INFLUENCE OF TIN ON CRYSTALLIZATION PROCESSES IN IRON-CARBON ALLOYS (REVIEW)

Abstract

Currently, iron foundries and production facilities are experiencing great difficulties in providing such an integral charge material for smelting cast iron as high-quality unalloyed steel scrap. Due to the fact that press and forging industries and enterprises are increasingly using high-strength steels to produce their products, which significantly reduce the weight of the products obtained, microalloyed with such elements-carbidizing agents as, for example, Mo, W, Nb, V, Ti, B, the charge yards of iron foundries are supplied waste “infected” with these elements. As a rule, in such industries, products are made from several grades of steels, both microalloyed with carbide-forming elements and without them, and due to the objective complexity, the waste sorting process is not organized organizationally, therefore, waste from all available grades of steel falls uncontrollably into steel bags, mixing in arbitrary proportions. In addition to carbide-forming elements, surfactants such as Cu, Sn, As and Sb are also the most common residual elements in steel and cast iron scrap. If the accumulation of carbide-forming elements to a certain extent can be considered a positive factor, then the accumulation of surfactants, which are practically impossible to remove from steel and cast iron, has a sharply negative effect on the mechanical and operational properties of iron-carbon alloys. Tin is used as an alloying element to produce both steels and cast irons with a fully pearlitic matrix. The addition of tin in an amount of no more than 0.10–0.15% seems to be the only practical way to avoid the growth of ferrite in a stable eutectoid reaction and completely transform the metal base of steel and cast iron into pearlite in a metastable eutectoid Fe–C system. At the same time, the question of how tin affects eutectoid transformations in steels and cast irons and, in general, the entire cycle of structure formation, is still a matter of debate. In this paper, an overview of the Fe–Sn system is performed, as well as experimental and industrial data available in the literature on the Fe–C–Sn system to assess the effect of tin on crystallization processes in iron-carbon alloys.