STRUCTURE AND PROPERTIES OF STEEL GRADE 7ХНМФБ FOR MANUFACTURING WOOD CUTTING SAWS

Abstract

The article covers issues related to the development of a new domestic tool alloy steel of the 7ХНМФБ brand for the manufacture of wood-cutting saws. It is noted that the aforementioned saws were previously made from alloyed tool steels of the 9ХФ and 9ХФМ grades, which were smelted in the Russian Federation (RF), and wood-cutting saws were also made from them in the Russian Federation. With the acquisition of independence, these saws became scarce, and the question arose of developing domestic tool alloy steel for the manufacture of these saws. The purpose of the research is to determine the structure and properties of steel grade 7ХНМФБ. Well-known alloyed tool steels were taken as a basis and such elements as niobium, calcium, aluminum and rare earth elements were added to their chemical composition. We received a new domestic alloyed tool steel of the 7ХНМФБ brand, which, in comparison with known steels, has a number of significant advantages. These include a significant reduction in the content of harmful sulfur and phosphorus impurities, which is achieved both by smelting technology and by introducing additional elements into the steel composition. The introduction of aluminum leads to a change in the quality and shape of the distribution of non-metallic inclusions, which increases the plastic characteristics and increases the resistance to fracture viscosity. The steel of the new brand is distinguished by a higher value of impact strength (especially at negative temperatures), resistance to the occurrence and propagation of cracks. Steel 7ХНМФБ also surpasses the indicators of steels 9ХФ and 9ХФМ in terms of fracture toughness and durability during cyclic bending with rotation. The choice of the alloying scheme ensures that the new brand of steel, with the same hardness, has almost the same strength and yield strength as 9ХФ and 9ХФМ steels.