Patent ID: 7713362

Claim:
Method for producing a plate of steel which is resistant to abrasion and whose chemical composition comprises, by weight: 0.24%≦C<0.35% 0%≦Si≦2% 0%≦Al≦2% 0.5%≦Si+Al≦2% 0%≦Mn≦2.5% 0%≦Ni≦5% 0%≦Cr≦5% 0%≦Mo≦1% 0%≦W≦2% 0.1%≦Mo+W/2≦1% 0%≦B≦0.02% 0%≦Ti≦1.1% 0%≦Zr≦2.2% 0.5%<Ti+Zr/2≦1.1% 0%≦S≦0.15% N<0.03% optionally up to 1.5% of copper, optionally at least one element selected from Nb, Ta and V at contents such that Nb/ 2+Ta/4+V≦0.5%, optionally at least one element selected from Se, Te, Ca, Bi, Pb at contents which are less than or equal to 0.1%, the balance being iron and impurities resulting from the production operation, the chemical composition further complying with the following relationships: C*=C−Ti/4−Zr/8+7×N/8≧0.095% and: 1.05×Mn+0.54×Ni+0.50×Cr+0.3×(Mo+W/2) 1/2 +K>1.8 with: K=0.5 if B≧0.0005% and K=0 if B<0.0005%, according to which the plate is subjected to a thermal quenching processing operation which is carried out in the heat for rolling in the hot state or after austenitization by reheating in a furnace, in order to carry out the quenching: the plate is cooled at a mean cooling rate greater than 0.5° C./s between a temperature greater than AC 3 and a temperature of from approximately T=800−270×C*−90×Mn−37×Ni−70×Cr−83×(Mo+W/2), to T-50° C., the plate is then cooled at a mean core cooling rate Vr<1150×ep −1.7 and greater than 0.1° C./s between the temperature T and 100° C., ep being the thickness of the plate expressed in mm, the plate is cooled as far as ambient temperature and optionally planishing is carried out.