| 摘要 |
PURPOSE:To reduce the amount of fuel required to temper a steel pipe by controlling the hardening time of the steel pipe by learning so that the hardening finish temp. is kept within a permitted range and by tempering the hardened steel pipe before the temp. of the steel pipe lowers. CONSTITUTION:When a steel pipe is subjected to on-line hardening and tempering, in the case where the hardening finish temp. of the last steel pipe exceeds the upper limit of a permitted range, a predetermined hardening time is prolonged. In the case there the hardening finish temp. is below the lower limit of the permitted range, the hardening time is shortened. Thus, the hardening finish temp. is kept within the permitted range. The hardened steel pipe is immediately tempered.
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