The importance of wall uniformity in large-diameter thick walled straight seam steel pipes

How to determine the grade of straight seam steel pipe welds in steel structures

According to the welding seam level according to the execution standards, it is divided into three levels, and the price of each level is also different. The first level welding seam undergoes inspection to see if there are any inclusions or fusion in the welding seam and the allowable repair length for the first level inspection is very small. Generally, only steel structure straight seam steel pipes or pile driving straight seam steel pipes use first level inspection and second level welding seams, the first level inspection is a test of the welding process and equipment of the manufacturer, as well as the experience of the operators. The second level inspection welding allows for several repairs compared to the first and loose welds, while the third level inspection is almost the same as the CB3091 standard. It is difficult to judge the quality of steel pipe welds with the naked eye. There is also an ultrasonic non-destructive testing method, which is convenient and can be manually tested outdoors. Most construction sites use this method to test the pipe connections.

The following is a brief introduction of the problems in submerged arc welding, such as the defects at the starting and stopping of air holes. The reason for the air holes in the weld is that the welding machine current is not well matched with the walking. If there are air holes in the weld, there is no lack of fusion under the flaw detection radiation. Hand welding is used to repair the problem. This happens in the process of metal and welding. When welding, there is single wire welding or double wire welding.