Kinetics of Evaporation of Manganese, Copper and Sulfur from Iron Alloys in Vacuum Induction Melting

Abstract

The eva/)oration-rate COllstallt K i (kg . m -2 .r l ).for each o.f mallgalleJe, cupper alld sulfur in the vacuum induction melting qf iroll alloys has beell rletermilled . The rale cOllslnll1 K v or K~ (kg . m-2 . r ' ).!or the va/Jori :;:alion o .f these elements al the vacuum-melt interface is calculaled. I II each Q( the Fe-C-Mn, F c-C-Cu and F c-C-Si-S vstems, the value Q( K i at a lower stirring rale is about one half o.f Ihat at a higher stirring rate; hence mass trans.fer in the m elt must be involved in the rate-determining ste/).fol' their evaporation at the lower slirring rale. In the Fe-C u and Fe-Mn syslems, the value of Kcu at J 973 K is obviously g realer thall that at J 873 K , but those of K M n at bolh lemperatures nre close to each olher. The rales o.f evap ora tion o .f manganese must be determined prer/ominanliv by Ihe rale qf ils trallsf er in Ihe meLl in view of the vaLues o.f p K ", at both temperatures, which were calcul(lted on Ihe basis q( th e equatioll K i = p K", K vl (.oK", + K v ) , where p (kg . m -O ) is the densi!)' o.f the meLt and K ,n (m . s-I ) is Ihe mass-tranrfer co~fficien t in the melt. i n the Fe-M n, Fe-Cu and Fe-S n sy slems at J 873 K , most o( the reported experimental values o.f K, II n' Kcu and KSn agree well with their respective values ca!CIl/ated from Ihe equatioll b_v laking .oK", = 6.8 x 10-1 (kg . m -2 . s -' ), but the present experimenlal values Qf Kcu are smaller than the calculaled value. The plols o .f Ksl.f s vs. as; in Ihe Fe-Sisystem are Linear at two different stirring rates. The rate (onstanls k, and k2 given by this linear relation at a lower stirring rale are smaller than those al a higher slirring role, respectively, and must involve K'lL' III the desulfuri;;ation (I .f Fe-S, F C-S, F e-S i -5 and Fe-C-Si-S alloys at temperatures in the range 1 688 -J 873 K , the relatioll between K s and K : is rep resented by a curve calculated .from the equation by taking K v= O.24 K : and p K,n =2. 5 regardless o.f the lemperatures and the alloy systems. This value o.f .oK", is much greater than the value o.f .o K", f or Fe-Mn , F e-C u and Fe-Sn systems. Oxy -gCll and sulfur hardly affect Ihe rate of evaporation o.f copper .from molten