The development of machine building is associated with the development of highly efficient processes of thermal hardening of machine parts that undergo wear, bending, impact and high contact loads. At present, in the total consumption of heat and energy resources by industrial enterprises, the share of production using heating operations in gas, electric furnaces and induction plants is more than 10 percent. At present, for these purposes, methods of thermal, laser, plasma or chemical-thermal treatment are used. Each of these methods has certain advantages and disadvantages.
The greatest spread in industry got the method of thermal hardening with the use of heating in chamber, shaft and other furnaces. This method is reliable, stable, universal and widely used in machine building enterprises. In recent years, heat treatment of parts in the shops of factories is mainly carried out in garden type furnaces (chamber furnaces, shaft furnaces, rotary hearth furnaces, carousels) and is carried out in furnaces with air medium with the use of manual labor during loading and unloading. The use of protective atmospheres takes place only in large enterprises. As a result - significant losses of metal in the scale, decarburization of surface layers, as well as unproductive costs for cleaning, etching, etc. Heating equipment at most of the republic's enterprises is outdated, has high energy intensity and does not meet modern requirements. Old processes of heat treatment in salt baths with harmful working conditions and negative impact on the environment are used extensively. Its major disadvantage is the decarburization of the surface, which necessitates the subsequent removal of the decarburized layer by grinding methods. On the other hand, this process is characterized by low efficiency and significant energy consumption for heating the furnaces.
Very promising for most parts working on wear or contact fatigue, it is necessary to consider surface heat treatment using high-frequency or induction heating. Such heat treatment allows to obtain surface-hardened layers 1-10 mm thick on inexpensive steels having high hardness and wear resistance. The use of induction heating has several advantages over conventional heating devices. First and foremost, the high efficiency is up to 97% and the compactness of the induction units allows them to be integrated in the machining lines, the high productivity of the heating operations, the formation of the thermally strengthened layers on the surface of the parts, which increase the performance characteristics and special properties. The use of induction heating dramatically reduces energy costs due to the unique possibility of local hardening of working surfaces, reduces or completely eliminates decarburization or oxidation, reduces warpage of parts during quenching, which allows to significantly reduce the allowances for machining. With surface induction hardening instead of cementation, the process duration is reduced hundreds of times, labor intensity and cost of hardening are reduced, electricity costs are reduced several times, the need for using natural gas, mineral oils, asbestos, heat-resistant and heat-resistant materials is eliminated, emissions of harmful substances and products of their decay.
It should be noted that induction heating is most often used in the operations of forging, stamping, pressing, volumetric and surface heat treatment of metals and alloys. It is very effective to use induction equipment when creating small-capacity melting devices. Such furnaces allow heating of small volumes of metals and alloys up to temperatures of 30000C both in normal atmosphere and in vacuum.
At present, induction heating is one of the main types of heating for processes of hot deformation of parts, surface hardening of crankshafts and camshafts, gears, cutting and measuring tools, is widely used for volume and surface hardening of dies, punches and other parts.
However, it should be noted that the pace of expansion of the field of induction heating is hampered by the problems of acquiring modern equipment, materials, the need to develop or adjust the technological processes that ensure high quality of products and reduce costs. No less acute are the problems of replacing or modernizing equipment, heating devices, improving the technological processes of heat treatment. There is also a problem associated with heating parts of a complex geometric shape. The use of high-frequency surface treatment requires an informed choice of steel grades, heating and cooling regimes, development and testing of heating and cooling devices, research of the structure and properties of reinforced parts. In this regard, studies aimed at the integrated development of the process of surface hardening of parts of complex geometric shapes are relevant.
In recent years, special attention is being paid to metal scientists by questions related to technological problems in obtaining functional gradient materials. Such materials have unique mechanical, technological and special properties. They allow to increase wear resistance, corrosion resistance, fatigue, etc. Studies in this field have shown that the use of induction, electrocontact and laser heating or their combination with traditional technologies of thermal, chemical-thermal or plasma treatment are the main basis for the development and creation of new highly efficient technologies allowing to form a structure on the surface with a differential distribution of properties over the section and to provide an increase in the service properties of the parts , working in conditions of intense impact of impact and contact loads or abrasive wear. At present, the PTI of the NAS of Belarus is carrying out research into the features of phase and structural transformations, recrystallization and grain growth processes, phase recrystallization, occurring in steels and alloys under conditions of high-speed heating and controlled cooling, which will establish the relationship between the structure and properties of high-strength steels, cobalt and titanium alloys, to develop new technological processes of high-speed or combined heat treatment. The results of the research are used in the development of continuous processes of surface hardening of steel parts, processes of surface hardening of parts of automotive and agricultural machinery.