Abstract
Problem Statement (Relevance): Heat treatment of metal products is an integral part of any machine building process. Heat treatment can either be an intermediate operation in the production cycle or the main final operation in machine part manufacturing process. Heat treatment is an energy consuming operation that requires considerable resources. Objectives: This research aims to study the optimum transient heat treatment modes for products made from various steel grades. Transient heat treatment is another type of heat treatment applicable to metals when metal is exposed to low heat for a short period of time resulting in enhanced mechanical properties at low energy costs. The objective of this research is to identify the optimum transient heat treatment modes for 150KhNM steel castings. Methods Applied: Spectroscopy was applied to analyse the chemical composition of the steel. Differential scanning calorimetry was applied for the thermal analysis of the steel castings. Originality: The heat treatment technique applied to medium-carbon roller steel of the above grade is quite complex and energy-intensive. Transient heat treatment provides a simpler heat treatment operation enabling to reduce the energy costs. 150KhNM is a hypereutectoid steel grade used for the manufacture of forged and cast rolls for hot rolling mills, as well as for cold rolling mill rolls. The heat treatment process applied to the 150KhNM steel includes preliminary triple annealing followed by final double normalizing and high-temperature tempering. A significant drawback of the steel after the heat treatment procedure described above includes the resultant low hardness caused by the low cooling rate after austenitization. Austenitization is a process similar to quench hardening of carbon steel when steel is heated to 1050-1100 °C followed by a short-term soaking (for 10 min.) and subsequent rapid cooling. Findings: The results of the experiments show that transient heat treatment applied to the 150KhNM steel can result in an increased hardness while saving the need for complex and energy-intensive heat treatment operations. Practical Relevance: As a result of the research, initial data were obtained for transient heat treatment modes applicable to 150KhNM steel castings.
Keywords
Steel, transient heat treatment, structure, hardness, wear resistance, temperature, heating, cooling.
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