| 摘要 |
PURPOSE:To produce stably a high tensile steel plate having an excellent drop weight characteristic by subjecting a steel slab contg. a specific ratio each of C, Si, Mn, P, S and Al to heating, rolling and cooling under specific conditions. CONSTITUTION:The steel slab contg., by weight %, 0.03-0.15% C, 0.05-0.80% Si, 0.5-2.0% Mn, <=0.025% P, <=0.007% S and 0.01-0.10% Al and consisting of the balance iron and inevitable impurities is prepd. Such steel slab is heated to <=1,000 deg.C and is subjected to >=50% rolling reduction at <=850 deg.C. The rolling finish temp. is adjusted to (Ar3+20) deg.C to (Ar3-40) deg.C. The steel plate is then cooled at >=10 deg.C/sec cooling rate on the steel plate surface from the temp. region of Ar3 or (Ar3-60) deg.C to an optional temp. of 400-200 deg.C. The high tensile steel plate having about <=-60 deg.C NDT temp., about >=50kgf/mm<2> tensile strength and excellent drop weight characteristic is thus stably obtd.
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