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This is the most common state for finished articles such as tools and machine parts. In contrast, the same steel composition in annealed state is softer, as required for forming and machining. Depending on the temperature and composition of the steel, it can be hardened or softened. To make steel harder, it must be heated to very high temperatures.
AerMet 340 is hardened differently from the other two varieties. The first hardening application is a solution treatment at 1,775 °F (968 °C) for 1 hour. It is then quenched to a temperature of 150 °F (66 °C) over 1 to 2 hours. The material may then be cold treated, where the material is cooled to −100 °F (−73 °C) for 1 hour.
Steel can be softened to a very malleable state through annealing, or it can be hardened to a state as hard and brittle as glass by quenching. However, in its hardened state, steel is usually far too brittle, lacking the fracture toughness to be useful for most applications. Tempering is a method used to decrease the hardness, thereby ...
This causes carbon to diffuse into the surface of the steel. The depth of this high carbon layer depends on the exposure time, but 0.5mm is a typical case depth. Once this has been done the steel must be heated and quenched to harden this higher carbon 'skin'. Below this skin, the steel core will remain soft due to its low carbon content.
Martensitic transformation, more commonly known as quenching and tempering, is a hardening mechanism specific for steel. The steel must be heated to a temperature where the iron phase changes from ferrite into austenite, i.e. changes crystal structure from BCC (body-centered cubic) to FCC (face-centered cubic). In austenitic form, steel can ...
RHA is homogeneous because its structure and composition are uniform throughout its thickness. The opposite of homogeneous steel plate is cemented or face-hardened steel plate, where the face of the steel is composed differently from the substrate. The face of the steel, which starts as an RHA plate, is hardened by a heat-treatment process.
The cooling rate will be highest at the end being quenched, and will decrease as distance from the end increases. Subsequent to cooling a flat surface is ground on the test piece and the hardenability is then found by measuring the hardness along the bar. The farther away from the quenched end that the hardness extends, the higher the ...
SAE Type 630 stainless steel (more commonly known as 17-4 PH, or simply 17-4; also known as UNS S17400) is a grade of martensitic precipitation hardened stainless steel. It contains approximately 15–17.5% chromium and 3–5% nickel, as well as 3–5% copper. [1] The name comes from the chemical makeup which is approximately 17% chromium and 4 ...