Case hardening compound

[zeppelin builder]

A blacksmith I knew regularly asked me to collect horses hoof for him for case hardening.
He preferred the little shavings that the rasp produced rather than the big lumps that got chopped off so it was a bit of a pain to try and collect him a bucket full!

He would put his part in a metal box with them, give it a rough purge with his mig torch then weld a lid on. Heat it to dull red then leave it sat on the edge.of the coal fire all day.

I am pretty sure something else was put in the mix as well but no idea what?

think casenit was mainly ground bone meal gardeners used similar
i have an old millwrights book with info on this . pack the item in a metal box or tube with leather and or hoof trimmings
fix the lid bring up the temp in a forge
and the depth will be in relation to time held a depth of up to 1/16'or more
can be had after rapid quenching in water

 

[zeppelin builder]

Making a guess that not many of us have a real hardness tester at our disposal, are there any reliable "DIY" methods to assess hardness?
IIRC, the real ones push a diamond in to the surface under a precise load and the width of the imprint is measured under a microscope. There's a table of hardness v ident widths.

a sharp file will just skid off it or a centre punch will not mark it

 

[Screwdriver]

think hi temp and hi pressure nitrogen atmosphere is nitriding /tuftriding

Nitriding and carburising (case hardening) are very similar processes. You just want to dope a metal surface with something to manipulate its properties. According to Google both processes rely on interstitial diffusion into the surface.

 

[zeppelin builder]

Nitriding and carburising (case hardening) are very similar processes. You just want to dope a metal surface with something to manipulate its properties. According to Google both processes rely on interstitial diffusion into the surface.

think nitriding requires a certain grade of steel iirc

 

[MattF]

think casenit was mainly ground bone meal gardeners used similar
i have an old millwrights book with info on this . pack the item in a metal box or tube with leather and or hoof trimmings
fix the lid bring up the temp in a forge
and the depth will be in relation to time held a depth of up to 1/16'or more
can be had after rapid quenching in water

Seem to recall reading similar in one of my books.

 

[Screwdriver]

Making a guess that not many of us have a real hardness tester at our disposal, are there any reliable "DIY" methods to assess hardness?
IIRC, the real ones push a diamond in to the surface under a precise load and the width of the imprint is measured under a microscope. There's a table of hardness v ident widths.

The file test is a very good indicator, you can feel the file slipping and it makes a distinct noise as it skates across the glassy surface.

You can also buy sets of files of varying hardness and test your workpiece by trying harder and harder files until one starts to "bite" into the hardened surface.

To discover if your material is hardenable (a steel with relatively high levels of carbon) you can test for it by hitting the surface with a grinder. The pattern of sparks will indicate whether or not it's a carbon steel as opposed to a mild steel or plain iron. The sparks split up at the ends and there's relatively more of them...

 

[Screwdriver]

think nitriding requires a certain grade of steel iirc

Yes but a similar mechanism for case hardening by doping the crystalline structure of the workpiece etc. But it is not a DIY process so - I'm out!

 

[ronan]

Kasenite did work, then they changed it and then it disappeared completely. Someone said it was because of the chemicals in it being banned now. Sugar ? Doesn't work, i tried it several times.

 

[Stueeee]

think nitriding requires a certain grade of steel iirc

EN40B is usually referred to as "Nitriding Steel". Every billet crank I've had made has been in this material.

I've had Tuftriding done too on existing cranks, but as it's a higher temperature process than Nitriding, there's a bigger risk of distortion when the piece comes back.

Nitrided cranks are finish ground after Nitriding. Both to correct any slight distortion, and to expose the area of maximum hardness/fatigue resistance which is (IIRC) about 8 thou' below the heat treated surface.

 

[Anguz]

I have lots of granulated carbon if anyone wants any?

 

[optima21]

my new tin of kasenit has a best before date of 30/03/97 wonder what it will be like when I eventually need to open it.

workshop practice series has a chapter devoted to the subject of case hardening.

Workshop Practice Series 01 Hardening, Tempering, And Heat Treatment : Free Download, Borrow, and Streaming : Internet Archive

Workshop practice series 1. Hardening, Tempering, And Heat Treatment

archive.org

I have got a paper copy of the book though.

 

[Misterg]

I'm normally a bit wary of Wikipedia, but their section on case hardening makes sense to me - it gives the mechanism for transfer of carbon to the steel as being via carbon monoxide gas. It's therefore necessary to exclude oxygen (to stop CO becoming CO2) and helpful to add carbonates that will evolve CO2 which can form additional CO in the presence of hot carbon and the absence of oxygen which makes some sense of the various recipes that are knocking around.

Case-hardening - Wikipedia

en.wikipedia.org

Kasenit used to contain a cyanide salt (potassium ferrocyanide?). It's possible that this contributed to hardening the steel directly (though nitriding) or that it just melted at the right temperature to seal in the carbon material against the metal and exclude oxygen. The speed with which it is reported to have worked suggests to me that the former was at least a factor.

 

[Agroshield]

Kasenit used to contain a cyanide salt (potassium ferrocyanide?)

The reason cyanide compounds were good is because cyanide is itself a carbon compound (i.e. it contains a carbon atom) that it can give up to the metal.

It is similar to why nitrous oxide is used in engines - it contains a lot of oxygen in its chemical make-up that can be used to burn the fuel.

 

[northwest]

Kasenit used to contain a cyanide salt (potassium ferrocyanide?)

It still does and the word "cyanide" is enough for many to have palpitations. I cannot remember the legislation but as always with these things, it was legislated out of existence.
I have done an enormous amount of work with case hardening and more specifically Colour Case Hardening for obvious reasons. Here are a couple of pics of stuff I created:





The amount of work and sheer effort to get these pieces to this point as a one-off is just not worth it. I did this for my own curiosity. Bone charcoal was the active medium and sealing the parts into a steel box which also had a strip of leather in it to kill off any O2 when it burned. I will not be doing this again in a rush.

Case hardening using Kasenit or one of the modern substitutes works well but you need to consider distortion and how tolerant your part is going to be. You can get small amounts such as here: http://www.knighton-tools.co.uk/acatalog/BETA_CASE_HARDENING_COMPOUND.html

Or a tub of it (and associated stuff) from here: https://www.rutpen.co.uk/product/beta-case-hardening-compound/ It all depends how much you want to put into the job.

 

[hotponyshoes]

Is there anything to stop you just using carbon powder?
Activated carbon powder is easily available and cheap.

Stuff the part into a bit of clay drainage pipe or something with a load of powder, seal the ends and wrap an induction heater coil around it?

What do the other ingredients do?
Act as some sort of flux?
Absorb oxygen?
Provide a limited amount of oxygen for combustion?

I'm wondering why you can't just heat a bit of metal in an inert environment (or even in a vacuum) and, providing you have more carbon around the metal than in the metal it should diffuse in?

Or do you also need to heat the carbon bearing compound enough to release the carbon atoms?
Ie, more than the heat from the metal would do to the surrounding material?

 

[Screwdriver]

Imagine a tub full of little boxes, all neatly arranged and packed tightly. Then shake the tub violently until the boxes are jumbled up and bouncing all over the place. If you throw some ping pong balls into the maelstrom, some of them will get wedged in the gaps between the boxes. It is not merely gravity that allows this to happen even in our thought experiment, gravity in this pop science explanation represents the forces which allow a metallic crystal lattice (the boxes) to align. Shaking the box is as good a metaphor for heating an object as any. The ping pong balls will diffuse into the tub full of boxes.

The longer you shake it for, the further the balls will diffuse into the surface. To push the analogy further, if you have a regular alignment of boxes, it would be easy to "shear" a long line of them and they would move quite easily. Once the regular alignment is jumbled up a bit with ping pong balls spoiling the alignment, it becomes more difficult. The structure has become "harder" due to the doping of the regular structure. This is not a bad way to imagine how a regular steel crystalline structure is affected by carbon atoms getting wedged in between the lattice structure.

The more fascinating aspect is that in a metal crystal, these "boxes" change shape when they are being shaken and want to change back once everything settles down.

 

[ronan]

It still does and the word "cyanide" is enough for many to have palpitations. I cannot remember the legislation but as always with these things, it was legislated out of existence.
I have done an enormous amount of work with case hardening and more specifically Colour Case Hardening for obvious reasons. Here are a couple of pics of stuff I created:

View attachment 310808

View attachment 310809

The amount of work and sheer effort to get these pieces to this point as a one-off is just not worth it. I did this for my own curiosity. Bone charcoal was the active medium and sealing the parts into a steel box which also had a strip of leather in it to kill off any O2 when it burned. I will not be doing this again in a rush.

Case hardening using Kasenit or one of the modern substitutes works well but you need to consider distortion and how tolerant your part is going to be. You can get small amounts such as here: http://www.knighton-tools.co.uk/acatalog/BETA_CASE_HARDENING_COMPOUND.html

Or a tub of it (and associated stuff) from here: https://www.rutpen.co.uk/product/beta-case-hardening-compound/ It all depends how much you want to put into the job.

Did you see this ?

 

[mtt.tr]

Where is tech Al when you need him.

 

[pressbrake1]

The old timers when I was a apprentice would put the part in with mouldy cheese in a nearly air tight container and put it a heat treatment oven for a good few hours
My father used straight carbon again in a container to trap the CO in and left in a heat treatment oven

I’m thinking the magic of the heat and dip of kasenit is the crust encases the process from atmosphere

 

[northwest]

Did you see this ?

Yes, it is more or less the same method I used on the parts above but I used iron wire, not copper.
Distortion, especially of the side plates, is a major consideration.