Abstract：Cleanliness of nonquenchandtempered steel with ultralow oxygen content for automobile semiaxis,produced by EAFLFVDCC process was investigated. It was found that several measures should be taken to produce billets with a total oxygen content below 0.0010%. Firstly, the basicity of LF slagw(CaO)/w(SiO2) ratiomust be controlled at 4.0 or higher. As well, (FetO+MnO) content in LF slag should be kept below 1% by control of bottomblown argon flow rate to avoid the pickup of it. Secondly, calcium oxide should be added during vacuum degassing to maintain a high basicity slag, with SiO2 lower than 10%.The time of argon blowing during vacuum degassing should be increased to promote the removal of inclusions from molten steel. Thirdly, reoxidization of the molten steel should be prohibited in the tundish as well as proper casting speed should be used to alleviate or even eliminate the entrapping of tundish slag.
2007, Vol. 42 
