Manufacturing method of copper alloy powder for metal AM

Abstract

To provide a method for producing copper alloy powder for metal AM, which is capable of stably producing a high-quality laminated molded product having high reproducibility of the fine structure of the laminated molded product produced by metal AM and little structural defects such as voids.SOLUTION: A molding apparatus comprises a molten copper feeding part for obtaining molten copper, a tundish for holding the molten copper in a non-oxidizing atmosphere, a connecting gutter for feeding the molten copper to the tundish while maintaining the non-oxidizing atmosphere, an addition part for adding an alloying element in the non-oxidizing atmosphere to obtain molten copper alloy, and a mold where the molten copper alloy is fed. A production method by the molding apparatus includes a molding process for producing a copper alloy ingot and an atomizing process for atomizing the copper alloy ingot in an inert gas or vacuum atmosphere. The copper alloy ingot has an O concentration of 10 massppm or less, a H concentration of 5 massppm or less, a total of O, H, and S of 20 massppm or less, and a total content of impurity elements (except for O, H, and S) of 0.04 mass% or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a manufacturing method for copper alloy powder for metal additive manufacturing (metal AM), which is optimal for metal AM technology. This application claims priority based on Japanese Patent Application No. 2022-169920, filed on October 24, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] In recent years, metal AM technology, which uses powder as the main raw material and creates products using a metal 3D printer, has been put to practical use as a method for manufacturing metal parts with various three-dimensional shapes. The main metal AM technologies that use metal powder include powder bed fusion (PBF) using electron beams or laser light, and the binder jet method. Copper alloys have many basic properties suitable for industrial applications, such as electrical conductivity, thermal conductivity, mechanical properties, wear resistance, and heat resistance, and are used as materials for various components. In recent years, attempts have been made to form components of various shapes by metal AM using copper alloy powder in various fields such as space and electrical component applications, and there is a growing need for copper and copper alloy parts manufactured by metal AM. For example, Patent Documents 1 and 2 propose a technique for producing an additive manufacturing object by metal AM using copper alloy powder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-211062 A [Patent Document 2] JP 2019-070169 A [Non-patent literature]

[0004] [Non-Patent Document 1] YM Arisoy et. al., "Influence of scan strategy and process parameters on microstructure and its optimization in additively manufactured nickel alloy 625 via laser powder bed fusion", The International Journal of Advanced Manufacturing Technology, Volume 90, pp 1393-1417 (2017). Summary of the Invention [Problem to be solved by the invention]

[0005] Metal structures created by metal AM are used as structural components for a variety of applications, so if voids are present in the additively manufactured object or if the microstructure of the metal material is uneven, it can cause problems in terms of thermomechanical and electrical reliability. Currently, the most commonly used building method for metal AM is laser PBF, and attempts have also been made to use laser PBF for copper and copper alloys. Incidentally, when performing additive manufacturing using a method of irradiating a laser beam or an electron beam, a thin layer of powder is first formed (powder bed), and then this powder bed is locally irradiated with a laser or an electron beam to melt and solidify the material. However, in the case of copper and copper alloys, compared to other metal materials such as iron, titanium, and nickel, copper itself has a high reflectance in the visible and infrared ranges, which causes the melting behavior of the copper alloy powder to become unstable during the laser PBF process, and voids are likely to occur inside the additively manufactured object, resulting in a number of issues such as unstable quality of the object manufactured by laser PBF and poor productivity, and there is a demand for improvements in the quality and productivity of copper and copper alloys manufactured by laser PBF.

[0006] Currently, the most widely used form of raw material for metal AM is powder. For example, in metal AM using laser PBF, the electromagnetic wave absorption characteristics of the particles due to the coupling and interaction between the surface layer of each particle constituting the raw material powder and the electromagnetic wave affect the melting behavior of the raw material powder, and greatly affect the productivity of the part and the quality including the defect density of the part. For example, in a metal AM process using a powder bed, the thickness of the powder bed formed in one lamination process is, for example, about several tens of μm (Non-Patent Document 1), and the raw material powder is melted by irradiating such a relatively thin powder bed with converged electromagnetic waves, and the desired molded structure is realized by repeating numerous laminations and melting and solidification. The electromagnetic wave absorption characteristics of solids have a significant effect on the elementary process of such additive manufacturing using a powder bed. For example, since the electromagnetic wave absorption characteristics of solids are affected by the material composition, it is extremely important to increase the uniformity of the material composition and microstructure of the powder in order to achieve stable quality and high productivity in the entire additive manufacturing product.

[0007] In addition, as a result of various past research and developments, materials that have achieved high mechanical strength while maintaining high electrical conductivity and materials with excellent heat resistance have already been developed for copper alloys, and there is a social demand for metal AM parts with desired shapes using existing materials with high-performance copper alloy compositions. However, when additive manufacturing is performed by irradiating a powder bed of raw material with such a known copper alloy composition with a laser beam or electron beam, if there is a lack of reproducibility of the microstructure related to the raw material powder, including the reproducibility of the composition of the powder particles at each location irradiated with the laser beam, the melting behavior of the powder becomes non-uniform, which may induce structural defects such as voids inside the molded object or cause deterioration of mechanical properties due to the non-uniformity of the metal composition of the molded object.

[0008] The reproducibility of the microstructure of such raw material powders, including the reproducibility of the powder's material composition, is a similar problem in other metal AM methods such as the binder jet method, and in particular, in the additive manufacturing of copper alloys, improving productivity has been a major challenge due to the issues with various raw materials. Conventional copper alloy powders for metal AM do not have sufficient material properties suitable for metal AM processes, and as a result, objects manufactured by various additive manufacturing processes are prone to defects, making it difficult to achieve sufficient productivity.

[0009] Furthermore, one of the factors that can cause structural defects in metal AM objects is the generation of voids due to the entrapment of gas, etc. When conventional copper alloy powder is used for additive manufacturing by the PBF method, gas is generated due to impurities contained in the copper alloy powder when the powder is melted, and the molten copper alloy or solidified copper alloy traps the gas components, which can cause voids to form inside the additive manufactured object, making it difficult to stably produce high-quality additive manufactured objects.

[0010] This invention has been made in consideration of the above-mentioned circumstances, and aims to provide a method for producing copper alloy powder for metal AM that can stably produce high-quality additively molded objects with high reproducibility of the microstructure of the additively molded objects produced by metal AM and with few structural defects such as voids. [Means for solving the problem]

[0011] In order to solve this problem, the inventors conducted extensive research and found that, when using powder produced from an atomization process in which a high-purity copper alloy ingot with sufficiently reduced O and H concentrations is used as a raw material and is melted and decomposed by atomization in an inert gas or vacuum atmosphere to pulverize the raw material, it is possible to significantly suppress the occurrence of voids inside the manufactured additive manufacturing product. Regarding void suppression in the laser PBF process, by increasing the purity of the raw material copper alloy powder, the reproducibility of the material composition throughout the powder is improved; in other words, the reproducibility of the powder composition at each location on the powder bed where the laser is irradiated is improved. As a result, the reproducibility of the melting and solidification behavior of the raw material powder due to laser irradiation is improved and stabilized. Furthermore, it is believed that the generation of voids in the additive manufacturing process can be suppressed due to effects such as the suppression of desorbed gas components such as HO that can be generated due to O and H in the raw material powder.

[0012] The present invention has been made based on the above-mentioned findings, and a method for producing copper alloy powder for metal AM according to a first aspect of the present invention is a method for producing copper alloy powder for metal AM to be used in metal AM, comprising: a molten copper supply section for melting a copper raw material made of high-purity copper having a purity of 99.99 mass% or more to obtain molten copper; a tundish arranged downstream of the molten copper supply section for holding the molten copper in a non-oxidizing atmosphere; a connecting launder arranged between the molten copper supply section and the tundish for supplying the molten copper to the tundish while maintaining a non-oxidizing atmosphere; and a copper alloying section for adding alloying elements of a copper alloy to the molten copper in the non-oxidizing atmosphere to obtain a copper alloy. The method includes a casting process for producing a copper alloy ingot by a casting device equipped with an adding section for obtaining molten gold and a mold to which the molten copper alloy is supplied, and an atomization process for using the copper alloy ingot as a raw material and pulverizing it by atomizing it in an inert gas or vacuum atmosphere to melt and decompose it, characterized in that the copper alloy ingot has an O concentration of 10 massppm or less, a H concentration of 5 massppm or less, a total O concentration, H concentration and S concentration of 20 massppm or less, and a total content of impurity elements other than Cu and alloying elements (excluding O, H, S) of 0.04 mass% or less.

[0013] According to the method for producing copper alloy powder for metal AM of aspect 1 of the present invention, the O concentration in the copper alloy ingot is 10 massppm or less, and the H concentration is 5 massppm or less. Therefore, by producing copper alloy powder using this copper alloy ingot as a raw material, it is possible to produce copper alloy powder for metal AM that can be used to stably produce high-quality additive manufacturing objects with high microstructural reproducibility and few structural defects such as voids.

[0014] In a second aspect of the present invention, in the method for producing a copper alloy powder for metal AM of the first aspect, it is preferable that the O concentration in the copper alloy ingot is 8 massppm or less and the H concentration is 3 massppm or less.

[0015] In a third aspect of the present invention, in the method for producing a copper alloy powder for metal AM of the first or second aspect, it is preferable that the total content of the alloying elements in the copper alloy ingot is within the range of 0.01 mass% or more and 5 mass% or less. According to the method for producing copper alloy powder for metal AM of aspect 3 of the present invention, the total content of the alloying elements in the copper alloy ingot is within the range of 0.01 mass% or more and 5 mass% or less, so it is possible to stably produce copper alloy powder for metal AM with a uniform content of alloying elements. In addition, because it contains alloying elements, it is possible to produce copper alloy powder for metal AM that has excellent properties such as electrical conductivity and thermal conductivity.

[0016] A fourth aspect of the present invention is a method for producing a copper alloy powder for metal AM according to any one of the first to third aspects, wherein the alloying elements include one or more selected from Cr, Zr, Si, Ni, Mg, Ti, Al, Zn, Ca, Sn, Pb, Fe, Mn, Te, Nb, Co, Sb, Bi, Ag, Ta, W, Mo, and P. According to the method for producing copper alloy powder for metal AM of aspect 4 of the present invention, since the copper alloy powder contains one or more of the above-mentioned alloying elements as alloying elements, it is possible to produce copper alloy powder for metal AM having excellent properties such as electrical conductivity and thermal conductivity. Effect of the Invention

[0017] According to the present invention, it is possible to provide a method for producing copper alloy powder for metal AM, which enables the stable production of high-quality additively molded objects with high reproducibility of the microstructure of the additively molded objects produced by metal AM and few structural defects such as voids. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a flow diagram of a method for producing a copper alloy powder for metal AM according to the present embodiment. [Diagram 2] FIG. 1 is a flow diagram of the melting and casting process in the manufacturing method of copper alloy powder for metal AM according to the present embodiment. [Diagram 3] FIG. 1 is a flow diagram of a copper alloy raw material preparation process in a method for producing copper alloy powder for metal AM according to the present embodiment. [Figure 4] FIG. 1 is a flow diagram of an atomization process in a method for producing a copper alloy powder for metal AM according to the present embodiment. [Diagram 5] FIG. 1 is a schematic explanatory diagram of a continuous casting device used in the method for producing copper alloy powder for metal AM according to the present embodiment. [Figure 6] FIG. 2 is a schematic explanatory diagram of another continuous casting device used in the method for producing copper alloy powder for metal AM according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, a method for producing a copper alloy powder for metal AM, which is one embodiment of the present invention, will be described with reference to the attached drawings. The method for producing copper alloy powder for metal AM according to the present embodiment is for producing copper alloy powder for use in metal AM. Note that, in the present embodiment, copper alloy powder suitable for the laser PBF method is produced.

[0020] The method for producing copper alloy powder for metal AM according to the present embodiment will be described with reference to the flow diagram in FIG. The manufacturing method of copper alloy powder for metal AM according to this embodiment includes a melting and casting step S01 for obtaining a copper alloy ingot, a copper alloy raw material preparation step S02 for processing the obtained copper alloy ingot into a wire rod to obtain a copper alloy raw material, and a powder processing step S03 for processing the copper alloy raw material into powder.

[0021] (Melting and casting process S01) First, a copper alloy ingot 1 having a predetermined composition is manufactured. The melting and casting process S01 includes a melting step S11, an alloy element adding step S12, and a continuous casting step S13, as shown in the flow diagram of FIG. In this embodiment, a copper alloy ingot 1 is obtained using a continuous casting apparatus 10 shown in FIG.

[0022] This continuous casting apparatus 10 includes a melting furnace 11, a tundish 12 arranged downstream of the melting furnace 11, a connecting trough 13 connecting the melting furnace 11 and the tundish 12, an addition section 14 for adding alloy elements in the tundish 12, a continuous casting mold 15 arranged downstream of the tundish 12, and a pouring nozzle 16 for pouring molten copper alloy from the tundish 12 into the continuous casting mold 15.

[0023] In the melting furnace 11 of the molten copper supply section, the copper raw material is melted in a non-oxidizing atmosphere (an inert gas atmosphere or a reducing atmosphere) to obtain the molten copper 3 (melting step S11). Here, the copper raw material melted in the melting furnace 11 is high-purity copper with a purity of 99.99 mass% or more (for example, high-purity electrolytic copper or oxygen-free copper). The copper raw material to be melted is high-purity copper of 4N grade (99.99 mass%) or more, more preferably high-purity copper of 5N grade (99.999 mass%) or more, and even more preferably high-purity copper of 6N (99.9999 mass%) or more. The obtained molten copper 3 is preferably oxygen-free molten copper.

[0024] In the connecting trough 13, the obtained molten copper 3 is supplied to the tundish 12 while maintaining a non-oxidizing atmosphere (an inert gas atmosphere or a reducing atmosphere). The connecting trough 13 is disposed between the melting furnace 11 and the tundish 12, and the molten copper 3 passes through the inside of the connecting trough 13 in a non-oxidizing atmosphere. In addition, in the tundish 12, the molten copper 3 is held in a non-oxidizing atmosphere (an inert gas atmosphere or a reducing atmosphere). In addition, since the melting furnace 11, the connecting trough 13, and the tundish 12 are in a non-oxidizing atmosphere (an inert gas atmosphere or a reducing atmosphere), the gas components (O, H) in the molten copper 3 are reduced.

[0025] Then, in the tundish 12, alloy elements are added to the molten copper 3 by using the adding section 14 (alloy element adding step S12). By adding alloying elements to the molten copper 3 in which the gas components (O, H) have been sufficiently reduced, the yield of the alloying elements added is good, so that the amount of the alloying elements used can be reduced, and the manufacturing cost of the copper alloy can be reduced. Furthermore, by adding alloying elements to the molten copper 3 flowing inside the tundish 12, the alloying elements can be uniformly dissolved, and a molten copper alloy having stable component values ​​can be continuously produced.

[0026] The obtained molten copper alloy is poured into a continuous casting mold 15 via a pouring nozzle 16 to continuously produce a copper alloy ingot 1 (continuous casting step S13).

[0027] In this embodiment, the obtained copper alloy ingot 1 has an O concentration of 10 massppm or less and an H concentration of 5 massppm or less. The O concentration is more preferably 8 massppm or less, and the lower limit is not particularly limited, but may be a value not including 0 (or a value exceeding 0), or may be 0.5 massppm. The H concentration is more preferably 3 massppm or less, and the lower limit is not particularly limited, but may be a value not including 0 (or a value exceeding 0), or may be 0.2 massppm. In the obtained copper alloy ingot 1, the S concentration is preferably 15 massppm or less. The S concentration is more preferably 11 massppm or less, and the lower limit is not particularly limited, but may be a value that does not include 0 (or a value that exceeds 0), and may be 0.01 massppm. Furthermore, in the obtained copper alloy ingot 1, the total content of impurity elements (excluding O, H, and S) other than Cu and alloy elements is preferably 0.04 mass% or less. In the obtained copper alloy ingot 1, the sum of the O concentration, the H concentration, and the S concentration is preferably 30 massppm or less. The sum of the O concentration, the H concentration, and the S concentration is more preferably 25 massppm or less, further preferably 22 massppm or less, and may be 20 massppm or less. The lower limit of the sum of the O concentration, the H concentration, and the S concentration is not particularly limited, but may be a value that does not include 0 (or a value that exceeds 0), and may be 0.71 massppm.

[0028] (Copper alloy raw material preparation process S02) Next, the copper alloy ingot 1 obtained in the melting and casting step S01 is processed into a wire rod to produce a copper alloy raw material. As shown in FIG. 3, the copper alloy raw material preparation process S02 includes an extrusion process S21, a drawing process S22, and a cutting process S23.

[0029] In the extrusion step S21, a copper alloy ingot having a circular cross section is heated and extruded into a rod having a predetermined diameter. In this embodiment, the heating temperature during the hot extrusion process is preferably set within a range of 700°C or more and 1000°C or less.

[0030] In the drawing step S22, the bar obtained by the extrusion process S21 is subjected to drawing to form a wire having a predetermined diameter. The drawing temperature is not particularly limited, but is preferably within the range of -200°C to 200°C, which corresponds to cold or warm rolling, and particularly preferably room temperature.

[0031] In the cutting step S23, the wire obtained in the drawing step S22 is cut to a predetermined length to obtain a copper alloy raw material. Here, it is preferable that the O concentration in the obtained copper alloy raw material is 10 massppm or less, and the H concentration is 5 massppm or less. In addition, it is preferable that the S concentration in the obtained copper alloy raw material is 15 massppm or less. Furthermore, the total content of impurity elements (excluding O, H, and S) other than Cu and alloying elements in the obtained copper alloy raw material is preferably 0.04 mass% or less.

[0032] (Powder processing process S03) Next, the copper alloy raw material obtained in the copper alloy raw material preparation step S02 is subjected to an atomization process to produce copper alloy powder for metal AM. As shown in FIG. 4, the powder processing step S03 includes a melting step S31, an atomizing treatment step S32, and a classification step S33.

[0033] In the melting step S31, the copper alloy raw material is heated and melted to obtain a molten metal. Here, in this embodiment, the atmosphere during melting is preferably a non-oxidizing atmosphere. In the atomization process S32, the molten metal obtained in the melting process S31 is sprayed with high-pressure gas to rapidly cool the droplets of the molten metal, thereby producing powder having a spherical or similar shape. Inert gases such as argon and nitrogen can be used as the gas used in the gas atomization method. The melting temperature of the copper alloy raw material in the gas atomization process (the melting temperature during the gas atomization process) is preferably equal to or higher than the melting point of copper and equal to or lower than 1500°C. The melting temperature during the gas atomization process may be equal to or higher than 1085°C and equal to or lower than 1500°C. In the classification step S33, the obtained powder is classified to obtain a copper alloy powder having a predetermined particle size distribution.

[0034] Through the above-mentioned steps, copper alloy powder for metal AM is produced. The copper alloy powder for metal AM produced by the method for producing copper alloy powder for metal AM of this embodiment contains various alloy elements, as described above. In this embodiment, the alloying elements refer to elements that are intentionally added in the method for producing a copper alloy powder for metal AM of this embodiment. In this embodiment, some of the alloying elements may be referred to as active metal elements. The copper alloy ingot of this embodiment preferably contains one or more alloying elements selected from Cr, Zr, Si and Ni. The alloying elements are not limited to the above components, and it is preferable that the alloying elements contain one or more selected from Cr, Zr, Si, Ni, Mg, Ti, Al, Zn, Ca, Sn, Pb, Fe, Mn, Te, Nb, Co, Sb, Bi, Ag, Ta, W, Mo, and P. In addition, the copper alloy ingot of this embodiment preferably contains one or more active metal elements as alloy elements. Active metal elements include Cr, Zr, Si, Ni, Mg, Ti, Ni, Al, Zn, Ca, Sn, Pb, Fe, Mn, Te, Nb, etc. In the copper alloy ingot of the present embodiment, the total content of the alloying elements is preferably within a range of 0.01 mass% to 50 mass%, more preferably 0.02 mass% to 45 mass%, and may be 5 mass% or less.

[0035] In addition, copper alloy powder for metal AM may contain impurity elements (excluding O, H, S, and N) other than alloy elements as long as they do not affect the characteristics. The impurity elements (excluding O, H, S, and N) are components that are unintentionally mixed in due to contamination during the manufacturing process or impurities contained in trace amounts in raw materials. In this embodiment, the impurity elements may be unavoidable impurities. Here, the total amount of impurity elements (excluding O, H, S, and N) in the copper alloy powder for metal AM may be 0.07 mass% or less, may be 0.06 mass% or less, may be 0.05 mass% or less, is preferably 0.04 mass% or less, is more preferably 0.03 mass% or less, is even more preferably 0.02 mass% or less, and is even more preferably 0.01 mass% or less. In addition, in a process carried out under a finite pressure, such as an atomization process, atmospheric components contained in the atmosphere or during the process may cause atmospheric components to be contained in the powder. For example, nitrogen may be contained in the powder as an atmospheric component. In the copper alloy powder for metal AM of this embodiment, the nitrogen concentration (N concentration) is preferably 30 massppm, more preferably 20 massppm, and even more preferably 10 massppm or less. In the copper alloy powder for metal AM of this embodiment, the nitrogen concentration (N concentration) is more preferably 5 massppm or less. In addition, the lower limit of the N concentration is not particularly limited, but may be a value that does not include 0 (or a value that exceeds 0). In addition, in the composition of the copper alloy constituting the copper alloy particles 50 of the copper alloy powder for metal AM, the error in numerical accuracy is ±10% (excluding O, H, S, and N).

[0036] The copper alloy powder for metal AM produced by the method for producing a copper alloy powder for metal AM according to the present embodiment contains one or more alloying elements selected from Cr, Zr, Si, and Ni, and the total content of the alloying elements may be in the range of 0.01 mass% to 50 mass%, more preferably in the range of 0.01 mass% to 10 mass%, and more preferably in the range of 0.01 mass% to 5 mass%, and may be 0.02 mass% or more. The alloying elements of the copper alloy powder for metal AM produced by the present embodiment are not limited to the above components, and examples of the alloying elements (active metal elements) include one or more selected from Cr, Zr, Si, Ni, Mg, Ti, Al, Zn, Ca, Sn, Pb, Fe, Mn, Te, Nb, Co, Sb, Bi, and Ag. Furthermore, since the O concentration in the copper raw material made of oxygen-free copper is 10 massppm or less and the H concentration is 5 massppm or less, the copper alloy powder for metal AM produced by the method for producing copper alloy powder for metal AM of this embodiment has low O concentration and H concentration.

[0037] According to the manufacturing method of copper alloy powder for metal AM of this embodiment configured as described above, the O concentration in the copper alloy ingot obtained in the melting and casting step S01 is 10 massppm or less, and the H concentration is 5 massppm or less. Therefore, by manufacturing copper alloy powder using this copper alloy ingot as a raw material, it is possible to manufacture copper alloy powder for metal AM that can be used to stably manufacture high-quality additive manufacturing objects with high reproducibility of microstructure and few structural defects such as voids.

[0038] In the manufacturing method of copper alloy powder for metal AM of this embodiment, when the S concentration in the copper alloy ingot is 15 massppm or less, S, which is a component that is easily contained in copper, can be sufficiently reduced. By manufacturing copper alloy powder using this copper alloy ingot as a raw material, it is possible to produce copper alloy powder for metal AM that has high reproducibility of microstructure and few structural defects such as voids, and can stably produce even higher quality additive manufacturing objects.

[0039] In the manufacturing method of copper alloy powder for metal AM of this embodiment, when the total content of impurity elements (excluding O, H, and S) other than Cu and alloying elements in the copper alloy ingot is 0.04 mass% or less, the amount of impurity elements is sufficiently reduced, and by manufacturing copper alloy powder using this copper alloy ingot as a raw material, it is possible to produce copper alloy powder for metal AM that has high reproducibility of microstructure and few structural defects such as voids, and can be used to stably produce even higher quality additive manufacturing objects.

[0040] In the manufacturing method of copper alloy powder for metal AM of this embodiment, when alloying elements are contained, it is possible to produce copper alloy powder for metal AM that realizes copper alloy shaped bodies with excellent properties such as electrical conductivity and thermal conductivity. Furthermore, the continuous casting apparatus 1 can obtain copper alloy ingots with a stable content of alloying elements, enabling the stable production of copper alloy powder for metal AM with a uniform content of alloying elements. Such a state in which the content of alloying elements is uniform in copper alloy powder for metal AM can be considered to realize uniform energy absorption throughout the powder bed in a PBF modeling process that uses, for example, an electron beam or laser light, resulting in an additive manufacturing object with high reproducibility and reliability.

[0041] In the method for producing copper alloy powder for metal AM of the present embodiment, when the copper alloy ingot is continuously produced by the continuous casting device 10, the copper alloy ingot 1 can be produced efficiently.

[0042] The above describes a method for producing copper alloy powder for metal AM, which is an embodiment of the present invention. However, the present invention is not limited to this and can be modified as appropriate without departing from the technical concept of the invention. For example, in the above-described embodiment, the powder is produced by gas atomization, but this is not limited thereto, and the copper alloy powder may be produced by water atomization, centrifugal atomization, inductively coupled plasma method, plasma atomization method, or the like.

[0043] In addition, the copper alloy powder for metal AM obtained as described above may be appropriately heat-treated to stabilize the structure, etc. During this heat treatment, an appropriate atmosphere such as an inert gas or vacuum may be selected. Furthermore, in this embodiment, the copper alloy powder for metal AM suitable for the PBF method using a laser has been described as being produced, but this is not limited thereto, and the copper alloy powder for metal AM may be applied to other metal AM methods. In addition, in the present embodiment, the copper alloy ingot is produced using the continuous casting apparatus shown in FIG. 5, but the present invention is not limited to this, and other casting apparatuses may be used.

[0044] For example, a continuous casting apparatus 101 shown in Fig. 6 may be used. This continuous casting apparatus 101 includes an oxygen-free copper supplying means (molten copper supplying section) 102 arranged at the most upstream portion, a heating furnace 103 arranged downstream thereof, a tundish 104 arranged downstream of the heating furnace 103 and to which molten copper is supplied, molten metal supplying passages 105a, 105b, and 105c connecting the oxygen-free copper supplying means 102 to the heating furnace 103, a trough 106 connecting the heating furnace 103 and the tundish 104, addition means (adding sections) 107 and 108 for adding alloy elements in a non-oxidizing atmosphere, and a continuous casting mold 142. The oxygen-free copper supplying means 102, the heating furnace 103, the tundish 104, the molten metal supplying passages 105a, 105b, and 105c, and the trough 106 each have a non-oxidizing atmosphere inside.

[0045] The oxygen-free copper supply means 102 is composed of a melting furnace 121 for melting the copper raw material, a holding furnace 122 for temporarily holding the molten copper obtained by melting in the melting furnace 121, a degassing treatment device 124 for removing oxygen and hydrogen from the molten copper, and molten metal supply paths 105a, 105b, and 105c connecting these.

[0046] The degassing treatment device 124 has a gas bubbling device as stirring means for stirring the molten copper therein, and removes oxygen and hydrogen from the molten copper by bubbling with an inert gas, for example. The molten metal supply passages 105a, 105b, and 105c have a non-oxidizing atmosphere therein to prevent the molten copper and the oxygen-free copper molten metal from being oxidized. The non-oxidizing atmosphere is formed by blowing an inert gas such as a mixture of nitrogen and carbon monoxide or argon into the molten metal supply passages.

[0047] As adding means for adding alloy elements, a first adding means 107 disposed in the heating furnace 103 and a second adding means 108 disposed in the tundish 104 are provided. When alloying elements are continuously or intermittently charged from first adding means 107 provided in heating furnace 103, the alloying elements are added to the oxygen-free copper molten metal stored in heating furnace 103. Here, the oxygen-free copper molten metal stored in the storage section is heated by a high-frequency induction coil, which promotes the melting of the added alloying elements. Furthermore, when alloying elements are continuously or intermittently charged from the second adding means 108 provided in the tundish 104, the alloying elements are added to the molten oxygen-free copper flowing in the tundish 104. Here, the molten oxygen-free copper flowing in the tundish 104 is heated in the heating furnace 103 and has a high temperature, and also flows within the tundish 104, which promotes the dissolution of the added alloying elements. EXAMPLES

[0048] In order to verify the effects of the present invention, a confirmatory experiment was carried out as follows.

[0049] (Example of the present invention) First, by the manufacturing method described in the embodiment, a copper raw material made of high purity copper of 4N grade was used to produce an ingot of C18000 having the composition shown in Table 1. The impurities shown in Table 1 are impurity elements (excluding O, H, and S). Next, the produced C18000 ingot was used as the raw material to produce copper alloy powder for metal AM with the composition shown in Table 2 by gas atomization using argon gas, and the powder was sieved to a particle size suitable for the powder bed of metal AM. The melting temperature during gas atomization was 1300°C. For the copper alloy powder for metal AM of the present invention, particle size distribution measurement was performed using a Microtrac MT3300EXII. The particle size distribution was as follows: 10% cumulative particle size by volume was 16 μm, 50% cumulative particle size was 28 μm, and 90% cumulative particle size was 45 μm. Then, using the copper alloy powder for metal AM of the present invention, a small piece of an additive manufacturing object was produced using a commercially available laser PBF device at an energy density of 13 J / mm2.

[0050] (Conventional example) As a conventional example, a commercially available C18000 powder for metal AM shown in Table 2 was prepared. A particle size distribution measurement was performed on the conventional C18000 powder for metal AM using a Microtrac MT3300EXII. The result was a particle size distribution with a 10% cumulative particle size by volume of 13 μm, a 50% cumulative particle size of 33 μm, and a 90% cumulative particle size of 57 μm. Then, using the conventional C18000 powder for metal AM and a commercially available laser PBF device, a small piece of an additively molded object was produced under the same molding conditions as the example of the present invention, including the layer thickness.

[0051] (Composition of copper alloy powder for ingot and metal AM) The O concentration was determined by inert gas fusion-infrared absorption method, the H concentration by inert gas fusion-thermal conductivity method, and the S concentration by combustion-infrared absorption method for the ingots shown in Table 1, the copper alloy powder for metal AM of the inventive example, and the copper alloy powder for metal AM of the conventional example. In addition, the concentrations of components other than these substances, except for copper, were determined by a combination of X-ray fluorescence spectrometry, glow discharge mass spectrometry, and inductively coupled plasma mass spectrometry. The results are shown in Table 2. The impurities shown in Table 2 are impurity elements (excluding O, H, S, and N).

[0052] (model density) The density of the layered object was evaluated from the cross section of the layered object and the area occupied by voids observed in the cross section of the layered object. In this specification, this density is defined as the density of the object. The density of the molded object was evaluated by first defining the cross-sectional area of ​​the object to be measured (this is called the evaluation cross-sectional area, 3.4 mm square), then identifying the voids within this measurement cross-sectional area, and calculating the area occupied by the voids in the evaluation cross-sectional area. The density of the molded object was then defined as (evaluation cross-sectional area - void occupied area) / evaluation cross-sectional area. The evaluation results of the density of the molded object are shown in Table 2.

[0053] [Table 1]

[0054] [Table 2]

[0055] As shown in Table 2, it was confirmed that additive manufacturing using the copper alloy powder for metal AM of the present invention achieved a molded product density of up to 99.3%. On the other hand, when the conventional C18000 powder for metal AM was used, the molded product density was 97.3%, which was a problematic density for practical use. From the above results, it was confirmed that by using the copper alloy powder for metal AM produced by the method for producing copper alloy powder for metal AM of the present invention, it is possible to produce additive manufacturing objects with sufficiently high density and few voids. It should be noted that the O concentration of the copper alloy powder for metal AM of the present invention is higher than that of the ingot in Table 1. However, because the original copper alloy ingot is of high purity, it is possible to suppress the degree of excess increase in O concentration in the subsequent processes, which is thought to contribute to improving the reproducibility of the microstructure of the additive manufacturing product.

[0056] It has been confirmed that the present invention can provide a method for producing copper alloy powder for metal AM, which enables the stable production of high-quality additively molded objects with high reproducibility of the microstructure of the objects produced by metal AM and few structural defects such as voids. [Explanation of symbols]

[0057] S14 Continuous casting process S32 Atomization process

Claims

1. A method for producing a copper alloy powder for metal AM used in metal AM, comprising: a casting process for producing a copper alloy ingot by a casting device including a molten copper supply section for melting a copper raw material made of high purity copper having a purity of 99.99 mass% or more to obtain molten copper, a tundish arranged downstream of the molten copper supply section for holding the molten copper in a non-oxidizing atmosphere, a connecting trough arranged between the molten copper supply section and the tundish for supplying the molten copper to the tundish while maintaining the non-oxidizing atmosphere, an addition section for adding alloy elements of a copper alloy to the molten copper in a non-oxidizing atmosphere to obtain a molten copper alloy, and a mold to which the molten copper alloy is supplied; an atomization process for atomizing the copper alloy ingot as a raw material in an inert gas or vacuum atmosphere to melt and decompose the copper alloy ingot into powder; It has The copper alloy ingot has an O concentration of 10 ppm by mass or less, an H concentration of 5 ppm by mass or less, a total of O concentration, H concentration and S concentration of 20 ppm by mass or less, and a total content of impurity elements (excluding O, H and S) other than Cu and alloy elements of 0.04 mass% or less.

2. 2. The method for producing a copper alloy powder for metal AM according to claim 1, wherein the copper alloy ingot has an O concentration of 8 ppm by mass or less and an H concentration of 3 ppm by mass or less.

3. 3. The method for producing a copper alloy powder for metal AM according to claim 1, wherein the total content of the alloy elements in the copper alloy ingot is within a range of 0.01 mass% or more and 5 mass% or less.

4. The method for producing a copper alloy powder for metal AM according to claim 1 or claim 2, characterized in that the alloying elements contain one or more selected from Cr, Zr, Si, Ni, Mg, Ti, Al, Zn, Ca, Sn, Pb, Fe, Mn, Te, Nb, Co, Sb, Bi, Ag, Ta, W, Mo, and P.

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