EXTRA-LOW CARBON STEEL SHEET FOR SPOT WELDING

摘要

PURPOSE: To produce an extra-low carbon steel sheet having both characteristics of workability and spot-weldability. ;CONSTITUTION: This steel sheet is the extra-low carbon steel sheet consisting of ≤0.004% C, ≤0.1% Si, ≤0.5% Mn, ≤0.010% P, ≤0.025% S, ≤0.010% N, 0.01-0.10% Al, and as necessary, further containing one or more kinds among 0.01-0.10% Ti, 0.005-0.060% Nb, 0.0001-0.0030% B and the balance Fe with inevitable impurities, and having C concd. layer on the surface layer satisfying the following inequalities. 0.007%≤Cs≤0.5%, 0.005%≤Ca≤0.1%, 100μm≤T≤0.3×tμm, wherein, Cs is C surface concn. of the C concd. layer (wt.%), Ca is average C concn. of the C concd. layer (wt.%), T, depth of C concd. layer (μm), and (t), sheet thickness (μm). This steel sheet can be applied to be as a surface treatment steel sheet basides as a hot-rolling sheet.;COPYRIGHT: (C)1995,JPO