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 an alloy powder. [Background technology]

[0002] Generally, water atomization and gas atomization are known as methods for producing alloy powder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4584350 Summary of the Invention [Problem to be solved by the invention]

[0004] However, alloy powders obtained by water atomization or gas atomization often vary in quality.

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

[0006] In the conventional rapid-cooling atomization method, the molten alloy is broken down into powder using gas or water, and then rapidly cooled in a coolant such as cooling water. However, the cooling rate varies depending on the size of the broken powder particles, and the falling point and falling speed of each powder particle differ. This results in differences in the amount of time the powder particles spend cooling in the air before reaching the coolant, resulting in variations in quality. In contrast, in the present invention, the molten alloy is supplied to a liquid film made of a high-speed fluid of a cooling liquid in a state where it remains as a lump or a flowing molten alloy to a certain extent so as not to be cooled, and the liquid film divides the molten alloy into powder and cools the powder particles. That is, according to the present invention, since the division and cooling of the molten alloy are carried out substantially simultaneously, it is possible to suppress differences in the degree of cooling among the powder particles, and to obtain uniform powder particles.

[0007] In addition, if the powder particles separated by the liquid film are not cooled properly, they will collide with the material that forms the bottom of the liquid film before solidification is complete, causing the powder particles to become misshapen. To avoid this, the acceleration in the thickness direction within the liquid film is set to 2.0 × 10 4 By setting the temperature at or above G and the thickness of the liquid film at or above 0.1 mm, it is possible to ensure adequate cooling capacity, which allows the powder particles to solidify before they reach the component that forms the bottom of the liquid film. This allows for powder particles that are relatively uniform in shape. The powder thus obtained has the following characteristics:

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

[0009] The present invention provides a first alloy powder as the second alloy powder, The separation marks have at least a crater structure, a hill-like protuberance aggregate structure, or a combination thereof. An alloy powder is provided.

[0010] The present invention provides a third alloy powder comprising the first or second alloy powder, The diameter of the dividing mark is less than the diameter of the powder. An alloy powder is provided.

[0011] The present invention provides a fourth alloy powder, which is the third alloy powder, The average diameter of the dividing marks is 2 / 3 or less of the diameter of the powder. An alloy powder is provided.

[0012] The present invention provides a fifth alloy powder, which is any one of the first to fourth alloy powders, An oxide layer is provided directly below the dividing mark that is thicker than the oxide layer directly below the periphery of the dividing mark. An alloy powder is provided.

[0013] The present invention provides a sixth alloy powder as the fifth alloy powder, the separation mark is formed by a combination of a crater structure and a hill-like protuberance aggregate structure located around the crater structure, The oxide layer located directly below the hill-like ridge cluster structure has a lower density than the oxide layer located directly below the crater structure. An alloy powder is provided.

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

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

[0016] The present invention provides a ninth alloy powder, which is the eighth alloy powder, The amount of Si element is 1 at% or less An alloy powder is provided.

[0017] The present invention provides a tenth alloy powder, which is the eighth or ninth alloy powder, The surface layer has phosphate An alloy powder is provided.

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

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

[0020] The present invention provides a thirteenth alloy powder, which is the twelfth alloy powder, 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. An alloy powder is provided.

[0021] The present invention provides a 14th alloy powder, which is the 12th alloy powder, 20 at % or less of Fe is substituted with at least one element of Co and Ni An alloy powder is provided.

[0022] The present invention provides a fifteenth alloy powder, which is any one of the first to fourteenth alloy powders, The crystallinity is 4% or less An alloy powder is provided.

[0023] The present invention provides a sixteenth alloy powder, which is any one of the first to fifteenth alloy powders, The dividing mark has a spherical shape. An alloy powder is provided.

[0024] The present invention provides a first nanocrystalline powder obtained by heat treating the first to sixteenth alloy powders, The grain size is 50 nm or less A nanocrystalline powder is provided.

[0025] The present invention provides a magnetic core using any one of the first to sixteenth alloy powders or the first nanocrystalline powder as a first magnetic core. [Effects of the Invention]

[0026] The alloy powder having the dividing marks of the present invention is one in which the difference in the degree of cooling between the powder particles is suppressed, and therefore the variation in quality is suppressed and the shape is also relatively uniform. Furthermore, the nanocrystalline powder obtained by heat treating the homogeneous alloy powder is also homogeneous. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a copy of an SEM image showing an alloy powder according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing an example of powder particles contained in the alloy powder of FIG. [Figure 3] 2 is a diagram showing another example of powder particles contained in the alloy powder of FIG. 1. FIG. [Figure 4] 1. FIG. 4 is a diagram showing still another example of powder particles contained in the alloy powder of FIG. [Figure 5] FIG. 1 shows a filamentous powder. [Figure 6] 1A and 1B are diagrams showing an example of a powder particle and its cross section. [Figure 7] FIG. 7 is an enlarged view showing a part of a cross section of the powder particle of FIG. 6. [Figure 8] 10A and 10B are diagrams showing another example of a powder particle and its cross section. [Figure 9] FIG. 9 is an enlarged view showing a part of a cross section of the powder particle of FIG. 8. DETAILED DESCRIPTION OF THE INVENTION

[0028] The alloy powder according to the embodiment of the present invention is produced by feeding a molten alloy in chunks through a liquid film made of a high-velocity fluid of a cooling liquid, breaking up the molten alloy with the liquid film, and pulverizing the molten alloy while simultaneously cooling the powder particles. That is, the alloy powder according to the embodiment is produced by substantially simultaneously breaking up and cooling the molten alloy, and has homogeneous properties. Note that, since the alloy is in the form of a powder in this embodiment, oxygen may be mixed into the powder from the raw materials or refractories, or during rapid cooling or drying. However, excessive oxidation can deteriorate the magnetic properties, so the oxygen concentration in the powder is preferably 5000 ppm or less, and more preferably 2000 ppm or less.

[0029] In particular, according to the above-described manufacturing method, unlike conventional rapid-cooling atomization methods, the alloy powder according to this embodiment is not cooled until it reaches the liquid film, but is rapidly cooled upon reaching the liquid film. Therefore, the alloy powder according to this embodiment has good amorphous properties. Specifically, the crystallinity of the alloy powder according to this embodiment is 4% or less. Furthermore, when this 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 this embodiment has separation marks 10 on a portion of the surface layer due to the above-described manufacturing method. The separation marks 10 are marks formed when a mass of molten alloy reaches the liquid film and is separated by the liquid film. It is presumed that the separation marks 10 were generated when the molten alloy, temporarily stretched during separation, became spherical particles due to surface tension. The separation marks 10 have at least a crater structure 11 shown in FIG. 2, a hill-like ridge aggregate structure 12, which is an aggregate of numerous hill-like ridges, shown in FIG. 3, or a combination of the crater structure 11 and the hill-like ridge aggregate structure 12, as shown in FIGS. 4, 6, and 8. Thus, the alloy powder according to this embodiment has separation marks 10, but is substantially spherical. Therefore, the fluidity of the alloy powder according to this embodiment is good.

[0031] 1 and 5, the powder particles produced by the above-described production method may contain, in addition to the spherical powder having the above-described division marks 10, filamentous powder 20 with a high aspect ratio. The filamentous powder 20 is presumed to have been generated when the molten alloy is stretched and divided in a coolant. While such filamentous powder 20 has little effect on the magnetic properties, it is expected to increase the strength and improve the moldability when made into a powder core.

[0032] The particle size of the powder is not particularly limited, but is preferably in the range of 1 to 100 μm. In particular, when used at high frequencies of 100 kHz or more, it is preferably about 30 μm or less.

[0033] The diameter of the dividing marks 10 is less than the diameter of the powder. Specifically, the diameter of the dividing marks 10 is generally 100 μm or less, and the average diameter of the dividing marks 10 is 2 / 3 or less of the diameter of the powder. Slag and oxides from the stretched portion are concentrated in the dividing marks 10. As a result, as shown in Figures 6 and 8, the oxide layer directly below the dividing marks 10 is thicker than the oxide layer other than directly below the dividing marks 10. Specifically, the thickness of the oxide layer is 30 nm or more, and many oxide layers with a thickness of 100 nm or more are observed.

[0034] 6 and 8, when the alloy powder has a separation mark 10 consisting of a combination of a crater structure 11 and a hill-like ridge aggregate structure 12, more specifically, the hill-like ridge 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 hill-like ridge aggregate structure 12 is lower than the density of the oxide layer located directly below the crater structure 11.

[0035] In particular, alloy powders containing P and 3 at% or less Si tend to produce spherical powder particles. Specifically, high Si content often leads to irregularly shaped powder particles. This is presumably because a hard oxide layer, such as SiO2, forms on the surface relatively early before the particles cool to their interior, preventing the particles from spheroidizing regardless of the solidification state of the particles. In contrast, when Si is reduced to 3 at% or less, the silica layer on the powder surface is reduced, reducing irregularly shaped powder. In particular, when the Si content is 1 at% or less, powder particles tend to become more rounded. On the other hand, when the molten alloy contains P, phosphate precipitates on the surface, facilitating the production of spherical powder particles. It is presumed that when a soft oxide layer, such as phosphate, forms on the surface, the surface tension acting on the particle surface promotes spheroidization even during cooling of the particle interior in the coolant. Therefore, the presence of an oxide layer, such as phosphate, on the surface not only improves the insulating properties of the powder particles, but also facilitates the production of spherical powder particles.

[0036] When the alloy powder contains P or Si, the oxide layer tends to contain P or Si. In particular, in relation to the separation marks 10, there is the following tendency: When the separation marks 10 have a crater structure 11, the oxide layer directly below the crater structure 11 tends to contain P, like phosphate. Furthermore, when the separation marks 10 have a hill-like ridge aggregate structure, the oxide layer directly below the hill-like ridge aggregate structure 12 tends to contain Si. In particular, the oxide layer directly below the hill-like ridge aggregate structure 12 tends to have a higher Si concentration than the oxide layer in other parts.

[0037] The preferred composition of the alloy powder described above contains inevitable impurities and contains Fe. a Si b B c P d Cu e C f and the formula is 80≦a≦90, 0≦b≦3, 3≦c≦18, 0≦d≦17, 0≦e≦1.2, and 0≦f≦5. More preferably, the formula is Fe a Si b Bc P d Cu e C f The following conditions are satisfied: 83≦a≦87, 0≦b≦1, 5≦c≦12, 4≦d≦10, 0.4≦e≦0.9, 0≦f≦1. In the above composition formula, up to 3 at% of Fe may be substituted with one or more of the following elements: 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. Small amounts of Al and Ti can be expected to improve corrosion resistance, but their addition tends to promote irregular morphology. To increase bulk density even slightly, a total amount of 0.1 at% or less is preferred. Furthermore, a total amount of 0.01 at% or less improves spheroidization, amorphousness, and magnetic properties. In the above composition formula, up to 20 at% of Fe may be substituted with at least one of Co and Ni. Co and Ni are responsible for magnetism and can suppress the deterioration of magnetic properties.

[0038] Among the elements constituting the above composition formula, Fe is the element responsible for magnetism. The higher the Fe content, the higher the saturation magnetic flux density, enabling cost reduction. Specifically, since the saturation magnetic flux density is 1.6 T or higher, the Fe content is preferably 80 at% or higher. Since the saturation magnetic flux density is 1.7 T or higher, the Fe content is more preferably 83 at% or higher. On the other hand, if the Fe content 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 content is preferably 90 at% or less. Furthermore, considering the amorphous-forming ability, the Fe content is preferably 87 at% or less, and preferably 85.5 at% or less to obtain good amorphous powder.

[0039] The alloy powder shown above has two exothermic peaks associated with crystallization, i.e., it exhibits two-stage crystallization behavior. In relation to this, in the composition formula shown above, Si is an element that can easily widen the difference ΔT (= Tx2 - Tx1) between the second crystallization onset temperature Tx2 and the first crystallization onset temperature Tx1, thereby suppressing compound precipitation. Adding a small amount of Si to the composition can improve amorphous-forming ability, but adding too much Si reduces amorphous-forming ability and results in irregularly shaped powder. From this perspective, the Si content is preferably 3 at% or less, with 1 at% being preferred, as this makes it easier to obtain spherical powder.

[0040] In the above composition formula, B is an essential element of the alloy powder, and the B content must be 3 at% or more. To improve the amorphous-forming ability, the B content is preferably 5 at% or more. Furthermore, the B content is preferably 18 at% or less to avoid a decrease in saturation magnetic flux density, and is preferably 12 at% or less to improve the amorphous-forming ability. Furthermore, a high B content makes nanocrystallization heat treatment difficult due to the effects of coarsening of the crystal grain size and the heat generated by crystallization. From this perspective, the B content is preferably 10 at% or less.

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

[0042] In the above composition formula, Cu is an element that precipitates as clusters during crystallization and promotes nanocrystallization. The addition of Cu also lowers the crystallization temperature, facilitating heat treatment. From this perspective, the Cu content is preferably 0.4 at% or more, and more preferably 0.55 at% or more. However, since excessive Cu content reduces the ability to form amorphous structures, the Cu content is preferably 1.2 at% or less, and more preferably 0.9 at% or less.

[0043] In the above composition formula, C is an element that is effective in improving amorphous formation, reducing the degree of crystallinity, and enabling reduction in raw material costs. However, since C coarsens the crystal grains, in order to reduce loss, the C content is preferably 5 at% or less, and more preferably 1 at% or less.

[0044] The above-mentioned alloy powders and nanocrystalline powders all have high fluidity. Therefore, by using these, magnetic cores with excellent properties can be obtained. When using the above-mentioned alloy powders and nanocrystalline powders, powders of different particle sizes or powders of different materials may be mixed to suppress thermal runaway, dissipate heat, or further improve fluidity.

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

[0046] (Examples 1 to 26 and Comparative Examples 1 to 4) Molten alloys having the compositions shown in Table 1 below were powdered, and their shapes, structures, and properties were evaluated. Of these, for Examples 1 to 26 and Comparative Example 1, the molten alloy was supplied in chunks to a liquid film composed of a high-speed fluid of a cooling liquid, and the molten alloy was broken up and powdered by the liquid film while the powder particles were cooled. Comparative Examples 2 and 4 were powdered by water atomization, and Comparative Example 3 was powdered by gas atomization. The evaluation results of the alloy powders produced in this manner are shown in Tables 2 and 3. In Table 2, Structure 1 has a crater structure as the division marks, and Structure 2 has a hill-like protuberance aggregate structure as the division marks, and the division mark content is the ratio of powder particles having division marks to all powder particles.

[0047] [Table 1]

[0048] [Table 2]

[0049] [Table 3]

[0050] Referring to Table 2, the alloy powders of Examples 1 to 26, which were produced by the production method of this embodiment, all had a crater structure (Structure 1) or a hill-like ridge aggregate structure (Structure 2), and were approximately spherical in shape. In contrast, none of the alloy powders of Comparative Examples 2 to 4, which were produced by water atomization or gas atomization, had such division marks. The alloy powders of Example 1 and Comparative Example 1 were both produced by the production method of this embodiment, but differed in their Si content. The alloy powder of Comparative Example 1 had an Si content of 4, so it could not be properly divided when the molten alloy was powdered, and the powder shape was also irregular. On the other hand, the alloy powder of Example 1 had an Si content of 3.5, which is lower than that of Comparative Example 1, so it could be divided, but many of the powder shapes were irregular, and it was not sufficient for the purpose of obtaining spherical powder.

[0051] According to Table 3, Examples 1 to 26, which have cutting marks, have bulk densities of 3.7 g / cc or more and tap densities of 4.0 g / cc or more. In addition, the alloy powders of Examples 1 to 26 have magnetic saturation densities of 1.6 T or more and coercive forces of 5 Oe or less. Therefore, by using such alloy powders, magnetic cores with excellent magnetic properties can be manufactured.

[0052] (Examples 31 to 36 and Comparative Examples 31 to 33) The molten alloys shown in Table 4 below were powdered, and the particle size distribution and properties were evaluated. Of these, in Examples 31 to 36, the molten alloys were supplied in a certain amount of chunks to a liquid film composed of a high-speed fluid of a cooling liquid, and the molten alloys were divided and powdered by the liquid film, and the powder particles were cooled. In Comparative Examples 31 and 32, the alloys were powdered by water atomization, and in Comparative Example 33, the alloys were powdered by gas atomization.

[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 Examples 31 and 33 have a high crystallinity and a high coercive force. In addition, the alloy powders of Examples 31 to 36 have a small average particle size, a D50 / D10 of 2.5 or less, and a D90 / D10 of 4 or more and 6 or less. Here, if the D90 / D10 value is less than 4, the yield is likely to decrease. Furthermore, if the D90 / D10 value exceeds 6, the amount of irregularly shaped powder increases, which deteriorates the powder flowability and the insulation properties when used in a core. Therefore, the D90 / D10 value is preferably 4 or more and 6 or less, as in the alloy powders of Examples 31 to 36. In contrast, the alloy powders of Comparative Examples 31 and 32 have a small average particle size but a large D50 / D10. That is, the alloy powders of Comparative Examples 31 and 32 have a high proportion of fine powder and are therefore prone to rust. Moreover, Comparative Example 33 has a large average particle size. [Explanation of symbols]

[0055] 10 Severance marks 11 Crater structure 12 Hill-like ridge aggregate structure 20 filamentous powder

Claims

1. An alloy powder having a dividing mark on a part of a surface layer, The oxide layer directly below the dividing mark is thicker than the oxide layer other than the oxide layer directly below the dividing mark. Alloy powder.

2. The alloy powder according to claim 1, The diameter of the dividing mark is less than the diameter of the powder. Alloy powder.

3. The alloy powder according to claim 2, The average diameter of the dividing marks 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, the separation mark is formed by a combination of a crater structure and a hill-like ridge aggregate structure which is an aggregate of a number of hill-like ridges located around the crater structure, The oxide layer located directly below the hill-like ridge cluster structure has a lower density than the oxide layer located directly below the crater structure. Alloy powder.

5. The alloy powder according to any one of claims 1 to 4, The thickness of the oxide layer is 30 nm or more. Alloy powder.

6. The alloy powder according to any one of claims 1 to 5, Contains P element and 3 at % or less of Si element Alloy powder.

7. The alloy powder according to claim 6, The amount of Si element is 1 at% or less Alloy powder.

8. The alloy powder according to claim 6 or claim 7, The surface layer has phosphate Alloy powder.

9. The alloy powder according to any one of claims 6 to 8, The oxide layer contains P or Si. Alloy powder.

10. The alloy powder according to any one of claims 1 to 9, The composition contains inevitable impurities, and Fe ａ Si ｂ B ｃ P ｄ Cu ｅ C ｆ and satisfying 80≦a≦90, 0≦b≦3, 3≦c≦18, 0≦d≦17, 0≦e≦1.2, and 0≦f≦5. Alloy powder.

11. The alloy powder according to claim 10, 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. Alloy powder.

12. The alloy powder according to claim 10, 20 at % or less of Fe is substituted with at least one element of Co and Ni Alloy powder.

13. The alloy powder according to any one of claims 1 to 12, The crystallinity is 4% or less Alloy powder.

14. The alloy powder according to any one of claims 1 to 13, The dividing mark has a spherical shape. Alloy powder.

15. A nanocrystalline powder obtained by heat treating the alloy powder according to any one of claims 1 to 14, The crystal grain size is 50 nm or less Nanocrystalline powder.

16. A magnetic core using the alloy powder according to any one of claims 1 to 14 or the nanocrystalline powder according to claim 15.

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