JP2000263194A - Nozzle for injecting molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a nozzle possible to injecting for a long time and to prevent such trouble as flow-out of molten metal by forming a molten metal injection hole at the tip part of the nozzle with the double structure of a ceramics having erosion resistance to this metal and a qualtz having a heat and impact resistance. SOLUTION: This nozzle is made essentially of the qualtz 1 and one or more of holes 2 as the outlets of the molten metal are opened at this tip part. Further, the ceramics 4 having a ceramic-made orifice 3 is set in the inside of the tip part of the nozzle, and the qualtz 1 and the ceramics 4 are made to tightly adhesion with both surfaces. This surface is named as the tight adhesive surface. This tight adhesive surface can be joined or not joined, but in the case of loading the internal pressure, this is necessary to have such structure as to load the compressive force to at least a part of the tight adhesive surface. The hole 2 bored in the qualtz is necessary to have larger diameter than that of at least the ceramic-made orifice 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a rare earth magnet alloy,
The present invention relates to a nozzle for injecting a molten metal used in a device capable of stably liquid quenching a molten alloy containing a rare earth metal as an essential constituent element such as a hydrogen storage alloy.

[0002]

2. Description of the Related Art By rapidly cooling a metal from a liquid state, it has become possible to exhibit characteristics that cannot be obtained by ordinary melting and casting processes on an industrial scale. A typical example of liquid quenching of a molten alloy containing a rare earth metal is rapid solidification of an Nd-Fe-B-based alloy, and it is possible to provide high-performance magnet powder by liquid quenching by a single roll method or the like. (For example, Japanese Patent Application Laid-Open No. 60-9852). Further, the liquid quenching method is also applied to a hydrogen storage alloy used for a negative electrode material of a nickel-metal hydride battery, and an alloy powder rapidly solidified with a rare earth metal-Ni system (JP-A-8-60265) is superior to a conventional material. It is disclosed to exhibit hydrogen storage properties. As described above, rare earth metals are indispensable constituent elements in many functional materials, but molten alloys containing them are highly reducible to refractory ceramics,
In the liquid quenching device, the corrosion resistance of the nozzle for injecting the molten metal, which is the most important component, becomes a problem.

The term "nozzle" used herein refers not only to the vicinity of the injection port but to the entire crucible including a reservoir portion having a function of temporarily holding the molten metal. The injection hole for controlling the injection amount is particularly called an orifice.

[0004] Typical examples of the liquid quenching method include a roll cooling method (single roll method and twin roll method) in which a molten alloy is sprayed toward a water-cooled rotating roll and cooled, and a gas atomization method in which spray cooling is performed using high-pressure gas. There is. In any method, the nozzle for injecting the molten metal is a key component for the quality and stable operation of the rapidly solidified product. In a small-capacity liquid quenching apparatus, quartz (generally, fused silica glass) is used as a material of the nozzle. Quartz is transparent and transmits radiant heat, so that it is easy to heat the molten metal from the outside, and because of its small coefficient of thermal expansion, it has excellent thermal shock resistance. Quartz is considered to be unsuitable for large-capacity liquid quenching because it softens and deforms at high temperatures exceeding 1000 ° C. However, it is also applicable to large-capacity liquid quenching of Nd-Fe-B alloy melt by applying a support member. There has been an example (JP-A-2-247304). Thermodynamically, quartz is reduced upon contact with the rare earth metal, the Si is eluted, and an oxide of the rare earth metal is formed instead. The elution of Si increases the orifice diameter. Also, if the generated rare earth metal oxide stays, the orifice is blocked. When the diameter of the orifice is enlarged, the ejection speed of the molten metal increases, and the quenching speed decreases, which causes a variation in the quality of the quenched solidified product. Further, when the orifice is closed, the operation is stopped at that time, and the yield is reduced. For these mass production issues, it is necessary to study the material of the orifice.

However, when the tip of the nozzle is made of ceramic, if the ceramic is cracked or the tip falls off from the joint between quartz and ceramic, a highly reactive molten metal blows out at once, and the lower part of the nozzle is a component. Parts, such as the vacuum chamber and the vacuum chamber, may be damaged.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a nozzle for injecting a molten metal in a device for rapidly quenching a molten metal containing a rare earth element, which can withstand a long-time injection and prevent an accident of molten metal outflow. .

[0007]

SUMMARY OF THE INVENTION The present invention provides a nozzle having a double structure in which a metal injection port at the tip of the nozzle is made of a ceramic having corrosion resistance to the metal and a quartz having thermal shock resistance at high temperatures. Things.

More specifically, a nozzle for injecting a molten metal composed of quartz 1 and ceramics 4 used in an apparatus for rapidly solidifying a molten metal from a liquid state, and an orifice 3 for controlling the amount of molten metal ejected is provided on the inner surface of the tip of the quartz. Provided ceramics 4 are closely contacted with each other, and a hole 2 larger than the orifice is provided on the discharge side of the molten metal at the tip end portion of the quartz so as to be continuous with the orifice 4. A nozzle for jetting molten metal, which has a double structure of quartz 1.

[0009]

1 and 2 show a typical embodiment of a nozzle according to the present invention. The figure is a cross-sectional view of the nozzle in the longitudinal direction (a)
(B) and FIG. (C) viewed from the front of the nozzle injection hole.
(A) is a cross-sectional view of a plane along a row of three orifices arranged in one row, and (b) is a cross-sectional view of a plane perpendicular to the plane.

The nozzle is mainly made of quartz 1 and is provided with one or more holes 2 at its tip end serving as an outlet for molten metal. Further, a ceramic 4 having a ceramic orifice 3 is installed inside the tip of the nozzle, and the quartz 1 and the ceramic 4 are in close contact with each other. Hereinafter, this surface is referred to as a close surface. The close contact surface may or may not be joined, but it is necessary that the close contact surface has a structure in which a compressive force is applied to at least a part of the close contact surface when an internal pressure is applied.

The molten metal 5 before spraying is held by quartz 1 and the diameter of the ceramic orifice 3 is set to a size such that the molten metal 5 cannot pass through unless the pressure exceeds a certain level.

The shape of the orifice 3 is selected from a round shape and a slit shape. In the case of a round shape, the diameter of the hole is usually set to 0.2 to 2 mm, and the thickness of the hole is 1 to 5 mm. In a large-capacity liquid quenching device, desired productivity can be obtained by using a large nozzle and increasing the number of holes of the orifice 3 provided at the lower end thereof. In the case of a slit shape, the width of the slit is usually set to 0.2 to 2 mm, and the thickness of the slit portion is also 1 to 5 mm.

The hole 2 at the outlet of the molten metal of the quartz 1 must have a diameter at least larger than that of the ceramic orifice 3 so as not to come into contact with the molten metal during the injection of the molten metal. However, this quartz hole 2 should be
When the molten metal 5 leaks from between the ceramics 4 and the quartz 1 or the ceramics 4 is damaged and the molten metal 5 directly enters, it is necessary to have a diameter such that a large amount of molten metal does not blow out at once. . Although this size depends on the viscosity and operating pressure of the molten metal, when the shape of the hole 2 is a circle, it is preferable that the radius is about 2.5 mm or less and the area is 20 mm ² or less.

The ceramics 4 is generally preferable as a material for forming an orifice because it has excellent corrosion resistance to a molten metal.

[0015]

FIG. 3 shows the arrangement of a single-roll type liquid quenching apparatus and nozzles used in the experiment.

The molten metal 5 is poured from the metal melting crucible 6 into the nozzle. At the same time, gas pressure is applied to the molten metal, and the molten metal is injected from the orifice 3 made of Celaxx provided at the lower end of the nozzle. The injected molten metal forms a paddle on the surface of the rotating water-cooled roll 7 and is rapidly cooled and solidified. The coagulated product 8 is in the form of a ribbon or flake and scatters in the direction of rotation of the roll. The whole system
It is closed in a vacuum chamber 9 and is processed in an inert gas.

The injection nozzle shown in FIG. 1 was prepared by using the ceramic part 4 as a sialon as a nozzle for injecting the molten metal, and attached to a single-roll type liquid quenching apparatus.
A casting experiment of a molten B-based magnet alloy was conducted.

FIG. 1 is an enlarged view of the tip of the nozzle. The quartz and ceramic at the nozzle tip are not bonded but are closely bonded at the surface, and when internal pressure is applied, a compressive force is applied to this surface and the molten metal does not enter the close surface. The quartz part was manufactured by dividing into a tip part which requires dimensional accuracy close to sialon and the other part, and these two parts were welded so as to sandwich sialon. Since the thermal contraction of quartz is smaller than that of sialon, a slight gap is formed between sialon and quartz at room temperature, but the sialon and quartz come into close contact by increasing the temperature and applying internal pressure.

The diameter of the orifice provided in the sialon was 1.0 mm.

In the experiment, the nozzle was set at 100 ° C./min for 1 hour.
The alloy was heated to 400 ° C., and the molten alloy was poured therein, and the molten metal was injected from the orifice. For comparison, a nozzle having the same number of holes and the same orifice diameter was manufactured using only quartz and the same experiment was performed.

As a result, it was possible to eject any of the nozzles, and the ejection was completed for 20 minutes. No change in the hole diameter was observed in the nozzle provided with Sialon. On the other hand, the orifice diameter of the nozzle made of only quartz is 1.3 mm.
The hole had widened to it. All of the obtained rapidly solidified products were in the form of flakes, and their thickness was 20 to 30 μm.

The above two types of rapidly solidified products were pulverized into powder having an appropriate particle size, and bonded with an epoxy resin to produce a resin-bonded magnet. As a result, for a magnet using a flake manufactured with a nozzle made of only quartz, the maximum energy product representing the magnet characteristics was 9 to 10 M for the powder in the previous injection period.
It was GOe, but 6-7 MGOe
Had fallen. On the other hand, in the magnet manufactured by the nozzle equipped with Sialon, there was no difference in the characteristics over the entire injection time, and a value of 9 to 10 MGOe was obtained in the maximum energy product. This result corresponds to the fact that the longer the injection time of the quartz nozzle, the larger the orifice hole diameter and the slower the cooling. It was found that a nozzle having a Sialon orifice did not have this problem, and that magnet powders with high characteristics could be obtained uniformly for all sprayed products.

Next, assuming that the sialon ceramics was broken, a preliminary crack was made in the center longitudinal direction of the sialon ceramics, and a similar experiment was performed.

When the molten Nd-Fe-B alloy was transferred to the nozzle, the crack propagated and the molten alloy spouted directly from the quartz nozzle hole through the crack without passing through the Sialon orifice 3. However, there was no problem in the rapid solidification apparatus itself including the copper roll. This is because the injection amount was limited by the quartz hole.

In the case of a structure as shown in FIG. 4 in which a ceramic nozzle is joined to the tip of a quartz crucible, or in the case of the structure of FIG. It is considered that there is a great possibility that a large amount of molten metal is spouted out, damaging rapid solidification devices such as copper rolls and chambers.

[0026]

The molten metal injection port at the tip of the nozzle has a double structure of ceramics having corrosion resistance to the molten metal and quartz having thermal shock resistance at a high temperature, so that the molten alloy containing the rare earth metal can be lengthened. The injection was stable over time, and the possibility of molten metal spillage was reduced.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of an injection nozzle according to the present invention, which is used in Examples. (A) is AA
It is sectional drawing and the surface along the row of three orifices arranged in a line, (b) is BB sectional drawing and shows the surface perpendicular to (a). (C) is the figure seen from the nozzle injection hole front.

FIG. 2 is a view showing another embodiment of the injection nozzle according to the present invention, and the configuration of the drawing is the same as that of FIG. 1;

FIG. 3 is a schematic diagram showing the position of an injection nozzle and its function in a single-roll type liquid quenching device.

FIG. 4 is the simplest structure of an injection crucible mainly made of quartz and having a ceramic tip at the tip, which is outside the scope of the present invention. The configuration in the figure is the same as that in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Quartz 2 Hole made in quartz 3 Ceramic orifice 4 Ceramics 5 Metal melt 6 Crucible for melting metal 7 Water-cooled rotary roll 8 Solidification product 9 Vacuum chamber 10 Heater 11 Pressure partition

Claims (1)

[Claims] 1. A nozzle for jetting molten metal composed of quartz and ceramic used in an apparatus for rapidly solidifying a molten metal from a liquid state, the ceramic having an orifice on the inner surface of the tip of the quartz for controlling the amount of molten metal jetted. The orifice is provided with a hole larger than the orifice on the discharge side of the molten metal at the tip end of the quartz so as to be continuous with the orifice. A nozzle for injecting molten metal.