Heat Treating with alcohol/ethanol

[xavier2089]

Hi all,
23:35 minutes into the video below, the guy (Dan Gelbert) talks about heat treating with ethanol/alcohol. I would love to get more info on this from those who know about it (I have never heard of this process before). Ultimately, I would like to modify my oven to be able to use this sort of set-up.

Dan Gelbart Workshop Tour HD - YouTube

So to create this sort of set-up, I'm thinking:
- Drip set-up with alcohol- faster is better than slower I'm assuming? (wasted ethanol is better than poor protective gas/ bad heat treat)
- A stainless tube entering from the bottom or top which introduces the ethanol to the oven? (would the introduced gas be lighter or heavier than air?)
- Depending on how well I can get it to seal, an exit port on the top or bottom of the oven?

If anyone knows the chemistry behind it, I would also be very interested to hear some of this information.

Has anyone else used this process before and was it effective?

Thanks guys,
Xavier

 

[john.k]

Id be kinda wary producing explosive vapours at elevated temperatures.........

 

[technocrat]

the chemistry is quite simple:
1. the oven is a purged with inert gas so there is no oxidation
2. methanol is dripped in as a carbon source. Anything which can make a carbon rich atmosphere will work.


this allows case hardening by enriching surface carbon levels. As well as case hardening, the carbon can remove oxide layers by forming CO or CO2

 

[52 Ford]

That's really interesting

As long as you aren't dripping the methanol onto the parts in the oven, I think you can introduce it anywhere that's convenient for you.

I don't know a lot about chemistry, but I THINK the gasses produced would be lighter than air. Don't take my word for it, though.

If that IS true, i'd introduce the methanol into a bottom corner, and vent the gas in the farthest away top corner.

 

[technocrat]

the vapour will be heavier than air and excess will combust / catch fire when it contacts air on exit from the furnace

 

[Milland]

I found a lot of information using the search terms:

Heat Treating with methanol protective atmosphere

 

[52 Ford]

the vapour will be heavier than air and excess will combust / catch fire when it contacts air on exit from the furnace

Huh... yeah so EXACTLY (180 degrees from) what I said. Figured I had a 50/50 shot LOL

You seem to know about it, so I have some questions. What gasses ARE produced when you heat the methanol up to 400C?

Also, what is the 'conventional' way to deal with the excess gas coming from the oven?

 

[Milland]

Also, what is the 'conventional' way to deal with the excess gas coming from the oven?

Marshmallows...

 

[Milland]

More helpfully: Endothermic atmospheres used for heat treating | Gear Solutions Magazine Your Resource to the Gear Industry

My quick understanding is that the methanol breaks down into Co or Co2 and prevents decarburising of the steel due to surface "carbon burning" in the presence of oxygen. The methanol can also supply an excess of carbon to help with case hardening/carburising.

This is probably not totally accurate, but close enough to get a basic handle on it.

 

[technocrat]

The methanol CH3-OH will get pulled apart into it's constituent C,H&O. In the high energy environment it will be unstable and all combinations will form and change. The Oxygen will be consumed by the H & C, but since there is not enough O, there will be an excess of C for the de-rusting and carbon enriching. The C & O will make some kinds of CO, CO2 plus water vapour from the H etc.

At 400C you will be below auto ignition temp so what actually happens will depend on surface temps of electric elements, hot spots etc. Combustion chemistry is very complex.

On discharge and cooling they will become stable, maybe some it condensing back as alcohol, but anything is possible. The exhaust gasses will be mostly carbon monoxide, water vapour and other potentially combustible hydrocarbons.

Generally the exhaust gesses will just oxidise in the room air, headed towards CO2 & water vapour. You won't see much when the volumes are small, but if a lot of alcohol is added, you can get flames in the exhaust. You can add equipment to burn the output in the exhaust flue or for small volumes just allow it oxidise with plenty of ventilation and noting that you may have carbon monoxide and other hazards.

 

[technocrat]

This is how oxy-acetylene welding of steel works. The heat and carbon can remove rust by burning out the oxygen in the oxide layers and the combustion gasses form a protective shield. No flux needed and rusted steel can be welded without inclusions.

 

[just4grins]

The company I retired from was trying to get away from vapor degreasing with trichloroethane, and went to alcohol vapor degreasers. After two of them exploded, they gave up and went to aqueous cleaners. Alcohol vapors are flammable in low concentrations, and if the equipment isn’t specifically designed for this application even a spark from a motor or relay can set it off. I suspect that the equipment used for this has everything sealed as a safety measure. The equipment my company used also did, but loose connections due to the incompetence of their crack maintenance staff defeated all of that. Not saying don’t do this, just be aware of the hazards.


Sent from my iPad using Tapatalk

 

[BugRobotics]

If you have any questions that you can't figure out Dan will usually respond within a few days to questions. I've had a few email conversations with him over the years. Extremely helpful, generous and humble guy.

 

[52 Ford]

Marshmallows...

Jumbo or mini?

 

[52 Ford]

Alcohol vapors are flammable in low concentrations

I remember watching an episode of Mythbusters where they were testing something related to rooms exploding due to gas leaks, I think. Anyway, as I remember it, there were bigger explosions when the gas was relatively less concentrated. Closer to an ideal stoichiometric ratio or something like that. Too much fuel didn't leave enough oxygen.

 

[Milland]

Jumbo or mini?

Depends on whether hot cocoa is at hand.



[Note to self: Do not confuse hot cocoa and hot cloaca in conversation. You will be stared at funny...]

 

[rcoope]

People should pay close attention to the video as Dan pretty much describes everything you need to know right there. He says you only need about five drops per minute and that it doesn't make sense to go any bigger with this approach as it will get dangerous, and he describes getting a big flame off at the end when he opens the oven. And no, more methanol doesn't help once you've got to a stochiometric balance. That furnace looks like its about 4" diameter, so when you're thinking about the stoichiometry it's like 0.1 of a mole's worth of atmosphere. It's also important that it's a two-stage oven with water cooling on the cold side so you can cool the part down without introducing oxygen. At larger scales you would use a vacuum oven with a controllable atmosphere, but these are perhaps expensive and maybe not the right size for a small shop. But Dan also likes exploring old methods and folk wisdom and other forgotten corners of the engineering world, hence the plasma needle arc welder and fludized bed coater. If I was wanted to get a good heat treat pipeline going I would certainly start by investigating what is done in common practice today and whether it can be done at whatever scale I need.

 

[Conrad Hoffman]

Just sounds like something where there should be a small notice at the bottom of the screen saying, "don't attempt this at home."

 

[TDegenhart]

The controlled atmosphere furnace we had where I worked had a loading door on an angle hinged to open outward. This was so that if the atmosphere ignited in the furnace, the door would swing outward to relieve the pressure

Tom

 

[52 Ford]

The controlled atmosphere furnace we had where I worked had a loading door on an angle hinged to open outward. This was so that if the atmosphere ignited in the furnace, the door would swing outward to relieve the pressure

Tom

I don't follow. You mean as opposed to one of the doors on linkages that sorta "translates" upward to open?