| 摘要 |
In a method of manufacturing a high tensile strength thick steel plate, a steel slab contains 0.03-0.055% of C, 3.0-3.5% of Mn, and 0.002-0.10% of Al, the amount of Mo is limited to 0.03% or less, the amount of Si is limited to 0.09% or less, the amount of V is limited to 0.01% or less, the amount of Ti is limited to 0.003% or less, the amount of B is limited to 0.0003% or less, and of which Pcm value representing a weld cracking parameter is fallen within the range of 0.20-0.24% and DI value representing a hardenability index is fallen within the range of 1.00-2.60, is heated to 950-1100°C. The steel slab is subjected to a rolling process with a cumulative draft of 70-90% when a temperature is in a range of 850°C or more, and then, the steel slab is subjected to a rolling process at 780°C or higher with a cumulative draft of 10-40% when a temperature is in a range of 780-830°C, and subsequently, accelerated cooling at a cooling rate of 8-80°C/sec is started from 700°C or higher and is stopped at a temperature between room temperature and 350°C.
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