JPH0824996A - Vertical type continuous casting method for metal billet and apparatus thereof - Google Patents

Abstract

PURPOSE:To avoid the bad influence caused by oxide and to stably cast a sound cast billet. CONSTITUTION:In a vertical type continuous casting for metal billet in which molten metal is supplied into a cylindrical mold open-ended at the upper and the lower parts and the casting is executed while controlling the molten metal level in the mold with a float type molten metal distributing device 6 arranged on the molten metal surface in the mold and the solidified cast billet is drawn out downward from the mold, the supply of the molten metal into the mold from the molten metal distributing device 6 is executed at 15 deg. to <90 deg. angle alphato the radius direction of the cast billet and the molten metal distributing device 6 is rotated. This method does not have any change in the conventional casting work and is suitable to the continuous casting for strong oxidizing metal, particularly, Al-Li alloy billet.

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 and apparatus for a metal billet, and more particularly, to a continuous columnar billet of a metal which is highly reactive and extremely easily oxidized, such as an Al--Li alloy. The present invention relates to a vertical continuous casting method and apparatus for metal billets suitable for casting.

[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 opened up and down, a bottom stand is arranged to close the lower part of the mold at the start of casting, and aluminum molten metal is introduced into the mold from a tap nozzle and supplied onto the bottom stand. While controlling the level of molten metal in the mold by a float type molten metal distributor such as a float distributor arranged above the molten metal in the mold, the ingot shell is formed by heat removal (primary cooling) from the inner wall of the mold, This is a casting method in which the solidified ingot is drawn out from the mold by lowering the table, and the entire ingot is completely solidified by further injecting a cooling agent (secondary cooling) to the ingot drawn out from the mold.

At present, most cylindrical billets used as materials for extruding aluminum and aluminum alloys are manufactured by DC casting, but in continuous casting by the DC casting method, the molten metal introduced into the mold is In the case of a metal melt that has strong reactivity and is easily oxidized because the surface is in contact with the atmosphere, oxides are remarkably generated on the surface of the melt in the mold, and the oxides formed are the surface of the ingot or the inside of the ingot. And the ingot quality is deteriorated, and it easily becomes a starting point of ingot cracking.

In the case of aluminum alloy, Al-Mg
This problem is likely to occur in Al-based alloys, Al-Cu-based alloys, and Al-Zn-Mg-based alloys. In Al-Mg-based alloys, defects due to oxide entrapment, Al-Cu-based alloys, and Al-
Cast cracks often occur in Zn-Mg alloys. In Al-Li alloys, this problem is more remarkable, and the generated oxide may enter the gap between the mold and the ingot, which results in uneven cooling of the ingot and solidification of the molten metal. However, there is a possibility that the casting will be delayed, and the molten metal will leak from the lower part of the mold, making it impossible to continue casting.

In the casting of highly reactive metals such as Al-Li alloys, it is possible to protect the molten metal surface by supplying an inert gas to the molten metal surface supplied to the mold to prevent the molten metal from being oxidized. However, it is practically impossible to completely suppress the oxidation reaction, and especially when the molten metal is supplied to the bottom stand at the beginning of casting, the water adsorbed on the mold and bottom stand is heated by the melt. It is also difficult to avoid the generation of a large amount of oxides due to the release of the oxides. The current situation is that it cannot be prevented.

In vertical continuous casting of metal billets,
The molten metal is supplied to the cylindrical mold opened up and down, and the casting is performed while controlling the molten metal level in the mold by a float type molten metal distributor, a so-called float distributor, which is conventionally arranged. As shown in FIGS. 5 and 6, the float distributor comprises a float unit 7 for floating on the molten metal surface, and a molten metal discharge amount control unit 8 provided with a molten metal supply port 10 for supplying the molten metal into the mold. The molten metal supply port 10 is oriented in the radial direction of the cylindrical mold, that is, in the radial direction of the billet to be cast.

As shown in FIG. 7, the float distributor 6 is floated on the molten metal surface 9 of the molten metal M supplied through the molten metal nozzle 1 into the cylindrical mold 2, and casting is performed while controlling the molten metal level. The coolant is jetted from the coolant chamber 3 of the cylindrical mold 2 through the slits 4 to solidify the molten metal M to form the solidified layer S, and the manufactured metal billet 5 is pulled out from below the cylindrical mold 2.

As a result of detailed investigations and studies on the state of oxide formation and mixing in the continuous casting of Al-Li alloy billets, the inventors have found that the oxide formed on the surface of the molten metal in the mold is gradually increased. It was found that the process of increasing the volume and mixing into the ingot at a certain volume was repeated intermittently. It has also been confirmed that when the oxide is mixed in at a thin stage, it mixes only on the surface of the ingot and does not affect the internal quality, but when the float distributor is used, the oxide is floated. It has been found that billet quality is deteriorated because it is easy to stick to the distributor and the stuck oxide peels off intermittently and mixes into the ingot.

[0009]

SUMMARY OF THE INVENTION The present invention is based on the above-mentioned investigations and examination results, and the above-mentioned conventional problems that occur in continuous casting of metal billets, such as Al-Li alloys, which have strong reactivity and are extremely easily oxidized. In order to solve the problem, it was made as a result of earnest studies on the casting method in which the generated oxide is mixed in a thin stage, and the purpose is to ingot quality due to the inclusion and inclusion of oxide during casting. To provide a vertical continuous casting method and apparatus for metal billets in which casting failure due to deterioration of molten metal and leakage of molten metal is eliminated, and particularly a vertical continuous casting method and apparatus for metal billets suitably used for casting Al-Li alloy billets. It is in.

[0010]

The vertical continuous casting method for a metal billet according to the present invention for achieving the above object comprises:
The molten metal is supplied to a cylindrical mold that has a coolant injection part at the bottom and is opened up and down, and casting is performed while controlling the molten metal level in the mold with a float type molten metal distributor arranged on the molten metal surface in the mold, In vertical continuous casting of a metal billet in which the solidified billet is drawn out from the lower part of the mold, the molten metal is supplied from the molten metal distributor into the mold at an angle of 15 ° or more and less than 90 ° with respect to the radial direction of the cast billet. It is characterized in that the molten metal distributor is caused to rotate on its own axis.

Further, the vertical vertical casting apparatus for metal billets according to the present invention is provided with a cylindrical mold which has a coolant injection part at the bottom and which is opened up and down, and the mold bottom is closed at the start of casting. A bottom stand and a float-type melt distributor disposed on the melt surface in the mold to control the level of the melt in the mold are provided, and casting is started by supplying the metal melt to the bottom stand. In a vertical continuous casting device for metal billets, in which the molten metal is discharged from the distributor to control the molten metal level, and the bottom table is lowered together with the solidified billet,
It is a structural feature that the float type molten metal distributor is provided with a plurality of molten metal supply ports through which the molten metal flows out into the mold at an angle of 15 ° or more and less than 90 ° with respect to the radial direction of the billet to be cast.

In the present invention, as shown in FIG. 7, a molten metal M is supplied through a molten metal nozzle 1 to a cylindrical mold 2 having a cooling medium chamber 3 and a cooling medium spraying portion 4 such as a slit. In vertical continuous casting in which the ingot 5 in which the solidified layer S is formed by the injection of the coolant is drawn to the lower side of the mold, a float type molten metal distributor 6 such as a float distributor is provided on the molten metal surface 9 in the mold 1. And a molten metal supply port 10 provided in the molten metal discharge amount control unit 8 of the float type molten metal distributor 6.
As shown in FIGS. 1 and 2, in the radial direction of the cylindrical mold 2,
That is, it is formed so as to form an angle α with the radial direction of the billet 5 to be cast.

With this structure, the molten metal is supplied from the molten metal supply port 10 of the molten metal distributor 6 into the mold 1 in a radial direction from the center of the ingot, which causes the molten metal distributor 6 to rotate, thereby causing the molten metal to rotate. The distributor 6 is rotated. When the melt distributor rotates during casting, the oxides formed do not stick to the melt distributor, so the oxides formed on the surface of the melt in the mold during casting are thin side surfaces of the ingot. Therefore, the adverse effect of oxide entrapment in the metal billet to be cast can be avoided, since it only moves to and is mixed into the surface of the ingot.

The supply angle α of the molten metal to the radial direction of the billet to be cast is preferably 15 ° or more and less than 90 °,
Effective rotational force works in this angle range. Molten metal supply port 10
In order to ensure stable rotation, it is preferable that the number is two or more, preferably three or more, and it is desirable to arrange them at equal intervals in the circumferential direction. The cross-sectional shape of the molten metal supply port 10 can be various cross-sectional shapes such as square and circular. As the size of the billet to be cast and the casting speed increase, the number of molten metal supply ports should be increased and the opening area of the molten metal supply ports should be increased.

Like the conventional float type molten metal distributor, the float type molten metal distributor according to the present invention has a lower specific gravity than the molten metal and is always floating on the surface of the molten metal, as shown in FIG.
And the molten metal amount control unit 8 located at the lower end of the molten metal nozzle 1, and when the amount of molten metal supplied exceeds the amount of the ingot drawn, the surface of the molten metal in the mold rises.
Further, the amount of hot water discharge control unit 8 also rises to close the lower end of the molten metal nozzle 1, so that the amount of hot water discharge decreases. When the molten metal supply amount becomes smaller than the ingot drawing amount, the molten metal surface in the mold lowers, and accordingly the float 7 and the molten metal amount control unit 8 lower, so that the lower end of the molten metal nozzle 1 opens and the molten metal amount increases. In the actual operation, the molten metal surface 9 is stable at a certain position and hardly moves up and down, and the amount of molten metal and the amount of drawn ingot are balanced.

FIGS. 3 and 4 show another embodiment of the float type molten metal distributor of the present invention, in which the float portion 7 of the molten metal distributor 6 is shown.
Has a polygonal shape. As a result of the experiment, it was confirmed that the molten metal distributor having the polygonal floating portion has a larger effect of preventing oxides from sticking than the molten metal distributor having the circular floating portion as shown in FIGS. 1 and 2. .

[0017]

In the present invention, the molten metal supply direction from the float type molten metal distributor disposed on the molten metal surface for controlling the level of the molten metal supplied into the mold is set in the radial direction of the cylindrical mold, that is, the casting. Since the angle range is set to a certain angle with respect to the radial direction of the billet to be formed, the rotating force acts as the molten metal flows out into the mold, and the molten metal distributor rotates about the molten metal nozzle. Is not adhered and the oxide formed on the surface of the molten metal in the mold is mixed into the surface of the ingot at a thin stage, so that it does not affect the internal quality of the ingot.

[0018]

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) was melted and continuously cast under the conditions shown in Table 1 by the continuous casting apparatus shown in FIG. The surface cutting amount required to extrude the manufactured ingot is 20 mm for test No. 1 and N for test.
Al-L cast according to the present invention having an o.2 of 15 mm
Oxides were not mixed inside the i alloy ingot, and the amount of surface cutting for rolling was small.

[0019]

[Table 1]

Comparative Example 1 An Al--Li alloy having the same composition as in Example 1 was used as in Example 1 using the apparatus shown in FIG. 7 under the conditions shown in Table 2 and the conventional composition shown in FIGS. When continuously cast using the float type molten metal distributor, Test No. 1 shows that the oxide entered the gap between the mold and the ingot and the surface quality deteriorated, so that the cast ingot was rolled. The required surface cutting amount was as large as 45 mm.

[0021]

[Table 2]

[0022]

As described above, according to the present invention, even if a metal having strong reactivity and extremely easy to oxidize, such as an Al-Li alloy, the adverse effect of the oxide is avoided, and the soundness is good. The ingot can be manufactured stably. The equipment structure is simple, no additional equipment is required, and the casting operation is completely the same as usual.

[Brief description of drawings]

FIG. 1 is a bottom view of an embodiment of a float type molten metal distributor used in the present invention.

2 is a cross-sectional view taken along the line AA of the float type molten metal distributor of FIG.

FIG. 3 is a bottom view of another embodiment of the float type molten metal distributor used in the present invention.

4 is a cross-sectional view taken along line BB of the float type molten metal distributor of FIG.

FIG. 5 is a bottom view of a conventional float type molten metal distributor.

6 is a sectional view taken along line CC of the float type molten metal distributor of FIG.

FIG. 7 is a partial cross-sectional view schematically showing a vertical continuous casting device for metal billets.

[Explanation of symbols]

 1 Molten Metal Nozzle 2 Mold 3 Coolant Chamber 4 Slit 5 Ingot 6 Float Type Molten Metal Distributor 7 Float Part 8 Molten Metal Amount Control Section 9 Molten Metal Surface 10 Molten Metal Supply Port M Molten Metal S Solidified Layer

Claims (2)

[Claims] 1. A molten metal is supplied to a cylindrical mold which has a coolant injection part at the bottom and which is opened up and down, and the molten metal level in the mold is controlled by a float type molten metal distributor arranged on the molten metal surface in the mold. In vertical continuous casting of a metal billet in which the solidified billet is pulled out from the lower part of the mold, the molten metal is supplied from the molten metal distributor into the mold by 15 ° or more 90 ° with respect to the radial direction of the billet to be cast. A vertical continuous casting method for a metal billet, characterized in that the molten metal distributor is caused to rotate by being performed at an angle of less than °. 2. A cylindrical mold which has a coolant injection part at the bottom and which is opened up and down, a bottom stand which is arranged to close the lower part of the mold at the start of casting, and to control the level of molten metal in the mold. Equipped with a float type molten metal distributor disposed on the molten metal surface in the mold, the casting is started by supplying the molten metal to the bottom table, and the molten metal is discharged from the floating metal type distributor to control the molten metal level, In a vertical continuous casting device for metal billets, which is designed to lower the base together with the solidified billet,
The float type molten metal distributor is provided with a plurality of molten metal supply ports for allowing the molten metal to flow into the mold at an angle of 15 ° or more and less than 90 ° with respect to the radial direction of the billet to be cast. Mold continuous casting equipment.