铌钛微合金化异型坯表面横裂纹的形成机理分析  被引量:4

Analysis of Formation Mechanism of Surface Transversal Crack in Nb-Ti Microalloyed Beam Blank

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作  者:樊超 杨忠民[1] 李昭东[1] 陈颖[1] 王慧敏[1] FAN Chao, YANG Zhongmin, LI Zhaodong, CHEN Ying, WANG Huimin(Department of Engineering Steels, Central Iron and Steel Research Institute, Beijng 100081, Chin)

机构地区:[1]钢铁研究总院工程用钢研究所

出  处:《热加工工艺》2018年第5期247-251,共5页Hot Working Technology

基  金:中信-CBMM铌钢R&D资助项目(2015-D081);国家863计划项目(2015AA03A502)

摘  要:在Gleeble-1500D热模拟试验机上进行了Nb-Ti复合微合金化钢的高温拉伸试验,测定了铌钛微合金钢的高温塑性曲线。针对S355ML H型钢异型坯出现的表面横裂纹现象,利用OM、SEM技术手段分析了异型坯表面裂纹的微观形貌及裂纹周边微观组织。结果表明:在低应变速率下,铌钛复合微合金化钢的高温塑性曲线存在两个脆性区间及一个高温塑性区间;铌钛微合金异型坯表面横裂纹形成是在高温塑性曲线的第Ⅲ脆性区间内,沿原奥氏体晶界先共析的铁素体网膜展开,呈现出沿晶断裂特征;晶界先共析转变形成的铁素体网膜及Nb/Ti(C,N)析出相共同导致了异型坯裂纹的产生,其中先共析铁素体网膜是主要因素。High temperature tensile test of the Nb-Ti microalloyed steel was carried out on the Gleeble-1500 thermal simulation testing machine. Its high temperature plastic curve was measured. Aiming at the phenomenon of surface transverse crack in $355ML H type steel beam blank, the morphologies of surface cracks and the microstructure around the crack were analyzed by means of OM and SEM. The results show that: at low strain rate, the high temperature plasticity curve of Nb-Ti microalloyed steel has two brittle areas and a high temperature plastic zone; the surface transverse cracks of the Nb-Ti microalloyed beam blank is in the third brittle zone of the high temperature plasticity curve, cracks along the proeutectoid ferrite omentum of the original austenite grain boundary spread, exhibiting the intergranular fracture characteristics; ferrite omentum and Nb/Ti omentum (C, N) precipitates formed by proeutectoid transition in grain boundary jointly lead to the formation of the cracks in beam blank and the proeutectoid ferrite omentum is the main factor.

关 键 词:H型钢 异型坯 铌钛复合微合金化 表面横裂纹 高温塑性 

分 类 号:TG249.7[金属学及工艺—铸造] TG142.33[一般工业技术—材料科学与工程]

 

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