IF钢连铸坯及热轧板夹杂物研究

Inclusions in IF steel continuous casting slab and hot rolled sheet

夹杂物是影响IF钢表面质量的重要因素。对某厂生产的IF钢连铸坯和热轧板取样,采用光学显微镜、扫描电镜、能谱、大样电解等多种检测分析方法,分析了夹杂物的形貌、尺寸、数量、分布以及成分等。研究发现,热轧工艺的轧制作用使连铸坯宽度方向1/4处聚集的夹杂物向边部迁移,最终造成热轧板边部夹杂物指数最高,说明夹杂物聚集带在轧制过程中具有遗传性。热轧板中20μm以下夹杂所占百分比与连铸坯中夹杂相比稍有增大,50μm以上夹杂所占百分比稍有降低。热轧工艺的轧制作用将连铸坯中大颗粒氧化铝夹杂挤压变形为热轧板中的长条状,容易形成表面条状缺陷。夹杂物在连铸坯距内弧侧30 mm处存在聚集现象,热轧板中距内弧侧0.5 mm处夹杂物指数最高,这是由于等效应变不同使夹杂物聚集带向表层迁移。IF钢连铸坯和热轧板中主要有4类显微夹杂,分别为Al2O3类、TiN、Al2O3-TiOx和SiO2类复合夹杂,且两者中各类夹杂物所占百分比差别不大。

Inclusions are important factors affecting the surface quality of IF steel.This paper studied the IF steel slab and hot-rolled plate produced by a domestic factory.The two-dimensional morphology,size,quantity,distribution and composition of inclusions were analyzed by optical microscope,scanning electron microscope and energy spectrum.The results show that the rolling action of hot rolling process makes the inclusion gathered at 1/4 of the width of continuous casting billet migrate to the edge.This results in the highest inclusion index at the edge of the hot rolled plate,indicating that the inclusion accumulation zone is hereditary during the rolling process.Compared with the constant casting billet,the inclusion percentage under 20 meters in the hot-rolled plate increases slightly,while the inclusion percentage above 50 meters decreases slightly.During the hot rolling process,the inclusion of large alumina particles in the continuous casting slab is extruded and deformed into long strip in the hot rolling plate,which is easy to form surface strip defects.The inclusion aggregation was found at 30 mm from the inner arc side of the casting billet,and the inclusion index was highest at 0.5 mm from the inner arc side of the hot rolled plate.The difference in equivalent strain caused the inclusion aggregation to migrate to the surface.There are mainly four kinds of microscopic inclusions in IF steel continuous casting slab and hot rolled plate,which are Al2O3,TiN,Al2O3-TiOx and SiO2 composite inclusions respectively,and there is little difference in the percentage of each kind of inclusions between them.