Manufacturing process for crack-resistant dispersion-strengthened copper electrode materials with high aluminum content

Abstract

The process for producing crack-resistant, high-aluminum dispersion-strengthened copper electrode materials involves the following steps: high-aluminum dispersion copper powder production, oxygen source production, powder mixing, cold isostatic pressing, integrated heat treatment (internal oxidation, reduction, sintering), oxygen-free copper coating, hot extrusion, drawing, and finishing. By coating the dispersion copper-high-aluminum powder ingot with oxygen-free copper, the surface condition of the high-aluminum dispersion copper rod is improved, resulting in low processing plasticity and preventing cracking during cold working and use. This solves the high cost of high-aluminum dispersion copper electrode materials produced by conventional pure nitrogen atomization and the high cracking rate of high-aluminum dispersion copper electrode materials produced by pure water atomization. This reduces the cracking rate during cold working and use of the high-aluminum dispersion copper electrode materials, thereby reducing production costs.

Description

Technical Field

[0001] The present invention relates to the technical fields of powder metallurgy and non-ferrous metal processing, and particularly relates to a manufacturing process of a dispersion-strengthened copper electrode material with crack resistance and a high aluminum content.

Background Art

[0002] Dispersion strengthening is a method of strengthening materials by introducing stable, uniform, and fine oxide particles, pinning dislocations, grain boundaries, and sub-grain boundaries into a metal matrix to prevent dislocation movement. Since fine and uniform oxide particles are dispersed and distributed in the copper matrix, dispersion-strengthened copper has high strength, a high softening temperature, and the finely dispersed and distributed oxide particles do not adversely affect the electrical conductivity and thermal conductivity of the copper alloy itself. Therefore, dispersion-strengthened copper can increase its strength while maintaining its excellent electrical conductivity and thermal conductivity.

[0003] Due to its excellent high temperature resistance, high strength, and high electrical conductivity, dispersion-strengthened copper alloy is considered a new functional material with great development potential and application prospects, and is widely used in many high-tech fields such as lead frames of very large scale integrated circuits, high pulse magnetic field conductors, high power microwave tubes, overhead lines for high-speed railway transportation, resistance welding electrodes, and crystallization devices of continuous casting machines.

[0004] In modern industry, automatic welding machines and robots are widely used in automobile production lines, and welding must be completed at high speed, with high rhythm and high quality. Thus, higher demands are placed on each component of the welding equipment. Resistance welding electrodes are in frequent contact with the workpiece under high temperature and pressure, and therefore must be replaced constantly during use. Chromium zirconium copper (Cu-Cr-Zr system), a currently widely used electrode material, is severely damaged due to its low softening temperature (approximately 500°C), significantly increasing welding costs and severely impacting the efficiency of welding equipment due to the need for constant replacement. With the development of the automotive industry, zinc-plated sheets, which have excellent corrosion resistance, are widely used. However, when using Cu-Cr-Zr system electrodes for spot welding, the zinc in the plating layer of the steel sheet tends to solidify with the electrode material, causing adhesion between the electrode and the steel sheet, affecting the quality of the joint, potentially disrupting automated production lines, and reducing productivity. For the reasons above, the use of alumina dispersion-reinforced copper (ODS / Cu) is increasing both domestically and internationally. Because this alumina-dispersed reinforced copper has high conductivity (>80% IACS) and excellent resistance to high-temperature softening (softening temperature ≥ 900°C), when welding galvanized steel sheets, the alumina protective layer formed on the working surface of the alumina-reinforced copper electrode effectively prevents the electrode surface layer from adhering to the steel sheet during welding of low-carbon steel sheets, significantly reducing electrode loss, extending the electrode's service life by 2 to 5 times, and greatly improving production efficiency.

[0005] Currently, high-aluminum-dispersed copper materials are mainly used for resistance welding electrodes in automobiles, and there are two core problems. First, the material needs to have high hardness. High hardness ensures the service life of the dispersed copper electrode material, and the higher the aluminum content of the dispersed copper, the higher the hardness. Generally, an HRB greater than 80 is required. Second, the material must not crack during cold working and use. High-aluminum-dispersed copper powder is mainly produced by water atomization and nitrogen atomization. In contrast, nitrogen atomization produces powder with less coarse alumina formed in the atomization due to protection by nitrogen gas, which is advantageous for cold working deformation of high-aluminum-dispersed copper, and cracks are less likely to occur during cold working deformation and subsequent use as an electrode material, but nitrogen atomization is costly to produce powder. In water atomization, the oxygen content of the water is high, and more coarse alumina is formed than in powder produced by nitrogen atomization, so cracks are more likely to occur during cold working and electrode use. Cracks in electrodes during use are extremely unacceptable in automotive automated welding production lines, as they can lead to production line interruptions and significant losses. Solving electrode material cracking and reducing production costs has long been a difficult technical challenge to overcome.

[0006] Based on the reasons mentioned above, manufacturing processes for dispersion-strengthened copper electrode materials that are crack-resistant and have a high aluminum content are currently being developed. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The objective of this invention is to overcome the shortcomings of the prior art and provide a manufacturing process for a dispersion-strengthened copper electrode material that is crack-resistant and has a high aluminum content. By applying an oxygen-free copper coating to a dispersion copper high-aluminum powder ingot, the surface conditions due to the high-content dispersion copper rod are greatly improved, and the low workability of the surface prevents cracks from occurring in the high-aluminum dispersion copper during cold working and use. This invention solves the problems of the high cost of high-aluminum dispersion copper electrode materials manufactured by atomizing with pure nitrogen to produce powder, and the high crack rate of high-aluminum dispersion copper electrode materials manufactured by atomizing with pure water to produce powder, thereby significantly reducing the crack rate of high-aluminum dispersion copper electrode materials during cooling and use, and reducing production costs.

[0008] To achieve the above objectives, the present invention adopts a technical scheme for manufacturing a crack-resistant and aluminum-content dispersed-strengthened copper electrode material, the process flow being: production of high-aluminum-dispersed copper powder - production of an oxygen source - powder mixing - cold isostatic forming - integrated heat treatment of internal oxidation, reduction and sintering - oxygen-free copper coating - hot extrusion - tension - finishing. [Means for solving the problem]

[0009] The first step is the production of high-aluminum dispersed copper powder. To produce the powder by atomizing with high-purity nitrogen, a 100 kg medium-frequency smelting furnace is used. First, high-purity oxygen-free electrolytic copper is added to the medium-frequency furnace and smelted for 40-70 minutes, covered with charcoal during smelting. Then, a copper-13% phosphorus intermediate alloy is added and deoxidized for 0.5-3 minutes. Next, a copper-30% aluminum intermediate alloy is added and smelted for 1-10 minutes, controlling the Al content in the Cu-Al alloy to 0.5-0.8 wt%. After that, it is atomized with high-purity nitrogen at a pressure of 0.5-1.5 MPa to produce powder, which is then dried and the Cu-Al alloy raw powder is sieved to -100 mesh for use.

[0010] The second step is the production of powder by water atomization. A 100 kg medium-frequency smelting furnace is used for smelting. First, high-purity oxygen-free electrolytic copper is added to the medium-frequency furnace and smelted for 40-70 minutes, with charcoal covering the furnace during smelting. Then, a copper-13% phosphorus intermediate alloy is added and deoxidized for 0.5-3 minutes. Next, a copper-30% aluminum intermediate alloy is added and smelted for 1-10 minutes to control the Al content in the Cu-Al alloy to 0.5-0.8 wt%, after which it is atomized with water at a pressure of 7-9.5 MPa to produce powder. After drying, the Cu-Al alloy raw powder is sieved to -100 mesh and ready for use.

[0011] The third step is the production of the oxygen source, in which the -100 mesh Cu-Al alloy raw powder atomized with water is sieved again to separate the -200 mesh Cu-Al powder, oxidized under conditions of 100°C to 500°C for 20 to 80 hours, and then decomposed into a solid oxygen source of cuprous oxide at 400°C to 950°C under nitrogen protection.

[0012] The fourth step is powder mixing, where the amount of oxygen source to be added is calculated according to the formula: M / N = 9A / 8B × P (where M is the weight of the raw powder, N is the weight of the oxidizer, A is the weight percentage of the oxygen content of the oxidizer, which is replaced by the hydrogen loss rate, B is the weight percentage of aluminum in the raw powder, and P is the excess coefficient of the oxidizer of 0.3 to 0.9), and the mixing time is 0.5 to 2.0 hours.

[0013] The fifth step is cold isostatic processing, in which dispersed copper alloy powder mixed according to the ratio is sealed in a cold isostatic rubber cover, vibrated with a vibrator for 1 to 3 minutes to make the bulk density uniform and the compacted powder density even, then sealed with a rubber cap and tightened with iron wire, the rubber cover containing dispersed copper powder is placed in a cold isostatic cylinder and cold isostatic processing is performed to produce cold isostatic powder ingots, with a press pressure of 150 to 300 MPa, a pressurization rate of 10 to 20 MPa / min, and a pressure holding time of 5 to 10 minutes.

[0014] The sixth step is an integrated heat treatment of internal oxidation, reduction, and sintering. The cold isostatic powder ingot is placed in the furnace tube of the heat treatment furnace, and the "integrated" heat treatment is performed in the order of internal oxidation, reduction, and sintering. The internal oxidation treatment converts the Al in the cold isostatic alloy powder ingot to Al2O3. Internal oxidation temperature: 830℃~950℃, internal oxidation time: 1~8 hours, protective atmosphere: nitrogen gas; reduction temperature: 880℃~950℃, reduction time: 1~8 hours, reducing atmosphere: high-purity hydrogen gas, dew point: -60℃.

[0015]

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[0016] The seventh step is oxygen-free copper coating, in which heat-treated powder ingots are sealed to a predetermined thickness, copper bushings of different thicknesses are selected according to the different sizes of powder ingots, and by measurement and calculation, the oxygen-free copper thickness of the outer layer of the Φ16 specification rod is ensured to be 0.4 mm.

[0017] The eighth step is hot extrusion, with a heating temperature of 830°C to 960°C for the powder ingot, a heating time of 1 to 5 hours, and an extrusion ratio of 10 to 35.

[0018] The ninth step is tensile work, in which the extruded billet is cut at the tip and end, straightened, and then tensile, with the pass rate controlled to within 15% to machine it to the size desired by the user.

[0019] The tenth step is the finishing touch, in which the stretched dispersed oxygen-free copper rod is straightened and the tip and end are cut. [Effects of the Invention]

[0020] The beneficial effects of the present invention are as follows: When nitrogen atomized dispersed copper powder and water atomized dispersed copper powder are mixed in a certain ratio, with the nitrogen atomized powder making up 60-80% and the water atomized powder making up 20-40%, adding 20-40% water atomized powder to the nitrogen atomized powder increases the tendency for cracks to occur in the high-aluminum dispersed copper electrode material. Based on measurements and calculations using the processing cost per ton of standard Φ16mm rod material, the cost per ton is reduced by more than 4000 yuan. This avoids the tendency for crack defects to occur in the electrode material during cold working and use when manufactured by pure water atomization. The crack rate of the high-aluminum dispersed copper electrode material manufactured with the mixed powder is reduced to within 5 / 10,000 compared to 1%-5% of that manufactured by pure water atomization, meeting the quality and performance requirements of automotive auto welding electrode materials.

[0021] By applying an oxygen-free copper coating to a dispersed copper-high-aluminum powder ingot, the surface conditions due to the high content of dispersed copper rods are significantly improved. The low workability of the surface prevents cracks from occurring in the dispersed copper during cold working and use. This invention solves the problems of high cost for dispersed copper electrode materials produced by atomizing with pure nitrogen and high crack rate for dispersed copper electrode materials produced by atomizing with pure water. The crack rate during cooling and use of dispersed copper electrode materials is significantly reduced, and production costs are lowered. Matters not described in detail in this invention are conventional techniques. [Modes for carrying out the invention]

[0022] The present invention will be described in more detail below with reference to examples and specific embodiments.

[0023] Example 1 A Φ16 rod material of a crack-resistant, low-cost dispersed copper electrode with a high aluminum content for automatic welding of automobiles, having an Al2O3 content of 0.58 wt%, is provided, and its manufacturing method includes the following steps.

[0024] Manufacture of a powder ingot with a specification of Φ93mm×290: Using the addition ratio of M / N = 9A / 8B×P, 75% of pre-pure nitrogen atomized powder and 25% of water atomized powder with an Al2O3 content of 0.58 wt% were added to an oxygen source with an oxygen content of 5.3%. The excess coefficient P was taken as 0.67 and mixed for 1 hour. It was put into a hydrostatic rubber cover for hydrostatic processing to manufacture a powder ingot with a specification of Φ93mm at a pressure of 200 MPa and a pressure holding time of 7 minutes. The cold hydrostatic powder ingot was put into the furnace tube of a heat treatment furnace. Internal oxidation temperature: 850°C, internal oxidation time: 2.5 hours, protective atmosphere: nitrogen gas, reduction temperature: 890°C, reduction time: 3 hours, reduction atmosphere: high purity hydrogen gas, dew point: -60°C,

[0025]

Number

[0026] The heat-treated powder ingot was put into an oxygen-free copper bush of Φ100 / Φ94×300 and sealed by argon arc welding.

[0027] The powder ingot of Φ100 / Φ94×300 was extruded by an 800-ton extruder and the powder ingot was heated in a resistance furnace. Heating temperature: 940°C, heating time: 3 hours, extrusion specification Φ25, extrusion ratio 16.

[0028] The extruded billet was cut at the tip and end and straightened, and then drawn to produce a product with a diameter of Φ16mm, and the pass processing rate was controlled within 15%. The drawn Φ16mm dispersion copper bar was straightened and cut at the tip and end.

[0029] Measured performance of Φ16mm dispersion copper

[0030] )]]

Table 1

[0031] Example 2 This is a Φ60 rod material of a crack-resistant, low-cost dispersed copper electrode with a high aluminum content for automatic welding of automobiles, and the Al2O3 content was 0.58 wt%.

[0032] Using the addition ratio M / N=9A / 8B×P, a 65% / 35% mixture of a pre-existing pure nitrogen atomized powder with an Al2O3 content of 0.58 wt% and a water atomized powder was added to an oxygen source with an oxygen content of 5.3%, with an excess factor P of 0.67. The mixture was mixed for 1 hour, placed in a hydrostatic rubber cover, and subjected to hydrostatic processing at a pressure of 200 MPa for a pressure holding time of 10 minutes to produce a Φ93 mm powder ingot. The cold hydrostatic powder ingot was then placed in the furnace tube of a heat treatment furnace. Internal oxidation temperature: 850°C, internal oxidation time: 3.5 hours, protective atmosphere: nitrogen gas; reduction temperature: 890°C, reduction time: 3.5 hours, reducing atmosphere: high-purity hydrogen gas, dew point: -60°C.

[0033]

number

[0034] Heat-treated powder ingots were placed in Φ245 / Φ235×400 oxygen-free copper bushings, and sealing was performed by argon arc welding.

[0035] Powder ingots with dimensions of Φ245 / Φ9235×300 were extruded using a 4000-ton extruder, and the powder ingots were heated in a circular gas furnace. The heating temperature was 950℃, the heating time was 2.5 hours, the extrusion specification was Φ60, and the extrusion ratio was 16.7.

[0036] The extruded billet was trimmed at the tip and end, and straightened to produce a Φ60mm product.

[0037] Actual performance of dispersed copper with a diameter of Φ60mm

[0038] [Table 2]

Claims

[Claim 1] The first step is the production of high-aluminum-dispersed copper powder. To produce the powder by atomizing with high-purity nitrogen, a 100 kg medium-frequency smelting furnace is used. First, high-purity oxygen-free electrolytic copper is added to the medium-frequency furnace and smelted for 40 to 70 minutes, covered with charcoal during smelting. Then, a copper-13% phosphorus intermediate alloy is added and deoxidized for 0.5 to 3 minutes. Next, a copper-30% aluminum intermediate alloy is added and smelted for 1 to 10 minutes, controlling the Al content in the Cu-Al alloy to 0.5 to 0.8 wt%. After that, it is atomized with high-purity nitrogen at a pressure of 0.5 to 1.5 MPa to produce powder, which is then dried and the Cu-Al alloy raw powder is sieved to -100 mesh for use. The second step is the production of powder by water atomization. A 100 kg medium-frequency smelting furnace is used for smelting. First, high-purity oxygen-free electrolytic copper is added to the medium-frequency furnace and smelted for 40-70 minutes, covered with charcoal during smelting. Then, a copper-13% phosphorus intermediate alloy is added and deoxidized for 0.5-3 minutes. Next, a copper-30% aluminum intermediate alloy is added and smelted for 1-10 minutes, controlling the Al content in the Cu-Al alloy to 0.5-0.8 wt%. Finally, the mixture is atomized with water at a pressure of 7-9.5 MPa to produce powder. The resulting Cu-Al alloy raw powder is dried and sieved to -100 mesh for use. The third step is the production of the oxygen source, in which the -100 mesh Cu-Al alloy raw powder atomized with water is sieved again to separate the -200 mesh Cu-Al powder, oxidized under conditions of 100°C to 500°C for 20 to 80 hours, and then decomposed into a solid oxygen source of cuprous oxide at 400°C to 950°C under nitrogen protection. The fourth step is powder mixing, where the amount of oxygen source added is calculated according to the formula: M / N = 9A / 8B × P (where M is the weight of the raw powder, N is the weight of the oxidizer, A is the weight percentage of the oxygen content of the oxidizer, which is substituted by the hydrogen loss rate, B is the weight percentage of aluminum in the raw powder, and P is the excess coefficient of the oxidizer of 0.3 to 0.9), and the mixing time of the materials is 0.5 to 2.0 hours. The fifth step is cold isostatic processing, where dispersed copper alloy powder mixed according to the ratio is sealed in a cold isostatic rubber cover, vibrated with a vibrator for 1 to 3 minutes to equalize the bulk density and compaction density, then sealed with a rubber cap and tightened with iron wire, the rubber cover containing the dispersed copper powder is placed in a cold isostatic cylinder, and cold isostatic processing is performed to produce cold isostatic powder ingots, with a press pressure of 150 to 300 MPa, a pressurization rate of 10 to 20 MPa / min, and a pressure holding time of 5 to 10 minutes. The sixth step is an integrated heat treatment of internal oxidation, reduction, and sintering. The cold isostatic powder ingot is placed in the furnace tube of the heat treatment furnace, and the "integrated" heat treatment is performed in the order of internal oxidation, reduction, and sintering. The internal oxidation treatment converts Al in the cold isostatic alloy powder ingot to Al2O3. Internal oxidation temperature: 830°C to 950°C, internal oxidation time: 1 to 8 hours, protective atmosphere: nitrogen gas; reduction temperature: 880°C to 950°C, reduction time: 1 to 8 hours, reducing atmosphere: high-purity hydrogen gas, dew point: -60°C. [Math 1] The seventh step is oxygen-free copper coating, in which heat-treated powder ingots are sealed to a predetermined thickness, copper bushings of different thicknesses are selected according to the different sizes of powder ingots, and by measurement and calculation, it is ensured that the oxygen-free copper thickness of the outer layer of the Φ16 specification rod is 0.4 mm. The eighth step is hot extrusion, with a heating temperature of 830°C to 960°C for the powder ingot, a heating time of 1 to 5 hours, and an extrusion ratio of 10 to 35. The ninth step is tensile, in which the extruded billet is cut at the tip and end, straightened, and then tensile, with the pass rate controlled to within 15%, and processed to the size desired by the user. The tenth step is the finishing touch, in which the stretched dispersed oxygen-free copper rod is straightened and the tip and end are cut. A manufacturing process for a dispersion-strengthened copper electrode material characterized by crack resistance and high aluminum content.

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