| 摘要 |
The invention concerns weldable steel building components whereof the chemical composition comprises, by weight: 0.10 % </= C </= 0,22 %, 0.50 % </= Si </= 1.50 %, AI </= 0.9 %, 0 % </= Mn </= 3 %, 0 % </= Ni </= 5 %, 0 % </= Cr </= 4 %, 0 % </= Cu </= 1 %, 0 % </= Mo + W/2 </= 1.5 %, 0.0005 % </= B < 0.010 %, N </= 0.025 %, optionally at least one element selected among V, Nb, Ta, S et Ca, in contents less than 0.3 %, and/or among Ti and Zr in contents not more than 0.5 %, the rest being iron and impurities resulting from preparation, the aluminium, boron, titanium and nitrogen contents, expressed in thousandths of %, of said composition further satisfying the following relationship: B </= 1/3 x K+ 0.5, (1) with K = Min (l*; J*), I* = Max (0; I) and J* = Max (0; J), I = Min(N; N-0.29(Ti-5)), J = Min {N; 0.5 (N 0.52 AI + 2ROOT j(N 0.52 AI)<2> + 283)}, the silicon and aluminium contents of the composition additionally verifying the following conditions: if C > 0.145, then Si + AI < 0.95 and whereof the structure is bainitic, martensitic or martensitic/bainitic and further comprises 3 to 20 % of residual austenite.
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