Some clarifications regarding the surface quality of stainless steel submerged arc welds
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In the fabrication of stainless steel equipment, when the welding process of submerged arc welding is used for the equipment’s cylinder body, local overheating (blackening of the surface) and phenomena similar to shallow surface cracks are observed on the weld surface; these appear intermittently along both sides of the weld. However, X-ray inspections usually do not reveal any defects, and surface PT testing also fails to detect such issues. This problem can only be resolved by grinding the surface to a depth of about 1.0 mm. Such phenomena generally occur on the surface of the top weld layer (and are still visible after pickling), while the intermediate weld layers see these issues resolved during subsequent welding processes. But sometimes, the RT test film shows defects (in rare cases), similar to cracks. :(
The problems with replacing the welding machine consumables and welding wire still exist: (