KR20000044840A - Method for molding edge of slab in continuous casting process - Google Patents

Abstract

PURPOSE: A method for molding an edge of a slab is provided to illuminate a grain boundary event of forming as a sector on an inner part around an edge of a slab and to prevent the excessive cooling of the edge. CONSTITUTION: An edge part of a slab(10) cast in a continuous casting process is molded in a semi-circular shape. Herein, the thickness of the slab is taken as a diameter. A central part of a side face plate and a supporting roll among a width variable mold of a continuous caster is formed in a semi-circular shape as a precondition for the edge part of slab to be semi-circular.

Description

Edge forming method of slab in continuous casting process

In the present invention, in the continuous casting process, the edge shaping method of the slab, more specifically, the corner portion of the slab produced by the continuous casting machine is molded in a round shape so that the thermal stress, frictional resistance and poor molding due to supercooling can be significantly reduced. It relates to a method of forming the edge of the slab in one continuous casting process.

In general, the slab (1) formed in the continuous casting process is because the edge of the cross section of the width direction is in the longitudinal direction close to the right angle, so that the degree is too high or weak as shown in Figure 1 in the process of solidifying through cooling The grain boundary 3 on bisector is continuous in the perpendicular part of the edge 2, and becomes a weak part in a post process.

The grain boundary (3) phenomenon of the corner (2) region is confirmed in the tissue model of the large ingot (4) of Figure 2, a narrow portion of fine granular grains are formed on the outside of the ingot in the solidified tissue and then At the site a zone of columnar grains is formed.

In addition, coarse granular grains are formed in the center of the ingot, but in actual casting, various structures are known to be mixed. In this case, the main axis direction of the columnar grains coincides with the direction of heat flow when cooled during solidification.

The slab made as described above is heated again in a hot rolling (hot rolling), continuous rolling or heating furnace of a hot rolling mill to perform a predetermined width rolling in a vertical scale breaker.

As shown in FIG. 3, in the hot rolling facility of the hot rolling mill, vertical rolls (V) for width rolling and first rough rolling mill (H) for horizontal rolling are installed adjacent to each other in pairs to perform reversible rolling in three to five stages. It is made of slab of dimension, and vertical roll (H) of the width rolling equipment adopts a conventional carver type (see FIG. 4A) to increase the width rolling efficiency, but passes between slabs through the slab as shown in FIG. In the process, as shown in FIG. 4B, extreme deformation is applied to the edges of both end faces of the slab, and thus, minute cracks are generated along the grain boundaries due to the difference in elongation and grain boundaries generated during casting. There was a problem.

On the other hand, the edge portion of the slab during the rolling is moved to the center of the slab width by the caliber and horizontal rolling characteristics of the vertical roll, which is also well known experimentally.

In addition, the edge portion of the slab that is supercooled during the rolling process is subjected to severe deformation, causing the wear (W) to the collar portion of the vertical roll (V) as shown in Figure 5 to cause a flaw in the edge of the slab well Known.

Looking at the surface of the slab or bar that has been adjusted in width and thickness through the above process, fine cracks remain on both surfaces and severe cracking occurs in such cases. The cracks remain on the surface of the finally obtained strip.

As described above, the damage caused by cracks remaining in the hot strip may show a sawtooth shape having a poor cutting surface when trimming after cold rolling. Particularly, cold rolling is performed using a hot rolled strip made by performing hot rolled rolling (HDR). When the pipe was made without the trimming of this part (linear flaw) due to the occurrence of fine scratches at the edges of the cold rolled steel sheet, the cracks, such as cracks in the weld heat affected zone, Cracking along molding defects has also become a probable problem.

The present invention has been made in view of the problems caused by the cross-sectional shape of the conventional slab as described above, the object is to remove the grain boundary formed by bisector inside the corner of the slab and to prevent the supercooling of the corner during hot rolling It is to provide a method for forming the edge of the slab in the casting process.

The present invention for achieving this object, the edge portion (E) of the slab to be cast in a continuous casting process is formed into a semi-circular shape of the thickness (t) of the slab, the precondition for the edge portion of the slab to be semi-circular. The semi-circular shape of the central part of the side plate and the support roll in the width-variable mold of the continuous casting machine is used to solve the thermal stress caused by supercooling during slab cooling, thereby improving the quality and reducing the frictional resistance. Stabilization can be achieved, and it is possible to simply change and manufacture using the conventional equipment, and to work with less rolling force than the conventional, it is characterized in that the use of the required power can be reduced.

1 is a cross-sectional view of a conventional slab by the continuous continuous casting,

2 is a solidification structure model diagram of a conventional large ingot,

3 is a configuration diagram showing an example of the width rolling equipment of a hot rolling mill,

Figures 4a and 4b is an exemplary view showing the deformation state generated in the edge portion of the slab after rolling and rolled vertical roll of the conventional Carver type,

Figure 5 is a side view showing the wear phenomenon generated in the collar portion of the rolled vertical roll,

6 is a cross-sectional view of a slab of an embodiment of the present invention;

7 and 8 are exemplary diagrams of equipment mounted on the mold of the continuous casting machine of the present invention.

<Description of Symbols for Major Parts of Drawings>

10 strip 20 side plate

30: support roll

Hereinafter, the method of forming the edge of the slab in the continuous casting process of the present invention will be described with reference to the accompanying drawings.

6 is a cross-sectional view of the slab of the embodiment of the present invention. The edge portion E of the slab 10 cast by the usual method in the continuous casting process is formed into a semicircle having a thickness t of the slab as a diameter.

As a precondition for the edge portion of the slab 10 to be semicircular, the side plate 20 of the variable width mold of the continuous casting machine is semicircular, and the central portion of the side support roll 30 is semicircularly formed.

On the other hand, while the edge portion (E) has been described as being semicircular, it is also possible to form a gentle curved surface than the semicircle.

Therefore, the present invention as described above, by removing the edge portion in the same casting conditions as the slab having a conventional corner, the friction in the casting mold is stabilized and stabilization due to the thermal stress of the edge portion that is supercooled compared to other parts Casting speed can be increased.

In addition, the heat flow generated in the slab is formed in the circumferential direction so that no grain boundary is formed along a specific line, and the surface area is reduced compared to the conventional slab having a right angled edge, thereby reducing the scale and crack incidence rate.

Comparative Example

The surface area ratio of the conventional slab and the slab having the same volume having the semicircle edge portion of the present invention at any slab length is shown in Table 1 below.

division existing Invention Comparative surface Volume V = WtL = ⅛πt ² L∴ W = π.t / 8 V = ½ × × L Surface area 2WL + tL = L (2 × πt / 8 + t) = tL (π / 4 + 1) = tL / 4 (π + 4) ½πtL Surface area ratio Invention area / existing area = (½πtL) / = 2π / (π + 4) = 6.2832 / 7.1415 = 0.8798

Comparing the surface area of the conventional slab and the slab of the present invention under the above conditions, it was confirmed that the surface area of about 12% was reduced in the slab of the present invention.

That is, while the cooling efficiency is increased by the reduction of the surface area, frictional resistance, cracking and scale generation are reduced, and damage to the side plate and the support roll of the mold can be prevented, thereby reducing the failure of the equipment.

In addition, if the same width rolling amount than the conventional slab rolling, much smaller rolling force is required to reduce the electric power unit, and it can be estimated that the width rolling amount can be further increased by improving the width adjustment efficiency.

In the continuous casting process of the present invention as described above, the edge forming method of the slab forms an edge portion of the slab into a semicircle or a curved shape close to the slab, thereby improving the quality by relieving thermal stress due to supercooling during the cooling of the slab. There is a tremendous effect on stabilizing the process by reducing the frictional resistance.

In addition, it is possible to simply change and manufacture using conventional facilities, and to reduce the use of power consumption by reducing the frictional force, and to work with less rolling force, and to increase productivity by increasing rolling amount. There is also.

Claims (1)

The edge portion E of the slab 10 to be cast in the continuous casting process is formed into a semicircle having a thickness t of the slab as a diameter, and the edge portion of the slab 10 is a precondition for the semi-circular shape of the continuous casting machine. Edge forming method of the slab in the continuous casting process, characterized in that the center portion of the side plate (20) and the support roll (30) of the variable width mold formed in a semicircle.