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300 mm diameter YG1500 high strength stainless steel was produced by

VIM + VAR + forging process，the simulation analysis of the vacuum self-consumption melting speed and the primary dendrite spacing was carried out by Meltflow-VAR software with the range 4.0 kg/min-5.0 kg/min. The Gleeble compression test was conducted at 0.1 s

-1

and 1 s

-1

compression rates under 950 ℃-1 100 ℃conditions. Industrial-scale production trials were ultimately implemented using vacuum self-consumption smelting at 4.2 kg/min， forging heating temperatures of 1 100 ℃，1 040 ℃， with strain rates of 0.1 s

-1

and 1 s

-1

. The resulting

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300 mm bar products underwent rigorous analysis through metallographic examination， grain boundary angle measurement， and mechanical property testing.The results show that： forging process was carried out at a temperature of 1 040 ℃，the fracture toughness of YG1500 steel produced by forging process with an average strain rate of 0.1s

-1

can reach105 MPa.m

1/2

-115 MPa.m

1/2

，20 MPa.m

1/2

-30 MPa.m

1/2

higher than another group of processes，At the same time， the martensite plates in the steel are more uniform and smaller， and the number of large and small angle grain boundaries in the steel greater.