What causes cracks in welding?
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Hello everyone. Axles made of 304 material, after being exposed to temperatures between 400 and 600 degrees, are now being welded using TIG welding; many small cracks appear at the weld seams. What should be done for welding in such cases?
Generally speaking, 304 material has good weldability. Cracks may occur due to insufficient surface preparation; in addition, it is advisable to keep the interlayer temperature during welding below 150 degrees. We have never encountered any cracks in 304.
It should be welding thermal stress; pay attention to the welding process, especially the quality of the electrodes, electrode diameter, welder current, welding techniques, heat retention, and material stress! !
Temperatures between 300 degrees and 600 degrees fall within the sensitization range for stainless steel, during which carbides precipitate; if cooling is performed isostatically before welding, the cracks may be liquidation cracks. We also need to test the chemical composition of your materials to see if the SP level is above the limit. These elements can form eutectics with low melting points, creating a liquid film at the grain boundaries, which leads to grain boundary cracks. :)
As mentioned on the 4th floor, the material issue should be checked. Under normal conditions, 304 stainless steel has fairly good weldability
Hello everyone, the shaft was taken out after being used for a period of time under conditions of 400–600 degrees. I wanted to weld small parts onto it, but this situation occurred unexpectedly. Is it the high temperature mentioned by the original poster that has caused changes in its structure?
Reply to 6# haifeng601: Austenitic stainless steel must not be used at such temperatures. Over a long period of time. Many carbides accumulate at the grain boundaries of the material. Intergranular corrosion will occur, and the intergranular strength will decrease. It cracks easily. I wonder how it would be to perform solution treatment on your shaft.
What is this shaft used for? Is it for stirring? What is the purpose of this 400-600 heat treatment process? Generally, one doesn’t do things like this. . If it’s to improve toughness and corrosion resistance? Why not use solidification treatment?