NOS525钢下底座本体热锻模具失效分析  

Failure analysis on hot forging mold for NOS525 steel bottom base body

作　　者：闫涛 李培震 李璐 董俊斌 杨智勇[2] Yan Tao;Li Peizhen;Li Lu;Dong Junbin;Yang Zhiyong(Baoji Bao De Li Electrification Equipment Co.,Ltd.,Baoji 721013,China;School of Mechanical and Electronic Control Engineering,Beijing Jiaotong University,Beijing 100044,China)

机构地区：[1]宝鸡保德利电气设备有限责任公司,陕西宝鸡721013 [2]北京交通大学机械与电子控制工程学院,北京100044

出　　处：《锻压技术》2024年第5期188-197,共10页Forging & Stamping Technology

基　　金：国家自然科学基金面上资助项目(NO.52372345)。

摘　　要：针对NOS525钢下底座本体热锻模具在早期服役过程中频繁发生表面塌陷和热疲劳裂纹失效的问题,结合下底座本体模具的失效形式及部位,采用直读光谱仪、洛氏硬度计、光学显微镜和扫描电镜分别对其材料成分、硬度和金相组织等进行了研究。同时,开展了模具不同深度及方向的取样设计,并进行了拉伸及冲击力学性能测试。此外,借助QForm软件对下底座本体的锻造过程进行仿真。试验和仿真结果表明:模具材料的显微组织中存在过长的针状马氏体和少量魏氏组织,属于晶粒粗大的过热组织,主要原因是模具在热处理过程中淬火温度过高或保温时间过长,加之回火不充分;下底座本体热锻过程中,模具工作面以及与飞边接触位置会产生明显的温度上升现象,模具工作时,型腔位置的最大应力接近试验所得的材料屈服强度,且超过了材料的疲劳强度,容易诱发模具上述部位发生表面塌陷和热疲劳裂纹,这与实际模具失效的情况相吻合。For the problems of frequent failure of surface collapse and thermal fatigue crack for hot forging mold of NOS525 steel bottom base body during early service,combined with the failure form and location of bottom base body mold,the material composition,hardness and metallographic structure were studied by direct reading spectrometer,Rockwell hardness tester,optical microscope and scanning electron microscope.Then,the sampling design of different depths and directions of the mold was carried out,and the tensile and impact mechanical properties were tested.Furthermore,the forging process of the bottom base body was simulated by software QForm.The test and simulation results show that there are excessively long acicular martensite and a small amount of Weinstein structure in the microstructure of the mold material,which belongs to the superheated structure with coarse grains.The main reason is that the quenching temperature of the mold is too high or the holding time is too long during the heat treatment process,and the tempering is not enough.During the hot forging process of the bottom base body,the temperature of the contact area between working surface of mold and flash edge obviously increases.When the mold is in operation,the maximum stress at the cavity position is close to the yield strength of the material obtained by the experiment,and exceeding the fatigue strength of the material,which is easy to induce surface collapse and thermal fatigue cracks in the above-mentioned parts of the mold,which is consistent with the actual failure of the mold.

关 键 词：NOS525钢 热锻模具 表面塌陷 热疲劳裂纹 失效分析 热处理 

分 类 号：TG147[一般工业技术—材料科学与工程]