METHOD OF HEAT TREATMENT OF STEELS WITH LOW (LH) AND REGULATED (RH) HARDENING ABILITY OF 4TH GENERATION Russian patent published in 2020 - IPC C21D9/00 C21D9/34 

FIELD: metallurgy.

SUBSTANCE: invention relates to heat treatment of reduced (RH) and controlled (CH) hardenability steel. Method of workpieces processing from steel with carbon content more than 0.35 wt % with regulated (RH) or low hardenability (LH) includes hot pressure treatment and heat treatment. Steel is subjected to treatment, modified with elements of Al, N, Ti, V, Zr, Nb, Ta and Ca, hot pressing is performed at 1,180–1,300 °C and finish at temperature not lower than 850 °C, then billets are cooled to 550 °C with cooling rate of not less than 5 °C/s and then in air, preliminary thermal treatment is carried out by heating to temperatures of austenitisation with provision of through heating and obtaining of grain size of austenite not rougher than N 7, final thermal treatment with heating to austenitizing temperature is carried out by volumetric-surface hardening with provision of grain size of austenite not rougher than N 8 or through quenching with provision of grain size of austenite not coarser than N 10 and subsequent cooling by liquid coolant with provision of heat release coefficient more than 40,000 kcal/m²·h·°C, then tempering is performed at temperature below temperature Ac₁.

EFFECT: use of the disclosed method eliminates flaking.

1 cl, 6 ex, 3 dwg