JPH0754059A - Impeller for cleaning molten metal - Google Patents

Abstract

PURPOSE:To prevent the development of cracking caused by heating of molten Al, etc., and use an impeller oven a long period of time by making the stirring impeller for eliminating gas and inclusion which are contained in the molten Al as impurity, the silicon nitride as raw material and a specific structure. CONSTITUTION:The molten Al is charged into a vessel 2 from a charging hole 7 and a vertical hollow rotary shaft 13 is rotated, and the impeller 14 at the lower end is rotated and fluxing gas ejected from the center is once stored in a gas storing part 25 and made to be fine by rotating blades 20 and ascended in bubble state in the molten Al. Degassing treatment is executed to the hydrogen gas, etc., in the molten Al and also, skin 5 included in the molten slag is floated up and discharged from a take-out 6. The clean molten Al which executes the degassing treatment and separates and removes the inclusion, comes into a treating chamber 4 through a communicating hole 11 at the lower end of a partition wall 12 and takes out from an outlet 8 as the clean molten Al. Inthis case, the impeller 14 is formed with a silicon nitride or sialon base ceramic, the development of crack caused by rapidly heating and rapidly cooling by inserting in/ separating from the molten Al is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impeller for cleaning molten metal, and more particularly to an impeller (rotor) used for degassing aluminum and removing inclusions.

[0002]

2. Description of the Related Art In the publicly known Japanese Patent Laid-Open No. 63-303014, an inert gas such as nitrogen or argon, or an inert gas obtained by mixing chlorine gas with this (generally called a fluxing gas) is disclosed. Describes a cleaning device that stirs aluminum or aluminum alloy melt (hereinafter referred to as aluminum melt) with an impeller while supplying the gas, degasses hydrogen gas floating in the aluminum melt, and removes inclusions such as oxides. Has been done. The structure of the cleaning device described in the above known example is as shown in FIGS.
Is a molten metal treatment tank made of refractory material, b is a molten metal inlet, c is a molten metal outlet, d is an aluminum molten metal, e is a floating slag separation and extraction chamber, f is a floating slag, and g is a central portion of the molten metal treatment tank a. A vertical hollow rotary shaft of the refractory provided, h is an impeller screwed to the lower end of the vertical hollow rotary shaft c. An enlarged view of the impeller h of the above-mentioned known example is as shown in FIG. 3 and FIG. 4, in which a screw cylinder j screwed from below into a screw portion of the lower end i of the rotating shaft g and an upper edge of the screw cylinder j. A horizontal circular disk part k that projects more like a brim,
It is formed of radial blades n provided on the lower surface side of the disk portion k. 5 to 6 are impellers h described in Japanese Utility Model Laid-Open No. 4-123250, in which the diameter of the screw cylinder j is made extremely large to serve also as the disk part k, and the lower surface of the screw cylinder j and the disk part k. The side is a flush surface, and the upper surfaces of the screw cylinder j and the disk portion k are inclined surfaces that become lower toward the outside. Eight radial stirring blades p are projected so as to extend as they are from the outer circumference of the disk portion j. A groove m is formed from the rotating shaft g to the tip of the stirring blade p.

[0003]

In addition to the degassing effect, each of the above-mentioned known examples has a problem that the impeller screw cylinder j and the disk portion k are cracked. For example, FIGS.
In the publicly known example shown in FIG. 1, the impeller h is described as only a refractory material, and the material thereof is not particularly described, but it is actually made of carbon.
The reason why the impeller h is made of carbon is to prevent cracking due to thermal shock even if it is put into a molten aluminum at a temperature higher than 700 ° C without preheating or if it is suddenly pulled out from the molten metal after use. Is. But,
The carbon impeller h is for the purpose of enhancing the degassing effect.
When rotating at a high speed of 300 rpm to 800 rpm, wear was inevitably remarkable, oxidation resistance was weak, and life was short, frequent replacement was required, workability was reduced due to frequent replacement, and it was economically disadvantageous. . In order to sufficiently withstand abrasion resistance and oxidation resistance even when the impeller h is rotated at a high speed, a ceramic material such as silicon nitride or a sialon-based ceramic should be used instead of carbon. However, if the impeller h is made of ceramic, as described above, if it is poured into the high-temperature aluminum melt without preheating, or if it is suddenly withdrawn from the high-temperature melt after use, the disk part k
Cracks (portion s in FIGS. 4 and 6) occur. The crack s is generated in the portion of the thick screw cylinder j on the inner side. This is because the screw cylinder j has a large wall thickness and a large heat capacity, so that expansion and contraction become non-uniform during heating and cooling. Therefore, thermal stress between the screw cylinder j and the peripheral portion is large,
It is considered vulnerable to thermal spalling. Further, the impeller h of FIGS. 5 to 6 is basically designed to atomize the gas induced by the groove m at the terminal end (outer edge) of the groove m, but if the gas amount is appropriate. It will be miniaturized,
When the amount of gas increases, the gas squeezes out and is not miniaturized, and there is a problem in the degassing effect. However, the ones shown in FIGS. 3 and 4 are made of silicon nitride or sialon-based ceramic so as to be resistant to wear,
Moreover, it is possible to prevent cracks from occurring as follows.

[0004]

It is an object of the present invention to obtain a silicon nitride or sialon ceramic impeller that is resistant to thermal shock.

[0005]

According to the present invention, therefore, a right circular rotary disk 13 is fixed to the lower end of a vertical hollow rotary shaft 13 by an arbitrary means, and a circular disk 19 of a regular circular shape having no cylindrical portion is provided.
A plurality of radial blades 20 that reach the outer peripheral edge 21 except the center side are fixed to the lower surface side of the blade 9. The downward protruding length of the blades 20 is long on the central side and short toward the outer peripheral edge 21, and the rotation is performed. The lower end 23 of the shaft 13 penetrates through the disc portion 19 and protrudes between the lower surface of the disc portion 19 and the lower ends of the blades 20, so that the lower end 23 of the rotary shaft 13 and the inner end 24 of the blade 20 are connected. This is an impeller for cleaning molten metal in which a gas reservoir 25 is formed. Further, according to the present invention, a small-diameter portion 15 having a diameter slightly smaller than that of the rotary shaft 13 is formed at the lower end of the vertical hollow rotary shaft 13, and a screw 17 is engraved on the outer surface of the small-diameter portion 15, and the screw 17 is Screw holes 18 formed in the center of a horizontal circular disk portion 19 having a right circular shape having no cylindrical portion in the central position from below are screwed into each other, and a plurality of disks reaching the outer peripheral edge 21 except the central side are formed on the lower surface side of the disk portion 19. The radial blades 20 are fixed, and the downward projection length of the blades 20 is long toward the center and short toward the outer peripheral edge 21, and the lower end 23 of the small diameter portion 15 is fixed.
Penetrates through the disk portion 19 and projects between the lower surface of the disk portion 19 and the lower ends of the blades 20, and the rotary shaft 13
Is a impeller for cleaning molten metal in which a gas reservoir 25 is formed between the lower end 23 and the inner end 24 of the blade 20.

[0006]

An embodiment of the present invention will be described with reference to the drawings.
The molten metal processing device may be the same as the known example, and the molten metal processing device shown in FIGS.
In FIG. 1, 1 is a molten metal treatment tank for molten aluminum, which is a treatment chamber 4 surrounded by a peripheral wall 2 and a bottom wall 3 made of refractory material.
And a separation and extraction chamber 6 for the floating slag 5 (skim). The processing chamber 4 is provided with a inlet 7 for supplying a molten metal such as an aluminum melt and an outlet 8 for a refined molten metal.
Between the molten metal processing chamber 4 and the separation / unloading chamber 6, an inflow port 9 through which the floating slag 5 floated in the processing chamber 4 flows into the separation / unloading chamber 6 is formed. Further, the tap hole 8 is partitioned by a partition wall 12 having a communication port 11 formed at a lower portion thereof so that the floating slag 5 does not flow out of the processing chamber 4 to the tap port 8.

In the central portion of the processing chamber 4, however, a vertical hollow rotary shaft 13 through which fluxing gas is passed from top to bottom.
Is provided at the lower end of the vertical hollow rotary shaft 13
Install 4. The impeller 14 is formed of, for example, silicon nitride or sialon-based ceramic as described above, and has the following configuration.

That is, in the embodiment, the stepped portion 1 is formed by forming a small-diameter portion 15 slightly thinner than the rotating shaft 13 at the lower end of the rotating shaft 13.
6 (a bulging portion may be formed instead of the step portion 16. When the bulging portion is formed, the bulging portion does not have to be a small diameter portion),
A screw 17 is engraved on the outer surface of the small-diameter portion 15 and a horizontal circular disc portion 19 having a screw hole 18 to be screwed from below is screwed to the screw 17 (not to screw screwing, but for fitting connection). When fixing, fix with mortar etc.). In screwing, if the direction of the screw is reversed with respect to the rotation direction of the rotary shaft 13, it will not come off during use. Although about 6 to 8 radial blades 20 are formed on the lower surface side of the disk portion 19, the cylindrical portion as shown in FIG. 3 is not provided. Even if the cylindrical part is formed,
Make it extremely small. Therefore, the central part of the impeller 14 has a small heat capacity, and even if it is immersed in a molten aluminum of high temperature suddenly, the thermal stress at the outer peripheral edge and the central part is small, and it is strong against thermal spalling (thermal shock).

The blade 20 is made to project downward at the center side, and the projecting length is made shorter toward the outer peripheral edge 21, so that the lower edge is an upwardly rising inclined edge 22. The disc portion 19 is screwed and attached to the lower end of the rotary shaft 13 until it hits the step portion 16. At this time, the lower end of the small diameter portion 15 has the disc portion 19
Through the disk portion 19 and project downward from the disk portion 19, but the small diameter portion 15
The lower end 23 of the blade does not reach the lower end of the blade 20 (it does not protrude from the blade 20), and a gas reservoir 25 is formed between the lower end 23 of the small diameter portion 15 and the lower end of the blade 20. As a result, the fluxing gas ejected from the lower end 23 of the small-diameter portion 15 is likely to accumulate and the bubbles are dispersed uniformly.

[0010]

[Operation] Next, the operation will be described. Although illustration is omitted, a motor is provided above the vertical hollow rotary shaft 13 via a joint. When the motor is energized, the vertical hollow rotary shaft 13 rotates, and the rotary shaft 13 rotates. The impeller 14 screwed to the lower end rotates. Thus, the fluxing gas passing through the inside of the rotary shaft 13 and ejected from the center of the impeller 14 has the lower end 23 of the rotary shaft 13 penetrating the rotary shaft 13 and reaching below the rotary shaft 13, and Since 23 is between the lower surface of the rotary shaft 13 and the lower end of the blade 20, and the gas reservoir 25 is formed between the lower end 23 of the rotary shaft 13 and the inner end 24 of the blade 20, the gas is gas. It is easy to accumulate in the reservoir 25, and is directly made finer by facing the upper and lower intermediate portions of the blades 20 to rise in the molten aluminum and degas such as hydrogen gas floating in the molten aluminum. Further, the molten aluminum is stirred by the rotation of the impeller 14 to float the slag, and the floated slag 5 is collected in the separation and extraction chamber 6 and scraped out.

In order to improve the degassing effect, the impeller 14 of the present invention is rotated at a high speed of 300 rpm to 800 rpm in order to atomize gas bubbles, but it is made of silicon nitride or sialon ceramics. Since it is formed, abrasion resistance and oxidation resistance are sufficient. Further, the impeller 14 formed of silicon nitride or sialon-based ceramic is not subject to thermal shock if it is used without being preheated in molten aluminum above 700 ° C, or if it is suddenly pulled out from the molten metal after use. Therefore, the impeller 14 of the present invention can be cracked, but the hollow rotating shaft 1
A circular disk 19 having a right circular shape is fixed to the lower end of 3 by an arbitrary means and does not have the cylindrical portion j as shown in FIGS. 3 to 4. Therefore, the heat capacity of the central part of the impeller 14 becomes small and the temperature suddenly becomes high. Even when the aluminum alloy is poured into the molten aluminum and soaked in it, the thermal stress between the outer peripheral portion and the central portion is small and it is strong against thermal spalling, so that cracking is unlikely to occur. Further, in the case of the embodiment, a small-diameter portion 15 having a diameter slightly smaller than that of the rotary shaft 13 is formed at the lower end of the hollow rotary shaft 13, and a screw 17 is engraved on the outer surface of the small-diameter portion 15 with respect to the screw 17. Although the screw hole 18 formed in the center of the horizontal disk portion 19 is screwed, the assembly is easy in this structure.

[0012]

All of the above-mentioned known examples have a problem that the impeller screw cylinder j and the disk portion k are cracked. In order to improve the degassing effect, the impeller h is rotated at high speed, but in order to prevent it from being worn and oxidized even at high speed rotation, if it is made of ceramic, it is put into the high temperature aluminum melt without preheating. Or, when it is suddenly drawn out from the molten metal at a high temperature after use, a crack s is generated in the thick screw cylinder j inside. This is because the screw cylinder j has a large wall thickness and a large heat capacity, so that the expansion and contraction become uneven during heating and cooling. Further, the impeller h of FIGS. 5 to 6 is basically designed to atomize the gas induced by the groove m at the terminal end (outer edge) of the groove m, but if the gas amount is appropriate. Although it is miniaturized, when it is increased, the gas spills out and is not miniaturized, and there is a problem in the degassing effect. However, according to the present invention, the right circular rotary disk 13 is fixed to the lower end of the vertical hollow rotary shaft 13 with a circular disk 19 having no cylindrical portion at the center by any means. A plurality of radial blades 20 reaching the outer peripheral edge 21 are fixed, the downward protruding length of the blades 20 is long on the center side and is shorter toward the outer peripheral edge 21, and the lower end 23 of the rotating shaft 13 is the disk portion 19. Through the lower end of the disk portion 19 and the lower end of the blade 20, and the lower end 23 of the rotary shaft 13 and the inner end 2 of the blade 20.
Since this is an impeller for cleaning the molten metal in which a gas reservoir 25 is formed between the horizontal disk portion 19 and the lower end of the rotating shaft 13, a horizontal disk portion 19 having no cylindrical portion at the center is fixed by any means. Since the horizontal disk portion 19 which does not have a cylindrical portion has the same thickness both inside and outside, the heat capacity is substantially equal both inside and outside, the thermal stress becomes small and it becomes strong against thermal spalling, and it can be poured into high temperature aluminum melt without preheating. Even after suddenly pulling out from high temperature molten aluminum after use,
No cracks occur. Further, according to the present invention, a small-diameter portion 15 having a diameter slightly smaller than that of the rotary shaft 13 is formed at the lower end of the vertical hollow rotary shaft 13, and a screw 17 is engraved on the outer surface of the small-diameter portion 15, and the screw 17 is A screw hole 1 formed in the center of a horizontal circular disc portion 19 having a right circular shape having no cylindrical portion at the center position from below.
8 are screwed together, and a plurality of radial blades 20 reaching the outer peripheral edge 21 except the center side are fixed to the lower surface side of the disk portion 19, and the downward protruding length of the blades 20 is long on the center side. The lower end 23 of the small-diameter portion 15 penetrates through the disc portion 19 and protrudes between the lower surface of the disc portion 19 and the lower ends of the blades 20, and the lower end of the rotary shaft 13 is formed. 23 and the inner end 24 of the blade 20 between the gas reservoir 2
Since this is an impeller for cleaning molten metal in which No. 5 is formed, the above effect can be achieved as it is, and the mounting becomes easier.

[Brief description of drawings]

FIG. 1 is a plan view of a known molten metal treatment tank.

FIG. 2 is a sectional view of a known molten metal treatment tank.

FIG. 3 is a sectional view of a vertical hollow rotary shaft and an impeller of a first known example.

FIG. 4 is a cross-sectional view of an impeller of a first known example.

FIG. 5 is a sectional view of a vertical hollow rotary shaft and an impeller of a second known example.

FIG. 6 is a bottom view of an impeller of a second known example.

FIG. 7 is a plan view of the molten metal treatment tank of the present invention.

FIG. 8 is a sectional view of the molten metal treatment tank of the present invention.

FIG. 9 is a sectional view of a vertical hollow rotating shaft and an impeller of the present invention.

FIG. 10 is a bottom view of the impeller of the present invention.

[Explanation of symbols]

1 ... Molten metal processing tank, 2 ... Peripheral wall, 3 ... Bottom wall, 4 ... Processing chamber, 5
… Floating slag, 6… Separation and unloading chamber of floating slag, 7… bath, 8…
Outlet port, 9 ... Inlet port, 10 ... Partition wall, 11 ... Communication port, 1
2 ... Partition wall, 13 ... Hollow rotating shaft, 14 ... Impeller, 15
… Small diameter part, 16… Step, 17… Screw, 18… Screw hole, 1
9 ... Horizontal disk part, 20 ... Blade, 21 ... Outer peripheral edge, 22 ... Sloping edge, 23 ... Bottom end, 24 ... Inner end, 25 ... Gas reservoir part.

Claims (2)

[Claims] 1. A vertical circular rotary shaft 13 is fixed to the lower end of a vertical circular rotary shaft 13 with a circular disc 19 having no circular cylinder at the center by any means. A plurality of radial blades 20 reaching the peripheral edge 21 are fixed, the downward protruding length of the blade 20 is long on the center side and is shortened toward the outer peripheral edge 21, and the lower end 23 of the rotary shaft 13 defines the disk portion 19. Through the bottom surface of the disk portion 19 and the blade 20
The lower end 23 of the rotary shaft 13
An impeller for cleaning molten metal, wherein a gas reservoir 25 is formed between the blade 20 and the inner end 24 of the blade 20. 2. A small-diameter portion 15 having a diameter slightly smaller than that of the rotary shaft 13 is formed at the lower end of the vertical hollow rotary shaft 13, and the small-diameter portion 1 is formed.
5, a screw 17 is engraved on the outer surface of the screw 5, and a horizontal circular disc portion 19 of a regular circle having no cylindrical portion at the center position from below the screw 17.
The screw hole 18 formed in the center of the
A plurality of radial blades 20 reaching the outer peripheral edge 21 except the center side are fixed to the lower surface side of the blades. The downward protruding length of the blades 20 is long on the center side and short toward the outer peripheral edge 21, The lower end 23 of the small-diameter portion 15 penetrates through the disc portion 19 and protrudes between the lower surface of the disc portion 19 and the lower end of the blade 20, and the lower end 23 of the rotary shaft 13 and the inner end 24 of the blade 20. An impeller for cleaning molten metal in which a gas reservoir 25 is formed between.