Abstract. The paper examines the process of surface hardening of steel 45 with the help of high energy heating by high frequency currents with simultaneous shower water cooling. We theoretically justified and experimentally proved a possibility of liquid phase forming in the course of heating not on the surface, but in the depth of the surface layer.
IntroductionSurface hardening of steel workpieces with concentrated energy sources is characterized by high rates of heating (tens of thousands of degrees a second) [1 -7]. Under these conditions the heating of steel is carried out up to the melting temperature for the completion of the austenitizing process. While using the surface sources of heating (laser or plasma) the maximum values of temperatures are definitely observed on the surface of material proper [8,9]. But for three-dimensional energy sources (electron beam, high frequency currents) this fact is not obvious. It is explained, first of all, by the physical nature of a three-dimensional source, i.e. by the law of energy distribution throughout the depth of a heated layer. A possibility of melted metal micro-volumes to form in the depth of material at heating with an electron beam in the atmosphere is shown in paper [10]. Ledeburite structure typical for the heat treatment of cast irons was registered in these areas during surface hardening of hypereutectoid steel.At heating of steels in air medium by a concentrated electron beam the emitted energy distribution in material is similar to that of high energy heating by high frequency currents (HEH HFC) [11]. In this case during the surface hardening with HEH HFC one can also expect a possibility of liquid phase local volumes emergence in the depth of material.The objective of this research is to determine the most heat-stressed layer during high energy heating of steel workpieces by high frequency currents with simultaneous shower cooling.
Quenching of steel 45 using high-frequency induction-heating (440000 Hz) with simultaneous shower water cooling was studied. The possibility of liquid-phase creation in the bulk (appr. 0.2 mm) in the material being treated in the absence of melting on the surface was clearly demonstrated by both numerical simulation of the temperature field in the material during hardening and experimental results
Surface layer modification methods using concentrated energy sources to ensure high heating rates of approximately 104 – 105 °C/s are becoming increasingly common in an attempt to improve operational performance of machine components. As a result, it is quite difficult to determine heat cycle parameters by means of experiments to predict the required intensity and distribution behavior of residual stresses and strains. The paper addresses the issue of numerical simulation of the stress-strain behavior during high energy heating by high frequency currents (HFC HEH). A finite element model has been generated using the ANSYS and SYSWELD software based on numerical computations of differential equations for transient heat conduction (Fourier equation), carbon diffusion (Fick's second law), and the elastic-plastic behavior of the material. The simulation data was verified by full-scale experiments using optical and scanning microscopy and mechanical and X-ray methods to determine residual stresses. It has been established that the level of residual compressive stresses on the component surface can be from-500 to-1000 MPa within the range of HFC HEH process variations under review. It is proven in theory and confirmed by experiments that the transition layer thickness must amount to 25 – 33 % of the hardened layer depth for the tensile stress peak to shift to deeper material layers while compressive stresses on the surface decrease by 6 – 10 %, in order to prevent hardening cracks.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.