Heating the surface of medium-carbon steel or cast iron with oxy-acetylene or oxy-propane flames until it austenitizes, then spraying or immersing it to quench. Cases of about 1.5 to 6 mm are typical, and the equipment can travel to big parts such as mill rolls, gear rims and machine ways that no furnace or coil can take. Uniform results depend on torch speed and standoff.
Lathe ways are getting flame hardened in place, keep the water shower right behind the torch.
Also heard as
- flame harden
- flame-hardened
Related terms
Induction hardening
Heating only the surface of a steel part with an alternating magnetic field, then quenching for a hard case.
Case
The hardened outer layer of a case-hardened part, as opposed to its softer, tougher core.
Cherry red
Color name for steel glowing at roughly 750 to 800 °C, near where most hardening heats begin.