JP2007084906A - Ag-based metal powder, Cu-based metal powder and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal powder having a small dimensional change rate, good ductility and low cohesiveness.
SOLUTION: An annular injection slit 2 for injecting an injection water flow of a water jet curtain is arranged downward to cause a molten metal flow to flow down along the central axis, and a constricted cavity 7 of the water jet curtain through which the injection water flow does not pass. Water atomizing method for producing metal powder by generating a jet water flow 12 of a single leaf hyperboloid water jet curtain with a step of jetting water in a direction having a descending angle θ and a turning angle ω The descent angle θ is 0-30 °, the turning angle ω is 1-20 °, the water pressure is 90-150 MPa, the water flow rate is 300-800 L / min, and the 50% diameter is 0.1-5 μm, sphericity of 0.6 to 0.9, particle size breadth index of 1 or less, the ratio of oxygen quantity 0.5~7mg / m ^2, specific water content to obtain a metal powder is 1 mg / m ² or less.
[Selection] Figure 1

Description

  The present invention relates to conductive paste for circuit design and electronic materials, micro MIM, Ag-based (Ag or Ag base alloy) metal powder and Cu used for forming fine parts and diamond tool binders. The present invention relates to a metal powder of a system (Cu or Cu base alloy) and a manufacturing method thereof.

  As is well known, the demand for Ag or Ag-based alloy metal powders or Cu or Cu-based alloy metal powders is increasing in the case of fine spherical powders of 5 μm or less with high filling properties, and the average particle size is 0.5 to 5 μm. A metal powder having a sphericity of 0.7 to 0.85 and an oxygen content of 500 to 3000 ppm has been proposed (Patent Document 1). As a method for efficiently producing a metal powder having a fine pseudospherical shape and a narrow particle size distribution, The molten metal flow is continuously discharged so as to surround the molten metal flow in a single-leaf hyperboloid with a swivel angle ω of 1 ° ≦ ω ≦ 20 ° and a descending angle θ of 5 ° ≦ θ ≦ 60 ° toward the molten metal flow. A metal powder manufacturing method (Patent Document 2) has been proposed in which the pressure in the vicinity of the hyperboloid constriction is reduced to 50 to 750 mmHg.

JP 2005-8930 A International Publication WO00 / 38865

  However, in recent years, a metal powder having a particle size of 5 μm or less and having both small dimensional change rate and good ductility sintering characteristics is required. However, in the metal powder, the 50% diameter (median of the powder) When the (diameter) is 5 μm or less, it is very easy to agglomerate, and there is a problem that the production cost increases to suppress this agglomeration. In addition, since the small dimensional change rate and having ductility are mutually contradictory characteristics, if sintered to obtain ductility that is soft against elongation and bending and that is difficult to break, the dimensional change will naturally occur. It was difficult to obtain a metal powder satisfying both of these characteristics.

  Further, the sphericity of the metal powder disclosed in Patent Document 1 is calculated from the average particle diameter and the specific surface area, but the specific surface area generally increases as the average particle diameter of the metal powder decreases. Therefore, the oxygen content of the metal powder is regarded as the content of the whole powder. The larger the specific surface area, the greater the oxygen content, but the oxygen content is due to individual powders. However, there is a problem that the characteristics of the metal powder cannot be expressed accurately.

  For this reason, when the conventional metal powder is used as a conductive paste for circuit design or electronic material, there has been a problem that the dimensional change and dimensional variation of the sintered body increase and the ductility is inferior. In addition, when screen printing is performed on a circuit board for conductive paste, and this is fired, there is a problem that the distortion of the bonded substrate increases and the circuit cracks, and the gap bonded to the ceramic substrate widens to improve airtightness. Problems such as inability to maintain and low-frequency conductivity have occurred. In addition, when used for micro MIM, modeling clay, etc., there are problems such as a problem that fine corner cracks occur due to shrinkage and poor ductility. Furthermore, even when used for diamond tools, the problem is that the ductility of the binder layer decreases and the gap between the diamond particles and the metal powder tends to open, so that the diamond particles can easily fall off and ultimately the life of the diamond tool is shortened. There was a problem.

  Therefore, the present inventor has a small 50% diameter 5 μm or less fine metal powder whose demand is increasing not only for electronic materials but also for applications such as modeling of finely shaped parts and diamond tools. As a technical issue, we have researched and experimented to obtain a metal powder that satisfies the dimensional change rate, good ductility, and low cohesiveness.

  First, conditions for obtaining a nearly spherical powder in Ag and Cu metal powders of 5 μm or less were examined.

  The metal powder close to a sphere having a diameter of 5 μm or less is a vertical sectional side view of the annular injection slit in the water atomization method, and the descending angle of the single leaf hyperboloid water jet curtain ejected from the annular ejection slit shown in FIG. As shown in FIG. 2 for explaining θ and FIG. 3 for explaining the turning angle ω, an annular injection slit 2 for injecting the jet water flow 1 of the water jet curtain is arranged downward, and the annular injection slit 2 is positioned on the surface. 3, a step of flowing the molten metal flow 6 along the central axis 5 running in the vertical direction perpendicular to the inner surface 4 with respect to the center of the inner surface 4, and supplying a high-pressure water flow to the annular injection slit 2 Accordingly, a perpendicular line 9 (into the inner surface 4) is formed parallel to the central axis 5 from one portion 8 of the annular jet slit 2 so that a constricted cavity 7 of the water jet curtain through which the jet water flow 1 does not pass is formed. And a tangent line 10 to the constricted cavity 7 projected from the partial position 8 onto the inner envelope surface 4 and the center from the partial position 8 to the center. And a step of injecting water in a direction having a turning angle ω that is an angle formed by the diameter 11 of the annular injection slit 2 crossing the shaft 5 to generate an injection water flow 1 of the one-leaf hyperboloid water jet curtain 12. It was manufactured by employing a water atomization method to obtain metal powder.

  As a result of examining the water pressure and flow rate, the swirl angle ω, and the descending angle θ of the jet water stream 1 as atomizing conditions in the water atomizing method, as shown in Table 1, when the swirl angle ω is 0 °, the sphericity is 0.6 or less. However, the sphericity was 0.6 or more at 1 ° or more, and it was confirmed that the turning angle ω and the sphericity were related.

  Further, when the turning angle ω is 1 to 20 °, the descending angle θ is 0 to 30 °, the water pressure is 90 to 150 MPa, and the water flow rate is 300 to 800 L (liter) / min, the 50% diameter is It was confirmed that Ag and Cu metal powder having a sphericity of 0.1 to 5 μm and a sphericity of 0.6 to 0.9 can be obtained (see Tables 3 and 4).

  Next, the relationship between the powder characteristics and the sintering characteristics of the obtained metal powder was examined.

Since the metal powder sinters at a lower temperature as the 50% diameter is smaller, the experiment was carried out by changing the sintering temperature for each 50% diameter metal powder. Since Cu powder undergoes oxidation in the atmosphere, it was sintered in nitrogen (N ₂ ), and Ag powder was sintered in air (Air) following the conventional sintering method. As a result, powders with a small dimensional change rate and good ductility (large bending angle) at the same specific surface area have a large dimensional change rate and poor ductility (small bending angle). Was confirmed to be considerably small (see Tables 3 and 4). In addition, when the 50% diameter is 2 μm or less, the specific surface area suddenly increases and both the amount of oxygen and the amount of water increase sharply. It was confirmed that it was inappropriate. Therefore, in order to obtain the amount of oxygen and the amount of moisture per unit surface area, the amount of oxygen and the amount of moisture were divided by the specific surface area of the powder. (in the Ag powder in 0.5~2mg / m ^2, Cu powder ^{2~7mg / m 2) 0.5~7mg / m} 2 was confirmed that in (see Table 3 and Table 4). Thus, the oxygen content per unit surface area is defined as the specific oxygen content, and the water content per unit surface area is defined as the specific water content to represent the powder characteristics.

  The relationship between the specific oxygen amount, the flow rate of water and the flow rate of molten metal in the water atomization method was examined.

  The ratio of the flow rate of water to the flow rate of molten metal (flow rate of water / flow rate of molten metal) was used as the water solution ratio, and the ability of atomization was evaluated based on the value of the water solution ratio and the specific oxygen amount. As a result, as shown in Table 2, the amount of oxygen clearly increased in Cu when the ratio of the hot water was small, and the specific amount of oxygen tended to be slightly higher in Ag when the ratio of the hot water was small. Thereby, in order not to raise the oxygen content of the metal powder, the ratio of the water solution was preferably 40 or more, and it was confirmed that the specific oxygen content of the powder tends to increase as the water solution ratio decreases.

  In addition, from the above examination results, as a metal powder having good sintering characteristics with a small dimensional change rate and large ductility, it is confirmed that it is preferably in the range of 0.1 to 5 μm, and in order to be able to sinter at a lower temperature 0.1 to 3 μm, more preferably 0.1 to 1 μm. Confirm that 0.1 to 0.5 μm is preferable in order to be able to sinter at even lower temperatures. When the 50% diameter exceeds 5 μm, the sintering temperature is as high as 900 ° C. or higher. Also, if it is less than 0.1 μm, the particles are very fine and the specific surface area becomes too large, so there is a possibility that sintering may start even at room temperature, and aggregation is likely to occur, so it is not suitable for each application. Was confirmed (see Table 3 and Table 4).

  In addition, the shape of the metal powder is expressed by adopting a sphericity represented by a ratio between a specific surface area of a sphere having the same shape as that of the actual powder and an actual specific surface area of the powder. The diameter of the powder was calculated using the laser diffraction scattering method, and the actual specific surface area was calculated using the BET method. As a result, the BET method also measures the specific surface area due to fine irregularities on the surface of the powder particles, and even if the powder was very close to a sphere when observed with an electron microscope, the numerical value exceeding the sphericity of 0.9 is actually It was confirmed that it was not observed, and when the sphericity was less than 0.6, the shape was not preferable, and it was confirmed that ductility was not obtained even after shrinkage after sintering. Thereby, it was found that the sphericity in the range of 0.6 to 0.9 was good.

  Next, a method for numerically expressing the distribution state of the metal powder as an aggregate was examined.

  The geometric standard deviation is adopted for the particle size width of the metal powder, but when the particle size distribution of the powder follows a lognormal probability distribution, the distribution is expressed by the slope of the approximate straight line, so there are some aspects where it is difficult to express the actual state. It was. The actual powder often does not have a normal probability distribution, and there are many cases where the distribution is biased, and there is often a difference between the fine powder side and the coarse powder side in the spread of the distribution. Therefore, in order to directly express the spread of the particle size distribution of the powder, it is close to both ends of the distribution based on the particle size distribution curve shown in FIG. 4 with the particle size (μm) on the horizontal axis and the frequency (%) on the vertical axis. Read the% diameter and the 95% diameter, take the logarithm of the 5% diameter and the 95% diameter with reference to the logarithmic notation often used in the particle size scale of the distribution, and find the difference between them to widen the particle size distribution When trying to express, when the 5% diameter is Aμm and the 95% diameter is Bμm, the log (B) -log (A), that is, the numerical value (particle size index) obtained by log (B / A) is It was confirmed that the particle size width can be simply expressed regardless of the 50% diameter of the powder, and that the width can be expressed by a relative value regardless of the 50% diameter in any of 0.1 μm to 5 μm. As a result, the width of the powder particle size existing between the 5% diameter and the 95% diameter of the particle size distribution, that is, when the particle size width index relatively representing the spread of the particle size distribution in the meantime is greater than 1 is 1 or less In comparison, the dimensional change of the sintered body was large and the ductility tended to be low. Therefore, it was confirmed that 1 or less is preferable if the dimensional change rate is reduced and the ductility is increased (see Tables 3 and 4).

  As for the relationship between the sphericity and the particle size width index, the smaller the particle size width index and the smaller the particle size width, the higher the sphericity tends to be seen. Even so, those having a wide particle size range contain a large number of fine powders relative to a small number of coarse powders, and it is considered that the specific surface area tends to increase. A tendency of high sphericity was observed in the actually small particle size range.

  From the results of the respective studies and experiments, the technical problem can be solved by the present invention as follows.

That is, the Ag-based metal powder according to the present invention has a 50% diameter of 0.1 to 5 μm, a sphericity of 0.6 to 0.9, and a particle size width index representing a spread relative value of the particle size distribution between the 5% diameter and the 95% diameter is 1 or less. , the ratio of oxygen quantity representing the amount of oxygen per unit surface area of 0.5~7mg / m ^2, the ratio amount of water which represents the water content per unit surface area of 1 mg / m ² or less of the metal powder.

Further, the Cu-based metal powder according to the present invention has a 50% diameter of 0.1 to 5 μm, a sphericity of 0.6 to 0.9, and a particle size width index representing a spread relative value of the particle size distribution between the 5% diameter and the 95% diameter is 1 or less. , the ratio of oxygen quantity representing the amount of oxygen per unit surface area of 0.5~7mg / m ^2, the ratio amount of water which represents the water content per unit surface area of 1 mg / m ² or less of the metal powder.

Further, in the method for producing an Ag-based metal powder according to the present invention, an annular injection slit for injecting an injection water flow of a water jet curtain is arranged downward and runs in the vertical direction at the center of the inner surface with the annular injection slit as a surface position. A step of causing the molten metal flow to flow down along the central axis and a high pressure water flow to the annular jet slit to form a constricted cavity of a water jet curtain through which the jet water flow does not pass. A descending angle θ, which is a swing angle of the molten metal flow with respect to a perpendicular line parallel to the central axis, and a tangent to the constricted cavity projected from the partial position onto the inner surface and the partial position Jetting water flow of a single leaf hyperboloid water jet curtain with a step of jetting water in a direction having a swivel angle ω, which is an angle formed by the diameter of the annular jet slit across the central axis Adopting a water atomization method for producing metal powder by generating, the descending angle θ is 0-30 °, the turning angle ω is 1-20 °, the water pressure is 90-150 MPa and the water flow rate is 300- Water is sprayed at 800 L / min to produce an Ag-based metal powder, and the Ag-based metal powder is classified to have a 50% diameter of 0.1 to 5 μm, a sphericity of 0.6 to 0.9, and between a 5% diameter and a 95% diameter. particle size range exponent representing the spread relative value of the particle size distribution is 1 or less, the ratio of oxygen quantity 0.5~7mg / m ² representing the amount of oxygen per unit surface area, per unit surface area water content representing specific water content 1 mg / m ² The following metal powder is obtained.

Furthermore, in the method for producing a Cu-based metal powder according to the present invention, an annular injection slit for injecting the water flow of the water jet curtain is disposed downward, and the center of the inner surface of the inner surface with the annular injection slit as a surface position runs in the vertical direction. A step of causing the molten metal flow to flow down along the central axis and a high pressure water flow to the annular jet slit to form a constricted cavity of a water jet curtain through which the jet water flow does not pass. A descending angle θ, which is a swing angle of the molten metal flow with respect to a perpendicular line parallel to the central axis, and a tangent to the constricted cavity projected from the partial position onto the inner surface and the partial position Spraying water in a one-leaf hyperboloid water jet curtain with a step of injecting water in a direction having a turning angle ω that is an angle formed by a diameter of an annular injection slit crossing the central axis Water atomization method is used to produce metal powder, the descending angle θ is 0-30 °, the turning angle ω is 1-20 °, the water pressure is 90-150 MPa, and the water flow rate is 300. Water is injected at a rate of ~ 800L / min to produce a Cu-based metal powder, and the Cu-based metal powder is classified to have a 50% diameter of 0.1 to 5μm, a sphericity of 0.6 to 0.9, and between a 5% diameter and 95% diameter The particle size distribution index representing the relative value of the spread of the particle size distribution is 1 or less, the specific oxygen amount representing the oxygen amount per unit surface area is 0.5 to 7 mg / m ² , and the specific water amount representing the water amount per unit surface area is 1 mg / m ^The metal powder which is ² or less is obtained.

According to the present invention, the 50% size is 0.1 to 5 [mu] m, a sphericity of 0.6 to 0.9, particle size breadth index of 1 or less, the ratio of oxygen quantity 0.5~7mg / m ² and the ratio water content 1 mg / m ² or less of Ag And Cu-based metal powders can be provided, and a sintered body having lower ductility than conventional metal powders, a small dimensional change rate, and excellent ductility that does not break even when bent by 90 ° can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  Reference numeral 100 is a water atomizing device for producing an Ag-based or Cu-based metal powder by generating a jet stream 1 of a single leaf hyperboloid water jet curtain 12 (see FIG. 1), 1 is a jet stream of the water jet curtain, An annular jet slit for jetting the jet water stream 1 with the jet port facing downward, 3 is a virtual plane position plane of the ring jet slit 2, and 4 is a virtual plane position 3 surrounded by the circular ring jet slit 2 The upper circular inner surface 5 is an imaginary central axis that runs vertically in the center of the inner surface 4 perpendicularly to the inner surface 4, 6 is a molten metal flow that flows down along the central axis 5, and 7 is a single-leaf biplane. A constricted cavity through which the jet stream 1 of the curved water jet curtain 12 does not pass, 8 is a part of each of the annular jet slits 2, and 9 is a hypothetical perpendicular (inclusive surface) drawn from the part 8 in parallel to the central axis 5. Right angle to 4), 10 is partly within 8 An imaginary tangent drawn to the constricted cavity 7 projected on the enveloping surface 4, 11 is an imaginary diameter of the annular injection slit 2 crossing the central axis 5 from the partial position 8. The descending angle θ is the swing angle of the molten metal flow 6 with respect to the perpendicular 9, and the turning angle ω is the angle formed by the tangent 10 and the diameter 11.

  The water atomizing device 100 has an annular injection slit 2 for injecting the jet stream 1 of the water jet curtain arranged downward, and a central axis 5 that runs in the vertical direction at the center of the inner surface 4 with the annular injection slit 2 as the surface position 3. A step of causing the molten metal stream 6 to flow down along the line, and the lowering so as to form a constricted cavity 7 of the water jet curtain through which the high-pressure water stream is supplied to the annular jet slit 2 and the jet water stream 1 does not pass through. The metal powder is produced by generating the jet water flow 1 of the single leaf hyperboloid water jet curtain 12 by the step of jetting water in the direction having the angle θ and the turning angle ω.

Adopting the water atomization method, the downward angle θ is 0-30 °, the turning angle ω is 1-20 °, the water pressure is 90-150 MPa and the water flow rate is 300-800 L / min. To produce a metal powder, and classify the metal powder to give a 50% diameter of 0.1-5 μm, a sphericity of 0.6-0.9, and a particle size distribution index representing a relative value of the spread of the particle size distribution between the 5% diameter and the 95% diameter but 1 or less, 0.5~7mg / m ² ratio of oxygen quantity representing the amount of oxygen per unit surface area, the specific amount of water which represents the water content per unit surface area to obtain a metal powder is 1 mg / m ² or less.

  According to the water atomization method, the molten metal stream 6 can be finely pulverized by the gas to be sucked and the subsequent high-speed water jet, and the collision between the particles can be greatly reduced by the one-leaf hyperboloid water jet curtain 12. As a result, the shape of the obtained metal powder can be made nearly spherical, and miniaturization becomes possible. In addition, because it cools rapidly so as to surround the fine molten droplets that have been split while reducing collisions with a single leaf hyperboloid, the amount of oxygen contained in the surface as well as the amount of oxygen on the surface can be kept low. A low amount of powder can be obtained.

  Since the perpendicular line 9 runs perpendicular to the inner surface 4, the descending angle θ is not less than 0 ° and can be satisfactorily atomized within the range of 0 ° to 30 °. However, if the angle exceeds 30 °, the ejector effect cannot be fully exerted, the flow rate of the sucked gas is insufficient, the primary splitting is insufficient, the powder becomes coarse, and the 50% diameter becomes coarse and the sphericity decreases. This is not preferable. In addition, when the turning angle ω is 1 ° or more, a decrease in collision, which is a characteristic of a single leaf hyperboloid jet, is seen, and it is difficult to obtain the turning angle ω exceeding 20 °.

  The pressure of water in the jet water stream 1 is not preferable because the yield of fine metal powder can be increased at 90 MPa or more, and the energy efficiency is reduced and the loss is increased at a pressure exceeding 150 MPa. In addition, the flow rate of water needs to be 300 L / min or more to generate the single-leaf hyperboloid water jet curtain 12, and it is preferable that the flow rate exceeds 800 L / min. This is not preferable because of increased waste.

The specific oxygen amount is 0.5 to 7 mg / m ² (Ag-based metal powder including an Ag-based alloy, Cu-based metal powder including a Cu-based alloy), but 0.5 to ² mg / m ^{2 in} the case of Ag powder. In the case of Cu powder that easily oxidizes, it is preferably in the range of ^{2 to} 7 mg / m ² . If the specific oxygen amount exceeds 7 mg / m ² , the increase in the thickness of the oxide film causes a decrease in the sinterability, the ductility does not increase, and the sintered body becomes brittle and easily broken. If the specific oxygen content is less than 0.5 mg / m ² or the Cu powder has a specific oxygen content of less than 2 mg / m ² , the C (carbon) residue in the paste is used when kneaded with resin and used as a paste. Is not preferable because it cannot be removed by burning.

If the specific water content exceeds 1 mg / m ² , abnormal dimensional changes and oxidation / aggregation during storage are not preferable.

  In the water atomizing apparatus 100, the shape of the annular injection slit 2 may be a circular shape or a square shape such as an ellipse or a triangle. Since the vertical direction in which the shaft 5 runs is a direction perpendicular to the inner envelope surface 4, the vertical direction has an inclination, and the molten metal flow 6 flows down along the central axis 5 with an inclination. The tangent line 10 is a tangent line drawn with respect to the inner circle or outer circle of the cavity 7 when the cavity 7 projected onto the inner envelope surface 4 has a thickness.

  Examples 1-10, Comparative Examples 1-8.

  By adopting the water atomization method shown in FIGS. 1 to 3 under the conditions shown in Tables 3 and 4, Cu metal powder (Examples 1 to 5, Comparative Examples 1 to 4) and Ag metal powder (Examples 6 to 10) Comparative Examples 5 to 8) were obtained.

  The 5% diameter, 50% diameter, and 95% diameter of each metal powder was measured using a laser diffraction scattering method (volume%) using a microtrack manufactured by Nikkiso Co., Ltd. The specific surface area was measured by the BET method. The sphericity was calculated from the ratio of the specific surface area of the true sphere that can be calculated from the 50% diameter to the specific surface area by the BET method. The particle size width index was calculated by log (95% diameter) -log (5% diameter). For example, in Example 1, the particle size width index = log (0.78) −log (0.13) = − 0.108 − (− 0.886) = 0.778, and the smaller the particle size width index, the smaller the particle size spread, that is, the particle size width Indicates narrow. The amount of oxygen was measured according to an infrared detection method for CO gas generated by reacting with C at high temperature. The moisture content was based on the value measured by the Karl Fischer method. In addition, classification was performed for each powder with a classifier corresponding to the target for each powder.

  In the agglomeration properties of the powders in the table, “◎” indicates a state in which there is almost no granular aggregation, “○” indicates a state in which granular aggregation is present but is uniformly dispersed, and “Δ” indicates irregular weak aggregation. The state, “x”, indicates a state where there is irregular strong aggregation.

  The rate of dimensional change and ductility were determined by forming each powder at 5MPa in thickness of about 1.5x width 12x length 30mm, sintering for 30 minutes in each temperature and atmosphere shown in Table 3 and Table 4, and then performing a bending test. went. The dimensional change before and after sintering was measured to calculate the dimensional change rate, and the angle until fracture was measured to determine the ductility. In the table, a bending angle of 90 ° indicates that no fracture occurred even at 90 °. In addition, since sintering progresses at low temperature, so that powder is fine, since appropriate sintering temperature changes with each median diameter, sintering temperature was changed with the median diameter.

Table 3 and according to Table 4, the 50% size is 0.1 to 5 [mu] m, a sphericity of 0.6 to 0.9, particle size breadth index of 1 or less, the ratio of oxygen quantity 0.5~7mg / m ² and the ratio water content 1 mg / m ² When the following metal powder was sintered, a powder having both a small dimensional change rate and high ductility was obtained.

  According to the present invention, since it is a metal powder that satisfies a small dimensional change rate, good ductility, and low cohesiveness, conductive paste for circuit design and electronic materials, micro MIM, clay for modeling, diamond, etc. It can be used as a binder for tools.

  Therefore, it can be said that the industrial applicability of the present invention is very high.

It is a longitudinal cross-sectional side view of the cyclic | annular injection slit in a water atomization method. It is a figure explaining descent angle (theta) of the single leaf hyperboloid water jet curtain injected from the annular injection slit shown in FIG. It is a figure explaining the turning angle (omega) of the one leaf hyperboloid water jet curtain injected from the annular injection slit shown in FIG. It is a graph of a particle size distribution curve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Jet water flow 2 Annular jet slit 3 Surface position 4 Inner surface 5 Center axis 6 Molten metal flow 7 Constricted cavity 8 One part 9 Perpendicular line 10 Tangent line 11 Diameter 12 Single-leaf hyperboloid water jet curtain 100 Water atomizing apparatus θ Descent angle ω Rotation angle

Claims (4)

50% diameter is 0.1-5μm, sphericity is 0.6-0.9, the spread of particle size distribution between 5% and 95% diameter is 1 or less, and the specific oxygen amount is the amount of oxygen per unit surface area. There 0.5~7mg / m ^2, Ag-based metal powder ratio water quantity representing the amount of water per unit surface area of 1 mg / m ² or less. 50% diameter is 0.1-5μm, sphericity is 0.6-0.9, the spread of particle size distribution between 5% and 95% diameter is 1 or less, and the specific oxygen amount is the amount of oxygen per unit surface area. There 0.5~7mg / m ^2, Cu-based metal powder ratio water quantity representing the amount of water per unit surface area of 1 mg / m ² or less. An annular injection slit for injecting the jet water flow of the water jet curtain is arranged downward and the molten metal flow is caused to flow down along the central axis that runs in the vertical direction on the center of the inner surface with the annular injection slit as the surface position. The molten metal with respect to a perpendicular drawn from one part of the annular jet slit in parallel with the central axis so as to form a constricted cavity of a water jet curtain that supplies a high-pressure water flow to the jet slit and does not allow the jet water flow to pass through The angle formed by the downward angle θ that is the deflection angle to the flow, the tangent to the constricted cavity projected from the partial position onto the inner envelope surface, and the diameter of the annular injection slit that crosses the central axis from the partial position A water atomization method for producing metal powder by generating a jet flow of a single leaf hyperboloid water jet curtain with a step of jetting water in a direction having a swivel angle ω The descent angle θ is 0 to 30 °, the turning angle ω is 1 to 20 °, the water pressure is 90 to 150 MPa, the water flow rate is 300 to 800 L / min, and water is injected to form an Ag system. Particle size index indicating the relative value of the distribution of the particle size distribution between the 5% and 95% diameters by producing the metal powder and classifying the Ag-based metal powder with a 50% diameter of 0.1 to 5 μm, a sphericity of 0.6 to 0.9, but less than 1, and characterized in that 0.5~7mg / m ² ratio of oxygen quantity representing the amount of oxygen per unit surface area, the specific amount of water which represents the water content per unit surface area to obtain a metal powder is 1 mg / m ² or less A method for producing an Ag-based metal powder. An annular injection slit for injecting the jet water flow of the water jet curtain is arranged downward and the molten metal flow is caused to flow down along the central axis that runs in the vertical direction on the center of the inner surface with the annular injection slit as the surface position. The molten metal with respect to a perpendicular drawn from one part of the annular jet slit in parallel with the central axis so as to form a constricted cavity of a water jet curtain that supplies a high-pressure water flow to the jet slit and does not allow the jet water flow to pass through The angle formed by the downward angle θ that is the deflection angle to the flow, the tangent to the constricted cavity projected from the partial position onto the inner envelope surface, and the diameter of the annular injection slit that crosses the central axis from the partial position A water atomization method for producing metal powder by generating a jet flow of a single leaf hyperboloid water jet curtain with a step of jetting water in a direction having a swivel angle ω The lowering angle θ is 0 to 30 °, the turning angle ω is 1 to 20 °, the water pressure is 90 to 150 MPa and the water flow rate is 300 to 800 L / min. A particle size index representing the relative value of the distribution of particle size distribution between a 5% diameter and a 95% diameter by producing a metal powder and classifying the Cu-based metal powder with a 50% diameter of 0.1-5 μm, a sphericity of 0.6-0.9, and a 5% diameter and a 95% diameter but less than 1, and characterized in that 0.5~7mg / m ² ratio of oxygen quantity representing the amount of oxygen per unit surface area, the specific amount of water which represents the water content per unit surface area to obtain a metal powder is 1 mg / m ² or less A method for producing Cu-based metal powder.

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