PID gas forge

Christian A Viola

Christian A Viola

Joined
Apr 4, 2020
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I want to make a stainless knife I understand you have to hold it at 1025/1050 deg C or 1877F to 1922F for 20 mins and wrap it up , I have my gas forge ready anything else I should do ?
 
Two-stage PID controlled forges are great. I love hearing them "breathe". By the look and sound of yours, I think you need to adjust your air/gas flow a bit. That is a huge yellow dragons breath indicating way too much gas.

Doing stainless HT in a forge is a bit tricky, but possible.
Direct exposure to the flamers will not work. You have to put the foil packet in a muffle pipe. A 3section of3" schedule 80 pipe is best.
Make sure your stainless foil is the right type and properly folded and crimped.

On issue to be dealt with is that the muffle pipe blocks off a lot of the port and reduces the exhaust volume. A forge needs sufficient exhaust to run right. If the forge has adjustable ports ( movable bricks) then you just adjust things, but with fixed ports it can be a big problem.
For example, if your forge had 3"X4" front and rear ports, that would be 24 sq.in. of exhaust port. Put a 3" pipe through the forge and you block off 14 sq.in. of that ... well over half of the exhaust is blocked. Now, for normal HT at 1500°F/815°C that would probably be fine. But, at 1900°F/1050°C, the forge is creating a lot more exhaust.
 
Hi thanks for your input, I had it set up so I did not have much dragons breath but it only reached 1382 F /750C so I turned up the pressure, the yellow might be due to the camera colour correction I will take a new video with the correct colour, should I add two more burners or just put up with the excessive DB, I have made a ribbon burner but I have yet to figure out a way of controlling it. can the muffle pipe be open at both ends and be in the furnace or does it have to stick out both ends of the furnace? I don't know what schedule 80 is, I bought the item in the picture
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Last edited:
Christian A Viola said:
can the muffle pipe be open at both ends and be in the furnace or does it have to stick out both ends of the furnace?
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I don't forge stainless, so I don't know if there are any special concerns, so feel free to correct me if necessary. I don't think it matters, the pipe is serving 2 purposes: 1) keep the blade out of the direct flame from the burners, and 2) with the thermocouple in the pipe with the blade, it'll help maintain a steadier, more accurate temperature.
 
Way back in the day I did stainless in a pid controller forge. Worked ok but the issue was the flame would burn holes in the foil. So you have that to contend with. Steel is not picky, it just needs a precisely controlled heat source. So if you can get that with flame then more power to you. Are you set up for plate quenching?
 
Christian, what part of the world are you in?

On the pipe you show it will work, but due to the thin wall (you said exhaust pipe) it will only last a short time before it burns out. BUT - it should do a couple of times at least, if not more. I'd stick the pipe in so the inside end is again the rear of forge. I'd not thought of it before but having the front sticking outside the forge should be good. You will need a TC tip inside the pipe where the blade will be..... BUT, with that thin wall I'll bet the TC that's controlling the forge will work, just give it a few minutes to stabilize the forge 'n muffler pipe. With the blade wrapped inside the SS HT foil I'd think it would work just fine, you might even consider double wrapping if needed, but I doubt double wrap will be required.

That forge sure does look like it's got too much propane for amount of air. The excess gas is burning outside the forge body. BUT, with that much dragon's breath you know there's not much oxygen inside to cause problems with the blade {g}

Be sure to let us know how it turns out.
 
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