WO2014155852A1 - ショット粒子の製造方法および装置 - Google Patents
ショット粒子の製造方法および装置 Download PDFInfo
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- WO2014155852A1 WO2014155852A1 PCT/JP2013/083221 JP2013083221W WO2014155852A1 WO 2014155852 A1 WO2014155852 A1 WO 2014155852A1 JP 2013083221 W JP2013083221 W JP 2013083221W WO 2014155852 A1 WO2014155852 A1 WO 2014155852A1
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- shot
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
- B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
- B22F9/10—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying using centrifugal force
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- the present invention relates to a method and an apparatus for producing shot particles. More specifically, the present invention relates to a method and apparatus for producing shot particles made of iron-based alloys such as cast steel shots and stainless steel shots used in various blasting devices such as shot blasting, various shot peening devices and the like, and particularly shot particles. The present invention relates to a method and an apparatus for producing shot particles by a centrifugal method, in which the product yield is improved.
- a water atomizing method As a general method for producing metal powder, various methods such as a water atomizing method, a gas atomizing method, a rotating electrode method, and a molten metal dropping method are conventionally known.
- iron powder used for powder metallurgy etc. reduced iron powder and atomized iron powder are widely used, and the water atomization method is the mainstream for producing atomized iron powder.
- the iron powder produced by this water atomization method has a particle size of approximately 0.2 mm or less, and the particles have an irregular shape.
- a substantially spherical iron powder is required, it is manufactured by a gas atomization method, but there is a problem that the manufacturing cost increases because a large amount of inert gas is consumed.
- the particle size (average particle size) used as shot particles is 0.03 to 4 mm, and the particle size range is very wide, and the particles are roughly spherical. Therefore, in order to produce shot particles, it is required to be able to meet a wide range of particle size requirements and to produce roughly spherical particles. Under such circumstances, it has been difficult to apply a general metal powder production method as it is to the production of shot particles.
- a typical method for producing shot particles used in the past is called the centrifugal method.
- a centrifugal disk and its rotating unit are installed in the center of a large water tank that stores water, and the tundish is placed above the centrifugal disk.
- the centrifugal system has a feature that the particle size distribution of shot particles to be manufactured can be controlled to some extent by changing the peripheral speed of the centrifugal disk (the speed of the outer peripheral edge of the disk from which molten droplets fly).
- the product yield was low (see US Pat. No. 2,310,590, Chinese Utility Model Publication No. 2541089).
- U.S. Pat. No. 2,310,590 relates to a method for producing a cast iron shot by a conventional centrifugal method.
- a centrifugal disk and its rotating unit in the center of a large water tank, drop a thin molten metal flow from above the centrifugal disk through a runner, and form molten droplets from the molten metal by the centrifugal force of the centrifugal disk
- a method of spraying pressurized water from a nozzle toward a flying molten droplet to make the molten droplet fine is disclosed.
- Chinese Utility Model Publication No. 2541089 relates to a conventional steel shot production apparatus using a centrifugal method.
- a basic device that installs a centrifugal disk and its rotating unit in the center of a large water tank, drops a thin molten metal flow from above the centrifugal disk via a tundish, and forms molten droplets from the molten metal by centrifugal force
- the configuration is the same as that of US Pat. No. 2,310,590
- an attempt is made to address the problem of an increase in the waste product rate (defective rate) due to a decrease in the molten metal temperature by arranging the melting furnace and the tundish integrally near the centrifugal disk. Yes.
- the conventional centrifugal method disclosed in the above-mentioned prior art document cannot sufficiently cope with the problem that the product yield is low.
- An object of the present invention is to provide a method and an apparatus for producing shot particles with further improved yield.
- the problem is that a coarse and unnecessary size or defective product is formed and the product yield is lowered, and the molten droplets ejected from the centrifugal disk are in the atmosphere. It addresses the problem of product yield reduction due to flight and inevitable high temperature oxidation. Therefore, an object of this invention is to provide the manufacturing method and apparatus of a shot particle which can improve a product yield.
- the method for producing shot particles of the present invention includes: A water surface of the water tank, and a cover provided so as to cover the periphery of the rotating centrifugal disk disposed above the water surface; In the molten droplet formation space covered by the tundish provided through the cover, A gas discharge step of discharging gas from an opening for discharging gas generated in the molten droplet formation space; A water film forming step of forming a water film on the inner surface of the cover; A molten metal supply step of injecting molten metal into the tundish, supplying the molten metal from the hole at the bottom of the tundish, and supplying the molten metal onto the rotating centrifugal disk; A molten droplet forming step of forming molten droplets by centrifugal force from the molten metal supplied to the rotating centrifugal disk; A droplet solidification step of causing the molten droplet to collide with the water film on the inner surface of the cover formed in the water film forming step to break it into
- the molten droplet formation space includes a gas discharge step, a water film formation step, a molten metal supply step, a molten droplet formation step, and a droplet solidification step. Inflow into the molten droplet formation space can be suppressed, and high-temperature oxidation of the molten droplet can be reduced.
- a cover is provided so as to cover the periphery of the rotating centrifuge disk, and a water film is formed on the inner surface of the cover, so the molten droplets formed by the centrifugal force of the centrifuge disk collide with the water film on the inner surface of the cover. It breaks up into smaller droplets than molten droplets, and then quickly cools and solidifies.
- the distance that the molten droplets fly can be shortened, high-temperature oxidation can be reduced.
- a coarse molten droplet approximately 5 mm or more in diameter
- it can be broken into smaller droplets than the molten droplet, so that it is possible to reduce the generation of coarse particles that do not become a product. Therefore, the product yield can be further improved by the two effects of reducing high temperature oxidation and generating coarse particles.
- the opening and closing of the valve connected to the opening can be controlled according to the pressure in the molten droplet formation space.
- the pressure in the molten droplet formation space is detected and controlled by opening and closing the valve so that the pressure is within a certain range, the gas generated in the molten droplet formation space is controlled.
- the air can be effectively discharged and the air can be prevented from flowing in excessively.
- An excessive flow of air is not preferable because the oxygen concentration in the molten droplet formation space increases and high-temperature oxidation increases.
- the opening and closing of the valve connected to the opening can be controlled by grasping the type and concentration of the gas in the molten droplet formation space.
- the opening and closing of the valve is controlled by grasping the type and concentration of gas such as water vapor, oxygen, and hydrogen generated in the molten droplet formation space, the gas concentration in the molten droplet formation space
- high-temperature oxidation can be reduced by stabilizing the temperature.
- high temperature oxidation can be effectively reduced.
- the opening degree K is less than 0.005, there is a risk of explosion, and if it exceeds 1.0, the atmosphere flows in and the oxygen concentration in the molten droplet formation space increases and high-temperature oxidation increases, which is not preferable.
- the opening degree K can be adjusted by forming an opening in the cover or by using a gap between the cover and the tundish. Or it is also possible to adjust by both the opening formed in the cover and the gap between the cover and the tundish.
- the water film forming step may be performed by setting the angle ⁇ between the cover having a frustoconical side and the inner surface of the cover colliding with the molten droplet to the water surface of the water tank to 20 to 80 degrees. it can.
- a droplet formed by splitting a molten droplet is likely to rebound toward the water surface of the water tank, so that there is an advantage that collision between the droplet and the molten droplet can be reduced.
- the angle ⁇ is less than 20 degrees, the molten droplets fly and the distance until it collides with the inner surface of the cover on which the water film is formed increases, so that high-temperature oxidation increases, and if the angle ⁇ exceeds 80 degrees, Is not preferable because it is difficult to rebound toward the water surface of the water tank and collision with molten droplets increases. It is not preferable that the droplet collides with the molten droplet because the deformed particles in which two or more droplets are combined increase and the product yield decreases.
- the angle ⁇ can be easily adjusted by preparing a plurality of covers having different angles and exchanging them.
- the water film forming step can be performed by setting an angle ⁇ between the inner surface of the cover colliding with the molten droplet and the water surface of the water tank to 30 to 70 degrees.
- the distance until the molten droplets fly and collide with the inner surface of the cover on which the water film is formed becomes small, high-temperature oxidation can be further reduced, and the collision between the small droplets and the molten droplets can be reduced. Since it can reduce and a product yield improves, there exists an advantage that it is more preferable.
- the molten droplet forming step can be performed by adjusting the distance L between the outer peripheral edge of the centrifugal disk and the inner surface of the cover with which the molten droplet collides within a range of 200 to 5000 mm.
- the distance L is adjusted to a range of 200 to 5000 mm, it is possible to control the particle size distribution and shape of the small droplets (shot particles) while reducing high-temperature oxidation of the molten droplets. If the distance L is less than 200 mm, the particle size distribution of the droplets (shot particles) formed by splitting the molten droplets becomes smaller as a whole, and high-temperature oxidation is reduced, but deformed particles with two or more droplets combined increase.
- the distance L can be easily adjusted by preparing and replacing a plurality of covers having different sizes.
- cooling water is supplied to the inner surface of the cover, and the thickness of the water film formed by the cooling water can be adjusted to 0.5 to 10 mm.
- the thickness of the water film is set to 0.5 to 10 mm, the molten droplet is not welded to the inner surface of the cover, and the molten droplet is split to form a small droplet. If the thickness of the water film is less than 0.5 mm, welding may occur on the inner surface of the cover and the product yield may be reduced. If the thickness exceeds 10 mm, the molten droplets are coarsened due to solidification in the middle of breaking into small droplets.
- the thickness of the water film means the thickness of the water film in the region where the molten droplet collides on the inner surface of the cover, and it is necessary to form a water film with a uniform thickness on the entire inner surface of the cover. Absent.
- the supply rate of supplying the molten metal onto the centrifugal disk can be adjusted to 70 to 600 kg / min.
- the particle size (average particle size) used as shot particles If the feed rate is less than 70 kg / min, the particle size (average particle size) of the droplets (shot particles) can be adjusted to become smaller, but the productivity cannot be secured, and if it exceeds 600 kg / min, the coarse melting Increasing the rate of formation of droplets (approximately 5 mm or more in diameter) reduces product yield because it cannot break into smaller droplets than molten droplets.
- the shot particle manufacturing apparatus of the present invention includes a water tank for storing water, a centrifugal disk positioned above the water surface of the water tank, a tundish installed above the centrifugal disk, and a periphery of the centrifugal disk.
- a cover that forms a molten droplet formation space with the water surface of the water tank and the tundish, an opening that is formed in the cover and discharges gas generated in the molten droplet formation space, and the cover A water injection nozzle that supplies cooling water to the inner surface of the water to form a water film.
- the shot particle manufacturing apparatus includes a water tank for storing water, a centrifugal disk positioned above the water surface of the water tank, a tundish installed above the centrifugal disk, and the centrifugal disk.
- a cover that covers the periphery and forms a molten droplet forming space with the water surface of the water tank and the tundish is provided, so that the atmosphere is prevented from flowing into the molten droplet forming space, and the high temperature oxidation of the molten droplet is performed. Can be reduced.
- a cover that covers the periphery of the centrifugal disk is provided, and a water injection nozzle that forms a water film by supplying cooling water to the inner surface of the cover is provided, so that the molten droplets formed by the centrifugal force of the centrifugal disk are on the inner surface of the cover. It collides with the water film and breaks up into smaller droplets than molten droplets, and then quickly cools and solidifies. Therefore, since the distance that the molten droplets fly can be shortened, high-temperature oxidation can be reduced.
- the product yield can be improved by the two effects of reducing high-temperature oxidation and generating coarse particles.
- the opening for discharging the gas generated in the molten droplet forming space is provided, gas such as water vapor, oxygen, hydrogen generated in the molten droplet forming space can be discharged. Therefore, it is possible to avoid the danger that the molten droplet formation space is filled with gas and an explosion or the like occurs, so that safety can be ensured.
- the device structure is simple, it is easy to manufacture and maintain the device.
- a centrifugal disk can be installed at the upper end of a rotating unit that rotates the centrifugal disk. According to the present invention, there is an advantage that the centrifugal disk can be easily replaced and maintained.
- the rotating unit can be installed below the water surface of the water tank with waterproof measures, and can be installed so that the upper end of the rotating shaft of the rotating unit is located above the water surface of the water tank.
- the cover is formed of a plate-like cover plate, and the cover can be axisymmetric with respect to the rotation axis of the centrifugal disk.
- a cover plate can be manufactured from general-purpose various steel plates, there is an advantage that manufacture and maintenance of the apparatus are easy.
- the cover is axisymmetric with respect to the rotation axis of the centrifugal disk, the distance L between the outer peripheral edge of the centrifugal disk and the inner surface of the cover where the molten droplet collides becomes uniform over the entire circumference in the horizontal direction, and shot particles The quality such as particle size distribution and shape is improved.
- the cover is formed of a plate-like cover plate, and the lower end of the cover can be located below the water surface of the water tank. According to the present invention, when the lower end of the cover is positioned below the water surface of the water tank, there is an advantage that safety can be ensured because there is no risk of the molten droplets and small droplets jumping out of the cover.
- the cover may have a truncated cone side part, and may have an inclined surface having an angle ⁇ of 20 to 80 degrees between the inner surface of the side part and the water surface of the water tank.
- a droplet formed by splitting a molten droplet is likely to rebound toward the water surface of the water tank, so that there is an advantage that collision between the droplet and the molten droplet can be reduced. If the angle ⁇ is less than 20 °, the distance until the molten droplets fly and collide with the inner surface of the cover plate on which the water film is formed increases, so that high-temperature oxidation increases.
- the droplets easily bounce off the surface other than the water surface of the water tank, the collision with the molten droplet increases, which is not preferable. It is not preferable that the droplet collides with the molten droplet because the deformed particles in which two or more droplets are combined increase and the product yield decreases.
- the angle ⁇ between the inner surface of the side portion and the water surface of the water tank can be 30 to 70 degrees.
- the angle ⁇ between the inner surface of the cover plate and the water surface of the water tank is 30 to 70 degrees, the distance until the molten droplets fly and collide with the inner surface of the cover on which the water film is formed becomes small. Therefore, high-temperature oxidation can be further reduced, and collision between small droplets and molten droplets can be reduced, thereby improving product yield.
- the shot particle manufacturing apparatus of the present invention can be provided with a hole through which molten metal flows out at the bottom of the tundish. According to the present invention, the molten metal can be stably supplied onto the rotating centrifugal disk, and the supply speed of supplying the molten metal onto the centrifugal disk can be adjusted by changing the size of the hole.
- a plurality of water injection nozzles can be installed above the upper end surface of the centrifugal disk with water injection ports for injecting cooling water positioned on the inner surface of the cover. According to the present invention, there is an advantage that it is possible to form a water film covering a region where the molten droplet collides on the inner surface of the cover.
- the cover has a central opening at the top, and the tundish can be provided through the central opening. According to the present invention, there is an advantage that it is easy to install the tundish directly above the centrifugal disk, and it is easy to replace and maintain the tundish.
- the degree of opening K is Vm 3 for the volume of the molten droplet formation space covered by the water surface of the cover, tundish and water tank, and the total area of the opening is Sm 2 .
- the opening degree K is set in the range of 0.005 to 1.0, the risk of an explosion or the like due to the filling of gas such as water vapor, oxygen, or hydrogen generated in the molten droplet formation space is avoided. can do.
- high temperature oxidation can be effectively reduced by reducing the oxygen concentration in the space.
- the opening degree K can be adjusted by the size and number of openings formed in the cover. Moreover, it can also adjust by providing a valve
- high-temperature oxidation can be reduced, and even when a coarse molten droplet (approximately 5 mm or more in diameter) is formed, Can break up into small droplets, which can reduce the generation of coarse particles that do not result in a product. Therefore, the product yield is improved by the two effects of reducing high-temperature oxidation and generating coarse particles.
- the shot particle manufacturing apparatus of the present invention it is possible to reduce high-temperature oxidation, and even when coarse molten droplets (approximately 5 mm or more in diameter) are formed, Since it can break into smaller droplets than droplets, it is possible to reduce the generation of coarse particles that do not become a product. Therefore, the product yield is improved by the two effects of reducing high-temperature oxidation and generating coarse particles. Furthermore, safety can be ensured because the danger of explosion and the like can be avoided. In addition, the apparatus structure is simple, and the manufacture and maintenance of the apparatus are easy.
- the shot particle manufacturing apparatus in the present embodiment includes a water tank 20 for storing water, a centrifugal disk 2 positioned above the water surface of the water tank 20, and a tundish installed above the centrifugal disk. 4 and the cover 3 that covers the periphery of the centrifugal disk 2 and forms the molten droplet formation space 5 by the water surface 1 of the water tank 20 and the tundish 4, and the gas generated in the molten droplet formation space 5 is discharged.
- An opening 6 and a water injection nozzle 15 for supplying cooling water to the inner surface of the cover 3 are provided.
- the automatic pouring device has a function of automatically running, and also has a function of injecting molten metal into the tundish by automatically tilting, moving up and down, and moving back and forth. it can.
- the water surface 1 of the aquarium 20 means the surface of the water in the aquarium 20 in which a cooling medium (water) for dropping and cooling and solidifying the droplets 13 is stored and opened upward.
- the water tank 20 can also utilize what was used in the conventional centrifugal system.
- it in order to carry out mass production continuously, it has a structure that can store a sufficient amount of water, and has a water circulation cooling facility so that the water in the water tank 20 does not exceed a set temperature (for example, 60 to 80 ° C.). It is desirable to have it.
- the cooled and solidified droplets 13 are dropped and temporarily accumulated on the bottom surface of the water tank 20, a sufficient water depth is ensured, and an inclination is provided on the bottom surface of the water tank 20 as necessary.
- the position where the droplets 13 (shot particles) are accumulated can be adjusted.
- the centrifugal disk 2 positioned above the water surface 1 of the water tank 20 is a container having a disk shape, a cup shape, or the like used for forming the molten droplet 12 from the molten metal 10 in the centrifugal system. It has a structure formed of a refractory material and reinforced with steel or the like, and has a strength that is not damaged by rotation. In the present invention, various centrifugal discs used in the conventional centrifugal method can be used. The centrifugal disk 2 is rotated by a rotating unit 7.
- the rotating unit 7 can be installed so as to be waterproofed and placed below the water surface 1 of the water tank 20 so that the upper end of the rotating shaft of the rotating unit 7 is located above the water surface 1 of the water tank 20. Then, the centrifugal disk 2 can be installed at the upper end of the rotary unit 7.
- the rotation unit 7 supports the centrifugal disk 2 with a rotation shaft, and rotates the centrifugal disk 2.
- the rotation unit 7 is typically a device that rotates a shaft by a motor (not shown), but may be another known structure.
- the cover 3 covering the periphery of the centrifugal disk plays an indispensable role for covering the periphery of the centrifugal disk 2 located above the water surface 1 of the water tank 20 and forming the molten droplet formation space 5. .
- the cover 3 can prevent the atmosphere from flowing into the molten droplet formation space 5, thereby reducing high-temperature oxidation of the molten droplet 12.
- the shape of the cover 3 is a shape in which the cup is turned down. That is, it has an upper circular plane and a side frustoconical shape.
- the cover 3 may have other shapes such as a hemispherical shape and a semi-ellipsoidal shape.
- the cover 3 is a plate-like cover plate, and the cover 3 can be axisymmetric with respect to the rotation axis of the centrifugal disk 2.
- the distance L between the outer peripheral edge of the centrifugal disk 2 and the inner surface of the cover 3 where the molten droplet collides is uniform over the entire circumference in the horizontal direction, and the particle size distribution of the shot particles and The quality such as shape is improved.
- the lower end of the cover 3 can be positioned below the water surface 1 of the water tank 20. When the lower end of the cover 3 is positioned below the water surface 1 of the water tank 2, there is no risk of the molten droplet 12 and the small droplet 13 jumping out of the cover 3, and safety can be ensured.
- the cover 3 has a frustoconical side portion, and can have an inclined surface having an angle ⁇ (see FIG. 3) between the inner surface of the cover 3 and the water surface 1 of the water tank 20 of 20 to 80 degrees. More preferably, the angle ⁇ between the inner surface of the cover 3 and the water surface 1 of the water tank 20 can be set to 30 to 70 degrees. As shown in FIGS. 1 and 3, the cover 3 has a frustoconical shape, and the angle ⁇ formed with the water surface is 20 to 80 degrees, more preferably 30 to 70 degrees. Since the droplets 13 formed by colliding with and splitting are likely to rebound toward the water surface 1 of the water tank 20, collision between the droplets 13 and the molten droplets 12 can be reduced.
- the cover 3 has a central opening 16 at the top, and the tundish 4 can be provided through the central opening 16. That is, the tundish 4 can be disposed immediately above the centrifugal disk 2, and the molten metal 10 from the tundish 4 can be reliably guided to the centrifugal disk 2.
- a cover board can be manufactured from general purpose various steel plates, such as a general structural rolled material, a rolled steel material for welded structures, a rolled steel material for boilers, and a stainless steel material. Further, the cover 3 can adopt an appropriate structure such as installing a support column for supporting and fixing the cover 3 in the water tank 20.
- the tundish 4 positioned above the centrifugal disk 2 stores the injected molten metal 10 at a constant rate while storing the injected molten metal 10 at a constant speed and supplies the molten metal 10 onto the centrifugal disk 2.
- the inner surface is formed of a refractory and the outer surface is reinforced with steel or the like.
- the molten droplet formation space 5 is a space covered with the water surface 1 of the water tank 20, the cover 3 covering the periphery of the centrifugal disk 2, and the tundish 4 installed above the centrifugal disk 2. Can be prevented from flowing into the molten droplet forming space 5, and high-temperature oxidation of the molten droplet 12 can be reduced.
- the opening 6 for discharging the gas generated in the molten droplet forming space 5 is provided in the molten droplet forming space 5 for discharging the gas generated in the molten droplet forming space 5. It is. That is, when the molten droplet 12 and the small droplet 13 come into contact with the water film 9 formed on the inner surface of the cover 3 and the water in the water tank 20, water vapor is generated, and further, a part of the water vapor is decomposed to generate hydrogen and oxygen. appear. For this reason, when the molten droplet formation space 5 is sealed, there is a risk that the generated gas is filled and explosion occurs. Therefore, an opening 6 for discharging the generated gas is provided.
- the opening 6 can be provided with a valve 8 for adjusting the amount of gas or the like discharged from the opening 6.
- the valves 8 may be provided only in some of the openings 6 without being provided in all the openings 6.
- the valve 8 may be adjusted in opening degree based on a measured value by a sensor (pressure gauge) (not shown) that measures the pressure in the molten droplet formation space 5.
- the sensor can be arranged at an arbitrary position, but it is preferable to arrange the sensor on the inner surface of the cover 3 (for example, the upper surface of the cover 3) above the centrifugal disk 2 so that the molten droplet 12 and the small droplet 13 do not collide with each other. .
- the opening degree K is less than 0.005
- the opening degree K exceeds 1.0, oxygen flows in the molten droplet formation space due to the inflow of air, resulting in high temperature oxidation. Is unfavorable because of an increase.
- the position, number, and shape of the opening 6 are not limited to the example shown in FIG. 3, and an arbitrary number of openings 6 of any shape are provided at positions where the molten droplet 12 of the cover 3 does not collide. Can do. Further, a gap may be formed between the central opening 16 at the top of the cover 3 and the tundish 4 to be used as the opening 6.
- a sensor for detecting the type and concentration of gas in the molten droplet formation space 5 may be provided.
- a sensor for detecting the type and concentration of gas in the molten droplet formation space 5 may be provided.
- an oxygen sensor or a hydrogen sensor is used as the sensor.
- the water injection nozzle 15 that supplies cooling water to the inner surface of the cover 3 is provided to form a water film 9 that covers a region where the molten droplet collides on the inner surface of the cover 3.
- a plurality of water injection nozzles 15 can be installed above the upper end surface of the centrifugal disc 2 with the water injection port 15 a for injecting the cooling water 14 positioned on the inner surface of the cover 3.
- the water injection port 15 a is located on the inner surface side of the cover 3, and the cooling water 14 discharged from the water injection port 15 a is disposed on the cover 3. It means that the water injection port 15a is disposed at a position close to the inner surface of the cover 3 so as to flow along the inner surface.
- the distance between the water inlet 15a and the inner surface of the cover 3 is, for example, 2 cm or less, or 1 cm or less.
- the shape of the water injection nozzle 15 is not limited to that shown in FIG. 3.
- the discharge port 15 a does not penetrate the upper surface of the cover 3, penetrates the side surface, and does not have a bent portion. You may face the center.
- the cooling water flows along the inner surface of the cover 3 by slowing the flow rate of the discharged cooling water 14.
- various commercially available nozzles can be used, and a nozzle having two or more water injection ports 15a can also be used.
- annular form is also contained in the water injection nozzle in this invention.
- the shot particle manufacturing method in the present embodiment is a cover provided so as to cover the water surface 1 of the water tank 20 and the periphery of the rotating centrifugal disk 2 disposed above the water surface 1.
- the droplet droplet 12 collides with the water film 9 on the inner surface of the cover 3 formed in the water film formation step to break up the droplet 13 smaller than the molten droplet 12, and then the droplet 13 is cooled and solidified. And a process.
- the gas discharge process will be described.
- the following phenomenon occurs in the molten droplet formation space 5. That is, when the molten droplet 12 and the small droplet 13 come into contact with the water film 9 formed on the inner surface of the cover 3 and the water stored in the water tank 20, water vapor is generated, and further, a part of the water vapor is decomposed to generate hydrogen. Oxygen is generated. For this reason, when the molten droplet formation space 5 is sealed, there is a risk of explosion due to filling of the generated gas as described above. Therefore, a gas discharge step for discharging the gas from the opening 6 is provided.
- the opening and closing of the valve 8 provided in the opening 6 can be controlled by the pressure in the molten droplet formation space 5. That is, it is possible to control the pressure to be within a certain range by disposing the valve 8 in the opening 6 and installing a sensor for detecting the pressure in the molten droplet formation space 5.
- the valve 8 When the pressure exceeds the upper limit value, the valve 8 is opened and the gas is discharged to prevent explosion.
- the valve 8 is closed to suppress the inflow of the atmosphere to perform high temperature oxidation. Can be reduced.
- the opening and closing of the valve 8 provided in the opening 6 can be controlled by grasping the type and concentration of the gas.
- the gas concentration in the molten droplet formation space 5 can be stabilized.
- the molten droplet 12 collides with the cover 3 and breaks into small droplets 13 smaller than the molten droplet 12.
- the cooling water 14 is supplied to the inner surface of the cover 3 to prevent the molten droplet 12 from being welded to the inner surface of the cover 3 to prevent the molten droplet 12 from welding to the inner surface of the cover 3.
- a water film forming step for forming the film 9 is provided. With the water film 9 formed by this water film forming step, the molten droplet 12 can be effectively divided into small droplets 13 without the molten droplet 12 being welded to the inner surface of the cover 3.
- the thickness of the water film 9 can be adjusted by changing the amount of cooling water supplied. Further, the water film forming step can be performed by setting an angle ⁇ between the inner surface of the cover 3 where the molten droplet 12 collides with the water surface 1 of the water tank 20 to 20 to 80 degrees. More preferably, the angle ⁇ can be set to 30 to 70 degrees. In addition, in the water film formation step, the thickness of the water film 9 formed by supplying cooling water to the inner surface of the cover can be adjusted to 0.5 to 10 mm.
- the angle ⁇ means an angle formed by a region where the molten droplet 12 collides with the water surface 1 of the water tank 20 on the inner surface of the cover 3, and is not necessarily a portion where the inner surface of the cover 3 is in contact with the water surface 1 of the water tank 20. It does not indicate an angle.
- the angle ⁇ is less than 20 degrees, the flying distance until the molten droplet 12 that has jumped out of the centrifugal disk 2 collides with the inner surface of the cover 3 on which the water film 9 is formed becomes long, and particularly jumps to a position close to the water surface 1.
- the molten droplet 12 becomes long and high-temperature oxidation increases.
- the angle ⁇ exceeds 80 degrees, the droplet 13 that collides with and reflects the inner surface of the cover 3 on which the water film 9 is formed is likely to be reflected not in the direction of the water surface 1 but in a direction close to the horizontal. Colliding with the droplet 12, the irregular shaped particles increase and the product yield decreases. Therefore, by setting the angle ⁇ to 20 to 80 degrees, more preferably 30 to 70 degrees, the flying distance of the molten droplet 12 is not long, high temperature oxidation is prevented, and the small droplet 13 and the molten droplet 12 is prevented and the product yield is kept high.
- the thickness of the water film 9 is the thickness of the water film 9 in the region where the molten droplet 12 collides.
- the molten droplet 12 is welded to the inner surface of the cover 3 and the product yield decreases.
- the thickness of the water film 9 exceeds 10 mm, the molten droplet 12 is solidified in the middle of being split into small droplets 13, and coarse deformed particles are generated, resulting in a decrease in yield.
- molten metal 10 melted to have a predetermined chemical component in a melting furnace (not shown) or the like is poured into the tundish 4, and the molten metal is injected from the hole 11 at the bottom of the tundish 4.
- a molten metal supply step is provided for supplying 10 onto the rotating centrifugal disk 2 that flows out.
- the tundish 4 flows out the molten metal 10 from the hole 11 at a constant speed and supplies it onto the centrifugal disk 2 while storing a fixed amount of the injected molten metal 10.
- the molten metal 10 can be supplied from the outside of the molten droplet formation space 5 onto the rotating centrifugal disk 2. Further, the supply speed for supplying the molten metal 10 onto the centrifugal disk 2 can be adjusted to 70 to 600 kg / min. The supply speed can be adjusted by changing the size and number of the holes 11 and changing the depth of the molten metal stored in the tundish 4.
- the particle size (average particle size) of the droplets (shot particles) can be adjusted to become smaller, but the productivity cannot be secured, and if it exceeds 600 kg / min, the coarse melting Increasing the rate of formation of droplets (approximately 5 mm or more in diameter) reduces product yield because it cannot break into small droplets of the desired particle size (eg, 0.03-4 mm). Therefore, by adjusting the supply speed to 70 to 600 kg / min, small droplets (shot particles) having a desired particle diameter can be produced appropriately.
- the centrifugal disk 2 is a container having a disk shape, a cup shape, or the like, has a structure formed of a refractory material and reinforced with a steel material, and has a strength that is not damaged by rotation.
- the centrifugal disk 2 is driven by the rotation unit 7 and rotates.
- the molten metal 10 supplied to the vicinity of the center of the rotating centrifugal disk 2 spreads to the outer peripheral edge of the centrifugal disk 2 by centrifugal force and is melted at the time of jumping out of the outer peripheral edge or during the flight.
- Drops 12 are formed.
- the molten droplet forming step can be performed by adjusting the distance L between the outer peripheral edge of the centrifugal disk 2 and the inner surface of the cover 3 with which the molten droplet 12 collides within a range of 200 to 5000 mm.
- the distance L When the distance L is less than 200 mm, the molten droplet 12 easily collides with the droplet 13 that divides and flies by colliding with the inner surface of the cover 3, and the number of deformed particles combined with two or more increases. This is not preferable because the particle size distribution of the whole becomes large and coarse particles are mixed. If the distance L exceeds 5000 mm, high temperature oxidation tends to occur, which is not preferable. Therefore, when the distance L is adjusted to a range of 200 to 5000 mm, it is possible to control the particle size distribution and shape of the small droplets (shot particles) while reducing high-temperature oxidation of the molten droplets. The distance L can be easily adjusted by preparing and replacing a plurality of covers having different sizes.
- the droplet coagulation process will be described.
- a droplet coagulation step for cooling and solidification is provided.
- the droplet solidification step it is estimated that the molten droplet 12 collides with the water film 9 on the inner surface of the cover 3 to be subjected to a mechanical impact and a shock caused by a local water vapor explosion, and is divided into droplets 13.
- the droplet 13 falls into the water of the water tank 20 and is cooled and solidified to become shot particles.
- the shot particles in the embodiment of the present invention are, for example, cast steel shots such as high carbon cast steel shots and low carbon cast steel shots defined in JIS Z0311 (2004) in Japan, and iron such as stainless steel shots made of stainless cast steel. It is a shot made of a base alloy.
- the shot particle size (average particle size) is in the range of approximately 0.03 to 4 mm, and various particle size shots are defined (JIS Z0311 (2004)).
- high-temperature oxidation can be reduced, and even when a coarse molten droplet (approximately 5 mm or more in diameter) is formed, Since it can break into smaller droplets than molten droplets, it is possible to reduce the generation of coarse particles that do not become a product. Therefore, the product yield is improved by the two effects of reducing high-temperature oxidation and generating coarse particles.
- the shot particle manufacturing apparatus of the present embodiment it is possible to avoid the risk of explosion and the like, and thus safety can be ensured.
- the apparatus structure is simple, and the manufacture and maintenance of the apparatus are easy.
- the shot particle manufacturing method of the present embodiment includes a gas discharge step, a water film formation step, a molten metal supply step, a molten droplet formation step, and a droplet solidification step, which will be described in this order. did.
- the present invention can be realized even if these several steps are performed simultaneously or some of them are reversed in order.
- the gas discharging step and the water film forming step may be performed in the reverse order or simultaneously.
- Test Example 1 of the present invention will be described.
- shot particles were produced from high carbon cast steel shots to confirm the effect of the present invention.
- the raw material composition is adjusted so that steel scrap, Fe-Si, Fe-Mn, carburized material, and the like are used as raw materials, and a 5000 kg raw material is prepared using a high-frequency induction furnace with an iron equivalent melting amount of 5000 kg. After dissolution, the entire amount was poured out and used for the test.
- the melting temperature was set to 1640 to 1680 ° C., and deoxidation with pure aluminum was performed immediately before tapping.
- the molten metal was divided into 10 portions of 500 kg, received in a ladle, and poured into the tundish 4 of the shot particle production apparatus shown in FIG. 3 to produce shot particles.
- the entire amount of the produced shot particles was recovered from the water tank 20, dried with hot air using a fluidized bed dryer, and the recovered weight was measured.
- the loss ratio by high temperature oxidation was calculated
- equation. Loss ratio due to high temperature oxidation (% by weight) (1 ⁇ shot recovered weight / dissolved weight) ⁇ 100.
- the molten metal supply speed to the centrifugal disk 2 is 170 kg / min
- the peripheral speed of the centrifugal disk 2 is 10.5 m / s
- the angle ⁇ between the inner surface of the cover 3 and the water surface 1 of the water tank 20 is 50 degrees
- the thickness L of 9 is 2 mm
- the opening degree K of the opening 6 is 0.3
- the distance L between the outer peripheral edge of the centrifugal disc 2 and the inner surface of the cover 3 is 1200 mm and 2500 mm. did.
- a centrifugal disc and its rotating unit are installed in the center of the water tank without a cover, a thin melt flow is dropped from above the centrifugal disc, and a conventional centrifugal centrifuge only forms molten droplets from the melt by the centrifugal force of the centrifugal disc.
- the system was compared with Examples 1 and 2 as Comparative Example 1.
- Table 1 shows the particle size distribution measurement results.
- Comparative Example 1 which is a conventional centrifugal method, the diameter of 3.350 mm or more was 8.4%, whereas in Example 1, it was 0.8%, and in Example 2, it was 2.9%. The occurrence of has decreased.
- shot particles of 3.350 mm or more were observed in Comparative Example 1, about half of them exceeded 4 mm, and it was necessary to redissolve them.
- Example 1 and Example 2 almost no shot particles exceeding 4 mm were contained, and it was confirmed that the product yield was improved because remelting was not necessary.
- Example 1 and Example 2 the particle size distribution is shifted to the finer overall as compared with Comparative Example 1, and the molten droplets formed by the centrifugal force of the centrifugal disk are applied to the water film on the inner surface of the cover. The effect of colliding and breaking into smaller droplets than molten droplets was confirmed. Further, regarding the influence of the distance L between the outer peripheral edge of the centrifugal disk 2 and the inner surface of the cover 3, the particle size distribution in Example 1 having a small L was slightly finer than that in Example 2. In Examples 1 and 2, there was no phenomenon in which molten droplets were welded to the cover or coarse irregular shaped particles were formed. Also, there was no phenomenon such as explosion due to gas generated in the molten droplet formation space. In Table 1, “PAN” refers to fine particles that have passed through the smallest sieve mesh.
- Test Example 2 In this test example, the effect of the present invention on high-temperature oxidation of shot particles was confirmed.
- Test Example 1 since the Example and the Comparative Example were manufactured under the same conditions (melt supply speed and centrifugal disc peripheral speed), the particle size distribution of Example 1 and Example 2 became finer than that of Comparative Example 1.
- the loss ratio (% by weight) due to high-temperature oxidation is affected by the particle size of shot particles, and generally high-temperature oxidation increases as the particle size decreases. Therefore, shot particles of Comparative Example 2 were manufactured so as to have a particle size distribution similar to that of Example 1.
- the production conditions of Comparative Example 2 were set such that the molten metal supply speed to the centrifugal disk 2 was 170 kg / min, and the peripheral speed of the centrifugal disk 2 was 15 m / s.
- Table 2 shows the measurement results of the particle size distribution
- Table 3 shows the results of determining the loss ratio (% by weight) due to high-temperature oxidation.
- Comparative Example 2 which is a conventional centrifugal method
- the ratio of less than 1 mm significantly increased to 49.3% (12.9% in Comparative Example 1).
- the ratio of less than 1 mm in Example 1 was 66.1%.
- Comparative Example 2 has a large loss ratio due to high-temperature oxidation even though the ratio of less than 1 mm is smaller than Example 1. This is because high-temperature oxidation proceeds significantly in the atmosphere in the molten droplets that have jumped out of the centrifugal disk.
- Test Example 3 In this test example, the influence of the opening degree K of the opening was confirmed.
- shot particles by high carbon cast steel shots were produced in the same manner as in Test Example 1, the molten metal supply speed to the centrifugal disk 2 was 220 kg / min, the peripheral speed of the centrifugal disk 2 was 11 m / s, and the cover 3
- the angle ⁇ between the inner surface of the water tank 20 and the water surface 1 of the water tank 20 was 40 degrees
- the thickness of the water film 9 was 1.5 mm
- the distance L between the outer peripheral edge of the centrifugal disk 2 and the inner surface of the cover 3 was 2000 mm.
- Example 3 where the opening degree K is in the range of 0.005 to 1.0, the opening degree K is 0.01, in Example 4, the opening degree K is 0.9, and in the comparative example 3 outside the range, the opening degree K is Was 0.003, and in Comparative Example 4, the opening degree K was 1.5. And the presence or absence of the explosion by the generated gas and the loss ratio by high temperature oxidation were measured.
- Table 4 shows the test results.
- Example 3 and Example 4 no explosion occurred, and the loss ratio (% by weight) due to high-temperature oxidation was 4% or less, whereas in Comparative Example 3, a small-scale explosion occurred.
- No. 4 no explosion occurred, but the loss ratio (wt%) due to high temperature oxidation exceeded 10%. Therefore, since the opening degree K is too small in Comparative Example 3, the hydrogen gas generated in the molten droplet formation space is not effectively discharged and explosion occurs.
- Comparative Example 4 the opening degree K is too large. It is estimated that the loss rate (wt%) due to high-temperature oxidation increased due to an increase in atmospheric inflow.
- the oxygen concentration in the molten droplet formation space was measured 2 minutes after the start of the molten metal supply step, it was 1.8 vol% in Example 3, but 14.2 vol% in Comparative Example 4. It was confirmed that the oxygen concentration was increased.
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Abstract
Description
遠心方式では、遠心ディスクの周速(溶融液滴が飛び出すディスク外周縁部の速度)を変えることによって、製造するショット粒子の粒度分布をある程度制御できる特徴がある。しかし、製品歩留りが低いという問題があった(米国特許第2310590号明細書、中国実用新案公告第2541089号明細書参照)。
このように、上記の先行技術文献に開示された従来の遠心方式では、製品歩留りが低いという問題に十分に対処できていない。
水槽の水面と、該水面の上方に配置された回転する遠心ディスクの周囲を覆うように設けたカバーと、
前記カバーを貫通して設けたタンディッシュと、によって覆われた溶融液滴形成空間内において、
該溶融液滴形成空間内に発生するガスを排出するための開口部からガス排出するガス排出工程と、
前記カバーの内面に水膜を形成する水膜形成工程と、
溶融金属を前記タンディッシュに注入して、前記タンディッシュ底部の孔部から溶融金属を流出して前記回転する遠心ディスク上に供給する溶融金属供給工程と、
前記回転する遠心ディスクに供給された溶融金属から遠心力によって溶融液滴を形成する溶融液滴形成工程と、
前記水膜形成工程で形成した前記カバー内面の水膜に前記溶融液滴を衝突させて前記溶融液滴よりも小さな小滴に分裂させた後、前記小滴を冷却、凝固させる小滴凝固工程と、
を含む。
このように、距離Lを200~5000mmの範囲に調整すると、溶融液滴の高温酸化を低減しつつ、小滴(ショット粒子)の粒度分布および形状の制御が可能となる。距離Lが200mm未満では、溶融液滴が分裂して形成される小滴(ショット粒子)の粒度分布は全体に小さくなり高温酸化は減少するものの小滴が2つ以上結合した異形粒子が増加し、5000mmを超えると、異形粒子が極めて少ない良好な形状が得られるものの高温酸化が増加し、小滴(ショット粒子)の粒度分布が全体に大きくなって粗大粒子が混入するため、好ましくない。なお、距離Lは、異なった大きさのカバーを複数準備し、交換することによって容易に調整できる。
また、本発明は以下の詳細な説明により更に完全に理解できるであろう。しかしながら、詳細な説明および特定の実施例は、本発明の望ましい実施の形態であり、説明の目的のためにのみ記載されているものである。この詳細な説明から、種々の変更、改変が、当業者にとって明らかだからである。
出願人は、記載された実施の形態のいずれをも公衆に献上する意図はなく、開示された改変、代替案のうち、特許請求の範囲内に文言上含まれないかもしれないものも、均等論下での発明の一部とする。
本明細書あるいは請求の範囲の記載において、名詞及び同様な指示語の使用は、特に指示されない限り、または文脈によって明瞭に否定されない限り、単数および複数の両方を含むものと解釈すべきである。本明細書中で提供されたいずれの例示または例示的な用語(例えば、「等」)の使用も、単に本発明を説明し易くするという意図であるに過ぎず、特に請求の範囲に記載しない限り本発明の範囲に制限を加えるものではない。
本実施形態におけるショット粒子の製造装置は、図3に示すように、水を貯蔵する水槽20と、水槽20の水面よりも上方に位置した遠心ディスク2と、遠心ディスクの上方に設置したタンディッシュ4と、遠心ディスク2の周囲を覆い、水槽20の水面1とタンディッシュ4とで溶融液滴形成空間5を形成するカバー3と、該溶融液滴形成空間5内に発生するガスを排出する開口部6と、前記カバー3内面に対して冷却水を供給する注水ノズル15と、を備えている。なお、図3における注湯装置17は溶解炉、または溶解炉から溶融金属を受湯する容器(取鍋等)であり、容器(取鍋等)は自動注湯装置に搭載されることができる。また、自動注湯装置は自動的に走行する機能を具備すると共に、容器(取鍋等)を自動的に傾動、上下動、前後動させて溶融金属をタンディッシュに注入する機能を備えることができる。
本実施形態におけるショット粒子の製造方法は、図4のフローチャートに示すように、水槽20の水面1と、該水面1の上方に配置された回転する遠心ディスク2の周囲を覆うように設けたカバー3と、カバー3を貫通して設けたタンディッシュ4と、によって覆われた溶融液滴形成空間5内において、
該溶融液滴形成空間5内に発生するガスを排出するための開口部6からガスを排出するガス排出工程と、
カバー3の内面に水膜9を形成する水膜形成工程と、
溶融金属10をタンディッシュ4に注入して、タンディッシュ4底部の孔部11から溶融金属10を流出して回転する遠心ディスク2上に供給する溶融金属供給工程と、
回転する遠心ディスク2に供給された溶融金属10から遠心力によって溶融液滴12を形成する溶融液滴形成工程と、
水膜形成工程で形成したカバー3内面の水膜9に溶融液滴12を衝突させて溶融液滴12よりも小さな小滴13に分裂させた後、小滴13を冷却、凝固させる小滴凝固工程と、を含む。
本発明の実施形態では、溶融液滴形成空間5内において以下のような現象が発生する。即ち、溶融液滴12および小滴13がカバー3の内面に形成された水膜9および水槽20に貯留された水と接触することによって水蒸気が発生し、さらに水蒸気の一部が分解して水素、酸素が発生する。このため、溶融液滴形成空間5を密閉した場合、前記のような発生ガスが充満して爆発等が発生する危険があるため、開口部6からガスを排出するためのガス排出工程を設ける。また、ガス排出工程は、溶融液滴形成空間5内の圧力により開口部6に設けたバルブ8の開閉を制御することができる。即ち、開口部6にバルブ8を配置すると共に、溶融液滴形成空間5内の圧力を検知するセンサーを設置して、圧力が一定の範囲内となるように制御することができる。圧力が上限値を超えた場合にはバルブ8を開いてガスを排出することによって爆発を防止し、圧力が下限値を下回った場合はバルブ8を閉じて大気の流入を抑制することによって高温酸化を低減できる。さらに、ガス排出工程は、ガスの種類および濃度を把握して開口部6に設けたバルブ8の開閉を制御することができる。即ち、ガスの種類および濃度を検知するためのセンサーを設置し、開口部6に配置したバルブ8の開閉を制御することによって、溶融液滴形成空間5内のガス濃度を安定化させることができる。加えて、ガス排出工程は、開口部6の開口度Kを、溶融液滴形成空間の体積をVm3、開口部6の総面積をSm2とした時に、K=S/V=0.005~1.0の範囲で制御することができる。
本発明の実施形態では、図2に示すように、溶融液滴12がカバー3に衝突して溶融液滴12よりも小さな小滴13に分裂する。この時、溶融液滴12が衝突するカバー3の内面温度が上昇し、溶融液滴12がカバー3の内面に溶着するのを防止するため、カバー3の内面に冷却水14を供給して水膜9を形成する水膜形成工程を設ける。この水膜形成工程によって形成された水膜9により、溶融液滴12がカバー3の内面に溶着することなく、効果的に溶融液滴12を小滴13に分裂させることができる。また、水膜9の厚さは供給する冷却水の水量を変えることによって調節できる。さらに、水膜形成工程は、溶融液滴12が衝突するカバー3の内面が水槽20の水面1となす角度θを20~80度に設定してなされることができる。より好適には、前記角度θを30~70度に設定してなされることができる。加えて、水膜形成工程は、カバーの内面に冷却水を供給して形成する水膜9の厚さを0.5~10mmに調整することができる。なお、角度θは、カバー3の内面において溶融液滴12が衝突する領域が水槽20の水面1となす角度を意味しており、必ずしもカバー3の内面が水槽20の水面1と接した部分の角度を示すものではない。角度θが20度未満では、遠心ディスク2から飛び出した溶融液滴12が、水膜9が形成されたカバー3の内面に衝突するまでの飛翔距離が長くなり、特に水面1に近い位置に飛ぶ溶融液滴12では長くなり、高温酸化が増加してしまう。また、角度θが80度を超えると、水膜9が形成されたカバー3の内面に衝突して反射する小滴13が水面1方向ではなく、水平に近い方向に反射し易くなり、溶融液滴12と衝突して、異形粒子が増加し製品歩留りが低下してしまう。そこで、角度θを20~80度、より好適には30~70度に設定することにより、溶融液滴12の飛翔距離も長くなく、高温酸化が防止され、かつ、小滴13と溶融液滴12との衝突が防止され、製品歩留りが高く維持される。また、水膜9の厚さとは、溶融液滴12が衝突する領域における水膜9の厚さのことである。水膜9の厚さが0.5mm未満だと、カバー3の内面に溶融液滴12が溶着して製品歩留りが低下する。また、水膜9の厚さが10mmを超えると、溶融液滴12が小滴13に分裂する途中で凝固してしまい、粗大な異形粒子が発生して、歩留りが低下する。水膜9の厚さを0.5~10mmとすることにより、製品歩留りを高く維持できる。
本発明の実施形態では、溶解炉(図示せず)等で所定の化学成分となるように溶解された溶融金属10をタンディッシュ4に注入して、タンディッシュ4底部の孔部11から溶融金属10を流出して回転する遠心ディスク2上に供給する溶融金属供給工程を設ける。ここで、タンディッシュ4は、注入された溶融金属10を一定量貯留しつつ、孔部11から溶融金属10を一定の速度で流出して遠心ディスク2上に供給する。さらに、カバー3を貫通してタンディッシュ4が設けられるので、溶融液滴形成空間5の外部から溶融金属10を回転する遠心ディスク2上に供給することができる。また、溶融金属10を遠心ディスク2上に供給する供給速度を、70~600kg/minに調整することができる。供給速度の調整は、孔部11の大きさや数を変更し、また、タンディッシュ4に貯留する溶融金属の深さを変更して、調整することができる。供給速度が70kg/min未満では、小滴(ショット粒子)の粒径(平均粒径)が小さくなる方向に調整することができるものの生産性が確保できず、600kg/minを超えると粗大な溶融液滴(概略直径5mm以上)が形成される割合が増加することによって、所望の粒径(たとえば、0.03~4mm)の小滴に分裂できなくなるため製品歩留りが低下する。そこで、供給速度を70~600kg/minに調整することにより、所望の粒径の小滴(ショット粒子)を適正に生産することができる。
本発明の実施形態では、回転する遠心ディスク2に供給された溶融金属10から遠心力によって溶融液滴12を形成する溶融液滴形成工程を設ける。ここで、遠心ディスク2は、円板状、カップ状等の形状を有する容器であり、耐火物によって形成され鋼材等で補強された構造を有し、回転によって破損しない強度を有する。遠心ディスク2は、回転ユニット7により駆動され、回転する。溶融液滴形成工程において、回転する遠心ディスク2の中心付近に供給された溶融金属10は、遠心力によって遠心ディスク2の外周縁部へと広がり、外周縁部から飛び出す時点あるいは飛翔中に溶融液滴12が形成される。また、溶融液滴形成工程は、遠心ディスク2の外周縁部と前記溶融液滴12が衝突する前記カバー3の内面との距離Lを200~5000mmの範囲に調整してなされることができる。距離Lが200mm未満では、溶融液滴12がカバー3の内面に衝突して分裂して飛翔する小滴13と衝突し易く、2つ以上結合した異形粒子が増加し、小滴(ショット粒子)の粒度分布が全体に大きくなって粗大粒子が混入するため、好ましくない。距離Lが5000mmを超えると、高温酸化し易くなり、好ましくない。そこで、距離Lを200~5000mmの範囲に調整すると、溶融液滴の高温酸化を低減しつつ、小滴(ショット粒子)の粒度分布および形状の制御が可能となる。なお、距離Lは、異なった大きさのカバーを複数準備し、交換することによって容易に調整できる。
本発明の実施形態では、水膜形成工程で形成したカバー3内面の水膜9に溶融液滴12を衝突させて溶融液滴12よりも小さな小滴13に分裂させた後、小滴13を冷却、凝固させる小滴凝固工程を設ける。小滴凝固工程において、溶融液滴12はカバー3内面の水膜9に衝突することによって機械的衝撃と局所的な水蒸気爆発による衝撃を受け、小滴13に分裂されると推定される。さらに小滴13は、図2に示すように、水槽20の水中に落下して冷却、凝固し、ショット粒子となる。
本発明の実施形態におけるショット粒子とは、例えば日本においてはJIS Z0311(2004年)に定められている高炭素鋳鋼ショット、低炭素鋳鋼ショット等の鋳鋼ショット、およびステンレス鋳鋼からなるステンレスショット等の鉄系合金からなるショットである。また、ショット粒子の粒径(平均粒径)は概略0.03~4mmの範囲内において、各種粒度のショットが規定されている(JIS Z0311(2004年))。
例えば、ガス排出工程と、水膜形成工程とは逆の順序でも、同時であっても良い。
以下、本発明の試験例1について説明する。
本試験例では高炭素鋳鋼ショットによるショット粒子を製作して本発明の効果を確認した。まず、スチールスクラップ、Fe-Si、Fe-Mn、加炭材等を原材料として所定の成分になるように原料配合を調整し、鉄換算溶解量5000kgの高周波誘導炉を使用して5000kgの原材料を溶解した後、全量を出湯して試験に供した。溶解温度は1640~1680℃として、出湯直前に純アルミニウムによる脱酸を行った。溶解した溶湯は、500kgずつ10回に分けて取鍋に受湯し、図3に示すショット粒子の製造装置のタンディッシュ4に注湯してショット粒子を製作した。製作したショット粒子は水槽20から全量を回収し、流動床式乾燥装置によって熱風乾燥した後、回収重量を測定した。そして、以下の式から高温酸化による損失割合を求めた。
高温酸化による損失割合(重量%)=(1-ショットの回収重量/溶解重量)×100。また、乾燥後のショット粒子を篩分けして粒度分布を測定した。なお、高温酸化によって形成された酸化物の多くは、水槽20の水によって急冷されてショット粒子から剥離し、且つ微細な粉末に破砕するため、乾燥中に集塵機へ吸引されてショット粒子と分離される。
本試験例では、ショット粒子の高温酸化に関する本発明の効果を確認した。試験例1では実施例と比較例を同じ条件(溶湯供給速度および遠心ディスクの周速)で製作したため、比較例1に対して実施例1および実施例2の粒度分布が細かくなった。ここで、高温酸化による損失割合(重量%)はショット粒子の粒度の影響を受け、一般に粒度が小さくなるほど高温酸化は増加する。そこで、実施例1と同程度の粒度分布となるように比較例2のショット粒子を製作した。比較例2の製作条件は、遠心ディスク2への溶湯供給速度を170kg/min、遠心ディスク2の周速を15m/s、に設定した。
本試験例では、開口部の開口度Kの影響について確認した。本試験例では、試験例1と同様の方法で高炭素鋳鋼ショットによるショット粒子を製作し、遠心ディスク2への溶湯供給速度を220kg/min、遠心ディスク2の周速を11m/s、カバー3の内面が水槽20の水面1となす角度θを40度、水膜9の厚さを1.5mm、遠心ディスク2の外周縁部とカバー3の内面との距離Lを2000mmとした。開口度Kが0.005~1.0の範囲内の実施例3では開口度Kを0.01、実施例4では開口度Kを0.9とし、範囲外の比較例3では開口度Kを0.003、比較例4では開口度Kを1.5とした。そして、発生するガスによる爆発の有無と、高温酸化による損失割合を計測した。
1 水槽の水面
2 遠心ディスク
3 カバー
4 タンディッシュ
5 溶融液滴形成空間
6 開口部
7 回転ユニット
8 バルブ
9 水膜
10 溶融金属
11 孔部
12 溶融液滴
13 小滴
14 冷却水
15 注水ノズル
16 中央開口部
17 注湯装置
20 水槽
Claims (19)
- 水槽の水面と、該水面の上方に配置された回転する遠心ディスクの周囲を覆うように設けたカバーと、前記カバーを貫通して設けたタンディッシュと、によって覆われた溶融液滴形成空間内において、
該溶融液滴形成空間内に発生するガスを排出するための開口部からガスを排出するガス排出工程と、
前記カバーの内面に水膜を形成する水膜形成工程と、
溶融金属を前記タンディッシュに注入して、前記タンディッシュ底部の孔部から溶融金属を流出して前記回転する遠心ディスク上に供給する溶融金属供給工程と、
前記回転する遠心ディスクに供給された溶融金属から遠心力によって溶融液滴を形成する溶融液滴形成工程と、
前記水膜形成工程で形成した前記カバー内面の水膜に前記溶融液滴を衝突させて前記溶融液滴よりも小さな小滴に分裂させた後、前記小滴を冷却、凝固させる小滴凝固工程と、
を含むショット粒子の製造方法。 - 前記ガス排出工程は、前記溶融液滴形成空間内の圧力に応じて前記開口部に接続したバルブの開閉を制御する請求項1に記載のショット粒子の製造方法。
- 前記ガス排出工程は、前記溶融液滴形成空間内のガスの種類および濃度を把握して前記開口部に接続したバルブの開閉を制御する請求項1に記載のショット粒子の製造方法。
- 前記ガス排出工程は、前記開口部の開口度Kを、前記溶融液滴形成空間の体積をVm3、前記開口部の総面積をSm2とした時に、K=S/V=0.005~1.0の範囲で制御されることを特徴とする請求項1に記載したショット粒子の製造方法。
- 前記水膜形成工程は、前記カバーが円錐台形の側部を有し、前記溶融液滴が衝突する前記カバーの内面が水槽の水面となす角度θを20~80度に設定してなされることを特徴とする請求項1に記載したショット粒子の製造方法。
- 前記水膜形成工程は、前記溶融液滴が衝突する前記カバーの内面が水槽の水面となす角度θを30~70度に設定してなされることを特徴とする請求項5に記載したショット粒子の製造方法。
- 前記溶融液滴形成工程は、前記遠心ディスクの外周縁部と前記溶融液滴が衝突する前記カバーの内面との距離Lを200~5000mmの範囲に調整してなされることを特徴とする請求項1に記載したショット粒子の製造方法。
- 前記水膜形成工程は、カバーの内面に冷却水を供給し、該冷却水により形成する水膜の厚さを0.5~10mmに調整することを特徴とする請求項1に記載したショット粒子の製造方法。
- 前記溶融金属供給工程は、溶融金属を前記遠心ディスク上に供給する供給速度が70~600kg/minに調整されることを特徴とする請求項1~8に記載したショット粒子の製造方法。
- 水を貯蔵する水槽と、
前記水槽の水面よりも上方に位置した遠心ディスクと、
前記遠心ディスクの上方に設置したタンディッシュと、
前記遠心ディスクの周囲を覆い、前記水槽の水面と前記タンディッシュとで溶融液滴形成空間を形成するカバーと、
前記カバーに形成され、前記溶融液滴形成空間内に発生するガスを排出する開口部と、
前記カバーの内面に対して冷却水を供給して水膜を形成する注水ノズルと、
を、備えたショット粒子の製造装置。 - 前記遠心ディスクは、前記遠心ディスクを回転させる回転ユニットの上端に設置される請求項10に記載のショット粒子の製造装置。
- 前記カバーは板状のカバー板で構成され、前記カバーは前記遠心ディスクの回転軸に対して軸対称である請求項10に記載のショット粒子の製造装置。
- 前記カバーは板状のカバー板で構成され、前記カバーの下端は前記水槽の水面よりも下に位置する請求項10に記載のショット粒子の製造装置。
- 前記カバーは円錐台形の側部を有し、該側部の内面は前記水槽の水面となす角度θが20~80度である傾斜面を有する請求項12または請求項13に記載のショット粒子の製造装置。
- 前記側部の内面が水槽の水面となす角度θが30~70度であることを特徴とする請求項14に記載したショット粒子の製造装置。
- 前記タンディッシュの底部に溶融金属を流出する孔部を設けた請求項10に記載のショット粒子の製造装置。
- 前記注水ノズルは、冷却水を注水する注水口がカバーの内面に位置し、且つ遠心ディスクの上端面よりも上方に複数設置された請求項10に記載したショット粒子の製造装置。
- 前記カバーは上部に中央開口部を有し、該中央開口部にタンディッシュを貫通して設けた請求項10に記載のショット粒子の製造装置。
- 前記開口部の開口度Kが、前記カバーと前記タンディッシュおよび前記水槽の水面で覆われる溶融液滴形成空間の体積をVm3、前記開口部の総面積をSm2とした時に、K=S/V=0.005~1.0であることを特徴とする請求項10に記載したショット粒子の製造装置。
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- 2013-12-11 WO PCT/JP2013/083221 patent/WO2014155852A1/ja active Application Filing
- 2013-12-11 US US14/779,492 patent/US10293408B2/en active Active
- 2013-12-11 BR BR112015024655A patent/BR112015024655A2/pt not_active Application Discontinuation
- 2013-12-11 KR KR1020157026283A patent/KR102144062B1/ko active IP Right Grant
- 2013-12-11 JP JP2015507959A patent/JP6041044B2/ja active Active
- 2013-12-11 CN CN201380075015.8A patent/CN105050756B/zh active Active
- 2013-12-11 MX MX2015013548A patent/MX2015013548A/es unknown
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Publication number | Publication date |
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JP6041044B2 (ja) | 2016-12-07 |
MX2015013548A (es) | 2016-02-05 |
KR20150136069A (ko) | 2015-12-04 |
KR102144062B1 (ko) | 2020-08-12 |
CN105050756B (zh) | 2017-07-21 |
US10293408B2 (en) | 2019-05-21 |
CN105050756A (zh) | 2015-11-11 |
US20160031014A1 (en) | 2016-02-04 |
JPWO2014155852A1 (ja) | 2017-02-16 |
BR112015024655A2 (pt) | 2017-07-18 |
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