JP4947659B2 - Copper-based metal powder - Google Patents

Description

The present invention relates to copper and a copper alloy having excellent fluidity and copper-based mixed powder used as a raw material powder for powder metallurgy.

Conventionally, among copper-based powders used in powder metallurgy, there are powders that are inferior in fluidity depending on the shape, particle size, and the like. For example, electrolytic copper powder has a very complicated dendritic shape, so that the powders are intertwined, resulting in poor fluidity. Further, even a powder having a nearly spherical shape produced by the atomization method, when the particle diameter becomes a fine powder having a particle size of 50 μm or less, the adhesion between the particles becomes stronger and the fluidity becomes worse.

In powder metallurgy, press molding is performed by filling powder into a molding die. In recent years, in particular, in order to manufacture thin-walled or complex-shaped parts, the gaps between the molds have become narrow and complicated. For this reason, when a powder having poor fluidity is used, bridging may occur and the powder may not be filled in the mold. In addition, even if the filling can be performed, if the filling is not performed uniformly, the filling density varies within the mold, causing a reduction in the strength of the compact and a reduction in the dimensional accuracy after sintering. Further, since the mold cannot be filled with powder smoothly, it is necessary to set the press forming speed low, and productivity is lowered.

In order to solve this, in iron-based powder, as shown in the following Patent Documents 1 to 3, fluidity is obtained by combining the main component powder and the subcomponent powder using an organic binder and granulating the powder. It has been proposed to improve.

In addition, in the copper-based powder, as shown in Patent Document 4, the auxiliary component powder coated with the binder and the main component powder leaked with water are mixed and dried, so that the excess binder is added to the copper-based powder. A method of adhering the main component powder and subcomponent powder so that it does not remain above, and using a very small amount of binder, mixing the main component powder, subcomponent powder and binder solution, and then lightly compressing the mixture A way to help bond is shown.

Patent Document 5 discloses a method of adding a metal oxide such as SiO ₂ having an average primary particle size of 40 nm or less as a fluidity improving material in an iron-based granulated powder.
Japanese Patent Publication No. 6-89362 Japanese Patent Laid-Open No. 5-86403 JP 2002-289418 A JP-A-8-13502 Special table 2003-508635 gazette

However, when the method of granulating using a binder that has been applied to conventional iron-based powders as shown in Patent Documents 1 to 3 is applied to copper-based powders, the solid solubility of carbon in copper As a result, there was a drawback that sintering was significantly inhibited even if the binder residue carbon remained slightly on the powder particle surface during sintering.

In addition, in the production of granulated powder with a binder that is difficult to inhibit sintering even if it is copper-based, as shown in Patent Document 4, a process for producing an auxiliary component powder coated with a binder, or a main component, an auxiliary component, and the like. Since the number of manufacturing steps such as a step of compressing the mixture of the component and the binder increases, the cost increases.

On the other hand, even if the method of adding a metal oxide such as SiO ₂ applied to improve the fluidity of the iron-based powder described in Patent Document 5 is applied to the copper-based powder as it is, the following reasons Therefore, sufficient fluidity cannot be obtained.

The adhesion force between powders that affects the fluidity of the powder is generally known to be composed of liquid crosslinking force, intermolecular force, electrostatic force, but as described in Non-Patent Document 1 below, Under normal humidity atmosphere, intermolecular force acts most. The intermolecular force is proportional to the Hamaker coefficient, but this coefficient is 21.2 for iron and 30.0 for copper, and copper exerts an intermolecular force 1.5 times that of iron. This indicates that even if the powder has the same particle shape and particle size, the copper powder has poor fluidity compared to the iron powder.
"Powder and powder metallurgy" Vol. 45, No. 9, 1998, pages 849-853

As described above, it is extremely difficult to improve the fluidity of the copper-based powder. However, in order to reduce the size, complexity, and cost of powder metallurgy parts in recent years, a powder having good fluidity has been eagerly desired even in a copper system. An object of this invention is to provide the copper-type powder which can meet such a request | requirement.

The present invention has been made for the purpose of solving such conventional problems. Hydrophobized SiO ₂ having an average particle diameter of 40 nm or less as a fluidity improver on a copper powder or a copper alloy powder. Alternatively, Al ₂ O _3, TiO _2, MgO or a mixture thereof is added and mixed in an amount of 1.0% by mass or less with respect to the copper-based powder to provide a copper-based powder having excellent fluidity It is.
The “copper alloy” in the present invention is one or two kinds selected from tin, lead, zinc, aluminum, nickel, bismuth, iron, phosphorus, manganese, cobalt, silicon, titanium, vanadium, chromium, and silver. A metal in which the above elements are dissolved.

Moreover, in this invention, subcomponent powder and a shaping | molding lubricant may be mixed with copper powder or copper alloy powder. Subcomponent powders include tin, lead, zinc, aluminum, nickel, bismuth, iron, phosphorus, manganese, cobalt, silicon, titanium, vanadium, chromium, silver powder, or alloy powders of two or more of these elements, or these Examples thereof include metal components such as alloy powders of element and copper, solid lubricants such as graphite, molybdenum disulfide, manganese sulfide, and calcium fluoride, and hard particles such as carbides and nitrides. The addition amount of the subcomponent powder can include up to 30% of the total mass of the copper or copper alloy powder, the subcomponent powder and the molding lubricant. Examples of the molding lubricant include metal soap, wax, and the like. The addition amount can include up to 5% of the total mass of copper or copper alloy powder, subcomponent powder, and molding lubricant. In the present invention, when the subcomponent powder and / or lubricant is added, it flows in an amount of 1.0% by mass or less with respect to the total mass of the copper powder or the copper alloy powder, the subcomponent powder and the molding lubricant. A property improving material is added.

SiO _2, Al ₂ O _3, TiO _2, and MgO are hydrophilic because they inherently have a hydrophilic group on the surface, but can be hydrophobized by reacting them with an organosilicon compound. Hydrophobized SiO ₂ and Al ₂ O _3, TiO ₂ and MgO significantly reduce the amount of water molecules adsorbed on the surface. Hydrophilic powders adhere to each other due to external moisture, and sufficient fluidity cannot be obtained, but when hydrophobized, there is no moisture layer that tends to adhere and fluidity is improved.
Hydrophobing treatment with an organosilicon compound may be a known method, for example, a reaction in which SiO ₂ having an average particle diameter of 40 nm or less and dimethylchlorosilane are heated to about 400 ° C. together with an inert carrier gas. What was manufactured by the method of supplying and reacting in a vessel is marketed.

As described above, copper-based powders have poorer fluidity than iron-based powders, and hydrophilic fluidity-improving materials have insufficient fluidity-improving effects, but can be added in small amounts by applying a hydrophobic treatment. A sufficient fluidity improving effect can be obtained.

As an effect of the present invention, the flowability of the copper-based powder improves, so that even when a thin-walled or complex-shaped part is manufactured, bridging occurs when the powder is supplied to the mold, and the powder is Avoid filling the mold or filling the mold evenly, causing uneven filling density in the mold and reducing the strength of the compact and dimensional accuracy after sintering. Is to be. In addition, since the mold can be filled with the powder smoothly, the press forming speed can be set fast, and the productivity can be increased.

Hereinafter, the present invention will be described in detail. For the copper powder of the present invention, powders produced by various production methods such as an electrolytic method, an atomizing method, a solution reduction method, and a redox method can be applied. As the alloy powder, powders produced by various methods such as an atomizing method, a heat treatment diffusion alloying method, and a redox method can be applied.

Moreover, in order to satisfy the required quality of parts manufactured using the powder of the present invention, tin, lead, zinc, aluminum, nickel, bismuth, iron, phosphorus, manganese, cobalt, silicon, Metal components such as titanium, vanadium, chromium, silver powder, alloy powders of two or more of these elements, or alloy powders of these elements and copper, solids such as graphite, molybdenum disulfide, manganese sulfide, and calcium fluoride Lubricants, secondary component powders such as hard particles such as carbides and nitrides, and molding lubricants such as zinc stearate and wax may be added.

In these base powders, 0.001 to 1.0% by mass of SiO _2, Al ₂ O _3, TiO ₂ or MgO having an average particle diameter of 40 nm or less is added and mixed as a fluidity improving material. The fluidity-improving material used in (1) must have a hydrophilic group on the surface hydrophobized with an organosilicon compound or the like. In addition, when the fluidity improving material has a particle size exceeding 40 nm, the fluidity improving effect cannot be obtained unless the addition amount is increased, and it inhibits the sintering or remains after the sintering and adversely affects the performance of the sintered part. Therefore, it is desirable to make it 40 nm or less. A more preferable average particle size is 5 to 35 nm, and a particularly preferable average particle size is 10 to 25 nm.

The optimum amount of flow improver depends on the particle size and shape of the base powder. That is, in the case of a powder with a very irregular shape such as an electrolytic copper powder having a dendritic shape, a part of the fluidity improving material enters the concave portion of the powder and does not contribute to the improvement of the fluidity. Alternatively, it is necessary to increase the amount of addition compared to the case of an irregular shape close to a sphere. Further, as the particle diameter of the base powder becomes smaller, the adhesion force between the powders becomes larger and the fluidity decreases, but in order to improve the fluidity, it is necessary to increase the amount of addition.
The addition amount of the fluidity improving material in the present invention is 0.01 to 1.0 mass% with respect to the copper powder when the shape of the copper powder particles is dendritic and the average particle size is about 30 to 150 μm. The range is optimal, but when the particle shape is dendritic and the average particle size is about 10 to 30 μm, the range of 0.3 to 1.0 mass% is optimal. In addition, when the shape of the copper powder particles is irregular and the average particle size is about 20 to 100 μm, the range of 0.001 to 1.0% by mass with respect to the copper powder is optimal. Is irregular and the average particle size is about 5 to 20 μm, the range of 0.1 to 1.0% by mass is optimal.
Use a V-type mixer, double-cone type mixer, ribbon-type mixer, rotary blade-type mixer, rake machine, etc., usually used for mixing metal powder to mix the base powder and fluidized material. Can do.

The present invention will be described in detail below based on examples.
The average particle diameter of the base powder described below is the median diameter measured by the laser diffraction scattering method, and the average particle diameter of the fluidity improving material is the median diameter measured by the dynamic light scattering method. Based on the JIS Z2502 standard, the fluidity was determined by measuring the time taken to flow 50 g of powder from an orifice of φ2.63 mm.
Table 1 shows the effect of improving fluidity by adding SiO ₂ when electrolytic copper powder is used as the base powder.

Electrolytic copper powder is said to be intertwined by its dendritic shape and inferior in fluidity, but as shown in Examples 1 to 3 and Comparative Examples 1 to 2, the average particle size is about 45 μm. With electrolytic copper powder, fluidity can be obtained by adding 0.01% SiO ₂ . Increasing the added weight to 0.05% improved fluidity, but increasing it to 0.3% showed a tendency to decrease.

As in Comparative Example 3, when SiO ₂ was added to a powder having a large average particle diameter and good fluidity without adding SiO ₂ , the fluidity was further improved as in Example 4.
Moreover, in electrolytic copper powder with a small particle size, it is necessary to increase addition amount rather than Examples 1-4, but as shown in Examples 5-6 and Comparative Examples 4-5, it is 0.3% addition. Fluidity was obtained. When the addition amount was increased to 1%, the fluidity was slightly lowered, and when it was increased to 2%, the fluidity was lost.

Table 2 shows the effect of improving fluidity by adding SiO ₂ when water atomized copper powder is used as the base powder.

As shown in Examples 7 to 8 and Comparative Example 6, with water atomized copper powder having an average particle size of 38 μm, fluidity could not be obtained with 0.0005% addition, but with 0.001% addition. Fluidity was obtained and was further improved when added to 0.01%.

When it becomes a fine powder having an average particle diameter of 11 μm, as shown in Examples 9 to 11 and Comparative Example 7, fluidity cannot be obtained with addition of 0.01%, and fluidity is obtained by increasing the addition amount to 0.1%. I was able to. After that, when it was increased to 0.3%, the fluidity was improved, but when it was increased to 1.0%, it decreased.
As shown in Examples 1 to 3 in Table 1 and Examples 7 to 8 in Table 2, even when the average particle size is equivalent, the water atomized powder is shaped so that the powders are intertwined like electrolytic copper powder. Therefore, the fluidity improving effect is manifested by adding a small amount of SiO ₂ .

Table 3 shows the presence of the hydrophobic treatment of the SiO _2, and the particle size of the SiO ₂ particles the effect on the fluidity. Commercially available SiO ₂ that was not hydrophobized and SiO ₂ that was hydrophobized were used.

As shown in Examples 1 to 3 and Comparative Examples 8 to 10, when SiO ₂ not subjected to hydrophobic treatment is used, the amount of addition is greatly increased as compared with the case where SiO ₂ subjected to hydrophobic treatment is used. It was necessary to let them. In addition, as shown in Examples 5 to 6 and Comparative Examples 12 to 13, in the case of fine electrolytic copper powder having an average particle diameter of about 19 μm, even if 1.0% of SiO ₂ not subjected to a hydrophobizing treatment is added. The fluidity could not be obtained.

This also applies to the atomized copper powder. As shown in Examples 9 and 11 and Comparative Examples 15 to 16, fluidity can be obtained even when 1.0% of SiO ₂ not subjected to the hydrophobization treatment is added. could not.

In addition, as shown in Example 2, Comparative Example 11, Example 5, Comparative Example 14, Example 9, and Comparative Example 17, even when SiO ₂ was subjected to a hydrophobization treatment, the particle size increased to 50 nm. The effect of improving sexiness was reduced.
Next, Table 4 shows the effect of improving fluidity of bronze which is a representative copper alloy.

Example 12 shows the fluidity improvement effect by adding SiO ₂ to water atomized bronze powder having an average particle size of 35.6 μm, and Example 13 to water atomized bronze powder having an average particle size of 10.3 μm. An improvement effect almost equal to that of water atomized copper powder having a particle size was observed.
Table 5 shows the fluidity improving effect of the powder obtained by mixing the sub-component powder and the lubricant with the copper powder as the base powder. In addition, the SiO ₂ addition amount in the following Table 5 is out% with respect to the total mass of the copper powder, the subcomponent powder and the lubricant.

Comparative Example 18 shows the result of adding 0.05% of SiO ₂ to the mixed powder obtained by adding electrolytic copper powder and 10% water atomized tin powder to Example 14 and 0.5 out% of zinc stearate as a molding lubricant. The results when no SiO ₂ is added are shown, but when 0.05% of SiO ₂ was added, a fluidity improving effect was observed.

The result of adding 0.05% of SiO ₂ to the mixed powder obtained by adding 0.5% by weight of EBS resin, which is an electrolytic copper powder and 2% graphite powder, and a wax-based lubricant as a molding lubricant to Example 15, Although the result when SiO ₂ is not added is shown in Comparative Example 19, a fluidity improving effect was observed when 0.05% of SiO ₂ was added.
Table 6 shows the use of Al ₂ O ₃ , or TiO ₂ , MgO and a mixture of SiO ₂ , Al ₂ O ₃ , TiO ₂ and MgO in a ratio of 1: 1: 1: 1 as a fluidity improver. Shows the fluidity improvement effect. Commercially available SiO _2, Al ₂ O _3, TiO _2, and MgO subjected to the hydrophobic treatment were used.

As shown in Examples 16 to 19, fluidity improving effects were obtained in all cases.
As described above, when the fluidity improving material used in the present invention is not hydrophobized, a sufficient fluidity improving effect cannot be obtained, and the average particle diameter is larger than 40 nm. However, sufficient fluidity improvement effect cannot be obtained.

There is an optimum amount of fluidity improver added depending on the shape and particle size of the base powder, but the fluidity improvement effect starts to appear at an addition amount of 0.001%, and the fluidity is increased to about 1%. There is a sex improvement effect. On the other hand, if the addition amount is more than this, the fluidity is lowered, so that the preferred addition amount of the fluidity improving material is in the range of 0.001% to 1%.

The copper-based powder according to the present invention can be used in the field of powder metallurgy as a powder having good fluidity and excellent mold filling property, but fluidity can be obtained even with a fine copper-based powder that has not been fluid at all. In the future, it may be applied to copper powder for electronic materials.

Claims (3)

A fluidity improver is added to and mixed with a copper-based powder made of copper or a copper alloy, and the fluidity improver is hydrophobized SiO ₂ or Al ₂ O having an average particle diameter of 40 nm or less. ₃ , TiO ₂ , MgO and a mixture thereof, and a copper-based metal characterized in that the addition ratio of the fluidity improver to the copper-based powder is 1.0% by mass or less Powder. Furthermore, tin, lead, zinc, aluminum, nickel, bismuth, iron, phosphorus, manganese, cobalt, silicon, titanium, vanadium, chromium, silver powder, or two or more of these elements are added to the copper powder or copper alloy powder. Metal powder selected from alloy powders or alloy powders of the above elements and copper, powders of subcomponents selected from solid lubricants selected from graphite, molybdenum disulfide and manganese sulfide, calcium fluoride, carbides and nitrides And / or at least one molding lubricant selected from metal soaps and waxes, and the addition ratio of the fluidity improver to the total amount of the copper-based powder and the subcomponent powder and / or molding lubricant The copper-based metal powder according to claim 1, wherein is 1.0 mass% or less. The copper-based metal powder according to claim 1, wherein the SiO ₂ , Al ₂ O ₃ , TiO ₂ , and MgO are hydrophobized with an organosilicon compound.