薄厚度板坯连铸机非稳态连铸坯中夹杂物分布  

Distribution of inclusions in unsteady slab of thin slab caster

作　　者：黄淑媛 杨健 李广帮[2] 康伟[2] 廖相巍[2] 田勇[2] HUANG Shuyuan;YANG Jian;LI Guangbang;KANG Wei;LIAO Xiangwei;TIAN Yong(State Key Laboratory of Advanced Special Steel,School of Materials Science and Engineering,Shanghai University,Shanghai 200444,China;Angang Steel Co.,Ltd.,,Anshan 114000,China)

机构地区：[1]上海大学材料科学与工程学院,省部共建高品质特殊钢冶金与制备国家重点实验室,上海200444 [2]鞍钢股份有限公司,辽宁鞍山114000

出　　处：《炼钢》2021年第5期67-75,共9页Steelmaking

基　　金：国家自然科学基金钢铁联合研究基金重点项目(U1960202)。

摘　　要：针对鞍钢股份有限公司薄厚度(200 mm)板坯连铸机生产的非稳态铸坯中夹杂物分布进行了研究。Factsage热力学计算结果表明,铸坯中的夹杂物类型主要为Al_(2)O_(3)、TiN、Ti_(2)S_(3)、MnS,及其复合夹杂物,该计算结果与夹杂物分析结果相符。在铸坯厚度方向上,内弧近表面侧的夹杂物类型主要为TiN,Ti_(2)S_(3)和Al_(2)O_(3)+TiN复合夹杂物,且数量密度最大,这是由于内弧近表面侧铸坯冷却速度较快,这些夹杂物均质形核析出所致。铸坯宽度方向上,宽度1/2处夹杂物的主要类型为Ti_(2)S_(3),(Ti,Mn)S,TiN和TiN+(Ti,Mn)S,并且数量密度最大,这主要是因为S和N元素在铸坯宽度1/2更容易偏析富集所致。由于尺寸不小于5μm夹杂物的数量密度按照头坯、过渡坯、正常坯、尾坯依次减少,所以研究中铸坯洁净度较好顺序是尾坯>正常坯>过渡坯>头坯。这与开浇初期中间包流动状态不稳定、夹杂去除条件差、存在二次氧化,大包交换过程中的拉速变动、结晶器液面波动加大等因素有关。铸坯中存在较多大于50μm的球形和不规则形"Al_(2)O_(3)+气泡"气泡型夹杂,意味着更大尺寸的"Al_(2)O_(3)+气泡"气泡型夹杂发生概率较大,这容易造成热镀锌汽车外板表面线状缺陷的发生,因此应该更加严格地控制浸入式水口吹氩流量。In this paper,the distribution of inclusions in the unsteady slab produced by Angang’s 200 mm slab caster was studied.The thermodynamic calculation results with Factsage show that the main types of inclusions in slab are Al_(2)O_(3),TiN,Ti_(2)S_(3),MnS and their composite inclusions.The calculation results are consistent with the analysis results of inclusions.In the direction of slab thickness,the main types of inclusions near the inner surface are TiN,Ti_(2)S_(3) and Al_(2)O_(3)+TiN,and the number density is the largest.This is due to the faster cooling rate of the slab near the slab surface to promote the homogeneous nucleation and precipitation of these inclusions.In the direction of slab width,the main types of inclusions at 1/2 width are Ti_(2)S_(3),(Ti,Mn)S,TiN and TiN+(Ti,Mn)S,and the number density is the largest,which is mainly due to the segregation and enrichment of S and N elements at 1/2 width of slab.Because the number density of inclusions with the size greater than 5μm decreases in the order of head slab,transition slab,normal slab and tail slab,the slab cleanliness should be in the sequence of tail slab>normal slab>transition slab>head slab in the present case.This is related to the unstable flow state of tundish at the initial stage of casting,the poor condition of inclusion removal,the existence of secondary oxidation,and the change of casting speed and the increase of fluctuation on mold liquid level during ladle exchange.There are more spherical and irregular“Al_(2)O_(3)+bubble”inclusions larger than 50μm in the slab,which means that there is a greater possibility of existence of“Al_(2)O_(3)+bubble”inclusions with the even larger size.This tends to cause the occurrence of linear defects on the surface of the hot-dip galvanized automobile exposed plate.Therefore,the argon blowing flow rate of submerged entry nozzle should be more strictly controlled.

关 键 词：薄厚度板坯连铸机 非稳态连铸坯 夹杂物分布 汽车外板 线状缺陷 

分 类 号：TF777.7[冶金工程—钢铁冶金]