Method For Altering The Cross-sections Of Continuously Cast Metal Pieces

Abstract

A method and a casting water cooled mold for altering the width dimension of a continuously cast metal piece during a continuous casting operation without the need of replacing the mold with different molds for producing cast pieces of different dimensions. The mold for carrying out the method has two water-cooled front walls and two water-cooled side walls, each of which walls are press-fixable and releasable to and from each other and all but one of the front walls being formed by two sections, said sections being movable in a horizontal direction and vertically press-fixable to each other.

Description

The present invention relates to a method for altering the cross-sections and particularly the width dimensions of cast pieces without replacing the mold during the continuous casting of a molten metal.

The continuous casting of molten metals as a means of manufacturing such crudely shaped materials as slabs, billets and blooms is much superior to conventional blooming methods both with respect to the equipment and productivity and is therefore has been extensively adopted.

Recently, as is generally known, in the field of casting steels serious studies are also being carried out and efforts are being exerted in practicing the results of the studies with great effect.

The principle of continuous casting of such molten metal as molten steel and the like is that the molten metal is continuously fed into a bottomless water-cooled mold, in which a dummy bar is positioned, and cast pieces are continuously pulled out of the bottom part of the water-cooled mold, while the molten metal is cooled, at a velocity corresponding to the molten metal pouring velocity.

In carrying out a continuous casting method, it is necessary to produce cast pieces with cross-sectional dimensions which are optimum for the cross-sectional dimensions of the products to be produced from the cast pieces in order to obtain cast pieces which can be easily worked and produce a high yield in the processing step, such as rolling, subsequent to the continuous casting step for producing the products. However, it has not been possible to alter the cross-section of the cast piece for a product to be finally produced while still using the same mold during the continuous casting. Consequently, usually in continuous casting the mold must be rearranged or modified to the desired cross-section or replaced by a prepared mold of other desired dimensions so that the cross-section of the cast piece to be produced can be altered. As a result thereof, continuous casting must be interrupted for a long time, because it takes, for instance, at least 1 hour to rearrange or modify the mold or to replace the same.

In a conventional continuous casting operation it is customary to use a water-cooled mold of fixed dimensions having an integral wall body. A few proposals have been made for using a water-cooled continuous casting mold having walls divided into several sections. However, the arrangement of mold walls in several sections is for the purpose of increasing the cooling effect, to improve the quality of cast pieces or to make the production of cast pieces of large size possible, as is disclosed, for instance, in the Japanese patents published in the Patent Office Bulletins Nos. 1461/1954 and 12301/1963.

The present invention has as its object to provide a method for continuously altering the cross-sections and particularly the width dimensions of cast pieces during the casting, in a manner which heretofore has not been possible in a continuous casting method.

More concretely, the present invention has as its object to provide a method which employs a continuous casting water-cooled mold, which is able to be taken into pieces, or in other words, a water-cooled mold constructed by a water-cooled front wall and water-cooled side walls, each of which walls is formed by two sections movable independently of each other.

The terms used in the disclosure of the present invention "water-cooled front wall" and "wall-cooled side wall" are to be understood as follows: the former designates a mold wall having a surface forming the front or back surface of a cast piece to be produced and the latter designates a mold wall having a surface forming each side surface of the above-mentioned cast piece.

Thus, the present invention has several novel features, as will be described hereinafter:

The primary feature of the present invention is to provide a method which utilizes a mold constructed by positioning respective water-cooled side walls on both the right and left sides between two water-cooled front walls, each of the side walls and one of the front walls having two sections, which are positioned one over the other, forming upper and lower stages, the remaining water-cooled front wall being an integral body.

A second feature of the present invention is to provide a method which utilizes a water-cooled mold, wherein a water-cooled front wall and two water-cooled side walls are formed by upper and lower sections each of said sections of each wall being movable horizontally independent of the other.

The horizontal movement of each wall section of the water-cooled front wall is in the thickness direction of a cast piece to be made. This is for the purpose of enabling the water-cooled side walls, or more exactly, the side wall sections to move horizontally as will be explained later. The water-cooled front wall which is not divided into two sections, can not move, but is fixed.

The horizontal movement of the water-cooled side wall sections is in the width direction of the casting being made. It is for the purpose of altering the width dimension of the above-mentioned casting.

The third feature of the present invention is to provide a method which utilizes a mold having a water-cooled front wall and water-cooled side walls, each of which has upper and lower sections horizontally movable independently of the other, wherein the upper and lower sections of each of the water-cooled front wall and the water-cooled side walls pressed tightly together so that they are fixed to each other respectively. This condition will hereinafter be referred to as "press fixing", or being "press-fixed."

In the case of the water-cooled front wall the press-fixing can be of two kinds: that is, one is where the upper and lower sections of the water-cooled front wall itself are vertically press-fixed to each other and the other is where the water-cooled side walls lying between two water-cooled front walls, that is, the fixed front wall and the water-cooled front wall formed by two sections are press-fixed to the fixed water-cooled front wall by the horizontal pressure of the other front wall formed by two sections.

In the case of the water-cooled side walls the press-fixing is the state wherein the upper and lower sections of each of the water-cooled side walls are vertically press-fixed to each other.

The fourth feature of the present invention is to provide a method which utilizes a mold having a water-cooled front wall and water-cooled side walls, each of which walls are formed by two sections horizontally movable independently of the other and press-fixable, wherein the respective upper and lower sections of the water-cooled side walls are L-shaped.

By using the L-shaped water-cooled side wall sections the width dimensions of cast pieces can be altered over a wider range, as will be later explained, because the contact surface between the upper and lower sections of the water-cooled side wall can be made large.

The fifth feature of the present invention is to provide a method of obtaining cast pieces of required dimensions, as the occasion demands, by altering the positions of the water-cooled side wall sections during the continuous casting of a molten metal by using the above-mentioned mold having the water-cooled front wall and water-cooled side walls, each of which walls are formed by the upper and lower sections horizontally movable independently of the other and which are press-fixable.

In the following the substance of the present invention will be explained in greater detail with reference to the attached drawings so that it can be more clearly understood.

In the attached drawings:

FIG. 1 is an exploded perspective view of a continuous casting water-cooled mold according to the present invention.

FIG. 2 is an explanatory view showing a mechanism for supporting and fixing the continuous casting water-cooled mold and a mechanism for press-fixing the said mold.

FIG. 3 is an explanatory view, partially in cross-section showing a press-fixing mechanism for the water-cooled front wall for horizontally press-fixing the water-cooled side walls.

FIG. 4 is an explanatory view showing a cotter driving mechanism for operating the press-fixing mechanism of the water-cooled front wall shown in FIG. 3.

FIG. 5 is an explanatory view showing a mechanism for supporting and fixing the water-cooled side walls and vertically press-fixing the said water-cooled side wall sections with respect to each other.

FIG. 6 is a sectional explanatory view showing a mechanism for horizontally moving the water-cooled side wall sections.

FIG. 7 is a magnified explanatory view of the part A in FIG. 2.

FIG. 8 is a vertical sectional explanatory view showing the cooling structure of the water-cooled side wall section.

FIG. 9 is a sectional explanatory view taken on line B--B in FIG. 8.

FIGS. 10 and 11 are sectional views taken on line C--C in FIG. 9 showing a modification of the cooling water circulating system.

FIG. 12 is a block diagram of a control circuit, showing schematically the continuous casting according to the present invention.

FIGS. 13a-13e are explanatory views showing the steps of altering the cross-section of a cast piece to a smaller size; and

FIGS. 14a.sub.1 - 14e.sub. 1 are explanatory views showing the steps of altering the cross-section of a cast piece to a larger size.

In FIG. 1 the mold 1 comprises a first water-cooled side wall having two sections 6 and 7, which are positioned one over the other, forming upper and lower portions, and another water-cooled side wall also formed by upper and lower sections 6' and 7'. These side walls are positioned opposite each other between a fixed water-cooled front wall 2 formed in one piece and a water-cooled front wall opposed thereto and formed by upper and lower sections 3 and 4, which are positioned one over the other. The fixed water-cooled front wall 2 can have the same construction as the water-cooled front wall formed by the upper and lower sections 3 and 4.

The mold of the present invention having the construction as described above is used during the continuous casting operation with the above-mentioned four walls being pressed tightly against and fixed to each other and with the upper and lower sections of each wall being vertically press-fixed to each other. When it is required to alter the width dimension of a cast piece, the space between the water-cooled side wall sections 6 and 6' and 7 and 7' must be altered, that is, widened or narrowed (see FIGS. 13 and 14). For this purpose they must be, of course, at first released from the front walls.

The mechanisms for press-fixing the water-cooled front walls and side walls and their sections to each other and for releasing them from each other will be described hereinafter.

The fixed water-cooled front wall 2 is fixed to a fixing device 8 by means of a supporting arm 9, as shown in FIG. 2. This water-cooled front wall 2 determines the location of the center of a cast piece E passing between pull-off rolls (see FIG. 12) used to pull the cast piece out of the mold 1.

The water-cooled front wall sections 3 and 4 can move forwardly and backwardly independently of each other and are connected to a press-fixing mechanism 10 for the side wall sections 3 and 4 for press-fixing the water-cooled side walls.

FIG. 3 shows an example of the press-fixing mechanism 10 for one of the water-cooled front wall sections 3 and 4.

In the drawing, 13 is a frame of the press-fixing mechanism 10. Within said frame there are provided four hollow shafts 14 for supporting the water-cooled front wall section 3, upper and lower pairs with corresponding shafts in the upper and lower pairs being vertically aligned. The hollow shafts themselves are supported by means of bearings 15 and 16 in frame 13.

The water-cooled front wall section 3 is supported on the ends of the above-mentioned hollow shafts by means of a notched part 17 at the end of each of said hollow shafts held between supporting metal pieces 18 provided on the water-cooled front wall section 3.

In the middle part of each of the outer periphery of the above-mentioned hollow shafts a threaded portion 19 is provided extending along the length of said hollow shaft a distance sufficient to move the shaft rightwards and leftwards a desired distance, and meshing with the said screw is an interiorly threaded portion 20 of a worm wheel 21. Said worm wheel 21 is rotatably supported at a fixed position by the above-mentioned bearings 15 and 16.

The worm wheel 21 is engaged with a worm 23 on a rotary shaft 22 on the frame 13. Said rotary shaft 22 can be rotated manually with a handle (not illustrated) or can be rotated by using a motor (not illustrated).

A shaft 25 is slidably positioned in the interior of each hollow shaft 14 and the shaft 25 is provided with a plate spring 26 at the front end thereof. The front end surface of said plate spring 26 is in contact with a metal piece 27 on the back of the water-cooled front wall section 3. At the rear end of the above-mentioned shaft 25 there is mounted a cotter 28 vertically movable through slots in the rear ends of shafts 14 and for pushing the shafts 25 forwards.

Frames 13 having the equipment as above described are provided for both the upper and lower wall sections 3 and 4 and together they constitute the press-fixing mechanism 10.

In press-fixing the water-cooled side wall sections 6 and 6' and 7 and 7' between the fixed water-cooled front wall 2 and the water-cooled front wall formed by sections 3 and 4 by pushing the water-cooled front wall formed by sections 3 and 4 towards the fixed water-cooled front wall 2, the above-mentioned cotter 28 for pushing the shafts 25 is an important element. The cotter 28 is driven vertically by a driving mechanism shown in FIG. 4.

FIG. 4 is a general view of a cotter driving mechanism for pushing the rear ends of the respective shafts 25 of the water-cooled front wall sections 3 and 4 forwards, wherein 29 and 30 are arms, which are rotatably mounted on the frame 13 on shafts 31 and 32.

Each of the above-mentioned arms 29 and 30 is provided with a hole 33, through which extends a metal piece 34 projecting from the cotter 28. The above-mentioned arms 29 and 30 are rotatably connected with each other at one end by an arm 35.

The other end of the arm 30 is pivotally connected with a rod 37 of a piston-cylinder mechanism 36 mounted on the frame 13.

When operating the thus constructed press-fixing mechanism 10 to assemble the water-cooled mold walls, the rotary shaft 22 in the mechanism 10 shafts 14 through worm gears 23 and 21, whereby the surfaces of the water-cooled front wall sections 3 and 4 and the water-cooled side wall sections 6 and 7 and 6' and 7' are brought into contact with each other and with the surface of the fixed front wall 2 such that the wall sections 6 and 6' and 7 and 7' can be moved by a sliding device 38, which will be described hereinafter. At this point rotation of the rotary shafts 22 is stopped.

Then, in order to press and fix all the mold walls to each other, the shafts 25 must be pushed in the forward direction. For this purpose the cotters 28 are moved by the operation of the arms 29 and 30 by driving the piston-cylinder mechanisms 36, whereby the shafts 25 are pushed in the forward direction and the water-cooled front wall parts 3 and 4 are pushed by the plate spring 26 so that the water-cooled side wall parts 6 and 6' and 7 and 7' are pressed against and fixed to the water-cooled front wall 2.

On the contrary, when the water-cooled side wall sections 6 and 6' are to be moved to alter the distance between them, the press-fixing action of the water-cooled front wall sections 3 and 4 must be eliminated by releasing the water-cooled wall sections 3 and 4 from pressing action of the shafts 25. This is done by driving the cotters 28 in the opposite direction.

Further, when disassembling the mold for the purpose of repair of the mold, the cotters 28 are operated to release the shafts 25 and thereafter the rotary shafts 22 are caused to rotate in the direction opposite to the above-mentioned direction. Then, the hollow shafts 14 are caused to withdraw to a determined position through the worm gears 23 and 21.

In the foregoing description there has been described the manner in which two water-cooled side walls are pressed and fixed between the fixed water-cooled front wall 2 and the water-cooled front wall formed by the sections 3 and 4 by advancing the hollow shafts 14 and the shafts 25. However, it is also possible to use a piston and cylinder instead of the hollow shafts 14 and the shafts 25. Further, an eccentric cam can be used instead of the cotter 28 for pushing each of the shafts 25.

The horizontal movement of the water-cooled side wall sections is carried out by means of the sliding devices 38, on which the water-cooled side wall sections 6 and 7 are supported and fixed by arms 39, as is shown in FIG. 5.

As shown in FIG. 6, the abovementioned sliding devices 38 rotate threaded shafts 41 through speed change gears 40 consisting of worm gears by the rotation of a motor (not illustrated), whereby the arms 39 meshing with said threaded shafts are advanced and withdrawn in the horizontal direction. 42 is a sliding surface supporting the arm 39 and bearings 43 are provided to support threaded shaft 41.

In order to be able to move the water-cooled side wall sections 6 and 6' or 7 and 7' horizontally in opposite directions by using the above-mentioned sliding device 38, it is, of course, necessary to release the water-cooled side wall sections 6 and 6' or 7 and 7' by operating the press-fixing device 10.

When the horizontal movement of the water-cooled side wall sections 6 and 6' or 7 and 7' is finished, however, it is important to press-fix them again by pressing the water-cooled front wall sections 3 or 4 toward the fixed wall 2.

Next, a mechanism for fixing the water-cooled front wall sections 3 and 4 to each other and water-cooled side wall sections 6 and 7 and 6' and 7' to each other will be described.

In order to fix the water-cooled front wall sections 3 and 4 to each other, it is necessary at first to support the lower section 4. For this purpose projections 44 are provided on both the lower parts of both ends of the water-cooled wall 2 and the section 4, and a hole 44' is provided in each projection 44. A bar member 45 is passed through said holes 44' and 44' and is fixed at the ends thereof to the fixing device 8 and the press-fixing mechanism 10 respectively, as shown in FIGS. 1, 2 and 5.

On the other hand, a projection 46 is provided on the lower part of each end of the water-cooled front wall section 3.

Further, a bar member 47 is rotatably pivoted at one end on a pin 48 on the mold side of the press-fixing mechanism 10, and is positioned on the above-mentioned projection 46. At the other end the bar member 47 is engaged with a fixed metal piece 49 provided on the fixing device 8.

As shown in FIG. 7, a tapered cotter 50 is inserted between said fixed metal piece 49 and bar member 47 so as to push the bar member 47 downwards and push down the projection 46.

Thus, the water-cooled front wall sections 3 and 4 are vertically press-fixed by means of the bar member 47 in collaboration with the bar member 45.

The advance and retreat of the above-mentioned cotter 50 is accomplished by means of a piston cylinder mechanism 51, as is shown in FIG. 7. Alternatively, a driving mechanism (not illustrated) consisting of a screw and gear may be adopted instead of the piston cylinder mechanism 51.

The devices for fixing the water-cooled front sections 3 and 4 to each other are provided on both right and left end parts of the water-cooled front wall sections 3 and 4.

Devices for fixing the water-cooled side wall sections 6 and 7 and 6' and 7' to each other will be described with reference to FIGS. 1, 2 and 5.

Supporting metal pieces 52 and 53 are securely mounted on the water-cooled side wall sections 6 and 6' and 7 and 7' respectively. The lower end of the supporting metal piece 53 for each of said water-cooled side wall sections 7 and 7' is in contact with the above-mentioned bar member 45.

Further, a bar member 54 is rotatably pivoted at one end on a pin 55 on the mold side of the fixing device 8, engages the supporting metal piece 52 of the water-cooled side wall sections 6 and 6', and is engaged at the other end with a fixed metal piece 56 provided on the press-fixing mechanism 10. By inserting a cotter 50' provided with a taper, like the cotter described in connection with FIG. 7, between said fixing metal piece 56 and bar member 54, the bar member 54 can be pushed downwards and the supporting metal piece 52 is pushed down. Thus, the water-cooled side wall sections 6 and 6' and 7 and 7' are vertically press-fixed to each other respectively by means of the bar member 54 in collaboration with the bar member 45.

As, in the present invention cast pieces are produced by using the continuous casting mold, wherein the above-mentioned water-cooled front wall sections 3 and 4 and water-cooled side wall sections 6 and 7 and 6' and 7' are respectively vertically press-fixed by means of the press fixing devices, by an ordinary continuous casting method comprising continuously feeding a fixed amount of molten metal, for instance, molten steel, while vertically vibrating the mold up and down.

In the foregoing there has been described the use of the cotters 50 and 50' as a means of pushing down the bar members 47 and 54 by inserting them, when press-fixing the water-cooled front wall sections 3 and 4 and water-cooled side wall sections 6 and 7 and 6' and 7' between the bar members 47 and 54 and the fixed metal pieces 49 and 56 respectively. However, it is also possible to replace the fix metal pieces 49 and 56 by piston cylinder mechanisms or eccentric cams (not illustrated) so that the bar members 47 and 54 may be directly pushed down thereby to vertically press-fix the water-cooled front wall sections 3 and 4 and water-cooled side wall sections 6 and 7 and 6' and 7' respectively.

Further, the water-cooled front wall sections 3 and 4 and water-cooled side wall sections 6 and 7 and 6' and 7' may be vertically press-fixed directly by means of a cotter or an eccentric cam respectively by inserting the cotter or positioning the eccentric cam between the projections provided on the water-cooled front wall sections 3 and 4 or water-cooled side wall sections 6 and 6' or 7 and 7' and projections (not illustrated) corresponding to the above-mentioned fixed metal pieces, on the press-fixing mechanism 10 for the water-cooled front wall sections 3 and 4 or on the sliding device 38 for the water-cooled side wall sections 6 and 6' or 7 and 7' on the side of the mold.

In the mold of the present invention, that is, in the mold composed of the water-cooled front wall and water-cooled side walls having two sections respectively, which sections are positioned one above the other, forming the upper and lower stages, and separately movable in the horizontal direction and capable of being press-fixed to each other, it is preferable to shape each of the water-cooled side wall sections 6 and 6' and 7 and 7' in the form of an L. Making the respective water-cooled side wall sections 6 and 6' and 7 and 7' L-shaped makes it possible to move the wall sections 6 and 6' relative to the wall sections 7 and 7' to a large extent, whereby the object of the present invention can be advantageously achieved, as will be later described.

FIG. 1 shows the embodiment, in which the above-mentioned L-shaped water-cooled side walls are used. As shown in FIG. 8 each of the water-cooled side wall sections, for instance, sections 6 and 6', consists of a side surface 57 and a sliding surface 58. As regards the cooling system for each of the L-shaped side wall sections it is preferable to provide the side surface and sliding surface with separate cooling systems respectively, as shown in FIGS. 8 and 9. In the cooling system for the side surface 57 there are provided water feeding and discharging ports 59 and 60 on the back side of the surface 57 and a plurality of rows of flow paths running parallel with the side surface 57 and communicating with said ports 59 and 60.

The port 60 for the water discharge is provided with a water discharging jacket 62 and the port 59 for the water feed is provided with a water feeding jacket 63. 64 is a water supply pipe and 65 is a water discharging pipe.

On the other hand, the cooling system for the sliding surface 58 has water feed and discharge ports 67 and 68 on the end surface 66 of the sliding surface 58 and is provided with a plurality of side by side flow paths running parallel with the sliding surface 58, as shown in FIGS. 10 and 11.

The ports 68 for the water discharge are provided with water discharging jackets 70 and the ports 67 for the water feed are provided with water feeding jackets 71. The arrangement of the inlets and outlets of the above-mentioned flow paths can be in the order of the inlet side -- outlet side -- outlet side -- inlet side, as shown in FIG. 10 or the flow paths can be concentrically arranged so that a plurality of inlets are connected to a single feeding jacket and a plurality of outlets are connected to a single discharging jacket, as shown in FIG. 11. In the drawings, 72 is a water feed pipe and 73 is a water discharge pipe.

With the cooling systems arranged as described the cooling capacity of the boundry part of the side surface 57 and the sliding surface 58 can be greatly increased.

Now, the operation of the continuous casting according to the method of the present invention and using the described apparatus will be explained with reference to FIG. 12. First of all, the water-cooled front wall 2 and each of the front wall sections 3 and 4 and the water-cooled side wall sections 6 and 6' and 7 and 7' from which the mold 1 is constructed, must have sufficient cooling capacity for performing an ordinary continuous casting. The water-cooled mold 1 is so compactly constructed that all wall sections may be jointly vertically vibrated in the conventional manner, and the water-cooled side wall sections 6 and 6' and 7 and 7' are so arranged that they may be separately moved independently of each other in the width direction of a cast piece E, as described hereinbefore.

On the side of the water-cooled mold 1 there is provided a radioactive ray position detecting device 77 to detect the level of a molten steel D poured-in through a pouring pipe 75 of a tundish 74, and a position detecting measuring signal from the said position detecting device 77 is impressed on a control device 78.

A stopper operating device 79 driven by an instruction from the said control device 78 moves a stopper 80 vertically to control the volume of the molten steel D poured into the mold.

The molten steel D poured into the water-cooled mold 1 through the pouring pipe 75 is cooled in the water-cooled mold 1 and is pulled as a cast piece E out of the bottom part of said water-cooled mold 1. To control the velocity with which the cast piece E is pulled out, the rotating velocity of the pull-out roll or guide roll 81 is detected by a pulse transmitter 82. Said pull-out velocity signal is impressed on the controlling device 78. 83 is a driving device for the pull-out roll or guide roll 81. Said driving device 83 is controlled by the control device 78. 84 is a device for lifting of the tundish 74.

On the basis of the cooling capacity of the water-cooled mold 1, the driving device 83 is operated at an appropriate velocity by the instruction from the control device 78 and the cast piece E is pulled out. At the same time, the stopper operating device 79 operates to control the volume of flow of the molten steel in response to the pull-out velocity of the cast piece E and the molten steel D is poured into the water-cooled mold 1 through the pouring pipe 25. The cast piece E cooled in the water-cooled mold 1 is pulled out at a controlled velocity.

During such continuous casting, the width dimension of the cast piece can be altered by the steps shown in FIGS. 13 or 14. FIGS. 13a to 13e show steps of altering the cross-section of the cast piece E from a fixed width dimension to a smaller width dimension. First of all, the configuration of the mold set for continuous casting as shown in FIG. 13a is changed to reduce the width dimension by changing the positions of the water-cooled side wall sections 6 and 6' in the upper stage, as shown in FIG. 13 (b). The horizontal movements of the side wall sections 6 and 6' for changing the distance between them to that shown in FIG. 13b are performed by carrying out steps as follows:

At first, the press-fixed condition of the sections 6 and 7 and 6' and 7' is released by releasing the bar member 54 engaging the above-mentioned sections by withdrawing the cotter 50'. Then, the press-fixed condition of the front wall sections 3 and 4 is released by releasing the bar member 47 from engagement with the said sections by withdrawing the cotter 50. Thereafter, the press-fixed condition of the side wall sections 6 and 7 and 6' and 7' and the front wall sections 3 and 4 is to be removed by withdrawing the shaft 25 by appropriately moving the cotter 25.

With the mold parts in the thus released state the sliding device 38 can operate to horizontally move the sections 6 and 6' in the direction toward each other, to the positions as shown in FIG. 13b. Then, the vertical vibrating movement of the water-cooled mold 1 is stopped and the pull-out of the cast piece E is stopped. Then, as shown in FIG. 13c, the amount of the molten steel D poured-in is increased by increasing the opening of the stopper 80 until the pouring level 76 along the water-cooled side walls 6 and 6' is reached. At the same time, the tundish 74 is elevated in response to the change in the molten steel level in the mold. When the surface of the molten steel approaches the pouring level 76 for the water-cooled side wall sections 6 and 6', the amount of the molten steel poured-in is reduced by controlling the stopper 80. Meanwhile, a shell (hatched part of the cast piece E) which allows the cast piece to be pulled out is formed on the outer periphery of the molten steel D in the mold over a period of time, for example, of 20 to 50 seconds, although the time is different depending on the cross-section of the cast piece, and then the pull-out of the cast piece E is started again.

At the moment, when the stepped part F of the casting, which is formed by the alteration of the width dimension of the cast piece E, has been shifted downwardly due to the pull-out of the cast piece E a distance greater than the stroke of the vertical vibratory movement of the water-cooled mold 1, the vertical vibratory movement of the water-cooled mold 1 is started.

Then, when the stepped part F of the cast piece E has moved below the water-cooled side wall sections 7 and 7' as shown in FIG. 13 (d), the positions of the water-cooled side wall sections 7 and 7' are shifted toward each other so that they coincide with the positions of the water-cooled side wall sections 6 and 6'.

Then, the molten steel pouring level is lowered to the pouring level 76 of the water-cooled side walls sections 7 and 7' if desired by controlling the stopper 80 to continue the continuous casting.

FIGS. 14a.sub.1 to 14e.sub.1 show steps of altering the cross-section of the cast piece E from a fixed width dimension to a larger width dimension. The configuration of the mold set for casting as shown in FIG. 14a.sub.1 is changed to increase the width dimension by changing the positions of the water-cooled side wall sections 6 and 6' as shown in FIG. 14 (b.sub.1). Then, the vertical vibrating movement of the water-cooled mold 1 is stopped, the pull-out of the cast piece E is stopped and, as shown in FIG. 14 (c.sub.1), the amount of the molten steel D poured-in is increased by increasing the opening of the stopper 80 until the pouring level 76 along the water-cooled side wall sections 6 and 6' is reached. At the same time, the tundish 74 is elevated in response to the change in the molten steel level in the mold. When the surface of the molten steel approaches the pouring level 76 along the water-cooled side wall sections 6 and 6', the amount of the molten steel poured-in is reduced by controlling the stopper 80. Meanwhile, a shell (hatched part of the cast piece E) which allows the cast piece to be pulled out is formed on the outer periphery of the molten steel D in the mold over a period of time of 20 to 50 seconds, although the time is different depending on the cross-section of the cast piece.

Then, as shown in FIG. 14 (d.sub.1), the positions of the water-cooled side wall sections 7 and 7' are changed so that they coincide with the positions of the water-cooled side wall sections 6 and 6'.

As the upper end parts of the water-cooled side wall sections 7 and 7' are separated from the stepped part F formed by the alteration of the width dimension of the cast piece E, the vertical vibrating movement of the water-cooled mold 1 and the pullout of the cast piece E are simultaneously started.

Then, as shown in FIG. 14 (e.sub.1), the molten steel pouring level is lowered to the pouring level 76 for the water-cooled side wall sections 7 and 7' if desired by controlling the stopper 80 to continue the continuous casting.

In the foregoing there has been described a method of altering the width dimension of a cast piece so that it is smaller or larger, wherein the stopping of the vertical vibrating movement of the water-cooled casting mold has been carried out after the positions of the upper sections of the water-cooled side walls have been changed to give the casting the desired dimension. However, the time of stopping the vertical vibrating movement of the said casting mold may be before the alteration of the width dimension of the cast piece.

When altering the width dimension of the cast piece E according to the method of the present invention, as is explained above, the vertical vibrating movement of the water-cooled casting mold is temporarily suspended, and therefore it is necessary to carry out quick and accurate alteration of the molten steel pouring level in the water-cooled mold. For that purpose, the tundish 74 may be provided with a plurality of pouring pipes 75.

When a plurality of pouring pipes 75 are provided, the poured amount per unit time can be varied widely and the control of the poured amount can be performed easily.

Claims

We claim:

1. A method of altering the width dimension of a continuously cast piece in the continuous production of the cast piece by continuous casting by pouring a molten metal into a water-cooled casting mold composed of a water-cooled front wall and water-cooled side walls, each of said walls being formed by two sections, said sections being one above the other forming upper and lower stages of the mold, while vertically vibrating said mold, and pulling the finished casting out of the bottom of the mold, said method comprising the steps of altering the distance between the two upper sections of the respective side walls to a distance less than the distance between the two lower sections of the respective side walls while producing the cast piece in the lower stage of the mold, suspending the pulling out of the cast piece, then elevating the pouring level of the molten metal up to near the top of the upper state of the mold, resuming the pulling-out of the cast piece after the molten metal in the upper stage of the mold has formed a shell on the outer periphery thereof, altering the distance between the two lower sections to bring them into correspondence with the upper sections after the portion of the cast piece formed in the lower stage of the mold has cleared the mold, and stopping the vibrating of the mold at the latest just before suspending the pulling out of the cast piece and starting the vibrating of the mold when portions of the cast piece which might be damaged are free of the mold.

2. The method as claimed in claim 1 in which the two upper sections of the side walls are horizontally moved equal distances toward each other to make the distance between them different from that between the corresponding two lower sections of the respective side walls to obtain the desired width in the upper stage of the mold.

3. The method as claimed in claim 1 in which the two upper sections of the side walls are horizontally moved different distances toward each other to make the distance between them different from that between the corresponding two lower sections of the respective side walls to obtain the desired width in the upper stage of the mold.

4. The method as claimed in claim 1 in which only one of the two upper sections of the side walls is horizontally moved to make the distance between the upper sections of the side walls different from that between the corresponding two lower sections of the respective side walls to obtain the desired width in the upper stage of the mold.

5. The method as claimed in claim 1 wherein the water-cooled front wall has upper and lower sections, further comprising the steps of, prior to moving the sections of the side walls, releasing the water-cooled front wall from horizontally press-fixing the water-cooled side walls to a fixed front wall, and releasing the press-fixing of the upper and lower sections of the said water-cooled front wall and then again press-fixing the upper and lower sections of the water-cooled front wall and the side walls to each other and press-fixing the water-cooled side walls the water-cooled front wall and the fixed front wall, after the water-cooled side walls have been moved in a desired amount.

6. The method as claimed in claim 1 wherein the vertical vibrating of the water-cooled casting mold is resumed at the moment when the gap formed between the stepped part of the cast piece between the larger dimension between the lower side wall sections and the smaller dimension between the upper side wall sections, and the under surface of the upper sections of the respective side walls becomes larger than the magnitude of the vertical vibration of the casting mold.

7. A method of altering the width dimension of a continuously cast piece in the continuous production of the cast piece by continuous casting by pouring a molten metal into a water-cooled casting mold composed of a water-cooled front wall and water-cooled side walls, each of said walls being formed by two sections, said sections being one above the other forming upper and lower stages of the mold, while vertically vibrating said mold, and pulling the finished casting out of the bottom of the mold, said method comprising the steps of altering the distance between the two upper sections of the respective side walls to a distance greater than the distance between the two lower sections of the respective side walls, while producing the cast piece in the lower stage of the mold, suspending the pulling out of the cast piece, then elevating the pouring level of the molten metal up to near the top of the upper stage of the mold, altering the distance between the two lower sections to bring them into correspondence with the upper sections, resuming the pulling-out of the cast piece having the altered dimension after the molten metal in the upper stage of the mold has formed a shell on the outer periphery thereof, and stopping the vibrating of the mold at the latest just before suspending the pulling-out of the cast piece and starting the vibrating of the mold when portions of the cast piece which might be damaged are free of the mold.

8. The method as claimed in claim 7 in which the two upper sections of the side walls are horizontally moved equal distances away from each other to make the distance between them different from that between the corresponding two lower sections of the respective side walls to obtain the desired width in the upper stage of the mold.

9. The method as claimed in claim 7 in which the two upper sections of the side walls are horizontally moved different distances away from each other to make the distance between them different from that between the corresponding two lower sections of the respective side walls to obtain the desired width in the upper stage of the mold.

10. The method as claimed in claim 7 in which only one of the two upper sections of the side walls is horizontally moved to make the distance between the upper sections of the side walls different from that between the corresponding two lower sections of the respective side walls to obtain the desired width in the upper stage of the mold.

11. The method as claimed in claim 7 wherein the water-cooled front wall has upper and lower sections, further comprising the steps of, prior to moving the sections of the side walls, releasing the water-cooled front wall from horizontally press-fixing the water-cooled side walls to a fixed front wall, and releasing the press-fixing of the upper and lower sections of the said water-cooled front wall and then again press-fixing the upper and lower sections of the water-cooled front wall and the side walls to each other and press-fixing the water-cooled side walls between the water cooled front wall and the fixed front wall, after the water-cooled side walls have been moved in a desired amount.

12. The method as claimed in claim 7 wherein the vertical vibrating of the water-cooled casting mold is resumed after the molten metal between the upper side wall sections coagulates sufficiently to withstand pulling-out at the stepped part of the cast piece between the larger dimension between the upper side wall sections and the larger dimension between the loser side wall sections and the lower side wall sections are brought into coincidence with the upper side wall sections.