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• The amount of carbon present in plain carbon steel has a pronounced effect on the properties of a steel and on the selection of suitable heat treatments to attain certain desired properties. • Heat treatment is a method used to alter the physical, and sometimes chemical properties of a material. The most common application is metallurgical • It involves the use of heating or chilling, normally to extreme temperatures, to achieve a desired result such as hardening or softening of a material • It applies only to processes where the heating and cooling are done for the specific purpose of altering properties intentionally Types • Annealing • Normalizing • Hardening • Carburizing • Tempering Annealing Steel is annealed to reduce the hardness, improve machine ability, facilitate cold-working, produce a desired microstructure. Full annealing is the process of softening steel by a heating and cooling cycle, so that it may be bent or cut easily. In annealing, steel is heated above the transformation temperature to form austenite, and cooled very slowly, usually in the furnace. Types of Annealing 1. Stress-Relief Annealing (or Stress- relieving) 2. Normalizing 3. Isothermal Annealing 4. Spheroidizing Annealing (or Spheroidizing ) 1. Stress-Relief Annealing • It is an annealing process below the transformation temperature Ac1, with subsequent slow cooling, the aim of which is to reduce the internal residual stresses in a workpiece without intentionally changing its structure and mechanical properties
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