Hardenability

Hardenability
Points : Hardenability, Definition Definition For many years men concerned with the heat treatment of steel have used qualitative terms to describe certain facts about the way in which a particular steel responds to heat treatment, especially in the hardening process. It is quite possible that two steels, produced by the same general process and which have the same nominal chemical analysis, will exhibit marked differences in the depth of hardening when they are quenched from the same hardening temperature and in the same medium. When such differences in hardening characteristics are noted, a complete review of the chemical, thermal, and mechanical history of the steel-making and- forming processes will, of course, reveal significant differences in the way in which the steels were manufactured.

It is desirable to discuss the effects of alloying elements in increasing the depth of hardening in detail. Steels very similar in chemical composition, and having the same section size, when quenched from the same austenitizing temperature and under the same quenching conditions may exhibit different patterns of hardness across their cross-sectioned surfaces. Instead of a term such as timbreo which was previously used to describe the hardening characteristics of the steel, it is now the usual practice to use the term harden ability as a general term and even to evaluate this term numerically. By means of a suitable number system steels can be described in terms of their inherent hardenability. Qualitatively, steels may be either shallow hardening or deep hardening. The steel may have imparted to it, by virtue of the details of steel mill practice, a personality which an he classified and described primarily in terms of charts or graphs, since usually no single number will tell the complete story. With this type of information it is possible for purchasers to state the hardenability characteristics desired by means of relatively simple specifications.