process for the production of stainless acciato

摘要

1451028 Making Cr-steels USS ENGS & CONSULTANTS Inc 27 Nov 1974 [28 Nov 1973] 51433/74 Heading C7D Cr-steel is produced by charging molten iron and up to 35% steel scap to a furnace, adding a basic slag-former (e.g. lime), blowing with 02 to reduce the P content to 0À03%, removing the slag formed, adding the desired amount of Cr-bearing material (preferably scrap and Fe-Cr) to the melt, subjecting the melt to a second blow in a bottom blown converter where O 2 is injected surrounded by a hydrocarbon protective (e.g. natural gas, propane) adding a basic slag former and continuing blowing until the desired C-content is reached, purging the furnace with an inert gas (e.g. Ar), adding Fe-Si to reduce oxidized Cr from the slag, and tapping the Cr-steel. The two blowing steps preferably occur in the same bottom blown converter although the first blow may occur in a basic oxygen furnace or a lance-blown open hearth or electric furnace) the O 2 in the first step also being jacketed by a hydrocarbon gas, although Ar may be used if required. The slag removal may be effected by tilting the furnace, using rakes, flushing with gas, or by tapping into a ladle, separating and returning to the furnace. The line is preferably added entrained in one of the injected gases, but in the second stage it may be added in bulk form. Some Ar may be used in the second blow in addition to the O 2 and hydrocarbon, or the melt may be subjected to a partial vacuum, both of which result in less oxidation of the Cr. Examples are given of the production of various grades of stainless steel.