Development of a New Stainless Steel Melting and Refining Process (LD-RHOB Process)

At }\lJurorall "Vorks, Nippon S teel CO/poration , a research has been started to produce stainless steel by LD cOllverter ill 1965.After various difficulties were overcome in th e COU TSe of the research, a new process to melt and refill e stainless steel ( LD-RHO B process) was successfully developed.Since 1972 aLL the stainless s teel has been fa vorably p roduced by the LD-RHOB p rocess and the p roducts were more than 90000 t in 1976.The LD-RHOB process consists of the f oLLowing five steps . 1 ) D esulpll1lrizatiol1 treatment: D esulphuri z atiol!qj•hot metal by KR treatment 2 ) B ase metal refining period: D e/Jlwsphoriza tion in LD converter 3 ) S e/Jara tion of slag from metal :T apping aud slagging off and then cha rging into the LD converter again 4 ) Ch ro mium melting period: H igh carbon ferro chromium melting into base metal 5 ) RHOB treatment: D ecarburiz ation under reduced IJ ressureThe special f eatures of LD-RHO B p rocess in elude the follo wings :(1 ) Chromium.yield and /Jrodu ctivity are equal to or better than those qf other /Jrocesses (A OD, VOD process) .(2 ) Chemical com/Jositioll can be freely controlled and tra m/J elements are lower than those ill electric jilT/wce s teels .It is remarkable that high pure stainless steels such as ultra-Iow -carbon-nitrogen stainless steel call be easily produced .(3) Th e /Jroducts are very soft and ensure good workability. I. Introduct ion