In order to study the evolution law of inclusions in 75Cr Tool steel in the whole process,the total oxygen and nitrogen contents of molten steel were analyzed by sampling in the whole process.In addition,ternary phase diagrams were prepared for two typical non-metallic inclusions,Al2O3-MgO-CaO and SiO2-Al2O3-MgO-CaO,and the melting point of the inclusions was analyzed.The results show that the number density of non-metallic inclusions in steel decreases in the whole process,and the inclusion removal effect is significant from LF station to hot rolled product,and the number density of inclusions in finished product is 5.1/mm2.The mean size of nonmetallic inclusions has little variation,ranging from 4.5 to 6.5 μm.Four types of inclusions were found in the whole process analysis,among which two main inclusions were Al2O3-MgO-CaO type and SiO2-Al2O3-MgO-CaO type.MnS compounded with the above inclusions were detected only in the billet and hot-rolled coil,with which two new inclusions were formed.At the same time,the melting point of Al2O3-MgO-CaO type inclusions is calculated,and the melting point is greater than 1 600 ℃,which belongs to high melting point inclusions.The inclusion of SiO2-Al2O3-MgO-CaO is basically located in the low melting point area,and the melting point is less than 1 400 ℃.
关键词
高碳工具钢/75Cr/夹杂物/铝镁尖晶石/MnS/数密度/熔点
Key words
high carbon tool steel/75Cr/inclusions/aluminum magnesium spinel/MnS/number density/melting point
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