| 摘要 |
PURPOSE:To produce a hot rolled steel sheet which can be formed and worked without requiring pickling and phosphate treatment and has excellent scale adhesion by subjecting a billet formed by adding a specific small amt. of Cr, Ni, etc. to a low- and middle carbon steel to hot rolling and quick cooling under specific conditions. CONSTITUTION:A billet formed by incorporating <=0.1% Cr, <=0.05% Ni and <=0.03% Cu or further <=0.1% 1 or >=2 kinds among Nb, Mo, V and Zr into a basic compsn. consisting of 0.03-0.25% C, <=0.04% Si, 0.2-1.0% Mn, <=0.025% P, <=0.015% S, <=0.08% Al and the balance Fe is reheated to >=1,100 deg.C. The billet is hot rolled at <=Ar3+50 deg.C to a sheet material and immediately after hot rolling, water is sprayed thereto to cool quickly the sheet down to <=500 deg.C at a cooling rate of >=40 deg.C/sec. Or the sheet is further cooled down to <=300 deg.C in a non-oxidative atmosphere in succession to said cooling, by which the production of the hot rolled steel sheet having excellent scale adhesion is made possible. |
