# Heat treat oven



## stevehuckss396 (Mar 13, 2010)

There is a company called Paragon that makes small ceramic kilns. They are affordable and come with an optional temp controller that allows very controlled temp curves and soak times.

http://www.clay-king.com/itempfirefly.html

I have made the treating fixture for the rings that will go in the straight 8 project. I have no way of heating the rings so I need to get something to heat them up. I was wondering if a kiln would serve as a heat treating oven. Has anybody used a kiln to treat metal? Any thoughts?


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## Metal Butcher (Mar 13, 2010)

Steve I have a Paragon furnace specifically sold for heat treating. I ordered it with a pyrometer temperature gauge and thermostatic control, its a KL-Q11A.

I don't know the difference between it and a 'kiln' model. It could be the temperature range of it, or the internal dimensions that differentiate between the two.

I bought in back in 1994 to heat treat some very simple to machine parts made of tool steel. I was totally clueless with machining operations back then, but got away with making them due to their simplicity. When the run of parts was completed I dropped the idea of continuing with production runs for profit. The machines sat dormant for years with my thoughts of taking it back up to learn how to use the machines, as a hobby when I retired. And here I am, on HMEM.

-MB


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## shred (Mar 13, 2010)

I have an old 'Burnout Oven' (aka 2000'F mini-kiln) with a programmable controller I've posted about a few times. I've done simple heat-treating with it; usually things like tempering drill rod tools. It works well for that, though from playing around with glass (another entertaining thing-to-do with a programmable kiln), the temperature can vary a bit depending where you are in the interior, so I set my pieces on a bit of soft firebrick or kiln shelf to get them off the bottom.

Kilns are something that show up on the local Craigslist with regularity, though most are big 220v honkers.


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## kendo (Mar 13, 2010)

Hi Steve
       The company i work for have a couple of kilns, which we use to 
       stress relieve componants, these are basic kilns. What we tend to do
       is set the kiln to the required temperature and leave the componants
       for the required length of time for that material, then switch it off, open 
       the door so its only ajar, and leave to cool naturally. We have never
       had any bad results.
                       Ken


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## Metal Butcher (Mar 13, 2010)

Steve, the model I have reaches 2300F compared too the other models that reached 2000F at that time, and shown in my old mid 1990's catalog. You might need to do a little research so that if you decide to shop around for one you are armed with specific parameters to look for in available offerings, whether new or used.

If I remember correctly, the temperature capability was a factor in my choice of model.

I think one of these furnaces could also serve a second purpose, and be used to melt small batches of aluminum to cast small parts.

-Rick


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## GailInNM (Mar 13, 2010)

Steve,
I use an old Cress kiln that goes to 2000 degree F for heat treating. I have had it for about 35 years. It has manual control so I have to keep an eye on it. Like shred, mine was made as a burnout kiln.

The Paragon Firefly would work well for heat treating the rings, but since it is top opening it would be more awkward to heat treat anything that has to be removed and quenched such as hardening tool steel or case hardening. Above 1500 degrees F, removing anything from my front opening kiln will take the hair off any exposed skin unless very long tongs are used or you are very fast. Radiated heat is quicker than I am. Leather gloves and long sleeves are the order of the day. I think that a top opening would be worse, but I have not used one.

Gail in NM


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## shred (Mar 13, 2010)

GailInNM  said:
			
		

> Above 1500 degrees F, removing anything from my front opening kiln will take the hair off any exposed skin unless very long tongs are used or you are very fast. Radiated heat is quicker than I am. Leather gloves and long sleeves are the order of the day. I think that a top opening would be worse, but I have not used one.
> 
> Gail in NM


Yeah, good reminder. I use a full-face mask from my grinder as well when peeking in at 1500'F. Another thing to look out for is if you have complex temperature profiles, a lot of the little kilns won't cool down rapidly since they're so insulated.

I melted a few pots of Al in it as a test, but I'd hate to have a flask failure.


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## Metal Butcher (Mar 13, 2010)

shred  said:
			
		

> I melted a few pots of Al in it as a test, but I'd hate to have a flask failure.



Shred, here's a thought. One could make a crucible from a piece of steel pipe with a welded on base. A slightly larger base would add stability. If contamination from the steel is a factor, then Stainless steel might work. The pipe and plate is real common scrap yard material. All you need is a welder, or know some one that can weld up the assembly for you.

Sorry if I'm taking this of topic a bit.

-Rick


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## stevehuckss396 (Mar 13, 2010)

Thanks for all the input.

For an extra 150 bucks i can get a front loader but the inside dimentions are much smaller. The PPE is not a problem. I can use the gloves and other gear that I use for the mini foundry.

The firefly is affordable and with a 8X8 inside, I can heat larger parts like cams and cranks if that is where the future leads.

I'm going to look into the heat treat specific ovens and make a discision. Want to get these rings done and get going on the project!!


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## stevehuckss396 (Mar 13, 2010)

Taking the advise given, I ordered a Q11A. It is a front load oven that will heat to 2350. Seems unloading will be easier but more importantly, SAFER! 

I have 2 sets of rings ready to be annealed. I'll report on how good it works as soon as possible. I have read that temps between 950 - 1100 will treat without worrying about scale.

http://www.clay-king.com/paragon_q11axpress.html


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## Metal Butcher (Mar 13, 2010)

stevehuckss396  said:
			
		

> Taking the advise given, I ordered a Q11A. It is a front load oven that will heat to 2350. Seems unloading will be easier but more importantly, SAFER!
> 
> I have 2 sets of rings ready to be annealed. I'll report on how good it works as soon as possible. I have read that temps between 950 - 1100 will treat without worrying about scale.
> 
> http://www.clay-king.com/paragon_q11axpress.html



Oh shoot! I wasn't trying to talk you into buying the one I have.

But you did really good on the price and the capacity!

Top loaders bother me too. The ID should cover the size projects that you build.

Heck, I paid more than that, and I paid extra for the shipping and the temp gauge in 1994!

Your gonna like it! Its also good for heating up sandwiches! Real fast! :big:

-Rick


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## stevehuckss396 (Mar 13, 2010)

Metal Butcher  said:
			
		

> Oh shoot! I wasn't trying to talk you into buying the one I have.
> But you did really good on the price and the capacity!
> Top loaders bother me too. The ID should cover the size projects that you build.
> Heck, I paid more than that, and I paid extra for the shipping and the temp gauge in 1994!
> ...



It is smaller than the firefly but better suited for what we do.

Should still be able to fit a Red Baron pizza in there!!


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## Metal Butcher (Mar 13, 2010)

stevehuckss396  said:
			
		

> It is smaller than the firefly but better suited for what we do.
> 
> Should still be able to fit a Red Baron pizza in there!!



Its the perfect size for sure! 8) 

I just checked, and and the standard size egg rolls will also fit, with plenty of room to spare! :big:

-Rickardo


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## GailInNM (Mar 13, 2010)

Steve,
I think you will like it. In all the years I have had mine I don't think I have done anything that would not fit in the one you are getting. Mine has the same power input so yours should heat up a lot faster with it's lower volume. Good choice.
Gail in NM


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## stevehuckss396 (Mar 13, 2010)

GailInNM  said:
			
		

> Steve,
> I think you will like it. In all the years I have had mine I don't think I have done anything that would not fit in the one you are getting. Mine has the same power input so yours should heat up a lot faster with it's lower volume. Good choice.
> Gail in NM



Now I just need to use it. From what I have read, the rings need to cook at 925 for about 30-60 minutes for a scale free ring.

Sound about right?


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## GailInNM (Mar 13, 2010)

Sounds about right, Steve.

Something that I have not tried, but has been recommended to me, it to wrap the fixture in some heavy duty aluminum foil with a few pieces of brown paper bag in with it. The foil can be tightly sealed and the paper gets most of the oxygen when it chars. Keeps oxygen scaling and damage down. This will work up to about 1050 degrees F. After that you start getting too close to the melting point of the aluminum. 

Gail in NM


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## potman (Mar 13, 2010)

Golly Gosh. Finally something here I know something about and could comment on and I've been gone all day to Portland.

I have an electric kiln with a computer controller I use to fire pottery at 1220C. I can set the controller to raise the temperature at a certain rate, say 300C per hour, hold at a certain temperature for a certain length of time then go higher or cool at a certain rate per hour. 

At the higher temperatures the kiln can cool pretty quickly 1000C per hour and at lower temperature if it isn't cooling quickly enough I could pull out the peep plugs to let a little cool air circulate through. If you want a crash cool though you would have to pull whatever you're treating from the kiln.

Steve, are you getting any shelves and posts with your kiln? Kilns heat more uniformly if you have a shelf raised up at least above the lowest heating element and below the top element. Also leave at least a two element space between shelves if that is where you are going to put your part to be treated.

Kilns go through two distinct phases of heating. At lower temperatures most of the heating occurs by convection but once you get into the glowing object regime then most of the heating occurs by radiation. This means that if you are operating at the higher temperatures shadow effects can come into play and prevent a part from heating evenly. If you hold at a certain temperature the object will eventually obtain a uniform temperature though. 

A word of caution, the Kanthal elements in electric kilns get very brittle after being heated to a high temperature so don't go poking them or trying to move them around. If when you get the kiln any elements seem out of place gently try to put them back where they belong before running the kiln. Also, the elements are dependent on an oxide coating for protection. You can create a reducing atmosphere in the kiln by including some wood or charcoal but you will be reducing their life span. If you do a reduction treatment it is best to next run the kiln in oxidation mode to let the coating reestablish itself.  

If you have any problem with your Paragon kiln you can contact Arnold Howard who is Manager of Manufacturing (or something like that) and I'm sure he will do his best to help you out or answer any questions. He routinely writes on the ClayArt pottery e-mail list ( do a google).

Oh, BTW: Best way to cook turkey and bake bread is in a kiln due to the elements surrounding what you are baking.  Hmmm, Hmmm, good. Nicely browned all the way around.

earl...


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## stevehuckss396 (Mar 13, 2010)

Thanks Earl!

I wish I understood some of that. I planned on setting the item to be treated on a small piece of round stock and also plan to lay a small piece of plate on the bottom of the oven. Just enough to keep it off the bottom of the furnace. Maybe a stainless steel piece as a perminant tray. would that be ok?

The text i read said to heat at 475C - 525C. 500C is 932F so I am going to try 925 for 30 minutes and then I will remove it from the furnace and let it cool naturally. Will I be OK?

Hello Gail!

I have seen somewhere to turn a sleeve that just fits over the fixture and wrap some brown paper around the rings and slip it in the sleeve. Think it was the model engine news site. I might just try the foil trick. Easier to turn up a piece of that!!


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## potman (Mar 14, 2010)

Steve, 
I took a look at the photo of the QA11 and see that it doesn't have any heating elements in the floor. This means that the floor will act as a heat sink and will be cooler than the rest of the kiln so getting your part up off the floor is good. Having an air space between the floor and what your part is resting on is better. A C-o-C of what I'm talking about is attached. 925F is just getting warmed up for what I do so this may not be that important, but it won't hurt.

Potters do coat clay bowls, plates, mugs and such with stuff like copper compounds and then wrap in aluminium foil to keep the vapours in. The ally doesn't melt as much as oxidise but still works to protect the part, or the kiln, whichever the case might be. I wouldn't at all hesitate to try it for heat treating or even case hardening. 

earl...


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## gbritnell (Mar 14, 2010)

Hi Steve, I just have to correct something. The foil that would be used is stainless foil, not aluminum. If you use aluminum it will melt all over your part. The tool suppliers label it as stainless tool wrap.
George


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## Kermit (Mar 14, 2010)

http://www.mcmaster.com/#3254k76

Something like this stuff here.


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## GailInNM (Mar 14, 2010)

George,
While the stainless steel foil is thr right stuff to use, I think that the aluminum will work OK for Steve for the rings as the temperature he is working with is still 250 degrees F below the melting point of the aluminum. Even allowing 50 degrees or so of overshoot on the temperature controller there should still be a fair safety margin. 

Still, it would be worth checking with some scrap before trying on a real part. 

One precaution with aluminum that anytime there is any possibility of it melting in the furnace, always protect the furnace floor. Molten aluminum is a very good solvent and will dissolve many things, including the insulating firebrick that is typically used for the floor of small kilns. Then you pry the offending part out of the floor and patch. I have several patches in the floor of my furnace from making mistakes over the years. 

I keep some insulating firebrick around to make holding fixtures to elevate the part above the floor. It is soft enough to easily work with hand tools, even a hobby knife, to provide support where needed and keep things in place when removing a part to quench.

Gail in NM


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