Induction Hardening? Consider Depth Variables

This is a question that is often asked of Zion Industries. Often times as a customer is reviewing a drawing, there may be incomplete or even incorrect information regarding the heat treat characteristic. As an engineer is designing a part to be used for a purpose, they must take many things into consideration, one of which may the properties of hardness desired. As they design a piece they may realize that there is surface that will be subject to wear or abrasion, but may not be 100% certain of the heat treat properties they desire, so it may be called out as a higher surface hardness but with few other details. Or perhaps it is wear surface but also important for strength. This requires additional consideration beyond just the surface hardness, the depth is also important. With some of the information potentially missing or perhaps incomplete, a customer will often ask us “how deep can we go?”

The depth of hardness is most dependent on material chemistry, with a few other factors also that need to be considered. The depth of hardness or hardenability of the material is determined for different material using the Jominy Test. For example certain alloys of material are ideal for shallower depths but harder surfaces. Typically low alloy but high carbon materials will be suitable for such applications. Other material will allow much deeper case depth to be achieved and will typically have both higher carbon content as well as other alloying agents.

The hardness of the depth can also be affected by part geometry. Features such as shoulder or holes that result in thin wall areas will be affected differently than straight wall shafts for example. A hollow tube may harden deeper or even through harden compared to solid shaft of the same dimensions.

At Zion we can help answer the questions “How deep can we go?”. Using published data for hundreds of different types of steel as well as our team’s many years of experience, we can help determine what would be possible or appropriate. We can also offer advice on what might not work so well, to prevent a detrimental experience. We look forward to evaluating your application!

Lou Ghinga
Plant Manager, Valley City, OH
Zion Industries, Inc.

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