Chain Heat Treat Practices: How to Achieve Optimum Strength?
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Chain Heat Treat Practices: How to Achieve Optimum Strength?

By Manufacturing Technology Insights | Tuesday, December 03, 2019

Heat TreatmentHeat treatment of metal assists in achieving desired toughness, ductility, and durability. These practices help the manufacturers in achieving optimum strength.

Fremont, CA: Heat treatment is a method of heating and cooling of metals to change their physical properties without changing its shape. Heat treatment is used to improving materials formability and machining while maintaining adequate toughness and ductility. By heating, rapidly cooling, and sometimes chilling the metal to extreme temperatures can help achieve desired results. Heat treatment of metals is also predominantly used in the manufacturing of glass, aluminum, steel, and other materials.   

Every metal has a specific microstructure, and those molecules shift when the metal is heated. When the metal is rapidly cooled, the molecules stay in their new microstructure and increase the toughness and hardness levels while increasing the durability and wear resistance of the components. In the manufacturing process of a chain, the components are heat treated separately before assembly facilitating the setting of target properties of each element to their ideal state. Out of all the chain heat treatment practices, these three are the most common methods.

Metal Working

Carburizing - Case Hardening

Carburizing is a heat treatment process in which steel or iron is heated to a temperature below the melting point and exposing it to carbon. Adding carbon to the heating process alters the chemistry of the metal, making it more responsive to heat treatment while maintaining softer and more tensile core hardness. During the carburizing process, the exposed surfaces absorb the carbon, and the depth of penetration is proportional to the time in the furnace.       

Through Hardening

Through Hardening hardens and strengthens the material by heating, quenching, and tempering. Different from other processes that harden the outer layer, Through Hardening toughen the material evenly throughout. As a result, the tempered steel is harder and stronger but at the same time, has sufficient ductility and toughness. The hardening process starts with heating the steel and keeping it at a consistent temperature until all pearlite is transformed into austenite and then rapidly cooling it in water or oil. The austentizing process is based upon the carbon content in the steel. To entirely turn the core into austenite, the heating time should be consistently increased. 

Induction Hardening

Induction Hardening is similar to Through Hardening, but it is done in a controlled fashion. The part of the metal is heated above their melting point while being placed inside water-cooled cooper oil by applying an alternating current to the coil. An alternating magnetic field is induced by an alternating current in the coil, which causes the outer surface of the part to heat to a temperature above the transformation range. 

Parts are kept at a consistent temperature until the desired hardening is achieved and then quenched in oil or coolant of choice. Induction hardening is chosen as a second option on top of through hardening. The induction process is a controlled process that limits the depth and pattern of the hardness. Induction Hardening is ideal for hardening a specific section of metal rather than the entire unit. While heat treating is an effective way to increase the quality of the chain, there are other chain heat treatment practices such as stamping, bending, and interference fits that make high-quality and long-lasting chains. 

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