Research On The Interaction Rule Between The Rare Earth Cerium And The Low Melting Point Metallic Tin In The Steel

Along with the dosage increasing of society to the steel products, it will be obtained the unceasing development that the electric arc furnace steel-making as the main raw material. During the period of circulation use of scrap steel, how- ever, it causes the content increase unceasingly of the low melting point metallic elements (such as Sn, Pb, Sb, As, Bi and so on) in the steel. The low melting point metallic elements will cause the serious harm to the properties of steel products. Therefore, there is a great need to discuss the method on how to remove the low melting point metallic elements in steelmaking process and control their contents in steel. The RE element is nearly only element that can be compound with harmful element of Pb, Sn and so on in the steel. It is because that the high chemical activity of RE element depends on the character of their electro-construction of 4f.In this paper, the formation enthalpies of Cerium-Tin compounds of Ce₅Sn₃, which has been produced between the RE earth of cerium and the low melting point metallic element of tin, was calculated by the Miedema the theory of binary formation enthalpies. The change of entropy of compound has been calculated by the principle of ionic entropy. And the standard formation energy of compound has been estimated through the absolutely entropy. The possibility of the reaction between the RE earth cerium and the tin of low melting point metallic element in the low oxygen and sulfur steels is studied thermodynamically.The high pure RE cerium and the low melting point metallic tin have been added to the low oxygen and sulfur industry ferrite in this experiment, which has been melted in the intermediate frequency vacuum induction smelting furnace. And some of the samples have been carried on annealing processing. It has been qualitative and quantitative analyzed that the casting samples and the annealing samples through the OM, SEM, XRD, EPMA and so on. The experimental results show that the RE cerium firstly interact with the oxygen and sulfur in the steel and form compounds of Ce₂O₃ and Ce₂O₂S. When the quantity of oxygen and sulfur reduce to the certain degree, the cerium begin to react with tin. The reaction is easy to carry out when the steel contain low content of oxygen and sulfur.The RE element cerium combine with the low melting point metallic tin and form the high melting point Ce₅Sn₃ compounds. A small amount of cerium and tin compound has also been produced and formed multi- phase organize by the core of Ce₂O₃ and Ce₂O₂S which have been formed previously. The particle size of multiphase organize is big, generally between 10μm and 100μm, and random distribute in the substrate. The cerium and tin compound which has been independent shaped nucleus is the deep grey spherical particle. The size of spherical particle is very small, generally between 1μm and...