Dry elongation
Gas flow L=[(10-12)d] L/min
The length of the wire protruding conductive nozzle is the dry elongation length. The general empirical formula is 10-15 times the wire diameter L = (10-15) d. When the standard is large, it is slightly larger. The specification is small, slightly smaller.
Dry stretching too long: When the length of the welding wire extends too long, the greater the resistance heat of the welding wire, the faster the melting speed of the welding wire, which can easily cause the welding wire to fuse in sections, splash, melt depth, and unstable arc combustion. At the same time, the gas protection effect is not good.
Dry stretch too short: easy to burn the conductive nozzle. At the same time, the conductive nozzle is easy to clamp wire when it heats up. Splashes tend to clog the nozzle and melt deeply.
Table 1 Matching relationship between current and dry elongation
| Welding current (A) | ≤200A | 200-350A | 350-500A |
| Dry elongation (mm) | 10-15mm | 15-20mm | 20-25mm |
Gas flow
Gas flow L=[(10-12)d] L/min
Too large: generates turbulence, causing air intrusion and pores, especially for gas-sensitive materials (such as aluminum alloys, magnesium alloys, etc., which are generally internal pores)
Too small: poor gas protection (you can refer to the limit conditions, which means there is no protective gas, and honeycomb-shaped pores are prone to appear).
The wind speed is not affected when ≤2m/s.
Measures should be taken when the wind speed is ≥2m/s.
① Increase the gas flow rate.
② Take windproof measures.
Note: When air leakage occurs, air holes will appear on the weld. The air leakage point must be handled and cannot be supplemented by increasing the flow rate. There is no way to repair the air holes without removing them. It will only become more welded. many.
Arc force
When different plate thicknesses, different positions, different specifications, and different welding wires, different arc forces are selected.
Too large: hard arc, big splash.
Too small: soft arc, small splash.
Pressure force
Too tight: The welding wire is deformed, the wire feeding is unstable, and it is easy to cause wire jams and increase splashing.
Too loose: The welding wire is slipped, the wire is sent slowly, the welding is unstable, and it will also cause splashing.
Current, voltage
Empirical formula for the relationship between current and voltage of gas-protective welding: U=14+0.05I±2
The welding current should be correctly selected based on the thickness of the base material, the joint form and the diameter of the wire. During short circuit transition, try to choose a small current while ensuring penetration, because when the current is too large, it is easy to cause the dissolution pool to roll, not only does it splash large, but the molding is also very poor.
The welding voltage must form a good coordination with the current. The welding voltage is too high or too low, which will cause splash. The welding voltage should increase with the increase of the welding current and should decrease with the decrease of the welding current. The optimal welding voltage is generally between 1-2V, so the welding voltage should be carefully debugged.
The current is too large: the arc length is short, the splash is large, the feeling of a top hand, the remaining height is too large, and the two sides are not fused well.
The voltage is too high: the arc is long, the splash is slightly larger, the current is unstable, the remaining height is too small, the welding is wide, and the arc is easily burned.
Effects of fast welding speed on welding
The welding speed has an important impact on the quality of the interior and appearance of the weld. When the current voltage is constant:
The welding speed is too fast: the melting depth, melting width, and residual height are reduced, forming a convex or hump welding bead, and the toes are biting the flesh. When the welding speed is too fast, the gas protection effect will be damaged and pores are easily generated.
At the same time, the cooling speed of welding metal will be accelerated accordingly, thereby reducing the plasticity and toughness of welding metal. It will also cause a edge to appear in the middle of the welding, resulting in poor molding.
The welding speed is too slow: the molten pool becomes larger, the welding bead becomes wider, and the welding toes are overflowing. The gas in the molten pool is easily discharged due to slow welding speed. The metal structure of the weld is thick or burned through due to overheating.
When selecting welding parameters, the following conditions should be followed: the weld is beautiful in appearance and has no defects such as burning through, undercuts, pores, cracks, etc. The melting depth is controlled within a suitable range. The welding process is stable and the splash is small. There was a rustling sound while welding. At the same time, the highest productivity should be achieved.
Post time: Mar-10-2025