EP1759789A1 - Ausgussdüsestruktur und Verfahren zum steigenden Giessen - Google Patents

Ausgussdüsestruktur und Verfahren zum steigenden Giessen Download PDF

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Publication number
EP1759789A1
EP1759789A1 EP06018010A EP06018010A EP1759789A1 EP 1759789 A1 EP1759789 A1 EP 1759789A1 EP 06018010 A EP06018010 A EP 06018010A EP 06018010 A EP06018010 A EP 06018010A EP 1759789 A1 EP1759789 A1 EP 1759789A1
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EP
European Patent Office
Prior art keywords
molten metal
flow
channel portion
swirling
pouring tube
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Granted
Application number
EP06018010A
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English (en)
French (fr)
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EP1759789B1 (de
Inventor
Shinichiro Yokoya
Pär Jönsson
Line Hallgren
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Krosaki Harima Corp
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Krosaki Harima Corp
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Publication of EP1759789A1 publication Critical patent/EP1759789A1/de
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
    • B22D41/50—Pouring-nozzles
    • B22D41/507—Pouring-nozzles giving a rotating motion to the issuing molten metal

Definitions

  • the present invention relates to a pouring tube structure and a pouring method for use in an uphill casting process designed to spout/pour molten metal into a mould from an inlet port formed in a lower portion of the mould so as to produce a metal ingot.
  • the present invention relates to a pouring tube structure adapted to fluidically transport with an inlet port formed in a lower portion of a mould, and a pouring method using the pouring tube structure.
  • This casting process is generally classified as an uphill casting process (uphill teeming or pouring process) or a downhill casting process (downhill teeming or pouring process).
  • the uphill casting process is designed such that a pouring tube adapted to allow passage of molten metal therethrough is fluidically connected to an inlet port (opening) formed in a lower portion of a mould, and molten metal in a molten metal transfer vessel, such as a ladle, is spouted/poured from the inlet port, i.e., from a lower position of the mould, into the mould through the pouring tube.
  • FIG. 11 is a vertical sectional view showing a conventional pouring tube for the uphill casting process.
  • a pouring tube 1 is connected to an inlet port 6 formed in a bottom of a mould 5, and molten metal is spouted/poured from the inlet port 6 into the mould 5 while passing through a space or flow channel 2 internally defined in the pouring tube 1.
  • a cylindrical-shaped tube having an approximately constant inner diameter has been typically used as the pouring tube 1.
  • a speed (energy) in an uphill or upward direction, i.e., in an axial direction of the pouring tube 1, at a terminal or upper end of the pouring tube 1 is relatively high.
  • the poured molten metal forms a flow locally raising the surface of preceding molten metal 7 in the mould 5 and wildly agitates the molten metal 7 while taking in slag or antioxidant (powder) [hereinafter referred to collectively as "slags"] floating on the surface of the molten metal 7, and dispersing/suspending the slags over the entire molten metal in the mould.
  • the slags incorporated in the molten metal 7 causes deterioration in quality of metal ingots.
  • the slags 8 are pushed aside to form a region where the molten metal is exposed to outside, so-called "open eye” 9 (see Fig. 11), causing adverse effects, such as oxidization of the molten metal.
  • the JP-A-09-239494 discloses a technique for stabilizing the surface of molten metal in a mould (hereinafter referred to as "molten metal surface").
  • molten metal surface a technique for stabilizing the surface of molten metal in a mould
  • a pouring tube used in this technique is designed such that an inner-diameter ratio of an upper end to a principal channel of a runner (pouring tube) is set at 1.1 or more, and the inner diameter is gradually increased in an uphill or upward direction to form an inverse-tapered channel portion having a length set at 0.2 to 2.0 times of the inner diameter of the upper end, so as to distribute a pouring pressure of molten metal to reduce an upward spouting speed or a flow speed in an axially central region of the molten metal.
  • a vessel such as a tundish for use in continuous casting process, allowing nonmetallic inclusions, such as alumina, to refloat before pouring molten metal into a mould, is not employed.
  • nonmetallic inclusions such as alumina
  • the microscopic nonmetallic inclusions are hardly expected to refloat, and highly likely to remain in a metal ingot in a dispersed state and cause deterioration in quality thereof.
  • the present invention provides a pouring tube structure for use in an uphill casting process designed to spout molten metal into a mould from an inlet port located in the lower portion of the mould.
  • the pouring tube structure comprises a pouring tube internally defining a flow channel for molten metal to provide fluid transport between a molten metal transfer vessel and the inlet port and feed molten metal from the molten metal transfer vessel to the mould, and a single or a plurality of swirling-flow generation means provided in the pouring tube and adapted to generate a swirling flow in the molten metal.
  • the present invention further provides a pouring method for an uphill casting process designed to spout molten metal into a mould from an inlet port formed in a lower portion of the mould.
  • the pouring method comprises generating a swirling flow in molten metal passing through a pouring tube which internally defines a flow channel for molten metal to provide fluid transport between a molten metal transfer vessel and the inlet port and feed molten metal from the molten metal transfer vessel to the mould.
  • the pouring tube structure of the present invention capable of generating a swirling flow in molten metal passing through the pouring tube can achieve the following effects.
  • a ratio (W/V) of a circumferential velocity (W) in a circumferential direction of the inlet port to a velocity (V) in an axial direction of the pouring tube i.e., a swirl number
  • W/V a ratio of a circumferential velocity (W) in a circumferential direction of the inlet port to a velocity (V) in an axial direction of the pouring tube
  • the pouring tube which internally defines a flow channel for molten metal to provide fluid transport between a molten metal transfer vessel and the inlet port and feed molten metal from the molten metal transfer vessel to the mould, has, in the entire length of the flow channel, an approximately vertical channel portion extending from immediately below the inlet port in an approximately vertically downward direction, an approximately horizontal channel portion extending in an approximately horizontal direction, and a bent channel portion making a transition from the approximately vertical channel portion to the approximately horizontal channel portion.
  • At least one of the swirling-flow generation means is located at any position in the approximately horizontal channel portion on an upstream side of the bent channel portion.
  • the above pouring tube structure designed to generate a swirling flow in molten metal passing through the pouring tube, by the swirling-flow generation means located in the approximately horizontal channel portion on the upstream side of the bent channel portion located below the inlet port, can achieve the following effect in addition to the aforementioned effects of the present invention:
  • the molten metal after passing through the swirling-flow generation means flows swirling a given distance between the swirling-flow generation means and the inlet port formed in the lower portion of the mould, and, in this period, nonmetallic inclusions causing quality deterioration can be concentrated around a tube axis (the center of the flow channel) of the pouring tube to reduce dispersion of the nonmetallic inclusions over molten metal in the mould.
  • the molten metal is molten steel at a temperature of about 1600°C; the pouring rate is about 1.3 t/min; and an inner diameter of the pouring tube is about 50 mm.
  • At least one of the swirling-flow generation means is located at a position on an upstream side of and possibly closer to the bent channel portion of the pouring tube where the approximately vertical channel portion extending vertically downward from immediately below the inlet port is changed to the approximately horizontal channel portion, to generate a swirling flow in the molten metal so as to allow the molten metal with the swirling flow to be spouted into the mould.
  • the reason is as follows.
  • the bent channel portion of the pouring tube has a curvature radius R of about 100 mm or less
  • the swirling flow is apt to be attenuated or disturbed.
  • it is required to allow the swirling flow to pass through the bent channel portion in a well-organized and undisrupted manner so as to minimize occurrence of the attenuation and turbulence.
  • the swirling-flow generation means is located in the vicinity of the bent channel portion, specifically, at a position spaced apart from and upstream of the bent channel portion by 1500 mm or less. This makes it possible to ensure a swirl number of 0.13 or more at the inlet port so as to maintain stability in a molten metal surface.
  • nonmetallic inclusions such as alumina, having a specific gravity less than that of the molten metal can be concentrated around the tube axis (center of the flow channel) of the pouring tube by a centrifugation action of the swirling flow of the molten metal flowing through the pouring tube.
  • the nonmetallic inclusions concentrated around the tube axis (center of the flow channel) are brought into contact with each other in high probability, so as to be enlarged through aggregation or clustering through fusion-bonding.
  • the enlarged or clustered nonmetallic inclusions receive a larger buoyant force which will further facilitate the concentration around the tube axis (center of the flow channel) during flow in the pouring tube.
  • the enlarged or clustered nonmetallic inclusions after being released from the inlet port also receive a larger buoyant force, and thereby have a larger upward flow speed to accelerate floatation.
  • the nonmetallic inclusions are hardly dispersed in a wide range of the molten metal in the mould, and allowed to be readily separated from the molten metal. This makes it easy to facilitate absorption of the nonmetallic inclusions in powder or the like on the molten metal surface, so as to further reduce dispersion over a metal ingot to be obtained.
  • the swirling flow is maintained in the range of 1000 mm or more from the bent channel portion in the upstream direction, i.e., at least one of the swirling-flow generation means is located at a position spaced apart from and upstream of the bent channel portion by 1000 mm or more.
  • At least one of the swirling-flow generation means is located in the approximately horizontal channel portion of the pouring tube at a position in the range of 1000 mm to 1500 from the bent channel portion in the upstream direction.
  • At least a second one of the swirling-flow generation means may be located at any position on an upstream or downstream side of the first swirling-flow generation means.
  • the position and number of the second swirling-flow generation means may be determined in consideration of the aforementioned requirement of obtaining a swirl number of 0.13 or more at the inlet port.
  • each of the swirling-flow generation means is used as each of the swirling-flow generation means.
  • the swirling-flow generation means may be a spiral or helical groove or protrusion formed in/on an inner wall of the pouring tube, or a plate-shaped grooved member to be located inside the pouring tube.
  • the twisted tape-like configuration means a screw-like configuration to be obtained by positioning a flat plate in parallel relation to a molten-metal flow direction (axial direction of the pouring tube) and then twisting one of opposite edges of the flat plate extending in a direction perpendicular to the molten-metal flow direction, in a direction perpendicular to the molten-metal flow direction while fixing the other edge of the flat plate.
  • the twisted tape-like configuration has a twist angle ranging from 30° to 180°. If the twist angle is less than 30°, the circumferential velocity of the swirling flow will be excessively lowered to cause difficulty in obtaining the intended effect of the swirling flow. If the twist angle exceeds 180°, the swirling-flow generation means will have an excessively long length, and inclusions contained in the molten metal are likely to undesirably attach on the swirling-flow generation means.
  • Each of the above swirl number and the twist angle is varied depending on the dimensions, configuration, mechanism and/or operating conditions of casting equipment. Thus, it is necessary to appropriately set it at an optimal value while observing a state of the molten metal surface.
  • the pouring tube provided with the swirling-flow generation means as in the first specific embodiment is formed with an inverse-tapered channel portion having an inner diameter gradually increasing toward the inlet port, at an upper end thereof on the side of the inlet port, so as to allow pour molten metal with a swirling flow to be poured into the mould therethrough. That is, in the pouring tube structure of the present invention, the pouring tube has an upper end on the side of the inlet port, and the upper end is formed with an inverse-tapered channel portion having an inner diameter gradually increasing toward the inlet port.
  • a flow along an inner surface of the inverse-tapered channel portion is generated by the centrifugation action of the swirling flow generated by the swirling-flow generation means.
  • the molten metal flow is gradually expanded in a radial direction of the pouring tube to additionally generate a flow along the inner surface of the inverse-tapered channel portion while smoothly maintaining a centrifugal force without occurrence of so-called "flow separation" due to vertical vortex-like flows caused by the upward flow, and then released from the inlet port. This makes it possible to largely reduce an upward spouting speed without lowering a pouring rate.
  • a ratio of an inner diameter (D1) of the upper end to an inner diameter of a lower end (D2) of the inverse-tapered channel portion i.e., an inner-diameter ratio (D1/D2), is set in the range of 1.36 to 6. If the inner-diameter ratio is less than 1.36, the effect of lowering the upward spouting speed along the axial direction of the pouring tube cannot be adequately obtained in the inverse-tapered channel portion.
  • the inner-diameter ratio exceeds 6, the circumferential velocity of the swirling flow generated by the swirling-flow generation means is excessively lowered to cause the risks of deterioration in the centrifugal force of the swirling flow and fluctuation around the peripheral region of the molten metal surface.
  • the inner-diameter ratio is preferably set to 4.2 or less.
  • An inverse-tapered angle or opening angle of the inverse-tapered channel portion is set preferably in the range of about 6° to 120°, more preferably at about 90° or less. If the opening angle is less than 6°, the effect of lowering the upward spouting speed along the axial direction of the pouring tube cannot be adequately obtained in the inverse-tapered channel portion. If the opening angle exceeds 120°, the circumferential velocity of the swirling flow generated by the swirling-flow generation means is excessively lowered to cause the risks of deterioration in the centrifugal force of the swirling flow and fluctuation around the peripheral region of the molten metal surface. With a view to stabilizing the molten metal surface, the opening angle is preferably set at 50° or less.
  • a vicinity of an intersecting point (measurement points of D2) between the inverse-tapered channel portion and a non-tapered channel portion on the side of the upper end of the pouring tube, and a vicinity of an intersecting point (measurement points of D1) between a bottom surface of the mould and the inverse-tapered channel portion are preferably formed in a smooth shape having a certain radius R or a transition curve instead of a sharp bent or an edged shape.
  • the inner surface of the inverse-tapered channel portion is preferably formed in a smooth flat or curved shape.
  • Each of the above inner-diameter ratio and opening angle of the inverse-tapered channel portion is varied depending on the dimensions, configuration, mechanism and/or operating conditions of casting equipment. Thus, it is necessary to appropriately set it at an optimal value while observing a state of the molten metal surface.
  • gas is injected from the vicinity of the swirling-flow generation means as described in the first or second specific embodiment, to additionally disperse gas bubbles over a swirling flow of molten metal in the pouring tube. That is, in the pouring tube structure of the present invention, the pouring tube includes a gas injection port in fluid communication with a region of the flow channel provided with at least one of the swirling-flow generation means.
  • the gas bubbles additionally dispersed over the swirling flow of molten metal makes it possible to capture nonmetallic inclusions in the molten metal so as to further enhance the effect of concentrating the nonmetallic inclusions around the tube axis (center of the flow channel), and enlarging/clustering the nonmetallic inclusions.
  • This effect is achieved by the following mechanism.
  • the gas bubbles themselves are capable of effectively absorbing nonmetallic inclusions dispersed over the molten metal.
  • a difference in specific gravity between the gas bubbles and the molten metal is fairly greater than that between the nonmetallic inclusions and the molten metal, and thereby the centrifugation action of the swirling flow more strongly affects the gas bubbles than the nonmetallic inclusions.
  • the gas is injected at a position adjacent to and downstream of the swirling-flow generation means, specifically at a downstream edge of the swirling-flow generation means or between the downstream edge and a position spaced away from the downstream edge by 100 mm in the downward direction.
  • the reason is as follows.
  • the gas bubbles are concentrated toward the tube axis (center of the flow channel) by the swirling flow, to create an air-bubble curtain as a film-shaped gas-bubble aggregate which is formed along a path of the gas bubbles swirlingly moving toward the tube axis (center of the flow channel).
  • the air-bubble curtain is quickly stabilized to exhibit enhanced effect of capturing the nonmetallic inclusions.
  • the gas is injected at a position spaced away from the downstream edge of the swirling-flow generation means beyond the above upper limit of 100 mm, a distance for allowing the gas bubbles to exist in the swirling flow is excessively reduced to cause deterioration in the gas-bubbles' effect of capturing the nonmetallic inclusions, concentrating the nonmetallic inclusions around the tube axis (center of the flow channel), and enlarging/clustering the nonmetallic inclusions. Moreover, the gas is injected at a position where the swirling flow is relatively weak, and thereby likely to cause destruction of the swirling flow.
  • the gas is injected from the entire circumference of the pouring tube as evenly as possible.
  • the gas bubbles can be reduced in size to increase a contact area with the molten metal and come into contact with the molten metal at a higher frequency. This allows the gas bubbles to have an opportunity of passing through a wider range of the molten metal, i.e., to have a higher probability of contact with nonmetallic inclusions dispersed over the molten metal, so as to achieve an enhanced effect of capturing nonmetallic inclusions.
  • the gas bubbles make it possible to capture the nonmetallic inclusions more effectively and quickly.
  • the distance between the bent channel portion and the swirling-flow generation means downstream edge of the swirling-flow generation means
  • the distance between the bent channel portion and the swirling-flow generation means is not necessarily set to 1000 mm or more as described in the first specific embodiment without the gas injection, but it is preferable to ensure that it is set to 150 mm or more.
  • At least one of the swirling-flow generation means are located in the approximately horizontal channel portion of the pouring tube at a position in the range of 150 mm to 1500 mm from the bent channel portion in the upstream direction.
  • inert gas having no chemical influence on the molten metal such as an oxidation reaction
  • a volume of gas to be injected is preferably set in the range of 0.0003 to 0.002 Nm 3 /min, in view of maximizing the gas-bubbles' effect while maintaining the swirling flow. If the gas volume is less than 0.0003 Nm 3 /min, almost no nonmetallic-inclusions capturing effect based on the gas injection can be obtained. If the gas volume exceeds 0.002 Nm 3 /min, the molten metal flowing through the pouring tube has an excessively low density to cause instability in the molten metal flow, and the risk of clogging of the pouring tube due to cooling in some cases.
  • the pouring tube structure is intended to further generate a stable swirling flow in the molten metal inside the pouring tube as compared with the first specific embodiment.
  • the pouring tube which internally defines a flow channel for molten metal to provide fluid transport between a molten metal transfer vessel and the inlet port and feed molten metal from the molten metal transfer vessel to the mould, has, in the entire length of the flow channel, an approximately vertical channel portion extending from immediately below the inlet port in an approximately vertically downward direction, an approximately horizontal channel portion extending in an approximately horizontal direction, and a bent channel portion making a transition from the approximately vertical channel portion to the approximately horizontal channel portion.
  • At least a first one of the swirling-flow generation means is located at any position in the approximately horizontal channel portion on an upstream side of the bent channel portion, and at least a second one of the swirling-flow generation means is located at any position in the approximately vertical channel portion on a downstream side of the bent channel portion.
  • At least a first one of the swirling-flow generation means is located at any position in the approximately horizontal channel portion, in the same manner as the first specific embodiment, and optionally one or more of the swirling-flow generation means are located on the upstream side of the first swirling-flow generation means.
  • at least a second one of the swirling-flow generation means is located at any position in the approximately vertical channel portion extending vertically downward from below the inlet port, is located on the downstream side of the first swirling-flow generation means, to further stably generate a swirling flow in the molten metal inside the pouring tube and allow the molten metal with the stable swirling flow to be poured into the mould.
  • the second swirling-flow generation means having the same configuration as that in the first specific embodiment can also be effectively located in the approximately vertical channel portion extending vertically downward from below the inlet port.
  • a specific configuration and function/effect of the second swirling-flow generation means are the same as those of the swirling-flow generation means described in the first specific embodiment.
  • the level of the swirling flow during pouring into the mould may be specifically determined on a case-by-case basis depending on actual conditions of casting equipment, a pouring rate, properties of molten metal, etc., and in consideration of the aforementioned requirement of allowing the swirling flow to have a swirl number of 0.13 or more during pouring into the mould.
  • Respective configurations and positions of the first and second swirling-flow generation means may be adjusted to meet the above conditions and this requirement.
  • the pouring tube provided with the plurality of swirling-flow generation means as in the fourth embodiment is formed with an inverse-tapered channel portion having an inner diameter gradually increasing toward the inlet port, in an upper end thereof on the side of the inlet port.
  • a flow along an inner surface of the inverse-tapered channel portion is created by a centrifugal force of the swirling flow generated by the swirling-flow generation means.
  • the molten metal is spouted from the inlet port after the swirling flow thereof is expanded to flow along the inner surface of the inverse-tapered channel portion while smoothly maintaining the centrifugal force without occurrence of the so-called "flow separation".
  • This makes it possible to distribute an upward spouting speed to be concentrated around the center of the flow channel, in a lateral direction of the mould, so as to largely reduce the upward spouting speed without lowering the pouring rate.
  • the conditions, such as shape, of this inverse-tapered channel portion are the same as those in the second specific embodiment.
  • gas is injected in a vicinity of each of the plurality of swirling-flow generation means as in the fourth specific embodiment to disperse gas bubbles over the molten metal in the pouring tube and allow the molten metal with the gas bubbles to be poured into the mould.
  • the gas bubbles dispersed over the swirling flow of the molten metal makes it possible to further enhance the gas-bubbles' effect of capturing the nonmetallic inclusions, concentrating the nonmetallic inclusions around the tube axis (center of the flow channel), and enlarging/clustering the nonmetallic inclusions.
  • the gas bubbles receiving a larger buoyant force than that received by the nonmetallic inclusions can accelerate the effect of floating the nonmetallic inclusions in the molten metal flow after being released from the inlet port into the mould.
  • the gas is injected at a position adjacent to and downstream of the upstreammost swirling-flow generation means, and from the entire circumference of the pouring tube.
  • the sixth embodiment is primarily intended to provide a compensation function when the function/effect of the pouring tube structure according to the third specific embodiment is not sufficient.
  • the gas injection port may be provided in the vicinity of each of the plurality of swirling-flow generation means. In this case, the same effect as that in the pouring tube structure designed to inject the gas only at a position adjacent to and downstream of the upstreammost swirling-flow generation means can be obtained.
  • the swirling flow becomes weak during pouring into the mould due to large attenuation caused by passing through the bent channel portion on the downstream side of the approximately horizontal channel portion, or the injected gas bubbles are increased in size and unevenly distributed, it is preferable to reduce the volume of gas to be injected in the vicinity of the swirling-flow generation means located in the approximately vertical channel portion, as compared with the pouring tube structure designed to inject the gas at a single position.
  • the total volume of gas to be injected is likely to be excessively increased so as to cause difficulty in obtaining the effect of forming a desirable swirling flow against the intended purpose.
  • a ratio between respective gas volumes from the plurality of gas injection positions so as to keep the total volume of gas to be injected from being changed depending on the number of gas injection positions.
  • the optimal ratio may be specifically determined on a case-by-case basis depending on actual conditions of casting equipment, a pouring rate, properties of molten metal, an intended quality of metal ingots, etc.
  • the level of the swirling flow during pouring into the mould and the level of gas distribution may be specifically determined on a case-by-case basis depending on actual conditions of casting equipment, pouring rate, properties of molten metal, an intended quality of metal ingots etc., and in consideration of the aforementioned requirement of allowing the swirling flow to have a swirl number of 0.13 or more during pouring into the mould.
  • Respective configurations and positions of the plurality of swirling-flow generation means may be adjusted to meet the above conditions and this requirement.
  • inert gas having no chemical influence on the molten metal such as oxidation reaction
  • the gas to be injected is used as the gas to be injected.
  • the total volume of gas to be injected is preferably set in the range of about 0.0003 to 0.002 Nm 3 /min, in view of the balance between maximization of the gas-bubbles' effect and maintenance of the swirling flow.
  • respective features of the first to third specific embodiments may be implemented all together to provide further enhanced effect of reducing nonmetallic inclusions to be contained in the molten metal in the mould, and further enhanced ingot quality, as compared with the cases of implementing the features individually.
  • each of the fourth to sixth specific embodiments is primarily intended to provide a compensation function when the function/effect of the pouring tube structures according to the first to third specific embodiments is not sufficiently obtained due to the bent channel portion on the downstream side of the downstreammost swirling-flow generation means etc., and therefore not necessarily implemented if the function/effect can be sufficiently obtained in the pouring tube structures according to the first to third specific embodiments.
  • the swirling-flow generation means for generating a swirling flow in the molten metal is located in the pouring tube internally defining a flow channel for molten metal to provide fluid transport between a molten metal transfer vessel and the inlet port and feed molten metal from the molten metal transfer vessel to the mould, at a position adjacent to the inlet port.
  • a swirling flow is generated in the vicinity of the inlet port by the swirling-flow generation means located in the pouring tube at a position adjacent to the inlet port.
  • an upward flow speed of the molten metal spouted from the inlet port is lowered, and the molten metal is spread based on a centrifugal force generated by the swirling flow, so as to reduce fluctuation of a molten metal surface and stabilize the molten metal surface to effectively suppress the phenomenon that the molten metal surface is locally raised, i.e., formation of "open eye".
  • an amount of slags on the molten metal surface to be taken in the molten metal can be reduced.
  • the stabilization of the molten metal surface makes it possible to reduce slags to be dispersed into the molten metal, and cut the risk that an antioxidant mold powder added onto the molten metal surface is unevenly located around a peripheral region of the molten metal surface, so as to allow a required amount of antioxidant to be drastically reduced.
  • the level of the swirling flow during pouring into the mould and the level of gas distribution may be specifically determined on a case-by-case basis depending on actual conditions of casting equipment, pouring rate, properties of molten metal, intended quality of metal ingots etc., and in consideration of the aforementioned requirement of allowing the swirling flow to have a swirl number of 0.13 or more during pouring into the mould.
  • the configuration and positioning of the swirling-flow generation means may be adjusted to meet the above conditions and this requirement.
  • the pouring tube provided with the swirling-flow generation means located adjacent to the inlet port as in the seventh specific embodiment is formed with an inverse-tapered channel portion having an inner diameter gradually increasing toward the inlet port, at an upper end thereof on the side of the inlet port, in the same manner as that in the second and fifth specific embodiments.
  • the swirling-flow generation means is located at an upstream region of the inverse-tapered channel portion.
  • a flow along an inner surface of the inverse-tapered channel portion is created by a centrifugal force of the swirling flow generated by the swirling-flow generation means.
  • the molten metal is spouted from the inlet port after the swirling flow thereof is expanded to flow along the inner surface of the inverse-tapered channel portion while smoothly maintaining the centrifugal force without occurrence of the so-called "flow separation".
  • This makes it possible to distribute an upward spouting speed to be concentrated around the center of the flow channel, in a lateral direction of the mould, so as to largely reduce the upward spouting speed without lowering the pouring rate.
  • the conditions, such as shape of this inverse-tapered channel portion are the same as those in the second and fifth specific embodiments.
  • gas is injected in a vicinity of the swirling-flow generation means located adjacent to the inlet port as in the seventh specific embodiment to disperse gas bubbles over the molten metal in the pouring tube and allow the molten metal with the gas bubbles to be poured into the mould.
  • the gas bubbles dispersed over the swirling flow of the molten metal makes it possible to further enhance the gas-bubbles' effect of capturing the nonmetallic inclusions, concentrating the nonmetallic inclusions around the tube axis (center of the flow channel), and enlarging/clustering the nonmetallic inclusions.
  • the gas bubbles receiving a larger buoyant force that that received by the nonmetallic inclusions can accelerate the effect of floating the nonmetallic inclusions in the molten metal flow after being released from the inlet port into the mould.
  • the gas is injected at a position adjacent to and downstream of the swirling-flow generation means, and from the entire circumference of the pouring tube.
  • the reason is the same as that described in the third specific embodiment.
  • the level of the swirling flow during pouring into the mould and the level of gas distribution may be specifically determined on a case-by-case basis depending on actual conditions of casting equipment, pouring rate, properties of molten metal, intended quality of metal ingots etc., and in consideration of the aforementioned requirement of allowing the swirling flow to have a swirl number of 0.13 or more during pouring into the mould.
  • the configuration and positioning of the swirling-flow generation means may be adjusted to meet the above conditions and this requirement.
  • inert gas having no chemical influence on the molten metal such as oxidation reaction
  • a total volume of gas to be injected is preferably set in the range of about 0.0003 to 0.002 Nm 3 /min, in view of the balance between maximization of the gas-bubbles' effect and maintenance of the swirling flow.
  • the flow channel in the pouring tube is not limited to a specific sectional shape in a direction perpendicular to the molten-metal flow direction.
  • the sectional shape of the flow channel is formed preferably in a shape without a corner having a certain radius R, more preferably in a circular shape.
  • the present invention provides the following effects.
  • a pouring tube 1 is connected to an inlet port 6 formed in a bottom of a mould 5. Molten metal is fed upward through a space or flow channel 2 internally defined in the pouring tube 1, and spouted/poured from the inlet port 6 into the mould 5.
  • the pouring tube 1 has an approximately vertical channel portion 1A extending from immediately below the inlet port 6 of the mould 5 in an approximately vertically downward direction, an approximately horizontal channel portion 1B extending in an approximately horizontal direction and a bent channel portion 1C making a transition from the approximately vertical channel portion 1A to the approximately horizontal channel portion 1B.
  • the flow control plate 3H serving as swirling-flow generation means is located in the approximately horizontal channel portion 1B on an upstream side of the bent channel portion 1C at space 2, a position spaced apart from the bent channel portion by about 300 mm.
  • An upper end of the flow channel 2 on a downstream side of the bent channel portion 1C (upper end of the approximately vertical channel portion 1A on the downstream side of the bent channel portion 1C) is formed as an inverse-tapered channel portion 4 having an inner diameter gradually increasing toward the inlet port 6.
  • the flow control plate 3H is operable to generate a swirling flow in the molten metal passing through the flow channel 2 and allow the molten metal with the swirling flow to be spouted/poured from the inlet port 6 into the mould 5.
  • the pouring tube 1 has a plurality of gas injection ports 10 arranged along a circumferential direction thereof at a position immediately downstream of the flow control plate 3H.
  • the pouring tube structure illustrated in FIG 1(a) further includes a flow control plate 3V located in the approximately vertical channel portion 1A. However, if an intended effect can be obtained only by the flow control plate 3H, the flow control plate 3V may be omitted.
  • FIG. 2 is an enlarged vertical sectional view showing the inverse-tapered portion in FIG. 1.
  • the inverse-tapered portion 4 is formed in an inverse-tapered shape which has an inner diameter gradually increasing from a lower end (inner diameter D2) to an upper end (inner diameter D1) thereof to define an inverse-tapered angle or opening angle ( ⁇ ), the upper end is fluidically connected to the inlet port 6.
  • FIG 3 shows one example of the flow control plate, wherein FIG 3(a) is a front view, and FIG 3(b) is a side view.
  • the flow control plate 3 has a screw-like configuration, i.e., a twisted tape-like configuration, having a twist angle ( ⁇ s) which is equivalent to a state after a flat plate is horizontally positioned parallel to a flow direction of molten metal in the flow channel 2 (molten-metal flow direction) and then a left edge 3a of the flat plate is twisted in a direction perpendicular to the molten-metal flow direction with respect to a right edge of the flat plate 3b.
  • ⁇ s twist angle
  • FIG 4 is a top view showing another example of the flow control plate.
  • a plate having a certain thickness in the molten-metal flow direction is formed with a plurality of grooves 3d each slightly inclined from an outer periphery to a central region thereof, and a circular space 3p formed in the central region to which the grooves 3d are gathered.
  • These grooves 3d are operable to give a circumferential velocity to molten metals passing therethrough, and move the molten metals toward the central region while increasing the circumferential velocity so as to form a swirling flow which swirls counterclockwise.
  • FIG 5 is a vertical sectional view showing a pouring tube structure according another embodiment of the present invention.
  • a pouring tube 1 is connected to an inlet port 6 formed in a bottom of a mould 5. Molten metal is fed upward through a space or flow channel 2 internally defined in the pouring tube 1, and spouted/poured from the inlet port 6 into the mould 5.
  • a flow control plate 3 serving as swirling-flow generation means is located in the flow channel 2 at a position adjacent to the inlet port 6, and an upper end of the flow channel 2 on a downstream side of the flow control plate 3 (upper end of the pouring tube 1) is formed as an inverse-tapered channel portion 4 having an inner diameter gradually increasing toward the inlet port 6.
  • the flow control plate 3 is operable to generate a swirling flow in the molten metal passing through the flow channel 2 and allow the molten metal with the swirling flow to be spouted/poured from the inlet port 6 into the mould 5.
  • Each of the inverse-tapered channel portion and flow control plate 3 has the same structure as that illustrated in FIGS. 2 and 3.
  • a tube used as the pouring tube illustrated in FIG 1 was formed with a bent portion (bent channel portion) having a curvature radius of about 120 mm, and a single flow control plate serving as the swirling-flow generation means was located in an approximately horizontal portion (approximately horizontal channel portion) of the tube at a position spaced apart from the bent portion by about 150 mm to about 1000 mm in an upstream direction.
  • the twisted tape-like flow control plate as shown in FIG. 3 was used as the swirling-flow generation means.
  • An axial length (L) and a twist angle ( ⁇ s) of the flow control plate were set in the range of 30 to 120 mm and in the range of 30° to 180°, respectively.
  • An inverse-tapered portion (inverse-tapered channel portion) was formed in the tube in a position corresponding to the upper end of the pouring tube.
  • An opening angle ( ⁇ ) and an inner-diameter ratio (D1/D2) of an upper end (D1) to a lower end (D2) of the inverse-tapered portion were variously changed.
  • Twelve holes each having a diameter of 0.5 mm and serving as the gas injection port were formed in the tube at a position adjacent to a downstream edge of the swirling-flow generation means and arranged along a circumferential direction of the tube at even intervals, to inject air therethrough while changing a total volume of the air.
  • a flow speed of the water just before passing through the flow control plate was set in the range of 0.7 to 1.5 m/s.
  • a swirl number was obtained from both a numerical calculation result and a flow-speed measurement result using a laser flowmeter in a water-model experimental apparatus.
  • the state of "open eye” was evaluated by checking a state of the water surface based on visual observation and a video image, and classifying a combination of a sensory evaluation result from the visual observation and a measure value from the video image, into a plurality of ranks.
  • the organic particles used as nonmetallic inclusions had a diameter of about 1 mm and a specific gravity of about 0.8, and a water-repellent was splayed to coat surfaces thereof so as to lower water wettability thereof.
  • the number of residual particles in a case used as an equivalent of the mould was measured by releasing the organic particles into water from a water supply port at a rate of 200 particles/min, and measuring behaviors of particles used as an equivalent of powder on the molten metal surface and the organic particles spouted from an inlet port of the case, in the case using a video image. Respective flow paths of the particles (inclusions) and gas bubbles in the water inside the tube were estimated by numerical analytical simulation.
  • the result of the above test was represented by a relative index on the basis of 100 representing a value of Comparative Example (Comparative Example (1) in Table 1) based on the conventional pouring tube structure.
  • FIG. 6 is a photograph showing a section of a water surface in the water model test for Inventive Example (6) in Table 1
  • FIG. 7 is a photograph showing a section of a water surface in the water model test for Comparative Example (1) in Table 1.
  • the swirl number (W/V) can be set preferably in the range of 0.13 to 2.5, more preferable in the range of 0.3 to 1.7.
  • the opening angle ( ⁇ ) of the inverse-tapered channel portion can be preferably set in the range of 6° to 90°, and the inner-diameter ratio (D1/D2) can be preferably set in the range of 1.36 to 6. More preferably, the opening angle ( ⁇ ) of the inverse-tapered channel portion can be set in the range of 16.8° to 50°, and the inner-diameter ratio (D1/D2) can be set in the range of 2 to 4.2.
  • the volume of air as the gas to be injected in Table 1 is a value converted to a volume of argon gas at a pouring rate of about 1.3 t/min in actual casting equipment.
  • this deemed volume of argon gas is set at 0.0003 Nm 3 /min or more, the number of residual organic particles as nonmetallic inclusions starts significantly decreasing.
  • the deemed volume of argon gas is 0.003 Nm 3 /min, the swirling flow starts being disturbed, and the molten metal surface (water surface) starts being destabilized.
  • the volume of argon gas to be injected can be preferably set in the range of about 0.0003 to 0.002 Nm 3 /min.
  • a pouring test was performed using casting equipment employing the pouring tube structure of the present invention illustrated in FIG. 5.
  • molten steel at a temperature of 1580° was used as the molten metal.
  • the pouring rate was 1.3 t/min, and a pouring volume was 10 t.
  • the length (L) was set at 60 mm, and the twist angle ( ⁇ s) was set at 60°.
  • the opening angle ( ⁇ ) was set at 32°, and the inner-diameter ratio (D1/D2) was set at 3.
  • An average circumferential velocity (W) after passing through the flow control plate, an average velocity in the axial direction of the pouring tube and a flow in the mould were calculated from both a numerical calculation result and a measurement result in a water-model experimental apparatus (a flow-speed measurement using a laser flowmeter and an "open eye” measurement using a video image), to obtain the following simulation result.
  • FIG 9 is a photograph showing a section of the water model test for Inventive Example (23) in Table 2
  • FIG. 10 is a photograph showing the water model test for Comparative Example (3) in Table 2.
  • the swirl number (W/V) can be set preferably in the range of 0.13 to 2.5, more preferable in the range of 0.3 to 1.7.
  • the opening angle ( ⁇ ) of the inverse-tapered channel portion can be preferably set in the range of 6° to 90°, and the inner-diameter ratio (D1/D2) can be preferably set in the range of 1.36 to 6. More preferably, the opening angle ( ⁇ ) of the inverse-tapered channel portion can be set in the range of 16.8° to 50°, and the inner-diameter ratio (D1/D2) can be set in the range of 2 to 4.2.
  • the present invention can be applied to casting of steel ingots based on uphill casting of molten steel, and a pouring operation to a mould for uphill casting of cast metal and any other molten metal.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)
EP20060018010 2005-08-30 2006-08-29 Ausgussdüsenstruktur und Verfahren zum steigenden Gießen Not-in-force EP1759789B1 (de)

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CN102794408A (zh) * 2012-07-23 2012-11-28 宁夏共享集团有限责任公司 一种铸钢件冒口补浇的方法
CN111421118A (zh) * 2020-04-27 2020-07-17 贵州莹月帆铝制品有限公司 一种便于晶粒控制的铝合金铸轧机双铸嘴结构

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102794408A (zh) * 2012-07-23 2012-11-28 宁夏共享集团有限责任公司 一种铸钢件冒口补浇的方法
CN102794408B (zh) * 2012-07-23 2015-07-15 宁夏共享集团有限责任公司 一种铸钢件冒口补浇的方法
CN111421118A (zh) * 2020-04-27 2020-07-17 贵州莹月帆铝制品有限公司 一种便于晶粒控制的铝合金铸轧机双铸嘴结构
CN111421118B (zh) * 2020-04-27 2023-07-21 贵州莹月帆铝制品有限公司 一种便于晶粒控制的铝合金铸轧机双铸嘴结构

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DE602006000811T2 (de) 2008-07-03
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