Case hardening using sugar

According to Tony :

Were you using the Kasenit in a box, or in the heat and dip manner? I suspect that it makes a difference. :-)

Enjoy, DoN.

Heh! Depends on what you consider "old".

I started in the trade in '57, at Sperry Utah Engineering Laboratories. They were founded in '56, a division of Sperry out of New York. Most of the top brass came from the Greatneck plant, as I understood it, although we also had a few from Bluebell, an operation in the south, Tennessee, I think. Anyway, the project was the Sergeant Missile. We produced the inertial guidance system. The roll pitch and yaw gimbals were all machined from precision aluminum castings, and, due to little miniaturization at that point in time, were fairly large items. The stable platform was approximately 18" in size, perhaps a little larger. Time has a way of erasing these things from your memory.

The point is, the gimbals were machined on a Warner Swasey turret lathe, using lard oil in the sump. While the smell wasn't very strong, it was one of the worst of smells I could think of.

Harold

It's all the same thing, Nick, just a matter of terminology, with pack hardening being one of the methods the objective is achieved. The item is "packed" in carbonaceous material in a container and heated. Another would be gas carburizing, where it's done by the atmosphere of the furnace. You'll even find it called pack carburization.

The purpose is to introduce carbon to the article in question to permit hardening. The case in and of itself does not harden the material, but allows the heat treat process to do so. Carbon content would be too low otherwise. The carbon is introduced in the form of carbon monoxide, a product of heating the carbonaceous materials in an oxygen poor atmosphere, and is absorbed by the steel, which has an affinity for carbon.

The "case" in question is the increased carbon area around the part, or, said another way, the mild steel inside is encased in higher carbon for the purpose of hardening.

Harold

I agree. Average depth of carbon infusion is approximately .010"/hour when pack hardening, and drops off rapidly as depth increases. Pretty much ceases after about .090".

Harold

I don't remember where I have read that. Either at the Kanthal-site (manufacturer of heating elements) or a seller for Kasenit and a box hardening powder.

Nick

Terminology was my problem, not technology. :-)

That's the trick. Now I understand the difference in the words.

Thanks, Nick

Did you ever work on the ST-80 and ST-120 stable platforms for the Redstone and Pershing missiles by any chance?

No-------at least no knowingly. My job with Sperry was specifically for the purpose of building the Sergeant, which was taken from the R&D stage through production and phase out in the facility. Fact is, I quit when the project ran out. I say not knowingly, because I have no way of knowing if guidance systems were being produced for others, but if they were, they were identical to the one used in the Sergeant.

Aside from building a huge alignment fixture for the Mariner project, the Sergeant was the only space related item that was built by Sperry Utah to that point in time. They went on to do other defense work, and became one of my customers when I ran my own shop.

Harold

I fill an old stainless steel baking pan (about pound cake size) with Kasenit powder, covering the parts to be hardened. It goes into my Lindbergh heat-treat oven. As the powder heats up and melts some smoke will be emitted, so I keep my garage door open. The Kasenit turns lava like during the process and there can be some tendency to creep over the sides of the pan, therefore its important not to overfill the pan when loading.

To bring the 220v oven to 1700deg it takes almost an hour, then the hardening time depending on the depth of case, I typically go for max depth unless there is a thin crosssection. Then quenching & clean up the whole job can take up to 3 hours. The oven typically needs 8 hours to cool back down with the door closed.

Tony

No, Ouch! For that kind of money, one can buy the best of English-only dictionaries, with change left over.

Actually, I'd get a large but ordinary American English dictionary first. These terms are all old enough that they have found their way into standard dictionaries.

Yes to both.

I did forget to mention that after adding the carbon to the outside layers, one must do the usual heat, quench, and temper process for the surface to actually be hard.

A standard trick is to do the carbonizing (or carburization) part of the case-hardening process, machine all but the intended hard area away, and then perform the heat, quench, and temper process. Because the metal is in the annealed state, machining is easy, regardless of carbon content. This yields very selective hardening, with sharp borders.

Well, you can call it that too. The terms are pretty much equivalent.

Joe Gwinn

There's arsenic in this Kasenite stuff? Are you quite sure? Wouldn't that harm the steel?

S.

I have a hunch he's talking about cyanide. It was commonly used for heat treat years ago.

Harold

The hardbound OED 20 volume set is GBP850 or USD895 or Eur900 (amazon.co.uk/.com/.fr)

That a book published by a British company and then shipped 3500 miles across the pond is only 53% of the price of shipping it 3 feet out of the door in Oxford doesn't surprise me in the least. Nor does the fact that the same book is 29% cheaper when shipped across the channel to the land of the cheese eating surrender monkeys.

Ripoff Britain lives up to its name.

P.S. the leatherbound edition is GBP4000, enough to buy a decent machine tool.