METHOD OF PRODUCING HIGHER-STRENGTH HOT-ROLLED STOCK Russian patent published in 2013 - IPC C21D8/04 C22C38/58 C22C38/20 B21B1/26 

FIELD: metallurgy.

SUBSTANCE: smelt steel contains following substances, in wt %: carbon - 0.06-0.15, silicon - 0.1-0.50, manganese - 1.35-2.0, sulfur - not over 0.012, phosphorus - not over 0.020, chromium - 0.01-0.30, nickel - 0.01-0.30, copper - 0.01-0.30, aluminium - 0.01-0.06, niobium - 0.01-0.10, nitrogen - 0.002-0.010 and one or several elements of the following group, i.e. vanadium - 0.02-0.15, titanium - 0.01-0.15, molybdenum - 0.003-0.35, calcium - 0.0003-0.005, boron - 0.0001-0.005, tin - not over 0.015, iron and unavoidable impurities making the rest. Note here that total amount of niobium, vanadium and titanium does not exceed 0.22%. Now, steel is teemed and hot rolled. Hot rolling at finishing train is carried out at breakdown exit temperature not exceeding 1020°C and total deformation making at least 78% and finishing temperature of 770-850°C.

EFFECT: Then, strip is water cooled and coiled at 480-560°C Produced strip features strength class 500-550 with, mainly, ferrite-perlite structure while strip of strength class 600-650 features ferrite-bainite-perlite structure.

EFFECT: higher strength at forging

5 cl, 5 tbl