阅读说明：本技术 制造Ag基电触头材料的方法、电触头材料和由此获得的电触头 (Method for manufacturing Ag-based electrical contact material, electrical contact material and electrical contact obtained thereby ) 是由 唐颖露 M·玻姆 S·博德里 于 2020-09-29 设计创作，主要内容包括：制造Ag基电触头材料的方法,其包括以下步骤：a.合成Me-xSn-y型的金属间化合物；b.球磨所述金属间化合物；c.将如此获得的金属间化合物粉末与银粉末混合；d.将所述混合粉末填充到生坯中；e.在烧结所述生坯的同时,通过使所述金属间化合物Me-xSn-y内部氧化,形成MeO-SnO-2簇结构。还公开了用所述方法获得的包括MeO-SnO-2簇结构的Ag基电触头材料和用其获得的电触头材料。(A method of making an Ag-based electrical contact material comprising the steps of: a. synthesis of Me x Sn y An intermetallic compound of type; b. ball milling the intermetallic compound; c. the metal thus obtainedMixing the intermediate compound powder with silver powder; d. filling the mixed powder into a green body; e. while sintering the green body by sintering the intermetallic compound Me x Sn y Internal oxidation to form MeO-SnO 2 A cluster structure. Also disclosed are compositions comprising MeO-SnO obtained by said process 2 Ag-based electrical contact materials of cluster structure and electrical contact materials obtained therewith.)

1. Method for manufacturing an Ag-based electrical contact material, characterized in that it comprises the following steps:

a. synthesis of Me_xSn_yAn intermetallic compound of type;

b. ball milling the intermetallic compound;

c. mixing the intermetallic compound powder thus obtained with silver powder;

d. filling the mixed powder into a green body;

e. while sintering the green body by sintering the intermetallic compound Me_xSn_yInternal oxidation to form MeO-SnO₂A cluster structure.

2. The method of claim 1, further comprising the steps of:

f. the material is densified by recompression and re-sintering to relieve additional strain.

3. The method of claim 1 or 2, wherein Me is selected from the group consisting of: copper, molybdenum, iron, manganese, nickel, indium and antimony.

4. The method of claim 3, wherein Me is copper.

5. The method according to one or more of the preceding claims, wherein synthesis step a) is carried out by mixing Me powder with Sn powder; melting the mixed powder; quenching and annealing the intermetallic compound.

6. The process according to one or more of the preceding claims, wherein ball milling step b) is carried out to obtain particles of intermetallic compound having a diameter d ranging from 1 μ ι η to 20 μ ι η.

7. The method of claim 6, wherein the diameter d is less than 5 μm.

8. The method according to one or more of the preceding claims, wherein the powder filling step d) is carried out by pressing the powder at a pressure of 50 Mpa to 200 Mpa.

9. Method according to one or more of the previous claims, wherein after step e) a further step f) is carried out, said step f) comprising:

f. the resulting material was densified.

10. Ag-based electrical contact material obtained by the method according to any one of the preceding claims.

An Ag-based electrical contact material, characterized in that it comprises MeO-SnO₂A cluster structure.

12. Ag-based electrical contact material according to claim 11, wherein Me is selected from: copper, molybdenum, iron, manganese, nickel, indium and antimony.

13. Ag-based electrical contact material as in claim 12, wherein Me is copper.

An Ag-based electrical contact comprising at least a portion of the material of any one of claims 10-13.

Technical Field

The present invention relates to a method for manufacturing Ag-based (silver-based) electrical contact materials, in particular to a method for manufacturing Ag-based electrical contact materials with improved fracture toughness, and to the related electrical contact materials and the electrical contacts obtained thereby.

Background

Typically, the silver-based electrical contact material comprises Ag-SnO₂(silver-tin oxide) composite material because it satisfies most of the properties required for electric appliances and because it is less harmful than its precursor Ag-CdO (silver-cadmium oxide). In fact, Ag-SnO₂Electrical contacts have been widely used in low voltage switchgear over the last few years.

However, such materials undergo crack formation when subjected to arc-induced thermomechanical stresses. Crack edge SnO₂Interfacial propagation between the particles and the Ag matrix leads to unpredictable material loss and, as a result, a large dispersion of the expected lifetime of the material.

This phenomenon has been found to be due to SnO in the composite material₂And poor adhesion between Ag.

In order to improve the interfacial adhesion between silver and tin oxide, different solutions have been proposed so far. Mainly, such solutions use different forms of added oxides, such as CuO (copper oxide) or Bi₂O₃(bismuth oxide) to strengthen Ag and SnO of the material₂Interface adhesion therebetween.

For example, a first known solution provides the use of powder metallurgy: ag powder and SnO₂And the added metal oxide powders are mixed by ball milling in a wet form (described in patent document CN103276235B, for example) or in a dry form (described in patent document CN104946957B, for example). The powder is then pressed into a green body, which is sintered and further densified.

There are some disadvantages to this approach. First, due to the mixing conditions, it leads to inhomogeneities in the final material, which cause compositional segregation and limit the improvement of the interface. Secondly, the interface between Ag and metal oxide is physically formed only by external pressure, which does not produce good adhesion.

A second solution known in the art provides the use of internal oxidation, for example as described in patent CN1230566C and in patent application CN 104498764A. In these solutions, powders of Ag, Sn (tin) and added Me (metal) are melted into prealloyed, then reduced in particle size by high energy ball milling or water atomization, and finally internally oxidized. The interface between Ag and the metal oxide is formed in situ, which provides better adhesion.

However, Ag/SnO₂An interface is inevitable. Thus, the adhesion problem is not overcome. Furthermore, in the initial pre-alloying step, there is a risk that the metal powder dissolves in the Ag matrix, which is detrimental to the electrical conductivity.

Another known solution utilizes chemical synthesis. This can be obtained with electroless plating (as known from patent documents CN104741602B and CN 106191495B), hydrothermal method (as known from patent application CN 106517362A) or sol-gel method (as known from patent application CN 106564937A). These chemical methods allow the silver powder to be uniformly coated with the metal oxide. In addition, the in situ chemical reaction improves interfacial adhesion.

However, these methods are complex and expensive.

Thus, in the prior art, all the methods of manufacturing Ag-based electrical contact materials of the known type, as well as the electrical contact materials and the electrical contacts obtained therefrom, present some drawbacks.

It is therefore an object of the present disclosure to provide a method of manufacturing an Ag-based electrical contact material, which allows to overcome the above-mentioned drawbacks.

In particular, it is an object of the present invention to provide a method of manufacturing an Ag-based electrical contact material, which allows improving the fracture toughness of the material, which is easy and inexpensive to manufacture.

Furthermore, it is an object of the present invention to provide a method of manufacturing an Ag-based electrical contact material, which allows improving the fracture toughness of the material without destroying the electrical conductivity of the material.

In addition, it is an object of the present invention to provide a method of manufacturing an Ag-based electrical contact material, which allows improving the fracture toughness of the material without reducing the homogeneity of the material.

Furthermore, it is an object of the present invention to provide Ag-based electrical contact materials with improved fracture toughness, which are reliable in terms of uniformity and electrical conductivity and which are relatively easy to manufacture at competitive costs.

It is another object of the present invention to provide an Ag-based electrical contact having the same advantages as the above-described Ag-based electrical contact material.

Disclosure of Invention

These and other objects are achieved by a method of manufacturing an Ag-based electrical contact material, comprising the steps of:

a. synthesis of Me_xSn_yAn intermetallic compound of type;

b. ball milling the intermetallic compound;

c. mixing the intermetallic compound powder thus obtained with silver powder;

d. filling the mixed powder into a green body;

e. by sintering the green body simultaneously with the intermetallic compound Me_xSn_yInternal oxidation to form MeO-SnO₂A cluster structure.

As better explained below, thanks to these steps, the above-mentioned drawbacks can be overcome.

In fact, the process of the invention avoids the problems associated with poor interfacial adhesion between silver and tin oxide, thus greatly improving the fracture toughness of Ag-based electrical contact materials and thus increasing their lifetime.

In particular, due to the formation of MeO-SnO₂The cluster structure step, may form an in-situ interface between Ag and MeO, which results in good adhesion and thus increased fracture toughness.

Furthermore, Me is an intermetallic compound synthesized_xSn_yThe method of the invention allows to avoid a decrease in the electrical conductivity of the material. In fact, as in the above-mentioned prior art, using intermetallic compounds instead of tin in metal and metallic form, the claimed process avoids their partial dissolution in the silver matrix and it therefore avoids the conduction of electricityLoss of sex.

Furthermore, the combination of the above five steps allows to avoid carrying out complex and expensive chemical syntheses.

In summary, the method of the present invention enables the manufacture of silver-based electrical contact materials with improved fracture toughness, high electrical properties, high uniformity, and at the same time, the method is easy to implement and inexpensive. Thus, it achieves each of the above objects.

Preferably, the metal of the intermetallic compound is selected from the following: copper (Cu), molybdenum (Mo), iron (Fe), manganese (Mn), nickel (Ni), indium (In) and antimony (Sb). These metals have been found to be more suitable in terms of the properties of the final material.

Most preferably, the metal is selected to be copper. In fact, the use of such metals allows the final material to achieve the longest mechanical and electrical lifetimes, as shown in the examples below.

According to a preferred embodiment, the synthesis step a) is carried out by mixing a metal powder with a tin powder, then melting the mixed powder, and finally quenching and annealing the intermetallic compound.

Preferably, step b) of ball milling is carried out to obtain particles of the intermetallic compound having a diameter d of 1 μm to 20 μm.

More preferably, such diameter d of the intermetallic compound is less than 5 μm. These diameter values have been shown to achieve the best mechanical properties in the final material, as will be shown in the examples below.

Advantageously, the powder filling step d) is carried out by pressing the powder at a pressure of between 50 Mpa and 200 Mpa. Generally, the green pressing pressure is selected not to be too great to limit oxidation during sintering, and at the same time not to be too small so that the pressed body can be in solid form and the particles have sufficient contact with each other to enable sintering.

In a preferred embodiment, after step e), a further step f) is carried out, comprising:

f. the resulting material was densified. Since the final density is critical to the mechanical properties, a recompression process can be employed to further increase the density of the resulting material. A re-sintering step is used to remove excess strain.

In another aspect, the present invention relates to Ag-based electrical contact materials obtained by the above-described method. Such materials have the advantages conferred by this method.

In another aspect, the invention also relates to an Ag-based electrical contact material, characterized in that it comprises MeO-SnO₂A cluster structure.

Such a structure ensures good adhesion between the silver and the cluster structure itself, thereby increasing the fracture toughness of the material. This means that early crack formation and material loss is avoided and the material life is increased.

Furthermore, the claimed material is homogeneous, which means better adhesion and maintains the desired conductivity. In addition, the Ag-based electrical contact material having such characteristics is also inexpensive because it is easy to manufacture.

Preferably, MeO-SnO₂The metal of the cluster structure is selected from: copper, molybdenum, iron, manganese, nickel, indium, antimony, as these metals give the final material better properties.

More preferably, the metal used is copper, since it has been found that better characteristics are obtained in terms of the mechanical and electrical life of the material, as shown later in the examples below.

In another aspect, the present invention also relates to Ag-based electrical contacts comprising at least a portion of the above materials. Electrical contacts comprising the above-described Ag-based materials have the same advantages as the above-described materials, namely, improved fracture toughness, uniformity, and good electrical conductivity, while being economical.

For the sake of clarity, it is to be noted that, in the present description and in the appended claims, the term "metal" and its abbreviation Me refer to chemical elements classified As metals or metalloids, that is to say not only those shown to the left of the metal-nonmetal boundary line in the periodic table of elements, but also arsenic (As), tellurium (Te).

Further, in the present context, chemical elements and compounds are represented by their chemical symbols, e.g. Ag for silver, Sn for tin, Cd for cadmium, SnO, as known in the art₂The method is used for preparing the tin oxide,CdO is used for cadmium oxide.

Drawings

Further features and advantages of the invention will become clearer from the description of preferred, but not exclusive, embodiments of a method for manufacturing Ag-based electrical contact materials, Ag-based electrical contact materials and electrical contacts according to the invention, such as shown in the description, examples and figures (incorporated in the examples), wherein:

figure 1 shows a time-temperature sintering diagram of a green body during step e) of a method according to a preferred mode of carrying out the invention;

figure 2 shows the energy absorbed by three samples during the charpy test;

FIG. 3 shows the uniaxial tensile test results of the same three samples of FIG. 2;

figure 4 shows the mechanical life test results of four samples;

figure 5 shows the results of electrical life tests of the same four samples of figure 4;

FIG. 6 is a graph showing Ag/FeSn oxidized at 900 ℃ for 2 hours₂SEM analysis of the microstructure of (d) (enlarged right image);

FIG. 7 shows Ag/Ni oxidized at 900 ℃ for 2 hours₃Sn₄SEM analysis of the microstructure of (d) (enlarged right image);

FIG. 8 is a graph showing the initial Cu with about 10 μm (left) and 4 μm (right) oxidized at 850 ℃ for 2 hours₃Ag/Cu of Sn particle size₃SEM analysis of the microstructure of Sn; and

FIG. 9 is a diagram showing reference Ag/SnO₂SEM analysis of the microstructure of (1).

Detailed Description

The method for manufacturing an Ag-based electrical contact material according to the invention provides a first step a) comprising the synthesis of Me_xSn_yIntermetallic compound of the type in which Me is a metal as defined above. In particular, stoichiometric quantities of Me and Sn powders were mixed and then melted at about 1000 ℃ for at least 30 minutes (please check). This step is preferably carried out under a protective atmosphere. Then, the intermetallic compound is subjected to quenching and annealing treatment under vacuum.

In terms of stoichiometryX and y may vary within wide ranges depending on the metal. However, it has been found that, for a given metal, Me_xSn_yPreferred values of x and y in the intermetallic compound are those giving higher y/x ratios in the range of availability of the intermetallic phase, since this enables a greater proportion of SnO₂And thus a higher resistance to arc erosion. For example, when Me is iron, both y/x-1 and 2 can be used, but FeSn is preferred₂. Other examples are Cu₃Sn、Ni₃Sn₄。

After step a), Me is ball-milled according to a second step b) of the invention_xSn_yAn intermetallic compound. This step is preferably carried out by using WC (tungsten carbide) balls in such a way as to obtain the desired grain size. The particle size is adjusted by changing the grinding time, the type of grinding balls and the mass ratio of the balls. As better shown in the examples below, the applicant found that carrying out step b) to obtain particles of intermetallic compound having a diameter d comprised between 1 μm and 20 μm and more preferably having a grain size smaller than 5 μm, the final Ag-based electrical contact material shows a higher fracture toughness.

After step b), the intermetallic compound powder thus obtained is mixed with silver powder according to step c) of the process of the invention. The mixing being with ZrO₂The (zirconium dioxide) balls are carried out in a suitable ball-to-feed ratio.

At this time, the mixed powder of silver and the intermetallic compound is filled into the green compact according to the following step d). Preferably, it is a loose-fill step, meaning that it is carried out by pressing the powder at a pressure of 50 MPa to 200 MPa for a time of 1 second to 30 seconds.

Subsequently, step e) is performed. By heat-treating the green body so as to cause sintering thereof and Me_x-Sn_yInternal oxidation of the intermetallic compound. This internal oxidation causes MeO-SnO₂And (4) forming a cluster structure. They are of high SnO₂Complex cluster structures containing nuclei and high metal content surfaces. This is due to the fact that the metal diffuses out compared to Sn. Thus, the silver contacts are predominantly MeO, and this in situ formation of MeO in Ag enables very good adhesion to be achieved, overcoming the disadvantages associated with these speciesThe above toughness problems associated with the materials of (a). In other words, the combination of steps of the present invention enables the replacement of bad Ag/SnO with a good Ag/MeO interface₂And (6) an interface. Furthermore, a high content of SnO in the structural core₂Ensuring good resistance to arc erosion.

According to a preferred embodiment of the invention, step e) is carried out in air at a temperature of about 850 ℃ for about 2 hours in the manner shown by way of example in fig. 1.

Advantageously, after step e), a further step f) of densifying the resulting material is carried out.

The purpose of this step is to obtain a final material with the desired microstructure and characteristics. Preferably comprising pressing the material with a pressure of 600 to 900 MPa for a time of 1 to 30 seconds and then sintering at a temperature of 300 to 600 ℃ for a time of 1 to 3 hours.

In a preferred embodiment, the metal of the intermetallic compound is selected from the group consisting of: copper, molybdenum, iron, manganese, nickel, indium, and antimony. However, the most preferred metal is copper, as it can be easily inferred from the following examples.

According to another aspect, the invention also relates to a composition comprising MeO-SnO₂An Ag-based electrical contact material of a cluster structure.

As previously mentioned, the metal of the cluster structure may be selected from metallic or metalloid elements. However, molybdenum, iron, manganese, nickel, indium, antimony and especially copper are preferred objects of the present invention.

The Ag-based electrical contacts of the present invention comprise such an alloy comprising MeO-SnO₂At least a portion of the tuft structure material.

Preferably, the entire electrical contact is made of said material.

Examples of the invention are given below according to some preferred embodiments.

Example 1

Synthesizing intermetallic phase Cu under protective atmosphere₃Sn (step a).

Stoichiometric Cu and Sn powders were mixed and melted at 1100 ℃ for 4 hours, followed by quenching and further vacuum annealing at 650 ℃.

The obtained Cu₃And (c) ball-milling the Sn compound and the WC balls (ball material mass ratio is 100:1) (step b) to a certain particle size. In particular, a first sample was ball milled up to 10 μm in diameter and a second sample was ball milled up to 4 μm in diameter to investigate the initial intermetallic phase Me_xSn_yThe effect of particle size on fracture toughness is shown in figures 2 and 3. In fact, these figures show the possibility of adjusting the microstructure and the mechanical properties by controlling the particle size.

Mixing Cu₃Sn powder and Ag powder with ZrO₂And (c) mixing the balls (the ball material mass ratio is 10: 1).

Mixing Ag/Cu₃The Sn powder was pressed at 100 MPa for 30 seconds (step d) and further sintered and oxidized at 850 deg.c in air for 2 hours (step e) as shown in fig. 1.

Ag/Cu to be sintered in this way₃The Sn sample was pressed at 750 MPa for 10 seconds and further sintered in air at 450 ℃ for 2 hours to achieve a density of at least 95% (step f).

As a comparative example, Ag/SnO₂The samples were also made using prior art methods. It is synthesized under CHRC and consists of 86 wt% Ag and 12 wt% SnO₂And 2% by weight of Bi₂O₃。

These three samples were tested and the results reported in figures 2 and 3 are shown.

Figures 2 and 3 show the following mechanical test results, respectively: as shown in the figure, Ag/SnO₂The sample (comparative) and the Ag/(Me, Sn) O sample have different initial particle sizes.

In particular, fig. 2 shows the energy absorbed during the charpy test, and fig. 3 shows the uniaxial tensile test. It is clear from the figures that the mechanical characteristics of the material manufactured by the method of the invention are greatly improved with respect to the reference material obtained by the methods of the prior art.

Example 2

The initial intermetallic phase Me was investigated_xSn_yThe effect of different metals on fracture toughness and electrical life is shown in fig. 4 and 5, respectively.

Specifically, four samples were prepared. AsComparative example, the first sample was Ag/SnO fabricated according to prior art methods₂Sample with a composition of 86 wt% Ag and 12 wt% SnO₂And 2% by weight of Bi₂O₃。

The remaining three samples were prepared using the method of the invention, starting from the synthesis of three different intermetallic compounds with a particle size of 1-4 μm:

i. intermetallic compound FeSn₂；

intermetallic compound Ni₃Sn₄；

intermetallic compound Cu₃Sn。

For manufacturing Cu₃The method of Sn is the same as that used in example 1.

For FeSn₂And Ni₃Sn₄Solid state reactions are used instead to minimize synthesis time and cost. At H₂Next, after heating to 250 ℃ over 1 hour, the sample was held at 250 ℃ for 2 hours to allow liquid Sn to diffuse, then heated to 750 ℃ over 2 hours, held at 750 ℃ for another 12 hours, and finally cooled over 1 hour. For Ni₃Sn₄Except for the main phase Ni₄₅Sn₅₅Besides, a trace amount of Sn was obtained. For FeSn₂An additional annealing step was performed at 475 ℃ for 2 days due to incomplete reaction. Then, the phase is mainly changed into FeSn₂With small amounts of FeSn and Sn.

The rod-shaped samples obtained were characterized by charpy test and tensile test to evaluate fracture toughness. Fig. 4 and 5 show the results.

Both test results show that the silver-doped tin-oxide (Ag/SnO)₂Sample comparison, Ag/FeSn₂And Ag/Ni₃Sn₄The fracture toughness and electrical life of the samples were slightly improved. At the same time, these two figures show the same Ag/SnO₂Sample comparison, Ag/Cu₃The fracture toughness of the Sn sample is greatly improved.

In addition, oxidized Ag/Me_xSn_ySEM analysis of fractured surfaces in the samples (fig. 6-8) has revealed a greater improvement in interfacial adhesion compared to the prior art samples (fig. 9).

As is apparent from the above description and examples, the method according to the present disclosure and the above Ag-based electrical contact material and associated electrical contact fully achieve the intended objects and solve the above-noted outstanding problems of the existing Ag-based material manufacturing method, Ag-based electrical contact material and Ag-based electrical contact.

In fact, they overcome the adhesion problem, improving the fracture toughness of the material of the invention, while, as previously mentioned, achieving a low price and guaranteeing a high electrical conductivity.

In addition to this, it has been found that the material of the invention is even more durable from an electrical point of view, as disclosed above in fig. 5. For this reason, it can be said that the method of the present invention improves both the mechanical and electrical properties of the material thus obtained.

Several variations are possible in the method of making the Ag-based electrical contact material, as well as in the electrical contact material itself and the associated electrical contact, all of which fall within the scope of the appended claims.