PRE-HARDENED MIRROR MOLD STEEL PLATE AND MANUFACTURING METHOD THEREFOR

A pre-hardened mirror mold steel plate, wherein the elemental composition thereof is: C: 0.28 to 0.36%, Si: 0.50 to 0.80%, Mn: 1.20 to 1.50%, P ≤ 0.020%, S ≤ 0.010%, Cr: 1.30 to 1.80%, Mo: 0.30 to 0.50%, Ni: 0.65 to 0.90%, V: 0.15 to 0.30%, H ≤ 1.5 ppm, and the balance of Fe and inevitable impurities. A pre-hardened mirror mold steel plate having high hardenability is obtained by using a manufacturing method comprising subjecting continuous casting billets to processes such as rolling, offline slow cooling, normalizing and tempering heat treatments. The advantages of the manufacturing method lie in that the production efficiency of continuous casting is high, the manufacturing costs are low, the hardness of the non-quenched and tempered state of a steel plate having a thickness of 20 - 180 mm reaches 38 - 42 HRC, the hardness fluctuation of the full thickness ≤ 2 HRC, and the level of flaw detection satisfies the requirement of GB/T2970I level. Plaque d'acier de moule à miroir pré-durci, sa composition élémen