摘要
制备了适用于汽车排气歧管的不含铌和含0.1%、0.3%、0.5%和0.7%Nb(质量分数,下同)的铸造铁素体不锈钢,并对其进行了1100℃保温2 h炉冷退火、1050℃保温1 h水冷固溶处理和900℃保温1.5 h空冷稳定化处理。采用光学显微镜(OM)、扫描电镜(SEM)和X射线衍射(XRD)研究了钢的显微组织,包括析出相、晶粒大小和碳化物类型等,并测定了钢的力学性能。结果表明:添加铌能细化钢的铁素体晶粒,增加晶内析出相的数量;随着铌含量的增加,析出相的平均尺寸减小,从而使钢析出强化,且碳化物类型由TiC转变为TiC和Nb6C5;含0.5%和0.7%Nb的钢有金属间化合物Fe2Nb析出;铌使Laves相的析出温度从490℃提高至930℃,使MC型碳化物的析出温度从1220℃提高至1360℃;含0.5%Nb的钢力学性能最佳,抗拉强度达405.4 MPa,断后伸长率达18.2%。
Cast ferritic stainless steels not containing niobium and containing 0.1%,0.3%,0.5%,and 0.7%Nb(mass fraction,the same below)suitable for automobile exhaust manifold were fabricated,and were subjected to annealing that consisted of soaking at 1100℃for 2 h and furnace-cooling,to solution treating that consisted of soaking at 1050℃for 1 h and water-cooling,and to stabilizing that consisted of soaking at 900℃for 1.5 h and air-cooling.The microstructures of steels,including precipitated phases,grain size and carbide type,were investigated by means of OM,SEM and XRD,and the mechanical properties of steels were measured,too.The results comprised the following:(a)the addition of niobium to the steels caused the grains of ferrite to become finer,and the phases precipitated in the grain to increase;(b)as niobium content increased,the average size of precipitated phases decreased with the result that the steels were precipitation strengthened,and the carbide type changed from TiC to TiC and Nb6C5;(c)intermetallic compound Fe2Nb was precipitated in the steels containing 0.5%and 0.7%Nb;(d)the addition of niobium raised the precipitation temperature of Laves phase from 490℃to 930℃,that of MC type carbide from 1220℃to 1360℃.Furthermore,the steel containing 0.5%Nb showed the best mechanical properties,tensile strength and elongation reaching 405.4 MPa and 18.2%,respectively.
作者
赵天天
滕铝丹
金洋帆
张家成
杨弋涛
ZHAO Tiantian;TENG Lyudan;JIN Yangfan;ZHANG Jiacheng;YANG Yitao(School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China)
出处
《上海金属》
CAS
北大核心
2020年第2期63-68,共6页
Shanghai Metals
关键词
铌
排气歧管
铁素体不锈钢
显微组织
力学性能
niobium
exhaust manifold
ferritic stainless steel
microstructure
mechanical property
