| 摘要 |
PURPOSE:To obtain effectively a hard steel wire having high strength and high toughness by controlling a cooling rate according to the content of C in the stage of cooling a wire formed by rolling from a carbon steel with water and coiling thereof then subjecting the wire to controlled air cooling. CONSTITUTION:The hard steel wire contg. 0.40-0.85wt% C is cooled with water and is wound into a ring shape. The wound wire is subjected to the controlled air cooling in a force air cooling zone. The controlled air cooling is executed at 650 deg.C quick cooling limiting temp. and 25-35 deg.C/sec cooling rate when 0.60%<=C<=0.85%. The quick cooling limiting temp. is made 600 deg.C and the cooling is executed at a cooling rate of 25-40 deg.C/sec when 0.40%<=C<=0.60%. The cooling rate from the quick cooling limiting temp. down to 400 deg.C is set at 10-20 deg.C/sec regardless of the carbon content. The high-strength high- toughness hard steel wire for direct rolling which does not require a lead patenting treatment is stably obtd. by the above-mentioned method. |
