High frequency induction hardening methods and theory analysis

　　The essence of the method is: the object is placed in hardened helical induction coil or be placed in a conductor (usually copper) below, in the induction coil or conductor through to high frequency AC current. So that the alternating current induced in the object, which induced current is concentrated on the surface of the object (the so-called skin effect), and the depth direction along the metal sharp decline. However, where the maximum current density will quickly heat the metal, thus, have not had time when the internal heating, the surface has been heated to a sufficient temperature quenching. As the depth of hardening depends on many factors still, and the first number is a current frequency (the number of cycles per second), the input power and the heating time.

　　If an induction heating method, the depth of the metal reached the number P depends on the frequency F, P and the specific resistance of the metal magnetic permeability of the U, as in the following equation:

　　P = C (P / U * F)

　　Where C is the scale factor.

　　Because more or less U and P are constant, so that from the formula, the heat reaches the depth of the current cycle is determined by the number, F increase, then P decreases.

　　But there should be emphasized that: This formula is described heat into the depths.

　　As the depth of heating, too, should decide on the power and pass the current length of time.

　　In fact, the higher the power supplied to the induction coil, the body of the induction heat the object surface should also be larger. On the other hand, the longer the induction of heat into the metal on the deeper (because the metal is heat conduction).

　　Therefore, the control cycle, the power and time so that the object can be heated to an arbitrary depth, the fraction of a millimeter up to tens of millimeters.

　　Then the surface has been cooling the heated object, you can get a hard was quenched surface layer, while the center remains the original organization. When an object is greater than 0.3-0.4% carbon, this method can be very effective in improving the hardness of the hardened surface. If large objects, you can also borrow to cool the interior surface has been heated, but can also be the object through an induction loop water (or other liquid) to cool down.