| 摘要 |
PURPOSE:To obtain a product for cold forging without an intermediate annealing stage after preforming by subjecting a specifically composed low and middle carbon Al killed steel to an overaging treatment then to a lubricating surface treatment with calcium zinc phosphate prior to the preforming and normal forming. CONSTITUTION:A steel bar or wire contg. <=0.45 C, <=0.35% Si, 0.20-2.00Mn, <=0.040% P, <=0.025% S, 0.030-0.090% Sol.Al and >=60ppm N, >=15 Sol.Al/N and consisting of the balance Fe and unavoidable impurities is used. Such wire is subjected to the overaging treatment at 200-500 deg.C after hot rolling and is then subjected to descaling followed by the lubricating surface treatment with zinc phosphate or calcium zinc phosphate (Ca/Zn=0.1-1.0) and the lubricating primary treatment using mainly C17H35.COOONa. The wire is subjected to the lubricating secondary treatment excluding the 'zinc phosphate' in the above-mentioned primary treatment after preforming and is then subjected to the normal forming, by which the product for cold forging such as screw is obtd. In the equation, T.S': the tensile strength (kg/mm<2>) of the age hardened material after drawing, T.S: the tensile strength (kg/mm<2>) of the as-drawn wire. |
