Big Trouble In Little Furnace

C

Chizdna

Joined
May 29, 2014
Messages
6
Hi all, I built a heat treat furnace about a year ago and I've been treating 1084, 5160, and 1095. Haven't had any issues up until trying to work with D-2.
After getting the D-2 up to temp (1850F) and holding for 30 minutes, the tool wrap was stuck to the tool hehe. Being that the tool wrap is 309 rated for 2200F, I'm thinking that there's some issue with either the PID or the thermocouple giving me a bad temp reading. Both I bought on the cheap on ebay, the pid is a CXTG-3000, with a K thermocouple (the kiln style with a bunch of ceramic insulators on it)
The oven is 240v with two Kanthal elements purchased from Budget Casting.
How hot would it be in there to make the wrap stick? And if it's way hotter than 1850, what could be the cause?

Thank you,
Chris
 
Stainless foil can fuse to the steel. Use a light dusting of baby powder on the knife to avoid it sticking. Probably not an issue with your forge.
 
Are you plate quenching?


If that is so, I will explain a little physics of metallurgy:

The temperature of the piece of steel and the wrap are at atmospheric pressure when sitting in the oven. Lets say it is 1850°. If the pressure on it is increased and they are pressed hard together, the temperature at the surface may climb hundreds of degrees. This is because temperature is merely a matter of energy. add more energy and the temperature goes up.

We see the same thing in forge welding. The hammer blow greatly increases the temperature at the spot where the hammer strikes and that spot welds itself together.

In plate quenching, the foil can get fused to the blade in the most pressed upon spots.

Take a piece of steel bar and heat it in the forge. Bring it up to about 1600F. Set on the anvil and let it cool until it has just about lost all glow. Strike hard with the hammer. You will see the spot where the blow hit glowing much redder than the rest of the bar. That is because you added a lit of energy there. Spot welding works using some of these principles.

These are examples of impulse fusion or fusion welding.


The other thing that can cause fusion is time. When done over time, it is called diffusion welding. If you leave two hot surfaces together long enough, they will fuse below the normal fusion temperature. We do this with mokume ( often using pressure to help the process). I don't know how much a long soak at 1850° will affect the diffusion between the foil and the blade, but if they are closely layered, it is possible that they can fuse a bit. I am sure low quality ( or wrong material) foil can equally add to the problem.
 
Stacy E. Apelt - Bladesmith said:
Are you plate quenching?


If that is so, I will explain a little physics of metallurgy:

The temperature of the piece of steel and the wrap are at atmospheric pressure when sitting in the oven. Lets say it is 1850°. If the pressure on it is increased and they are pressed hard together, the temperature at the surface may climb hundreds of degrees. This is because temperature is merely a matter of energy. add more energy and the temperature goes up.

We see the same thing in forge welding. The hammer blow greatly increases the temperature at the spot where the hammer strikes and that spot welds itself together.

In plate quenching, the foil can get fused to the blade in the most pressed upon spots.

Take a piece of steel bar and heat it in the forge. Bring it up to about 1600F. Set on the anvil and let it cool until it has just about lost all glow. Strike hard with the hammer. You will see the spot where the blow hit glowing much redder than the rest of the bar. That is because you added a lit of energy there. Spot welding works using some of these principles.

These are examples of impulse fusion or fusion welding.


The other thing that can cause fusion is time. When done over time, it is called diffusion welding. If you leave two hot surfaces together long enough, they will fuse below the normal fusion temperature. We do this with mokume ( often using pressure to help the process). I don't know how much a long soak at 1850° will affect the diffusion between the foil and the blade, but if they are closely layered, it is possible that they can fuse a bit. I am sure low quality ( or wrong material) foil can equally add to the problem.
Click to expand...

Yes sir, I am plate quenching. And the tool wrap I'm using is from usaknifemaker.
And wow! Thank you for info!
Do you think the suggestion above from S. Alexander of using baby powder will help even though I'm using the plates?
Thanks for your time
 
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