Introduction
Silver Electrical For Contactor materials in low-voltage electrical appliances are mostly silver-based materials, and extrusion processes are often used in production. The main purposes of the extrusion process are twofold: one is extrusion molding, that is, extruding AgMe ingots into AgMe plates or wires; the other is to increase the density and strength of the material, which is mainly for AgMeO and AgMe ingots prepared by powder metallurgy. The extrusion process determines the surface state, uniformity of the structure, and density of the extruded material. The choice of extrusion process is the basis for determining the stability of the performance of Silver Contact Components for Electrical materials.
1 Conventional hot extrusion process and its disadvantages
The conventional extrusion process is shown in Table 1. The conventional extrusion defects are shown in Table 2.
Among many extrusion defects, the extrusion surface peeling and blistering defects have the most influencing factors and are the most likely to occur. Surface blistering will lead to poor product bonding strength and unstable electrical properties. The main reason for surface peeling and blistering is that a layer of Silver Conductive Electrical Contacts material remains on the inner wall of the extrusion barrel during the extrusion process. This layer of material is dense. In the subsequent extrusion process, the shedding of this layer of material will cause blistering or peeling problems, and the surface of the extruded material needs to be treated. If it is an extruded sheet, surface turning or planing needs to be added in the subsequent processing to remove the surface blistering or peeling; if it is an extruded wire, the wire peeling operation needs to be added in the subsequent processing. Since the contact material is mostly silver alloy material, many contact manufacturers do not treat the material surface in order to improve the material utilization rate, resulting in unstable electrical properties of Silver Electrical Contacts materials.
With the continuous improvement of product quality requirements, it is necessary to produce materials with stable and single performance. At the same time, energy saving and consumption reduction do not allow the use of extruded materials to remove the blistering and peeling of the material surface. The best solution is that there is no problem with the extruded material. By consulting relevant reference books, it is confirmed that the reverse extrusion peeling extrusion process can achieve extrusion without blistering or peeling on the material surface.
2 Feasibility analysis of peeling extrusion process
2.1 Reverse peeling extrusion
The reverse peeling extrusion process is shown in Figure 1. As shown in Figure 1, the outer diameter of the extrusion die is 4 mm to 10 mm smaller than the inner diameter of the extrusion barrel. During the extrusion process, the outer layer of the Silver Electrical Connector Contacts material ingot 2 mm to 5 mm is retained on the inner wall of the barrel and will not flow into the finished product, and there will be no subcutaneous bubbles or peeling problems.
Reverse extrusion is selected because the flow area of reverse extrusion is small, the outer layer of the spindle material will not have strong turbulence, and the quality of the extruded product is relatively easy to control. If forward extrusion is used, in order to ensure that the peeling and pressurization can proceed smoothly, the thickness of the extruded peeling layer must be further increased, thereby further reducing the material utilization rate.
2.2 Main process parameters of reverse peeling and extrusion
The main process parameters of reverse peeling and extrusion are shown in Table 3.
3 Preliminary test results
3.1 Test parameters
The extruder is a 1100 t reverse extruder, the inner diameter of the extrusion barrel is 110 mm, and the extrusion die sizes φ are 110 mm, 107 mm, 105 mm, 103 mm, and 100 mm respectively. The extrusion material is AgNi(10) prepared by the mixed powder process, the material ingot specification is φ105 mm×(240 mm～300 mm), and the mass is 20 kg. The extrusion specification is φ7 mm wire.
In order to ensure the consistency of the peeling extrusion process, the extrusion die and the reverse extrusion rod are connected by three positioning pins, and a special feeler gauge is used to ensure that the gap between the extrusion die and the extrusion barrel is consistent, so as to ensure that the barrel center and the extrusion die center are on the same center line, as shown in Figure 2.
3.2 Test results
Each mold was tested 20 times, and the extrusion process (extrusion temperature, extrusion speed, etc.) remained unchanged. After each extrusion, the head and tail materials were removed, and the appearance of the extruded products was compared for blistering, tissue inclusions, and shell peeling. The comparison is shown in Table 4. After cutting off the head and tail and the serious blistering and inclusions on the surface, the mass of the qualified products was weighed and the yield rate was calculated. The comparison of the yield rate is shown in Table 5.
3.3 Result analysis
(1) When the skin thickness is less than 2.5 mm, the skin is incomplete and the purpose of peeling and extrusion cannot be achieved.
(2) Without considering the yield waste caused by blistering, the yield of peeled extruded materials will be reduced.
(3) When the skin thickness of AgNi(10) material is ≥3.5 mm, the skin is complete, and there are no defects such as blistering and inclusions on the surface of the extruded material. At the same time, the material yield is basically the same as that of non-peeling extrusion.
(4) Due to the different properties of different materials, the thickness of the peeled skin needs to be confirmed after different attempts.
4 Conclusion
(1) The peeling and extrusion process is used in the production of silver-based contact materials, which can effectively solve the problems of blistering and inclusions caused by residual material on the barrel wall.
(2) The skin thickness of the silver-based Silver Metal Electrical Contacts material must be between 2 mm and 4 mm to ensure the integrity of the skin.
(3) The properties of different contact materials are different. In order to ensure the integrity of the skin, the skin thickness needs to be tested separately according to different materials.
(4) The thickness of the skin should be within a reasonable range to ensure that the material performance is improved while the material utilization rate is not reduced. Different materials need to be tested and confirmed separately for specific situations.
Our Silver Contact Components for Electrical use high-purity silver. Silver's good electrical and thermal conductivity ensures stable current transmission, reduces energy loss, and makes equipment run more efficiently. Advanced manufacturing technology and precision processing technology, strict stamping and molding, ensure dimensional accuracy and surface quality. Unique riveting technology allows silver contacts to be tightly combined with other components, enhancing mechanical strength, preventing loosening and falling off, and improving reliability and stability. At the same time, silver contacts have excellent corrosion resistance and oxidation resistance, and can maintain good performance in harsh environments and extend service life.
