JPH0947843A - Pull-up continuous casting method and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the height of a projecting line caused on the inner surface of a tubular body to be cast as less as possible by setting a cooling mold so that stepped parts formed by making the diameter of the upper stepped part lower than that of the lower stepped part around the inner surface of a sleeve are positioned at specific positions and casting the tubular body having the outer diameter corresponding to the small diameter of the sleeve. SOLUTION: The lower stepped part 60 has the function for fixing the pull-up lower end position of the molten metal solidified layer 50 to prevent an inadvertent breakage, namely breakout of the solidified layer in the molten metal on the way of pulling up. The upper stepped part 6 has the function for causing an annular air gap 8 corresponding to the stepped difference at the time of passing the molten metal solidified layer 50 whose the outer shape is formed by being solidified below the stepped part 60 through the stepped part 6 to drastically reduce the cooling action of the sleeve 2. Then, the cooling mold 1 is set so that the upper stepped part 6 in the sleeve 2 always positions at the part lower than the molten metal surface by 5-15mm. The molten metal 5 entered into the sleeve 2 from the lower end opening hole of the sleeve 2 is cooled and solidified by coming in contact with the sleeve 2 and intermittently pulled up.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method in which a lower part of a cooling mold having a sleeve penetrating vertically is immersed in a molten metal so that the molten metal penetrates through a lower end opening of the sleeve, and the molten metal is cooled and solidified around the sleeve. The present invention relates to a continuous pull-up casting method and apparatus for pulling it intermittently to form a tubular body.

[0002]

2. Description of the Related Art A cooling mold used in a pulling continuous casting apparatus
As shown in FIG. 3, (1) is equipped with a cylindrical sleeve (2) made of a material having high heat conductivity and excellent heat resistance in the center of an annular cooling jacket (11), and a jacket ( The outer periphery of 11) is protected by a refractory layer (14). The inner surface of the sleeve (2) is a mold hole corresponding to the outer diameter of the pipe body (51) to be manufactured.

The upper part of the cooling mold (1) is exposed from the surface of the molten metal, the lower part is immersed in the molten metal (5), and the molten metal is introduced from the lower opening of the sleeve (2). The solidified layer (50) is pulled up by the pinch rollers (71) (71) while cooling and solidifying the molten metal (5) along the inner surface of the sleeve by the cooling water in the cooling jacket (11) surrounding the sleeve (2). The pipe (51) is continuously cast by intermittently pulling up with the device (7). This intermittent pulling up is, for example, a cycle in which the pinch rollers (71) (71) are rotated in the pulling direction for 0.15 seconds and stopped for 0.75 seconds, for example.

[0004]

As shown in FIG. 4, the surface tension of the molten metal causes the surface tension of the molten metal to go around the inner surface of the molten metal coagulating layer (50) at each pitch of 0.2 to 0.3. mm ridge (5
2) is formed. The ridges (52) grow as the stopping time for intermittent pulling increases. When the tube body (51) is used as it is cast, the ridges (52) serve as resistance to the fluid passing through the inner surface of the tube. Even when the inner surface of the pipe is smoothed by machining, the ridges (52) act as cutting resistance, which lowers workability.
The present invention clarifies a pull-up continuous casting method and apparatus capable of solving the above problems by suppressing the height of the convex stripes (52) generated on the inner surface of the pipe body to be cast as low as possible.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a cooling mold (1) of the present invention.
(1) shows that the cooling mold (1) (1) surrounds a copper cylindrical mold (12) with an annular cooling jacket (11), and the outer periphery of the jacket (11) is a refractory layer ( It is protected by 14). Water chamber (13) filled with cooling water inside the cooling jacket (11)
Are formed.

On the inner surface of the lower end of the copper mold (12), there is formed a recess (10) which is recessed from the vicinity of the bottom surface height position of the cooling jacket (11) to the lower end over the entire circumference. The boundary (15) of the recessed step (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 is made of graphite, and has two stepped portions which are formed so as to go around the lower inner surface of the sleeve (2) and in which the upper portion is recessed more than the lower portion. Upper step
(6) is located 5 to 15 mm below the surface of the bath, and the step is 1 to
2 mm, the lower step (60) is ± 10 mm from the boundary (15) of the concave step (10) of the copper mold (12), that is, the bottom height of the water chamber of the cooling jacket (11). It is located in the vicinity of, and the step is 1 to 10 mm.

The upper step (6) and the lower step (60) have completely different purposes. The lower step portion (60) is a molten metal coagulation layer, as the applicant previously disclosed in Japanese Patent Laid-Open No. 305398/1993.
This is for fixing the pulling lower end position of (50) to prevent accidental breakage of the molten metal solidified layer during pulling, that is, breakout. The upper step portion (6) corresponds to a step difference when the molten metal solidification layer (50) whose outer shape is determined by solidifying below the step portion (6) passes through the step portion (6). Annular air gap
(8) is generated, and the cooling ability from the sleeve (2) is significantly reduced.

However, the cooling mold (1) is so arranged that the upper step (6) of the sleeve (2) is always located 5 to 15 mm below the molten metal surface.
Set. From the bottom opening of the sleeve (2) to the sleeve
The molten metal (5) that has entered the inside (2) contacts the sleeve (3) and is cooled and solidified, and the solidified layer (50) is intermittently pulled up to form the tubular body (51).

At the boundary (61) of the lower convex step (60), the molten metal solidified layer (50) is very easily broken, and the molten metal solidified layer (50)
The lower end of pulling up is limited to the step position. Therefore, even if the temperature condition of the sleeve, the temperature of the molten metal, and the solidified 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 (50) can be prevented.

As described above, when the molten metal solidified layer (50) which is solidified and has the determined outer shape passes through the upper step (6), the sleeve
An annular air gap (8) is formed between (2) and the molten metal solidification layer (50) corresponding to the step difference, and the cooling ability from the sleeve (2) is significantly reduced. As a result, in the conventional case, due to the synergistic effect with the surface tension of the molten metal surface, the height of the annular convex step portion on the inner surface of the molten metal solidification layer (50) formed to a height of about 0.2 to 0.3 mm is The height can be suppressed to less than 0.05 mm.

If the step of the upper step (6) is 1 mm or less, the effect of lowering the cooling capacity of the sleeve is small, and if the step is 2 mm or more, the overall thickness of the sleeve becomes large, which is uneconomical. Is. Also, if the height of the upper step (6) is higher than the range of 5 to 15 mm below the molten metal surface, the molten metal surface position will be below the step (6) due to an error in the control of the molten metal surface height adjustment. May come or the cooling capacity does not deteriorate. At a low position, the thickness of the molten metal solidified layer (50) does not grow sufficiently and there is a risk of breakout.

Even if there is a level difference of about 0.05 mm on the inner surface of the cast pipe, there is almost no problem in flowing the fluid, and the pipe can be used as cast. Further, even when the inner surface of the cast pipe body is machined to be smooth, since the step is small, the cutting efficiency can be improved. The present invention is not limited to the configuration of the above-described embodiment, and it goes without saying that various modifications can be made within the scope described in the claims.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of a solidified state of a molten metal in the vicinity of an upper stage portion of a sleeve.

FIG. 3 is a cross-sectional view of a conventional cooling mold.

FIG. 4 is an explanatory diagram of a solidified state of a molten metal near a molten metal surface in a conventional example.

[Explanation of symbols]

 (1) Cooling mold (2) Sleeve (6) Step (60) Step

Claims (3)

[Claims] 1. A tubular sleeve (2) made of a material having high heat conductivity and excellent heat resistance is mounted inside an annular cooling jacket (11), and the cooling jacket (11) is provided with a refractory layer. (14)
The lower part of the cooling mold (1) formed by being protected by is soaked in the molten metal, the upper part is exposed from the molten metal surface, and the molten metal that has flowed into the sleeve (2) from the lower end is guided along the inner surface of the sleeve (2) to form a cylinder. In the pull-up continuous casting method, in which the solidified layer (50) is intermittently pulled up to form a continuous tubular body, the sleeve (2)
The cooling mold (1) is arranged so that the stepped portion (6) formed around the inner surface of the upper part and recessed from the lower part is always located 5 to 15 mm below the molten metal surface. A continuous casting method for a tubular body, comprising casting a tubular body (51) having an outer diameter corresponding to the small diameter portion of the stepped portion (6). 2. A tubular sleeve (2) made of a material having high heat conductivity and excellent heat resistance is mounted inside the annular cooling jacket (11), and the cooling jacket (11) is provided with a refractory layer. (14)
The lower part of the cooling mold (1) formed by being protected by is soaked in the molten metal, the upper part is exposed from the molten metal surface, and the molten metal that has flowed into the sleeve (2) from the lower end is guided along the inner surface of the sleeve (2) to form a cylinder. In a continuous pull-up casting apparatus in which a solidified layer (50) is intermittently pulled up to form a continuous tubular body, a stepped portion in which the upper portion is recessed more than the lower portion around the inner surface of the sleeve (2). (6) is formed, and the stepped portion (6) is located 5 to 15 mm below the molten metal surface,
A continuous casting machine for pulling up pipes with steps of 1 to 2 mm. 3. A tubular sleeve (2) made of a material having high heat conductivity and excellent heat resistance is mounted inside the annular cooling jacket (11), and the cooling jacket (11) is provided with a refractory layer. (14)
The lower part of the cooling mold (1), which is protected by, is immersed in the molten metal, the upper part is exposed from the molten metal surface, and the molten metal flowing into the sleeve (2) from the lower end is solidified along the inner surface of the sleeve (2). In the continuous pull-up casting apparatus for intermittently pulling up the solidified layer (50) to form a continuous pipe, the stepped portion in which the upper part is recessed more than the lower part is formed around the inner surface of the sleeve (2) in two steps. The upper step (6) is located 5 to 15 mm below the surface of the molten metal, and the lower step (60) is located near the bottom height of the water chamber of the cooling jacket (11). Lifting continuous casting equipment.