JPH067893A - Cooling mold for pulling-up continuous casting - Google Patents

Abstract

PURPOSE:To prevent stopping of the continuous casting due to breakout of molten metal solidifying layer by forming an annular projection on the inside surface of a sleeve which is mounted on the inner side of a water-cooled jacket. CONSTITUTION:A cylindrical mold 12 made of copper is surrounded by an annular water-cooled jacket 11 in a cooling mold 1, and the external circumference of the jacket 11 is protected by a refractory layer 14. A circular sleeve 2 is fitted within the water-cooled mold 12, and an annular projection 6 which goes around the inner surface of the lower part of the sleeve 2 is provided. The vertical position of the projection 6 is corresponded to a boundary 15 of a recessed stepped part 10 of the copper mold 12. When the solidified layer is pulled up, the solidified layer 50 of the molten metal which is solidified at the part lower than the projection 6 is broken by a large pulling-up resistance to be exerted by the projection 6, and the lower pulling-up end of the solidified layer 50 of the molten metal is limited to the position of the projection 6. The lower pulling-up end is not moved even when the solidified condition of the molten metal is changed, preventing the break of the continuous casting by the breakout of the solidified layer 50 of the molten metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention immerses the lower part of a cooling mold having a mold hole penetrating up and down into the molten metal to allow the molten metal to penetrate from the lower opening of the mold hole and cool the molten metal from the periphery of the mold hole. ,
The present invention relates to a cooling mold used for pulling continuous casting in which a tube is formed by intermittently pulling up while solidifying.

[0002]

2. Description of the Related Art As shown in FIG. 9, a cooling mold used in a pulling continuous casting apparatus is a material having a high heat conductivity and a high heat resistance in the center of an annular cooling jacket (11). The tubular sleeve (2) formed in (1) is attached, and the outer periphery of the jacket (11) is protected by the refractory layer (14). The inner surface of the sleeve (2) forms a die hole corresponding to the outer diameter of the pipe body (51) to be manufactured.

The cooling mold (1) has its upper part exposed from the molten metal surface, its lower part immersed in the molten metal (5), and the molten metal penetrates through the lower opening of the sleeve (2). The cooling water in the cooling jacket (11) surrounding the sleeve (2) causes the molten metal to flow along the mold cavity.
While solidifying (5) by cooling, the solidified layer is intermittently pulled up by a pulling device (7) such as a pinch roller to continuously cast the tubular body (51).

Below the surface of the molten metal in the cooling mold (1), a portion where the molten metal solidifies and can be pulled up, and a portion which is not sufficiently solidified and cannot withstand pulling are continuous, and the sleeve
The part where the inner surface of (2) intersects becomes the pulling lower end of the molten metal solidification layer.

The height position of the pulling lower end is determined by the temperature condition of the sleeve and the temperature and solidification condition of the molten metal. If these situations change, the pulling lower end position of the molten metal solidification layer moves up and down. Especially in the initial stage of casting, the above-mentioned situation changes greatly and the pulling lower end position tends to move upward, reaching the molten metal surface before reaching a stable state, and there is a problem that so-called breakout occurs in which continuous casting is interrupted. there were. The present invention reveals a cooled mold that can prevent breakout.

[0006]

According to the cooling mold of the present invention, a tubular sleeve (2) made of a material having high heat conductivity and heat resistance is mounted inside an annular water cooling jacket (11), In the cooling casting mold for pulling up continuous casting in which the cooling jacket (11) is protected by the refractory layer (14), the inner surface of the sleeve (2) is wound around to form an annular ridge (6).

[0007]

[Operation and effect] When the solidified layer is pulled up, the molten metal solidified layer (50) which is solidified below the ridge (6) breaks due to the large pulling resistance acting by the ridge (6), and The lower end of pulling up the molten metal solidified layer is limited to the position of the ridge (6).

Even if the temperature condition of the sleeve, the temperature of the molten metal, and the solidified state of the molten metal are changed to some extent, the pulling lower end position does not move,
It is possible to prevent interruption of continuous casting due to breakout of the molten metal solidified layer.

[0009]

EXAMPLE FIG. 1 shows a cooling mold (1) according to the present invention. The cooling mold (1) comprises a copper cylindrical mold (12) surrounded by an annular cooling jacket (11), and a jacket. The periphery of (11) is protected by a refractory layer (14). A water chamber (13) filled with cooling water is formed inside the cooling jacket (11).

On the inner surface of the lower end of the copper mold (12), a concave step (1) is formed over the entire circumference corresponding to the height of the bottom surface of the cooling jacket (11).
0) is formed, and the boundary (15) of the concave step portion (10) serves as a cooling lower end for the sleeve (2) described later.

A cylindrical sleeve (2) having excellent heat conductivity and heat resistance is fitted in the mold (12). The sleeve (2) of the embodiment has an upper portion formed of graphite and a lower portion formed of boron nitride, and has a ring-shaped ridge (6) that goes around the lower inner surface of the sleeve formed of boron nitride. The height position of the ridge (6) corresponds to the boundary (15) of the concave step (10) of the copper mold (12).

The upper surface of the ridge (6) is a horizontal portion (61) orthogonal to the axis of the mold (12), and a peripheral wall (62) is formed vertically from the inner edge of the annular horizontal portion (61). A conical wall (63) is continuous from the lower edge of the peripheral wall (61) to the inner surface of the sleeve. The protruding height H of the ridge (6) is about 5 mm, the width W ₁ of the peripheral wall (62) is about 1 mm, and the width W ₂ from the horizontal part (61) to the lower end of the conical wall (63) is about 15 mm.
Is.

Then, the cooling mold (1) is immersed in the molten metal (5) to a depth such that the molten metal surface reaches above the ridges (6) of the sleeve (2). The molten metal (5) that has penetrated into the sleeve (2) through the lower end opening of the mold (1) contacts the sleeve (2) and is cooled and solidified,
The solidified layer (50) is intermittently pulled up by the pulling device to form the tubular body (51).

During pulling up of the solidified layer, the molten metal solidified layer (50) solidified below the ridges (6) ruptures due to the large pulling resistance exerted by the ridges (6), and therefore the molten metal The pulling lower end of the solidified layer is limited to the position of the ridge (6). Even if the temperature condition of the sleeve, the temperature of the molten metal, and the solidification state of the molten metal change to some extent, the pulling lower end position does not move, and interruption of continuous casting due to breakout of the molten metal solidified layer can be prevented.

The reason why the raised lower end of the molten metal solidification layer (50) is limited to the position of the ridge (6) by the ridge (6) is as follows. The lower end position of the molten metal solidified layer is shown in Fig. 3.
It is limited to the lower end of the peripheral wall (62) of the ridge (6) shown in FIG. This is because the solidified layer receives a large pulling resistance due to the protrusion of the conical wall (63) of the ridge (6).

In one cycle of intermittent pulling, first, when the state of the solidified layer (50) immediately after pulling moves to above the ridge (6) as shown in FIG. 4, the next solidified layer (50a immediately before pulling up The state of () is any one of a to c in FIG.

That is, in FIG. 5a, the lower end position of the solidified layer (50a) is higher than the horizontal portion (61) of the ridge (6). In FIG. 5b, the lower end position of the solidified layer (50a) is in the range from the upper end A to the lower end B of the peripheral wall (62). In Fig. 5c, the lower end position of the solidified layer (50a) is a ridge.
It is lower than (6).

In the case of FIG. 5b, if it is pulled up as it is, the state becomes substantially the same as that of FIG. 4, and there is no problem. In the case of FIG. 5c,
When the solidified layer is pulled up, the molten metal solidified layer (50a) solidified below the ridge (6) ruptures due to a large pulling resistance due to the ridge (6), and as a result, it is the same as FIG. 5b. Therefore, the pulling lower end of the molten metal solidified layer (50) is limited to the position of the ridge (6).

The problem is that, as shown in FIG. 5a, the lower end position of the solidified layer is above the ridge (6). This is due to the upper end A of the peripheral wall (62) of the ridge and the previous solidified layer. During the lower end C, for example, the new solidified layer breaks at the point D in FIG. 6, and the breaking strength of DD ′ is the inertial force of the solidified layer below the point D, the sleeve resistance of the〃, the molten metal resistance of the〃 The rupture strength of the solidified layer at the point is smaller than the sum of the above items.

When the constriction between D-D 'is remarkable, or when D
If the temperature between -D 'is higher than that of the other part, the condition of the fracture of the molten metal solidified layer may be satisfied. However, it is possible to prevent breakage of the molten metal solidified layer as shown in FIG. 5a by optimally setting the heat removal cooling condition from the sleeve.

The shape of the ridges (6) is not limited to the above, and various shapes such as a triangular cross section shown in FIG. 7 and a semicircular cross section as shown in FIG. 8 can be used. However, it is desirable that the following conditions be met.

Since the ridges (6) have a role of breaking the solidified layer of the molten metal, avoid sharp portions so as not to cause cracking or chipping due to frictional resistance with the solidified layer. For example, as shown in FIG. It is desirable that the sharp edge portion (60) at the inner end of the ridge (6) be rounded or rounded.

Further, since the ridge (6) regulates the condition immediately before the formation of a new solidified layer, the molten metal can smoothly flow in and be filled after being pulled up, for example, in FIG. When the distance between the upper end A and the lower end B of the peripheral wall of the ridge (6) is long, the molten metal does not easily wrap around the horizontal portion (61) of the ridge (6) to form an annular space, which results in a casting pipe body. There is a drawback that circumferential groove-shaped wrinkles are formed at substantially equal intervals on the outer circumference of the tubular body in correspondence with the pulling distance for each intermittent pulling.

The position of the ridges (6) is extremely important because the cooling conditions are involved, but the total optimization of the mold construction, such as the heat conduction characteristics of the sleeve and the wall thickness, is a problem, and it is simply Although it is not possible to limit only the position, it is desirable to be near the lower end position in contact with the sleeve-fitting copper mold (12) of the ridge (6) as in the above embodiment. The present invention is not limited to the configurations of the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the claims.

[Brief description of drawings]

FIG. 1 is a sectional view of a cooling mold of the present invention.

FIG. 2 is a sectional view of a lower portion of a sleeve.

FIG. 3 is a sectional view of a sleeve ridge.

FIG. 4 is an explanatory diagram showing a lower end position of a molten metal solidified layer immediately after one cycle of intermittent pulling is finished.

FIG. 5 is an explanatory view showing a state of a solidified layer next to FIG.

FIG. 6 is an explanatory view when the molten metal solidified layer is cut above the ridge.

FIG. 7 is an enlarged view of another embodiment of the sleeve ridge.

FIG. 8 is an enlarged view of another embodiment of the sleeve ridge.

FIG. 9 is a sectional view of a conventional example.

[Explanation of symbols]

 (1) Cooling mold (2) Sleeve (6) Ridge

Claims (1)

[Claims] 1. A tubular sleeve (2) is mounted inside an annular water cooling jacket (11), and the cooling jacket (11) is provided with a refractory layer.
A cooling mold for pulling continuous casting, in which the annular projection (6) is formed around the inner surface of the sleeve (2) in the pulling continuous casting cooling mold protected by (14).