摘要
针对50 mm厚规格的NM500耐磨钢板经火焰切割后存在的延迟裂纹现象,从裂纹形貌、夹杂物和组织特征、硬度分布以及产生机理等方面进行了研究.火焰切割后的宏观形貌表明:在NM500钢板的厚度中心区域存在明显的横向和纵向裂纹,火焰切割是产生横裂纹的主要原因,而纵裂纹主要是由横裂纹诱导产生的.采用光学显微镜(OM)、扫描电镜(SEM)、能谱分析仪(EDS)、透射电镜(TEM)和维氏硬度等技术,研究了厚规格NM500耐磨钢经火焰切割后出现延迟裂纹的机理.结果表明,裂纹扩展的驱动力主要为组织应力,体现在:1)连铸坯中存在的大尺寸硬质TiN夹杂经轧制后破碎形成尖角和孔洞,易聚H而产生较大的应力集中;2)火焰切割使马氏体析出大量碳化物,降低了热影响区的硬度,无法保证高强度的约束,从而在组织应力的作用下,促使横裂纹在TiN夹杂处萌生.
This paper describes the phenomenon of delayed cracks formed after cutting the 50 mm thick NM500 wear-resistant steel plates,based on the crack morphologies,TiN inclusion and microstructural features,hardness distribution and formation mechanism.Both internal transverse and longitudinal cracks were found in the center of NM500 steel plates along the through-thickness direction.The underlying mechanism of delayed cracking was studied by OM,SEM,EDS,TEM and Vickers hardness techniques.The results show that the main driving force was dominated by the internal structural stress,based on the following two aspects:1)A large number of large-sized TiN inclusions were formed in the cast slabs,and then underwent rolling to easily form sharp corners and holes,which tends to aggregate H and cause large stress concentration;2)Flame cutting resulted in a large amount of carbides in the martensite,decreasing the hardness of steel plates in the heat-affected zone(HAZ).Thus,it was difficult to ensure a high-strength constraint,so that cracks were easily generated at the TiN inclusions due to the effect of structural stress.
作者
吴翔
左秀荣
蔡明晖
赵威威
Wu Xiang;Zuo Xiurong;Cai Minghui;Zhao Weiwei(Key Laboratory of Material Physics,Ministry of Education,Zhengzhou University,Zhengzhou 450052,China;School of Materials Science and Engineering,Northeastern University,Shenyang 110819,China)
出处
《材料与冶金学报》
CAS
北大核心
2019年第4期280-285,299,共7页
Journal of Materials and Metallurgy
基金
河南省科技开放合作项目(NO.182106000016)
