The effect of relative process specifications such as LF+VD melting process, ingot mold design, argon protective casting process, high temperature homogenizing process and forging process for heavy ingots, quenching process and high temperature tempering process for mould blocks on material purity and hardness uniformity were systematically investigated. The test results show that: sulfur content can be controlled as low as 0.005%, and total oxygen content as low as 12×10-6 if slag basicity of LF and VD were kept within 3.5~4.0 and 3.0~3.5 respectively; rejection rate caused by inclusions at ingot bottom was reduced from 6.81% to 1.55% by optimizing the design of the 28 t ingot mold bottom taper shape and ingate chamfering; it was confirmed by argon protective casting test that argon flow rate should be controlled at 4~8 m3/h; the macro segregation and hardness deviation were improved from ≤ grade 3.0 and ≤ 5.0HRC to ≤ grade 2.0 and ≤ 3.5HRC respectively by adopting high temperature homogenizing process; the macro porosity and the ultrasonic testing result was improved from ≤ grade 3.0 and C/d to ≤ grade 2.0 and D/d respectively by applying FM forging method instead of drawing by flat anvil; the hardness deviation on the cross section of 650 mm×1 080 mm mould blocks was ≤ 3.5HRC by pre-hardening treatment (water-air alternatively timed quenching + high temperature tempering by electrical heating furnace).