Molding method and molding die for silver-based composite strip

Abstract

Compared with traditional silver sleeve welding, the forming method and the forming die for the silver-based composite strip have the advantages that the mode of winding thin silver strips layer by layer is adopted, only the tail end is welded and fixed after winding, the welding seam defect of a silver sleeve is eliminated, and a silver layer and a spindle are combined more tightly; procedures are simplified, and the silver layer inclusion risk is reduced; the thickness of the silver strip is uniform and controllable, the coating quality is stable, a'one-to-three 'backward extrusion die design is adopted, a feeding end is chamfered, a die hole edge fillet R is 1.0-2.0 mm, and the extrusion resistance is reduced; the distance between the center of the forming die cavity and the center of the cylindrical base is smaller than or equal to 45 mm, and metal flow uniformity is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of electrical contact materials technology, specifically to a method for forming a silver-based composite strip and a forming mold. Background Technology

[0002] In the electrical contact industry, silver-based contacts are key conductive components, and their performance plays a decisive role in the reliability and service life of electrical equipment. Currently, there are two main silver-plating methods for sheet-like silver-based contacts: hot-rolled silver plating and reverse-extruded silver plating.

[0003] The traditional reverse extrusion silver plating process has the following problems: (1) Silver plating method: silver plate is rolled into tubes and then welded. The weld is prone to cracking, resulting in silver layer inclusion and affecting product quality; (2) Extrusion mold: the "one out two" structure is generally adopted. In order to ensure a reasonable extrusion ratio, the output thickness is usually designed to be thick (≥4mm), resulting in as many as 6 to 8 subsequent rolling passes, resulting in low production efficiency. Summary of the Invention

[0004] To address the technical deficiencies of existing technologies, this invention provides a molding method and molding die for silver-based composite strips. Through synergistic innovation of the process and the die, both product quality and production efficiency are improved.

[0005] The technical solution adopted in this invention is: a method for forming a silver-based composite strip, comprising the following steps: S1. Using silver ingots as the base material and auxiliary materials, AgMeO ingots are produced through pre-oxidation and powder metallurgy processing. S2, Silver coating layer: Thin silver strips are wrapped around the outside of the AgMeO ingot described in S1 layer by layer to form AgMeO / Ag ingot; S3, Reverse Extrusion Molding: After heating the AgMeO / Ag spindle described in S2, three AgMeO / Ag strips are obtained by reverse extrusion using an extrusion die; S4. Rolling: The AgMeO / Ag strip obtained in S3 is rolled multiple times to obtain a silver-plated strip that meets the thickness requirements. Further configured, the auxiliary material includes cadmium, tin, zinc metal or their metal oxide powder.

[0006] Further, in step S2, the silver coating layer is formed by wrapping silver strips layer by layer around the outside of the AgMeO ingot. The thickness of the silver strips is 0.1~1mm, and the width is 10~30mm greater than the height of the AgMeO ingot. The overall thickness of the silver strips is 4~6mm. After wrapping, the ends of the silver strips are welded and fixed to the AgMeO ingot.

[0007] The silver strip is further configured to be annealed before use, with an annealing temperature of 500~800℃ and an annealing time of 1~3 hours.

[0008] Further, in step S3, the extrusion die needs to be preheated before extrusion, with a preheating temperature of 300~500℃ and a holding time of 2~4 hours.

[0009] The setting is further configured such that the heating temperature of the AgMeO / Ag spindle in step S3 is 650~900℃ and the holding time is 2~6h.

[0010] Further configured, in step S3, the width of the three AgMeO / Ag strips is 30~50mm and the thickness is 2~4mm.

[0011] An extrusion die used in a method for forming a silver-based composite strip includes a cylindrical base. The upper end of the cylindrical base is a feed end, and the lower end is a discharge end. The feed end is provided with a Y-shaped symmetrical flow divider. The Y-shaped symmetrical flow divider is higher than the surface of the feed end of the cylindrical base. The Y-shaped symmetrical flow divider divides the surface of the feed end of the cylindrical base into three identical fan-shaped regions. Each of the three fan-shaped regions is provided with a forming die cavity. The forming die cavity penetrates the feed end and the discharge end of the cylindrical base. The three forming die cavities are distributed in an equilateral triangle.

[0012] A further setting is that the straight-line distance between the center of the molding cavity and the center of the feed end of the cylindrical base does not exceed 45mm.

[0013] A further provision is that the upper cavity edge of the molding cavity is provided with a radius of R1.0~2.0mm.

[0014] The beneficial effects of this invention are as follows: This invention provides a method for forming silver-based composite strip and a forming mold. Compared with traditional silver sleeve welding, this invention adopts a method of winding thin silver strip layer by layer. After winding, only the end is welded and fixed, eliminating defects in the silver sleeve weld and making the silver layer and ingot more tightly bonded. It simplifies the process and reduces the risk of silver layer inclusions. The thickness of the silver strip is uniform and controllable, and the coating quality is stable.

[0015] The "one-out-three" reverse extrusion die design has the following advantages: Basic structure: circular mold base, Y-shaped symmetrical flow distribution cavity, and three forming mold cavities arranged in an equilateral triangle; Feed optimization: Chamfer C1~C3 at the feed end, radius R1.0~2.0mm at the die hole edge to reduce extrusion resistance; Flow channel layout: The distance between the center of the die hole in the forming mold cavity and the center of the cylindrical base is ≤45mm to ensure uniform metal flow. Attached Figure Description

[0016] Figure 1 This is a three-dimensional sectional view of the extrusion die in Embodiment 1 of the present invention.

[0017] Figure 2 This is a top view of the extrusion die in Embodiment 1 of the present invention.

[0018] Wherein 1-cylindrical base; 2-Y-shaped symmetrical flow divider; 3-forming mold cavity; 11-feed end; 12-discharge end. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: a. Raw material preparation: 22 kg of 200 mesh atomized silver powder and 3 kg of SnO2 powder are mixed and sintered by isostatic pressing to obtain AgSnO2 ingots with an ingot diameter of about 90 mm and a height of about 380 mm. b. Silver coating: The AgSnO2 ingot is coated layer by layer with a thin silver strip with a specification of 0.5x400xLmm, and the whole ingot is coated with a 4mm silver layer. c. Reverse Extrusion Molding: The chamfer size of the die feed end is C2. The edge of the die cavity is rounded with R1.5mm for transition. The straight-line distance between the center of the die cavity and the center of the feed end of the cylindrical base is 30mm. The sizing band height of the die core is 3mm. Refer to the example drawing for the rest of the design. The extrusion die is preheated at 400℃ for 2 hours, and the AgSnO2 / Ag ingot is heated at 700℃ for 6 hours. After heating, reverse extrusion is performed on an 1100T extruder with an extrusion ratio of approximately 150, producing 3 AgSnO2 / Ag strips with a specification of 45x2mm. d. Rolling: The strip undergoes four hot rolling processes, reducing the strip thickness to 0.8 mm, and increasing the hot rolling production efficiency of a single strip by 50%.

[0021] Example 2; a. Raw material preparation: 22.5 kg of 200-mesh atomized silver powder and 2.5 kg of SnO2 powder are mixed and sintered by isostatic pressing to obtain AgSnO2 ingots with a diameter of about 90 mm and a height of about 380 mm. b. Silver coating: The AgSnO2 ingot is coated layer by layer with thin silver strips of 0.6x400xLmm in size, resulting in a total silver coating of 4.8mm. c. Reverse Extrusion Molding: The chamfer size of the die feed end is C1.5, and the edge of the die cavity is rounded with R2.0mm for transition. The straight-line distance between the center of the die cavity and the center of the feed end of the cylindrical base is 45mm. The sizing band height of the die core is 4mm. The rest of the design is shown in the example drawing. The extrusion die is preheated at 300℃ for 4 hours, and the AgSnO2 / Ag ingot is heated at 650℃ for 6 hours. After heating, reverse extrusion is performed on an 1100T extruder with an extrusion ratio of approximately 200, producing 3 AgSnO2 / Ag strips with a specification of 45x1.5mm. d. Rolling: The strip undergoes two hot rolling processes, reducing the strip thickness to 0.8 mm, which increases the hot rolling production efficiency of a single strip by 75%.

[0022] Example 3: a. Raw material preparation: 22.68 kg of silver ingots and 1.80 kg of cadmium ingots are atomized to obtain AgCd powder with a silver content of 90%. After drying, sieving, oxidation, pressing and sintering, AgCdO ingots are obtained with an ingot diameter of about 85 mm and a height of about 300 mm. b. Silver coating: The AgCdO ingot is coated layer by layer with thin silver strips of 0.5x400xLmm in size, and the whole ingot is coated with a 5mm silver layer. c. Reverse Extrusion Molding: The chamfer size of the die feed end is C3. The edge of the die cavity is rounded with R1.5mm for transition. The straight-line distance between the center of the die cavity and the center of the feed end of the cylindrical base is 30mm. The sizing band height of the die core is 3mm. The rest of the design is shown in the example drawing. The extrusion die is preheated at 300℃ for 3 hours, and the AgCdO / Ag ingot is heated at 800℃ for 4 hours. After heating, reverse extrusion is performed on an 1100T extruder with an extrusion ratio of approximately 200, producing 3 strips of 45x1.5mm silver-tin oxide silver-coated silver. d. Rolling process: The strip is hot rolled three times, reducing the strip thickness to 0.8mm and improving hot rolling production efficiency by 75%.

[0023] Please note to all technical personnel: Although the present invention has been described according to the specific embodiments above, the inventive concept of the present invention is not limited to this invention. Any modifications that utilize the inventive concept will be included within the scope of protection of this patent.

[0024] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method of forming a silver-based composite strip, characterized by, It comprises the following steps: S1, taking silver ingot as a basic raw material, collocating auxiliary materials, producing by pre-oxidation and powder metallurgy processing to obtain AgMeO ingot; S2, coating silver layer: winding silver tape on the outer side of the AgMeO ingot in S1 to form AgMeO / Ag ingot; S3, reverse extrusion forming: heating the AgMeO / Ag ingot in S2 and using an extrusion die to obtain three AgMeO / Ag tapes; S4, rolling: rolling the AgMeO / Ag tapes obtained in S3 to obtain complex silver tapes meeting the thickness requirements.

2. The molding method according to claim 1, characterized by, The auxiliary materials include cadmium, tin, zinc metal or metal oxide powder thereof.

3. The molding method according to claim 1, characterized by, In the step S2, the silver layer is coated by winding silver tape on the outer side of the AgMeO ingot, the thickness of the silver tape is 0.1-1mm, the width is greater than the height of the AgMeO ingot by 10-30mm, the overall thickness of the silver tape is 4-6mm, and the end of the silver tape is welded and fixed to the AgMeO ingot after winding.

4. The molding method according to claim 3, characterized by The silver tape needs to be annealed before use, the annealing temperature is 500-800℃, and the annealing time is 1-3 hours.

5. The molding method according to claim 1, characterized by, The extrusion die in the step S3 needs to be preheated before extrusion, the preheating temperature is 300-500℃, and the holding time is 2-4h.

6. The molding method according to claim 1, characterized by, The heating temperature of the AgMeO / Ag ingot in the step S3 is 650-900℃, and the holding time is 2-6h.

7. The molding method according to claim 1, characterized by, The width of the three AgMeO / Ag tapes obtained in the step S3 is 30-50mm, and the thickness is 2-4mm.

8. An extrusion die used in a method of forming the silver-based composite strip of claim 1, characterized by, It comprises a cylindrical base (1), the upper end of the cylindrical base is a feeding end (11) and the lower end is a discharging end (12), a Y-shaped symmetrical flow dividing part (2) is arranged on the feeding end, the Y-shaped symmetrical flow dividing part is higher than the surface of the feeding end of the cylindrical base, the Y-shaped symmetrical flow dividing part divides the surface of the feeding end of the cylindrical base into three identical fan-shaped areas, a forming die cavity (3) is further arranged in each of the three fan-shaped areas, the forming die cavity penetrates the feeding end and the discharging end of the cylindrical base, and the three forming die cavities are distributed in a regular triangle shape.

9. The extrusion die of claim 8, wherein, The center of the forming die cavity and the center of the feeding end of the cylindrical base are linearly spaced by no more than 45mm.

10. The extrusion die of claim 8, wherein, An R1.0-2.0mm round corner is arranged on the upper cavity edge of the die hole of the forming die cavity.

Images