Magnesium melting practices

IMA Erickson, S. E. King, J. F. and Mellerud, T. "Recommended practices for the conservation of sulphur hexafluoride in magnesium melting operations". International Magnesium Association, technical committee report. 

Particulates coEected in foundry atmospheres have been found to contain compounds of 2inc, copper, lead, iron, aluminum, magnesium, and sEicon as weE as carbon and oEy material. The specific composition and concentration of any smoke depends on the composition of the material being melted and on the melting and pouring practice. 

The lowest temperature to which the stoichiometric mixture of UF4 and magnesium must be preheated to just melt the reaction products without heat loss may be found by reference to Fig. 5.24, in which the enthaipies of 1 mol of UF4, 2 mol of magnesium, and their mixture are plotted against temperature. The temperature at which the enthalpy change of the mixture from 25°C is 6.8 kcal, or 192°C, is the desired minimum preheat temperature. In practice, it is necessary to preheat the charge to a higher temperature to compensate for heat losses and because a sli t excess of magiesium is used, as illustrated by Prob. 5.6. 

The quantities of SFe used in various operating conditions are given in Table 3.26 (pressure diecasting) and Table 3.27 (gravity die-casting). These concentrations need to be maintained close to the melt surface [191, IMA, et al.]. The tabled values are the recommended practice for the use of SFe from the International Magnesium Association (IMA). In practice, higher concentrations are sometimes used (e.g. 99.4 % CO2, 0.6 % SFg) [202, TWG, 2002]. 

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