Beryllium bronze is a kind of precipitation hardening alloy with very wide application. After solid solution and aging treatment, the strength can reach 1250-1500MPa (1250-1500 kg). Its heat treatment characteristics are: after solution treatment, it has good plasticity and can be deformed by cold working. But after aging treatment, it has an excellent elastic limit, while the hardness and strength are also improved.
1 Solution treatment of beryllium bronze
Generally, the heating temperature of solution treatment is between 780-820℃. For materials used as elastic components, 760-780℃ is used to prevent the coarse grains from affecting the strength. The temperature uniformity of the solution treatment furnace should be strictly controlled at ±5°C. The holding time can generally be calculated as 1 hour/25mm. When beryllium bronze is solid-solution heated in air or oxidizing atmosphere, an oxide film will form on the surface. Although it has little effect on the mechanical properties after aging strengthening, it will affect the service life of the cold working mold. In order to avoid oxidation, it should be heated in a vacuum furnace or ammonia decomposition, inert gas, and reducing atmosphere (such as hydrogen, carbon monoxide, etc.) to obtain a bright heat treatment effect. In addition, pay attention to shorten the transfer time as much as possible (in this quenching), otherwise it will affect the mechanical properties after aging. Thin materials should not exceed 3 seconds, and general parts should not exceed 5 seconds. Quenching medium generally uses water (no heating requirement), of course, oil can also be used for parts with complex shapes to avoid deformation.
2 Aging treatment of beryllium bronze
The aging temperature of beryllium bronze is related to the content of Be, and alloys with Be less than 2.1% should be aged. For alloys with Be greater than 1.7%, the best aging temperature is 300-330℃, and the holding time is 1-3 hours (according to the shape and thickness of the part). For highly conductive electrode alloys with Be less than 0.5%, the best aging temperature is 450-480℃, and the holding time is 1-3 hours due to the rising melting point. In recent years, two-stage and multi-stage aging have also been developed, that is, first aging at high temperature for short time, and then aging at low temperature for a long time. The advantage of this is that the performance is improved but the deformation is reduced. In order to improve the dimensional accuracy of beryllium bronze after aging, clamps can be used for aging, and sometimes two separate aging treatments can be used.
3 Stress relief treatment of beryllium bronze
The stress relief annealing temperature of beryllium bronze is 150-200℃, and the holding time is 1-1.5 hours. It 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 .