The solubility product of manganese sulfide in 3 pct silicon-iron at 1270 to 1670 K
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=-10,590/T
+ 4.092
where T is in kelvins. This line lies between the values reported in two previous and nonconcordant investigations; at 1490 to 1540 K, the three sets of results roughly converge. Determination of the solubility product should help in understanding the application of manganese-sulfide precipitates to texture control in 3 pet silicon-iron alloys. AN essential part of obtaining required textures in metals or alloys is the control of boundary migration during recrystallization and grain growth with a suitable dispersion of precipitate particles. In particular, the improvement in the magnetic properties of some silicon-iron alloys for electrical applications has been accomplished by this means. Among the dispersed phases most frequently used in these alloys is manganese sulfide, the precipitation of which depends upon the concentrations of manganese and sulfur in the alloy as well as upon the processing treatments that effect a critical dispersion of the precipitate particles. The temperature dependence of the solubility product of manganese sulfide in 3 pet siliconiron* has been determined experimentally by Ainslie '''Pct'' denotes weight percent in this paper.
and Seybolt' and by Fiedler, 2 but their results are not concordant. The calculations of Brown" are not in agreement with either investigation. The present investigation was undertaken to establish the relationship up to 1670 K, a temperature higher than those used in earlier studies. Because there is always some iron present in the phase termed "manganese sulfide" in silicon-iron, the chemical symbol for the phase, "MnS", will be used with quotation marks to indicate its inexact nature. MATERIALS AND EXPERIMENTAL METHODS The solubility product of "MnS" in 3 pct siliconiron was determined by two methods, which we term "electron-microscopy" and "chemical-exchange". Both methods made use of the same three alloys, melted and cast under vacuum, which contained approximately 3 pet silicon, different small cone enH. A. WRIEDT and HSVN HV are Senior Scien tist and Sta ff Scientist, respectively, Research Laboratory, V.S. Steel Corporation. Monroeville, PA 15146. Manuscript submitted February 21, 1975. METALLURGICAL TRANSACTIONS A
trations of manganese. and sulfur, and the balance iron with residual impurities. The principal raw materials for the melting were electrolytic iron (Glidden Co, Plast-Iron Grade A-104), silicon metal, electrolytic manganese, iron sulfide and aluminum. The 11 kilogram ingots were hot-rolled to 2.5 cm thick plate. After being cut and machined to 1.9 cm thickness for surface conditioning, pieces of the plate 4.5 cm wide were reheated to 1500 K and further hot-rolled to bands 0.28 cm thick. Blanks for coldrolling, 0.23 cm thick and 3.8 cm wide, were machined from the hot-rolled band, with the same amount of stock removed from each face. These blanks were cold-rolled to strips 0.036 cm thick and 3.8 cm wide. The strip was sheared laterally into pieces 3.8 cm by 1.3 cm. The pieces were embossed with patterns, which served to
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