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Case Hardening

written by: Senadheera Jayakody • edited by: Lamar Stonecypher • updated: 2/27/2010

Case hardening is a process that is used to harden the outer layer of case hardening steel while maintaining a soft inner metal core. The case hardening process uses case hardening compounds for the carbon addition. Steel case hardening depth depends upon the application of case hardening depth.

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    What Is Case Hardening

    Case hardening is a technique in which the metal surface is reinforced by the adding of a fine layer at the top of another metal alloy that is generally more durable. Case hardening steel is normally used to increase the object life. This is particularly significant for the manufacture of machine parts, carbon steel forgings, and carbon steel pinions. Case hardening is also utilized for other applications. Case hardening is also called surface hardening. Case hardening has been in use for many centuries, and was frequently used for producing horseshoes and different kinds of cooking utensils that were subjected to substantial wear and tear. Case hardening is essentially a group of processes that are used to increase the surface hardness to an extent that is higher than that of the bulk material. Case hardening is performed normally locally on the top surface, and for a limited depth. Greater hardness is usually related with better wear and fatigue resistance.WHAT IS CASE HARDENING 

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    Case Hardening Process

    The addition of carbon to the iron surfaces is common. Case hardening involves the use of metal that has low carbon contents, and combining it with a metal that has more carbon content. The grouping of metals is likely to produce the product that is much harder. The adding of the low carbon metal creates a material that can be molded easily into the desired shapes. The surface improvement not only increases the product strength, but also assists to avoid the iron weakening. Consequently, items like fireplace equipment, cast iron wash pan, and frying utensils would continue to be serviceable for long periods of time. Case hardening is frequently utilized in the constructing industry for reinforcing girders, metal doors, and metal panels. Case hardening is generally performed after the formation of the component into its ultimate form.CASE HARDENING PROCESS 

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    Components that are subjected to severe impacts and high pressures are generally case hardened. The surfaces that need special hardness may be selectively hardened, without performing case hardening of the remaining object. Firearms are a usual item that is case hardened, as they need accuracy in machining and higher hardness for performing the desired functions. Another general application of the case hardening is on camshafts and special purpose screws, mainly the self drilling screws. Case hardening is less complex for fasteners and screws since it is performed simply by heating and quenching. Case hardening of smaller items is performed by repetitive heat application.APPLICATIONS 

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    Steel Case Hardening

    Carbon is penetrated into the metal skin to create mild steel that has an external covering with more carbon than the nucleus. The mild steel is subjected to heating at a particular temperature, till it is bright red. While the mild steel is soft, it is immersed into a carbon compound that covers the outer surface. One dipping may not be adequate, and several re-heating and dipping may be necessary. This procedure will produce a skin that is rich in carbon. Subsequently, the metal is reheated and dropped in water for hardening. Case hardening is useful for objects that need to be hardened externally to endure wear and tear, but soft internally to withstand shock.STEEL CASE HARDENING