Copper-based alloy powder and method for producing same

Abstract

This copper-based alloy powder is composed of an aggregate of copper-based alloy particles containing copper and nickel. Within the copper-based alloy particles contained in the copper-based alloy powder, the NiO segregated particle abundance rate, which is the numeric ratio of particles in which the area ratio of NiO is 2% or higher when observed in cross-section, is 4.0% by number or lower. The nickel content is preferably 1.0-20.0 mass%. Additionally, the copper content is preferably 80.0-99.9 mass%. Additionally, the phosphorus content is preferably 0.007-0.5 mass%.

Description

Copper-based alloy powder and its manufacturing method

[0001] The present invention relates to a copper-based alloy powder and a method for producing the same.

[0002] Atomization is known as a relatively inexpensive method for producing alloy powders used in various applications such as electronic materials, powder metallurgy, paints, etc. For example, Patent Document 1 describes a method in which copper raw material ingots and nickel raw material ingots are melted in a crucible, and the resulting molten metal is used to produce copper-nickel alloy powder by gas atomization.

[0003] International Publication No. 2018 / 207770

[0004] Alloy powder obtained by atomization is generally classified to obtain a particle size distribution suitable for the desired application. The non-grade powder removed by classification can be melted and reused as a raw material for atomization. However, when copper-nickel alloy powder obtained by a conventional atomization method such as that described in Patent Document 1 is melted and reused as a raw material for atomization, dross is generated in the molten metal obtained by melting the copper-nickel alloy powder, resulting in a decrease in the yield of the copper-nickel alloy powder obtained using the molten metal. Therefore, an object of the present invention is to provide a copper-based alloy powder that can suppress the generation of dross during melting, and a method for producing the same.

[0005] The present invention provides a copper-based alloy powder comprising an aggregate of copper-based alloy particles containing copper and nickel, wherein the copper-based alloy powder contains a NiO segregated particle abundance rate, which is the number ratio of particles having an NiO area rate of 2% or more when cross-sectionally observed, of 4.0% or less.

[0006] The present invention also provides a method for producing a copper-based alloy powder, the method comprising: a melting step for obtaining a molten metal containing copper and nickel; and a granulation step for using the molten metal to obtain a copper-based alloy powder consisting of an aggregate of copper-based alloy particles containing copper and nickel by an atomization method, wherein an induction furnace is used in the melting step, and the output of the induction furnace is set to 100 kW or more to obtain the molten metal.

[0007] Fig. 1 is a scanning electron microscope image showing a cross section of a copper-based alloy powder of the present invention. Fig. 2 is an image showing a region for measuring the area of ​​the cross section shown in Fig. 1. Fig. 3 is an image showing a NiO region observed in the cross section shown in Fig. 1. Fig. 4 is an image showing a region not included in the NiO region shown in Fig. 3. Fig. 5 is an image showing another NiO region observed in the cross section shown in Fig. 1. Fig. 6 is an image showing yet another NiO region observed in the cross section shown in Fig. 1. Fig. 7 is a graph showing the relationship between the temperature of the molten metal used in the examples and comparative examples and the abundance ratio of NiO segregated particles in the copper-based alloy powder.

[0008] The present invention will be described below based on preferred embodiments. The present invention relates to a copper-based alloy powder. The copper-based alloy powder is composed of an aggregate of copper-based alloy particles. The copper-based alloy powder of the present invention is composed essentially of copper-based alloy particles, but is allowed to contain unavoidable impurities. If the copper-based alloy powder of the present invention contains unavoidable impurities, the amount of such impurities is preferably 0.01 mass % or less, since the inherent properties of the copper-based alloy powder are unlikely to be impaired.

[0009] The copper-based alloy particles are made of an alloy mainly composed of copper and containing elements other than copper. The other elements may be, for example, either metallic or non-metallic elements. For example, nickel may be used as a metallic element. On the other hand, phosphorus may be used as a non-metallic element. An example of the copper-based alloy particles is a particle of an alloy containing copper and nickel, with the balance consisting of inevitable impurities. Another example of the copper-based alloy particles is a particle of an alloy containing copper, nickel, and phosphorus, with the balance consisting of inevitable impurities.

[0010] The copper content in the copper-based alloy particles is preferably 80.0% by mass or more, more preferably 85.0% by mass or more, and even more preferably 87.0% by mass or more, from the viewpoint of sufficiently increasing the electrical conductivity of the copper-based alloy powder. Also, the copper content in the copper-based alloy particles is preferably 99.9% by mass or less, more preferably 95.0% by mass or less, and even more preferably 92.0% by mass or less, from the viewpoint of sufficiently increasing the oxidation resistance of the copper-based alloy powder.

[0011] The nickel content in the copper-based alloy particles is preferably 1.0% by mass or more, more preferably 5.0% by mass or more, and even more preferably 8.0% by mass or more, from the viewpoint of sufficiently increasing the oxidation resistance of the copper-based alloy powder. Also, the nickel content in the copper-based alloy particles is preferably 20.0% by mass or less, more preferably 15.0% by mass or less, and even more preferably 13.0% by mass or less, from the viewpoint of sufficiently increasing the electrical conductivity of the copper-based alloy powder.

[0012] When the copper-based alloy particles contain phosphorus, the phosphorus content is preferably 0.007% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.012% by mass or more, and even more preferably 0.013% by mass or more, from the viewpoint of sufficiently enhancing the oxidation resistance of the copper-based alloy powder. Furthermore, the phosphorus content in the copper-based alloy particles is preferably 0.5% by mass or less, even more preferably 0.2% by mass or less, and even more preferably 0.1% by mass or less, from the viewpoint of sufficiently enhancing the electrical conductivity of the copper-based alloy powder. The reason why the inclusion of phosphorus in the copper-based alloy particles enhances oxidation resistance is that, during the production process of the copper-based alloy particles, phosphorus is sacrificially oxidized instead of nickel being oxidized, effectively suppressing the segregation of NiO (an oxide formed by combining divalent nickel and divalent oxygen), as described below. Furthermore, since phosphorus sublimes after sacrificial oxidation, it is unlikely to remain in the copper-based alloy particles, which is advantageous in that the electrical conductivity of the copper-based alloy particles is unlikely to decrease. When phosphorus is contained in the copper-based alloy particles, as described later in the preferred method for producing copper-based alloy particles, phosphorus can be, for example, Cu. ３P is preferably added to a molten metal containing copper.

[0013] The proportions of copper, nickel, and phosphorus contained in the copper-based alloy particles can be measured by ICP atomic emission spectroscopy of a sample solution obtained by dissolving the copper-based alloy particles in an acid such as hydrochloric acid.

[0014] It is preferable that the copper-based alloy particles contain a small amount of oxygen, from the viewpoint of sufficiently enhancing the electrical conductivity of the copper-based alloy powder. From this viewpoint, the oxygen element content in the copper-based alloy particles is preferably 1.0 mass% or less, more preferably 0.8 mass% or less, even more preferably 0.7 mass% or less, even more preferably 0.65 mass% or less, and particularly preferably 0.6 mass% or less. The smaller the amount of oxygen contained in the copper-based alloy particles, the more preferable it is from the viewpoint of improving electrical conductivity, and most preferably zero.

[0015] The oxygen content of the copper-based alloy particles of the present invention can be measured by the following method. For example, an oxygen / nitrogen analyzer EMGA-920 manufactured by Horiba, Ltd. can be used. 1 g of copper-based alloy powder is weighed, placed in a nickel capsule, and then combusted in a graphite crucible, whereby the oxygen content can be determined.

[0016] The copper-based alloy particles contain a low amount of NiO. The inventors have found through their investigations that this can suppress the amount of dross (molten slag) generated when the copper-based alloy powder is melted. Ideally, copper-based alloy particles would be free of NiO; however, in practice, nickel is oxidized and NiO is inevitably generated during the production process of the copper-based alloy particles. When copper-based alloy particles containing NiO are melted, dross due to NiO may be generated in the molten liquid. The generation of dross is one factor that reduces the productivity of copper-based alloy particles. In contrast, the present invention makes it possible to reduce the amount of dross generated when copper-based alloy powder is melted, thereby increasing the productivity of copper-based alloy particles.

[0017] The amount of NiO contained in copper-based alloy particles can be evaluated by the abundance of NiO segregated particles. In this specification, the abundance of NiO segregated particles refers to the percentage (number %) of particles in which, when cross-sectionally observed, the area ratio of NiO present inside the particles is 2% or more among the copper-based alloy particles contained in the copper-based alloy powder. In the copper-based alloy powder of the present invention, from the viewpoint of effectively suppressing dross generation, the abundance of NiO segregated particles is preferably 4.0% by number or less, more preferably 3.0% by number or less, even more preferably 2.0% by number or less, and particularly preferably 1.0% by number or less. The smaller the abundance of NiO segregated particles, the more preferable it is from the viewpoint of suppressing dross generation, and most preferably zero.

[0018] The reason why the area ratio of NiO in the definition of the abundance ratio of NiO-segregated particles in the present invention is set to 2% or more is because it was found that the adoption of this area ratio value can effectively suppress the generation of dross. It should be noted that the surface of copper-based alloy particles may inevitably be oxidized to form oxides during the production process and / or storage. These oxides may contain NiO. However, in the present invention, NiO present on the particle surface is not included in the calculation of the above-mentioned abundance ratio of NiO-segregated particles. The NiO that is included in the calculation of the abundance ratio of NiO-segregated particles in the present invention is only that present inside the particles. The reason why only NiO present inside the particles is included in the calculation of the abundance ratio of NiO-segregated particles is that NiO present on the particle surface can be removed by various reduction treatments, whereas NiO present inside the particles is extremely difficult or impossible to remove, and therefore essentially causes the generation of dross. The presence of NiO inside the particles is particularly pronounced in atomized powders, which are powders produced by atomization.

[0019] In the copper-based alloy powder of the present invention, the average area ratio calculated for particles having an area ratio of 2% or more is preferably 30% or less, more preferably 20% or less, and even more preferably 12% or less. By setting the average value to the above-mentioned value or less, the amount of dross generated when the copper-based alloy powder is melted can be further suppressed. From this perspective, the smaller the average value, the better.

[0020] Whether or not NiO is observed in the cross section of a copper-based alloy particle can be determined by image analysis using a scanning electron microscope-energy dispersive X-ray analysis method (hereinafter also referred to as "SEM-EDX"). In an SEM image of a copper-based alloy particle obtained using SEM-EDX, regions where NiO is present are displayed with a contrast different from regions where NiO is not present (i.e., regions that are copper-nickel alloys). Specifically, as shown in the SEM image of the cross section of a copper-based alloy particle shown in FIG. 1, regions where NiO is not present have a bright contrast, and regions where NiO is present have a dark contrast. When the image in FIG. 1 is elementally mapped using SEM-EDX (not shown), it is confirmed that regions with dark contrast in the copper-based alloy particle in the same figure contain higher concentrations of Ni and O than other regions in the copper-based alloy particle. Therefore, the regions with dark contrast can be considered to be regions where NiO is present. Furthermore, it has been confirmed that the bright contrast regions in the copper-based alloy particles in Figure 1 have (i) higher Cu concentrations, (ii) lower Ni concentrations, and (iii) similar Cu and Ni concentrations compared to the regions where NiO is present. Therefore, the bright contrast regions can be considered to be regions where a copper-nickel alloy is present. The area of ​​NiO observed in the cross section of the copper-based alloy particle can be measured using image analysis software. The specific method for measuring the area of ​​NiO is as follows.

[0021] First, a sample for EDX observation is prepared. To prepare the sample, copper-based alloy particles are embedded in resin, then a cross section is cut out and polished. Next, a metal (e.g., platinum) is sputtered onto the cross section to complete the sample preparation. This sample is observed with a scanning electron microscope (hereinafter also referred to as "SEM"). An example of an SEM image is shown in Figure 1. In the figure, the dark gray region extending along the longitudinal direction of the particle is the region where NiO segregates. The light gray region surrounding this region consists of a copper-nickel alloy. To measure the area of ​​NiO, the cross-sectional area of ​​the particle and the area of ​​the region where NiO segregates are determined. The cross-sectional area of ​​the particle is calculated from the hatched area S2 shown in Figure 2. The area of ​​the region where NiO is segregated is the sum of the value (S3-S4) obtained by subtracting the area S4 of the hatched region shown in FIG. 4 from the area S3 of the hatched region shown in FIG. 3, the area S5 of the hatched region shown in FIG. 5, and the area S6 of the hatched region shown in FIG. 6. That is, S3-S4+S5+S6. The area ratio of NiO is calculated by dividing this value by the previously calculated S2 and multiplying by 100, i.e., (S3-S4+S5+S6) / S2×100. The above operation is performed for 100 or more particles. The ratio (unit: number%) of particles with a NiO area ratio of 2% or more to the total number of particles for which the NiO area ratio is measured is defined as the abundance ratio of NiO segregated particles.

[0022] The particle size of the copper-based alloy powder of the present invention can be adjusted appropriately depending on the application. When the copper particles of the present invention are used to form fine electrical wiring by means of, for example, screen printing, dispensing, or inkjet printing, the primary particle size is preferably set to 50 nm to 2 μm, and more preferably 200 nm to 1 μm. The primary particle size of the copper particles can be measured, for example, using image analysis particle size distribution measurement software MacView (manufactured by Mountec Co., Ltd.).

[0023] The copper-based alloy powder of the present invention, as produced, has a volume cumulative particle size D at 50% cumulative volume by a laser diffraction / scattering particle size distribution measurement method. ５０The volume cumulative particle diameter D of the copper-based alloy powder of the present invention is preferably 0.3 μm or more, more preferably 0.6 μm or more, and even more preferably 1.0 μm or more. ５０ is preferably 15.0 μm or less, more preferably 10.0 μm or less, and even more preferably 8.0 μm or less.

[0024] The copper-based alloy powder of the present invention has a volume-cumulative particle size D at 10% by volume of the cumulative volume as produced. １０ The volume cumulative particle diameter D of the copper-based alloy powder of the present invention is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. １０ The copper-based alloy powder of the present invention has a volume cumulative particle size D at 90% by volume of the cumulative volume in the as-produced state. ９０ The volume cumulative particle diameter D of the copper-based alloy powder of the present invention is preferably 1.0 μm or more, more preferably 2.0 μm or more, and even more preferably 2.5 μm or more. ９０ is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 35 μm or less.

[0025] In the present invention, the copper-based alloy powder may be classified before use depending on the specific application of the copper-based alloy powder. Even if the copper-based alloy powder is classified, the volume-cumulative particle size D １０ , D ５０ and D ９０ are preferably within the above ranges.

[0026] The shape of the copper-based alloy particles constituting the copper-based alloy powder of the present invention is not particularly limited, and various shapes, such as spherical, flake, plate, and dendritic, can be used. The shape of the copper-based alloy particles to be used can be appropriately determined depending on the specific application of the copper-based alloy powder of the present invention. The shape of the copper-based alloy particles generally depends on the manufacturing method. Spherical copper-based alloy particles can be manufactured by, for example, atomization or wet reduction. Flake-shaped particles can be manufactured by, for example, mechanically plastically deforming spherical particles. The copper-based alloy powder of the present invention may also be a mixture of copper-based alloy particles of various shapes. For example, the copper-based alloy powder of the present invention may be a mixture of spherical particles and flake-shaped particles.

[0027] Next, a preferred method for producing the copper-based alloy powder of the present invention will be described. As described above, the copper-based alloy particles can be produced by, for example, atomization or wet reduction. From the viewpoint of easily producing a copper-based alloy powder in which the abundance ratio of segregated NiO particles is controlled, it is preferable to employ the atomization method.

[0028] When producing copper-based alloy powder by atomization, a melting step is carried out before atomization to obtain a molten metal containing copper and nickel. In the melting step, copper and nickel bullion, which are the raw materials for the molten metal, are heated to a predetermined temperature in the atmosphere and melted. In addition to or instead of copper bullion or nickel bullion, copper-nickel alloy bullion can also be used. As copper bullion and nickel bullion, any bullion known in the art can be used without particular limitation. For example, electrolytic copper can be used as copper bullion. The same applies to nickel, and electrolytic nickel can be used as the bullion.

[0029] Various heating furnaces can be used as heating means to heat copper and nickel ingots as raw materials to obtain a molten metal. Examples of heating furnaces include induction furnaces and combustion furnaces. An induction furnace is a furnace that uses electromagnetic induction to heat the ingot. In an induction furnace, an alternating current is passed through a coil provided therein to induce an electromotive force within the coil, generating eddy currents in the conductor within the coil. The ingot is heated using Joule heat generated by this eddy current. On the other hand, a combustion furnace is a furnace that uses heat generated by burning fuels such as propane, city gas, LNG, kerosene, and heavy oil to heat the ingot. The inventors' research has revealed that using an induction furnace, in particular, to heat the ingot makes it difficult for NiO to segregate in the resulting copper-based alloy particles. This is thought to be because, when heating using an induction furnace, the molten metal flows along the magnetic field during heating, which causes NiO to disperse into small particles and makes it difficult for segregation to occur. In particular, when the lining material of the induction furnace is carbon (for example, when a graphite crucible is used in the induction furnace), the generated NiO reacts with the carbon to be reduced, which has a synergistic effect, making the NiO more easily dispersed into smaller particles.In contrast, when heating using a combustion furnace, the flow of the molten metal during heating is not active, which is thought to make NiO more likely to segregate.

[0030] When an induction furnace is used in the metal melting step, it is advantageous to obtain a molten metal by setting the output of the induction furnace to preferably 100 kW or more, more preferably 130 kW or more, and even more preferably 150 kW or more, since this further suppresses the segregation of NiO. From the viewpoints of energy saving and production efficiency, the output of the induction furnace is set to preferably 250 kW or less, more preferably 230 kW or less, and even more preferably 200 kW or less.

[0031] When obtaining a molten metal using an induction furnace, it is preferable to heat the molten metal to a predetermined temperature in a short time from the viewpoint of suppressing NiO segregation. From this viewpoint, it is preferable to perform the atomization method within 120 minutes, particularly within 100 minutes, and especially within 90 minutes after starting to energize the induction furnace. The shorter this time, the more preferable it is from the viewpoint of suppressing NiO segregation. However, since the capacity of the induction furnace is limited, the lower limit of this time is approximately 50 minutes.

[0032] The temperature when performing the atomization method, in other words, the temperature when the base metal is melted using an induction furnace, is preferably set to a relatively low temperature in order to suppress the oxidation of nickel and the segregation of NiO. From these viewpoints, the temperature when the base metal is melted using an induction furnace is preferably set to 1850°C or less, more preferably 1600°C or less, and even more preferably 1500°C or less. This temperature is preferably as low as possible as long as the molten metal has sufficient fluidity. Specifically, the lower limit of the temperature is approximately 1100°C.

[0033] From the viewpoint of suppressing oxidation of nickel and suppressing segregation of NiO, it is desirable to apply as little heat as possible to nickel. From this viewpoint, when obtaining a molten metal, it is preferable to first heat and melt copper base metal, and then add and melt nickel base metal to obtain a molten metal containing copper and nickel.

[0034] When copper and nickel are heated to obtain a molten metal, Cu is added. ３ It is preferable to add P (copper (I) phosphide). ３ The addition of P has the advantage that phosphorus is oxidized (sacrificial oxidation) before nickel in the molten metal is oxidized, thereby suppressing the formation of NiO. ３ The amount of P added is Cu ３ The phosphorus content of the molten metal after adding P is preferably 0.007% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.02% by mass or more, calculated as phosphorus element. ３ The amount of P added is set to be 0.05 to 0.15 from the viewpoint of sufficiently increasing the electrical conductivity of the copper-based alloy particles. ３The content of phosphorus in the molten metal after adding P is preferably 1.0 mass % or less, more preferably 0.7 mass % or less, and even more preferably 0.5 mass % or less, calculated as phosphorus element. ３ The mass of the P element in the copper-based alloy particles obtained after adding P is ３ The mass of Cu converted to elemental phosphorus may be less than that of the elemental phosphorus. This is presumably because elemental phosphorus may sublimate during the production of the particles (see Example 12 below). ３ The amount of P added may differ from the phosphorus content in the copper-based alloy particles. The phosphorus content in the copper-based alloy particles is preferably 0.007% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.012% by mass or more, and even more preferably 0.013% by mass or more. The phosphorus content in the copper-based alloy particles is preferably 0.5% by mass or less, more preferably 0.2% by mass or less, and even more preferably 0.1% by mass or less.

[0035] When copper and nickel ingots are heated to obtain a molten metal, it is also preferable to additionally add a carbonaceous material. The addition of a carbonaceous material has the advantage of suppressing the formation of NiO because carbon is oxidized before nickel in the molten metal is oxidized. From this perspective, the amount of carbonaceous material added is preferably 0.5% by mass or more, more preferably 0.8% by mass or more, and even more preferably 1.0% by mass or more, based on the molten metal after the addition of the carbonaceous material. Furthermore, from the perspective of sufficiently increasing the electrical conductivity of the copper-based alloy particles, the amount of carbonaceous material added is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 2.0% by mass or less, based on the molten metal after the addition of the carbonaceous material.

[0036] Examples of the carbonaceous material that can be used include charcoal, activated carbon, and graphite. Examples of the carbonaceous material include a group of carbonaceous materials called carbon black. Specific examples of the carbonaceous material that can be used include Ketjen Black (registered trademark), oil furnace black, channel black, lamp black, thermal black, and acetylene black. In the present invention, the type of carbonaceous material is not particularly limited, and the effect of suppressing NiO formation can be achieved regardless of the type of carbonaceous material used.

[0037] Once the molten metal has been obtained by the above procedure, the molten metal is used in a granulation step by atomization to obtain copper-based alloy powder consisting of an aggregate of copper-based alloy particles containing copper and nickel.

[0038] As the atomization method, gas atomization and water atomization can be preferably used. When uniform particle shape is desired, gas atomization is preferably used. On the other hand, when fine particles are desired, water atomization is preferably used. Of gas atomization and water atomization, high-pressure atomization is particularly preferred because it can produce fine and uniform particles. High-pressure atomization is a method in which, in the case of water atomization, atomization is performed at a water pressure of about 50 MPa or more and 150 MPa or less. In the case of gas atomization, it is a method in which atomization is performed at a gas pressure of about 0.5 MPa or more and 3 MPa or less.

[0039] Once atomized powder, i.e., copper-based alloy powder, is obtained by atomization, it may be used as is, or may be classified to obtain a powder with a specific particle size distribution. When classification is performed, it is desirable from an economical standpoint to reuse the copper-based alloy powder removed by classification. For example, the copper-based alloy powder removed by classification can be recovered and supplied to a melting process for copper and nickel ingots to be used as a raw material for the molten metal described above. The copper-based alloy powder supplied to the melting process is made of copper-based alloy particles with a low proportion of NiO segregated particles, which has the advantage of suppressing the generation of dross when the copper-based alloy powder is supplied to the melting process to obtain the molten metal.

[0040] The recovered copper-based alloy powder can be heated together with copper and nickel bullion, or alternatively, after the copper bullion is heated to obtain a molten copper metal, the nickel bullion and the recovered copper-based alloy powder can be added to the molten copper metal and melted to obtain a molten copper and nickel-containing metal.

[0041] The particles constituting the copper-based alloy powder obtained by atomization are generally spherical. The spherical copper-based alloy powder may be used as is, or may be flattened to form flakes before use. Furthermore, the spherical copper-based alloy powder may be mixed with a flaky copper-based alloy powder, or with a spherical or flaky copper powder.

[0042] The copper-based alloy powder thus obtained can be used to form fine electrical wiring by means of, for example, screen printing, dispensing, inkjet printing, etc., taking advantage of its high electrical conductivity and oxidation resistance, or can be used as an internal or external electrode of a multilayer ceramic chip capacitor.

[0043] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, "%" means "% by mass."

[0044] Example 1 Electrolytic copper and electrolytic nickel ingots were prepared. These ingots were used in the amounts shown in Table 1 and simultaneously charged into an induction furnace. Furthermore, charcoal was charged into the induction furnace in the amount shown in Table 1. The output of the induction furnace was set to 150 kW, and the ingots were heated in the atmosphere to obtain a molten metal at the temperature shown in Table 1. The obtained molten metal was poured into a tundish in a water atomization apparatus. While the molten metal was falling from a nozzle at the bottom of the tundish, water was jet-sprayed into the molten metal from the injection holes of a full-cone nozzle in an inverted cone-shaped stream to produce an atomized powder consisting of an aggregate of spherical particles. The time from the start of heating to the start of atomization was as shown in Table 1. The obtained atomized powder was classified using a classification apparatus to obtain the desired copper-based alloy powder.

[0045] Examples 2 to 7 Copper-based alloy powders were obtained in the same manner as in Example 1, except that the conditions for obtaining the molten metal were as shown in Table 1.

[0046] Example 8 Instead of electrolytic nickel ingot, copper-nickel alloy ingot (copper:nickel=85%:15%) was used. The conditions for obtaining the molten metal were as shown in Table 1. Except for these, a copper-based alloy powder was obtained in the same manner as in Example 1.

[0047] [Examples 9 and 10] After electrolytic copper ingot was melted to obtain a molten copper metal, electrolytic nickel ingot was added and melted to obtain a molten copper metal containing copper and nickel. The conditions for obtaining the molten metal are shown in Table 1. Except for these, a copper-based alloy powder was obtained in the same manner as in Example 1.

[0048] Example 11 In addition to electrolytic copper and electrolytic nickel ingots, copper-nickel alloy powder was used. The amounts used were as shown in Table 1. This copper-nickel alloy powder was the atomized powder obtained in Example 1 that had been removed by classification. After the electrolytic copper ingot was melted to obtain a molten copper metal, the electrolytic nickel ingot and copper-nickel alloy powder were added and melted to obtain a molten metal containing copper and nickel. The conditions for obtaining the molten metal were as shown in Table 1. A copper-based alloy powder was obtained in the same manner as in Example 1, except for the above.

[0049] [Example 12] In Example 11, the electrolytic copper base metal was melted to obtain molten copper, and then electrolytic nickel base metal, copper-nickel alloy powder, and Cu ３ P was added and melted to obtain a molten metal containing copper and nickel. ３ The amount of P added was set to 0.03 mass % in terms of elemental phosphorus in the molten metal. The conditions for obtaining the molten metal were as shown in Table 1. Except for these, a copper-based alloy powder was obtained in the same manner as in Example 11.

[0050] Examples 13 to 17 Copper-based alloy powders were obtained in the same manner as in Example 1, except that the conditions for obtaining the molten metal were as shown in Table 1. Note that, although Example 13 was produced under the same production conditions as Example 2, the particle size distribution of the resulting copper-based alloy powder differed from that of Example 2 due to the difference in atomization batch.

[0051] Comparative Example 1 Electrolytic copper and electrolytic nickel ingots were prepared. These ingots were used in the amounts shown in Table 1 and simultaneously charged into a combustion furnace fueled by propane. Charcoal was also charged into the combustion furnace in the amount shown in Table 1. The ingots were heated to obtain a molten metal at the temperature shown in Table 1. The obtained molten metal was subjected to water atomization under the same conditions as in Example 1 to produce an atomized powder. The time from the start of heating to the start of atomization was as shown in Table 1. The obtained atomized powder was classified under the same conditions as in Example 1 to obtain the desired copper-based alloy powder.

[0052] Comparative Example 2 In addition to electrolytic copper and electrolytic nickel ingots, copper-nickel alloy powder was used. The amounts used were as shown in Table 1. This copper-nickel alloy powder was the atomized powder obtained in Example 1 that had been removed by classification. The conditions for obtaining the molten metal were as shown in Table 1. A copper-based alloy powder was obtained in the same manner as in Example 1, except for the above.

[0053] Comparative Example 3 In Comparative Example 2, the amount of charcoal used was changed to that shown in Table 1. Other than this, a copper-based alloy powder was obtained in the same manner as in Example 11.

[0054]

[0055] [Evaluation] The copper-based alloy powders obtained in the examples and comparative examples were measured for the abundance of NiO segregated particles by the method described above. Furthermore, the particle size distribution was measured by the following method. Furthermore, the copper-based alloy powders were subjected to elemental analysis and measurement of the amount of dross generated by the following methods. The results are shown in Table 2.

[0056] [Particle size distribution] 0.1 g of a measurement sample was mixed with 100 ml of a 20 mg / L aqueous solution of sodium hexametaphosphate and dispersed for 10 minutes using an ultrasonic homogenizer (US-300T manufactured by Nippon Seiki Seisakusho Co., Ltd.). Then, the particle size distribution was measured using a laser diffraction scattering particle size distribution measuring device (Microtrac MT3300EX-II manufactured by Nikkiso Co., Ltd.). The volume cumulative particle size D at 10% by volume of the cumulative volume was calculated. １０ , volume cumulative particle size D at cumulative volume 50% by volume ５０ , and the volume cumulative particle size D at 90% by volume of the cumulative volume ９０ asked for.

[0057] [Elemental Analysis] The proportions of copper, nickel, and phosphorus were measured by ICP atomic emission spectroscopy on a sample solution obtained by dissolving copper-based alloy particles in an acid such as hydrochloric acid. The proportion of oxygen contained in the copper-based alloy particles was measured as follows: 1 g of copper-based alloy powder was weighed, placed in a nickel capsule, and then combusted in a graphite crucible. The oxygen content was determined using an oxygen / nitrogen analyzer (EMGA-920, manufactured by Horiba, Ltd.).

[0058] [Amount of Dross Generated] After melting and atomization, the residues in the induction furnace and tundish were collected and weighed.

[0059]

[0060] As is clear from the results shown in Table 2, the copper-based alloy powders obtained in each example have a low rate of NiO segregation particles and a low amount of dross. In particular, it can be seen that the rate of NiO segregation particles is low when a molten metal prepared by melting copper and then adding nickel is used. Furthermore, it can be seen that the rate of NiO segregation particles is low the shorter the time from when current is applied to the induction furnace until the atomization method is performed. Furthermore, when Cu is added to the molten metal, ３ When P is added, Cu ３It can be seen that the abundance ratio of segregated NiO particles is lower than when no P is added. Figure 7 is a graph showing the relationship between the temperature of the molten metal used in the examples and comparative examples and the abundance ratio of segregated NiO particles in the copper-based alloy powder. As is clear from the graph shown in the figure, it can be seen that the abundance ratio of segregated NiO particles is suppressed even when atomization is performed at a high molten metal temperature. It can also be seen that the lower the temperature of the molten metal, the lower the abundance ratio of segregated NiO particles tends to be.

[0061] According to the present invention, there are provided a copper-based alloy powder that can suppress the generation of dross when melted, and a method for producing the same.

Claims

1. A copper-base alloy powder comprising an aggregate of copper-base alloy particles containing copper and nickel, wherein the copper-base alloy powder contains copper-base alloy particles, and the presence rate of NiO segregated particles, which is the number ratio of particles having an NiO area rate of 2% or more when observed in cross section, is 4.0% or less by number.

2. The copper-based alloy powder according to claim 1, wherein the nickel content is 1.0 mass % or more and 20.0 mass % or less.

3. The copper-based alloy powder according to claim 1 or 2, wherein the copper content is 80.0 mass % or more and 99.9 mass % or less.

4. The copper-based alloy powder according to claim 1 or 2, wherein the phosphorus content is 0.007 mass % or more and 0.5 mass % or less.

5. The copper-base alloy powder according to claim 1 or 2, wherein the average area ratio calculated for the particles having an area ratio of 2% or more is 30% or less.

6. The copper-based alloy powder according to claim 1 or 2, which is an atomized powder.

7. A method for producing a copper-base alloy powder, comprising: a melting step for obtaining a molten metal containing copper and nickel; and a granulating step for obtaining a copper-base alloy powder consisting of an aggregate of copper-base alloy particles containing copper and nickel by an atomizing method using the molten metal, wherein an induction furnace is used in the melting step, and the output of the induction furnace is set to 100 kW or more to obtain the molten metal.

8. The method according to claim 7, wherein the melting in the induction furnace is carried out at 1850°C or less.

9. The method according to claim 7 or 8, wherein the atomization is carried out within 120 minutes after starting to energize the induction furnace.

10. In the melting step, Cu ３ P is added, Cu ３ The amount of P added is Cu ３ The method according to claim 7 or 8, wherein the amount of phosphorus added to the molten metal after the addition is 0.005% by mass or more and 1.0% by mass or less in terms of phosphorus element.

11. The method according to claim 7 or 8, wherein in the melting step, nickel is added and melted after copper is melted.

12. The method according to claim 7 or 8, wherein a carbonaceous material is added in the melting step.

13. The method according to claim 7 or 8, wherein the copper-based alloy powder obtained in the granulation step is classified, and the powder removed by classification is supplied to the melting step.

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