JPH05228582A - Method for controlling thickness in drawing-up casting - Google Patents

Abstract

PURPOSE:To control the thickness of a cast pipe body in drawing-up casting. CONSTITUTION:In a drawing-up casting for forming the pipe body by dipping the lower part of a cooling mold 2 having mold hole 21 vertically penetrated into molten metal 9 in a molten metal storing furnace 1, invading the molten metal 9 from the lower opening hole of the mold hole 21 and drawing up solidified layer 91 while cooling and solidifying the molten metal 9, the molten metal storing furnace 1 having almost the fixed horizontal cross sectional area in the molten metal storing part is used between the bottom surface and the molten metal surface height, and while descending the cooling mold at the fixed speed, the drawing-up casting is executed. Therefore, by roughly knowing only the molten metal surface height (h) and the molten metal temp. to the cold mold and suitably selecting the solidified layer 91, the control can be executed so as to become the fixed thickness in the pipe body without severely controlling particularly the molten metal temp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the wall thickness of a cast pipe in pull casting.

[0002]

2. Description of the Related Art In the conventional pull-up casting, as shown in FIG. 2, the upper part of the cooling mold (2) is exposed from the surface of the molten metal, and the lower part of the mold is immersed in the molten metal (9). The molten metal (9) is introduced into the die hole (21) through the lower opening of the hole (21).

The starting rod (8) is inserted into the mold hole (21) from above the cooling mold (2), and the molten metal (9) is attached to the shaft body (81) projecting from the lower end of the rod to form the mold. After the outer peripheral portion of the hole (21) is solidified, the pulling device (7) pulls up the starting rod (8). Starting rod (8)
The solidified layer (91) that continuously rises is pulled up by the pulling device (7) to form a long tube.

The wall thickness of the solidified layer (91) becomes larger as the molten metal is in contact with the die cavity (21) for a longer time, that is, as the level h of the molten metal relative to the die cavity (21) becomes higher. The shorter the time of contact with 21), that is, the lower the level h of the molten metal in the mold cavity 21, the smaller.

The amount of the molten metal gradually decreases as the casting progresses. Therefore, in order to keep the molten metal level h to the mold cavity (21) constant, the cooling mold is lowered or the molten metal accommodating furnace is kept in accordance with the decrease of the molten metal. You must raise or pour the molten metal.

Further, if the temperature of the molten metal is low, the wall thickness of the cast pipe is large, and if it is high, the wall thickness is thin.

[0007]

As described above, in the case of producing a tubular body having a uniform wall thickness by pulling casting, the solidified layer (9
It is important to keep the pulling speed of 1), the level of the molten metal surface relative to the mold cavity (21), and the molten metal temperature constant.

However, although it is possible to easily control the pulling rate of the solidified layer (91) to be constant,
It is difficult to control the temperature of the molten metal due to the accuracy of the temperature detector, the passage of time, the addition of molten metal, etc.

Furthermore, it is more difficult to control the level h of the molten metal because the thickness of the solidified layer (91) is not constant due to the above circumstances. The present invention clarifies a method for controlling the wall thickness of a continuous pull-up casting pipe which solves the above problems.

[0010]

According to the wall thickness control method of the present invention, the lower part of a cooling mold (2) having a mold hole (21) penetrating vertically is immersed in the melt (9) in a melt containing furnace (1). In the pull-up casting in which the molten metal (9) is introduced from the lower opening of the die hole (21) and the molten metal (9) is cooled and solidified, the solidified layer (91) is pulled up to form a tubular body, The furnace (1) is one in which the horizontal cross-sectional area of the molten metal storage part is substantially constant from the bottom to the level of the molten metal, and pull-up casting is performed while the cooling mold (2) is lowered at a constant speed.

[0011]

[Action and effect]

h: molten metal surface level S: horizontal cross-sectional area S of the housing portion of the molten metal accommodating furnace ': casting the cross-sectional area So orthogonal to the axis of the casting tube': cross-sectional area of the casting pipe, which is determined with respect to the desired thickness S ₁ ' : Horizontal cross-sectional area excluding the mold cavity of the cooling mold V: Constant descent rate of the cooling mold V ': Cross-sectional area S of the casting pipe determined for a desired wall thickness
Suitable pulling speed for o '

The descent rate of the cooling mold

[Equation 1] As a result, the relationship between h and S'is expressed by the formula that is seen from the increase and decrease of the molten metal level.

[0013]

[Equation 2]

[0014]

[Equation 3]

Descent of the mold Vdt ....

Reduction of molten metal level due to casting

[Equation 4]

If the sum of ,, dh (increment of h after the lapse of a minute time dt) S '>So', then dh / dt <0, and ds '/ dt <0, which approaches So'. If S '<So', then dh / dt> 0 and ds '/ dt> 0, approaching So'. That is, the wall thickness can be controlled to be constant.

Even if there is an error or variation ΔS in the horizontal cross-sectional area of the molten metal storage furnace, it is extremely small because it is reflected in the error and variation after the casting cross-section at the ratio ΔS / S.

[0019]

EXAMPLE As shown in FIG. 1, a molten metal storage furnace is mounted on a base (3).
(1) is provided, and a cooling mold (2) is suspended and supported in the furnace.

The frame (4) for suspending the cooling mold (2) is
Vertical columns at four symmetrical positions around the cooling mold (2) on the base (3)
(41) is provided, and the upper ends of the columns are connected by a rectangular frame (42).

Inside each pillar, a screw shaft (43) is arranged vertically, and an elevating table (5) is arranged across each screw shaft (43).

The lifting table (5) has screw holes (51) at four corners, and the screw shaft (43) is screwed into the screw holes (51). The four screw shafts (43) are connected to one motor (44) at the upper part of the frame (4) through a rotation transmission means (45), and the forward rotation of the motors causes the lifting table (5) ) Is rotated all at once in a direction of raising, and by the reverse rotation of the motor, the elevator (5) is simultaneously rotated in a direction of lowering.

A hanging frame (52) is provided on the lower surface of the center of the lift table (5), and a cooling mold is suspended and supported by the hanging frame. A pulling device (7) for pulling up the casting pipe is provided in the center of the frame (4), and the pulling device sandwiches the pulling transition path of the casting pipe and a pair of pinch rollers (71) (71). ) Are arranged to face each other, and a drive motor (72) is connected to the pinch roller.

Then, the mold cavity (21) is introduced from above the cooling mold (2).
The starting rod (8) is inserted into the mold, the molten metal (9) is attached to the lower end of the rod, the outer periphery of the mold cavity (21) is allowed to solidify, and the starting rod is pulled up at a constant speed.

The descending speed of the cooling mold

[Equation 5] As a result, the relationship between h and S'is expressed by the formula that is seen from the increase and decrease of the molten metal level.

[0026]

[Equation 6]

[0027]

[Equation 7]

Descent of mold Vdt ............ Reduction of molten metal by casting and reduction of molten metal level

[0029]

[Equation 8]

If the sum of ,, dh (increment of h after a lapse of a minute time dt) S '>So', then dh / dt <0, and ds '/ dt <0, which approaches So'. If S '<So', then dh / dt> 0 and ds '/ dt> 0, approaching So'. That is, the wall thickness can be controlled to be constant.

Errors and variations ΔS in the horizontal sectional area of the holding furnace
Even if there is, it is extremely small because it is reflected in the error and variation after the casting cross section in the ratio of ΔS / S.

The present invention is not limited to the configuration of the above embodiment, and various modifications can be made within the scope of the claims.

[Brief description of drawings]

FIG. 1 is a sectional view of a pull-up casting apparatus used in the present invention.

FIG. 2 is a conventional explanatory view.

[Explanation of symbols]

 (1) Molten metal storage furnace (2) Cooling mold (5) Lift table

Claims (1)

[Claims] 1. A lower part of a cooling mold (2) having a vertically passing mold hole (21) is immersed in a molten metal (9) in a molten metal storage furnace (1),
The molten metal (9) is introduced from the lower opening of the die hole (21) to
In pull-up casting in which the solidified layer (91) is pulled up while cooling and solidifying (9) to form a pipe body, the molten metal storage furnace (1) is located horizontally from the bottom to the level of the molten metal. A thickness control method in pulling casting in which pulling casting is performed while lowering the cooling mold (2) at a constant speed by using one having a substantially constant cross-sectional area.