What is the difference between high frequency and medium frequency low frequency quenching and what is their role? -Excellent high frequency quenching
There are many kinds of quenching in the heat treatment process of steel. Among them, what are the differences between the high frequency, medium frequency and low frequency quenching process, and are their functions the same? Friends who want to learn the heat treatment process of steel can come and see Kehua share the following some expertise. High frequency, medium frequency and low frequency quenching What does quenching mean? The quenching of steel is to heat the steel to a temperature above the critical temperature Ac3 (hypo-eutectoid steel) or Ac1 (hypereutectoid steel), keep it for a period of time to make it all or part of austenitizing, and then cool it at a temperature greater than the critical cooling rate. A heat treatment process for martensite (or bainite) transformation by rapid cooling to below Ms (or isothermal near Ms). The solution treatment of aluminum alloy, copper alloy, titanium alloy, tempered glass and other materials or the heat treatment process with rapid cooling process is also called quenching. High frequency, medium frequency and low frequency quenching current frequency and difference: The frequency is different. The shorter the heating time, the higher the efficiency, but the thinner the hardened layer. The high frequency is generally 0.5 to 2 mm, the intermediate frequency is generally 2 to 10 mm, and the power frequency is about 10 to 15 mm. Each is suitable for workpieces of different sizes and different hardened layers. High-frequency, medium-frequency and low-frequency quenching High-frequency quenching High-frequency quenching is mostly used for surface quenching of industrial metal parts. Induction heating equipment, that is, equipment for induction heating of workpieces for surface quenching. The principle of induction heating: the workpiece is placed in the inductor, and the inductor is generally a hollow copper tube inputting intermediate frequency or high frequency alternating current (1000-300000Hz or higher). The alternating magnetic field generates an induced current of the same frequency in the workpiece. The distribution of this induced current in the workpiece is uneven, it is strong on the surface, but very weak in the interior, and it is close to 0 in the center. This skin effect is used. , the surface of the workpiece can be heated rapidly, the surface temperature rises to 800-1000 ℃ in a few seconds, and the temperature of the core part is very small. Intermediate frequency quenching Intermediate frequency quenching is to put a metal part in an induction coil, the induction coil is connected with alternating current, an alternating electromagnetic field is generated, and an alternating current is induced in the metal part. Due to the skin effect, the current is mainly concentrated on the surface of the metal part, so The temperature of the surface is the highest, and water spray cooling or other cooling is followed immediately below the induction coil. Since the heating and cooling are mainly concentrated on the surface, the surface modification is obvious, while the internal modification is basically absent, which can have a very special heat treatment effect. (Work) Low-frequency quenching Power-frequency heating surface quenching is the use of power-frequency (50Hz) induction heating electricity, which is directly taken from the power transformer, and the power is often in the hundreds to 1000~2000kW. Use three-phase power transformer or single-phase, three-phase electric furnace transformer. The depth of the hardened layer is often greater than 15mm. After demagnetization during heating, it penetrates 70~80mm into the steel, but the heating speed is slow (several degrees per second), so it is not easy to overheat, and the entire heating process is easy to control. The performance of power frequency heating and quenching workpiece is close to that of furnace heating. Due to the use of inductive circuits, the power factor is low (cosφu003d0.2~0.4), and large-capacity capacitors are often required to compensate. Power frequency surface quenching is suitable for large workpieces, such as cold rolls, rails and crane wheels. In addition to surface quenching, power frequency heating is also commonly used in non-ferrous metal smelting, steel forging heating, normalizing, quenching and tempering of bars and pipes. Regarding the difference between high-frequency, medium-frequency and low-frequency quenching processes, I believe that everyone who has read the knowledge shared by Kehua Xiaobian can understand that different quenching current frequencies and equipment have different effects.