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| Hardening of Cams |
| Through Hardening: Good |
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Through Hardening involves heating the steel to a point beyond its transformation point so that it becomes entirely austenitic in structure, the steel is then quenched at a rate faster than its critical rate (which depends on the materials carbon content, amount of alloying elements present other than carbon and the grain size of the austenite) to produce a martensitic structure. The hardness range varies depending upon carbon content from 460 - 710 Brinell (49 - 63 Rockwell C).
When a steel is through hardened it becomes very brittle, much as in the same way as a piece of glass, through hardening is suitable for some components but when a through hardened component is subjected to a shock load such as an emergency stop in a cam indexer then small cracks will be generated in the cam, after a period of time even with out another E-stop incidence the crack can propagate and eventually cause the cam to fail. |
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| Nitride Hardening : Better |
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The steel part is heated to a temperature of 900-1150 degrees F in an atmosphere of ammonia gas and dissociated ammonia for an extended period of time that depends on the case depth desired. A thin, very hard case results from the formation of nitrides. Strong nitride-forming elements are required to be present in the steel, and often special nonstandard grades containing aluminum are used. The major advantage of this process is that parts can be quenched and tempered then machined prior to nitriding because only a little distortion occurs during the process.
Nitride hardening is used by some of our competitors because it is relatively cost effective and the components can be finish machined and then hardened, because only a very thin 0.005-0.020” outer case is hardened the part is relatively stable and does not distort, a surface hardnesses of 55 HRC to 70 HRC can be achieved. |
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| Induction Hardening : BEST |
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The hardening of steel by means of induction heating and subsequent quenching in either liquid or air is particularly applicable to parts that require localized hardening or controlled depth of hardening to irregularly shaped parts, such as cams that require uniform surface hardening around their contour.
There are several advantages for induction hardening cams, firstly the depth of hardening can be controlled very accurately this means that the core of the cam remains ductile and therefore will resist shock loading, also because only the desired surfaces are being hardening distortion is kept to a minimum. Induction hardening also offers a much shorter heating cycle, with components can be hardening and finished in a fraction of the time required for other methods. |
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