JPH06210413A - Single belt type continuous casting method - Google Patents

Abstract

PURPOSE:To provide a single belt type continuous casting method, by which coating material coated on the metallic belt is protected and the aim of slow cooling in a cast slab is achieved. CONSTITUTION:The coating material 13 is coated on the metallic belt 1 in the single belt type continuous casting apparatus and a gap delta in between this coating material 13 and a rear surface weir 5 is kept to 0.1-0.5mm to execute the casting. By this method, the prescribed gap is kept in between the coating material 13 and the rear surface weir 5 to protect the coating material 13, and by slowly cooling a cast slab, the good quality cast slab without surface crack is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-belt type continuous casting method for preventing peeling of a coating material applied on a metal belt and achieving the purpose of gentle cooling of a slab.

[0002]

2. Description of the Related Art The single-belt continuous casting method is about to be widely used instead of the conventional vertical continuous casting method and twin-roll or twin-belt continuous casting method in which thin steel plates are symmetrical. The feature is that low temperature / semi-solidification injection is possible and injection is easy, and since it is horizontal casting, no undue correction force is applied to the slab during the solidification process, and bulging is eliminated. Good quality slabs can be obtained with minimal intervention of materials and macro segregation.

In the general structure of the single belt type continuous casting apparatus, as shown in FIG. 3, a metal belt 1 is endlessly stretched substantially horizontally between an entrance side pulley 2a and an exit side pulley 2b. The cooling device 3 is installed on the back surface of the casting side of the.

On the metal belt 1, side weirs 4 which run in synchronization with the width of the slab are provided. Further, a rear weir 5 is attached at a predetermined position near the entrance side pulley 2a of the metal belt 1.

The molten metal is poured from a tundish 6 installed near the rear weir 5 into a pool 7 formed by the metal belt 1, the side weir 4 and the rear weir 5. The molten metal in the pool 7 is cooled by the metal belt 1 to form a bottom solidified shell 8 on the metal belt 1 and, at the same time, a side solidified shell is formed by the cooling effect of the side dam 4, and these solidified shells grow. It runs following the running of the metal belt 1,
A cast piece having a constant thickness is taken out from the pool 7.
Further, this slab is subjected to a light reduction or a reduction by a reduction device 9 provided on the downstream side, and a slab 10 having a predetermined thickness is manufactured.

[0006]

In the above casting method, when the molten metal from the tundish 6 is directly poured onto the metal belt 1, the molten metal is rapidly cooled by the cooling device 3 on the back surface of the belt 1 and the inside of the solidified shell 8 is cooled. A large thermal stress occurs in the slab, causing cracks on the surface of the slab.

Further, due to the difference in speed between the metal belt 1 and the solidified shell 8 due to the contraction of the solidified shell, friction is generated between them, which not only causes a flaw on the surface of the slab but also reduces the service life of the metal belt 1. It will be.

As a means for solving such a problem, it has been proposed to coat the surface of the metal belt. As the coating material, for example, alumina (Al ₂ O ₃ ) or zirconia (ZrO ₂ ) powder is applied in a thickness of about 20 to 50 μm. However, since the rear weir 5 is generally in pressure contact with the metal belt, the applied coating material is peeled off by the rear weir, and the effect is not sufficient.

Further, for example, in Japanese Unexamined Patent Publication No. 03-169459, in a single belt type continuous casting machine, a refractory is arranged on a portion facing the pool and a roller is arranged on a portion facing the metal belt. A rear weir has been proposed in which the contact surface pressure of the weir is received by a roller and the heat shock from the molten metal is received by a refractory.

However, in this structure, the rear weir itself and the metal belt are kept in non-contact with each other, but there is no description about the relationship between the coating material and the rear weir, and in the case of horizontal casting, the slab plate thickness is When it becomes large, the static pressure of the molten metal increases, and the rear surface weir cannot be held in a non-contact state, which causes a simmer or a leak of molten metal.

The present invention prevents the coating material applied on the metal belt from being peeled off by appropriately defining the gap between the rear weir and the coating material, and achieves the purpose of slow cooling of the cast slab. Provide a way.

[0012]

According to the present invention, an endless metal belt is stretched in the casting direction between an inlet side pulley and an outlet side pulley, and the belt has an interval corresponding to the width of the slab. The rear weir is fixed by fixing the side weir that runs in synchronization with the metal belt and the metal belt on the outlet pulley side near the inlet pulley, and pouring molten metal into the pool formed by the side weir and the rear weir. In the single-belt continuous casting method to be performed, a coating material is applied onto the metal belt, and casting is performed while maintaining a gap between the coating material and the rear weir to 0.1 to 0.5 mm. It is a belt type continuous casting method.

[0013]

The appropriate gap between the rear weir and the metal belt or coating is slightly different depending on factors such as the type of molten metal, the degree of superheat, the viscosity of the molten metal, the static pressure of the pool and the casting speed. The smaller this gap is, the better, but if it is too small, the rear weir and the coating material come into contact with each other and peel off, damaging the belt surface and further causing cold shut. Also, if this gap becomes too large, it may cause hot water leaks and jugs, which may cause wrinkles.

In FIG. 1, the horizontal axis represents the gap (mm) between the coating material and the rear weir, and the vertical axis represents the metal belt speed (m / min). FIG. 2 is a drawing showing a line of wrinkle generation limit (C), a contact possibility area (D) between the coating material and the rear weir, and a line of 5 m / min (E) which is the lower limit of the belt speed during normal casting.

FIG. 2 is a detailed view showing the relative positions of the metal belt, the rear weir, and the coating material. In FIG. 2, 11 is a coating material coating machine, 12 is a coating material drying machine, and 13 is a coating material coated on a metal belt.

In FIG. 1, the water heater 14 becomes less likely to occur as the belt speed becomes slower and the gap δ becomes smaller, and the cold shut 15 conversely occurs as the belt speed becomes faster and the gap becomes larger. Hard to do. Further, the wrinkle indicates that the turbulence of the molten metal flow becomes large when the gap δ is 0.5 mm or more regardless of the belt speed.

In the present invention, the gap δ between the coating material 13 and the rear weir 5 is set to 0.1 mm or more because
If it is less than mm, the possibility of contact is large considering the coating unevenness of the coating material 13, the deformation of the belt, the mounting accuracy of the rear surface dam 5, and the like, which is not practical. Also, if the lower limit of the belt speed is 5 m / min, the cold shut 15 is less likely to occur if the gap δ is 0.1 mm or more.

The gap δ between the coating material 13 and the rear weir 5 is set to 0.5 mm or less because the larger the gap is, the higher the pouring limit becomes, and when it exceeds 5 mm, the melt flow is disturbed at the triple point. Will become large, and wrinkles will also occur on the back surface of the slab. Therefore, if the gap δ is set to 0.5 mm or less, when the lower limit of the belt speed is set to 5 m / min, it is possible to suppress the generation of the water bottle 14 and prevent the generation of wrinkles.

By thus maintaining the gap between the coating material and the rear weir at 0.1 to 0.5 mm and performing casting, it is possible to prevent the occurrence of jugs, cold shuts and wrinkles, and to prevent the coating material from forming. It is possible to protect the coating material without peeling off and to achieve the purpose of gentle cooling of the slab.

[0020]

EXAMPLES Examples of the present invention will be described below.

Using a single belt type continuous casting apparatus as shown in FIG. 3, the speed of the metal belt: 10 m / min, the clearance setting of the rear weir: 0.2 mm, the cast plate thickness: 20 mm, the material of the rear weir: AG (Alumina graphite) Coating material: Al ₂ O ₃ (Alumina) Coating thickness: 20 μm Molten metal: As a result of continuous casting under the conditions of ordinary steel, no slag, cold shut, or wrinkle is generated Good slabs without cracks on the front and back surfaces were obtained.

[0040]

As described above, according to the continuous casting method of the present invention, casting is performed by maintaining the gap between the coating material applied on the metal belt and the rear weir at 0.1 to 0.5 mm. It can prevent the generation of hot water, cold shut, and wrinkle, and can achieve the purpose of gentle cooling of the slab without the coating material peeling off, improving the service life of the metal belt and The solidified structure of the piece becomes finer, and a good quality slab without surface cracks can be cast.

[Brief description of drawings]

FIG. 1 is a drawing showing a limit of occurrence of molten metal, a limit of occurrence of cold shut, a limit of occurrence of wrinkle, a possibility of contact between a coating material and a rear weir, and a lower limit of belt speed during casting in continuous casting.

FIG. 2 is a detailed view showing the relative positions of the metal belt, the rear weir, and the coating material in the present invention.

FIG. 3 is a schematic side sectional view showing a general structure of a single belt type continuous casting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal belt 2a, 2b Pulley 3 Cooling device 4 Side weir 5 Rear weir 6 Tundish 7 Hot water pool 8 Bottom solidification shell 9 Reduction device 10 Cast slab 11 Coating material applicator 12 Coating material dryer 13 Coated material 14 15 Cold shut δ Gap

Claims (1)

[Claims] 1. An endless metal belt is stretched between the inlet side pulley and the outlet side pulley in the casting direction, and the belt runs in synchronization with the metal belt at intervals corresponding to the width of the slab. In the single-belt continuous casting method in which the side weir and the inlet side pulley are fixed to positions on the outlet side pulley side metal belt, the rear side weir is provided, and the molten metal is injected into the pool formed by the side and rear side weirs , A coating material is applied on the metal belt, and a gap between the coating material and the rear weir is reduced to 0.
A single-belt type continuous casting method, characterized in that casting is carried out while maintaining the thickness at 1 to 0.5 mm.