Welding knowledge 4

1. What is low-frequency pulse? What welding is suitable for?
Answer: The pulse arc with a pulse frequency of 0.5-30 Hz is called low-frequency pulse welding. It is mainly used for TIG welding of non-ferrous metals such as stainless steel, steel and titanium.
2. What is medium-frequency pulse? What welding is suitable for?
Answer: The pulse arc with a pulse frequency of 30-500 Hz is called medium-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, titanium and other non-ferrous metals and MIG welding of stainless steel, aluminum and aluminum alloys.
3. Why does CO2 welding have spatter?
Answer: The molten droplet at the end of the welding wire is in short-circuit contact with the molten pool (short-circuit transition). Due to the strong overheating and magnetic contraction, the molten droplet explodes and produces spatter. The output reactor and waveform control of the CO2 welding machine can reduce spatter to a minimum.
4. Why can MIG/MAG high-current welding achieve jet transition without spatter?
Answer: During mig/mag welding, all metals have a critical current value for the transition from short-circuit transition to jet transition (e.g., φ1.2 carbon steel, stainless steel welding wire, current i≥260-280A). At this time, the arc is in a jet transition state, achieving spatter-free welding.
5. Why does mig/mag low-current welding require a pulsed power supply to achieve jet transition and spatter-free?
Answer: For mig/mag welding, when the welding current is lower than the critical current value, a pulsed power supply is used, and its pulse current is greater than the critical current value. The arc can also be in a jet transition state, achieving spatter-free welding (e.g., using Panasonic ag2/ge2 pulse mig/mag welding machine, φ1.2 carbon steel, stainless steel, aluminum and aluminum alloy welding wire has achieved pulse droplet transition when the current i≥80A, and its pulse current ip≥350A).
6. Why does the current display value change when the wire extension length changes during CO2 welding?
Answer: The longer the wire extension length (i.e., dry extension length) is, the greater the resistance of the wire is, the greater the current consumed by the resistance heat is, the smaller the welding current display value is, and the actual welding current is also smaller. Therefore, the wire extension length is generally set within the range of 12--20mm.
7. 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 wire feeding speed; adjust the arc voltage, that is, adjust the wire melting speed; obviously, the wire melting speed and feeding speed must be equal to ensure stable arc welding.
〈1〉When the welding current is constant, adjust the arc voltage to a higher level, the wire melting speed increases, the arc length increases, the molten droplets cannot transition normally, and generally fly out in large particles, and the spatter increases.
〈2〉When the welding current is constant, the arc voltage is adjusted to a low level, the melting speed of the welding wire is reduced, the arc length is shortened, the welding wire penetrates into the molten pool, the spatter is large, and the weld is poorly formed.
〈3〉The best matching effect of welding current and arc voltage: high droplet transfer frequency, minimal spatter, and beautiful weld formation.