| 摘要 |
A process for manufacturing a medium-carbon steel plate having a graphitization of 50% or more with improved formability and weldability is disclosed, the process comprises the steps of: hot rolling a steel with a finishing temperature of 700 DEG -900 DEG C., the alloy composition of the steel consisting essentially of, by weight %: C: 0.20-0.70%, Si: more than 0.20 but not more than 2.00%, Mn: 0.05-0.50%, P: not more than 0.020%, S: not more than 0.010%, sol. Al: 0.01-1.00%, B: 0.0003-0.0050%, N: 0.002-0.010%, B/N: 0.2-0.8, Cu: 0-1.00%, Ni: 0-2.00%, Ca: 0-0.010%, and Fe and incidental impurities: balance, cooling the resulting hot-rolled steel plate at a cooling rate of 5 DEG -50 DEG C./s, coiling the steel plate at a temperature of 400 DEG -650 DEG C., and optionally, cold rolling the hot-rolled steel plate with a reduction in thickness of 20-85%, and annealing the cold-rolled steel plate at a temperature of 600 DEG - Ac1 for 1 hour or longer.
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