| 摘要 |
The invention concerns a method for making hardenable steel plates by firing comprising: preparing a steel whereof the composition comprises, expressed in weight percent: 0.03 = C = 0.06, 0.50 = Mn = 1.10, 0.08: = Si = 0.20, 0.015 = A1 = 0.070, N = 0.007, Ni = 0.040, Cu = 0.040, P = 0.035, S = 0.015, Mo = 0.010, Ti = 0.005; provided that it comprises boron in an amount such that 0.64 = B/N = 1.60 the rest consisting of iron and impurities resulting from production; casting a slab of said steel, then hot rolling of said slab to obtain a plate, the final rolling temperature being higher than the point Ar3; winding said plate at a temperature ranging between 500 and 700 DEGREE C; then cold rolling of said plate at a reduction rate ranging between 50 and 80%; continuous annealing heat treatment for a time interval less than 15 minutes; and strain hardening with a reduction rate ranging between 1.25 and 2.5%. The invention also concerns the hardenable plates and the parts obtainable therefrom.
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