Inert Gas with Paragon KM14D furnace

[hookman7]

I just upgraded to a Paragon KM14D furnace and spent the additional money for the inert gas system including the flow meter and the selonoid control wired through the Sentry system. Inert gas injection and purge sounded like a neat way to reduce are eliminate decarburization.

Paragon has been very helpful and sugguested Argon at temperatures above 800 F starting with 5CFH and decreasing to 1-2 CFH to sustain the purge. They also stated that they had included the gas injection system at the request of their customers and implied that inert gas injection was more of an art than a science.

Has anyone been succuesful in reducing or eliminating decarburization with this system? What gases have you tried? Different flow rates or gases for different steel? I am also curious about why argon and not nitrogen?

[mete]

Argon is an inert gas, nitrogen is not .Argon is readily available since the atmisphere is 1% argon.

[hookman7]

Thanks I come from the refining industry and we used nitrogen to purge everything as a means to reduce and remove oxygen. Argon makes sense now becuase it not only purges the oxygen but will nor interact with the material.

[plain ol Bill]

I got the gas system with my Paragon also. I could not get much info at all from Paragon about using it at the time I got mine. I still don't understand why they even have a flow meter on the furnace since it is not a high pressure one and the flow meter on the bottle is the high pressure meter needed. Still I gave it a try and frankly I went back to using the stainless tool wrap in my furnace. I do not feel the extra money for the gas system was worthwhile in my case.

[Quenchcrack]

Please be aware that Argon is slightly heavier than air and will settle into low places and displace the oxygen you breath. A fan can be helpful in keeping the argon from filling up a small work area.

[TexasJack]

Question: Nitrogen is not inert, but is also not likely to remove any carbon at that temperature. In fact, if nitrides are formed on the blade, doesn't that make the surface harder? I haven't checked prices, but would have to assume that nitrogen is a lot cheaper.

I'm not trying to stir up an issue, just wondering what I'm missing here.

[RJ Martin]

I am no expert at this, but, I will tell you what I know. You can eliminate scale in the Paragon furnaces by pumping Argon in during the HT. However, you're going to be exposing the blades to the air during quench. That's why I use foil. Some guys like their Argon setups, and, I have never tried it myself. From what I understand, Argon probably costs about the same as using foil.
I used a commercial HT outfit that used nitrogen as the quench medium in a vacuum furnace. I assume that the nitrogen was introduced into the furnace from a tank of liquid nitrogen, to maximize it's heat absorption capacity.

[hookman7]

Thanks to everyone for the continuoing discussion. I first read about using nitrogen in the book "Step by Step Knifemaking" by David Boye, now the copyright on that book is 1977 but it is still sold as and is a great general reference book.

Still looking for someone who has had some sucess using a blanketing gas during heat treating.

For plain ol Bill I'll keep you in mind if I find some good information on what works and what doesn't. No use having all those expensive gadgets hanging on our furnaces if we can't use them.

Quenchcrack, Love the name and thanks for the safety reminder.

[RJ Martin]

The guy I talked to who used Argon gas simply drilled a hold in the top of his furnace, and inserted a pipe from the argon tank. He had a regulator, and, used abround 5 PSI, I believe. It was a simple setup!

[fitzo]

I think Ray Rogers uses argon... you might ask him.

[rhrocker]

RJ, do you mean that you quench, foil and all? Otherwise it seems that the foil method would also let a little air hit the blade between the time it's removed from the foil and is quenched.

[RJ Martin]

Robert: Yes, I quench right in the foil using quench plates. My blades come out a bright grey color-some have a rainbow effect from what little gas burns off inside the packet.
This is the best quenching technique for air hardening steels-It will provide the fastest quench rate and the shortest time from furnace to quench.

[SteveS]

RJ - you get the rainbow to!?

Cool, I thought it was some weird thing I was doing. Doesn't sound like something I need to worry about.

Steve