color case hardening

[robert bw]

I know that case hardening refers to a surface layer.But, how do they obtain the color?Im assuming something to do with heat treatment?

Not sure, but it sure is pretty.Does this hardening also resist corrosion?If so, how?Thanks fellas

 

[bubba.50]

don't know exactly how it works but, Dixie Gun Works used to have a recipe for case-hardenin' small parts by wrappin' it in leather, put it in a tin can, fold top of the can over, then heat the can with a torch to a certain color for a specified length of time. believe you had to cool it just right too or maybe even oil-quench it. don't know where my catalog is right off or I'd see if it was still in there.

luck have a good'en, bubba.

 

[robert bw]

Thanks Bubba!

 

[Onojutta]

I just hardened some lock screws by heating them to cherry red, then dunking in linseed oil. Then I annealed them by heating to grey/blue (not as hot as red) color and letting cool. Both screws are now a very distinct blue color. I don't know anything about blacksmithing so I don't know why this happened, but it was a pleasant surprise and looks pretty good.

 

[robert bw]

Hey, Moderators, ever considered a "Historic metallurgy"section ? Just a random thought.

Colonial gunsmiths probably knew more about this than we currently give them credit for(I suspect).

 

[nwtradegun]

true color case hardening is a hole new word. you need a metal crucval, that has a tight air proof lid. bone meal, and a hot fire. it is involved. if not done right you wind up with warped parts or cracked, https://www.youtube.com/watch?v=A9ExouQ2byY

 

[bubba.50]

I believe you hafta have pretty precise temperature control too.

 

[Bo T]

When you temper them (after hardening), especially with a torch or hot piece of metal, a thin layer of oxide forms. The color of the oxide allows you to predict the temperature that you tempered the piece.

 

[Bo T]

If you know someone with a ceramic kiln that can be set at a fixed temperature, you can experiment on clean pieces of the same metal you will be working. If you need to case harden a part, there are coatings that you can use to accomplish the task.

 

[dave_person]

Hi,
Color case hardening and simple case hardening are essentially the same process except hardening temperatures used are lower to achieve good colors. Also there are tricks such as wrapping the part with metal wire and bubbling air into the water quench that help to enhance colors. Other than temperature, a critical part for achieving colors is that the pack (parts packed in charcoal within a box or crucible) must enter the quench as a solid unit so none of the parts are exposed to air before immersion in the water. Unfortunately, although beautiful, case colors are not very robust to wear and eventually fade even when lacquered. A case hardened surface is much more resistant to rust than unhardened steel.

dave

 

[LRB]

I seriously doubt that you actually hardened the screws. Common screws do not have enough carbon in them to harden. The steel has to be of a medium to high carbon content in order for it to harden to any real degree, or you would have to case harden the screws. As mentioned, the color is a thin oxide coating from the heat. What you did is called "fire bluing", and can be very pretty if the steel is first highly polished. The oxide coating does not hold up well to wear, but can be redone when need be. Some modern gun screws, such as some scope mounting screws are hardened, but I don't know if they are case hardened, or of a high enough carbon steel.

 

[matt denison]

I seriously doubt that you actually hardened the screws. Common screws do not have enough carbon in them to harden. The steel has to be of a medium to high carbon content in order for it to harden to any real degree, or you would have to case harden the screws. As mentioned, the color is a thin oxide coating from the heat. What you did is called "fire bluing", and can be very pretty if the steel is first highly polished. The oxide coating does not hold up well to wear, but can be redone when need be. Some modern gun screws, such as some scope mounting screws are hardened, but I don't know if they are case hardened, or of a high enough carbon steel.

What Wick said. Some people do harden screws but they coat them with a high carbon compound such as Kasinit or Cherry Red first as they heat them. Then polish back to bare metal and heat blue them to the degree they want.

 

[jerrywh]

I have done case hardening for about 45 years and color case hardening for about 20 years.
Both processes are essentially the same except there are strict guidelines that must be adhered to if one wishes to obtain good colors.
The temperature required for case or color hardening a piece of steel when quenched must be between 1450°F and 1550°F. If the metal is quenched at a lower temp. Good colors might be the result but the hardness will suffer.
Case hardened part are a lot more rust
resistant than if left soft. In fact it is a little difficult to brown a case hardened part because of that.
I do not want to do a tutorial on color case hardening on the forum for too reasons.
#1 it takes too long to give one in sufficient detail.
# 2 too many people who don't know will argue about it.
The argument doesn't bother me but it only serves to confuse anybody who really wants to learn how to do it correctly.
The best way for one to learn how is to buy the supplies from Brownells. Brownells will also send you complete instructions on the process. Well almost complete.
There are a lot of tricks that will enhance and manipulate the colors. And you must learn how to control the warp-age that can occur.
Any time I think something is simple I find I just don't know much about it.
This is not directed at anybody in particular. Just stating the facts.
Wick know a lot.

 

[nhmoose]

Color of color case hardening is only microns thick. When it is not protected by varnish or shellac or nowadays plastic coating or lacquer it will be rubbed off very fast.

You want to use a finish that a solvent like alcohol or acetone can remove when the covering get nasty looking so it will not remove the color as any mechanical means will remove it,

 

[ZUG]

+1 -- I still have 1-1/2 cans of the old formula kasenit left and I use it to put a surface hardness on lock & tang bolts - not for the small screws :v then I use the oil /flame treatment to get color - just not too hot of a flame.

 

[Onojutta]

Here's a neat video on color case hardening firearm parts:
https://www.youtube.com/watch?v=sFWLQeTCJ4s

 

[54ball]

While most types of metal finishes that we talk about in traditional gun building date back hundreds of years, some of these finishes or treatments can be very time, place and culture specific.

For instance...
Color Cased Hardening
In short, it's more of a 19th Century style.

In the 18th Century locks were polished after hardening. The English lockmakers in the 18th Century considered the colors a defect to be polished away.

Of course as often repeated in any historical research, there
could be and usually is exceptions.

As you get into the 19th Century case colors become "fashionable."

Something to consider or look into if you are emulating a particular era.

 

[robert bw]

Right after posting this thread I went to Brownells and learned a lot.

Case hardening sure seems to be an art,
not unlike many craftsman produced one offs.Like any other craft, time ,patience and persistence seems key .Thanks fellas for the input!SC

 

[dave_person]

Hi,
William Bailes is credited with introducing the fashion of color case hardening at least in England during the 1760s. It was commonly used in the late 18th century but as you mentioned, it became much more popular during the late flint and percussion periods during th 19th century.

dave

 

[mooman76]

Hey, Moderators, ever considered a "Historic metallurgy"section ? Just a random thought.

Colonial gunsmiths probably knew more about this than we currently give them credit for(I suspect).

I wouldn't mind that. I have a few springs that need some work and probably have to make a spring or two.