Hardening and tempering

[Beanwood]

Today was a good day - I finally made a 35mm punch and die set that cut's 6 perfectly circular 3mm holes nicely (In one go).
Excited by this, I thought I'd probably better try and harden the die (The punch pins are already hardened) before use in case I wear it out, and the holes get sloppy, leaving tags on the rear side.

I sorted out a bath of engine oil ready for the quenching, and off I went. Heated it up to glowing red hot, and dropped it gently into the engine oil. Half an hour later - some nice warm oil, and a blackened die.

It was then that very excited me tried the file test - fully expecting (OK Hoping beyond hope) the file would skid happily away from the surface, without even leaving a mark....

No such luck. The file left some very nice file marks - evidenced by the bright silver over the darkened colour that remained after the oil bath.

It was then I remembered I'd practiced making this die so many time, I'd used all my 'good tool like steel' and used mild steel.

Is there anything I can sensibly do to make this any better/harder? Assuming there isn't, and I just need to remake it AGAIN (It should be much easier the 5th time ) but out of higher carbon steel, does anyone have any additional pointers on hardening that Youtube doesn't? Also - as it's a die, and unliely to suffer impact - do I need to temper it?

 

[MattF]

Case hardening. Casenit was one option, I believe, though not sure if that's still available.

 

[Beanwood]

Thanks @MattF - and a quick search for Casenite (Actually Kasenite) comes straight back to the forum that knows everything- but now I know what I'm looking for!

Just been watching the Clickspring videos - and it looks fairly straight forward to achieve case hardening - I just need to get the charcoal, some clay, and get the wood burner going one evening.

Does anyone know if ordinary charcoal is the same as leather charcoal?

 

[Seadog]

Case hardening. Casenit was one option, I believe, though not sure if that's still available.

Not for many years. It contains ... CYANIDE!!!

 

[Beanwood]

Not for many years. It contains ... CYANIDE!!!

Yep - old thread here for reference:
Kasenit

 

[The_Yellow_Ardvark]

You need to heat it to bright red heat, hold it at tat temp until the bright red is even.
Then plunge into cold salted water, remove as soon as the bubbles stop.

Then to blacken it.
Clean up with emery cloth, gently warm to a dull red and plunge into old engine oil, again until the bubble stop.

That should sort you out.


Case hardening can be done by heating to bright red and dropping into charcoal powder.

 

[Farside]

Thanks @MattF - and a quick search for Casenite (Actually Kasenite) comes straight back to the forum that knows everything- but now I know what I'm looking for!

Just been watching the Clickspring videos - and it looks fairly straight forward to achieve case hardening - I just need to get the charcoal, some clay, and get the wood burner going one evening.

Does anyone know if ordinary charcoal is the same as leather charcoal?

What about mixing soot and oil?
Last time I used case hardening gunge I was thinking it was fairly like that.

 

[MattF]

Couldn't it also be done by burying it in something carbon rich & holding it at a certain heat for a few hour?

 

[Beanwood]

You need to heat it to bright red heat, hold it at tat temp until the bright red is even.
Then plunge into cold salted water, remove as soon as the bubbles stop.

Then to blacken it.
Clean up with emery cloth, gently warm to a dull red and plunge into old engine oil, again until the bubble stop.

That should sort you out.


Case hardening can be done by heating to bright red and dropping into charcoal powder.

Does it have to be old engine oil? I have enough unused stuff here that nobody seems to want…

 

[Beanwood]

Couldn't it also be done by burying it in something carbon rich & holding it at a certain heat for a few hour?

That is pretty much what YouTube is saying- mixes vary from leather made charcoal to ordinary briquettes ground down, all mixed with something to make a paste then baked at high heat for an hour or so - probably within a clay cocoon.

 

[minimutly]

You can't harden mild steel. Adding casenit (if you could find some) is just a surface hardening to reduce wear, it won't survive impact. Get some drill rod tool steel.

 

[Kram]

Any part that is through hardened should be immediately (or before use) tempered at 220c or so, otherwise it will be extremely brittle and shatter.

The case hardening process can achive thick/through hardening by keeping the part at red heat with a carbon source for an extended time. I believe clickspring had a good video on that.

For better results the part and carbon source wrapped around it, should be sealed in clay or a steel container while heating. That keeps the CO close to the metal.

 

[piman]

Hello Beanwood,

is there sufficient material to let in a ring of steel into the die, that you can harden, much like a valve set insert?

Alec

 

[oldbikedavey]

There's a variety of good books on the subject , but in essence, the part to be case hardened needs to be in a sealed gas -tight container packed with carbonaceous material , and heated up to a bright red heat for a couple of hours or so .
Sodium carbonate and barium carbonate were beneficially added to the base charcoal mixtures, and urea has an effect besides.
An author to look out for on the subject is Harry Brearley....

 

[hotponyshoes]

How long did it take to make the part?

It may be quicker and easier to remake it than case harden it (with a better result as well)

If you plan to case harden other parts in the future then it may be worth getting setup now for that?

I probably wouldn't bother to temper after case hardening. Certainly not if I was using the punch/die in a press. Maybe I would if you are using it with a hammer and it is seeing some shock loading.
Even done perfectly you'll only ever get a comparatively thin hardened layer and it won't be that hard. I'd think it's unlikely to crack/shatter as the hardening is progressive from the outside to the core so remains fairly ductile with support from the underlying material.

 

[hotponyshoes]

Apparently the fillings from horses hooves make for a good case hardening compound.
I don't know why so I've never bothered to try and collect enough of them to try it!

 

[Agroshield]

An author to look out for on the subject is Harry Brearley....

I suspect one of these two might be useful:

The analytical chemistry of uranium : Brearley, Harry, b. 1871 : Free Download, Borrow, and Streaming : Internet Archive

vi p., 1 l., 45 p. 22 cm

archive.org

The case-hardening of steel; an illustrated exposition of the changes in structure and properties induced in mild steels by cementation and allied processes : Brearley, Harry : Free Download, Borrow, and Streaming : Internet Archive

xv, 164, [5] p. 23 cm

archive.org

 

[Newlands]

Case hardening is a total waste of time for a die, especially doing it in a home workshop. You just won't get enough depth of carbon rich material - maybe a thou or two if you're lucky. Best bet is to get hold of some gauge plate or similar med-carbon steel that you can harden and temper after you've knocked it into shape. Or you can make a few more mild steel copies and treat them as consumables.

 

[Beanwood]

Hello Beanwood,

is there sufficient material to let in a ring of steel into the die, that you can harden, much like a valve set insert?

Alec

Nice idea, but probably not for this one. It's only a small die - I'll spend my time better by making new out of higher carbon steel.

There's a variety of good books on the subject , but in essence, the part to be case hardened needs to be in a sealed gas -tight container packed with carbonaceous material , and heated up to a bright red heat for a couple of hours or so .
Sodium carbonate and barium carbonate were beneficially added to the base charcoal mixtures, and urea has an effect besides.
An author to look out for on the subject is Harry Brearley....

Thanks @oldbikedavey I suspect I'm better putting effort into finding a decent piece of steel and remaking it than investing in a small quantity of barium carbonate and clay to add to my already cluttered workshop, which may at best give me average results. I'll just have to bite the bullet and remake it properly.

 

[Beanwood]

How long did it take to make the part?

It may be quicker and easier to remake it than case harden it (with a better result as well)

If you plan to case harden other parts in the future then it may be worth getting setup now for that?

I probably wouldn't bother to temper after case hardening. Certainly not if I was using the punch/die in a press. Maybe I would if you are using it with a hammer and it is seeing some shock loading.
Even done perfectly you'll only ever get a comparatively thin hardened layer and it won't be that hard. I'd think it's unlikely to crack/shatter as the hardening is progressive from the outside to the core so remains fairly ductile with support from the underlying material.

The first ones tooks DAYS.
I have now had much practice (And more tools) so it can be made fairly quickly . The trick is getting the holes for pins and holes in the die lined up perfectly. If it's just one, that's easy - but 6 or 8 in a perfect circle, at the right spacing, on the correct diameter........ My cheapie rotary table helps a lot, but on my old and frankly worn out kit, it's proving 'less easy'. But I have now located a small piece of brighter looking steel (Origin/grade unknown) that I shall make and retry the hardening with.