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Case Hardening Experiments Mod-Up

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SwarfnStuff:
For what it's worth,
     I recalled reading somewhere that case hardening could be done in old sump oil. Easy to get some from my mechanic friend then recalling that it was supposed to be the carbon in the oil I ground some charcoal in a pestle & mortar, tossed it into the oil and left it for a few days. I had made a pair of mini bottle jacks from some scrap steel and thought they were good candidates. So, heated them to as red as my propane torch would get them and dropped them into the old oil. No hardening evident after trying the scratch test but hey! they had a nice black finish that looked good. (Now, this black finish bit I recall from blacksmithing class in junior tech school.)

 After reading the earlier posts perhaps I should have re-heated and quenched??

    Also tried sugar on some scrap but apart from the sweet smell nada. This thread will be interesting to follow. John B   :proj:

SwarfnStuff:
Another thought VT, you were wondering about trying to combine charcoal making and hardening -  later in the post you also wondered if the charcoal may be too pure in carbon to exude the monoxide. My thinking would be to try the steel in with whatever wood you were going to carbonise in the not fully sealed container (just need to exclude air ingress but allow pressure to escape. End of safety reminder.  :coffee:) and there should be plenty of CO amongst the other fumes.

Eugene:
Steve,

What your experiment demonstrated was the effect of "flame hardening" rather than case hardening. If you heat a bit of medium carbon steel to cherry red and quench it, it will produce a hardening effect, wether or no you have an external carbon source such as sugar. The process takes a couple of minutes.

"Case hardening" was traditionally applied to low carbon steels where an external carbon source was provided in the form of charcoal, the classical usage being in gun making. The advantage in using the mild steel was that it could be filed, drilled, ground, and engraved in the soft easily worked state, and then hardened to give wear resistance afterwards. The process takes hours rather than minutes, to allow for absorption of the carbon into the surface layer, quite a slow business. I'd guess all your sugar did was to make it more difficult to judge the colour changes, there wouldn't be enough time for a significant degree of absorption.

I've only done case hardening to produce the traditional colouring effect that is seen on gun actions, and I used the old style method of placing the parts together with charcoal into an iron box which went into a home made (and distinctly dodgy :() muffle. Getting the colours right is a bit of an art and is typically surrounded by a "bodyguard of lies", but the hardening effect is quite easy to obtain, it's depth depending on the soak time.

I think you'll be fine with home made wood charcoal if it's reasonably graded in size; small enough to contact the parts but big enough to allow the oxygen from the air to be present in good quantities. The oxygen isn't used up as the process continues, it merely has to be present to begin with.

I have some printed work on this iron box method; if you like I could scan it and send it to you. Let me know. Brownells in the US supply materials for the colour case process and may well have some info online; worth a shot.

In the far off days when I was alive, we used to copper plate steel parts in selective areas prior to them being hardened. The coating acted as a barrier to the carbon and left those areas soft. Only The Gubbernmint could afford it!

Eug

vtsteam:

--- Quote ---What your experiment demonstrated was the effect of "flame hardening" rather than case hardening. If you heat a bit of medium carbon steel to cherry red and quench it, it will produce a hardening effect, wether or no you have an external carbon source such as sugar. The process takes a couple of minutes.

--- End quote ---

Eugene, I would say that the experiment so far demonstrated conventional hardening on the first sample steel, since it contained enough carbon throughout to harden, using a conventional method. And no "flame" or case hardening of the second.

JohnB, exactly what I was intending to try. I've made charcoal through a number of different methods over the years. There are plenty of variables to play with.

Please anybody jump in here with your own experiments -- using whatever appeals to you. We have only my photographed experimental results so far. Somebody with an acet torch could do the soot and heat method,, oil method, etc. As I've said before, method is as important as ingredients -- small differences can produce different results for different people. That's the point of documenting what you try.

vtsteam:
Continuing with the last experiment with sugar, I cut a piece of .002" stainless steel tool wrap and sharpened the non-hardenable steel threaded rod:

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