Hardenability
1834808
156005371
2007-09-06T07:02:49Z
DocWatson42
38455
Moved the "External links" section.
[[Image:Jominy_test.png|thumb|right|300px|Cross-section of Jominy test apparatus. Water from a pipe cools the bottom of the specimen and then hardness measurements are taken across the length of the specimen.]]
The '''hardenability''' of a [[metal]] [[alloy]] is its capability to be hardened by [[heat treatment]]. It should not be confused with [[hardness]], which is a measure of the material's resistance to indentation or scratching. It is an important property for [[welding]], since it is inversely proportional to [[weldability]], that is, the ease of welding a material.
The hardenability of [[ferrous]] alloys, namely [[steel]]s, is a function of the [[carbon]] content and other alloying elements, the grain size of the [[austenite]], and the cooling rate. The relative importance of the various alloying elements is calculated by finding the [[equivalent carbon content]] of the material. The fluid used for [[quench]]ing the material influences the cooling rate due to varying [[thermal conductivity|thermal conductivities]] and [[specific heat]]s. Substances like [[brine]] and [[water]] cool much more quickly than [[oil]] or [[air]]. Additionally, if the fluid is agitated, cooling occurs even more quickly. The geometry of the part also impacts the cooling rate; if the surface area to volume ratio is high, the material will cool faster.
To test the hardenability of a ferrous alloy, a [[Jominy test]] is used. A round metal bar of standard size is transformed to 100% austenite through heat treatment. It is then quenched on one end with room temperature water. As a result, the cooling rates throughout the material will vary significantly, being highest at the end being quenched. The hardenability is then found by measuring the hardness throughout the bar. The farther away from the quenched end that the hardness exists, the higher the hardenability.
==References==
*Kalpakjian, Serope, et al. (2001). ''Manufacturing Engineering and Technology''. Pearson Education.
==External links==
*[http://www.doitpoms.ac.uk/tlplib/jominy/hardenability.php Description]
*[http://www.matter.org.uk/steelmatter/metallurgy/7_1.html Hardenability vs. hardness]
*[http://www.matter.org.uk/steelmatter/metallurgy/7_1_1.html Jominy test simulation]
[[Category:Metalworking]]
[[Category:Alloys]]
[[ja:焼入れ性]]