Folx,

I've been using home made kiln (omega PID + SSR + nichrome wire +
some refractory bricks) to heat treat A2 and similar for some time
now and it all works great.

I am thinking about moving up - expanding the internal volume somewhat
and that will require going 240V (I want to be able to reach reqd temps
in minutes and with my 9x4x4 cavity 110V @ 15A barely makes it).

I will keep most of electronics - only replace the spiral to longer
one. About wiring - do I get it hooked up between 2 hot legs of 240
( in series with SSR of course) ? I will use the ground to ground the
oven . Otherwise I'd need to use 2 spirals in parallel (hots to
neutral) and doing that will
require 2 SSRs (what pros/cons of these 2 methods ?). Was thinking
about getting an electrician to give me a dedicated 240V in garage,
with 20A breaker .

And about argon: for now I use tool wrap steel and it works OK, but
I do get some scaling and softer decarb in the outer layer - which I
grind off. Even using the paper-in-the-foil-bag trick. Assuming I have
a top-load oven and it's rather air tight below the lid, can I simply
flood the interior with 2-3 CF of argon before starting the heat treat
cycle ? Being heavier than air , will it stay "put" inside of the oven
- even when heated up to 1800F-2000F ?

I know some people keep moving inert gas through the oven throughout
the cycle (at slower rate), might need to do the same. Drill a smallish
hole through firebrick, stick some time of copper tubing with connector
to attach the argon hose to - am I correct in my thinking ?


What are typical prices for smaller argon bottles (need pure argon I
reckon, not the CO2 or Oxy mixes) ? Will also need a flow meter .
Also am I correct in assuming that argon is 100% to use ?



Any advice's most appreciated

You would hook the heating element between the two hot legs to get 240
volts.
You could get another element exactly the same as your existing one and
hook the new element in series with the old element. Or get a new 240
volt element.
I have not used argon for an inert atmosphere, but I don't think you
can put some in and have it stay put. Since it will be hot, it will
expand and probably become lighter than air. I think you will have to
keep putting in some gas to keep any oxygen out. I expect you could
use CO2 just as effectively. I don't know if CO2 breaks down at 1800
to 2000 F but if it does part of it is C. So might work anyway.

If you have a place that is really fireproof, like outside in a car
port, you could use natural gas or propane. You would need to supply
the gas and drive out all the air before getting the temperature going.
You probably ought to light the gas as it escapes from the kiln too.

I have seen commercial melting of alloys ( not steel ) at Westco where
they used natural gas for the heat and to have an inert ( well
non-oxygen anyway ) atmosphere. The gas burned supplied to the inside
of the ovens burned as it escaped.

Dan


rashid111 wrote:
Folx,

I've been using home made kiln (omega PID + SSR + nichrome wire +
some refractory bricks) to heat treat A2 and similar for some time
now and it all works great.

I am thinking about moving up - expanding the internal volume somewhat
and that will require going 240V (I want to be able to reach reqd temps
in minutes and with my 9x4x4 cavity 110V @ 15A barely makes it).

I will keep most of electronics - only replace the spiral to longer
one. About wiring - do I get it hooked up between 2 hot legs of 240
( in series with SSR of course) ? I will use the ground to ground the
oven . Otherwise I'd need to use 2 spirals in parallel (hots to
neutral) and doing that will
require 2 SSRs (what pros/cons of these 2 methods ?). Was thinking
about getting an electrician to give me a dedicated 240V in garage,
with 20A breaker .

And about argon: for now I use tool wrap steel and it works OK, but
I do get some scaling and softer decarb in the outer layer - which I
grind off. Even using the paper-in-the-foil-bag trick. Assuming I have
a top-load oven and it's rather air tight below the lid, can I simply
flood the interior with 2-3 CF of argon before starting the heat treat
cycle ? Being heavier than air , will it stay "put" inside of the oven
- even when heated up to 1800F-2000F ?

I know some people keep moving inert gas through the oven throughout
the cycle (at slower rate), might need to do the same. Drill a smallish
hole through firebrick, stick some time of copper tubing with connector
to attach the argon hose to - am I correct in my thinking ?


What are typical prices for smaller argon bottles (need pure argon I
reckon, not the CO2 or Oxy mixes) ? Will also need a flow meter .
Also am I correct in assuming that argon is 100% to use ?



Any advice's most appreciated

"rashid111" wrote in message
oups.com...

And about argon: for now I use tool wrap steel and it works OK, but
I do get some scaling and softer decarb in the outer layer - which I
grind off. Even using the paper-in-the-foil-bag trick. Assuming I have
a top-load oven and it's rather air tight below the lid, can I simply
flood the interior with 2-3 CF of argon before starting the heat treat
cycle ? Being heavier than air , will it stay "put" inside of the oven
- even when heated up to 1800F-2000F ?

I know some people keep moving inert gas through the oven throughout
the cycle (at slower rate), might need to do the same. Drill a smallish
hole through firebrick, stick some time of copper tubing with connector
to attach the argon hose to - am I correct in my thinking ?


What are typical prices for smaller argon bottles (need pure argon I
reckon, not the CO2 or Oxy mixes) ? Will also need a flow meter .
Also am I correct in assuming that argon is 100% to use ?



I think you need to make a retort. This is a container that is sealed shut
except for your gas input and output. This might be more complex than a
home shop justifies.

A friend of mine worked at a place that used hydrogen as their gas, and they
burned off the exhaust. They did mostly furnace brazing there. They had
two types of retorts. one was a metal can about the size of a common trash
can. It had a flange formed on one end and the other end had a pipe flange
welded on. A flat lid with another pipe flange was then welded to the
flange to seal the retort and then an electric furnace was lowered on the
base.

These had to be ground open after each heat and were tossed after about 10
heats.

The other style had the can inverted and was sealed against a water cooled
gasket.

I don't think hydrogen would be good for all material as in some cases it
may cause imbrittlement.

--

Roger Shoaf

About the time I had mastered getting the toothpaste back in the tube, then
they come up with this striped stuff.

wrote: (clip) I expect you could use CO2 just as
effectively. I don't know if CO2 breaks down at 1800 to 2000 F but if it
does part of it is C.(clip)
^^^^^^^^^^^^^^^^^
CO2 is used in shielded arc wire-feed welding, so it ought to work in your
kiln. (And its cheap.)

You and I have about the same setup. I tried using argon from my
welding setup in my furnace I set the
argon to 5 cubic feet per min the oven had a few cracks in it so I set
the flow high just to see if it would work.Well it did'nt work and it
used alot of argon expensive .

I had a freind he was a dentist he had an oven about the size of yours
it was in a steel box and had about a 2 inch air space between the oven
and the box.

He used a compressor from a refrigerator to create a vacum .He would
heat the oven up to about 2000 deg. and but some kind of dental work in
it close the doors and turn on the vacum pump. I noticed the tempature
would drop a few hundred deg. when he turned the pump on but it would
quickly go back up.

I was wanting to try the same thing but never got around to it. Another
thing i was woundering about is when the part comes out of the
atmosfere controled furnace would it get the scale on it cooling down?
And how high of a vacum does it take?
TIM

http://metalworking.com/dropbox/_200...es/furnace.jpg
http://metalworking.com/dropbox/_200...ce-control.jpg

Roger Shoaf wrote:

A friend of mine worked at a place that used hydrogen as their gas,

I don't think that you want H in an environment where steel is heat
treated of hours. Hydrogen will diffuse into the steel and will make it
brittle.

Nick
--
Motormodelle / Engine Models:
http://www.motor-manufaktur.de
Ellwe 2FB * VTM 87 * DLM-S3a * cubic
more to come ...

Leo Lichtman wrote:

CO2 is used in shielded arc wire-feed welding, so it ought to work in your
kiln. (And its cheap.)

But you also know, what really is happening with the CO2?
At welding temperatures:
If you have, say, SS, it will absorb C (CO2 - CO + O AND CO - C +
O). On the other hand, if you have a high carbon steel, it will loose
it's C!
There is a balance between the C-content of the gas, the C-content of
the wire and the C-content of the material. If you add C through the
wire, it has to be removed by the gas. And vice-versa.
You can observe this happening with Ar+18%CO2. And it surely will happen
with 100% CO2. You will add C to the steel (at 2000°C).
Also the O will catch some of the Cr (+Nb), if there is any in the
steel.


**But** I don't have the temperatures at hand, when CO2 dissoziates.


Nick
--
Motormodelle / Engine Models:
http://www.motor-manufaktur.de
Ellwe 2FB * VTM 87 * DLM-S3a * cubic
more to come ...

"Nick Müller" wrote in message
...
Roger Shoaf wrote:

A friend of mine worked at a place that used hydrogen as their gas,

I don't think that you want H in an environment where steel is heat
treated of hours. Hydrogen will diffuse into the steel and will make it
brittle.

Nick
--

Isn't that what I said?

I don't think hydrogen would be good for all material as in
some cases it
may cause imbrittlement.

--

Roger Shoaf

About the time I had mastered getting the toothpaste back in the tube, then
they come up with this striped stuff.

Roger Shoaf wrote:

Isn't that what I said?

Ooops! Sorry, didn't read till the final sentence.


Nick
--
Motormodelle / Engine Models:
http://www.motor-manufaktur.de
Ellwe 2FB * VTM 87 * DLM-S3a * cubic
more to come ...

In doing argon replacement of the atmosphere in the furnace, the lower the
flow rate, the better off you will be. The problem here is that you have to
heat the gas to the temp of the oven in order to allow the gas into the
chamber. Failure to do so makes the surfaces you are heating cool. Note
that the sealing doesn't need to be inside the furnace but can also be
outside the furnace. Extra insulation followed by even just a styrofoam
sealing/insulation layer can help things immensely.
Excellent would be a nice sealing door for the furnace with a pressure
limiter so the oven doesn't blow out and you loosen a valve during purge and
then shut it and keep the pressure to some value after that.

--
Why do penguins walk so far to get to their nesting grounds?

Herr Müller,

I accept your Ooops.

It is nice to know I am not the only one that does these kind of things.

--

Roger Shoaf

About the time I had mastered getting the toothpaste back in the tube, then
they come up with this striped stuff.



"Nick Müller" wrote in message
...
Roger Shoaf wrote:

Isn't that what I said?

Ooops! Sorry, didn't read till the final sentence.


Nick
--
Motormodelle / Engine Models:
http://www.motor-manufaktur.de
Ellwe 2FB * VTM 87 * DLM-S3a * cubic
more to come ...