The invention relates to an
alloy structure steel 42CrMo slab and a production method thereof. The method comprises the following steps: (1) charging molten iron containing less than or equal to 0.030% of S, less than or equal to 0.120% of P and less than or equal to 0.85% of Si into a furnace; (2)
smelting steel rods containing more than or equal to 0.10% of C and less than or equal to 0.008% of P in the converter at the temperature of 1650-1680 DEG C; (3) performing LF (
low frequency) refining and adjusting the target values of the components, so that C is 0.41-0.43% of C, Si is 0.23-0.27%, Mn is 0.58-0.62%, S is less than or equal to 0.010%, P is less than or equal to 0.015%, Cr is 0.92-0.98%, Mo is 0.17-0.19%, Cu is less than or equal to 0.20% of Cu and Ni is less than or equal to 0.30%, wherein the
discharge temperature of
molten steel is 1560+45 DEG C in a first furnace and 1550+45 DEG C in a
continuous casting furnace; (4) performing VD (vacuum degassing) refining under the vacuum of less than or equal to 67Pa for 15 minutes, meanwhile, performing weak
argon blowing stirring of 0.15-0.20MPa, feeding 140-150m of CaSi wire with the
diameter of phi13mm after breaking, and then performing weak
argon blowing for more than or equal to 10 minutes, wherein the
discharge temperature is 1560+ / -5 DEG C in the first furnace and 1550+ / -5 DEG C in the
continuous casting furnace; and (5) performing
continuous casting: controlling the water distribution of each secondary cooling zone of a
slab caster by adopting a primary water meter, wherein the light pressing interval fs is 0.45-0.95, the distribution coefficients are shown in table 2, and the pressing quantity is 3.8mm. The method meets the production requirements of large-section 42CrMo slabs.