JPH04309441A - Side weir of belt type continuous casting machine - Google Patents

Abstract

PURPOSE:To obtain the shape of a side weir block in the belt type continuous casting machine capable of giving good surface state without any crack in an ingot corner part, and the ingot itself of a satisfactory shape. CONSTITUTION:In the belt type continuous casting machine in which a mold is constituted of a pair of belts which are provided in parallel to each other, and also, rotate in each opposite direction by synchronizing roughly with an ingot, and side weirs of many blocks which are inserted and provided between both side ends of said blets and move by synthronizing with the belts, a shape of the inside surface side of the side weir blocks inserted and provided between the belts is formed in a recessed shape. In such a way, ingot defects such as a failure of an ingot short side shape which occurs at the time of casting by using the belt type continuous casting method, and an edge crack generated in an intersection of a long side and a short side, etc., are prevented, by which the quality of an ingot can be improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the shape of a side weir block in a belt-type continuous casting machine, which makes it possible to obtain slabs with good surface quality and shape without cracks at the corners of the slab. The so-called present invention is a technology belonging to the field of belt-type continuous casting in which thin slabs having a thickness of 100 mm or less are obtained from molten steel by continuous casting.

0002

[Prior Art] Conventionally, as a type of continuous casting, for example,
JP-A-58-107255, JP-A-60-166
No. 145, Japanese Unexamined Patent Publication No. 1-293956, etc., disclose a pair of endless metal belts facing each other with a predetermined interval in a partial region of the running route, and a belt sandwiched between the metal belts. A cross-sectional shape corresponding to a desired slab is formed by a metal belt and a pair of blocks that move in synchronization with the thin slab, and the metal belt and blocks are moved along a predetermined movement path by a guide roll and a guide rail. In addition to guiding and supporting the robot to move circularly along the
A jet nozzle and a cooling pad are arranged on the back side of the metal belt between each guide roll, and the metal belt is cooled by a fluid film formed by jetting cooling fluid on the back side of the metal belt, while the metal belt is injected from above the casting space. Molten steel is injected through a nozzle to generate a solidified shell along the mold wall of the metal belt or block group, and the slab produced by the growth of the solidified shell is pulled out from the casting space from the lower end via a guide roll. A belt-type continuous casting machine called a "belt caster" has been proposed. In this belt-type continuous casting machine, the side weir block uses a metal block, mainly a copper block, with a flat inner surface (contacting surface of the slab).

0003

[Problems to be Solved by the Invention] The purpose of casting steel using such a belt-type continuous casting machine is to obtain a thin slab, but as the slab becomes thinner, the reduction ratio during rolling in the subsequent process becomes smaller. Therefore, good slab shape and surface quality are required. That is, if defects exist in the slab, the defects will not disappear even after rolling, leading to product defects.

[0004] One of such defects is (1) defective shape of the short side of the cast slab, and (2) edge cracking occurring at the intersection of the long side and the short side. These defects are caused by poor slab guidance of the side weir blocks.

[0005] The defective slab guidance of the side weir block, which is the cause of these slab defects, is caused by thermal deformation of the block. Conventionally, a method for preventing this thermal deformation has been to cool the block with water.

However, in order to ensure the strength of the block, when the block shape is increased, water cooling is insufficient, and a large temperature difference occurs between the contact surface of the block with the molten steel/slab and the non-contact surface. A phenomenon occurs in which the block is thermally deformed. The thermal deformation that occurs in this way causes poor slab guidance, which causes defects in the shape of the short sides of the slab and edge cracks that occur at the intersections of the long sides and short sides. Therefore, a method for preventing block deformation other than block water cooling is required.

Therefore, the present invention aims at deforming the side weir of a belt type continuous casting machine, specifically, the side weir block, so as not to substantially cause slab defects that occur during casting in the belt type continuous casting method. The object of the present invention is to establish a side weir that maintains a good shape and improves the shape and surface quality of the slab without causing any problems.

[0008]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides the following side weir for a belt type continuous casting machine. A pair of belts that are arranged parallel to each other and rotate in opposite directions in almost synchronization with the slab, and a number of side blocks that are sandwiched between both ends of the belt and move in synchronization with the belt. A side weir for a belt type continuous casting machine in which a mold is constituted by a weir, characterized in that the inner surface of a side weir block sandwiched between the belts is concave.

Furthermore, a pair of belts are arranged parallel to each other and rotate in opposite directions in substantially synchronization with the slab, and a belt is sandwiched between both ends of the belt and moves in synchronization with the belt. In a belt-type continuous casting machine where a mold is made up of a large number of block side weirs, when the inner surface of the side weir block sandwiched between the belts is made into a concave shape,
A side weir for a belt-type continuous casting machine, characterized in that the concave surface is a circular arc, and the arc length l is as follows when the block length is a: l=a×α×ΔT. Here, α is the linear expansion coefficient of the block material, and ΔT is the difference between the maximum block surface temperature during casting and the initial temperature, which is a value between 200°C and 500°C.

0010

[Operation] As a result of detailed investigation into the causes of the above defects, the present inventors found that the side weirs were not guiding the slabs well due to thermal deformation of the blocks of the side weirs. Based on this fact, in order to prevent slab defects, we investigated various side weir structures and found that by making the inner surface of the side weir block concave, defective slab shapes and edge cracks can be prevented. found.

The principle is as follows. Side weir 2
As shown in FIG. 1, the block 3 enters the molten steel while moving, and then moves to the lower end of the mold in synchronization with the slab 1. During this period, the contact surface of the block 3 with the slab follows a temperature history approximately as shown by the solid line in FIG. Further, the surface of the block 3 opposite to the slab contact surface follows a temperature history as shown by the broken line in FIG. 2, and there is not much temperature change. When a temperature difference occurs between both sides of the block, the block 3 is thermally deformed and deforms into the shape shown in FIG. At this time, the block 3 is deformed into a convex shape on the casting side 4, so the short side of the slab is compressed by the block, and its shape changes. In addition, since the convexly deformed blocks are lined up in the casting direction as shown in FIG. 4, when the slab 1 undergoes heat shrinkage, the shrinkage is restrained, causing edge cracks to occur.

[0012] As described above, defective slab shape and edge cracking are caused by convex deformation caused by the temperature difference between the two surfaces of the block. Therefore, in order to prevent defects, it is necessary that the block surface be flat when a temperature difference occurs, and for this purpose, the shape of the block 3 in the cold state is concave, as shown in Figure 5. It must be processed in advance.

[0013] The shape at this time is inappropriate if the degree of concavity is too strong or too weak. If the deformation is too strong, even after the block is thermally deformed, the surface is not completely deformed to a flat surface, and the block remains concavely deformed, which also causes poor slab shape and edge cracking. If it is weak, the same phenomenon as when the block is left unprocessed will occur, and defects cannot be prevented.

Therefore, in advance processing of the block, it is necessary to make the concave surface into a circular arc and set the arc length l to be l=a×α×ΔT, where the block length is a. Here, α is the linear expansion coefficient of the block material, and ΔT is the maximum temperature on the block surface during casting, which is a value between 200°C and 500°C.

[0015]

[Example] Using various shapes of side weir blocks, continuous casting experiments were conducted under the following casting conditions. (1) Continuous casting conditions ■ Steel type: 0.15% C medium carbon Al-K steel ■ Casting size: 1200 mm x 50 mm ■ Casting speed: 1
0m/min ■Block length a: 100mm ■Block surface arc length: 100mm, 100.3mm
, 100.4mm, 100.7mm, 101.0mm,
101.2mm, 6 types ■Block material: Copper, linear expansion rate 2 x 10-6/℃ (2)
Casting results

[0016]

[Table 1]

[0017]No. 3, 4, and 5 are within the scope of the present invention. No. 1
, 2 and 6 are comparative examples.

[0018]

[Effects of the Invention] As described above, the present invention solves problems such as defects in the shape of short sides of slabs and edge cracks that occur at the intersections of long sides and short sides, which occur when casting using the belt type continuous casting method. By preventing defects in the slab, it has become possible to improve the quality of the slab, which has a great effect on the field of art.

[Brief explanation of drawings]

[Fig. 1] Fig. 1 is a diagram schematically showing a side weir block in a belt-type continuous casting machine;

[Figure 2] Diagram showing the temperature history of the side weir block,

[Figure 3
] Diagram schematically showing the thermal deformation state of the side weir block,

FIG. 4 is a diagram schematically showing a state in which heat shrinkage of a slab is restrained by a block.

FIG. 5 is a diagram showing the shape of the side weir block proposed in the present invention.

[Explanation of symbols]

1 Slab
2 side weir 3 block
4 Slab contact surface 5 Molten steel
6 Hot water level 7 Tensile stress due to contraction

Claims (2)

[Claims] [Claim 1] A pair of belts arranged parallel to each other and rotating in opposite directions in substantially synchronization with the slab, and a belt sandwiched between both end portions of the belt and moving in synchronization with the belt. A belt-type continuous casting machine in which a mold is constructed from a large number of block side weirs, characterized in that the inner surface of the side weir block sandwiched between the belts is concave. side weir. [Claim 2] A pair of belts that are arranged parallel to each other and rotate in opposite directions in substantially synchronization with the slab, and a belt that is sandwiched between both ends of the belt and moves in synchronization with the belt. In a belt-type continuous casting machine where a mold is made up of a large number of block side weirs, when the inner surface of the side weir block sandwiched between the belts is made into a concave shape, the concave surface is made into an arc, and the arc length is A side weir of a belt-type continuous casting machine, characterized in that when the block length is a, l=a×α×ΔT. Here, α is the linear expansion coefficient of the block material, and ΔT is the difference between the maximum block surface temperature during casting and the initial temperature, which is a value between 200°C and 500°C.