Hardness

Hardness
Points : Hardness, Definition Definition Hardness can be thought of as the resistance of a metal to scratching, denting, drilling, filing, or other deformation. The hardness of metal has been placed on arbitrary scales. The first hardness scale developed compared metals to organic materials and is called Mohs’ scale. Mohs’ scale is commonly used to determine the hardness of rocks and minerals. On this scale 1 is talc, 2 is gypsum, 7 is quartz, 8 is to paz 9, is sapphire, and 10 s diamond.

The hardness of a metal may be changed by heat-treating. For example, a chisel may be made out of a medium-carbon steel and then heat-treated. In its heat-treated condition, the chisel can cut the ‘very metal from which it was made. The amount of hardness which it was made. The amount of hardness in a metal also indicates its brittleness. Generally, as the hardness of a metal increases its brittleness increases, proportionately. The hardness of the metal, however, does not relate directly to the hardenability of the metal. The hardenability of a metal is determined by a Jominy test that determines how well a metal hardens from its center to its interface. Many metals can be hardened only on the surface, while the interior remains unhardened. These metals are said to have low hardenability. A metal that is capable of being hardened throughout its structure is said to have high hardenability.