Gas welding of medium complexity and complex assemblies. Qualification characteristics

Methodical development: lesson on the topic "Welding transformers".

Outline of the lesson "Welding transformers"

Lesson Objectives:

Educational:

To study the design features and principle of operation of welding transformers;

To consolidate knowledge about the external current-voltage characteristics of welding equipment;

To generalize and systematize knowledge about the tools of an electric welder;

Contribute to the development of skills for solving practice-oriented problems.

Developing:

To develop in students the ability to highlight the main thing in the material being studied;

Contribute to the formation of the ability to apply the acquired knowledge in practical activities

Educational:

- to promote the formation of students' respect for the chosen profession;

- contribute to the education of purposefulness;

- show the connection of the subject with industrial practice;

General competencies:

OK 1. Understand the essence and social significance of your future profession, show a steady interest in it.

OK 2. Organize their own activities, based on the goal and ways to achieve it, determined by the head.

OK 3. Analyze the working situation, carry out current and final control, evaluation and correction of their own activities, be responsible for the results of their work.

OK 4. Search for information necessary for the effective performance of professional tasks.

OK 6. Work in a team, communicate effectively with colleagues, management, clients.

OK 7. Perform military duty, including using the acquired professional knowledge.

Professional competencies:

PC 2.1. Perform gas welding of medium complexity and complex assemblies, parts and pipelines made of carbon and structural steels and simple parts made of non-ferrous metals and alloys.

PC 2.2. Perform manual arc and plasma welding of medium complexity and complex parts of apparatuses, assemblies, structures and pipelines made of structural and carbon steels, cast iron, non-ferrous metals and alloys.

PC 2.3. Perform automatic and mechanized welding using a plasma torch of medium complexity and complex devices, assemblies, parts, structures and pipelines made of carbon and structural steels.

PC 2.4. Perform oxygen, air-plasma cutting of metals of straight and complex configuration.

PC 2.6. Ensure the safe performance of welding work at the workplace in accordance with sanitary and technical requirements and labor protection requirements.

Lesson type: primary learning lesson

Teaching methods:

- explanatory and illustrative(explanation, show)

-partial search ( solving cognitive problems and problem situations)

Means of education:

Video "Automation of welding production"

Presentation "Welding transformers";

Slides and task cards “Characteristics of the main types of welding transformers”, “Transformer device TSK-500”, “Commandments of a welder”;

Tests with tasks

During the classes:

Slide 1 "The topic of the lesson"

1. Organizational moment:

Greeting students; test readiness for the lesson.

2.Goal setting and motivation. Emotional mood.

Teacher:

Today our lesson will be held under the motto: "Modern technical progress is inextricably linked with the improvement of welding production"

Showing the video "Automation of welding production"

Slide 2: What do we know?

Teacher: We will continue to study the topic "Equipment of the welding station" and consolidate our knowledge on the topic "Requirements for power sources of the welding arc."

Slide 3 lesson plan

Slide 4 "Lesson goals"

Teacher: Please write the plan and objectives of today's lesson in your notebook.

Slide 5: What do we know?

3. Actualization of basic knowledge

(form of conducting - professional dictation)

Teacher: I will dictate the beginning of the sentence to you, and you need to add its ending to your notebook, then check your answers with the answers of your friend. Find errors, if any.

Slide 5 "External characteristics of power supplies"

Teacher: You and I know that current sources for powering the welding arc must have a special external characteristic. What is called the external characteristic of the power supply?

: The external characteristic of the power supply is the dependence of the voltage at its output terminals on the load current.

Teacher: What are the external characteristics of power supplies?

Estimated student response: steeply dipping, gently dipping, hard, increasing.

Teacher: What are the characteristics of welding transformers?

Estimated student response: Transformers have a steeply falling external characteristic.

4. Work on the topic of the lesson

Slide 6 "Characteristics of the main types of welding transformers"

Teacher: Welding transformers are divided into two groups according to the principle of operation and design: transformers with normal magnetic dissipation and transformers with increased magnetic dissipation.

Transformers STN, STE, TSD are transformers with normal magnetic dissipation - they are used for automatic and semi-automatic submerged arc welding.

The principle of operation of transformers with increased magnetic dissipation is based on the use of magnetic shunts, moving coils or stepped (turn) regulation.

Transformers with moving coils TS, TSK, TD are single-station transformers. TD transformers are currently being replaced by more advanced TDM transformers.

Now the most widely used welding transformers are TS and TSK.

Transformers with magnetic shunts OSTA, STAN, STSH are not currently produced, but are still quite often used in production.

Transformers with magnetizable shunt and step regulation are used for automatic submerged arc welding. These are TDF 1001 and TDF 2001 transformers.

So, we got acquainted with the types of transformers that our industry produces. Please write in your notebook how transformers are classified. Specifically, we will study each type of transformer in the following lessons.

Slide 7 "Transformer device TSK-500"

Explanation of the device of the TSK-500 transformer on the layout.

Teacher: The TSK-500 transformer consists of: - a core-magnetic core made of transformer steel;

Primary and secondary windings are placed on the core;

The transformer is connected to an alternating current network with a voltage of 380V;

The primary winding is fixed motionless, and the secondary moves along the core, adjusting the amount of welding current.

To move the coils, a vertical screw with a tape thread is used, equipped with a handle.

The principle of operation of the welding transformer is simple (explanation on the layout):

When the coils approach each other, the magnetic leakage and the inductive resistance of the windings caused by it decreases, and the welding current increases;

When the coils move away from each other, most of the magnetic flux is scattered, i.e., it does not pass completely through the steel core, but partially goes through the air space surrounding them. This increases the E.D.S. self-induction directed against the main E.D.S., i.e., it increases the inductive resistance of the windings, which leads to a decrease in the current in the welding circuit;

The magnitude of the welding current is regulated by moving the coils along the magnetic circuit;

To accurately determine the magnitude of the welding current, an ammeter is used;

The capacitor serves to improve the power factor.

I ask you to name the main parts of the welding transformer and show on the layout: magnetic circuit, primary and secondary coils.

Teacher: How is the welding current adjusted?

Estimated student response: The magnitude of the welding current is regulated by moving the primary coil along the magnetic circuit.

Teacher: At what position of the coils will the current be greater?

Estimated student response: When the coils approach each other, the inductive resistance of the windings decreases, and the strength of the welding current increases.

Teacher: What is a capacitor used for?

Estimated student response: The capacitor is used to improve the power factor.

Slide 8 "Rules for the operation of welding transformers"

Teacher: When servicing welding transformers, the following rules must be observed:

Regularly check the condition of the welding and grounding circuit, tightening of the fasteners of the core and casing;

Lubricate the adjusting mechanism more often;

When moving the apparatus, use the handles or lifting rings of the transformer casing.

Please copy the table from the screen "Rules for the operation of welding transformers" into your notebook

Slide 9 "Note to the welder"

Teacher: And now, we will consider what type of service and in what terms it is necessary to carry out maintenance and overhaul of welding transformers (students are involved in the discussion)

Slide 10 "Solution of the situational problem"

5. Consolidation of the studied material

Teacher: To consolidate the material covered, you are offered the following tasks:

1. In the cards - tasks "Device of a welding transformer" mark the correct answer. You can check your answers with the correct answers on the red cards that are on your tables.

2. Safety precautions when working with welding equipment you repeat every lesson in industrial training and in the lessons of our subject. We studied the rules for providing first aid at the very beginning of the school year. The second task offers you a test in which you need to analyze the situations that may arise during the performance of welding work and give the correct answer. You need to check your answers with the answers of your comrades and find errors, if any, (a brief analysis of the answers to the tests with the involvement of students for discussion).

Slide 11 "Five commandments of a welder"

5. Summing up the work

Teacher: And, as a result of our work, the commandments of the welder when working with welding equipment.

(the help of students who read the commandments aloud and comment on them).

Slide 12 "What have you learned and why do you need this knowledge"

(a brief survey of students on the topic studied)

(students compare the objectives of the lesson and its result, evaluate their work, draw conclusions, argue the answers).

Behavior of the results (voicing the names of the students who worked most actively in the lesson).

Homework: write a summary of the last lesson

6. Final word of the teacher

Today in the lesson, studying the design features and principle of operation of welding transformers, we were convinced of the importance of theoretical knowledge for mastering a profession, for developing professional and general competencies.

I hope that the knowledge gained will help you in practice when working with welding equipment, because the modern labor market requires a specialist with high professional mobility, the ability to quickly adapt to new working conditions, and who are confident in their professional knowledge.

Conclusion

In the modern world, welding is of fundamental importance in the construction and creation of many structures without which it is difficult to imagine everyday life: cars, houses, bridges, etc.

The welding process requires serious knowledge and skills, you can’t just take a welding machine and put a seam.

A professional welder will have to master the technology of melting metals, the methods and principles of operation of the units and equipment used. He will have to understand the physical essence of all ongoing processes, to know the features of welding different types of metals.

And taking into account the fact that technologies do not stand still and are constantly evolving, the welder is required to constantly improve their skills and study modern promising trends.

The flexibility of welding production is determined primarily by the versatility of welding equipment and the high qualification of welders.

Bibliography

1. Gerasimenko electric gas welding. - Rostov / ND: Phoenix, 2006.

2. Borilov manual arc welding. - Rostov/ND: Phoenix, 2008.

3. http://www. profvibor. en/catalog/article. php

4. http://www. edu. ru/abitur/act.86/index. php

Applications.

Technical dictation

Exercise: complete the sentence

Test

"Safety when working with welding equipment"

During the welding work with the welder, one of the cases occurred. Your actions in this case: (choose the correct answer)

§ 47. Electric and gas welder 4th category

Attention! This qualification characteristic was excluded by order of the Ministry of Labor of Russia dated April 9, 2018 N 215

Characteristics of works. Manual arc, plasma and gas welding of medium complexity of parts, assemblies, structures and pipelines made of structural steels, cast iron, non-ferrous metals and alloys and complex parts of assemblies, structures and pipelines made of carbon steels in all spatial positions of the weld. Manual oxygen, plasma and gas straight and shaped cutting and cutting with petrol and kerosene cutting machines on portable, stationary and plasma cutting machines, in various positions of complex parts from various steels, non-ferrous metals and alloys according to marking. Oxygen flux cutting of parts made of high-chromium and chromium-nickel steels and cast iron. Oxygen cutting of ship objects afloat. Automatic and mechanical welding of medium complexity and complex devices, assemblies, pipeline structures made of various steels, cast iron, non-ferrous metals and alloys. Automatic welding of critical complex building and technological structures operating in difficult conditions. Manual electric arc air planing of complex parts from various steels, cast iron, non-ferrous metals and alloys in various positions. Welding of cast iron structures. Surfacing of defects in complex parts of machines, mechanisms, structures and castings for machining and test pressure. Hot straightening of complex structures. Reading drawings of various complex welded metal structures.
Must know: the device of various electric welding and gas cutting equipment, automatic and semi-automatic devices, features of welding and electric arc planing on alternating and direct current; the basics of electrical engineering within the scope of the work performed; types of defects in welds and methods for their prevention and elimination; basics of metal welding; mechanical properties of welded metals; principles of selection of the mode of welding by instruments; brands and types of electrodes; methods for obtaining and storing the most common gases: acetylene, hydrogen, oxygen, propane-butane, used in gas welding; gas cutting process of alloy steel.
Work examples
1. Equipment, vessels and containers made of carbon steel, operating without pressure - welding.
2. Equipment and vessels for chemical and petrochemical industries: tanks, separators, vessels, etc. - cutting holes with beveled edges.
3. Pipeline shut-off valves made of non-ferrous metals and alloys under test pressure over 1.6 to 5.0 MPa (over 15.5 to 48.4 atm) - deposition of defects.
4. Transformer tanks - welding of branch pipes, welding of boxes for terminals, cooler boxes, current settings and tank covers.
5. Rudder stocks, propeller shaft brackets - hardfacing.
6. Cylinder blocks of car engines - surfacing of shells in castings.
7. Crankshafts - surfacing of necks.
8. Bronze and brass inserts - surfacing on steel bearings.
9. Headset and bodies of burners of boilers - welding.
10. Details from sheet stainless steel, aluminum or copper alloys - gas-electric cutting with beveled edges.
11. Parts made of cast iron - welding, surfacing with and without heating.
12. Parts made of sheet steel with a thickness of more than 60 mm - manual cutting according to the markup.
13. Parts and assemblies made of non-ferrous metals - welding followed by pressure testing.
14. Carriage retarders - welding and welding of units under operating conditions.
15. Cast iron gear teeth - hardfacing.
16. Products from non-ferrous alloys thin-walled (covers of air coolers, bearing shields, fans of turbogenerators) - welding with brass or silumin.
17. Large cast iron products: frames, pulleys, flywheels, gears - fusing of shells and cracks.
18. Chambers of impellers of hydraulic turbines - welding and surfacing.
19. Structures of blast furnaces (casings, air heaters, gas pipelines) - cutting with beveled edges.
20. Frames of industrial furnaces and boilers - welding.
21. Crankcases of large motors and housings of mechanical transmission of diesel locomotives - welding.
22. Lower crankcases - welding.
23. Coils of poles of electrical machines from strip copper - welding and welding of jumpers.
24. Gas exhaust manifolds and pipes - welding.
25. Rings regulating hydraulic turbines - welding and surfacing.
26. Housings and bridges of the drive wheels of the harvester - welding.
27. Cases of compressors, low and high pressure cylinders of air compressors - cracking.
28. Rotor housings up to 3500 mm in diameter - welding.
29. Cases of stop valves for turbines up to 25,000 kW - welding.
30. Cases of brush holders, segments of reversers, rotors of electric motors - hardfacing.
31. Fastening and supports for pipelines - welding.
32. Brackets and fastenings for locomotive pivot bogies - welding.
33. Sheets of large thicknesses (armor) - welding.
34. Masts, drilling and operational towers - welding in workshop conditions.
35. Aluminum furniture - welding.
36. Fundamental plates of large electrical machines - welding.
37. Struts, axle shafts of aircraft landing gear - welding.
38. Heaters - welding of a holder, a hot-water pipe with a holder, a cone, rings and flanges.
39. Bearings and bushings, axle boxes, drawbars - fusing along the frame and fusing cracks.
40. Pistons of pneumatic hammers - build-up of shells and cracks.
41. Dust and gas pipelines, fuel supply units and electrostatic precipitators - welding.
42. Spool frames, pendulums - welding.
43. Porthole frames made of aluminum alloys - welding.
44. Frames of conveyors - welding.
45. Air trolleybus tanks - welding.
46. ​​Reservoirs for petroleum products with a capacity of less than 1000 cubic meters. m - welding.
47. Rail butt joints - welding in operational conditions.
48. Rails and prefabricated crosses - welding ends.
49. Single and twisted metal meshes for pulp and paper production - soldering the ends with silver solder.
50. Crusher beds - welding.
51. Beds and housings of electric machines welded-cast - welding.
52. Cast iron beds of large machine tools - welding.
53. Beds of working stands of rolling mills - welding.
54. Air-cooled turbogenerator stators - welding.
55. Tubes for sensors with a radioactive isotope - welding.
56. Pipe elements of boilers, armor plates, etc. - hot editing.
57. Pipelines of external and internal water supply and heating networks - welding at installation.
58. Pipelines of external and internal low-pressure gas supply networks - welding in workshop conditions.
59. Drill pipes - welding of couplings.
60. Technological pipelines of the 5th category - welding.
61. Half-timbered houses, communications, lanterns, runs, monorails - welding.
62. Milling cutters and complex dies - welding and surfacing of a quick cut and hard alloy.
63. Brass refrigerators - welding seams for hydrotesting at pressures up to 2.5 MPa (24.2 atm.).
64. Cylinders of car blocks - shell fusing.
65. Automobile tanks - welding.
66. Balls, floats and tanks made of special aluminum alloys - welding.

From July 1, 2016, employers are required to apply professional standards if the qualification requirements that an employee needs to perform a certain job function are established by the Labor Code, federal laws or other regulatory legal acts (Federal Law of May 2, 2015 No. 122-FZ).
To search for approved professional standards of the Ministry of Labor of the Russian Federation, use

Unified Tariff and Qualification Directory of Works and Professions of Workers (ETKS), 2019
Part No. 1 of issue No. 2 ETKS
The issue is approved by the Decree of the Ministry of Labor of the Russian Federation of November 15, 1999 N 45
(as amended by the Order of the Ministry of Health and Social Development of the Russian Federation of November 13, 2008 N 645)

gas welder

§ 6. Gas welder of the 2nd category

Job Description. Tacking of parts, products from structures in all spatial positions of the weld. Preparation of joints for welding and cleaning of seams after welding. Preparation of gas cylinders for work. Maintenance of portable gas generators. Gas welding of simple parts, assemblies and structures made of carbon steels in the lower and vertical position of the weld. Surfacing of simple details. Elimination of shells and cracks by surfacing in simple castings. Heating of structures and parts during straightening.

Must know: device and principle of operation of serviced gas welding machines, gas generators, oxygen and acetylene cylinders, reducing devices and welding torches; types of welds and joints; rules for the preparation of simple products for welding; types of sections and designations of welds in the drawings; handling rules and basic properties of gases and liquids used in welding; permissible residual gas pressure in cylinders; purpose and brand of fluxes used in welding; causes of defects in welding, characteristics of the gas flame; colors of cylinders; arrangement of communications for supplying gas to places of consumption and rules for connecting to them.

Work examples

1. Box bolts, column bolts and center bolts - surfacing of working places.

2. Necks of gas tanks of cars - soldering.

3. Details of side awning frames - tacking and welding.

4. Portholes and covers - welding.

5. Cones of oil pumps and filters of automobiles - surfacing of shells in castings.

6. Protective covers - welding.

7. Gutter covers for undercar lighting - welding.

8. Brackets for attaching the muffler to the car frame - surfacing of cracks.

9. Flasks - welding ears.

10. Pallets for machines - welding.

11. Receiving pipes - welding of safety nets.

12. Car fender reinforcements - welding.

13. Corner sheets of the inner and outer sheathing of the tram - welding of cuts.

14. Clamps of hydraulic mechanisms of dump trucks - welding.

§ 7. Gas welder of the 3rd category

Job Description. Gas welding of medium complexity assemblies, parts and pipelines made of carbon and structural steels and simple parts made of non-ferrous metals and alloys in all spatial positions of the weld, except for ceiling ones. Elimination of shells and cracks in parts and assemblies of medium complexity by surfacing. Hardfacing of simple parts. Preliminary and concomitant heating when welding parts in compliance with the specified mode.

Must know: arrangement of serviced gas welding equipment; structure of welds and methods of their testing; basic properties of welded metals; rules for preparing parts and assemblies for welding and surfacing; rules for choosing a metal heating mode depending on its grade and thickness; causes of internal stresses and deformations in welded products and measures to prevent them; basic technological methods of welding and surfacing of parts made of steel, non-ferrous metals and cast iron.

Work examples

1. Fittings made of tin bronzes and silicon brass under test pressure up to 1.6 MPa (15.5 atm.) - elimination of defects by welding.

2. Crankshafts and camshafts of automobiles - deposition of defective semi-finished forgings with special steels.

3. Silencers - welding.

4. Internal combustion engines (fuel and air system) - welding.

5. Car parts (oil heater necks, box crankcase, crankcase covers) - elimination of defects by welding.

6. Bronze brake discs - elimination of shells.

7. Casings of elastic couplings - welding.

8. Rear axles of cars - elimination of shells in castings.

9. Facing of a car radiator - elimination of cracks.

10. Level regulator floats (fittings) - welding.

11. Frame profile windows of the driver's cabin - welding.

12. Pantograph frames - template welding.

13. Reservoirs for non-flammable liquids and brake systems of rolling stock - welding.

14. Bulkhead shaft seals - fusing of the body and pressure sleeve.

15. Rear wheel hubs, rear axle and other car parts - malleable iron soldering.

16. Ventilation pipes - welding.

17. Copper exhaust pipes - welding.

18. Tied fire tubes in boilers and superheater tubes - welding.

19. Pipes of the brake line - welding.

20. Non-pressure pipelines for water (except for main ones) - welding.

21. Pipelines of external and internal networks of water supply and heating - welding in workshop conditions.

22. Brass (open) gasifier balls - welding.

§ 8. Gas welder of the 4th category

Job Description. Gas welding of complex parts, structures and pipelines from carbon and structural steels and parts of medium complexity from non-ferrous metals and alloys in all spatial positions of the weld. Surfacing with hard alloys using ceramic fluxes in a protective gas of parts and assemblies of medium complexity. Elimination of defects in large cast iron and aluminum castings for machining and test pressure welding. Elimination of shells and cracks by welding in machined parts and assemblies. Hot straightening of complex structures.

Must know: methods for establishing metal welding modes depending on the configuration and thickness of the parts to be welded; methods of welding non-ferrous alloys, cast iron; testing of welds from non-ferrous metals and alloys; basic rules for the weldability of metals; general concepts of methods for obtaining and storing the most common gases used in gas welding (acetylene, hydrogen, oxygen, propane-butane, etc.); types of defects in welds and methods for their prevention and elimination; rules for reading drawings.

Work examples

1. Shut-off valves made of non-ferrous metals and alloys under test pressure over 1.6 to 4.9 MPa (over 15.5 to 48.4 atm) - elimination of defects by welding.

2. Babbit filling of bearings - welding.

3. Cylinder blocks of car engines - elimination of shells in castings.

4. Crankshafts - fusing of necks.

5. Bronze and brass bushings - hardfacing on steel bearings.

6. Parts and assemblies made of non-ferrous metals - welding followed by pressure testing.

7. Spool frames, pendulums - welding.

8. Teeth of cast iron gears - hardfacing.

9. Products from non-ferrous alloys thin-walled (air cooler covers, end shields, fans of turbogenerators) - body welding with brass or silumin.

10. Large cast iron products (frames, pulleys, flywheels, gears) - elimination of cavities and cracks.

11. Crankcases of large motors and housings of mechanical transmission of diesel locomotives - welding.

12. Coils of poles of electrical machines from strip copper - welding of jumpers.

13. Cases of brush holders, segments of reversers, rotors of electric motors - hardfacing.

14. Aluminum furniture - welding.

15. Heaters - welding of a holder, a hot-water pipe with a holder, a cone, rings and flanges.

16. Pistons of pneumatic hammers - elimination of shells and cracks.

17. Bearings and bushings, axle boxes, drawbars - fusing along the frame and fusing cracks.

18. Porthole frames made of aluminum alloys - welding.

19. Air trolleybus tanks - welding.

20. Single and twisted metal meshes for pulp and paper production - soldering the ends with silver solder.

21. Tubes for sensors with a radioactive isotope - elimination.

22. Pipe elements of boilers, armor plates, etc. - hot editing.

23. Pipelines of external and internal networks of water supply and heating - welding at installation.

24. Technological pipelines (category 5) - welding.

25. Pipelines of external and internal low-pressure gas supply networks - welding in workshop conditions.

26. Brass refrigerators - welding seams for hydrotesting at pressures up to 2.5 MPa (24.2 atm).

27. Balls, floats and tanks made of special aluminum alloys - welding.

§ 9. Gas welder of the 5th category

Job Description. Gas welding of complex parts, assemblies, mechanisms, structures and pipelines made of high-carbon, alloyed, special and corrosion-resistant steels, cast iron, non-ferrous metals and alloys, designed to work under dynamic and vibration loads and under pressure. Surfacing with hard alloys of complex parts, assemblies, structures and mechanisms. Welding and elimination of cracks and cavities in thin-walled products and in products with hard-to-reach places for welding. Heat treatment with a gas burner of welded joints after welding.

Must know: mechanical and technological properties of welded metals, including high-alloy steels, as well as deposited metal; rules for choosing the technological sequence of suturing and welding modes; methods of control and testing of welds; the influence of heat treatment on the properties of the welded joint.

Work examples

1. Blast furnace embrasures - welding of shells and cracks.

2. Pipe fittings made of tin bronze and brass (silicon) - welding under test pressure over 5 MPa (48.4 atm).

3. Cylinders, caps, spheres operating in vacuum - welding.

4. Lead baths - welding.

5. Bronze and brass propellers - correction of defects by welding.

6. Details of gas welding equipment - silver soldering.

7. Copper coils - welding.

8. Caissons of open-hearth furnaces (hot repair) - internal welding.

9. Bellows-type expansion joints made of corrosion-resistant steels - soldering.

10. Manifolds of complex configuration of 20 or more parts made of corrosion-resistant steels and heat-resistant steel with macrostructure verification using X-ray - welding.

11. Cast iron bodies, covers, tees, elbows, cylinders - elimination of defects by welding.

12. Steam boilers - cracking.

13. Aluminum and bronze castings, complex and large - surfacing of shells and cracks.

14. Molds - welding in hard-to-reach places.

15. Rotors of electrical machines - welding of short-circuited rings, rods, welding.

16. Complex beds, aprons of large lathes - welding, surfacing of cracks.

17. Tubes for impulse control and automation systems - welding.

18. Pipe elements of steam boilers with pressure up to 4.0 MPa (38.7 atm.) - welding.

19. Pipelines of external and internal low-pressure gas supply networks - welding at installation.

20. Technological pipelines of the 3rd and 5th categories (groups), pipelines of steam and water of the 3rd and 5th categories - welding.

21. Lead pipes - welding.

22. Pipelines of external gas supply networks of medium and high pressure - welding at installation.

23. Brass refrigerators - welding of seams for hydrotesting at pressures above 2.5 MPa (24.2 atm.).

24. Cylinders of internal combustion engines - welding of internal and external shirts.

25. Tires, tapes, compensators for them from non-ferrous metals - welding.

§ 10. Gas welder of the 6th category

Job Description. Gas welding of complex parts, components of mechanisms, structures and pipelines made of high-carbon, alloyed, special and corrosion-resistant steels, cast iron, non-ferrous metals and alloys, designed to work under dynamic and vibration loads and under high pressure. Surfacing with hard alloys of complex parts, assemblies, structures and mechanisms.

Must know: variety of light and heavy alloys, their welding and mechanical properties; types of corrosion and factors causing it; metallography of welded seams; methods of special tests of welded products and the purpose of each of them.

Work examples

1. Blocks for separation of air-oxygen shops - welding of parts from non-ferrous metals.

2. Parts and assemblies made of non-ferrous metals, operating under pressure over 4.0 MPa (38.7 atm.) - welding.

3. Vacuum and cryogenic tanks, caps, spheres and pipelines - welding.

4. Blades of rotors and stators of turbines - soldering.

5. Wiring impulse turbines and boilers - welding.

6. Pipe elements of steam boilers with pressure over 4.0 MPa (38.7 atm.) - welding.

7. Pipelines of external gas supply networks of medium and high pressure - welding during installation.

8. Technological pipelines of the 1st and 2nd category (groups), as well as steam and water pipelines of the 1st and 2nd categories - welding.

Gas welding technique

Gas welding is a universal method, but when performing it, it must be remembered that a sufficiently large area around the welded joint is subjected to heating. Therefore, it is impossible to exclude the occurrence of warpage and the development of internal stresses in structures, and they are more significant than with other welding methods. In this regard, gas welding is more suitable for such joints, for which a small amount of deposited metal and low heating of the base metal are sufficient. First of all, we are talking about butt, corner and end joints (regardless of their spatial position - lower, horizontal, vertical or ceiling), while tee and lap joints should be avoided (although they can also be carried out).

In order for the weld to have high mechanical properties, the following steps are required:

- prepare the edges of the metal;

- select the appropriate burner power;

– adjust the burner flame;

- take the necessary filler material;

- correctly orient the burner and determine the trajectory of its movement along the seam being performed.

As with arc welding, the gas edge of the metal to be welded must be prepared. They are cleaned (by 20–30 mm on each side) from rust, moisture, oil, etc. To do this, it is enough to warm up the edges. In the case of welding non-ferrous metals, mechanical and chemical cleaning methods are used.

When making butt joints (Table 42), you should remember some rules for cutting edges:

- when welding thin sheet metal (up to 2 mm), additives are not used - it is enough to flang the edges, which then melt and form a weld bead. This option is also possible: weld the edges end-to-end without cutting and gap, but using filler material;

- when welding metal with a thickness of less than 5 mm, you can do without bevel edges and conduct one-sided gas welding;

- when joining metal with a thickness of more than 5 mm, the edges are beveled at an angle of 35–40 °, so that the total opening angle of the seam is 70–90 °. This will allow the metal to be welded to its full thickness.

Table 42

Note: a – gap size; a1 is the amount of blunting; S and S1 are the thickness of the metal.

When making corner joints, filler material is not used, and the seam is formed by melting the edges of the metal.

Lap and tee joints are allowed only when welding metal up to 3 mm thick, since with a greater thickness, local heating of the metal is uneven, which leads to the development of significant internal stresses and deformations, as well as to the appearance of cracks both in the weld metal and in the base metal.

So that during the welding process the parts do not move and the gap between them does not change, they are fixed either with special devices or tacks. The length, number and gap between the latter depend on the thickness of the metal, the length and configuration of the seam:

- if the metal is thin, and the seams are short, the length of the tacks is 5-7 mm with an interval between them of 70-100 mm;

- if the metal is thick and the seams are long, then the length of the tacks is increased to 20–30 mm, and the distance between them is up to 300–500 mm.

During welding, the flame of the burner is directed to the metal in such a way that it enters the reduction zone and is 2–6 mm from the core. When welding low-melting metals, the flame of the burner is mainly oriented towards the filler material, and the core zone is moved to an even greater distance from the weld pool.

When welding, it is necessary to control the rate of heating and melting of the metal. To do this, they resort to such actions (Fig. 91):

- change the angle of the mouthpiece;

- manipulate the mouthpiece itself.

Rice. 91. Methods for adjusting the rate of heating and melting of metal by changing: a - the angle of inclination of the mouthpiece; b – trajectories of movement of the mouthpiece and wire; 1 - when welding thin sheet metal; 2, 3 - when welding thick sheet metal

When welding, make sure that:

- the core of the flame did not come into contact with the molten metal, since the latter can carburize from this;

– the weld pool was protected by a flame zone and a reduction zone, otherwise the metal will be oxidized by atmospheric oxygen.

In the process of using a gas burner, you must follow the rules for handling it:

1. If the burner is in good condition, then the flame that it gives is stable. In the event that any deviations are observed (combustion is unstable, the flame breaks off or goes out, back blows occur), special attention must be paid to the burner components and adjusted.

2. To check the injection burner, connect the oxygen hose, attach the tip to the body. After tightening the union nut, carefully unscrew the acetylene valve, set the appropriate oxygen pressure with an oxygen reducer, and then open the oxygen valve.

3. If the finger attached to the acetylene nipple is sucked, this means that oxygen creates a vacuum. If this does not happen, the injector, mixing chamber or mouthpiece may be clogged. They should be cleaned.

4. Repeat the vacuum test (suction). Its value is determined by the gap between the end of the injector and the inlet to the mixing chamber. By unscrewing the injector, the gap is adjusted.

There are two methods of gas welding (Fig. 92):

Rice. 92. Methods of gas welding (the arrow indicates the direction of welding): a - left; b - right; 1 - filler wire; 2 - welding torch

– left hand welding, in which the torch is moved from right to left and held behind the filler wire. In this case, the welding flame is focused on the not yet welded seam. This method does not allow sufficient protection of the metal from oxidation, is accompanied by a partial loss of heat and gives low welding performance;

- right hand welding, in which the torch is moved from left to right and held in front of the filler wire. In this case, the flame is oriented towards the finished seam and the end of the filler wire. This method makes it possible to direct a greater amount of heat to the melting of the metal of the weld pool, and the oscillatory transverse movements of the mouthpiece and wire are carried out less frequently than with the left method. In addition, the end of the filler wire is constantly immersed in the weld pool, so it can mix it, which contributes to the transition of oxides into slag.

The right method is usually used if the thickness of the metal to be welded exceeds 5 mm, especially since the welding flame is limited on the sides by the edges of the product, and behind - by the weld metal bead. As a result, heat loss is reduced and it is used more efficiently.

The left method has its advantages, because, firstly, the seam is always in the field of view of the welder and he can adjust its height and width, which is of particular importance when welding thin sheet metal; secondly, when welding, the flame can spread over the surface of the metal, reducing the risk of burnout.

When choosing one or another welding method, one must also be guided by the spatial position of the weld:

– when making the bottom seam, the thickness of the metal should be taken into account. It can be applied both to the right and to the left. This seam is the easiest, since the welder can observe the process. In addition, the liquid filler material flows into the crater and does not spill out of the weld pool;

– for a horizontal seam, the right-hand method is preferred. To prevent leakage of liquid metal, the walls of the weld pool are made with some skew;

- for a vertical seam on the rise - both left and right, and for a vertical seam on the descent - only the right way;

– the ceiling seam is easier to apply in the right way, since the flame flow is directed to the seam and does not allow the liquid metal to flow out of the weld pool.

A method that guarantees the high quality of the weld is bath welding (Fig. 93).

Rice. 93. Welding with trays: 1 - direction of welding; 2 - trajectory of the filler wire; 3 - trajectory of the mouthpiece

This method is used for welding thin sheet metal and pipes made of low-carbon and low-alloy steels with lightweight seams. It can also be used when welding butt and corner joints with a metal thickness of up to 3 mm.

The process of welding with baths proceeds as follows:

1. Having melted the metal with a diameter of 4–5 mm, the welder places the end of the filler wire into it. When its end melts, he introduces it into the flame's recovery zone.

2. At the same time, the welder, having slightly shifted the mouthpiece, makes circular movements with it in order to form another bath, which should overlap the previous one somewhat (by about a third of the diameter). In this case, the wire must continue to be kept in the reducing zone in order to prevent its oxidation. The core of the flame must not be immersed in the weld pool, otherwise the weld metal will be carburized.

In gas welding, the seams are single or multilayer. If the thickness of the metal is 8-10 mm, the seams are welded in two layers, with a thickness of more than 10 mm - three layers or more, with each previous seam being pre-cleaned of slag and scale.

Multi-pass seams are not practiced in gas welding, since it is very difficult to apply narrow beads.

During gas welding, internal stresses and deformations arise, since the heating area turns out to be more extensive than, for example, in arc welding. Appropriate measures must be taken to reduce deformations. For this we recommend:

– evenly heat the product;

– select an adequate welding mode;

- evenly distribute the deposited metal over the surface;

- adhere to a certain order of suturing;

- do not get carried away with the implementation of tacks.

Various methods are used to combat deformations:

1. When making butt joints, the weld is applied in a reverse step or combined way, dividing it into sections 100–250 mm long (Fig. 94). Since the heat is evenly distributed over the surface of the weld, the base metal is practically not subject to warping.

Rice. Fig. 94. The sequence of applying a seam when welding butt joints: a - from the edge; b - from the middle of the seam

2. The reduction of deformations is facilitated by their balancing, when the subsequent seam causes deformations that are the opposite of those caused by the previous seam.

3. The method of reverse deformations also finds application, when, before welding, the parts are laid so that after it, as a result of the action of deformations, they take the desired position.

4. The preheating of the parts to be joined also helps to fight deformations, as a result of which a smaller temperature difference between the weld pool and the product is achieved. This method works well when repairing cast iron, bronze and aluminum products, as well as if they are made of high carbon and alloy steels.

5. In some cases, they resort to forging the weld (in a cold or hot state), which improves the mechanical characteristics of the weld and reduces shrinkage.

6. Heat treatment is another way to eliminate developed stresses. It can be preliminary, carried out simultaneously with welding, or an already finished product is subjected to it. The heat treatment mode is determined by the shape of the parts, the properties of the metals being welded, conditions, etc.

Cold welding method at home You can weld the joints of linoleum panels in two ways - hot, that is, with infrared rays and hot air, and cold. The first welding method is mainly used in production, and at home -