JPH03130307A - Method for controlling atmospheric pressure at the time of manufacturing mish metal alloy flake - Google Patents

Abstract

PURPOSE:To manufacture mish metal alloy flake having the prescribed structure with high yield by independently controlling atmospheric pressures in a melting chamber and a flaking chamber and keeping the injecting pressure of molten metal to constant. CONSTITUTION:The atmospheric pressure in the melting chamber 32 is controlled so that the injecting pressure of the molten mish metal alloy 44 flowing toward a cooling drum 47 from an injecting nozzle 41 becomes constant with an evacuating device 1. The upper limit of the injecting pressure is made to 0.4kg/cm<2> and the lower limit thereof is made to 0.2kg/cm<2>. The atmospheric pressure in the flaking chamber 51 is finely adjusted in the range of 0.05-0.5atm with an evacuating device 2. By this method, air pocket caused by involution of inert gas between the molten mish metal alloy caused to flow down from the injecting nozzle 41 and the outer circumferential face of cooling drum 47, is not developed and uniform contacting condition of the molten alloy with the cooling drum 47 is secured.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides rapid cooling and cooling by supplying Mitshu metal alloy melted in a melting container placed in an inert atmosphere such as argon gas to the outer peripheral surface of a cooling drum. The present invention relates to a method of controlling atmospheric pressure when forming flakes by solidification.

[Conventional technology]

BACKGROUND ART The method of producing metal ribbon by rapidly solidifying molten metal has attracted attention for its advantages following the development of amorphous alloys, and is now in the spotlight as a means for developing new materials. This technology for producing metal ribbon using the rapid solidification method involves spraying a high-temperature molten material onto the outer surface of a cooling drum that is rotating at high speed and rapidly cooling it to produce an amorphous or near-crystalline material. . When using this technology, machining is difficult.
For example, ribbons of materials that cannot be cold rolled can be obtained directly from molten metal. Furthermore, it is possible to transform a high-temperature phase into an amorphous state at room temperature, which is impossible with ordinary cooling means.

On the other hand, as a technique for manufacturing Nd-Fe-B permanent magnets, which are typical examples of rare earth permanent magnets, by a rapid solidification method, Japanese Patent Application Laid-open No. 57-210934 and Japanese Patent Application Laid-Open No. 60-9852 are known.
There is a method introduced in the publication. In addition, many similar methods have been reported as research results by universities, companies, etc.

However, all of the conventional techniques are laboratory-scale, in which a small amount of the alloy is melted in a quartz crucible and rapidly solidified.

Therefore, the present inventors have developed an apparatus having the equipment configuration shown in FIG. 4 as an apparatus for manufacturing Mitshu metal-Fe-B permanent magnets by a rapid solidification method. In this device, the inside of the device body 31 is divided into a melting chamber 32 and a flaking chamber 3.
3, and each is connected to a vacuum exhaust device 34. A melting container 36 equipped with a high-frequency coil 35 is tiltably arranged in the melting chamber 32 .

A partition wall 37 that partitions the melting chamber 32 and the flaking chamber 33
A bellows 38 is attached to the bellows 38.
A funnel 39 and a pouring container 40 are attached to.

An injection nozzle 41 is provided at the lower end of the pouring container 40, and a high-frequency coil 42 for maintaining the main body of the pouring container 40 and the injection nozzle 41 at a predetermined temperature is arranged around them. In addition, the pouring container 4 by the high frequency coil 42
A graphite block 43 is interposed between the pouring container 40 and the high-frequency coil 42 in order to efficiently heat the melt.

Furthermore, an outer crucible 45 is disposed between the graphite block 43 and the high-frequency coil 42 to support the pouring container 40.

After a predetermined amount of the Mitshu metal-FeB alloy raw material is melted in the melting container 36, the melting container 36 is tilted to transfer the molten Mitshu metal alloy 44 from the melting container 36 to the pouring container 40 via the funnel 39. In addition,
The inside of the dissolution chamber 32 is opened or sealed by opening and closing the dissolution chamber door 46.

The melt supplied to the pouring container 40! 44 is sprayed onto the outer peripheral surface of the cooling drum 47 from the spray nozzle 41 located at the bottom of the pouring container 40. The molten metal 44 hits the paddle 48 on the outer circumferential surface of the cooling drum 47 and flies off as flakes 49 due to the heat removed through the cooling drum 47. This flake 4
9 are collected in a flake chamber 51 via a duct 50.

The flakes 49 collected in the flake chamber 51 are crushed into a predetermined size after removing the iron particles, and become a magnet material.

[Problem to be solved by the invention]

In this flake manufacturing apparatus, in order to manufacture flakes 49 with a predetermined crystal structure, it is necessary to maintain the paddle 48 stably on the outer peripheral surface of the cooling drum 47 and to keep the cooling conditions of the Mitshu metal alloy molten metal 44 constant. It is. Therefore, it is required that the molten metal alloy 44 flowing out from the injection nozzle 41 provided at the lower part of the pouring container 40 be supplied to the outer peripheral surface of the cooling drum 47 in a rectified state with a constant thickness.

However, the injection pressure of the Mitshu metal alloy molten metal 44 flowing out from the injection nozzle 41 tends to fluctuate depending on the difference in atmospheric pressure between the melting chamber 32 and the flaking chamber 33 and the static pressure of the Mitshu metal alloy molten metal 44 poured into the pouring container 40. . If this injection pressure fluctuates, the flow state of the Mitshu metal alloy molten metal 44 supplied from the injection nozzle 41 to the outer peripheral surface of the cooling drum 47 will change irregularly, making it impossible to obtain flakes 49 that have received a predetermined cooling effect. .

If the atmospheric pressure is simply controlled to offset this variation in injection pressure, inert gas such as argon will be entrained in the flow of Mitshu metal alloy molten metal 44 supplied from the injection nozzle 41 to the outer peripheral surface of the cooling drum 47.

The entrained inert gas is transferred to the cooling drum 47 and the paddle 4.
Discipline the insulation layer between 8 and Mitshu metal alloy molten metal 4
The cooling and solidification of 4 is delayed, resulting in a structure with coarse crystal grains. Furthermore, if an attempt is made to eliminate the influence of fluctuations in the static pressure of the molten metal using only the atmospheric pressure in the flaking chamber, the jet flow sent to the cooling drum 47 will not become constant, and flakes will be produced under unstable conditions. Moreover, since coarsening of crystal grains occurs irregularly, flakes 4, which are used as Mitsushi Metal-Fe-B permanent magnets with high magnetic property values,
The yield of 9 is reduced.

Therefore, the present invention independently controls the atmospheric pressure in the melting chamber and the flaking chamber, thereby supplying the molten metal alloy from the injection nozzle to the cooling drum at a constant injection pressure, and at the same time controlling the atmospheric pressure in the flaking chamber. The purpose is to prevent atmospheric gas from being entrained between the outer peripheral surface of the cooling drum and the molten metal alloy by controlling the pressure so that there is no fluctuation.

[Means to solve the problem]

In order to achieve the objective, the atmospheric pressure control method of the present invention transfers molten Mitshu metal alloy from a melting container placed in a melting chamber to a pouring container, and then transfers the molten metal alloy to a flaking chamber located below the melting chamber. When producing flakes by injecting the Mitshu metal alloy molten metal onto the outer circumferential surface of the cooling drum from the injection nozzle provided at the bottom of the pouring container and rapidly cooling and solidifying it, both the melting chamber and the flaking chamber are heated to a reduced pressure. An active atmosphere is created, and the atmospheric pressure in the melting chamber is controlled so as to offset fluctuations in the static pressure of the molten Mitshu metal alloy in the pouring container, and the injection pressure of the molten Mitshu metal alloy flowing out from the injection nozzle is set to 0.2. ~0.4 kg/
crl, and the atmospheric pressure in the flaking chamber is finely adjusted within a range of 0.05 to 0.5 atm.

[Effect]

In the present invention, as shown in FIG. 1, equipment is used in which each of the melting chamber 32 and the flaking chamber 33 is connected to a vacuum evacuation device 1.2 equipped with an atmospheric pressure control mechanism. Note that it is also possible to control the atmospheric pressure of each of the melting chamber 32 and the flaking chamber 33 with a single evacuation device by adjusting the valve opening degree, adding argon, or the like. Then, the atmospheric pressure in the melting chamber 32 is independently controlled by the evacuation device 1, and the atmospheric pressure in the flaking chamber 33 is independently controlled by the evacuation device 2. Moreover, the gap between the bellows 38 and the pouring container 40 is sealed with a ring 3 so that atmospheric gas does not diffuse between the melting chamber 32 and the flaking chamber 33. In addition, in the same figure,
Components corresponding to those shown in FIG. 4 are indicated by the same reference numbers.

The atmospheric pressure in the melting chamber 32 is controlled so that the injection pressure P of the Mitshu metal alloy molten metal 44 flowing out from the injection nozzle 41 toward the cooling drum 47 is constant. This injection pressure is
It is the sum of the difference between the atmospheric pressure P in the melting chamber 32 and the atmospheric pressure P in the flaking chamber 33, and the static pressure of the Mitshu metal alloy molten metal 44 being poured into the pouring container 40, and the static pressure is It changes approximately in proportion to the meniscus level of the molten metal alloy 44 in the container 40. Therefore, the meniscus is detected using, for example, a T-ray, and the molten metal static pressure P1 is calculated from the detected value. Then, the differential pressure ΔF (=P−P,
+P, ) is calculated, and the atmospheric pressure P in the melting chamber 32 is changed by an amount corresponding to this pressure difference ΔP. As a result, the injection pressure P of the Mitshu metal alloy molten metal is always maintained constant.

The atmospheric pressure P3 in the flaking chamber 33 is controlled by the cooling drum 47.
In order to minimize the occurrence of air pockets caused by entrainment of argon gas between the outer periphery of the paddle 48 and the paddle 48,
It is controlled to be under reduced pressure and with little fluctuation. From this point of view, the appropriate range of the atmospheric pressure P is 0.05 to 0.5 atm. If the atmospheric pressure P3 is higher than 0.5 atm, argon gas will be more entrained, air pockets, that is, flakes with many coarse particles will be likely to be formed, and the magnetic properties will be deteriorated. Conversely, when the atmospheric pressure P becomes less than 0.05 atm,
A phenomenon is observed in which an oxide film is easily generated in the jet stream, the condition of the jet stream deteriorates, and normal flakes cannot be obtained. The reason for this reduction in pressure is not known in detail, but as the pressure of the highly reactive active Mitshu metal alloy molten metal decreases, the evaporation rate increases, and the surface of the jet becomes more active, causing the molten metal contained in the atmosphere to become more active. It is thought that the tea reacts with a small amount of oxygen and forms an oxide film.

On the other hand, in order to ensure an appropriate injection speed for each nozzle, the target injection pressure P varies depending on the size of the nozzle hole diameter. For example, when a nozzle with a small nozzle hole is used, the injection pressure P is set high, and when a nozzle with a large nozzle hole diameter is used, the injection pressure P is set low. The nozzle used for spraying the molten Mitshu metal alloy is 0.
A nozzle having a diameter of 7 to 1.2 mm is used.

When the nozzle hole diameter is 0.7 mm, the standard injection pressure P is 0.4 kg/crl, and when the nozzle hole diameter is 1.2 mm, the standard injection pressure P is 0.2 kg/crl. For these reasons, the upper limit of the injection pressure P is set to 0.4 kg/cut,
The lower limit is set at 0.2 kg/ctl.

On the other hand, the atmospheric pressure P in the flake chamber 51 is 0.05 to 0.
．． Finely adjusted in a range of 5 atm. When the atmospheric pressure P is within this range, no air pockets are generated between the molten metal alloy flowing down from the injection nozzle 41 and the outer peripheral surface of the cooling drum 47 due to the entrainment of inert gas, and the cooling drum 47 Uniform contact between the molten Mitshu metal alloy and the molten metal is ensured.

Therefore, the cooling and solidification of the Mitshu metal alloy molten metal is carried out under certain conditions, and the production yield of flakes 49 with a predetermined structure is improved. Fine adjustment within the range is necessary.

〔Example〕

Mitsushi metal alloy (Ce7) heated to 1400℃
atomic%, La 3 atomic%, Nd 2 atomic%,
Pr 1 atomic%, Co 8 atomic%, B 7 atomic%,
Iron balance weight molten metal is poured into a pouring container 40 from a melting container 36 placed in a melting chamber 32 with an atmospheric pressure P2 = 0.4 atm, and a nozzle hole provided at the bottom of the pouring container 40 has a diameter of 0.9.
The liquid was injected onto the outer circumferential surface of the cooling drum 47 from the injection nozzle 41 having a large diameter. The pouring container 40 used had a cross section with an inner diameter of 180 mm and an effective height of 390 mm. Mitshu metal alloy molten metal was poured into this pouring container 40 with the upper limit height of the meniscus set to 180 mm. The meniscus level of the poured Mitshu metal alloy molten metal was measured using a T-ray bell meter, and the molten metal static pressure P was calculated from the measured value.

Figure 2 shows the meniscus level and molten metal static pressure P1 at this time.
This is a graph showing the relationship between In this way, the static pressure P of the molten metal applied to the injected molten metal alloy varies depending on the meniscus level. This variation causes the injection pressure P ejected from the injection nozzle 41 to vary. Therefore, the atmospheric pressure P2 in the melting chamber 32 was controlled so as to offset the fluctuations in the molten metal static pressure P1. the result,
The injection pressure P of the Mitshu metal alloy molten metal showed a fairly constant value (0.30 kg/cat).

On the other hand, the atmospheric pressure P in the flaking chamber 33 was maintained at a constant value of 0.2 atmospheres. Atmospheric pressure P is the flake storage atmospheric pressure when a sudden pressure change occurs in the flaking chamber 33, such as when a sudden pressure drop occurs due to the expansion of argon gas in the chamber at the start of injection. The control device immediately returns the pressure to a constant level and maintains it at that value.

By controlling the atmospheric pressure, the molten metal alloy is injected into the cooling drum 47 from the injection nozzle 41 in a rectified stream having a constant thickness, and is uniformly cooled on the outer peripheral surface of the cooling drum 47. As a result, as shown in FIG. 3, the magnetic properties of the Mitshu metal-Fe-B permanent magnet were high, and the yield of flakes was improved. In addition, the third
The yield in the figure is expressed as the ratio of magnet powder having the characteristics shown in the figure to the Mitsushi metal alloy raw material.

On the other hand, in a comparative example in which flakes were manufactured by controlling only the atmospheric pressure in the melting chamber 32 and the flaking chamber 33 and maintaining the injection pressure at 0.3 kg/CrI as much as possible, the cooling drum 34
The flow rate of the Mitshu metal alloy molten metal supplied to the outer peripheral surface of No. 7 varied greatly, and the thickness of the molten metal flow was not determined.

As a result, insufficient cooling or overcooling occurs, and even in a steady state, cooling conditions become uneven due to air pockets, and coarse crystal grains, amorphous particles, iron particles, etc. are mixed into the resulting flakes. The proportion of magnetic properties was high, and both the magnetic property values and the yield were low.

〔Effect of the invention〕

As explained above, in the present invention, the atmospheric pressure in the melting chamber and the flaking chamber are controlled independently, and the molten metal alloy is injected from the injection nozzle while canceling out fluctuations in the static pressure of the molten metal. By maintaining the pressure constant, flakes are produced under uniform cooling conditions and without generating air pockets due to entrainment of atmospheric gases. As a result, coarse grains, amorphous grains.

The generation of granular iron, etc. is suppressed, and flakes with a predetermined crystal structure are produced at a high yield.

[Brief explanation of the drawing]

FIG. 1 shows a flake production facility in which the atmospheric pressures of the melting chamber and the flaking chamber are independently controlled, FIGS. 2 and 3 are graphs specifically expressing the effects of the present invention, and FIG. shows a flake manufacturing apparatus without independent atmospheric pressure control. 1: Vacuum exhaust device 2: Vacuum exhaust device 3: ○ ring

Claims (1)

[Claims] 1. Transfer the molten misch metal alloy from the melting container placed in the melting chamber to the pouring container, and place it on the outer peripheral surface of the cooling drum placed in the flaking chamber below the melting chamber at the bottom of the pouring container. When producing flakes by injecting the molten misch metal alloy from a provided injection nozzle and rapidly cooling and solidifying it, both the melting chamber and the flaking chamber are in a depressurized inert atmosphere, and the misch metal alloy in the pouring container is The atmospheric pressure in the melting chamber is controlled to offset fluctuations in the static pressure of the molten metal alloy, and the injection pressure of the molten misch metal alloy flowing out from the injection nozzle is set to 0.2 to 0.4 kg/c.
A method for controlling atmospheric pressure during the production of misch metal alloy flakes, characterized in that the atmospheric pressure in the flaking chamber is finely adjusted within a range of 0.05 to 0.5 atm.