COOLING ROLL AND MANUFACTURING APPARATUS OF AMORPHOUS ALLOY STRIP

Abstract

A cooling roll includes flow channels piercing a side surface of the cooling roll in a rotation-axis direction. The flow channels are arranged at uniform spacing on two or more concentric circles having a rotation axis of the roll as a center. A manufacturing apparatus of an amorphous alloy strip includes the cooling roll. Thereby, the amorphous alloy strip having a large thickness can be manufactured in industrial scale.

Claims

1. A cooling roll for amorphous alloy strip manufacturing, the cooling roll comprising flow channels piercing a side surface of the cooling roll in a rotation-axis direction, the flow channels being arranged at uniform spacing on two or more concentric circles having a rotation axis of the roll as a center.

2. The cooling roll according to claim 1, wherein each of the flow channels has a diameter of 20 to 50 mm.

3. A manufacturing apparatus of an amorphous alloy strip, comprising the cooling roll according to claim 2.

4. A manufacturing apparatus of an amorphous alloy strip, comprising the cooling roll according to claim 1.

5. A method for manufacturing an amorphous alloy strip, comprising contacting a melt to an outer circumferential surface of a cooling roll rotating, the cooling roll including flow channels piercing the cooling roll in a rotation-axis direction of the cooling roll, the flow channels being arranged at uniform spacing on two or more concentric circles, controlling water amounts flowing through the flow channels independently for each of the concentric circles.

6. The method according to claim 5, wherein each of the flow channels has a diameter of 20 to 50 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a perspective view illustrating a manufacturing apparatus of an amorphous alloy strip according to a first embodiment;

[0021] FIG. 2A is a front view illustrating the manufacturing apparatus according to the first embodiment; and FIG. 2B is a side view illustrating the manufacturing apparatus according to the first embodiment;

[0022] FIG. 3A is a schematic view of the apparatus according to the modification of the first embodiment when viewed from the front of the cooling roll; and FIG. 3B is a drawing of the through-hole inlet provided with a protrusion having a brim-like configuration when viewed from the side surface of the cooling roll;

[0023] FIGS. 4A to 4C are schematic views illustrating the cooling water channel structure of the cooling roll of the second embodiment. FIG. 4A is a schematic front view illustrating the manufacturing apparatus of the amorphous alloy strip of the second embodiment and shows one cooling water channel system. FIG. 4B is a schematic side view illustrating the cooling roll and the vicinity; and FIG. 4C is a front view showing another cooling water channel system of the cooling roll;

[0024] FIG. 5 is a side view illustrating the manufacturing apparatus of the amorphous alloy strip according to the modification of the second embodiment;

[0025] FIG. 6 is a side view illustrating the state (the puddle) at the nozzle tip where the alloy melt contacts the cooling roll of FIG. 1. This is a conceptual view showing the puddle vicinity and the double-slit nozzle; and

[0026] FIG. 7 is a front view of an apparatus illustrating a twin cooling roll method used when manufacturing an amorphous alloy strip having a large thickness that cannot be achieved by the single roll.

DETAILED DESCRIPTION

[0027] Embodiments of the invention will now be described with reference to the drawings.

[0028] First, a first embodiment will be described.

[0029] FIG. 1 is a perspective view illustrating a manufacturing apparatus of an amorphous alloy strip according to the embodiment; FIG. 2A is a front view illustrating a cooling roll and a cooling water channel and FIG. 2B is a side view of the cooling roll of the manufacturing apparatus according to the embodiment.

[0030] In the manufacturing apparatus 1 of the amorphous alloy strip according to the embodiment as shown in FIG. 1, a cooling roll 11, a cooling water supply unit 12 that causes cooling water to flow through inside the cooling roll 11, a drive unit 13 (including a water drain unit) that causes the cooling roll 11 to rotate, and a melt supply unit 17 that supplies the melt to an outer circumferential surface 11a of the cooling roll 11 are provided. In the melt supply unit 17, a melting furnace 14 that melts an alloy, a crucible 15 that holds the melt A, and a nozzle 16 that is mounted to the bottom surface of the crucible 15 and dispenses the melt inside the crucible 15 downward are provided. The nozzle 16 is disposed above the cooling roll 11 to be separated from the outer circumferential surface 11a of the cooling roll 11 by a slight gap. The manufacturing apparatus 1 is an apparatus for manufacturing the amorphous alloy strip S. Here, amorphous alloy is 50% amorphous or more by volume fraction and includes, as the remainder, a multi-phase alloy that has an amorphous parent phase and has nanometer (nm) sized microcrystals dispersed and precipitated. Also, for a material of which 50% or more is crystalline, the manufacturing apparatus and the manufacturing method of the embodiment can be used to control the crystal grains. Specifically, the embodiment is effective for controlling the crystal grain size of a permanent magnet including neodymium-boron.

[0031] Operations of the manufacturing apparatus of the amorphous alloy strip configured as described above, i.e., the method for manufacturing the amorphous alloy strip according to the embodiment, will now be described.

[0032] First, by the melting furnace 14, an alloy that is used as the source material of the amorphous alloy strip S is melted; and the melt A is poured into the crucible 15. The melt A includes a total of 70 atomic % to 95 atomic % of at least one type of Fe, Co, or Ni and includes, other than the three types of ferromagnetic metal elements, 5 atomic % to 30 atomic % of at least one type of element of the semimetal B, Si, C, or P. Further, at least one type of Cr, V, Nb, Mo, W, Ta, Cu, or Sn in the range of 0.01 atomic % to 5 atomic % may be added to a portion of the ferromagnetic elements recited above. It goes without saying that, excluding inevitable impurities, the sum total of the content ratio of the elemental components must be 100%.

[0033] Among the added elements recited above, Cu is an essential element when making a so-called nanocrystalline material made of fine crystal grains in the range of several nanometers to 100 nanometers by crystallizing by annealing after making the amorphous foil. Also, other than a nanocrystalline material, the solitary addition of Cu in the (Fe, Co, Ni)(B, Si, C, P) alloy in the range of 0.1 atomic % to 2.5 atomic % to realize the subdivision of the magnetic domains by partially promoting crystallization to improve the high frequency magnetic properties is within the scope of the invention.

[0034] Sn is effective when manufacturing an amorphous strip of an Fe-based alloy including a high content of Fe because Sn acts to suppress the crystallization by segregating in a thin layer of the surface of the foil. Although surface crystallization by annealing occurs easily and the magnetic properties such as the iron loss, the permeability, etc., degrade drastically for an alloy containing 82 atomic % or more of Fe, if 0.1 mass % to 1 mass % of Sn is included, the crystallization does not occur even after the annealing; and the original excellent soft magnetic properties are maintained. Further, a trace addition of S (sulfur) also acts similarly to Sn. An added amount of S in the range of 0.003 to 0.5 mass % is favorable.

[0035] The description of the function of the manufacturing apparatus 1 of the embodiment will now be continued. The drive unit (also used as the water drain unit) 13 causes the cooling roll 11 to rotate while the cooling water supply unit 12 causes cooling water W to flow through a flowing water path 21 inside the cooling roll 11. In this state, the melt A of the alloy poured into the crucible 15 from the melting furnace 14 is dispensed toward the outer circumferential surface 11a of the cooling roll 11 from the nozzle 16.

[0036] At this time, the melt A forms a puddle between the nozzle 16 and the outer circumferential surface 11a of the cooling roll 11. By the rotating cooling roll 11, the puddle that is cooled by the cooling roll 11 becomes a high viscosity supercooled melt at the vicinity contacting the outer circumferential surface 11a, is extracted in the rotation direction of the roll and quenched by the cooling roll 11, and is coagulated while having the supercooled melt structure. Thereby, the amorphous alloy strip S that has a strip configuration is formed. After the amorphous alloy strip S moves with the outer circumferential surface 11a of the cooling roll 11 to a prescribed position, the amorphous alloy strip S is guided in a direction away from the cooling roll 11 and is taken up. On the other hand, the heat that is conducted to the cooling roll 11 from the melt A moves to the cooling water flowing through the cooling roll interior and subsequently is dissipated outside the cooling roll 11 by the cooling water W flowing through the flowing water path 21.

[0037] The amorphous alloy strip manufacturing apparatus of the embodiment will now be described more specifically. FIG. 2A shows one embodiment of the invention. Through-holes 21a, 21b, and 21c that pierce the side surface of the cooling roll 11 are formed in the cooling roll 11. The through-holes are provided at uniform spacing on multiple concentric circles having the roll rotation axis shown in FIG. 2B as a center C. The side view of the cooling roll 11 of FIG. 2B illustrates the state in which the through-holes are arranged at uniform spacing in three concentric circles. On the same concentric circle, the diameters of the through-holes are the same size.

[0038] The side surfaces of the cooling roll 11 are covered respectively with covers 23a and 23b at both sides. The covers perform the role of supplying or receiving the cooling water to or from the through-holes without allowing the cooling water to escape to the outside. Although an example is shown in FIGS. 2A and 2B in which the cooling water is supplied from the water supply side, and the cooling water that passes through the through-holes is caused to flow to the opposite side, it is also possible for the main flow channel to have a double pipe structure as in FIG. 3A and for the water to pass through the roll central portion of a main pipe 24, subsequently strike the cover 23b mounted on the opposite face of the cooling water supply side, subsequently pass through the through-holes from the backside, and subsequently pass through the double pipe and be drained. In the latter, air does not remain easily; and the water easily flows uniformly through the through-holes.

[0039] As a modification of the first embodiment, by providing protrusions 26 having semicircular brim (eave) configurations such as that of FIG. 3B at the end portions of the through-hole inlets of the surface on the side opposite to the water supply side in FIG. 3A (the side distal to the rotation axis), the flow of the water becomes smooth; and it is easy to increase the uniformity of the water amount flowing through the through-holes. The brims (the eaves) are unnecessary on the outlet side of the through-holes. However, the brims may be provided on the outlet side as well if balance is difficult to achieve when the roll rotates.

[0040] In FIGS. 2A to 3B, it is convenient to provide valves 27 in the covers 23 to release the air. There are cases where the air may remain in the cooling flow channels. The remaining air hinders the uniformity of the cooling water passing through the through-holes and reduces the cooling efficiency of the roll. Prior to starting the casting, the cooling water is caused to flow; the valves that are provided in the cover (and may be multiply provided in one cover) are opened while slowly rotating the roll; the air is released; and the valves are closed. By repeating the opening and closing of the valves while slowly rotating, the air that remains in the flow channels of the roll can limitlessly approach zero.

[0041] A second embodiment will now be described.

[0042] FIGS. 4A to 4C show an example in which the mutually-adjacent through-holes on the concentric circles in FIG. 2B illustrating the arrangement of the through-holes piercing the side surface of the cooling roll shown in the first embodiment are connected by U-shaped pipes made of a metal. FIG. 4A is a front view of the cooling roll illustrating the second embodiment; and 4B is a side view of the cooling roll. Also, FIG. 4C is a drawing showing the flow channels of the cooling water provided on concentric circles proximal to the outermost outer circumference of the roll when viewed from the front of the apparatus. FIG. 4A shows the cooling water channels provided on the second concentric circle from the roll outer circumference.

[0043] In FIGS. 4A to 4C, 62a, 62b, and 62c show, in order when viewed from the roll side surface, the flow channels of the cooling water most proximal to the outer circumference, the flow channels on the second concentric circle from the outer circumference, and the flow channels on the third concentric circle from the outer circumference.

[0044] FIGS. 4A to 4C illustrating the second embodiment show the mutually-adjacent through-holes on a concentric circle being connected by U-shaped pipes 64. Thereby, the through-holes that are on the same concentric circle form one flow channel branched from the main pipe flow channel 21. Because FIGS. 4A to 4C show an example of three concentric circles, the three flow channels 21a, 21b, and 21c exist. The end portion of each is coupled to a rotating flow branching device rotary joint 63 provided along the rotation axis of the roll. Thereby, even when the roll rotates, the branched flow channels are connected to the main pipe (not illustrated) of the water supply and the water drain aligned with the rotation axis.

[0045] In the second embodiment, a flow rate adjustment valve 65 is provided in each of the flow channels 62a, 62b, and 62c branched from the main flow channel. By having the flow rate adjustment valve in each flow channel, the optimal flow rate distribution can be provided according to the width and thickness of the sheet to be cast. For example, in the case where the width and the thickness of a sheet are relatively small, it is sufficient to supply the cooling water with particular emphasis on the flow channel most proximal to the roll outer circumferential surface. As the thickness and the width of the sheet become larger, the water supply distribution for the flow channels on the second and third concentric circles also are increased. Thereby, even in the case where the thickness and the width of a sheet become larger, insufficient cooling capacity does not occur.

[0046] More specifically, when manufacturing an amorphous alloy strip having a plate thickness of 30 m, it is sufficient for 90% or more of the cooling water to be supplied with particular emphasis on the flow channel most proximal to the roll outer circumference. As the thickness of the foil increases, the manufacture of an amorphous strip having thicknesses of 50 m, 75 m, and 100 m is possible by increasing the flow rate of the cooling water flowing in the second and third flow channels. Substantially 100% of the heat that cannot be absorbed by the first flow channel is absorbed by the second and third flow channels. The portion that surrounds the cooling flow channels of the roll has no thermal resistance portions because the portion is one body and is not multiple rings or sleeves connected mechanically by shrink-fitting, etc.; therefore, the flow of the heat can utilize the original high thermal conductivity of the Cu alloy.

[0047] A modification of the second embodiment will now be described.

[0048] FIG. 5 is a side view illustrating a cooling roll of the modification. For convenience in FIG. 5, through-holes 67 (referring to FIG. 4A) and the U-shaped pipes 64 (referring to FIG. 4A) are not illustrated; and the through-holes 21a to 21c which are the flowing water paths are shown by broken lines.

[0049] As shown in FIG. 5, in the cooling roll 61a of the modification, the flowing water path of each level is divided into three. Thereby, compared to the second embodiment described above, the number of pipes (flow channels) coming together at the rotary joint increases (3 times in the illustrated example); the temperature increase of the cooling water can be suppressed; and it is possible to increase the heat dissipation capacity of the cooling roll more effectively. This is because the pressure loss of the cooling water channels decreases.

[0050] In the manufacturing apparatus of the amorphous alloy strip of the embodiment in which the side surface through-holes are distributed, the heat dissipation effect is improved by providing an apparatus that cools the cooling water partway through the water supply path.

[0051] The diameter and width of the cooling roll used in the embodiment will now be described. These are dependent on the strength of the support mechanism such as the roll rotation axis, the bearings, etc., that support the weight of the roll. If the diameter is too large, the cooling power is improved; but the load of the support mechanism becomes large. Also, if the diameter is too small, the number of branches of the flow channel is insufficient; and the cooling power is insufficient. The diameter should be determined according to the desired thickness of a strip. For example, a diameter of 40 to 60 cm is sufficient for a sheet thickness of 30 to 60 m; and a diameter of 60 to 80 cm is appropriate for a thickness of 60 to 90 m. Similarly 80 to 100 cm is favorable for 90 to 110 m.

[0052] For the width of the cooling roll as well, the cooling capacity increases as the width widens. However, compared to a conventional one-stage cooling roll, the effect of widening the width is small. In the case of one-stage cooling, by setting the wall thickness of the roll (the distance between the cooling water channels and the roll surface) to be large, the heat flows two-dimensionally and is conducted to the cooling water in a wide area. However, in the multistage cooling water channels (the water paths arranged on two or more concentric circles) proposed in the embodiment, the effect of widening the width of the roll is limited because much of the heat amount flows one-dimensionally (the temperature gradient is large in the radial direction of the roll). To put it strongly, it is sufficient for the width of the roll to somewhat exceed the width of the sheet.

[0053] The size of the through-hole will now be described. Basically, it is sufficient for the total surface area of the through-holes to be such that all of the heat moved from the melt to the cooling roll is sufficiently absorbed by the cooling water. The details are described below. The ease of making the holes, the processing cost, etc., are important points for the size of the through-hole. Also, the pressure that causes the cooling water to flow through must be in an appropriate range. Considering these points, it is favorable for the diameter of the through-hole to be 20 to 50 mm.

[0054] The nozzle (the opening for dispensing the alloy melt onto the cooling roll) used in the embodiment basically is a multi-slit nozzle. An example of a double nozzle is shown in FIG. 6. Conventionally, generally, a single-slit nozzle has been used; but the thickness of the foil remains at a constant value and cannot exceed the constant value even if the width of the nozzle (the dimension of the rectangular opening measured in the roll movement direction) is set to be large. According to experiments of the inventors and calculations based on the experiments, it was ascertained that the thickness of the foil is dependent on the heat transfer coefficients of the melt and the cooling roll. It is favorable for the widths of the double nozzle each to be in the range of 0.2 to 0.8 mm. Also, because the width of the bridge can be large if the slit width on the upstream side is set to be large, this is advantageous from the perspective of the anti-wear properties and the strength of the bridge portion. Because the sheet thickness becomes thicker according to the multiplicity of the nozzle, it is sufficient to use a triple nozzle for a thickness of 60 to 80 m, and a quadruple or quintuple nozzle for 80 to 110 m. It is confirmed that an alloy sheet in the amorphous state can be manufactured up to at least quintuple.

[0055] In other words, the surface temperature of the cooling roll in the initial casting is low. The Cu or Cu alloy roll that is used due to high thermal conductivity has poor affinity with Fe-based alloys. As shown by the equilibrium diagram of CuFe alloys, the proportion that melts together is slight at low temperatures (including room temperature). Because of the mutual repulsion, the heat that is conducted by lattice vibrations also is not conducted easily. The heat transfer coefficient is low. If the heat transfer coefficient is low, coagulation does not occur no matter how much of the melt is supplied. In other words, the plate thickness does not become thick. The excessively-supplied melt merely becomes beads and scatters at the periphery. A stable puddle (the melt pool maintained between the nozzle and the roll) is not formed.

[0056] It is necessary to increase the roll temperature to increase the heat transfer coefficient. Therefore, the dispensing pressure is set to be low in the initial casting; and an amount of the melt that is commensurate with the heat transfer coefficient is supplied. Then, the puddle is stabilized; all of the heat that is emitted in the coagulation or high viscosity supercooled-liquification is absorbed by the roll; and the temperature of the roll increases. Thereby, the heat transfer coefficient increases; and a higher heat amount is absorbed. That is, the thickness of the foil can be thick.

[0057] To date, it has been said that a thick foil is not possible by a multi-slit nozzle method. This is because a melt that surpasses the thermal absorption capacity of the roll is supplied even though the temperature of the cooling roll is low. The overflowing melt scatters; and a stable puddle is not formed. Because the heat is not absorbed by the roll, the temperature of the roll never increases; and a thick foil is not formed. Although exceedingly common-sense, this appears to be generally not recognized.

[0058] The method illustrated in FIGS. 4A to 4C is effective to quicken the temperature increase of the cooling roll in the initial casting as described above. For example, the water supply to the flow channel of the outermost circumference is not performed when starting the casting. The flow rate adjustment valve 65 of this flow channel is closed in advance. Then, the outer circumference temperature of the roll increases quickly. The dispensing pressure is increased accordingly. Because the state is a state of a high heat transfer coefficient, the coagulation rate increases; and the sheet thickness becomes large. Water supply is performed also to the flow channel of the outermost circumference at the timing when the desired sheet thickness is reached. Because the temperature of the roll outer circumferential surface at this timing is high, the incoming and outgoing heat are balanced. In other words, the heat amount that is absorbed by the roll and the heat removal capacity of the roll are equal.

[0059] When the sheet thickness becomes thicker than a constant, for example, 30 m, the heat cannot be removed by only the flow channel of the outermost circumference. The heat that cannot be absorbed is absorbed by the water flowing through the second water path from the outer circumference. The water of the third flow channel is utilized when the sheet thickness is even thicker. Thus, it is sufficient to increase the flow channels according to the desired sheet thickness. The three levels of flow channels shown in FIGS. 4A to 4C and FIG. 5 are not limited thereto and may be increased or reduced according to the sheet thickness.

[0060] When implementing the embodiment, the arrangement of the through-holes, i.e., the distance from the roll outer circumferential surface, must be determined. However, although the wall thickness of the roll is important in the case where the cooling water channels are set only at the outermost circumference as conventionally, this cannot be designated in the embodiment. As long as a Cu or Cu alloy having a high thermal conductivity (the thermal conductivity being 70% or more of that of pure Cu) is used, if the sum total of the surface area of the through-holes piercing the side surface of the roll can absorb the heat amount incident on the roll per unit time, it is unnecessary to designate the wall thickness. The heat amount that is conducted to the cooling water can be estimated using the sum total of the surface area of the flow channels of the cooling water and the forced convective heat transfer coefficient of the water (1.2 to 5.8)10.sup.3 W/kg. The heat transfer coefficient recited above refers to Illustrated Study of Heat Transfer Engineering, Ohmsha, Ltd., Kaneyasu Nishikawa (Editor) and Naokata Kitayama (published Jan. 1, 1985).

[0061] In the case where an extremely thick amorphous alloy sheet is desired, the number of flow channels when viewed from the roll side surface may be four or more. When the number of flow channels becomes large, the diameter of the roll must be large. If the roll becomes too large, problems occur with the strength of the support mechanism such as the rotation axis, the bearings, etc., supporting the roll. In such a case, two rolls are arranged and used as in FIG. 7. A specific example and an operation method of the apparatus already are discussed in the Patent Literature 1; and a description is therefore omitted. Modifications are shown in the Patent Literature 2 and the Patent Literature 3.

[0062] If the cooling roll of the invention is used in combination with one of the Patent Literatures 1, 2, or 3, the productivity increases because the time until roll replacement lengthens. The work efficiency also is improved.

[0063] According to the invention, a manufacturing apparatus of an amorphous alloy strip can be realized in which a thick amorphous alloy strip can be manufactured at an industrial scale using a single roll.