METHOD FOR MANUFACTURING HIGH-STRENGTH FASTENERS FROM ALLOY STEEL Russian patent published in 2023 - IPC C21D8/06 C22C38/32 C22C38/18 

FIELD: ferrous metallurgy.

SUBSTANCE: invention relates to methods for manufacturing high-strength fasteners and other critical products from alloy steel for transport, construction, mining and other types of equipment by cold die forging. The method of manufacturing high-strength fasteners from alloy steel using the cold die forging method includes smelting, out-of-furnace processing and continuous casting of steel, hot rolling, coiling and cooling of hot-rolled steel, spheroidizing annealing and calibration of round steel, production of fasteners from calibrated rolled steel using the cold die forging method followed by austenitization, hardening and tempering, while rolled products are made from steel containing, mass fraction of elements, %: C 0.30-0.35; Si 0.17-0.37; Mn 0.90-1.20; A1 0.010-0.070; Mo 0.30-0.50; Ti 0.02-0.06; N≤0.010; Cr 0.40-0.55; B 0.0005-0.007; Ni≤0.35; Cu≤0.30; P≤0.025; S≤0.025, iron and inevitable impurities - the rest, cooling of hot-rolled steel coiled is carried out at a speed of 0.1-0.4°C/s, and spheroidizing annealing is carried out by heating at a speed of 0.05-0.15°C/s to Ac1+(5-25)° C followed by slow cooling at a rate of 0.001-0.005°C/s to Ac1-(40-65)°C, austenitization of steel during final heat treatment of fasteners is carried out by holding at a temperature of 850-870°C for 0.5-1.5 hours followed by quenching in oil, tempering is carried out at 425-500°C for 0.5-1.5 hours.

EFFECT: production of high-strength fasteners of strength class 12.9 from alloy steel using the cold die forging method.

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