METHOD OF PRODUCTION OF HIGH-STRENGTH ROLLED PRODUCTS WITH HIGH COLD RESISTANCE Russian patent published in 2017 - IPC C21D8/02 C22C38/44 B21B1/26 

FIELD: metallurgy.

SUBSTANCE: hot-rolled steel with a thickness of 8-50 mm and an increased level of cold resistance is produced at low temperatures, steel is made containing, wt %: carbon 0.07-0.12, manganese 0.20-0.70, silicon 0.10-0.50, chromium 1.00-1.40, nickel 1.50-2.00, molybdenum 0.10-0.30, copper 0.20-0.50, niobium 0.02-0.05, aluminium 0.01-0.06, nitrogen no more than 0.008, sulfur no more than 0.005, phosphorus no more than 0.010, iron is the rest. Slabs are produced. The slabs are heated in furnaces up to 1240-1260°C and rolled in a heavy plate mill to sheets of a final thickness at the rolling finishing temperature of not more than 890°C. They are cooled in the air. Then, the sheets are heated up to 920-940°C with total holding of 2.0-3.0 min/mm followed by water quenching and tempered at 690-740°C with a holding time of 1.5-2.8 min/mm, depending on the thickness in air cooling.

EFFECT: increased strength, toughness and contraction ratio in the direction of rolled product thickness.

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