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Pack hardening a frizzen---asking for recommendations based on your successes

dgfoster

Diamond
Joined
Jun 14, 2008
Location
Bellingham, WA
First off, this is not a sub-forum I follow and so my inquiry may be the hundredth time the subjuect has come up. If so, my apologies. I did a search and did find a thread with Geo Wilson and others from four or five years ago. But I hoped there might be additional information to be gleaned.

Second, the usual recommendations of "a)farm it out b)buy the damn part c) why waste your time" really will not help the situation as I was asked by a friend to help him harden the frizzen on his old kit muzzle-loader. I would like to help him. the gun and frizzen are not irreplaceable antiques, but he wold like to get it to make a good functioning spark again.

I do have available a pretty good programmable electric kiln to use to cook a pack for a prolonged time. Making up a pipe pack would be very easy. The part in question is about 1" x1" x 1/4"

I am aware of and have two varieties of Kasenit-like products with which a thin case could be applied using my O/A torch. A deeper case is desired.

I have modest experience heat treating 4140, O1, and A2 steels and have surface hardened a few parts using Kasenit. So, once carburized, I think I can properly harden and temper the part for the intended purpose.

So, if some of you have tried-and-true methods you could share, I'd be most appreciative.

Denis
 
I was asked to provide a part for a Flobert once. I milled the part (A36 scrap,) to as near net as possible and heated with O A and when desired temp, or close, was attained ,I turned off the o and smutted the part cool. Glass hard results. Grinding was the only option to finish.
 
I was asked to provide a part for a Flobert once. I milled the part (A36 scrap,) to as near net as possible and heated with O A and when desired temp, or close, was attained ,I turned off the o and smutted the part cool. Glass hard results. Grinding was the only option to finish.

Yes, that method as well as Kaaenit and others are well known for providing a very thin skin of high-carbon hardenable steel. I've used those methods in the past where appropriate. But, in the case of the frizzen, it is subjected to repeated abrasion from the flint dragging over it and scraping off bits of metal each time. The existing frizzen was supplied in a thin case-hardened state. But, the owner fires the gun occasionally and it did not take long to wear through the original case.

That is the reason I am asking specifically about pack hardening and not just doing the simpler and much quicker methods that result in a very thin skin. From my reading, it is evidently possible to acheive 1mm deep hardening pretty easily and even 1.5mm deep hardening with pack hardening.
I am hoping to harden this frizzen to a depth of 1mm or more. That depth would last for hundreds if not thousands of cycles.

Denis
 
Use the Kasenit type products in an air-tight stainless steel pouch.

Brownells has the foil and instructions for use.

BROWNELLS STAINLESS STEEL HEAT TREAT FOIL | Brownells

The only place you need a deep case is on the face of the frizzen so put it face down over a layer of the powder when you wrap it up. The toe of the frizzen which rides on the frizzen spring requires only a shallow case. Quench in oil and temper at 350°F immediately after quenching as a thin section may get case hardened deep enough to crack under stress.

PS: I have case hardened frizzens by the old heat, dunk in powder, heat, dunk in powder (at least 3 times) before quenching and it gives a deeper case.
 
When Krags were being produced in the late 1890s several of the parts were case hardened with the usual charred bone, leather and charcoal packs. Portions of parts that needed extra deep and hard case were coated with a cyanide paste prior to being packed. Cyanide sounds dangerous but looking at the ingredients it is carbon. nitrogen. and oxygen, can not see how it would be too back after cooking. If Kasenit does not get hard enough maybe cyanide or some other recommended paste could be added to the portions than need it.
 
Use the Kasenit type products in an air-tight stainless steel pouch.

Brownells has the foil and instructions for use.

BROWNELLS STAINLESS STEEL HEAT TREAT FOIL | Brownells

The only place you need a deep case is on the face of the frizzen so put it face down over a layer of the powder when you wrap it up. The toe of the frizzen which rides on the frizzen spring requires only a shallow case. Quench in oil and temper at 350°F immediately after quenching as a thin section may get case hardened deep enough to crack under stress.

PS: I have case hardened frizzens by the old heat, dunk in powder, heat, dunk in powder (at least 3 times) before quenching and it gives a deeper case.
Thanks, Scott, that makes a lot of sense. The Kasenit probably, as supplied, has the carbonates often included in pack hardening recipes since it is designed to give as good a case as possible simply using a torch. I have a good-sized roll of SS foil purpose-made for heat treating as I fairly often anneal cast iron and harden 4140 and A2. This sounds like a good canditidate for a trial.

The question one confronts using any method is non-destructively knowing how deep a case has been acheived. George Wilson cleverly (I think) included common uncoated nails in the pack. He then periodically removed one and snapped it. Examination of grain structure visually revealed depth of case. (Like a whole lot of other iron casters, I use a wedge-fracture test looking at grain structure to detect glass-hard cast iron.)

Denis
 
When Krags were being produced in the late 1890s several of the parts were case hardened with the usual charred bone, leather and charcoal packs. Portions of parts that needed extra deep and hard case were coated with a cyanide paste prior to being packed. Cyanide sounds dangerous but looking at the ingredients it is carbon. nitrogen. and oxygen, can not see how it would be too back after cooking. If Kasenit does not get hard enough maybe cyanide or some other recommended paste could be added to the portions than need it.

Interesting that you should mention cyanide. Hydrogen cyanide will kill you quickly. Other forms not so likely if not reacted with acids or alkalais to produce hydrogen cyanide.

Kasenit's SDS shows it contains SODIUM Cyanide likely for just the reason you indicated.

(As a former Black and White photographer I used a lot of potassium cyanide to selectively bleach prints. It was harmless unless combined with strong acid.)

Denis
 
Thanks, Scott, that makes a lot of sense. The Kasenit probably, as supplied, has the carbonates often included in pack hardening recipes since it is designed to give as good a case as possible simply using a torch. I have a good-sized roll of SS foil purpose-made for heat treating as I fairly often anneal cast iron and harden 4140 and A2. This sounds like a good canditidate for a trial.

The question one confronts using any method is non-destructively knowing how deep a case has been acheived. George Wilson cleverly (I think) included common uncoated nails in the pack. He then periodically removed one and snapped it. Examination of grain structure visually revealed depth of case. (Like a whole lot of other iron casters, I use a wedge-fracture test looking at grain structure to detect glass-hard cast iron.)

Denis

Not to make more work for you but at some future point the frizzen will need dressing to remove ridges and if the sanding/grinding cuts through the case just redo it. Even a triple heat/dunk case will last quite a while if only used a few times a year.

PS: I'm too lazy to re-brown my frizzens after service so I just use Oxpho-Blue to get a dark gray that blends well on a well-used lock. I remember years back when I was bitching about char marks on the wood near the pan on my OMG expensive best flintlock and one of the older guys said "That's called patina, and it's what you get when you use a gun instead of hanging it on the wall as a decoration". After that I didn't worry, just used it, cleaned it, and touched up minor wear on metal and wood in a manner that said "Used, but cared for".
 
T

The question one confronts using any method is non-destructively knowing how deep a case has been acheived. George Wilson cleverly (I think) included common uncoated nails in the pack. He then periodically removed one and snapped it. Examination of grain structure visually revealed depth of case. (Like a whole lot of other iron casters, I use a wedge-fracture test looking at grain structure to detect glass-hard cast iron.)

Denis
Use of nails certainly is clever.
 
Traditionally wire was used,as the long length can be pulled from the furnace and quenched and broken ,without interfering with the job.


How did that work with pack hardening? Generally, I thought packs were pretty well sealed. How does the wire exit and,after checking it, how doe sit re-enter the pack?

Denis
 
You dont try to get the wire back in.....because if needed ,you use more than one wire.......Anyway,you can do the process however you like...You say you only want hardness...a lot of the involved processes are for bright case colours,which are sensitive to sealing.
 
Thanks for the replies, all. For my situation and desired outcome, I think I will use scrap to test the Kasenit in a foil pouch idea. That seems like the simplest approach and should not cause ugly scale on the part. I’ll try 1700 for 6 hours to see how much penetration we get and how well the foil pouch holds up against the heat and chemical action of the Kasenit components.

Denis
 
Denis,
If I recall correctly, in the packing you need also some sawdust or other combustible materials to remove any oxygen, avoiding therefore the formation of scale (fairly important, since you are working on a finished part and you do not want to alter the dimensions of machined surfaces).

Paolo
 
I could see some small nails or coat hanger wire pushed through the foil to be removed for testing without opening the pack. How much oxygen leak in though a couple of small holes especially if the foil was doubled?
 
Denis,
If I recall correctly, in the packing you need also some sawdust or other combustible materials to remove any oxygen, avoiding therefore the formation of scale (fairly important, since you are working on a finished part and you do not want to alter the dimensions of machined surfaces).

Paolo

Yes, lots of carbonaceous material like leather and bone have been used as well as charcoal (sawdust in essence) to consume oxygen and generate CO—-the carbon donor for the metal. I suspect bone contains carbonates that are used, in proprietary recipes, to catalyze the process.

I could see some small nails or coat hanger wire pushed through the foil to be removed for testing without opening the pack. How much oxygen leak in though a couple of small holes especially if the foil was doubled?

True that the leak would be small. However, where one nail excuses itself another could be slipped into its place thus plugging the hole pretty well...

Denis
 
You should note that if you intend to use cyanide,it melts to liquid at carburizing temp.....consequently ,any pack containing cyanide must be liquid tight ,or a pot type container......Cyanide makes for the cleanest finish,pack hardening will have scale.
 
I finally got to trying pack hardening with Kasenit. I used SS foil wrap (the high temp version) and put a couple 1” pieces of common A36 structural steel bar 1/8 x 1 and 1/4 x 1 in an envelope with a quarter cup of Kasenit. I had ground the mill scale off the bar. I used a hammer to double fold and tightly close the edges and put the whole lot into my kiln. I set it on 1650F for 5 hours hold. I erred in closing the lid so that when I went to retrieve my pack 5 hours later I could see the kiln indicated it had only been at 1650 for two hours and the foil pouch was just wisps of steel essentially vaporized due to the chemical action of the Kasenit.

947595D5-4DAD-46F7-B41E-E2E13EBB1EC7.jpg

I used a long plier to snatch the pieces out of the bright red kiln and dropped them into water.

First I tried to bend the 1/8 piece in a vise by inserting it half way and hammer it. It snapped off cleanly after 1 or two blows! The grain structure looked uniform throughout. I could not break or bend more than a few degrees the 1/4” piece. Ordinarily, if unhardened, both should have bent to 90 deg.

I then hardness tested the 1/4” piece. It tested Rc50 after light hand grinding to remove a black coating (no real scale) from the surface. I then quickly step ground it on my surface grinder in .010 steps to .050” depth. At .050 it tested 35. I used a calibrated Wilson bench hardness tester to determine hardness.

Conclusion: Kasenit drove carbon beyond .050 into the A36 after an unknown effective exposure for 2 or 3 hours of a failed envelope enclosure. Lots of unknowns, I agree. But, I am encouraged to make a proper SS pipe pack and sustain exposure for 5 or 6 hours. I feel pretty sure that very good penetration will occur. I will include test pieces with the frizzen and will more carefully step grind to assess better penetration.

Overall, penetration was better than I expected.

Denis
 
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