The depth of hardening can be an inverse relationship between temperature and time. Meaning you can get the same depth of hardening with low temperature and longer soak time as you would get with higher temperature and shorter soak time.
The old can of Kasenit of mine has the following instructions on the label.
FOR MILD STEEL:- Heat part uniformly to a bright red (approximately 1650 degrees Fahrenheit).
- Dip or roll in compound to form a fused shell arond area to be hardened. Reheat to a bright red.
- Quench immediately in clean, cold water using a scrubbing action to ensure maximum cooling rate.
To increase depth, repeat operation No. 2 before quenching. To insure maximum of hardness, reheat and repeat operation No. 3.
FOR DEEPER CASES ON MILD STEEL:Immerse part in compound using open, shallow receptacle. Subject to heat of 1650 degrees Fahrenheit for a period of from 15 to 60 minutes, depending upon depth of case required. Use dry tong to remove part from molten compounds. Quench part only in clean, cold water.