I was actually referring to dry burning, when it glows red-hot. What temperature is that?
I understood what you were talking about... I provided the table to see if we are even getting it to within the annealing temp. That is why I was suggesting to possibly use the temp control built in to the DNA40, but I see it only goes up to 600 *F.
I have an IR thermometer (a few) and some thermocouples... but I don't think the IR will work correctly due to the wavelengths emitted from the coil and I'll have to see if my thermocouples are rated for these temps, but I'm willing to compare what I get in real world tests to the link provided by Woofer... dang, except I don't have any Ni20x handy,... well, I might.
Perhaps this helps Temperature of a "Red Hot"Object
Temperature of a "Red Hot"Object
I'm just brainstorming here...
Color | | Approximate Temperature | |
| °F | °C | K |
Faint Red | 930 | 500 | 770 |
Blood Red | 1075 | 580 | 855 |
Dark Cherry | 1175 | 635 | 910 |
Medium Cherry | 1275 | 690 | 965 |
Cherry | 1375 | 745 | 1020 |
Bright Cherry | 1450 | 790 | 1060 |
One thing to note would be that 'Bright Cherry' seems to start around 790... which should be under the 815 that marks the start of open annealing for Ni200. Generally, there is more to the annealing process just like the hardening/tempering process... but annealing is such a quick interaction and given the tiny mass of our coils... that I think we would find that just a couple seconds above the 'open' temp will have the effect.
A couple simple tests would be to make two identical coils (within reason) and attach a small weight to one and measure how much it stretches (Nickel = very small weight )... and then do the same thing with the other coil after you dry-burn it. If it's still tempered, then it should deform the same under the same forces... but we would have to consider the stress release at the lower temp as well.
Otherwise, I think the simple fix would simply be to not glow the coil as much or even to only dry burn it at the 600 °F the DNA40 can temp limit.
If someone wanted to get fancy... they could make an attachment which would alter the measured resistance to enable to DNA40 to limit the temp at a higher level. Since the resistance goes up with temp on Ni200... this could be as simple as adding resistance externally to the posts for a net result of lowered resistance. Something with a much lower thermal coefficient (like Kanthal) might be suitable.