Low cost temperature control?

J

James Hall

Joined
Sep 18, 2013
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85
I'm relatively new to making, and recently built a soup can forge with a MAPP gas torch for HT. It works well, heating up well above critical, however there is inherently no temperature control. Reading up about kilns, salt baths and the like, I wanted to create something that will let me adjust heat, if not soak for a couple of minutes. Building even a small kiln seems rather complicated and too expensive for my lowly budget, albeit cheaper than buying one new.

On another forum, I was given this advice about using a pyrometer:
With the pyrometer you should be able to meter the amount of heat in the forge by simply adjusting the gas with good accuracy. Your flame will be smaller and it will probably take a little bit longer to get the work to an even heat, but you can easily get a 5 degree variance by keeping a watchful eye.
I recommend using propane and using this torch head. http://www.bernzomatic.com/item.html?id=19
This is what i use for metering temps, I make sure that the probe is touching the work piece. http://www.auberins.com/index.php?main_page=product_info&cPath=17&products_id=199
Click to expand...

Does anyone have any experience or opinions about this? I have an almost identical torch (ts8000), and switching to propane will probably help to prevent overheating.

Thanks in advance,
J.P.
 
I use an Auberins probe and pyrometer. With a 10 brick forge and a tiger torch, I could hold temp within 5deg f. for 10+ minutes. I use both propane and MAPP in a 2 brick forge. It was difficult to get the MAPP torch below 1500f. It was just too hot. Propane worked much better.
 
The evenness of heat depends on how well you set up the forge, and if you get a good vortex going. I have successfully treated 12" blades in my 10 brick forge. There are better ways to do this, but if its set up well, it will work. The temp is more even when using a cylindrical forge with a muffle pipe.
 
My soup can setup has a great vortex that you can see straight through. I'm starting to get optimistic about this :)
 
I honestly didn't think this would work either. I thought this would be a brief temporary work around to use with steels that require little soak, but I have used 1095, O1, 15N20, 52100, W2, 1084, 1075 and now that I have my hardness tester, I know I was basically on the money. I do have a piece of 1/4" steel lining the floor of my forge. I think it helps even the temp and hold temp. I wondered if the larger number of fire bricks helped as well. They hold a certain amount of heat and radiate it back out. Once at temp, I pump the blade back and forth in the forge to prevent hot spots in the steel. You will be surprised how little heat you need from the torch. I have to run my torch so low its almost shutting off to keep the temps below 1500f.
 
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I've heard that a section of pipe will help even out the heat as well. I've got a decent size section so I'll probably move my blades around in that.
 
I just put a post in the thread about inexpensive thermocouples. It has some info you should read. Also, the Sticky on PID control and such has lots of info with specifics you will need to know.

A pipe muffle will only work in a forge with enough chamber sze. A 3-4" chamber that is 12-16" long can benefit from a pipe muffle. I guess a smaller forge will get some gain from one, but the pipe won't overcome most of the deficits of a small poorly engineered forge.....AKA coffee/soup/bean can forge.
 
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