Abstract
Inoculation of cast iron has become a commonly used metallurgical process, which is carried out in a foundry in order to improve the mechanical properties of utility alloys. It consists in changing the physicochemical state of the melted alloy. This change is caused by the introduction of cast iron with a low ability to nucleate graphite, shortly before pouring a small mass of the substance—an inoculant that increases the number of active nuclei. It is also justified that the literature often connects an increase in the tensile strength UTS of the inoculated grey cast iron, with changes in the characteristics of the particles of graphite. However, in strongly hypoeutectic cast iron, in which a large number of primary austenite grains crystallize, the interdendritic distribution of graphite is usually the result. It also follows that the nature of the graphite precipitates is determined by the mutual relations between the interfacial distances in eutectic grains and the interdendritic distances in the grains of primary austenite occurring in the Fe–C alloys. The article presents the influence of the inoculant on the characteristics of the precipitation of primary austenite grains in relation to the sulphur content in grey cast iron with flake graphite. The study also showed that primary grains in grey cast iron have a great influence on mechanical properties, such as the tensile strength UTS. In this case, the key is to know the value of the degree of undercooling ΔT. The type of inoculant used affects the ΔT value. The study related the number of N primary austenite grains with the degree of undercooling ΔT and the tensile strength UTS with the number of primary austenite N grains.
Highlights
In industrial conditions, during the production of iron castings, the procedure of molten alloy inoculation consists of introducing a small amount of the inoculant, which significantly increases the ability of the molten alloy to nucleate
Z9–Z11 melts were used to compare the effect of inoculation on the UTS tensile strength value in increased sulfur content in cast iron
The study shows that the inoculation proposed in this paper for cast iron with reduced and increased sulfur content gives noticeable effects of increasing UTS tensile strength
Summary
In industrial conditions, during the production of iron castings, the procedure of molten alloy inoculation (with low nucleation capacity) consists of introducing a small amount of the inoculant, which significantly increases the ability of the molten alloy to nucleate. As a result of increasing the number of substrates for heterogeneous nucleation of graphite, a much finer microstructure is obtained and, the properties of castings made of this iron are improved [1,2,3,4]. The most important indicator of the inoculation process assessment used in the cast iron technology is the increase in the number of eutectic grains [5,6,7,8]. After the inoculation procedure, changes in the characteristics of the flake graphite particles are assessed.
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