Influence of the Method of Producing High-Carbon Tool Steel U10A on the Physical, Mechanical, Technological and Corrosion Properties

Abstract

Purpose of research is study of the effect of the quality of the original charge on the complex of physical, mechanical, technological and corrosion properties of high-carbon tool steel U10A.Methods. High-carbon tool steel U10A, smelted at Tulachermet PJSC using metallized sponge iron pellets, scrap metal and a billet obtained by the fluidized slag blanket, has been chosen as the object of study. Steel was smelted in a three-ton arc furnace, subjected to out-of-furnace vacuum treatment in a ladle, cast into billets with a cross section of 280 × 320 mm and cooled slowly together with the furnace. Then, the obtained blanks were forged into a square of 150 × 150 mm (for making dies) and 40 × 40 mm (for samples) with cooling in sand and subsequent annealing. The experimental study of the chemical composition of U10A steel melts was determined by the method of photoelectric spectral analysis using an atomic emission spectrometer SA 2000 according to GOST 18895-97. Results. It has been found that the use of pure original charge has a positive effect on the properties of the melted metal. Steel U10A, smelted on the original charge, is not inferior in strength characteristics to steel on OMSH, surpassing the latter in terms of its plastic properties and especially in toughness. It is shown that steel smelted on the original charge is characterized by a lower content of micro-impurities, has less resistance to austenite decomposition and lower hardenability. It is revealed that, due to the lower stability of austenite, steel melted on the original charge must have a higher critical hardening rate, which should be taken into account when choosing heat treatment modes. It is established that the long-term strength of U10A steel in a medium that causes hydrogen cracking, largely depends on the heat treatment conditions and on the purity of the steel. Cleaner steel has a higher resistance to hydrogen cracking and, therefore, greater durability during operation.Conclusion. The results can be used to create resource-saving processes for processing metal alloys and composite materials.