Case hardening in which low-carbon steels such as 8620, 4320 or 9310 are held at about 900 to 955 °C in a carbon-rich atmosphere until carbon diffuses into the surface, typically to 0.7 to 0.9 percent. After quench and temper the case reaches 58 to 62 HRC over a tough core. Case depth grows with the square root of time, so doubling the case takes about four times as long at the same temperature. Gas carburizing in endothermic atmosphere is the workhorse, with vacuum carburizing common on gear lines.
8620 pinions, carburize to 0.040 effective, quench, temper at 350, standard drill.
Carburize deeper than the print minimum when the part will be finish ground, because every bit ground off the flank comes straight out of the case.
Also heard as
- carburize
- gas carburizing
- carb
- case carburizing
Related terms
Case
The hardened outer layer of a case-hardened part, as opposed to its softer, tougher core.
Carbon potential
The carbon content a furnace atmosphere would give the surface of plain steel at equilibrium.
Endothermic gas
A carrier atmosphere of carbon monoxide, hydrogen and nitrogen made by reacting natural gas with air.
Vacuum carburizing
Carburizing at low pressure in a vacuum furnace using pulses of hydrocarbon gas, then a gas or oil quench.
Boost and diffuse
Carburizing schedule that first floods the surface with carbon, then lowers the potential so it spreads inward.