Color Case Hardening???

[Shifty]

Jerry that Lock is just beautiful!

 

[M. De Land]

Good stuff Alexander! I got my last bone charcoal from Berger Bros. as I ran out of Brownell's which probably came from Bergers anyway.
I found to my surprise that the bone charcoal had no hasmat restrictions on it but the hardwood charcoal did so I tried a substitute that was locally available and find it works just as well.
Coconut charcoal for water purification.
I've settled on 3-1 wood to bone for the colors seen on the examples pictured. I've tried bone only, 50-50 and several other ratios and additives but pretty much like the results from 3-1 overall.
I find the finish on the metal greatly effect the color brightness as well.
I usually work out the forging striations stone and sand flat than hit it with 70 grit garnet sand followed by glass beads which give the surface a flat sheen. It seems to give the colors a bit better bite and a bit more case depth from what has been seen when I drill and tap for tang sights after words.
I was concerned about repeat heatings and quenchings on these eamples after color failures but have found as long as no cracking or unusual wharping or over heating occurs and the steel is not burned it can be done repeatedly with no ill effect.
I completely agree about the quench drop height effecting coloring.
Gaddy taught this along with the addition of wire, bolts and washers to locate and some what position patterning.
I use the same approximate time and temperatures you are and aerate my quench with a fish tank micro bubbler.
I picked up a another tip from a British double gun maker that proved very effective for me.
Letting the crucible rest for full two minutes fresh out of the oven before the quench drop.
The internal temperature drops very little in that time but it sure makes a difference in the colors that come out for some reason.

 

[M. De Land]

I was thinking the same thing shifty! Beautiful work Jerry!

 

[jerrywh]

I know some guys that quench at 1250°F they get better colors but loose a lot of hardness. If you letting the case set you are basically doing the same thing but you can't know what the temp is. I have quenched as low as 1350° and still got pretty hard results but better colors. Since I do a lot of case hardening with intricate gold inlays and overlays I have to have perfect temp control. Gold inlays will alloy or melt out at about 1575°F.
PS a word of warning as far as colors go, if you heat over 1600 the hotter you go up the less colors you will end up with. At 1750 it just comes out gray and grainy looking.

 

[denster]

Midway USA has a video on color case hardening also a good source for bone and wood charcoal.
Some pretty nice colors seen here. Do any of you use an aerated quench?

 

[M. De Land]

Yes, I do. I use a mini bubble fish tank unit.
I start the bubbler going about a half hour before quench which is over kill but it does a nice job.
I also use distilled water about half new and half one time used which also tends to give more color.
I have an Even-heat twelve stage programmable heat treating furnace which takes all the guess work out of time and temperature.
The crucibles are of both stainless and mild steel, small and large for different sized work.
I have no idea what the internal heat is with the two minute rest, fresh out of the oven but it yields nice color and the case depth in about .005 would be my guess having drilled through a number of times for tapping, and with test strips of mild steel.
It can't be loosing to much heat internally in that amount of time. I was quite impressed how deep it was with this technique and am well satisfied with the depth and colors.
It is completely adequate for shotguns and black powder arms.
Shot guns do well with pretty shallow casing in the ,.003-.005 range I've read.
High intensity actions require .007-012 range which is what some Mausers are on top the ring and bridge. They use a much higher heating of 1550-1600 F. and are oil quenched.
Springfield used a double heating and quenching after WW I.

 

[jerrywh]

MD.
Please tell me about your heat treating furnace if you will.
I made 6 different furnaces for my own use. In testing them I find that the temp inside of the furnaces varies as far as 100° or more from one area of the furnace to another. Therefore I always put a digital pyrometer probe right on the flask. For accuracy.
I have been trying for a couple of years to achieve even temp within the furnace especially the one I use for bluing long barrels. I have a ceramic glass top electric furnace for that and use 6 probes over the length.

 

[M. De Land]

The new one is from Even-heat and has a chamber of 13 inch cube.
My largest crucible fits nicely inside for whole action casing.
I used to have to do receivers in two parts now I can do the whole thing at once.
It has one pyrolink in back center of the chamber but heating elements top to bottom on two sides and back. The door and floor is two inches of fire brick.
It is designed for heat treating steel alloy and has a range up to 2000 degrees F.
The thing I love about it is you can program in twelve separate multistage sequences turn it on and go do something else.
Time and temperature changes are done by the computer program where as in my other furnace I had to baby sit them.
This is particularly useful in staged heat treating tool steel alloy like A-2 which I use a lot of for gun parts and cutting tool fabrication.
It automatically monitors and adjusts the temperature programmed in to the sequence to less than five degrees top to bottom.

 

[jerrywh]

I have to baby sit all mine. It would be nice to be able to go do something else. I don't know how hot mine will get but I have had it to 1800. It is constructed of heavy fire brick that will take 3000.00 My big furnace is about 18 cu. ft. with a front opening door. I use it for burnout. When I was casting commercially I used to run as much as 23 flask at once. It weighs about 700 lbs. I use propane crucible furnaces for melting Brass and silver when casting. When I started pack case hardening about 25 years ago I used the crucible furnaces and checked them with a type K stainless probe.