| 摘要 |
PURPOSE:To improve the ultrasonic flaw detectability of a tubular part made of a cast steel product and to make possible the inspection of the material for defect during use by deforming compressively the end of said part then recrystallizing the same to form the structure having the finer grains. CONSTITUTION:The end 2 of the tubular part 1 to be welded to the other part is cast to a larger outside diameter and a larger wall thickness in the stage of casting said part of an austenitic stainless steel, etc. of a 2-phase type having a ferrite phase. Such part is pressurized by a mandrel 5 and dies 4, 4 and is plastically deformed, by which the wall thickness is decreased and the part is stretched in the longitudinal-axial direction. The part is then heated to >=1,080 deg.C above the recrystallization temp. to form the finer crystal grains of the structure, by which the ultrasonic flaw detectability is improved.
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