JPH09209057A - Cu-Cr system contact material and its manufacturing method - Google Patents

Abstract

(57) Abstract: In a sintering process, evaporation of high vapor pressure elements such as Bi, Te, Sb, etc. is suppressed, a Cu-Cr-based contact material is firmly bonded, and a predetermined amount of high-content alloy is formed in the alloy. The vapor pressure element remains. SOLUTION: At least one kind of powder selected from Bi, Te and Sb is contained in an amount of 0.01 to 8% by weight, Cr powder is included in an amount of 5 to 60% by weight, and the balance is substantially Cu powder. The mixed powder is used as a starting material, and the solidified body obtained by compacting the powder is heated to a temperature range of 700 ° C to 1050 ° C. The mixed powder of the starting material is subjected to mechanical mixing, pulverization and alloying treatment, and the heating rate at the time of heating the solidified body which has been compacted into powder is set to 100 ° C./minute or more, and the atmosphere for heating is not changed. Activated gas, reducing gas, or in vacuum.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a contact material for a vacuum circuit breaker.

[0002]

2. Description of the Related Art Cu-Cr alloys, which have been proposed as contact materials for vacuum circuit breakers, are two-phase separated alloys in which Cu and Cr do not form a solid solution with each other. Manufactured.

According to the casting method, there is a drawback that the structure that precipitates becomes coarse due to the melting and solidification process. This is because Cu and Cr hardly form a solid solution with each other as described above.
If the cooling rate is low, a stable alloy structure is formed in the casting and solidification process, that is, a structure in which both pure Cu and pure Cr are separated and coarsened is formed. As a result, when used as a contact material for a vacuum circuit breaker, Cr is generated during arc discharge.
Peels off from the base material and causes contact surface roughening,
There arises a problem that the cutting current value is increased and the breaking characteristic is deteriorated. When the breaking characteristic deteriorates, the current at the time of breaking is instantaneously cut off, and due to a phenomenon such as the return of an arc, the contact heat is greatly generated and the contact is damaged.

Therefore, in JP-A-6-96647, "Contact Alloy and Method for Producing the Same", Cu-C having a fine structure layer is formed by controlling the cooling rate in the casting method.
We have proposed r-based alloys. However, here, the fine Cr phase is not metallurgically firmly adhered to the Cu of the base material, that is, the reaction layer or the diffusion layer is not formed at the interface between Cu and Cr. During arc discharge, the Cr phase falls off from the base material due to arc impact,
This causes the surface of the contact to become rough, making it difficult to obtain stable contact characteristics due to an increase in the contact resistance value.

On the other hand, according to the powder metallurgy method, there is a method in which a Cr powder is first sintered to produce a skeleton (skeleton) having a high porosity, and then a Cu alloy is melted and impregnated into the pores of the skeleton. However, in this impregnation method, fine Cr
It is difficult to obtain a skeleton of a structure composed of particles, and even if a skeleton of Cr particles can be produced, when Cu is infiltrated, voids are likely to remain in the pores of the skeleton, so a dense structure can be obtained. As a result, it is difficult to obtain excellent characteristics as a contact material for a vacuum circuit breaker.

Therefore, in order to realize finer Cr particles and denser sintered body, Japanese Unexamined Patent Publication (Kokai) No. 6-330101 discloses a method for producing a Cu—Cr composite material, which is a mechanical alloying method (mechanical alloying). Therefore, it is proposed that a structure in which Cu and Cr are close to a uniform forced solid solution and Cr particles are finely precipitated can be realized by applying (hereinafter simply referred to as MA). In the Cu-Cr-based material created by this manufacturing method, fine Cr particles are uniformly dispersed in the copper base material, and when it is used for a contact for a vacuum circuit breaker, a material manufactured by another powder metallurgy method or a casting method. It has been confirmed that it has excellent contact characteristics, especially welding resistance characteristics and high breaking characteristics, compared to

However, after the Cu-Cr composite powder that has been MA-treated by the above-mentioned manufacturing method is compacted and then sintered at around 1000 ° C., the cutting current value which is one of the required characteristics as a contact material is Bi, T added to reduce the size
High vapor pressure elements such as e and Sb (vapor pressure during evaporation is Cu or C
Since it is higher than r, it refers to an element group that is more easily evaporated than Cu or Cr. The same shall apply hereinafter) causes the problem of evaporation during the sintering process. Therefore, it is difficult to contain a large amount of these high vapor pressure elements due to restrictions in the manufacturing method, and thus it is difficult to reduce the cutting current value in the Cu—Cr based contact material.

[0008]

DISCLOSURE OF THE INVENTION The present invention does not perform high temperature sintering for the purpose of suppressing the evaporation of high vapor pressure elements such as Bi, Te, Sb in the sintering process, and thus has a relatively short thermal history, that is, Cu-Cr having a stable low cutting current value by establishing a manufacturing method for strongly bonding Cu-Cr powder under heating conditions at low temperature for a short time and leaving a predetermined amount of high vapor pressure element in the alloy The purpose is to create a system contact material.

[0009]

The present inventors have conducted various experiments and studies in order to achieve the above-mentioned object, and as a result, C
A manufacturing method was established in which a high vapor pressure element such as Bi, Te, Sb was contained in a u-Cr alloy, and as a result, a low cutting current value characteristic was obtained when used as a contact material for a vacuum circuit breaker. Invented a Cr-based contact material. Cu-C of the present invention
The structure relating to the method for producing the r-based contact material is as follows.

At least one kind of powder selected from Bi, Te, and Sb is 0.01 to 8% by weight of the whole, and Cr powder is 5%.
As a starting material, a mixed powder containing 60 to 60% by weight and the remainder being substantially Cu powder is mechanically mixed, ground, and
Alloying treatment (MA). Next, the solidified body obtained by compacting the MA powder is heated to a temperature range of 700 ° C to 1050 ° C. At that time, the solidified body obtained by compacting the starting material into
The heating rate when heating to the temperature range of 0 ° C to 1050 ° C is 1
The heating temperature was set to 00 ° C./min or more, and the atmosphere for heating was set to an inert gas, a reducing gas, or a vacuum.

Further, after the heating temperature is maintained for 30 seconds or more and 40 minutes or less, it is immediately put into a heated closing mold and solidified under pressure to obtain a true density ratio of 98% or more. In addition, manufactured C
When the u-Cr-based contact material is further heated in the temperature range of 300 to 800 ° C. to remove the processing strain in the powder forged body, good performance with improved electric conductivity and thermal conductivity is obtained. This C
The u-Cr-based contact material contains 5 to 60% by weight of dispersed Cr particles having an average particle size of 25 μm, and 0.01 to 8% by weight of at least one of Bi, Te and Sb particles.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Cr is a material having arc resistance and has an effect of improving electrode characteristics such as contact resistance, cutting current value and breaking characteristic. If the addition amount is less than 5% by weight, such an effect is not sufficiently obtained, while if it is added in an amount exceeding 60% by weight, the effect is not further improved. Therefore,
The proper content of Cr is 5 to 60% by weight. In particular, Cr
Regarding the particle size, when the average particle size of Cr particles dispersed in the matrix is larger than 30 μm, a region where Cr does not exist,
That is, the probability that an arc will be generated in the Cu base region increases, and as a result, the arc is locally concentrated and a contact loss occurs due to melting of the copper base portion.

Further, it has been found that the smaller the Cr particle size, the less likely voids are formed inside the sintered body during sintering. Therefore, in order to prevent local concentration of the arc and to realize stable contact characteristics and arc wear resistance, the average particle diameter of the Cr particles dispersed in the copper matrix is 30 μm.
The following is preferred. Specifically, by mechanically pulverizing / mixing / alloying (MA) the powder, the average particle size of Cr particles can be reduced to 30 μm or less, and the Cr particles can be uniformly dispersed in the copper powder matrix.

By containing at least one of the elements Bi, Te and Sb, the contact characteristics of the Cu-Cr material can be further improved. In particular, it is considered that these high vapor pressure elements exist at a high vapor pressure between the contacts during arc discharge, and as a result, have an effect of stabilizing the cutting current value in a low state. In order to obtain such effects, it is necessary to contain at least one of these elements in a total amount of 0.01% or more.

However, since these elements have relatively low melting points, if the content exceeds 8% by weight, problems occur such that they flow out during the brazing process of the contact material and deteriorate the mechanical properties of the sintered material. . Therefore, Bi, Te, Sb
The proper content of is 0.01 to 8% by weight. In the present invention, the main component is copper, from the viewpoint of improving the electrical conductivity, which is one of the required characteristics as a contact material.

Next, the powder blending / forming heating / hot forging and the heating (annealing) after forging in the Cu-Cr type contact material of the present invention will be explained. Powder blending / molding Cu powder, Cr powder, and one or more powders selected from the high vapor pressure elements of Bi, Te, and Sb satisfying the above-described composition of the present invention are blended, and the powders are blended. First, powder compaction is performed to produce a solidified body. At that time, mechanical alloying (M
A) Cr particles are finely pulverized by mechanically pulverizing / mixing / alloying the powder typified by the treatment, and Cu
Disperse evenly in the powder body. That is, the grain size of Cr particles is 30 μm by performing such mechanical alloying treatment.
By making the structure finer as described below, the contact characteristics such as the arc wear resistance are improved as described above.

Heating / hot forging This powder solidified body is heated to a temperature range of 700 to 1050 ° C. and held at the heating temperature for 30 seconds or more and 40 minutes or less,
Immediately put into a heated closed mold and pressurize to solidify to a true density ratio of 98% or more.

With respect to the heating temperature range, when the temperature is lower than 700 ° C., the plastic deformability of the powder is large, and therefore, when pressure is applied in the mold,
As a result of the powders not being sufficiently deformed with each other, voids remain inside the powder forged body, resulting in a decrease in strength and a decrease in electrical conductivity. On the other hand, when the heating temperature exceeds 1050 ° C., there arises a problem that the liquid phase of Cu forming the base material starts to flow out, the dimensional change of the solidified body is remarkable, and the evaporation of the high vapor pressure element becomes remarkable.

With respect to the holding time, if the time is less than 30 seconds, the plastic deformability of the powder is large, so that when the powder is pressed in the mold, the powders are not sufficiently deformed with each other. Also, the electric conductivity is lowered. On the other hand, if the holding time exceeds 40 minutes, there arises a problem that the evaporation of the high vapor pressure element becomes remarkable.

In the present invention, the rate of temperature increase during heating is preferably 100 ° C./minute or more. Especially 80
When heating to 0 ° C. or higher, if the heating rate is lower than 100 ° C./minute, the heating time becomes long, and the heat in the heating and holding process as well as the heating in the heating process affects the solidification in the solidified body. The problem arises that high vapor pressure elements evaporate. In addition, the atmosphere of the heating step is preferably an inert gas, a reducing gas, or a vacuum, which is limited for the purpose of suppressing the oxygen concentration and suppressing the formation of nitrides. In particular, hydrogen gas or argon gas, Alternatively, it is preferably in a vacuum.

Further, the mold temperature is preferably maintained at 400 ° C. or higher. The reason is that when the heated powder solidified body is put into the mold, the heat of the powder solidified body is conducted to the mold side, and as a result, the temperature of the powder solidified body immediately before pressurization is remarkably reduced and the powders are separated from each other. This is because it becomes impossible to bond them sufficiently firmly, which causes a problem that the strength of the forged body is reduced.

Heating after forging (annealing) When hot forging is performed as described above, processing strain remains in the obtained powder forged body, and the electrical conductivity and thermal conductivity are reduced. On the other hand, by heating and holding (annealing) in the temperature range of 300 to 800 ° C., there is an effect that the processing strain is removed and the electric conductivity and the thermal conductivity can be improved. Here, if the annealing temperature is less than 300 ° C., the working strain cannot be sufficiently removed, and conversely, even if heating is performed at more than 800 ° C., the above effect is not further improved. On the contrary, Bi, Te, Sb, etc. Induces the evaporation phenomenon of high vapor pressure elements. Particularly, a temperature range of 400 ° C to 600 ° C is preferable. The heating (annealing) time depends on the shape and size of the powder forged body, but by annealing for about 30 minutes or more, the processing strain can be removed and the electrical conductivity and thermal conductivity can be improved.

[0023]

【Example】

(Example 1) Electrolytic Cu powder, Cr powder, and Bi powder were prepared, and Cu-30% Cr-2.
After blending so as to be 5% Bi, mechanical alloying (MA) treatment was performed using a vibrating ball mill to uniformly disperse Cr particles and Bi particles crushed to an average particle size of 25 μm in the Cu matrix. The composite powder was prepared and compacted at room temperature under a surface pressure of 6 t / cm ² . The obtained green compact was solidified under the production conditions shown in Table 1.

[0024]

[Table 1]

The true density ratio, Bi and oxygen content, tensile strength and electric conductivity of each solidified powder were measured. Table 2 shows the results. The true density ratio (%) was 100% when the powders were completely bonded together. For example, 98.3% means that 1.7% of spaces (holes) remain. The sample piece for obtaining the tensile strength (Kg / mm ² ) is 3 mmφ × 1
It is a round rod of 0 ml. The electric conductivity (% IACS) is a value with Cu as 100.

[0026]

[Table 2]

As can be seen, the powder forgings solidified in Nos. 1 to 6 satisfying the manufacturing conditions described in the present invention are densified to a true density ratio of 98% or more, and do not oxidize during heating. , And a certain amount of B in the alloy without evaporation of Bi
It can be seen that i remains and has excellent mechanical properties and electrical properties. The cutting current value of No. 1 to 6 is 1
A low cutting current value is maintained at A or less. On the other hand, in the comparative example
It was found that Nos. 7 to 13 had the following problems and did not have satisfactory properties.

No. 7: Since the heating temperature is as low as 600 ° C., the powders are not sufficiently bonded to each other, and as a result, the true density ratio of the forged body does not reach 98% and sufficient strength cannot be obtained. No. 8: Liquid phase of Cu flows out in the heating process and B in the forged body
When i is evaporated, a forged body having sufficient strength cannot be obtained. No. 9: Since the heating and holding time is as short as 12 seconds, the powders are not sufficiently bonded to each other, and as a result, the true density ratio of the sintered body does not reach 98% and sufficient strength cannot be obtained. No.10: B in the forged body because the heating and holding time is as long as 1 hour
When i is evaporated, a forged body having sufficient strength cannot be obtained. No.11: The heating rate is 5 in the heating process up to 900 ℃
Since it is as small as 0 ° C./minute, Bi in the forged body is evaporated during heating and sufficient strength cannot be obtained. No. 12: Since heating is performed in the atmosphere, the oxidation phenomenon progresses, the oxygen content in the forged body increases, and a forged body having sufficient strength cannot be obtained. No.13: Since the annealing temperature is as high as 900 ° C, Bi in the forged body
Is evaporated and it becomes difficult to secure a predetermined amount of Bi.

Example 2 After mixing the powders so as to have the blending composition shown in Table 3, mechanical alloying (MA) treatment was performed using a vibrating ball mill to remove Cr and Bi or Te or Sb. A composite powder uniformly dispersed in each of the Cu substrates was produced, and the composite powder was compacted at room temperature under a surface pressure of 6 t / cm ² . The obtained green compact was heated in an Ar gas atmosphere to 900 ° C. under a temperature rising rate of 150 ° C./min and held at that temperature for 2 minutes,
Immediately, hot forging was performed in the heat-closed mold (mold temperature: 480 ° C.). The properties of the obtained powder forged body are shown in Table 4.

[0030]

[Table 3]

[0031]

[Table 4]

As can be seen, the powder forgings solidified in Nos. 1 to 6 satisfying the manufacturing conditions described in the present invention are densified to a true density ratio of 98% or more, and do not oxidize during heating. It is also found that the high vapor pressure elements (Bi, Te, Sb) remain in the alloy in a predetermined amount without evaporating, and have excellent mechanical properties and electrical properties. No.
The cutting current values of 1 to 6 are 1 A or less, and the low cutting current value is maintained. On the other hand, it was found that Comparative Examples Nos. 7 to 11 had the following problems and did not have satisfactory characteristics.

No. 7: Since it does not contain a high vapor pressure element, it does not have low cutting current value characteristics. No. 8: Since the content of Bi, which is a high vapor pressure element, is as high as 10%, mechanical properties are deteriorated. No. 9: Since the content of Te, which is a high vapor pressure element, is as large as 10%, mechanical properties are deteriorated. No.10: Since it does not contain Cr, the amount of wear due to arc is large and it cannot be used as an electrode. No. 11: Even if the Cr content is as high as 68%, the electrical characteristics are not improved and the mechanical characteristics are deteriorated.

Example 3 Electrolytic Cu powder, Cr powder (average particle size 45 μm) and Bi powder were prepared, and these were blended so as to be Cu-40% Cr-2% Bi on a weight basis. Is a mixed powder as it is as a starting material, and the other is mechanically alloyed (MA) using a vibrating ball mill to uniformly distribute Cr particles and Bi particles crushed to an average particle size of 25 μm in a Cu matrix. A dispersed composite powder was prepared and used as a starting material. Then, both powders were compacted at room temperature under a surface pressure of 6 t / cm ² , and the compacted compact thus obtained was heated to 950 ° C. in an Ar gas atmosphere at a heating rate of 120 ° C./min. After heating and holding at that temperature for 1 minute, it was immediately inserted into a closed heating die (die temperature: 450 ° C.) and hot forged. Table 5 shows the characteristics of the obtained powder solidified products.

[0035]

[Table 5]

As can be seen, the average particle size of Cr particles in the forged body obtained by solidifying the powder subjected to MA treatment is about 25 μm.
On the other hand, in the forged body obtained by solidifying the mixed powder that has not been subjected to the MA treatment, the average particle diameter of Cr particles is as large as about 45 μm. As a result, in the material not subjected to MA treatment, Cr
Due to the coarse particles, the mechanical properties and electrical properties are lower than those of the MA-treated material.
Also, assuming that it will be used as a contact material for electrodes,
It was installed as an electrode material for a vacuum circuit breaker, and the current was interrupted in a vacuum to visually inspect the damage on the surface of the material when exposed to arc discharge. As a result, the MA treatment was performed to remove the Cr particles. It has been confirmed that it is possible to suppress the above and suppress the abrasion damage due to the arc.

[0037]

According to the manufacturing method of the present invention, it becomes possible to firmly bond Cu-Cr powders under a relatively short thermal history without heating at high temperature, that is, under heating conditions of low temperature and short time. Therefore, a certain amount of Bi, Te, S in the powder solidified body
A high vapor pressure element such as b can be left, and as a result, a Cu-Cr-based contact material having a low cutting current value of 1 A or less can be obtained and can be used as a contact material for a vacuum circuit breaker.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H01H 1/02 H01H 1/02 C 33/66 33/66 B

Claims (6)

[Claims] 1. At least one kind of powder selected from Bi, Te, and Sb is contained in an amount of 0.01 to 8% by weight, Cr powder is included in an amount of 5 to 60% by weight, and the balance is substantially Cu powder. The mixed powder is used as a starting material, and the solidified body obtained by compacting the powder is heated to a temperature range of 700 ° C. to 1050 ° C., and held at the heating temperature for 30 seconds or more and 40 minutes or less, and then immediately heated in a closed mold. 98% in true density ratio by charging and pressurizing
A method for producing a Cu-Cr-based contact material characterized by being solidified as described above. 2. Mechanical mixing of the mixed powder of the starting materials
The method for producing a Cu-Cr-based contact material according to claim 1, wherein pulverization / alloying treatment is performed. 3. A solidified body obtained by compacting the starting material into a compacted body.
The method for producing a Cu-Cr-based contact material according to claim 1 or 2, wherein a heating rate at the time of heating to a temperature range of 00 ° C to 1050 ° C is 100 ° C / minute or more. 4. A solidified body obtained by compacting the starting material into a compacted body.
The method for producing a Cu-Cr-based contact material according to claim 3, wherein the atmosphere for heating to a temperature range of 00 ° C to 1050 ° C is an inert gas, a reducing gas, or a vacuum. 5. The C according to claim 1, wherein
A method for manufacturing a u-Cr-based contact material, further comprising 300 to 8
Cu-Cr characterized by heating in a temperature range of 00 ° C
Method for manufacturing system contact material. 6. A Cu—Cr-based contact material manufactured by the manufacturing method according to claim 1.