ROLLED SHEET MADE FROM HIGH-STRENGTH STEEL Russian patent published in 2020 - IPC C22C38/46 C21D8/02 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely to rolled sheet with thickness of up to 50 mm from high-strength steel for shipbuilding, crane building, transport and heavy machine building. Steel contains elements at following ratio, wt. %: carbon 0.08–0.10, silicon 0.15–0.35, manganese 1.20–1.35, chrome 0.80–1.00, nickel 1.85–2.00, copper 0.40–0.50, molybdenum 0.25–0.35, vanadium 0.07–0.09, aluminium 0.018–0.05, calcium 0.0001–0.005, barium 0.0001–0.005, sulphur not more than 0.005, phosphorus not more than 0.010, nitrogen not more than 0.007, tin not more than 0.010, bismuth not more than 0.010, iron is the rest, wherein carbon equivalent of CET, calculated by expression CET = C + (Mn + Mo)/10 + (Cu + Cr)/20 + Ni/40, is not more than 0.40 %. After tempering, the share of rack martensite in the middle of the thickness of rolled stock is not less than 25 %, and the difference Δ between the lath of the rack martensite on the surface and in the middle over the thickness of the rolled metal is not more than Δ = 0.043t² − 1.46t + 23, where t is rolled metal thickness, mm.

EFFECT: obtaining rolled stock with required mechanical properties, namely, guaranteed yield point 960 MPa, relative elongation value of not less than 10 %, relative narrowing in thickness direction of not less than 35 %, average impact value at test temperature of −20 and −40 °C not less than 46 J.

1 cl, 2 tbl, 1 ex