| 摘要 |
The purpose of the solution is reduction of the surface hardness of pipes and thereby a reduction in the wear of cutting tools with simultaneous shortening of thermal processing and reduction of production costs. The essence of the solution is that first the pipes are heated to 920 to 940 degrees C with retardation of 80 to 100 min., then it is cooled in a furnace without rate limitation to 710 to 730 degrees C with retardation of 60 to 120 min. according to the thickness of the walls of the pipe, whereupon the pipe is cooled in the furnace to 500 to 510 degrees C at a rate of 20 to 30 degrees C/hour and then cooled in air.
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