The first two - casehardening and full-hardening steels - are interchangeable for some kinds of service, and the choice is often a matter of personal opinion. In the case of some of the alloys, better machining qualities or the possibility of machining at higher hardnesses.Įach of the two general classes of gear steels may be further subdivided as follows: 1) Casehardening steels 2) full-hardening steels and 3) steels that are heat-treated and drawn to a hardness that will permit machining.Finer grain size, with the resulting higher impact toughness and increased wear resistance.Increased toughness, as indicated by the higher values of yield point, elongation, and reduction of area.
Ability to obtain the same surface hardness with a less drastic quench and, in the case of some of the alloys, a lower quenching temperature, thus giving less distortion.Increased surface hardness and depth of hardness penetration for the same carbon content and quench.The advantages obtained from using heat-treated alloy steels in place of heat-treated plain carbon steels are as follows: The points to be considered in determining whether to use heat-treated plain carbon steels or heat-treated alloy steels are: Does the service condition or design require the superior characteristics of the alloy steels, or, if alloy steels are not required, will the advantages to be derived offset the additional cost? For most applications, plain carbon steels, heat-treated to obtain the best of their qualities for the service intended, are satisfactory and quite economical. The use of untreated alloy steels for gears is seldom, if ever, justified, and then, only when heat-treating facilities are lacking. Alloy steels are used to some extent in the industrial field, but heat-treated plain carbon steels are far more common. Gear steels may be divided into two general classes - the plain carbon and the alloy steels. This article provides a review of the different metallic and non-metallic gear materials, gear applications, as well as power transmission calculations. The selection of specific material types for use in the fabrication of gears ultimately is a balance between needed strength, durability, and cost.