Abstract: Grade (/% ：0.3C-1.6Si-0. 8Mn-1.1Cr-0.48Mo-0.1 V)of ultra high strength steel has been melted by 6 t vacuum induction & vacuum arc remelting processes. Through comparing the structures and mechanical properties of this steel melt with different superheat degree,the test results show that the rating of banding structure decreases from 2.5 to 1 and the fracture toughness average value increases from 85 MPa . m^1/2 to 116. 3 MPa . m^1/2 when VIM casting temperature decreases from (1 600 ± 10) °C to (1 560 ± 10) °C . So the low temperature casting process is the key to improve the uniform of material.

Key words: Casting Temperature,Ultra High Strength Steel,Fracture Toughness ,

摘要： 超高强度钢（/%:0.3C-1.6Si-0.8Mn-1.1Cr-0.48Mo-0.1V）采用6 t真空感应加真空自耗双联工艺冶炼。通过对比真空感应工序不同浇注温度冶炼钢的组织和力学性能,结果表明,当VIM浇注温度从（1 600±10)°C 降至（1 560±10)℃时,带状评级结果从2.5级降为1级,断裂韧性均值从85 MPa. m^1/2提高到116.3 MPa.m^1/2。因此,低温浇注是改善材料均匀性的关键方法。