| 摘要 |
PURPOSE:To finish the surface roughness in a U-tube into a very small smooth surface by bright-annealing a stainless steel tube, bending it into a U-tube and polishing its inner surface electrolytically. CONSTITUTION:A stainless steel blank tube is cold-drawn, degreased, pickled and cut into stainless steel tube having a prescribed size, then, bright-annealed and made free from residual strain generated in cold drawing stage. The cold drawing and bright annealing are repeated several times, then, the stainless steel tube is bent and formed by heat treatment into U-shaped cross section. This U-shaped stainless steel tube is fixed with its opening upward, an electrode rod is set so that it does not take an eccentric position in the U-tube, then, electrolyte is sent into the U-tube, an electrical voltage is impressed between the U-tube and an electrode rod to polish the inner surface of the U-tube electrolytically and to obtain a smooth finished surface having <=1mum surface roughness. The inner surface of a stainless steel tube having a U-shaped bending radius part can be easily polished to obtain smooth surface.
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