Manufacturing process for crack-resistant, high-aluminum dispersion strengthened copper electrode material

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 in particular to a process for producing crack-resistant, high-aluminum dispersion strengthened copper electrode material. [Background technology]

[0002] Dispersion strengthening is a method of strengthening materials by introducing stable, uniform, and fine oxide sites, pinning dislocations, grain boundaries, and subgrain boundaries into a metal matrix to prevent dislocation movement. Dispersion strengthened copper has fine, uniform oxide sites dispersed and distributed throughout the copper matrix, resulting in high strength and a high softening temperature. Furthermore, the finely dispersed and distributed oxide sites do not adversely affect the electrical and thermal conductivity of the copper alloy itself, so dispersion strengthened copper maintains its excellent electrical and thermal conductivity while increasing its strength.

[0003] Dispersion strengthened copper alloys are considered to be novel functional materials with great development potential and application prospects due to their excellent high temperature resistance, high strength, and high electrical conductivity, and are widely used in many high-tech fields, such as lead frames for ultra-large scale integrated circuits, high-pulse magnetic field conductors, high-power microwave tubes, overhead lines for high-speed rail traffic, resistance welding electrodes, and crystallizers for continuous casting machines.

[0004] In modern industry, the widespread use of automatic welding machines and robots on automotive production lines requires high-speed, high-rhythm, and high-quality welding. This places higher demands on each component of the welding equipment. Resistance welding electrodes frequently come into contact with the workpiece under high temperatures and pressures, requiring constant replacement during use. The currently widely used electrode material, chromium zirconium copper (Cu-Cr-Zr), has a low softening temperature (approximately 500°C), which can cause serious damage, significantly increase welding costs, and require frequent replacement, significantly impacting the efficiency of welding equipment. With the development of the automotive industry, galvanized sheets, which have excellent corrosion resistance, are widely used. However, when Cu-Cr-Zr electrodes are used for spot welding, the zinc in the coating layer of the steel sheet is prone to solid solution in the electrode material, causing adhesion between the electrode and the steel sheet, affecting joint quality, causing interruptions to the automated production line, and reducing productivity. For these reasons, the use of alumina dispersion strengthened copper (ODS / Cu) is increasing both domestically and internationally. This alumina dispersion strengthened copper has high electrical conductivity (>80% IACS) and high resistance to high-temperature softening (softening temperature ≥ 900°C). Therefore, when welding galvanized steel sheets, the alumina protective layer formed on the top working surface of the alumina strengthened copper electrode effectively prevents the electrode surface layer from sticking 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 significantly improving production efficiency.

[0005] Currently, high-aluminum-dispersed copper materials are primarily used in automotive resistance welding electrodes, but they face two key issues. First, the material must have high hardness to ensure the service life of the dispersed copper electrode material. The higher the aluminum content of the dispersed copper, the higher the hardness; generally, an HRB of greater than 80 is required. Second, the material must be free from cracks during cold working and use. High-aluminum-dispersed copper powder is typically produced by water atomization or nitrogen atomization. Nitrogen atomization, on the other hand, produces less coarse alumina during atomization due to the protection provided by nitrogen gas. This is advantageous for cold working deformation of high-aluminum-dispersed copper and reduces cracking during cold working deformation and subsequent use as an electrode material. However, nitrogen atomization is expensive. Water atomization produces powder with a high oxygen content, resulting in more coarse alumina formation than nitrogen atomization, making it more susceptible to cracking during cold working and electrode use. The occurrence of cracks in electrodes during use is the most taboo in the automated welding production line of automobiles, leading to interruptions in the production line and causing huge losses. How to solve the cracks in electrode materials and reduce production costs has been a technical challenge that has been difficult to solve for a long time.

[0006] For these reasons, processes are currently being developed to produce dispersion strengthened copper electrode materials that are crack resistant and have a high aluminum content. Summary of the Invention [Problem to be solved by the invention]

[0007] The objective of the present invention is to overcome the shortcomings of the prior art and provide a process for producing dispersion-strengthened copper electrode materials with high aluminum content and crack resistance. By applying an oxygen-free copper coating to a dispersion-strengthened copper powder ingot, the surface condition of the high-content dispersion-strengthened copper rod is significantly improved, and the surface layer has low processing plasticity, preventing cracks from occurring in the high-aluminum dispersion copper during cold working and use. The present invention solves the problems of the high cost of high-aluminum dispersion copper electrode materials produced by atomizing powder with pure nitrogen and the high crack rate of high-aluminum dispersion copper electrode materials produced by atomizing powder with pure water, 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 object, the present invention employs a technical solution for producing a dispersion strengthened copper electrode material with crack resistance and a high aluminum content, which has a process flow of producing high aluminum-dispersed copper powder - producing an oxygen source - powder mixing - cold isostatic pressing - integrated heat treatment of internal oxidation, reduction and sintering - oxygen-free copper coating - hot extrusion - drawing - finishing. [Means for solving the problem]

[0009] The first step is to produce high-aluminum-dispersed copper powder. The powder is produced by atomizing with high-purity nitrogen using a 100 kg medium-frequency smelting furnace. First, high-purity oxygen-free electrolytic copper is added to the medium-frequency furnace and smelted for 40 to 70 minutes. The furnace is covered with charcoal during smelting, and 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. The Al content in the Cu-Al alloy is controlled to 0.5 to 0.8 wt%, and then the powder is produced by atomizing with high-purity nitrogen at a pressure of 0.5 to 1.5 MPa. The powder is then dried and sieved through a -100 mesh to obtain the Cu-Al alloy raw powder, which is then used.

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

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

[0012] The fourth step is powder mixing. The prepared -200 mesh cuprous oxide oxygen source, 65% nitrogen atomized raw powder, and 35% water atomized raw powder are mixed according to the formula: M / N=9A / 8B×P (M is the weight of the raw powder, N is the weight of the oxidizer, A is the weight percent of the oxygen content in the oxidizer, replaced by the hydrogen loss rate, B is the weight percent of aluminum in the raw powder, and P is the oxidizer excess coefficient, 0.3-0.9). The mixing time is 0.5-2.0 hours.

[0013] The fifth step is cold isostatic pressing. The dispersed copper alloy powder mixed according to the ratio is sealed in a cold isostatic rubber cover, and vibrated by a vibrator for 1-3 minutes to make the bulk density uniform and the green density uniform. Then, the rubber cover is sealed with a rubber cap and tightened with an iron wire. The rubber cover containing the dispersed copper powder is placed in a cold isostatic cylinder to undergo cold isostatic treatment to produce a cold isostatic powder ingot. The pressing pressure is 150-300 MPa, the pressure increase rate is 10-20 MPa / min, and the pressure holding time is 5-10 minutes.

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

[0015]

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[0016] The seventh step is the oxygen-free copper cladding, in which the heat-treated powder ingot is sealed to a predetermined thickness. Different thicknesses of copper bushings are selected depending on the size of the powder ingot. Through measurement and calculation, the oxygen-free copper thickness of the outer layer of the Φ16 rod is ensured to be 0.4 mm.

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

[0018] The ninth step is drawing, in which the extruded billet is cut at the top and bottom ends, straightened, and then drawn to a size desired by the user, with the pass processing rate controlled within 15%.

[0019] The tenth step is finishing, in which the drawn 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: Nitrogen-atomized copper powder and water-atomized copper powder are mixed in a certain ratio, with the ratio being 60-80% nitrogen-atomized powder and 20-40% water-atomized powder. Adding 20-40% water-atomized powder to nitrogen-atomized powder increases the tendency for cracks to form in high-aluminum-dispersed copper electrode materials. Based on the processing cost per ton of standard 16mm diameter bar, the cost per ton is reduced by more than 4,000 yuan. This avoids the tendency for cracks to form in electrode materials during cold working and use when produced using pure water atomization. The crack rate of high-aluminum-dispersed copper electrode materials produced from the mixed powder is reduced to within 5 / 10,000 compared to the 1-5% rate of those produced using pure water atomization, thereby meeting the quality and performance requirements for automotive automatic welding electrode materials.

[0021] By applying an oxygen-free copper coating to a dispersed copper-high aluminum powder ingot, the surface layer conditions of the dispersed copper rod with a high content are significantly improved, and the surface layer has low processing plasticity, preventing cracks from occurring in the dispersed aluminum copper during cold working and use. The present invention solves the problems of the high cost of the dispersed aluminum copper electrode material produced by atomizing the powder with pure nitrogen and the high crack rate of the dispersed aluminum copper electrode material produced by atomizing the powder with pure water, thereby significantly reducing the crack rate during cooling and use of the dispersed aluminum copper electrode material and reducing production costs. The details not described in detail in this invention are conventional techniques. DETAILED DESCRIPTION OF THE INVENTION

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

[0023] Example 1 A crack-resistant, low-cost, high-aluminum dispersion copper electrode rod with a diameter of 16 mm for use in automatic welding of automobiles, with an Al2O3 content of 0.58 wt%, is manufactured by the following steps:

[0024] Manufacturing of powder ingots with Φ93mm x 290 specifications: The pure nitrogen atomized powder with 0.58 wt% Al2O3 and water atomized powder were added to the oxygen source with an oxygen content of 5.3% in a 75% / 25% ratio with an M / N=9A / 8B×P ratio, resulting in an excess coefficient P of 0.67. The mixture was mixed for one hour, then placed in an isostatic rubber cover and subjected to isostatic processing at a pressure of 200 MPa and a pressure holding time of 7 minutes to produce a powder ingot with a diameter of 93 mm. The cold isostatically pressed powder ingot was then placed in the furnace tube of a heat treatment furnace. The internal oxidation temperature was 850°C, the internal oxidation time was 2.5 hours, the protective atmosphere was nitrogen gas, the reduction temperature was 890°C, the reduction time was 3 hours, and the reduction atmosphere was high-purity hydrogen gas, with a dew point of -60°C.

[0025]

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[0026] The heat-treated powder ingot was placed in a Φ100 / Φ94×300 oxygen-free copper bushing and sealed by argon arc welding.

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

[0028] The extruded billet was cut at the top and bottom, straightened, and then drawn to produce a Φ16mm product, with the pass processing rate controlled within 15%. The drawn Φ16mm dispersed copper rod was straightened and the top and bottom were cut.

[0029] Actual measured performance of Φ16mm dispersed copper

[0030] [Table 1]

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

[0032] The pure nitrogen atomized powder with 0.58 wt% Al2O3 and water atomized powder were added to the oxygen source with an oxygen content of 5.3% at a ratio of 65% / 35% (M / N = 9A / 8B x P). The excess coefficient P was 0.67. The mixture was mixed for 1 hour, then placed in an isostatic rubber cover and subjected to isostatic processing at a pressure of 200 MPa and a pressure holding time of 10 minutes to produce a 93mm diameter powder ingot. The cold isostatically pressed powder ingot was then placed in the furnace tube of a heat treatment furnace. The internal oxidation temperature was 850°C, the internal oxidation time was 3.5 hours, the protective atmosphere was nitrogen gas, the reduction temperature was 890°C, the reduction time was 3.5 hours, the reduction atmosphere was high-purity hydrogen gas, and the dew point was -60°C.

[0033]

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[0034] The heat-treated powder ingot was placed in a Φ245 / Φ235×400 oxygen-free copper bushing and sealed by argon arc welding.

[0035] Powder ingots 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°C, the heating time was 2.5 hours, the extrusion specifications were Φ60, and the extrusion ratio was 16.7.

[0036] The extruded billet was cut at the top and bottom and straightened to produce a product with a diameter of 60 mm.

[0037] Actual measured performance of Φ60mm dispersed copper

[0038] [Table 2]

Claims

1. The process flow is as follows: production of high-aluminum-dispersed copper powder – production of oxygen source – powder mixing – cold isostatic pressing – integrated heat treatment of internal oxidation, reduction and sintering – oxygen-free copper coating – hot extrusion – drawing – finishing. This is a manufacturing process for dispersion strengthened copper electrode material that is crack-resistant and has a high aluminum content.

2. The first step is to produce high aluminum dispersed copper powder. The powder is produced by atomizing with high purity nitrogen using a 100 kg medium frequency smelting furnace. First, high purity oxygen-free electrolytic copper is added to the medium frequency furnace and smelted for 40-70 minutes. The furnace is 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. The Al content in the Cu-Al alloy is controlled to 0.5-0.8 wt%, and then the powder is produced by atomizing with high purity nitrogen at a pressure of 0.5-1.5 MPa. The powder is dried and sieved through a -100 mesh to obtain the Cu-Al alloy raw powder for use. The second step is to prepare powder by water atomization, which is smelted using a 100 kg medium frequency smelting furnace. First, high purity oxygen-free electrolytic copper is added to the medium frequency smelting furnace and smelted for 40-70 minutes, and covered with charcoal during smelting. Then, copper-13% phosphorus intermediate alloy is added and deoxidized for 0.5-3 minutes. Next, copper-30% aluminum intermediate alloy is added and smelted for 1-10 minutes, and the Al content in the Cu-Al alloy is controlled to 0.5-0.8 wt%, and then water atomization is performed at a pressure of 7-9.5 MPa to prepare powder, which is then dried and sieved to obtain the -100 mesh Cu-Al alloy raw powder for use. The third step is the preparation of an oxygen source, which involves sieving the water-atomized Cu—Al alloy raw powder through −100 mesh again, sieving the Cu—Al powder through −200 mesh, oxidizing it at 100°C to 500°C for 20 to 80 hours, and then decomposing it into a solid oxygen source of cuprous oxide at 400°C to 950°C under nitrogen protection; The fourth step is powder mixing. The oxygen source of the prepared -200 mesh cuprous oxide, 65% of the nitrogen atomized raw powder, and 35% of the water atomized raw powder are mixed together according to the formula: M / N=9A / 8B×P (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 oxidizer excess coefficient, which is 0.3-0.9). The mixing time of the materials is 0.5-2.0 hours. The fifth step is cold isostatic pressing, in which the dispersed copper alloy powder mixed according to the ratio is sealed with a cold isostatic rubber cover, and is vibrated by a vibrator for 1-3 minutes to make the bulk density uniform and the green density uniform, and then the rubber cover is sealed with a rubber cap and fastened with an iron wire, and the rubber cover containing the dispersed copper powder is placed in a cold isostatic cylinder to carry out cold isostatic treatment to produce a cold isostatic pressed powder ingot, with a pressing pressure of 150-300 MPa, a pressure increase rate of 10-20 MPa / min, and a pressure holding time of 5-10 minutes; The sixth step is the integrated heat treatment of internal oxidation, reduction and sintering. The cold isostatic pressing powder ingot is put into the furnace and the "integrated" heat treatment is carried out in the order of internal oxidation, reduction and sintering. The internal oxidation treatment is to convert the Al in the cold isostatic pressing alloy powder ingot into Al ２ O ３ wherein the internal oxidation temperature is 830°C to 950°C, the internal oxidation time is 1 to 8 hours, the protective atmosphere is nitrogen gas, the reduction temperature is 880°C to 950°C, the reduction time is 1 to 8 hours, the reduction atmosphere is high-purity hydrogen gas, and the dew point is -60°C. [Equation 1] The seventh step is oxygen-free copper cladding, which is used to seal the heat-treated powder ingot to a predetermined thickness. Depending on the size of the powder ingot, different thicknesses of copper bushings are selected. Through measurement and calculation, the oxygen-free copper thickness of the outer layer of the Φ16 rod is ensured to be 0.4 mm; The eighth step is hot extrusion, in which the heating temperature of the powder ingot is 830°C to 960°C, the heating time is 1 to 5 hours, and the extrusion ratio is 10 to 35; The ninth step is drawing, in which the extruded billet is cut at the top and bottom, straightened, and then drawn. The pass processing rate is controlled within 15% and the billet is processed to the size desired by the user. The tenth step is finishing, in which the drawn dispersed oxygen-free copper rod is straightened and the tip and end are cut.

2. The process for producing the crack-resistant, high-aluminum dispersion strengthened copper electrode material according to claim 1.

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