脱りんプロセスをともなう工業的なAC4CH合金溶湯の処理方法

抄録

  Minute amounts of phosphorus impurities in hypo-eutectic Al-Si alloys have adverse effects on mechanical properties, shrinkage characteristics, and reverse segregation. The authors showed that dephosphorylation is possible by adding sodium improvement flux to the molten metal and removing the dross after vigorous stirring. In this experiment, attempts were made to put the dephosphorylation process into practical application by melting 500kg of commercial alloy ingot (JIS-AC4CH) in an industrial electric furnace. Use of a rotary degassing apparatus was tested as a stirring method, after addition of sodium improvement flux. Industrial problems were reviewed using this method, and the following results were obtained.

  1) The process can decrease phosphorus content from 12ppm to 2ppm in molten metal. 2) For the amount of flux to be added for the treatment, 5% and 1% were found to be too much, and 0.2% and 0.5% too little. Moreover, treatment time of 10 minutes was too long. 3) The process can decrease phosphorus content, gas content, and inclusions at the same time. 4) The phosphorus content increased from 2ppm to 8ppm with long molten metal holding time, which may be due to contamination from graphite crucible. 5) These findings confirm that dephosphorylation using the rotary degassing apparatus is useful for industrial purposes.