JPH0151531B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to electrical contact materials, particularly composite contact materials in which metal oxides are dispersed in an Ag alloy matrix. As a composite contact material using metal oxides,
Ag-CdO contact materials are widely used. Ag-
CdO contact materials exhibit averagely excellent performance in terms of contact resistance, welding resistance, arc wear resistance, etc. required for contact materials, so they are used in relays, power switches for household electronics, switches for automobile electrical components, etc. It is often used in load current ranges of several amperes or more. However, in recent years, various power switches have been required to have improved contact reliability in line with safety regulations, or to be easier to operate and smaller for ease of use. There is a trend to reduce the size of contacts from the viewpoint of performance, and as a result, there are expectations for drastic improvements in the switching performance of contact materials. The present invention relates to oxide composite contact materials such as the above-mentioned Ag-CdO contact materials, and is particularly applicable to applications where the load is direct current and an inrush current is applied at the time of closing, such as in switches for automotive electrical components. The present invention relates to contact materials useful for switchgear. When switching such a load, generally a considerable amount of displacement occurs in the switching contacts, and welding is also likely to occur, so there are strict requirements for the properties of contact materials. In addition, in the mechanism that drives the contacts, sliding motion is often applied to the contacts in order to prevent contact reliability from being degraded due to contaminants such as dust entering between the contacts.
It is desired to improve mechanical strength such as wear resistance. In view of the above points, the present invention basically consists of
This paper proposes improvements in the properties of Ag-Bi ₂ O ₃ contact materials. A contact material in which Bi ₂ O ₃ is dispersed in an Ag matrix is a contact material with low contact resistance and excellent welding resistance, as disclosed in JP-A-52-133569. However, a drawback was found to be a large amount of arc consumption. The inventors
In order to improve this point, we have conducted various studies and developed a material in which Bi ₂ O ₃ and SnO ₂ are dispersed and reacted in an Ag matrix to convert them into a composite oxide of Bi and Sn (Bi ₂ Sn ₂ O ₇ ). It has been found that the arc wear resistance is significantly improved, and the welding resistance is also improved. Furthermore, as mentioned above, there is a tendency to downsize the contact shape due to the soaring price of Ag, but in order to prevent the drop in welding resistance due to this, in addition to the above-mentioned oxides of Bi and Sn, it is necessary to It has been found that adding an oxide of In is effective. However, as mentioned above, under conditions where transfer occurs, such as DC loads, and when the operating mechanism of the contacts involves sliding, etc., as a result of the oxide-containing material, the contact on the side that has transferred and increased in volume ( In switches for automotive electrical equipment, an Ag-rich layer with oxides removed (generally on the negative electrode side) is formed on the contact surface, and this layer is easily worn out by sliding action, so it forms as wear powder around the contact. It scatters and causes deterioration of the withstand voltage between the switch contacts. In addition, since the Ag-rich layer is soft, it sometimes causes adhesion on both sides of the contact.
This may lead to problems such as the inability to open/close the switch. Based on the above, the present invention focuses on the fact that if the transferred contact surface product is a wear-resistant material, the above drawbacks can be greatly improved, and the present invention uses an Ag matrix.
The present invention aims to provide a contact material that uses an Ag alloy matrix to improve wear resistance and prevent adhesion by hardening the alloy, and maintains adhesion resistance by using Bi oxide and the like. Next, the structure of the material of the present invention will be explained in detail. The material of the present invention has a
It is a material in which a Bi-Sn composite oxide is dispersed as the main oxide, and further contains a small amount of Sn oxide or Bi oxide depending on the composition ratio of Bi and Sn. In addition to the above-mentioned oxides, an oxide of In is added especially when higher wear resistance is desired. The material of the present invention has the above-mentioned structure, and the content of these constituent materials is 2 to 40% by weight of Cu in the Ag-Cu alloy matrix and 2 to 40% by weight of each oxide. In terms of metal, Bi is 1.5 to 5% by weight, Sn is 0.5 to 8% by weight within a range not exceeding twice the amount of Bi, and the balance is Ag.
When adding an oxide of In, the amount of Sn is 0.5 to 5% by weight within a range not exceeding twice the amount of Bi, and is added in an amount of 1 to 5% by weight in terms of metal. In the material of the present invention, the Ag-Cu alloy constituting the Ag alloy matrix imparts mechanical strength to the transfer products generated by switching on and off the DC load, and provides wear resistance. , shows the effect of reducing adhesion, but in addition, Cu itself has a large effect of reducing transfer. Therefore, due to the synergistic effect, the reliability of opening and closing as a switch contact is greatly increased. The lower limit of the amount of Cu added in the Ag alloy matrix is determined by the minimum amount to bring out the above-mentioned effects. On the other hand, its upper limit is primarily limited by contact resistance characteristics.
As the amount of Cu increases, Cu oxide begins to adhere to the contact surface, resulting in a gradual increase in contact resistance. Bi−, the main oxide contained in the material of the present invention
Sn composite oxide (Bi ₂ Sn ₂ O ₇ ) has Bi oxide (Bi ₂ O ₃ ) and Sn oxide (SnO ₂ ) in a molar ratio of 1:1.
By heating in the range of 700°C to 900°C at a ratio of 2 parts, it is produced as an oxide with a yellowish stone structure.
Its melting point is over 1200℃, and it exhibits sublimation property.
−By dispersing in the Cu alloy matrix,
Significant improvement in welding resistance and abrasion resistance. Ag-
In the Cu alloy matrix, the above Bi-Sn oxide,
Alternatively, as a method to further disperse In oxides, create an alloy powder by adding Bi, Sn, and In to Ag, heat this in an oxidizing atmosphere, and select Bi, Sn, and In. A so-called internal oxidation method is used to oxidize the alloy, producing an internally oxidized alloy powder, which is then mixed with separately produced Ag-Cu alloy powder.
During molding and sintering, internal oxidation of the Ag in the alloy powder
A method is adopted in which oxides are dispersed in the Ag-Cu alloy matrix by mutually diffusing the and Ag-Cu alloy powder. In this method, the Bi-Sn oxide is first
It is produced in alloy powder with Ag as a matrix,
In order to generate Bi-Sn oxide in the state of composite oxide Bi ₂ Sn ₂ O ₇ , convert from the above molar ratio,
When Bi weight x and Sn weight y, the relationship y/x≈0.57 needs to exist. However, since Bi tends to segregate in alloys, it is difficult to reliably convert it into the Bi ₂ Sn ₂ O ₇ state in internal oxidation treatment, and Bi oxide (Bi ₂ O ₃ ) and Sn Some amount of oxide (SnO ₂ ) may also be present alone. Also, as a matter of course, the value of y/x above is
If it is larger than 0.57, the chances of Bi oxide existing alone will decrease, and the Sn oxide content will increase. If the value of y/x becomes smaller than 0.57,
It is clear that the opposite trend will occur. However, in small contacts with large switching currents, for which the material of the present invention is mainly used, the value of y/x is larger than 0.57, and the Sn oxide coexists with the Bi-Sn oxide. Less consumption. However, as the amount of Sn oxide increases, workability tends to deteriorate, and this tendency is particularly noticeable when In oxide is added to reduce the amount of wear. Therefore, it is possible to suppress the Sn amount to about Y/X=2.
When adding In oxide, it can be said that further reducing Sn in terms of quantity brings overall benefits. Here, the functions and amounts of the added oxides will be summarized in detail. First, regarding bismuth, when it is added as an oxide, the minimum addition content at which an effect of improving welding resistance is observed is 1.5% by weight in terms of metal value. As the added content increases, the welding resistance is improved, and furthermore, by forming a composite oxide with tin, the wear resistance of the contact is improved. However, if it is contained in a large amount, it tends to segregate in the silver alloy, causing bismuth oxide to exist alone and causing coarse particles, which increases the amount of consumption and makes it less desirable. You can't expect results. Therefore, it is practical to set the upper limit to 5.0% by weight in terms of metal. Regarding tin, it is compounded with bismuth oxide as an oxide and exhibits an effect on wear resistance as described above, but the minimum addition content at which this effect is recognized is 0.5% by weight in terms of metal value. On the other hand, if the added content is increased, the mechanical workability decreases, so in consideration of ease of handling, it is practical to set the maximum added content to 8.0% by weight in terms of metal value. Note that when indium oxide is added in consideration of wear resistance, machinability decreases, so it is desirable that the added content of tin oxide is at most 5.0% by weight in terms of metal. Regarding indium, it is used as an oxide substitute for tin, and if consideration is given to wear resistance, it is desirable to add at least 1.0% by weight in terms of metal value. As a result, arc wear resistance deteriorates.
In addition, it naturally reduces machinability, so it is practical to set the maximum added content to 5.0% by weight. The material of the present invention may further contain a Ni oxide as an additive oxide. This oxide reduces arc consumption by extinguishing arc discharge in a switching mechanism where the contact opening/closing speed is relatively slow, and is also effective in improving welding resistance. In order to add Ni oxide, a method is used in which it is added as a metal in advance to the alloy powder before internal oxidation of the internally oxidized alloy powder. When adding nickel oxide, a suitable amount is 0.1 to 0.5% by weight in terms of nickel metal. The lower limit of the composition range is
This is the minimum amount that exhibits this effect; on the other hand, if the amount exceeds the above amount, it will segregate when alloyed with silver, bismuth, tin, etc. due to the small solid solubility limit, and if it is oxidized in this state, it will become difficult to work. In addition, it also has a characteristic effect in terms of welding resistance, which tends to cause adverse effects. The materials of the present invention explained above will be explained in more detail based on Examples. According to the composition of the present invention, Ag, Cu, Bi, Sn, In
Weigh out a total of 200g of Ni. Then, alloys such as Ag, Bi, Sn, In, and Ni are used to make internal oxidation alloy powder and Cu is added to the matrix.
The Ag and Cu alloys are separately melted and ingots are made for each. At this time, in the ingot for internally oxidized alloy powder, Bi, Sn, and especially Bi are likely to segregate, so in order to increase the amount of Ag, the AgCu alloy ingot is melted with 10 to 20% by weight of Ag and the balance Cu. Next, each ingot is melted again and powdered using a molten metal atomizer using pressurized nitrogen gas to form a powder that passes through a 50-mesh filter. The internal oxidation alloy powder is then heat-treated in the atmosphere at 700°C for 50 hours to convert it into internal oxidation alloy powder in which Bi, Sn, In, Ni, etc. contained therein are selectively oxidized. Furthermore, after homogeneously mixing this alloy powder with the AgCu alloy powder prepared earlier, it was loaded into a cylindrical mold with a diameter of 20 mm.
Molding is performed at a pressure of 8 tons/cm ² . Next, this molded body is heated to a temperature of 30 to
Sintering and homogenization of the AgCu alloy matrix are performed by heat treatment in nitrogen gas at a temperature lower than 50° C. for 3 hours. And by warm extrusion at 550-600℃
Processed into wire rods with a diameter of 20mm to 3mm. after that,
The wire is cold-drawn to a diameter of 1.5 mm and finally heat treated at 500°C for 1 hour to produce contact wire material. The material obtained as described above was processed into a contact stud having a spherical head with a diameter of 3 mm and a radius of curvature of 6 mm, and was subjected to a contact opening/closing test. Contact characteristics were evaluated by tests conducted using the circuit shown in FIG. That is, FIG. 1 shows the electric circuit of the contact opening/closing tester. In the figure, 3 is a test switch. When switch 3 is open, switch 4 is temporarily closed, capacitor 10 is charged through thyristor 8, and when switch 3 is closed, a rush current is applied so that the charge in capacitor 10 is discharged through diode 9 and resistor 5. The circuit was configured. The voltage of battery 1
28V, resistor 2 is 2.8Ω, capacitor 10 capacity is
1140μF, resistance 5 is 0.46Ω, steady current 10A,
The inrush current was set to 70A. Note that 6 and 7 are resistors for controlling the operation of the thyristor 8. FIG. 2 is a schematic front view showing the main parts of the contact switching tester. The common trial switch 3 connected as described above has a test movable contact 11 that moves in the direction of the arrow 19 and a test fixed contact 12 that is fixed to one end of a plate connecting member 16 attached to the outer periphery of the bearing 15. It is made up of. A plate-shaped connecting member 17 to which a coil-shaped contact force setting spring 18 is attached is attached to the outer periphery of the bearing 15. A leaf spring 14 is attached to the shaft of the bearing 15 to fix the bearing 15 and to set the separating force of the test contacts 11 and 12. By doing so, when the movable contact 11 under test slides on the fixed contact 12 under test, the fixed contact 12 under test can easily rotate around the bearing 15, and the contact force setting spring 18 Contact 1 for test
Set the contact force between 1 and 12 to 50g. The opening force when the test contacts 11 and 12 open is set to 200 g by the leaf spring 14. The stopper 13 defines the height of the fixed contact 12 under test and functions to ensure that both contacts can slide. Contact opening/closing conditions (1) Contact force...50g (2) Opening force...200g (3) Opening/closing speed...5mm/sec (4) Voltage...DC28V (5) Steady current...10A (7) Inrush current ...70A The evaluation of the contact characteristics is the number of welds when the contact is opened and closed 3 × 10 ⁴ times under the above conditions, that is, the number of times a force exceeding 200 g is required to open the contact, and 2
×10 This was determined by the amount of contact wear after opening and closing ^four times. The number of test pairs was 3 each, and the table shows the number of welding cycles and the variation in weight loss of the positive electrode. In addition, Ag, Ag-Cu (70 wt% Ag), Ag-CdO (13% by weight) were used as reference samples.
A similar test was attempted for (wt% CdO), but
Ag and Ag-Cu cause frequent welding, and Ag-
The part of the CdO that comes into contact when the contact opens and closes becomes rough due to mechanical wear, material transfer, etc., making sliding motion impossible, and the test was stopped after 1.5 x 10 ⁴ cycles for each reference sample.

[Table] Measurement became impossible.
As is clear from the results in the table, the contact material according to the present invention has particularly excellent wear resistance performance for switches in which the contacts have a sliding action.
Further, even under simple opposing opening/closing conditions, the contact material according to the present invention exhibited good performance. As described above, according to the present invention, wear resistance, welding resistance,
It is possible to provide a contact material that has excellent arc wear resistance and is inexpensive. Furthermore, when the contact material according to the present invention is used in the contacts of a switch configured so that the contacts perform a sliding action, a switch having particularly excellent wear resistance can be provided.

[Brief explanation of drawings]

FIG. 1 is an electrical circuit diagram of a contact opening/closing tester for evaluating the characteristics of contact materials, and FIG. 2 is a schematic front view showing the main parts of the testing mechanism of the same device. 1... Battery, 2, 5, 6, 7... Resistor, 3...
Switch under test, 4... Switch, 8... Thyristor, 9... Diode, 10... Capacitor, 11... Movable contact under test, 12... Fixed contact under test, 13... Stopper, 14... Board Spring, 15...
... Bearing, 16, 17 ... Plate-shaped connecting material, 1
8... Contact force setting spring, 19... Test movable contact 1
1 sliding direction.

Claims (1)

[Claims] 1. In an electrical contact material in which a metal oxide is dispersed in an Ag alloy matrix, the metal oxide contains Bi in an amount of 1.5 to 5.0% by weight and Sn in an amount not exceeding twice that of Bi. An electrical contact material characterized by containing 0.5 to 8.0% by weight within the range of 0.5 to 8.0% by weight, and further containing 2.0 to 40.0% by weight of Cu as an Ag alloy matrix component. 2 In an electrical contact material in which a metal oxide is dispersed in an Ag alloy matrix, the metal oxide contains 1.5 to 5.0% by weight of Bi and 0.5 to 8.0% by weight of Sn within a range not exceeding twice the amount of Bi. %, Ni 0.1~
An electrical contact material characterized in that it contains 0.5% by weight and further contains 2.0 to 40.0% by weight of Cu as an Ag alloy matrix component. 3 In an electrical contact material in which a metal oxide is dispersed in an Ag alloy matrix, the metal oxide contains 1.5 to 5.0% by weight of Bi and 0.5 to 5.0% by weight of Sn within a range not exceeding twice the amount of Bi. %, In 1.0 ~
5.0% by weight of each, and further contains 2.0 to 40.0% by weight of Cu as an Ag alloy matrix component. 4 In an electrical contact material in which a metal oxide is dispersed in an Ag alloy matrix, the metal oxide contains 1.5 to 5.0% by weight of Bi and 0.5 to 5.0% by weight of Sn within a range not exceeding twice the amount of Bi. %, In 1.0 ~
5.0% by weight, 0.1 to 0.5% by weight of Ni, and 2.0 to 40.0% of Cu as an Ag alloy matrix component.
An electrical contact material characterized by containing % by weight.