Case hardening in a vacuum furnace, also called low-pressure carburizing, in which acetylene or propane is injected in boost pulses at a few millibar, alternating with diffuse steps. It often runs hotter than atmosphere carburizing, 950 to 1,050 °C, so cycles are shorter, and with no oxygen present it avoids intergranular oxidation. A high-pressure gas quench afterward cuts distortion on gears.
We moved the ring gears to vacuum carburizing, acetylene pulses at 980 and a 15-bar nitrogen quench.
Also heard as
- LPC
- low-pressure carburizing
Related terms
Carburizing
Diffusing carbon into the surface of low-carbon steel at high heat, then quenching for a hard case.
Vacuum furnace
A sealed, pumped-down furnace that heats parts with no atmosphere, then quenches with pressurized gas or oil.
Boost and diffuse
Carburizing schedule that first floods the surface with carbon, then lowers the potential so it spreads inward.
Sooting
Free carbon depositing in a furnace or on parts when the atmosphere carries more carbon than it can hold.