of fusion welding, which was called electroslag. Electroslag welding plays a huge role in the development of heavy engineering, as it allows welding of very thick metal (more than 1 m). An example of the use of electroslag welding is the manufacture of a press at the Novokramotorsk Machine-Building Plant by order of France, which can create an effort 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, the industry has mastered the method of arc welding in an environment of carbon dioxide, which has recently become the most common welding method and is used in almost all machine-building enterprises.

Welding is actively developing in the following years. From 1965 to 1985, the volume of production of welded structures in the USSR increased 7.5 times, the fleet 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, an ordinary passenger car has more than 5 thousand welded joints. The pipeline through which gas is supplied from Siberia to Europe is also a welded structure with more than 5,000 kilometers of welded seams. No 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. Quality is ensured due to the sharp focusing of the monochromatic laser beam and the most accurate dosage of welding time, which can last 10-6 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 irreplaceable technological process in the manufacture of supersonic aircraft and aerospace vehicles. The electron beam allows welding 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 ships, platforms for oil production, and submarines. The modern nuclear submarine, which is about 200 m high and a 12-storey building, is a fully welded structure made of high-strength steels and titanium alloys.

Without welding, the current achievements in space would not have been possible. For example, the final assembly of the missile system is carried out in a welded assembly workshop weighing about 60 thousand and 160 meters high. The missile containment system consists of welded towers and masts with a total weight of about 5 thousand tons. All critical structures at the launch site are also welded. Some of them have to work in very difficult conditions. The impact of a powerful flame at the start of the rocket is taken over by a welded flame divider weighing 650 tons, 12 m high. Complex welded structures are tanks for storing fuel, a system for feeding it to the tanks and the fuel tanks themselves. They have to withstand enormous hypothermia. For example, a liquid oxygen tank has a capacity of over 300,000 liters. It is manufactured with a double wall - stainless steel and mild steel. The diameter of the outer sphere is 22 m. The tanks for liquid hydrogen are designed in a similar way. The liquid hydrogen supply line is welded from a nickel alloy, it is inside another aluminum alloy line. The kerosene and superactive fuel lines are welded from stainless steel, and the oxygen line is from aluminum.

By welding, multi-ton BelAZ and MAZ trucks, tractors, trolleybuses, elevators, cranes, scrapers, refrigerators, televisions and other industrial and consumer goods are manufactured.

1. TECHNOLOGICAL SECTION

1 Description of the welded structure and its purpose

The fan casing works in particularly harsh conditions. It is directly exposed to dynamic and vibration loads.

The fan casing consists of

Pos 1 Body 1 piece

V \u003d π * D * S * H \u200b\u200b\u003d 3.14 * 60.5 * 0.8 \u003d 151.98 cc.

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

Pos 2 Flange 2 pcs.

fan welding deformation arc

V \u003d π * (D bed 2. - D inside 2) * s \u003d 3.14 * (64.5 2 -60.5 2) * 1 \u003d 1570 cc. cm

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

Pos 3 Ear 2 pcs

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

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

Cross-sectional area of \u200b\u200bthe weld

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

2 Justification of the material of the welded structure

Chemical composition of steel

Equivalent carbon content

Se \u003d Cx + Cp

Cx - chemical equivalent of carbon

Cx \u003d C + Mn / 9 + Cr / 9 + Mo / 12 \u003d 0.16 + 1.6 / 9 + 0.4 / 9 \u003d 0.38

Cp - 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 a welded structure

The fan casing works in particularly harsh conditions. It is directly exposed to dynamic and vibration loads.

4 Determination of 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 production type

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

5 Selection and justification of assembly and welding methods

This structure is made of steel 16G2AF, which belongs to the group of well-welded steels. When welding, preheating 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 carbon dioxide with wire Sv 08 G2S

1.6 Definition of welding modes

sv \u003d h * 100 / Kp

where: h - penetration depth

Кп - proportionality coefficient

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

Arc voltage

20 + 50 * Iw * 10⁻³ / d⁰² В

20 + 50 * 387 * 10 ⁻³ / 1.6⁰² \u003d 20 + 15.35 \u003d 35.35 V

Welding speed

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

1 * 387 / 7.85 * 24.3 * 100 \u003d 34.6 m / hour

where K n is the coefficient of surfacing, g / A * hour

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 \u200b\u200bthe deposited metal. mm 2

7 Selection of welding consumables

Steel 16G2AF can be welded by any type of welding using various types of welding consumables. Therefore, for welding we use wire SV 08 G 2 C. Wire SV 08 G2S has good weldability, low emission of welding aerosols, 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 \u003d 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

Carbon dioxide consumption

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

Power consumption

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

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

8 Selection of welding equipment, technological equipment, tools

MAGSTER WELDING SYSTEM

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

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

· It is 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.

· Infinitely adjustable wire feed.

· Gas pre-purge.

· Thermal overload protection.

· Digital voltage indicator.

· High reliability and ease of management.

· Synergistic system of the welding process - after loading the type of wire and diameter, the correspondence of the feed rate and voltage is set automatically by means of a microprocessor (for model 400,500).

· Multi-functional liquid crystal display - showing the parameters of the welding process (for models 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).

· Delivered as ready-to-use sets and include: power source, feeder with transport trolley, 5 m connecting cables, 5 m power cable, "MAGNUM" welding torch 4.5 m long, clamp for the workpiece.

AGSTER 400 plus MAGSTER 500 w plus MAGSTER 501 w Maximum power consumption, 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 torch. 20 kg. 20 kg. 20 kg.

9 Determination of technical standards for assembly and welding times

Calculation of technical standards for assembly and welding of the unit.

	Parameter	Time rate min	Time min	Source
Remove oil, rust and other contaminants from welding areas.		0.3 per 1 m. Seam
Install det pos 2 into the tool.	Weight children. 12.33 kg
Install det pos. 1 for children pos 2
Grab children poses 1 to children poses 3 for 3 tacks		0.09 1 ad
Install det pos. 2 for children pos 1	Weight children. 12.33
Grab children poses 2 to children poses 1 to 3 tacks		0.09 1 ad
Install 2 pieces of pos. 3 for children pos 1	Weight children. 0.39
Grab 2 children poses 3 to children poses 1 to 4 tacks		0.09 1 ad
Remove the assembly unit and put it on the welder's table	Weight sat. units 32.07 kg
	L seam \u003d 1.9 m	1.72 min / m seam
Weld the edges of det pos 1 to each other	L seam \u003d 0.32 m	1.72 min / m seam
Weld det pos 2 to det pos 1	L seam \u003d 1.9 m	1.72 min / m seam
Remove splashes from the weld seam.	Lzach \u003d 4.12 m	0.4 min / m seam
Control by a worker, a foreman
Remove assembly unit

Table 1

table 2

Time for the installation of parts (assembly units) when assembling metal structures for welding

Assembly type	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 device and place them at the storage site

Main time for welding 1 m. Seam

F - cross-sectional area of \u200b\u200bthe weld

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

a - deposition coefficient

a \u003d 17.1 g / a * hour

T about. tsh \u003d \u003d 1.72 min / 1 m seam

10 Calculation of the amount of equipment and its load

Estimated amount of equipment

C p \u003d \u003d \u003d 0.09

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

T gi \u003d \u003d \u003d 308.4 n-hour

F d o - annual effective 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 the full duration and reduced;

n is the number of work shifts per day;

K p - coefficient taking into account the time spent by the equipment in repair (K p \u003d 0.92-0.96).

Load factor

K z \u003d \u003d \u003d 0.09

Ср - estimated amount of equipment;

Spr - accepted amount of equipment Spr \u003d 1

11 Calculation of the number of employees

The number of main workers employed directly performing technological operations is determined by the formula

Ch o.r. \u003d \u003d \u003d 0.19

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

Ф д р - annual real fund of working time of one worker, in h;

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

Annual active fund of working time of one worker

F d p \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 the full duration and reduced;

K nev - coefficient of absenteeism for good reasons (K nev \u003d 0.88)

12 Methods for dealing with welding deformations

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

Activities that are carried out before welding;

Activities in the welding process;

Post-weld activities.

Pre-welding deformation control measures are implemented at the design stage of the welded structure and include the following activities.

Welding of the structure should have a minimum volume of weld metal. The legs should not exceed the calculated values, butt seams, if possible, should be performed without cutting edges, the number and length of seams 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 respect, CO 2 welding is preferable to manual welding, and electron beam and laser welding are preferable to arc welding.

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

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

Measures used in the welding process

A rational sequence of overlapping 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, therefore, the stiffness of the fastenings should be assigned taking into account the metal to be welded.

Preliminary deformation of the welded parts.

Swaging or rolling of the weld, which is carried out immediately after welding. In this case, the shortening plastic deformation zone undergoes plastic upsetting in 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 obtained welded joints.

.) Control of 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 welded parts in the appropriate position relative to each other when welding T-joints, control the perpendicularity of the welded parts. When checking the quality of the tacks, pay attention to the surface condition and the height of the tacks.

.) Control of the welding process includes visual observation of the process of metal melting and formation of a seam, control of the stability of the mode parameters and the equipment operability.

.) Inspection of welded joints. After welding, welded joints are usually inspected visually. The weld and the heat-affected zone are inspected. 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 welded seams are:

· Seam width;

· Amplification and penetration height;

Smooth transition from gain to base metal, etc.

1.14 Safety, fire prevention and environmental protection

The harmful effects of welding and thermal cutting on a person and industrial injuries during welding 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 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). The minimum design resistance of the human body is 1000 ohms. There are two types of electric shock: electrical shock and injury. An electric shock affects the nervous system, muscles of the 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.

Light radiation from the arc, acting on the 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. Long-term exposure to arc light under such conditions can lead to more serious diseases - (electrophthalmia, cataract). The harmful effect of the rays of the welding arc on the organs of vision affects the distance up to 10 m from the welding place.

Harmful substances (gases, vapors, aerosols) during welding are emitted as a result of physicochemical processes arising from 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 temperatures of welding heat sources. The air in the welding zone is contaminated with 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. Prolonged exposure to welding aerosol can lead to the appearance of 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 in welding and cutting, the use of gas generators, cylinders with compressed gases, etc. Explosive chemical compounds of acetylene with copper, silver and mercury. Danger is posed by kickbacks in the gas network when working with burners and low pressure torches. When repairing used tanks and other containers for storing flammable liquids, special measures are required to prevent explosions.

Thermal burns, bruises and injuries are caused by the high temperature of the welding heat sources and significant heating of the metal during welding and cutting, as well as the limited visibility of the surrounding area due to work using shields, masks and goggles with light protective glasses.

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

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

2. MEASURES TO ENSURE ELECTRICAL SECURITY

It is necessary to reliably ground the body of the welding machine or installation, the terminals of the secondary circuit of the welding transformers, which are 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 devices, metal structures of buildings and technological equipment as a return wire of the welding circuit. (During construction or repair, metal structures and pipelines (without hot water or an explosive atmosphere) can be used as a return wire for the welding circuit and only in cases when they are welded.)

4. Protect the welding leads from damage. When laying welding wires and each time they are moved, do not damage the insulation; contact of wires with water, oil, steel ropes, sleeves (hoses) and pipelines with combustible gases and oxygen, with hot pipelines.

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

6. Only electrotechnical personnel have the right to repair welding equipment. Do not repair live welding equipment.

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

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

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

allocate an insuring worker, who must be outside the tank, to monitor the safety of the welder. The welder is supplied with an assembly belt with a rope, the end of which must be at least 2 m long in the hands of the belayer. There must be an apparatus (switch, contactor) near the belayer to disconnect the mains voltage from the welding arc power source.

Welders in wet gloves, shoes and overalls must not be allowed to arc welding or cutting.

9. Cabinets, consoles and frames of contact welding machines, inside which there is equipment with open live parts that are energized, must have an interlock that relieves the voltage when they are opened. The pedal start buttons of contact machines must be grounded and the reliability of the upper guard, which prevents unintentional 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 live parts using dry materials at hand (pole, board, etc.) and then put it on a mat;

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

in case of unconsciousness and lack of breathing in the victim, release him from the restraining clothing, open his mouth, take measures against the tongue sinking and immediately start artificial respiration, continuing it until the doctor arrives or the restoration of normal breathing.

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-light filters are inserted that absorb ultraviolet rays and a significant part of light and infrared rays. The outside of the filter is protected from splashes, drops of molten metal and other contaminants with ordinary transparent 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 and welding current strength, using the data in Table. 3. When welding in an inert gas shielding environment (especially when welding aluminum in argon), a darker filter must be used than when welding with an open arc at the same current strength.

Table 3. Light filters to protect eyes 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 non-combustible materials are used (with a non-permanent workplace of the welder and large products). In stationary conditions and with relatively small sizes of the welded products, welding is performed in special cabins.

3. To weaken 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 light reflection, as well as to provide good illumination of the surrounding objects.

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

Protection against harmful gases 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, the supply of 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'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 carried out supply and exhaust with fresh air supply to the welding areas and its heating in cold weather.

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

LITERATURE

1. Kurkin SA, Nikolaev GA Welded constructions. - M .: Higher school, 1991 .-- 398p.

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

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.

Similar works on - Fan casing manufacturing technology

A person is faced with the question of the correct organization of ventilation during the construction of a small house in the country, and during the construction of industrial workshops, and during the arrangement of office buildings. For each case, you can choose the best ventilation option, but the use of galvanized steel air ducts can be considered a universal solution in any situation.

On the advantages of galvanizing

In general, they can be made from the following materials:

plastic - the price of such a solution is minimal, but the scope is also limited to private construction;

aluminum - they are corrosion resistant, but aluminum is a rather ductile metal, so such ventilation ducts do not tolerate possible loads;
made of galvanized steel - practically have no drawbacks;
from scrap materials. For example, an air duct can be built even from ordinary thick boards that fit well to each other.

Note! Plank ventilation ducts can be recommended exclusively for airing outbuildings, for example, cellars or basements in the country.

Galvanized ventilation ducts can be used practically without restrictions. They will cope without any problems with the transportation of hot air or vapors of aggressive substances. In addition, steel is able to withstand high temperatures while maintaining sufficient strength.

Plastic is completely unable to withstand prolonged exposure to elevated temperatures, and it will not be able to oppose anything to the effects of chemicals. The only advantage of this material is its low weight and ease of installation.

Ventilation pipes made of galvanized steel can withstand without compromising technical and operational indicators:

temperature about + 80ᵒС - no time limit;

Note! For the safety of personnel, air ducts transporting hot air are usually equipped with a heat-insulating layer.

within a short time, the air temperature may rise to + 200ᵒС. even in the event of a fire at the enterprise, the ventilation system will prevent smoke from the territory;
galvanized pipes for ventilation do not require additional protection from moisture. A thin layer of zinc coating prevents corrosion.

Note! Even if the integrity of the zinc layer is violated, for example, by cutting in a self-tapping screw, the steel still remains protected. The fact is that steel and zinc form a galvanic pair, and as a result of a chemical reaction, a thin oxide film covers the cut.

Methods for the production of galvanized air ducts

The technology directly depends on the shape of the pipe cross-section.

Ventilation pipes can be:

round section - optimal aerodynamic characteristics;

square or rectangular section - slightly worse aerodynamics, but easier to install thanks to flat surfaces.

The raw material for the manufacture of galvanized air ducts is thin galvanized sheet steel. As a rule, sheet thickness does not exceed 1.0 mm, this provides a balance between acceptable weight and sufficiently high rigidity.

The production of galvanized ventilation is carried out according to one of 2 methods:

in the case of a circular cross-section, either spiral-wound technology is used, or simple rolling of sheet metal with subsequent seam joining of the edges;
for profile air ducts, only one technology is used - the galvanized sheet is passed through a series of rollers, which give it the desired shape. Then the edges of the future ventilation duct are connected.

Spiral wound technology

It has an extremely high productivity, the machine processes about 60 m of strips per minute. The production of galvanized ventilation using this technology consists in the fact that the machine simply bends the steel strip so that a round-section pipe is obtained.

At the same time, adjacent turns are overlapped, due to strong tension, the edge of the strip is slightly deformed and a tightness of the joint is achieved.

In addition to high productivity, pipes produced using this technology are characterized by high rigidity. The screw seam plays the role of a stiffener, so that under equal conditions such air ducts will withstand a greater load than its longitudinal seam counterpart.

Straight seam pipes

Galvanized ventilation pipes produced using this technology in terms of technical and operational indicators almost do not differ from spiral-wound pipes. Unless they have a little less rigidity.

The entire technical process can be divided into 3 stages:

strips of the required length are cut;
it is passed through a series of rollers;
joining the adjacent edges of the metal.

As for the profile pipeline, quite often everything is prepared at the ends of the section for the subsequent flange connection. The same technology is used to manufacture ventilation ducts from galvanized steel.

Galvanized ventilation elements

When installing a ventilation system, you will need not only galvanized ventilation ducts, but also a number of shaped elements. For example, bends for different angles of rotation, plugs, grilles, tees, etc. Without these elements, installation is simply impossible.

Bends

This is one of the most common types of shaped elements, used in cases when it is necessary to ensure a smooth rotation of the duct. The main characteristic of the retraction is the angle of rotation; variants are available that provide a rotation angle from 15ᵒ to 90ᵒ.

Note! Galvanized ventilation will perform significantly worse if the duct is turned at a large angle many times. This reduces the air flow rate.

As for the production of elbows, a strip of variable width is used for this. Due to the unequal width when folded, its ring width is different. The entire bend consists of several such rings, by adjusting the strip width, it is theoretically possible to obtain any bend angle, but for convenience they are produced in 15ᵒ increments.

Ventilation box

Strictly speaking, a ventilation box is simply a vertical rectangular or square duct in which several smaller ducts are located. Depending on the operating conditions, plastic, aluminum or galvanized ventilation ducts can be used.

If you mentally dissect this structure across, then the observer will see not 1, but 3 channels. The largest one is a common ventilation duct, and two smaller ones provide removal of unpleasant odors from the underlying apartment. Typically 1 bend is used in the kitchen and 1 in the bathroom or restroom.

Given the small area of \u200b\u200bkitchens and bathrooms of most apartments, many people think about how to minimize the area of \u200b\u200bthe box and make it invisible. Galvanized ventilation ducts can help with this.

Note! Residents of multi-storey buildings are often mistaken, considering the ventilation box as their property, and demolish it. If it comes to trial in court, then the would-be builders will have to restore the destroyed with their own hands.

Other fittings

In addition to the bends during the installation of ventilation, you may need such shaped elements as:

transitions or wefts - used to offset the duct. In parallel with the displacement due to the reduction in diameter, the air flow rate can be adjusted;

plugs - used if necessary to close the free end of the pipe;
gates - regulating devices;
fire dampers;
crosses and tees - are used to create complex nodes of the ventilation network;

nipples - used when installing pipes;
galvanized steel ventilation grilles - used to protect against insects, small animals and debris from the ventilation duct.

About mounting technology

As for attaching the channel to the walls or ceiling, you can do with ordinary clamps or even just hang the pipe on a metal tape. In industrial buildings, a bracket is embedded in the wall for laying the air duct, and the pipe rests on it.

Note! If the air velocity is high, then fastening the duct with clamps or with a metal tape will not provide sufficient rigidity. The pipe will rattle, so a more secure mount is needed.

Special attention should be paid to the tightness of the joints of individual sections.

The connection can be done in several ways:

nipple... The nipple itself is a section of a pipe of a slightly smaller diameter, it is simply inserted into the duct with effort and rotated. The instructions for making a sleeve connection look the same, and the only difference is that the diameter of the sleeve is larger than the diameter of the duct;

flanged - joint strength is achieved by simply tightening the bolts;

folded - a reliable joint is provided due to joint deformation of the metal of different pipe sections.

Materials used in the manufacture of air ducts, basic technological processes and types of machines required for the implementation of this production cycle.

1. Dependence of the duct wall thickness on its cross-sectional area.

2. The main types of machines required for the manufacture of steel galvanized air ducts.
· Guillotine.
· Bending machine.
· Folded rolling machine.
· Folding machine.
· Stiffening machine.
· Pucklevochny machine.
· ZIG machine.
· Apparatus for the production of work on spot welding.
· Spiral wound machine.
· The machine for the manufacture of bends of circular section Gariloker (GORELOCKER).
· Rolling machine.

1. Materials used for the manufacture of galvanized steel air ducts.

Galvanized steel air ducts are mainly made of sheet with a thickness of 0.5 - 1.2 mm, depending on their standard sizes, for example:
rectangular duct, ranging from 100x100 mm, and up to 500x200 mm, is made of galvanized steel sheet 0.5 mm thick;
rectangular duct, ranging from 500x300 mm, and up to 800x200 mm, is made of galvanized steel sheet 0.7 mm thick;
rectangular air duct, ranging from 800x300 mm, and up to 1000x1500 mm, is made of galvanized steel sheet 1.2 mm thick.

The grade of the used steel is ST-3, ST-6.

2. The main types of machines required for the manufacture of galvanized steel air ducts:

Each machine is designed to perform one unique or several related technological operations for the processing of galvanized steel sheet, gradually turning it into a semi-finished product, a set of shaped products and, finally, a ready-to-use air duct consisting of a system of air ducts and ventilation equipment.

Guillotine.

The machine is designed for cutting steel sheet across the entire width of the coil and nothing else. Structurally, it is a workbench on which a knife is mounted with a counterweight or an electric drive.

Bending machine.

The machine is designed to bend steel sheet to the required angle (from 00 to 3600). Structurally, it is a bed with two movable and fixed guides. The movable guide bends the sheet. The drive can be manual or electric.

Folded rolling machine.

It is intended for the production of several types of locks connecting the edges of the steel sheet, and, accordingly, for connecting different sections of longitudinal seam ducts: single lock, double lock. Structurally, it is a frame with a rolling mechanism and an electric motor.

Folding machine.

This device is intended for tightening (settling) the corner at the junction of the extreme edges of two steel sheets, that is, to close the lock and obtain a hermetic connection of two adjacent sections of the longitudinal seam duct with each other.

Stiffening machine.

It is intended for the manufacture of stiffening ribs, which serve to reduce the vibration of the duct walls during the passage of air and, accordingly, reduce noise. The air ducts, the walls of which are equipped with stiffening ribs, do not rattle during operation and “keep their shape” better.

Pucklevochny machine.

Serves for processing the joints of the air duct with the flange and giving them the necessary rigidity, strength and tightness. In fact, the machine pushes the flange and air duct sheets, ensuring the strength and immobility of their connection to each other.

ZIG machine.

It is intended for the production of correct angles on the edges of sheets at the points of connection to the sections of air ducts of the following shaped products made of galvanized steel sheet: bends, semi-bends, reductions and tie-ins. In fact, the machine produces flanging and tightening of the edges of parts previously cut from galvanized steel sheet on other types of machines, for example, GORELOCKER.

Spot welding machine.

Carries out welding operations on joining steel sheets by spot welding. It is used for the manufacture of cross-section transitions of galvanized steel air ducts, mixing and distribution chambers of central and duct air conditioners, sections of silencers and adapters.

Spiral winding machine.

It is used in the manufacture of exclusively circular air ducts. The thickness of the steel sheet used for the manufacture of spiral-wound air ducts directly depends on the cross-sectional area of \u200b\u200bthe air duct - the larger the area, the thicker the sheet.

The circular air duct, starting from a diameter of 100 mm and up to a diameter of 500 mm, is made of galvanized steel sheet 0.5 mm thick;
a circular air duct, starting from a diameter of 500 mm and up to a diameter of 900 mm, is made of galvanized steel sheet 0.7 mm thick;
a circular duct with a diameter of 900 mm and up to a diameter of 1250 mm is made of galvanized steel sheet 1 mm thick.

The maximum allowable cross-sectional area of \u200b\u200bthe air duct that this machine can digest is 1.13 m2, with a diameter of 1250 mm.

Garilocker (GORELOCKER).

The machine of this type is designed for cutting galvanized steel sheet into segments, and further production of bends and semi-bends with a diameter from 100 mm to 1250 mm inclusive.

Rolling machine.

This device is designed for the production of round longitudinal seam air ducts. Allows to manufacture fittings and inserts with a length of 50 mm. up to 1250 mm. inclusive: adapters and cross-section transitions (from rectangular to round, and vice versa). It is possible to manufacture a straight section of the air duct, however, its length will be limited to 1250 mm.

The above machine park is used in the production of galvanized steel air ducts and fittings of the following types:
- Straight-seam galvanized steel air ducts of square cross-section with a length of 10 cm to 2.5 m inclusive;
- Longitudinal steel galvanized circular air ducts with a length of 5 cm to 1.25 m inclusive;
- Spiral wound galvanized steel air ducts with a length from 50 cm to 5 m inclusive.
- Cross-section transitions (designed to connect air ducts of various diameters and cross-sectional shapes).
- Elbows (Designed to rotate the air duct by 900, can be either round or square).
- Semi-bends (Designed to rotate the duct by 450, can be either round or square).
- Tees (Designed for dividing the air duct into two parts of the same section, in a non-standard version, it can be divided into equal parts with a transition to a larger section, for example (100x100 / 100x100) / 200x100).
- Adapters (Designed for attaching grilles of both ceiling and wall types. Non-standard detail requiring the development of an individual drawing. Structurally, the adapter is a steel box with a cut-in from the top or side).

Reduction (Shaped part designed for transition from a main pipe to an air duct of a smaller diameter. Reductions are used both rectangular and circular. Structurally, they are divided into straight inserts and saddle inserts. The insertion length cannot be more than 20 cm).

We remind: Here you can buy wholesale components and spare parts for industrial ventilation systems: fastening of air ducts, air conditioners, rectangular and round air ducts, traverse, mounting bus, galvanized corners, bracket for connecting flanges, mounting tape, perforated, tape clamp, aluminum tape, brackets, grilles and anemostats, sheet and roll insulation, galvanized metal sheets. We also carry out wholesale of fasteners: threaded studs, self-tapping screws, screws, bolts, screws, nuts, washers, rivets, drop-in anchors. Deliveries go all over Russia, from a warehouse in Moscow.

It might be helpful to read:

Description of the technological process of making galvanized air ducts. How to choose galvanized steel air ducts: dimensions, diameters, GOSTs and installation rules. Documents required to organize a business

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Introduction

Manual arc welding equipment

Station for manual arc welding

Welding inverter ARC-160 BRIMA

Welding wires

Holder for electrodes

Consumable material

Preparation of metal for welding

Tenderloin

Markup

Cutting

For stripping

Edit

Edge preparation

Bending

Selecting MMA Mode

Technological process

Labor protection instruction for electric welder

1. GENERAL PROVISIONS.

2. Safety requirements before starting work.

3. Safety requirements during the performance of work.

4. Safety requirements at the end of work.

5. Safety requirements in emergency situations.

Individual protection means

Bibliography

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