高温扩散退火对4Cr5Mo2V热作模具钢显微组织与冲击性能的影响

doi:10.13251/j.issn.0254-6051.2024.11.018

摘要/Abstract

摘要： 采用光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD),并结合冲击试验,探究了高温扩散退火及其顺序对4Cr5Mo2V热作模具钢组织和性能的影响。结果表明:高温扩散退火显著改善了4Cr5Mo2V热作模具钢电渣锭中的枝晶偏析,使热轧后的带状组织较轻。钢锭中Cr、Mo和V等合金元素充分溶入基体,保证了后续热处理过程中元素的扩散和再配分,让球化退火组织中的碳化物分布更均匀,也增加了残留奥氏体的稳定性,使4Cr5Mo2V钢中保留了一定量的薄膜状残留奥氏体,进一步提升冲击性能。经3种工艺制备的4Cr5Mo2V热作模具钢淬火回火态碳化物均以MC、M₃C、M₆C和M₇C₃型为主。此外,热轧前进行高温扩散退火是解决4Cr5Mo2V热作模具钢电渣锭带状偏析和液析碳化物最经济高效的工艺,且提高冲击性能最明显。经高温扩散退火的试样冲击断口有较多韧窝,表现为韧性断裂;未经高温扩散退火的试样断口有较多解理面,表现为脆性断裂,且断口中的液析碳化物加速了裂纹的产生。

关键词: 高温扩散退火, 热作模具钢, 带状偏析, 液析碳化物, 冲击性能

Abstract: Effects of high temperature diffusion annealing and its sequence on the microstructure and properties of 4Cr5Mo2V hot working die steel were investigated by means of OM, SEM, TEM, XRD and in combination with impact tests. The results show that high temperature diffusion annealing can significantly improve dendritic segregation in the electroslag ingots of the 4Cr5Mo2V hot working die steel, so that the band segregation after hot rolling is lighter. The alloying elements such as Cr, Mo and V in the ingots are fully dissolved into the matrix, which ensures the diffusion and reallocation of the elements during the subsequent heat treatment, allowing for more uniformly distributed carbides in the spheroidizing annealed microstructure. It also increases the stability of the retained austenite to obtain a certain amount of thin-film retained austenite in the 4Cr5Mo2V steel, which can further enhance the impact property. Meanwhile, from the study of carbide evolution patterns, the carbides in the 4Cr5Mo2V steel prepared by the three processes after quenching and tempering are dominated by MC, M₃C, M₆C and M₇C₃ types. In addition, the high temperature diffusion annealing before hot rolling is the most cost-effective and efficient process to solve the band segregation and eutectic carbides in the electroslag ingots of the 4Cr5Mo2V steel and improve the impact property most obviously. The impact fractures of the specimens with high temperature diffusion annealing have more dimples and thus exhibit ductile fracture. The fractures of the specimens without high temperature diffusion annealing have more cleavage planes, and exhibit brittle fracture, meanwhile, the uneliminated eutectic carbides in the fracture accelerate cracking.

Key words: high temperature diffusion annealing, hot working die steel, band segregation, eutectic carbide, impact property

中图分类号:

TG156.2

左鹏鹏, 岳斌, 朱月凡, 唐宇轩, 张攀, 郭富玉, 闵娜. 高温扩散退火对4Cr5Mo2V热作模具钢显微组织与冲击性能的影响[J]. 金属热处理, 2024, 49(11): 123-131.

Zuo Pengpeng, Yue Bin, Zhu Yuefan, Tang Yuxuan, Zhang Pan, Guo Fuyu, Min Na. Effect of high temperature diffusion annealing on microstructure and impact property of 4Cr5Mo2V hot working die steel[J]. Heat Treatment of Metals, 2024, 49(11): 123-131.

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