| 摘要 |
PURPOSE:To manufacture the titled steel plate superior in low temp. toughness, by cooling molten steel contg. Ti, N to steel slab under a specified condition, reheating then hot rolling said slab. CONSTITUTION:Molten steel having compsn. contg. by weight, 0.01-0.15% C, 0.005-0.015% Ti, <0.006% N, under 1.0-3.5 Ti/N ratio is cooled by >=10 deg.C/min average rate from temp. at pouring time into mold to 1,100 deg.C of finally solidified part, to enter contained Ti into solid solution as large as possible, next, cooled slowly so that average cooling rate is regulated to <=5 deg.C/min up to the finally solidified part of 1,100-800 deg.C, to ppt. Ti in solid soln. state as extremely fine TiN. The slab is reheated to 900-1,250 deg.C, and hot rolled to manufacture the titled steel sheet superior in low temp. toughness of welded joint by large heat input welding.
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