High-strength silver tungsten carbide contact and method of making same

Abstract

The application provides a high-strength silver tungsten carbide contact material and a preparation method thereof. Alloy powder is prepared by refining and atomizing additives iron, cobalt and nickel, is modified by oxidation, and forms a special structure, so that the wettability of silver and tungsten carbide is significantly improved, the interface energy between dissolved silver and the tungsten skeleton is reduced, and the problems of traditional additive simple metal iron powder and cobalt powder are well overcome, such as local blackening of the appearance of the product after infiltration, uneven welding surface, black fracture surface, many internal hole defects, poor product bonding strength, large arc burning of the moving silver point in the breaking test, and test failure; high-speed rotation is used to make each alloy oxide be equally extruded, impacted, sheared and dispersed, so that the additives are uniformly wrapped on the surface of the tungsten carbide, a bridge between silver and tungsten carbide is established, and the effect of the additives is better played; meanwhile, nano silver powder is wrapped on the surface of the additives, the difficulty of forming a preliminary pressure compact is greatly reduced, and a foundation is laid for manufacturing high-tungsten carbide material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrical contact materials, and particularly relates to a high-strength silver tungsten carbide electrical contact material and a preparation method thereof. BACKGROUND

[0002] The electrical contact is also called a contact or a junction, and is a contact element of an electrical appliance switch, an instrument and the like, and bears the task of on-off current, so the performance of the electrical contact directly influences the reliable operation of the switch electrical appliance.

[0003] Silver is the most important and economic noble metal contact material among all metals, and is suitable for medium load and heavy load electrical appliances, because silver has the best heat conductivity, excellent processability and high oxidation resistance. However, silver has low hardness and melting point, is not resistant to wear, forms a silver sulfide film on the surface in a humid and high-temperature environment, and forms an electrical erosion spike under the action of direct current due to the low hardness and easy volatilization of silver. In addition, silver contact elements are prone to form an electric arc under a heavy load condition. Tungsten carbide has the characteristics of high hardness, high density, high melting point, low electrical conductivity and very low burn loss. Silver and tungsten carbide are combined to have the respective advantages. The WC content in the AgWC contact material is generally 20% to 80%, and the AgWC contact material has the advantages of good heat and electrical conductivity, electrical wear resistance, anti-welding performance, oxidation resistance and the like. With the increasing requirement for the reliability of electrical appliances, the requirement for arc burn loss is higher and higher, and electrical appliance manufacturers continuously launch high-index voltage distribution products.

[0004] In the silver tungsten carbide material, the WC has the characteristics of high melting point, high hardness and good wear resistance, can withstand strong arc corrosion, has good anti-welding performance and wear resistance, and achieves the effect of silver saving. The material has high hardness and poor processability, and only a liquid phase sintering (infiltration) method can obtain a high-density material. However, when the tungsten carbide content in the silver tungsten carbide powder is too high and the tungsten carbide particles are too small, the tungsten carbide mass percentage is increased to 60% to 80%, the dispersibility and processability of the tungsten carbide particles are greatly increased, the tungsten carbide particles in the powder itself are the same as the material of the mother form during the forming process, the wear of the mother form in the pressing area is large, and the product is cracked after the lower punch is ejected. The tungsten carbide particles have ultra-high hardness, and almost no plastic deformation occurs when the particles are in contact and pressed, so the particles cannot be interlocked, cracks are easily generated in the pressed blank, and even the pressed blank cannot be formed. Even if the pressed blank is formed, the appearance of the infiltrated product is locally black, the welding surface is uneven, the fracture surface is black, there are many internal hole defects, the product has poor bonding strength, the arc of the breaking test burns the silver point, and the test fails.

[0005] Therefore, it has been a difficult problem in the industry to produce a high-strength silver tungsten carbide material with uniform and consistent fracture color. This problem has also limited the improvement of the breaking performance of the electrical appliance to a great extent. SUMMARY

[0006] The present application aims to overcome the shortcomings and deficiencies of the prior art, and provides a high-strength silver tungsten carbide contact material and a preparation method thereof.

[0007] The technical scheme adopted by the present application is as follows: a preparation method of a high-strength silver tungsten carbide contact, comprising the following steps:

[0008] S1, proportioning silver tungsten carbide contact material additives, the additives including iron, cobalt, nickel;

[0009] S2, adding the proportioning obtained in S1 into a medium-frequency induction furnace for smelting and atomization to form alloy powder;

[0010] S3, performing grading treatment on the alloy powder formed in S2 to sort out alloy powder;

[0011] S4, adding the alloy powder sorted out in S3 into an internal oxidation furnace to generate corresponding alloy oxide powder through internal oxidation treatment;

[0012] S5, adding the alloy oxide powder in S4 and tungsten carbide powder into a powder compounding device to form composite powder of the additives wrapped tungsten carbide;

[0013] S6, adding the composite powder of the additives wrapped tungsten carbide in S5 and nano silver powder into a powder compounding device to form semi-finished powder of silver wrapped additives and tungsten carbide;

[0014] S7, uniformly mixing the semi-finished powder in S6 with nano silver powder to form mixed powder particles through high-temperature sintering;

[0015] S8, pressing the mixed powder particles formed in S7 into a green compact;

[0016] S9, stacking the green compact formed in S8 with a silver-copper alloy sheet, and placing them in a sintering furnace in an ammonia decomposition atmosphere for sintering and infiltration to obtain a silver tungsten carbide contact material.

[0017] Preferably, in S1, the mass ratio of the iron, cobalt and nickel ranges from 1:1:1 to 2:1:1.

[0018] Preferably, in S2, the smelting temperature is 1600-1800℃, the refining time is 10-20min, the atomization parameters are as follows: the inert gas is argon, the inert gas pressure is 0.5-1.0MPa, the inert gas flow is 400-1000L / min, and the high-pressure water atomization spray disc water pressure is 20-200MPa.

[0019] Preferably, in S3, the grading treatment adopts a superfine sorting machine.

[0020] The preferable parameters of the superfine classifier are as follows: air pressure 0.6-0.8 MPa, grading wheel rotating speed 75-150 Hz, and particle size less than or equal to 1 um.

[0021] The preferable parameters of the internal oxidation in S4 are as follows: oxidation temperature 300-600 DEG C, oxygen pressure 0.3-0.8 MPa, and oxidation time 4-12 h.

[0022] The preferable parameters of the powder compounding equipment in S5 are as follows: rotating speed 3000-6000 r / min, and the compounding stirring rod is made of tungsten carbide.

[0023] The preferable parameters of the powder compounding equipment in S6 are as follows: rotating speed 3000-6000 r / min, and the compounding stirring rod is made of tungsten carbide.

[0024] The preferable parameters of the sintering furnace in S9 are as follows: the sintering furnace is a continuous furnace, the temperature is divided into four zones, the temperature of the first zone is 650-750 DEG C, the temperature of the second zone is 850-930 DEG C, and the temperature of the third and fourth zones is 1050-1150 DEG C.

[0025] The high-strength silver-tungsten carbide contact prepared by the preparation method of the high-strength silver-tungsten carbide contact.

[0026] The beneficial effects of the present application are as follows:

[0027] 1. The present application can significantly improve the wettability of silver and tungsten carbide by adding alloy powder prepared by atomizing, refining and adding iron, cobalt and nickel, modifying and forming a special structure, and can reduce the interface energy of dissolved silver and tungsten skeleton, and can overcome the problems of local blackening of the product appearance after infiltration, uneven welding surface, black fracture surface, many internal hole defects, poor product bonding strength, and test failure caused by large arc burning of the moving silver point during the breaking test caused by traditional additive metal iron powder and cobalt powder.

[0028] 2. The present application can separate superfine additive alloy powder by using a high-speed classifier, and the alloy has the advantages of oxidation powder and tungsten carbide powder compounding, high-speed rotation and rotation, equal extrusion, impact and shearing of each alloy oxide, good dispersion effect, uniform wrapping of the additive (alloy oxide powder) on the surface of the tungsten carbide, and establishment of a bridge between silver and tungsten carbide, which can better play the role of the additive.

[0029] 3. The present application can greatly reduce the difficulty of initial pressure compaction by wrapping nano-silver powder on the surface of the additive, and the tungsten carbide particles and the surface of the particles almost do not deform plastically when they are in contact and pressed, so they cannot interlock, which leads to cracks in the compaction, and the high-tungsten carbide material cannot be made, and the compaction cannot be formed. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to these drawings without creative labor.

[0031] Figure 1 For the process route of the present application;

[0032] Figure 2 For the conventional process section photograph;

[0033] Figure 3 For the process section photograph of the present application. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application will be further described in detail below with reference to the accompanying drawings.

[0035] Example 1

[0036] A preparation method of a silver tungsten carbide contact material, comprising the following steps:

[0037] a. Fe, Co, Ni are proportioned according to the mass ratio of 1:1:1;

[0038] b. Fe, Co, Ni are added into a medium frequency induction furnace, the smelting temperature is 1700℃, the refining time is 15min, the atomization parameters are that the inert gas hole is argon, the inert gas pressure is 0.75MPa, the inert gas flow is 600L / min, and the high-pressure water atomization spray disc water pressure is 100MPa;

[0039] c. The dried atomized alloy powder is added into a superfine separation equipment, the separation parameters are that the air pressure is 0.7Mpa, and the grading wheel rotating speed is 100Hz, and the particle size is less than or equal to 1um;

[0040] d. The separated powder is loaded into a stainless steel disc and placed into an internal oxidation furnace, the oxidation temperature is 500℃, the oxygen pressure is 0.5MPa, and the oxidation time is 8h;

[0041] e. The alloy oxide powder and tungsten carbide powder are added into a powder compounding equipment, the powder compounding equipment parameters are that the rotating speed is 5500r / min, and the compounding stirring rod adopts a tungsten carbide rod;

[0042] f. The nano-silver powder is continuously added into the powder compounding equipment, and the powder compounding equipment parameters are that the rotating speed is 3500r / min, and the compounding stirring rod adopts a tungsten carbide rod;

[0043] g. The f-wrapped powder and silver powder are added into a powder mixer, the mixing time is 3h, the powder burning and granulating temperature is 850℃, and the time is 2h.

[0044] h, the powder particles of the sintered powder are pressed into a green compact;

[0045] i, the green compact is stacked with silver copper sheets, and is placed in a continuous furnace protected by ammonia decomposition atmosphere, the temperature is divided into four zones, the temperature of the first zone is 700 DEG C, the temperature of the second zone is 900 DEG C, the temperature of the third zone and the fourth zone is 1050 DEG C; the holding time of the third zone and the fourth zone is 2h; the high-strength silver tungsten carbide material is obtained by cooling in the cooling zone.

[0046] Figure 2 the silver tungsten carbide material prepared by the conventional process is shown in the cross-section photo, Figure 3 the silver tungsten carbide material prepared by the embodiment is shown in the cross-section photo, and it can be seen that the fracture color of the material prepared by the embodiment is uniform.

[0047] Example 2

[0048] A preparation method of a silver tungsten carbide contact material, comprising the following steps:

[0049] a, the iron, cobalt and nickel are proportioned as 2:1:1;

[0050] b, the iron, cobalt and nickel are added into a medium-frequency induction furnace, the smelting temperature is 1750 DEG C, the refining time is 20min; the atomization parameters are that the inert gas hole is argon, the inert gas pressure is 0.9MPa, the inert gas flow is 900L / min, and the high-pressure water atomization spray disc water pressure is 150MPa;

[0051] c, the dried atomized alloy powder is added into a superfine separation device, and the separation parameters are that the air pressure is 0.8Mpa, and the grading wheel rotating speed is 150Hz, and the particle size is less than or equal to 1um;

[0052] d, the separated powder is loaded into a stainless steel disc, and is placed into an internal oxidation furnace, the oxidation temperature is 600 DEG C, the oxygen pressure is 0.8MPa, and the oxidation time is 7h;

[0053] e, the alloy oxide powder and the tungsten carbide powder are added into a powder compounding device, and the powder compounding device parameters are that the rotating speed is 6000r / min, and the compounding stirring rod adopts a tungsten carbide rod;

[0054] f, the nano-silver powder is continuously added into the powder compounding device, and the powder compounding device parameters are that the rotating speed is 3000r / min, and the compounding stirring rod adopts a tungsten carbide rod;

[0055] g, the powder wrapped in f and the silver powder are added into a powder mixer, the mixing time is 4h, the sintering and granulating temperature is 900 DEG C, and the time is 2h;

[0056] h, the powder particles of the sintered powder are pressed into a green compact;

[0057] i. The green compact is stacked with silver copper sheet, and is placed in a continuous furnace protected by ammonia decomposition atmosphere. The temperature is divided into four zones. The temperature of the first zone is 750 DEG C, the temperature of the second zone is 910 DEG C, the temperature of the third zone and the fourth zone is 1100 DEG C. The holding time of the third zone and the fourth zone is 2 hours. The high-strength silver tungsten carbide material is obtained by taking out the furnace in the cold zone.

[0058] The above disclosure is only the preferred embodiment of the present application, and of course cannot limit the scope of the present application. Therefore, the equivalent changes made according to the claims of the present application are still within the scope of the present application.

Claims

1. A method of making a high-strength silver tungsten carbide contact, characterized by, It comprises the following steps: S1, proportioning silver tungsten carbide contact material additives, the additives include iron, cobalt, nickel; S2, the ingredients obtained in S1 are added to a medium frequency induction furnace for smelting and atomization to form alloy powder; S3, the alloy powder prepared in S2 is subjected to grading treatment to sort out alloy powder; S4, the alloy powder sorted out in S3 is added to an internal oxidation furnace to generate corresponding alloy oxide powder through internal oxidation treatment; S5, the alloy oxide powder in S4 and tungsten carbide powder are added to a powder compounding device to prepare composite powder of tungsten carbide wrapped with additives; S6, the composite powder of tungsten carbide wrapped with additives in S5 is added to a powder compounding device together with nano silver powder to prepare semi-finished powder of silver wrapped with additives and tungsten carbide; S7, the semi-finished powder in S6 is mixed with nano silver powder uniformly, and high-temperature sintering is performed to prepare mixed powder particles; S8, the mixed powder particles prepared in S7 are pressed into a green compact; S9, the green compact prepared in S8 is stacked with a silver-copper alloy sheet and placed in a sintering furnace in an ammonia decomposition atmosphere for sintering and infiltration to obtain silver tungsten carbide contact material; In S1, the mass ratio of iron, cobalt and nickel ranges from 1:1:1 to 2:1:1; In S2, the smelting temperature is 1600-1800℃, the refining time is 10-20min, the atomization parameters are: inert gas is argon, inert gas pressure is 0.5-1.0MPa, inert gas flow is 400-1000L / min, and high-pressure water atomization spray disc water pressure is 20-200MPa; In S3, the grading treatment adopts a superfine sorting machine; the superfine sorting machine parameters are: air pressure 0.6-0.8MPa, grading wheel rotating speed: 75-150Hz, and particle size ≤1μm; In S4, the internal oxidation parameters are: oxidation temperature 300-600℃, oxygen pressure 0.3-0.8MPa, and oxidation time 4-12h; In S5, the powder compounding device parameters are: rotating speed 3000-6000r / min, and the compounding stirring rod adopts tungsten carbide rod; In S6, the powder compounding device parameters are: rotating speed 3000-6000r / min, and the compounding stirring rod adopts tungsten carbide rod; In S9, the sintering furnace is a continuous furnace, and the temperature is divided into four zones, the first zone temperature is 650-750℃, the second zone temperature is 850-930℃, and the third zone and fourth zone temperature is 1050-1150℃.

2. The high-strength silver tungsten carbide contact prepared by the preparation method of claim 1.

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