Case Hardening

[larry53]

I have to case harden parts for a customer I have. I have been using a compound name Kasnite which works good but leaves a scale on the parts which has to be removed. I do this by glass beading the parts,which is very time comsuming. Does anyone know of another compound or process that will not leave a scale on the surface of the heat treated part? The customer will not go to tool steel but requires 12L14 steel to be used. Thanks for any replys.

[HuFlungDung]

Have you tried contacting a professional heat treating facility? The modern method is gas carburizing, which does not seem to produce any scale or surface damage whatsoever.

[Mcgyver]

you could pickle them. you know Kasenit will only give a couple thou case - is that enough? I use it often but for more serious jobs that need grinding afterwards or otherwise a deeper case, I send stuff out and get a better soak, they can take it up to 50 thou deep. imo for a lot apps its a far better approach than using tool steel.

[Geof]

Why not use 4140 leaded?

http://www.niagaralasalle.com/products/4140L.html

[larry53]

the customer will not used anything but 12 L14.

[Geof]

Originally Posted by larry53 the customer will not used anything but 12 L14.

Well I suppose the customer is always right.

[PeterCharles]

Looking at the analysis I would expect it to be suitable for gas carburising followed by oil quench.

[DareBee]

You could always buy a vacuum furnace. It is the reaction with atmosphere the creates the scale.

Unless I am desperate for time I always send at all heat treating.

[NC Cams]

How much of a case do you want?

How much of a case does the user NEED?

What are they trying to achieve?

For some applications, 1010~1020 may be better suited. Yet on others, 8620 would be superior or even 5015 or 4820.

Carbonitride, case carburize, deep case carburize are all processes that should work on the material you are being forced to use.

HOWEVER, the spec's material may not give the optimum performance for all situations when case hardened - 12L14 is typically chosen for super machineability and/or low cost as opposed to any superior metallurgical properties. Some guys call it "leadloy" and it does qualify as being able to rust, sink and be magnetic.

The above noted processes are listed in order of effective case depth potential, thinnest to thickest.

[HuFlungDung]

How does the lead in the steel affect the heat treatment? What about sulferized steels? Or does the lead or sulfer get cooked out of the surface during carburizing anyway?

[Geof]

Originally Posted by HuFlungDung How does the lead in the steel affect the heat treatment? What about sulferized steels? Or does the lead or sulfer get cooked out of the surface during carburizing anyway?

Whether or not the lead does anything during the carburizing, I think the purpose of the lead defeats the case hardening. Leaded steel has a low yield strength, it is noticeably softer to plastic deformation than 1018 or even A36. Putting a case on leaded is something like putting a skin of ice on soft snow; I think if it is subjected to an appreciable load it is likely to deform under the case which is likely to crack. This forms a perfect starting point for a fatigue crack and leaded is more fatigue prone that non-leaded low carbon steels. I would never contemplate using leaded in an application requiring a hard surface.

[NC Cams]

Case hardening 12L14 is like putting lipstick on a PIG. THe above comments about sub surface yielding potenail are absolutely true. THe case can only support what the substrate can withstand w/o yielding and 12L14 ain't very robust - it rusts, it sinks and it's magnetic.

We don't know why the end user is spec'ing 12L14 but that's what they want. It may suck but that's what they want. ANYTHING BUT 12L14 could/would be better but (see post #5).

From what I went thru this past week trying to make the part better than what the client wants/needs, the best thing to do is to follow a very precise MIL spec.

MIL TFP 4.1 which translates into

"Make it like the frigging print for once"