Martensitic stainless steel pump case product for manufacturing spray pump of containment for nuclear power plant

The invention relates to a martensitic stainless steel pump case product for manufacturing a spray pump of a containment for a nuclear power plant. High purity molten steel with low gas content and uniform components is obtained by intermediate frequency furnace and VOD duplexing smelting; process parameters are obtained by system design of industrial analysis, chromite sands are used in a pump case runner, and the outer layer of the chromite sands is cast by furan resin sands to ensure that the runner is smooth and level; the accuracy of a core assembly and a lower core is ensured by using a snap-gauge, so that the dimensional tolerance of the runner satisfies the requirement; thermal treatment process parameters are adjusted through a process test, in-furnace temperature, temperature raising rate, insulating temperature, quenching temperature and quenching transfer time are controlled, and the problems of low impact performance and high hardness are solved through tempering twice. The problem that previous cast product is more in porosity defect, severe in surface sand burning, poor in dimensional precision of the runner and relatively poor in mechanical property is solved, and the corrosion-resistant martensitic stainless steel pump case cast which is high in dimensional precision, few in technical defect, compact in internal tissue and free of sand burning in the cavity of the runner is obtained.