Using an inert gas in a heat treat oven. | Heat Treating | Forum

I have a Paragon HT oven with that option. Tried it, and went back to using foil instead. To get enough coverage to prevent scaling I had to really pump in the argon. Stainless just worked out cheaper for me.

Using electric heat and gas barriers for heat treating sounds like a headache to me, in more ways than one. I understand exposure to high temperature for extended periods can cause improper grain structure growth, and I think controlling the temperature of parts of varying size in a gas would be far from easy so waiting for the parts to even out might be a problem. To be honest I’ve never been overly concerned about heat treating, but now that I’ve decided to get into knives I’ll need to pay attention.

I am intending to use an idea I had for HT knives until I can get some salt pots built. What I had in mind was placing salts in a tray and heating it within the forge. For reasonable temperature control I thought a pyrometer probe placed within the salts should work. Quenching could be done in a second tray with low temp. salts in an ordinary oven or in any preferred liquid. Seems like a doable scenario for me and perhaps others, the amount of salt used would be minimized and the danger of introducing water into the salts when in a hot forge would be small. Replacing small amounts of salt at a time when necessary would be much less painful on the pocket. You guys with experience, or anybody else for that matter, using salt baths see a problem with this idea?

Paragon is an old time kiln builder, they are using barrier gas to get a reducing atmosphere in an electric kiln for ceramic glazes. They know how to control kilns but probably have little knowledge of HT requirements. I don’t know if you have much mig welding experience but using pure CO2 will cause the weld to have less penetration, this is a good trick when welding thin sheets, as it will not ‘blow out’ the weld as easily.

EDIT please read: Bill I know you understand the dangers of using CO2 but I want to add a precaution about using CO2 for those who don’t. CO2 is heavier than air if you use it indoors and get below the level of the gas you may die, you cannot smell it you may not even know what is happening, most people just feel silly and then pass out, often followed by their funeral.

I intended to control the forge with the pyrometer in the salts, you must have missed that part or I mangled the words bad enough to obscure the meaning. As for the price of the salts I don’t have a clue what they are, but the lack of availability looks more of an issue in the forums I read.

While I’ll be the first to admit I’m a fool (see avatar), and you may be right, but I’m fairly certain you don’t mean to say CO2 is easily detected and not to worry. If you start out in an ordinary atmosphere and enter a pure CO2 one I’m sure you would notice and would leave if possible, however that may not be the case in practice. Please do not use CO2 indoors without adequate ventilation, and be aware of your mental condition. OK, no wise cracks.
Edit: I forgot to add ventilate from the lowest possible point, if you pull air up it will mix with the rooms oxygen, short term would give you a nice headache, long term not healthy.
Edit #2: I hope you experienced smiths don’t think I’m preaching to you, my concerns are for inexperienced and or young people reading the forum. I do not want to discourage them from pursuing whatever quest they may be on, but I would not want them to be harmed by anything in this forum and especially from anything I may have posted.

Good points, especially on the basement thing, living in the Deep South most of my life doesn’t make me think about those spaces much, but caught in a hole in the ground with no O2 would make a bad end for a day, or a life. You would be surprised how quickly and severely a lack of O2 will confuse you if you don’t know what’s going on, best thing is prevention, and get an alarm if you can afford it.

With my sweet personality and witty style it seems like there’s always someone around willing to cut off my air supply. I’m use to the confusion it’s the blue face that concerns me.

Thanks Lewis, with all my babbling the main points do seem to get lost, don’t they? The concern I have for CO2 is the sheer volume of displacement capacity in a small tank, it can push out the normal air in a closed space in a very short time. It can mix into the air in busy closed spaces while pushing out the O2. If you're distracted working, especially if working hard (or worse, having a few also) it may hit you like a brick, if you go down, you may never recover. CO from fuel burners are a danger in the winter and the alarms are reasonably priced if you need one, CO2 alarms are pricey. My opinion is use CO2 in spaces you don’t occupy and / or leave a door to the outside open so the volume of gas can escape low and quickly.

Edit: Lewis, you’ve done a good job of condensing the essential information here why not post a version into the safety section, perhaps Grant will sticky it. Since I’m handing out jobs like a foreman, while you’re at it don’t forget metal poisoning from zinc and lead. Oh yea an …… Lewis where’d you go???