JPH0736942B2 - Highly tough and highly flexible metal fibers with unidirectional dendritic structure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high toughness and high flexibility metal fiber having a novel metallographic structure, and more specifically, a primary arm of a dendritic structure along a fiber axis direction. It relates to a metal fiber that has a grown special metal structure, has extremely good toughness, is useful as a structural material such as a composite material, and can be utilized as a magnetic material by taking advantage of structural anisotropy. is there.

[Prior Art] Regarding metal fibers, many researches and proposals have been made, including research on new materials and application development, and the application fields tend to expand more and more.

Various methods as described below are known as methods for producing metal fibers.

A method of drawing a rod-shaped metal material with a die made of cemented carbide or diamond.

In this method, a multi-stage drawing process must be performed to obtain a thin fiber, and an annealing process is required to remove internal strain generated in the wire drawing process. There is also a problem with productivity.

A method of cutting a solid metal material to cut out fine linear objects.

This method is simpler and requires fewer steps than the above method. However, not only the cross-sectional shape of the fiber is not uniform, but notches and defects are likely to occur on the surface, and there is a problem in the homogeneity of the fiber.

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

This method includes a glass coating spinning method, a water stream spinning method, a rotating liquid spinning method and the like, and by these methods, crystalline fibers or amorphous fibers made of various metals or alloys are produced. However, at present, it is considered to be a more effective method than the above method in terms of both performance and productivity of metal fibers.

Under such circumstances, the inventors of the present invention have been researching a method for producing a metal fiber using a melt spinning method, particularly, a spinning submerged spinning method, and as a part of such research, JP-A-62-56393 has been previously mentioned. The invention described in Japanese Patent Publication was developed. This invention obtains a metal fiber having a special structure having a structure in which single crystals having various lengths are continuously connected in a bamboo shape with a grain boundary as a boundary by controlling coagulation conditions and the like in melt spinning. The development of applications in various fields is underway.

[Problems to be Solved by the Invention] Although the inventors of the present invention have since continued research on a method for producing a metal fiber mainly composed of a rotating submerged spinning method and an improvement in physical properties,
Under the circumstances as described above, the present invention has a crystal structure that is different from conventional metal fibers by devising various conditions such as melt spinning conditions, so that the field of application thereof can be further expanded. It is intended to provide a stable metal fiber.

[Means for Solving the Problems] The constitution of the metal fiber according to the present invention is such that the primary arm exhibits a dendrite group texture grown at an angle within 20 degrees with respect to the metal fiber axis. It has the gist.

[Operation] As is well known, the rotating submerged spinning method is that a cooling liquid layer is formed on the inner peripheral surface side of a rotating cylindrical hollow drum by centrifugal force, and melted from a thin nozzle into the cooling liquid layer. This is a method in which the metal is ejected in the form of a fine wire, rapidly solidified, and then wound as it is to the inner peripheral surface side of the hollow drum or another appropriate device, and various metal materials can be made into fine fibrous shapes.

By the way, depending on the type of alloy, the toughness of the metal fibers obtained by the above spinning liquid spinning method varies depending on the fiber diameter, and particularly those with a large diameter are very brittle, and easily bent when bent over 90 degrees or more. May be difficult and lack versatility. Looking at the internal structure of such a conventional metal fiber having poor toughness, two or more crystal grains are always present (in any cross section) in the cross section orthogonal to the fiber axis. It has been confirmed that it has a so-called polycrystalline structure. On the other hand, for example, the diameter
In the case of a thin metal fiber having a diameter of about 130 μm, as described in JP-A-62-56393, the “bamboo knot” -shaped single crystalline portions are arranged at irregular intervals of about 0.1 to 5 mm in the fiber axis direction. The structure has a continuous structure, and the toughness of the portion having the single crystal structure is very good, and it becomes flexible without breaking even when it is closely bent to 180 degrees.

However, even with this metal fiber, the toughness of the "bamboo knot" portion corresponding to the grain boundary is poor, and there is a risk of breaking when the "bamboo knot" portion is bent 180 degrees.

However, as a result of further research after that, when the diameter of the spinning nozzle for spinning in liquid was set to 100 μm or less and the cooling rate when the molten metal solidified was further increased, the dendrites (basic unit A schematic diagram is shown in FIG. 3 (a)), and the texture is such that the groups are arranged side by side. The smaller the spinning nozzle diameter and the smaller the fiber diameter, the more the primary arm of the dendrite and the fiber axis are separated. The angle formed becomes smaller. It was revealed that the smaller the angle, that is, the closer the primary arm is to the fiber axis, the better the flexibility of the metal fiber. The metal fibers having an angle of 20 degrees or less between the primary arm of the dendrite and the fiber axis (see FIGS. 3 (b) and 3 (c)) have the “bamboo knot” shape described in the above publication. It was confirmed that the toughness was even better than that of metal fibers.

When producing metal fibers by the spinning liquid spinning method, by setting the fiber diameter (corresponding to the diameter of the spinning nozzle) to 100 μm or less, the “bamboo knot” -shaped crystal grain boundaries disappear, and It has not been theoretically clarified whether a crystal structure is generated, but the cooling rate in the cooling liquid layer changes due to the difference in the thickness of the molten metal flow during spinning, and the formation and growth of crystals change. Probably because it happened. In any case, the metal filament having such a unidirectional dendritic structure becomes very flexible, and it is possible to perform tight bending, and also the elongation is significantly increased in the tensile test. It is a material that is easy to handle. Moreover, since this metal fiber does not have a "bamboo knot" portion that is a stress concentration portion, it is possible to perform higher-order processing (drawing, rolling, etc.).

Although various kinds of metals can be considered as the metals used in the present invention, Fe is most effective in exhibiting the features of the present invention.
-Si-based alloy, Fe-Al-based alloy, Fe-Si-Al-based alloy,
The iron alloys containing a proper amount of one or more rare earth metals are also preferable. The rare earth metal is particularly preferably selected from the lanthanum series having atomic numbers of 57 to 71, and specifically,
La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, which may be contained alone or in combination of two or more You can also Among the above rare earth metals, Ce is particularly preferable. Further, in practicing the present invention, it is possible to further mix other alloy components depending on the use and required characteristics of the metal fiber.

Next, a method for producing the metal fiber according to the present invention will be described. The basic structure of this method is disclosed in JP-A-55-64948 and JP-A-6-64948.
The spinning submerged spinning method disclosed as 2-56393 is followed. For example, FIGS. 1 and 2 are a schematic front view and a partially cutaway side view illustrating the method, in which the cooling liquid layer 8 is formed on the inner peripheral surface side by rotating the rotating drum 6 at a high speed. And the crucible 1 which is directed toward the liquid surface 9 of the cooling liquid layer 8 or the liquid
The molten metal is jetted from the jet nozzle 2 on the lower surface, and the metal is formed into fibers 4 and rapidly cooled and solidified, and is wound around the inner peripheral wall of the rotary drum 6. In the figure, 3 is a heater for melting metal, 5 is an inert gas for ejecting molten metal, 7 is a motor,
10 indicates belts respectively. And the peripheral velocity of the cooling liquid layer,
If the molten metal jet speed from the jet nozzle 2 is set to be substantially the same as or slightly faster than the jet speed of the molten metal, it is easy to obtain a metal fiber having a uniform cross-sectional size and shape. The cooling liquid used here may be a pure liquid, a solution, an emulsion or the like, but water is most preferable in terms of cost and cooling efficiency. Although the rotating drum may be horizontal or vertical, the surface velocity of the cooling liquid layer in the drum is about 300 to 800 m / min, the angle of penetration of the molten metal into the cooling liquid layer is 40 to 80 °, the jet nozzle 2 and the liquid Distance to surface 9 is 0.5
About 4 mm is suitable for each.

When adopting this rotating submerged spinning method, it should be noted that the diameter of the jet nozzle 2 should be 100 μm or less and the diameter of the spun metal fiber should be 100 μm or less. That is, when the diameter of the jet nozzle 2 is larger than 100 μm, the diameter of the spun metal fiber exceeds 100 μm, and the cooling rate cannot be sufficiently increased, and the primary dendritic structure is not formed. The angle between the arm and the fiber axis exceeds 20 degrees, and satisfactory toughness and flexibility cannot be obtained. On the other hand, 100μ
If a jet nozzle with a small diameter of m or less is used, the diameter will be 100μ.
m or less, the primary arm of the dendritic tissue is in the fiber axis direction
The structure has an angle of 20 degrees or less, and metal fibers having excellent toughness and flexibility can be obtained.

[Example] Example 1 A spin-in-liquid spinning method as shown in Figs.
Iron-based metal fibers with various diameters were produced using 6.5 wt% Si as raw material and various spinning nozzles with different diameters. Water (15 ° C) was used as the cooling liquid. The spinning conditions also change when the diameter of the spinning nozzle changes, but basically, the rotation speed of the drum and the metal are adjusted so that the surface velocity of the water layer in the rotating drum becomes equal to or slightly faster than the jet velocity of the molten metal. By controlling the spouting speed of the molten metal, a diameter of 200
Three kinds of metal fibers of μm, 160 μm and 70 μm were obtained.

Among them, in the fiber having a diameter of 200 μm, a dendritic tissue was observed, but the angle formed by the primary arm and the fiber axis was not uniform, and as a result, it showed a polycrystalline structure and lacked flexibility over the entire length. It was a thing. On the other hand, in the metal fiber with a diameter of 160 μm, there is a part where the primary arm of the dendritic tissue grows at an angle of about 20 degrees with respect to the fiber axis,
This part was flexible and capable of close contact bending, but the flexibility of other parts was insufficient, and for fibers with a diameter of 70 μm, the angle between the primary arm of the dendritic tissue and the fiber axis was 5 degrees or less. It had a uniformly arranged structure, and was capable of closely bending over the entire length of the fiber.

Further, the metal fiber having a diameter of 70 μm had excellent soft magnetic properties, such as a saturation magnetic flux density of 2.0 stella, a coercive force of 0.4 eerted, a relative magnetic permeability of 31,000 and a squareness ratio of 0.8 in a DC magnetization measurement.

Example 2 In the same manner as in Example 1, two kinds of iron-based metal fibers having different diameters (diameter 210 μm and 70 μm) were spun from molten Fe-25 wt% Al. All 210 μm diameter metal fibers are polycrystalline and very brittle over their entire length.
The metal fibers of μm had a texture of unidirectional dendrites over the entire length, and the angle formed between the primary arm and the fiber axis was about 4 °, and close bending was possible at any position.

Example 3 An iron-based metal fiber having a diameter of 220 μm and a diameter of 65 μm was produced in the same manner as in Example 1 using an iron-based metal of Fe-5.2 wt% Al-2.7 wt% Si.

Metal fibers with a diameter of 220 μm are all polycrystalline and very fragile over their entire length, whereas metal fibers with a diameter of 65 μm have a unidirectional dendritic structure over their entire length and their primary arms are The angle formed with the fiber axis was about 3 degrees, and it was extremely flexible and could be bent in close contact.

[Advantages of the Invention] The present invention is configured as described above, and while maintaining the original excellent properties of the metal fiber, it is possible to modify the fragility to give the property of being extremely flexible and easy to bend. It was possible to significantly improve the sex. Moreover, since the growth direction of dendrites is oriented in one direction and has excellent magnetic properties, it can be easily applied to, for example, magnetic sensors and magnetic cores, and it is expected that the field of application will be greatly expanded.

[Brief description of drawings]

FIGS. 1 and 2 are views for explaining the spinning method in a rotating liquid, FIG. 1 is a schematic front view, and FIG. 2 is a partial cross-sectional side view. Further, FIG. 3 (a) is a schematic diagram of the basic unit of dendrites, and (b) and (c) show a unidirectional dendritic structure in which the angle between the primary arm and the fiber axis is 20 degrees or less. It is a schematic diagram. 1: crucible 2: ejection nozzle 3: heater, 4: fiber 5: inert gas, 6: rotating drum 7: motor, 8: cooling liquid layer 9: cooling liquid level, 10: belt

Claims (6)

[Claims] 1. The primary arm exhibits a dendrite group texture grown at an angle within 20 degrees with respect to the metal fiber axis and has a diameter of
Highly tough and highly flexible metal fibers having a unidirectional dendritic structure characterized by having a size of 100 μm or less. 2. The metal fiber according to claim 1, which has a circular cross section. 3. The metal is Fe-Si alloy, Fe-Al alloy, Fe.
The metal fiber according to claim 1 or 2, which is selected from the group consisting of -Si-Al alloys. 4. The metal is Fe-Si-rare earth metal alloy, Fe-Al.
Claim 1 which is selected from the group consisting of -rare earth metal alloys and Fe-Si-Al-rare earth metal alloys.
Item or the metal fiber according to item 2. 5. The metal fiber according to claim 4, wherein the rare earth metal is one or more metals selected from the lanthanum series having atomic numbers 57 to 71. 6. A method according to claim 5, wherein the rare earth metal is Ce.
The metal fiber according to item.