Electric contact material based on PCHM plasma cold hearth smelting method and manufacturing method thereof

Abstract

The invention belongs to the field of electrical material manufacturing, and particularly relates to an electrical contact material based on a PCHM plasma cold hearth smelting method and a manufacturing method of the electrical contact material. The method comprises the following steps that firstly, an Ag ingot, an Sn ingot and additive elements are melted to form alloy melt through a PCHM plasma cold hearth smelting technology, then the evenly-smelted alloy melt is cast into an AgSn alloy ingot, then the AgSn alloy ingot is formed into a wire through hot extrusion, the wire is drawn, cut off, oxidized, pressed, sintered and extruded into an AgSnO2 finished wire, and the rivet-shaped contact is machined through cold heading. Smelting is completed through the plasma cold hearth smelting technology, alloy components of different vapor pressures can be guaranteed, no obvious burning loss exists in the smelting process, and the defects of air holes, material segregation and the like in traditional metallurgy can be overcome. The prepared electric contact material is excellent in processability, and has more excellent electric life under an alternating current or direct current condition.

Description

Technical Field

[0001] The invention belongs to the field of electrical material manufacturing, and in particular relates to an electrical contact material based on a PCHM plasma cold hearth melting method and a manufacturing method thereof. Background Art

[0002] Silver tin oxide is a type of silver-based electrical contact material. It uses a second phase or multi-phase enhancement method to obtain excellent electrical properties under large currents and various complex loads. With the efforts of various colleges and universities and engineering and technical personnel in this industry, electrical contact materials with good resistance to welding and strong resistance to burning have been developed, and have been widely used in various relays. At present, the main methods for preparing AgSnO2 are alloy internal oxidation method, atomization method, and powder metallurgy method. There are problems such as pores and material segregation in the electrical contact materials made by the internal oxidation process, which leads to fracture and oxide aggregation during subsequent wire processing or internal oxidation, increasing the manufacturing cost. At the same time, when the material is prepared into rivet contacts, bonding will occur, which will eventually cause the relay to fail, which has a great impact on the reliability of electrical equipment.

[0003] Through the relevant literature search, the patent literature retrieved for preparing silver tin oxide materials is as follows:

[0004] Patent CN115662810A, a method for preparing silver tin oxide wire for rivet-type contacts, adopts a bidirectional hot pressing process to greatly improve the density of the ingot, so that the finished wire reaches nearly full density, improves the plastic processing deformation ability of the wire, and avoids abnormal cracking caused by subsequent rivet making due to poor material density; a low-hardness pure silver coating is formed by spraying on the surface of the ingot, and the high-hardness silver tin oxide layer is directly avoided from contacting with the extrusion lining, extrusion die, extrusion nozzle, drawing die and annealing tooling during hot extrusion, hot drawing and annealing, thereby greatly improving the surface quality of the final finished wire, thereby improving the abnormal cracking of the final rivet making, but it still cannot solve the problems of holes, looseness, component segregation, etc. existing inside the electrical contact material.

[0005] In the traditional process of preparing silver tin oxide materials, it is impossible to solve the problems of component segregation of AgSn multi-element alloys during smelting and ingot porosity, which leads to low material density, oxide aggregation, and processing difficulties. As a result, mass production cannot be achieved and the electrical life of the final electrical products is poor. Therefore, it is necessary to improve the existing electrical contact material manufacturing process. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide an electrical contact material based on a PCHM plasma cold hearth melting method and a method for making the same.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A method for manufacturing an electrical contact material based on a PCHM plasma cold hearth melting method, comprising the following steps:

[0009] (1) Preparation of alloy ingots by PCHM method: According to the formula of AgSn alloy, silver plate, tin ingot and additives are added into the crucible of the melting furnace, the exciting gas is He gas, the plasma gun is started for melting, and the vacuum degree of the melting area is 10 -1 ~10 -3 Pa, the initial current of the plasma gun is 300-400A, and the current is increased to 500-600A after the plasma gun enters the smelting zone. The cold hearth adopts copper water-cooling material, and the cold hearth adopts copper water-cooling material. The smelting zone and the refining zone are separated. The liquid melt flows through the smelting zone and the refining zone in turn to increase the time of the molten metal in the liquid state. Finally, the alloy melt flows into the mold, and finally the ingot is pulled out by the ingot pulling mechanism to obtain the AgSn alloy ingot;

[0010] (2) AgSn extrusion: the AgSn ingot obtained in step (1) is formed into a wire using an extruder;

[0011] (3) Drawing and cutting of AgSn alloy: The wire prepared in step (2) is drawn by cold working and then cut;

[0012] (4) Internal oxidation and ingot pressing: the AgSn wire cut in step (3) is added to an internal oxidation furnace, oxygen is introduced, and the wire in the furnace is turned upside down to make it oxidized evenly. The oxidized material is formed into a cylindrical ingot using a hydraulic press;

[0013] (5) Sintering, AgSnO2 extrusion: The cylindrical ingot obtained in step (4) is sintered in a sintering furnace and formed into AgSnO2 wire by a hot extrusion process;

[0014] (6) Finally, the obtained AgSnO2 wire is processed into a finished product and formed into an electrical contact rivet using a cold heading method.

[0015] Preferably, the silver plate, tin ingot and additives are calculated by weight percentage as follows: Ag 85-92%, Sn 7.5-13%, and additives 0.5-2%.

[0016] Preferably, the additive is one or more of indium, bismuth, copper and rare earth elements.

[0017] Preferably, in step (3), the wire material prepared in step (2) is cold-worked and drawn to φ1.0-3.0 mm, and the cutting length is 30-40 mm.

[0018] Preferably, in step (4), the furnace of the internal oxidation furnace is connected to a rotation drive device, and the rotation drive device drives the furnace to rotate so that the wire in the furnace flips up and down.

[0019] Preferably, in step (4), the oxygen pressure is 0.5-1.5 MPa, the oxidation temperature is 700-800° C., and the oxidation time is 20-40 h.

[0020] Preferably, in step (5), the sintering temperature is 700-900° C. and the holding time is 2-12 h.

[0021] The silver tin oxide electrical contact material is prepared by the electrical contact material manufacturing method based on the PCHM plasma cold hearth melting method as described above.

[0022] PCHM (Plasma Cold Hearth Melting) plasma cold hearth melting technology is an advanced metal melting and refining technology that uses the high-temperature plasma arc generated by a plasma torch as a heat source to melt the metal raw materials in a cold hearth. In this process, the metal raw materials gradually melt, flow and mix in the hearth to separate and remove impurities. At present, it is mainly used to manufacture titanium alloys with high quality requirements in the aerospace or medical fields, as well as special metal materials used in nuclear reactors.

[0023] The present invention applies PCHM plasma cold hearth melting technology to the field of electrical material manufacturing for the first time, and uses the plasma arc generated by the ionization of inert gas as a heat source. The melting can be completed in a wide pressure range from low vacuum to near atmospheric pressure, and the alloy components with different vapor pressures can be guaranteed. There is no obvious burning loss during the melting process. It is found that the prepared AgSn alloy has no component segregation, no pores in the ingot, and low impurity content. The material oxidized by this process has less internal agglomerates, and the material density is higher than that of the existing process materials. There is no problem of fracture during the wire processing. The rivet-shaped contact finally prepared has high density, so it has a better electrical life under AC or DC conditions. And the prepared electrical contact material has a life of more than 120,000 times under certain current conditions, and has good resistance to fusion welding and burning. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying creative labor, other drawings obtained based on these drawings still belong to the scope of the present invention.

[0025] Figure 1 This is the metallographic image of the sample after oxidation in Example 1;

[0026] Figure 2 For comparison, the metallographic image of the sample after oxidation in Figure 1. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0028] A method for manufacturing an electrical contact material based on a PCHM plasma cold hearth melting method comprises the following steps:

[0029] (1) Preparation of AgSn alloy by PCHM method: According to the formula of AgSn alloy, silver plate, tin ingot, indium ingot and other raw materials are added into the crucible of the melting furnace, the exciting gas is He gas, the plasma gun is started for melting, and the vacuum degree of the melting area is 10 -3 Pa, the initial current of the plasma gun is 320A, and the current is increased to 530A after the plasma gun enters the smelting zone. The cold hearth adopts copper water-cooling material, and the cold hearth is separated into a smelting zone and a refining zone (specifically, the smelting zone and the refining zone are sequentially formed by two water-cooled copper crucibles). The liquid melt flows through the smelting zone and the refining zone in sequence to increase the time of the molten metal in the liquid state. Finally, the alloy melt flows into the mold, and finally the ingot is pulled out by the ingot pulling mechanism to obtain the AgSn alloy ingot;

[0030] (2) AgSn extrusion: The AgSn ingot obtained in step 1 was formed into a φ8 mm wire using an extruder at an extrusion temperature of 750°C and an extrusion speed of 4 mm / s;

[0031] (3) AgSn alloy drawing and cutting: The φ8 mm wire prepared in step (2) is processed into φ2 mm by cold working and cut into φ30 mm in length;

[0032] (4) Internal oxidation and ingot pressing: The AgSn wire obtained in step (3) is added to a self-made internal oxidation furnace, and oxygen of 1.5 MPa is introduced, the temperature is 700°C, and the heat preservation time is 30 h. At the same time, the rotating device in the oxidation furnace is started to turn the wire up and down in the furnace to ensure uniform oxidation. The oxidized material is formed into a cylindrical ingot using a hydraulic press for the next step of forming;

[0033] (5) Sintering, AgSnO2 extrusion: The cylindrical ingot obtained in step (4) is sintered in a sintering furnace at a sintering temperature of 700°C and a holding time of 10 h, and is simultaneously formed into a φ6.0 mm AgSnO2 wire by a hot extrusion process;

[0034] Finally, the obtained AgSnO2 wire is processed into a φ1.2mm finished product and formed into an electrical contact rivet using a cold heading method.

[0035] In step (4), the metallographic image after oxidation is obtained, such as Figure 1 As shown, it can be seen that this embodiment has no problems such as segregation and pores.

[0036] Embodiment 2:

[0037] The difference from Example 1 is that the raw material content is different. It is configured according to 10 kg per time, and the input formula ratio is Ag 89wt.%, SnO2 9wt.%, and additives 2wt%.

[0038] Embodiment 3:

[0039] The difference from Example 1 and Example 2 is that the raw material content is different, and it is configured according to 10 kg per time, including 91wt.%, SnO2 8wt.%, and 1wt% of additives.

[0040] Comparative Example:

[0041] The AgSnO2 electrical contact rivets were prepared by a conventional alloy internal oxidation method, and the formula ratio was the same as that in Example 1.

[0042] After the internal oxidation step is completed, the metallographic image after oxidation is obtained, such as Figure 2 shown.

[0043] The above method was used to make AgSnO2 / Cu rivet contacts for simulated electrical performance experiments. The rivet specifications were R4.2x1.5(0.5)+2.6x1.2SR15 for the moving contact and F4.2x1.5(0.5)+2.6x1.2 for the static contact. The simulated electrical performance experimental conditions were as follows: 250VAC, 15A, closing force 75g, breaking force 45g, contact frequency 30 times / minute; 12VDC, 5A, closing force 75g, breaking force 45g, contact frequency 30 times / minute. The experimental results are shown in Table 1.

[0044] Table 1 Parameter settings and test results of different embodiments and comparative examples

[0045]

[0046] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for producing an electrical contact material based on a PCHM plasma cold hearth melting method, characterized in that The steps include: (1) Preparation of alloy ingots by PCHM method: According to the formula of AgSn alloy, silver plate, tin ingot and additives are added into the crucible of the melting furnace, the exciting gas is He gas, the plasma gun is started for melting, and the vacuum degree of the melting area is 10 -1 ~10 -3 Pa, the initial current of the plasma gun is 300-400A, and the current is increased to 500-600A after the plasma gun enters the smelting zone. The cold hearth adopts copper water-cooling material. The cold hearth is separated into a smelting zone and a refining zone. The liquid melt flows through the smelting zone and the refining zone in turn, and finally the alloy melt flows into the mold, and finally the ingot is pulled out by the ingot pulling mechanism to obtain an AgSn alloy ingot; (2) AgSn extrusion: the AgSn ingot obtained in step (1) is formed into a wire using an extruder; (3) Drawing and cutting of AgSn alloy: The wire prepared in step (2) is drawn by cold working and then cut; (4) Internal oxidation and ingot pressing: the AgSn wire cut in step (3) is added to an internal oxidation furnace, oxygen is introduced, and the wire in the furnace is turned upside down to make it oxidized evenly. The oxidized material is formed into a cylindrical ingot using a hydraulic press; (5) Sintering, AgSnO2 extrusion: The cylindrical ingot obtained in step (4) is sintered in a sintering furnace and formed into AgSnO2 wire by a hot extrusion process; (6) Finally, the obtained AgSnO2 wire is processed into a finished product and formed into an electrical contact rivet using a cold heading method.

2. The method for producing an electrical contact material based on a PCHM plasma cold hearth melting method according to claim 1, characterized in that: Silver plate, tin ingot and additives, calculated by weight percentage: Ag 85-92%, Sn 7.5-13%, additives 0.5-2%.

3. The method for manufacturing an electrical contact material based on a PCHM plasma cold hearth melting method according to claim 2, characterized in that: The additive is one or more of indium, bismuth, copper and rare earth elements.

4. The method for manufacturing an electrical contact material based on a PCHM plasma cold hearth melting method according to claim 1, characterized in that: In step (3), the wire material prepared in step (2) is cold-worked and drawn to φ1.0-3.0 mm, and the cutting length is 30-40 mm.

5. The method for manufacturing an electrical contact material based on a PCHM plasma cold hearth melting method according to claim 1, characterized in that: In step (4), the furnace of the internal oxidation furnace is connected to a rotation drive device, and the rotation drive device drives the furnace to rotate so that the wire in the furnace turns up and down.

6. The method for manufacturing an electrical contact material based on a PCHM plasma cold hearth melting method according to claim 1, characterized in that: In step (4), the oxygen pressure is 0.5-1.5 MPa, the oxidation temperature is 700-800° C., and the oxidation time is 20-40 h.

7. The method for manufacturing an electrical contact material based on a PCHM plasma cold hearth melting method according to claim 1, characterized in that: In step (5), the sintering temperature is 700-900° C. and the holding time is 2-12 hours.

8. The silver tin oxide electrical contact material prepared by the electrical contact material manufacturing method based on the PCHM plasma cold hearth melting method as claimed in any one of claims 1 to 7.

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