For heating metal parts and surface hardening, hardening depth of 2mm-6mm, such as diamond saw blades, drill bits, turning tools, carbide, gear, automobile universal joints, crankshafts, fasteners, etc., particularly for transformers. Induction heating is a heating surface hardening the best way. Due to the skin effect and proximity effect, but the workpiece near the outer skin penetration depth when induction heating is constant layer of direct heat, less internal heat; if you control the heating time, increasing heating power, direct heating layer The heat is too late to propagate to the internal parts, so to meet the requirements of surface hardening. As shown induction coil surface hardening great frequency current to flow through while the workpiece surface heating. General workpiece heating time only a few seconds, a total of no time the interior temperature to rise, then the breakpoint, and quickly so that the surface water to cool. Induction coil through water-cooled copper tube, the coil shape to just wrap the workpiece, the gap between it and the workpiece to be as small as possible. Depth of hardening layer is an important process requirements, quality of its products has a great influence. Depth of hardening layer is mainly determined by the heating power of the frequency, the higher the frequency, the smaller the penetration depth, direct heating layer and hardening the more shallow depth. Quenching into IF frequency power supply (2.5 and 8khz) and high frequency (70-300kz) two categories. IF quenching power relationship between the depth and frequency of the mains frequency: 8khz hardened layer depth 1.3-3.5mm, 2.5khz hardened layer depth 2.4-10mm .. The power supply also have an impact on the depth of hardened layer. The greater the power, the heating time is short, heat directly to the heating layer is too late to spread inside. The more shallow hardened layer. IF quenching power needed to supply quenching area, generally take power per unit area of ??(0.5-2) kw / cm.