Processes of formation and preventing burns on steel castings

Burns on steel castings produced in non-metallic forms remain an urgent problem in the foundry industry. Their removal is very costly and deteriorate the production ecology. However, for the last thirty years this process has been neglected despite the fact that in the process of burns formation there are still many obscure things, especially when the role of the burning fluid as “the carrier” of burning substances is concerned. This question has been studied in laboratory and industrial conditions, attention is paid to the emergence and the development of the burning fluid, its wetting ability of various moulding materials, the influence of the oxygen potential of the form gas atmosphere on the separation of the burns from the casting surface. The thermometry of forms made from different mixtures revealed the mechanism of the beneficial effect of such materials as chromite and the like, consisting of refractory oxides and oxygen in the form of iron oxides. Their influence is not only in the fact that the casting cooling rate increases, but rather, in the fact that the maximum form heating reduces, and therefore the burning fluid hardens, and the movement of burns in the form depth stops. Based on the conducted research and taking into account the industrial experience, the article presents the concept of formation and prevention of burns on steel castings by means of increasing the melting temperature of the burning fluid and decreasing the temperature of the maximum form heating. Favorable influence of these parameters on surface purity is evident even with the introduction in the moulding mixture low-melting components in combination with refractory oxides.