JPH0774363B2 - Low oxygen metal powder production equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to the provision of an improved means for producing low-oxygen metal powder by the “water atomization method” known as a means for producing various metal powders.

(Prior Art) Metal powder has been widely used not only in the field of conventional powder metallurgy but also in the field of injection molding, and the properties required for it are lower in oxygen, finer, and higher in quality. Is oriented. As a known means for producing the metal powder at a mass production level, there are roughly two types, namely, a "water atomizing method" and a "gas atomizing method" as known, but the former is compared with the latter,
The cost of the spray medium is low, and the high pressure, which is indispensable for pulverization, is easy to perform, so it is currently the mainstream.

However, in the "water atomizing method", when this is carried out in the atmosphere, there is a problem that the amount of oxygen in the produced powder becomes high because the molten metal is oxidized. In order to solve this problem, a means for pulverizing the molten metal by jetting a water jet has been already proposed for the molten metal flowing down from the tundish under the surrounding atmosphere of a non-oxidizing atmosphere gas such as an inert gas. It is also known that For example, Japanese Patent Publication No. 52-49874,
Alternatively, as disclosed in JP-B-55-31161,
The molten metal flowing down from the tundish surrounds the molten metal powdering position where it collides with the water jet, and blows and replaces a non-oxidizing gas atmosphere such as an inert gas to prevent the generated powder from oxidizing. In addition, even when performed in the atmosphere, there is a method in which oxygen in the atmosphere flowing into the molten metal powdering position is reduced by a flame curtain by city gas combustion to obtain the same effect.

(Problems to be Solved by the Invention) The conventional “water atomizing method” described above is a method generally used for powder metallurgy, which is a method for producing a metal powder having an average diameter of several tens of μm. The effect to some extent is recognized as it is, for example, in the one using the frame curtain method described above, the atmospheric oxygen amount at the molten metal powdering position reaches 0.5% or less, and as a result, the oxygen amount of the iron-based powder is 0.4%. It decreased to a certain extent
With the means disclosed in JP-B No. 55-31161 and JP-B No. 55-31161, the decrease in oxygen content is recognized to some extent. On the other hand, recently, the use of metal powder has expanded, and finer particle size, for example, a metal powder having an average diameter of about several μm has been required.
It is also known that ultra-high pressure water atomizing means for increasing the pressure to nearly 1000 kgf / cm ² has been developed and is about to be put into practical use. Since this ultrahigh-pressure water atomizing means uses a high-speed water jet, the ejector effect causes a large amount of atmospheric gas to be sucked into the gas chamber for atmospheric gas. As a result, in the one disclosed in JP-B-52-49784, the melt outlet in the tundish is cooled to cause clogging trouble of the melt flow.
In the one disclosed in Japanese Patent No. 31161, a large amount of atmospheric gas is blown toward the molten metal flow, resulting in turbulence in the molten metal flow, making stable operation impossible. Further, in the frame curtain system that burns city gas or the like to reduce oxygen in the atmosphere, it is uneconomical because the amount of city gas that corresponds to the large amount of inflow gas is required, which is uneconomical. The risk of blowout and inflow of raw gas into the chamber increases. Whichever method is used, in order to use the conventional oxygen reduction technology for the ultrahigh pressure water atomization, a large amount of inert gas or city gas, as well as equipment for supplying this, is required, and a large amount of money is required. Increased costs will be incurred. In addition, when it is not possible to supply the inert gas or low oxygen air commensurate with the suction of this super high pressure water jet (for example, when the cross-sectional area of a part where the gas flows is small), the upper part of the water jet nozzle ( The gas chamber side) becomes lower than the atmospheric pressure, and in contrast, the generated powder and water are blown up from the lower atomizing chamber that stores the generated powder and water, resulting in the suspension and suspension of operation. That is, it is difficult to stably and economically operate the ultra-high pressure water atomizer with the conventional production technology of the conventional oxygen-lowering powder. Further, as the average diameter of the powder decreases, the specific surface area (surface area / volume) of the powder increases conversely, so that the powder is easily oxidized. In short, in the ultra-high pressure water atomizing means for producing fine powder, it is necessary to establish a more advanced low oxidation technology, but at present, no solution to this has been made.

(Means for Solving the Problem) In order to solve the problems of the above-described ultra-high pressure water atomizing means in the conventional oxygen reduction technology, the present invention provides an atmosphere by jetting water into a gas chamber for atmosphere gas. While reducing the amount of gas suctioned as much as possible, even if the gas chamber is in a depressurized state, it is designed so that the generation of powder or water from the atomizing chamber under atmospheric pressure does not occur. A tundish 1 for flowing a molten metal, a gas chamber 11 which is closely attached to the lower surface of the tundish 1 and which is capable of adjusting the supply amount of a non-oxidizing atmosphere gas and has a decompression means, and the gas chamber 11
High pressure water jet nozzle 3 which is provided in communication with the lower part or inside thereof, an atomizing chamber 5 into which the generated fine powder and water are introduced, and a cylindrical flow path 4 which connects the nozzle 3 and the atomizing chamber 5. In the apparatus for producing low oxygen metal powder, the tubular flow path 4 has an upper end opening that is expanded upward.
20 and the atomizing chamber 5 following the upper opening 20
In order to prevent blowing up of the generated powder and water in the inside, a straight cylindrical portion 21 having a narrowed cross-sectional area and a lower end opening 22 formed in a downward expanding manner following the straight cylindrical portion 21 are provided, and the upper end opening 20 is the water. The powdering point a of the molten metal, which is formed on the tapered surface 19 parallel to the jetting direction of the jet nozzle 3 and flows down from the tundish 1, is located at the boundary between the upper end opening 20 and the straight tube portion 21. .

(Operation) According to the above technical means of the present invention, the molten metal flowing down from the outlet 16 of the tundish 1 in FIG.
In contrast, the water jet nozzles 18 and 18 of the water jet nozzle 3 are surrounded by a non-oxidizing atmosphere gas such as N ₂ gas continuously supplied into the gas chamber 11 through the gas inflow valve 15 and the orifice 12. When the powder and water generated by spraying are introduced and contained through a tubular flow path 4 that is provided in communication between the water jet nozzle 3 and the atomizing chamber 5 under the atmospheric pressure, the powder and water are introduced. , The upper end opening 20 surrounding the flow path 4 having tapered surfaces 19 and 19 parallel to the jetting direction of the water jets 18 and enclosing the molten metal powdering position a Straight tube part 21 with large resistance,
Since the cross-sectional area and the shape of the lower end opening 22 following the straight cylindrical portion 21 are formed, the pressure difference between the upper portion and the lower portion of the flow passage 4 is different from that of the conventional straight square tubular flow passage. Even if it is large, the powdering work can be obtained without being affected by each other. Especially, due to the presence of the straight tube portion 21 having a reduced cross-sectional area and a large passage resistance, the gas inside the gas chamber 11 is Is sucked out by the water jet injection to reduce the suction amount toward the atomizing chamber 5 side as much as possible, and at the same time, the gauge pressure in the gas chamber 11 becomes -75.
Even when the pressure reaches about 0 mmHg, the generated powder and water do not squirt upward from the inside of the atomizing chamber 5 under the atmospheric pressure condition, and the stable operation can be continued. Further, since the glass chamber 11 can be operated in a decompressed state by this, the use amount is reduced by reducing the mass flow rate of the atmospheric gas flowing into the gas chamber 11, and even when the gas chamber 11 is air, oxygen in the atmosphere is reduced. This has the effect of reducing the amount of oxidation as the partial pressure is reduced by the amount of reduced pressure. Also, due to the reduction in the amount of atmospheric gas used, the molten metal will fall correctly to the powdering position a without disturbing the molten metal flow. Also, the effect of stable operation can be obtained. In addition, the reduced pressure in the gas chamber 11 also causes a force to suck out the molten metal in the tundish 1 that is in close contact with the upper part of the chamber, increasing the molten metal outflow rate per unit time and improving the productivity. Since there is no possibility of blocking the outlet 16 of No. 1 and the like, the production of low-oxygenated powder by the ultra-high pressure water jet can be obtained smoothly.

(Embodiment) An embodiment of the device of the present invention will be described with reference to FIGS. 1 to 6.

In FIG. 1, the apparatus of the present invention has a molten metal outlet on its bottom surface.
A gas chamber 11 in which a non-oxidizing atmosphere gas such as N ₂ gas is continuously blown on the lower surface of a known tundish 1 provided with 16 has an O-ring at its opening or a contact portion with other parts. It is provided so as to be in close contact with the outside and prevent outside air from entering through the airtight seal member 13 such as the above and to maintain the inside of the chamber in a reduced pressure state. The chamber 11 has a sufficiently large volume in order to uniformly disperse the inflowing gas, and the diameter and the number of gas inflow ports are also determined in consideration of this point. The volume of the chamber 11 is about 0.4 m ³ for a gas amount of 0.6 m ³ / sec, and the gas inlet 14 is provided at four locations on the circumference of the inlet 14 formed by, for example, an SGP80A pipe, and the gas inlet valve is provided. 15, the opening of the valve 15 is adjusted while checking the flow rate measurement value by the orifice 12, and the gauge pressure in the gas chamber 11 is set to 0 m during operation.
It is operated under reduced pressure below mHg and above -750 mmHg. Inside or below the gas chamber 11 described above,
A water jet nozzle 3 (for generating a water jet having a V-shaped cross section in this embodiment) for an ultra-high pressure water jet (about 1000 kgf / cm ² ) is provided, and the water jet nozzle 3 and the generated fine powder and water are provided. The cylindrical flow path 4 of the present invention is provided so as to communicate with the atomizing chamber 5 for introducing and accommodating the. In order to solve the problems in the conventional flow passage of this kind, the tubular flow passage 4 reduces the amount of suction gas generated in the gas chamber 11 at the time of water jet injection as much as possible and reduces the pressure inside the gas chamber 11. Even if it becomes a state, the generated powder and water are prevented from being spouted from the atomizing chamber 5 side under the atmospheric pressure state. Instead of the conventional straight rectangular tubular flow path, By narrowing the cross-sectional area and increasing the passage resistance, the amount of sucked gas is reduced and the spraying of the generated powder and water is effectively suppressed. In the practice of the present invention, models of tubular flow passages of various shapes and cross-sectional areas were prepared, and in an open state without a gas chamber, a water jet injection test, an atomization test, and a closed state with a gas chamber attached. As a result of repeatedly comparing the water jet injection tests in the state, it was confirmed that the tubular flow path 4 according to the embodiment illustrated in FIGS. 1 and 2 and 3 was optimal. That is, the water jet 1 in the water jet nozzle 3
An upper end opening 20 having tapered surfaces 19 and 19 parallel to the injection direction of 8 and 18 and surrounding the molten metal powdering position a, a straight cylindrical portion 21 having a narrowed cross-sectional area following the opening 20, and a straight cylindrical portion 21. It has a cross-sectional area and shape by a lower end opening 22 provided in an expanded shape at the lower end. Although the reason for this is not clear, first, in the tubular flow path 4, since the upper end opening 20 has tapered surfaces 19 and 19 parallel to the water jets 18 and 18, separation vortices are less likely to occur. As shown in FIG. 5, the taper surfaces 19a and 19a that are not parallel to the water jet injection direction are superior to those that generate separation vortices. Therefore, the downward suction pressure distribution at the water jet center point is As shown in FIG. 6, (in FIG. 6, the symbol ▲ is the flow path 4 of the present invention,
All other A to F show other models), and the pattern gradually increases as it goes downward, which indicates that the flow in the flow channel smoothly moves only downward. In other model channels, separation vortices are generated between the water jet and the tapered surface, and the pressure distribution is such that a pattern that maximizes suction pressure on the channel upper surface, that is, a flow that pushes up from below is also generated. Therefore, it is considered that the generated powder and water will blow up. Incidentally, in the example, the direction perpendicular to the jet direction of the water jet viewed from the plane is a straight surface, and compared with the flow path model in which the perpendicular direction is also tapered, the molten metal droplets scattered during atomization are One of the advantages is that it is difficult to adhere. By performing the pulverization work in the flow path 4 having the cross-sectional area and the shape determined as described above, the gas in the gas chamber 11 during the water jet is sucked out to the atomizing chamber 5 side under the atmospheric pressure. The amount can be reduced as much as possible, and even if a large depressurized state occurs, it is possible to effectively prevent the generated powder or water from being spouted from the atomizing chamber 5 side, and thereby to stably obtain the depressurized operation.

Further, in the embodiment shown in FIG. 1, the tubular flow path 4 is not directly connected to the atomizing chamber 5, but it is of course possible to directly connect this.

Lastly, the following table is an experimental data table showing the results of atomizing operation according to the present invention, and the old method in the table is the first
The apparatus is constructed by removing the gas chamber 11 and its attached structure (reference numerals 12 to 15, etc.) from the apparatus illustrated in the figure, and this method is based on the present invention. is there.

Next, the operation of the present invention will be described. It was developed as a new oxygen-reducing technology for ultra-high pressure water atomization performed by a water pressure close to 1000 kgf / cm ² , and in particular, a cylindrical flow path where pulverization work is performed. 4, the taper surface 1 parallel to the water jets 18 and 18 at the upper end opening 20 is different from the conventional one.
When viewed in cross-sectional shape with 9,19, shrink from the top →
By using the tubular flow path 4 having a unique shape of constant → expansion, even if the pressure difference between the upper and lower flow paths is significant, the atomizing work can be performed without mutual influence, and the high pressure water By the jet injection, the gas (atmosphere gas) in the gas chamber 11 is sucked out to the atomizing chamber 5 side, and even if the gauge pressure in the gas chamber 11 reaches −750 mmHg, it is generated from the atomizing chamber 5 side under atmospheric pressure. It is possible to easily continue stable atomizing work since powder and water are not blown up, and since the gas chamber can be operated with reduced pressure, the mass flow rate of the inert gas flowing into the gas chamber 11 is reduced, Not only is the usage reduced, but even if the gas chamber 11 is air,
Since the oxygen partial pressure in the atmosphere is reduced by the reduced pressure, the amount of powder oxidation is reduced. In addition, since the mass flow rate of gas also decreases, its momentum also decreases, without disturbing the falling flow of molten metal
The molten metal flows down correctly to the pulverization position, which enables stable atomizing operation.Because the chamber is decompressed, a force to suck out the molten metal in the tundish closely attached to the chamber is generated, and the molten metal flows out per unit time. Not only does it increase the amount and improve the productivity, but it also does not cause inconvenience such as clogging of the molten metal at the tundish outlet, and it can immediately respond to ultra-high pressure water jet atomization that conventional hypoxia technology cannot deal with. is there. Further, as can be seen from the table shown above, the present invention can exert its effect even in atomizing at low pressure. That is, in atomizing at a water pressure of 60 kgf / cm ² ,
In the old method and this method, the oxygen content is reduced from 0.90% to 0.10%. In the frame curtain method described above in the prior art, the amount of powder oxygen around 60 μm is remarkably improved as compared with the limit of 0.4%. High pressure 700kgf / c
It is also clear that the hypoxic effect on m ² is reduced from 1.20% to 0.21%. As described above, the application of the conventional technique is impossible at such a high pressure.

Focusing on the molten metal outflow rate, it is 1.8 times, 2.2 times, and 3.2 times, respectively, due to the pressure reduction effect in the gas chamber 11. This indicates that the production volume per hour has increased, and in the past, if the molten metal flow rate increased in this way, the operation became unstable when the flow of the molten metal was disturbed even a little. However, in the present invention, the mass flow rate of the gas that disturbs the flow of the molten metal is reduced, so that extremely stable operation is possible. The No. 3 example has a molten metal diameter of 2.5 m.
It is assumed to be m. It is known that when the diameter of the molten metal is reduced, the particle size becomes proportionally smaller, and it has been conventionally performed to reduce the diameter of the molten metal in order to obtain finer powder. However, in the case of the diameter of 2.5 mm as in this example, the spontaneous outflow rate is as slow as 50 g / sec, and the temperature of the molten metal lowers before the total amount flows out, causing the problem of solidification at the tundish outlet. On the other hand, when the apparatus of the present invention was used, the productivity was 3.2 times, and therefore the entire amount of the molten metal in the tundish could be discharged without solidifying.

As described above, according to the present invention, the tubular flow path that connects the nozzle and the atomizing chamber has a taper surface whose upper end opening is in an upward expanding shape and is parallel to the injection direction of the nozzle. Since the molten metal is formed, it does not disturb the falling (flowing) flow of the molten metal, and the molten metal is properly flowed to the powdering position, which enables stable atomizing operation.

Further, since the pulverization point of the molten metal that flows down from the tundish is located at the boundary between the upper end opening and the straight tube portion whose cross-sectional area is narrower than this, suction pressure can be understood from the suction pressure distribution shown in FIG. Since the force is large, the effect of suppressing the blow-up of molten metal and water is large.

Further, since the lower end opening is formed in a downward expanding shape to reduce the pressure loss of the mixed flow at the outlet of the tubular flow path, the suction force to the atomizing chamber can be increased and the blowing up of water can be suppressed.

Therefore, according to the present invention, the effect is great in that low-oxygen metal powder can be produced with high productivity and stably without trouble by high-pressure water jet atomization.

[Brief description of drawings]

FIG. 1 is an embodiment view of the device of the present invention, FIG. 2 is a plan view of the tubular flow passage, FIG. 3 is a sectional view of the same main portion, and FIG. , Fig. 5 is a sectional view of the main part, and Fig. 6 is 700k.
Graph of suction pressure distribution graph in gf / cm ² . 1 ... Tundish, 3 ... Water jet nozzle, 4 ...
… Cylindrical channel, 5 …… Atomize chamber, 11 …… Gas chamber, 12 …… Orifice, 13 …… Airtight seal member, 14
…… Gas inlet, 15 …… Gas inlet valve, 18 …… Water jet, 19 …… Tapered surface, 20 …… Top opening, 21 …… Straight tube part, 22 …… Bottom opening.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Eiji Toda Eiji Toda 13-8, Hitomi Town, Akashi City, Hyogo Prefecture (56) References JP-A-50-54563 (JP, A) JP-A-49-131941 (JP, A) ) Actual development Sho 55-80333 (JP, U)

Claims (1)

[Claims] 1. A tundish for flowing a molten metal (1)
A gas chamber (11) that is provided in close contact with the lower surface of the tundish (1) and that is capable of adjusting the supply amount of non-oxidizing atmosphere gas and that is equipped with a pressure reducing means;
A high pressure water jet nozzle (3) provided in communication with the lower part or inside of 1), an atomizing chamber (5) into which the generated fine powder and water are introduced, the noise (3) and an atomizing chamber (5) In a low-oxygen metal powder production apparatus comprising: a tubular flow path (4) communicating with the above, the tubular flow path (4) has an upper end opening ( 20) and the upper end opening (20), followed by a straight tube portion (21) having a narrowed cross-sectional area to prevent blow-up of the produced powder and water in the atomizing chamber (5), and the straight tube portion (2).
1) followed by a bottom opening (2
2), the upper end opening (20) is formed on a taper surface (19) parallel to the jet direction of the water jet nozzle (3), and the melting point (a) of the molten metal flowing down from the tundish (1) is ) Is positioned at the boundary between the upper end opening (20) and the straight tube portion (21), and the low oxygen metal powder production apparatus is characterized.