Atmospherically Controlled?

Michael J. Spangler

Michael J. Spangler

Joined
Oct 8, 2003
Messages
2,181
alright guys. i know it may be a long shot but how hard is it to set up a flow of argon into your kiln? i know paragon sells set-ups that look pretty basic and extremely easy. but i'm an idiot so fill me in here. i'm sure argon isn't too expensive right? and you might just need some type of quick connect set up with a regulator right? thanks in advance
 
Consumption of gas in the type of unsealed furnaces we use can be high because it will need a constant flow to replace escaping gas. Argon is one of the more expensive of unmixed gases. The guys I know who have argon on their furnaces didn't use it after a couple times and stick to using foil, Michael.

If you coat your furnace inside to cut down the porosity and can manage to somehow gasket your door, it might work much better. You might also be able to build a fully welded metal case around the chamber/bricks, too. There are, after all, numerous models of atmosphere-controlled industrial furnaces.
 
Seems like it would be a lot of work and expense to run it that way. Have you looked into high-temp PBC anti-scale?

-d
 
Got a question for you Mike:
In a non-atmospherically controlled oven, what is the extent of de-carb/carbon loss in a blade? I know that's a vary vague question and there are other variables here.
Is it based on time? Steel type? Thickness?
I'm talking about an un-protected blade - plain clean steel in a regular heat treat oven.
How deep is the carbon loss?
How much steel needs to be removed before you get to unaffected steel?
 
Been there, done that and went baack to using foil in a rapid fashion. For money spent on argon you can buy a BIG load of foil and have more predictaable results to boot.
 
Karl, I don't have an answer for you, sorry. I feel sure mete studied that subject and would be qualified to speak on it, but not me. Maybe he'll chime in.

At SS temps, the damage is pretty bad in a 30 minute run. I saw an S30V blade where the controller on the furnace went out and there was a "thermal excursion" until it shut down. The blade looked like some ancient antique that was rusted away.

Perhaps a good way to check is to make a test piece with a narrow edge and find out how deep you have to file to get to "skates like glass" steel. That would give you a crude idea.
 
Mike S
just to add to the good info here..
once you take the blade from the oven no matter what, when the hot blade hits the air to air quench it you'll have decarb anyway.. that is why even in foil you have to wait untill the blade cools some before you remove it from the foil even.... ..
 
Thats true, for air hardening, but carbon steel; would be a different treatment. I use a gas fired, closed system, that can be argon injected. The time it takes to move the blade from closed cannister to quench is: 3 seconds, no more.
I don't know, how long it takes, for decarb to take place.
Give us a hand there, metallurgist. At what rate, does decarb take place? :confused: Fred
 
Dan, I remember that knife in your avitar. Still looks great! Michael, stick with foil for your high alloys and use plates to quench while still in the foil wrap. You can even leave in foil after quench and hold in your tempering oven until ready to austenitize a second time.

rlinger
------
 
I can easily add argon to my oven - it has sealed exterior metal shield. It is also
top load, so argon won't escape through side door. I have a flow meter and argon
bottle (refill is something like $35) - from me TIG. But I don't do it for one simple reason: foil works and it is 100% predictable.

I tried PBC Special - complete with report here, and went back to foil. Not worth the
hassle and _uncertainty_ of PBC . If you miss a spot, it just might pit so deeply that the
blade itself will be destroyed. Aintworthit
 
If you do NOT grind to a full finish, and leave, say .010 at the cutting edge, which to bring to a full cutting edge will require removal from the sides as well, is de-carb a non-issue?
Will your "clean-up" remove all of the steel that has experienced de-carb?
I get virtually no "pitting" what-so-ever in any of my blades the way it is.
 
kbak - when you say that, you mean:

- using no protection @ all
- using PBC special
- foil ?

There seem to 2 different schools when it come to HT and finishing:

- some do 150 grit and it goes to HT
- some go all way up to 600, where it is nearly polished

Methink that 2nd group outsources HT to Bos - and with vacuum ovens, the blades
come back as shiny as they went in.

Both groups leave nuff meat to correct for warpage, if any and not to let cutting edge
itself to warp - which it sometimes does if it is too thin. Air-kool steels have excellent
dimensional stability when quenching and thusly don't (ever) warp.

Oil-quenching ones is an altogether different story - these will warp like SOBs of left too thin @ the edge. At least 60 thou is a must.
 
damn this thread took off....

seems like you all have good points, about de carb and such. and the fact that why not go with foil... it works. and now that i think about it. how many times do you think you could fire your oven before that argon is gone? where as foil is really inexpensive if you look at it per knife. especially since i got that 50yd roll for 10 bucks :D

and if i'm going to be plate quenching i can just leave it in the foil and the same for tempering if i needed to.

and for something like O1 its not soaking long, so theres no need for it.

alright guys you all rock. thats for steering me away from it.

I should have the oven wired up and fired up today.... as soon as i do i'm going to take pics.. and HT some knives!! thanks guys
 
rashid11 said:
kbak - when you say that, you mean:

- using no protection @ all
- using PBC special
- foil ?

There seem to 2 different schools when it come to HT and finishing:

- some do 150 grit and it goes to HT
- some go all way up to 600, where it is nearly polished

Methink that 2nd group outsources HT to Bos - and with vacuum ovens, the blades
come back as shiny as they went in.

Both groups leave nuff meat to correct for warpage, if any and not to let cutting edge
itself to warp - which it sometimes does if it is too thin. Air-kool steels have excellent
dimensional stability when quenching and thusly don't (ever) warp.

Oil-quenching ones is an altogether different story - these will warp like SOBs of left too thin @ the edge. At least 60 thou is a must.
Click to expand...

OK.
I use an Even Heat oven for heat treating as well as sometimes doing OA for edge quenching.
Mostly I use 5160. In the last three years, maybe 150-175 completed knives, I have had two blades warp, and they were W1, and about 10 inch blades.
Most of the time I grind to full finish with a nice 220 hand-finish running lengthwise.
Never heard of such a thing like .060. I might leave .020, and that is rare, maybe if I got lazy, which rarely happens.
Main reason I got to almost full finish, if you go to all the trouble of taking a knife all the way through hardening and tempering, why in God's name take that blade BACK to the grinder and start grinding away with the possibility of introducing heat right into that cutting edge? You can exceed tempering temp with a blade edge in a split second and RUIN everything you just accomplished.
From my experience, warpage more than likely comes from a blade NOT being ground to almost finish. Warpage is a cooling "difference" in geometry - for example, on a blade that is NOT ground to its full finished symmetry, you will get cooling variances on quench - one side cools faster/slower than the other side due to thickness differences and then warps.
Warpage is not an issue in my shop even when I grind to full finish. I think doing so actually eliminates warpage.
Do that, along with proper normalizing, spherodizing, etc. and "warp" shouldn't even be a word in your vocabulary.
I'm just trying to figure out, with all things being lined-up, proper temps, etc., what is the normal depth of de-carb in the average maker's shop when using non-atmospherically controlled equipment if temps and time are watched so as not to exceed extreme temps for long periods of time.
Proper procedures followed, bare naked steel, what is the depth of de-carb?
 
I recall seeing somewhere, a while back, that it was something like 1 thou every 5 mins .

Warpage could also be due to defect in the steel itself - as they roll it, it introduces
stresses here and there and if these are not properly relieved, they might show up during
quench.

Another interesting question is: for water/oil cooling steels, just how deep is the hardened level ? The fact these don't harden all the way through, is probably more of an advantage, as far as knifes are concerned. You get hard exterior and softer, less prone to snapping , core.
 
Fred the 25' Atmospherically Controlled oven I used a good 30 years ago during my tool and die days was for carbon steel with that one the steel just dumped out the closed in end right into the quench, it had no O2 there so it worked great...
I had a lot of fun toys to play with then :D

Mike where did you get all the foil for that kind of money WOW
is it the high temp stuff too?
 
rashid11 said:
I recall seeing somewhere, a while back, that it was something like 1 thou every 5 mins .

Warpage could also be due to defect in the steel itself - as they roll it, it introduces
stresses here and there and if these are not properly relieved, they might show up during
quench.

Another interesting question is: for water/oil cooling steels, just how deep is the hardened level ? The fact these don't harden all the way through, is probably more of an advantage, as far as knifes are concerned. You get hard exterior and softer, less prone to snapping , core.
Click to expand...

The 5160 I use starts out as 1" square - it's not rolled flat stock. By the time I forge it down, forge the blade, normalize, spherodize, etc., I'd say it's pretty evened out!
Might be another reason I get no warpage.
I recall Don Hanson saying not all that long ago that W1 only hardened .090" in the process we makers use. I think that's why he said he used W2 is that it was a little deaper hardening. He can correct me if I'm wrong.
So, if a piece of 1/4" W1 was hardened, .070 in the middle would not be hard.
Now that I think of it, I've believe I have heard the same "rule" - .001"/5 m. caron loss at the correct temp.
When it comes down to it, that's not bad.
 
rlinger said:
Dan, I remember that knife in your avitar. Still looks great!
Click to expand...

Thanks Roger
you know, thinking about it now, that thing went out ages ago, though fairly late because of pictures and for the prototype making of the recon which ended up the XLII , I got no word back on it since :confused: I wonder what happened to it :confused:
 
rashid11 said:
Another interesting question is: for water/oil cooling steels, just how deep is the hardened level ? The fact these don't harden all the way through, is probably more of an advantage, as far as knifes are concerned. You get hard exterior and softer, less prone to snapping , core.
Click to expand...

I believe deep hardening, in water/oil quenched steels, is controlled by the proportion of manganese contained in the steel. You need 1.35% or above, to deep harden. This is from memory and may not be correct.

Fred
 
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