JP3115189B2 - Vertical continuous casting of metal - 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 a metal, and more particularly to a metal suitable for continuous casting of a highly reactive and highly oxidizable metal such as an Al-Li alloy. The present invention relates to a vertical continuous casting method.

[0002]

BACKGROUND OF THE INVENTION Ingots of metals, especially aluminum and its alloys, are semi-continuous water-cooled castings (Di-
rect chill casting-DC casting).
DC casting uses a water-cooled mold that is opened up and down, arranges a bottom so as to close the lower part of the mold at the start of casting, introduces molten aluminum into the mold from a tapping nozzle and supplies it to the bottom, While controlling the molten metal level in the mold by the float type float distributor arranged on the molten metal in the mold, the ingot shell is formed by heat removal (primary cooling) from the inner wall of the mold, and the bottom is lowered to solidify This is a casting method in which the cast ingot is drawn out of the mold, and a coolant is further injected into the ingot ejected from the mold (secondary cooling) to completely solidify the entire ingot.

Currently, ingots for rolling, extruding, and forging aluminum and aluminum alloys are mostly manufactured by DC casting, but in continuous casting by DC casting, molten metal introduced into a mold is used. Since the surface of the metal is in contact with the atmosphere, particularly in the case of a metal melt having high reactivity and easily oxidizing, such as an Al-Li alloy, the generation of oxides is remarkable on the surface of the molten metal in the mold, and the metal is generated. Oxide is mixed into the surface of the ingot or the inside of the ingot to deteriorate the quality of the ingot and easily becomes a starting point of the occurrence of cracks in the ingot. Oxide generated may enter the gap between the mold and the ingot, so the cooling of the ingot becomes uneven and the solidification of the molten metal is delayed,
In some cases, molten metal leaks from the bottom of the mold, making it impossible to continue casting.

[0004] In the casting of highly reactive metals such as Al-Li alloys, an inert gas is supplied to the molten metal surface supplied into the mold to protect the molten metal surface and prevent oxidation of the molten metal. However, at present, it is impossible to prevent generation of oxides, deterioration of ingot quality due to mixing and entrainment of the generated oxides, and leakage of molten metal during casting.

[0005]

SUMMARY OF THE INVENTION The present inventors have proposed Al-L
As a result of various studies on the formation mechanism of oxides in the vertical continuous casting of the i-alloy, it was found that a large amount of oxides was formed in the Al-Li alloy when the molten metal was supplied to the bottom at the beginning of casting. After the start, it was confirmed that even if the molten metal surface was kept in an inert atmosphere, it was not possible to prevent the incorporation or entrapment of oxides.

[0006] The present invention has been developed based on the results of the above studies.
-The purpose of the present invention is to solve the above-mentioned conventional problems that occur in continuous casting of highly reactive and highly oxidizable metals such as Li alloys. It is an object of the present invention to provide a vertical continuous casting method for metal which eliminates deterioration of ingot quality due to entrainment and casting failure due to molten metal leakage, and particularly a vertical continuous casting method for metal suitably used for casting Al-Li alloys. .

[0007]

In order to achieve the above object, a vertical continuous casting method for metal according to the present invention is characterized in that a lower part of a mold is closed by a vertically opened mold having a coolant injection part at a lower part. In the vertical continuous casting of metal, the casting is started by supplying a molten metal to the bottom, and the bottom is lowered together with the solidified ingot. After supplying the molten metal to the base, the supply of the molten metal is temporarily stopped and maintained for a predetermined time, and then the molten metal is supplied again to start casting.

According to a second feature of the present invention, in the above method, an enclosure is provided on the upper surface of the mold to block the molten metal supplied into the mold from the atmosphere, and an inert gas flows into the enclosure. To forcibly exhaust air outside the enclosure.

In the vertical continuous casting of metal, as shown in FIG. 1, a lower portion of a mold 1 is closed in a mold 1 having a coolant chamber 4 and a slit 5 serving as a coolant injection portion, which is opened up and down. The casting is started by arranging the base 3 so as to perform the casting and supplying the molten metal 8 to the molten metal receiving portion of the bottom 3 through the molten metal supply nozzle 2. In the process of studying the mechanism of oxide formation in continuous casting, it was determined that the water adsorbed on the mold and the bottom was heated and released by the molten metal 8 supplied to the bottom 3 to oxidize the molten metal.

[0010] Although measures to remove moisture adsorbed on the mold and the base were also studied, it was impossible to completely remove the moisture adsorbed on the mold and the base, and continuous casting was performed according to a conventional method. In such a case, the inconvenience caused by oxide formation cannot be eliminated. The inventors assumed that oxide formation at the start of casting is inevitable, and that casting to prevent oxides generated during the supply of molten metal to the base at the beginning of casting from being mixed into the surface of the ingot or inside the ingot. As a result of studying the method, the present invention has been achieved.

In the present invention, as shown in FIG.
After the molten metal is supplied to the extent that the molten metal does not overflow, the supply of the molten metal is temporarily stopped, and the molten metal is held for a predetermined time according to the size of the base, ie, the size of the ingot to be cast. During this time, the water adsorbed on the inner wall of the mold 1 and the bottom 3 is heated and released by the molten metal to oxidize the molten metal, but the molten metal 8 supplied to the bottom 3 is in contact with the bottom 3 during holding. The solidified layer 9 is formed from the part and solidified, and at this time, the generated oxide is captured. In the continuous casting of the Al-Li alloy, an enclosure 6 is provided on the upper surface of the mold 1 to block the molten metal supplied into the mold from the atmosphere. Since the strong molten metal acts as a reducing agent during solidification, it reacts with oxygen in the atmosphere inside the mold to remove it and also plays a role of improving the atmosphere inside the mold.

After coagulation or not completely coagulated,
After the oxide generated by holding for a predetermined time is captured, FIG.
As shown in (1), when the molten metal 8 is again supplied to the mold 1 through the molten metal supply nozzle 2 and casting is started, the influence of oxides generated in the initial stage of casting is avoided, and the oxygen content in the atmosphere in the enclosure is also reduced. Since the casting is performed while flowing an inert gas into the enclosure and forcibly evacuating to the outside of the enclosure, oxidation of the molten metal surface 10 in the mold hardly occurs, thereby avoiding adverse effects of the oxide. it can. As the casting proceeds, the base 3 descends, and the coolant 4 of the mold is injected from the slit 5 provided at the lower part of the mold to cool the ingot 11 drawn from the mold. In FIGS. 1 to 3, reference numeral 7 denotes a monitoring window in the mold.

[0013]

In the present invention, the molten metal is supplied to the base at the start of continuous casting, and the supply of the molten metal is temporarily stopped and held for a predetermined time. In addition, since the water adsorbed on the mold and the base is trapped by the oxide generated by being heated and released by the molten metal, the influence of the initial oxide is avoided, and furthermore, the oxidizing property is strong. In the case of molten metal, since it acts as a reducing agent during solidification, the atmosphere in the mold also becomes a non-oxidizing atmosphere, and when casting is started by supplying the molten metal again, subsequent oxidation hardly occurs, and Mixing of things,
A sound ingot without entanglement is obtained.

[0014]

Hereinafter, examples of the present invention will be described in comparison with comparative examples. Example 1 AA8090 (AL-2.5wt% Li-1.3wt% Cu-1.0wt% Mg-0.08wt%
Zr), and by the method of the present invention shown in FIGS.
Continuous casting was performed under the conditions shown in Table 1. The amount of surface cutting required to roll the manufactured ingot is 20 mm for test No. 1,
Test No. 2 was 30 mm and was cast according to the invention.
-No oxide was mixed into the surface and inside of the Li alloy ingot, and the amount of surface cutting for rolling was small.

[0015]

[Table 1]

COMPARATIVE EXAMPLE 1 An Al-Li alloy having the same composition as in Example 1 was sunk at the start of casting under the conditions shown in Table 2 using the apparatus shown in FIGS. After the molten metal was supplied to the table, the molten metal supply was temporarily stopped, and continuous casting was performed according to a normal method without holding for a predetermined time.As a result, in Test No. 1, the surface cutting amount required for rolling was increased to 40 mm, No.2 caused leakage of molten metal due to uneven cooling due to oxide entrainment,
Casting could not be continued.

[0017]

[Table 2]

[0018]

As described above, according to the present invention, even if the metal is highly reactive and extremely easily oxidized, for example, an Al-Li alloy, the adverse effect of the oxide can be avoided and the sound quality can be improved. The ingot can be manufactured stably.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a stage of supplying molten metal to a bottom in an early stage of casting according to the present invention.

FIG. 2 is a schematic cross-sectional view showing a stage of solidification of a molten metal supplied to a bottom in an early stage of casting according to the present invention.

FIG. 3 is a schematic sectional view showing a casting stage of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Molten nozzle 3 Base 4 Coolant 5 Slit 6 Enclosure 7 Monitoring window 8 Molten 9 Solidified layer 10 Molten surface 11 Ingot

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-287453 (JP, A) JP-A-58-167057 (JP, A) JP-A-57-160556 (JP, A) JP-A-1- 271037 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B22D 11/106 B22D 11/041 B22D 11/08

Claims (2)

(57) [Claims] 1. A bottom base is disposed in a vertically opened mold having a coolant injection part in a lower part so as to close a lower part of the mold,
Casting is started by supplying a molten metal to the base,
In vertical continuous casting of metal with the bottom lowered together with the solidified ingot, after the molten metal is supplied to the bottom at the start of casting, the supply of the molten metal is stopped once, held for a predetermined time, and then supplied again. A vertical continuous casting method for metal, characterized by starting casting. 2. The method according to claim 1, wherein an enclosure is provided on an upper surface of the mold so that molten metal supplied into the mold is shielded from the atmosphere, and an inert gas flows into the enclosure and is forcibly exhausted to the outside of the enclosure. The vertical continuous casting method for metal according to claim 1.