JP7288368B2 - Cu alloy powder - Google Patents

Description

The present invention relates to a metal powder suitable for processes involving rapid melting, rapid cooling and solidification, such as three-dimensional additive manufacturing, thermal spraying, laser coating, and build-up. In particular, the present invention relates to powder whose material is a Cu alloy.

3D printers are used to manufacture objects made of metal. With this 3D printer, a modeled object is manufactured by the layered manufacturing method. In the layered manufacturing method, the spread metal powder is irradiated with a laser beam or an electron beam. The irradiation melts the metal particles of the powder. The particles are then solidified. This melting and solidification bonds the particles together. Irradiation is selectively applied to a portion of the metal powder. The parts of the powder that were not irradiated do not melt. A bonding layer is formed only in the irradiated portions.

A metal powder is further spread over the bonding layer. This metal powder is irradiated with a laser beam or an electron beam. The irradiation melts the metal particles. The metal then solidifies. This melting and solidification causes the particles in the powder to bond together to form a new bonding layer. The new tie layer is also bonded to the existing tie layer.

As a result of repeated bonding by irradiation, aggregates of bonding layers gradually grow. Through this growth, a model having a three-dimensional shape is obtained. A modeled object having a complicated shape can be easily obtained by the layered manufacturing method. An example of the additive manufacturing method is disclosed in Japanese Patent No. 4661842.

High conductivity is required for alloys used in high-frequency induction heating devices, heat sinks for cooling motors, and the like. Cu alloys are suitable for such applications.

Japanese Patent Application No. 2014-544456 discloses a Cu-based alloy whose main component is Cu and which contains Zr. The content of Zr in this Cu-based alloy is 5 at % to 8 at %.

Japanese Patent Application No. 2005-090521 discloses a nanocrystalline powder whose main component is Cu and which contains Zr. The content of Zr in the Cu alloy, which is the material of this powder, is 0.05% by mass to 45% by mass. The particle size of this powder is from 2 nm to 1000 nm.

Japanese Patent No. 4661842 Japanese Patent Application No. 2014-544456 Japanese Patent Application No. 2005-090521

In additive manufacturing, metallic materials are rapidly melted and quenched to solidify. Conventional Cu alloys are unsuitable for powders used in processes involving such rapid melting, rapid cooling, and solidification. It is difficult to obtain high-density molded objects from conventional Cu alloy powders. Conventional Cu alloys are also unsuitable for other rapid melting, rapid cooling and solidification processes such as thermal spraying, laser coating, and overlaying.

It is an object of the present invention to provide a Cu alloy powder from which shaped objects with excellent properties can be obtained by a process involving rapid melting, rapid cooling and solidification.

A Cu alloy powder according to the present invention is a mixture of a first powder P1 and a second powder P2. The material of this first powder P1 is
(1-1) One or more selected from the group consisting of Cr, Fe, Ni, Zr and Nb: 0.20% by mass or more and 10.0% by mass or less and (1-2) inevitable impurities Cu alloy containing The material of the second powder P2 is
(2-1) One or more selected from the group consisting of Cr, Fe, Ni, Zr and Nb: less than 0.20% by mass (including cases where it is 0.00% by mass)
and (2-2) pure Cu or Cu alloy containing unavoidable impurities. The ratio of the average particle diameter _D502 of the second powder P2 to the average particle diameter _D501 of the first powder P1 ( _D502 / _D501 ) is 1.05 or more and 6.00 or less. The volume mixing ratio of the first powder P1 and the second powder P2 is 1.05 or more and 9.00 or less.

Preferably, the ratio (D ₅₀ 2/D ₅₀ 1) is 1.05 or more and 3.00 or less.

Preferably, the volume mixing ratio is 1.05 or more and 4.00 or less.

Preferably, the sphericity of the Cu alloy powder is 0.80 or more and 0.95 or less.

Shaped objects with excellent properties are obtained from the Cu alloy powder according to the present invention by a process involving rapid melting and rapid solidification.

The Cu alloy powder P according to the present invention is an aggregate of many particles. This powder P is a mixture of a first powder P1 and a second powder P2.

The laser reflectance of pure Cu is higher than that of Fe-based alloys, Ni-based alloys, Co-based alloys, and the like. When pure Cu powder is used in processes involving rapid melting and rapid solidification, much heat is released to the atmosphere due to the high laser reflectivity. Therefore, sufficient heat is not provided to the powder to melt it. Lack of heat leads to poor bonding between particles. Due to the lack of heat, unmelted particles remain inside the shape obtained from this powder. The relative density of this model is low.

If the pure Cu powder is irradiated with a laser with a high energy density, the remaining unmelted particles are suppressed. However, a large amount of spatter occurs due to irradiation with a laser having a high energy density. This sputter adheres to the previously formed bonding layer. When more powder is laid down on top of this bonding layer, dense packing is inhibited by spatter. Spatter causes internal defects in the build.

When the Cu alloy powder P according to the present invention is irradiated with a laser, the first powder P1 having a high alloying element content is melted first. The heat of fusion of the first powder P1 also melts the second powder P2. The melting of the Cu alloy powder P does not require a high energy density laser. In the process using this powder P, the generation of spatter is suppressed. The second powder P2, which has a low content of alloying elements, can contribute to the electrical conductivity of the shaped article. From this Cu alloy powder P, a shaped article having high density and excellent electrical conductivity can be obtained.

[First powder P1]
The material of the first powder P1 is a Cu alloy. This Cu alloy is
(1-1) alloying elements and (1-2) unavoidable impurities. Preferably, the balance is Cu.

The alloy element (1-1) is Cr (chromium), Fe (iron), Ni (nickel), Zr (zirconium) or Nb (niobium). The first powder P1 may contain two or more alloying elements (1-1).

The solubility limit of each alloying element (1-1) in Cu on the equilibrium diagram is small. However, when the powder is obtained by a method involving rapid solidification such as the atomization method, the alloying element (1-1) can form a supersaturated solid solution in Cu. This supersaturated solid solution suppresses the laser reflectivity. When the Cu alloy powder P is subjected to a process involving rapid melting and rapid solidification, the first powder P1 melts easily.

The content of the alloy element (1-1) is 0.20% by mass or more and 10.0% by mass or less. The first powder P1 having a content of 0.20% by mass or more melts easily. From this viewpoint, 0.30% by mass or more is more preferable, and 0.50% by mass or more is particularly preferable. The first powder P1 having a content of 10.0% by mass or less does not significantly impede the conductivity of the shaped article. From this point of view, the content is more preferably 5.0% by mass or less, and particularly preferably 3.0% by mass or less.

Typical unavoidable impurities (1-2) are Si, P and S.

[Second powder P2]
The material of the second powder P2 is pure Cu or a Cu alloy. This metal
It contains (2-1) alloying elements and (2-2) unavoidable impurities. Preferably, the remainder is Cu.

The alloy element (2-1) is Cr (chromium), Fe (iron), Ni (nickel), Zr (zirconium), or Nb (niobium), like the alloy element (1-1) of the first powder P1. . The second powder P2 may contain two or more alloying elements (2-1).

The content of alloying element (2-1) is less than 0.20% by mass. The second powder P2 having a content of less than 0.20% by mass can contribute to the electrical conductivity of the shaped article. From this point of view, the content is more preferably 0.15% by mass or less, particularly preferably 0.10% by mass or less. This content may be zero. In other words, the alloy element (2-1) is not an essential component in the second powder P2. When the second powder P2 contains the alloy element (2-1), the material of the second powder P2 is a Cu alloy. When the second powder P2 does not contain the alloying element (2-1) (that is, when the content is 0.00% by mass), the material of the second powder P2 is pure Cu (containing only Cu and unavoidable impurities metal).

Typical unavoidable impurities (2-2) are Si, P and S.

[Volume mixing ratio (V1/V2)]
The ratio (V1/V2) between the volume content V1 of the first powder P1 and the volume content V2 of the second powder P2 in the Cu alloy powder P is preferably 1.05 or more and 9.00 or less. A powder P having a ratio (V1/V2) of 1.05 or more can provide a high-density model. From this point of view, the volume mixing ratio is more preferably 1.50 or more, and particularly preferably 2.00 or more. A powder P having a ratio (V1/V2) of 9.00 or less can provide a modeled article with excellent conductivity. From this point of view, the volume mixing ratio is more preferably 7.00 or less, particularly preferably 4.00 or less.

[Average particle size]
The ratio of the average particle diameter _D502 of the second powder P2 to the average particle diameter _D501 of the first powder P1 ( _D502 / _D501 ) is preferably 1.05 or more and 6.00 or less. In the Cu alloy powder P having a ratio (D ₅₀ 2/D ₅₀ 1) of 1.05 or more, the first powder P1 is likely to melt during laser irradiation. From this point of view, the ratio (D ₅₀ 2/D ₅₀ 1) is more preferably 1.10 or more, particularly preferably 1.20 or more. In the Cu alloy powder P having a ratio (D ₅₀ 2/D ₅₀ 1) of 6.00 or less, the heat of melting of the first powder P1 generated by laser irradiation easily melts the second powder P2. From this point of view, the ratio (D ₅₀ 2/D ₅₀ 1) is more preferably 4.00 or less, particularly preferably 3.00 or less.

The average particle diameter D ₅₀₁ of the first powder P1 is preferably 5 μm or more and 40 μm or less, particularly preferably 10 μm or more and 20 μm or less. The average particle diameter D ₅₀₂ of the second powder P2 is preferably 15 μm or more and 50 μm or less, and particularly preferably 20 μm or more and 30 μm or less.

In measuring the average particle size, the total volume of the powder is taken as 100% and the cumulative curve is obtained. The particle size at the point where the cumulative volume is 50% on this curve is the average particle size. The average particle size is measured by a laser diffraction scattering method. As an apparatus suitable for this measurement, Nikkiso's laser diffraction/scattering particle size distribution measuring apparatus "Microtrac MT3000" can be mentioned. Powder is poured into the cell of this device together with pure water, and the particle size is detected based on the light scattering information of the particles.

[Sphericality]
The sphericity of the Cu alloy powder P is preferably 0.80 or more and 0.95 or less. The powder P having a sphericity of 0.80 or more has excellent fluidity. From this point of view, the sphericity is more preferably 0.83 or more, and particularly preferably 0.85 or more. The powder P having a sphericity of 0.95 or less can suppress laser reflection. From this point of view, the sphericity is more preferably 0.93 or less, particularly preferably 0.90 or less.

For measurement of sphericity, a test piece in which powder P is embedded in resin is prepared. This test piece is subjected to mirror polishing, and the polished surface is observed with an optical microscope. The magnification of the microscope is 100x. Image analysis is performed on 20 randomly selected particles to measure the sphericity of the particles. The average of 20 measurements is the sphericity of the powder P. The sphericity of a particle is the ratio of the length in the direction perpendicular to the longest line segment that can be drawn within the contour of the particle to the length of the longest line segment.

[Method for producing powder]
Examples of methods for producing the first powder P1 and the second powder P2 include a water atomization method, a single roll quenching method, a twin roll quenching method, a gas atomization method, a disc atomization method, and a centrifugal atomization method. Preferred manufacturing methods are the single roll cooling method, the gas atomization method and the disc atomization method. The powder may be subjected to mechanical milling or the like. Examples of mechanical milling methods include a ball mill method, a bead mill method, a planetary ball mill method, an attritor method and a vibration ball mill method. A Cu alloy powder P is obtained by mixing the first powder P1 and the second powder P2 by a known method.

[molding]
Various shaped objects can be manufactured from the Cu alloy powder P according to the present invention. The manufacturing method of this molding is
(1) a step of producing a first powder P1 and a second powder P2;
(2) mixing the first powder P1 and the second powder P2 to obtain a Cu alloy powder P;
and (3) a step of melting and solidifying the Cu alloy powder P to obtain an unheated shaped article. A process of melting and solidifying the Cu alloy powder P includes a rapid melting, rapid cooling and solidification process. Specific examples of this process include three-dimensional additive manufacturing, thermal spraying, laser coating and overlaying. In particular, this metal powder is suitable for three-dimensional additive manufacturing.

A 3D printer can be used for this additive manufacturing method. In this layered manufacturing method, the spread Cu alloy powder P is irradiated with a laser beam or an electron beam. The irradiation causes the particles to heat up rapidly and melt rapidly. The particles then rapidly solidify. This melting and solidification bonds the particles together. Part of the Cu alloy powder P is selectively irradiated. The parts of the powder P that were not irradiated do not melt. A bonding layer is formed only in the irradiated portions.

A Cu alloy powder P is further spread over the bonding layer. This powder P is irradiated with a laser beam or an electron beam. The irradiation causes the particles to melt rapidly. The particles then rapidly solidify. This melting and solidification causes the particles in the powder to bond together to form a new bonding layer. The new tie layer is also bonded to the existing tie layer.

As a result of repeated bonding by irradiation, aggregates of bonding layers gradually grow. Through this growth, a model having a three-dimensional shape is obtained. By this layered manufacturing method, a complicated shaped object can be easily obtained.

[Conditions for modeling]
Energy density when sintering in a rapid melting, rapid cooling and solidification process such as additive manufacturing E. D. is preferably 100 J/mm ³ or more and 220 J/mm ³ or less. energy densityE. D. is 100 J/mm ³ or more, sufficient heat is given to the Cu alloy powder P. Therefore, the remaining unmelted powder inside the model is suppressed. The relative density of this shaped object is high. From this point of view, the energy density E. D. is more preferably 120 J/mm ³ or more, particularly preferably 140 J/mm ³ or more. energy densityE. D. is less than or equal to 220 J/mm ³ , no excessive heat is applied to the powder. Therefore, the bumping of the molten metal is suppressed, and the generation of spatter is also suppressed. From this point of view, the energy density E. D. is more preferably 210 J/mm ³ or less, and particularly preferably 205 J/mm ³ or less.

[Relative density]
The relative density of the shaped article obtained by the rapid melting, rapid cooling and solidification process (that is, the shaped article before heat treatment to be described later) is preferably 90% or more. This non-heat-treated shaped article is excellent in dimensional accuracy and electrical conductivity. From this point of view, the relative density is more preferably 93% or higher, more preferably 95% or higher.

The relative density is calculated based on the ratio between the density of a 10 mm square test piece produced by lamination molding or the like and the bulk density of Cu alloy powder P as a raw material. The density of a 10 mm square test piece is measured by the Archimedes method. The bulk density of Cu alloy powder P is measured by a dry density measuring instrument.

[Heat treatment]
Preferably, the method for manufacturing a shaped article includes:
(4) It further includes a step of heat-treating the unheated molded article obtained in step (3) to obtain a molded article. A preferred heat treatment is aging treatment. Due to the aging treatment, a single phase of the alloying element or a compound of Cu and the alloying element precipitates at the grain boundaries. This precipitation increases the purity of Cu in the crystal grains. This grain can contribute to the electrical conductivity of the shaped article.

[Conditions for heat treatment]
In aging, an untreated shaped article is held at a predetermined temperature for a predetermined period of time. The aging temperature is preferably 350°C or higher and 1000°C or lower. By aging at a temperature of 350° C. or higher, a single phase of alloy elements or a structure in which compounds of Cu and alloy elements are sufficiently precipitated is obtained. From this point of view, the aging temperature is more preferably 400° C. or higher, particularly preferably 450° C. or higher. Aging at a temperature of 1000° C. or less suppresses solid solution of the alloying elements into the crystal grains. From this point of view, the aging temperature is more preferably 950° C. or lower, particularly preferably 900° C. or lower.

The aging time is preferably 1 hour or more and 10 hours or less. By aging for 1 hour or more, a single phase of the alloy element or a structure in which the compound of Cu and the alloy element is sufficiently precipitated can be obtained. From this point of view, the aging time is more preferably 1.3 hours or longer, and particularly preferably 1.5 hours or longer. Aging times of 10 hours or less reduce energy costs. From this point of view, the time is more preferably 9.7 hours or less, particularly preferably 9.5 hours or less.

[Electrical conductivity of model]
The electrical conductivity of the shaped article after heat treatment is preferably 30 IACS% or more. A shaped article having an electrical conductivity of 30 IACS% or more has excellent electrical conductivity. From this point of view, the electrical conductivity is more preferably 40IACS% or more, and particularly preferably 50IACS% or more.

The effects of the present invention will be clarified by examples below, but the present invention should not be construed in a limited manner based on the description of these examples.

[Example 1]
In a vacuum, the raw material was heated by high-frequency induction heating in an alumina crucible and melted. The molten metal was dropped from a nozzle formed at the bottom of the crucible and having a diameter of 5 mm. This molten metal was sprayed with argon gas to obtain a large number of particles. These particles were classified to remove particles with a diameter exceeding 63 μm to obtain a first powder P1. The material of the first powder P1 is a Cu alloy containing 0.2% by mass of Cr. A second powder P2 was obtained from a raw material different from that of the first powder P1 in the same manner as the first powder P1. The material of the second powder P2 is a Cu alloy containing 0.10% by mass of Cr. The powder P of Example 1 was obtained by mixing the first powder P1 and the second powder P2. The volume mixing ratio (V1/V2) of this powder P was 3.00.

[Example 2-18 and Comparative Example 1-18]
Powders P of Examples 2-18 and Comparative Examples 1-18 were obtained in the same manner as in Example 1, except that the specifications were as shown in Tables 1 and 2 below.

[Molding]
Using this powder P as a raw material, the layered manufacturing method was performed by a three-dimensional layered manufacturing apparatus (EOS-M280) to obtain a non-heat-treated model. Energy Density in Additive Manufacturing E. D. are shown in Tables 1 and 2 below. The shape of the modeled object was a cube, and the length of one side was 10 mm.

[Heat treatment]
A heat treatment (aging treatment) was applied to the non-heat-treated molded article. Aging temperatures and aging times are shown in Tables 1 and 2 below.

[Measurement of electrical conductivity]
A test piece (3×2×60 mm) was prepared, and the electric resistance value (Ω) was measured by the four-probe method based on "JIS C 2525". For the measurement, an apparatus "TER-2000RH" manufactured by ULVAC-RIKO was used. The measurement conditions are as follows.
Temperature: 25°C
Current: 4A
Distance between voltage drops: 40mm
The electric resistivity ρ (Ωm) was calculated based on the following formula.
ρ = R/I × S
In this formula, R is the electrical resistance value (Ω) of the test piece, I is the current (A), and S is the cross-sectional area (m ² ) of the test piece. The electrical conductivity (S/m) was calculated from the reciprocal of the electrical resistivity ρ. Also, the electrical conductivity (%IACS) of each test piece was calculated with 5.9×10 ⁷ (S/m) as 100%IACS. The results are shown in Tables 1 and 2 below.

[rating]
Each gold powder was graded based on the following criteria regarding the electrical conductivity of the shaped article.
Evaluation 1: Electric conductivity is 90% IACS or more.
Evaluation 2: Electric conductivity is 70%IACS or more and less than 90%IACS.
Evaluation 3: Electric conductivity is 50%IACS or more and less than 70%IACS.
Evaluation 4: Electric conductivity is 40%IACS or more and less than 50%IACS.
Rating 5: Electrical conductivity is less than 40% IACS.
The results are shown in Tables 1 and 2 below.

From the evaluation results in Tables 1 and 2, the superiority of the present invention is clear.

The powder according to the invention is also suitable for 3D printers in which the powder is ejected from a nozzle. This powder is also suitable for laser coating methods in which the powder is ejected from a nozzle.

Claims (4)

A mixture of the first powder P1 and the second powder P2,
The material of the first powder P1 is
(1-1) One or more selected from the group consisting of Cr, Fe, Ni, Zr and Nb: 0.20% by mass or more and 10.0% by mass or less and (1-2) inevitable impurities A Cu alloy containing
The material of the second powder P2 is
(2-1) One or more selected from the group consisting of Cr, Fe, Ni, Zr and Nb: less than 0.20% by mass (including cases where it is 0.00% by mass)
and (2-2) pure Cu or Cu alloy containing unavoidable impurities,
The ratio of the average particle diameter _D502 of the second powder P2 to the average particle diameter _D501 of the first powder P1 ( _D502 / _D501 ) is 1.05 or more and 6.00 or less,
Cu alloy powder, wherein the volume mixing ratio of the first powder P1 and the second powder P2 is 1.05 or more and 9.00 or less. The Cu alloy powder according to claim 1, wherein the ratio ( _D502 / _D501 ) is 1.05 or more and 3.00 or less. The Cu alloy powder according to claim 1 or 2, wherein the volume mixing ratio is 1.05 or more and 4.00 or less. The Cu alloy powder according to any one of claims 1 to 3, having a sphericity of 0.80 or more and 0.95 or less.