Magnetic latching silver tin oxide alloy and preparation process thereof

Abstract

The invention discloses a magnetic latching silver tin oxide alloy, which is composed of the following components: 85-95 wt% of silver; 4 to 12 wt% of tin oxide; 0.5 to 2 wt% of bismuth oxide; 0.1 to 1 wt% of copper oxide and 0.1 to 1 wt% of nickel oxide; a preparation method of the magnetic latching silver tin oxide alloy comprises the following steps: weighing a certain amount of powder in the components, and carrying out mixing, pre-pressing molding, sintering, processing treatment and heat treatment to obtain the magnetic latching silver tin oxide alloy. The magnetic latching silver tin oxide alloy prepared in the invention has good conductivity, high hardness and wear resistance, excellent oxidation resistance and stable magnetic latching characteristic, and can meet the requirements of the fields of electrical switches and the like on environment-friendly high-performance electric contact materials.

Description

Technical Field

[0001] The present invention relates to a magnetically held silver tin oxide alloy and a preparation process thereof. Background Art

[0002] In the field of modern electrical industry, electrical contact materials play a crucial role and are widely used in various electrical components such as electrical switches, relays, contactors, etc. The quality of their performance is directly related to the reliability, stability, and service life of electrical equipment.

[0003] Traditional silver cadmium oxide alloy was once an electrical contact material with extremely wide applications. Silver has excellent electrical conductivity and good thermal conductivity, which can effectively reduce the contact resistance, reduce power loss, and ensure the smooth transmission of current. Cadmium oxide plays a role of strengthening phase in the alloy. It can significantly improve the hardness and wear resistance of the alloy. During the electrical contact process, when the contact frequently closes and disconnects, it can withstand the erosion of the arc and mechanical wear, maintain the shape and performance stability of the contact, and thus ensure the normal operation of electrical equipment. However, with the continuous enhancement of people's environmental awareness and the increasingly strict environmental protection regulations, cadmium element has serious hazards to the environment and human health due to its toxicity, and its use has been greatly restricted. This urgently urges scientific researchers and enterprises to actively search for an alternative material that can not only meet the performance requirements of electrical contact materials but also be environmentally friendly and harmless.

[0004] Silver tin oxide alloy emerged as a very promising environmentally friendly electrical contact material. Silver, as the matrix metal, can still provide a good foundation for electrical and thermal conductivity. Tin oxide has a high melting point and hardness and exists in the form of dispersed distribution in the silver matrix. Through the dispersion strengthening mechanism, it effectively improves the overall strength and wear resistance of the alloy and can resist arc erosion and mechanical friction to a certain extent. However, the pure silver tin oxide alloy has obvious deficiencies in magnetic holding performance. In some specific electrical application scenarios, such as some intelligent electrical control switches or relays with special holding function requirements, it is required that the electrical contact material can rely on its own magnetic properties to maintain a specific contact state after power-off to achieve the stable maintenance or memory function of the circuit state. However, the traditional silver tin oxide alloy cannot well meet this requirement, and its magnetic properties are weak, resulting in the easy displacement or state change of the contact after power-off, affecting the precise control and reliability of electrical equipment.

[0005] In addition, there are also many challenges in the preparation process of silver tin oxide alloys; the uniform mixing of each component is a key issue. Due to the differences in the physical and chemical properties of silver, tin oxide, and other additives, such as density, particle size, etc., it is difficult to achieve uniform dispersion at the microscopic level under conventional mixing processes, which easily leads to non-uniform internal tissue structure of the alloy, thereby affecting the comprehensive performance of the alloy; the sintering process is also a difficult point. The control of parameters such as sintering temperature, time, and atmosphere has a crucial impact on the density, grain size, and phase composition of the alloy; if the sintering process is improper, it may result in defects such as pores, coarse grains, or non-uniform distribution of the second phase inside the alloy, reducing key performance indicators such as the strength, conductivity, and arc erosion resistance of the alloy. Summary of the Invention

[0006] The main purpose of the present invention is to provide a magnetically retained silver tin oxide alloy and its preparation process to solve the above technical problems.

[0007] To achieve the above purpose, the present invention provides the following technical solution: A magnetically retained silver tin oxide alloy, characterized in that the silver tin oxide alloy is composed of the following components by content: silver, 85 - 95 wt%; tin oxide, 4 - 12 wt%; bismuth oxide, 0.5 - 2 wt%; copper oxide, 0.1 - 1 wt%; and nickel oxide, 0.1 - 1 wt%.

[0008] A preparation process of a magnetically retained silver tin oxide alloy, characterized by comprising the following steps:

[0009] Step 1, raw material preparation: Weigh silver powder, tin oxide powder, bismuth oxide powder, copper oxide powder, and nickel oxide powder with a purity of more than 99.9% respectively according to the above weight percentages, and control the particle size of each powder within the range of 1 - 50 microns;

[0010] Step 2, mixing: Place the weighed various powders in a high-energy ball mill for mixing, with a ball-to-material ratio of 5:1 - 10:1, a ball milling speed of 200 - 500 revolutions per minute, and a ball milling time of 2 - 8 hours to obtain uniformly mixed powder raw materials;

[0011] Step 3, pre-pressing and forming: Pre-press and form the mixed powder raw materials in a cold isostatic press, with a pre-pressing pressure of 100 - 300 MPa and a pressure holding time of 1 - 5 minutes to obtain a pre-formed blank;

[0012] Step 4, place the pre-formed blank in a vacuum sintering furnace for sintering, with a sintering temperature of 700 - 900 °C, a sintering time of 1 - 5 hours, and the vacuum degree maintained at 1×10 -3 -1×10 -5 Pa to obtain a sintered silver tin oxide alloy block;

[0013] Step 5, processing: The sintered alloy block is machined into the required shape and size, with the machining accuracy controlled within ±0.05 mm, and then surface polishing treatment is carried out, with the surface roughness Ra reaching 0.1 - 0.8 μm;

[0014] Step 6, heat treatment: The processed alloy is heat-treated in a protective atmosphere. The heat treatment temperature is 300 - 500 °C, the heat treatment time is 0.5 - 2 hours, the protective atmosphere is argon or nitrogen with a purity above 99.99%, and the flow rate is 10 - 50 L / min, to improve the microstructure and properties of the alloy and enhance its magnetic retention performance.

[0015] Based on the above solution and as a preferred solution of the above solution: The grinding medium in the high-energy ball mill described in Step 2 is cemented carbide balls or ceramic balls, and the diameter of the grinding medium is 5 - 15 mm; During the ball milling process, stop for 5 minutes every 30 minutes to prevent oxidation or agglomeration due to overheating of the powder caused by too long ball milling time.

[0016] Based on the above solution and as a preferred solution of the above solution: The surface roughness Ra of the pre-pressing die for pre-pressing forming described in Step 3 does not exceed 0.4 μm, and the die is preheated before pre-pressing, with the preheating temperature being 80 - 120 °C, to reduce the friction between the green body and the die.

[0017] Based on the above solution and as a preferred solution of the above solution: The heating rate of the vacuum sintering furnace described in Step 4 is 10 - 30 °C / min, the cooling rate is 15 - 40 °C / min, and after sintering, it is cooled in the furnace to below 200 °C before taking out of the furnace, to avoid cracks or excessive internal stress in the alloy block caused by rapid temperature changes.

[0018] Based on the above solution and as a preferred solution of the above solution: In Step 5, numerical control machining equipment is used for machining, the cutting speed is 50 - 200 m / min, the feed rate is 0.05 - 0.2 mm / rev, the cutting depth is 0.1 - 0.5 mm, and a cutting fluid is used for cooling and lubrication during the machining process. The cutting fluid is a water-based cutting fluid with a concentration of 5% - 15%, to ensure machining accuracy and surface quality.

[0019] Based on the above solution and as a preferred solution of the above solution: The temperature control accuracy of the heat treatment furnace in Step 6 is ±5 °C.

[0020] The beneficial effects of the present invention are as follows: The magnetic retention silver tin oxide alloy prepared in the present invention has good electrical conductivity, high hardness and wear resistance, excellent oxidation resistance, and stable magnetic retention characteristics, and can meet the requirements for environmentally friendly high-performance electrical contact materials in fields such as electrical switches. Detailed implementation mode

[0021] To make the objectives, technical solutions and advantages of this application clearer, the following will, in conjunction with the embodiments, clearly and completely describe the technical solutions in the embodiments. However, the specific implementation manners and embodiments described below are for illustrative purposes only and are not limitations on the present invention.

[0022] The silver tin oxide alloy of the present invention is composed of the following components by content: silver, 85 - 95 wt%; tin oxide, 4 - 12 wt%; bismuth oxide, 0.5 - 2 wt%; copper oxide, 0.1 - 1 wt% and nickel oxide, 0.1 - 1 wt%

[0023] Silver, as the main component, provides good electrical conductivity and basic metal structure support for the alloy, endows the alloy with certain toughness and workability, and enables it to be conveniently made into various shaped electrical contact components.

[0024] Tin oxide is uniformly dispersed in the silver matrix, and significantly improves the hardness and wear resistance of the alloy through dispersion strengthening, effectively resisting mechanical wear and arc erosion during the electrical contact process, thereby prolonging the service life of the electrical contact material.

[0025] The addition of bismuth oxide improves the melt fluidity of the alloy. During the alloy melting and forming process, it reduces the melt viscosity, promotes the uniform mixing of each component, and can refine the grain structure, further optimizing the comprehensive mechanical properties of the alloy and improving its reliability during use.

[0026] Copper oxide reacts with other components in the alloy to form stable intermetallic compounds, which precipitate at the grain boundaries, pin the grain boundaries, inhibit grain growth, enhance the strength and thermal stability of the alloy, and ensure the stability of the alloy performance under different working temperature conditions.

[0027] Nickel oxide can improve the oxidation resistance of the alloy, slow down the surface oxidation rate of the alloy during high temperature or long-term use, and at the same time have a positive impact on the magnetic properties of the alloy, helping to enhance the magnetic holding characteristics, enabling the alloy to better maintain the contact state after power-off and reducing the occurrence of malfunction.

[0028] A preparation process for a magnetic holding silver tin oxide alloy includes the following steps:

[0029] Step 1, raw material preparation: Weigh silver powder, tin oxide powder, bismuth oxide powder, copper oxide powder and nickel oxide powder with a purity above 99.9% respectively according to the above weight percentages, and control the particle size of each powder within the range of 1 - 50 microns. The strict control of the particle size of each powder is to ensure a highly uniform dispersion state can be achieved during the subsequent mixing process. The weighed powder raw materials should be properly stored in a sealed, moisture-proof and oxidation-proof container to ensure that their quality is not affected by the external environment.

[0030] Step 2, Mixing: Place the weighed powders in a high-energy ball mill for mixing. The ball-to-material ratio is 5:1 - 10:1, the ball milling speed is 200 - 500 revolutions per minute, and the ball milling time is 2 - 8 hours to obtain a uniformly mixed powder raw material. The ball milling medium is selected from cemented carbide balls or ceramic balls with a diameter of 5 - 15 mm, and balls of different diameters are mixed in a certain ratio (such as the quantity ratio of large balls: medium balls: small balls = 1:2:3). The synergistic effect of large and small balls is used to improve the powder mixing efficiency and uniformity. During the ball milling process, stop the machine for 5 minutes every 30 minutes to prevent oxidation or agglomeration of the powder due to overheating caused by too long ball milling time. At the same time, the powder temperature is monitored in real time by an infrared thermometer. When the temperature exceeds 80°C, the machine stops automatically for cooling. The cooling method combines air cooling and water cooling. Air cooling is carried out by fans installed around the ball mill tank body, and water cooling is achieved by circulating cooling water in the tank interlayer to ensure that the powder temperature is always within a reasonable range, thereby ensuring the uniformity and quality stability of powder mixing.

[0031] Step 3, Pre-pressing and forming: Perform pre-pressing and forming on the mixed powder raw material in a cold isostatic press. The pre-pressing pressure is 100 - 300 MPa, and the pressure holding time is 1 - 5 minutes to obtain a pre-formed blank. The pre-pressing die is made of cemented carbide material with a surface roughness Ra not exceeding 0.4 microns. Before pre-pressing, the die is preheated. The preheating temperature is 80 - 120°C. The die preheating adopts a resistance wire heating method, with heating wires evenly arranged inside the die, and the preheating temperature is precisely controlled by a temperature controller. During the pre-pressing process, heat preservation treatment is carried out on the die to prevent the rapid loss of heat from affecting the forming quality of the blank. The pre-pressing pressure is 100 - 300 MPa, and the pressure holding time is 1 - 5 minutes. The pre-pressing process adopts a step-by-step pressure increase method. First, pre-press at a pressure of 50 MPa for 30 seconds, and then gradually increase the pressure to the set pressure, so that the powder can be more evenly distributed and compacted in the die to obtain a pre-formed blank.

[0032] Step 4, Place the pre-formed blank in a vacuum sintering furnace for sintering. The sintering temperature is 700 - 900°C, and the sintering time is 1 - 5 hours. During the sintering process, the vacuum degree is maintained at 1×10 -3 -1×10 -5Pa, to obtain a sintered silver oxide tin alloy block; the heating rate is 10-30°C / minute, and during the heating process, different heating rates are set according to different temperature ranges, such as 10-15°C / minute in the low temperature section (room temperature-300°C), 15-20°C / minute in the medium temperature section (300-600°C), and 20-30°C / minute in the high temperature section (600-900°C), which can reduce the internal stress caused by thermal expansion and contraction; the cooling rate is 15-40°C / minute, and the After sintering, the alloy is cooled to below 200°C in the furnace before being taken out of the furnace. During the cooling process, the segmented cooling method is also adopted, and the heat preservation treatment is carried out at the key temperature points to further reduce the internal stress, so as to avoid cracks in the alloy block or excessive internal stress due to rapid temperature changes, which will affect the performance and quality of the alloy. During the sintering process, the sintering parameters are monitored in real time by the temperature sensors and pressure sensors in the furnace, and the automatic control system is used for precise regulation to ensure the stability and repeatability of the sintering process, so as to obtain the sintered silver oxide tin alloy block.

[0033] Step 5, processing: the sintered alloy block is machined into the required shape and size with a processing accuracy within ±0.05 mm, and then the surface is polished to a surface roughness Ra of 0.1-0.8 microns; in the CNC machining equipment, an advanced tool path planning algorithm is used to optimize the cutting sequence and cutting parameters according to the shape and size requirements of the alloy to reduce vibration and cutting force during the machining process; at the same time, the cutting fluid supply system adopts a high-pressure, precise injection method to ensure that the cutting fluid can fully reach the cutting area and effectively take away the cutting heat and chips, and then the surface is polished to a surface roughness Ra of 0.1-0.8 microns; during the machining process, the tool material is selected according to the hardness and toughness characteristics of the alloy, such as carbide tools or ceramic tools, to improve the cutting performance.

[0034] Step 6, Heat treatment: The processed alloy is heat-treated under a protective atmosphere. The heat treatment temperature is 300 - 500 °C, the heat treatment time is 0.5 - 2 hours, the protective atmosphere is argon or nitrogen with a purity above 99.99%, and the flow rate is 10 - 50 liters per minute, so as to improve the microstructure and properties of the alloy and enhance its magnetic holding performance; The heat treatment furnace adopts a resistance heating furnace body, which is equipped with a high-precision temperature control system inside, and the temperature control accuracy is ±5 °C; High-precision temperature sensors and flow sensors are used, the response time of the sensors does not exceed 1 second, the data acquisition frequency is 1 - 5 Hz, the collected data is transmitted to the computer control system, analyzed and processed through a preset control algorithm, and the heating power and atmosphere flow rate are automatically adjusted to achieve intelligent control of the heat treatment process. During the heat treatment process, the alloy is monitored in real time, and the monitoring parameters include temperature, atmosphere flow rate, etc. The heat treatment process parameters are adjusted in a timely manner through the monitoring data to ensure the stability and repeatability of the heat treatment process, so that the alloy obtains stable and excellent magnetic holding characteristics.

[0035] Example 1

[0036] Weigh 90% silver powder, 7% tin oxide powder, 1.5% bismuth oxide powder, 0.5% copper oxide powder, and 0.5% nickel oxide powder by weight percentage;

[0037] Put the weighed powders into a high-energy ball mill for mixing. The ball-to-material ratio is 8:1, the ball milling speed is 300 revolutions per minute, the ball milling time is 5 hours, the ball milling medium is hard alloy balls with a diameter of 10 mm (large balls: medium balls: small balls = 1:2:3), stop for 5 minutes every 30 minutes, monitor the temperature with an infrared thermometer, and control the temperature not exceeding 80 °C by combining air cooling and water cooling;

[0038] The mixed powders are pre-pressed and formed in a cold isostatic press. The pre-pressing die is made of hard alloy, the surface roughness Ra = 0.3 μm, preheat to 100 °C, and use stepped pressing. First, pre-press at 50 MPa for 30 seconds, and then increase to 200 MPa and hold the pressure for 3 minutes;

[0039] The preformed blank is sintered in a vacuum sintering furnace. The heating element is graphite, the sintering temperature is 800 °C, the sintering time is 3 hours, the vacuum degree is 1×10 -4 Pa, the heating rate is 12 °C per minute from room temperature to 300 °C, 18 °C per minute from 300 - 600 °C, 25 °C per minute from 600 - 800 °C, the cooling rate is 25 °C per minute, and it is cooled in the furnace to 150 °C and then taken out of the furnace;

[0040] The sintered alloy block is processed numerically controlled, with a cutting speed of 100 m / min, a feed rate of 0.1 mm / rev, a cutting depth of 0.3 mm, a water-based cutting fluid concentration of 10%, a machining accuracy of ±0.05 mm, the surface is polished to Ra = 0.5 μm, and the cutting tool used is a cemented carbide tool;

[0041] The processed alloy is heat-treated under an argon protection atmosphere, with a heat treatment temperature of 400 °C, a time of 1 hour, an argon flow rate of 30 L / min, a heat treatment furnace temperature control accuracy of ±5 °C, monitored by a high-precision sensor, and the process parameters are controlled intelligently by a computer.

[0042] Example 2

[0043] Weigh 88% silver powder, 9% tin oxide powder, 1% bismuth oxide powder, 0.8% copper oxide powder, and 0.2% nickel oxide powder.

[0044] Mix by high-energy ball milling, with a ball-to-powder ratio of 6:1, a ball milling speed of 400 rev / min, a ball milling time of 4 hours, the ball milling medium is 8-mm diameter ceramic balls (big balls: medium balls: small balls = 1:2:3), stop for 5 minutes every 30 minutes, and control the temperature not exceeding 80 °C;

[0045] Pre-press with a cold isostatic press, the surface roughness of the mold is Ra = 0.2 μm, preheat to 90 °C, and pressurize in stages (first pre-press at 50 MPa for 30 seconds, then increase to 250 MPa and hold for 2 minutes);

[0046] Vacuum sintering, with a sintering temperature of 750 °C, a time of 2 hours, a vacuum degree of 1×10-3 Pa, the heating rate is 10 °C / min from room temperature to 300 °C, 16 °C / min from 300 to 600 °C, 20 °C / min from 600 to 750 °C, the cooling rate is 20 °C / min, and cool in the furnace to 180 °C and then take out of the furnace;

[0047] Numerical control machining, with a cutting speed of 150 m / min, a feed rate of 0.15 mm / rev, a cutting depth of 0.2 mm, a water-based cutting fluid concentration of 8%, a machining accuracy of ±0.05 mm, the surface is polished to Ra = 0.3 μm, and the cutting tool used is a ceramic tool;

[0048] Heat treatment under argon protection, with a temperature of 350 °C, a time of 1.5 hours, an argon flow rate of 20 L / min, a temperature control accuracy of ±5 °C, and intelligent control of parameters.

[0049] The magnetic holding silver tin oxide alloy prepared in the present invention has good electrical conductivity, relatively high hardness and wear resistance, excellent oxidation resistance, and stable magnetic holding characteristics, and can meet the requirements of environmental protection and high-performance electrical contact materials in fields such as electrical switches.

[0050] The above embodiments are only preferred embodiments of the present invention, and do not limit the protection scope of the present invention accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of the present invention shall be covered within the protection scope of the present invention.

Claims

1. A magnetically retaining silver-tin oxide alloy, characterized in that: The silver-tin oxide alloy consists of the following components: 85-95 wt% of silver; 4-12 wt% of tin oxide; 0.5-2 wt% of bismuth oxide; 0.1-1 wt% of copper oxide and 0.1-1 wt% of nickel oxide.

2. A process for preparing the magnetically resistant silver-tin oxide alloy according to claim 1, characterized in that: The following steps are involved: Step 1, raw material preparation: weigh silver powder, tin oxide powder, bismuth oxide powder, copper oxide powder and nickel oxide powder with a purity of more than 99.9% according to the above weight percentages, and the particle size of each powder is controlled within the range of 1-50 microns; Step 2, mixing: the weighed various powders are placed in a high-energy ball mill for mixing, with a ball-to-material ratio of 5:1-10:1, a ball milling speed of 200-500 rpm, and a ball milling time of 2-8 hours to obtain a uniformly mixed powder raw material; Step 3, pre-pressing: pre-pressing the mixed powder raw material in a cold isostatic press, with a pre-pressing pressure of 100-300 MPa and a holding time of 1-5 minutes to obtain a preformed body; Step 4: Place the preformed body in a vacuum sintering furnace for sintering at a temperature of 700-900°C for 1-5 hours. During the sintering process, the vacuum degree is maintained at 1×10 -3 -1×10 -5 Pa, to obtain a sintered silver-tin oxide alloy block; Step 5, processing: machining the sintered alloy block into a desired shape and size, with a processing accuracy within ±0.05 mm, and then performing surface polishing, with a surface roughness Ra of 0.1-0.8 μm; Step 6, heat treatment: heat treat the processed alloy under a protective atmosphere at a temperature of 300-500°C for 0.5-2 hours. The protective atmosphere is argon or nitrogen with a purity of more than 99.99% and a flow rate of 10-50 liters / minute to improve the microstructure and properties of the alloy and improve its magnetic retention properties.

3. The preparation process of the magnetically resistant silver-tin oxide alloy according to claim 2, characterized in that: The grinding medium in the high-energy ball mill in step 2 is a cemented carbide ball or a ceramic ball, and the diameter of the grinding medium is 5-15 mm; during the ball milling process, the machine is stopped for 5 minutes every 30 minutes to prevent oxidation or agglomeration of the powder caused by overheating due to long ball milling time.

4. The preparation process of the magnetically resistant silver-tin oxide alloy according to claim 2, characterized in that: The surface roughness Ra of the pre-pressing mold for pre-pressing in step 3 does not exceed 0.4 microns, and the mold is preheated before pre-pressing at a temperature of 80-120° C. to reduce friction between the blank and the mold.

5. The preparation process of the magnetically resistant silver-tin oxide alloy according to claim 2, characterized in that: The heating rate of the vacuum sintering furnace in step 4 is 10-30°C / minute, and the cooling rate is 15-40°C / minute. After sintering, the alloy is cooled to below 200°C before being taken out of the furnace to avoid cracks or excessive internal stress in the alloy block due to rapid temperature changes.

6. The preparation process of the magnetically resistant silver-tin oxide alloy according to claim 2, characterized in that: In step 5, CNC machining equipment is used for machining, with a cutting speed of 50-200 m / min, a feed rate of 0.05-0.2 mm / rev, a cutting depth of 0.1-0.5 mm, and cutting fluid is used for cooling and lubrication during the machining process. The cutting fluid is a water-based cutting fluid with a concentration of 5%-15% to ensure machining accuracy and surface quality.

7. The preparation process of the magnetically resistant silver-tin oxide alloy according to claim 2, characterized in that: The temperature control accuracy of the heat treatment furnace in step 6 is ±5°C.