Case hardening (case coloring) wrought iron?

[Black Frog]

I'm wondering about case coloring original old wrought iron.

I don't know a lot about it, but from what I'm gathering is the wrought iron (being fairly soft with low carbon content) was case hardened to give the exterior surface some hardness. 

 

Anyone ever try W.I. for this process?

[jmccustomknives]

Can't say I have.  Wondering why one would do that.  The case hardened layer is so thin is would wear away or rust off so fast it wouldn't be worth the trouble.  At least that's my thought. 

[Black Frog]

Isn't case hardening how they approached some gun parts before we had higher carbon metals?

 

The original wrought iron proved to be fairly soft, and someone must've figured out how to make the parts more durable and hard by infusing carbon into the surface.

 

I'm not so much looking for the performance of the case hardening, but rather the colors that result from it.

And wondering about getting those colors from wrought iron?

[ThomasPowers]

Blister Steel was a case hardened wrought iron with the case hardening done for long times.  However I don't know the colour effects.  I would assume that very high grade wrought iron would be required though.

[HWooldridge]

Brilliant colors can be attained with cyanide salts - it won't provide a deep hardness but is pretty to look at. Care must be used with these chemicals as they are dangerous to handle by the untrained. Check out Doug Turnbull's custom guns for some really gorgeous pictures.

WI should color just fine - although packing in straight bone black may not provide bright colors. Obviously, it will need to be polished beforehand.

BTW, many gun parts are still case hardened for performance. It's an easy way to machine parts from soft steel and still get a hard surface to endure wear.

[Frank Turley]

The video, "The Gunsmith of Williamsburg" shows the case hardening process on wrought iron lock parts. I don't think he was concerned with color, however. Color case hardening is probably a trade secret. There is not much in print. One book shows that the cased parts are quenched in an aerated water bath. Air is supplied by a hose to the water thereby creating bubbles throughout. One old gunsmith told me that "leather gives red and bone gives blue."

[Black Frog]

Thanks for the info. 

I've seen Turnbull's stuff, and while fantastic looking I'm not too interested in dealing with poisonous salts and fumes....

 

I was thinking more along the lines of a heat treating oven and bone & wood charcoals and such.....  would like to know more about adding leather in there too!

 

But like T.Powers mentioned that blister steel was a bit different than the wrought iron?

I have old wrought iron fenching pickets.  There's some things I'd like to try to forge, and then case color them for appeance sake only.

I doubt they used high grade W.I. for the fencing pickets I have.

 

Frank,

I've seen several people who quench in the aerated water bath, some YouTube vids showing it as well.

That part isn't too difficult.  It is getting the crucible, the proper mix of charcoals, the temperatures, and the times down to a repeatable process.

.....this could be a fun experimentation if I could get pointed in the right direction.

[Black Frog]

Also,  I don't have a heat treating oven, but a reasonably-sized kiln popped up locally on CL that can go up to 2300F.

Nice bench top model with a 10" cubed interior.

 

Wondering if that would work decently enough?

[ThomasPowers]

Blister steel was made from wrought iron, wrought iron rods were packed in large stone chests filled with the carbon donor and kept at low red for close to a week.  The process is described in detail in "Steelmaking before Bessemer, vol 1, Blister Steel"

 

Most folks doing it nowadays use much higher temps and lower times; Ric did some as part of his "3 ways to make steel" demo at Quad State one year 

 

I was suggesting higher grade wrought iron as it's more homogeneous; though you could use lower grades and go on and make shear steel from it after blistering it to help deal with non-homogeneity.