Does Case Hardening Change the Natural Frequency?

[EdDanzer]

I would like to know if there is any information about case hardening steel either by carburizing or induction hardening changing the natural frequency of a steel bar.

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com

 

[Maui]

The general answer is a qualified yes, but without any idea of why you are asking the question I don't know what else to tell you. What is the purpose of your question?

http://www.EngineeringMetallurgy.com

 

[EdStainless]

It could, if you nitride or carborize you are forming a different compound.
You are also radically changing the residual stress conditions.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[EdDanzer]

The application is machine tool boring bars and rotating tool holders. Over the last 15 years we have been forced to make or modify some holders for unique applications. It seems that none heat treated materials don’t chatter as bad (they seem dead) the problem is the chips damage the soft surfaces. The current direction is to try is to carburize C1018.

We have tried a material that has a 100,000 yield core and a 50 RC induction hardened case and it vibrated like a tuning fork.

Is it also correct that the heat treat does not actually change the deflection amount until you get close to yield on carbon steel bar?

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com

 

[Maui]

The amount of elastic deflection the part undergoes is a function of the loading (load distribution and severity), the geometry of the part, and the elastic moduli of the steel it is constructed from. Since the elastic moduli don't change significantly during heat treatment, the amount of elastic deflection that you should see won't change after heat treat is completed, provided the other factors mentioned above remain the same.

http://www.EngineeringMetallurgy.com

 

[CoryPad]

Material damping capacity is not widely analyzed, but likely is playing a role here. In general, martensitic steels (hardened) provide less damping than ferrite-pearlite steels (unhardened).

 

[EdStainless]

There is some data regarding acoustic dampening, microstructure plays a huge role in this so I would expect similar issues with your applications.
The catch may be how to surface harden the part without getting full heat treatment.
What if you used higher carbon steels, simply normalized, then surface induction hardened them?
Steel HT guys, what do you think?

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[EdDanzer]

Where would I find information about microstructure and acoustic dampening? Carbide bars are good for reducing vibration and allowing longer L/D ratios could this be because of the material being sintered more than being tungsten? I have done a static FEA on both 1118 carbon steel and tungsten boring bars in Algor but I don't know if the default values for tungsten are for sintered or wrought material or if there is a difference. The steel does deflect more than the tungsten with default material values. The frequency FEA results are different between the two materials but I'm not sure what it means from an application stand point.

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com

 

[EdStainless]

I believe that the difference that you are seeing is driven strictly by the difference in bulk modulus.
W and Mo are not only stiffer, but also dampen very well.
For long bars there isn't anything better.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube