AOD prodn. of low phosphorus, chromium steels

摘要

A low P, Cr steel is mfd. in a vessel equipped with a top blowing oxygen lance and a bottom injection tuyere (pref. a double pipe tuyere) for injecting oxidising and/or non-oxidising gases into a molten chromium-contg. pig iron contg. max. 4.5 wt.% C, at least 0.010 wt.% P and at least 3.0 wt.% Cr. - The process comprises: (a) adding a solid carbon source to the melt to produce a carbon content of at least 4.5 wt.% at the end of subsequent step (d); (b) stirring the melt by bottom blowing of a non-oxidising gas; (c) oxygen-blowing to produce a melt with a Si content of max. 0.15 wt.%, a C content of at least 4.5 wt.% and a temp. of 1500-1700 deg.C; (d) completing de-slagging the melt; (e) adding a dephosphorising flux; (f) stirring the melt by bottom blowing with a non-oxidising gas for effecting contact of the pig-iron with the formed slag which has an iron oxide content maintained at at least 1.0 wt.%; (g) completely deslagging the melt; and (h) oxygen blowing to decarburise the pig iron while bottom blowing with a non-oxidising gas.