US 10,308,995 B2 · Steel sheet having very high mechanical properties of strength and ductility

Abstract

The invention relates to the manufacture of a cold-rolled steel sheet having a strength of more than 900 MPa, an elastic limit of more than 700 MPa and distributed elongation of more than 12%, the composition of which includes, the contents being expressed as weight percentages: 0.26%≤C≤0.45%, 1.0%≤Mn≤3.0%, 1.0%≤Si≤3.0%, Al≤0.10%, 0%≤Cr≤1.5%, S≤0.005%, P≤0.020%, Nb≤0.1%, Ti≤0.020%, V≤0.015%, N≤0.01%, the remainder of the composition being iron and inevitable impurities resulting from the production process. The microstructure, given in surface proportions, comprises 13% to 25% residual austenite and 13% to 30% MA islands, the remainder consisting of bainite and possibly ferrite.

Claims16

Dependent claims

A cold-rolled and annealed steel sheet with mechanical strength greater than or equal to 900 MPa, an elastic limit greater than 700 MPa and uniform elongation greater than or equal to 12%, the composition of which comprises, expressed in percent by weight:

0.26%≤C≤0.45%;
1.0%≤Mn≤3.0%;
1.0%≤Si≤3.0%;
Al≤0.1%;
Cr≤1.5%;
S≤0.005%;
P≤0.020%;
Nb≤0.1%;
Ti≤0.02%;
V≤0.015%;
and
N≤0.01%;
a balance of the composition including iron and unavoidable impurities resulting from processing;
256xC+47xMn+150xCr+2260xNb>142;
and
a microstructure of the steel sheet including, in area percentages:
from 13 to 25% residual austenite;
and
from 13 to 30% islands of residual austenite and martensite;
a balance of the microstructure including bainite formed at a temperature from 360 to 440 degrees C.

17 more elements

Dependencies are inferred from the claim text.

Steel sheet having very high mechanical properties of strength and ductility

Life of this patent

Steel sheet having very high mechanical properties of strength and ductility

Life of this patent

Abstract

Claims16