As a wannabe-blacksmith (I have recently acquired a Peter Wright anvil and am starting to buy hammers and think about a forge, so take what I say with huge grains of salt) I have been reading up on the quenching process and one of the tests to see if a piece of steel is ready for quench is to hold a magnet against and if there is no magnetic attraction, the steel is hot enough for quenching.
No idea what that means or if I am describing it right, just putting it out there as a random fact.
Not the Curie Temperature in this case. At 730°C, steel transforms into austenite, with a different, nonmagnetic structure. Austenite has better properties, so it’s more desirable.