Method for preparing silver-tungsten-nickel graphite through infiltration method

Abstract

The invention discloses a method for preparing silver-tungsten-nickel graphite through an infiltration method. The preparation method specifically comprises the steps that S1, raw materials are prepared and mixed, and mixed raw material powder and nickel graphite powder are mixed; s2, the mixed powder is subjected to pressing, dewaxing sintering and sintering infiltration, and a product is formed; s3, cleaning and drying the product; the nickel is added into the silver-tungsten graphite, the silver-tungsten-nickel graphite powder raw material is mixed and granulated, and dewaxing, sintering and infiltration are performed in the protective atmosphere, so that the wettability problem of liquid silver and solid substances at the infiltration temperature, particularly the wettability problem of silver and graphite, is solved, and the sintering and infiltration can be smoothly completed; the relative density of the prepared AgWNi / C reaches 97% or above, the electric conductivity IACS% can be improved by about 5%-40%, the tensile strength is improved by 80 Mpa-300 Mpa, and the use amount of AgW / C electric contact silver is reduced by 5%-50%.

Description

Technical Field

[0001] This invention relates to the field of silver-tungsten-nickel graphite preparation technology, specifically a method for preparing silver-tungsten-nickel graphite by melt infiltration. Background Technology

[0002] AgW / C electrical contact materials are widely used in circuit breakers. Currently, the heat treatment process for preparation involves solid-state sintering at 780 to 880 degrees Celsius. However, the relative density of AgW / C materials prepared by this method can only reach about 95%. In addition, there are many internal interfaces, resulting in low conductivity. Furthermore, due to the low sintering temperature, the bonding strength of the material is also low. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing silver-tungsten-nickel graphite by melt infiltration, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing silver-tungsten-nickel graphite by melt infiltration, wherein the preparation method specifically includes: S1. Prepare and mix the raw materials and mix the mixed raw material powder with nickel graphite powder; S2. Press, dewax, sinter, and sinter infiltration of the mixed powder to form the product; S3. Clean and dry the product.

[0005] Preferably, step S1 specifically includes: a1. Prepare raw material powders: 20%–85% silver powder, 15%–80% tungsten powder, and 0.5%–6.0% paraffin binder, and mix them according to the formula ratio; a2. Dry the mixed raw material powder; a3. Mix the dried raw material powder with nickel graphite powder; a4. Form the powder mixed in step a3 into granules to obtain powder particles of 30 mesh to 250 mesh.

[0006] Preferably, step S2 specifically includes: b1. Press the obtained powder particles into shape; b2. The pressed green blank and silver sheet are dewaxed, sintered and infiltrated in a protective atmosphere; b3. Re-press the sintered product.

[0007] Preferably, step b2 specifically includes: b21. Dewaxing and sintering are carried out in a protective atmosphere furnace by raising the temperature from room temperature to 150℃~930℃, and the holding time is set to 100min~1000min. b22. The protective atmosphere furnace is then heated to between 965℃ and 1350℃ for sintering and melting, and the holding time is set to 3 min to 300 min. b23. After sintering and melting, the furnace is cooled to room temperature in a protective atmosphere before being removed from the furnace.

[0008] Preferably, in step a2, the drying temperature is set to 50℃~250℃, and the drying time is set to 1h~24h.

[0009] Preferably, in step a3, the nickel-graphite powder contains 1%–80% nickel and 1%–60% graphite. Preferably, in step b1, the pressure during the pressing process is set to 1 MPa to 300 MPa.

[0010] Preferably, in step b2, the protective atmosphere comprises a mixture of hydrogen and nitrogen, wherein the proportion of hydrogen is 10% to 100%.

[0011] Preferably, in step b3, the pressure during the pressing process is set to 400 MPa to 1600 MPa.

[0012] Compared with the prior art, the beneficial effects of the present invention are: This invention discloses a method for preparing silver-tungsten-nickel graphite by melt infiltration. Nickel is added to the silver-tungsten-nickel graphite, and the raw materials are mixed and granulated. Dewaxing, sintering, and melt infiltration are then performed under a protective atmosphere. This method solves the problem of wettability between liquid silver and solid materials at the melt infiltration temperature, specifically the wettability between silver and graphite, allowing the sintering and melt infiltration to be completed smoothly. The prepared AgWNi / C has a relative density of over 97%, its conductivity (IACS%) can be increased by about 5% to 40%, its tensile strength can be increased by 80 MPa to 300 MPa, and the amount of silver used in the AgW / C electrical contacts can be reduced by 5% to 50%. Detailed Implementation

[0013] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0014] In the description of this invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicating orientation or positional relationships, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0015] In the description of this patent, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection or setting, a detachable connection or setting, or an integrated connection or setting. Those skilled in the art can understand the specific meaning of the above terms in this patent according to the specific circumstances.

[0016] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a number" means two or more, unless otherwise explicitly specified.

[0017] Example 1 This invention provides a method for preparing silver-tungsten-nickel graphite by melt infiltration: the preparation method specifically includes: S1. Prepare and mix the raw materials and mix the mixed raw material powder with nickel graphite powder; a1. Prepare raw material powders: 20%–85% silver powder, 15%–80% tungsten powder, and 0.5%–6.0% paraffin binder, and mix them according to the formula ratio; a2. Dry the mixed raw material powder at a temperature of 75℃ for 6 hours. a3. Mix the dried raw material powder with nickel graphite powder, wherein the nickel graphite powder contains 80% nickel and 20% graphite. a4. Form the powder mixed in step a3 into granules to obtain 200-mesh powder particles; S2. Press, dewax, sinter, and sinter infiltration of the mixed powder to form the product; b1. Press the obtained powder particles into shape, and set the pressure to 60 MPa during the pressing process; b2. The pressed green blank and silver sheet are dewaxed, sintered and infiltrated in a protective atmosphere, which includes a mixture of hydrogen and nitrogen, with hydrogen accounting for 50%; b21. Dewaxing and sintering are carried out in a protective atmosphere furnace by raising the temperature from room temperature to 150℃~930℃, and the holding time is set to 100min~1000min. b22. The protective atmosphere furnace is then heated to between 965℃ and 1350℃ for sintering and melting, and the holding time is set to 3 min to 300 min. b23. After sintering and melting, the furnace is cooled to room temperature in a protective atmosphere before being removed from the furnace. b3. The sintered product is repressed, and the pressure during the pressing process is set to 400Mpa~1600Mpa; S3. Clean and dry the product.

[0018] Example 2 This invention provides a method for preparing silver-tungsten-nickel graphite by melt infiltration: the preparation method specifically includes: S1. Prepare and mix the raw materials and mix the mixed raw material powder with nickel graphite powder; a1. Prepare raw material powders: 20%–85% silver powder, 15%–80% tungsten powder, and 0.5%–6.0% paraffin binder, and mix them according to the formula ratio; a2. Dry the mixed raw material powder at a temperature of 50℃~250℃ for 1-24 hours. a3. Mix the dried raw material powder with nickel graphite powder, wherein the nickel content in the nickel graphite powder is 1% to 80% and the graphite content is 1% to 60%; a4. Form the powder mixed in step a3 into granules to obtain powder particles of 30-250 mesh. S2. Press, dewax, sinter, and sinter infiltration of the mixed powder to form the product; b1. Press the obtained powder particles into shape, and set the pressure to 1Mpa~300Mpa during the pressing process; b2. The pressed green blank and silver sheet are dewaxed, sintered and infiltrated in a protective atmosphere, which includes pure hydrogen. b21. Dewaxing and sintering are carried out in a protective atmosphere furnace by raising the temperature from room temperature to 150℃~930℃, and the holding time is set to 100min~1000min. b22. The protective atmosphere furnace is then heated to between 965℃ and 1350℃ for sintering and melting, and the holding time is set to 3 min to 300 min. b23. After sintering and melting, the furnace is cooled to room temperature in a protective atmosphere before being removed from the furnace. b3. The sintered product is repressed, and the pressure during the pressing process is set to 400Mpa~1600Mpa; S3. Clean and dry the product.

[0019] Comparative Example 1 Another method for preparing silver-tungsten-nickel graphite via melt infiltration is provided: the preparation method specifically includes: S1. Prepare and mix the raw materials; a1. Prepare raw material powders: 20%–85% silver powder, 15%–80% tungsten powder, and 0.5%–6.0% paraffin binder, and mix them according to the formula ratio; a2. Dry the mixed raw material powder at a temperature of 90℃ for 6 hours. a3. Form the powder mixed in step a2 into granules to obtain 200-mesh powder particles; S2. Press, dewax, sinter, and sinter infiltration of the mixed powder to form the product; b1. Press the obtained powder particles into shape, and set the pressure to 45 MPa during the pressing process; b2. The pressed green blank and silver sheet are dewaxed, sintered and infiltrated in a protective atmosphere, which includes a mixture of hydrogen and nitrogen, with hydrogen accounting for 40%; b21. Dewaxing and sintering are carried out in a protective atmosphere furnace by raising the temperature from room temperature to 150℃~930℃, and the holding time is set to 100min~1000min. b22. The protective atmosphere furnace is then heated to between 965℃ and 1350℃ for sintering and melting, and the holding time is set to 3 min to 300 min. b23. After sintering and melting, the furnace is cooled to room temperature in a protective atmosphere before being removed from the furnace. b3. The sintered product is repressed, and the pressure during the pressing process is set to 400Mpa~1600Mpa; S3. Clean and dry the product.

[0020] Comparative Example 2 Another method for preparing silver-tungsten-nickel graphite via melt infiltration is provided: the preparation method specifically includes: S1. Prepare and mix the raw materials and mix the mixed raw material powder with nickel graphite powder; a1. Prepare raw material powders: 20%–85% silver powder, 15%–80% tungsten powder, and 0.5%–6.0% paraffin binder, and mix them according to the formula ratio; a2. Dry the mixed raw material powder at a temperature of 50℃~250℃ for 1-24 hours. a3. Form the powder mixed in step a2 into granules to obtain powder particles of 30-250 mesh. S2. Press, dewax, sinter, and sinter infiltration of the mixed powder to form the product; b1. Press the obtained powder particles into shape, and set the pressure to 10Mpa~200Mpa during the pressing process; b2. The pressed green blank and silver sheet are dewaxed, sintered and infiltrated in a protective atmosphere, which includes pure hydrogen. b21. Dewaxing and sintering are carried out in a protective atmosphere furnace by raising the temperature from room temperature to 150℃~930℃, and the holding time is set to 100min~1000min. b22. The protective atmosphere furnace is then heated to between 965℃ and 1350℃ for sintering and melting, and the holding time is set to 3 min to 300 min. b23. After sintering and melting, the furnace is cooled to room temperature in a protective atmosphere before being removed from the furnace. b3. The sintered product is repressed, and the pressure during the pressing process is set to 400Mpa~1600Mpa; S3. Clean and dry the product.

[0021] In summary, through Examples 1, 2, Comparative Examples 1 and 2, it was found that by adding nickel to silver-tungsten-nickel graphite raw materials, mixing and granulating the raw materials, and then performing dewaxing, sintering, and melting infiltration in a protective atmosphere, the wettability problem of liquid silver with solid materials at the melting infiltration temperature, especially the wettability problem of silver with graphite, was solved, thus enabling the sintering and melting infiltration to be successfully completed.

[0022] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing silver-tungsten-nickel graphite by melt infiltration, characterized in that: The preparation method specifically includes: S1. Prepare and mix the raw materials and mix the mixed raw material powder with nickel graphite powder; S2. Press, dewax, sinter, and sinter infiltration of the mixed powder to form the product; S3. Clean and dry the product.

2. The method for preparing silver-tungsten-nickel graphite by melt infiltration according to claim 1, characterized in that: Step S1 specifically includes: a1. Prepare raw material powders: 20%–85% silver powder, 15%–80% tungsten powder, and 0.5%–6.0% paraffin binder, and mix them according to the formula ratio; a2. Dry the mixed raw material powder; a3. Mix the dried raw material powder with nickel graphite powder; a4. Form the powder mixed in step a3 into granules to obtain powder particles of 30 mesh to 250 mesh.

3. The method for preparing silver-tungsten-nickel graphite by melt infiltration according to claim 1, characterized in that: Step S2 specifically includes: b1. Press the obtained powder particles into shape; b2. The pressed green blank and silver sheet are dewaxed, sintered and infiltrated in a protective atmosphere; b3. Re-press the sintered product.

4. The method for preparing silver-tungsten-nickel graphite by melt infiltration according to claim 3, characterized in that: Step b2 specifically includes: b21. Dewaxing and sintering are carried out in a protective atmosphere furnace by raising the temperature from room temperature to 150℃~930℃, and the holding time is set to 100min~1000min. b22. The protective atmosphere furnace is then heated to between 965℃ and 1350℃ for sintering and melting, and the holding time is set to 3 min to 300 min. b23. After sintering and melting, the furnace is cooled to room temperature in a protective atmosphere before being removed from the furnace.

5. The method for preparing silver-tungsten-nickel graphite by melt infiltration according to claim 2, characterized in that: In step a2, the drying temperature is set to 50℃~250℃, and the drying time is set to 1h~24h.

6. The method for preparing silver-tungsten-nickel graphite by melt infiltration according to claim 2, characterized in that: In step a3, the nickel-graphite powder contains 1% to 80% nickel and 1% to 60% graphite.

7. The method for preparing silver-tungsten-nickel graphite by melt infiltration according to claim 3, characterized in that: In step b1, the pressure during the pressing process is set to 1 MPa to 300 MPa.

8. The method for preparing silver-tungsten-nickel graphite by melt infiltration according to claim 3, characterized in that: The protective atmosphere in step b2 includes a mixture of hydrogen and nitrogen, wherein the proportion of hydrogen is 10% to 100%.

9. The method for preparing silver-tungsten-nickel graphite by melt infiltration according to claim 3, characterized in that: In step b3, the pressure during the pressing process is set to 400 MPa to 1600 MPa.