On Application of Internal Heat Sink Sources when Producing Castings from Wear-Resistant Chromium Cast Iron

The features of the formation of castings from chromium cast iron during casting in a combined mold are studied using internal sources of heat removal introduced into the melt. A series of experiemеnts has been carried out with wear-resistant chromium cast iron. The following macrocoolers have been used: a 0.5 mm thick silumin plate containing 3–5 % Ti; a mixture of borax and crushed ferrochrome (1–4 mm); white cast iron shot. The phase composition of the samples has been determined by X-ray diffraction analysis, and their microstructure has been also studied. Hardness testing has been carried out on specimens obtained with cast iron shot. The most effective method of using an internal source of heat removal, which has a significant effect on the cooling rate of the casting and its microstructure, has been determined. The most promising was a mixture of borax and crushed ferrochrome particles, which did not dissolve in the melt and formed zones with local structure refinement, as well as white cast iron shot, a more technological alternative to ferrochrome. The use of white cast iron shot has led to a refinement of the structure of the part “Backing sheet У3.1,1 [U3.1.1]” made of wear-resistant chromium cast iron, as well as to an increase in the hardness of its working surface by 2.6 HRC. Almost all of the shot introduced into the melt has been melted. As a result of the research, it has been revealed that the use of ferrochrome and white cast iron shot is an effective way of local structure refinement and a practical possibility of obtaining a part made of chromium cast iron with increased hardness. All this can increase the wear resistance of parts of crushing and grinding equipment.