JP2003010948A - Thin strip casting, and casting method and casting device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the missing of the end part of a casting due to the floating from the peripheral face of a drum caused by the solidification/shrinkage in the strip width on both ends of a shell, the edge-up of the casting, and the cracking of the casting, in casting a thin strip casting by a twin drum type continuously casting device. SOLUTION: In the casting method for the thin strip casting using a pair of cooling drums 1a, 1b, out of the cooling drums 1a, 1b during the casting, the peripheral face of one cooling drum 1a is made to be a recessed crown, and the peripheral face of the other cooling drum 1b is made flat. By making the thickness of a solidification shell S2 generated on the peripheral face of the cooling drum 1b uniform in the lateral direction, the floating from the peripheral face of the drum caused by the solidification/shrinkage on the both ends of the shell is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strip cast cast using a pair of cooling drums and a method and apparatus for casting the strip cast.

[0002]

2. Description of the Related Art A twin-drum type continuous casting apparatus shown in FIG. 5 is known as an apparatus for casting a strip cast using a pair of cooling drums. In this device, a pair of side dams 2 and 2 (only the front side is shown by imaginary lines) are pressed against both end surfaces of a pair of cooling drums 1 and 1 rotating in opposite directions to form a hot water pool portion 3, The molten steel M is supplied to the pool portion 3 through the pouring nozzle 4, and the molten steel M is cooled on the peripheral surfaces of the cooling drums 1 and 1 to generate the solidified shells S and S. The solidified shells S and S are formed at the drum closest contact point kp. Crimping is performed to obtain a strip cast c.

The strip slab is sent to a cold rolling process and rolled to a predetermined size. In order to obtain a good shape in the cold rolling, the cross section of the slab has a slight convex crown. It is preferably shaped. Therefore, as shown in FIG. 6, a concave crown corresponding to the convex crown of the cast slab is attached to the peripheral surface of the cooling drum 1.

[0004]

However, when casting is performed using the cooling drum 1 having a concave crown, the solidified shell S shrinks in the direction of the arrow as it cools, so that both ends of the solidified shell S are A force is exerted in the direction of separating it from the drum peripheral surface. As a result, the solidified shell itself is contracted and deformed so as to be attracted in the width center direction, both ends of the solidified shell S are lifted from the drum peripheral surface, and a gas gap g is generated between the solidified shell S and the drum peripheral surface. The size of the gas gap g is as small as several tens of μm at the most, but the increase in heat transfer resistance due to it is not negligible.

Therefore, the cooling of both ends of the solidified shell S becomes weaker than that of the central part, and as a result, the unsolidified thickness of the end of the slab increases, resulting in a thickening phenomenon of the end plate thickness (hereinafter referred to as edge up). ) Occurs, and both ends of the solidified shell S are insufficiently crimped, and both ends of the slab are weakened, resulting in the lack of ends, and further, the solidification of both ends of the solidified shell S with the central part Since it is delayed compared to the above, cracks are generated at both ends of the slab due to uneven solidification.

[0006] When the edge-up or the edge missing occurs, it becomes difficult or impossible to wind up the slab, surface cracks and wrinkles occur on the slab, and defective shapes occur in cold rolling. However, rolling may not be possible. In order to avoid these problems, a large amount of trimming and surface grinding are required, which causes problems that the process becomes complicated, the production efficiency is lowered, and the yield is reduced.

Therefore, in the present invention, in casting a thin strip cast by a twin-drum type continuous casting device, the edge of the cast is lifted up from the drum peripheral surface at both ends of the shell, and the edge of the cast is raised, the end is missing, and the surface is cracked. The challenge is to prevent it.

[0008]

SUMMARY OF THE INVENTION The present invention is based on the idea that lifting of both ends of the shell from the peripheral surface of the drum occurs in both of the pair of cooling drums. It is configured so that it does not occur on both sides, but only on one side.
It is as follows.

(1) A strip casting cast using a pair of cooling drums, one surface of the strip casting being a convex crown, and the other surface being flat or concave. A thin strip slab characterized by being a crown.

(2) In the method of casting a strip cast using a pair of cooling drums, one of the pair of cooling drums during casting has a concave crown on the peripheral surface and the other cooling drum. The method for casting a strip cast product, wherein the casting is performed using a cooling drum having a flat peripheral surface or a convex crown.

(3) In an apparatus for casting a strip casting using a pair of cooling drums, one of the pair of cooling drums has a peripheral surface of a cooling drum having a concave crown, and the other cooling drum. A strip casting apparatus, comprising a cooling drum having a flat peripheral surface or a convex crown.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a solidification shell S1 during casting in the case where the peripheral surface of one cooling drum 1a is a concave crown and the peripheral surface of the other cooling drum 1b is flat in the casting method and the casting apparatus of the present invention. Indicates S2 state.

When the solidified shell S1 formed on the peripheral surface of the cooling drum 1a having the concave crown is contracted and deformed in the direction of the arrow due to cooling, both ends of the solidified shell S1 are lifted from the peripheral surface of the drum. As a result, a gas gap g is generated between the drum peripheral surface and the drum peripheral surface, which weakens the cooling and reduces the shell thickness. On the other hand, when a contracting force in the arrow direction accompanying cooling is applied to the solidified shell S2 generated on the flat peripheral surface of the cooling drum 1b, both ends of the solidified shell S2 contract in the arrow direction along the drum peripheral surface, In this case, both ends of the solidified shell do not float above the peripheral surface of the drum. as a result,
Since the cooling of the solidified shell S2 is uniform over the entire width of the drum, the thickness is also uniform.

Since the solidified shell S1 having thin ends is pressure-bonded with the solidified shell S2 having a uniform thickness at the drum closest contact point, the solidified shell S1 is firmly bonded as compared to the conventional pressure bonding of thin solidified shells. As a result, it is possible to eliminate the crimping defects at both ends of the shell and prevent the end of the slab from falling off, and because the shell thickness is made uniform in the drum width direction, it is possible to prevent edge up due to uneven shell thickness. Furthermore, since the solidification rate of the shell is made uniform in the width direction, cracking of the slab due to uneven solidification can be prevented. In addition, since the flat cooling drum 1b has a slight concave crown at room temperature during casting, the cooling drum 1b in the casting apparatus of the present invention having a normal temperature has a slight concave crown.

FIG. 2 shows an example in which one surface of the strip casting of the present invention has a convex crown and the other surface has a flat surface.
The cross section in the drum nearest contact of the strip slab C1 cast by the cooling drums 1a and 1b of FIG. 1 is shown. The surface of the concave drum that is in contact with the cooling drum 1a is formed with a convex crown corresponding to the concave crown, while the surface of the flat peripheral surface that is in contact with the cooling drum 1b is flat. The thin strip slab C1 has different shapes on the front surface and the back surface and is not symmetrical, but since the crown amount is the same as the conventional one, a cold-rolled sheet having a good shape can be obtained in cold rolling.

FIG. 3 shows that, in the casting method and casting apparatus of the present invention, the peripheral surface of one cooling drum 1c has a concave crown,
The peripheral surface of the other cooling drum 1d shows the state of the solidified shells S3 and S4 during casting when a convex crown is used. When the solidified shell S3 generated on the peripheral surface of the cooling drum 1c provided with the concave crown is subjected to shrinkage deformation in the direction of the arrow due to cooling, both ends of the solidified shell S3 float up from the peripheral surface of the drum in the same manner as described above. Since the gap g is generated, the cooling becomes weak and the shell thickness becomes thin. On the other hand, the solidified shell S4 produced on the peripheral surface of the cooling drum 1d with the convex crowd
When shrinkage deformation in the arrow direction due to cooling is applied to the solidified shell S4, both ends of the solidified shell S4 shrink in the arrow direction along the drum peripheral surface and thus do not float up from the drum peripheral surface. As a result, the solidified shell S4 is cooled uniformly over the entire width of the drum, and the thickness is also uniformed.

Since the solidified shell S3 having thin ends is crimped to the solidified shell S4 having the uniform thickness at the drum closest contact point, similarly to the above, the solidified shell S3 is firmly crimped as compared with the conventional crimping of the solidified shells having thin ends. To do. As a result, it is possible to eliminate crimping defects at both ends of the shell and prevent the end of the slab from falling off, and because the shell thickness is made uniform in the drum width direction, edge up of the slab due to uneven shell thickness occurs. Can be prevented and, moreover, since the solidification rate of the shell is made uniform,
It is possible to prevent the slab from cracking due to uneven solidification.

FIG. 4 shows an example of the thin strip cast product according to the present invention in which one surface has a convex crown and the other surface has a concave crown. The thin film cast by the cooling drums 1c and 1d shown in FIG. The cross section of the drum closest contact of the strip slab C2 is shown. A convex crown corresponding to the concave crown is formed on the surface contacting the cooling drum 1c provided with the concave crown, while a concave crown is formed on the surface contacting the cooling drum 1d provided with the convex crown. Incidentally, the thin strip cast C2 is not symmetrical because the shape is different between the front surface and the back surface, but similarly to the above, since the crown amount is the same as the conventional one, a cold-rolled sheet having a good shape in cold rolling is obtained. To be

In the casting apparatus of the present invention, if the convex crown of the cooling drum 1d is increased, the concave crown of the cooling drum 1c must be increased accordingly. If the concave crown of the cooling drum 1c is too large, the plate shape of the cold-rolled sheet may be impaired. Therefore, it is preferable that the convex crown of the cooling drum 1d be as close to zero (flat) as possible.

[0020]

EXAMPLES The effects of the present invention will be described below based on examples. The cast molten steel is SUS304 stainless steel. The cooling drum used has a diameter of 1200 mm and a width of 140
It is 0 mm. Table 1 shows the main casting conditions and results such as the drum crown before casting. In addition, in the drum crown black triangles 50 and 80 of Experiment Nos. 2 and 4, in order to make the crown of the cooling drum during casting zero (flat), the crown of the cooling drum before casting was a slight concave crown. It is a thing. As shown in Table 1, when the drum crown was under the conditions of the present invention, neither edge up nor edge loss occurred in the thin strip cast.

[0021]

[Table 1]

[0022]

According to the present invention, of the pair of cooling drums, one of the cooling drums has a flat peripheral surface or a convex crown to solidify the shell formed on the peripheral surface of the cooling drum. Since the thickness can be made uniform in the width direction, the pair of solidified shells can be firmly press-bonded at the drum closest contact point. As a result, since the crimping defects at both ends of the shell are eliminated, it is possible to prevent the exfoliation of the slab due to the defective crimping of the shell, and because the shell thickness is made uniform in the drum width direction, the slab due to the uneven shell thickness It is possible to prevent the edge-up from occurring, and moreover, since the solidification rate of the shell becomes uniform, it is possible to prevent cracking of the slab due to uneven solidification.

[Brief description of drawings]

FIG. 1 is a plan sectional view showing an example of a casting method and apparatus according to the present invention.

FIG. 2 is a cross-sectional view showing an example of a thin strip cast product according to the present invention.

FIG. 3 is a plan sectional view showing another example of the casting method and apparatus according to the present invention.

FIG. 4 is a cross-sectional view showing another example of the thin strip cast piece according to the present invention.

FIG. 5 is a side view of a conventional twin-drum type continuous casting device.

FIG. 6 is a plan sectional view showing a state where both ends of the solidified shell are lifted up from the peripheral surface of the drum.

[Explanation of symbols]

1 ... Cooling drum (conventional) 1a to 1d ... Cooling drum (present invention) 2 ... Side weir 3 ... Hot water pool 4… Pouring nozzle S ... solidification shell S1 to S4 ... Solidification shell c ... Thin strip slab g ... Gas gap between cooling drum and solidification shell kp ... Drum closest contact M ... Molten steel

Claims (3)

[Claims] 1. A ribbon casting product cast by using a pair of cooling drums, wherein one surface of the ribbon casting product is a convex crown and the other surface is flat or concave crown. A thin strip slab characterized by being 2. A method of casting a strip cast using a pair of cooling drums, wherein, of the pair of cooling drums during casting, one cooling drum has a concave crown on the peripheral surface and the other cooling drum has a concave crown. A method for casting a thin strip slab, which comprises casting using a cooling drum having a flat peripheral surface or a convex crown. 3. An apparatus for casting a strip cast using a pair of cooling drums, wherein one of the pair of cooling drums has a peripheral surface having a concave crown, and the other cooling drum. And a cooling drum having a flat crown or a convex crown.