Abstract: The developed new steel 4Cr3. 75MoSiV for extrusion wheel （/% ： 0. 39C, 0. 95Si, 0. 35Mn, 3. 75Cr, 1. 25Mo, 0. 99V, 0.009 5N） and common steel 4Cr5MoSiV for extrusion wheel （/% ： 0. 42C, 1. 20Si, 0. 38Mn, 5. 04Cr, 1. 14Mo, 0. 85V, 0.035 ON） are melted by a 10 kg vacuum induction furnace, and forged to Φ18 mm bar for test, then 880 ℃ 1 h +720 °C. 1 h spheroidal annealing, 108 0 ℃ 15 min oil quenching, 550 ℃ 2 h +530 ℃ 2 h double tempering. The morphology, size, precipitates ratio and distribution of main carbide precipitates in both steels as well as the effect of precipitates on 500 times 600 °C -ambient continuous thermal fatigue behavior are studied. Results show that V₄C₃ + VC amount to 12% of total precipitates and there is 26% Cr₂₃C₆ precipitate in common steel 4Cr5MoSiV containing 5. 04% Cr, while in developed new steel 4Cr3. 75MoSiV the V₄C₃ + VC, which are favourable to increase thermal fatigue behavior, amount to 31% of total precipitates and the Cr₂₃C₆ precipitate has not been found in new steel ； after continuous thermal fatigue test the surface crack of steel 4Cr5MoSiV with thermal fatigue factor 3. 18 x 10^-3 is coarser and larger than that of steel 4Cr3.75MoSiV with thermal fatigue factor 1. 77 x 10^-3.

摘要： 开发的新型挤压轮用钢4Cr3.75MoSiV(/%:0.39C、0.95Si、0.35Mn、3.75Cr、1.25Mo、0.99V、0.009 5N)和常用挤压轮钢4Cr5MoSiV(/%:0.42C、1.20Si、0.38Mn、5.04Cr、1.14Mo、0.85V、0.035 0N)由10 kg真空感应炉熔炼,并锻成Φ18 mm试验用棒材,然后经880℃1 h+720℃1 h球化退火,1 080℃15 min油淬,550℃2 h+530℃2 h两次回火处理。研究了两种钢主要析出碳化物形貌、尺寸,析出比例和分布以及对500次600℃-室温连续热疲劳性能的影响。结果表明,含5.04%Cr的4Cr5MoSiV常用钢的析出物中V₄C₃+VC占12%,并有26%Cr₂₃C₆析出,而开发的4Cr3.75MoSiV新型钢中有利于提高热疲劳性能的析出物V₄C₃+VC占31%,未发现Cr₃₃C₆析出物;4Cr5MoSiV钢热疲劳损伤因子3.18×10^-3,连续热疲劳试验表面裂纹比热疲劳损伤因子为1.77×10^-3的新型4Cr3.75MoSiV钢表面裂纹粗大。 

关键词: 新型挤压轮钢4Cr3.75MoSiV, 析出相, 热疲劳性能