Questions and Answers about Welding Basics (1)

First, the basic knowledge
1. What is welding?
A: Two or more materials (same or different), by heating or pressurizing or a combination of the two, to achieve the combination of atoms to form a permanent connection process called welding.


2. What is arc?
Answer: A strong and long-lasting gas discharge phenomenon is called between the two poles, which is supplied by the welding power source.
<1> According to the type of current, it can be divided into: alternating current arc, direct current arc and pulse arc.
<2> According to the state of the arc, it can be divided into: a free arc and a compressed arc (such as a plasma arc).
<3> According to the electrode material, it can be divided into: a melting arc and an infusible arc.


3. What is the base material?
A: The metal being welded - called the base metal.


4. What is a droplet?
Answer: The liquid metal droplets, which are melted at the tip of the wire and melted into the molten pool, are called droplets.


5. What is a molten pool?
Answer: The part of the liquid metal with a certain geometry formed on the weldment during welding is called the molten pool.


6. What is a weld?
A: 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, welding rod, etc.).


8. What is protective gas?
Answer: The gas used in the welding to protect the metal droplets and the molten pool from the harmful gases (hydrogen, oxygen, nitrogen) invaded.


9. What is welding technology?
A: The general name of various welding methods, welding materials, welding processes and welding equipment and its basic theory - called welding technology.


10. What is the welding process? What does it have?
A: A complete set of process procedures and technical regulations during the welding process. The contents include: welding method, pre-weld preparation, assembly, welding materials, welding equipment, welding sequence, welding operation, welding process parameters and post-weld treatment.


11. What is CO2 welding?
A: MIG welding with a purity of > 99.98% CO2 as a shielding gas - called CO2 welding.


12. What is MAG welding?
Answer: A gas-shielded gas shielded welding gas with a mixed gas of 75--95% Ar + 25--5 % CO2 (standard ratio: 80% Ar + 20% CO2) is called MAG welding.


13. What is MIG welding?
Answer: <1> Use a high-purity argon Ar ≥ 99.99% as a shielding gas to protect the welding of aluminum and aluminum alloys, copper and copper alloys and other non-ferrous metals;
<2> A process for welding a solid stainless steel wire by a gas-impregnated gas shield using 98% Ar + 2% O 2 or 95% Ar + 5% CO 2 as a shielding gas - called MIG welding.
<3> MIG welding with protection of æ°¦ + argon inert gas mixture.


14. What is TIG (Tungsten Arc Welding) welding?
Answer: Inert gas shielded arc welding with pure tungsten or activated tungsten (tantalum tungsten, tantalum tungsten, zirconium tungsten, tantalum tungsten) as the infusible electrode, referred to as TIG welding.


15. What is SMAW (electrode arc welding) welding?
A: The arc welding method of welding by manual manipulation of the 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 a compressed air (pressure 0.5-0.7 MPa) to blow the molten metal. Commonly used for weld root removal, planing groove, repair defects, etc.


17. Why is CO2 welding more efficient than electrode arc welding?
Answer: <1> CO2 welding is 1-3 times higher than the welding arc welding speed and melting coefficient;
<2> The section of the groove is reduced by 50% compared with the electrode, and the amount of deposited metal is reduced by 1/2;
<3> The auxiliary time is 50% of the electrode arc welding.
The total of three items: the efficiency of CO2 welding is increased by 2.02--3.88 times compared with electrode arc welding.


18. Why is the quality of the welded joint of the CO2 welded joint better than the electrode arc welding?
Answer: The CO2 weld has a small heat affected zone and small welding deformation; the CO2 weld has low hydrogen content (≤1.6ML/100g), and the porosity and crack tendency are small; the CO2 weld is well formed, the surface and internal defects are few, and the test pass rate is low. Higher than electrode arc welding.


19. Why is the overall cost of CO2 welding lower than 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> Equipment station fee is reduced by 67-80% compared with electrode arc welding, and the cost is reduced by 20-40%;
<4> Reduce labor costs, working hours, and reduce costs by 10-16%;
<5> Saving auxiliary working hours, auxiliary material consumption and correcting deformation costs;
According to the comprehensive five items, CO2 welding can reduce the total welding cost by 39.6-78.7%, with an average reduction of 59%.


20. What is a low frequency pulse? Which welding is suitable?
Answer: A pulsed arc with a pulse frequency of 0.5-30 Hz 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 the IF pulse? Which welding is suitable?
Answer: A pulsed arc with a pulse frequency of 30-500 Hz 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 non-ferrous metals such as thin stainless steel, steel and titanium, and MIG welding of stainless steel and aluminum and aluminum alloy.


22. Why is there a splash in CO2 welding?
Answer: The droplets at the end of the wire are in short-circuit contact with the molten pool (short circuit transition). The molten droplets break due to strong overheating and magnetic contraction, causing splashes. The output reactor and waveform control of the CO2 welder minimizes splashing.


23. Why does MIG/MAG high current welding achieve jet transition without splashing?
Answer: When MIG/MAG is welded, all metals have a critical current value that is converted from a short-circuit transition to a jet transition (eg φ1.2 carbon steel, stainless steel welding wire, current I≥260-280A). At this time, the arc is in a jet transition state. , to achieve no splash welding.


24. Why does MIG/MAG low 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, the pulsed power supply is used, the pulse current is greater than the critical current value, and the arc can also be in the jet transition state to achieve spatter-free welding (eg, using Panasonic AG2/GE2) Pulse MIG/MAG welding machine, φ1.2 carbon steel, stainless steel, aluminum and aluminum alloy welding wire have achieved pulsed droplet transition when current I≥80A, and its pulse current Ip≥350A).


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