The features of steel surface hardening with high energy heating by high frequency currents and shower cooling

Abstract

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.

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