Heat Treatment
Heat treatment is a process used in materials engineering and metallurgy to change the physical properties of metals and alloys. Treatments include annealing, hardening, stress relieving, normalizing, tempering, and quenching. Heat treatment is used to improve or alter the mechanical, electrical, and chemical properties of a material. Heat treating requires an understanding of various thermochemical reactions in order to choose the best method to achieve the desired outcome.
Heat treatment is used in the production of metals, ceramics, and other materials. Metals are transformed into a variety of shapes, sizes, and qualities by the application of heat. The process allows metals to go through stages of softening, hardening, and tempering. During these changes, the chemical composition of the metal remains the same, but its mechanical and physical properties are altered. Depending on the heat treatment process, metals can increase in strength while retaining their ductility.
The heat treatment process used depends on the type of metal being treated. Aluminum, for instance, is generally annealed, cold worked, and then aged at a predetermined temperature. Steel is typically heated at high temperatures in order to produce a desired hardness, strength, and ductility.
Heat treatment is most commonly used to form martensite microstructure. This microstructure consists of small crystals that are hardened within the steel or alloy. In order to create martensite structure, the steel or alloy is rapidly cooled to below a certain temperature. This rapid cooling process is known as quenching. Quenching yields a end product characterized by excellent wear resistance, high tensile strength, and low ductility.
Heat treatment can also be achieved by a process known as carburizing or case hardening. Carburizing or case hardening is the process of introducing carbon into the metals’ surface layer to increase the carbon content and attain higher strength, wear resistance, and fatigue strength. The carbon is introduced to the metals’ surface layer using a carburizing gas, salt bath, or pack carburizing.
Heat treatment is an integral process in manufacturing, it is essential for creating specific properties within the metal that are otherwise not achievable. Heat treatment is used to improve the strength, wearability, and durability of various metals and alloys. By understanding the different heat treatment methods, manufacturers can ensure the desired results are achieved.
