# Calculating power of induction heating of brass

I got this project to make, to anneal brass pipe edges (to be more precise, empty brass gun-shells) of diameter about 8mm. I would like to raise the temperature up to about 450-500°C in few seconds, not minutes. I was working with 120W induction module (as seen on photo below) which was able to properly raise the temperature, but in few minutes instead of seconds. I don't expect it to be hot in 2 seconds, but not more than 15 should be per cartridge. I'm not sure if induction goes linear in comparison with time (power x2 = 1/2 time) so therefor I'm asking, how am I able to calculate the power needed for induction?

Current setup:

Power supply: U=12V I=9.5-10A (current draw slightly varies)

Coil: Number of turns: 10 turns Diameter of wire: 2.1mm 20mm is inner diameter of copper wire Lenght of coil is 25mm

Brass, that I want to heat up is marked with red color. The end bullet is not present (obviously). If there is few millimeters more to the left heated up, there's no problem at all. Just the red part need to reach 450-500°C. Wall thickness is 0.4mm.

• Twice the power for half the time basically.. Commented Oct 18, 2021 at 14:56
• @Andyaka: You're trying to say, it's going by square up? Commented Oct 18, 2021 at 15:21
• I'm wondering if a slug of brass might absorb more power than a ring of brass, which is actually a one-turn coil? Orienting a ring at right-angles inside your coil might make a difference? Commented Oct 18, 2021 at 17:14