HIGH-STRENGTH COLD-ROLLED STEEL SHEET AND STEEL SHEET WITH COATING THAT FEATURES EXCELLENT THERMAL HARDENABILITY AND MOULDABILITY AND METHOD OF THEIR PRODUCTION Russian patent published in 2014 - IPC C22C38/12 C21D8/02 C23C2/00 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, particularly to production of cold-rolled steel sheet to be used in motor-car production, various structures, instrument boards, etc. Sheet is made of steel containing in wt %: 0.0010-0.0040 of C, 0.05 or less of Si, 0.10-1.0 of Mn, 0.10 or less of P, 0.03 or less of S, 0.10 or less of Al, 0.0050 or less of N, 0.005 to 0.025 of Nb, Fe and unavoidable impurities making the rest. [% Nb]/[% C] ratio makes ≤10, [% Mn]/[% C] ratio makes ≥100. Sheet features tensile strength (TS) of at least 340 MPa, thermal hardening of at least 30 MPa, uniform elongation of at least 18% and elongation corresponding to yield strength (YP-EL) after ageing not over 1.0%.

EFFECT: higher thermal hardenability and mouldability.

18 cl, 7 dwg, 3 tbl, 1 ex