METHOD FOR MANUFACTURING HIGH-STRENGTH FASTENING PRODUCTS OF STRENGTH CLASS 14.9 FROM ALLOY STEEL BY COLD VOLUME FORGING METHOD Russian patent published in 2023 - IPC C21D8/06 C22C38/42 C22C38/44 C22C38/46 

FIELD: 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 for manufacturing high-strength fasteners from alloy steel up to strength class 14.9 includes hot rolling of steel, coiling, cooling, spheroidising annealing, sizing of round rolled products, manufacturing fasteners by cold die forging followed by austenitisation, quenching and tempering. Hot rolling of steel is performed, containing, wt.%: C 0.33-0.38, Si 0.17-0.37, Mn 0.60-0.95, Al 0.010-0.070, Mo 0.35-0.45, V 0.10-0.25, Cr 0.90-1.20, Ni 1.30-1.60, Cu≤0.30, P≤0.025, S≤ 0.025, iron and inevitable impurities - the rest, cooling of hot-rolled product coiled into a bundle is carried out at a speed of 0.1-0.4°C/s, and spheroidising annealing is carried out by heating at a rate of 0.05-0.25°C/s to Ac1+(5-25)°C followed by slow cooling at a rate of 0.001-0.007°C/s to Ac1-(40-65)°C, austenitisation of fasteners is carried out by holding at the temperature of 850-870°C for 0.5-1.5 hours, followed by quenching into oil, tempering is carried out at 400-500°C for 0.5-1.5 hours.

EFFECT: high-strength fasteners of strength class 14.9 are produced.

1 cl, 3 tbl, 5 ex