Is it possible to magnetize steel (hard magnetic material) with an ac source?
I'm quite certain it can not. An AC current makes an oscillating B-field. The time-averaged value of the B-field is therefore, zero. Hence, no magnetization greater than the remanence can be achieved, and depending on the frequency (keep in mind that the magnetization of a ferromagnet is a highly non-equilibrium process and time constants for changes in magnetization can be of the order of seconds, even at normal temperatures) it could be significantly smaller.
This sounds like a very dangerous home-made experiment waiting to happen
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