JP3408222B2 - How to start continuous casting - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for easily starting continuous casting without causing leakage of molten metal or the like.

[0002]

2. Description of the Related Art For example, an aluminum ingot is cast by a water-cooled continuous casting method.
As shown in FIG. 3, a bottom block 2 is arranged below the water-cooled mold 1, and an aluminum molten metal 4 (hereinafter abbreviated as molten metal) transferred through a gutter 3 is supplied into the water-cooled mold 1 to After cooling with the water-cooled mold 1 and the bottom block 2 to solidify a predetermined thickness, the bottom block 2 is moved to the hydraulic cylinder 5.
Is gradually lowered to continuously draw out the ingot 6 from the water-cooled mold 1, and the cooling water 7 after cooling the water-cooled mold 1 is directly jetted to the outer peripheral surface of the ingot 6 to be drawn out.

However, the ingot 6 drawn from the water-cooled mold 1
As shown in FIG. 4, when the cooling water 7 is directly injected into the ingot, the solidified shell 8 of the ingot 6 is rapidly solidified and contracted, and the ingot bottom is greatly warped (bat curl), and the space between the bottom block 2 and the bottom block 2 is increased. A gap is generated, and the ingot 6 is not cooled partially.
As a result, the solidified shell 8 is redissolved by the heat of the molten metal 4 inside the ingot, the molten metal leaks out, and cracks may occur from the molten metal leak portion, or in the worst case, steam explosion may occur.

Under these circumstances, a method has been proposed in which cooling water is intermittently injected at the start of casting to weaken the cooling (pulsed water system). However, this method causes uneven cooling and rather cracks. There was a problem that it was likely to occur. Therefore, a method of injecting air or carbon dioxide into cooling water and gradually cooling it has been proposed. Of these, the former (Alc
The an (turbo system) is less effective, so the latter (Alcoa: A729 system) is mainly used.

The reason why the gradual cooling effect is obtained by injecting carbon dioxide gas into the cooling water is that when the cooling water in which the carbon dioxide gas is injected is injected into the ingot, the temperature of the cooling water rises and the carbon dioxide gas is released. This is because this carbon dioxide gas forms a bubble film on the surface of the ingot. As shown in FIG. 5, the gradual cooling effect of the carbon dioxide gas greatly changes up to the solubility limit amount of carbon dioxide gas, and the effect decreases when the solubility limit amount is exceeded. This is because if the solubility limit is exceeded, carbon dioxide will be dispersed in the cooling water as bubbles, and most of these bubbles will diffuse into the atmosphere before being sprayed onto the ingot surface. The carbon dioxide gas is continuously injected while the cooling water 7 is transferred from the water tank 9 to the water-cooled mold 1 by the water pump 10 as shown in FIG. After the injection, the cooling water 7 is stirred by a stirring device (not shown) in order to accelerate the dissolution of carbon dioxide gas.

[0006]

However, in the conventional slow cooling method by injecting carbon dioxide gas, as shown in FIG. 5, a moderate annealing effect C can be stably obtained by injecting a small amount of carbon dioxide gas. , (1) Relatively small (hereinafter abbreviated as small)
When the gradual cooling effect A is to be obtained, there is a problem that the gradual cooling effect greatly changes even if the injection conditions of the carbon dioxide gas (cooling water temperature, injection pressure, stirring conditions, etc.) are slightly changed.
(2) If a relatively large (hereinafter abbreviated as large) slow cooling effect B is to be obtained, a large amount of carbon dioxide gas needs to be injected, which complicates the work. The present invention has been made to solve such a problem,
The purpose thereof is that a small slow cooling effect A (see FIG. 5) can be stably obtained, and a large slow cooling effect B can be stably obtained by injecting a small amount of carbon dioxide gas, so that no hot water leak occurs. It is to provide a method for easily starting continuous casting.
That is, the present invention is the addition of aluminum sulfate p H
Is a method for stably reducing the cooling effect, or adding ethylene glycol or the like to stably increase the slow cooling effect by injecting a small amount of carbon dioxide gas.

[0007]

The invention according to claim 1 is
The ingot during casting start drawn from the water-cooled mold, the carbon dioxide beyond its solubility limit amount in p H 5.0 or less of the cooling water
A continuous casting start method characterized by injecting the injected coolant Te.

According to a second aspect of the present invention, aluminum sulfate is added in an amount of 50 to 50 in the ingot at the start of casting drawn from the water-cooled mold.
It is a continuous casting start method characterized by adding 2000 ppm and further injecting cooling water into which a predetermined amount of carbon dioxide gas has been injected.

According to the third aspect of the invention, at least one of ethylene glycol, propylene glycol or glycerin is added to the ingot at the start of casting which is drawn from the water-cooled mold.
A continuous casting start method is characterized in that the seeds are added in a total amount of 5 to 1000 ppm, and further, a predetermined amount of carbon dioxide gas is injected and cooling water is injected.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 is directed to cooling water.
By defining p H (hydrogen ion concentration) 5.0 below, as shown in FIG. 1, which has reduced the solubility limit of carbon dioxide gas to the cooling water, which small slow cooling effect is obtained Is.

In order to obtain a small gradual cooling effect A with this cooling water, carbon dioxide must be injected in excess of the solubility limit amount. Therefore, even if the carbon dioxide injection amount changes a little, the gradual cooling effect is significantly increased. The ingot does not fluctuate, the ingot is cooled slowly, and the casting can be started without causing the ingot to crack or explode due to the leakage of the molten metal.

In the present invention, the cooling water has a pH of 5.0.
To below, performs the cooling water by the addition of any compound that the p H of aluminum sulfate to 5.0 or less. In the case of aluminum sulphate, it is 5 to adjust pH to 5.0 or less.
It is necessary to add 0 ppm or more. On the other hand, the effect is saturated even if added in a large amount, so the upper limit is 2000 ppm, which is advantageous in terms of cost.

The invention according to claim 3 is ethylene glycol
2, an organic compound of propylene glycol or glycerin is added, carbon dioxide is bonded to the alcohol group of the organic compound to increase the amount of carbon dioxide dissolved in the cooling water, and as shown in FIG. When trying to obtain a large gradual cooling effect B, compared to conventional cooling water (see FIG. 5),
A stable slow cooling effect can be obtained by injecting a small amount of carbon dioxide gas. When the carbon dioxide gas bonded to the alcohol group comes into contact with the ingot, the carbon dioxide gas is easily released to effectively contribute to the slow cooling effect.

[0014] Before disappeared Ji glycol, propylene glycol, also in glycerin is added alone, or two or more may be added in combination, but the amount of the total added, the effect is not sufficiently obtained in less than 5 ppm. On the other hand, even if added in a large amount, the effect is saturated, so the upper limit of 1000 ppm is advantageous in terms of cost.

In the present invention, whether the slow cooling effect is reduced or increased is selected depending on the type of ingot to be cast (alloy composition, ingot size, etc.).

[0016]

EXAMPLES The present invention will be described in detail below with reference to examples. (Example 1) According to the water-cooled continuous casting method shown in FIG.
4 (Al-Mn-based) alloy ingot (section size 500 mm x 1
800 mm) continuous casting start experiment was conducted. A predetermined amount of aluminum sulfate was added to the cooling water in the water storage tank 9, and carbon dioxide gas was continuously injected into the cooling water transferred from the water storage tank 9 to the water-cooled mold 1 and stirred. Carbon dioxide is 500 liters /
Injected the amount. Immediately before the start of casting, cooling water 7 was flown into the water-cooled mold 1 in an amount of 1400 liters / minute. Carbon dioxide is 15
Infused for a minute. Addition amount of aluminum sulfate is 50 to 20
It was changed in the range of 00 ppm. The temperature for supplying the molten Al alloy to the mold was 720 ° C., and the descending speed of the bottom block was 60 mm / min. The p H was determined by a conventional method cooling water emerging from the water-cooled mold immediately after the start of casting (the cooling water to be injected into the ingot) by sampling.

(Comparative Example 1) Whether aluminum sulfate is added to the cooling water in the water tank,
A continuous casting start experiment was conducted in the same manner as in Example 1 except that 30 ppm was added.

Table 1 shows the starting conditions of casting in Example 1 and Comparative Example 1.

[0019]

[Table 1]

As is clear from Table 1, N of the present invention example
o. In Nos. 1 to 4, no molten metal leak occurred, and casting could be started without problems. On the other hand, in Comparative Example No.
5 and 6, for both p H exceeds 5.0, injection volume of carbon dioxide gas becomes less solubility limit amount, cooling fluctuates slow cooling effect is increased with a slight change in the implantation conditions of carbon dioxide not It became stable, and as a result, molten metal leaked, causing ingot cracking in the former and small explosion in the latter.

(Embodiment 2) By the same water-cooled continuous casting method as shown in FIG.
A continuous casting start experiment of an S5083 (Al-Mg based) alloy ingot was conducted. Ethylene glycol in the cooling water in the water tank,
Propylene glycol or glycerin 5-1 respectively
The same method as in Example 1 was used except that 000 ppm was added.

Comparative Example 2 JIS 508 was prepared in the same manner as in Example 2 except that the organic compound containing an alcohol group was not added to the cooling water in the water storage tank.
A continuous casting start experiment of 3 alloys was performed.

(Comparative Example 3) JIS 5083 was carried out in the same manner as in Example 2 except that the organic compound containing an alcohol group was not added to the cooling water in the water tank and carbon dioxide gas was injected at a rate of 8000 l / min.
An experiment for starting continuous casting of the alloy was conducted.

Table 2 shows the starting conditions of casting in Example 2 and Comparative Examples 2 and 3.

[0025]

[Table 2]

As is clear from Table 2, N of the present invention example
o. No. 11 to 16 did not leak molten metal and could start casting without problems. On the other hand, in Comparative Example No. 1
In Nos. 7 and 18, since no organic compound containing an alcohol group was added, the former was not able to obtain the desired large gradual cooling effect, ingot cracks caused by leakage of molten metal occurred, and the latter was liable to have a large gradual cooling effect. It was necessary to inject a large amount of carbon dioxide gas in order to obtain it stably.

[0027]

As described above, according to the present invention,
A small slow cooling effect can be stably obtained, and a large slow cooling effect can be stably obtained by injecting a small amount of carbon dioxide gas. Therefore, continuous casting can be started easily without causing leakage of molten metal, which has a remarkable industrial effect.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a gradual cooling effect showing a first embodiment of cooling water used in the present invention.

FIG. 2 is an explanatory diagram of a gradual cooling effect showing a second embodiment of cooling water used in the present invention.

FIG. 3 is an explanatory diagram of a casting start method in a water-cooled continuous casting method.

FIG. 4 is an explanatory diagram of a molten metal leakage occurrence state at the start of casting in the water-cooled continuous casting method.

FIG. 5 is an explanatory diagram of a gradual cooling effect of cooling water used in a conventional water-cooled continuous casting method.

[Explanation of symbols]

1 Water-cooled mold 2 bottom block 3 gutter 4 molten aluminum 5 hydraulic cylinder 6 ingot 7 cooling water 8 solidified shell 9 water tank 10 water pump

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Claims (3)

(57) [Claims] The ingot during casting start drawn from 1. A water-cooled mold, the dissolved carbon dioxide in the p H of 5.0 or less of the cooling water
A method for initiating continuous casting, which comprises injecting cooling water injected in excess of a limit amount . 2. A continuous casting start method, characterized by adding 50 to 2000 ppm of aluminum sulfate to a ingot at the start of casting drawn out from a water-cooled mold and further injecting cooling water into which a predetermined amount of carbon dioxide gas has been injected. . 3. A total of 5 to 100 of at least one of ethylene glycol, propylene glycol or glycerin is added to the ingot at the start of casting drawn from the water-cooled mold.
A method for starting continuous casting, which comprises adding 0 ppm and injecting a predetermined amount of carbon dioxide gas to inject cooling water.