Dephosphorisation of hot metal

In a tough economic climate and faced with increasing environmental awareness, Japanese steel makers developed a number of processes in the early 1980s to desiliconise and dephosphorise hot metal prior to decarburisation in the BOF. These processes used both CaO and Na2O based slags. Dephosphorisation has not been considered an issue in Australia due to the abundance of low phosphorus ores. The BOF has been capable of removing phosphorus without excessive impact on the productivity of the furnace. However, the availability of low phosphorus ores is not something that should be taken for granted, particularly, if the ability to use lower grade ores results in a large increase in useful domestic ore reserves. This paper summarises the technologies available for dephosphorisation of hot metal using both CaO and Na2O based slags. It can be seen that a reduction of in the phosphorus concentration of hot metal below 0.010% can be achieved prior to decarburisation using a relatively simple process and resulting in significant cost savings.