ideal location temp readings in forge

D

Dakota 11

Joined
Apr 14, 2006
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Ok so have decided that i am overheating my o1 and it is causing me some problems as per my previous post. So i bought a digital thermometer form omega. Says it a k type and has a temp reading to 2000 F, with a accuracy of looks like if i read it right .03%. also am building a smaller type forge for my heat treat. the forge will be 10 inches deep buy 4 inch diameter. will have the wool , stantinte , and itc 100 all from darren ellis i believe. were would be the ideal location to install the probe end of the thermometer? or does it matter at all were it goes. with this set up i should be able to control within a few degress of were i need to be and get much better results from my 01.
 
I don't know what kind of heat treat your planning to do , but I think a high-temp oven would be better than a forge.
If you're willing to build a forge, you could easily make a salt pot, which will increase your HT options quite a bit.
Type K is supposed to be good for 2000F, but you'll find it degrade really fast in the atmosphere of a forge. They last quite a while in an oven.
 
High temperature salts are used to heat the material to a specific temp in a atmosphere free environment. The salts melt at higher temps around 1300f. the blades are put in to soak at the proper temp and then removed and quenched in standard quenchant or low temp salts. The low temp salts allow for martempering. This is a process for bringing the quenchant to the tempering heat and then quenching and soaking the blade to improve toughness. If you have not already done so,I would recommend getting Wayne Goddards books, The Wonder of Knifemaking and The $50 Knife Shop. He covers many of the heat treating processes and explaines what is appening to the steel. This forum is also a great source of info but some explanations can be a bit long to put here. There are a couple of things you can do to prevent the degrading of your Type K. Get a well made of SS. This will hold up in the forge environment. Also if you are just Heat Treating with the forge then it should not go over 1550f any way, The atmosphere will not be too harsh and the probe shuld last quite a while.

Chuck
 
Search for salt pots on this forum, Don Fogg's forum, and see Kevin Cashen's website. That said, salt pots cost quite a bit more than a simple forge, and are quite a bit more dangerous.

Look into Don Fogg's drum forge--or a scaled down version if you are not into swords--for a simple design that will hold temp +/- 5 degrees.

Also, all you need to do is drill multiple holes--3 is plenty--along the length of your forge, and then move the probe around to figure out differences in temp, if any. Obviously, things like wide open doors and direct flame contact will lead to variations in temp. Mimimizing these things is part of a good design.

John
 
Good post by Chuck. I would only add that Iconel will hold up better than stainless, and that I have already melted two Iconel probes in my welding forge:(.


John
 
thanks for all the comments so far. i did a search here and dont think i have an interest in salt pots looks like to much danger involved for me . i wil only be working with o1 and 5160 and maybe 1095 when i get some . i will only be making hunting type knifes and am after very sharp, great edge holding knifes. and so far o1 seems to be good for that. before i was just using a 1 brick forge and it caused me problems cause i could not get the temp right. i believe now that i was over heating the blades. with the thermometer i should be able to get were i need to be.
 
What I was insinuating earlier was that it's a lot easier to control the environment of an oven vs. a forge. I don't think a forge is as good a tool for standard heat treating ops. as an oven, and a salt pot is a very powerful tool offering numerous advantages. To me making any of these is roughly the same trouble.
You can get an old ceramics kiln, for instance, take your type K and get a digital controller on ebay for $100 or so (make sure you get one with a manual so you know how to work it). This way you can control temp with great accuracy for minimum $$. There are also other lab ovens and such available if you keep your eyes open.
I have not found salt pots to be particularly dangerous compared with other things we do making knives. (I have four on natural gas w/digital controllers).
Don Fogg's site is a good place for info on building this equipment easily and on the cheap, not to mention a wealth of other neat stuff.
 
I will be getting an oven in the future it is on my to do list for sure. main problem is time and money right now. hunting season is fast approching and i will be in many states this year it looks like. For me and this may sound dumb but there is a kinda of novalety and romance involved with fire and metal. I really like doing this and have learned alot so far and even more tonight just reading up on salt pots. one other thing is on the eletric ovens is how much juice they use? i just got my eletric bill and it was 400 dollars, mainly cause teh way it is tierd, since im in teir 3 already wondering how much kilowatts would this add to my existing house bill. and me thinks my next bill is going to be more, ouch
 
Dakota 11 - Ignore this if you were stating the inside dimensions of the chamber after construction. -
I think you would be better off to make the HT forge a bit larger in diameter (depth ,too, if possible). At 4" it would barely fit a blade in after the wool and satanite was added.
The larger area in the forge will allow a more even heat of the chamber.The best way to avoid hot spots and overheating is to mount a piece of 2"ID stainless pipe (or larger if needed) inside the forge. This is called a muffle ,and it keeps the corrosive flames off the blade as well as evens out the heat.Place the thermocouple inside the pipe and you will be reading the exact environment of the blade being treated (and the probe will last a lot longer).Add a solenoid valve and a controller to the rig and you have a temperature controlled forge.Set it at 1500 (or whatever) light the burner,and it will settle in at exactly 1500.
 
Stacy is, of course, exactly right.

The muffled device described above is what I'd call a GAS OVEN. If you build it with the tube facing up, and fill it with salt, you've got a salt pot.
Regardless of what you decide to do, the digital controller is worth it's weight in gold.
 
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