Flame Hardening 1. In the process of hardening the steel is developed in such controlled conditions,by rapid quenching, that the transformation is disallowed at the lower critical point and by doing so we force the change to take place at a much lower temperature. Hardening is a heat treatment process carried out to increase the hardness of Steel. Induction hardening is commonly used to heat treat gears as it is a quick process that takes very little time. They may be required to withstand various types of stresses and as tool materials to have hardness, specially red hardness, combined with toughness along with anon-brittle cutting edge. The main purpose of spheroidise annealing is to produce a structure of steel which consists of globules or well dispersed spheroids of cementite in ferrite matrix. Hardening: Hardening is a heat treatment process in which steel is rapidly cooled from austenitising temperature. Held at this temperature for a considerable time to ensure thorough penetration of heat at this temperature well inside the component and then allowed to cool separately by quenching in water oil or brine solution. Cooling the metal at a predetermined rate in a suitable media so as to force the metal to acquire a desired internal structure and thus, obtain the desired properties to the required extent. Tempering is a low temperature (below A1) heat treatment process normally performed after neutral hardening, double hardening, atmospheric carburising, carbonitriding or induction hardening in order to reach a desired hardness/toughness ratio. For oil heating the bath temperature is first raised to the required tempering range and then partially heated component is immersed in it. There are different Heat Treatment processes are available. However, a brief review is given: 6.3 Classification of Heat Treatment Processes. By rapid cooling the time allowed to the metal is too short and hence transformation is not able to occur at the lower critical temperature. Heat Treatment of steels is called the heating and cooling process to achieve certain microstructural features for a wide range of applications. It is especially true in case of the tools. Precipitation hardening, also called age or particle hardening, is a heat treatment process that helps make metals stronger. To increase the Hardness of the Metals. Stress relieving 6. Case hardening is also famous as surface hardening. The higher the frequency or the shorter the heating time, the lower the hardness layer depth. Then full annealing is performed. Tempering 7. Normalising 3. On the basis of the ranges of temperatures to which the components are reheated for tempering, the tempering procedures are classified as follows: This treatment results in reduction of internal stresses and improvement in toughness and ductility without any appreciable loss in hardness. The internal structure of the metal gets stabilized through this process. They may be required to bear static or dynamic loads,revolve at extremely high speeds, operate in highly corrosive media, carry an extremely hard skin with a tough core, subjected to fatigue and creep, etc.Such varying condition of their applications require these materials to possess specific properties of the required order to successfully serve under these conditions. The purpose of process annealing is to remove the ill effects of cold working and often the metal so that its ductility is restored and it can be again plastically deformed or put to service without any danger of its failure due to fracture. The aim of this process variant is the creation of bright metallic workpiece surfaces which render further mechanical processing unnecessary. Holding it at that temperature for sufficient time so that the structure of the metal becomes uniform throughout. The hardening process consists of heating the components above the critical (normalizing) temperature, holding at this temperature for one hour per inch of thickness cooling at a rate fast enough to allow the material to transform to a much harder, stronger structure, and then tempering. A hardened steel piece, due to martensitic structure, is extremely hard and brittle, due to which it is found unsuitable for most practical purposes. The isothermal annealing consists of heating steel to austenite state and then cooling it down to a temperature of about 630oC to 680oCat a relatively faster rate. 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