| 摘要 |
PURPOSE:To produce inexpensively a large-diameter chain having excellent toughness and high tensile strength by forming a steel material made of the specified compsn. consisting of C, Si, Mn, Cr, P, S, Ca, Al, N and Fe then normalizing the steel material at an adequate temp. and allowing the same to cool. CONSTITUTION:The steel material having the compsn. consisting of 0.25-0.45% C, 0.15-0.55% Si, 1.00-1.90% Mn, <=0.50% Cr, <=0.040% P, <=0.005% S, 0.0010- 0.0080% Ca, 0.025-0.080% sol. Al, 0.0060-0.0200% sol. N, 2-6 Al/N ratio by weight and the balance substantially Fe with inevitable impurities is formed to a chain and is then subjected to a normalizing treatment by heating the same to the AC3 transformation point or above -950 deg.C; thereafter the chain is allowed to cool or is cooled preferably at about 0.1-1.0 deg.C/sec cooling rate of the surface layer from the heating temp. down to the A1 transformation point. The large- diameter and long-sized chain having >=70kg/mm.<2> tensile strength and excellent toughness is thus obtd. at the low cost of the steel material.
|
