Compositions Based on Nanosized Powders Carbides of Tungsten and Titanium, Obtained by the Method Self-Propagating High Temperature Synthesis for the Modification of Gray Cast Iron and Steel 110g13L

Abstract

Iron-based alloys (steel and cast iron) are currently the main structural materials that provide a high level of mechanical and technological properties along with a relatively low cost. Increasing the performance characteristics (tensile strength, hardness, wear resistance, corrosion resistance and, ultimately, service life) of cast irons and steels is an urgent task. The quality of castings made of cast iron and steel depends on many technological parameters that affect the processes of crystallization of the melt (casting temperature, molding mixture, chemical composition, volume of casting, overheating of the metal during smelting, etc.). It is possible to improve the quality of castings without changing the technology of smelting and pouring metal into molds, if you learn how to manage the crystallization process. The laboratories have grown defect – free iron crystals with a tensile strength of more than 1000 kg/m2 (strength of carbon steel-40 kg/m2). Attempts to improve the mechanical properties by creating a single crystal are not justified, so you have to go the opposite way-to influence the crystallization process to get a lot of small crystals (grains), which also allows you to achieve high mechanical properties. The dependence of the strength characteristics on the grain size is well described by the law of Hall-Petch, according to which when the average grain size is reduced by 3...5 times there is an increase in the hardness of the material, with a further decrease in the average grain size by more than 10 times – an increase in plasticity. Influence on the processes of crystallization of iron and steel melts (change the size of metal grains, change the shape, size and distribution of graphite inclusions) can be the introduction of small additives substances (modifiers), not chemically interacting with the matrix. The use of modifiers to increase the rate of crystallization, reduce the structural heterogeneity of castings has good prospects. In addition, unlike doping, modification does not require a large number of expensive additives and, accordingly, slightly increases the final cost of production.