The solution is to preheat the metal before welding. Propane, standard gas or acetylene welding torch is used to preheat the welding area of the workpiece, and the preheating temperature is 150~260 °C, and then welded. The purpose of preheating the weld area metal is to prevent the weld area from cooling too quickly and not causing the weld to crack or not fuse.
First, in order to prevent thin metal from burning through and reduce the welding current, the thin metal cover cannot be welded to the thick steel pipe at this time; Second, the welding current is too high to burn through the thin metal cover. What should I do at this point? There are two main workarounds: (1) Adjust the welding current to avoid burning through the thin metal cover, and at the same time preheat the thick steel pipe with a welding torch, and then weld the two metal structures by thin plate welding process. (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 90% and reduce the residence time on the thin metal cover. It should be noted that a good welded joint can only be obtained when proficient in this technique.
Yes, mainly in the welding process using a heat dissipation rod. If a solid round rod is inserted into a thin-walled round tube, or a solid rectangular rod is inserted into a rectangular tube, the solid rod will take away the heat of the thin-walled workpiece and prevent burnout. In general, solid round or rectangular rods are tightly fitted in most hollow or rectangular tube materials supplied. When welding, care should be taken to keep the weld away from the end of the tube, the end of the tube is the weakest area that is most prone to burnout. A schematic of using the built-in heat sink to avoid burn-through is shown in Figure 1.
The best process method is to file or grind the area around the weld before welding, because galvanized or chromium-containing metal sheets not only contaminate and weaken the weld, but also release toxic gases during welding.