Seguridd system for perfonas that are susceptible to drowning.

摘要

Method for producing a workpiece, specifically a sheet, steel resistant to abrasion whose chemical composition comprises, by weight: 0.1% _ C 0.23% 0% _ _ Si _ 2% 0% _ Al 0.5% 2% _ _ Si + Al _ 2% 0% Mn _ _ 2.5% 0% Ni _ _ 5% 0% Cr _ _ 5% 0% _ Mo 1% 0% _ _ W _ 2% 0.05% _ Mo + W / 2 _ 1% 0% _ B 0.02% 0% _ _ Ti _ 0 67% 0% Zr _ _ 1.34% 0.05% Ti + Zr / 2 _ 0.67% 0% _ S _ 0.15% N 0.03% - optionally 0% to 1.5% copper - optionally at least one taken from Nb, Ta and V in contents such that Nb element / 2 + Ta / 4 + V _ 0.5%, - optionally at least one element taken from se, Te, Ca, Bi, Pb in less than or equal to 0.1% content, the balance being iron and impurities resulting from the smelting, the chemical composition furthermore satisfying the following relationships: C * = C - Ti / 4 - Zr / 8 + 7 × N / 8 _ 0, 095% and Ti + Zr / 2 - 7 × N / 2 _ 0, 05% and 1, 05xMn + 0, 54xNi + 0, 50xCr + 0, 3x (Mo + W / 2) 1/2 + K 1, 8 with K = 1 if B _ 0.0005% and K = 0 if B 0.0005%, in which the part or the plate to heat treatment hardening, made to heat and hot forming such laminate or after austenitization by reheating in a furnace is subjected, for tempering: - 270xC * - - 90xMn - 37xNi - 70XCr the part or the plate at a speed higher average cooling at 0.5 ° C / s between a temperature above AC3 and a temperature between T = 800 cools - 83x (Mo + W / 2), and T-50 approximately, - then the part or the plate is cooled at a mean cooling rate in the heart Vr 1150xep- 1.7 and exceeding 0.1 ° C / s between T and 100 ° C temperature, ep the thickness of the part or plate expressed in mm, - the part or the plate is cooled to room temperature and is effected, optionally, a flattened.