The investigations result in a guideline according to which the case depth of slewing bearing rings can be determined, if the load on the rolling elements, their size, and the number of load cycles are known. Induction hardening is applied mostly to hardenable steels, although some slowly cooled carburised parts are also induction hardened. the hardness and the hardening depth, is defined by the carbonization depth, the receptiveness and thus the hardenability of the steel, and the quenching. [3], Induction surface hardened low alloyed medium carbon steels are widely used for critical automotive and machine applications which require high wear resistance. Prohibited Content 3. Normalised state also shows this but to a lesser extent. Classification of Aluminium Alloys | Metallurgy, Unconventional Machining Processes: AJM, EBM, LBM & PAM | Manufacturing, Material Properties: Alloying, Heat Treatment, Mechanical Working and Recrystallization, Design of Gating System | Casting | Manufacturing Science, Forming Process: Forming Operations of Materials | Manufacturing Science, Generative Manufacturing Process and its Types | Manufacturing Science, Types of Induction Coils for Induction-Hardening, Metallurgical Control in Induction-Hardening, Advantages and Disadvantages of Induction-Hardening. Methods 5. Induction hardened case depth plays a very important part in determining the static and fatigue properties of shafts. Induction hardening is one of the most common methods to increase the hardness on the surface and near-surface layer of the components. When the component is rotated within the inductor, the width of the inductor is equal to the breadth of the surface area to be hardened. This aspect should be taken into account in assigning heating conditions. With the aid of Maxwell’s equations it can be shown that the current density decreases exponentially with depth. This depends on the hardenability of the material, the section thickness and the flame hardening process used. With a conventional method (or if we induction hardened the entire length for that matter), there would be significantly more warpage. Heat is produced within the surface layer of an object using a non-contact heating process based on the principles of Electromagnetic Induction. The depth of hardening below the base of the spline should at least be equal to the height of the spline ribs. This is normally also the distance between turns. 8.69 illustrates some loop type and Zig-Zag type inductors to be used for surface hardening of flat components. In this article we will discuss about:- 1. An accurate design requires exact detail about each gear tooth based upon the actual profile presented Figure 1: Macroetched cross-section showing differences in induction hardened case depth due to a 350ºF preheat. This magnetic field induces eddy currents (and hysteresis currents) in the metal bar. Low-alloy and medium-carbon steels with 0.4 to 0.55% C (e.g., SAE 1040, 15B41, 4140, 4340, 4150, 1552) are commonly used in induction gear hardening. A through-hardened gear tooth with a hardness exceeding 62 HRC is typically too brittle and will often experience a premature fracture. When an electric current passes through a coil, a magnetic field flows through the coil. But when high frequency alternating current is passed through this coil, highly concentrated varying magnetic field is setup. [4], Early last century the principles were explored as a means to melt steel, and the motor generator was developed to provide the power required for the induction furnace. 8.59. Other parts may be tempered to required hardness values. 8.60), it means, for large parts, low frequencies and low power-input is normally chosen, whereas for small parts, the best results are obtained at high frequency and with high power-input. For induction and flame hardened cases, the criterion for measuring effective case depth up to different hardness values depending on the carbon content of the steel is given below: Preparation of the specimens for case depth measurement by any of the three following methods should be done very carefully particularly taking care that no grinding or cutting burn occurs. The Fig. All process parameters were the same for each trial. 8.63 (a) illustrates the effect of initial microstructure during induction-hardening a AISI 1070 steel. The workpiece to be heated is placed within this alternating magnetic field where eddy currents are generated within the workpiece and resistance leads to Joule heating of the metal. ... Conversely, the adjustment of the electromagnetic frequency ensures precise control of hardening depth, so repeatable results are much easier to achieve. But, during induction-hardening, the chromium carbides are not dissolved and hence, the steel responds poorly to induction-hardening treatment. For a high surface hardness – for example, 60 HRC – a carbon content of 0.1-0.3% is not sufficient. This normally needs valve-generator set for high frequency current. Higher frequencies are obtained with valve-generators. Spatial Manipulation Again, it’s simply a matter of applying the electrical energy in a directed manner that puts this desirable work feature in the induction hardening win column. i.e. The spray quench at incidence angle of 40° to 50° should be used so that it sprays the surface with an even film of water or oil producing an even depth or hardness and eliminates local over hardened spots. These normally employ a digital encoder and programmable logic controller for the positional control, switching, monitoring, and setting. In double hardening, a variation could be made in which the first austenitising temperature could be at higher temperature to obtain better carbon (and some alloying elements) diffusion and more uniform distribution. Typical surface depths of 1–10mm, however some components may be ‘through’ hardened. b. Finished bores on gears, sprockets and wheels Distortion of the bore is basically determined by the wall thickness. There are two alternative methods of induction hardening: conventional “scanning hardening” and the less common “single-shot hardening.” This article looks at the induction hardening process and discusses these options. At the same time, the heating rate is reduced. Induction hardening is a type of surface hardening in which a metal part is induction-heated and then quenched. Types of Induction Coils for Induction-Hardening of Steels: The coils, also called inductors are made of copper tubes and are cooled during operation by internal water flow as these too get heated up by electric current as well as by radiation from the heated steel. Induction hardening is a method of quickly and selectively hardening the surface of a metal part. The workpiece weight is also the same, and the 8-ton load corresponds to 2,667 shafts. single shot hardening, traverse hardening or submerged hardening. Gregory A. Fett * Dana Corp. Maumee, Ohio *Member of ASM International and member, ASM Heat Treating Society his article updates work origi-nally published in February 1985 Metal Progress, which … 8.67 b). The whole depth can be penetrated by using low frequencies, and the low power input does not permit over heating of the surface layers. 3. A transfer function was generated from the calibration data. Induction Hardening Machines & Equipment. 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