Welding Basic Knowledge Collection

1. What is welding?

Answer: Two or more materials (same or different) are heated or pressurized or both are used to achieve the bonding between atoms to form a permanent connection. The process is called welding.

2. What is an arc?

Answer: It is supplied by the welding power source and produces a strong and long-lasting gas discharge phenomenon between the two poles-called arc. 〈1〉According to the current type, it can be divided into: AC arc, DC arc and pulse arc. 〈2〉According to the state of the arc, it can be divided into: free arc and compressed arc (such as plasma arc). 〈3〉According to the electrode material, it can be divided into: melting electrode arc and non-melting electrode arc.

3. What is base metal?

Answer: The metal being welded is called the base metal.

4. What is molten drop?

Answer: The liquid metal droplet that melts at the tip of the welding wire and transitions to the molten pool is called molten droplet.

5. What is a molten pool?

Answer: The liquid metal part with a certain geometric shape formed on the weldment during fusion welding is called the molten pool.

6. What is a weld?

Answer: The joint formed in the weldment after welding.

7. What is weld metal?

Answer: The part of the metal formed by the solidification of the molten base metal and filler metal (welding wire, electrode, etc.).

8. What is shielding gas?

Answer: The gas used in welding to protect the metal droplet and the molten pool from the intrusion of harmful gases (hydrogen, oxygen, nitrogen) from the outside-the protective gas.

9. What is welding technology?

Answer: The general term for various welding methods, welding materials, welding processes and welding equipment and their basic theories-called welding technology.

10. What is the welding process? What does it have?

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, etc.

11. What is CO2 welding?

Answer: MIG welding using CO2 with purity> 99.98% as shielding gas is called CO2 welding.

12. What is MAG welding?

Answer: Use mixed gas 75-95% Ar + 25–5% CO2, (standard ratio: 80% Ar + 20% CO2) as shielding gas MIG welding—called MAG welding.

13. What is MIG welding?

Answer: <1> Use high-purity argon Ar≥99.99% as shielding gas to weld aluminum and aluminum alloys, copper and copper alloys and other non-ferrous metals;

〈2〉Melting electrode gas shielded welding of solid stainless steel wire with 98% Ar + 2% O2 or 95% Ar + 5% CO2 as shielding gas is called MIG welding.

<3> MIG welding with helium + argon inert gas as protection.

14. What is TIG (tungsten argon arc welding) welding?

Answer: Inert gas shielded arc welding with pure tungsten or activated tungsten (thorium tungsten, cerium tungsten, zirconium tungsten, lanthanum tungsten) as the infusible electrode, referred to as TIG welding.

15. What is SMAW (electrode arc welding) welding?

Answer: The arc welding method of welding with manual welding rod.

16. What is carbon arc gouging?

Answer: A surface processing method that uses a carbon rod as an electrode to generate an arc between the workpiece and the molten metal with compressed air (pressure 0.5-0.7Mpa). It is often used for root removal of welds, beveling, repairing defects, etc.

17. Why is CO2 welding more efficient than electrode arc welding?

Answer: <1> CO2 welding is 1-3 times higher than the melting speed and melting coefficient of electrode arc welding;

〈2〉The section of the groove is reduced by 50% compared with the welding rod, and the amount of deposited metal is reduced by 1/2;

<3> The auxiliary time is 50% of the electrode arc welding.

Three items in total: The ergonomics of CO2 welding is increased by 2.02–3.88 times compared with electrode arc welding

18. Why is the quality of CO2 welded joints better than that of electrode arc welding?

Answer: CO2 welds have a small heat-affected zone and small welding deformation; CO2 welds have low hydrogen content (≤1.6ML/100g), and have small pores and cracks; CO2 welds are well formed, with few surface and internal defects, and flaw detection qualification rate Higher than the electrode arc welding.

19. 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〉Compared with electrode arc welding, the equipment shift fee is reduced by 67-80%, and the cost is reduced by 20-40%;

〈4〉Reduce labor costs and working hours, and reduce costs by 10-16%;

〈5〉Save auxiliary man-hours, auxiliary material consumption and deformation correction costs;

Combining the five items, CO2 welding can reduce the total welding cost by 39.6-78.7%, an average reduction of 59%.

20. What is low frequency pulse? Which welding is applicable?

Answer: A 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.

21. What is an intermediate frequency pulse? Which welding is applicable?

Answer: A pulsed arc with a pulse frequency of 30-500Hz is called intermediate frequency pulse welding. Due to the arc compression effect, the arc is concentrated and the stiffness is good. It is mainly used for TIG welding of thin stainless steel, steel and titanium and other non-ferrous metals and MIG welding of stainless steel, aluminum and aluminum alloy.

23. Why is there spatter in CO2 welding?

Answer: The droplet at the end of the welding wire is in short-circuit contact with the molten pool (short-circuit transfer). Due to the strong overheating and magnetic shrinkage, the droplet bursts and splashes. The output reactor and waveform control of the CO2 welding machine can reduce spatter to a minimum.

23. Why can MIG/MAG high current welding achieve jet flow transition without splashing?

Answer: During MIG/MAG welding, all metals have the critical current value for short-circuit transition to jet transition (such as: φ1.2 carbon steel, stainless steel welding wire, current I≥260—280A), and the arc is in jet transition state. , Realize spatter-free welding.

24. Why does MIG/MAG low-current welding need to use a pulsed power supply to achieve jet transition without splashing?

Answer: For MIG/MAG welding, when the welding current is lower than the critical current value, use a pulsed power source. The pulse current is greater than the critical current value, and the arc can also be in a jet transition state to achieve spatter-free welding (such as: use Panasonic AG2/GE2 Pulse MIG/MAG welding machine, φ1.2 carbon steel, stainless steel, aluminum and aluminum alloy welding wire has realized pulse droplet transition when current I≥80A, and its pulse current Ip≥350A).