Refining technology for high purity steel.

Recently the refining technology for high purity steel has been studied over the world.Secondary refining technologies to obtain less than 40ppm phosphorus and less than 30ppm nitrogen was investigated in our LF-RH process.In order to produce low phosphorous steel, the combination of the tapping without killing, dephosphorization injection and deslagging in the ladle led to reduce phosphorus to less than 40ppm easily.In the case of producing the low nitrogen steel, the degassing under less than 30ppm sulfur content is effective in denitrogenigation because sulfur is adsorbed positively at surface phase and retard the chemical reaction (2N→N2), then this degassing method makes it possible easily to reduce nitrogen to less than 30ppm in mass production.