JPH06339755A - Method for producing aluminum slab by twin roll continuous casting - Google Patents

Abstract

(57) [Abstract] [Purpose] An aluminum slab with excellent surface properties is manufactured by twin roll type continuous casting. [Composition] A contact limiting plate is disposed so as to be close to the casting roll, the lower end thereof is below the molten metal bath surface, and the upper end is above the molten metal bath surface. The lower end of the contact limiting plate and the casting roll surface are arranged. And are not contacted and are kept at a distance of 2 mm or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing aluminum strip slabs by twin roll type continuous casting.

[0002]

2. Description of the Related Art FIG. 4 is an explanatory view of forming a slab by ordinary twin roll type continuous casting. The molten metal 5 in FIG.
It is poured into a basin 2 formed by two casting rolls 1-1 and 1-2 arranged horizontally and parallel to each other and a side weir 12 which rotate in a direction. The molten metal is cooled by a casting roll to form solidified shells 3-1 and 3-2. Solidification shell 3-1
3-2 grows while moving following the rotation of the casting rolls 1-1 and 1-2, but they are integrated at the kiss point 4 where the gap between the casting rolls 1-1 and 1-2 is minimum, The piece 6 is taken out downward from the kiss point 4.

When the molten aluminum is cast by the twin roll type continuous casting machine shown in FIG. 4, an oxide film is formed on the bath surface 7 of the molten metal. Further, the pouring molten metal flow 5 causes the bath surface 7 of the molten metal to rock. Therefore, in the continuous casting machine shown in FIG. 4 in which the bath surface 7 of the molten metal is in contact with the surface of the casting roll, the swinging oxide film is caught in the solidified shell, and the surface of the slab 6 has wavy surface flaws (ripple mark). ) Is formed.

[0004]

According to the twin roll type continuous casting method, since the aluminum slab having a small thickness can be obtained, the subsequent rolling step can be greatly simplified, but when the ripple mark is generated on the surface, , The surface of aluminum products has uneven luster and the quality is impaired. Further, as will be described later in detail, whiskers-like flaws may occur on the surface of the aluminum slab, but these shaving-like flaws also impair the quality of the slab. An object of the present invention is to provide a method for reducing and preventing the generation of ripple marks and dent defects in the production of aluminum cast pieces by twin roll type continuous casting.

[0005]

FIG. 1 is an explanatory view of the method of the present invention. The present invention relates to a pair of casting rolls 1
-1 and 1-2 are brought close to the respective casting rolls of the twin roll type continuous casting machine, and on the casting roll 1-2 side, the lower end 10 is below the bath surface 7 of the molten metal pool, The contact limiting plate 9 is disposed so that the upper end thereof is above the bath surface 7 of the molten pool and holds the bath surface 7 of the molten pool and the surface of the casting roll in non-contact with each other. Bottom end 10 of the casting roll and the surface of the casting roll 1-2 are not in contact with each other and are 2 m
It is a method for producing an aluminum slab by twin roll type continuous casting, which is characterized in that the casting roll 1-1 side is cast in the same manner while keeping the distance of m or less.

In the present invention, the contact limiting plate 9 is made of a refractory material, for example, a graphite refractory material. Since the refractory has a heat insulating property, the injected molten aluminum 5 is
The solidification is not started on the bath surface 7 of the molten metal, but the solidification is started at a point 11 below the bath surface 7 of the molten metal, which is in contact with the casting roll 1-2. In particular, graphite refractories have poor wettability with molten aluminum, so that molten aluminum is unlikely to adhere.
Therefore, the graphite-based refractory material is preferable as the material for the contact limiting plate.

At the time of pouring the molten metal, an oxide film is formed on the molten metal bath surface 7, and the molten metal bath surface 7 sways, but in the case of FIG. 1, solidification occurs below the molten metal bath surface 7. To start, the oxide film on the molten metal bath surface 7 is not caught on the surface of the slab 6, and even if the molten metal bath surface swings, the solidification start point does not swing. Therefore, the ripple mark on the surface of the slab 6 is reduced.

However, according to the knowledge of the present inventors, when the contact limiting plate is placed in contact with the casting roll in the molten metal, the surface of the aluminum slab tends to have a bald defect having a gloss different from the others. . In addition, many fine surface cracks are observed in the barbed flaws. Therefore, in the present invention, the lower end 1 of the contact limiting plate
0 is kept out of contact with the surface of the casting roll 1-2.

However, when the distance between the lower end 10 of the contact limiting plate and the surface of the casting roll is more than 2 mm, the molten metal pours into the gap between the contact limiting plate and the casting roll and damages the contact limiting plate. Therefore, in the present invention, the gap between the lower end of the contact limiting plate and the casting roll is kept at 2 mm or less.

The reason why the bald defects occur when the contact limiting plate is brought into contact with the casting roll is not always clear, but in this case, the contact limiting plate is scraped off by the casting roll,
It is considered that a heat insulating layer of refractory powder is formed on the surface of the casting roll, and this heat insulating layer hinders smooth growth of the solidified shell. That is, when the contact limiting plate is brought into contact with the casting roll, a thin portion of the solidified shell locally occurs,
It is thought that fine surface cracks are generated in this part during heat shrinkage, resulting in bald spots.

FIG. 2 is an explanatory view of an example of a jig used for keeping the lower end of the contact limiting plate and the surface of the casting roll in a non-contact state with a distance of 2 mm or less. That is, the contact limiting plate 9 is attached to a holder 13 having a rotating roll 12, and the holder 13 is pulled in the direction of arrow 15 via an arm 14 provided on the holder. Prior to the start of casting, the lower end 9 of the contact limiting plate is not in contact with the surface of the casting roll 1-2 and is 2 m
The jigs are set so that the distance is m or less.

During casting, the roller 12 rotates following the rotation of the casting roll 1-2. The roller 12 is a casting roll 1-
The lower end of the contact limiting plate 9 swings following the swing of the roller 12 as the second roll moves and the surface shape of the casting roll 1-2 changes. Therefore, the lower end 10 of the contact limiting plate is not affected by the movement of the casting roll 1-2, the shape of the surface, or the like, and is always kept in non-contact with the casting roll 1-2 and at a distance of 2 mm or less.

[0013]

EXAMPLES The present inventors cast aluminum alloys having the components of JIS H4000 alloy numbers 1100, 3004, and 5282 using the continuous casting apparatus shown in FIG. The casting rolls 1-1 and 1-2 were made of a water-cooled cylinder having a diameter of 400 mm and a cylinder length of 350 mm, and were rotated at a peripheral speed of 40 m / min. The obtained slab has a plate thickness of about 3 mm and a plate width of about 350 m.
It is a strip of m.

During casting, the gap between the lower end 10 of the contact limiting plate and the surface of the casting roll is set to 0.1 mm, 0.5 mm, 1 m.
The effect on the surface properties of the aluminum slab was investigated by changing to m, 2 mm, and 3 mm. FIG. 3 is a diagram showing an example of the result.

When the horizontal axis of FIG. 3 is 0, that is, when the lower end of the contact limiting plate is brought into close contact with the surface of the casting roll, the surface of the cast slab frequently has a lot of bald defects. Further, when the distance between the lower end of the contact limiting plate and the surface of the casting roll is 3 mm, in the case of alloy 1100 and alloy 5282, pouring occurs. When the lower end of the contact limiting plate and the surface of the casting roll were not in contact with each other and the distance was 2 mm or less, the surface of the cast slab was good without ripple marks or bald marks.

[0016]

EFFECTS OF THE INVENTION By carrying out the present invention, it is possible to manufacture an aluminum slab without ripple marks or bald marks.

[Brief description of drawings]

FIG. 1 is an explanatory view of an example of a twin roll type continuous casting method of the present invention.

FIG. 2 is an explanatory view of an example of a method for holding the contact limiting plate used in the present invention.

FIG. 3 is a diagram showing the relationship between the arrangement of the contact limiting plates and the surface piece surface flaw in the example.

FIG. 4 is an explanatory diagram of normal twin roll type continuous casting.

[Explanation of symbols]

1-1, 1-2: Casting roll, 2: Hot water pool, 3-1
3-2: Solidified shell, 4: Kiss point, 5: Molten metal (molten metal flow), 6: Cast slab, 7: Bath surface of molten metal pool, 8: Rotating direction of casting roll, 9: Contact limiting plate, 10: Lower end of contact limiting plate, 11: solidification start point, 12: roller, 1
3: Holder, 14: Arm, 15: Direction of tension applied to the arm.

Continuation of front page (72) Inventor Shiomi Kiyomi 20-1 Shintomi, Futtsu City, Chiba Nippon Steel Co., Ltd. Technology Development Division

Claims (1)

[Claims] 1. A twin roll type continuous casting machine having a pair of casting rolls, which is located close to each casting roll, has a lower end lower than a bath surface of the molten pool and an upper end from a bath surface of the molten pool. Place the contact limiting plate so that it is also above,
Characterized in that the bath surface of the molten pool is held in non-contact with the surface of the casting roll, and the lower end of the contact limiting plate and the surface of the casting roll are kept in non-contact and kept at a distance of 2 mm or less. A method for producing an aluminum slab by twin roll continuous casting.