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However, it is not beyond doubt that the passage describes deliberate quench-hardening, rather than simply cooling. [8] Likewise, there is a prospect that the Mahabharata refers to the oil-quenching of iron arrowheads, but the evidence is problematic. [9] Pliny the Elder addressed the topic of quenchants, distinguishing the water of different ...
Unlike differential hardening, where the entire piece is heated and then cooled at different rates, in flame hardening, only a portion of the metal is heated before quenching. This is usually easier than differential hardening, but often produces an extremely brittle zone between the heated metal and the unheated metal, as cooling at the edge ...
The quenching is required since the material otherwise would start the precipitation already during the slow cooling. This type of precipitation results in few large particles rather than the, generally desired, profusion of small precipitates. Precipitation hardening is one of the most commonly used techniques for the hardening of metal alloys.
Diagram of a cross section of a katana, showing the typical arrangement of the harder and softer zones. Differential hardening (also called differential quenching, selective quenching, selective hardening, or local hardening) is most commonly used in bladesmithing to increase the toughness of a blade while keeping very high hardness and strength at the edge.
The term hardened steel is often used for a medium or high carbon steel that has been given heat treatment and then quenching followed by tempering. The quenching results in the formation of metastable martensite, the fraction of which is reduced to the desired amount during tempering. This is the most common state for finished articles such as ...
The two important aspects of quenching are the cooling rate and the holding time. The most common practice is to quench into a bath of liquid nitrite-nitrate salt and hold in the bath. Because of the restricted temperature range for processing it is not usually possible to quench in water or brine, but high temperature oils are used for a ...
Quenching is the process of cooling metal very quickly after heating, thus "freezing" the metal's molecules in the very hard martensite form, which makes the metal harder. Tempering relieves stresses in the metal that were caused by the hardening process; tempering makes the metal less hard while making it better able to sustain impacts without ...
Many different methods and cooling baths for quenching have been attempted during ancient times, from quenching in urine, blood, or metals like mercury or lead, but the process of tempering has remained relatively unchanged over the ages. Tempering was often confused with quenching and, often, the term was used to describe both techniques.