CN114453584A - Preparation method of silver graphite electrical contact material - Google Patents
Preparation method of silver graphite electrical contact material Download PDFInfo
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- CN114453584A CN114453584A CN202111619954.7A CN202111619954A CN114453584A CN 114453584 A CN114453584 A CN 114453584A CN 202111619954 A CN202111619954 A CN 202111619954A CN 114453584 A CN114453584 A CN 114453584A
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- H—ELECTRICITY
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- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
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Abstract
The invention relates to the technical field of silver-graphite electrical contact materials, in particular to a preparation method of a silver-graphite electrical contact material. The method comprises the following steps: (1) mixing silver and graphite, and then pressing and sintering to prepare a silver graphite ingot blank; (2) coating a silver layer on the surface of the silver graphite ingot blank to prepare a silver-coated ingot blank; (3) preparing the silver-coated ingot blank into a profile; the step (2) comprises the following steps: decarbonization: performing decarburization treatment on the silver graphite ingot blank; sand blasting: carrying out sand blasting treatment on the surface of the decarbonized silver graphite ingot blank; coating silver: coating a silver layer on the surface of the silver graphite ingot blank subjected to sand blasting; and (3) sintering: and sintering the silver graphite ingot blank coated with the silver layer on the outer layer. This application is through the processing mode of decarbonization, sandblast, covering silver and sintering for silver graphite ingot blank and cladding silver layer combine closely, have guaranteed the homogeneity of silver layer thickness simultaneously, have improved silver graphite electrical contact material's reliability and uniformity.
Description
Technical Field
The invention relates to the technical field of silver-graphite electrical contact materials, in particular to a preparation method of a silver-graphite electrical contact material.
Background
The silver graphite electric contact material has the characteristics of good fusion welding resistance, low and stable contact resistance and the like, and is widely applied to the fields of circuit breakers, leakage protectors, motor switch protection and the like. Along with higher requirements of various electrical appliance manufacturers on the reliability and consistency of electrical appliances, the silver graphite material is produced by assembling parts by adopting automatic welding equipment step by step. In order to meet the requirement of automatic welding, the silver graphite material is supplied in the form of a sheet or a section, which is a development trend in the industry of electrical contact materials.
Due to poor wettability among the silver graphite material, the solder and the copper contact bridge, the welding strength and the welding area between the contact and the contact bridge cannot meet the requirements after direct welding. Therefore, in order to ensure the welding strength of the silver graphite and the contact bridge, reduce the contact resistance and temperature rise of the contact, and improve the reliability and electrical property of the electric appliance, a pure silver layer needs to be compounded on the welding surface as a transition layer in the contact processing process.
At present, silver graphite strip preparation methods comprise two methods, one method is extrusion strip rolling, and then single-side decarburization or double-side decarburization is carried out, wherein the strip with double-side decarburization also needs to remove a silver layer on one side by mechanical grinding or chemical corrosion to obtain the silver graphite strip with a silver layer on one side; the silver graphite contact material processed by the extrusion rolling decarburization process has the advantages that due to the existence of pores in the welding silver layer, moisture is easily absorbed in the storage process, the silver layer is easily foamed in the welding process, and the extrusion rolling decarburization process is long in production period, low in efficiency and high in silver consumption rate. For example, patent document No. CN108067612A discloses a method for preparing a solderable parallel silver graphite ribbon contact material, which comprises mixing silver powder and graphite powder in proportion, isostatic pressing to obtain a silver graphite ingot blank, decarburizing the silver graphite ingot blank to form a decarburized silver layer on the surface of the ingot blank, sintering, extruding, rolling, and processing into a silver graphite/silver composite strip. This preparation method may have the following disadvantages: firstly, the surface-coated silver layer is obtained in a decarburization mode, the temperature, time, gas flow, placement mode and the like of decarburization can influence the thickness of the surface-coated silver layer, the requirement on the control precision of the preparation process is high, and the uniformity of the thickness of the surface-coated silver layer is difficult to ensure; secondly, the decarburized silver graphite ingot blank is sintered, the ingot blank shrinks in different degrees along the diameter direction and the length direction in the sintering process, the difference of the thickness of the surface-coated silver layer is further aggravated, the thickness distribution of the silver layer of the extruded strip is extremely uneven, and the risk that the thickness of the silver layer of a local welding surface is too thin to influence the welding strength of a contact exists.
The other is by extruding a strip of material which is laminated on one side with a layer of pure silver during the extrusion process. For example, in the method for preparing the silver-graphite electrical contact strip disclosed in patent document CN101693955A, silver powder and graphite powder are mixed uniformly in proportion, then the mixture is pressed into an ingot and sintered, a silver layer is coated on the outer side of the ingot, and an extrusion silver coating process is adopted to prepare the silver-graphite/silver composite strip. This processing method has the following problems: the silver graphite ingot blank and the silver jacket layer are difficult to ensure to be tightly combined in the production process, a gap exists between the silver graphite ingot blank and the silver jacket layer, a small amount of air can be remained in the extrusion process, the bubbling phenomenon can easily occur on the silver layer of the strip after extrusion, the friction force between the silver jacket layer and the silver graphite ingot blank and the friction force between the silver jacket layer and the extrusion cylinder are different, the problems of shedding of the silver jacket layer, cracking of the silver jacket layer and the like easily occur in the extrusion process, and the yield of the material is influenced. On the bonding interface between the silver graphite ingot blank and the silver sleeve layer, a small amount of oil stains and impurities are easily introduced in the production process, the interface bonding strength between the silver graphite ingot blank and the silver sleeve layer is influenced, the phenomenon that the bonding strength of a local area is low exists between the silver graphite layer and a welding silver layer, and the risk that a contact falls off exists in the use process of an electric appliance.
Disclosure of Invention
The invention aims to solve the problems and provides a preparation method of a silver graphite electrical contact material.
The technical scheme for solving the problems is to provide a preparation method of the silver-graphite electrical contact material, which comprises the following steps:
(1) mixing silver and graphite, pressing into ingots, and sintering to obtain silver graphite ingot blanks;
(2) coating a silver layer on the surface of the silver graphite ingot blank to prepare a silver-coated ingot blank;
(3) preparing the silver-coated ingot blank into a molding material;
the step (2) comprises the following steps:
decarbonization: performing decarburization treatment on the silver graphite ingot blank;
sand blasting: carrying out sand blasting treatment on the surface of the decarbonized silver graphite ingot blank;
coating silver: coating a silver layer on the surface of the silver graphite ingot blank subjected to sand blasting;
and (3) sintering: and sintering the silver graphite ingot blank coated with the silver layer on the outer layer.
In the application, firstly, the silver graphite ingot blank is decarburized, mainly in order to form a thin silver surface layer on the surface of the ingot blank, and when the silver is coated subsequently, the coated silver layer is contacted with the silver surface layer, so that the wettability of the silver graphite ingot blank and the coated silver layer can be improved, and the combination tightness between the silver graphite ingot blank and the coated silver layer is improved. Preferably, in the decarbonization step, the decarbonization temperature is 600-750 ℃, and the decarbonization time is 10-30 min.
On the one hand, an active surface can be obtained, the adhesive force of silver powder for coating the silver layer subsequently is further improved, and meanwhile, the effective combination of an interface can be promoted in the subsequent sintering process; on the other hand, the thickness of the surface silver layer formed by decarburization treatment can be leveled, the problem of uneven thickness of the surface silver layer is solved, and the thickness uniformity of the whole silver layer is improved. Preferably, in the sand blasting step, the alumina abrasive is adopted for dry sand blasting, the grain diameter of the alumina abrasive is 20-150 μm, and the sand blasting pressure is 0.4-1.5 MPa.
After the decarburization and the sand blasting are finished, the silver layer is coated on the surface of the silver graphite ingot blank, and the coated silver layer with tight combination and uniform thickness can be obtained. The silver coating mode can adopt any one of the prior art, and as the optimization of the invention, in the silver coating step, the isostatic pressing treatment process is adopted to coat the silver layer on the surface of the silver graphite ingot blank. The ingot blank is coated with the silver layer in an isostatic pressing mode, an extra isolating device is not needed for powder loading, the ingot blank is only needed to be fixed in an isostatic pressing die sleeve in a centering mode, the operation is easy, the problems of coating and matching of the silver layer and the silver graphite ingot blank are solved, the thickness of the coated silver layer is uniform and controllable, and the problem of uneven thickness caused by ingot blank decarburization treatment is further solved. In the present invention, the isostatic pressure is preferably 50 to 300 MPa. Preferably, after coating with silver, the obtained silver coated ingot blank has a diameter increased by 10 to 25mm relative to the silver graphite ingot blank.
After silver is coated, sintering treatment is carried out, the silver graphite and the silver are still integrated after sintering, foreign matter pollutants influencing the bonding strength cannot be introduced into a composite interface, and the bonding strength of the interface between the silver graphite and the silver is ensured. Preferably, in the sintering step, the sintering temperature is 850-920 ℃, the sintering time is 1-3 h, and the protective atmosphere is hydrogen. The higher sintering temperature is adopted, on one hand, the higher sintering temperature is based on the melting point of the silver powder, on the other hand, the higher sintering temperature is beneficial to eliminating the internal pores of the material, and is beneficial to improving the electrical property of the contact material.
Although the ingot blank can be directly used for forming the section after sintering, the ingot blank can shrink to different degrees along the diameter and the length direction due to sintering, and in order to further improve the bonding tightness between the silver graphite ingot blank and the silver coating layer, therefore, as the optimization of the invention, the step (2) further comprises the following steps: and after the sintering step, carrying out hot repressing treatment on the obtained sintered ingot blank to obtain the silver-coated ingot blank. The silver-coated ingot blank with a regular shape can be obtained through the hot re-pressing treatment, and is convenient to be made into a section bar subsequently. The preferable temperature of the hot repressing is 750-850 ℃, and the pressure maintaining time is 20-60 s.
Preferably, in step (3), the silver-coated ingot blank is subjected to reverse hot extrusion to obtain a strip, and the strip is made into the profile, so that the reliability and consistency of the bonding strength between the silver graphite ingot blank and the silver-coated layer are further improved through large-deformation extrusion. In the backward extrusion, because there is no relative movement between the surface layer of the ingot blank and the inner lining of the extrusion container, the mechanical condition of metal flowing in the extrusion container is changed, the non-uniformity of deformation and extrusion force are reduced, and simultaneously, because the metal flows uniformly, the outer surface layer of the ingot blank can completely enter the surface layer of the extruded product. The heating temperature of the reverse hot extrusion is 750-850 ℃, and the protective atmosphere is hydrogen.
After the strip is made by reverse hot extrusion, the strip is preferably trimmed at the end and rolled on a rolling mill to the desired thickness, preferably with at least one intermediate annealing treatment to stabilize the dimensions. Preferably, the annealing is carried out in a hydrogen protective atmosphere at the temperature of 500-700 ℃ for 1-6 h.
After rolling to a desired thickness, the profile can be formed by any means, for example, punching the profile with a stamping die, or slitting and profile rolling the strip to obtain the profile.
In addition, since the ingot blank shrinks to different degrees in the diameter and length directions during the sintering process in step (1), the silver graphite ingot blank with uneven surface is directly decarburized, and the uniformity of the thickness of the silver layer and the silver coating layer on the subsequent surface is still influenced, therefore, as a preferred aspect of the present invention, the silver graphite ingot blank is subjected to the lathe processing and then subjected to the decarburizing process. The turning can eliminate the difference of the shrinkage size of the silver graphite ingot blank prepared after sintering in the diameter direction, and can ensure the consistent diameter size of the silver graphite ingot blank.
In the present invention, it is preferable that the mixing method is a dry mixing method and the mixing time is 1.5 to 5 hours when the silver and the graphite are mixed in the step (1). Preferably, when silver and graphite are mixed, the mass ratio of each component is as follows: 2-6% of graphite and the balance of silver. Preferably, when silver and graphite are mixed and then are subjected to ingot pressing and sintering to prepare a silver graphite ingot blank, the diameter of the ingot blank obtained by ingot pressing is 60-110 mm, and the length of the ingot blank is 150-550 mm; the sintering temperature is 850-920 ℃, and the sintering time is 2-6 h.
The invention has the beneficial effects that:
1. this application is through the processing mode of decarbonization, sandblast, covering silver and sintering for silver graphite ingot blank and cladding silver layer combine closely, have guaranteed the homogeneity of silver layer thickness simultaneously, have improved silver graphite electrical contact material's reliability and uniformity.
2. The method improves the original preparation process of the silver-graphite material, realizes rapid compounding by a reverse hot extrusion method, and is assisted with an isostatic pressing silver compounding technology to prepare the silver-graphite electrical contact material with the characteristics of good welding performance, high interface bonding strength, oxide dispersion distribution and fibrous structure. The method integrates the advantages of a reverse hot extrusion composite process and an isostatic pressing silver coating process, can adjust the size ratio of the silver graphite ingot blank to the silver coating layer according to the requirements of customers, increases the extrusion ratio, reduces the extrusion specification of the strip, shortens the production period and improves the production efficiency.
Drawings
FIG. 1 is a process flow diagram of a method for preparing a silver graphite electrical contact material;
fig. 2 is a 200-fold metallographic structure diagram of the silver graphite electrical contact profile prepared in example 1.
Detailed Description
The following are specific embodiments of the present invention and are further described with reference to the accompanying drawings, but the present invention is not limited to these embodiments.
Example 1
A preparation method of a silver graphite electrical contact material is shown in figure 1, and comprises the following steps:
(1) mixing silver and graphite, pressing into ingots, and sintering to obtain silver graphite ingot blanks;
6 parts of graphite powder and 94 parts of silver powder are mixed by a dry method according to the parts by mass, and the mixture is mixed for 1.5 hours to obtain mixed powder. Pressing the mixed powder into an ingot blank in an isostatic pressing device, wherein the diameter of the ingot blank is 60mm, the length of the ingot blank is 150mm, and the isostatic pressing pressure is 50 MPa. And then, sintering the ingot blank in a hydrogen atmosphere at the sintering temperature of 850 ℃ for 6h to obtain the silver graphite ingot blank.
(2) Coating a silver layer on the surface of the silver graphite ingot blank to prepare a silver-coated ingot blank;
decarbonization: and (3) carrying out decarburization treatment after turning the prepared silver graphite ingot blank, wherein the decarburization temperature is 750 ℃, the decarburization time is 10min, and the oxygen flow is 8L/min.
Sand blasting: and carrying out sand blasting treatment on the surface of the decarbonized silver graphite ingot blank, wherein the sand blasting mode is a dry method, the grain diameter of the aluminum oxide grinding material is 20 mu m, and the sand blasting pressure is 0.4 MPa.
Coating silver: and placing the silver graphite ingot blank subjected to sand blasting into isostatic pressing equipment, and pressing the silver graphite ingot blank into a silver-coated ingot blank under the isostatic pressing pressure of 50MPa, wherein the diameter of the silver-coated ingot blank is 85mm, and the length of the silver-coated ingot blank is 150 mm.
And (3) sintering: and sintering the silver-coated ingot blank obtained by coating silver in a protective atmosphere, wherein the sintering temperature is 850 ℃, the sintering time is 3h, and the protective atmosphere is hydrogen.
Hot repressing: and carrying out hot repressing treatment on the sintered silver-coated ingot blank, wherein the hot repressing temperature is 750 ℃, and the pressure maintaining time is 20 s. (3) Preparing a molding material from the silver-coated ingot blank;
and performing reverse hot extrusion on the silver-coated ingot blank subjected to the hot repressing treatment to obtain a silver graphite/silver strip, wherein the heating temperature is 750 ℃ and the protective atmosphere is hydrogen during the reverse hot extrusion. Cutting off the head and the tail of the silver graphite/silver strip obtained by reverse hot extrusion, rolling the silver graphite/silver strip on a cold rolling mill to a required thickness, annealing at least once in the midway, and annealing in a hydrogen protective atmosphere at the temperature of 500 ℃ for 6 hours. And punching the strip rolled to the required thickness into the silver graphite/silver electric contact section by adopting a stamping die.
The metallographic structure diagram of the silver graphite/silver electric contact section bar which is 200 times is shown in figure 2, and it can be seen that the metallographic structure of the silver graphite/silver electric contact section bar prepared by the method is uniform, no crack, interlayer, aggregate and pore exist, and the thickness consistency of the silver layer is good.
Example 2
This embodiment is substantially the same as embodiment 1, except that:
and (3) longitudinally shearing and type rolling the strip rolled to the required thickness to obtain the silver graphite/silver electric contact section.
Example 3
This embodiment is substantially the same as embodiment 1, except that:
the hot repressurization step was not performed.
Example 4
This embodiment is substantially the same as embodiment 1, except that:
no turning process is performed.
Example 5
This embodiment is substantially the same as embodiment 1, except that:
and (3) cutting off the head and the tail of the silver graphite/silver strip obtained by reverse hot extrusion, rolling the silver graphite/silver strip on a cold rolling mill to a required thickness, and not annealing in the midway. And punching the strip rolled to the required thickness into the silver graphite/silver electric contact section by adopting a stamping die.
Example 6
A preparation method of a silver graphite electrical contact material is shown in figure 1, and comprises the following steps:
(1) mixing silver and graphite, pressing into ingots, and sintering to obtain silver graphite ingot blanks;
4 parts of graphite powder and 96 parts of silver powder are mixed by a dry method according to the parts by mass, and the mixture is mixed for 3 hours to obtain mixed powder. Pressing the mixed powder into an ingot blank in an isostatic pressing device, wherein the diameter of the ingot blank is 80mm, the length of the ingot blank is 350mm, and the isostatic pressing pressure is 200 MPa. And then, sintering the ingot blank in a hydrogen atmosphere at 880 ℃ for 4h to obtain the silver graphite ingot blank.
(2) Coating a silver layer on the surface of the silver graphite ingot blank to prepare a silver-coated ingot blank;
decarbonizing: and (3) carrying out decarburization treatment after turning the prepared silver graphite ingot blank, wherein the decarburization temperature is 650 ℃, the decarburization time is 20min, and the oxygen flow is 6L/min.
Sand blasting: and carrying out sand blasting treatment on the surface of the decarbonized silver graphite ingot blank, wherein the sand blasting mode is a dry method, the grain diameter of the aluminum oxide grinding material is 100 mu m, and the sand blasting pressure is 1.0 MPa.
Coating silver: and (3) placing the silver graphite ingot blank subjected to sand blasting treatment in an isostatic pressing device, and pressing the silver graphite ingot blank into a silver-coated ingot blank under the isostatic pressing pressure of 200MPa, wherein the diameter of the silver-coated ingot blank is 98mm, and the length of the silver-coated ingot blank is 350 mm.
And (3) sintering: and sintering the silver-coated ingot blank obtained by coating silver in a protective atmosphere, wherein the sintering temperature is 880 ℃, the sintering time is 2h, and the protective atmosphere is hydrogen.
Hot repressing: and carrying out hot repressing treatment on the sintered silver-coated ingot blank, wherein the hot repressing temperature is 800 ℃, and the pressure maintaining time is 40 s. (3) Preparing a molding material from the silver-coated ingot blank;
and carrying out reverse hot extrusion on the silver-coated ingot blank subjected to the hot repressing treatment to obtain a silver graphite/silver strip, wherein the heating temperature is 800 ℃ and the protective atmosphere is hydrogen during the reverse hot extrusion. Cutting off the head and the tail of the silver graphite/silver strip obtained by reverse hot extrusion, rolling the silver graphite/silver strip on a cold rolling mill to a required thickness, annealing at least once in the midway, and annealing in a hydrogen protective atmosphere at the temperature of 600 ℃ for 3 hours. And punching the strip rolled to the required thickness into the silver graphite/silver electric contact section by adopting a stamping die.
Example 7
A preparation method of a silver graphite electrical contact material is shown in figure 1, and comprises the following steps:
(1) mixing silver and graphite, pressing into ingots, and sintering to obtain silver graphite ingot blanks;
and (2) mixing 2 parts of graphite powder and 98 parts of silver powder by a dry method according to parts by mass, and mixing for 5 hours to obtain mixed powder. Pressing the mixed powder into an ingot blank in an isostatic pressing device, wherein the diameter of the ingot blank is 110mm, the length of the ingot blank is 550mm, and the isostatic pressing pressure is 300 MPa. And then, sintering the ingot blank in a hydrogen atmosphere at the sintering temperature of 920 ℃ for 2h to obtain the silver graphite ingot blank.
(2) Coating a silver layer on the surface of the silver graphite ingot blank to prepare a silver-coated ingot blank;
decarbonization: and (3) carrying out decarburization treatment after turning the prepared silver graphite ingot blank, wherein the decarburization temperature is 600 ℃, the decarburization time is 30min, and the oxygen flow is 4L/min.
Sand blasting: and carrying out sand blasting treatment on the surface of the decarbonized silver graphite ingot blank, wherein the sand blasting mode is a dry method, the grain diameter of the aluminum oxide grinding material is 150 mu m, and the sand blasting pressure is 1.5 MPa.
Coating silver: and placing the silver graphite ingot blank subjected to sand blasting in isostatic pressing equipment, and pressing the silver graphite ingot blank into a silver-coated ingot blank under the isostatic pressing pressure of 300MPa, wherein the diameter of the silver-coated ingot blank is 120mm, and the length of the silver-coated ingot blank is 550 mm.
And (3) sintering: and sintering the silver-coated ingot blank obtained by coating silver in a protective atmosphere, wherein the sintering temperature is 920 ℃, the sintering time is 1h, and the protective atmosphere is hydrogen.
Hot repressing: and carrying out hot repressing treatment on the sintered silver-coated ingot blank, wherein the hot repressing temperature is 850 ℃, and the pressure maintaining time is 60 s. (3) Preparing a molding material from the silver-coated ingot blank;
and performing reverse hot extrusion on the silver-coated ingot blank subjected to the hot repressing treatment to obtain a silver graphite/silver strip, wherein the heating temperature is 850 ℃ and the protective atmosphere is hydrogen during the reverse hot extrusion. Cutting off the head and the tail of the silver graphite/silver strip obtained by reverse hot extrusion, rolling the silver graphite/silver strip on a cold rolling mill to a required thickness, annealing at least once in the midway, and annealing in a hydrogen protective atmosphere at the temperature of 700 ℃ for 1 h. And punching the strip rolled to the required thickness into the silver graphite/silver electric contact section by adopting a stamping die.
Comparative example 1
This comparative example is essentially the same as example 1 except that:
refer to the extrusion pressure silver recovery process disclosed in patent publication No. CN 101693955A:
and (3) after the preparation of the silver graphite ingot blank in the step (1) is finished, coating a silver layer on the surface of the ingot to prepare a silver coated ingot blank, wherein the diameter of the silver coated ingot blank is 85mm, and the length of the silver coated ingot blank is 150 mm. Then, the silver-coated ingot blank is extruded on an extruding machine with the thickness of 1100mm under the pressure for silver coating, the extruding temperature is 750 ℃, and the heating time is 150 min. And rolling the obtained silver-coated ingot blank on a cold rolling mill to the required thickness, annealing at least once in the process, and annealing in a hydrogen protective atmosphere at the temperature of 500 ℃ for 6 hours. And punching the strip rolled to the required thickness into the silver graphite/silver electric contact section by adopting a stamping die.
Comparative example 2
This comparative example is essentially the same as example 1 except that:
refer to the decarbonization and silver-coating process disclosed in the patent document with publication number CN 108067612A:
after the preparation of the silver graphite ingot blank in the step (1) is finished, placing the silver graphite ingot blank in a decarburization furnace, introducing compressed air into the decarburization furnace, wherein the air flow is 5L/min, heating to 650 ℃, preserving heat and decarburizing for 6h to obtain a decarburized silver graphite ingot blank; and placing the decarbonized silver graphite billet into a sintering furnace, and sintering under the condition of hydrogen protection at the sintering temperature of 800 ℃ for 6 hours to obtain the sintered silver graphite billet. Extruding the sintered silver graphite billet into a strip material according to a conventional extrusion process, wherein the extrusion temperature is 850 ℃, and the extrusion ratio is 100; and rolling the strip obtained by extrusion at normal temperature according to the rolling deformation of 25% in each pass to the thickness of a finished product (0.55mm) to obtain the finished product strip.
[ PROPERTIES DETECTION ]
Conductivity:for the profiles prepared in examples and comparative examples, 10 arbitrary points on the profiles were taken as detection points, the conductivities of the 10 detection points were respectively detected, and the average value of the 10 conductivities was found, thereby finding the standard deviation between the 10 conductivities and the average value.
Bonding strength between the silver graphite ingot blank and the coated silver layer:the sections obtained in examples and comparative examples were cut off from the interface by shearing using a Zwick/Roell electronic universal material tester, and the shearing force was measured, and the larger the force required to cut off the interface, the larger the shearing force, the larger the force required to cut off the interface, the more the profile was expressedThe better the interfacial bond. The shear strength was calculated by dividing the shear force by the bonding area. The results of the measurements are shown in Table 1 below.
The results of the measurements are shown in Table 1 below.
Table 1.
As shown in table 1, it can be seen from example 1 and comparative example 1 that, in the present application, the bonding strength between the silver graphite ingot blank and the silver coating layer can be effectively improved by a series of means of decarburization, sand blasting, silver coating and sintering, compared with the extrusion pressure silver coating means in the prior art. As can be seen from the example 1 and the comparative example 2, the difference of the conductivity between the detection points on the section bar prepared in the application is small, which shows that the section bar prepared in the embodiment has the advantages of uniform thickness of the silver layer on the surface and good uniformity of the conductivity. In contrast, in comparative example 2, the silver layer obtained by decarburization had high bonding strength with the silver graphite ingot, but the silver layer had a non-uniform thickness, resulting in non-uniform conductivity.
The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.
Claims (10)
1. A preparation method of a silver graphite electrical contact material comprises the following steps:
(1) mixing silver and graphite, pressing into ingots, and sintering to obtain silver graphite ingot blanks;
(2) coating a silver layer on the surface of the silver graphite ingot blank to prepare a silver-coated ingot blank;
(3) preparing the silver-coated ingot blank into a molding material;
the method is characterized in that: the step (2) comprises the following steps:
decarbonization: performing decarburization treatment on the silver graphite ingot blank;
sand blasting: carrying out sand blasting treatment on the surface of the decarbonized silver graphite ingot blank;
coating silver: coating a silver layer on the surface of the silver graphite ingot blank subjected to sand blasting;
and (3) sintering: and sintering the silver graphite ingot blank coated with the silver layer on the outer layer.
2. The method for preparing a silver graphite electrical contact material according to claim 1, wherein: in the sand blasting step, aluminum oxide abrasive is adopted for dry sand blasting, the particle size of the aluminum oxide abrasive is 20-150 mu m, and the sand blasting pressure is 0.4-1.5 MPa.
3. The method for preparing a silver graphite electrical contact material according to claim 1, wherein: and in the silver coating step, a silver layer is coated on the surface of the silver graphite ingot blank by adopting an isostatic pressing treatment process.
4. The method for preparing silver graphite electrical contact material according to claim 3, wherein: in the silver coating step, the isostatic pressure is 50-300 MPa.
5. The method for preparing a silver graphite electrical contact material according to claim 1, wherein: in the sintering step, the sintering temperature is 850-920 ℃, the sintering time is 1-3 h, and the protective atmosphere is hydrogen.
6. The method for preparing a silver graphite electrical contact material according to claim 1, wherein: the step (2) further comprises the following steps: and after the sintering step, carrying out hot repressing treatment on the obtained sintered ingot blank to obtain the silver-coated ingot blank.
7. The method for preparing a silver graphite electrical contact material according to claim 1, wherein: and (3) performing reverse hot extrusion on the silver-coated ingot blank to obtain a strip material, and then manufacturing the strip material into the section.
8. The method for preparing silver graphite electrical contact material according to claim 7, wherein: when the strip is made into the section, the strip is annealed at least once midway.
9. The method for preparing silver graphite electrical contact material according to claim 8, wherein: the annealing treatment is carried out in a hydrogen protective atmosphere at the temperature of 500-700 ℃ for 1-6 h.
10. The method for preparing a silver graphite electrical contact material according to claim 1, wherein: and carrying out the decarburization step after the turning treatment is carried out on the silver graphite ingot blank.
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