Case hardening

heat it up and drop (not too hot, it shouldnt glow)it in a pail of oil. motor oil seems to work ok. 2 stroke even. i have never tried it with parts that need to spark, but i have done it a number of times to other things. Use a magnet when the part doesnt stick to the mag anymore, then its time for the oil bath. If you want to get really fancy, heat the oil too so its good and hot when you drop the piece in.
 
JaysonCraig said:
heat it up and drop (not too hot, it shouldnt glow)it in a pail of oil. motor oil seems to work ok. 2 stroke even. i have never tried it with parts that need to spark, but i have done it a number of times to other things. Use a magnet when the part doesnt stick to the mag anymore, then its time for the oil bath. If you want to get really fancy, heat the oil too so its good and hot when you drop the piece in.
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Heat the oil too? Sounds like a recipe for disaster. Quenching oil has a higher boiling poin/flash point than conventional oil, and is designed to be heated unlike conventional lubricating oils. If you use conventional lubricating oil, DO NOT heat it up, and be cautious with open flame around it. Otherwise, the above applies and should work OK for you.....
 
Do you have any industrial supply places in Peace River? Buy some Kasenite, heat the frizzen red hot and sprinkle the kasenite on it. Keep it hot and soaking for 3 minutes or so and quench in water. If the frizzen is mild steel, a water quench is not going to hurt it. You will probably have to add kasenite two or three times during the process as it tends to burn away. Finish by polishing the frizzen face and reheating to a light golden brown and quench again.

cheers mooncoon
 
gunasauras said:
Heat the oil too? Sounds like a recipe for disaster. Quenching oil has a higher boiling poin/flash point than conventional oil, and is designed to be heated unlike conventional lubricating oils. If you use conventional lubricating oil, DO NOT heat it up, and be cautious with open flame around it. Otherwise, the above applies and should work OK for you.....
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never had a problem with heating it myself. engine oils dont get hot? it should be fine. guess it just depends how hot he tries to get it.
 
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Another option is to face the frizzen with a piece of hardened high carbon alloy steel. Carburizing the frizzen is all very well, but the layer is not very thick, and will be cut through in time.
 
Hardening long

I would like to see pictures of this as well.
You have had some good replies/advice for this project. If you haven't proceeded with it, I'll thow in 2 cents worth. when heating the piece for hardening, heat to dull red and slowly bring the temp higher, touching it with a magnet. when the magnet doesn't stick to the steel any longer, you are at the right temp for hardening that type of steel. Since it is a small piece, it won't have to soak long... a couple of minutes.
heating the quenching oil is a method of controlling the rate of hardening. warming the oil slows the quenching process and lowers the chance of micro-cracks appearing in the metal. It doesn't need to be hot, but above room temperature helps.
remember that hardening steel makes it more brittle so be sure to do the second half of the process which is tempering! For your application, shine up the piece so you can see the steel, reheat until you just get a blue or purple color in the steel and re-quench. This will harden and temper to the consistancy of spring steel. it should give you enough hardness for the spark without being brittle enough to break.
 
Quenching in oil, and then drawing back the hardness as appropriate is a proper treatment for oil hardening steel. If the frizzen is surface hardened mild steel, oil quenching isn't going to work, and Kasenite is an option.
 
You guys are talking about two different processes (as tiriaq says). First is martensitic hardening (the heat-quench-temper method) and the second is case hardening (such as carburising among a few other varieties).

The ability to martensitically harden a steel depends on the type of steel among other things. You need to know the steel type and hardenability in addition to the heat treatment schedule (including type of quench and temper etc.) to properly attempt this.

Carburising works by having the steel draw up carbon at the surface, hardening it to a depth, while leaving the core more ductile. You are probably less likely to make the metal brittle this way.
 
It has been my impression from hardening or rehardening a number of frizzens, that if the frizzen is too hard it will not spark well. I now draw the temper to a brown colour whether I am using a heat treatable steel or case hardening mild steel. I also heat the corner between the pan cover and the striking face to about blue to reduce the risk of a break in that area.
I have also noticed that as a frizzen face gets worn, it tends to become rippled and these ripples seem to slow the flint down and therefore fewer sparks so that if I am redoing a frizzen, I grind the ripples smooth before recasing.

cheers mooncoon
 
Lots of good advise here but if you don't know what kind of metal you are dealing with you won’t get the intended results.

Carbon steel
1-first you must stress relieve by heating it to an even dark red and letting it cool naturally to room temperature. Preferably on a brick or cement block. This is done to remove any hardening that remained and will stabilize the metal.

2-heat it up to a bright orange for a couple of minutes

3- quench it in room temperature oil and make sure there is there is plenty of it because if there is to little the oil will ignite. Ordinary 10w or 5w 30 motor oil will do.

3-Once cooled clean of the black scale (slag) until you expose the metal.

4-finaly you must temper it to make it tough, this is a little tricky because it must be heated slowly until the metal turns light gold in color, if it turns brown or blue you missed your the mark and you will have to repeat the whole process.

If it is mild steel then oil hardening it will not do anything because mild steel can only be carb-hardened
This method very delicate and difficult to control because the cooling process should take hours in a carbon rich media. This gradual cooling will allow the carbon from the media to impregnate the surface of the carbonless mild steel up to 1/32 to 1/16 while the core remains soft.
 
I am going to take exception to a number of things said here.
1. As a basis to begin with, the striking surface of the frizzen has to be hard and have lots of carbon. Hard in this case borders on file hard and if drawing the temper, represents brown on the oxidation scale. At a guess it is around 500 F if using a thermometer but that is a guess. It is below 600 F

2. oil hardening does not put significant carbon into low carbon steel. It does not harden low carbon steel. Most foreign reproduction guns use low carbon (mild steel) parts that are case hardened. Some but not all american guns use high carbon heat treatable steels. If the part is high carbon then it will be hard all the way through and a small amount of wear will not affect sparking except if there are major ridges or ripples which slow the flint down. If the part is low carbon case hardened, it only takes a few thousands of wear to break through the high carbon portion into soft low carbon metal.

3. tempering is really better described as rapid cooling from red hot to make the high carbon portions of the metal brittle hard then drawing the hardness by partial reheating to make it a workable hardness. Steels can be air hardening, oil hardening or water hardening depending on their composition. In my experience at least, floating 1/4" or so of oil on top of a water quench will break the shock enough to allow you to water quench an oil hardening steel and still allow you to harden water hardening steels. At least it has worked so far for me.

4. normalizing may be necessary in a perfect world but I have never found it necessary with frizzens that I have worked with and I doubt that it is necessary with case hardened parts of mild steel.

5. you do not have to cool a re carbed mild steel slowly and in fact that would defeat the whole attempt to create a hard surface. You do need to keep the part red hot with kasenite or equivalent on it for several minutes because it takes time for the carbon to be absorbed. The number I have heard quoted was it penetrates .001" per minute of soak but I don't know how accurate that statement is.

cheers mooncoon
 
I've seen video of a very amateurish attempt at hardening.

Used motor oil was the quenching medium (I know, I know). A fairly small volume was used, and a reasonable amount of steel was quenched.

The result was fairly predictable to someone with a reasonable knowledge of thermodynamics...which is ironic since at least one of the people on the video had the background to know better.

I'd probably ensure that I had at least one 20 pound ABC extinguisher around. Maybe even a more upscale extinguisher setup if I had a lot of quenching oil on hand or was trying to harden a lot of steel. Foam designed for hydrocarbon fires comes to mind. If it's got a source of heat immersed in it, the oil could take a while before stopped wanting to burn.
 
one advantage of using oil floating on water is that the part passes through the oil and most of the cooling is done in water hence greatly reduced smoke and flame from oil vapours. Using oil by itself, the part stays hot enough to vapourize oil for some time and you get lots of smoke and usually some flames. In terms of small parts for muzzle loaders which is what started this thread, the flames are unlikely in my experience to start a fire but the absence of smoke and flame is certainly very desireable.

The only thing that I have ever had crack with a water quench was a home made twist drill about 3/4" diameter with deep flutes. The crack ran down the flutes as I recall.

relative to John's suggestion, you need to be sure that the hardened filler rod is so because it has 1% carbon rather than because of being a hard alloy of other metals. You need lots of carbon to make a frizzen spark.

cheers mooncoon
 
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