| 摘要 |
PURPOSE:To manufacture a refined steel pipe having uniform strength and a small difference in strength between both ends by making the temps. of both ends of a pipe different from each other before quenching. CONSTITUTION:A steel pipe contg. <=0.15wt% C is quenched and tempered to manufacture a refined steel pipe. At this time, the pipe to be heat treated is heated once in the austenite temp. range so that the temp. of one end of the pipe corresponding to the downstream side of a flow of quenching water is made higher than the temp. of the other end corresponding to the upper stream side. The pipe is then quenched.
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