color case hardening

[Don Halter]

I've been doing some other projects lately and have recently got into antique finishes. One of which is color case hardening. I think this would look pretty cool for a D-Guard bowie fittings or something similar.

Here's the first test. This was some scrap 1022 and a small hunk of 1050.

Using a chopsaw is quick on bone...but holy cow does it stink!


The "crucible" is just some pipe tack welded to a small sheet of steel. I used a solid rod to break up the charcoal and bone in the crucible, then lpartially emptied it, then loaded in the steel and repacked all the mix. I shook it and poured in the left over fines, ramming it down tight. Another sheetmetal section was loosley placed on top to seal while heating.



Pretty tight fit in the oven!

[Don Halter]

Here's the final products. Kind of a crappy pic. They looked pretty nice in sunlight with a little oil on them. I'll make sure and get better pics of the new stuff and the redo on these.



Test one:
Video on youtube (you have to listen for the kids reaction when the charcoal dust ignites!):
Color Case Hardening


Some more CCH. This was on one of the actual pieces for the rifle. This is just some A36 1/4" structural plate steel. This usually is about equivalent to 1018-1020 low carbon steel...with a few other scrap alloys in small percentages. I crushed the bone fragments much smaller for this one as well. About the size of granola. Looking at the results, I need it just a hair bigger, but smaller than the first run. Guess I'll have to make a sifter to size them.

I was looking at some of the results over the last few days. It seems if I can keep a vapor jacket a wee bit longer, the colors should be a little more intense. This can be done by using a plate loosely clamped around it, or by using wire or some similar object. I chose to wrap it with stainless wire. This worked surprisingly well. The areas under the wire had significantly more color.

For this run, I used my small propane knifeforging furnace since the assembly wouldn't fit in my electric furnace. I pre heated the forge to equilibrium at 8 psig. This is about 2200* for this forge. I then stuck the assembly in, then shut the forced air off, turned the gas pressure down a hair and ran it in a greatly reducing atmosphere (this limits chances of igniting the charcoal dust and greatly reduces the air currents inside as well as drops the temp down around 1400-1500*F).

After about an hour of soak time, I then got my 8-month pregnant wife to come out and act halfway excited over the whole event and video the mushroom cloud for me. She was thrilled to help.


color case hardening 2

[Crockett]

Very nice, I appreciate the opportunity to see what you're doing, thanks for posting it!

I've long had an interest in CCH but have never had enough time to dabble in it.

Don

[David Broadwell]

Not bad, Don. But, where is the horse pee? I was told years ago by a gun smith and muzzleloader builder, Bill Mowry, how color case hardening was done way back in the day. One of the ingredients used was a crystal compound made from horse urine. It came from France. They'd have barns and stalls with drains and the urine would be collected that way. He recommended sheep bone and scraps of leather, and pack it tight.

Now I don't really know if you actually have to have horse pee, but I do believe the leather scraps would be a big help.

David

[Don Halter]

Hah...well, out here in Katy I'm sure I could get all the horse pee I wanted, but I'll pass. I'm guessing they were just reducing it to urea crystals. I have some Viking recipes for browning steel that call for the urine of a virgin red-headed boy. I guess horses are easier to find in Europe than virgin anythings!

I have a pretty lengthy writeup on a week's worth of experiments with the coloring and such over on a weapons building forum. I'm mostly looking for coloring on medium carbon simple steels and alloys with disregard to the case hardening properties. For the rifles I'm doing, 1050, 1065, 4130...in any "partially hardened" condition are fine. I think any organic material that has keratin, or callagen would probably work for the effect. Those seem to be the common compounds in all the odd ingredients of the recipes I've run across. From what I've seen with the bone, it's leaving a coating on the steel that protects it from oxidation within the vapor jacket formed in the bubbling during quenching, and thus leaves the "clear" areas on the steel. Even after quenching from 1500*, there's still a white chalky residue that rubs off leaving the spots.

I've done a lot of heat coloring on armour with my medieval stuff. The only thing that seems to make the colors more vibrant is length of time and ability to control temp. I think on CCH, the key is heat removal time and the temp at which the vapor jacket collapses to nucleate boiling and then degrades to liquidus. If I can dial that vapor jacket collapse temp in to the "purple" temp for a particular steel and have it still be boiling for a bit through the purple and down through the yellows and bronze temps I'll have it perfect. I figure a decade and a dissertation or two and I'll have that accomplished.

[cdent]

Hi Don,
I asked about the same process a bit ago, and Jerry Huddleston, a fine muzzleloader maker responded over at Don Fogg's beginners forum back in May '06. He did a great little write up that really got me in the ball park right away.

A couple of points seemed to work out. Hold tight temp controls no higher than 1400*, and try to exclude air during the cook and quench. You can get blue color and transitions of purple splashes by adding a little potassium nitrate (stump killer) to the water quench.

In case you ever wanted to track down real bone charcoal, you can get reasonably priced 4 lb. pails from ebonex. Sorry if you were aware of these things, and to go on and on, but I like the effect and appreciate your writeup.

Best of luck nailing the look you want, Craig

[Lee Cochrane]

wish I could get Turnbull's "recipe." Don't know how functional, but what a looker bowie

[Anthony Chaney]

Hey Don, I have a small book on this and had actually forgot about it. Good stuff. When I first came across it, I thought it would be neat for bolsters/guards and such.

Katy???? When did you move???