Carburising And Case Hardening

Carburising and Case Hardening

Carburising, also referred to as Case Hardening, is a Case Hardening that produces a surface that is resistant to wear, while maintaining the toughness and strength of the core. This treatment is applied to low-carbon steel parts after machining, as well as high alloy steel bearings, gears, and other components.

Carburising increases strength and wear resistance by diffusing carbon into the surface of the steel creating a case while retaining a substantially lesser hardness in the core. This treatment is applied to low-carbon alloy steels after machining.

Strong and very hard-surface parts of intricate and complex shapes can be made of relatively lower-cost materials that are readily machined or formed prior to heat treatment.

Carburising is a time/temperature process; the carburising potential is controlled by careful salt additions that are introduced into the furnace at various times and the parts are held in the bath at a time and temperature to ensure the correct depth of the case.

After carburising, the work is either slow cooled for later quench hardening, or quenched directly into oil, water, or salt. Quench selection is made to achieve the optimum properties with acceptable levels of dimensional change.

All Case Hardened components are tempered after heat treatment.  In some cases, the product is tempered, then cryogenically processed to convert retained austenite to martensite, and then retempered.

MTE carries out carburising in molten cyanide salt baths at temperatures from 880 – 900oC.  The versatility of salt baths allows different treatments to be carried out in the same furnace and enhances our jobbing capability.

Our salt baths operate at a carbon potential of 0.6 – 0.8% C and this has proved ideal for most engineering materials.  Our processes run from 1 hour to 60 hours and we can achieve case depths ranging from 0.1 – 3mm.  We also have water, oil, and mar quench facilities which ensures that we can process a wide range of engineering materials.

MTE has 5 carburising furnaces which are also used for hardening, we usually operate with 4 furnaces while the 5th is kept as a backup in the event of a breakdown.