Equilibria of nitride forming reactions in liquid iron alloys
- PDF / 589,743 Bytes
- 8 Pages / 583.28 x 777.28 pts Page_size
- 47 Downloads / 220 Views
I.
INTRODUCTION
THE thermodynamic knowledge on nitride forming reactions and interactions between nitrogen and various alloying elements in liquid iron are important from theoretical and practical points of view. Control of nitrogen and various alloying elements to desirable levels is important in steelmaking processes. However, there have been few reliable data on the equilibria on the nitride forming reactions in liquid iron alloys, while the solubility of nitrogen in liquid iron and steel has been studied by many investigators. In this work, published thermodynamic data on the nitride forming reactions in liquid iron alloys containing A1, B, Nb, Ta, Ti, V, and Zr were critically reviewed. Also new data on vanadium nitride forming reaction in liquid Fe-V alloys recently obtained by the authors are presented. A series of possible nitride forming reactions in liquid iron alloys are discussed in terms of the standard Gibbs energy and enthalpy of formation on nitrides, atomic numbers of nitride forming elements, and interaction parameters. II.
NITRIDE FORMING REACTIONS IN
LIQUID IRON ALLOYS CONTAINING
AI, B, Nb, Ta, Ti, V, AND Zr Although some investigations have previously been carried out on the solubility of nitrogen in liquid iron alloys and various nitride forming reactions, these results do not agree with each other because of various difficulties in the experimental techniques. In this section, the thermodynamic data on the nitride forming reactions in liquid iron alloys containing A1, B, Nb, Ta, Ti, V, and Zr are critically reviewed. These data are summarized in Table I. A . F e - A l - N System
Studies on the equilibrium for the reaction in liquid FeA1-N alloys have been made and the results 1-4 are summarized in Table I. Evans et al. ,2 Adachi et al. ,3 and Wada et al. 4 have reported aluminum nitride to be A1N in liquid
Fe-A1-N alloys. On the other hand, Morozov et al. ~ have determined the nitride as AlxN. Nevertheless, the value o f x of AlxN has not been reported in their study. Figure 1 shows a plot of log K of the reaction A1N(s) = AI + N against 104/T. As can be seen from this figure, ~-e tem--perature dependencies of the equilibrium constant do not agree well among the foregoing results in which the aluminum nitride was shown to be A1N. In these results, the study by Wada et al. has most recently been made. Considering the advancement of the experimental techniques and the improvement of the accuracy of the measurement, their values are regarded as most reliable. B. F e - B - N System
A few studies concerning the equilibrium for the reaction in liquid Fe-B-N alloys have been made, and these studies 5'6'7 are shown in Table I. Each result shows that the boron nitride is BN in equilibrium with liquid Fe-B-N alloys, as indicated in this table. Schenck et al. 7 have reported the value of log K only at 1873 K; however, Evans et al. 5 and Isaev et al. 6 have given the temperature dependence of log K, and particularly Evans et al. measured log K using both Sieverts' method and the sampling method. He
Data Loading...
