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

Synopsis The eva/)oration-rate COllstallt K i (kg . m2 .r l ).for each o.f mallgalleJe, cupper alld sulfur in the vacuum induction melting qf iroll alloys has beell rletermilled . The rale cOllslnll1 Kv or K~ (kg . m2 . r ' ).!or the va/Jori :;:alion o.f these elements al the vacuum-melt interface is calculaled. I II each Q( the FeCMn, FcCCu and FcCSiS 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 melt must be involved in the rate-determining ste/).fol' their evaporation at the lower slirring rale. In the FeCu and FeMn syslems, the value of Kcu at J 973 K is obviously g realer thall that at J 873 K , but those of KM n at bolh lemperatures nre close to each olher. The rales o.f evaporation 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 pK ", at both temperatures, which were calcul(lted on Ihe basis q( the equatioll K i = p K",Kvl (.oK", + Kv ), where p (kg .mO) is the densi!)' o.f the meLt and K ,n (m . sI ) is Ihe mass-tranrfer co~fficien t in the melt. i n the Fe-M n, Fe-Cu and FeS 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 101 (kg . m2. s' ), but the present experimenlal values Qf Kcu are smaller than the calculaled value. The plols o.f Ksl.fs vs . as; in Ihe FeSisystem 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 FeS, F CS, Fe-Si -5 and FeCSiS alloys at temperatures in the range 1 688J 873 K , the relatioll between K s and K: is rep resented by a curve calculated .from the equation by taking Kv= 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 .oK", f or FeMn , F e-C u and FeSn systems. Oxy gCll and sulfur hardly affect Ihe rate of evaporation o.f copper .from molten iroll at J 873 K .