I, being a metallurgist, am absolutely in awe of this new heat treat book, put out by a furnace company, Seco Warwick.
Now, before you all throw up your hands in HORROR at the detailed stuff only a metallurgist could love -
Take a look at pages 56, 83, 84 and 98. Just these pages.
page 56 - gives times & temperatures for different depths of carburization (case hardening, the depth of case one gets)
page 83 - heating, and tempering colors, described.
page 84 - melting points of lotsa metals
page 98 - quenching matters. Tells just exactly why a brine quench is superior to plain water. I sorta knew this, but not so exactly.
Grit your teeth and download this book.
https://www.secowarwick.com/assets/Documents/Books/HeatTreatingDataEBook.2011.pdf(dunno how to make it a link here, ya gotta cut 'n paste)