Structure Properties and Treatment of Steels - Assignment Example

There are only two factors that will change the position of the curves of the I-T diagram, namely, chemical composition and austenitic grain size. With few exceptions, an increase in carbon or alloy content or in grain size of the austenite always retards transformation   (moves the curves to the right), at least at temperatures at or above the nose region. This, in turn, slows up the critical cooling rate, making it easier to form martensite. This retardation is also reflected in the greater hardenability or depth of penetration of hardness of steel with higher alloy content or larger austenitic grain size.

The first three methods change the chemical composition, carburizing by the addition of carbon, nitriding by the addition of nitrogen, and cyaniding by the addition of both carbon and nitrogen. The flame hardening and induction hardening processes do not change the chemical composition of the steel and are essentially shallow-hardening methods. Inflame and induction hardening the steel must be capable of being hardened, therefore the carbon content must be about 0.30 percent or higher. So in the case of 0.

6 % plain carbon steel, we have got only two surface hardening processes left and these are flame hardening and induction hardening process. These two are essentially the shallow hardening methods. Selected areas of the surface of steel are heated into the austenite range and then quenched form martensite. Therefore, it is necessary to start with steel which is capable of being hardened. Generally, this is in the range of 0.3 to 0.6 percent carbon. So depending upon the other required properties of the steering shaft the most appropriate method of surface hardening is induction hardening.