A micro-nano AgSnO2 contact material resistant to welding and its preparation method

Abstract

The present invention discloses a micro-nano AgSnO2 contact material resistant to welding, which is composed of the following components by mass percentage: 4% - 12% of SnO2, 0.1% - 2.0% of graphite material, and the balance is Ag. The preparation method of the material of the present invention is as follows: First, weigh the raw materials; Second, prepare a powder suspension; Third, prepare a graphite material dispersion; Fourth, heat and magnetically stir the powder suspension; Fifth, add the graphite material dispersion to the powder suspension to obtain agglomerated powder; Sixth, grind the agglomerated powder; Seventh, anneal; Eighth, sinter after primary pressing; Ninth, re-sinter after re-pressing. By introducing the graphite material into the contact material, the present invention helps to weaken the strength of the welding area, reduce or even eliminate the welding phenomenon, and improve the welding resistance performance of the contact material; the present invention uses heating and magnetic stirring to promote the uniform dispersion of the graphite material, improves the physical properties and arc erosion resistance performance of the contact material, and is applicable to the field of electrical systems.

Description

Technical Field

[0001] The invention belongs to the technical field of electrical engineering materials (electrical contact materials), and particularly relates to a micro-nano AgSnO2 contact material with anti-welding property and a preparation method thereof. Background Art

[0002] Contacts are the core components of relays and circuit breakers, which play the roles of connecting current, carrying current and disconnecting current, and are widely used in various electrical systems. Their performance directly affects the reliability, stability and service life of electrical systems. Silver-based contact materials are widely used in the field of low-voltage electrical appliances due to their excellent electrical conductivity and antioxidant ability. AgCdO contact materials have excellent electrical and thermal conductivity, arc erosion resistance, anti-welding property, and low and stable contact resistance. However, the "cadmium toxicity" generated during its production and use endangers the environment and human health.

[0003] AgSnO2 contact materials have become the most promising contact materials to replace AgCdO due to their excellent arc erosion resistance. However, AgSnO2 contact materials also have the problem of easy welding under large load or large current impact. At the same time, with the development of industrialization and the rise of new industries, higher requirements are put forward for the performance of contact materials. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a micro-nano AgSnO2 contact material with anti-welding property aiming at the deficiencies of the above-mentioned prior art. By introducing graphite materials into the AgSnO2 contact material, the strength of the welding area can be weakened, the welding phenomenon can be reduced or even eliminated, and the CO2 generated by the reaction of the graphite material with O2 in the air has an arc extinguishing effect, further reducing arc erosion, thereby reducing the welding phenomenon and improving the anti-welding property of the AgSnO2 contact material, and solving the problem of easy welding of the AgSnO2 contact material under large load or large current impact.

[0005] To solve the above technical problem, the technical solution adopted by the present invention is: a micro-nano AgSnO2 contact material with anti-welding property, characterized in that it is composed of the following components by mass percentage: 4% - 12% of SnO2, 0.1% - 2.0% of graphite material, and the balance is Ag; the graphite material is nano-graphite flakes, 1 - 3 layers of graphene or carbon nanotubes.

[0006] The present invention uses nano-graphite flakes, 1 to 3 layers of graphene or carbon nanotubes as the graphite material in the micro-nano AgSnO2 contact material. The scales of these nano-materials are relatively small, and they are easy to be uniformly dispersed in the Ag matrix. Moreover, their own electrical conductivities are relatively good, and the damage to the electrical conductivity of the contact material is very small. At the same time, these nano-materials all have a large specific surface area. After being uniformly dispersed in the material, they form more interfaces, which have the effect of dispersing the arc during service, can reduce ablation, and improve the service performance of the micro-nano AgSnO2 contact material. In addition, due to the uniform distribution of these nano-materials in the Ag matrix, the damage to the processing performance of the micro-nano AgSnO2 contact material is also relatively small, and the composition within the region is more uniform.

[0007] The above-mentioned anti-welding micro-nano AgSnO2 contact material is characterized in that it is composed of the following components by mass percentage: SnO2 6% - 10%, graphite material 0.1% - 0.4%, and the balance is Ag.

[0008] The above-mentioned anti-welding micro-nano AgSnO2 contact material is characterized in that it is composed of the following components by mass percentage: SnO2 8%, nano-graphite flakes 0.2%, and the balance is Ag.

[0009] In addition, the present invention also discloses a method for preparing the above-mentioned anti-welding micro-nano AgSnO2 contact material, which includes the following steps:

[0010] Step 1: Weigh Ag powder, SnO2 powder and graphite material according to the composition of the target micro-nano AgSnO2 contact material.

[0011] Step 2: Mix the Ag powder and SnO2 powder weighed in Step 1, add absolute ethanol, and the addition ratio is 100 mL of absolute ethanol for every 10 g of powder. Then, perform ultrasonic and stirring treatments for 5 min - 10 min to obtain a powder suspension.

[0012] Step 3: Add absolute ethanol to the graphite material weighed in Step 1, and the addition ratio is 1 L of absolute ethanol for every 1 g of graphite material. Then, perform ultrasonic treatment for 30 min - 60 min to obtain a graphite material dispersion.

[0013] Step 4: Place a heating magnetic stirrer in the fume hood. Then, place the powder suspension obtained in Step 2 together with the container on the heating magnetic disk of the heating magnetic stirrer. Insert the thermocouple into the powder suspension until the bottom of the container, and place a magnetic rotor to perform heating magnetic stirring on the powder suspension, and the heating temperature is 65°C - 74°C.

[0014] Step 5: Gradually add the graphite material dispersion obtained in Step 3 to the powder suspension under heating and magnetic stirring in Step 4 and mix them to obtain a mixed solution. After the addition of the graphite material dispersion is completed, continue to maintain the heating and magnetic stirring state and turn on the fume hood to evaporate and remove the absolute ethanol in the mixed solution, obtaining agglomerated powder.

[0015] Step 6: Mechanically grind the agglomerated powder obtained in Step 5 using a mortar to obtain composite powder.

[0016] Step 7: Place the composite powder obtained in Step 6 in a ceramic boat and anneal it in a tube furnace. The annealing temperature is 200°C - 260°C, the heating rate is 5°C / min - 10°C / min, the holding time is 1 h, and the atmosphere is argon or air.

[0017] Step 8: Load the annealed composite powder obtained in Step 7 into a steel mold and perform primary pressing and forming using a tablet press. The pressure for primary pressing and forming is 100 MPa - 140 MPa, the pressure holding time is 1 min, and the cyclic pressing method is adopted. After demolding, place the obtained primary pressed green body in a tube furnace and sinter it at 700°C - 900°C. The heating rate is 5°C / min - 10°C / min, the holding time is 2 h, and the atmosphere is argon, obtaining a sintered block.

[0018] Step 9: Place the sintered block obtained in Step 8 in a steel mold and perform secondary pressing using a tablet press. The pressure for secondary pressing is 800 MPa - 850 MPa, the pressure holding time is 1 min, and the cyclic pressing method is adopted. After demolding, place the obtained secondary pressed green body in a tube furnace and re-sinter it at 600°C. The heating rate is 5°C / min - 10°C / min, the holding time is 2 h, and the atmosphere is argon, obtaining a micro-nano AgSnO2 contact material with anti-welding property.

[0019] In the above method, it is characterized in that the particle size of the Ag powder in Step 1 is 0.1 μm - 2 μm, and the mass purity is not less than 99.9%; the particle size of the SnO2 powder is 0.3 μm - 1 μm, and the mass purity is not less than 99.9%. The present invention uses micro-nano Ag powder as a raw material. On the one hand, it ensures the uniform dispersion of the reinforcing phase graphite material in the Ag matrix material. The dispersed graphite material and SnO2 hinder the grain growth, so that the Ag in the AgSnO2 contact material exists in the form of micro-nano grains. On the basis of improving the basic arc erosion resistance of the AgSnO2 contact material, the anti-welding performance of the AgSnO2 contact material is further strengthened.

[0020] The above method is characterized in that, during the heating and magnetic stirring process in step four, the initial rotational speed of the magnetic rotor is set to 500 rpm. When the liquid level height of the powder suspension is lower than 1.5 cm, the rotational speed of the magnetic rotor is reduced to 350 rpm. When the viscosity of the powder suspension increases to the point where it cannot flow, the rotational speed of the magnetic rotor is reduced to 0 rpm. During the heating and magnetic stirring process of the present invention, a relatively high rotational speed is first adopted to achieve sufficient mixing of Ag powder and SnO₂ powder in the powder suspension. As anhydrous ethanol evaporates and the powder suspension decreases, the rotational speed is correspondingly reduced to prevent liquid splashing.

[0021] The above method is characterized in that, in step five, a fan is placed around the mixed solution, and the airflow generated by the rotation of the fan is directed at the container opening containing the mixed solution. The blade length of the fan is 5 cm, the number of blades is 2 - 3, and the rotational speed is 1500 rpm. The present invention utilizes the air flow in the fume hood to accelerate the evaporation and diffusion of anhydrous ethanol in the container for removal. Similarly, the present invention can also use a fan to replace or enhance the function of the fume hood to accelerate the evaporation of anhydrous ethanol, shorten the preparation cycle, and reduce power consumption.

[0022] The above method is characterized in that, in steps eight and nine, the operation process of the cyclic pressing method is as follows: When loading, a 1 - mm - thick gasket is added between the lower punch of the steel mold and the bottom of the mold. The gasket is removed at the start of pressing. When the lower punch moves upward by 1 mm relative to the mold, the pressure is unloaded. Then, the 1 - mm - thick gasket is re - placed between the lower punch and the bottom of the mold, and pressure is loaded to make the upper punch of the steel mold move downward by 1 mm, and the gasket is removed again for pressurization; Repeat the process of the lower punch moving, re - placing the gasket, loading pressure to make the upper punch move, and removing the gasket again for pressurization until the pressure rises to the set value.

[0023] The above method is characterized in that, during the sintering process in step eight, the temperature is first raised to 600 °C at a heating rate of 10 °C / min, and then raised to the target temperature at a heating rate of 5 °C / min.

[0024] The above method is characterized in that, during the sintering process in step nine, the temperature is first raised to 500 °C at a heating rate of 10 °C / min, and then raised to the target temperature at a heating rate of 5 °C / min.

[0025] In the two - step sintering process of the present invention, a heating rate of first fast and then slow is adopted. By rapidly raising the temperature in the early stage, the gas in each green compact can be quickly discharged to avoid the occurrence of closed pores on the material surface due to too slow a heating rate, resulting in the gas being trapped inside the material and reducing the material properties. By slowly raising the temperature in the later stage, the temperature control of the sintering furnace is more accurate to prevent the temperature from exceeding the set value due to thermal inertia; In addition, after the gas inside the material is exhausted in the early stage, slowly raising the temperature in the later stage helps to make the material heat evenly, thereby improving the material structure uniformity.

[0026] The present invention has the following advantages compared with the prior art:

[0027] 1. The fusion welding phenomenon is caused by the direct contact of the melting areas on the surfaces of the moving and static contacts. If the strength of the welding area is too large and exceeds the maximum mechanical breaking force, it will lead to the adverse consequence that the circuit cannot be disconnected. The present invention introduces graphite materials, including nano-graphite flakes, 1 - 3 layers of graphene, or carbon nanotubes, into the AgSnO2 contact material. During the service process of the contact material, the presence of the graphite material helps to weaken the strength of the fusion welding area. Therefore, it is easier for the mechanical device to separate the fused contacts to achieve the purpose of cutting off the current, thereby reducing or even eliminating the fusion welding phenomenon. Moreover, the CO2 generated by the reaction of the graphite material with O2 in the air has an arc extinguishing effect, further reducing the arc erosion and then reducing the fusion welding phenomenon, and improving the anti-fusion welding performance of the AgSnO2 contact material.

[0028] 2. In the AgSnO2 contact material of the present invention, the graphite material is dispersed in the Ag matrix to form a three-dimensional continuous or discontinuous network structure, which, together with the dispersed SnO2 particles, prevents the growth of Ag grains, maintains the micro-nano structure of the Ag matrix, has the effect of dispersing the arc energy and reducing the arc erosion, and further improves the anti-fusion welding performance of the AgSnO2 contact material.

[0029] 3. In the preparation method of the present invention, the Ag powder, SnO2 powder, and graphite material are first dispersed in anhydrous ethanol respectively, and heating magnetic stirring is used to fully mix the Ag powder and SnO2 powder and remove the anhydrous ethanol. Then, the graphite material dispersion liquid is added and heating magnetic stirring is continued to promote the uniform dispersion of the graphite material, solving the problem that it is difficult to achieve the uniform dispersion of the graphite material in the material by the conventional mechanical ball milling or powder mixing method, and improving the physical properties and anti-arc erosion performance of the micro-nano AgSnO2 contact material.

[0030] 4. In the preparation method of the present invention, annealing is carried out on the composite powder to reduce its surface activity and improve its forming and sintering properties. Combined with the cyclic pressing forming method, uniform stress on the upper and lower surfaces of the green compact is achieved, making the density distribution of the green compact uniform, improving the densification performance of the micro-nano AgSnO2 contact material, and further ensuring its physical conductivity and anti-fusion welding performance, overcoming the problems that the micro-nano Ag powder has large sintering activity and the gas cannot be discharged during the sintering process, resulting in an incompact sintered body.

[0031] 5. The present invention adopts the cyclic pressing forming method, which makes the whole green compact displace relative to the inside of the mold, prevents the cold welding between the green compact and the inner wall of the mold, is conducive to discharging the gas inside the green compact, and further improves the densification of the micro-nano AgSnO2 contact material.

[0032] 6. The micro-nano AgSnO2 contact material prepared by the present invention has a uniform distribution of graphite material, uniform structure, good electrical conductivity, hardness and high anti-welding performance, excellent service performance, and is suitable for the field of contact materials for electrical systems.

[0033] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments. Brief Description of the Drawings

[0034] Figure 1 It is a process flow chart for the preparation of the anti-welding micro-nano AgSnO2 contact material of the present invention.

[0035] Figure 2 It is a micrograph of the micro-nano Ag-8SnO2-0.2Gr contact material prepared in Example 2 of the present invention.

[0036] Figure 3 It is a comparison chart of the welding force between the micro-nano Ag-8SnO2-0.2Gr contact material prepared in Example 2 of the present invention and the traditional Ag-8SnO2 contact material. Detailed Embodiments

[0037] Example 1

[0038] The anti-welding micro-nano AgSnO2 contact material of this example is composed of the following components by mass percentage: 8% SnO2, 0.1% nano-graphite flakes, and the balance is Ag.

[0039] As Figure 1 shown, the preparation method of the anti-welding micro-nano AgSnO2 contact material of this example includes the following steps:

[0040] Step 1: Weigh Ag powder, SnO2 powder and nano-graphite flakes according to the composition of the target micro-nano AgSnO2 contact material; the particle size of the Ag powder is 0.1 μm to 2 μm, and the mass purity is not less than 99.9%; the particle size of the SnO2 powder is 0.3 μm to 1 μm, and the mass purity is not less than 99.9%.

[0041] Step 2: Mix the Ag powder and SnO2 powder weighed in Step 1, add absolute ethanol, and the addition ratio is 100 mL of absolute ethanol for every 10 g of powder, and then perform ultrasonic and stirring treatment for 5 min to obtain a powder suspension.

[0042] Step 3: Add absolute ethanol to the nano-graphite flakes weighed in Step 1, and the addition ratio is 1 L of absolute ethanol for every 1 g of nano-graphite flakes, and then perform ultrasonic treatment for 30 min to obtain a nano-graphite flake dispersion.

[0043] Step 4: Place a heating magnetic stirrer in the fume hood, and then place the powder suspension obtained in Step 2 together with the container on the heating magnetic disk of the heating magnetic stirrer. Insert the thermocouple into the powder suspension until it reaches the bottom of the container, and place a magnetic rotor to perform heating magnetic stirring on the powder suspension. The heating temperature is 72°C, and the initial rotational speed of the magnetic rotor is set to 500 rpm. When the liquid level height of the powder suspension is lower than 1.5 cm, the rotational speed of the magnetic rotor drops to 350 rpm. When the viscosity of the powder suspension increases to the point where it cannot flow, the rotational speed of the magnetic rotor drops to 0 rpm;

[0044] Step 5: Gradually add the nano-graphite sheet dispersion obtained in Step 3 to the powder suspension under heating magnetic stirring in Step 4 and mix them to obtain a mixed solution. After the addition of the nano-graphite sheet dispersion is completed, continue to maintain the heating magnetic stirring state and turn on the fume hood to evaporate and remove the absolute ethanol in the mixed solution to obtain agglomerated powder. When the conditions in the fume hood cannot meet the condition for evaporating and removing the absolute ethanol, place a fan around the mixed solution, and direct the airflow generated by the rotation of the fan towards the mouth of the container containing the mixed solution. The blade length of the fan is 5 cm, the number of blades is 2, and the rotational speed is 1500 rpm;

[0045] Step 6: Mechanically grind the agglomerated powder obtained in Step 5 into powder using a mortar to obtain composite powder;

[0046] Step 7: Place the composite powder obtained in Step 6 in a ceramic boat and anneal it in a tube furnace. The annealing temperature is 220°C, the heating rate is 5°C / min, the holding time is 1 h, and the atmosphere is argon;

[0047] Step 8: Load the annealed composite powder obtained in Step 7 into a steel mold and perform initial pressure forming using a tablet press. The pressure for initial pressure forming is 120 MPa, and the pressure holding time is 1 min. Use the cyclic pressing method. The operation process is as follows: When loading the composite powder, place a 1-mm-thick gasket between the lower punch of the steel mold and the bottom of the mold. Remove the gasket at the start of pressing. Unload the pressure when the lower punch moves 1 mm upward relative to the mold. Then place the 1-mm-thick gasket between the lower punch and the bottom of the mold again. Apply pressure to make the upper punch of the steel mold move downward by 1 mm, and remove the gasket again for pressurization. Repeat the process of the lower punch moving, re-placing the gasket, applying pressure to make the upper punch move, and removing the gasket again for pressurization until the pressure rises to 120 MPa; After demolding, place the obtained initial pressure compact in a tube furnace, first raise the temperature to 600°C at a heating rate of 10°C / min, and then raise the temperature to 800°C at a heating rate of 5°C / min for sintering. The holding time is 2 h, and the atmosphere is argon to obtain a sintered block;

[0048] Step 9: Place the sintered block obtained in Step 8 in a steel mold and perform re-pressing using a tablet press. The re-pressing pressure is 850 MPa, the pressure holding time is 1 min, and the cyclic pressing method is adopted. The operation process is as follows: When loading the sintered block, place a 1-mm-thick spacer between the lower punch of the steel mold and the bottom of the mold. Remove the spacer at the start of pressing. Unload the pressure when the lower punch moves 1 mm upward relative to the mold, then place the 1-mm-thick spacer between the lower punch and the bottom of the mold again. Apply pressure to make the upper punch of the steel mold move downward by 1 mm, and remove the spacer again for pressurization. Repeat the process of the lower punch moving, re-placing the spacer, applying pressure to make the upper punch move, and removing the spacer again for pressurization until the pressure rises to 850 MPa. After demolding, place the obtained re-pressed compact in a tube furnace. First, heat it to 500 °C at a heating rate of 10 °C / min, and then heat it to 600 °C at a heating rate of 5 °C / min for re-sintering. The holding time is 2 h, and the atmosphere is argon to obtain a non-weldable micro-nano AgSnO₂ contact material, namely, a micro-nano Ag-8SnO₂-0.1Gr contact material.

[0049] Example 2

[0050] The non-weldable micro-nano AgSnO₂ contact material of this example is composed of the following components by mass percentage: 8% SnO₂, 0.2% nano-graphite flakes, and the balance is Ag.

[0051] The difference in the preparation method of the non-weldable micro-nano AgSnO₂ contact material of this example from that of Example 1 is that the annealing temperature in Step 7 is 240 °C, and finally a micro-nano Ag-8SnO₂-0.2Gr contact material is obtained.

[0052] Figure 2 is the microstructure diagram of the micro-nano Ag-8SnO₂-0.2Gr contact material prepared in this example. From Figure 2 it can be seen that SnO₂ and nano-graphite flakes in this contact material are evenly distributed on the Ag matrix.

[0053] The preparation method of the traditional Ag-8SnO₂ contact material is as follows: Weigh Ag powder and SnO₂ powder according to the composition of the target micro-nano AgSnO₂ contact material, and place them in a V-type mixer for mixing. The ball-to-material ratio is 1:1, the mixing rotation speed is 200 rpm, and the mixing time is 2 h. Then, use a tablet press to press and form at a pressure of 1 GPa. After demolding the green compact, sinter it at 850 °C for 2 h.

[0054] Figure 3 is the comparison chart of the welding force between the micro-nano Ag-8SnO₂-0.2Gr contact material prepared in this example and the traditional Ag-8SnO₂ contact material. From Figure 3It can be seen that, compared with the traditional Ag-8SnO2 contact material, the micro-nano Ag-8SnO2-0.2Gr contact material prepared in this embodiment has significantly reduced welding frequency and maximum welding force, and significantly enhanced anti-welding performance.

[0055] Example 3

[0056] The anti-welding micro-nano AgSnO2 contact material of this embodiment is composed of the following components by mass percentage: 8% SnO2, 0.4% nano-graphite flakes, and the balance is Ag.

[0057] The preparation method of the anti-welding micro-nano AgSnO2 contact material of this embodiment is the same as that of Example 2, and finally the micro-nano Ag-8SnO2-0.4Gr contact material is obtained.

[0058] Example 4

[0059] The anti-welding micro-nano AgSnO2 contact material of this embodiment is composed of the following components by mass percentage: 8% SnO2, 1.2% nano-graphite flakes, and the balance is Ag.

[0060] The preparation method of the anti-welding micro-nano AgSnO2 contact material of this embodiment is the same as that of Example 2, and finally the micro-nano Ag-8SnO2-1.2Gr contact material is obtained.

[0061] Example 5

[0062] The anti-welding micro-nano AgSnO2 contact material of this embodiment is composed of the following components by mass percentage: 4% SnO2, 0.2% carbon nanotubes, and the balance is Ag.

[0063] The difference between the preparation method of the anti-welding micro-nano AgSnO2 contact material of this embodiment and that of Example 2 is that: the sintering temperature in Step 8 is 900 °C; the pressure of re-pressing in Step 9 is 800 MPa, and finally the anti-welding micro-nano AgSnO2 contact material is obtained.

[0064] Example 6

[0065] The anti-welding micro-nano AgSnO2 contact material of this embodiment is composed of the following components by mass percentage: 12% SnO2, 0.2% carbon nanotubes, and the balance is Ag.

[0066] The preparation method of the anti-welding micro-nano AgSnO2 contact material of this embodiment is the same as that of Example 5.

[0067] Example 7

[0068] The anti-welding micro-nano AgSnO2 contact material of this embodiment is composed of the following components by mass percentage: 12% SnO2, 2.0% nano-graphite flakes, and the balance is Ag.

[0069] The difference between the preparation method of the anti-welding micro-nano AgSnO2 contact material of this embodiment and that of Example 1 is as follows: in Step 2, the ultrasonic stirring treatment time is 10 min; in Step 3, the ultrasonic treatment time is 60 min; in Step 4, the heating temperature is 65 °C; in Step 5, the number of blades is 3; in Step 7, the powder annealing temperature is 260 °C, the atmosphere is air, and the heating rate is 10 °C / min; in Step 8, the forming pressure is 140 MPa, and the sintering temperature is 900 °C, finally obtaining the micro-nano Ag-12SnO2-2.0Gr contact material.

[0070] Example 8

[0071] The anti-welding micro-nano AgSnO2 contact material of this embodiment is composed of the following components by mass percentage: 12% SnO2, 0.3% graphene with 1 - 3 layers, and the balance is Ag.

[0072] The difference between the preparation method of the anti-welding micro-nano AgSnO2 contact material of this embodiment and that of Example 1 is as follows: in Step 3, the ultrasonic treatment time is 60 min; in Step 4, the heating temperature is 74 °C; in Step 7, the powder annealing temperature is 200 °C; in Step 8, the forming pressure is 100 MPa, and the sintering temperature is 700 °C, finally obtaining the micro-nano Ag-12SnO2-0.3Gr contact material.

[0073] The properties of the micro-nano Ag-8SnO2-0.2Gr contact materials prepared in Examples 1 - 6 of the present invention were compared with those of traditional Ag-8SnO2 contact materials, and the results are shown in Table 1 below.

[0074] Table 1

[0075] Sample Name Conductivity / %IACS Hardness / HV Example 1 75.39 59.4 Example 2 61.42 92.1 Example 3 61.25 80.3 Example 4 57.72 70.6 Example 5 78.32 60.5 Example 6 57.91 69.8 <![CDATA[Traditional Ag-8SnO2 contact material]]> 77.07 59.5

[0076] As can be seen from Table 1, compared with the traditional Ag-8SnO2 contact material, due to the addition of graphite material, the conductivity of the micro-nano Ag-8SnO2-0.2Gr contact material prepared by the present invention has decreased, but the hardness has increased significantly. In addition, compared with the traditional Ag-8SnO2 contact material, the anti-welding property of the micro-nano Ag-8SnO2-0.2Gr contact material prepared by the present invention has been significantly enhanced, indicating that the contact material prepared by the present invention can be used under more stringent electrical parameters.

[0077] In summary, the AgSnO2 contact material prepared by the present invention has excellent comprehensive properties.

[0078] The above are only the preferred embodiments of the present invention and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent variations made to the above embodiments based on the technical essence of the invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A preparation method of a micro-nano AgSnO2 contact material resistant to welding, and the AgSnO2 contact material consists of the following components by mass percentage Composition: 4% - 12% SnO2, 0.1% - 2.0% graphite material, the balance being Ag; the graphite material is nano - graphite flakes, 1 - 3 layers of graphene or carbon nanotubes; the method comprises the following steps: Step 1: Weigh Ag powder, SnO2 powder and graphite material according to the composition of the target micro - nano AgSnO2 contact material. Step 2: Mix the Ag powder and SnO2 powder weighed in Step 1, add absolute ethanol, and the addition ratio is 100 mL of absolute ethanol per 10 g of powder. Then carry out ultrasonic and stirring treatment for 5 min - 10 min to obtain a powder suspension. Step 3: Add absolute ethanol to the graphite material weighed in Step 1, and the addition ratio is 1 L of absolute ethanol per 1 g of graphite material. Then carry out ultrasonic treatment for 30 min - 60 min to obtain a graphite material dispersion. Step 4: Place a heating magnetic stirrer in the fume hood, then place the powder suspension obtained in Step 2 together with the container on the heating magnetic disk of the heating magnetic stirrer. Insert the thermocouple into the powder suspension until the bottom of the container, and put a magnetic rotor to carry out heating magnetic stirring on the powder suspension, and the heating temperature is 65°C - 74°C. Step 5: Gradually add the graphite material dispersion obtained in Step 3 to the powder suspension in the state of heating magnetic stirring in Step 4 and mix them to obtain a mixed solution. After the addition of the graphite material dispersion is completed, continue to maintain the heating magnetic stirring state and open the fume hood to evaporate and remove the absolute ethanol in the mixed solution to obtain agglomerated powder. Step 6: Mechanically grind the agglomerated powder obtained in Step 5 with a mortar to obtain a composite powder. Step 7: Place the composite powder obtained in Step 6 in a ceramic boat and anneal it in a tube furnace. The annealing temperature is 200°C - 260°C, the heating rate is 5°C / min - 10°C / min, the holding time is 1 h, and the atmosphere is argon or air. Step 8: Load the annealed composite powder in Step 7 into a steel mold, carry out primary pressing and forming with a tablet press. The pressure of primary pressing and forming is 100 MPa - 140 MPa, the pressure holding time is 1 min, and the cyclic pressing method is adopted. After demolding, place the obtained primary - pressed green compact in a tube furnace and sinter it at 700°C - 900°C. The heating rate is 5°C / min - 10°C / min, the holding time is 2 h, and the atmosphere is argon to obtain a sintered block. Step 9: Place the sintered block obtained in Step 8 in a steel mold, carry out secondary pressing with a tablet press. The pressure of secondary pressing is 800 MPa - 850 MPa, the pressure holding time is 1 min, and the cyclic pressing method is adopted. After demolding, place the obtained secondary - pressed green compact in a tube furnace and re - sinter it at 600°C. The heating rate is 5°C / min - 10°C / min, the holding time is 2 h, and the atmosphere is argon to obtain a micro - nano AgSnO2 contact material resistant to welding.

2. The preparation method of a micro-nano AgSnO2 contact material resistant to welding according to claim 1, characterized in that, Composed of the following components by mass percentage Composition: 6% - 10% SnO2, 0.1% - 0.4% graphite material, the balance being Ag.

3. The preparation method of a micro-nano AgSnO2 contact material resistant to welding according to claim 2, characterized in that, Composed of the following components by mass percentage Composition: 8% SnO2, 0.2% nano-graphite flakes, and the balance is Ag.

4. The preparation method of a micro-nano AgSnO2 contact material resistant to welding according to claim 1, characterized in that, In Step 1, the particle size of the Ag powder is 0.1 μm to 2 μm, and the mass purity is not less than 99.9%; the particle size of the SnO2 powder is 0.3 μm to 1 μm, and the mass purity is not less than 99.9%.

5. The preparation method of a micro-nano AgSnO2 contact material resistant to welding according to claim 1, characterized in that, In Step 4, during the heating and magnetic stirring process, the initial rotation speed of the magnetic rotor is set to 500 rpm. When the liquid level height of the powder suspension is lower than 1.5 cm, the rotation speed of the magnetic rotor drops to 350 rpm. When the viscosity of the powder suspension increases to the point where it cannot flow, the rotation speed of the magnetic rotor drops to 0 rpm.

6. The preparation method of a micro-nano AgSnO2 contact material resistant to welding according to claim 1, characterized in that, In Step 5, a fan is placed around the mixed solution, and the airflow generated by the rotation of the fan is directed at the mouth of the container containing the mixed solution. The blade length of the fan is 5 cm, the number of blades is 2 to 3, and the rotation speed is 1500 rpm.

7. The preparation method of a micro-nano AgSnO2 contact material resistant to welding according to claim 1, characterized in that In Steps 8 and 9, the operation process of the cyclic pressing method is as follows: When loading, a 1-mm-thick gasket is placed between the lower punch of the steel die and the bottom of the die. The gasket is removed at the start of pressing. When the lower punch moves 1 mm upward relative to the die, the pressure is unloaded. Then, the 1-mm-thick gasket is placed between the lower punch and the bottom of the die again, and pressure is applied to make the upper punch of the steel die move downward 1 mm. The gasket is removed again for pressurization; repeat the process of the lower punch moving, re-placing the gasket, applying pressure to make the upper punch move, and removing the gasket again for pressurization until the pressure rises to the set value.

8. The preparation method of a micro-nano AgSnO2 contact material resistant to welding according to claim 1, characterized in that, In the sintering process in Step 8, first, the temperature is raised to 600 °C at a heating rate of 10 °C / min, and then to the target temperature at a heating rate of 5 °C / min; in the re-sintering process in Step 9, first, the temperature is raised to 500 °C at a heating rate of 10 °C / min, and then to the target temperature at a heating rate of 5 °C / min.

Images