21-4N气阀钢模铸坯组织、夹杂物及碳化物解析  

Analysis of microstructure,inclusions and carbide of 21-4N gas valve steel by mold cast billet

作　　者：吴强 朱浩然 张晓宇 季灯平 刘斌 付建勋 WU Qiang;ZHU Haoran;ZHANG Xiaoyu;JI Dengping;LIU Bin;FU Jianxun(Center for Advanced Solidification Technology,School of Materials Science and Engineering,Shanghai University,State Key Laboratory of Advanced Special Steel,Shanghai 200444,China;Zhejiang Qingshan Iron and Steel Co.,Ltd.,Lishui 323000,China;Angang Group Beijing Research Institute,Beijing 102200,China)

机构地区：[1]上海大学材料科学与工程学院先进凝固技术中心,省部共建高品质特殊钢冶金与制备国家重点实验室,上海200444 [2]浙江青山钢铁有限公司,浙江丽水323000 [3]鞍钢集团北京研究院,北京102200

出　　处：《冶金分析》2023年第11期12-21,共10页Metallurgical Analysis

基　　金：国家自然科学基金(52074179)。

摘　　要：21-4N奥氏体气阀钢是制造发动机排气门的关键材料,钢基体组织、夹杂物、碳化物的分布状态,对产品服役寿命有重要影响。本文基于Thermo-Calc 2020b计算了21-4N气阀钢相转变及碳化物析出情况,使用金相腐蚀、金相显微镜、扫描电镜以及扫描电镜自带的能谱仪和X射线衍射(XRD)检测技术对该钢模铸坯夹杂物、组织和碳化物进行解析。研究表明:21-4N气阀钢夹杂物主要是以Cr-Mn-Al-Ti-O为主的氧化物、以Cr-Mn-Al-Ti-O-N为主的氧氮复合夹杂物和以MnS为主的硫化物,夹杂物密度、平均等效直径、面积比例分别为45~61个/mm^(2)、2.9~3.2μm、0.044%~0.061%,夹杂物等效直径集中分布于2~5μm;21-4N气阀钢晶粒平均直径由边部的76.3μm线性增大到心部的119.2μm,基体组织由奥氏体和碳化物组成,其中碳化物包括沿晶界析出的M23C6块状碳化物和由γ+M23C6构成的“类珠光体组织”。从边部至中心,“类珠光体组织”平均等效直径、密度以及面积百分比,分别从10.3μm增长到26.3μm、85个/mm^(2)增长到148个/mm^(2)、1.85%增长到8.52%,总体呈增大趋势。21-4N austenitic gas valve steel is the key material for manufacturing engine exhaust valves.The distribution state of steel matrix structure,inclusions and carbides has an important impact on the service life of the products.In this paper,the phase transformation and carbide precipitation of 21-4N valve steel were calculated based on Thermo-Calc 2020b.The inclusions,microstructure and carbides in mold billet were analyzed by means of metallographic corrosion,metallographic microscope,scanning electron microscope(SEM),energy dispersive spectrometer and X-ray diffraction(XRD)equipped in SEM.The researches showed that the inclusions in 21-4N gas valve steel were mainly composed of Cr-Mn-Al-Ti-O-based oxides,Cr-Mn-Al-Ti-O-N-based oxygen-nitrogen compound inclusions and MnS-based sulfides,and the inclusion density,average equivalent diameter,and area ratio was 45-61 pieces/mm^(2),2.9-3.2μm,and 0.044%-0.061%,respectively.The equivalent diameter of inclusions was concentrated in 2-5μm.The average grain diameter of 21-4N gas value steel increased linearly from 76.3μm at the edge to 119.2μm in the center.The matrix structure was composed of austenite and carbide,where in the carbides included M23C6 massive carbides precipitated along the grain boundaries and the"pearlite-like structure"composed ofγ+M23C6.From the edge to the center,the average equivalent diameter,density and area percentage of the"pearlite-like structure"increased from 10.3μm to 26.3μm,from 85 pieces/mm^(2) to 148 pieces/mm^(2),and from 1.85%to 8.52%,showing an overall increasing trend.

关 键 词：21-4N 气阀钢 模铸坯 夹杂物 碳化物 扫描电镜(SEM) X射线衍射(XRD) 

分 类 号：TF03[冶金工程—冶金物理化学]