Heat treatment is used to change the physical properties of a material, typically to increase the strength and wear characteristics of a chain, while maintaining strength and ductility suitable for the application. Heat treating involves using heating, rapid cooling (hardening), and sometimes even cooling components to extreme temperatures to achieve the desired result. All metals are made up of a certain microstructure. Molecules change position when heated. When metals are hardened, the molecules remain in a new microstructure with increased hardness levels and the desired increase in component strength and wear resistance. Chain components are heat treated separately before assembly, which makes it easy to set the target properties of each component to its ideal state. There are many heat treatment methods used to customize the hardness level and depth.
The three most common heat treatment methods for chain components are:
Through hardening
Through hardening is a process of heating, tempering and tempering the part. This process hardens and strengthens the material throughout the entire section of the part, unlike some methods that harden the outer layer. The result is a tempered steel that is harder and stronger, but still has adequate ductility and toughness.
Carburization
Carburizing is the process of hardening steel by exposing it to carbon while the metal is heated. Adding carbon to the surface of the steel changes the chemistry and makes it more sensitive to heat treatment, while maintaining a softer, more ductile core hardness. Carbon is absorbed only on exposed surfaces and the depth of penetration is proportional to the oven time, hence the term hardened. Layer hardening creates the potential for harder steel than other hardening methods, but deep layers can take longer and be very expensive.
Induction hardening
Similar to Through Hardening, as it requires a heating and switching off process, but the application of heat is done in a controlled manner through an induction process (strong magnetic fields). Induction hardening is generally applied as a secondary process in addition to hardening. Induction process control limits the depth and pattern of hardness change. Induction hardening is used to harden specific sections of a part rather than the entire unit.
While heat treating is an effective and critical way to increase chain quality, there are many other manufacturing processes, such as stamping, bending, and interference fits, required to make a high-quality, long-lasting chain.
