Small vacuum HT Furnace

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Jun 9, 2015
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I wonder why anyone didn't try to make it ? At first glance don't look to much complicated ? Make steel chamber install inside ordinary HT oven close the door , vacuum it and let the gas inside ? What i m missing ? I wonder how bricks would handle vacuum with all that trapped air inside bubbles? Maybe ceramic fiber board ? Quenching multiple knives would be little tricky ..maybe two man job ? But for two three blade should not be problem to do that ?
What do you think ......? What i m missing here ? I already start to look around me for some parts :)
 
What I see missing is the "WHY". Is there a problem with your current HT oven?
 
What I see missing is the "WHY". Is there a problem with your current HT oven?
On which one you think ? I have four now :D And no one of them is vacuum .
WHY ? Why not if it is doable ? That s why I open thread to see what other think .Do you have something to say about this topic :D
 
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Sorry, I wasn't trying to start an argument. It may be a translation issue.

I was asking why you needed a vacuum oven. I know you have many ovens already and thought you were quite happy with them.

Vacuum ovens are usually for larger batch HT. Sealing things vacuum tight and maintaining a vacuum at 2000°F/1100°C isn't all that simple.

Build one and have fun.
 
i think he is asking if there is any reason ?? people don't build them??
i have wondered about a Argon gas filling the oven to prevent scale/decarb
instead of foil pouches.. thus saving cleanup after..
either way ill check back on this....
 
Sorry, I wasn't trying to start an argument. It may be a translation issue.

I was asking why you needed a vacuum oven. I know you have many ovens already and thought you were quite happy with them.

Vacuum ovens are usually for larger batch HT. Sealing things vacuum tight and maintaining a vacuum at 2000°F/1100°C isn't all that simple.

Build one and have fun.
No problem :thumbsup:
My ovens works but this is something different ....no decarburization on carbon steel ,no foil for stainless ..have advantage.
About maintaining a vacuum at 2000°F/1100°C ..... Why on 2000°F ? Pull air out ,close the valve ? Temperature IN chamber would be far , far more down.....2000 will be only inside oven ?
Sealing chamber is easy part , I think . Temperature will be very low inside chamber , heated only from outside of oven temperature ? Actually how will heat pass from oven to chamber if there is vacuum ......no air no convection , no radiation ?? As far I know radiation start only on very high temperature ?
 
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We are talking about DIY build ............Something like this , maybe ?
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What I see missing is the "WHY". Is there a problem with your current HT oven?
Ok , let s first clear something about me ...So, WHY ? Because , I don t want to spend my free time watching Tv or hanging on social network , I have no profile on any of them....poor me :D So I spend part of my free time working on something that relax me ....except when I work on installing 300 HP Maserati V6 engine in small Honda for my son ...:mad:
Now , back to this MF of bomb :)
This vacuum HT ovens looks like atomic bomb :D They need to heat and quench steel so they must be complicated .....But if we cut part which is important to us , what is left is simple heat treat oven just sealed to keep vacuum and gas inside oven ?


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I think that i will keep FAN ..........


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So I think that outside chamber is not necessary .We can save lot of gas this way . Normal HT oven with bricks , ONLY frame should be made little different.Stronger frame and make door sealed .Of course outlet for gas and vacuum , HT elements wire and TC wire sealed too .I don t see any problem to do that . We deal with LOW temperature in all that points so ...........
What i wonder is ......CAN furnace work only on vacuum without gas? How will TC measure in vacuum is question ?
vacuum pump , vacuum and gas pressure meter for gas is all I need extra..and some valve of course .
I decide to try this ...with small , very small furnace ...25 x 12 x 10 cm. Most time for stainless folder blade /I have some idea for folders lock / so i need small furnace to play with stainless steel . I will install FAN to i think .....that is good thing for heat uniformity. I will use only bricks for this and HT element only on top/roof. Inlet for vaccum/gas is best to be located from bottom side i think ?
To start with project I need some tool to precisely cut some bricks so after one hour work i come to this ......will serve to purpose :D

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i think he is asking if there is any reason ?? people don't build them??
i have wondered about a Argon gas filling the oven to prevent scale/decarb
instead of foil pouches.. thus saving cleanup after..
either way ill check back on this....
Thanks , that is question . I don t understand why people don t discuss ..I know lot of them here who can write something on topic and to help so we can find what is good what not...Probably i should do the same ...do whatever I do ...out of public ?
 
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So i'm still curious why not just fill the oven with Argon gas before you start the heat ?? Argon is heavier than air so covering the parts should be easy
Argon is used in TIG Welding ,so the Temp required should not matter..
couple of my knife making friends have thought about/discussed it but don't think anyone has done it..
maybe not worth the trouble?? don't know....ill be watching to see results.....hopefully it turn out well
 
So i'm still curious why not just fill the oven with Argon gas before you start the heat ?? Argon is heavier than air so covering the parts should be easy
Argon is used in TIG Welding ,so the Temp required should not matter..
couple of my knife making friends have thought about/discussed it but don't think anyone has done it..
maybe not worth the trouble?? don't know....ill be watching to see results.....hopefully it turn out well
I don t know my friend , all this is new to me :) Is it still heavier when heated on 2000F ?With vacuum you are sure that there is almost no air inside .Look ,when vacuum is on it will improve sealing of doors /depend how was that done/ and then we let argon in......Say we make normal , one atmosphere pressure inside , sealing not need to be like on Space shuttle .
I think i found solution for HT element on top of oven.This is 3.5mm Kanthal wire and i think that will hold HT element on place .


This is what i think would work....

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OK ............I solved another one problem . For vacuum meter and pressure meter i will use independent pipe line and I need valves ......ONE WAY automatic valves so they can work without help .This kind of valves can be found on older diesel engine and they can be adjusted and have very slim profile ...they are something like on picture in different designs ...For rest I will use fittings and pipes from automobile break system.
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Now to find other problem to solve ....the more I think about this the newer problems pop up :D
 
Sorry, I wasn't trying to start an argument. It may be a translation issue.

I was asking why you needed a vacuum oven. I know you have many ovens already and thought you were quite happy with them.

Vacuum ovens are usually for larger batch HT. Sealing things vacuum tight and maintaining a vacuum at 2000°F/1100°C isn't all that simple.

Build one and have fun.
I will quote you again:) Don t think that sometimes i don t ask myself about that .....Why i need to do this ? I can adapt my large Tube furnace to be vacuum furnace in one hour , at least that is easy and simple .But ..............i have no idea , no answer why i do this :D What I know is that one day i will do that to ............ That s me , and I cannot change :)
 
Hey Natlek, I really think it's the strength of the chamber that is going to define your success or failure.

Vacuum is strong! Once you have a vacuum, and you get to high temperature your chamber will want to collapse, maybe it'll work if you make some cross bracing out of something strong in compression and heat resistant? Maybe ceramic? I don't know. Good luck, and have fun with your build.

I think this is the reason that they build big ones with the vacuum chamber on the outside. They can insulate the chamber from the high heat.
 
so im just making a (Discussion here) but when me and the others talked about this .. Argon is Heavier than oxygen therefore it should come from the top allowing gravity to help the Argon cover the parts being heated thus removing the Oxygen required to form Oxides in heat treating... once the door was opened to retrieve the hot parts you would potentially still expose them to oxygen causing oxides... but say you could make wall or something to allow you to fish the parts out of the Argon bath
the parts time exposed to oxygen would only be moving into hot oil for the quench..
im curious if a "Curtain" of argon could not be used instead of a door on the oven?? that way the oxygen does not have much chance getting onto the parts while going in/out
again just thinking out loud here.. i would think creating a curtain to contain the argon might not be too hard as it is more dense than the oxygen..
still watching...... hope it works out...
 
What about a length of 2” stainless tube instead of foil? Cap one end and put a simple latched cap on the other, perhaps with a ceramic fiber gasket. Some wood or paper on the inside can scavenge the oxygen.
When the cycle is done, grab your “crucible” with a hook or some tongs, pop the latch and dump out the blade between your quench plates. Is there a reason that wouldn’t work at least as well as foil? Just thinking out loud.
 
In your tube furnace thread you posted a portion of Carbolite Gero’s manual, that has information on a vacuum tube furnace, is this similar/same as that?
 
Hey Natlek, I really think it's the strength of the chamber that is going to define your success or failure.

Vacuum is strong! Once you have a vacuum, and you get to high temperature your chamber will want to collapse, maybe it'll work if you make some cross bracing out of something strong in compression and heat resistant? Maybe ceramic? I don't know. Good luck, and have fun with your build.

I think this is the reason that they build big ones with the vacuum chamber on the outside. They can insulate the chamber from the high heat.

I understand the power of vacuum :thumbsup: I hope you think on strength of the steel chamber ? I will overbuild that part .I can even use hardened steel if needed .I have over 3 foot Dia. and 10mm thick circular saws/diamond/ from granite/marble factory near me . Plan is to reinforce all side of steel chamber from OUT side with angle iron in several location ...now about bricks.....i have no idea how they will react on vacuum ?
This is how i imagine to operate this oven ...Insert knife inside ,close the door , make vacuum , let the argon inside and turn the oven ON ? Under vacuum oven should be very short period of time ...Or heat it up to some say 1000 F and then start process ? As soon as there is none air inside it will be no problem that steel is inside longer . I will try to make this oven to heat as far as is possible but maybe on the contrary, maybe slowly heating together with the oven is better for steel than putting cold steel in a 2000 F temperature ?
 
In your tube furnace thread you posted a portion of Carbolite Gero’s manual, that has information on a vacuum tube furnace, is this similar/same as that?
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No Dan , I don t use tube here .This one will work on the same principle but , no ceramic tube .Plan is simple HT oven like all other one BUT little more stronger /reinforced and sealed . But lot of information there :thumbsup: If you start to build tube furnace you should think about making in to be capable to work under argon ...it is much easier to do that in that kind of oven:thumbsup:
 
so im just making a (Discussion here) but when me and the others talked about this .. Argon is Heavier than oxygen therefore it should come from the top allowing gravity to help the Argon cover the parts being heated thus removing the Oxygen required to form Oxides in heat treating... once the door was opened to retrieve the hot parts you would potentially still expose them to oxygen causing oxides... but say you could make wall or something to allow you to fish the parts out of the Argon bath
the parts time exposed to oxygen would only be moving into hot oil for the quench..
im curious if a "Curtain" of argon could not be used instead of a door on the oven?? that way the oxygen does not have much chance getting onto the parts while going in/out
again just thinking out loud here.. i would think creating a curtain to contain the argon might not be too hard as it is more dense than the oxygen..
still watching...... hope it works out...
I know nothing for now ....no need argon to come from top in vacuum .Maybe no vacuum ? Just some port from which air can go out of oven so argon under pressure can push out air ? But that way we will never know when is done and how much air is pushed out ?
Look , I really can t see why this way should not work ? Vacuum air from oven, let argon in . When time comes open door take knife and quench ? Can several second on air make some reaction on steel and how much ? Honestly I have no idea for now ..
 
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