ANALYSIS AND CONTROL OF POOR POURABILITY OF GRINDING BALL STEEL B2
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 Al2O3-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 SiO2-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 Al2O3-SiO2-CaO,Al2O3-SiO2-CaO-MnO,and Al2O3-SiO2-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.
grinding ball steelpourabilityliquidityinclusionslag entrapmentrefining slagflow field
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