Preventing kiln decarb with argon

P.Brewster

P.Brewster

Joined
Jul 25, 2007
Messages
1,380
I'm running argon into my kiln at a rate of 4 LPM (8.48 CFH). The kiln chamber is 16L; I would think 4 LPMs is more than enough to purge out the oxygen.

If I go below 4 LPM, I start to see surface scale/pitting. If I go above 5 LPM, the heating elements can't keep up with the incoming cold argon.

At 4 LPM, my knives come out with little/no scaling/pitting, but the surface hardness is 5 points below the core hardness. The decarb layer is more than a few thousandths thick.

Those who are running argon into a kiln - what flow rate are you using? Any recommendations as to how I might seal the oven door when firing? Thanks
 
I had a friend that bought the argon system from Paragon and could not get it work properly. He finally gave up on it. I've never talked with anyone that is successfully running argon in a kiln. Sorry I couldn't help.
 
P.Brewster said:
I'm running argon into my kiln at a rate of 4 LPM (8.48 CFH). The kiln chamber is 16L; I would think 4 LPMs is more than enough to purge out the oxygen.

If I go below 4 LPM, I start to see surface scale/pitting. If I go above 5 LPM, the heating elements can't keep up with the incoming cold argon.

At 4 LPM, my knives come out with little/no scaling/pitting, but the surface hardness is 5 points below the core hardness. The decarb layer is more than a few thousandths thick.

Those who are running argon into a kiln - what flow rate are you using? Any recommendations as to how I might seal the oven door when firing? Thanks
Click to expand...
Do you have small port on the top for air to escape ?
Google this Adventures in Argon Injection
 
Last edited:
J. Hoffman said:
I had a friend that bought the argon system from Paragon and could not get it work properly. He finally gave up on it. I've never talked with anyone that is successfully running argon in a kiln. Sorry I couldn't help.
Click to expand...
That is helpful - thank you.

Natlek said:
Do you have small port on the top for air to escape ?
Google this Adventures in Argon Injection
Click to expand...
I'm checking it out now, thanks. No I don't have an exhaust port but I'll experiment with that.
 
One problem is that argon is heavier than air. In a regular HT oven this means it flows across the oven floor and leaks out of the rather loosely sealed door. Where an argon oven works best is a vertical oven.

As noted by Natlek, if a horizontal oven is well closed you will need a top vent hole to allow the air to be pushed out.
 
My buddies at Dragons Breath Forge use Argon in their Paragon HT oven. I will see if I can get a pic of their setup next time I stop by!
 
Stacy E. Apelt - Bladesmith said:
One problem is that argon is heavier than air. In a regular HT oven this means it flows across the oven floor and leaks out of the rather loosely sealed door. Where an argon oven works best is a vertical oven.

As noted by Natlek, if a horizontal oven is well closed you will need a top vent hole to allow the air to be pushed out.
Click to expand...
I would say that it is advantage not problem , it will stay where we want and will push air out . If It is mine oven and I want to heat treat multiple knives at once I would make tray . I spend one hour last night and i can not find in which folder i put that catalog .Catalog from respected manufacturer of HT ovens , i think that it is from Germany .I don t even recall name of brand!! In that catalog they sell small tray for HT small parts from stainless steel .Something about economic ....the reason is economic in nature, why to fill a cube of space with argon if you can do it in a small adequate box ? If you are careful and not disturb gas inside tray you can HT multiple knives at once .In oven when you open door all is gone ...so only first knife will have not decarb . last one ?
 
Last edited:
The oven is not well sealed, as evidenced by the fact that I can send a very high flow of argon into the oven without any back pressure. For this reason I don't think an exhaust port is necessary, and my assessment is consistent with Paragon's guidelines.

I'm going to make a pan from stainless foil, and run the argon line into that pan - this will prove/disprove the matter of argon sinking. Argon is heavier than air, but I think we may be failing to recognize the complexity of the matter when 70° argon is piped into a 1500° kiln - I would think the gas inside the kiln may be moving around in complex/unpredictable ways due to the enormous temperature gradient.

I tried adding a piece of steel wool into the kiln along with the argon - the idea is that the oxygen in the kiln will be consumed by the reaction with the steel wool - but it didn't improve the end results.

It's really important to establish the benchmark for success/failure when we're talking about this "working" - I would say that success is a surface hardness within 2 points of the core hardness.
 
P.Brewster said:
The oven is not well sealed, as evidenced by the fact that I can send a very high flow of argon into the oven without any back pressure. For this reason I don't think an exhaust port is necessary, and my assessment is consistent with Paragon's guidelines.

I'm going to make a pan from stainless foil, and run the argon line into that pan - this will prove/disprove the matter of argon sinking. Argon is heavier than air, but I think we may be failing to recognize the complexity of the matter when 70° argon is piped into a 1500° kiln - I would think the gas inside the kiln may be moving around in complex/unpredictable ways due to the enormous temperature gradient.

I tried adding a piece of steel wool into the kiln along with the argon - the idea is that the oxygen in the kiln will be consumed by the reaction with the steel wool - but it didn't improve the end results.

It's really important to establish the benchmark for success/failure when we're talking about this "working" - I would say that success is a surface hardness within 2 points of the core hardness.
Click to expand...
I am 100 % sure that pan would work .Pans are used in welding small parts .Watch this video if you have time
 
look how easy argon replace air ,watch from 3 min. If your oven is better sealed and full with argon why you should worry how it moves inside ?
 
Natlek said:
look how easy argon replace air ,watch from 3 min. If your oven is better sealed and full with argon why you should worry how it moves inside ?
Click to expand...
I have a lot of laser welding experience and I'm very comfortable/familiar with argon shielding in a welding application. My kiln cycle is close to 45 mins, whereas a weld cycle (in one spot) is seconds, and for this reason I think it's a huge logic error to think that what works for welding will also work for a kiln cycle.

I should worry about how argon moves inside the oven because we are attempting to explain/understand how/why it isn't working. If it works, I don't care what the argon is doing. It isn't working, and so far the only input has been theoretical/hypothetical in nature. In theory, argon should settle on the kiln floor and block the oxygen. In reality, it doesn't. In theory, a tiny flow of argon should be enough to block the oxygen. In reality, it isn't. We must reconcile theory and reality if we are to solve this problem.
 
P.Brewster said:
I have a lot of laser welding experience and I'm very comfortable/familiar with argon shielding in a welding application. My kiln cycle is close to 45 mins, whereas a weld cycle (in one spot) is seconds, and for this reason I think it's a huge logic error to think that what works for welding will also work for a kiln cycle.

I should worry about how argon moves inside the oven because we are attempting to explain/understand how/why it isn't working. If it works, I don't care what the argon is doing. It isn't working, and so far the only input has been theoretical/hypothetical in nature. In theory, argon should settle on the kiln floor and block the oxygen. In reality, it doesn't. In theory, a tiny flow of argon should be enough to block the oxygen. In reality, it isn't. We must reconcile theory and reality if we are to solve this problem.
Click to expand...
Look, I really don't want this to turn into arguing . Argon would not move inside the oven if your oven is sealed .Your problem is that you have not pure argon atmosphere inside oven , it is simple like that .To get that you need to seal your oven and top vent so air can be pushed out . There is no need for a constant flow of argon once the chamber is completely filled with argon IF it is well sealed .Letting cold gas all time into the chamber while the steel is inside on set temperature and time is running is not smart if you ask me .Also oxygen sensor would be a good thing so you know when chamber is full with argon . Problem is what if you have, say, five pieces of knives inside , once you open the door , ciao atmosphere .
Clean argon atmosphere inside clean steel out , simple like that !
 
Last edited:
P.Brewster said:
In theory, argon should settle on the kiln floor and block the oxygen. In reality, it doesn't.
Click to expand...
Of course it doesn't .Argon will just SINK future down because when we talk about gas, your oven is like Swiss cheese .And you have LOT of air inside .............don't forget that the ambient environment is one ATM .
 
I worked on a project for two years that entailed putting a tiny amount of a compound highly sensitive to oxygen in a vial under argon. It was done in a large glove box much like shown above but 4 stations and two air locks. The compound itself was the test for how effective we were in creating an anoxic environment.

It took four days of steady purging and 5x300ft^3 tanks of gas to get the oxygen down to acceptable levels. And that was in an incredibly well-sealed environment.

My only point here matches what Natlek says. Your furnace is a porous system. You'll have a heckuva time pouring enough argon through to get no decarb at all. Also bear in mind that argon mixes with air and doesn't just force it out.

Another point is, be careful if one has pets who frequent the shop, especially if you are in a basement where the gas will settle on the floor without a lot of place to go. The lower they are to the floor, the bigger the risk. Argon doesn't leave the lungs readily after they're filled.

My 2 cents, likely worth even less in today's market. Good luck! Hope you can make it work.
 
Last edited:
Probably this is only thing that should work inside ordinary oven
pi0gI7X.png

rqU6rTN.jpg
 
Last edited:
No need to re-invent the wheel. The round wheel works just fine.
You guys are taking something very simple - a stainless foil wrapped packet - and trying to make it very complicated.
 
You must log in or register to reply here.
Back
Top