Alloy powder

Abstract

To provide homogeneous alloy powder.SOLUTION: Alloy powder in this invention is produced by feeding an alloy molten metal to a liquid film composed of a high speed fluid made of a coolant as a certain lump, breaking the alloy molten metal in the liquid film so as to be powdered and executing the cooling of the powder grains. Namely, the alloy powder in this invention is produced by substantially simultaneously executing the breaking and the cooling of the alloy molten metal, and due to this production method, a part of a surface layer has broken scars 10, where it is guessed that the broken scars 10 are scars broken in the liquid film when the lump of the alloy molten metal reaches the liquid film and are produced when the temporarily stretched alloy molten metal are made into spherical grains by surface tension.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to alloy powder.

Background Art

[0002] Generally, as methods for manufacturing alloy powder, the water atomization method and the gas atomization method are known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, alloy powders obtained by the water atomization method or the gas atomization method are often qualitatively variable.

[0005] Therefore, an object of the present invention is to provide a homogeneous alloy powder.

Means for Solving the Problems

[0006] In the conventional rapid cooling type atomization method, the molten alloy was divided into powder by gas or water and then rapidly cooled with a coolant such as cooling water. However, due to the difference in the cooling rate depending on the size of the divided powder particles and the difference in the dropping point and dropping speed of each powder particle, there was a difference in the cooling time in the air until the coolant reached between the powder particles, resulting in quality variations. [[ID=4۷]] On the other hand, in the present invention, the molten alloy is supplied to a liquid film composed of a high-speed fluid that is a coolant in the form of a certain lump or a stream of molten metal so that it does not cool, and the molten alloy is divided into powder by the liquid film and the powder particles are cooled. That is, according to the present invention, since the division and cooling of the molten alloy are substantially performed simultaneously, it is possible to suppress the occurrence of a difference in the degree of cooling between the powder particles, and homogeneous powder particles can be obtained.

[0007] In addition, if the powder particles segmented by the liquid film are not properly cooled, they will collide with the member constituting the bottom of the liquid film before solidification is completed, thereby causing the powder particles to become deformed. To avoid this, the acceleration along the thickness direction within the liquid film is set to 2.0×10 4 G or more, and the thickness of the liquid film is set to 0.1 mm or more, thereby ensuring an appropriate cooling capacity and solidifying the powder particles before they reach the member constituting the bottom of the liquid film. As a result, powder particles with a certain degree of uniformity can be obtained even on the shaped surface. The powder obtained in this way has the following characteristics.

[0008] The present invention provides, as a first alloy powder, an alloy powder having a fracture mark on a part of the surface layer.

[0009] The present invention provides, as a second alloy powder, the first alloy powder, wherein the fracture mark comprises at least a crater structure, an aggregate structure of mound-like protrusions, or a combination thereof alloy powder.

[0010] The present invention provides, as a third alloy powder, the first or second alloy powder, wherein the diameter of the fracture mark is less than the diameter of the powder alloy powder.

[0011] The present invention provides, as a fourth alloy powder, the third alloy powder, wherein the average diameter of the fracture mark is 2 / 3 or less of the diameter of the powder alloy powder.

[0012] The present invention provides, as a fifth alloy powder, any one of the first to fourth alloy powders, having an oxide layer thicker than that directly under the periphery of the fracture mark directly under the fracture mark alloy powder.

[0013] The present invention provides, as a sixth alloy powder, the fifth alloy powder, The dividing mark is composed of a combination of a crater structure and an aggregate structure of hill-like protrusions located around the crater structure, The oxide layer located directly below the aggregate structure of hill-like protrusions has a lower density than the oxide layer located directly below the crater structure Provided is an alloy powder.

[0014] The present invention provides, as a seventh alloy powder, the fifth or sixth alloy powder, The thickness of the oxide layer is 30 nm or more Provided is an alloy powder.

[0015] The present invention provides, as an eighth alloy powder, any one of the fifth to seventh alloy powders, which contains P element and contains Si element of 3 at% or less Provided is an alloy powder.

[0016] The present invention provides, as a ninth alloy powder, the eighth alloy powder, wherein the amount of Si element is 1 at% or less Provided is an alloy powder.

[0017] The present invention provides, as a tenth alloy powder, the eighth or ninth alloy powder, which has a phosphate on the surface layer Provided is an alloy powder.

[0018] The present invention provides, as an eleventh alloy powder, any one of the eighth to tenth alloy powders, wherein the oxide layer contains P or Si Provided is an alloy powder.

[0019] The present invention provides, as a twelfth alloy powder, any one of the first to eleventh alloy powders, the composition contains inevitable impurities, Fe a Si b B c P d Cu e C fand satisfies 80≦a≦90, 0≦b≦3, 3≦c≦18, 0≦d≦17, 0≦e≦1.2, 0≦f≦5 to provide an alloy powder.

[0020] The present invention provides, as a 13th alloy powder, a 12th alloy powder, wherein 3 at% or less of Fe is substituted with one or more elements selected from O, N, S, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Zr, Hf, Nb, Ta, Mo, W, Ag, Au, Zn, Sn, Sb, Bi, and rare earth elements to provide an alloy powder.

[0021] The present invention provides, as a 14th alloy powder, a 12th alloy powder, wherein 20 at% or less of Fe is substituted with at least one element of Co and Ni to provide an alloy powder.

[0022] The present invention provides, as a 15th alloy powder, any one of the alloy powders from the 1st to the 14th, having a crystallinity of 4% or less to provide an alloy powder.

[0023] The present invention provides, as a 16th alloy powder, any one of the alloy powders from the 1st to the 15th, having a spherical shape with the fracture marks to provide an alloy powder.

[0024] The present invention provides, as a 1st nanocrystalline powder, a nanocrystalline powder obtained by heat-treating the alloy powders from the 1st to the 16th, having a crystal grain size of 50 nm or less to provide a nanocrystalline powder.

[0025] The present invention provides, as a 1st core, a core using any one of the alloy powders from the 1st to the 16th or the 1st nanocrystalline powder.

Advantages of the Invention

[0026] Alloy powders having cleavage marks like those of the present invention are ones in which differences in the degree of cooling between powder grains are suppressed, so that variations in quality are suppressed and the powders are also uniform to some extent in terms of their shape surfaces. Further, the nanocrystalline powders obtained by heat-treating homogeneous alloy powders are also homogeneous.

Brief Description of the Drawings

[0027]

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Embodiments for Carrying Out the Invention

[0028] The alloy powder according to the embodiment of the present invention is produced by supplying a molten alloy in the form of a certain mass to a liquid film composed of a high-speed fluid consisting of a coolant, fragmenting the molten alloy in the liquid film to form powder, and cooling the powder particles. That is, the alloy powder according to the present embodiment is produced by substantially simultaneously fragmenting and cooling the molten alloy, and has uniform characteristics. In the present embodiment, since the form of the alloy is powder, oxygen may be mixed into the powder from the raw materials or refractories, or oxygen may be mixed into the powder during rapid cooling or drying. However, if it is excessively oxidized, the magnetic properties will deteriorate. Therefore, the oxygen concentration contained in the powder is preferably 5000 ppm or less, and more preferably 2000 ppm or less.

[0029] In particular, according to the manufacturing method described above, unlike the conventional rapid cooling type atomization method, the alloy powder according to the present embodiment is not substantially cooled until it reaches the liquid film and is rapidly cooled when it reaches the liquid film. Therefore, the alloy powder according to the present embodiment has good amorphousness. Specifically, the crystallinity of the alloy powder according to the present embodiment is 4% or less. Further, when such an alloy powder is heat-treated, a high-quality nanocrystalline powder with a crystal grain size of 50 nm or less can be obtained.

[0030] Referring to FIG. 1, the alloy powder according to the present embodiment has a fracture mark 10 on a part of the surface layer due to the manufacturing method described above. Here, the fracture mark 10 is a mark formed by fragmenting the mass of the molten alloy by the liquid film when the mass of the molten alloy reaches the liquid film, and is presumed to be formed when the molten alloy temporarily stretched during fragmentation becomes spherical particles due to surface tension. The fracture mark 10 includes at least a crater structure 11 shown in FIG. 2, a mound-like ridge aggregate structure 12 which is an aggregate of a large number of mound-like ridges shown in FIG. 3, or a combination of the crater structure 11 and the mound-like ridge aggregate structure 12 as shown in FIGS. 4, 6 and 8. Thus, although the alloy powder according to the present embodiment has the fracture mark 10, it is substantially spherical. Therefore, the fluidity of the alloy powder according to the present embodiment is good.

[0031] Referring to FIGS. 1 and 5, among the powder particles manufactured by the above-described manufacturing method, in addition to the spherical powder having the above-described fracture mark 10, there may be included filamentous powder 20 having a high aspect ratio. The filamentous powder 20 is presumed to be generated when the molten alloy is drawn and divided in the coolant. Such filamentous powder 20 is expected to enhance the strength and improve the formability when made into a compacted magnetic core while having a small influence on the magnetic properties.

[0032] Regarding the particle size of the powder, there is no particular size requirement, but a range of 1 to 100 μm is preferred. In particular, when used at a high frequency of 100 kHz or more, about 30 μm or less is preferred.

[0033] The diameter of the fracture mark 10 is less than the diameter of the powder. Specifically, the diameter of the fracture mark 10 is generally 100 μm or less, and the average diameter of the fracture mark 10 is 2 / 3 or less of the diameter of the powder. In this fracture mark 10, slag and oxides of the drawn portion are concentrated. As a result, as shown in FIGS. 6 and 8, the oxide layer directly below the fracture mark 10 is thicker than the oxide layer other than directly below the fracture mark 10. Specifically, the thickness of the oxide layer is 30 nm or more, and many cases where the thickness of the oxide layer is 100 nm or more are also found.

[0034] Referring to FIGS. 6 and 8, when the alloy powder has a fracture mark 10 composed of a combination of a crater structure 11 and a mound-like aggregate structure 12, specifically, the mound-like aggregate structure 12 is located around the crater structure 11. Referring to FIGS. 7 and 9, the density of the oxide layer located directly below the mound-like aggregate structure 12 is lower than the density of the oxide layer located directly below the crater structure 11.

[0035] In particular, when the alloy powder contains P element and Si element at 3 at% or less, spherical powder particles are likely to be obtained. Specifically, when there is a large amount of Si, the powder particles often have irregular shapes. This is presumably because a hard oxide layer such as SiO2 is formed on the surface layer at a relatively early stage before the inside of the particles is cooled, and thereby the spheroidization of the powder particles stops regardless of the solidification state inside the particles. On the other hand, when Si is 3 at% or less, the silica layer on the powder surface decreases and the amount of irregular-shaped powder decreases. In particular, when the amount of Si element is 1 at% or less, the powder particles tend to become rounder. On the other hand, when the molten alloy contains P element, phosphates are precipitated on the surface layer, and spherical powder particles are easily obtained. This is presumably because when a soft oxide layer such as phosphate is formed on the surface layer, spheroidization proceeds due to the surface tension acting on the surface layer of the particles even while the inside of the particles is cooled in the coolant. Therefore, when an oxide layer such as phosphate is present on the surface layer, there is an advantage that not only the insulation property of the powder particles is improved but also spherical powder particles are easily obtained.

[0036] When the alloy powder contains P element or Si element, the oxide layer tends to contain P or Si. In particular, in relation to the fracture mark 10, there is the following tendency. When the fracture mark 10 has a crater structure 11 the oxide layer directly below the crater structure 11 tends to contain P element like phosphate. Also, when the fracture mark 10 has a mound-shaped protrusion aggregate structure, the oxide layer directly below the mound-shaped protrusion aggregate structure 12 tends to contain Si. In particular, the oxide layer directly below the mound-shaped protrusion aggregate structure 12 tends to have a higher Si concentration compared to the oxide layer in other parts.

[0037] The preferable composition of the alloy powder described above includes inevitable impurities and, Fe a Si b B c P d Cu e C fand those satisfying 80 ≦ a ≦ 90, 0 ≦ b ≦ 3, 3 ≦ c ≦ 18, 0 ≦ d ≦ 17, 0 ≦ e ≦ 1.2, and 0 ≦ f ≦ 5 can be mentioned. More preferably, in the composition formula Fe a Si b B c P d Cu e C f it satisfies 83 ≦ a ≦ 87, 0 ≦ b ≦ 1, 5 ≦ c ≦ 12, 4 ≦ d ≦ 10, 0.4 ≦ e ≦ 0.9, and 0 ≦ f ≦ 1. In the above composition formula, 3 at% or less of Fe may be substituted with one or more elements among O, N, S, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Zr, Hf, Nb, Ta, Mo, W, Ag, Au, Zn, Sn, Sb, Bi, and rare earth elements. Among these, Al, Ti, etc. can be expected to have effects such as corrosion resistance in small amounts, but the tendency is for the formation of abnormal shapes to progress with the addition. When it is desired to increase the bulk density even slightly, it is preferable that the total amount is 0.1 at% or less, and when it is further 0.01 at% or less, spheroidization, amorphousness, and magnetic properties become good. Also, in the above composition formula, 20 at% or less of Fe may be substituted with at least one element of Co and Ni. Co and Ni are responsible for magnetism and can suppress the decrease in magnetic properties.

[0038] Among the elements constituting the above composition formula, Fe is an element responsible for magnetism. The higher the proportion of Fe, the higher the saturation magnetic flux density, and cost reduction becomes possible. Specifically, since the saturation magnetic flux density becomes 1.6 T or more, the Fe amount is preferably 80 at% or more, and since the saturation magnetic flux density becomes 1.7 T or more, the Fe amount is more preferably 83 at% or more. On the other hand, when the Fe amount exceeds 90 at%, the melting point becomes high and the amorphous forming ability decreases, making it difficult to produce high-quality powder. Therefore, considering the melting point, the Fe amount is preferably 90 at% or less. Further, considering the amorphous forming ability, the Fe amount is preferably 87 at% or less, and in order to obtain good amorphous powder, it is preferably 85.5 at% or less.

[0039] The above-mentioned alloy powder has two exothermic peaks associated with crystallization, that is, it exhibits a two-stage crystallization behavior. In relation to this, in the above-mentioned composition formula, Si is an element that easily widens the difference ΔT (= Tx2 - Tx1) between the second crystallization start temperature Tx2 and the first crystallization start temperature Tx1 and can suppress the precipitation of compounds. By adding a small amount of Si to the composition, it becomes possible to improve the amorphous forming ability. However, if too much is added, the amorphous forming ability decreases and the powder becomes irregular in shape. From this perspective, the Si content is preferably 3 at% or less, and 1 at% is preferred as it is easy to obtain spherical powder.

[0040] In the above-mentioned composition formula, B is an essential element of the alloy powder, and the B content needs to be 3 at% or more. In order to improve the amorphous forming ability, the B content is preferably 5 at% or more. Also, the B content is preferably 18 at% or less in order to avoid a decrease in the saturation magnetic flux density, and preferably 12 at% or less for improving the amorphous forming ability. Furthermore, in a high B composition, it becomes difficult to perform nanocrystallization heat treatment due to coarsening of the crystal grain size and the influence of crystallization heat generation. From this perspective, the B content is preferably 10 at% or less.

[0041] In the above-mentioned composition formula, P is an element effective for improving the amorphous forming ability, refining the crystal grains, sphericalizing the powder, improving the corrosion resistance, lowering the melting point of the alloy, and lowering the heat treatment temperature. However, if too much is added, ΔT (Tx2 - Tx1) becomes narrow, making it difficult to nanocrystallize αFe. Therefore, the P content is preferably 18 at% or less, and preferably 10 at% or less for improving the saturation magnetic flux density. In addition, from the perspective of suppressing crystal grains, the P content is preferably 4 at% or more, and in a large core, the P content is preferably 5 at% or more.

[0042] In the above composition formula, Cu precipitates as clusters during crystallization and is an element that promotes nanocrystallization. Also, when Cu is added, the crystallization temperature can be lowered, making heat treatment easier. From such a perspective, the amount of Cu is preferably 0.4 at% or more, and more preferably 0.55 at% or more. On the other hand, if too much Cu is added, the amorphous forming ability is lowered, so the amount of Cu is preferably 1.2 at% or less, and more preferably 0.9 at% or less.

[0043] In the above composition formula, C has an effect on the amorphous forming ability, lowers the crystallinity, and is an element that can reduce the raw material cost. However, since it coarsens the crystal grains, for low loss, the amount of C is preferably 5 at% or less, and more preferably 1 at% or less.

[0044] Any of the above-described alloy powders and nanocrystal powders has high fluidity. Therefore, by using these, magnetic cores with excellent properties can be obtained. When using the above-described alloy powders and nanocrystal powders, powders with different particle sizes may be mixed or powders with different materials may be mixed for suppressing thermal runaway, heat dissipation, or further improving fluidity.

[0045] Hereinafter, embodiments of the present invention will be described more specifically with reference to examples.

[0046] (Examples 1 to 26 and Comparative Examples 1 to 4) The molten alloy with the composition shown in Table 1 below was atomized, and its shape, structure, and properties were evaluated. Among these, for Examples 1 to 26 and Comparative Example 1, the molten alloy was supplied in a certain lump form to a liquid film composed of a high-speed fluid as a coolant, and the molten alloy was fragmented and atomized by the liquid film while cooling the powder particles, thereby being atomized. For Comparative Examples 2 and 4, atomization was carried out by the water atomization method, and for Comparative Example 3, atomization was carried out by the gas atomization method. The evaluation results of the alloy powders produced in this way are shown in Tables 2 and 3. In Table 2, Structure 1 has a crater structure as a fracture mark, Structure 2 has an aggregate structure of hill-like protrusions as a fracture mark, and the fracture mark content rate is the ratio of the powder particles having fracture marks to the whole powder particles.

[0047]

Table 1

[0048]

Table 2

[0049]

Table 3

[0050] Referring to Table 2, all of the alloy powders of Examples 1 to 26 manufactured by the manufacturing method of the present embodiment have a crater structure (Structure 1) or an aggregate structure of hill-shaped protrusions (Structure 2), and have a substantially spherical powder shape. On the other hand, none of the alloy powders of Comparative Examples 2 to 4 manufactured by the water atomization method or the gas atomization method had such fracture marks. The alloy powders of Example 1 and Comparative Example 1 were both manufactured by the manufacturing method of the present embodiment, but there was a difference in the Si content. Since the Si content of the alloy powder of Comparative Example 1 was 4, it could not be properly fragmented when the molten alloy was atomized into powder, and the powder shape was also irregular. On the other hand, the alloy powder of Example 1 had a Si content of 3.5 and was less than that of Comparative Example 1, so it could be fragmented, but many of the powder shapes were irregular and could not be said to be sufficient for the purpose of obtaining spherical powder.

[0051] According to Table 3, Examples 1 to 26 having fracture marks have a bulk density of 3.7 g / cc or more and a tap density of 4.0 g / cc or more. In addition, the alloy powders of Examples 1 to 26 have a magnetic saturation density of 1.6 T or more and a coercive force of 5 Oe or less. Therefore, by using such alloy powders, a magnetic core having excellent magnetic properties can be manufactured.

[0052] (Examples 31 to 36 and Comparative Examples 31 to 33) The molten alloy shown in Table 4 below was atomized into powder, and the particle size distribution and properties were evaluated. Among these, for Examples 31 to 36, the molten alloy was supplied as a certain lump to a liquid film composed of a high-speed fluid serving as a coolant, and the molten alloy was fragmented and atomized by the liquid film and the powder particles were cooled, thereby atomizing the powder. For Comparative Example 31 and Comparative Example 32, atomization was performed by the water atomization method, and for Comparative Example 33, atomization was performed by the gas atomization method.

[0053]

Table 4

[0054] Referring to Table 4, the alloy powders of Examples 31 to 36 have a low crystallinity of 2% or less and a good coercive force of 2 Oe or less. In contrast, the alloy powders of Comparative Example 31 and Comparative Example 33 have a high crystallinity and a large coercive force. In addition, the alloy powders of Examples 31 to 36 have a small average particle size, D50 / D10 is 2.5 or less, and D90 / D10 is 4 or more and 6 or less. Here, when the value of D90 / D10 is less than 4, the yield tends to decrease. Also, when the value of D90 / D10 exceeds 6, there are many irregularly shaped powders, and the flowability of the powder and the insulation property when used as a core deteriorate. Therefore, the value of D90 / D10 is preferably 4 or more and 6 or less, like the alloy powders of Examples 31 to 36. In contrast, the alloy powders of Comparative Example 31 and Comparative Example 32 have a small average particle size but a large D50 / D10. That is, the alloy powders of Comparative Example 31 and Comparative Example 32 have a large proportion of fine powders, and thus rust is likely to occur. Also, Comparative Example 33 has a large average particle size.

Explanation of symbols

[0055] 10 fracture mark 11 crater structure 12 mound-like protrusion aggregate structure 20 filamentous powder

Claims

1. An alloy powder having a fracture mark on a part of the surface layer, wherein the fracture mark comprises at least a crater structure, a mound-like aggregate structure which is an aggregate of a number of mound-like protrusions, or a combination of the crater structure and the mound-like aggregate structure Alloy powder.

2. The alloy powder according to Claim 1, wherein the diameter of the fracture mark is less than the diameter of the powder Alloy powder.

3. The alloy powder according to Claim 2, wherein the average diameter of the fracture mark is 2 / 3 or less of the diameter of the powder Alloy powder.

4. The alloy powder according to any one of Claims 1 to 3, having an oxide layer thicker than that other than directly under the fracture mark directly under the fracture mark Alloy powder.

5. The alloy powder according to Claim 4, wherein the fracture mark is composed of a combination of the crater structure and the mound-like aggregate structure located around the crater structure, and the oxide layer located directly under the mound-like aggregate structure has a lower density than the oxide layer located directly under the crater structure Alloy powder.

6. The alloy powder according to Claim 4 or 5, wherein the thickness of the oxide layer is 30 nm or more Alloy powder.

7. The alloy powder according to any one of Claims 4 to 6, containing P element and containing Si element of 3 at% or less Alloy powder.

8. The alloy powder according to Claim 7, wherein the amount of Si element is 1 at% or less Alloy powder.

9. The alloy powder according to Claim 7 or Claim 8, having a phosphate on the surface layer Alloy powder.

10. The alloy powder according to any one of Claims 7 to 9, wherein the oxide layer contains P or Si Alloy powder.

11. The alloy powder according to any one of Claims 1 to 10, the composition contains inevitable impurities and is FeaSibBcPdCueCf, satisfying 80 ≦ a ≦ 90, 0 ≦ b ≦ 3, 3 ≦ c ≦ 18, 0 ≦ d ≦ 17, 0 ≦ e ≦ 1.2, 0 ≦ f ≦ 5 Alloy powder.

12. The alloy powder according to Claim 11, wherein 3 at% or less of Fe is substituted with one or more elements among O, N, S, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Zr, Hf, Nb, Ta, Mo, W, Ag, Au, Zn, Sn, Sb, Bi and rare earth elements Alloy powder.

13. The alloy powder according to Claim 11, wherein 20 at% or less of Fe is substituted with at least one element of Co and Ni Alloy powder.

14. The alloy powder according to any one of Claims 1 to 13, having a crystallinity of 4% or less Alloy powder.

15. The alloy powder according to any one of Claims 1 to 14, having a spherical shape with the above-mentioned fracture marks Alloy powder.

16. A nanocrystalline powder obtained by heat-treating the alloy powder according to any one of Claims 1 to 15, having a crystal grain size of 50 nm or less Nanocrystalline powder.

17. A magnetic core using the alloy powder according to any one of Claims 1 to 15 or the nanocrystalline powder according to Claim 16.

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