JP6042604B2 - Magnet strip manufacturing method and manufacturing apparatus - Google Patents

Description

  The present invention relates to a method and apparatus for manufacturing a magnet ribbon by rapid solidification.

Rare earth magnets typified by neodymium magnets (Nd ₂ Fe ₁₄ B) are used in various applications as permanent magnets with high magnetic flux density and extremely high strength. In order to obtain excellent magnetic properties, it is necessary to stably secure a microstructure composed of nano-sized crystal grains or amorphous. Therefore, a method of forming a ribbon (quenched ribbon) by rapidly solidifying a molten alloy having a composition of a rare earth magnet by a single roll method, a twin roll method or the like is performed.

  For example, Patent Document 1 proposes a method of manufacturing a permanent magnet by rapid solidification as described above.

  However, since the temperature of the cooling roll surface that rapidly solidifies the alloy melt fluctuates and the cooling rate fluctuates, it is not possible to stably obtain a nanocrystalline structure or an amorphous structure. Or a coarse crystal grain structure is generated, or these three kinds of mixed structures are generated, and there is a problem that excellent magnetic properties cannot be secured stably.

Japanese Patent No. 03488942

  The present invention provides a magnet ribbon capable of achieving a uniform microstructure and excellent magnetic properties by preventing temperature fluctuations on the surface of the cooling roll when producing a ribbon of magnet alloy by rapid solidification. It is an object of the present invention to provide a method and an apparatus for manufacturing the device.

In order to achieve the above object, according to the present invention, in a method for producing a magnet ribbon that rapidly solidifies by discharging a molten metal alloy onto the surface of a cooling roll,
There is provided a method for producing a magnet ribbon, wherein the cooling roll is continuously reciprocated perpendicularly to the magnet ribbon production direction.

In order to achieve the above object, according to the present invention, in a magnet ribbon manufacturing apparatus that rapidly cools and solidifies by discharging a molten metal alloy onto the surface of a cooling roll,
There is also provided a magnet ribbon manufacturing apparatus comprising means for continuously reciprocating the cooling roll perpendicularly to the magnet ribbon generation direction.

  According to the present invention, the cooling roll continuously reciprocates perpendicular to the magnet ribbon generation direction, that is, in the rotation axis direction of the cooling roll, with respect to the molten metal discharge site. Concentrates on the same circumference and does not impinge on the melt discharge flow, and always hits the position shifted in the direction of the rotation axis. Therefore, a stable cooling rate is always maintained without decreasing the cooling rate of the melt due to the temperature rise on the roll surface. Therefore, a desirable fine structure can be secured stably.

FIG. 1 shows a rapid solidification means by a cooling roll for carrying out the present invention. FIG. 2 shows the single roll furnace used in the examples. FIG. 3 shows an arrangement for temperature measurement. FIG. 4 shows in detail the relationship between the discharged molten metal and the surface of the cooling roll in FIG. FIG. 5 is a graph showing the relationship between the discharge time and the cooling rate for the example and the comparative example. FIG. 6 shows the state of rough discharge and adhesion of the discharge flow for the comparative example. FIG. 7 is a graph showing a demagnetization curve for the example and the comparative example. FIG. 8 shows SEM images of the sintered body structure for Examples and Comparative Examples.

  FIG. 1 shows a rapid solidification means using a cooling roll for carrying out the present invention.

  The cooling roll R rotates around the rotation axis X in the V direction. The melt M of the magnet alloy is discharged from the nozzle N onto the surface S of the cooling roll R, rapidly cooled, solidified, and formed into a ribbon (quenched ribbon) B in the D direction.

  Conventionally, since the molten metal M is discharged to a position on the same circumference of the surface S of the cooling roll R, the roll surface S on the circumference of the molten metal discharge position is heated, and the cooling rate is lowered, which is desirable. There was a problem that the cooling rate could not be maintained.

  In order to eliminate the above-described conventional problems, the present invention is characterized in that the cooling roll R is perpendicular to the generation direction D of the magnet ribbon B with respect to the discharge portion of the molten metal M, that is, the rotation axis of the cooling roll R. Continuously reciprocates (T) in the X direction. As a result, the discharge flow of the molten metal M does not hit the position on the same circumference of the surface S of the cooling roll R and always hits another position shifted in the direction of the rotation axis X. A stable cooling rate is always maintained without lowering the cooling rate of the molten metal M due to the temperature, and a desirable fine structure can be stably secured.

  The speed of the reciprocating movement can be set in advance by preliminary experiments for the apparatus to be used. About the apparatus which this inventor used in the Example mentioned later, about 0.1 mm / s-50 mm / s is desirable. If it is too slow, the rapid cooling effect cannot be obtained, and if it is too fast, the discharge molten metal flow is disturbed on the surface of the cooling roll, so that the adhesion between the molten metal and the surface of the cooling roll is lowered.

  As shown in FIG. 1, an induction coil H for heating the molten metal is provided in the nozzle N that discharges the molten metal. Since the surface S of the cooling roll R is heated by the induction coil H, the temperature rise of the surface S caused by this also causes the cooling rate fluctuation.

  In order to prevent this, in a desirable mode of the present invention, a shielding plate P is provided to shield the surface S of the roll R from the induction coil H for heating the molten metal M immediately before discharging. This prevents the surface S of the cooling roll R from being heated by the induction coil H.

  When the shielding plate P is not provided, in order to avoid heating the cooling roll surface S, it is necessary to provide a sufficiently wide interval between the induction coil H and the cooling roll surface S. In this case, the distance between the position where the molten metal M is heated by the induction coil H and the surface S of the cooling roll increases, and the slow cooling interval until the molten metal M contacts the surface S increases, so that the rapid cooling effect decreases. By providing the shielding plate P, the induction coil H can be arranged close to the surface of the cooling roll, and the rapid cooling effect can be enhanced.

  Since the shielding plate P generates heat when a high frequency is applied, it is desirable to cool the shielding plate P itself by arranging a water cooling pipe. As this cooling water, the cooling water normally used for the induction coil can be shared.

  Hereinafter, the present invention will be described in more detail with reference to examples.

A neodymium magnet alloy having a composition of Nd _14.7 Fe _79.03 B _5.67 Ga _0.3 Cu _0.1 Al _0.2 was melted in an arc melting furnace, and in a single roll furnace shown in FIG. An alloy ribbon (quenched ribbon) was prepared. In FIG. 2, the generated ribbon B becomes fine flakes as it solidifies, and is recovered in the recovery mechanism A. Table 1 shows the manufacturing conditions.

  The reciprocating speed of the roll was 3 mm / s.

  Using a high frequency shielding plate P made of Cu, the space between the induction coil H and the cooling roll surface S was shielded. A Cu pipe for water cooling was provided in close contact with the surface of the shielding plate P, and cooling water having a water temperature of 30 ° C. was flowed therein to cool the shielding plate P.

  As shown in FIG. 3, the melt temperature before and after solidification was measured with an infrared camera K (manufactured by NEC Avio: TS9230H-A01), and the quenching rate during discharge was evaluated.

  That is, as shown in FIG. 4, the range immediately before the molten metal contacted the cooling roll was set with an infrared camera, and the maximum temperature within the range was defined as T1. A range of distance L (m) was set after solidification on the surface S of the cooling roll, and the maximum temperature within the range was defined as T2. The cooling rate was calculated from the temperature difference ΔT between T1 and T2. In this embodiment, L = 0.005 m.

  The obtained alloy ribbon was sintered by spark plasma sintering (SPS) under heating at 570 ° C. under a pressure of 100 MPa and holding for 5 minutes.

[Comparative Example]
As a comparative example, the reciprocating movement of the cooling roll and the installation of the shielding plate were not performed, and the other conditions were the same as in the example to obtain a sintered body.

  About the sintered compact obtained by the Example and the comparative example, the measurement of the magnetic characteristic by VSM and the structure | tissue observation by SEM were performed.

  FIG. 5 shows the relationship between the discharge time and the cooling rate for the example and the comparative example. As shown in the drawing, in the example in which the cooling roll was reciprocated and the shielding plate was installed, a substantially constant and stable cooling rate was obtained. On the other hand, in the comparative example in which the reciprocating movement of the cooling roll and the shielding plate were not performed, the cooling rate fluctuation (oscillating temperature change) for a short time was repeated during the discharge, and the cooling rate was further reduced in the second half of the discharge. It was significantly reduced (the circled portion in FIG. 5).

  As shown in FIG. 6, the significant decrease in the cooling rate in the latter half is considered to be because the melt solidified on the cooling roll and the roll surface was rough, and the solidification process of the melt became unstable. FIG. 6 (1) is a high-speed camera photograph taken from the end face direction of the cooling roll R, where the molten metal M discharged from the nozzle N tip collides with the cooling roll surface S, and FIG. 6 (2) shows the state. It is a schematic diagram shown. As the molten metal M is discharged to the same circumferential position on the surface of the cooling roll S, the molten metal M is intermittently adhered to the surface of the cooling roll (Z) and discharged to the adhesion portion Z that has circulated. Drop Y is flying.

  FIG. 7 shows demagnetization curves of the sintered bodies by VSM for the examples and comparative examples. It can be seen that the examples in which stable rapid solidification was achieved had a much improved coercive force than the comparative example in which rapid solidification was unstable.

  In FIG. 8, the SEM image of a sintered structure is shown about an Example and a comparative example. In the example, a sintered structure composed of a thin ribbon having a uniform fine structure is obtained, whereas in the comparative example, the structure of the thin band constituting the sintered structure is not uniform, and foreign matters such as voids and oxides are obtained. The mixing of is also accepted.

  The shape of the shielding plate P is not particularly limited, and the through hole is provided so that the induction coil H and the cooling roll surface S are shielded and the molten metal can be discharged from the nozzle and reach the cooling roll surface. Need to be. The planar shape of the through hole can be various shapes such as a slit shape and a circular shape. In this embodiment, as shown in FIG. 1, consideration was given so as to prevent the progress of the generated ribbons by making the end portions of the slits in the ribbon generation direction open.

  According to the present invention, when producing a ribbon of magnet alloy by rapid solidification, a magnet that can achieve a uniform microstructure and excellent magnetic properties by preventing temperature fluctuations on the surface of the cooling roll. A method and apparatus for manufacturing a ribbon is provided.

R Cooling roll S Surface of cooling roll R X Rotating shaft of cooling roll R V Rotating direction of cooling roll R T Reciprocating direction of cooling roll R M Molten metal alloy N Nozzle H Induction coil P Induction coil surface and cooling roll surface Shielding plate provided between them B Magnetic alloy ribbon (quenched ribbon)
D Formation direction of ribbon

Claims (2)

In the manufacturing method of the magnet ribbon that discharges the molten metal alloy onto the surface of the cooling roll and rapidly solidifies,
Reciprocating continuously vertically above cooling roll against the production direction of the magnet strip, and reciprocating speed of the cooling roll is 0.1 mm / s to Ri 50 mm / s der,
A shielding plate is used to shield the surface of the roll against an induction coil for heating the molten metal immediately before discharging, where the through-hole of the shielding plate has a slit shape, and the end of the slit in the ribbon production direction A method for producing a magnet ribbon, wherein the portion is open . In a magnet ribbon manufacturing apparatus that rapidly cools and solidifies by discharging a molten metal alloy onto the surface of a cooling roll,
Further comprising means for reciprocating continuously vertically above cooling roll against the production direction of the magnet strip, and reciprocating speed of the cooling roll is 0.1 mm / s to Ri 50 mm / s der,
A shield plate is provided to shield the surface of the roll against the induction coil for heating the molten metal immediately before discharge. Here, the through-hole of the shield plate is slit-like, and the end of the slit in the ribbon production direction is provided. A magnet ribbon manufacturing apparatus characterized in that the portion is open .