| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a bar and a wire rod by which excellent cooling workability is obtained and wire drawing by one time can be enabled. SOLUTION: This production method of the bar and the wire rod is characterized in that a steel slab for rolling composed of a high quenchable middle carbon steel containing 0.25-0.50 wt.% C as the essential composition is extracted from a heating furnace at <=950 deg.C extracting temperature, and the maximum reaching temperature at the center part of a material to be rolled is limited to <=990 deg.C in the rolling time at the front stage in the finish-rolling line. Then, the temperature at the center part of the material to be rolled just before the finish-rolling line, is regulated to 650-850 deg.C, and also, the finish-rolling is performed in >=2 passes and the reduction of area per one pass is performed at >=6%. Further, the surface temperature in the coiling time is regulated to <=850 deg.C, and after coiling, this material is cooled to <=200 deg.C at >=5 deg.C/sec cooling rate. Successively, after applying heat treatment kept in the temperature range of 740-800 deg.C for 10-10000 min, this material is cooled at 5-300 deg.C/hr cooling rate.
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