Molten metal ejection apparatus for manufacturing alloy strips, alloy strip manufacturing apparatus, and alloy strip manufacturing method

Abstract

This invention provides a molten metal ejection device for manufacturing alloy strips that can reliably dispense molten alloy at a stable ejection rate, thereby enabling the production of high-quality alloy strips. [Solution] A molten metal ejection device 1 comprises a storage container 2 for storing molten alloy M, a dispensing nozzle 3 provided to protrude downward from the bottom of the storage container 2, and an induction coil 4 wound around the storage container 2, and produces an alloy strip B by ejecting molten alloy M from the dispensing nozzle 3 onto the outer surface of a rotating cooling roll 20, further comprising a plate-shaped susceptor 10 made of a conductor located below the storage container 2, the susceptor 10 having an insertion hole 11 into which the dispensing nozzle 3 is inserted, the dispensing nozzle 3 fits into the insertion hole 11 and is heated by electromagnetic induction of the induction coil 4.

Description

Technical Field

[0001] The present invention relates to a molten metal ejection device for manufacturing an alloy strip, an alloy strip manufacturing device, and an alloy strip manufacturing method. More specifically, the present invention relates to a molten metal ejection device for manufacturing an alloy strip, an alloy strip manufacturing device, and an alloy strip manufacturing method used for manufacturing an alloy strip by a single-roll molten metal rapid cooling method.

Background Art

[0002] The single-roll molten metal rapid cooling method is a method for manufacturing a metal strip by ejecting molten metal from a nozzle onto a rapidly rotating metal roll and rapidly cooling it, and has been widely known conventionally. As a molten metal ejection device for performing the single-roll molten metal rapid cooling method, Patent Document 1 discloses a configuration in which molten metal stored in a molten metal storage container is ejected from the tip of an ejection nozzle extending downward from the bottom of the molten metal storage container. Around the molten metal storage container and the ejection nozzle, a high-frequency induction heating coil for the molten metal storage container and a high-frequency induction heating coil for the ejection nozzle are provided, respectively. Due to the electromagnetic induction of each induction heating coil, a flow is generated in the molten metal in the molten metal storage container toward the ejection nozzle.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the single-roll molten metal rapid cooling method, it is important to quickly remove the heat from the ejected molten alloy and maintain a uniform molten metal rapid cooling state in order to produce high-quality alloy strips. To achieve this, it is necessary to maintain a constant balance between heat input and heat removal by not only keeping the amount of heat removed from the molten metal by the cooling roll constant, but also by stably maintaining the temperature of the ejected molten metal and the ejection rate. The molten metal ejection method disclosed in Patent Document 1 above maintains a certain range of ejection rates by optimizing the outer diameter ratio, spacing, frequency ratio, etc., of the high-frequency induction heating coil for the storage container and the high-frequency induction heating coil for the ejection nozzle. However, the installation of two heating coils not only increases manufacturing costs, but also risks making the work of precisely adjusting each heating coil complicated.

[0005] Furthermore, in order to maintain the hot water nozzle at the desired temperature, it is necessary to ensure a certain number of turns in the high-frequency induction heating coil for the hot water nozzle. This inevitably increases the protrusion length of the hot water nozzle from the bottom of the hot water storage container. As a result, the mechanical load acting on the hot water nozzle increases, and it becomes more susceptible to damage from external impacts, which could lead to molten metal leakage.

[0006] Therefore, the present invention aims to provide a molten metal ejection device, an alloy strip manufacturing device, and an alloy strip manufacturing method for producing alloy strips that can reliably dispense molten alloy at a stable ejection rate to produce high-quality alloy strips. [Means for solving the problem]

[0007] The object of the present invention is achieved by a molten metal ejection device for producing alloy strips, comprising a storage container for storing molten alloy, a dispensing nozzle provided to protrude downward from the bottom of the storage container, and an induction coil wound around the storage container, wherein the molten alloy is ejected from the dispensing nozzle onto the outer surface of a rotating cooling roll, and the device further comprises a plate-shaped susceptor made of a conductor located below the storage container, the susceptor having an insertion hole into which the dispensing nozzle is inserted, and the dispensing nozzle is fitted into the insertion hole and heated by electromagnetic induction of the induction coil.

[0008] Preferably, the tip of the hot water nozzle protrudes downward from the lower surface of the susceptor.

[0009] The height from the tip of the hot water nozzle to the lower end of the induction coil is preferably 0 mm or more and 50 mm or less.

[0010] The susceptor preferably has a notch consisting of a plurality of slits or through holes.

[0011] Furthermore, the aforementioned object of the present invention is achieved by an alloy strip manufacturing apparatus comprising the molten metal ejection device described above and a cooling roll positioned below the molten metal ejection device, wherein molten alloy is ejected from the molten metal ejection device onto the outer surface of the rotating cooling roll to produce an alloy strip.

[0012] Furthermore, the aforementioned object of the present invention is achieved by an alloy strip manufacturing method using the molten metal ejection device described above, the method comprising the step of producing an alloy strip by ejecting molten alloy from the molten metal ejection device onto the outer surface of a rotating cooling roll. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a molten metal ejection device for manufacturing alloy strips, an alloy strip manufacturing device, and an alloy strip manufacturing method that can reliably eject molten alloy at a stable ejection rate to produce high-quality alloy strips. [Brief explanation of the drawing]

[0014] [Figure 1] A schematic diagram of an alloy thin strip manufacturing apparatus according to one embodiment of the present invention. [Figure 2] Figure 1 shows a bottom view of the main components of the alloy thin strip manufacturing apparatus. [Figure 3] A schematic diagram illustrating the operation of the alloy thin strip manufacturing apparatus shown in Figure 1. [Figure 4] A figure showing the measurement results of an embodiment of the present invention. [Figure 5]A diagram showing the measurement results of the comparative example of the present invention.

Embodiments for Carrying out the Invention

[0015] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of an alloy ribbon manufacturing apparatus according to an embodiment of the present invention. As shown in FIG. 1, the alloy ribbon manufacturing apparatus 100 includes a molten metal ejection device 1 and a cooling roll 20 disposed below the molten metal ejection device 1.

[0016] The molten metal ejection device 1 includes a molten metal storage container 2 for storing the alloy molten metal M, a hot water discharge nozzle 3 provided at the bottom of the molten metal storage container 2, an induction coil 4 provided so as to surround the molten metal storage container 2, and a plate-like susceptor 10 disposed below the molten metal storage container.

[0017] The molten metal storage container 2 is made of a heat-resistant material such as graphite and is formed in a bottomed cylindrical shape with an open upper portion. A discharge port that gradually tapers downward is formed at the center of the bottom of the molten metal storage container 2.

[0018] The hot water discharge nozzle 3 is made of ceramic or the like, the base end portion (upper end portion) is fixed to the discharge port of the molten metal storage container 2 by welding or the like, and the tip end portion (lower end portion) protrudes downward from the lower surface of the molten metal storage container 2. A slit-shaped opening 3a is provided at the tip of the hot water discharge nozzle 3. The opening 3a in the present embodiment is formed by a single slit, but may be a plurality of slits.

[0019] The induction coil 4 is wound around the molten metal storage container 2 so as to cover substantially the entire height direction of the molten metal storage container 2, generates a high-frequency magnetic field of several kHz to several tens of kHz by energization, and inductively heats the alloy molten metal M accommodated in the molten metal storage container 2.

[0020] The susceptor 10 is made of a metal material such as stainless steel or a heat-resistant conductor such as graphite (for example, having a melting point of 1200 °C or higher), and is heated by electromagnetic induction of the induction coil 4. The susceptor 10 is formed in a disc shape with substantially the same diameter as the diameter of the hot water storage container 2, and an insertion hole 11 is formed at the center. The tip of the hot water outlet nozzle 3 is inserted and fitted into the insertion hole 11 so that the outer periphery is in close contact with the inner periphery of the insertion hole 11. The susceptor 10 can support the hot water storage container 2 from below by being attached to a bracket or the like (not shown). However, the hot water storage container 2 can also be supported by providing a flange portion or the like at the upper part and using this flange portion.

[0021] It is desirable that the hot water outlet nozzle 3 slightly protrudes downward from the lower surface of the susceptor 10 so as to ensure an appropriate distance (for example, 0.1 mm or more and 2.0 mm or less) between the opening 3a at the tip and the outer peripheral surface of the cooling roll 20. However, if the protruding length of the hot water outlet nozzle 3 becomes too long, it may be difficult to heat the protruding portion by the susceptor 10. Therefore, the protruding length of the hot water outlet nozzle 3 from the lower surface of the susceptor 10 is preferably 0.1 to 10.0 mm, and more preferably 0.2 to 5.0 mm.

[0022] The cooling roll 20 is a metal roll generally used in the single roll melt quenching method, and can be rotated at a high speed at a desired rotational speed.

[0023] In the alloy strip manufacturing apparatus 100 having the above configuration, a high-frequency magnetic field is generated by a high-frequency current flowing through the induction coil 4 around the alloy melt M, and eddy currents flow in the circumferential direction in the alloy melt M in the hot water storage container 2 due to this high-frequency magnetic field. Due to these magnetic fields and eddy currents, a pinch force directed toward the center of the hot water storage container 2 acts on the alloy melt M. By this pinch force, the alloy melt M in the hot water storage container 2 is stirred as shown by the arrow in FIG. 1, and a flow of the alloy melt M directed toward the hot water outlet nozzle 3 occurs at the lower part of the hot water storage container 2.

[0024] Furthermore, the susceptor 10 positioned below the hot water storage container 2 is also heated by electromagnetic induction. As a result, the molten alloy M in the hot water nozzle 3 is heated by the heat from the susceptor 10, while electromagnetic induction is suppressed. This prevents a drop in temperature inside the hot water nozzle 3 due to the wind swirled in by the high-speed rotation of the cooling roll 20, and reliably prevents the formation of a flow of molten alloy M in the hot water nozzle 3 that would hinder hot water discharge due to electromagnetic induction. As a result, the molten alloy M can be discharged while stably maintaining the hot water discharge rate within a certain range, regardless of changes in the head pressure P. The molten alloy M ejected from the hot water ejection device 1 is rapidly cooled and solidified on the outer surface of the rotating cooling roll 20 to form an alloy strip B.

[0025] Furthermore, since the tip of the hot water outlet nozzle 3 is fitted into the insertion hole 11 of the susceptor 10, the connection of the hot water outlet nozzle 3 to the hot water storage container 2 can be structurally assisted, so that even if a mechanical load is applied to the hot water outlet nozzle 3, the connection between the hot water storage container 2 and the hot water outlet nozzle 3 can be stably maintained. In addition, since the molten alloy M inside the hot water outlet nozzle can be heated without providing a separate induction coil for the hot water outlet nozzle in addition to the induction coil for the hot water storage container, as in the conventional method, the protrusion length of the hot water outlet nozzle 3 from the lower surface of the susceptor 10 can be sufficiently reduced, which also suppresses the mechanical load on the hot water outlet nozzle 3 and ensures stable operation over a long period of time.

[0026] The vertical upward height H from the tip of the hot metal nozzle 3 to the lower end of the induction coil 4, as shown in Figure 1, is preferably 0 mm or more and 50 mm or less. If the height H is negative (less than 0 mm), the tip of the hot metal nozzle 3 will be inside the induction coil 4, making it difficult to secure an appropriate distance between the opening 3a of the hot metal nozzle 3 and the outer surface of the cooling roll 20. On the other hand, if the height H is greater than 50 mm, the induction heating of the susceptor 10 by the induction coil 4 will be insufficient, which may make it difficult to stably eject the molten alloy M from the hot metal nozzle 3. The height H is preferably 2 mm or more and 40 mm or less, and more preferably 5 mm or more and 30 mm or less.

[0027] Figure 2 is a bottom view of the molten metal ejection device 1 shown in Figure 1. As shown in Figures 1 and 2, the insertion hole 11 of the susceptor 10 is formed in a rectangular shape when viewed from the bottom, with its longitudinal direction parallel to the rotation axis 21 of the cooling roll 20, and the tip of the molten metal nozzle 3, which has a rectangular end face, is fitted into this insertion hole 11. The opening 3a of the molten metal nozzle 3 is formed in a slit shape with its longitudinal direction parallel to the rotation axis 21 of the cooling roll 20.

[0028] A notch 12 is formed around the insertion hole 11 of the susceptor 10. The notch 12 consists of a plurality of slits 13 and a plurality of through holes 14. Each slit 13 is arranged parallel to each other on both sides in the short direction of the insertion hole 11, extending perpendicular to the insertion hole 11, and the through holes 14 are located between adjacent slits 13.

[0029] The notch 12 of the susceptor 10 is not essential in this invention, and the susceptor 10 may be configured without the notch 12. However, in this case, as shown in Figure 3(a), the path of the eddy current due to electromagnetic induction becomes larger, which may cause the susceptor 10 to be subjected to excessive induction heating. In contrast, the susceptor 10 of this embodiment, by having a notch 12, can block a portion of the eddy current and reduce the path of the eddy current, as shown in Figure 3(b). This suppresses excessive induction heating of the susceptor 10 and reliably prevents the susceptor 10 from melting. The shape and arrangement of the slit 13 and through hole 14 constituting the notch 12 are not particularly limited as long as the susceptor 10 can be reliably kept below the melting temperature. Furthermore, the notch 12 may be configured by arranging multiple slits 13 or through holes 14.

[0030] As an embodiment of the present invention, a molten metal ejection device 1 shown in Figure 1 was fabricated and the following tests were conducted. The hot water storage container 2 was an alumina tundish (inner diameter 200 mm, height 800 mm), and the hot water outlet nozzle 3 was a single-slit nozzle made of BN with an opening 3a of 0.5 mm × 20 mm. The induction coil 4 had an outer diameter of 400 mm and a height of 650 mm, and the height H from the tip of the hot water outlet nozzle 3 to the lower end of the induction coil 4 was set to 32 mm. The susceptor 10 was made of SS200 plate material having a notch 12 as shown in Figure 2, and the height from the bottom surface of the susceptor 10 to the lower end of the induction coil 4 was set to 30 mm (i.e., the protrusion length of the hot water outlet nozzle 3 from the bottom surface of the susceptor 10 was 2 mm). The hot water storage container 2 was made of Fe 80 Si 6.5 B 12.5 A 50 kg ingot with an alloy composition of Fe(remainder)-Si(3.34)-B(3.65) by mass% was introduced to achieve an alloy composition of 1 atomic percent carbon. The ingot was heated to 1450°C using an induction coil 4 with a high-frequency output of 80 kW and 1.5 kHz to generate molten alloy M. After that, the molten alloy M was continuously ejected from the outlet nozzle 3, and the weight change of the molten alloy M in the storage container 2 was measured.

[0031] When the molten metal ejection was stopped after 16 minutes from the start, the ejected weight was 49.8 kg, and 0.2 kg of molten metal remained in the ejection nozzle 3. Figure 4 shows the change in the weight of molten metal in the storage container 2 and the expected change in molten metal head pressure associated with the ejection, with the molten metal ejection time as the horizontal axis.

[0032] On the other hand, as a comparative example of the present invention, the same tests as in the examples were conducted using the configuration disclosed in Patent Document 1. The hot water storage container and the hot water outlet nozzle were configured in the same way as in the examples, and a high-frequency induction heating coil for heating the hot water outlet nozzle, with an outer diameter of 100 mm and a height of 60 mm, was placed 20 mm below the bottom of the high-frequency induction heating coil for heating the hot water storage container, which had an outer diameter of 400 mm and a height of 650 mm. After heating the ingot under the same conditions as in the examples to generate molten alloy, the molten alloy was continuously ejected from the hot water outlet nozzle, and the weight change of the molten alloy in the hot water storage container was measured.

[0033] When the molten metal ejection stopped after 15 minutes and 11 seconds from the start, the ejected weight was 49.9 kg, and 0.1 kg of molten metal remained in the ejection nozzle. Figure 5 shows the changes in the weight of molten metal in the storage container and the expected change in molten metal head pressure associated with molten metal ejection, with the molten metal ejection time as the horizontal axis.

[0034] As shown in Figures 4 and 5, it was confirmed that the molten metal ejection device 1 of the embodiment can reliably eject molten alloy at a stable ejection rate comparable to that of the comparative example, regardless of changes in the molten metal head pressure. [Industrial applicability]

[0035] The present invention allows for the discharge of molten alloy from a discharge nozzle with one or more slits at a stable discharge rate and temperature, and is also suitable for mass production. Therefore, it is suitable for the production of soft magnetic materials such as nanocrystalline RE-Fe-B isotropic magnets or nanocrystalline Sm-Fe-N isotropic magnets applied to various high-performance DC brushless motors and magnetic sensors, or Fe-Si-B amorphous or nanocrystalline soft magnetic materials applied to various passive elements, power conditioners, and compacted magnetic cores for motors. [Explanation of Symbols]

[0036] l Molten metal ejection device 2. Hot water storage container 3. Hot water nozzle 4. Induction coil 10 Susceptors 11 Insertion hole 12 Notches 20 Cooling Rolls 100 Alloy Thin Strip Manufacturing Equipment

Claims

1. The device comprises a storage container for storing molten alloy, a hot water nozzle provided to protrude downward from the bottom of the storage container, and an induction coil wound around the storage container. A molten metal ejection device for producing a thin alloy strip by ejecting molten alloy from a ejection nozzle onto the outer surface of a rotating cooling roll, The hot water storage container is further provided with a plate-shaped susceptor made of a conductor, located below the container. The susceptor has an insertion hole into which the molten metal nozzle is inserted, and the molten metal nozzle is fitted into the insertion hole and heated by electromagnetic induction of the induction coil in a molten metal ejection device for manufacturing alloy strips.

2. The molten metal ejection device according to claim 1, wherein the tip of the molten metal nozzle protrudes downward from the lower surface of the susceptor.

3. The molten metal ejection device according to claim 1, wherein the height from the tip of the molten metal nozzle to the lower end of the induction coil is 0 mm or more and 50 mm or less.

4. The molten metal ejection device according to claim 1, wherein the susceptor has a notch consisting of a plurality of slits or through holes.

5. The molten metal ejection device according to claim 1 and a cooling roll positioned below the molten metal ejection device are provided. An alloy strip manufacturing apparatus that produces an alloy strip by ejecting molten alloy from a molten metal ejection device onto the outer surface of a rotating cooling roll.

6. A method for manufacturing alloy strips using the molten metal ejection apparatus described in claim 1, A method for manufacturing alloy strips, comprising the step of producing an alloy strip by ejecting molten alloy from a molten metal ejection device onto the outer surface of a rotating cooling roll.

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