JPH0810904A - Drawing-up continuous casting method - Google Patents

Abstract

PURPOSE:To promote the supply of molten metal into a sleeve in the starting step of casting and to prevent the discontinuity of continuous casting caused by the breakout of a solidified layer in the molten metal. CONSTITUTION:In the drawing-up continuous casting method, a cooling mold 1 for drawing-up continuous casting, in which a cylindrical sleeve 2 is fitted in the inside of an annular cooling jacket 11 and an annular brake ring 3 is arranged at the lower end of the sleeve 2, is dipped into the molten metal. Then, the molten metal on the mold hole 21 formed in the inner part of the sleeve 2 is solidified by being cooled with the cooling jacket 11, and a pipe body 51 is cast by drawing up the solidified layer with a drawing-up device 6. At the time of dipping the mold 1 into the molten metal in the starting step of the casting, the drawing-up of the pipe body 51 is started with the drawing-up device 6 before reaching a prescribed dipping depth, and at the same time, the mold 1 is gradually descended till reaching a prescribed dipping depth.

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 a molten metal and solidifies the molten metal that has penetrated from the lower opening of the mold hole by cooling around the mold cavity. The present invention relates to a continuous pull-up casting method in which a seamless tubular body of infinite length is formed by intermittently pulling up.

[0002]

2. Description of the Related Art As shown in FIG.
In (1), a cylindrical mold (12) is mounted inside an annular cooling jacket (11) protected by a refractory layer (14), and the inner surface of the mold (12) has a high thermal conductivity, Fit a cylindrical sleeve (2) made of a material with excellent heat resistance,
An annular break ring (3) is provided at the lower end of (2).
The lower end portion of the sleeve (2) is thinned in order to form a gradient in the cooling ability of the sleeve (2) cooled by the mold (12) and to form an inclined solidified shell, thereby reducing the thickness of the mold (12).
I try not to contact with. The pull-up continuous casting mold (1) having the above-mentioned structure is suspended and supported by a suspension table (74),
The suspension base (74) engages with the lifting device (7) provided on the frame (71) and moves up and down while supporting the mold (1). In the lifting device (7), a plurality of rotary screw shafts (73) are vertically arranged side by side, the upper and lower ends are supported by the frame (71), and the control motor (72) provided on the upper part of the frame (71) is installed. It is connected to the upper part of the rotary screw shaft (73). By the controlled rotation of the control motor (72), the screw shaft (73) controls the height of the mold (1) while supporting the mold (1). Also, the lifting / lowering platform (74) and frame of the lifting / lowering device (7)
In the center of (71), there is a through hole (76) through which the pulled pipe passes.
(75) are opened respectively, and a pipe pulling device (6) is provided around the hole (75) of the frame (71).

Cooling water is circulated by the cooling water inflow port (15) and outflow port (16) provided in the cooling jacket (11) of the continuous drawing mold to cool the sleeve (2). At the start of casting, in the holes (75) (76) of the frame (71) and the lifting platform (74),
Insert the starting rod (61) and insert the lower end of the starting rod (61) into the mold hole (21) of the sleeve (2) of the mold (1).
, And insert the upper end into the pulling device (6).

A conventional pipe casting method which is performed by using the above continuous casting apparatus will be described below. A mold (1) which is hung and supported by a lifting / lowering platform (74) by rotating a control motor (72).
By lowering the mold (1), the upper part of the mold (1) is exposed from the surface of the molten metal, while the lower part is immersed at a predetermined immersion depth in the molten metal (5) and the molten metal ( Insert 5) into sleeve (2). Starting Rod (61)
After the shaft (62) protruding at the tip of the mold is immersed in the molten metal (5) and the mold (1) is lowered to a predetermined immersion depth, the mold is left stationary for a certain period of time to form on the inner surface of the sleeve (2). Molded cavity (2
The molten metal (5) that has penetrated into 1) is cooled by the cooling jacket (11) and its surface layer is solidified, and adheres and solidifies on the shaft body (62). At this point, the starting rod (61) is pulled up by the pulling device (6). After pulling up the solidified layer to a certain height, the pulling up is interrupted and the molten metal is placed in the mold cavity (21).
It waits for (5) to re-enter and the molten metal (5) to be cooled along the mold cavity (21) to form a solidified shell (54). When the solidified shell (54) is formed again, the solidified shell (54) is pulled up by the pulling device (6). When the surface of the molten metal (5) falls further below the specified range, the molten metal (5) is added or the mold (1) is lowered to keep the molten metal surface level constant and the pipe body (51) is continuously cast. To do.

[0005]

However, before the start of casting, the cooling effect of the cooling jacket (11) is transmitted from the mold (12) to the sleeve (2) and further to the break ring (3). The sleeve (2) has an excessive cooling capacity. The cooling capacity is much higher than the cooling capacity of the sleeve (2) when the equilibrium state is reached due to heating by the molten metal (5) and cooling by the cooling jacket (11) after a sufficient time has passed from the start of casting. Is a big one. The sleeve (2) that retains this excessive cooling capacity is
If it is lowered to a predetermined immersion depth without stopping,
As shown in FIG. 7, a thick initial solidified shell (54) is formed on the inner surface of the sleeve (2). Thick initial solidified shell (54) sleeve
If it is formed in the mold cavity (21) on the inner surface of (2), the supply of the molten metal (5) to the sleeve (2) is significantly hindered, so at the start of casting, a part of the molten metal solidified layer is thick. A thin portion or a discontinuous portion is formed, which causes a so-called breakout in which the pipe body (51) breaks when the pipe body (51) is pulled up.

[0006]

In order to solve the above-mentioned problems, in the pulling continuous casting method of the present invention, when the mold (1) is immersed in the molten metal (5) at the casting start stage, Before reaching the immersion depth of, the shaft of the tip of the starting rod (61) fitted in the mold hole (21) of the sleeve (2) at a shallow position (initial immersion depth) in the molten metal (5). The body (62) is immersed in the surface layer of the molten metal (5), and the mold cavity (2) formed inside the sleeve (2) is
After the surface layer of the molten metal (5) that has penetrated into 1) is solidified, the pulling device (6) starts pulling up the starting rod (61). Simultaneously with pulling up the starting rod (61), the mold (1) is lowered. Since the molten metal re-enters the die hole (21) of the sleeve (2), the molten metal (5) is cooled and the solidified shell (52) is formed, and then the starting rod is again formed.
Pull up at (61). This is repeated until the mold (1) reaches a predetermined immersion depth, and the mold (1) is gradually lowered,
At the same time, the pulling is continued intermittently.

After lowering the mold (1) to a predetermined immersion depth, the same pulling operation and adjustment of the molten metal surface as in the conventional case are performed.

[0008]

[Operation and effect] The mold (1) is lowered to the initial immersion depth, at the same time, the pulling is intermittently continued, and gradually lowered to the predetermined immersion depth, whereby the molten metal (5) enters the sleeve (2). Can be promoted. Sleeve (2)
Since the penetration of the molten metal (5) into the sleeve is promoted, the sleeve
The cooling capacity held by (2) reaches an equilibrium state by the heating by the molten metal (5) and the cooling by the cooling jacket (11) after a sufficient time has passed after the start of casting, and the initial solidified shell (52) is cooled. Since formation is reduced, interruption of continuous casting due to breakout of the molten metal solidified layer at the start of casting can be prevented.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. As shown in Fig. 1, pulling continuous casting mold (1)
Insert the copper cylindrical mold (12) into the annular cooling jacket (1
1) and surround the outer circumference of the cooling jacket (11) with a refractory layer (1
It is protected by 4). Inside the cooling jacket (11), a water chamber (13) having a cooling water inflow port (15) and a cooling water outflow port (16) and filled with circulating cooling water is formed.

A cylindrical sleeve (2) is fitted on the inner surface of the copper mold (12) in the hole direction. Also, tubular sleeve (2)
Is made of a material such as boron nitride, which has excellent thermal conductivity and heat resistance and has poor wettability with molten metal, graphite, etc., and the lower end of the tubular sleeve (2) is similar to the sleeve (2). An annular break ring (3) made of material is provided. In addition, the lower end portion of the sleeve (2) is thinned in order to form a gradient in the cooling ability of the sleeve (2) cooled from the mold (12) and to incline the formation of the solidified shell. It is designed to be in non-contact with 12).

The pulling continuous casting mold (1) having the above-mentioned structure is installed in the lifting device (7). The lifting device (7) has a mold at the center of a lifting platform (74) that moves up and down by the rotation of a rotary screw shaft (73) controlled by a control motor (72) fixed to the upper part of the frame (71). (1) is suspended, and the control motor is
The vertical movement of the mold (1) is controlled by rotating the (72). Further, holes (76) (75) for passing the pulled pipes are formed in the center of the lifting / lowering platform (74) and the frame (71) of the lifting device (7), and the frame (71 ) Hole (75)
The peripheral portion is provided with a pulling device (6) such as a pinch roller for pulling up the pipe body.

Cooling jacket (11) for pulling continuous mold (1)
Cooling water is circulated to cool the sleeve (2). The starting rod (61) is inserted into the holes (75) and (76) of the frame (71) and the lifting / lowering platform (74). The starting rod (6
One end of 1) is inserted into the mold hole 21 of the sleeve 2 of the mold 1, and the other end is fitted into the pulling device 6. A shaft body (62) is projectingly provided at an end of the starting rod (61) on the sleeve (2) side.

At the stage before casting, the starting rod (6
The joint surface between 1) and the shaft body (62) is adjusted to match the initial immersion depth.

Due to the cooling effect of the cooling jacket (11), the tubular sleeve (2) is kept at a low temperature through the mold (12) surrounded by the cooling jacket (11).

The lower end of the break ring (3) has a refractory layer (14)
The inner diameter of the through hole of the break ring (3) is reduced at the upper part. The inner diameter of the upper end of the break ring (3) is smaller than the diameter of the mold hole (21) of the sleeve (2) and protrudes with respect to the mold hole (21) of the sleeve (2).

The relative height of the upper end surface of the break ring (3) to the surface of the molten metal (5) and the relative height of the lower end of the starting rod (61) joining the shaft body (62) to the surface of the molten metal (5) are , As shown in FIG. After the work is started, the mold (1) is lowered, and once the mold (1) approaches the surface of the molten metal, the mold (1) is temporarily stopped and the radiant heat of the molten metal (5) preheats the mold (1) (FIG. 3).

Next, the mold (1) is lowered to the initial immersion depth (second step, FIG. 4). When the mold (1) is lowered to the initial immersion depth, the lower end of the starting rod (61) coincides with the surface layer of the molten metal (5). Molten metal (5) in sleeve (2)
The surface layer of is solidified, and the surface solidified layer is attached to the shaft body (62). At this time, the mold (1) may be stationary or may continue to descend.

Then, the pulling device (6) starts pulling up the starting rod (61). Simultaneously with the start of pulling, the mold (1) is lowered. After the molten metal (5) is cooled along the mold hole (21) of the sleeve (2) to form a solidified shell (52), the newly formed solidified shell (52) is pulled up by a starting rod (61). , Casting the tubular body (51) (3rd
Stage).

After the mold (1) is lowered to a predetermined immersion depth, the molten metal (5) is supplied and the mold (1) is moved up and down so that the relative height of the molten metal surface to the mold is always constant. (4th stage, FIG. 5).

In the pre-casting stage, the sleeve (2) has an excessive cooling capacity due to the cooling heat of the cooling jacket (11). Therefore, in the pre-casting stage, the lifting device (7) is used. ,
Although the mold (1) is lowered and stopped when it comes close to the surface of the molten metal, the mold (1) is preheated by the radiant heat of the molten metal (5) (Fig. 3), but at the casting start stage, that is, the mold.
At the moment when (1) is immersed in the molten metal (5), a thick initial solidified shell (52) is formed in the mold cavity (21) of the sleeve (2). The initial solidified shell (53) is also attached to the break ring (3) at the lower end of the sleeve (2).
Is formed.

Therefore, as shown in FIG. 4, the surface layer (55) of the molten metal (5) which has penetrated into the mold cavity (21) at the initial immersion depth before reaching the predetermined immersion depth of the mold (1). To solidify. At this time, the mold (1) may be stationary or may continue to descend. After forming the surface coagulation layer (55), by pulling up the pipe body (51) with a pulling device (6) such as a pinch roller, the mold (1) is gradually lowered again to a predetermined immersion depth. The solidified shell (52) formed in the mold cavity (21) is formed when the solidified shell (52) is suddenly lowered to the predetermined immersion depth.
Since it is thinner than the thickness of (54), the mold cavity of sleeve (2)
The amount of molten metal (5) supplied to (21) increases. Therefore, it is possible to prevent interruption of continuous casting due to breakout of the molten metal solidified layer at the start of casting.

As shown in FIG. 5, the mold is cast to a predetermined immersion depth.
After lowering (1), the molten metal (5) is supplied, or the mold (1) is lowered by the elevating device (7).
The relative heights of the surface layers of (1) and the molten metal (5) are kept constant.

From the bottom opening of the break ring (3),
The molten metal (5) that has entered the sleeve (2) is cooled along the mold cavity (21) of the sleeve (2) by the cooling water in the cooling jacket (11) that surrounds the sleeve (2), and the solidified layer is formed. Is pulled up intermittently with a pulling device (6) such as a pinch roller,
A tube body (51) having an outer diameter corresponding to the die hole (21) of the sleeve (2) is continuously cast.

When a sufficient time has passed after the start of casting, the cooling capacity of the sleeve (2) is maintained by the cooling jacket.
Since the thermal equilibrium state between the cooling by (11) and the heating by the molten metal (5) has been reached and is stable, a thick solidified shell is not formed.

As shown in FIG. 5, when casting a tubular body having an outer diameter A of the product of 60 mm and a wall thickness B of about 6 to 10 mm, a predetermined immersion depth C is 50 to 100 mm, as shown in FIG. , The initial immersion depth D of the mold (1) is from the molten metal surface to the upper end surface (3) of the break ring (3).
It is desirable that the depth up to 2) is about 20 mm, and the sleeve
The rest time for forming the surface solidification layer of the molten metal (5) in (2) is
0 to 6 seconds is desirable.

Further, it is desirable that the descending speed when the mold (1) is lowered from the initial immersion depth to a predetermined immersion depth is about 5 mm per second. This descent may be intermittent.

When the mold (1) is immersed in the molten metal (5), solidified shells (52) and (53) are formed on the surfaces of the sleeve (2) and the break ring (3).
The solidified shell (53) on the break ring (3) is formed on the sleeve (2) when the tube body (51) is pulled up by the pulling device.
This hinders the supply of molten metal (5) to the tank. Therefore, when the radius difference E between the inner diameter of the upper end of the break ring (3) and the mold hole (21) of the sleeve (2) is 5 mm or less, the broken line portion (7) shown in FIG.
The molten metal (5) is supplied smoothly to prevent breakout. After the mold (1) is dipped at a predetermined immersion depth, the molten metal solidified layer is pulled up at a maximum speed of about 5 mm per second per pitch, and it is desirable to pull up and stand still for 0.5 seconds per pitch.

The above description of the embodiments is for the purpose of illustrating the present invention, and should not be construed as limiting the invention described in the claims or limiting the scope. The configuration of each part of the present invention is not limited to the above-mentioned embodiment, and it goes without saying that various modifications can be made within the technical scope described in the claims.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state in which a pulling continuous casting mold is not immersed in a molten metal.

FIG. 2 is a graph showing relative heights of a molten metal surface, a break ring upper end surface, and a starting rod lower end surface.

FIG. 3 is a cross-sectional view in which the mold is approached to the molten metal and preheating is performed.

FIG. 4 is a cross-sectional view in which the mold is lowered to the initial immersion depth.

FIG. 5 is a cross-sectional view in which the mold is lowered to a predetermined immersion depth.

FIG. 6 is an enlarged cross-sectional view of the lower end of the sleeve of FIGS. 4 and 5.

FIG. 7 is a cross-sectional view of a mold according to a conventional method.

[Explanation of symbols]

 (1) Cooling mold (11) Cooling jacket (12) Mold (2) Sleeve (21) Mold hole (3) Break ring (5) Molten metal (6) Pulling device (7) Lifting device

Claims (1)

[Claims] 1. A cooling mold which is surrounded on the outside by a cooling jacket (11) and has a mold hole (21) penetrating vertically inside.
The lower part of (1) is immersed in the molten metal (5) to a predetermined depth, and the mold cavity (21)
In the continuous pulling casting method, the molten metal that has entered through the lower opening of the mold is solidified by cooling around the die hole (21), and the solidified layer is pulled up by the pulling device (6) to cast the tubular body (51). When immersing the starting mold (1) in the molten metal (5),
Before the predetermined immersion depth is reached, pulling up of the pipe body (51) is started by the pulling device (6), and at the same time, the mold (1) is gradually lowered again until the predetermined immersion depth is reached. Pulling continuous casting method.