Ultra-purification of iron by ultra-high vacuum melting

The properties of iron and steel have been improved by the development of the processes of refining, the alloying of useful elements and the control of microstructure. For the refining process of iron and steel making, the harmful impurities are removed by the transportation into slag. However, there is a technological limit to making ultra-high purity iron and steel by slag reaction. Consequently, ultra-purification technology is demanded for remarkable development of iron and steel. In the present investigation, a new induction melting furnace containing a copper-cold-crucible has been designed and constructed using ultra-high vacuum technology for purification of iron. The main chamber can be evacuated to 6.7 x 10(-8) Pa as the base pressure. The furnace can melt iron of 10 kg, at most, within 300 s. By melting under atmosphere of 7.5 x 10(-6) Pa, the total amount of carbon, nitrogen, oxygen, sulfur and hydrogen in iron of 10 kg is able to be reduced to less than 10 mass ppm. Especially, the melting process in the atmosphere of ultra-high vacuum is effective for the reduction of oxygen in iron. It is concluded that ultra-high vacuum melting technology is quite useful for ultra-purification of iron, especially the reduction of gaseous impurities. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.