case hardening with ashes from fire

[Sid]

A simplification , not everyone here is a metallurgist.

True. No offence meant.

Heat treatments of steels and attempts at a process like case hardening though only really stand a chance if you study what's happening. (Or at least your likelihood of success.) I found it an interesting subject to read about. What this says about me, I dread to think!

 

[BrokenBiker]

i have to dis agree with that. I have case hardened loads of things during my apprenticeship, well before learning how and why it worked. As long as you know the order in which to do things and how to do them safely there is no reason the process wont work. It was a good six months after i learnt how to case harden before i learnt what was actually going on with regards to the structure of the metals and so on

 

[Sid]

i have to dis agree with that. I have case hardened loads of things during my apprenticeship, well before learning how and why it worked.

True. What I wrote didn't quite tally with what I meant.

I never had anyone to show me how to do this, just a guide in a book, and it took a few attempts to get any joy. The degree of success for me improved by understanding the process. Not being able to _observe_ how it's done and follow the process, was a real handicap.

So yes, you can case harden without understanding what's happening.

 

[Sid]

A member on a model engineering forum was recommending aquarium charcoal as a hardening compound, i suppose if its carbon rich it will work to some extent.

A book I have suggests charcoal, with the addition of Sodium Carbonate (not Bicarbonate) as an "Activator". Add 1% by weight. I've not tried this myself though. Charcoal by itself was deemed "slow acting".

 

[BrokenBiker]

i have been told about the addition of sodium carbonate but have never tried it either. Will be trying a few test runs with coal, charcoal and ash later on in the week so will post results as and when they happen, may even be able to get some Rockwell scores if I can get into the quality room in work

 

[ronan]

Or...........the eu/health and safety could leave things alone and just let us pop down to the engineers suppliers and buy a tub of kasenit that works. Wow that would be so simple and efficient.

 

[brightspark]

Or...........the eu/health and safety could leave things alone and just let us pop down to the engineers suppliers and buy a tub of kasenit that works. Wow that would be so simple and efficient.

i dont know how im still healthy after 60 years using casenit red lead paint, 2k .silica sandblasting . working in sooty attics using genuine crosote . spraying with carbon tet thinners smokin 60 a day fags and im still here

 

[BrokenBiker]

my old man sprayed 2k for 20 years without a mask, only started using one when he gave up fags and gave up spraying about 6 months later. Doctor says he has the lungs of a 20 year old (he is 51 this year)

 

[MattF]

Doctor says he has the lungs of a 20 year old

He should know better than to nick things.

 

[MattF]

I do agree with Sid to a degree. Knowing how something works will improve your abilities to do something well, rather than just good enough.

 

[graffian]

A book I have suggests charcoal, with the addition of Sodium Carbonate (not Bicarbonate) as an "Activator". Add 1% by weight. I've not tried this myself though. Charcoal by itself was deemed "slow acting".

I did read somewhere that you can buy the sodium ferocyanide[I think it's what kasenit is] quite easily, I gather it's a really good activator.
I scrounged some carbon powder from a place that sell brushes.
I will have to rig up an oven and try it.

 

[BrokenBiker]

IIRC sodium ferrocyanide is an anti caking agent added to salt

 

[bill_gj]

Modern Kasenit not as good as the old stuff - another one of those 'when I was a lad...' stories, and I agree.
Used Kasenit at school and college in the '70s and it did seem to improve the hardness of stuff we made, even if the tutors didn't really seem to understand how to get the best from it.

I am with the train of thought that gets the powder in a container and packed nicely around the part that needs to be hardened and then heated in an oven/kiln/forge to the bright red heat stage for some time (hours), then cooled slowly. Should increase the carbon content of the surface skin.
Not too sure about post case-hardening heat treat though. Whether you'd treat it the same way as an homogenous piece of equivalent carbon content steel I'm not sure.
https://www.google.co.uk/#q=kasenit+case+hardening+powder

 

[julianthegypsy]

Modern Kasenit not as good as the old stuff - another one of those 'when I was a lad...' stories, and I agree.
Used Kasenit at school and college in the '70s and it did seem to improve the hardness of stuff we made, even if the tutors didn't really seem to understand how to get the best from it.

I am with the train of thought that gets the powder in a container and packed nicely around the part that needs to be hardened and then heated in an oven/kiln/forge to the bright red heat stage for some time (hours), then cooled slowly. Should increase the carbon content of the surface skin.
Not too sure about post case-hardening heat treat though. Whether you'd treat it the same way as an homogenous piece of equivalent carbon content steel I'm not sure.
https://www.google.co.uk/#q=kasenit+case+hardening+powder

That's the way we were trained back in...oh, you know, the victorian era. We put our parts in a box full of fine charcoal and it went into an oven for about 48 hours. I shall have to research this further as I can't remember temperatures, either for the oven or for hardening afterwards, but I seem to remember heating to bright red then quenching.

 

[BrokenBiker]

in college we were taught to bring material up to red then stick it the powder, fully submerged then leave to cool, around 2 hours, and repeat until skin depth was acheived. We never tested the depth, just went by out tutor telling us that each cycle added something like 5thou depth each time. In work however the general method is bring it up to red in an induction heater, bury it in powder then bake for 24 hours and allow to cool naturally. Seems to work alot better and im sure a few things have been tempered but most of the stuff we harden is only for wear resistance so brittleness isn't an issue

 

[julianthegypsy]

in college we were taught to bring material up to red then stick it the powder, fully submerged then leave to cool, around 2 hours, and repeat until skin depth was acheived. We never tested the depth, just went by out tutor telling us that each cycle added something like 5thou depth each time. In work however the general method is bring it up to red in an induction heater, bury it in powder then bake for 24 hours and allow to cool naturally. Seems to work alot better and im sure a few things have been tempered but most of the stuff we harden is only for wear resistance so brittleness isn't an issue

It was so long ago that I forget, but I seem tonremember we cut halfway through oieces of round bar, then left one, heated and quenched one, heated, quenched then tempered another, we did four different ones then put them all in a vice and belted them with a hammer till they broke to see which one was strongest. Horrifyingly, that was almost forty years ago :-(

 

[BrokenBiker]

I did similar with various aluminium alloys to demonstrate heat treatment and how alloys act differntly

 

[ronan]

I am with the train of thought that gets the powder in a container and packed nicely around the part that needs to be hardened and then heated in an oven/kiln/forge to the bright red heat stage for some time (hours), then cooled slowly. Should increase the carbon content of the surface skin.
Not too sure about post case-hardening heat treat though. Whether you'd treat it the same way as an homogenous piece of equivalent carbon content steel I'm not sure.
https://www.google.co.uk/#q=kasenit case hardening powder

Surely when you have soaked the part in the oven/kiln etc for some time, you then quench it in water, brine or oil ? Its the quenching that gives the hard outer skin and tough softer core ?

 

[bill_gj]

Personally, I try to never start with 'surely' as there will be someone along to tell me I am wrong - I just wonder what the best post case-harden process is to get the best from the skin. Don't know whether a heat-quench-temper is best. Perhaps someone can tell us?

 

[ronan]

Well when you heat a ferrous metal to red heat and quench it it will be full hard , if you heat it and allow it to cool slowly it will be much softer. As the whole purpose of this type of heat treatment is to get a hard wear resistant skin or case then the quench from red heat is the usual operation ? I have never heard of a case being itself heat treated , tempered or whatever, not to say of course it isn't done.