Heat treatment of beryllium bronze
May 17, 2019
Beryllium bronze is an extremely versatile precipitation hardening alloy. After solid solution and timely treatment, the strength can reach 1250-1500MPa (1250-1500 kg). The heat treatment characteristics are: good plasticity after solution treatment, and cold work deformation. However, after the aging treatment, it has an excellent elastic limit, and the hardness and strength are also improved.
(1) Solution treatment of beryllium bronze
Generally, the heating temperature of the solution treatment is between 780 and 820 ° C. For the material used as the elastic component, 760-780 ° C is used, mainly to prevent the coarse grain from affecting the strength. The temperature uniformity of the solution treatment furnace should be strictly controlled at ±5 °C. The holding time can be generally calculated as 1 hour / 25 mm, and when the beryllium bronze is subjected to solution heat treatment in air or an oxidizing atmosphere, an oxide film is formed on the surface. Although it has little effect on the mechanical properties after aging strengthening, it will affect the service life of the tool during cold working. In order to avoid oxidation, it should be heated in a vacuum furnace or ammonia decomposition, an inert gas, a reducing atmosphere (such as hydrogen, carbon monoxide, etc.) to obtain a bright heat treatment effect. In addition, care should be taken to minimize the transfer time (when this is quenched), otherwise it will affect the mechanical properties after aging. Thin materials must not exceed 3 seconds, and general parts should not exceed 5 seconds. Quenching media generally use water (no heating requirements), of course, parts with complex shapes can also be used to avoid deformation.
(2) Aging treatment of beryllium bronze
The aging temperature of beryllium bronze is related to the content of Be, and the alloy containing Be less than 2.1% is suitable for aging treatment. For alloys with Be greater than 1.7%, the optimum aging temperature is 300-330 ° C and the holding time is 1-3 hours (depending on the shape and thickness of the part). For high conductivity electrode alloys with Be below 0.5%, the optimum aging temperature is 450-480 ° C and the holding time is 1-3 hours due to the increase of melting point. In recent years, two-stage and multi-stage aging has also been developed, that is, aging at a high temperature for a short period of time, and then aging for a long time at a low temperature, which has the advantage of improved performance but reduced deformation. In order to improve the dimensional accuracy of the beryllium bronze after aging, the clamp can be used for aging, and sometimes two separate aging treatments can be used.
(3) De-stressing treatment of beryllium bronze
Beryllium bronze stress relief annealing temperature is 150-200 ° C, holding time 1-1.5 hours, can be used to eliminate residual stress caused by metal cutting, straightening treatment, cold forming, etc., to stabilize the shape and dimensional accuracy of parts in long-term use.
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