低氧高碳铬轴承钢LF-VD精炼时洁净度与夹杂物特征变化

研究了低氧高碳铬轴承钢在LF-VD精炼时洁净度与夹杂物类型、数量、尺寸等特征的变化规律,并关注了个别大尺寸夹杂物.试验中采用了二元碱度约为7、Al2 O3质量分数约30％ 的高碱度高Al2 O3精炼渣.LF精炼前期和中期钢中夹杂物主要为Al2 O3和MgO-Al2 O3:由于与钢液润湿性较差能够较好地去除,数量密度由L...

Study on the variations of cleanliness and inclusions in low oxygen high-carbon-chromium bearing steel during LF-VD refining process

In present paper,variations of total oxygen(T.O) and inclusions(including the type,number density,size,chemistry,etc.) in Al deoxidized high-carbon-chromium bearing steel were investigated by pilot trials,and special attention was paid to large inclusions. During refining,high basicity high alumina content slag was used,which was featured by weight ratio of CaO to SiO2 about 7 and Al2O3 mass fraction about 30 %. Inclusions were mainly solid alumina and MgO-Al2O3 spinel at initial and middle stage of LF refining. Because of poor wettability in molten steel,alumina and spinel indicated efficient removal. As a result,the mass fraction of T.O was obviously reduced from 0.001 2 %-0.001 4 % to 0.000 6 %-0.001 4 %,accompanied by decreased inclusion number density from 11.3-15.4 N/mm2 to 4.9-6.7 N/mm2 from initial to middle stage of LF refining. At the end of LF refining,T.O mass fraction was in the range of 0.000 6 %-0.001 0 % and inclusions were changed into solid calcium magnesia aluminates. After VD vacuum refining,calcium magnesia aluminate inclusions had been largely changed into liquid state and T.O mass fraction was furtherly reduced to 0.000 4 %-0.000 5 %. While inclusion number density witnessed an obvious decrease from 3.4-4.3 N/mm2 at the end of LF to 1.2-2.5 N/mm2 at the end of VD vacuum refining. In the afterwards Ar-bubbling,inclusion number density was roughly kept in the range of 1.3-3.0 N/mm2,while the average size of them indicated a tendency of increase. Particularly,the maximum size of inclusion was about 36,16,48 μm at the end of LF refining,VD refining and Ar gas bubbling,respectively.