热处理对电弧增材制造低碳马氏体不锈钢构件均匀性的影响  

Effect of heat treatment on homogeneity of CMT wire arc additive manufacturing low carbon martensitic stainless steel

作　　者：田宛平 金志起 谢广明[1] TIAN Wanping;JIN Zhiqi;XIE Guangming(State Key Laboratory of Rolling and Automation,Northeastern University,Shenyang 110819,Liaoning,China)

机构地区：[1]东北大学轧制技术及连轧自动化国家重点实验室,辽宁沈阳110819

出　　处：《钢铁》2024年第6期72-82,共11页Iron and Steel

基　　金：国家重点研发计划资助项目(2018YFA0707304);国家自然科学基金资助项目(52274378);国家自然科学基金资助项目(51774085)。

摘　　要：采用冷金属过渡(cold metal transfer,CMT)电弧熔丝技术制备了低碳马氏体不锈钢薄壁构件。为研究热处理工艺对构件微观组织和力学性能均匀性的影响,采用OM、SEM、EBSD、XRD等技术进行了组织表征,并通过拉伸和硬度试验测试构件力学性能。结果表明,沉积态构件底部为等轴晶,组织为板条马氏体+回火马氏体;顶部为粗大柱状晶,沿构件高度生长,组织为单一板条马氏体。自构件底部至顶部,沉积态构件硬度由314HV上升至361HV;抗拉强度先上升后下降,伸长率由23.5%下降至12.0%。拉伸断裂形式均为韧性断裂,但相比于底部拉伸断口,顶部的韧窝明显更大更浅,表明塑性急剧下降。晶粒形貌、相组成等变化是由随沉积高度增加,热积累增加、冷速下降以及自回火程度降低所导致。因此,沉积态构件的组织和性能存在不均匀性。另外,由构件中部的织构特征和横、纵向力学性能可知,沉积态构件的组织和性能存在各向异性。经热处理后,构件各处的自回火程度差异被消除,相组成全部变为回火马氏体与弥散分布的逆转变奥氏体,因此获得了均匀分布的硬度及拉伸性能。另外,由于热处理过程中发生了奥氏体重结晶,构件的各向异性也被消除。揭示了热处理对电弧增材低碳马氏体构件微观组织与力学性能变化的影响机制,为工程应用提供了指导。Low carbon martensitic stainless steel thin-walled components were prepared using cold metal transfer(CMT)wire arc additive manufacturing process.To investigate the effect of the heat treatment process on the microstructure and mechanical properties homogeneity of components,OM,SEM,EBSD,and XRD were used for microstructure characterization,and the mechanical properties of components were tested by tensile and hardness testing.The results show that the bottom of as-deposited component is composed of equiaxed crystal,and the phase is lath martensite+tempered martensite;the top is coarse columnar crystal,growing along the component height,and the phase is lath martensite.From the bottom to the top,the hardness of the as-deposited component increased from 314HV to 361HV.The tensile strength first increased and then decreased,and the elongation decreased from 23.5%to 12.0%.The tensile fractures are all ductile fractures.Compared to the bottom tensile fracture,the toughness dimples at the top are significantly larger and shallower,indicating a sharp decrease in plasticity.The changes in grain morphology and phase composition result from degree with the increasing of deposition height,the increase in heat accumulation,the decrease in cooling rate,and the decrease in self-tempering degree.Therefore,there is heterogeneity in the microstructure and mechanical performance of as-deposited components.Furthermore,the texture characteristics and transverse and longitudinal mechanical properties in the middle of the component reveal that the microstructure and properties of the deposited component are anisotropy.After heat treatment,the difference in self-tempering degree in various parts of the component is eliminated,and the phase composition is completely transformed into tempered martensite and dispersed reverse austenite,thus obtaining uniformly hardness and tensile properties.In addition,due to the occurrence of austenite recrystallization during the heat treatment process,the anisotropy of the components is also eliminate

关 键 词：低碳马氏体不锈钢 电弧增材 热处理 不均匀性 各向异性 

分 类 号：TG142.71[一般工业技术—材料科学与工程] TG156[金属学及工艺—金属材料]