THE INFLUENCE OF TECHNOLOGICAL FACTORS ON THE WEAR RESISTANCEOF WHITE CAST IRON

Abstract

Wear-resistant cast irons with a martensitic matrix or a martensitic-austenitic matrix, in which carbides of
the M7C3 type are evenly distributed, possess the best service properties. The main axes of the carbides are directed towards the working surface of the casting. The presence of the M3C cementite type or carbides of the M23C5 type in the structure of carbides reduces wear resistance. In addition, the presence of primary carbides in the structure also has a negative effect. One of the sources of primary hypereutectic carbides is high-carbon ferrochrome, which is used for smelting high-chromium cast irons. Large chromium carbides entering the melt from such a charge apparently do not
have time to completely dissolve during the cast iron melting process and remain in the structure after the alloy solidifies. The use of low carbon ferrochrome may not always be economically feasible. In this case, two grades of ferrochrome can be used ‒ low-carbon and high-carbon. When using high-carbon ferrochrome grades FKh650 and FKh800 for the preparation of white cast iron, it can be recommended to improve the properties by homogenizing the melt at a temperature
of 1500‒1550 °C for 5‒15 minutes. This reduces the amount of primary carbides and increases wear resistance. Cooling rate is the most significant factor determining the characteristics of the primary cast structure of white wear-resistant cast irons. The cooling rate of the casting is determined mainly by the reduced thickness of the casting, the type of casting mold, the pouring temperature and it is not the same on the surface and in the center of the casting, especially the massive one. The influence of cooling rate on the structure and properties of cast iron by means of the influence of the casting wall thickness, its reduced size and the type of the casting mold. The research was carried out on two new compositions of wear-resistant cast iron.