Carburising flame vs Kasenite

Wes,

As a not too WAG, I'd say Kasenite would be the way to go. You are applying carbonaceous material as well as the carburizing flame of the torch. You should be able to do this with an ordinary propane, or MAPP gas torch if you don't have ready access to acet..

12L14 because that is what I had on hand.

I have some new formulation Kasenite and access to an OA torch. I understand a carburizing flame can harden mild steel and of course so can Kasenite.

Which would be the better choice?

Thanks,

Wes

IIRC it takes a while to get the carbon into the part. We used to put about a 0.020 case on millions of bolts and it took about 1 1/2 hours in a furnace with a high carbon atmosphere, I think. I doubt if you'd do much good with the torch because you'd still be oxidixing the part as you go. Read the label on the Kasenite. All you can do is to get a 20 thou or so case on the part. That isn't what you need for the chuck key. You have chosen about the softest steel one can find. I'd suspect that the problem will be twisting the business end anyway and the case won't help much if you do get it.

Pete Stanaitis

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Wes wrote:

Hey Wes,

I would bow to Bob Swinney and Pete Stanaitis on the issue of which method is easier/best, but it has been my understanding that while

12L14 is wonderful to machine (especially to "turn"), it will always be a "soft" metal due to it's metallurgic composition.

I would think that now that you have had the practice of making this neat sounding gadget (PICTURES PLEASE!!!) that if you just remake the same thing but using drill rod, you'd have a better chance, and easier than case-hardening too.

Take care.

Brian Lawson, Bothwell, Ontario.

My Kasenite method is dead easy. heat part red hot, dip in kaesnite can, let cool. Repeat as often as you want- case harden goes deeper each time. Last time you heat, dip in water instead to quench and harden.

Karl

You'll fail with just the flame. Heat to red, dip in Kasenit and hold the heat for some minutes. Directly quench and don't temper. Yes, I know, it should be done different! Works good enough for what you need. I hardened the head of a self-made screw (out of free cutting steel) that way years ago and it still is good enough (no more perfect, but it is used often).

Nick

Now I am a bit confused. I looked up the properties of 12L14 and 4140

11600 ksi shear modulus

11600 ksi shear modulus

IIRC from my junior college days mild steel has about 60,000 psi shear so this modulus number must mean something else. I googled a bit but didn't really understand the explainations.

Given the typical length of a chuck key handle, I don't think I'm going to twist the end off.

Wes

Shear modulus refers to stiffness, not to strength. The shear, tensile, and compressive moduli for all steels fall in a very narrow range relative to each other, regardless of their strength or hardness. Stainless is somewhat lower.

The tensile yield strengths of the two materials are 60.2 kpsi for 12L14 and

143 kpsi for 4140, respectively -- at the respective Brinell hardness tested by your website source, anyway.

The softness or hardness of a steel grade generally relates closely to its strength. In this case, the hardness of the 12L14 reported on your site is

163 Brinell, versus 311 Brinell for the 4140. This actually varies over quite a long range in the case of 4140, depending on heat treatment. But that's about it for 12L14, unless it's carburized and heat-treated.

I don't know if 12L14 can be carburized successfully, in any case. The question has come up here before but I forget the answer.

I haven't read this thread but 12L14 is not a good choice if you need more strength than that of mild steel. Case-carburizing with a reducing flame is not going to give you a thick enough case to add any significant strength, regardless of whether 12L14 can be carburized. You could do it with Kasenit, perhaps, using a pack-hardening method in a clay, stainless-foil, or tin-can-steel pack, in a furnace of some kind. But Kasenit is really for surface hardening for wear-resistance, not for the kind of deep case-hardening sometimes used in industry for increasing strength.

-- Ed Huntress

Wes, I read the thread and I see you're just trying to harden the drive ends. You can do that with Kasenit, using one of the methods others have described here. As Nick says, just quench, don't temper.

You'll still want a pretty good case. You'll want to repeat at least two or three times (only quench on the final treatment), as someone else suggested. Getting a case thicker that 0.005" or so with Kasenit generally requires pack-hardening. But 5 thousanths ought to do it OK.

-- Ed Huntress

Wes,

12L14 readily takes case hardening, however to reach maximum case depth requires packing in Kasenit & soaking in a heat treat oven for up to one hour (.030 case depth) at 1600 degrees. Merely heating the part with a torch and dipping will only provide a superficial case depth. I have even less confidence in using only a carburizing torch flame.

However I would question the need to even harden a chuck key, I never felt the need to do harden my shop made keys, and I have milled factory keys to adapt and those were soft too.

Tony

The tap wrench I made as an apprentice that was hardened by heating, dipping and heating is still good after thirty years :-)

Mark Rand RTFM