METHOD OF MANUFACTURE OF COLD-ROLLED HIGH-ENDURANCE BARS FROM DUAL-PHASE FERRITIC-MARTENSITIC STEEL Russian patent published in 2021 - IPC C21D1/26 C21D8/02 C21D9/46 C22C38/04 C22C38/12 C22C38/18 

FIELD: metallurgy.

SUBSTANCE: invention relates to manufacture of cold-rolled high-endurance bars from dual-phase ferritic-martensitic steel used in automobile industry. The method includes melting, teeming hot-rolling, cold-rolling and recrystallization annealing of steel. The steel is melted containing, in % wt.: carbon 0.11 to 0.15, silicon 0.02 to 0.50, manganese 2.0 to 2.4, chrome 0.25 to 0.55, molybdenum 0.10 to 0.30, niobium 0.01 to 0.03, iron and other unavoidable impurities. The finishing temperature of hot-rolling is 830 to 880 °C. Annealing is performed in a continuous annealing aggregate under conditions including heating to the annealing temperature of 760 to 800 °C, holding, slow cooling to a temperature lower than Ar₃, fast cooling to the starting overaging temperature, overaging and final cooling. The finishing temperature of fast cooling is 250 to 300 °C. The tension of the bar at the stages of heating and holding corresponds with unit load of 8 to 10 N/mm ², 9 to 10 N/mm² at the stages of slow and fast cooling and 6 to 8 N/mm ² at the overaging stage.

EFFECT: increased formability of a cold-rolled high-endurance bar from dual-phase ferritic-martensitic steel is achieved.

1 cl, 2 tbl