JPH01150445A - Single crystal quality metallic fiber and production thereof - Google Patents

Abstract

PURPOSE:To improve ductility and flexibility of metallic fiber by forming cooling liquid layer in rotating cylindrical drum, injecting molten metal from a nozzle having the specific diameter and forming the single crystal quality metallic fiber having the prescribed diameter and fiber length. CONSTITUTION:The injecting nozzle 2 having <=100mum diameter is arranged in the rotating drum 6 in a molten spinning apparatus of rotating liquid spinning method, etc., and the molten metal composing of Fe-Si based alloy, etc., is injected toward the cooling liquid layer 8. Then, the molten metal is rapidly cooled to form fine fiber 4 having <=100mum diameter and primary arm of the dendritic structure forms the dendritic structure at the angle within 20 deg. to the axial direction. Successively, heat treatment is executed to it, to form single crystal quality having >=40mm fiber length. By this method, as the structure having all the same angle of the primary arm at <=20 deg. is formed, the ductility and flexibility of the metallic fiber are improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The fibers of the present invention have extremely fine fiber diameters, are monocrystalline throughout the entire length, and have extremely good toughness, making them useful as constituent materials for composite materials. In addition, it relates to metal fibers that are expected to function as magnetic materials and their manufacturing methods.

[Prior Art] A lot of research and proposals have been made regarding metal fibers, including research into new materials and application development, and there is a tendency for the fields of application to further expand.

Various methods as shown below are known as methods for manufacturing metal fibers.

■A method of drawing a rod-shaped metal material into a wire using a die made of cemented carbide or diamond.

This method requires multiple stages of wire drawing to obtain small-diameter fibers, and an annealing step is required to remove the internal strain that occurs during the wire drawing process. There is also a problem with productivity.

■A method of cutting solid metal materials into thin wires.

This method is simpler and requires fewer steps than method (2) above. However, not only the cross-sectional shape of the fibers is non-uniform, but also notch defects etc. are easily formed on the surface, and there are problems with the homogeneity of the fibers.

■A melt spinning method in which molten metal is extruded through a small diameter nozzle and cooled and solidified.

These methods include glass-covered spinning, underwater spinning, rotating liquid spinning, etc., and these methods produce crystalline fibers and amorphous fibers made of various metals or alloys. This method is currently considered to be more advantageous than methods (1) and (2) above in terms of both metal fiber performance and productivity.

Under these circumstances, the inventors of the present invention have been conducting research for some time on a method for manufacturing metal fibers using the melt spinning method, particularly the spinning method in a rotating liquid. The invention described in the publication was developed.

This invention obtains metal fibers with a special structure in which single crystals of various lengths are continuously connected in a bamboo-like manner with grain boundaries as boundaries, by controlling the solidification conditions during melt spinning. The development of applications in various fields is progressing.

[Problems to be Solved by the Invention] Since then, the present inventors have continued to conduct research on the manufacturing method of metal fibers, mainly using spinning in a rotating liquid, and on improving the physical properties. Alternatively, by variously devising the subsequent heat treatment conditions, etc., we aim to provide a metal fiber and its manufacturing method that has a crystal structure different from that of conventional metal fibers and can further expand its field of use. It is something to do.

[Means for Solving the Problems] The structure of the metal fiber according to the present invention is characterized in that the fiber diameter is 100 μm or less, the fiber length is 40 mm or more, and the metal fiber is single crystal over the entire length. be. 15 such single-crystalline metal fibers with a diameter of 100 mm are placed in a cooling liquid layer formed along the inner peripheral surface of a rotating cylindrical drum.
It can be obtained by ejecting molten metal through a micrometer or less nozzle and heat-treating the rapidly solidified metal fiber to homogenize it.

The term "single crystal" as used in the present invention does not mean an ideal single crystal grown from a single nucleus, without grain boundaries, and consisting of a space lattice in which molecules and atoms are regularly arranged.
A crystal that contains defects such as dislocations and subgrain boundaries. Further, the term "sub-grain boundary" as used herein means a boundary where crystal orientations differ by an angle of several orders of magnitude or less.

[Operations] As is well known, the spinning method in a rotating liquid is a method in which a cooling liquid layer is formed on the inner peripheral surface of a rotating cylindrical hollow drum by centrifugal force, and melting is carried out into the cooling liquid layer from a small diameter nozzle. This is a method in which metal is ejected in a thin wire, rapidly cooled and solidified, and then wound up as it is on the inner peripheral surface of a hollow drum or other suitable device, and various metal materials can be made into thin fibers.

By the way, depending on the type of alloy, the toughness of the metal fiber obtained by the above-mentioned spinning liquid spinning method may be 1ai! l! It varies depending on the diameter, and in particular, large diameter ones are very brittle and easily break when bent more than about 90 degrees, making them difficult to handle and sometimes lacking in versatility. Looking at the internal structure of conventional metal fibers with poor toughness, we find that there are always two or more crystal grains in a cross section perpendicular to the fiber axis (no matter which cross section you look at). It has been confirmed that it has a so-called polycrystalline structure. On the other hand, for example, in the case of a thin metal fiber with a diameter of about 130 μm, as described in Japanese Patent Application Laid-open No. 62-56393, there is a "bamboo knot gap".
It has a structure in which single-crystalline parts are joined at irregular intervals of about 0.1 to 5 mm in the fiber axis direction, and the toughness of the part with the single-crystal structure is very good, and it is possible to form a tight target at 180 degrees. It is flexible and will not break even if it is bent.

However, even with this gold am fiber, the toughness and flexibility of the "bamboo knots" corresponding to grain boundaries are poor, and the "bamboo knots"
If the part is bent 180 degrees, there is a risk of breakage.

Therefore, we thought that if we could eliminate these "bamboo knots" and make the material monocrystalline throughout its length, we would be able to further improve its toughness and flexibility, and proceeded with our research. As a result, ■If the diameter of the rotating submerged spinning nozzle is set to 100 μm or less and the cooling rate when the molten metal solidifies is further increased, a texture will be obtained in which dendrite groups are arranged in the fiber axis direction. (2) The smaller the spinning nozzle diameter and the smaller the fiber diameter, the smaller the angle between the primary arm of the dendrite and the fiber axis; (2) The smaller the angle between the primary arm of the dendrite and the fiber axis; Although the aligned metal Ml fibers are very homogeneous over the entire length, the cross section of the fibers does not consist of a single dendrite, but two or more dendrites are observed; However, when the metal fiber of the above (■) is heat-treated, the mi
Although some dislocations and subgrain boundaries were observed in the cross section of point a, clear grain boundaries were no longer observed, and it became clear that the cross section was single-crystalline over the entire length.

As a result of repeated research for the purpose of further quantitatively understanding the findings from ■ to ■ above, we found that the diameter of the spinning nozzle during spinning in a rotating liquid was 100 μm.
When set to m or less (more preferably 90 μm or less),
The angle between the primary arm of the dendrite and the fiber axis is approximately 2
Uniform dendritic structure below 0 degrees (spinning nozzle diameter 9
When the thickness is 0 μm or less, the temperature is about 10 degrees or less), and it is clear that when this is heat-treated, it becomes a single crystal over the entire length. Furthermore, the heat-treated fibers exhibit superior flexibility compared to those before heat treatment, and do not break even when they are closely targeted at 180 degrees. Moreover, since this metal fiber is single-crystalline, the crystals have a specific orientation in the fiber axis direction, and the magnetic properties are also very excellent.

Note that whiskers are known as single-crystalline fibrous materials made of metal. The expression "whisker" refers to its form and is not clearly defined, but the most common whisker is a whisker with a diameter of several μm obtained by vapor phase growth, etc.
m ~ several hundred μm 1 length of several mm ~ several tens of mm, short fibers made of highly perfect needle-like crystals, and as in the present invention, they contain defects such as dislocations and subgrain boundaries. It is distinguished from single-crystalline long fibers (usually having an aspect ratio of 400 or more).

There are various metals that can be used to manufacture the fibers of the present invention, but among them, the metals that most effectively exhibit the characteristics of the present invention are Fe-5L alloy, Fe-Al alloy, and Fe-Al alloy.
Preferred examples include 5L-Al alloys, which contain an appropriate amount of one or more rare earth metals in these iron alloys. Particularly preferred rare earth metals are those selected from the lanthanum series having an atomic number of 57 to 71, specifically La and Ce.

Pr, Nd, Pm, Sm, Eu, Gd, Tb.

These are Dy, Ho, Er, Tm, Yb, and Lu, and these can be contained alone or in combination of two or more types. Among the above rare earth metals, Ce is particularly preferred. Further, in carrying out the present invention, it is also possible to further mix other alloy components depending on the use and required characteristics of the metal fiber.

Next, a method for manufacturing metal fibers according to the present invention will be explained. In carrying out this method, Japanese Patent Application Laid-Open No. 55-64948
The method of spinning in a rotating liquid disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 62-56393 is utilized. for example'! Figure J1.2 is a schematic front view and a partially cutaway side view illustrating the spinning method in a rotating liquid, in which a cooling liquid layer 8 is formed on the inner peripheral surface of the rotating drum 6 by rotating it at high speed. Then, the molten metal is ejected from the ejection nozzle 2 on the lower surface of the crucible 1 toward the liquid surface 9 of the cooling liquid layer 8 or into the liquid, and the metal is rapidly solidified into fibers 4 and wound around the inner circumferential wall of the rotating drum 6. To go. In the figure, 3 is a heater for melting metal, 5 is an inert gas for blowing out molten metal, 7 is a motor, and 10 is a belt. Then, the circumferential velocity of the cooling liquid layer is determined by the jet nozzle 2.
If the speed is set to be substantially the same as or slightly faster than the molten metal jetting speed, it is easy to obtain metal fibers with uniform cross-sectional dimensions and shapes. Further, the cooling liquid used here may be a pure liquid, a solution, an emulsion, etc., but in view of cost and cooling efficiency, water is most preferable. The rotating drum may be oriented horizontally or vertically, but the surface velocity of the cooling liquid layer within the drum is 300
Approximately 800 m/min, the angle of entry of the molten metal into the cooling liquid layer is 40 to 80 degrees, and the distance between the jet nozzle 2 and the liquid surface 9 is approximately 0.5 to 4 mm, respectively.

When employing this rotating liquid spinning method, special attention must be paid to the fact that the diameter of the jet nozzle 2 must be 100 μm or less, and the diameter of the spun metal fiber must be 100 μm or less. In other words, if the diameter of the jet nozzle 2 is larger than 1100A, the diameter of the spun metal fiber will exceed 1100A, making it impossible to sufficiently increase the cooling rate, and the primary dendritic structure The angle between the arm and the fiber axis is less than 20 degrees, which does not form a uniform dendritic structure, and even after subsequent heat treatment, it is not possible to form a single crystal over the entire length, resulting in unsatisfactory toughness and flexibility. I can't get anything sexual. On the other hand, if a jet nozzle with a small diameter of 100 μm or less is used, a structure with a diameter of 100 μm or less and a structure in which the primary arms of the dendritic structure are uniformly aligned at an angle of 20 degrees or less with respect to the fiber axis direction is created, and then the following By subjecting the metal fiber to various heat treatments, it can be made into a single crystalline material over its entire length, resulting in a metal fiber with excellent toughness and flexibility.

The heat treatment should be carried out in an appropriate window depending on the type of metal so that dendrites during rapid solidification can be substantially eliminated and new single crystals can be generated and homogenized. As a general standard, in order to homogenize the metal fibers in a short time without melting,
] and above the melting point of the alloy. Further, the heat treatment is preferably performed in a vacuum or in an inert gas atmosphere such as argon in order to prevent oxidation of the metal fibers.

[Example] Example 1 The rotating liquid spinning method as shown in Fig. 1.2 was adopted, and F
Using e-6.5wt% Si alloy as a raw material, iron alloy metal fibers with various diameters were produced using various spinning nozzles with different diameters. Water (15°C) was used as the cooling liquid. If the diameter of the spinning nozzle changes, the spinning conditions will also change, but basically the rotational speed of the drum and the metal should be adjusted so that the surface speed of the water layer in the rotating drum is equal to or slightly faster than the jet flow speed of the molten metal. By controlling the ejection speed of the molten metal, three types of metal fibers with diameters of 150 μm, 90 μm, and 70 μm were obtained, and then heat-treated at 1100°C for 2 hours in a vacuum atmosphere (5X 10-'Torr or less) using an electric furnace. .

Among these, the fibers with a diameter of 150 μm had a dendritic structure observed before heat treatment, but the angle between the second arm and the fiber axis was large, and even after heat treatment, the fibers exhibited a polycrystalline structure over the entire length. It lacked flexibility. On the other hand, in a metal fiber with a diameter of 90 μm, some arms of the dendritic structure grow uniformly at an angle of about 7 degrees to the fiber axis, and although subgrain boundaries can be seen when the structure is observed after heat treatment. No clear grain boundaries were observed, and the specimen was flexible over its entire length and could be bent in close contact. In addition, fibers with a diameter of 70 μm have a structure in which the angle between some arms of the dendritic structure and the fiber axis during heat treatment is uniformly equal to about 4 degrees or less, and tight bending occurs over the entire length of the fiber. It was possible.

In addition, for metal fibers with a diameter of 70 μm, the fiber axis direction and the orthogonal direction were wet-polished, and crystallographic microbits of approximately 10 to 204 m in length were moderately distributed on the sample surface using the etch bit method. When the shape and orientation with respect to the fiber axis direction were observed, it was found that the shape of the etch bit in a cross section perpendicular to the fiber axis direction was almost the same, and the orientation was also the same.

In addition, the shape and orientation of the etch bits in the cross section in the fiber axis direction were all almost the same, but in some places they were continuously inclined with respect to the fiber axis. From these facts, it is clear that although this metal fiber has sub-grain boundaries and contains defects, it is substantially single-crystalline. The metal fiber with a diameter of 70 μm has a saturation magnetic flux density of 2.4 Tesla, a coercive force of 0.14 Oersteds, a relative magnetic permeability of 121,000, and a squareness ratio of 0.98 in DC magnetization measurements.
It had excellent soft magnetic properties.

Example 2 In the same manner as in Example 1, two kinds of iron-based metal fibers with different diameters (160 μm in diameter and 7
0 μm) was spun in a vacuum atmosphere (3 x 10 ””Tor
The mixture was homogenized by heat treatment at 1,150° C. for 2 hours under (below). Clear grain boundaries were observed in the metal fibers with a diameter of 160 μm, but in the metal fibers with a diameter of 70 μm, although the presence of sub-grain boundaries was partially observed, there were no clear grain boundaries, and the metal fibers were essentially single. It was crystalline.

Example 3 Fe-5,2wt%A 1-2.7wt%St iron-based metal was used, and the diameter was 200μ in the same manner as in Example 1.
m, 155 μm and 65 μm iron-based metal fibers were prepared,
After that, vacuum atmosphere (2X10-'Torr) 1100
The mixture was homogenized by heat treatment at ℃ for 10 hours.

As a result, the presence of grain boundaries was observed in both metal fibers with diameters of 220 μm and 155 μm, but
Although subgrain boundaries were observed in the metal fiber of No. m, clear grain boundaries did not exist, and the metal fiber was single crystalline.

[Effects of the Invention] The present invention is configured as described above, and while maintaining the original excellent properties of metal fibers, it is possible to modify the brittleness and give extremely flexible and bendable properties, and the handling thereof can be improved. I was able to significantly improve my sexuality. Moreover, since it is single crystal and has excellent magnetic properties, it can be easily applied to magnetic sensors and magnetic cores, for example, and is expected to expand its application fields significantly.

[Brief explanation of the drawing]

1.2 are diagrams for explaining the spinning method in a rotating liquid, FIG. 1 is a schematic front view, and FIG. 2 is a partially sectional side view. 1: Crucible 2: Spout nozzle 3: Heater
4: Fiber 5: Inert gas 6: Rotating drum 7: Motor
8: Cooling liquid layer 9: Cooling liquid surface 10:
Belt Figure 1 Figure 2

Claims (11)

[Claims] (1) A single-crystalline metal fiber having a fiber diameter of 100 μm or less, a fiber length of 40 mm or more, and being single-crystalline over its entire length. (2) The metal fiber according to claim 1, which has an aspect ratio of 400 or more. (3) The metal is a Fe-Si alloy, a Fe-Al alloy,
The metal fiber according to claim 1 or 2, which is selected from the group consisting of Fe-Si-Al alloys. (4) Metal is Fe-Si-rare earth metal alloy, Fe-A
The metal fiber according to claim 1 or 2, which is selected from the group consisting of l-rare earth metal alloy and Fe-Si-Al rare earth metal alloy. (5) The metal fiber according to claim 4, wherein the rare earth metal is one or more metals selected from the lanthanum series having an atomic number of 57 to 71. (6) The metal fiber according to claim 5, wherein the rare earth metal is Ce. (7) Molten metal is jetted through a nozzle with a diameter of 100 μm or less into a cooling liquid layer formed along the inner peripheral surface of a rotating cylindrical drum, and the rapidly solidified wire is heat-treated to homogenize it. A method for producing a single-crystalline metal fiber, characterized in that the metal fiber has a diameter of 100 μm or more, a fiber length of 40 mm or more, and is single-crystalline over its entire length. (8) The metal is Fe-Si alloy, Fe-Al alloy, F
The manufacturing method according to claim 7, wherein the material is selected from the group consisting of e-Si-Al alloys. (9) The metal is Fe-Si-rare earth metal alloy, Fe-A
8. The manufacturing method according to claim 7, wherein the material is selected from the group consisting of l-rare earth metal alloy and Fe-Si-Al-rare earth metal alloy. (10) The manufacturing method according to claim 9, wherein the rare earth metal is one or more metals selected from the lanthanum series having an atomic number of 57 to 71. (11) Claim 10 in which the rare earth metal is Ce.
The manufacturing method described in section.