Simply put, if you are heat treating in a forge darken the room and quench at reddish orange to orange and the nonmagnetic temperature is 1413 and you need to get about 60 degrees hotter, so pull the metal out and test it with a magnet once it starts to turn red. If the magnet doesn't stick and it isn't reddish orange pop it back in for a few seconds to minute depending how long it took to get to dull red (time it out). Once ready have 120 degree heated oil ready and quench point/edge down first quickly, don't let it cool down before quench. Then temper at 400 for one hour first as soon as you have wiped the oil off. Let it cool to room temp in the air by shutting off oven and open the door. If you buy some inexpensive 1084 you can have precise HT instructions btw. Test after first temper with a good file, if it doesn't dig in (it shouldn't if decent steel and good heat) and just skips over the blade then temper for another hour.
But using a mix of steels I cannot take you further. Not all mower blades are the same steel sometimes not even from the same company and the same for leaf springs. Leaf springs used to be made with 5160 mostly and that needs to get hotter in the forge a lot, like around 1550-1650 degrees and that is yellowish bright orange, someone please correct me if my memory is incorrect on the 5160. Here is a link to a steel company for blades I suggest 1080 or 1084 to start. Oh 5160 is usually hammered to knife shape, tempered and then finish ground.
http://newjerseysteelbaron.com/
Coal forge or propane?