JP2008224049A - Rotating body for stirring molten bath - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotating body for stirring molten bath capable of stabilizing a bubble releasing amount to the molten bath, and keeping high fine dispersibility of bubbles, even when dispersion is found in an inert gas supply amount, and preventing change in degassing performance and slag eliminating performance with time. <P>SOLUTION: In this rotating body for stirring molten bath, constituted by fixing a disc-shaped rotor 2 to a lower portion of a hollow pipe-shaped shaft 1 having an inert gas introduction hole 11, the inside of the rotor is provided with a gas storing portion 21 opened at its bottom surface and storing an insert gas, an outer peripheral edge portion of the rotor is provided with groove-shaped recessed portions 22 and projecting portions 23 held between the recessed portions in adjacent to each other, and a plurality of gas jetting ports 24 are formed on the recessed portions in a state of being communicated with the gas storing portion. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rotating body for stirring a molten metal that releases inert gas such as nitrogen or argon gas into a molten metal such as an aluminum alloy to remove impurities such as gas such as hydrogen or oxide in the molten metal. About.

  In a molten metal such as an aluminum alloy, in order to float and remove impurities and hydrogen gas in the molten metal, bubbles are made fine by bubbling an inert gas such as nitrogen or argon gas in the molten metal while stirring the molten metal. A rotating body for molten metal stirring is used that is made uniform and uniformly dispersed in the molten metal.

  For example, Patent Document 1 discloses a method for purifying a molten metal by introducing a purification gas into a molten aluminum and rotating a rotor installed in the molten metal to finely disperse the gas in the molten metal. In addition, there is described a method for refining molten aluminum in which a gas is temporarily retained in a gas retaining portion formed at the lower end of the rotor in the molten metal and having an open lower surface, and the rotor is rotated. It is described that the gas retaining portion is a bowl shape whose upper surface and side surfaces are sealed by a wall member and whose lower surface is opened, that is, a truncated conical shape spreading under the side surface, and a notch is provided at the lower end of the side surface of the wall member.

  In Patent Document 2, a bubble refining and rotating body is attached to the lower end of a vertical rotation shaft having a gas supply path therein, and the lower end of the gas supply path is opened at the bottom surface of the rotating body. A plurality of grooves extending from the opening of the gas supply path to the periphery are provided radially, and a recess having a lower end opened at the periphery of the bottom surface of the rotating body is provided between the openings of the grooves on the peripheral surface of the rotating body. A rotating body for molten metal stirring is described.

  Patent Document 3 includes a vertical rotation shaft that has a gas passage extending in the lengthwise direction and is disposed in a liquid, and a bubble discharge / dispersion rotator provided at the lower end of the rotation shaft. In a device that discharges gas in the form of fine bubbles in the liquid and disperses it throughout the liquid, the rotating body has a gas outlet that is connected to the gas passage of the rotating shaft on the circumferential surface in the circumferential direction. There is described a bubble discharge / dispersion device comprising a plurality of disk-shaped main bodies and a ring-shaped porous body attached to the peripheral surface of the disk-shaped main body.

JP 58-144438 A Japanese Patent Publication No. 61-40737 Japanese Patent Laid-Open No. 4-308047

  In Patent Document 1, since inert gas is stored in a bowl-shaped gas retention part, even if variations in the supply amount of inert gas occur, the amount of bubbles released into the molten metal does not vary greatly, which is good. However, it cannot be said that the fine dispersion of the bubbles is sufficient in the structure in which the bubbles are released from the open portion on the lower surface of the gas retention portion.

  Patent Document 2 discloses that the inert gas bubbles released from the lower end of the vertical rotation shaft into the molten metal are fine by a mechanical shearing action by a radial groove provided in the bottom surface of the rotating body and a recess opened in the peripheral edge of the bottom surface. Disperse. This is because if the supply amount of the inert gas varies, the ability to finely disperse the bubbles decreases, and it is difficult to obtain the expected degassing performance and degassing performance.

  In Patent Document 3, the pores of the porous body are gradually blocked by long-term use, the porosity is lowered, and the supply amount of inert gas per unit time to the molten metal is lowered. Further, since the inert gas passes through the gas outlet having a small hole diameter provided in the rotating body, it is necessary to set the supply pressure high in order to increase the supply amount of the inert gas. When the supply amount of the inert gas is increased, the gas is generated as large bubbles after passing through the porous body, and the degassing performance and the degassing performance are likely to be deteriorated.

  In the present invention, even when the supply amount of the inert gas varies, the amount of bubbles released to the molten metal is stable, and the ability to finely disperse the bubbles is maintained high. It is an object of the present invention to provide a rotating body for molten metal stirring that does not change over time.

  The present invention relates to a molten metal stirring rotator in which a disc-shaped rotor is fixed to a lower portion of a hollow tubular shaft having an inert gas introduction hole, and a gas retention in which an inert gas is retained by opening a bottom surface inside the rotor. And a plurality of gas jets communicating with the gas retention portion in the concave portion, and a projection portion sandwiched between the groove-shaped concave portion and the adjacent concave portion at the outer peripheral edge portion of the rotor. .

  In the present invention, in addition to the gas jet port provided in the concave portion, a plurality of gas jet ports communicating with the gas retention portion are further provided in the protrusion. Further, the gas jet port formed in the recess and the gas jet port formed in the projection are formed in the shape of a round hole or a slit.

  When gas outlets are formed in the recess and the protrusion, the sum of the opening areas of the plurality of gas outlets provided in the recess is larger than the sum of the opening areas of the plurality of gas outlets provided in the protrusion. And A reverse concave notch is provided at the lower end of the open bottom of the rotor.

  In the case where the gas outlet is formed as a round hole in the recess or in the recess and the protrusion, the maximum diameter of the round hole is smaller than the minimum diameter of the inert gas introduction hole of the shaft. Moreover, when the gas ejection port is formed in the said recessed part or the recessed part and the projection part with the slit, the maximum width dimension of the slit is 5 mm or less, It is characterized by the above-mentioned. Furthermore, the maximum height dimension of the rotor is within a range of 1/4 to 1/2 of the maximum outer diameter of the rotor.

  In the present invention, a gas retention portion in which the bottom surface is opened inside the rotor and the inert gas is retained is provided, and the inert gas supplied from the inert gas introduction hole is temporarily stored therein. A small opening area through which the stored inert gas communicates with a groove-like recess in the outer peripheral edge of the rotor, or a gas retention part provided in a protrusion sandwiched between adjacent recesses. The gas is finely dispersed as small bubbles into the molten metal through a plurality of gas outlets. With this configuration, even when the supply amount of the inert gas varies, there is a gas retention portion, which is stable, and the finely divided bubbles can be reliably dispersed in the molten metal.

  The small bubbles of the inert gas discharged from the gas outlet are sheared and further refined by a groove-like recess or protrusion provided in the outer peripheral edge of the rotor. In order to maximize the miniaturization due to the shearing action, it is preferable to provide the gas outlet in a recess surrounded by three wall surfaces in the depth. Considering the balance between the amount of inert gas supplied and the total area of the gas outlets, the amount of gas coming out of the gas outlets is insufficient and leaks into the melt as large bubbles from the opening at the bottom of the rotor. In the case where it is assumed that the gas jetting exits, a gas ejection port is provided in the protrusion in addition to the recess of the rotor. When providing gas outlets in both the recesses and the protrusions, the sum of the opening areas of the gas outlets provided in the recesses on the outer peripheral edge of the rotor is equal to the opening area of the gas outlets provided in the protrusions. By making it larger than the total, the shearing effect is increased, which is preferable.

  In addition, even if the inert gas leaks into the molten metal as a large bubble from the opening at the bottom of the rotor, a reverse concave shape is formed at the lower end of the bottom of the rotor so as not to greatly reduce the degassing performance or the degassing performance. Provide multiple notches. By the shearing action of the molten metal by this notch, relatively large bubbles coming out from the opening at the bottom of the rotor can be made fine and dispersed.

  When the gas outlet is formed in a round hole, the maximum diameter of the round hole is smaller than the minimum diameter of the inert gas introduction hole of the shaft, and when the gas outlet is formed with a slit, the slit The maximum width dimension of 5 mm or less is preferable for fine dispersion of bubbles. Further, the maximum height dimension of the rotor is preferably in the range of 1/4 to 1/2 of the maximum outer diameter of the rotor.

  In order to stably exhibit the degassing performance and the degassing performance, it is desirable to form the rotor and the shaft, which are constituent members of the molten metal stirring rotor, with ceramics that do not change its shape even during the molten metal. Of these, silicon nitride and sialon are preferred.

  FIG. 1 is a partial cross-sectional view showing an embodiment of a rotating body for molten metal stirring according to the present invention. FIG. 2 is a plan view of the rotor of FIG. The rotating body for molten metal stirring according to the embodiment of the present invention is configured by screwing and fixing a disk-shaped ceramic rotor 2 to a lower portion of a hollow tubular ceramic shaft 1.

  The shaft 1 is made of a sintered body mainly composed of silicon nitride, and has a hollow inert gas introduction hole 11 for supplying an inert gas such as nitrogen or argon gas therein. The inert gas is supplied into the space of the gas retention portion 21 of the rotor 2 through the opening at the lower end of the inert gas introduction hole 11. A male screw portion for joining to the rotor 2 is formed in the lower portion of the shaft 1. The sintered body mainly composed of silicon nitride has a relative density of 99.4%, a thermal conductivity at room temperature of 55 W / (m · K), and a four-point bending strength at room temperature of 905 MPa.

  Like the shaft 1, the rotor 2 is made of a sintered body containing silicon nitride as a main component, and a female screw portion 13 for joining the shaft 1 is formed in the central hole portion 12 on the upper surface of the rotor 2. A gas retention portion 21, which is a space in which a reverse concave inert gas whose bottom surface is opened, is retained inside the rotor 2. On the outer peripheral edge of the rotor 2, groove-like recesses 22 and eight protrusions 23 sandwiched between the adjacent recesses 22 and projecting in the radial direction are provided every 45 degrees in the circumferential direction.

  A gas outlet 24 having a round hole with a diameter of 5 mm communicating with the gas retention part 21 was drilled in the recess 22 of the rotor 2. Five gas outlets 24 were provided for each recess 22. Further, a round gas outlet 25 having a diameter of 5 mm communicating with the gas retention part 21 was drilled in the protruding part 23 of the rotor 2. Three gas outlets 25 were provided for each protrusion 23.

  A reverse concave cutout 27 is provided at the lower end of the open bottom surface 26 of the rotor 2. The bottom surface portion 26 is constituted by the bottom surface of the concave portion 22 and the protruding portion 23, but the notch portion 27 is provided on the bottom surface of the concave portion 22.

  The maximum height of the rotor 2 (dimension from the bottom surface to the top surface of the rotor) is 96 mm, and the maximum outer diameter of the rotor 2 (the length between the tips of the opposing protrusions) is 240 mm. The maximum diameter 5 mm of the round holes of the gas outlet 24 and the gas outlet 25 was made smaller than the minimum diameter 50 mm of the inert gas introduction hole 11 of the shaft 1. Further, the total area of the opening areas of the gas outlets 24 provided in the recesses 22 was made larger than the total area of the opening areas of the gas outlets 25 provided in the protrusions 23.

  The molten metal stirring rotator according to the embodiment of the present invention thus configured is immersed in molten aluminum at 680 ° C., the shaft is rotated at a high speed by a driving device, and an inert gas is supplied from an inert gas introduction hole. When subjected to rotary stirring for floating impurities in the molten metal, the effect of finely dispersing bubbles was sufficiently obtained. It was also confirmed that the amount of bubbles released to the molten metal was stable and the ability to finely disperse the bubbles was maintained even when the supply amount of the inert gas varied.

  According to the molten metal stirring rotator of the present invention, even when the amount of inert gas supplied varies, the amount of bubbles released to the molten metal is stable and the ability to finely disperse the bubbles is maintained high. There is no secular change in degassing performance and removal performance.

It is a partial cross section figure which shows the Example of the rotary body for molten metal stirring of this invention. It is a top view of the rotor of FIG.

Explanation of symbols

1 shaft, 2 rotor, 11 inert gas introduction hole, 12 central hole,
13 thread part, 21 gas retention part, 22 recessed part, 23 protrusion part,
24 gas outlet, 25 gas outlet, 26 bottom face, 27 notch

Claims (8)

In a rotating body for molten metal stirring in which a disk-shaped rotor is fixed to a lower part of a hollow tubular shaft having an inert gas introduction hole, a gas retaining portion in which a bottom surface is opened inside the rotor and inert gas is retained, and the rotor Rotation for molten metal agitation characterized in that a groove-shaped recess and a protrusion sandwiched between adjacent recesses are provided on the outer peripheral edge of the gas and a plurality of gas jets communicating with the gas retention portion are provided in the recess. body. The rotating body for molten metal stirring according to claim 1, wherein a plurality of gas outlets communicating with the gas retention portion are provided in the protrusion. 3. The molten metal agitating rotator according to claim 1, wherein the gas outlet is formed in the shape of a round hole or a slit. The rotation for melt stirring according to claim 2, wherein the sum of the opening areas of the plurality of gas jets provided in the recess is larger than the sum of the opening areas of the gas jets provided in the protrusion. body. The rotating body for molten metal stirring according to any one of claims 1 to 4, wherein a reverse concave cutout is provided at the lower end of the bottom surface of the rotor. 6. The gas jet nozzle according to claim 1, wherein the gas outlet is formed by a round hole, and the maximum diameter of the round hole is smaller than the minimum diameter of the inert gas introduction hole of the shaft. The rotating body for molten metal stirring described in 1. The molten metal stirring rotator according to any one of claims 1, 2, 4, and 5, wherein the gas ejection port is formed by a slit, and the maximum width of the slit is 5 mm or less. 2. The molten metal agitating rotor according to claim 1, wherein the maximum height of the rotor is within a range of [1/4] to [1/2] of the maximum outer diameter of the rotor.