On 2018-08-08 14:48:54
Heat treatment of beryllium bronze
Beryllium bronze is a widely used precipitation hardening alloy. After solid solution and aging treatment, the strength can reach 1250-1500 mpa (1250-1500 kg). Its heat treatment characteristic is: after the solid solution treatment has the good plasticity, may carry on the cold processing deformation. However, after the aging treatment, it has an excellent elastic limit, and the hardness and strength are also improved.
(1) solid solution treatment of beryllium bronze
Generally, the heating temperature of solid solution treatment is between 780-820℃. For materials used as elastic components, 760-780℃ is adopted to prevent the grain size from affecting the strength. The temperature uniformity of solid solution treatment furnace should be strictly controlled at ±5℃. The holding time can be calculated as 1 hour /25mm in general. When beryllium bronze is heated by solid solution in air or oxidizing atmosphere, the surface will form an oxide film. Although it has little effect on the mechanical properties after aging, it will affect the service life of the cold working die. To avoid oxidation, heat in vacuum furnace or ammonia decomposition, inert gas, reducing atmosphere (such as hydrogen, carbon monoxide, etc.), so as to obtain bright heat treatment effect. In addition, attention should be paid to minimize the transfer time (when the water is quenched), otherwise it will affect the mechanical properties after aging. The thin material shall not exceed 3 seconds, and the general parts shall not exceed 5 seconds. Quenching medium is generally water (no heating requirements), of course, the shape of complex parts in order to avoid deformation can also be used oil.
(2) aging treatment of beryllium bronze
The aging temperature of beryllium bronze is related to the content of Be. All alloys containing Be less than 2.1% should Be aging treatment. For the alloy with Be greater than 1.7%, the optimal aging temperature is 300-330℃ and the holding time is 1-3 hours (according to the shape and thickness of the parts). The best aging temperature is 450-480℃ and the holding time is 1-3 hours for the high conductivity electrode alloy with Be less than 0.5% due to the increase of dissolution point. In recent years, a two-stage and multi-stage aging system has been developed, that is, a short-time aging system at high temperature and a long-term aging system at low temperature. This method has the advantage of improving performance but reducing deformation. In order to improve the dimensional accuracy of beryllium bronze after aging, clamping devices can be used for aging, and sometimes two separate aging treatments can be used.
(3) destress treatment of beryllium bronze
The annealing temperature of beryllium bronze is 150-200℃ and the holding time is 1-1.5 hours, which can be used to eliminate the residual stress caused by metal cutting, straightening, cold forming, etc., and stabilize the shape and dimensional accuracy of parts in long-term use.