What is the Difference Between Intermediate Frequency Quenching and High Frequency Quenching?

What is medium frequency quenching? What about high frequency quenching? To understand the difference between the two, we need to have a detailed understanding of these two devices, and then we can understand their differences. Let's take a detailed look at the differences between high frequency quenching and medium frequency quenching!

Medium frequency quenching is to put the metal parts in an induction coil, which is connected to an alternating current, producing an alternating electromagnetic field. The metal parts induce an alternating current inside, and the current is concentrated mainly on the surface of the metal parts due to the skin effect, so the surface temperature is also high. The induction coil is followed by water spray cooling or other cooling. Since heating and cooling are mainly concentrated on the surface, the surface modification is very obvious, while the internal modification is basically negligible. This can have very special heat treatment effects.

The medium frequency quenching equipment is mainly used for the heating of metal materials before forging, extrusion and bending, as well as the overall tempering, annealing and tempering of metal materials.

The working principle of high-frequency quenching and medium frequency quenching is the same

Both are induction heating equipment principles: that is, the workpiece is placed in the inductor, which is generally a hollow copper tube for inputting medium frequency or high frequency AC (1000-300000Hz or higher).

An alternating magnetic field is generated to produce an induction current of the same frequency in the workpiece. This induction current is non-uniformly distributed in the workpiece, strong on the surface and weak inside, approaching zero at the core. Utilizing this skin effect can quickly heat the surface of the workpiece. The surface temperature rises to 800-1000℃ in a few seconds, while the core temperature rises very little.

However, during the heating process, the distribution of the induced current in the workpiece is uneven, and the heating effect produced by different current frequencies is also different.

The difference between high frequency quenching and medium frequency quenching

High frequency quenching

The current frequency is above 30kHz;

The hardened layer is shallow (1.5-2mm).

Advantages of high-frequency quenching: high hardness, not easily oxidized, small deformation, good quenching quality, high production efficiency.

High frequency quenching is suitable for parts that work under friction conditions, such as small gears and shafts (materials used are 45# steel and 40Cr).

Medium frequency quenching

The current frequency is 0.5-10KHz;

The hardened layer is deeper (3-5mm).

Medium frequency quenching is suitable for parts that withstand twisting and pressure loads, such as crankshafts, large gears, and grinder spindles (materials used are 45# steel, 40Cr, 9Mn2V and ductile iron).

In summary, a significant difference between high-frequency quenching and medium frequency quenching is that their heating thickness is different. High-frequency quenching can quickly harden the surface of the workpiece in a short time, while the surface stress of medium frequency quenching is smaller than that of high frequency quenching.