Practical heat treatment

Abstract

Components are heat treated to produce a change in mechanical properties by changing the type and proportion of phases present in the solid, the morpology of microconstituents or the concentration and distribution of crystal defects. Relieving stress, normalizing, annealing are some types of heat treatments. The heat treatments, such as carburising, nitriding and brazing, modify the chemical composition of the surface layer. The various phase transformations occur in metals according to thermodynamic basis, microstructural basis and mechanical basis. The microstructure of steels consists of a spatial arrangement of crystalline aggregates of different phases. The size, shape, distribution, composition, and crystal structure of these phases essentially control the final properties of any given steel, including hardness, strength, ductility, impact toughness, and creep strength. Heat treating of stainless steel serves to produces changes in physical condition mechanical properties and residual stress level and to restore maximum corrosion resistance when that property has been adversely affected by previous fabrication or heating. Both satisfactory corrosion resistance and satisfactory mechanical properties are obtained by means of same heat treating. In this section, we will investigate more detailed all of the these matters. © 2010 Nova Science Publishers, Inc. All rights reserved.