Cu-based powder and method for producing the Cu-based powder

Abstract

To provide Cu-based powder capable of manufacturing a Cu-based alloy with less effects of P on thermal conductivity and electrical conductivity because P and element M contained in the Cu-based powder are removed by heat treatment from a Cu mother phase to form a phosphide, the Cu-based powder containing the element M that tends to form a phosphide.SOLUTION: Cu-based powder contains an element M that forms a phosphide with a standard free energy of formation per 1 mol of phosphorus less than that of Cu3 P at the temperature range of 298K-1,300K. A phosphide with the lowest standard free energy of formation in the above temperature range among phosphides formed by the element M is represented by MxPy (where, x>0, y>0) and A is represented by [A=mass% of P×(x / y)×(atomic weight of M / atomic weight of P)]. The Cu-based powder has a content of the element M of A×0.3 mass% or more and A×1.2 mass% or less and a content of the P of 0.01 mass%-1.0 mass%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a Cu-based powder. Specifically, the Cu-based powder is produced from a molten metal containing P, and since P reacts with oxygen to form gaseous phosphate, reducing the amount of oxygen, and thus preventing deterioration of the fluidity of the molten metal due to oxygen, it can be produced by an atomization method with excellent productivity and safety. Furthermore, since the Cu-based powder contains element M, which easily forms phosphides, the P contained in the Cu-based powder can form phosphides with element M by heat treatment and precipitate from the Cu matrix, and therefore the Cu-based powder can be used to produce a Cu-based alloy with little effect of P on thermal conductivity and electrical conductivity. [Background technology]

[0002] When manufacturing Cu-based powders using the atomization method, fluidity of the molten metal is always required when spraying, for the sake of productivity and work safety.

[0003] Oxygen affects the fluidity of molten metal, and if the amount of oxygen is high, the fluidity deteriorates. Furthermore, if the molten metal contains a large amount of oxygen, the amount of oxygen in the produced powder will increase, causing surface oxidation and internal oxidation, which may cause defects or deterioration in the properties of products produced from such powder.

[0004] As a method for reducing oxygen, the addition of charcoal or flux to the molten metal has been established.

[0005] The added charcoal or flux reacts with oxygen in the molten metal to form oxides, reducing the amount of oxygen, thereby improving the fluidity of the molten metal.

[0006] However, because the added charcoal and flux float to the top of the molten metal, oxidation cannot be suppressed at the moment the metal is poured out, resulting in a sudden deterioration in fluidity. In addition, because the charcoal and flux are difficult to remove, there is the problem that the charcoal, flux, or flux oxides may be mixed into the produced Cu-based powder.

[0007] One way to solve this problem is to add copper phosphorus, which is made of copper and copper phosphide, to the molten metal.

[0008] When phosphorus copper is added to molten metal, phosphorus (P) reacts with oxygen in the molten metal to form gaseous phosphorus oxide, which reduces the amount of oxygen, thereby preventing the fluidity of the molten metal from deteriorating.

[0009] Furthermore, gaseous phosphorus oxide does not need to be physically removed as with charcoal or flux.

[0010] However, it is known that when P is present in the Cu matrix of a Cu-based alloy, it significantly reduces the thermal and electrical conductivity, which are excellent features of the Cu-based alloy.

[0011] When copper phosphorus is added in excess of the oxygen content in the molten metal to produce a Cu-based powder, and then the powder is heat-treated, the resulting Cu-based alloy has P remaining in the Cu matrix, resulting in a problem of reduced thermal and electrical conductivity compared to alloys without the addition of copper phosphorus.

[0012] With atmospheric melting, the fluidity of the molten metal can be maintained without adding phosphorus copper, but since a vacuum device is required, it is not suitable for mass production and there are problems with increased manufacturing costs.

[0013] Furthermore, P may be contained in Cu-based powders as an unavoidable impurity derived from the raw materials.

[0014] In view of the above problems, there is a need for the development of Cu-based powders that have little effect of P on the thermal conductivity and electrical conductivity of Cu-based alloys produced by heat-treating Cu-based powders, even if the Cu-based powders are produced from molten metals melted by conventional melting methods and to which phosphorus copper or the like has been added, or even if the Cu-based powders contain P as an unavoidable impurity. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Patent Publication No. 6-93351 Summary of the Invention [Problem to be solved by the invention]

[0016] Patent Document 1 discloses a method in which an oxidizing gas is blown onto the molten metal to remove P from the molten metal, and then a reducing gas is blown onto the molten metal to reduce the amount of oxygen.

[0017] However, when the method disclosed in Patent Document 1 is applied to powder production by atomization, although it is possible to remove P using an oxidizing gas, there is a problem in that it is not easy to add a reduction step in the event of overoxidation.

[0018] The present inventors have set solving the above-mentioned problems as a technical task, and as a result of numerous trial and error trials and experiments, have discovered a Cu-based powder containing element M, P, and Cu, wherein the element M is an element whose standard free energy of formation per 1 mol of phosphorus of the element M in a temperature range of 298K to 1300K is equal to or less than the standard free energy of formation per 1 mol of phosphorus of Cu3P in the same temperature range, and among the phosphides of the element M, the phosphide with the lowest standard free energy of formation in the above temperature range is M x P y (where x>0, y>0), where A is expressed as "A=mass% of P×(x / y)×(atomic weight of M / atomic weight of P)", the content of the element M in the Cu-based powder is A×0.3 mass% or more and A×1.2 mass% or less, and the content of P is 0.01 mass% to 1.0 mass%, so that the fluidity of the molten metal is high, and therefore excellent productivity and safety can be ensured even when the Cu-based powder is produced by an atomization method. Furthermore, since the Cu-based powder contains the element M which easily forms phosphide, by heat treating the Cu-based powder, P and the element M form phosphide, and P can be precipitated from the Cu matrix. This is a remarkable finding that has led to the achievement of the above technical object. [Means for solving the problem]

[0019] The above technical problems can be solved by the present invention as follows.

[0020] The present invention provides a Cu-based powder containing element M, P, and Cu, wherein the element M is an element whose standard free energy of formation per mole of phosphorus of the element M in a temperature range of 298K to 1300K is equal to or less than the standard free energy of formation per mole of phosphorus of CuP in the same temperature range, and among the phosphides of the element M, the phosphide having the lowest standard free energy of formation in the temperature range is M. x P y (where x>0, y>0), and A is represented by the following formula (formula), the content of the element M in the Cu-based powder is A×0.3 mass% or more and A×1.2 mass% or less, and the content of P is 0.01 mass% to 1.0 mass%. (Formula) A = mass% of P × (x / y) × (atomic weight of M / atomic weight of P)

[0021] The present invention also relates to the Cu-based powder, which contains 0.1% by mass to 3.0% by mass of Sn.

[0022] The present invention also relates to the Cu-based powder, wherein the O content is 0.1 mass % or less.

[0023] The present invention also relates to the Cu-based powder, which is for powder metallurgy or additive manufacturing.

[0024] The present invention also relates to the Cu-based powder produced by an atomization method.

[0025] The present invention also provides a Cu-based powder obtained by adding 0.1% by mass to 1.0% by mass of a lubricant to the Cu-based powder. [Effects of the Invention]

[0027] The Cu-based powder of the present invention can contain P by adding copper phosphorus or the like, which has a deoxidizing effect, to the molten metal. This allows P and oxygen to form a gaseous phosphate oxide, reducing the amount of oxygen in the molten metal and resulting in a molten metal with high fluidity. Therefore, the powder can be produced by the atomization method while ensuring excellent productivity and safety.

[0028] Furthermore, the phosphorus oxide formed is in the gas phase and does not need to be physically removed like charcoal or flux.

[0029] Furthermore, the Cu-based powder of the present invention contains, excluding unavoidable impurities, the element M in an amount of 0.3 to 1.2 times by mass the amount of A represented by the formula (1). Therefore, when the Cu-based powder is heat-treated, the P that remains without reacting with oxygen reacts with the element M to form a phosphide, which can be precipitated from the Cu matrix. This makes it possible to produce a Cu-based alloy in which the influence of P on thermal conductivity and electrical conductivity is small.

[0030] Furthermore, if the Cu-based powder contains 0.1% by mass to 3.0% by mass of tin (Sn), the melting point will be lowered, which will further improve the fluidity of the molten metal during production and also improve the parent phase strength of the Cu-based alloy.

[0031] Furthermore, if the oxygen (O) content is 0.1 mass % or less, internal oxidation of the powder can be suppressed, resulting in a Cu-based powder that is less likely to cause defects or deterioration in the properties of the Cu-based alloy.

[0032] Furthermore, by adding 0.1 mass % to 1.0 mass % of a lubricant to Cu-based powder, the lubricity is improved, resulting in a Cu-based powder that is easy to mold into compacts in powder metallurgy.

[0033] Therefore, the present invention provides a Cu-based powder that can be used in powder metallurgy applications involving sintering, as well as in additive manufacturing applications, by performing heat treatment such that P and / or element M diffuse and form a phosphide between P and element M, thereby obtaining a Cu-based alloy in which P has little effect on thermal conductivity and electrical conductivity. DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention is a Cu-based powder that is subjected to a heat treatment to produce a Cu-based alloy.

[0035] The heat treatment may be any heat treatment that diffuses the P and / or element M contained in the Cu-based powder and causes the P and element M to form a phosphide, and examples of the heat treatment include sintering, aging after sintering, and melting with a laser and an electron beam followed by aging.

[0036] The heat treatment may be carried out once or multiple times.

[0037] The Cu-based powder of the present invention can be produced from a molten metal containing P. Since a molten metal containing P has excellent fluidity, it can be produced by an atomization method while ensuring excellent productivity and safety.

[0038] The produced Cu-based powder contains P that remains in the molten metal without forming gaseous phosphate oxide with oxygen, and P that is mixed in as an unavoidable impurity in the raw materials.

[0039] The P content is preferably 0.01% by mass to 1.0% by mass, and more preferably 0.05% by mass to 0.5% by mass.

[0040] If the P content is less than 0.01% by mass, the deoxidizing effect in the molten metal is low, and there is a risk that the molten metal will not have high fluidity. On the other hand, if the P content exceeds 1.0% by mass, even if the element M is contained in an amount of 0.3 to 1.2 times by mass the amount of A expressed by the formula, the excess P that does not form a phosphide with the element M will remain in the Cu matrix of the Cu-based alloy, and there is a risk that the thermal conductivity and electrical conductivity will be affected.

[0041] P is preferably added to the molten metal.

[0042] The added P may be in any form, such as copper phosphorus or nickel phosphorus, as long as it has a deoxidizing effect, but a material with a low melting point is preferred, and between copper phosphorus and nickel phosphorus, copper phosphorus is more preferred.

[0043] The Cu-based powder in the present invention contains element M, which forms a phosphide whose standard free energy of formation per mole of phosphorus in a temperature range of 298 K to 1300 K (this temperature range may be referred to as "the same temperature range" or "the temperature range") is equal to or less than the standard free energy of formation per mole of phosphorus of CuP in the same temperature range.

[0044] The standard free energy of formation of phosphide per mole of phosphorus can be calculated by dividing the literature value of the standard free energy of formation per mole of phosphide by the number of moles of phosphorus.

[0045] An element M whose standard free energy of formation per mole of phosphorus is equal to or less than the standard free energy of formation per mole of phosphorus of Cu3P in the above temperature range is an element that easily forms a phosphide. Therefore, since a phosphide can be formed by heat treatment that diffuses P and / or element M, P is fixed and can be precipitated from the Cu matrix, making it possible to produce a Cu-based alloy in which P has little effect on thermal conductivity and electrical conductivity.

[0046] Examples of the element M include nickel (Ni / atomic weight 58.69), cobalt (Co / atomic weight 58.93), manganese (Mn / atomic weight 54.94), and aluminum (Al / atomic weight 26.98).

[0047] The content of element M in the Cu-based powder is determined by determining whether the phosphide of element M has the lowest standard free energy of formation per mol of phosphorus in the above temperature range. x P y It is represented by (formula), and A is 0.3 to 1.2 times by mass % of A when A is represented by (formula).

[0048] (Formula) A = mass% of P × (x / y) × (atomic weight of M / atomic weight of P)

[0049] The values ​​of "atomic weight of M" and "atomic weight of P" in the formula may have any number of decimal places as long as the number of decimal places is the same.

[0050] A represented by (equation) is M x P y This value represents the amount of element M that is neither too much nor too little relative to the amount of P contained in the material.

[0051] If the content of element M is less than 0.3 times the mass% of A, the amount of excess P that does not form phosphides remaining in the Cu matrix will be large, which may increase the effect of P on the thermal conductivity and electrical conductivity of the Cu-based alloy.

[0052] If the content of element M exceeds 1.2 times the mass percent of A, the influence of the excess element M that does not form phosphide and remains in the Cu matrix becomes significant, and there is a risk that the thermal conductivity and electrical conductivity of the Cu-based alloy will be lower than when element M is not added.

[0053] For example, when calculating the range of the content of element M in Example 1 described below, the mass % of P contained in the Cu-based powder is 0.01, the element M is Co, the phosphide with the lowest literature value for the standard free energy of formation of Co in the above temperature range is CoP, so x = 2, y = 1, the atomic weight of P is 30.97, and the atomic weight of Co is 58.93, and therefore, when applied to (formula), the value of A is 0.038. Therefore, the Co content is preferably in the range of 0.011 mass % to 0.046 mass %.

[0054] M x P y can be determined from the literature value of the standard free energy of formation.

[0055] In the present invention, in the case of a special element in which the phosphide with the lowest standard free energy of formation per mole of phosphorus changes in the above temperature range, that is, M x P y is the phosphide with the lowest standard free energy of formation per mole of phosphorus, but at αK to 1300K, M a P bFor elements such that the phosphide with the lowest standard free energy of formation per mole of phosphorus is the phosphide with the lowest standard free energy of formation per mole of phosphorus (M in the above case), x P y (which is the case) will be used to find the value of A.

[0056] The Cu-based powder in the present invention may be in any form as long as it contains the element M.

[0057] Since it is preferable to add the element M in an amount that can convert all of the P remaining in the Cu matrix of the Cu-based alloy into phosphide, a simple powder or base metal of the element M may be added in accordance with the expected amount of P remaining in the molten metal, and then pulverized to form a Cu-based alloy powder.

[0058] Furthermore, the content (mass%) of P remaining in the produced Cu-based powder may be measured, and the powder may be mixed with a powder of element M according to the P content to form a Cu-based mixed powder, or may be mixed with an alloy powder containing element M to form a Cu-based mixed powder.

[0059] The Cu-based powder in the present invention may contain tin (Sn).

[0060] When Sn is added to a molten metal, it is possible to lower the melting point of the alloy, thereby further improving the fluidity of the molten metal, and it is also possible to improve the strength of the Cu matrix in a Cu-based alloy.

[0061] The Sn content in the Cu-based powder is preferably 0.1 mass % to 3.0 mass %, and more preferably 0.5 mass % to 2.0 mass %.

[0062] If the Sn content is less than 0.1 mass%, the melting point of the alloy will not decrease and the strength of the Cu matrix will not improve. On the other hand, if the Sn content exceeds 3.0 mass%, Sn has a greater effect on thermal conductivity and electrical conductivity than P, and the thermal conductivity and electrical conductivity of the Cu-based alloy will decrease compared to when no Sn is added.

[0063] Sn is preferably added to the molten metal.

[0064] The contents of the elements M, P and Sn remaining in the Cu-based powder can be measured by absorptiometry or ICP emission spectrometry.

[0065] The Cu-based powder of the present invention inevitably contains oxygen (O), but it is preferable to keep the O content to 0.1 mass % or less.

[0066] When the content is 0.1 mass % or less, internal oxidation of the powder is suppressed, and defects and deterioration of the properties of the Cu-based alloy are less likely to occur.

[0067] The oxygen content of the Cu-based powder can be measured by inert gas fusion infrared absorption spectroscopy.

[0068] Although there are no particular limitations on the method for producing the Cu-based powder in the present invention, it is preferable to produce it by a known atomization method.

[0069] This is because the resulting molten metal has high fluidity, allowing for production with productivity and safety ensured.

[0070] Known atomization methods include water atomization, gas atomization, and centrifugal atomization.

[0071] A lubricant can be added to the Cu-based powder of the present invention. Addition of a lubricant improves lubricity, making it easier to form a green compact in powder metallurgy.

[0072] The amount of lubricant added is preferably 0.1% by mass to 1.0% by mass, and more preferably 0.2% by mass to 0.8% by mass.

[0073] If the amount is less than 0.1% by mass, the lubricity is not significantly improved, and if the amount is more than 1.0% by mass, the sinterability decreases. Furthermore, if the amount of evaporation of the lubricant is large, there is a risk that the sintering furnace may be soiled.

[0074] The lubricant used in the present invention is not particularly limited, but metal soaps such as zinc stearate and EBS waxes can be suitably used. [Example]

[0075] Examples of the present invention will be described below, but the present invention is not limited to these.

[0076] (Preparation of molten metal) The Cu-based powders of the examples and comparative examples were prepared by heating raw copper to 1100° C. or higher to make it molten, and then adding element M, phosphorus copper, and Sn powder or base metal to produce a molten metal.

[0077] (Powder production) The alloys were produced by a water atomization method in which the molten Cu-based alloy components (molten metal) of the examples and comparative examples were dropped into contact with high-pressure water of about 15 MPa to rapidly cool and solidify them.

[0078] Example 15 was produced by adding 1.14 mass % of Co powder to 98.86 mass % of Cu-based powder (Cu / P=Bal. / 0.3 mass %) produced by water atomization.

[0079] (fluidity of molten metal) The fluidity of the molten metal was evaluated by visual inspection, with samples where the drop of the molten metal did not deteriorate being rated as ◯, samples where the drop of the molten metal began to deteriorate but powder production could be continued being rated as △, and samples where the drop of the molten metal deteriorated so much that powder production had to be interrupted being rated x.

[0080] (Measurement of each element in powder) The contents of the elements M, Sn, P, and O listed in Table 1 were obtained by measuring the respective amounts of the produced powders.

[0081] The elements M and Sn were measured using an ICP optical emission spectrometer iCAP7600 (manufactured by Thermo Fisher Scientific K.K.), P was measured using a spectrophotometer UV-1850 (manufactured by Shimadzu Corporation), and O was measured using an EMGA-920 (manufactured by Horiba Ltd.) using an inert gas fusion infrared absorption method.

[0082] (Heat treatment) Each of the Cu-based powders in the examples and comparative examples had a green density of 8.0 g / cm after adding 0.3 mass % of zinc stearate as a lubricant. 3 The samples were sintered by heat treatment at 1000°C for 120 minutes in a hydrogen atmosphere, then cooled with water, and aged again by heating at 550°C for 120 minutes in a hydrogen atmosphere. After that, the samples were water-cooled to obtain sintered bodies.

[0083] (Evaluation of electrical conductivity) The electrical conductivity (thermal conductivity) was evaluated by measuring the electrical conductivity (%IACS) converted into true density.

[0084] Each sintered body was cut into a size of 5 mm x 30 mm x 1 mm, and the volume resistance value at a terminal distance of 20 mm was measured using a resistance meter 3541 (manufactured by Hioki E.E. Corporation) to determine the conductivity (%IACS) converted into true density.

[0085] The electrical conductivity (%IACS) of each Cu-based alloy of the examples containing the element M and the comparative examples not containing the element M was measured, and the Cu-based alloy containing the element M with a higher electrical conductivity than the Cu-based alloy not containing the element M with the same P content was evaluated as "improved," while the Cu-based alloy with the same or lower electrical conductivity was evaluated as "not improved."

[0086] The Vickers hardness of the sintered bodies of Examples 5 to 8 was measured using a microhardness tester HMV-G (manufactured by Shimadzu Corporation) under a load of 25 gf.

[0087] The results are shown in Tables 1 and 2. In Tables 1 and 2, the mass % of P and "M x P y" was used to calculate A for each of the phosphides listed in ", and A × 0.3 mass% was used as the minimum value of element M and A × 1.2 mass% was used as the maximum value. If the content of element M in each Cu-based powder was within the range between the minimum and maximum values, a circle was displayed in the compatibility column, and if it was outside the range, an × was displayed.

[0088] [Table 1]

[0089] [Table 2]

[0090] As shown in Examples 1 to 15, it was confirmed that all of the Cu-based alloys produced from the Cu-based powder of the present invention had higher electrical conductivity than the Cu-based alloys produced from the Cu-based powders with the same P content but without adding element M shown in Comparative Examples 2 to 4.

[0091] It was also confirmed that the addition of Sn improves the strength of the matrix. It was observed that the molten metal of the example to which Sn was added had improved fluidity compared to the molten metal of the example to which Sn was not added. [Industrial Applicability]

[0092] In the present invention, since the alloy is produced from a molten metal containing P, the P reacts with oxygen to form a gaseous phosphate, which reduces the amount of oxygen, thereby preventing the deterioration of the fluidity of the molten metal due to oxygen. Therefore, the alloy can be produced by the atomization method while ensuring excellent productivity and safety. Furthermore, since the Cu-based powder contains element M, which easily forms phosphides, heat treatment can cause the P contained in the Cu-based powder and element M to form phosphides that precipitate from the Cu matrix, making it possible to produce a Cu-based alloy in which P has little effect on thermal conductivity and electrical conductivity. Therefore, the present invention has high industrial applicability.

Claims

1. A Cu-based powder containing elements M, P, and Cu, The element M is such that the standard free energy of formation of the phosphide of the element M per 1 mol of phosphorus in the temperature range of 298K to 1300K is equal to that of Cu in the same temperature range. ３ It is an element with a standard free energy of formation per mole of phosphorus equal to or less than that of P, Among the phosphides of the element M, the phosphide with the lowest standard free energy of formation in the temperature range is M ｘ P ｙ (where x>0, y>0), and A is represented by the following formula (formula), the content of each element M in the Cu-based powder is A×0.3% by mass or more and A×1.2% by mass or less, the content of P is 0.01% by mass to 1.0% by mass, and Sn is 3.0% by mass or less (including 0). (Formula) A = mass % of P × (x / y) × (atomic weight of M / atomic weight of P)

2. 2. The Cu-based powder according to claim 1, wherein the O content is 0.1 mass % or less.

3. The Cu-based powder according to claim 1 or 2, which is for powder metallurgy or additive manufacturing.

4. 4. A Cu-based powder obtained by adding 0.1% by mass to 1.0% by mass of a lubricant to the Cu-based powder according to claim 1.

5. A method for producing a Cu-based powder according to any one of claims 1 to 3, which is produced by an atomization method.

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