Problems and Solutions Related to Welding Process of Thick and Thin Plates
1. What should be done if the thickness of the steel workpiece exceeds the maximum welding current that the welding machine can achieve when using gas metal arc welding (GMAW) and flux cored wire gas arc welding (FCAW) to weld steel workpieces?
The solution is to preheat the metal before welding. Preheat the welding area of the workpiece using propane, standard gas or acetylene welding torch, with a preheating temperature of 150-260 ℃, and then proceed with welding. The purpose of preheating the metal in the welding area is to prevent the weld area from cooling too quickly, so as not to cause cracks or incomplete fusion in the weld.
2. If it is necessary to use melting electrode gas shielded welding or flux cored wire gas shielded welding to weld a thin metal cover onto a thicker steel pipe, if the welding current cannot be adjusted correctly during welding, it may lead to two situations:
One is to reduce the welding current to prevent thin metal from burning through, and at this time, the thin metal cover cannot be welded to the thick steel pipe; Secondly, excessive welding current can burn through thin metal caps. How should this be handled?
There are mainly two solutions:
① Adjust the welding current to avoid burning through the thin metal cover, preheat the thick steel pipe with a welding torch, and then use thin plate welding technology to weld the two metal structures.
② Adjust the welding current to be suitable for welding thick steel pipes. When welding, maintain 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 proficient in this technique can good welding joints be obtained.
- When welding a thin-walled circular or rectangular thin-walled pipe to a thick plate, the welding rod is prone to burn through the thin-walled pipe part. Apart from the above two solutions, are there any other solutions?
Yes, mainly using a heat dissipation rod during the welding process. If a solid round rod is inserted into a thin-walled circular 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 or rectangular rods are tightly installed in most of the supplied hollow or rectangular tube materials. When welding, attention should be paid to keeping the weld away from the end of the pipe, which is the most vulnerable area to burn through. The schematic diagram of using the built-in heat sink to avoid burning through is shown in Figure 1.
- How should galvanized or chromium containing materials be welded to another part?
The best process method is to file or polish the area around the weld before welding, as galvanized or chromium containing metal plates not only contaminate and weaken the weld, but also release toxic gases during welding.