Heat Treating

Heat treating can be broadly defined as the process of heating metal, holding for some period of time, and then cooling the metal at various rates to achieve the desired mechanical properties.  A wide range of properties can be obtained from metal of the same chemical content using different heat treatments.  CMC Impact Metals heat treating operations are primary focused around various grades of carbon and low alloy steels.  Below are short descriptions of common heat treating processes.

Quench and Temper

The typical goal of this process is to harden and strenghten the steel.  Strength and hardness can be increased by over 50% with this process, with no loss and sometimes even increasing ductility and impact toughness of the steel.  This process can also be used to create steels of very high hardness (400 Brinell Hardness and above) that are used in abrasion resistant and armor plate applications.  The typical cycle for Quench and Temper involves heating the steel to 1550-1700F until fully uniform, and then rapidly quenching (cooling) in water or other quenchant like oil or polymer solution.  Then the steel is typically tempered at 800-1200F depending on the desired final properties.  The higher the temper the lower the resulting hardness of the steel.

Normalizing

This process is performed to make the internal structure of the steel more uniform.  It involves heating the steel to 1600-1750 F, holding until the material is fully, and then cooling in air.  This treatment will often improve the impact resistance and ductility properties of the material with little or no decrease in strength.  Often material is quenched and tempered after a normalizing cycle.  The normalizing will often improve a steel's response to quenching and tempering.

Annealing

The primary purpose of annealing is to produce a soft, pliable material suitable for machining, drawing, or other cold working processes.  The Annealing process involves heating the material to about 1500 F, and then cooling very slowly until the material reaches 1250-1300 degrees, and then cooling in still air.  Varying the speed of the 1500F to 1250F cooling cycle results in different internal structures in the steel that are tailored to the intended subsequent processing.