Originally Posted by
JDM61
Mike, in looking at the graph, it appears the start of the curve is at around 1300F for O1 austenized at 1490F. The Curie point for iron is 1043K or around 1417F. I have been told that can move up or down a tiny bit depending on alloying, but does the chart reflect something else that I have heard which is that while the conversion to austenite as the heat rises is at the Curie point and above, hence checking to see when the steel becomes non-magnetic, but, for hardening purposes, the undesirable conversion back into stuff like pearlite (assuming no partial martenstic or bainitic formation from air cooling like in stuff like Crucible Champaloy) starts at that lower point as the temperature falls?