Hardening of Cam from A2 Tool Steel 1

[rrossey]

I am machining a cam from A2 Air hardening Tool Steel.
The outer dia is approx 6" and thickness of the cam is 7/8"

I require the outer surface to be hardened to a depth of 1/16" to 1/8"

What should be the hardness of the cam surface if a regular roller bearing of 1-1/2" OD is to be used as follower for a load of 900 lbs?

Can a 15kva induction heating machine be used for heating the surface?

To what temp. the outer dia is to be heated?
This temp is required to be maintained for some time or not?
Can we use a infrared measuring device to record the temp?

I will appreciate if some body can describe the correct procedure.

Thanks.

 

[redpicker]

Save yourself a lot of time and trouble and take it to a commercial heat treater. The cost you pay him will be less than you will pay to make it over. A2 is a pretty easy job, so it shouldn't cost too much.

You had better figure of finish grinding after heat treatment. The surface will be softer than the core because of a loss of carbon at the surface. Finish grinding of 0.010" - 0.015" should be enough.

The heat treater should be able to tell you what hardness you can expect. A2 can get pretty hard, at least 60 HRC.

rp

 

[tbuelna]

rrossey,

Your description of the cam shape, bearing and loads is a bit limited. But based on what you provided, here's some suggestions:

A2 tool steel is an air hardening alloy. You can find HT data on A2 here:

http://latrobesteel.com/technical_datasheets.cfm

A load of 900lbf on a 1.5" dia x 0.88" wide follower contacting a cam lobe with a radius of curvature of approx. 3" should produce very low contact stress, assuming no misalignments. In fact, reducing the (much larger radius of curvature) cam lobe hardness slightly below that of the roller follower will help to equalize the relative strains produced in the mating parts, and should result in a much better overall fatigue life.

As for the optimum hardness/depth profile required in your cam lobe surface, that can quickly be determined by a simple Hertzian contact analysis. The cam surface hardness/depth profile will be established by where the cam contact's point of max sub-surface shear stress occurs.

Hope that helps.
Terry

 

[unclesyd]

We run cams made from both A2 and D2. These cams are up to 12" dia. and 1/2" to 5/8" and run all sorts of rpm and loads. These cams are through hardened and run as is with no treatment of the edges other than polishing. The nominal hardness after heat treating is Rc 60-62 after triple tempering. Some of these cams have been operating for over 25 years with no problems that I can recall.
We used both A@ and D2 in a good number of machine and gear pump components with excellent results even in self mated wear conditions.

 

[arunmrao]

unclesyd,star for you. You were being missed!

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[metman]

...reducing the (much larger radius of curvature) cam lobe hardness slightly below that of the roller follower will help to equalize the relative strains produced in the mating parts.

I agree with your post except for the above statement. Strain is directly proportional to stress and indirectly proportional to Modulus of Elasticity. Heat treatment (hardness) does not change the MoE rather it changes the proportional limit.

Maybe you meant something different?