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1. What is welding?
Answer: Two or more materials (the same or different), through heating or pressure or the combination of the two, to achieve the combination of atoms and form a permanent connection process called welding.
2. What is the welding process? What does it contain?
Answer: A set of technological procedures and technical regulations in the welding process. The content includes: welding method, pre-welding preparation processing, assembly, welding materials, welding equipment, welding sequence, welding operation, welding process parameters and post-welding treatment.
3. What is welding technology?
Answer: The general name of various welding methods, welding materials, welding processes and welding equipment and their basic theories-called welding technology.
4. What kinds of welding methods are there for electric welding (manual welding)?
Answer: Manual welding is manual arc welding, which is a manual operation welding method that uses arc as a heat source to melt the welding rod and the base metal to form a weld. According to the manual arc welding process standard, it mainly includes four welding methods: flat welding, vertical welding, horizontal welding and overhead welding.
5. what is co2 welding?
a: use co2 with a purity of> 99.98% to do the MIG welding of shielding gas-called co2 welding.
6. What is the welding power source?
Answer: In the electric welding machine, the equipment that supplies the electric energy required for welding and has the electrical characteristics suitable for welding is called the welding power source.
7. Why are there special requirements for arc welding power supplies? What are the requirements?
Answer: In order to ensure stable combustion of welding arc and adapt to various welding process requirements, arc welding power supply has the following special requirements:
<1> Static characteristics (or external characteristics) of arc welding power supply-that is, the relationship between steady-state output current and output voltage, with falling characteristics (constant current characteristics) and flat characteristics (constant voltage characteristics). The external characteristics of
A, electrode arc welding, TIG welding and carbon arc gouging power supply are falling (constant current) characteristics; The external characteristics of
B, CO2/MAG/MIG arc welding power supply are flat characteristics (constant voltage characteristics).
<2> dynamic characteristics of arc welding power supply-when the load state changes instantaneously (e. g. short circuit transition of droplet, particle transition, jet transition, etc.), the relationship between the output current and output voltage of arc welding power supply and time is used to characterize the response capability to load transient (I. e. dynamic response capability), referred to as "dynamic
characteristics".
<3> No-load voltage-the voltage displayed by the power supply before arc ignition.
<4> adjustment characteristics-change the external characteristics of the power supply to meet the requirements of the welding specification.
8. What is arc?
Answer: It is supplied by the welding power supply and produces a strong and lasting gas discharge phenomenon between the two poles-called arc.
<1> according to the type of current can be divided into: AC arc, DC arc and pulse arc.
<2> according to the state of the arc can be divided into: free arc and compression arc (such as plasma arc).
<3> according to the electrode material can be divided into: melting pole arc and non-melting pole arc.
9. Why does the arc voltage change when the arc length changes?
Answer: Determined by the external characteristics of the arc welding power supply, the longer the arc, the higher the arc voltage; the shorter the arc, the lower the arc voltage.
10. What is arc stiffness?
Answer: The degree to which the arc straightens along the axial direction of the electrode under the effects of thermal contraction and magnetic contraction.
11. What is arc spot welding?
Answer: The thin plate lap joint, using TIG/MIG/MAG/CO2 welding method, using a certain welding current, in a set time, forming a surface nugget, connecting the upper and lower plates of the welding method.
12. What is the base metal?
Answer: The metal to be welded is called the base metal.
13. What is a molten drop?
Answer: The liquid metal drop that melts after the tip of the welding wire is heated and transitions to the molten pool --- is called a molten drop.
14. What is a molten pool?
A: The liquid metal part with a certain geometric shape formed on the weldment during fusion welding is called a molten pool.
15. What is a weld?
A: The joint formed in the welded part after welding.
16. What is the weld metal?
Answer: The part of the metal formed by the solidification of the molten base metal and filler metal (welding wire, electrode, etc.).
17. What is protective gas?
Answer: The gas used to protect the metal droplets and the molten pool from the intrusion of harmful gases (hydrogen, oxygen, nitrogen) in welding --- protective gas.
18. What is mag welding?
Answer: Use mixed gas 75-95% AR +25-5% CO2 (standard ratio: 80% AR + 20% CO2) for MIG welding of shielding gas-called mag welding.
19. What is mig welding?
Answer: <1> Non-ferrous metals such as aluminum and aluminum alloy, copper and copper alloy are welded under molten electrode gas shielding with high purity argon ar≥ 99.99 as shielding gas; <2> the process method of welding solid stainless steel welding wire under molten electrode gas shielding with 98% ar + 2% o2 or 95% ar + 5% co2 as shielding gas-called mig welding. <3> MIG shielded welding with helium + argon inert gas mixture.
20. what is tig (argon tungsten arc welding) welding?
answer: inert gas shielded arc welding with pure tungsten or activated tungsten (thoriated tungsten, cerium tungsten, zirconium tungsten, lanthanum tungsten) as non-melting electrode is called tig welding for short.
21. what is smaw (electrode arc welding) welding?
a: the arc welding method of welding with a manually operated electrode.
22. What is carbon arc gouging?
Answer: It is a surface processing method that uses carbon rod as electrode to generate arc with workpiece and blow molten metal with compressed air (pressure 0.5-0.7mpa). Commonly used for weld root cleaning, groove gouging, repair defects, etc.
23. why is co2 welding more efficient than electrode arc welding?
a: <1> co2 welding is 1-3 times higher than electrode arc welding melting speed and melting coefficient;
<2> groove section is 50% smaller than electrode, and the amount of deposited metal is 1/2 smaller;
<3> auxiliary time is 50% of electrode arc welding.
Total of the three items: the work efficiency of co2 welding is increased by 2.02-3.88 times compared with that of electrode arc welding
24. Why is the co2 welding joint better than that of electrode arc welding?
Answer: co2 weld has small heat affected zone and small welding deformation. Co2 weld has low hydrogen content (≤ 1.6ml/100g) and small tendency of pores and cracks. Co2 weld is well formed, with few surface and internal defects, and the qualified rate of flaw detection is higher than that of electrode arc welding.
25. Why is the overall cost of co2 welding lower than that of electrode arc welding?
Answer: <1> The cross-sectional area of the groove is reduced by 36-54%, saving the amount of filler metal;
<2> Reduce power consumption by 65.4;
<3> The unit shift fee for equipment is 67-80% lower than that for electrode arc welding, and the cost is 20-40% lower.
<4> Reduce labor cost, labor cost and cost by 10-16%;
<5> Save auxiliary working hours, auxiliary materials consumption and deformation correction costs;
Combining five items, co2 welding can reduce the total welding cost by 39.6-78.7%, with an average reduction of 59%.
26. What is a low-frequency pulse? Which welds are suitable for?
Answer: Pulse arc with a pulse frequency of 0.5-30hz is called low-frequency pulse welding. Mainly used for tig welding of non-ferrous metals such as stainless steel, steel and titanium.
27. What is an intermediate frequency pulse? Which welding is suitable for?
A: Pulse arc with a pulse frequency of 30-500hz is called intermediate frequency pulse welding. Due to the arc compression effect, arc concentration and good stiffness, it is mainly used for tig welding of thin stainless steel, steel, titanium and other non-ferrous metals and mig welding of stainless steel, aluminum and aluminum alloys.
28. why is there spatter in co2 welding?
answer: the molten drop at the end of the welding wire is in short-circuit contact with the molten pool (short-circuit transition). due to the effect of strong overheating and magnetic contraction, the molten drop will burst and spatter will occur. The output reactor and waveform control of the co2 welder can reduce spatter to a small degree.
29. Why mig/mag high current welding can realize jet transition without spatter?
Answer: During mig/mag welding, all kinds of metals have the critical current value for short circuit transition to jet transition (such as φ1.2 carbon steel and stainless steel welding wire, current i≥ 260-280a). At this time, the arc is in the state of jet transition, realizing spatter-free welding.
30. Why does mig/mag small current welding use a pulsed power supply to achieve jet transition without spatter?
Answer: mig/mag welding, when the welding current is lower than the critical current value, a power supply with pulses is used, the pulse current is greater than the critical current value, and the arc can also be in a jet transition state to realize spatter-free welding (e.g. using Panasonic ag2/ge2 pulse mig/mag welding machine, Φ 1.2 carbon steel, stainless steel, aluminum and aluminum alloy welding wires have realized pulse drop transition when the current i≥ 80a, its pulse current ip ≥ 350a).
31. Why does the current display value change when the wire sticking length changes during CO2 welding?
Answer: The longer the wire sticking length (I. e. dry elongation), the greater the resistance of the wire, the greater the current consumed by resistance heat, the smaller the welding current display value, and the smaller the actual welding current. Therefore, the wire extension length is generally set in the range of 12-20mm.
32. Why should the welding current and arc voltage be strictly matched during CO2/MAG/MIG welding?
Answer: During CO2/MAG/MIG welding, adjust the welding current-that is, adjust the feeding speed of the welding wire; adjust the arc voltage-that is, adjust the melting speed of the welding wire; Obviously, the melting speed and feeding speed of the welding wire must be equal to ensure stable arc welding.
<1> When the welding current is constant, the arc voltage is adjusted on the high side, the melting speed of the welding wire becomes larger, the arc length increases, the droplet cannot transition normally, and generally large particles fly out and spatter increases.
<2> when the welding current is constant, the arc voltage is adjusted to be low, the melting speed of the welding wire is reduced, the arc length is shortened, the welding wire is inserted into the molten pool, spatter is large, and the weld formation is poor.
<3> Welding current and arc voltage matching effect: high droplet transfer frequency, small spatter, and beautiful weld formation.
33. Why does the welding arc have the phenomenon of partial blowing?
Answer: During the welding process, the center of the arc deviates from the electrode axis due to the interference of the airflow, the effect of the magnetic field or the influence of the eccentricity of the electrode.
34. What is magnetic bias blowing?
Answer: When DC arc welding, the arc bias blowing is caused by the electromagnetic force in the welding circuit. By changing the position of the ground wire or reducing the welding current and changing the angle of the electrode, the influence of magnetic deflection can be reduced.
35. What is the self-regulation characteristic of the CO2 power arc system? Why is the fine welding wire used for CO2 welding?
Answer: Under the constant speed wire feeding system, when the arc length changes, the current and melting speed change, so that the function of arc length recovery becomes the self-regulation function of the power arc system. The smaller the diameter of the welding wire used, the stronger the self-regulating effect of the arc, the more stable the arc, and the less splash. This is the principle of fine welding wire for CO2 welding. Tangshan Panasonic CO2 welding machine through advanced control technology, the self-regulation of the arc is good, stable performance.
36. What is the load continuation rate of the welding machine?
Answer: The load continuation rate refers to the ability of the welding power supply to work continuously under a certain current. The national standard stipulates that the rated load continuation rate of manual welding is 60%, and that of automatic or semi-automatic welding is 60% and 100. For example, the rated current of 500KR2 welding machine is 500A when the rated load duration is 60%, and the welding current is ≤ 387A when the actual load duration is 100 (automatic welding).
37. What is the load persistence rate of the welding torch?
Answer: Refers to the ability of the welding torch to work continuously under a certain current.
<1> for example, the rated load duration rate of 350KR welding torch is 70% and the rated current is 350A during CO2 welding; When the actual load duration rate is 100 (automatic welding), the welding current is ≤ 290A. In MAG welding, the rated load continuation rate is 35%, and when the actual load continuation rate is 100, the maximum welding current is ≤ 207A.
<2> for example, the rated load duration rate of 500KR welding torch is 70% and the rated current is 500A during CO2 welding. When the actual load duration rate is 100 (automatic welding), the welding current is ≤ 418A. In MAG welding, the rated load continuation rate is 35%, and when the actual load continuation rate is 100, the maximum welding current is ≤ 296A.
38. What is the positive connection method?
Answer: During DC arc welding, the weldment is connected to the positive pole of the output end of the welding machine, and the welding gun (welding tongs) is connected to the negative pole of the output end. It is called "positive connection method" and also called positive polarity.
39. What is the reverse connection method?
Answer: When DC arc welding, the weldment is connected to the negative pole of the output end of the welding machine, and the welding gun (welding tongs) is connected to the positive pole of the output end. It is called "reverse connection method", also called reverse polarity. Alkaline welding rod (junction 507, etc.), carbon arc gouging, CO2 welding are reverse connection method.
40. What is the lag gas stop time?
Answer: After the welding arc is extinguished, the shielding gas delays 0 or 3-5 seconds and then stops the gas supply time; Generally, the lag gas stop time of TIG welding aluminum, stainless steel, titanium and other metals should be as long as 3-5 seconds.