METHOD FOR PRODUCING CALIBRATED COLD-HEADING STEEL Russian patent published in 2022 - IPC C21D1/20 C21D1/32 C22C38/44 C21D8/00 

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of metallurgy, namely, to manufacture of hot-rolled cold-heading steel. Steel is smelted with a chemical composition containing, wt.%: carbon 0.37 to 0.44, manganese 0.50 to 0.80, silicon 0.17 to 0.37, sulphur no more than 0.020, phosphorus no more than 0.020, chromium 0.40 to 0.90, nickel 0.40 to 1.65, copper no more than 0.20, molybdenum 0.15 to 0.25, nitrogen no more than 0.008, iron the rest. The steel is poured into a workpiece on a continuous casting machine and hot-rolled. During hot rolling, accelerated cooling is executed at a winding temperature of 763 to 772°C followed by accelerated air cooling at a rate of 2.1 to 8.7°C /s up to temperatures of 350 to 550°C providing production of a bainite steel structure. Spheroidising annealing is executed by heating in a furnace to a temperature of 720 to 725°C followed by isothermal holding for 4 hours and final air cooling to obtain a microstructure containing no less than 80% of granular perlite.

EFFECT: hot-rolled steel is produced, exhibiting a structure of granular perlite beneficial for subsequent cold stamping after rolling and hardware processing.

1 cl, 4 dwg