特厚板坯厚度方向上夹杂物分布及中心裂纹形成机理  

Inclusion distribution in the thickness direction of ultra-thick continuous casting slab and mechanism for the central crack formation

作　　者：盖一铭 徐龙云 杨健 GAI Yiming;XU Longyun;YANG Jian(School of Materials Science and Engineering,Shanghai University,Shanghai 200444,China;Hunan Hualing Xiangtan Iron and Steel Co.,Ltd.,Xiangtan 411200,China)

机构地区：[1]上海大学材料科学与工程学院,上海200444 [2]湖南华菱湘潭钢铁有限公司,湖南湘潭411200

出　　处：《炼钢》2025年第1期63-73,共11页Steelmaking

摘　　要：采用EVO18型扫描电镜-能谱仪(SEM-EDS)对特厚板坯厚度方向上非金属夹杂物的数量、尺寸、成分、分布规律进行了研究,同时对铸坯中心裂纹处金相组织进行了观察分析。结果表明,特厚板坯中夹杂物的主要类型为Al_(2)O_(3)、MnS、TiN以及上述三种夹杂物的复合夹杂物。特厚板坯厚度方向上主要存在距内弧面1/4处的夹杂物聚集区。由于Mn元素和Ti元素的偏析作用,夹杂物MnS、TiN、MnS-TiN在坯厚度中心附近氧化物表面析出,所以大尺寸夹杂物在厚度中心处数量密度较大。从Al_(2)O_(3)+MgO+CaS+TiN的三维形貌及能谱图可以看出,由于特厚板坯厚度较大,冷却速度较慢,Al_(2)O_(3)在降温过程中率先析出,随着温度的降低,硫化物、氮化物在Al_(2)O_(3)周围析出。特厚板坯中心裂纹主要有两种产生原因,一是细小析出物钉扎组织晶界造成晶界处产生聚合孔洞,孔洞进一步长大形成中心裂纹;二是在铸坯凝固前沿,矫直应变容易造成沿晶撕裂产生裂纹。EVO18 scanning electron microscopy and energy dispersive spectroscopy(SEM-EDS)was used to detect the number,size,compositions and distribution of non-metallic inclusions in the thickness direction of ultra-thick continuous casting slabs.At the same time,the microstructures near the center crack in the slab was also observed.The results show that the main types of inclusions in the ultra-thick continuous casting slabs are Al_(2)O_(3),MnS,TiN,and their composite inclusions.In the thickness direction of the ultra-thick continuous casting slab,there is mainly an inclusion accumulation area 1/4 away from the inner arc surface.Due to the segregation effect of Mn and Ti elements,MnS,TiN,and MnS-TiN precipitate on the oxide surface near the thickness center of the continuous casting slab,resulting in a higher number density of large-sized inclusions at the thickness center.From the three-dimensional morphology and energy spectrum of Al_(2)O_(3)+MgO+CaS+TiN,it can be seen that due to the large thickness of the continuous casting slab and slow cooling rate,Al_(2)O_(3) precipitates first during the cooling process.As the temperature decreases,sulfides and nitrides precipitate around Al_(2)O_(3) particles.There are two main reasons for the formation of central cracks in the ultra-thick continuous casting slab.Firstly,small precipitates pin the grain boundaries of the microstructure,causing the formation of aggregated pores at the grain boundaries,which further grow to form central cracks.Secondly,at the solidification front of the slab,straightening strain can easily cause intergranular tearing and crack formation.

关 键 词：特厚板坯 非金属夹杂物 中心裂纹 厚度方向 

分 类 号：TF777.1[冶金工程—钢铁冶金]