Welding crack problems in stainless steel containers
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Recent 304 containers manufactured through manual arc welding for vertical seams developed cracks; these cracks were located on the weld seam, present in both longitudinal and transverse directions. Material analyses of the base metal and welding materials conducted afterward revealed no issues, and no cracks appeared during horizontal seam welding. Experts, please analyze why this happened. I’m a newbie, please give me your support!
Did the crack appear during welding or after welding? 1. What type of welding rod are you using? Check if it is suitable for vertical welding? Check the welding rod. 2. Use a low wire energy.
The cracks appeared after welding; A102 welding rods were used, and material analysis of these rods showed no issues.
Austenitic stainless steel welds have a certain tendency to develop thermal cracks, especially in single-phase austenitic stainless steels with high nickel content (such as types 25–20), where such cracks are more likely to occur during welding. The main reasons for the occurrence of thermal cracks are as follows: 1. The thermal conductivity of austenitic stainless steel is less than 1/3 that of low-carbon steel, while its linear expansion coefficient is much higher; therefore, significant welding stresses are generated in the joint after welding. 2. Elements in stainless steel such as carbon, sulfur, phosphorus, nickel, etc., will form low-melting eutectics in the molten pool. For example, the melting point of Ni3S2 formed from Si and Ni is 645°C, whereas the melting point of the Ni–Ni3S2 eutectic is only 625°C. 3. The liquid-solid distance in stainless steel is large, the crystallization time is long, and impurity segregation is relatively severe. Methods to reduce the tendency of thermal cracking in stainless steel welding: 1. Use a welder with low wire energy. 2. Use a narrow groove. 3. Rapid cooling after welding
Thank you for the answer from the 4th floor, but the problem is that no cracks appeared in the transverse welds. The welding material and parameters were all the same; in fact, the current used during transverse welding was even higher than that used during vertical welding.
Elements in stainless steel such as carbon, sulfur, phosphorus, nickel, etc., form low-melting eutectics in the molten pool. During cooling, crystallization occurs at a later stage, so these impurities accumulate on the surface of the weld. Your welding rod and base material are of satisfactory quality, but the content of elements that form low-melting-point eutectic impurities may be close to the upper limit allowed for satisfactory quality. Furthermore, during vertical welding, the weld metal tends to flow downward, and low-melting eutectics accumulate on the surface of the weld to a greater extent than during horizontal welding; this is why, as the original poster mentioned, cracks occur in vertical welding while no cracks appear in horizontal welding
Well, I basically agree with what was said on floor 6.
It’s really a teacher; I’ve also learned a lot from them. Thank you first.
Preheat the base material first, maintain the interpass temperature during welding, and give it a try