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case hardening quench


cdent
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hi to all,

i'm hoping someone can comment on the quench part of a color case hardening 'recipe' that i'd like to try. this would be for appearance on 1018 mild steel misc. parts. it calls for a mild bubble agitation of a water quench. i assume (not good) they are trying to speed up the quench. how would brine or one of the 'superquench' formulas compare to the agitated water as far as speed? and, is there a chance that those various salts, soaps etc. affect the formation of the colors?

i ask because i think i could make the process more predictable/repeatable with the tools and materials that i have. i'll be trying test pieces, but don't have the experience to guess if i'm headed way off base.

thanks for your patience from a beginer/hobbiest. i'm a long time lurker who appreciates the info that don (and the hundreds of members) sat right at my fingertips.

take care, craig

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Agitating the water is not to make a faster quench, it's just to break up the vapor phase. Color case hardening is a tricky thing and it's going to take some experimanting to get things right. Be patient !!

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Mete's right, the bubbles are to break up the uniformity of the quench. That's how you get the color spots, they are temper colors (oxide films of differing thickness). If you use superquench or any other quench without the bubbles, you'll just get a uniform color. Color casing works by quenching the same part at the entire range of temper color temperatures, which is quite a trick! You need serious bubbles and swirl in there.

 

Water-soluble gun blue can work for a fake color cased look. Get your part polished and absolutely clean, so that water sheets on it rather than beads up. Get the thinnest possible sheet of water on it that you can, then take a toothpick or q-tip dipped in blueing solution and flick, tap, or otherwise apply the blueing in a random way. You can see the clors change and thin as it flows and gets diluted. Let it set, and hopefully it worked. A uniform blue flicked with water while the blue is still wet can work too. Birchwood-Casey instant liquid (not paste) gun blue works, but avoid the blackening ones with selenium, they don't color the same.

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Agitating the water is not to make a faster quench, it's just to break up the vapor phase. Color case hardening is a tricky thing and it's going to take some experimanting to get things right. Be patient !!

 

 

Well, that is partially right. Agitation will make a faster quench - because it does break up the vapor phase and start nucleate boiling. Agitation also helps keep the heat transfer uniform on all sides.

 

Maybe I don't understand the terminology - but coloring is one thing, and case hardening is another. Case hardening is achieved by adding additional carbon in the surface of the part, then quenching and tempering. Coloring by using temper colors actually is the creation of a patina on the part. For instance, you can create a nice blue color by tempering at about 500-600F (depends on the steel). You can make it even more blue by adding a bit of water or tempering when the air is humid. Other colors are possible. Black oxide is achieved using special salts that create a tightly adherent magnetite (Fe3O4?) on the part. It is a good protective surface.

 

I don't know of other ways - can some one tell me?

 

Scott

D. Scott MacKenzie, PhD

Heat Treating (Aluminum and Steel)

Quenching (Water, Polymer, Oil, Salt and Mar-Tempering)

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thanks very much for all the comments. i'll stick to the water quench, and try some samples. i got the idea from brownells and i've seen reports on getting the mottled colors with some cold blues, but i'm hoping to get that old time look and make expanded use of tools and materials that i already have on hand.

 

take care, craig

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Scott, we're talking about the technique used to create the mottled blue-brown-bronze-yellow splotchy colors on the receivers of some antique and reproduction firearms, the most commonly seen are the frames of 1873 Colt SAAs or Harrington & Richardson shotgun receivers. Yeah, the color and the case are two different things, but for marketing reasons it's known as color case hardening. B)

 

Edited to add: The parts are case hardened, originally wrought iron or mild steel. The colors are just a decorative touch that was fashionable for some reason. Since in the original technique you packed the part in a sealed container with leather and bonemeal as the carbon sources, and dumped the whole contents into the quench, I'd bet that bits of charred stuff would have stuck to the part like clay on a blade with hamon, thus helping the colors a bit...

Edited by Alan Longmire
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Also to add; colour case-hardening has the added benifit of being quite a bit more durable than just simple oxide colours from a draw or heating, since it is also a very superficial depth case hardening the surface is pretty durable and somewhat more scratch resistant than just straight colouring from oxides.

 

There is an almost infinite range of effects that can be had by adjusting all kinds of variables, amount and type of agitation, temp of the water, how the parts are arranged in the box, the height of the drop to the water, how hot and how long you soak the parts in the box, etc etc....

Randal

www.rhgraham.simpl.com

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Here's a color case hardening how-to by one of the best modern (high dollar) muzzleloading rifle makers......you can see some of his work here - http://www.jwh-flintlocks.net/

Case hardening for colors. Requirements

 

#1 Clean charcoal. Preferably wood and bone

 

# 2 Polished Metal--carbon steel --no chrome or stainless.

 

# 3 Pack properly Container type and construction Best type is stainless or cast iron box or pipe with properly fitted lid. however a lain mild steel box of 1/8" thickness is sufficient for about a dozen or more heats

 

Pack parts with at least 1/2" of charcoal around all parts preferably with the parts not touching. note--- touching will do no harm as long as box or contents are not over heated. and no improper metal is in the pack--aluminum etc.

 

#4 Accurate temperature is absolutely necessary. I recommend a type K thermocouple pyrometer with a submersible probe . approximate cost new 175.00 or less - this type of thermocouple is very versatile and can be used for casting or heat treating springs etc. also.

 

Steel or iron will begin to absorb carbon at approx 1200 deg maybe lower should be held at 1250 to 1450 for at least 1 hour. carbon depth approx .008" per hour at 1450 F. If a temperature of over approximately 1500 is exceeded colors will begin to disappear fast. If the temperature is not at least 1350 at quench the metal will not harden.

 

note -- Some people have discovered that by quenching at too low of a temperature enhanced colors will be produced . remember that hardening is the prime requirement if it is not hardened it is not color case hardened. Keep the temperature at least 1400 F at quenching. Remember that when you regulate temperature it will take about 10 to 15 minutes for the inside of the pack to arrive at the same temp as the outside.

 

#5 Quenching.

A--- The quenching material must be water. The water should fresh out of the faucet and be about room temperature and clean. The purpose for this is to help reduce the possibility of cracking.

 

B--- all precision parts , long flat parts such as lock plates must be blocked to hold warping at a minimum. Lock plates will warp almost every time. Parts like revolver frames, Sharps rifle receivers etc. must be blocked with jigs that are made for the purpose. Blocks must be made so as to allow the water quench and the carbon material to reach all parts of the object that case hardening is critical to.

 

C----- When the pack is dumped into the quench the parts must not be exposed to oxygen before they hit the water. In order to accomplish this the lid must remain on the pack until the pack is dumped. For this reason it is recommended that the lid not fit too tight on the container. It is not necessary for the lid to be air tight in order to keep oxygen out of the pack the charcoal will accomplish this chore. If a heat source is used that is anything other than electric the flame should be either neutral or very slightly reducing. A good electric furnace is automatically reducing or neutral and fairly cheap to make. HOLD THE PACK AS CLOSE TO THE WATER AS POSSIBLE WHEN DUMPING. DO NOT THROW THE WHOLE BOX INTO THE QUENCH it will only serve to reduce the life of the box and cause other problems.

 

DANGER!!!! USE A FULL FACE MASK AND WEAR A HAT OR DAMPEN YOUR HAIR. WEAR FIRE PROOF GLOVES AND DO NOT WET YOUR GLOVES. WET GLOVES ARE DANGEROUS BECAUSE IF THEY GET HOT FAST THE STEAM WILL BURN YOU MUCH WORSE THAN IF YOUR GLOVES WERE DRY. WHEN THE PACK IS DUMPED THE STEAM FROM THE HOT CONTENTS HITTING THE WATER WILL THROW STEAM AND HOT CHARCOAL UP IN THE AIR IF YOU ARE NOT READY FOR THIS IT WILL BE QUITE STARTLING.

 

Manipulating and enhancement of colors.

 

As stated previously the colors on the steel are caused by oxidation . The oxidation in this case is allowed to occur by the steam bubbles in the water. There are three or four ways to manipulate the colors to my knowledge.

 

#1 One way is to put other pieces of steel in close proximity to the part being case hardened. For example -- bolt another piece of steel with holes in it close to the part being quenched or you might wrap some large or small wire around the part. Any place where another piece of steel or other metal is touching the part that is quenched will cause a play of colors to occur there. also it will usually occur around screw holes or parts that very in thickness . you will notice that on a lock plate if you put your block on the back of it you will have a great display of colors on the back but not many on the front. This is because the block traps steam between the lock plate and the block. If you want more colors on the front put your block on the front. for finer colors drill more holes in the block etc. My personal preference is to wrap with wire it is easy ,fast and effective.

 

#2 Some people build a system that aerates the quench bath to put bubbles in it. I suggest that if you do this the bubble must be very small and numerous. I have never tried this but I think it would be hard to control and you will have to do much experimentation to get it as you want it to be because no one is going to help you . All the professional case hardeners I know are very secretive about their systems. However if you get it adjusted correctly it may be a very good system.

 

#3 You can put potassium nitrate in the quenching bath to get more blue color . This is effective but can be easily overdone. 1/4 of a cup in five gallons will result in almost the whole part coming out blue. so I would suggest that you use no more than two heaping tablespoons full.

 

#4 Colors will be enhanced if you put your parts in an oven for 1 hour at 350 deg F. to 400F after quenching Don't go over 400 or the colors will begin to merge . This will also reduce stress within the parts and reduce the possibility of cracks showing up later on. Also in the event that one of your parts is solid tool steel it will stop it from breaking later on

 

I repeat my preference is the wire wrap method.

 

#5 Color hardening is not a real durable finish for it to be durable you must do a baking lacquer finish over it. These supplies are available from Brownells - you can use a gloss or a matte finish . Some case hardeners prefer to leave it as it comes from the quench. It will last quite some time and is almost rust proof.

 

I am going to answer one question now so I won't have to answer it five hundred times later. People ask--Jerry why don't I see more color case hardening on your guns if you know so much about it. The answer is I am basically an engraver at heart and color case hardening does not flatter engraving. It is very hard to see clearly fine engraving thru color case hardening for that reason you will only see a minimum of colors on my guns.

 

GOOD LUCK HAVE FUN - Jerry Huddleston

Chuck Burrows

Wild Rose Trading Co

chuck@wrtcleather.com

www.wrtcleather.com

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Thank you WildRose - I appreciate it. I am trying to understand the physics/chemistry of what is happening. From what I understand from what you wrote, it is the color formation that occurs during quenching, from the formation of bubbles, selectively oxidizing the parts. The color is esentially the temper color of the temperature of the part localally when the bubble breaks?

 

Surface roughness can effect how long the bubbles attach - the smoother the part, the more adherant the bubble - something to do with surface tension of the part vs. the surface tension of the bubble.

 

That is pretty cool!

D. Scott MacKenzie, PhD

Heat Treating (Aluminum and Steel)

Quenching (Water, Polymer, Oil, Salt and Mar-Tempering)

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wow jerry h. (chuck b. ?)

please be assured your time and knowledge is truely appreciated. thanks again to everyone for working with this topic.

take care, craig

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