How to do Color Case Hardening

[TomG]

Here is a link to a little tutorial on how to color case harden that favorite project.

Color Case Hardening

And another link to a thread on color case hardening from the Marlin Collectors Association:

Marlin Collectors Association

[Mayhem]

I remember getting my Starrett 711 DTI of eBay and then looking at it and trying to figure out why the metal was all funny colours. After seeing this, I figured it may be case hardening.

Thanks for the links Tom. I am really looking forward to seeing you do this to your Stevens.

[Harry Eales]

Hello TomG,

I have been following the Marlin thread since it started, and it really excellent. The two articles by the late Dr. Oscar Gaddy whilst well written and published elsewhere showed he fairly experimented well, but didn't really hit the nail on the head. His temperatures appeared to me to be too high. The Marlin thread shows good colours at far lower temperatures. That's the one I am going to follow.

This may be my first post on this forum but I'm in my 69th year and have been working metal for more than 55 years mostly connected with work on firearms. It's good to see another metalworking forum, and I'm glad to have joined up.

Harry

[DaveH]

(07-22-2012, 09:29 AM)Harry Eales Wrote: This may be my first post on this forum but I'm in my 69th year and have been working metal for more than 55 years mostly connected with work on firearms. It's good to see another metalworking forum, and I'm glad to have joined up.

Harry

Hi Harry,
Where have you been then?

Welcome to MetalworkingFun,
Very nice to have you here.

DaveH

[Highpower]

(07-22-2012, 09:29 AM)Harry Eales Wrote: This may be my first post on this forum but I'm in my 69th year and have been working metal for more than 55 years mostly connected with work on firearms. It's good to see another metalworking forum, and I'm glad to have joined up.

Harry

And we are glad to have you here Harry.
I'm looking forward to learning some things from someone with your experience.

Willie

[TomG]

(07-22-2012, 09:29 AM)Harry Eales Wrote: Hello TomG,

I have been following the Marlin thread since it started, and it really excellent. The two articles by the late Dr. Oscar Gaddy whilst well written and published elsewhere showed he fairly experimented well, but didn't really hit the nail on the head. His temperatures appeared to me to be too high. The Marlin thread shows good colours at far lower temperatures. That's the one I am going to follow.

This may be my first post on this forum but I'm in my 69th year and have been working metal for more than 55 years mostly connected with work on firearms. It's good to see another metalworking forum, and I'm glad to have joined up.

Harry

Welcome Harry, it's good to have another experienced member aboard.

I'm getting close to color case hardening the receiver on my Steven's which is why I've been researching the process. The Marlin thread is very thorough and should greatly shorten the learning curve when the time comes to try it myself.

I've also derived that lower temperatures are key to vivid colors, along with some sort of cage to hold the charcoal in contact with the parts as long as possible.

Tom

[Harry Eales]

Hello Tom,

One little tip here I wish to pass on. Now everyone who has worked with red hot metal knows that it gets a scale build up on all surfaces exposed to air.

When CC Hardening we don't want any of that happening to a polished part, do we? Now, no matter how careful you are in packing charcoal and bone into a crucible there will be air in the gaps between the grains of hardening compound.

The air can be eliminated simply by folding up a sheet of paper until it fits inside the top of the crucible beneath the lid. When the crucible heats up the paper will ignite, consuming the oxygen inside the crucible and what is left behind is carbon so there's no conflict likely it's simply adding to the carbon already present.

Harry

[TomG]

(11-17-2012, 04:07 AM)Harry Eales Wrote: Hello Tom,

One little tip here I wish to pass on. Now everyone who has worked with red hot metal knows that it gets a scale build up on all surfaces exposed to air.

When CC Hardening we don't want any of that happening to a polished part, do we? Now, no matter how careful you are in packing charcoal and bone into a crucible there will be air in the gaps between the grains of hardening compound.

The air can be eliminated simply by folding up a sheet of paper until it fits inside the top of the crucible beneath the lid. When the crucible heats up the paper will ignite, consuming the oxygen inside the crucible and what is left behind is carbon so there's no conflict likely it's simply adding to the carbon already present.

Harry

Hello Harry,

I had heard of that tip before to consume the oxygen, but thanks for reminding me.

Speaking of conflict, I got a message from a guy named Alex Johnson criticizing the Marlin thread for using a lower quench temperature. He pointed out that while it may lead to brighter colors, quenching below the critical temperature may not harden the part sufficiently. It's been a while since I've taken any classes in metallurgy, but he probably has a point. It sounds like some experimentation will be required.

Tom

[dallen]

the question then is are you wanting to color the part or harden it, does the part require case hardening?

[TomG]

Dallen,

This is one of those rare cases where it's possible to have your cake and eat it too. Firearms manufacturers like Steven's and Marlin have been color case hardening their guns for years and they are both colorful and hard. I have a Steven's single shot shotgun that has amazing colors on the receiver. So you don't need to sacrifice one for the other, you just need to come up with the right technique to achieve the desired results.

Tom