Case hardening materials

[thefodenman]

Hi everyone,
I need to case harden new crosshead guidebars for my 5" gauge 9F.
Many years ago I seem to remember you heated the part up and dipped the item in a powder then reheated? . Now heres the question where can I buy the powder? or source a similar material to do case hardening. Failing that what can I use if its not available anymore. Cheers, Andy

[Shawki Shlemon]

If cross head or( slippers on top & bottom ) is made of bronze or gunmetal then you don't need to case harden the guide bars not for this life at least . Just make sure they are lubricated .

[thefodenman]

Thanks for that, there is a bronze slipper on the top of the crosshead but not for the two side guide bars, looking on Chronos website, they advertise case hardening powder, anybody got any experiance with that?

[abby]

Kasenit is still very much available in the UK, bought some a couple of years ago . I was told by my metalwork teacher many years ago that Kasenit is ground up animal bones , that had been roasted - similar to charcoal burning- so if you can't get any in OZ perhaps you could make some !
Abby

[Myford Matt]

EKP sell it, and because it weighs little posting it to Oz won't cost too much:

www.ekp.supplies.btinternet.co.uk/

MM

[thefodenman]

Much as I would like to be in Oz, Iam located in Derbyshire!!!!!! and before anybody says yes iknow everybody has there cross to bear!!!

[paul]

I was told by College Engineering that they no longer sell it because it is believed to be a carcinogen. I wanted some to harden a toolmakers clamp I planned on making.

[John Lee]

paul said:

I was told by College Engineering that they no longer sell it because it is believed to be a carcinogen. I wanted some to harden a toolmakers clamp I planned on making.

Ohh well, Blackgates sell it for one; I guess other suppliers will do also

John

[SteveW]

Andy,

The version I got from school was to use any source of animal carbon. Hair (horse hair) was the example used but I'd imagine it'll pong like hell.

It also occurs that the heat cycling could cause distortion. It it worth the risk? Maybe make two sets now, one now and one for later.

[houstonceng]

Guys

Words of wisdom heard from me old dad way back - might have lost a little in the translation and from the memory banks - was as follows.

It shouldn't really matter what material is used to make the carbon so long as the end product is near pure carbon. Some people say animal bones others hair, some prefer oak other fruit stones or shells from walnuts. What you don't want is any "odd chemicals" or metalic substances in the carbon because these could adversely affect the part being case hardened so no wood with paint on it (could be lead based), for example.

You pack the raw material into relatively airtight containers (with some small vents in them to let out the gasses) and heat it in a fire so that the content turns to charcoal. In other words, it's not burnt, but rather has the gasses and tars driven out in the same way that coke is made. The gasses will ignite and burn at the holes.

Then you need to add some activators. Generally Sodium Carbonate and Barium Carbonate (The latter is very poisonous so that's probably the carcinogenic content. Back in the old days, no-one seemed to worry about buying and using poisons judging by the recipes in books like "Machinery's Handbook".) Sodium Carbonate is "washing soda" so that's relatively harmless. The two are made into a mixture with water and poured onto the carbon after which it's dried.

(No wonder that most of us buy Kasenit or another brand of ready made "case hardening" powder.)

Actually, "Case Hardening" isn't really the correct term What you are really doing initially is Carburizing/Carburising mild steel. In other words, getting it to absorb carbon into the outside layer of the job, thereby turning that outside layer into high-carbon steel. You can either heat your MS to red heat and dip it into Kasenit (or your home-made mixture) - one or more times - in which case (no pun intended) it will not have a very deep layer of High-carbon content OR you can pack the part into an airtight container packed tightly with the activated carbon mixture and heat the whole to red and hold it there for a set time. Too long and it will all be turned into high-carbon steel which you probably don't want. Ideal temp, of memory serves, was 1600 to 1700 degs Fahrenheit.

If the part is then left to cool slowly, it will be carburised, but not hardened. Somewhat similar to raw "Silver Steel" (aka "Drill Rod" in the US of A). So you can do some more machining on it if required. (Ideal if you want a thread on it , for example). You then reheat it to red and quench - after which it will be "hardened right out". Some people say you should always do this rather than quench directly from the carburising as it give a better grain structure to the remaining MS in the middle. If you do try this, it's recommended that you protect the part from scaling by repacking in plain charcoal or coating it with something loke "plumbers smudge", Tipex, soft soap, or one of the commercial products sold for the purpose.

You can, if you want, then temper the hard layer exactly like you'd do with any tool made from high-carbon steel, however, the main reason that case hardened MS is used rather than making a part from high-carbon steel is that you want a fully hardened wear resistant outside but retain the ductility of the MS core. A fully hardened high-carbon part might shatter.

I think that's about all I remember being told. I don't think my dad ever made his own mixture. I certainly only remember the Kasinit tin in his workshop and the use of the "open coal fire" we had in the living room (as a makeshift furnace) - when Mum allowed.

Andy

[alanstepney]

stevew said:

Andy,

Hair (horse hair) was the example used ....

Biggest problem is getting the horse to stand still whilst you help yourself to its coat!

You can also use old bones, leather, or many other things.
One that used to be quite common was crushed coke, when we had it which was back when we had those nice smelling gas works.

I reckon a tin of shop-bought whatever, is far easier.

[thefodenman]

Hi all from good ol Derbyshire (AKA Oz? ha ha)
I knew this would get interesting, ironically we (well my daughter actually) has a horse, I could wait til spring and collect her molting hair, however I suspect it will be easier to buy a tin of case hardening compound, but probably not half as much fun!!!!!!
thanks to all for your advise and help, is'nt this site great.
Andy

[Shawki Shlemon]

I looked in my workshop and found the product I used in the past and I still have a very small amount but I don't remember where I bought it from. It is called HARDITE . I found a company here on the net who stock it, it is Mitchell's Engineers Supplies - Product Range . You can check it out and may be they can send you some.ON the other hand you can use silver steel flat of the correct thickness , cut and mill to size and no need for further action and if you still want you can harden and temper or harden by quenching in oil , it will give you similar effect as harden and temper.I hope this may help .

[Noddy]

Time is short so I'll try to be quick.

I gather kasenit contains both cyanides and a source of carbon, so hardens by both carburizing and nitriding.

I'm begining to form a theory that oldtimers used to have a macho competition going to see who could come up with the most toxic and dangerous concoction, then (and only then) try to find a use for it...


The straight carburizing mixtures consisted of:

a source of carbon, such as charcoal or coke, and;

an "activator" which released carbon dioxide at just above the critical temperature of the piece being hardened.

The carbon dioxide reacted with the carbon fuel to give carbon monoxide, which then donated some of its carbon to the steel and could again react with more carbon fuel.

Charcoals made from bones or leather contain a little of their own activators, but remain relatively slow working.

Incorporating a little of a metal carbonate which breaks down at the appropriate temperature, greatly speeds up and intensifies the process.

Barium carbonate (eating 4 grams gives a 50 : 50 chance of killing a human, so pretty poisonous) breaks down at just about the right temperature, hence its use.

I'm away from my reference books, but I think that calcium carbonate (limestone) is probably a little to high a temp to be as useful. Dolomite I remember as breaking down at a lower temp.

The decomposition of carbonates absorbs a lot of heat, so getting the temperature right is important.

Higgins; engineering metallurgy gives a good coverage on heat treatment of case hardened steels, even covering refining the grain and hardening and tempering the core as well as the case (again, I don't have my copy to hand).

Case hardening was (and is) widely used in gun parts and for rock drill internal parts.

There are several little tricks available for selective case hardening. One I have read about involves dipping a part in accidified copper sulphate solution to get a copper coating, then finish grinding (or filing) the wearing surfaces that require hardening. This leaves the remaining surfaces coated in copper and unreceptive to carbon, so that they can be tapped or peened.