Description
Static contacts refer to the contacts of switches, relays, and contactors that do not move with the actuator, also called static contacts. The opposite is a moving contact. The connection and disconnection of high-voltage switches depend on it, and its service life determines the life of the high-voltage switch, and thus determines the safe operation of the high-voltage transmission and transformation network. When the contact is working, it relies on its rigidity to generate a pressing force on the moving contact. Therefore, in addition to requiring high conductivity, the contact parts are also required to have high strength and rigidity.
Static contacts are key components of high-voltage switches. The connection and disconnection of high-voltage switches depend on it, and its service life determines the life of the high-voltage switch, and thus determines the safe operation of the high-voltage transmission and transformation network. When the contact is working, it relies on its rigidity to generate a pressing force on the moving contact. Therefore, in addition to requiring high conductivity, the contact parts are also required to have high strength and rigidity. However, the manufacturing department often produces contacts as a simple electrical appliance in an extensive manner and does not pay enough attention to product design, material selection, processing technology, and quality control. With the increase in voltage level and transmission capacity of power transmission and transformation lines, the traditional forming process of high-voltage switch contact parts can no longer meet the requirements of the high-voltage switch industry for parts performance. Based on the structural characteristics of a certain type of high-voltage switch static contact, the traditional production method of contact blank and its advantages and disadvantages are analyzed, a two-time reverse extrusion forming process is proposed, and an extrusion die is designed.
Forming process analysis of high-voltage switch static contact
1. Technical requirements of parts
The material of high-voltage switch static contact is copper-chromium alloy, which has good plasticity, strength, and excellent conductivity. The contact parts are bottomless cup-shaped parts with thin and uneven wall thickness. The parts have high quality requirements and the surface needs to be silver-plated. Before silver plating, grinding must be performed to meet the surface quality requirements.
2. Analysis of the traditional forming process
Before 1995, many high-voltage switch manufacturers often used thick-walled pipes + cutting processing technology to produce circuit breakers due to small production batches. Pipe blanks needed to be prepared during production. Due to the inconsistency between the upper and lower inner diameters of the parts, the required pipe wall thickness is large, a lot of waste is generated during turning, the material utilization rate is low, and the process cost is high, so it has been eliminated. Some manufacturers use forging bars + cutting to produce contacts. The material utilization rate has been improved, but the production efficiency and yield rate are low, so it is rarely used.
Many manufacturers use centrifugal casting to produce static contacts. This process has a low production cost, but the product is prone to shrinkage and looseness, and the material density is low, which leads to low conductivity and strength of the parts. The high-voltage switch contacts produced by the centrifugal casting process are easy to break and fall off during the final processing step, that is, the milling process, and when the finished product is installed on the high-voltage switch for long-term use, it is easy to break and fall off under the elastic deformation of the self-powered contact, causing major accidents. Therefore, the quality of the static contacts produced by centrifugal casting is unstable and the performance is poor. Strictly speaking, it cannot meet the performance requirements of high-voltage switch contacts and cylinders.