MORPHOLOGYAND MECHANICAL PROPERTIES OF GRAPHITIZED CARBON STEEL NEAR WELDED REGIONS

摘要

Carbon steel contains two structures, namely α-ferrite and pearlite. (Pearlite is a combination of a-ferrite and the metastable phase Fe_3C). If thermodynamics are considered, the stable forms of the elements present in carbon steels are α-ferrite and carbon in the form of graphite. As a consequence Fe_3C may decompose to form ferrite and graphite. At low temperatures, the kinetics of the Fe_3C decomposition reaction is slow, and therefore it is likely that other less stable phases may decompose faster than Fe_3C. Such less stable phases exist in close proximity to welds and are associated with material that was heated during the arc welding process.