摘要
灰铁制动鼓在长时间行车过程中因连续制动导致温度升高而发生过早失效。利用金相显微镜、扫描电镜、高温拉伸试验机和常温拉伸试验机研究了HT250试样在常温至600℃范围的组织演变及拉伸性能;同时对500℃和600℃热暴露72 h后的HT250试样进行了组织观察及拉伸性能研究。结果表明:HT250显微组织主要由片层状珠光体和A型片状石墨组成,随着拉伸温度提高(室温~600℃),珠光体层片间距由室温的0.20μm逐渐增大到0.54μm。从400℃开始,珠光体片层组织开始出现粒状化,600℃时珠光体片层大部分已经完成粒化,此时石墨片也明显粗化。HT250常温拉伸强度为342 MPa,随拉伸温度升高抗拉强度逐渐下降,当试验温度升高到600℃时,抗拉强度下降至169 MPa。HT250在500℃和600℃热暴露72h后,珠光体片层间距宽化且片层组织部分粒状化,片状石墨明显粗化,抗拉强度分别为309 MPa和222 MPa,较同温度下高温拉伸强度大很多,同时HT250材料表层有一定氧化。提高HT250高温抗氧化性能及高温强度是提升其使用寿命的重要措施。
Gray iron brake drum failed prematurely due to the rapid temperature rise caused by continuous braking during driving.The microstructure and tensile properties of HT250 samples at high temperature and room temperature were studied by metallographic microscope,scanning electron microscope,high temperature tensile testing machine and room temperature tensile testing machine.At the same time,the microstructure and tensile properties of HT250 samples after thermal exposure for 72 h at 500℃and 600℃were also researched.The results show that the microstructure of HT250 is mainly composed of pearlite and A-type flake graphite.With the increase of tensile temperature(room temperature-600℃),the pearlite lamellar spacing gradually increases from 0.2μm at room temperature to 0.54μm at 600℃.Staring from 400℃,the lamellae in the pearlite group began to granulate.At 600℃,most of the pearlite lamellae had been granulated,and the graphite flakes were coarsened obviously.The tensile strength of HT250 is 342 MPa at room temperature,and gradually decreases to 169 MPa at 600℃with the increase of tensile temperature.After HT250 was exposed at 500℃and 600℃for 72 h,the spacing of the pearlitic lamellae was wide,the lamellae structure was partly granular,and the flake graphite was coarser obviously.The tensile strength was 309 MPa and 222 MPa respectively,which was much larger than that at the same temperature.At the same time,the surface layer of HT250 material was oxidized to some extent.Improving the oxidation resistance and strength of HT250 at high temperature is an important measure to improve its service life.
作者
于玉城
王振玲
YU Yu-cheng;WANG Zhen-ling(Panzhihua University,College of Vanadium and Titanium,Panzhihua 617000,Sichuan,China)
出处
《铸造》
CAS
北大核心
2023年第9期1140-1146,共7页
Foundry
基金
材料腐蚀与防护四川省重点实验室开放基金项目(2022CL13)。
关键词
灰铸铁
力学性能
氧化性能
显微组织
高温
grey iron
mechanical properties
oxidative properties
microstructure
high temperature
