Welding problems of thick and thin plates and their solutions

1. When welding steel workpieces with molten electrode gas shielded (GMAW) and flux-cored gas shielded welding (FCAW), if the thickness of the workpiece exceeds the maximum welding current that the welder can reach, how will it be handled?

The solution is to preheat the metal before welding. Use propane, standard gas or acetylene welding torch to preheat the welding area of ​​the workpiece, the preheating temperature is 150-260℃, and then the welding is carried out. The purpose of preheating the metal in the welding area is to prevent the weld area from cooling too fast, and to prevent the weld from cracking or not fusing.

2. If it is necessary to weld a thin metal cover to a thicker steel pipe by using MIG or FW-wire gas shielded welding, if the welding current cannot be adjusted correctly during welding, two situations may result:

One is to prevent the thin metal from burning through and reduce the welding current. At this time, the thin metal cover cannot be welded to the thick steel pipe; the second is to burn through the thin metal cover if the welding current is too high. What should be done at this time?

There are two main solutions:

① Adjust the welding current to avoid burning through the thin metal cover. At the same time, use the welding torch to preheat the thick steel pipe, and then use the thin plate welding process to weld the two metal structures.

② Adjust the welding current to suit the welding of thick steel pipes. When welding, keep the residence time of the welding arc on the thick steel pipe at 90% and reduce the residence time on the thin metal cover. It should be pointed out that only when you are proficient in this technology can you get a good welded joint.

3. When welding a thin-walled round pipe or a rectangular thin-walled pipe fitting to a thick plate, the welding rod is likely to burn through the thin-walled pipe. In addition to the above two solutions, are there other solutions?

Yes, it mainly uses a heat sink during the welding process. If a solid round rod is inserted into a thin-walled round tube, or a solid rectangular rod is inserted into a rectangular pipe fitting, the solid rod will take away the heat of the thin-walled workpiece and prevent burning through. Generally speaking, solid round rods or rectangular rods are tightly installed in most of the hollow or rectangular tube materials supplied. When welding, keep the weld away from the end of the pipe. The end of the pipe is the weakest area that is most likely to burn through.

4. When it is necessary to weld galvanized or chromium-containing material with another part, how should the operation be performed?
The best method is to file or sand the area around the weld before welding, because galvanized or chromium-containing metal plates will not only contaminate and weaken the weld, but also release toxic gases during welding.