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1. Inert gas shielded welding:
At present, gas shielded welding is widely used in automobile repair stations and repair shops, but there are still many problems in practical applications.
1. Selection of body welding machine:
Most of the gas shielded welds selected by many repair shops are some industrial welders, not welders for body welding. The thickness of the body panel is generally about 1mm. The current requirement during welding is small and stable, otherwise it will be easy to weld or penetrate. In general industrial welding machines, the current is not stable enough during welding, and the fluctuation current of the grid voltage fluctuates, which is disadvantageous for the welding of thin plates.
2. Selection of welding consumables:
Nowadays, the welding wire of some small repair shop bodies is very random, and various grades of welding wire are available. The welding wire grade for body welding should be AWS-ER70S-6, the diameter of the wire is 0.6mm, and many repair shops are using 0.8mm wire. The 0.8mm welding wire is suitable for welding steel plates with a thickness of 1.2mm, and is not suitable for plates with a thickness of about 1.0mm for the integral body.
3. Selection of protective gas:
The general protective gas selected by the repair shop is 100% carbon dioxide. 100% carbon dioxide will have a large penetration during welding, and it is easy to cause problems such as melt penetration when welding thin plates. Therefore, the shielding gas should be a mixture of argon and carbon dioxide, the ratio of argon is 75%, and the proportion of carbon dioxide is 25%. This mixture is best when welding body parts.
When welding the body, follow the repair manual provided by the manufacturer, and the welding method required for each plate is different. Frequently used welding methods include lap welding, butt welding and plug welding. For the welding of body panels, pay attention to the current as small as possible. Do not use high current welding with small current welding. Segment welding is used for welding so that each weld can be sufficiently cooled to prevent deformation of the plate.
Second, resistance spot welding:
Resistance spot welding, which is widely used in body manufacturing, is now gradually being applied in repairs.
With the development of automotive materials, some ultra-high strength steels cannot be welded by gas shielded welding. The heat of gas shielded welding will destroy the internal structure of ultra-high strength steel and reduce its strength. Therefore, only resistance spot welding can be used for repair. Another advantage of resistance spot welding is that it is less affected by the operator. As long as the welding pressure, welding current and welding time are adjusted, the welding quality of each solder joint will not be greatly deviated, and the welding quality is relatively stable. .
In the repair work of resistance spot welding, attention should be paid to the control of welding quality. The welding current of a general resistance spot welding machine can reach about 6000A, and it can be welded to the general plate on the vehicle body. However, for some ultra-high strength steels, the welding current may reach more than 9000A, otherwise the solder joints cannot guarantee sufficient strength. Because the panel is not welded from the appearance, it is necessary to find the same material for test welding before making resistance spot welding. During the test welding, the three parameters of pressure, current and time of the welding are continuously adjusted, and then a destructive test is performed to verify whether the welding strength is reached.
In soldering, the density of solder joints is different from that of gas shielded solder. Gas shielded welding requires the same welds as in the original manufacturing, while resistance spot welds have 30% more solder joints than normal solder joints and cannot be soldered where they were originally soldered. The solder joint strength will increase as the density increases during soldering. However, if the solder joint distance is small to a certain extent, the strength will not increase but will decrease.
Welding methods used in the body: mainly inert gas shielded welding and resistance spot welding.