Cracking in the spin-welded seam of 304 end caps
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Recently, our company has been manufacturing 304 stainless steel end caps, and the welds keep cracking. Please help us identify the reasons for this issue as well as possible preventive measures
What are the diameter and plate thickness of the end cap?
It might be because the plate is too thick; consider heat forming
Head sizes from 1 meter to 2.8 meters, with thicknesses of 8–14 available
It’s not very thick; ones with a thickness of 8/10 mm crack, and heat forming is costly along with the need for solution treatment
In my opinion, we should start by looking at the following negative aspects: 1. Determine whether there are significant changes in the geometry at the crack site, such as excessive weld height. 2. Inspect the welds and analyze any defects present. 3. Conduct chemical analysis on the raw materials to examine their chemical composition.
These points make sense. In the past, cracks have occurred during elbow forming, and that is due to impurities
For a previous unit here, the two stainless steel end caps (DN3000X12) were returned from an external supplier; after being welded together, cracks were found.
It is recommended that for the formed head, the following tests be conducted: 1. Ferrite content testing 2. Hardness testing； If all the limits are exceeded and cracking occurs, it’s hard to say
For stainless steel end caps, molding should be preferred; if the thickness is large, heat pressing combined with solution treatment should be used for reinforcement. Also, try not to use flat plates as materials for making end caps.
According to the specifications you mentioned, it is indeed not thick. If the issues related to the head manufacturing process are resolved, then we should consider what was mentioned in point 6# regarding the base material and jointing processes, such as whether the welds are polished smoothly