Welding defects and measures of austenitic stainless steel seamless pipe

1. Intergranular corrosion and its prevention
Intergranular corrosion is common in the welding of austenitic stainless steel seamless pipes. This type of defect mainly occurs at the grain boundary and is a more dangerous type of defect. Especially as the corrosion deepens and intensifies, the damage problem caused by it becomes more serious. It cannot be ignored. Intergranular corrosion is mainly caused by the loss of chromium on the surface of grains during welding, which makes it easy to be corroded in these chromium-deficient areas, eventually leading to a decrease in strength and the risk of fracture along grain boundaries.

In order to better prevent intergranular corrosion problems, it is necessary to strictly control the selection of welding rods. It is not only necessary to control its carbon content, but also to give priority to welding rods containing higher stable elements such as titanium or niobium, to better optimize the subsequent welding effect. . During the welding process, it is even more necessary to standardize the welding operation. It is required to speed up the welding speed as much as possible to avoid staying in a certain area for too long. At the same time, the cooling treatment of the high-temperature area is ensured to ensure the formation of a uniform austenite structure and avoiding corrosion. Phenomenon.

2. Thermal cracks and their prevention
Hot cracks are also a common defect in the welding process of austenitic stainless steel seamless pipes. The occurrence of such problems will also reduce the strength of austenitic stainless steel seamless pipes, which may lead to serious fracture risks in the future. Thermal cracks are mainly concentrated at the grain boundaries because the excessive temperature range occurs during the welding process, which can easily lead to the problem of impurity segregation. It is easy for large stress to occur during cooling shrinkage, and then obvious deformation.

Preventing and treating this hot crack defect also requires strict control of the entire welding process. For example, during the treatment of the weld metal, it should be promoted to present a dual-phase structure, and the iron element should be strictly controlled while avoiding possible S and P impurities. In this way, we can better control the welding quality, avoid serious problems of impurity segregation, and optimize the overall anti-cracking effect. Strictly control the cooling rate during the welding process to avoid temperature runaway problems, which can also better improve the prevention and control effect of hot cracks.

3. Stress corrosion cracking and its prevention
The phenomenon of severe stress corrosion cracking during the welding of austenitic stainless steel seamless pipes cannot be ignored. It is mainly caused by severe corrosion problems in the corresponding welded joints under the action of tensile stress, which in turn causes cracking hazards and ultimately directly leads to the failure of the welded joints.