CN114086022B - Method for preparing Ag-based tungsten-containing electric contact material based on foaming infiltration process and product thereof - Google Patents

Abstract

The invention discloses a method for preparing an Ag-based tungsten-containing electric contact material based on a foaming infiltration process and a product thereof, in particular to a method for preparing an Ag (W, WC) electric contact material with high silver content and low resistivity by an infiltration process. Adding a foaming agent into the Ag-based mixed powder for sintering reinforcement, wrapping the sintering-reinforced Ag-based powder with a separant, sintering the wrapped Ag-based powder to a liquid phase, crushing and screening to obtain high-strength porous Ag-based powder, pressing the porous Ag-based powder into a framework, arranging a pure silver sheet above the framework, and carrying out liquid-phase infiltration on the framework at high temperature to obtain the Ag-based electric contact material with high silver content and low resistivity. The invention solves the problem that the high-silver-content Ag-based electric contact material can only be manufactured by adopting a solid-phase sintering process, and compared with the Ag-based electric contact material with the same silver content prepared by adopting the sintering process, the high-silver-content Ag-based electric contact material has higher density and burning loss resistance, lower resistivity, greatly improved service performance such as electric service life and the like.

Description

Method for preparing Ag-based tungsten-containing electric contact material based on foaming infiltration process and product thereof

Technical Field

The inventionRelates to the field of electrical contact materials, in particular to a method for preparing an Ag-based tungsten-containing electrical contact material based on a foaming infiltration process and a product thereof.

Background

Ag-based electric contact materials, in particular AgW and AgWC electric contact materials, are applied to circuit breakers, miniature circuit breakers and earth leakage protection switches, and are generally manufactured by adopting an infiltration process, wherein the WC content is between 30 and 80 weight percent or the W content is between 40 and 80 weight percent. In recent years, due to the consideration of energy consumption and safety, the requirement for the temperature rise of the switch in the design of the switch is higher and higher, particularly in a miniature circuit breaker, the contact resistance of a material with the WC content higher than 30 wt% or the W content higher than 40 wt% is difficult to meet the use requirement, while an electric contact material with the high Ag content and the low WC (W) content can only be prepared by adopting a solid phase sintering process, and due to the poor bonding strength of silver and WC (W) and the slightly poor compactness of the material, the prepared electric contact material has insufficient burning loss resistance, cannot meet the requirements of the short-circuit breaking capacity and the electric service life performance of the switch, and the development of the industry is severely restricted.

The powder metallurgy process is adopted to prepare the electric contact material, and the infiltration process is well known to obtain the optimal material performance. Compared with a solid-phase sintering process, the density, the hardness, the conductivity and the bonding strength of the material prepared by the infiltration process are obviously improved, and the porosity is obviously reduced; the electric arc burning resistance and the mechanical abrasion resistance of the corresponding contact material are obviously improved. However, the preparation of the electric contact material by the infiltration process can be realized only when the material meets certain characteristics, and can only be prepared by adopting a solid-phase sintering mode under the unsatisfiable condition. The electric contact material needs to meet the following characteristics and is prepared by adopting an infiltration process:

1. in order to ensure the shape of a semi-finished product after infiltration, the volume of infusible particles in the framework is more than 25 percent in the infiltration process;

2. the framework has better wettability with the infiltration metal;

3. the skeleton and the infiltration metal are not mutually fused or have small solubility.

The AgWC material can satisfy the above 3 conditions when the silver content is less than 60 wt%, so contact materials with low silver content such as AgWC40, AgWC50, AgWC60, AgW50, AgW60, AgW70, etc. are generally prepared by infiltration process, and contact materials with high silver content such as AgWC10, AgWC15, AgWC20, AgW10, AgW20, AgW30, and other AgWC extension materials such as AgWC12C3, AgWC22C3, AgWC27C3, etc. are prepared by solid phase sintering-re-pressing process or solid phase sintering-extrusion process because they cannot satisfy infiltration condition (1).

The invention patent of China with the publication number of CN108531764A provides a material of AgWCNiC, which relates to a pressure infiltration process, and because the problem that the volume of infusible particles in a framework is more than 25 percent in the infiltration process is not solved, a solid phase sintering process at 800-900 ℃ is selected when the content of tungsten carbide is 12-25 percent by weight, and a pressure infiltration process is selected when the content of tungsten carbide is more than 25 percent by weight and contains graphene, nickel and the like. Although graphite alkene can increase the infusible phase volume, also can increase resistance simultaneously, owing to with graphite alkene and the nonwetting characteristic of silver liquid under the ordinary pressure, can cause silver liquid phase to ooze out from the skeleton backward behind the sintering liquid phase temperature simultaneously, seriously influence material bonding strength and resistivity, the intervention of external pressure has certain improvement to bonding strength harmfully, nevertheless can't avoid completely. The process conditions of the infiltration temperature of 980-1100 ℃ and the gas pressure of 100MPa-1GPa can be realized only by a hot isostatic pressing machine, and the process cost is too high.

The Chinese patent with publication number CN110373566A provides a preparation process of AgWC (W), which relates to a method for manufacturing an electrical contact material by infiltrating, compacting and crushing AgWC (W) material, uniformly mixing with C, Ag according to a certain proportion, and then adopting a solid phase sintering process. The manufactured product contains partial infiltration tissues, the main structure is still a solid-phase sintering tissue, and the uniformity of the tissue is difficult to ensure. Meanwhile, due to the high ductility and toughness of silver and the high strength of WC (W), the AgWC (W) is infiltrated and compacted, the material is very difficult to crush, the material is more difficult to crush into powder with ideal particle size distribution, and the process is difficult to realize large-scale production.

In the Chinese patent publication No. CN104209520A, pores are increased by adding a polyacrylate pore-forming agent into powder, the strength of the powder prepared by the method is low, the production requirement can be met when preparing a low-silver-content Ag (W, WC) material, and when preparing an Ag-based electric contact material with WC content of less than 30 wt% or W content of less than 40 wt%, the framework collapse and even burst and cannot be formed due to severe deformation of the pores in the infiltration process.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for preparing an Ag-based tungsten-containing electric contact material based on a foaming infiltration process and a product thereof. The foaming infiltration process is a breakthrough innovation of the traditional infiltration process, provides a new idea and method for preparing the silver-based electric contact material with low resistivity and high silver content, and has higher density and burning loss resistance and greatly improved service performances such as electric service life and the like compared with a solid-phase sintering process.

In order to achieve the above object, a first aspect of the present invention provides a method for preparing a framework for use in an infiltration preparation process of a tungsten-containing electrical contact material, comprising:

(1) foaming: adding a foaming agent into the Ag-based mixed powder, uniformly stirring and sieving to obtain Ag-based mixed powder particles wetted by the foaming agent, and heating and foaming the sieved Ag-based mixed powder particles in an oven, wherein the Ag-based mixed powder comprises the following components: 55 wt% -77 wt% of Ag, and the balance of W or WC;

(2) solid-phase sintering and strengthening: solid-phase sintering the Ag-based mixed powder particles foamed in the step (1) to form fixed pores inside the particles;

(3) packaging release agent: heating and stirring the sintering-reinforced Ag-based mixed powder particles in a stirrer, and spraying a paraffin solution at the same time to wrap the powder with the paraffin and dry a solvent of the paraffin solution in the stirring process;

(4) powder liquid phase sintering: carrying out high-temperature liquid phase sintering on the Ag-based mixed powder particles wrapped with the paraffin in the step (3), crushing and screening after sintering to obtain high-strength porous prefabricated powder with good fluidity;

(6) and (3) pressing and forming: and (4) pressing the high-strength porous prefabricated powder in the step (4) into a framework.

Further setting the adding amount of the foaming agent in the step (1) according to the mass ratio of the effective components to the Ag-based mixed powder of 1: 100-1000.

Further setting that the spraying amount of the paraffin solution in the step (3) is 1:100-1:500 according to the mass ratio of the paraffin to the Ag-based mixed powder.

The foaming agent is one or a combination of ammonium bicarbonate, ammonium carbonate, ammonium hydrogen oxalate, ammonium oxalate and hydrogen peroxide.

Further setting that the powder screening process in the step (1) is 100-mesh and 300-mesh screening, and the post-screening foaming process is as follows: the foaming temperature is 60-200 ℃, and the foaming time is 30-60 minutes.

The solid phase sintering process in the step (2) is further set as follows: the sintering temperature is 500-800 ℃, the sintering time is 30-120 minutes, and the sintering atmosphere is reducing or vacuum atmosphere.

Further setting the heating temperature in the step (3) to be 60-100 ℃, the paraffin content in the paraffin solution to be 1-10 wt percent, and the solvent to be gasoline;

the liquid phase sintering process in the step (4) is further set as follows: the gradient sintering process includes sintering at 400-500 deg.c for 60-120 min, sintering at 600-700 deg.c for 60-120 min, sintering at 800-900 deg.c for 60-120 min, and sintering at 1000-1100 deg.c for 60-120 min in reducing atmosphere or vacuum atmosphere. The liquid phase sintering and screening process in the step (4) is to screen the powder by 50-100 meshes.

In addition, the invention also provides a method for preparing the Ag-based tungsten-containing electric contact material based on the foaming infiltration process, and the method is based on the skeleton prepared by the method, and the skeleton is infiltrated with silver by the infiltration process to form the Ag-based tungsten-containing electric contact material.

The temperature of the infiltration process is 1000-1100 ℃, the infiltration time is 60-120 minutes, and the infiltration atmosphere is a reducing atmosphere or a vacuum atmosphere;

in addition, the invention also provides the Ag-based tungsten-containing electric contact material prepared by the method, the Ag-based tungsten-containing electric contact material is a silver-tungsten electric contact material or a silver-tungsten carbide electric contact material, and the electric contact material after infiltration comprises one of AgWC (20-29) and AgW (30-35) according to the mass ratio.

The invention has the beneficial effects that:

1. the invention provides a preparation method of an infiltration process Ag (W, WC) electric contact material, which is used for preparing a high-silver-content and low-resistance infiltration process Ag (W, WC) electric contact material, wherein the silver content of the material is 65-80 wt%, the high silver content ensures low and stable contact resistance and lower bulk resistance in the electric contact process, the temperature rise of a contact in the electric contact process can be ensured to be low and stable, the electric arc burning resistance and the mechanical wear resistance of the material are ensured by adopting an infiltration mode, and the electric service life of the material is prolonged.

2. The high-strength porous powder is prepared and used as a matrix material of a product framework, and more liquid silver is filled in the pores of the high-strength framework in the infiltration process, so that the requirement of the infiltration process on the volume of a solid phase is met. The high-temperature stability of the porous powder is ensured by adopting the liquid phase sintering process, and the powder does not have the adverse phenomena of severe particle rearrangement, deformation, collapse and the like in the liquid phase sintering process, so that the stability of the matrix skeleton shape in the infiltration process is ensured, and the infiltration process can be smoothly carried out. The high framework porosity can cut the distribution of liquid silver in the electric contact process, and prevent the fusion welding phenomenon caused by the aggregation of local liquid silver in the effective contact area of the moving contact and the static contact.

3. In order to realize the preparation of the high-strength porous powder particles, the foaming material is used as an expanding agent for sintering the Ag-based powder particles, so that the size of the internal pores of the Ag-based powder is increased, and the filling of more silver liquid in the infiltration process is facilitated. Paraffin wrapped outside the powder particles is used as an isolating agent, so that the problem that the particles cannot be broken and separated due to the fact that liquid-phase silver bridges are formed among the particles in the liquid-phase sintering process of the powder particles is solved. The paraffin is selected as the wrapping isolating agent because the paraffin is strong in wrapping performance by spraying, the wrapped powder is mutually isolated, the paraffin is slowly decomposed in the gradient sintering process before liquid phase sintering, the residue of the trace graphite film remained after decomposition has good anti-bonding capability, the problem that silver bridge adhesion is difficult to break and separate in the liquid phase sintering process of powder particles can be solved, and meanwhile, the trace graphite residue is broken and granulated and separated and broken by pressing a framework film, so that the infiltration process is not influenced.

4. The particle size distribution of the sintered powder can be adjusted by adjusting the dosage of the foaming agent and the release agent and the liquid phase sintering temperature, and the addition amount of the foaming agent and the release agent and the liquid phase sintering temperature in the method are the optimal choices comprehensively considered in multiple aspects such as bulk particle flowability, powder friability, framework weight stability, framework infiltration stability and the like through multiple experiments.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is within the scope of the present invention for those skilled in the art to obtain other drawings based on the drawings without inventive exercise.

FIG. 1 is an SEM topography 500X of a liquid phase sintered porous powder provided by an embodiment of the invention;

FIG. 2 is an SEM image 5000X of a liquid phase sintered porous powder provided by an embodiment of the invention;

fig. 3 is a gold phase diagram 100X after infiltration of the contact material according to the embodiment of the present invention, in which a structure after infiltration of coarse porous powder is shown in a dotted line, and a light-colored substance is a silver liquid filled in pores in the structure. The tissue outside the dotted line is fine particle porous powder tissue which is distributed around the coarse particles and plays a role in filling the skeleton.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.

Example one

Weighing 5kg of AgWC40 mixed powder, respectively adding 100g of 5 wt% ammonium bicarbonate solution and 5 wt% ammonium carbonate solution, uniformly stirring, and sieving the stirred powder by using a 300-mesh stainless steel sieve to obtain AgWC powder particles wrapped by the foaming agent;

putting the screened powder into a graphite boat, transferring the graphite boat into a vacuum oven, heating the graphite boat to 200 ℃, preserving heat for 60 minutes, transferring the foamed powder and the graphite boat into a hydrogen atmosphere sintering furnace, sintering the graphite boat at 800 ℃, and preserving heat for 30 minutes;

stirring the sintering-strengthened powder in a stirrer, heating the powder, spraying 0.5kg of 10wt% paraffin-gasoline solution, completely wrapping the powder, and heating and stirring until the gasoline in the powder is dried;

loading the powder coated with the calcined paraffin into a boat, sintering at 400 ℃, 120 minutes, 600 ℃, 120 minutes, 800 ℃, 120 minutes and 1000 ℃, 60 minutes in a hydrogen atmosphere, cooling, crushing and sieving with a 100-mesh sieve after sintering to obtain high-strength porous prefabricated AgWC40 powder with fluidity;

pressing porous prefabricated AgWC40 powder into an AgWC40 porous framework with the single weight of 10g, arranging pure silver sheets with the single weight of 3.8g on the AgWC40 porous framework, and carrying out infiltration in an infiltration furnace in a hydrogen atmosphere at the infiltration temperature of 1100 ℃ for 120 minutes to obtain an infiltration method AgWC29 contact material;

the resistivity of the contact material AgWC29 tested by the infiltration method is 2.51 mu omega cm, and the resistivity is reduced by 0.41 mu omega cm compared with the resistivity of 2.92 mu omega cm compared with the resistance of the contact material tested by the sintering method.

Example two

Weighing 10kg of AgWC30 mixed powder, respectively adding 1kg of 10wt% hydrogen peroxide solution, uniformly stirring, and sieving the stirred powder by using a 100-mesh stainless steel sieve to obtain AgWC powder particles coated by a foaming agent;

putting the screened powder into a graphite boat, transferring the graphite boat into a vacuum oven, heating the graphite boat to 60 ℃, preserving heat for 30 minutes, transferring the foamed powder and the graphite boat into an ammonia decomposition atmosphere sintering furnace, sintering the powder and the graphite boat at 500 ℃, and preserving heat for 120 minutes;

stirring the sintering-strengthened powder in a stirrer, heating the powder, spraying 2kg of 1wt% paraffin-gasoline solution, completely wrapping the powder, and heating and stirring until the gasoline in the powder is dried;

loading the powder coated with the calcined paraffin into a boat, sintering at 500 ℃, 60 minutes, 700 ℃, 60 minutes, 900 ℃, 60 minutes, 1100 ℃ and 60 minutes under an ammonia decomposition atmosphere, cooling, crushing and sieving with a 50-mesh sieve after sintering to obtain high-strength porous prefabricated AgWC30 powder with fluidity;

pressing porous prefabricated AgWC30 powder into an AgWC30 porous framework with the single weight of 5g, arranging a pure silver sheet with the single weight of 1g on the AgWC30 porous framework, and carrying out infiltration in an infiltration furnace with ammonia decomposition atmosphere at the infiltration temperature of 1000 ℃ for 60 minutes to obtain an infiltration method AgWC25 contact material;

the resistivity of the AgWC25 contact material tested by the infiltration method is reduced by about 0.37 mu omega cm compared with the resistivity of 2.66 mu omega cm compared with the sintering method.

EXAMPLE III

Weighing 5kg of AgWC23 mixed powder, respectively adding 200g of 6 wt% ammonium oxalate solution and 200g of 6 wt% ammonium hydrogen oxalate solution, uniformly stirring, and sieving the stirred powder by using a 200-mesh stainless steel sieve to obtain AgWC powder particles coated by a foaming agent;

putting the screened powder into a graphite boat, transferring the graphite boat into a vacuum oven, heating the graphite boat to 100 ℃, preserving heat for 60 minutes, transferring the foamed powder and the graphite boat into a vacuum sintering furnace, sintering the graphite boat for 600 ℃, and preserving heat for 60 minutes;

stirring the sintering-strengthened powder in a stirrer, heating the powder, spraying 0.5kg of 4% paraffin-gasoline solution, completely wrapping the powder, and heating and stirring until the gasoline in the powder is dried;

loading the powder coated with the calcined paraffin into a boat, sintering at 450 ℃, 90 minutes, 650 ℃, 90 minutes, 850 ℃, 90 minutes, 1050 ℃, 90 minutes in a vacuum atmosphere, cooling, crushing and sieving with a 80-mesh sieve after sintering to obtain high-strength porous prefabricated AgWC23 powder with fluidity;

pressing porous prefabricated AgWC23 powder into an AgWC23 porous framework with the single weight of 6g, arranging a pure silver sheet with the single weight of 0.9g on the AgWC23 porous framework, and carrying out infiltration in a vacuum infiltration furnace at the infiltration temperature of 1050 ℃ for 90 minutes to obtain an infiltration method AgWC20 contact material;

the resistivity of the AgWC20 contact material tested by the infiltration method is reduced by 0.34 mu omega cm compared with the resistivity of 2.35 mu omega cm compared with the sintering method.

Example four

Weighing 5kg of AgW40 mixed powder, respectively adding 100g of 2 wt% ammonium oxalate solution, 2 wt% ammonium hydrogen oxalate solution, 2 wt% ammonium bicarbonate solution, 2 wt% ammonium carbonate solution and 1wt% hydrogen peroxide solution, uniformly stirring, and sieving the stirred powder by using a 200-mesh stainless steel sieve to obtain AgW powder particles coated by a foaming agent;

putting the screened powder into a graphite boat, transferring the graphite boat into a vacuum oven, heating the graphite boat to 150 ℃, preserving heat for 50 minutes, transferring the foamed powder and the graphite boat into an ammonia decomposition furnace, sintering the powder and the graphite boat for 700 ℃, and preserving heat for 50 minutes;

stirring the sintering-strengthened powder in a stirrer, heating the powder, spraying 0.6kg of 3% paraffin-gasoline solution, completely wrapping the powder, and heating and stirring until the gasoline in the powder is dried;

loading the powder coated with the calcined paraffin into a boat, sintering the powder in a hydrogen atmosphere, wherein the sintering process is 450 ℃, 60 minutes, 650 ℃, 60 minutes, 850 ℃, 60 minutes, 1050 ℃, 60 minutes, cooling, crushing and sieving the powder with a 60-mesh sieve after sintering to obtain high-strength porous prefabricated AgW40 powder with fluidity;

pressing porous prefabricated AgW40 powder into an AgW40 porous skeleton with the single weight of 6g, arranging pure silver sheets with the single weight of 1.27g on the AgW40 porous skeleton, and carrying out infiltration in a vacuum infiltration furnace at the infiltration temperature of 1070 ℃ for 80 minutes to obtain an infiltration method AgW33 contact material;

the contact material tested by the infiltration method AgW33 has the resistivity 2.21 mu omega cm reduced by 0.21 mu omega cm compared with the resistivity 2.42 mu omega cm compared with the sintering method.

EXAMPLE five

Weighing 10kg of AgW37 mixed powder, respectively adding 200g of 2 wt% ammonium oxalate solution, 2 wt% ammonium hydrogen oxalate solution, 4 wt% ammonium bicarbonate solution and 4 wt% ammonium carbonate solution, uniformly stirring, and sieving the stirred powder by using a 120-mesh stainless steel sieve to obtain AgW powder particles coated by a foaming agent;

putting the screened powder into a graphite boat, transferring the graphite boat into a vacuum oven, heating the graphite boat to 120 ℃, preserving heat for 40 minutes, transferring the foamed powder and the graphite boat into a vacuum sintering furnace, sintering the powder and the graphite boat to 750 ℃, and preserving heat for 45 minutes;

stirring the sintering-strengthened powder in a stirrer, heating the powder, spraying 0.5kg of 8% paraffin-gasoline solution, completely wrapping the powder, and heating and stirring until the gasoline in the powder is dried;

loading the powder coated with the calcined paraffin into a boat, sintering at 500 ℃, 120 minutes, 700 ℃, 120 minutes, 900 ℃, 120 minutes and 1100 ℃, 120 minutes in a vacuum atmosphere, cooling, crushing and sieving with a 80-mesh sieve after sintering to obtain high-strength porous prefabricated AgW37 powder with fluidity;

pressing porous prefabricated AgW37 powder into an AgW37 porous framework with the single weight of 8g, arranging pure silver sheets with the single weight of 1.87g on the AgW37 porous framework, and carrying out infiltration in a hydrogen atmosphere furnace at the infiltration temperature of 1090 ℃ for 100 minutes to obtain an infiltration method AgW30 contact material;

the resistivity of the contact material tested by the infiltration method AgW30 is reduced by 0.23 mu omega cm compared with the resistivity of 2.3 mu omega cm by the sintering method.

EXAMPLE six

Weighing 10kg of AgW45 mixed powder, adding 0.5kg of 2 wt% hydrogen peroxide solution, uniformly stirring, and sieving the stirred powder by using a 150-mesh stainless steel sieve to obtain AgW powder particles coated by a foaming agent;

putting the screened powder into a graphite boat, transferring the graphite boat into a vacuum oven, heating the graphite boat to 100 ℃, preserving heat for 45 minutes, transferring the foamed powder and the graphite boat into an ammonia decomposition atmosphere sintering furnace, sintering the powder and the graphite boat for 500 ℃, and preserving heat for 100 minutes;

stirring the sintering-strengthened powder in a stirrer, heating the powder, spraying 2kg of 1wt% paraffin-gasoline solution, completely wrapping the powder, and heating and stirring until the gasoline in the powder is dried;

loading the calcined paraffin coated powder into a boat, sintering at 500 ℃, 80 minutes, 700 ℃, 80 minutes, 900 ℃, 80 minutes and 1100 ℃, 80 minutes under an ammonia decomposition atmosphere, cooling, crushing and sieving with a 50-mesh sieve after sintering to obtain high-strength porous prefabricated AgW45 powder with fluidity;

pressing porous prefabricated AgW45 powder into an AgW45 porous framework with the single weight of 5g, arranging pure silver sheets with the single weight of 1.43g on the AgW45 porous framework, and carrying out infiltration in an infiltration furnace with ammonia decomposition atmosphere at the infiltration temperature of 1000 ℃ for 60 minutes to obtain an infiltration AgW35 contact material;

the contact material tested by the infiltration method AgW35 has the resistivity of 2.27 mu omega cm reduced by 0.18 mu omega cm compared with the resistivity of 2.45 mu omega cm compared with the sintering method.

The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is therefore to be understood that the invention is not limited by the scope of the appended claims.

Claims (7)

1. A preparation method of a framework for an Ag-based tungsten-containing electric contact material infiltration preparation process is characterized by comprising the following steps:

foaming: adding a foaming agent into the Ag-based mixed powder, uniformly stirring and sieving to obtain Ag-based mixed powder particles wetted by the foaming agent, and heating and foaming the sieved Ag-based mixed powder particles in an oven, wherein the Ag-based mixed powder comprises the following components: 55 wt% -77 wt% of Ag, and the balance of W or WC;

solid-phase sintering and strengthening: solid-phase sintering the Ag-based mixed powder particles foamed in the step (1) to form fixed pores inside the particles;

packaging release agent: heating and stirring the sintering-reinforced Ag-based mixed powder particles in a stirrer, and spraying a paraffin solution at the same time to wrap the powder with the paraffin and dry a solvent of the paraffin solution in the stirring process;

powder liquid phase sintering: carrying out high-temperature liquid phase sintering on the Ag-based mixed powder particles wrapped with the paraffin in the step (3), crushing and screening after sintering to obtain high-strength porous prefabricated powder with good fluidity;

and (3) pressing and forming: pressing the high-strength porous prefabricated powder in the step (4) into a framework;

the adding amount of the foaming agent in the step (1) is that the mass ratio of the effective components to the Ag-based mixed powder is 1: 100-;

spraying amount of the paraffin solution in the step (3) is 1:100-1:500 according to the mass ratio of the paraffin to the Ag-based mixed powder;

the liquid phase sintering process in the step (4) comprises the following steps: the gradient sintering process includes sintering at 400-500 deg.c for 60-120 min, sintering at 600-700 deg.c for 60-120 min, sintering at 800-900 deg.c for 60-120 min, and sintering at 1000-1100 deg.c for 60-120 min in reducing atmosphere or vacuum atmosphere.

2. The method of claim 1, wherein: the foaming agent is one or a combination of ammonium bicarbonate, ammonium carbonate, ammonium hydrogen oxalate, ammonium oxalate and hydrogen peroxide.

3. The method of claim 1, wherein: the powder screening process in the step (1) is a 100-mesh and 300-mesh screening process, and the foaming process after screening is as follows: the foaming temperature is 60-200 ℃, and the foaming time is 30-60 minutes.

4. The method of claim 1, wherein: the solid phase sintering process in the step (2) comprises the following steps: the sintering temperature is 500-800 ℃, the sintering time is 30-120 minutes, and the sintering atmosphere is reducing or vacuum atmosphere.

5. The method of claim 1, wherein: in the step (3), the heating temperature is 60-100 ℃, the paraffin content in the paraffin solution is 1-10 wt%, and the solvent is gasoline.

6. A method for preparing an Ag-based tungsten-containing electric contact material based on a foaming infiltration process is characterized by comprising the following steps of: the method is based on a framework prepared by the method of any one of claims 1 to 5, and the framework is infiltrated with silver by an infiltration process to form the Ag-based tungsten-containing electrical contact material.

7. The Ag-based tungsten-containing electrical contact material prepared by the method for preparing the Ag-based tungsten-containing electrical contact material based on the foaming infiltration process according to claim 6, wherein the Ag-based tungsten-containing electrical contact material is a silver-tungsten electrical contact material or a silver-tungsten carbide electrical contact material.

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