Temperature fluctuation?

Pelallito

Well-Known Member
Hello,
I recently put together a pid controller in a small tool box and can finally get a read out of what temps I actually have in my 2 brick forge. It is essentially a copy of Len Lunstroms(spelling?).
I was watching the temperature stabilize at say 1475 and it would stay there for a few minutes( or so it seemed to me), then it would start creeping either up or down. I did have an oscillating fan on, but I turned it off and nothing changed
I have a mini side arm burner on that forge. I am wondering if my 0 to 60 PSI regulator could be the problem or something else. The regulator is ancient and who knows what kind of shape the diafragms are in.
Any advice happily accepted.
Fred
 
Temp fluctuation is just a given with most forges.... if the forge is well made and well insulated, you should be able to "dial it in" where it stays within a reasonable range, but don't expect any forge to be capable of being "set" to a specific temp and have it stay there....it's just the nature of the beast.

Generally, I run my forges in a manner that they are nearly constantly "climbing"...meaning that the temp inches up as things warm up, and will somewhat "level out" with up/down fluctuations. It's not unusual to see a ka-wool type forge vary as much as 300F when a large billet is put in. Like I said, a forge is never gona give you "exact" temps....they're just not designed to do that.
 
after using several gas forges and an electric furnace, Imho it is the nature of the beast. especially with a small unit. what i found is you watch the temp, when it gets 10 over turn the heat down a notch; 10 under up a notch. the good thing is 1475 means basic carbon steel or low alloy tool steel so you are talking 10 to 20 minute soaks and steel that everyone says is pretty forgiving if the temp varies a few degrees.
 
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Thank you both for the replies and advice!! I forgot to mention that I was heat treating o1.
I thought that if you set the needle valve at a specific setting, the temperature wouldn't fluctuate that much.
I did expect a drop when putting a blade in it after it had achieved a certain temp. :31:
Thank you again. I will probably have more dumb questions in the near future. LOL
Fred
 
The problem that you have when you are heat treating with a forge is that the steel will not be the same temperature. Even the pyrometer will only show how hot the forge, not the steel, is at the point of the thermocouple. Simpler steels can be heat treated in a forge if you are checking with a magnet and/or watching for decalesence and recalesence. A baffle inside the forge will even out the temperature more but to get the best heat control you will need a regulated, preferably programable, kiln or a molten salt pot. There is no such thing as too much heat control.

Doug
 
Doug,
My blade was next to the thermocuple, actually leaning against it. I expected to see a drop in temperature when something at room temp goes into the forge. What surprised me, until it was explained by Scott and Ed that forge temps go up and down even if you don't change the needle valve setting. Could it be the propane gas, and or do I need a better metering system? I will be building a bigger forge soon.
Thanks again,
Fred
 
No, that is probably the best that you can do with a gas forge. If you have to soak the steel at temperature for any length of time you will end up having to watch the steel and try to keep it at the same level of brightness by taking the blade out of the fire for a few seconds and then back in. It's just the nature of the beast.

Doug
 
Doug, Thank you. Having the PID is going to open all sorts of doors for me!LOL
I still have not wired in the SSRs. I need to build a larger forge. I am considering copying Wayne Coes design for a propane tank. I think that a freon bottle would be too close to what I have. Unless I join two freon bottles.
Any advise? I want to use two burners so I can set up a solenoid valve set up
Thanks again,
Regards,
Fred
 
IMHO, Shop till you drop and find a nice electric kiln for cheap. I just bought a paragon E9A(9"x9"x4.5"hi) for $250. will let you know how it works once I have my temp controller hooked up to it.
 
I think that you will find that putting a PID controller on your forge is not going to give you the temperature control that you are looking for. Regardless of what you set the PID for, the propane will burn at a given temperature. I think that Ed Caffrey has had some experience with people who have made that modification to their gas forges. You might want to drop him a line before you go to the trouble of installing one of those to your forge. Scott made a very good suggestion about the electric kiln, that or a heat treating oven. Another possibility would be a molten salt tank but they have their problems too, besides being more dangerous to operate.

Doug
 
Doug and Scott,
I will probably build a kiln. This is the second time Scott has recommended an electric kiln to me, so it is time I follow a great suggestion.:) He also told me to stay away from the salt pots for now until I get more experience under my belt.
I have had a lead pot blow up once, when some humid lead went into it. It was only at about 600 to 700 degrees, but it scared the living heck( so to speak) out of me. I luckily never had to explain the lead splatter on the ceiling, since I did it in a garage.LOL
Eventually, that is what I really want to build.
Thanks again,
Fred
 
Doug and Scott,
I will probably build a kiln. This is the second time Scott has recommended an electric kiln to me, so it is time I follow a great suggestion.:) He also told me to stay away from the salt pots for now until I get more experience under my belt.
I have had a lead pot blow up once, when some humid lead went into it. It was only at about 600 to 700 degrees, but it scared the living heck( so to speak) out of me. I luckily never had to explain the lead splatter on the ceiling, since I did it in a garage.LOL
Eventually, the salt pot, is what I really want to build.
Thanks again,
Fred
 
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