Welding of Thick and Thin Plates

1. When welding steel workpiece with GMAW and FCAW, if the thickness of workpiece exceeds the maximum welding current that the welder can reach, how to deal with it?

The solution is to preheat the metal before welding. The welding area of the workpiece is preheated by propane, gas or acetylene torch as specified in the standard. The preheating temperature is150-260℃, and then the welding is carried out. The purpose of preheating the metal in the weld area is to prevent the weld area from cooling too fast and from cracking or fusing.

2. When a thin metal cover is welded to a thicker steel pipe by using gas shielded arc welding (GMAW) or flux-coredarc welding (FCAW), if the welding current cannot be adjusted correctly, two kinds of situations may occur:

First, in order to prevent the thin metal from burning through and reduce the welding current, the thin metal cover can not be welded to the thick steel pipe at this time. Second, the welding current will burn through the thin metal cover. How should we deal with this?

There are two main solutions.

Firstly, adjust welding current to avoid burning through thin metal cap. At the same time, preheat thick steel pipe with welding torch, and then use thin plate welding process to weld the two metal structures. Secondly, adjusting the welding current to suit the welding of thick steel pipe. During welding, the residence time of welding arc on thick steel tube is 90%, and the residence time on thin metal cover is reduced. It should be noted that only skilled in this technology can get a good welded joint.

3. When a thin-walled pipe or rectangular thin-walled pipe fittings are welded to a thick plate, the welding rod is easy to burn through the thin-walled pipe part. In addition to the above two solutions, are there any other solutions?

Yes, the way is to use a heat sink in the welding process. If a solid bar is inserted into a thin-walled tube or a solid rectangular bar is inserted into a rectangular tube, the solid bar will take away the heat of the thin-walled workpiece and prevent burning through. Generally speaking, solid round or rectangular bars are tightly installed in most of the hollow or rectangular tube materials supplied. When welding, attention should be paid to keeping the weld away from the end of the pipe, because the end of the pipe is the most vulnerable area to burn-through.

The following Figure shows the use of built-in radiator rods to avoid burning through.

20181222170534

4. When galvanized or chromium-containing materials must be welded with another part, how should they be operated?

The best process is to file or grind the area around the weld before welding, because galvanized or chromium-containing metal sheets not only pollute and weaken the weld, but also release toxic gases during welding.

 

Relevant Welding Machine: 

MIG -270 800-800 MIG -350 800-800

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Post time: Dec-22-2018