磨球钢B2可浇性差的成因分析与控制

ANALYSIS AND CONTROL OF POOR POURABILITY OF GRINDING BALL STEEL B2

针对河北某厂磨球用钢B2在浇注过程,偶发中间包塞棒上涨,可浇性差的现象,采用金相显微镜、扫描电镜及能谱仪对冶炼过程中各工序钢水内的显微夹杂物、大型夹杂物以及精炼渣进行了分析。结果表明,精炼造渣操作不稳定;RH冶炼过程及静吹结束后,夹杂物去除率分别为9.3%、8.1%、8.7%,中间包内显微夹杂物种类主要为Al_(2)O_(3)-MnS夹杂,钙铝酸盐夹杂,硅铝酸盐夹杂和MnS夹杂,来自RH出站时夹杂物的继承,还有少量SiO_(2)-CaO-MgO复合夹杂物,为卷渣产物;大型夹杂物含量分别为23.9 mg/10 kg、32.7 mg/10 kg、22.8 mg/10 kg,平均含量为26.5 mg/10 kg,高于国内同类钢种的先进水平5 mg/10 kg。大型夹杂物种类主要以Al_(2)O_(3)-SiO_(2)-CaO、Al_(2)O_(3)-SiO_(2)-CaO-MnO、Al_(2)O_(3)-SiO_(2)-CaO-MnO-MgO复合脱氧产物为主,约占夹杂物总量的90%以上,大小分布在50~300μm。其中部分脱氧夹杂物含有K、Na等元素,说明夹杂物主要为脱氧产物在上浮过程中粘附钢包渣、中间包渣,反映出钢包渣和中间包渣吸附夹杂物能力不足。明确了可浇性差的主要原因是精炼渣和中间包渣吸附夹杂物效果不理想,LF炉造渣不稳定,且中间包钢水流场易造成卷渣,生成了大型夹杂物。通过优化精炼渣和更换中间包渣,优化中间包钢水流场等措施,基本杜绝了钢水流动性问题,钢水质量得到了有效提高。

In response to the phenomenon of occasional increase in tundish stopper and poor castability during the pouring process of grinding ball steel B2 in a certain factory in Hebei,metallographic microscopy,scanning electron microscopy,and energy spectrum analysis were used to analyze the micro inclusions,large inclusions,and refining slag in the molten steel of each process during the smelting process.The analysis results indicate that the refining slag making operation is unstable;During RH smelting and after static blowing,the inclusion removal rates are 9.3%,8.1%and 8.7%respectively.The micro inclusions in the tundish are mainly Al_(2)O_(3)-MnS inclusion,calcium aluminate inclusion,silicon aluminate inclusion and MnS inclusion,which are derived from the inheritance of inclusions when RH leaves the station,and a small amount of SiO_(2)-CaO-MgO composite inclusions,which are slag entrapment products;The content of large inclusions is 23.9 mg/10 kg,32.7 mg/10 kg,and 22.8 mg/10 kg respectively,with an average content of 26.5 mg/10 kg,which is higher than the advanced level of 5 mg/10 kg of similar steel grades in China.The main types of large inclusions are Al_(2)O_(3)-SiO_(2)-CaO,Al_(2)O_(3)-SiO_(2)-CaO-MnO,and Al_(2)O_(3)-SiO_(2)-CaO-MnO-MgO composite deoxygenation products,accounting for over 90%of the total amount of inclusions,with sizes ranging from 50μm to 300μm.Some deoxidized inclusions contain elements such as K and Na,indicating that the inclusions are mainly deoxidized products that adhere to ladle slag and tundish slag during the upward floating process,reflecting the insufficient ability of ladle slag and tundish slag to adsorb inclusions.The results indicate that the poor castability is mainly due to the unsatisfactory adsorption effect of refining slag and tundish slag on inclusions,unstable slag formation in LF furnace,and easy slag entrapment and generation of large inclusions in the tundish steel water flow field.By optimizing the refining slag,replacing the tundish slag,and optimizing the steel flow field in the tundish,the problem of steel fluidity has been basically eliminated,and the quality of steel has been improved.