| 摘要 |
PURPOSE: Provided is a method for producing Cr-Mo steel which has an improved strength and weldability by reducing the carbon contents to 0.10% or less and optimizing conditions for the normalizing thermal treatment. CONSTITUTION: The method is performed by subjecting a hot rolled steel plate containing 0.10 wt% or less of C, 0.80 wt% or less of Si, 0.1 to 1.0 wt% of Mn, 0.8 to 3.5 wt% of Cr, 0.3 to 1.6 wt% of Mo, 0.08 wt% or less of Al, 0.010 wt% or less of P, 0.004 wt% or less of S, 0.006 wt% or less of N and containing one or two or more selected from a group consisting of 0.5 wt% or less of Cu, 0.5 wt% or less of Ni, 0.10 to 0.40 wt% of V, 0.005 to 0.1 wt% of Nb, 0.005 to 0.035 wt% of Ti and 0.0005 to 0.004 wt% of B(provided that the sum of Cu and Ni does not exceed 0.5 wt%) to a normalizing thermal treatment; and cooling the steel plate to a temperature of Ar1 to 500 deg.C at a speed of 2 to 10 deg.C/sec, followed by tempering and annealing.
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