Problems after pickling of submerged arc welds in 304 stainless steel
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Deities of Haichuan: During my inspections, I found that the 304 base material used for submerged arc welding had a thickness of 12 mm. The welding parameters were as follows: current of 380 A, voltage of 22 V, and welding speed of 420 mm/min for the root pass; current of 390 A, voltage of 35 V, and welding speed of 350 mm/min for the cover pass. The flux used was type 601. After acid washing and passivation, multiple defects were found on the surface of the product (please see the images). Upon investigation, it was determined that the welding had been done on newly opened and dried material. I would like to ask the experts here: what are the causes of this defect, and how can it be avoided? I am extremely grateful.
It’s not possible to make a judgment simply based on photos; first, radiographic testing should be carried out to check for any remaining internal defects, and to determine what type of defects they are – pores, inclusions, cracks? Only by determining the nature of the defect can further analysis be carried out, right?
The RT test was successful before pickling; I forgot to mention that in the post. It has been observed that after acid washing and passivation, a phenomenon similar to local cracking appears on the surface; the depth of penetration detected by PT testing is very shallow. Initially, it was suspected that this was caused by excessive reuse of flux, but upon investigating the situation on site, it was found that this type of weld was created using flux 601, which was heated and dried before use. This has led to blind spots in my ability to detect such surface defects; after calculating the relevant parameters, the heat input value turns out to be acceptable – what a headache……
This doesn’t seem to be a weld defect. It’s just a surface issue with the weld.
Surface problems are something that is often seen; they occur in submerged arc welding as well. Why is that? I don’t know
I consulted an expert yesterday, and they said it was caused by excessive heat input. I’m also not sure now whether it’s the excessive heat input caused by the welding process, or it’s a problem with the flux...