球铁型材保温炉中熔体贫氧处理的研究

Surface Deoxygenating Process of Mg RE Ductile Iron Melts in the HCC Holding Furnace

研究了不同条件下连铸保温炉内铁液球化衰退的过程。结果表明，与砂型铸造相比，连铸球墨铸铁型材在保证球化率＞ ８０％ 时，临界残留球化元素的含量显著降低，其中 Ｍｇ残 和 Ｍｇ残＋ Ｒ Ｅ残 分别为０．００９ ７％ 和０．０２０％ 。与无液面保护相比，在液面利用火焰加热贫氧处理结合熔渣覆盖铁液表面，球化衰退时间延长了一倍。

In the horizontal continuous casting (HCC) iron bars, magnesium (Mg) and rare earth (RE) fading and loss of nodularity of treated ductile iron melts in the holding furnace is the key factor influencing the quality of the bars. We present a new method to deal with such a problem. Such a method, to our best knowledge, has not been reported in the open literatures. The fading and loss of nodularity is caused mainly by surface oxygenation of Mg and RE. We overcome it by using a surface deoxygenating process. Fig.1 shows schematically the HCC holding furnace, where the part marked 7 is a flame nozzle. The flame protects Mg and RE from oxygenating. Our conclusions from test results are: (1) The critical residual of Mg is 0.009 7%, and that of Mg+RE is 0.020%; thus nodularity is kept at above 80%. (2) The holding time of the melt is over 32 min, more than twice the holding time without deoxygenating process, allowing that each pouring of melt into holding furnace can be quite large instead of a little at a time.