A Short Intro to Induction Hardening

Induction hardening is a traditional method that strengthens metal components used in a variety of industries. It’s a process that results in a very high surface hardness for metal materials, making it ideal for use in the production of components that are subjected to heavy loading. Here’s a brief introduction to induction hardening methods and how they can improve the strength of a variety of metal components.

The induction hardening process

The typical induction hardening process consists of two main steps. First, induction heating is used to electrically conduct metals that are heated with an electromagnet and an electronic oscillator. As currents are sent through the electromagnet, they create eddy currents that heat whatever object is held within the induction coil. Through induction heating, the object’s surface is hardened to a depth of up to 8mm.

The second step of induction hardening is called quenching. Immediately after induction heating, the object must be quenched, or cooled down. After it’s heated, the object is put in a tank of oil or water to cool it down quickly. Not only does this step ensure that the surface of the metal object is sufficiently hardened, it also ensures heat hasn’t impacted the core of the material to avoid phase transformations. The quenching process also improves the tensile strength of the metal object.

Properties that are improved with induction hardening

There are specific material properties that are enhanced through the process of induction hardening. These include:

• Finer grain size: The quenching portion of induction hardening methods instantly makes metal objects stronger. Quenching results in a finer grain size on the surface of an object, making the surface harder and more difficult to penetrate.
• Wear and fatigue resistance: The actual structure of a metal surface layer is altered during induction hardening. The end result is a hardened area that greatly reduces wear and enhances fatigue resistance, strengthening the object as much as possible.
• Improved case depth: Induction hardening allows for incredible surface penetration of a material. While the exact depth depends on the circumstances of each individual situation and the material’s properties, you get a deeper case depth generally with induction hardening.

Benefits of induction hardening

In addition to improving the material properties of a metal, induction hardening provides other important benefits. Just a few include:

• Selective hardening: Very few heat treatment processes are able to achieve selective hardening with no masking required. Any areas of post-welding or post-machining on a metal component will stay soft after induction hardening.
• Works with low-cost steels: Low-cost steels like 1045 are ideal for induction hardening. This readily machinable, low-cost material responds well to induction heating, and there’s very low risk of cracking.
• Flexibility: Metal parts can easily be tempered after induction hardening, allowing you to have the flexibility to adjust hardness levels as desired. Since the heat treatment results in a martensitic structure, the metal can be tempered to reduce hardness without resulting in brittleness.

Induction hardening methods result in stronger components that withstand heavy use. Learn more about the process of induction hardening by contacting the experts at J.F. Heat Treating Inc. We’re happy to answer any and all questions you have about this complex process and how it can benefit your unique applications.