The process described here does not even remotely resemble case-hardening in my opinion. This process gives a through hardening, though it appears to be somewhat limited as to thickness of mat'l it can be applied to.
Worked on a lot of lathes over the years which were described as having "Flame Hardened" ways. This was of course done to cast iron & gave a surface hardness to the part. After the bed ways had been finish machined a very hot flame traveled down their length, followed immediately behind by a spray of cold water. The depth of hardness was dependant upon how deep the critical temp of the metal was reached. This was controlled by how closely the spray followed the flame & the speed of travel down the bed. One might quite easily refer to this as a "Flash Hardening" though.
Case Hardening is of course normally applied to a low carbon steel & requires a prolonged soak at high temp in a carbon rich mixture. This results in the steel absorbing the carbon gases released into its surface. Depth of case is dependant some on temp, but predominately upon time. It definitely is not a flash process.
