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Case Hardening Experiments Mod-Up

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vtsteam:
The  first trial, done mainy out of curiosity was the sugar coated trial.

The strip of steel was heated to cherry red (my estimate) and plunged into the sugar. The sugar carmelized into a pool immediately, boiling off steam, and darkening quickly to near black. There was flame above the sugar for a short time. When the bubbling had settled down a bit and I judged the coating would stay on the metal, but before it hardened in the cup - about 30 sec. I removed it.

vtsteam:
Here's the coating:

vtsteam:
I then heated it to cherry red again and plunged it into the water. Result: the metal was hardened and I was able to scratch strip C with it. I was quite pleased! Gosh, sugar works to harden ordinary hot rolled steel !!!

So, next to test the control, I heated strip A (with no sugar) to cherry red and plunged that into the cold water. Result: that, too was hardened and I was able to scratch strip C with it. Well, so much for the first conclusion!

Well, which was harder S, or A?

Scratching them against eachother, it seemed that A would scratch S slightly but not the reverse. Well this was too much, I wanted to make sure, so I sharpened both on a fine stone to give clearer results, and repeated the same case hardening method with each to hopefully increase case depth, and give a better indication.

The result: A definitely scratched S, while S only removed discoloration, but did not scratch into A. And not only that, but clamping C (the unheated control) in a vise and using A as a chisel, I was easily able to cut right into the unhardened control piece. You can see the notch made above A in this photo, and also the deep scratches it made on S. 



I also found it possible for a file to remove a small amount of metal from S, but not at all from A.

Conclusion, simply heating and plunging these particular steel pieces into cold water makes a harder tool than using sugar does. If I had done this experiment without a control, I might have assumed sugar was responsible for case hardening this steel.

In fact it appears it may inhibit hardening.

vtsteam:
As a followup experiment to determine whether possibly a carbeurizing flame in the MAPP gas torch somehow case hardened piece A, or whether the material was itself hardenable, I ground the cutting edge back on the grinder and repeated the scratch experiment on C and S. No change. So my conclusion is that this steel is hardened all the way through, and therefore a hardenable material.

It is interesting that the sugar treatment seems to have reduced the degree of hardness.

Bluechip:
[1] Please note I know nothing about the subject.

[2] If you had some carbonising material ie. sugar and applied a flame I see no reason for the carbon to go into the steel.  I would assume it would be CO2. in fairly short order.

Dave

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