Hardenability is often the single most important factor in selecting steel for heat treating parts. Hardenability describes the ability of a steel part to be quench hardened by martensitic transformation and is related to parameters such as austenitizing temperature, cooling rate after austenitizing, part size and shape. Hardenability is also often referred to as the inverse measure of the quench severity required to quench a steel heated at the austenitizing temperature into martensite without the formation of diffusion transformation structures such as P and B.
The hardenability of a steel is a function of the carbon content, other alloying elements, and the austenite grain size. The relative importance and influence of the various alloying elements are calculated by determining the carbon equivalent of the steel. In general, the higher the carbon content, the higher the hardenability. Alloying elements such as Ni, Mn, Cr, Mo tend to increase the depth of hardening.
It depends on the carbon content and other alloying elements and the grain size of the austenite phase. Methods have been found to calculate hardenability based on the chemical composition of the steel. The relative importance and influence of the various alloying elements are determined by calculating the carbon equivalent. One advantage of calculated hardenability is that it can be predicted for various steels using a limited number of experimentally measured data (based on end quench test procedures as well as grain size and chemical composition data). A more practical advantage of calculated hardenability is the potential for individualization of heat treatment processes, which can be tailored to suit the hardness profile cross section of the final heat treatment to specific customer requirements.
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