Intermediate frequency quenching USES: used for heating metal parts and partial surface quenching, quenching layer depth of 2 mm to 6 mm, such as diamond saw blade, drill, lathe tools, carbide, gear, automobile universal joint, crankshaft, fasteners, etc.
Induction heating is the ideal heating method for surface quenching. Due to the proximity effect and the effect of the skin effect, induction heating is only a layer of direct heat which is close to the outer epidermal penetration depth in the workpiece, and the internal heating is very few. If the heating time is controlled and the heating power is increased, the heat of the direct heating layer can not be reached inside the workpiece so that the surface quenching can be satisfied.
Surface quenching is shown as the induction coil flows through a large medium - frequency current and heats the workpiece surface. The heating time of general workpiece is only a few seconds. The internal temperature of the common piece can not rise at all, then the breakpoint, and spray water quickly to cool the workpiece surface. The induction coil is cooled by copper tube, and the shape of the coil should be exactly wrapped in the workpiece. The clearance between it and the workpiece should be as small as possible.
The depth of the quenching layer is an important process requirement, which has a great influence on the quality of the products. The depth of the quenching layer is mainly determined by the frequency of the heating power supply, the higher the frequency, the smaller the penetration depth, the lighter the direct heating layer and the quenching depth. The frequency of quenching heating power is divided into two categories: intermediate frequency (2.5 and 8khz) and high frequency (70-300kz). The relationship between the medium frequency quenching depth and the frequency of the power supply is the power frequency: the depth of 8khz quenching layer is 1.3-3.5mm, 2.5khz quenching layer depth 2.4-10mm.
The power supply has an effect on the depth of quenching. The higher the power, the shorter the heating time, and the heat of the direct heating layer can not be transmitted internally. The hardening layer is lighter. The power power required by medium frequency quenching is related to the area of quenching. The power of the average unit area is (0.5-2) kw/ cm2.
Intermediate frequency quenching in medium frequency quenching transformer refers to medium frequency induction hardening heat treatment heating.
The secondary coil of the intermediate frequency quenching transformer is an ac induction coil.
The workpiece is placed in the ac induction coil and heated under alternating magnetic field.
Heating is concentrated in the workpiece surface layer, which is called the skin effect. The speed of heating and the depth of heating are related to the ac frequency of the induction coil. The frequency is high and the temperature is high, but the heating layer is thin, which is suitable for handling small precision workpieces. Low frequency (frequency) heating layer, suitable for handling large load. The intermediate frequency effect is somewhere in between.