Magnetically graduated steel rod having improved tensile and fatigue strength - is composed of 30-60 vol. per cent martensite with areas of non-magnetic austenite

摘要

Magnetically graduated steel rod is of compsn. (wt.%): 0.02-0.10 C, 0.50-1.0 Mn, 0.5-1.0 Si, 17-20 Cr, 5-8 Ni, 5-8 total C plus N, with balance being Fe and prodn. derived impurities. Cold-working results in 30-60 vol.% martensite steel, with localised heating producing areas of nonmagnetic austenitic structure. Tensile strength of min. 1275 MPa (130 Kgf/mm2) and fatigue strength of min. 588 MPa (60 kgf/mm2) are exhibited by the steel rod. Steel compsn. (wt.%) is pref. 17-18 Cr, 5-7 Ni, and 0.05-0.15 total C plus N. After cold-working, martensite content is 40-55 vol.% (allowing for a 25-45% reduction in cross-sectional area). A magnetically graduated steel rod having 30-60 vol.% martensite content (after cold-working), areas of nonmagnetic structure (due to localised melting), a tensile strength of min. 1275 MPa (130 kgf/mm2) and a fatigue strength of 588 MPa (60 kgf/mm2) has the following compsn. (9n wt.%): 0.05 C, 0.80 Mn, 0.80 Si, 17-20 Cr, 5-8 Ni, 0.05-0.20 total C plus N with the balance being Fe and prodn. -derived impurites. USE/ADVANTAGE - In control equipment for constuction machinery and hydraulic components in automobile suspensions. Improved fatigue strength.