| 摘要 |
PURPOSE: Provided is a rolling method of Bi-S free cutting steel rod wire with no surface microcrack due to hot brittleness. CONSTITUTION: In the rolling method of Bi-S free cutting steel rod wire comprising C 0.10wt.% or less, Si 0.05wt.% or less, Mn 1.20-1.40wt.%, P 0.0-0.09wt.%, S 0.27-0.33wt.%, Al 0.01wt.% or less, Bi 0.05-0.15wt.%, B 70-130ppm, balance Fe and other inevitable impurities in the temperature range of 1100 to 1250deg.C through rough rolling, process rolling, and finish rolling, this method is characterized in that Bi-S free cutting steel is subjected to rough rolling at a reduction ratio less than 10% through 1 to 2 pass, and through 3 to 5 pass, reduction ratio is 10-20%.
|
