Don t forget radiation from tube .............I think that this is not that simple ............
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Forge ability to control heat for a soak
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Don t forget radiation from tube .............I think that this is not that simple ............
Willie71
Warren J. Krywko
- Joined
- Feb 23, 2013
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This is why we let the oven equalize for 30 min before putting the blade in. The surface of the fire brick and air can equalize. Even then, we get a temp gradient from front to back. I'm not saying the forge can't do it, but don't be fooled to think it is for sure doing it. I heat treated my fair share of knives in a forge with a thermocouple. It can be done, but the oven is a step more reliable, unless you go full pid two burner forge like in the stickies. With a well designed lining, it should be pretty much the same as an oven. Having sufficient thermal mass to hold temp to minimize variations is important.
Then you are using direct visual temperature observation, which I'm sure some people can do very well.
If you know the temp of what is actually heating the blade, and it changes temperature more gradually than steel, then the steel will likely be a similar temperature after not very long.
But consider your electric kitchen oven. It is heated by coils that glow bright orange, the food cooks from the air temp in the oven, which is what you are measuring on the temp control, and the ceramic pizza stone takes 3 times as long as the oven air to heat up. So depending on where you put something in your oven you can heat to the set temp, a much higher temp (coils) or a lower temp if you put the food flat on the not yet hot pizza stone.
What do you think about this .........IF you put blade to rest on spine on same flat steel plate heated to say 1500 F ....? You will never get blade on 1500 F
What do you think about this .........IF you put blade to rest on spine on same flat steel plate heated to say 1500 F ....? You will never get blade on 1500 F
Maybe. What is the temp of the air surrounding the rest of the blade, and how do you know what the steel plate's temperature is?
That's the problem with what is being discussed - for the air in the tube to be 1500°, the tube itself is likely hotter than that. Then the blade is going to be one temp at the spine and another on the edge. Are you okay quenching a blade with a 1600° spine and tip?
As a technique for moderating and observing temp, a muffle, a good eye and good technique sounds really good. As a quasi-oven, a metal tube that the blade sits on and temp measured in the air is pretty haphazard, since you are heating the blade simultaneously through conduction and convection.
A strip of ceramic would insulate the blade from fast metal on metal conduction heating.
Direct conduction, radiation (infrared), acetylene are all used in vacuum ovens, depending on the goal. Probably induction, too.