The 3 Most Common Chain Heat Treatment Practices
Heat treatment is used to alter the physical properties of a material – typically to increase the strength and wear characteristics of a chain while maintaining adequate toughness and ductility for the application. Heat treatment involves the use of heating, rapid cooling (quenching), and sometimes even chilling components to extreme temperatures to achieve a desired result.
All metals consist of a certain microstructure. The molecules shift positions when heated. When the metals are quenched, the molecules stay in a new microstructure with increased hardness levels and the desired increase in the strength and wear resistance of the components. The components of the chain are heat treated separately prior to assembly, which facilitates setting the target properties for each component to their ideal state. There are many different heat treatments methods that are used to tailor the hardness level and depth. The three most common methods of heat treatment for chain components are:
Through Hardening is a process of heating, quenching, and tempering the part. This process hardens and strengthens the materialevenly throughout the entire section of the part, unlike some methods which just harden the outer layer. The outcome is tempered steel that is harder and stronger, but still has adequate ductility and toughness.
Carburizing - Case Hardening
Carburizing is the process of hardening steel by exposing it to carbon while the metal is being heated. The addition of carbon to the surface of the steel changes the chemistry and makes it more responsive to heat treatment while maintaining a softer and more ductile core hardness. The carbon is only absorbed at exposed surfaces, and the depth of penetration is proportional to the time in the furnace – hence the term case hardened. Case Hardening does create the potential for a harder steel than other hardening methods, but deep cases can take more time and be very expensive.
Similar to Through Hardening in that it requires a process of heating and then quenching, but the application of the heat is done in a controlled fashion through an induction process (strong magnetic fields). Induction Hardening is usually applied as a secondary process on top of through hardening. Controlling the induction process limits the depth and pattern of the hardness change. Induction Hardening is used to harden specific sections of a part instead of the entire unit.
While heat treating is an effective, and critical, way to increase the quality of your chain there are many other manufacturing processes such as stamping, bending and interference fits that are required to make a high quality and long-lasting chain.
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