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It exists several processes to harden a metal:
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The second one is to work harden the metal (pure or alloyed) by cold forming. That's true for all metals or alloys whatever they are. When a metal is formed, it is so "hard", then it has no longer its "flexibility" and its deformation ability. For giving back its "flexibility" and for softening it, just heat up it and bake. The metal or the alloy is so in its softer state called annealing and symbolized by the letter "O".
Work hardening condition: The work hardening conditions are symbolized by the letter "H" followed by the figure 1 and a figure that represents the work hardening quantity, indicating the hardness level. Partially annealed: The intermediate work hardening conditions are obtained from an annealed metal by a partial work hardening. To obtain the corresponding mechanical characteristics to these states, it exists an other process: from a totally work hardening condition, the product is reheated at a lower temperature than the one of the work hardening. Stabilized conditions: The products obtained by work hardening of which the state is symbolized by H1x, keep internal stresses during that deformation process, they are "fibrous". That may be prejudicial to their use. To eliminate these stresses, they are put in a low temperature furnace for making them a stress relief and stabilization
treatment. That treatment does not very much modify the mechanical characteristics obtained during the work hardening process. ·
The third process to harden an alloy can be used only for some alloys; for the aluminum, only the alloys from series 2000, 6000 and 7000 can be hardened by this way that is called age hardening. The strain hardening and the age hardening can, of course, be combined for these alloys; they can so reach very strong mechanical characteristics. The delivery states for the products having had an age hardening treatment are symbolized by the letter "T" followed by one or several figures depending if they are aged or artificial aged, simply quenched or strain hardened after quenching. |
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Initial states: F : Without treatment: no age hardening or strain hardening control has been used and no properties limit has been given. O : Annealing: it is applied to the wrought products that are annealed to obtain the lowest mechanical resistance state. It is also applied to the cast products that are annealed for increasing their ductility and their size stability. The letter O can be followed by a figure. O1 : Annealed at a high temperature and slow cooling - O2: Special heat treatment - O3 : Homogenized. H : Strain hardening (only wrought alloys): it is applied to the products of which the resistance is increased by strain hardening, with or without added heat treatments that decrease the resistance. T : Heat treatments to obtain a stable state other than F, O or H with or without added strain hardening. W : Solution treatment : that unstable temper is applied only to the alloys that spontaneously age at an ambient temperature after a heat treatment. The designation is used when the aging period is indicated, for example: W 1/2 h. |
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Hardening by strain hardening (series 1000, 3000, 5000): |
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In addition, it exists other strain hardened tempers: Age hardening (series 2000, 4000, 6000, 7000) : |
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| The alloys from the families 2000, 6000 and 7000 can be hardened by heat solution treatment and quenching followed by an age hardening that is made:
T51, T56 : standardized state only in the European standard NF EN 515 (October 1993). The quenching that follows the heat solution treatment introduces in a lot of products some internal stresses that deform them and that may damage to some processes; so, the products are stress relieved by extension, by compression or by both of them; the designation of the corresponding states is obtained by adding after the above mentioned figures following the letter "T", the following figures: Txx51 ou Txx510 : stress relief by extension with no added straightening after the extension. |
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The old tempers designation according to NFA is defined as follows: The letter X followed by three figures (ex X616) The first figure represents the working out process:
The second figure represents the treatment:
The third figure represents the hardness level:
Example X446 : Hot rolling + quenching + planishing + natural aging |
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Tempers of wrought coppers and alloys of coppers: |
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Some alloys may be hardened by heat treatment; the corresponding states although listed in the
standard NF A 02-008 are rarely used; the following terms are preferred:
TR : quenched - artificial aged These alloys are lightly alloyed coppers such as CuCr, CuCrZr, CuFe, CuCo (TER or TRE), CuNiSi (TER), CuBe2, CuCoBe and some cupro-nickels ( TE or TER). |
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| Non tempering tempers (Copper with beryllium): | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Special alloys tempers:
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Generally, the designation of the tempers includes 4 alphanumeric characters: The first character must be a capital letter that indicates a characteristic obligatory for pointing out:
The ranks 2 to 4 correspond to 3 figures showing the minimum value of the specified compulsory property (except for D, G and M). For D and M, not any other character follows. For the properties of G, the 3 figures indicate the median value of the obligatory property. A fourth figure may also be added, for example for some high tensile strength alloys able to be treated at high temperature. If a stress relief treatment is necessary, the suffix S is added. |
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Correspondences of the tempers of copper alloys according to the standards:
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