HARDENED MARTENSITIC STEEL WITH LOW CONTENT OF COBALT, METHOD FOR MAKING PART FROM THAT STEEL, AND PART OBTAINED BY MEANS OF ABOVE SAID METHOD Russian patent published in 2013 - IPC C22C38/58 C22C38/54 C22C38/52 C21D6/04 C21D1/78 

FIELD: metallurgy.

SUBSTANCE: steel of the following composition, wt %, is made: C 0.18 - 0.30, Co 1.5 - 4, Cr 2 - 5, Al 1 - 2, Mo+W/2 1 - 4, V traces - 0.3, Nb traces - 0.1, B traces - 30 ppm, Ni 11 - 16, Si traces - 1.0, Mn traces - 4.0, Ca traces - 20 ppm, rare-earth metals traces - 100 ppm, O traces - 50 ppm, N traces - 20 ppm, S traces - 20 ppm, Cu traces - 1, P traces - 200 ppm; with that, if N ≤ 10 ppm, then Ti+Zr/2 traces - 100 ppm; with that, Ti+Zr/2 ≤ 10 N and if 10 ppm < N ≤ 20 ppm, then Ti+Zr/2 traces - 150 ppm, and iron and inevitable impurities are the rest. A part is made from the obtained steel and softening is performed at 600-675°C during 4-20 hours with further cooling in the air, tempering at 900-1000°C during at least 1 hour with further oil cooling or cooling in the air, which is rather fast to avoid emissions of intergranular carbides in matrix of austenite, and ageing at 475-600°C during 5-20 hours.

EFFECT: steel has high impact strength and mechanical strength.

26 cl, 1 dwg, 2 tbl