JPH08243688A - Mold for continuous casting - Google Patents

Abstract

PURPOSE: To uniformize the thickness of solidified shell by forming each side of a mold to a parabola line or linear taper in the casting direction toward the inside of the mold and gradually increasing the average tapered rate from the center part to the corner parts. CONSTITUTION: In the upper end inner surface wall 1 of the mold, Ru is the radius of the corner roundness part, lu is the inside distance between mutually faced two sides and Lu is the diagonal inside distance. Each side is circumscribed to the corner roundness part and formed with the arc having radius Ro on the side center line having the center at the out of the mold. In the inner surface wall 2 at the lower end of the mold, Rb is the radius of the corner roundness part, lb is the inside distance between mutually faced two sides, and Lb is the diagonal inside distance. At the time of using H for the height in the casting direction, the average tapered rate at the center part of the side is Tm=(ln-lb).lb.H. The average tapered rate at the corner part is Tc=(Lu-Lb)/Lb.H. Further, the surface and the inner characteristics of the product can be improved by regulating as Tm<Tc and Rb<Ru.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting mold for continuous casting which makes the thickness of solidified shell during casting of billets and blooms of metal, especially steel billet uniform, and enables improvement of surface and inner surface properties of slab. Regarding

[0002]

2. Description of the Related Art In the continuous casting of billets and blooms, uniform growth of the solidified shell is extremely important for maintaining the shape of the slab and surface and inner surface defects. However, in the initial state of solidification, the air gap between the solidification shell and the mold, which is generated at the corners as the sides contract, is
This causes insufficient cooling at the corners and delays solidification of the shells at the corners. (See Fig. 5)

Therefore, conventionally, the lower part of each side is linearly or stepwise inclined inside the mold (referred to as a straight line or multi-step taper mold) (see FIGS. 6 and 7) and each side of the upper part of the mold. A tube mold (referred to as convex morphed) having a convex shape on the outside of the mold and having an inclination in the casting direction (see FIG. 8) was used.

However, the straight or multi-step taper mold cannot completely eliminate the air gap generated at the corners, and cannot delay the solidification of the corners. Further, in the convex mold, since the central portion of the side is strongly narrowed, the resistance at the time of drawing out the cast piece increases, and the risk of sticking and breakout increases.

[0005]

The object of the present invention is to secure the shape of the mold corner portion along with the solidification shrinkage of the slab as much as possible, and to keep each side of the slab at the bottom of the mold straight. As a result, it is an object of the present invention to provide a continuous casting mold capable of improving the surface and inner surface properties of a billet or bloom and preventing rhombus deformation.

[0006]

[Means for Solving the Problems] It is virtually impossible to actually measure the shrinkage shape of the solidified shell formed in the mold. Therefore, in the present invention, the total heat flow velocity transmitted from the molten steel to the mold by a plurality of thermocouples embedded in the mold is obtained, and from this, the air gap amount at the side center part and the corner part is estimated, and the solidification shrinkage of the slab is further calculated. The shape was measured (see FIGS. 3 and 4).

As shown in FIG. 4, it can be seen that the air gap amount at the corner portion increases as it advances in the casting direction as compared with that at the center portion of the side. Therefore, in the present invention, the corner portion is preliminarily recessed from the side center portion to the outside of the mold, and the average taper toward the lower portion of the mold is gradually increased from the side center portion to the corner portion, thereby solidifying the slab. The shape of the mold follows the profile, and the shape at the lower end of the mold is a straight line on each side.

[0008]

The casting mold of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing a 1/4 model of the mold of the present invention. As shown in the figure, the mold short side wall of the present invention has a linear (may be parabolic) taper toward the inside of the mold, and its average taper amount gradually increases from the central part toward the corner part. There is. Corner R at the top of the mold
The value, Ru, decreases in the casting direction and has Rb in the lower part of the mold.

When casting is performed using a mold having an inner wall as described above, the adhesion between the mold and the solidified shell becomes extremely good, the shell is cooled uniformly, and a solidified shell having a uniform thickness is formed. Further, particularly in the corner portion, as the corner R decreases, a compressive force is applied to the inner surface of the shell, compensating the tensile force generated in the corner portion due to solidification shrinkage on each side, and therefore, the occurrence of corner cracking can be prevented. .

[0010]

Embodiment An embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows a 1/4 cross section of the mold of the present invention, 1 is the inner wall of the upper end of the mold, and 2 is the inner wall of the lower end of the mold. The upper end of the mold has corners R and Ru, and each side is formed by an arc having a radius Ro circumscribing the corners R and Ru and having a center outside the mold and on the center line of the side. Has an inner dimension of lu and a diagonal inner dimension of Lu. The lower end dimension of the mold is a quadrangular cross section having corners R and Rb, and the opposing face-to-face dimension is lb and the diagonal inner dimension is Lb. Here, when the height of the casting mold in the casting direction is H, the average taper Tm at the center of the side is represented by (lu-lb) / lb · H, and the average taper Tc at the corner is (Lu-Lb) / Lb · H.
Represented by H. At this time, 1b = 135 mm, Rb =
5.0 mm, H = 800 mm, the average taper amount at the center of the side is 1.0 (% / m), and the average taper amount at the corner is 2.0 (% / m), lu = 136.1, Ru =
It becomes 6.5 mm and Ro = 2028.5 mm. In the present invention, the taper shape of the inner wall surface of the mold in the casting direction may be parabolic or linear.

Molten steel of medium carbon steel ([C]: 0.3% by weight) was cast using the above-mentioned inventive mold, and a casting test was carried out at a casting speed of 3.0 m / min to 3.5 m / min. As a result, internal cracking, surface cracking, and rhomboidal deformation were remarkably improved as compared with a slab in casting using a normal linear taper mold (average taper amount of the center of the side of 1.0 (% / m)). Was obtained.

[0012]

As described above, by using the mold of the present invention, it is possible to form a solidified shell having a uniform thickness, which results in prevention of rhombus deformation and internal cracks at corners.
It is possible to prevent surface cracks.

[Brief description of drawings]

FIG. 1 shows a solidified shell and air gap growing in a mold.

FIG. 2 shows a 1/4 model view of a linear taper mold.

FIG. 3 shows a 1/4 model diagram of a two-step taper mold.

FIG. 4 shows a 1/4 model view of a convex mold.

FIG. 5 shows the relationship between the heat flow rate between the solidified shell and the mold and the distance from the meniscus.

FIG. 6 shows the relationship between the air gap amount and the distance from the meniscus.

FIG. 7 shows a 1/4 model view of the mold of the present invention.

FIG. 8 shows a quarter sectional view of the mold of the present invention.

[Explanation of symbols]

 1 Mold upper end inner wall 2 Mold lower end inner wall

[Procedure amendment]

[Submission date] April 26, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 shows a 1/4 model view of a mold of the present invention.

FIG. 2 shows a 1/4 cross section of a mold according to the invention.

FIG. 3 shows the relationship between the heat flow rate between the solidified shell and the mold and the distance from the meniscus.

FIG. 4 shows the relationship between the air gap amount and the distance from the meniscus.

FIG. 5 shows a solidified shell and air gap growing in a mold.

FIG. 6 shows a quarter model view of a linear taper mold.

FIG. 7 shows a 1/4 model diagram of a two-step taper mold.

FIG. 8 shows a 1/4 model view of a convex mold.

[Explanation of reference numerals] 1 inner wall of the mold upper end 2 inner wall of the mold lower end

Claims (2)

[Claims] 1. A continuous casting mold for billets and blooms, wherein each side of the mold has a parabolic or linear taper in the casting direction with each side facing the inside of the mold, and the average taper amount is from the center of the side. A continuous casting mold characterized by gradually increasing toward the corners. 2. The continuous casting mold according to claim 1, wherein a corner R of the mold is larger in the upper part of the mold than in the lower part of the mold.