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Production method of excellent thick high-strength steel plate to brittle fracture propagation stop characteristics and high heat input welding heat affected zone toughness, and, thick high-strength steel sheet excellent in brittle fracture propagation stop characteristics and high heat input welding heat affected zone toughness
Production method of excellent thick high-strength steel plate to brittle fracture propagation stop characteristics and high heat input welding heat affected zone toughness, and, thick high-strength steel sheet excellent in brittle fracture propagation stop characteristics and high heat input welding heat affected zone toughness
As for production method of this thick high intensity steel sheet, mass % with, C: 0.05 - 0.12%, Si: 0.3% or less, Mn: 1 - 2%, P: 0.015% or less, S: 0.005% or less, B: 0.0003 - 0.003% and V: 0.01 - 0.15%, Al: 0.001 - 0.1%, Ti: 0.005 - 0.02%, N: 0.002 - 0.01%, and O: It contains 0.004%, or less after cooling the continuous casting throb which includes the iron and the inevitable impurity as a remainder to below the Ar3 200 , it re-heats to 950 - the 1100 , next, it does rolling where above the 900 the quantity under cumulative pressure is 30% or more roughly in continuous casting throb, next, it finishes finish rolling where above the 700 the quantity under cumulative pressure is 50% or more, rolling start temperature and finished rolling end temperature, together, the next formula {the 0.5 (throb heating temperature ( ))+1325} ( ) with going under the conditions which make below the temperature which is displayed making the rolling original plate, next, applying acceleration cooling and cooling the rolling original plate to below the 500 the B quantity which it makes the steel sheet, as for the aforementioned continuous casting throb, in the austenite body before the transforming the solid solution it does {the effective B quantity: Bef (%)}Calculation value is 0% or less, carbon equivalent Ceq satisfies 0.32 - 0.42% ranges.
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