Quality objection processing: stainless steel polishing pits
Case Overview:
The customer complained that the surface of the purchased batch of stainless steel coils was slightly pitted during polishing.
Case Study:
By checking first, the batch of stainless steel is made of 304 material with 2B surface with a thickness of 1.0mm, all of which are first-class materials of regular large steel plants.
No surface defects can be observed on the surface of the raw material, and there are slight pits on the polished workpiece, which are densely distributed.
After sampling and analysis, the pits are irregular in shape, mainly long strips, and the size of the pits is relatively small. Through chemical analysis, Fe, Cr, and O are the main elements in the composition.
According to preliminary judgment, the possible reason for the defects is that the oxide scale produced during the annealing process is relatively thick, and there are tiny residues during the pickling process.
After the SPM leveling process, the inspectors cannot detect it with naked eyes during the finishing process but are exposed during the grinding and polishing process, forming pitting defects.
Process Result:
These pits can be eliminated by increasing the amount of grinding.