Spheroidizing

Thermal treatments for steel that causes the carbides to agglomerate in the form of small spheres, or globules. Steel is spheroidized to obtain minimum hardness with maximum ductility for further cold-forming operations. This improves the machinability of high carbon steels but reduces it for low-carbon steels. There are several methods for spheroidize annealing, all of which include heating to a specified temperature followed by very slow cooling. The specific treatment depends on several factors, including the chemical composition of the steel, its microstructure and forming history, and the condition and properties required in the product. When applied to wire or rod for the purpose of facilitating subse­quent drawing, it is common to make provision for air, or air and steam, to be admitted to the furnace to promote scaling of the material.