VIEWS: 9 PAGES: 2 POSTED ON: 2/18/2011
There are several procedures of heat treatment for steel and other materials, annealing being one of them. Different industries have different mechanization requirement for steel and other materials, and the different processes of heat treatment are a way to impart characteristics like optimal hardness and adequate malleability to the materials. In the annealing process steel is heated to a specific temperature in the austenite area and then cooled gradually. The procedure is used to gain rough equilibrium state in materials, for instance steel is subjected to the process to get a ferrite-pearlite microstructure. There are several advantages of the process, which are also the reason why this process is so widely used across the industry. Improves and enhances machinability of steel Enhances ductility of the material The material is softened through the process The material becomes stronger The molecular structure of the element becomes more homogenous and hence the material becomes more industrially usable. The grain structure of the element is refined and improved. The material becomes ready for further heat treatment through other processes. There are several derivatives of the annealing process depending on specific thermal cycles. And, depending on the materials that need heat treatment and the result specifications, the processes may differ. For the treatment of steel it is heated through an annealing furnace or sometimes even through other sources of heat. The material is often kept in touch with carbon for it to be carburized in the process and is heated to a particular temperature, depending on its carbon content. The general rule of thumb is that the higher the carbon content of the steel the lower the temperature required. The temperature that is normally required for a successful treatment ranges from 760 to 910 degrees Celsius. Heating steel to these temperatures changes the internal molecular structure of the element. Before the process is undertaken, steel is usually pearlite, which means it normally has overlapping layers of alpha-ferrite and cementite. Alpha-ferrite usually constitutes 88% of steel and is dissolved through this process forming austenite crystals. It is advisable to let the steel cool very slowly and gradually during the process. Particularly because it is during the cooling process that the austenite gradually transforms back into pearlite crystals, leaving significant changes to the composition of the element. After a successful treatment procedure, steel contains the large ferrite molecules interspersed between the pearlite crystals. The slower the cooling process the better the formation of this structure. Again, heating the steel to temperatures that are beyond the specified limit may cause the steel to be brittle due to the formation of large austenite crystals. To conduct annealing or any other heat treatment process successfully, hence, heating to the right temperature and then cooling at a specified rate is very important. There are several processes of annealing like bright annealing, process annealing, recrystallization annealing, sub critical annealing, spheroid annealing, isothermal annealing, full annealing, etc. Each process is instrumental in producing different varieties of steel that can be used for different industry requirements. For instance, spheroid annealing is used to produce alloys of steel, and recrystallization annealing is done to impart a distinguishing grain structure to the element. Annealing is popularly used heat treatment process in the industry to impart strength and flexibility to industrial metals like steel. Log on to www.heat-treat.co.uk to find professional annealing and other heat treatment services at reasonable prices.
Pages to are hidden for
"Annealing And Heat Treatment "Please download to view full document