JP3197806B2 - Vertical continuous casting method of aluminum - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical continuous casting method for aluminum (including an aluminum alloy; the same applies hereinafter), and more particularly to a vertical continuous casting method for aluminum suitable for continuous casting of an aluminum alloy containing lithium.

[0002]

2. Description of the Related Art Aluminum ingots used for rolling, extrusion or forging are generally manufactured by a vertical continuous casting method called DC casting. In this method, as shown in FIG. 1, a molten metal M is supplied by a nozzle 2 from above a cylindrical water-cooled mold 1 having a vertically open cross section having a circular or rectangular shape, and a solidified ingot C is cast into a mold. 1 from below,
Immediately below the mold 1, the surface of the ingot C is directly cooled by the cooling water 3 flowing out of the mold 1. Numeral 5 denotes a base and B denotes a solid-liquid interface.

[0003] Reference numeral 4 denotes a cooling water flow flowing down on the surface of the ingot C. The cooling water flowing down accumulates in the casting pit 7, and the accumulated cooling water 8 is circulated by a pump and used again as mold cooling water. However, since the cooling water is always maintained at a certain depth in the pit 7, the ingot C is dropped by the casting table 6 into the pit 7 where the cooling water is stored. become.

The above-mentioned DC casting method has been established as a method for efficiently producing aluminum ingots and billets, and has been used for many years. However, so-called molten metal leakage or breakout in which molten metal leaks from a lower part of a mold is known. When this occurs, it has been experienced that an explosion is caused by rapid evaporation of water due to contact between the high-temperature molten metal and the low-temperature cooling water. In particular, in a lithium-containing aluminum alloy, there is a danger of a severe explosion causing serious damage due to a chemical reaction between the molten aluminum and water.

[0005] Regarding steam explosion of molten aluminum, there is a study by G. Long of Alcoa of the United States (M.
ETAL PROGRESS, May 1957, pp. 107-112) Based on this study, basic operating standards for explosion prevention have been developed. According to this, it is considered that explosion can be prevented even if a molten metal leaks by storing cooling water at a depth of 3 feet or more in the casting pit.

[0006] However, by maintaining the water depth in the pit at 3 feet or more, it is possible to prevent steam explosion. However, as in the case of molten aluminum alloy containing an active metal such as lithium, it is difficult to prevent the explosion. It has been found that it is difficult to prevent an explosion when a chemical reaction occurs with cooling water.

Attention has been paid to the excellent properties of Al-Li alloys containing lithium, and with increasing interest in practical use thereof, DC of lithium-containing aluminum alloys has been increasing.
Various studies have been conducted on measures for safely performing casting. For example, a method using an organic coolant such as ethylene glycol, which hardly causes a chemical reaction with a molten aluminum alloy, as a coolant (Japanese Patent Publication No. 4-69019) Publication), a method of performing casting by continuously removing cooling water from the casting pit so that water pools do not accumulate in the pit (
No. 6-75748).

According to the former method, the danger of explosion is avoided and the method is effective for enhancing safety. However, since an organic coolant such as ethylene glycol has a different cooling characteristic from water, the casting condition is basically limited. Need to be changed
The organic coolant may burn and cause a fire. In the latter method, the control for preventing the accumulation of the cooling water in the pit is not easy, and there is a risk that a serious accident may occur if any failure occurs in the control device.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to overcome the difficulties of the above-mentioned method proposed for safely performing DC casting of aluminum, particularly an aluminum alloy containing highly reactive lithium. And
The aim is to eliminate the steam explosion when DC casting aluminum without fundamentally changing the operating conditions of the conventional method using water as a coolant and without complicated control of the casting method. Explosion can be prevented even when a chemical reaction occurs between the molten metal and the coolant.
An object of the present invention is to provide a vertical continuous casting method of aluminum effective for C casting.

[0010]

SUMMARY OF THE INVENTION To achieve the above object, a vertical continuous casting method of aluminum according to the present invention comprises:
The molten metal is supplied to a cylindrical mold that is opened up and down, the solidified ingot is drawn out below the mold, and a coolant is sprayed on the surface of the ingot just below the mold to cool the ingot, and pits in which the coolant is accumulated. A first feature of the method for continuously casting aluminum by being lowered into the inside is that a water-oil emulsion is used as a cooling agent.

[0011] Further, the water-oil emulsion has a volume ratio of
Secondly, the fact that the mixture was formed by mixing water at a ratio of 95 to 50% with respect to 5 to 50% of the oil, that the oil was composed of a water-soluble cutting fluid, and that the aluminum was an aluminum alloy containing lithium. This is a third and fourth feature.

The conditions necessary for the properties of the coolant so as not to cause an explosion when it comes into contact with the molten aluminum are as follows. Difficult to evaporate so that an explosion does not occur due to evaporation of the coolant. That is, high boiling point and low vapor pressure. In addition, a vapor film that is stable and inhibits heat transfer is formed even when it evaporates in contact with the molten aluminum.

It is difficult to react with molten aluminum so that explosion due to chemical reaction does not occur. That is, the free energy change due to the chemical reaction between the coolant and the molten aluminum is small, and it is chemically stable. Even if a slight reaction occurs, the reaction rate is sufficiently reduced by forming a reaction product at the reaction interface that can prevent the subsequent reaction from occurring. Or, even if a considerable reaction occurs, the release of energy is small and does not lead to an explosion.

[0014] Preferably, the characteristics of the cooling agent for DC casting are not significantly different from those of conventionally used water. That is, the cooling capacity is almost the same as that of water, the viscosity is low and the change with time is small like water. There should be no problems other than explosions, such as fire, and no harm to the human body. Inexpensive and do not affect industrial production costs.

The conventional cooling water does not satisfy the above-mentioned basic conditions, and the organic coolant such as ethylene glycol has a problem because it has a risk of fire. ~
A low-viscosity oil is one that satisfies the above condition. Low-viscosity oils, like ethylene glycol, may cause a fire, but are more cost effective.

From the above viewpoints, the inventors have conducted extensive experiments and studies in order to find conditions for applying a low-viscosity oil as a cooling agent in continuous casting of aluminum. It has been used. Oils in water-oil emulsions include base oils,
It comprises an emulsifier, an extreme pressure additive and an oil agent, and the base oil is preferably a mineral oil.

The emulsifier is preferably an ether type nonionic surfactant such as polyoxyethylene alkyl ether or polyoxyethylene alkylphenyl ether, or an ester type nonionic surfactant such as polyhydric alcohol fatty acid ester. Used is a chlorine-sulfur compound.

As the oily agent, animal and vegetable oils obtained by purifying animal or vegetable oils and fats, ester oils comprising compounds of higher fatty acids such as stearic acid and oleic acid and alcohols, and the like are preferably used. As the oil agent of the water-oil emulsion that can be used in the present invention, a water-soluble cutting oil agent (JIS
K2241) can be applied as a preferred oil agent. Among them, water-soluble cutting oil W2 is most preferable, and these oils are mixed with a predetermined amount of water and used as a water-oil emulsion.

The preferred mixing ratio of oil to water in the water-oil emulsion is 5 to 50% oil and 95 to 50% water by volume.
Range. If the oil content is less than 5%, steam explosion tends to occur, and if the oil content exceeds 50%, the risk of ignition and combustion increases. It is more preferable to mix 10 to 50% of oil and 90 to 50% of water. By mixing water and oil emulsified in water at the above ratio to form an emulsion, the oil content satisfies the above conditions and the water satisfies the above conditions. An explosion due to explosion and chemical reaction is avoided, there is no danger of ignition, and a coolant for continuous casting of aluminum having excellent cooling ability that is the same as water as a coolant is obtained.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a preferred embodiment of the present invention, when performing vertical continuous casting of aluminum in an apparatus configuration as schematically shown in FIG. Supply oil emulsion. The water-oil emulsion supplied into the water-cooled mold flows out from under the mold, is solidified and is sprayed on the surface of the ingot drawn out from under the mold to directly cool the ingot.

The water-oil emulsion sprayed on the surface of the ingot flows down on the surface of the ingot, accumulates at the bottom of the pit, is pumped up by a circulation pump, and is supplied to the mold again.
The greater the depth of the water-oil emulsion that accumulates in the pit, the greater the potential for steam explosions and explosions due to chemical reactions if the aluminum melt leaks,
Preferably, it is 10 mm or less, and more preferably, it is completely discharged from the pit.

[0022]

【Example】

Example 1 Soluble type water-soluble cutting oil “Band saw machine heavy cutting type HD” manufactured by Amada Co., Ltd.
IS K2241-1986 Water-soluble cutting oil W2 class 2
No.), a water-oil emulsion diluted with tap water so as to have a mixing ratio of oil shown in Table 1 was placed in a mild steel container having an inner diameter of 155 mm and a height of 200 mm, and 15 mm from the bottom of the container.
5 kg of a 2.5 wt% Li-containing aluminum alloy melt heated to 750 ° C. from 00 mm above was dropped 10 times into a container, and the state of explosion was investigated. Table 1 shows the results. In this experiment, the container made of mild steel was regarded as a casting pit, but the ratio of the supply amount of molten metal to the capacity of the container was much larger than in the case of an actual oil leak. This is a condition that easily occurs.

As shown in Table 1, according to the coolant according to the present invention, when the oil content is 10 to 50% by volume, the depth of the coolant accumulated in the pits No explosion occurred regardless of the explosion. When the oil content was 5%, steam explosion occurred when the depth of the coolant accumulated in the pit was large, but no explosion was observed when the depth of the coolant was 10 mm or less. No ignition or burning was observed in any case.

[0024]

[Table 1]

Comparative Example 1 Using the same oil agent as in Example 1, a water-oil emulsion having an oil mixing ratio shown in Table 2 was placed in a container having the same dimensions as those used in Example 1, and Using the same molten aluminum alloy, the explosion condition was observed under the same conditions as in Example 1. Table 2 shows the results.

[0026]

[Table 2]

Example 2 As an oil agent, a soluble type water-soluble cutting oil manufactured by Amada Co., Ltd. "General-purpose type R for light cutting of band saw machine"
(JIS K2241-1986 water-soluble cutting fluid W2 class No. 1) and double with tap water (cutting fluid mixing ratio 50
%) To 20 times (a cutting oil mixture ratio of 5%) was diluted to prepare a water-oil emulsion, and the water-oil emulsion was placed in a container having the same dimensions as those used in Example 1, and the same as in Example 1. 15 drops and explosion tests were conducted under the same conditions as in Example 1 (however, the depth of the coolant in the pit was 10 mm) using a molten metal of a lithium-containing aluminum alloy of Example 1, and no explosion occurred. There was no ignition and no combustion of the coolant.

Example 3 As a fluid, a soluble type water-soluble cutting fluid "Band saw machine light cutting type RS" manufactured by Amada Co., Ltd.
(JIS K2241-1986 water-soluble cutting fluid W2 type 1 No. 1) with tap water 10 times (cutting fluid mixing ratio 10
%) And a water-oil emulsion diluted 5 times (mixing ratio of cutting oil: 20%) was prepared, and this water-oil emulsion was placed in a container having the same dimensions as those used in Example 1, and C
Using an aluminum alloy melt containing u: 2.7 wt% and Li: 2.4 wt%, 10 drops under the same conditions as in Example 1 (the depth of the coolant in the pit is 100 mm). As a result of an explosion test, no explosion occurred and neither ignition nor combustion of the coolant occurred.

[0029]

As described above, according to the present invention, during the DC casting operation of aluminum, the molten metal leaks, and even when the leaked high-temperature molten metal comes into contact with the coolant, the explosion can be avoided. The present invention provides a vertical continuous casting method for an aluminum alloy containing:

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing vertical continuous casting of aluminum.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Molten metal supply nozzle 3 Coolant 4 Coolant flowing down 5 Bottom base 6 Casting table 7 Casting pit 8 Coolant accumulated in pit M Molten metal C Ingot B Solid-liquid interface

Continuation of front page (56) References JP-A-9-122862 (JP, A) JP-A-3-106538 (JP, A) JP-A-60-127059 (JP, A) JP-A 8-141706 (JP) JP-A-63-286547 (JP, A) JP-A-54-128436 (JP, A) JP-A-60-180656 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) B22D 11/124 B22D 11/00 B22D 11/049

Claims (4)

(57) [Claims] 1. A molten metal is supplied to a cylindrical mold which is opened up and down, a solidified ingot is drawn out below the mold, and a coolant is sprayed on a surface of the ingot just below the mold to cool the ingot. A vertical continuous casting method of aluminum, wherein a water-oil emulsion is used as a cooling agent, in a method of continuously casting aluminum by lowering it into a pit in which an agent is accumulated. 2. A water-oil emulsion, wherein the volume ratio of oil 5
The vertical continuous casting method for aluminum according to claim 1, wherein water is mixed at a ratio of 95 to 50% with respect to 50 to 50%. 3. The method according to claim 2, wherein the oil comprises a water-soluble cutting oil. 4. The continuous casting method for aluminum according to claim 1, wherein the aluminum is an aluminum alloy containing lithium.