JPH07179956A - Treatment of molten metal - Google Patents

Abstract

PURPOSE:To minimize a quantity of Al alloy in dross by shortening the length of a buffle plate dipped under molten metal surface, floating up pulverized gas bubbles and adding a specific quantity of selected flux into revolving flow. CONSTITUTION:The buffle plate 12 fixed to a frame 15 is cut to shorten so as to be dipped under the molten metal surface by about 50mm. Inert gas is ejected from the tip part of a rotary blade 9 provided in a hollow shaft 10 dipped into the molten metal 8. Under this condition, the rotary blade 9 is sunk to the bottom part of the molten metal 8. The rotary blade 9 is rotated to revolve the molten metal 8, and the inert gas is pulverized and its flow rate is increased. Just after that, the selected flux is charged on the molten metal 8 surface by an amt. of 0.03-0.07wt.% based on the molten metal. The flux is floatingly moved on the revolving flow of the molten metal 8 and the flux is dispersed, evaporated and reacted on the revolving flow of the molten metal 8 on the way of aggregating non-metallic inclusion and adsorbing gaseous H2 to be floated up and making the non-metallic inclusion and metallic Al alloy easy to separate from each other. The dross 24 is involved in the revolving flow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for purifying a molten aluminum alloy before casting.

[0002]

2. Description of the Related Art Generally, in a casting plant, an aluminum alloy ingot is melted in a reverberatory furnace or the like and transferred to a holding furnace on the casting machine side for casting. However, with such a process alone, the cast product contains non-metallic inclusions such as gas and oxides dissolved in the molten metal, and its quality deteriorates. When is necessary, that part has a notch effect and does not result in a sound product. Therefore, in general, a flux suitable for an aluminum alloy (molten metal ratio of 0.1% by weight) is charged into the molten metal in the holding furnace and stirred to disperse gas such as H2 or oxide such as Al2 O.
3rd grade has been removed. Recently, the GBF device (trade name) shown in Fig. 1 is used in a ladle that is transported from a reverberatory furnace to a holding furnace on the casting machine side before casting, and degassing and deoxidizing (hereinafter, removal of oxides, etc.). Meaning) is adopted by some aluminum alloys.

In this degassing method using the GBF device 1, a hollow shaft 5 having a rotor 4 at its tip is immersed in the bottom of a molten metal 3 filled in a ladle 2, and baffle plates 6 and 6 are also up to 500 mm below the molten metal surface. When immersed, the inert gas is ejected from the center of the rotor 4 through the core of the hollow shaft 5 and the rotor 4 rotates to become fine bubbles that float up, and the fine bubbles mainly adsorb and float H2 gas contained in the molten metal and desorb it. To gas. At this time, non-metallic inclusions such as impurities also float as dross and float in layers on the molten metal surface. The advantages of this method are that there is no smoke and that there is no deposit on the inner wall of the ladle, but the disadvantage is that the metal aluminum alloy is 0.7% of the weight of the molten metal in the dross that floats on the molten metal surface after degassing and deoxidizing. It is a wasteful method because it is contained in a large amount and needs to be separated again in a later process. Further, the above-mentioned method using the flux does not change in that non-metallic inclusions such as impurities are floated on the surface of the molten metal as dross, but a large amount of dust smoke is generated as a defect, especially in the smoke.
Since it contains l2 gas and it is not good for the work environment and requires smoke exhaust equipment, it is not perfect.

[0004]

Therefore, the problem to be solved by the present invention is to minimize the amount of metallic aluminum alloy contained in the dross generated on the surface of the molten metal during the degassing and deoxidizing process of the molten metal, and still to reduce the powder smoke. It does not occur.

[0005]

[Means for Solving the Problems] Therefore, as a result of trial and error, it was discovered that the following means can solve the problem. That is, G
The baffle plate of the BF device is cut and cut so that it is immersed 50 mm below the surface of the molten metal, and the lower end of the device is immersed in the bottom of the molten metal in the ladle that transfers to the holding furnace, and an appropriate amount of inert gas is ejected from its rotor blades. A means for floating the non-metallic inclusions while adsorbing the gas floating in the melt by the finely divided bubbles riding on the swirling flow caused by cutting and shortening it, and the selected flux to the ladle. A flux treatment is carried out at the same time, in which 03 to 0.07% by weight is added and floating is performed while causing a dispersion reaction in the swirling flow.

[0006]

[Function] As a result, the fine bubbles of the inert gas rising and floating vertically due to the shortening of the baffle plate cause a swirling flow by the rotor blades, and the fine bubbles swim in the molten metal for a long time and become dissolved gas. The chances of contact increase, and the force to pick up the metal aluminum alloy becomes weaker, and stirring by the swirling flow is efficiently performed. Besides degassing and deoxidizing the flux itself, inert gas also enlarges non-metallic inclusions. Since it floats and adsorbs H2 gas, a small amount of flux may be added. Furthermore, the introduction of the selected flux and its dispersed heat increase the wettability between the dross and the metallic aluminum alloy, thereby promoting their separation. At the same time, the effect of the flux that suppressed the Cl component was able to suppress the generation of dust. Furthermore, by stopping the submerged immersion of the baffle plate to the thickness of the dross and suppressing the oscillation of the dross so that the floating dross is not caught in the molten metal again, the amount of flux used can be reduced by using the above means together.
The generation of dust and smoke was prevented, the aluminum alloy was not wastefully discharged as dross, and the quality of H2 gas was reduced to 0.3 cc or less per 100 g of aluminum alloy, and the molten metal could be efficiently purified.

[0007]

In the following, embodiments will be described with reference to the drawings.
FIG. 2 is a longitudinal sectional view of the device A used in the present invention in use.
It shows a state in which the ladle 7 is filled with the molten metal 8 and the carbon hollow shaft 10 having the carbon rotary blade 9 at the tip is immersed in the bottom of the molten metal 8 and used. The hollow shaft 10 is connected to a hollow shaft 11 made of steel by a flange 12. A pulley 13 is attached to the hollow shaft 11 and is fixed to the frame 15 by bearing cases 14 and 14. A motor 16 is installed on the frame 15, and a V-belt 18 is hung on the pulley 17 and the pulley 13 to transmit the rotational force.

A hose 20 for pressure-feeding argon gas is connected to the tip of the hollow shaft 11 via a swivel joint 19. Further, the baffle plates 21, 21 are fixed to the frame 15 and are formed so as to be immersed 50 mm below the molten metal surface. Also, a plurality of height setting bolts 22, 2
2, are also fixed to the frame 15. Further, the heat shield plate 23 is also fixed to the frame 15. These are moved up and down by a hoist (not shown) connected to the frame 15. 24 is a dross generated after the purification of the molten metal. FIG. 3 shows the device positioned directly above a ladle filled with unpurified molten metal.

Next, the purification method will be described from the point where the state shown in FIG. 3 is reached. The ladle 7 is filled with 400 kg of the JIS standard ADC10 and the molten metal 8 of Al-Si based aluminum alloy pumped out from a melting furnace (not shown). Then, after confirming that the hollow shaft 10 is located right above the ladle 7, first, when a switch (not shown) of a control panel (not shown) of the device is turned on, it is connected to the hose 20. The solenoid valve (not shown) is opened, and 5 l / min of argon gas having an original pressure of 2 kg / cm 2 is ejected from the tip of the rotary blade 9.
In that state, move the hoist (not shown) to move the frame 15
To lower the rotary blade 9 to the bottom of the molten metal 8 to obtain the height positional relationship shown in FIG. In FIG. 2, argon gas is ejected. Next, when another switch (not shown) of the control panel (not shown) is turned on, the motor 16 starts to rotate, the rotor 9 is rotated at 550 rpm by the transmission system, the molten metal 8 is swirled, and the argon gas is atomized. The flow rate is also increased to 20 l / min.

Immediately after that, the selected half of the conventional flux (composition, Na; 16 to 25%, K; 13 to 19%,
Cl; 10 to 16%, F; 1 to 9%, Si; 5 to 10
%, Other; balance) 200 g (molten metal ratio 0.05% by weight)
However, when the flux is cast on the surface of the molten metal 8, the flux rides on the swirling flow of the molten metal and disperses and swims in the molten metal to form non-metallic inclusions (Al
2 O3, SiO2, Al2 O3 · MgO and other oxides) and H2 gas not only have the effect of enormously levitating, but also argon gas, which has become fine bubbles, rides on the swirling flow of the molten metal and swims inside the molten metal. During the process of concentrating the inclusions and adsorbing and floating the H2 gas, the flux rides on the swirling flow of the molten metal 8 and causes the dispersion exothermic reaction to wet the surface of the enormous non-metallic inclusions and the non-metallic inclusions and the aluminum metal alloy. Are easily separated, and the flux itself serves as a nucleus that collects non-metallic inclusions, so that the synergistic action with the argon gas increases the purification capacity. Since the baffle plates 21 and 21 serve to keep the dross 24 stationary while the molten metal is swirling, the dross 24 is prevented from being caught in the swirling flow again.

After 1 to 3 minutes from the introduction of the flux, the rotation of the rotor blades 9 is stopped, the flow rate of the argon gas is returned to 5 l / min, and then the hoist (not shown) is used to restore the original state of FIG. After stopping, the dross 2 floated on the surface of the molten metal as a result of removing H2 gas and non-metallic inclusions from the molten metal.
4 was scooped up by a disc-shaped descaling device (not shown) in the form of lotus roots having a plurality of 15 mm through holes. Then, 1.1 kg of the aluminum metal alloy (0.3% by weight of the molten metal) was recovered from the dross in the subsequent process. In this way, the metallic aluminum alloy contained in the dross is reduced by about 60% as compared with the conventional purification using only argon gas, and a quality of 0.3 cc or less per 100 g of Al alloy, which is the H2 gas content standard, is achieved. The molten metal could be purified with good efficiency. Then, Table 1 shows the evaluation results of the experiments in which the above-mentioned flux input amount and other factors were changed, and Table 2 shows the evaluation criteria. The evaluation of H2 gas content was 0.3 cc per 100 g of Al alloy.
The following was judged to be none. Therefore, from Table 1, the amount of flux is 0.03 to 0.07% by weight and the amount of argon gas is 10 to 10.
The 30 l / min range proved to be optimal and the inert gas was unchanged in the experiments with N2 gas.

[0012]

As described above, the swirling flow molten metal purification by fine bubbles of inert gas and the molten metal purification by a small amount of selected flux are simultaneously used, so that the yield of metal aluminum alloy is improved by about 60% and it is applied to the workplace. The generation of dust and harmful gas was prevented, and there was no deposit on the inner wall of the ladle, and it was possible to achieve the purification of molten metal with excellent casting quality.

[Brief description of drawings]

FIG. 1 shows a longitudinal sectional view of a conventional GBF device in use.

FIG. 2 shows a longitudinal section in use of the device of the invention.

FIG. 3 shows a longitudinal sectional view of the device of the present invention before use.

[Table 1] The evaluation results of the experiment are shown.

[Table 2] The evaluation criteria of Table 1 are shown.

[Explanation of symbols]

 1 GBF device 2 ladle 3 molten metal 4 rotor 5 hollow shaft 6 baffle plate 7 ladle 8 molten metal 9 rotor blade 10 hollow shaft 11 hollow shaft 12 flange 13 pulley 14 bearing case 15 frame 16 motor 17 pulley 18 V belt 19 swivel joint 20 Hose 21 Baffle plate 22 Height setting bolt 23 Heat shield plate 24 Dross A Device used in the present invention

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C22B 21/06

Claims (1)

[Claims] 1. A method for purifying a melted molten Al-Si aluminum alloy in a container transferred from a melting furnace before casting, the tip of a rotating blade inserted into the bottom of the container and rotating. A means for ejecting a more inert gas to cause non-metallic inclusions floating in the molten metal to be finely atomized and floated by the swirling of the rotary blade to float, and to adsorb and float the H2 gas dissolved in the molten metal is selected. Flux 0.0
3 to 0.07% by weight A method for purifying a molten metal is characterized in that a means for separating and dispersing a metallic aluminum alloy and a floating non-metallic inclusion in the swirling flow is simultaneously used.