Hardening and tempering

There isn?t a ?one size fits all? formula, it depends on the composition and required hardness.

Your approach probably will result in initial hardening and some degree of tempering but exactly where you will end up on the Rockwell scale is debatable. If done a bit of reading around the topic to made things in the past and some advocate multiple tempering cycles. There is quite a bit on YouTube but mainly related to making knives rather than tools.

Dunno, but watching Guy Martin doing the sword in Our Guy in Japan was interesting.

Don't quite understand your table, can you explain it better?

The key parameter is likely to be the carbon level, and what you are trying to do with the final product.

I didn't realise that they used fireclay to heat the cutting edge to a different temperature than the rest of the blade.

Not too critical, (vice jaws)hard but not brittle.

Directly from metal analysis instrument.

I don?t pretend to be an expert but I would have looked at Case Hardening. I was shown how to do this at school (as a pupil) when I made an adjustable spanner. Basically you heat the metal to red heat and plunge it into a carbon powder. You get a hard surface but the tool isn?t brittle. I seem to recall the powder was called Casemite - there were square tins used for storage around the metal work room.

After the process you have to clean off the crust with a wire brush but the finish seems to last. I?ve still got the spanner I made over 40 years ago.

I have done it before but It is now too expensive and hard to get as several brands have disappeared.You can make your own but I already have the heat treatable ones almost made.

I was told at the time it was essentially carbon made from Coke and, as I recall, it looked like crushed coke. Probably more like fine-sand than powder but it was a long time ago. I?m 63 and it was in my school days.

Also from school metalwork classes, we were taught that a quick and dirty way to case-harden something was to plunge the red-hot article into a box of flour. The particles, teacher said, would instantly carbonise and bond with the red-hot surface molecules of iron. You might have to do it more than once for best effect and you might have the odd minor blaze to put out but teacher was quite serious about the technique. Plain or self-raising was not specified.

Nick

Ah, I vaguely recall something similar but haven't tried it. I expect there are many 'old fashioned' methods which work after a fashion.

Maybe I've missed, but the one I recall was dunking the hot object in oil.

Andy

Oil or water, yes. Mr Murtz, the OP, started there. Case hardening was suggested as an alternative and this flour thing was mentioned.

Through history, numerous techniques/ concoctions have been used- including animal dung I believe.

No, oil rather than water.

You get the rapid cooling _and_ the high carbon surface all in one. Even if it doesn't make the things harder it looks a lot better than bare iron does after a couple of years.

Andy

Blood. Lot's of iron in blood. Always temper magic swords in virgins blood :-)

With respect, that doesn't answer the question. I suppose it could be the mean and standard deviation of the elemental content.

In which case, I would come back and say just tell us what you know about the component. Seems likely it is a carbon manganese steel. But without being able to estimate the carbon content, and to know what performance you want from it, you don't need a metallurgist, you need a psychic.

That is to cool it more quickly than you can in water, because the steam bubbles provide insulation. There would be hardly any time for carbon to diffuse deep enough into the structure before it cooled down. IIRC case hardening compounds contain plenty of heavy oil / pitch etc which will convert fairly quickly to carbon. You would typically be heating for several hours to get the carbon to diffuse in to a depth of a millimetre or so.

Agreed. Only a thin surface though. And most of the carbon is in a sort of lacquer on the surface, a bit like the finish of a well used iron frying pan or pot. It is surprisingly adherent and provides good corrosion resistance.