JPH0557400A - Method and apparatus for continuously casting aluminum - Google Patents

Abstract

PURPOSE:To provide continuous casting method and apparatus for preventing crack in a cast billet and warp and constriction in bottom part of the cast billet developed at the initial stage of casting. CONSTITUTION:At the time of casting Al by using a water cooled mold 1, a bubble dispersing device composed of a guide vane 9 and a current cutter 10, is inserted on the way of cooling water passage 7, and cooling medium is used by mixing gas from a gas cylinder 11 as extremely fine bubbles having micron order or finer into the cooling water.

Description

Detailed Description of the Invention

[0001]

[Industrial application] Regarding continuous casting of aluminum,
In particular, the present invention relates to a continuous casting method for eliminating cracks in the ingot, warpage at the bottom of the ingot, and constriction that occur at the beginning of casting, and a manufacturing apparatus therefor.

[0002]

2. Description of the Related Art In continuous casting of aluminum, as shown in FIG. 4, a molten aluminum is poured into a space between a water-cooled mold 1 having a water channel 2 and a base 3 to form a solidified shell.
Lower the bottom stand, pour cooling water from the bottom of the water-cooled mold,
It is performed by casting while directly cooling.

Further, in the case of electromagnetic casting, since there is no primary cooling by the mold as shown in FIG. 5, cooling water is poured while the molten metal is held by electromagnetic force to form a solidified shell, and then the bottom is formed. Lower the platform. After that, casting is continuously performed only by this direct cooling (secondary cooling).

In these methods, "warping" occurs at the bottom of casting, and "constriction" occurs as shown in FIG.
If the degree of these is large, "cracking" or casting failure may occur.

In these continuous casting methods, as a method for preventing warpage at the bottom of the ingot, a method is known in which the heat extraction from the ingot at the initial stage of casting is reduced and the heat extraction is gradually increased with the pouring time. .

For example, as shown in FIG. 7, a solenoid valve 4 is inserted into a cooling water pipe of a mold to intermittently inject the cooling water in the water-cooled mold into a pulse casting method {Canadian Metal Radical Quarterly.
ETALLURGICALQUATERLY) Volu
me 7 Number 1}, as shown in FIG. 8, a pump or a static mixer 5 for dissolving carbon dioxide gas is inserted in a cooling water pipe 6 of the mold, and cooling water for dissolving 50% or more of carbon dioxide gas in the initial stage of casting is used as a mold. Method (Japanese Patent Publication Sho 55-
No. 42903), and as shown in FIG. 9, an air turbo system (USP-4693298) in which compressed air is blown to bubbling the cooling water flowing out of the mold 1.
No.) etc.

[0007]

The method of injecting cooling water that dissolves carbon dioxide into the mold at the initial stage of casting has some effects, but the amount of gas that dissolves in cooling water is large, and the dissolution treatment is also performed. There are drawbacks in that ancillary equipment such as a water tank and a high-pressure pump is required, and that carbon dioxide, which has the highest solubility, must be used because it is dissolved.

Therefore, the present invention realizes slow cooling by attaching a simple device to a pipe for introducing into a mold to eliminate cracks in the ingot, warpage at the bottom of the ingot, and constriction that occur at the beginning of casting. An ingot cooling method and apparatus are provided.

[0009]

Means for Solving the Problems In casting aluminum using a water-cooled mold having an open lower end, a refrigerant containing carbon dioxide gas is injected into the mold at the initial stage of casting to form an ingot. In the continuous casting method of slowly cooling, in the continuous casting method of aluminum using a refrigerant mixed with fine gas bubbles of micron order or less, and in casting aluminum using a water-cooled mold with an open lower end, the initial casting Injecting a refrigerant containing a gas in the mold, in a continuous casting device for slowly cooling the ingot, in the middle of the pipe for injecting the refrigerant into the water-cooled mold, a guide vane, insert a bubble disperser consisting of a current cutter,
This is a continuous casting device for aluminum in which a gas pipe is joined in front of the guide vanes and a flow control valve is provided in the gas pipe. That is, gas bubbles can be made extremely fine by attaching a fluid instantaneous mixing system to a reactor as shown in FIG. The present invention has been completed by using the heading and utilizing it. Figure 3
Inside, 7 is a cooling water passage, 8 is a gas passage, 9 is a guide vane, 10 is a current cutter, and 11 is a gas cylinder. The gas in the gas cylinder 11 passes through a regulator 14 equipped with a primary pressure gauge 12 and a secondary pressure gauge 13, and is mixed with the cooling water flowing in the cooling water passage 7 via the gas passage 8.
Then, a swirling flow is formed at the guide vanes 9 and they are mixed, but at this time, the central part of the flow is in a low pressure state, and a large pressure difference occurs in the circumferential direction. Further, the cooling water and the gas mixture fluid are sheared by the current cutter 10, agitated, and dispersed into ultrafine bubbles. In addition, 15 is a flow meter provided suitably.

The present invention is applied to casting in which an ingot is directly cooled by using a refrigerant mixed with such extremely fine gas bubbles, and is applied to so-called DC casting method and electromagnetic casting method.

Carbon dioxide is mainly used as the gas,
The effect does not change with other gases such as air.

The initial stage of casting referred to in the present invention is difficult to specify because it varies depending on the size of the ingot, but it is about 10 to 120 mm after the cooling water begins to hit the ingot, and in the DC casting method. It is preferably 80 to 120 mm, and 10 to 80 mm in the electromagnetic casting method.

When cooling water containing extremely fine gas bubbles is injected into the surface of the ingot, a heat insulating layer is formed on the surface of the ingot, heat extraction is prevented, warpage of the bottom of the ingot and cracking of the ingot are prevented. Has an effect on.

The amount of the gas mixed with the cooling water is preferably 5 to 45% with respect to the cooling water, and 400 to 400% of the cooling water in the DC casting method.
50 to 150 l / min gas for 700 l / min,
In the electromagnetic casting method, gas 2 for 250 to 500 l / min
It is preferable to contain 5 to 100 l / min.

[0015]

EXAMPLES Example 1 Al-4.3% Mg-0.33% Mn-based aluminum alloy was melted, and this was cast using a DC casting apparatus shown in FIG.
It was cast into a 500 × 960 mm ingot. The apparatus shown in FIG. 1 is a water channel 2 for injecting a refrigerant into a water-cooled mold 1 of an ordinary DC casting apparatus.
The reactor shown in FIG. 3 is installed in the middle of the process, and the carbon dioxide gas cylinder 11 is used to disperse ultrafine carbon dioxide gas bubbles in the cooling water, which is then supplied to the water-cooled mold 1 for ingot formation. did. At this time, the carbon dioxide gas forms a heat insulating layer in the mold and weakens the heat extraction from the ingot A. At this time, the pressure of the cooling water is 144 kPa, the pressure of the CO ₂ gas is 192 kPa, and the temperatures are both 20 to 30 ° C.
The measured pH value of the CO ₂ gas mixed water was 5.3.
Table 1 shows the casting conditions in this case.

[0016]

[Table 1]

In the obtained ingot, the occurrence of cracks, warps and constrictions occurring in the early stage of casting was reduced.

Example 2 Using the same molten aluminum alloy as in Example 1, an ingot of 500 × 960 mm was cast using the electromagnetic casting apparatus shown in FIG. A part of the reactor is omitted and modified, but it is essentially the same as the reactor of FIG. The casting conditions are shown in Table 2, but other conditions were the same as in Example 1.

[0019]

[Table 2]

In the obtained ingot, the occurrence of cracks, warps and constrictions occurring in the early stage of casting was reduced.

When the reactor shown in FIG. 3 is not used, the gas is not atomized, and the gas is randomly discharged at the cooling water discharge portion around the mold, resulting in a water drainage phenomenon in each part. Therefore, casting becomes impossible.

[0022]

EFFECTS OF THE INVENTION According to the present invention, since the cooling water in the continuous casting can be finely mixed with the gas so that the cooling at the initial stage of the casting can be slowed down, warpage and constriction at the bottom of the ingot can be reduced, for example, 500 × 980 mm. At some size, the warpage is reduced from 30 mm to 10 mm and the waist is reduced from 20 mm to almost zero.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a DC casting apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an electromagnetic casting apparatus according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a reactor used in the present invention.

FIG. 4 is an explanatory view of a conventional continuous casting device.

FIG. 5 is an explanatory view of a conventional electromagnetic casting apparatus.

FIG. 6 is an explanatory diagram of a defect of an ingot.

FIG. 7 is an explanatory diagram of conventional pulse casting.

FIG. 8 is an explanatory view of a preceding casting method of a type in which carbon dioxide gas is dissolved in cooling water.

FIG. 9 is an explanatory diagram of a prior art air turbo system casting method.

[Explanation of symbols]

 1 Water Cooling Mold 2 Water Channel 3 Bottom 4 Solenoid Valve 5 Pump or Static Mixer 6 Cooling Water Piping 7 Cooling Water Channel 8 Gas Channel 9 Guide Vane 10 Current Cutter 11 Gas Cylinder 12 Primary Pressure Gauge 13 Secondary Pressure Gauge 14 Regulator 15 Flowmeter

Claims (2)

[Claims] 1. A continuous casting method for casting aluminum using a water-cooled mold having an open lower end, in which a refrigerant containing carbon dioxide gas is injected into the mold at the initial stage of casting to slowly cool the ingot, A continuous casting method for aluminum, characterized in that a refrigerant mixed with fine gas bubbles of micron order or less is used. 2. When casting aluminum using a water-cooled mold having an open lower end, a refrigerant containing a gas is injected into the mold at an early stage of casting to continuously cool the ingot in a continuous casting apparatus. Aluminum which is characterized in that a bubble distributor consisting of a guide vane and a current cutter is inserted in the middle of the pipe for injecting the refrigerant into the mold, the gas pipe is joined in front of the guide vane, and a flow control valve is provided in the gas pipe. Continuous casting equipment.