question on gas purging the paragon oven

[sparky-01]

i have bought a paragon oven equiped with the gas purge option.
i was amased to find out that they wont tell you what gas to use or what temp to start the gas flow and what flow rate .
can anyone help?

 

[Justin.Mercier]

typically a heat treat oven uses argon as the shielding gas, similar to an argon sheilded welder. I'm sure if you contact paragon they would let you know exactly everything you need to know.

 

[george tichbourne]

You can purge with almost any gas except oxygen.

I have used natural gas to purge lead and zinc pouring ladles and burned it off as it leaked out the spout. The only safety concerns were to make sure that it is being burned off and that the gas was shut off when the machine is shut down....before the oven door is opened.

Flow rate was determined by having a stable flame on the burn off bunsen burner. Too little gas and the flame would go out, too much and the flame would be too high.

My heat treater uses vacuum ovens shielded with nitrogen then for the quench uses nitrogen again.

 

[First Twin]

I really hate to bring up old threads, but I'm having the same problem as sparky-01. Paragon didn't mind selling an oven with the gas purge option, but they haven't been forth coming with any information on how to use it. We have asked directly and were initially and finally told that they did not provide information on the use of this feature. We asked for an engineer to return our call, but thought this might be quicker. We need some information on the pressure level of argon to supply the oven in order to purchase a regulator and some directions on how to use this feature on the oven. Does anyone have this information from Paragon or experience using this option?

We know all about using foil and anti-scale, we've been using them for years. We have a need for being able to temper steel without using anti-scale or foil and thought that this was the answer. We already have the oven which came with instructions that failed to to mention the gas purging option at all. Any help will be appreciated.

 

[Nathan the Machinist]

When I use argon I use a regulator set to about 3 CFH. But my Lindberg Blue may need more or less gas than your Paragon. Mine is small and reasonably well sealed.

I came to this setting through experimentation. That may be in order for you too.

 

[johnnym]

When i purchased my paragon, i was on the phone with one of their technicians
trying to get some info on the gas option. He could not provide any information
that made me comfortable enough to buy the option. The only thing he said that was useful was that the lack of oxygen reduces the life of the element. I wonder if that is why they don't push the option that hard.

 

[burke531]

I don't use this option but know a little about it. Using argon does shorten the life of the elements significantly. this is because of the cleaning action of the argon and the lack of the oxide layer that normally forms on the elements. what tends to happen is you run the oven normally and build an oxide on the element no problem then you run using the argon which breaks down and removes this oxide coating still not a big deal right? the problem comes after multiple cycles of this happening and the element getting smaller in diameter after each cycle until it burns in two. There is an ITC coating that is supposed to help prevent the elements from oxidizing in the first place so the life of the heating elements should be extended. Also it is my understanding that if you were to use a sheilding gas every time you used your furnace from start up too cool down you shouldn't see this problem. You should only need enough shielding gas to purge all the oxygen in the oven and then enough flow to create a positve pressure in the chamber while heating the metal. but if/when you open the door while at temp, like to take a blade out to quench it, oxygen will rush in cause the oxidation, scale that you are trying to avoid any way so it seems like kind of a waste of time and effort to me. I learned all of this while working in the semi conductor industry twenty years ago so some things may ahve changed by now so anyone who knows better please speak up.

 

[rashid11]

Argon being heavier than oxygen, it will displace it out . What works the best is the top load oven, otherwise (for front load ones) the door has to shut airtight and there need to be a small hole toward the top for air to escape.

I don't believe argon will have any cleansing action - but you do want to fire up the spiral at 1900F for 30m in _air_ or so when you first fire it up. It will build up a layer of Al oxide (glass) on the spiral that should stay there ever after. The spiral will become very brittle after that first firing.