Carburizing
Carburizing turns up in 2 fields: heat treating, gears. Here is what it means to the people in each one.
Carburizing in heat treating
Diffusing carbon into the surface of low-carbon steel at high heat, then quenching for a hard case.
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."
Carburizing in gears
A heat treatment that diffuses carbon into the surface of low-carbon steel gears, then quenches for a hard case.
The heat treatment behind most high-capacity gears. Parts made of low-carbon alloy steels such as 8620, 4320 or 9310 are held around 900 to 950 C in a carbon-rich atmosphere until carbon diffuses to the required depth, then quenched and tempered. The result is a case of about 58 to 62 HRC over a tough core, giving the highest bending and pitting capacity of common steel gear treatments, at the cost of distortion that usually needs grinding.
"Carburizing load is in the pit furnace for twelve hours, so the gears won't be back for grinding till Monday."