JPH0999348A - Roll segment device of continuous caster - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce the center segregation in a cast slab by efficiently applying rolling reduction only to an unsolidified part, in a bulging rolling reduction method which can easily and quickly change pushing force and rolling reduction rate to the variations of a casting kind of steel, casting speed and size of the cast slab and uses comparatively small rolling reduction load, at the time of casting under the light rolling reduction. SOLUTION: In a roll segment device 10 provided with plural roll pairs in a frame arranged in the drawing-out direction of the cast slab just a below mold for continuous casting, the segment roll 14 is divided into plural number in the width direction of the cast slab. A hydraulic cylinder 15 is arranged in each divided roll and each divided roll can individually be elevated/lowered. The elevating/lowering position of each divided roll 14 is detected by a positional detector 16 and each hydraulic cylinder 15 is automatically controlled. Only the necessary drawing-out force is given to the solidified part of the cast slab with the end part rolls 14B, 14C and the rolling reduction is efficiently applied to the bulging unsolidified part with the center part roll 14A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roll segment device for guide rolls and pinch rolls arranged in a drawing direction from immediately below a mold of a continuous casting machine to behind a cast piece completely freezing point. The present invention relates to a roll segment device capable of reducing center segregation that occurs at the center of thickness.

[0002]

2. Description of the Related Art In continuous casting, generally, molten steel cast in a mold is primarily cooled by cooling water in the mold to form a solidified shell on an outer shell, which is then secondarily cooled and solidified in a group of guide rolls. Is a method of continuously producing a slab by withdrawing while guiding and supporting the slab with a guide roll group and a pinch roll group, and in the guide roll group and the pinch roll group, a predetermined number of roll pairs are framed. To form a roll segment device, and conventionally, a roll segment device having a structure as shown in FIG. 5 has been used.

In FIG. 5, the roll segment device is
It consists of a fixed lower segment frame 50 as a reference and a movable upper segment frame 51, and each of these frames 50, 51 is provided with a plurality of segment rolls 52, 53, respectively. The upper segment frame 51 is attached to the lower segment frame 50 by the connecting columns 54 arranged at the four corners, and is supported so as to be movable in the thickness direction of the slab, and in the width direction of the slab installed in the upper segment frame 51. The upper and lower roll intervals are set by the pair of hydraulic cylinders 55, and the upper segment roll 53 is pressed against the slab 2.

Further, between the roll chock of the upper segment roll 53 and the upper segment frame 51,
By laying a liner or thin shim plate 56, the amount of light reduction per pair of upper and lower rolls (usually 0.3 to 1.5 m
m)) to enable light pressure casting. Such a structure can be applied only to light reduction casting in which the reduction amount is fixed.

[0005]

However, in the structure of the conventional roll segment device described above, the amount of reduction cannot be changed during the casting because of the adjustment by the shim plate or the like, so that the steel type, the slab width, the cast piece There is a problem that it is not possible to deal with the case where the pressing force, the reduction amount, etc. are changed in accordance with the change in the driving speed.

Further, in continuous casting for preventing the center segregation of the slab, the pressing force in the transverse section of the slab at the final stage of solidification requires a solidified portion at both ends of the slab which is sufficient to produce the required drawing force, and a large reduction force. The pressing force and the amount of reduction of the central unsolidified portion of the slab cannot be optimized, but rather, the central unsolidified portion shows the crown shape of the slab 2 due to the bending of the roll or the frame (Fig. 5).
(See (b)), which is a structure that deteriorates in quality.

More specifically, in continuous casting, an internal defect called center segregation in which the molten steel components such as C, S, P and Mn are positively segregated in the final solidified portion becomes a problem. This center segregation is a particularly serious problem in thick plate materials, and is known to cause a decrease in toughness in the segregation component and hydrogen-induced cracking. Such center segregation causes macroscopically the residual molten steel between dendrite (dendritic) trees at the end of solidification toward the crater end part of the final solidification part due to solidification shrinkage of the molten steel or bulging of the solidification shell. It has been found that this occurs due to migration and local accumulation of concentrated molten steel.

Therefore, as a measure for preventing the center segregation, there is a method of reducing the movement of the residual molten steel or the accumulation of the concentrated molten steel by reducing the vicinity of the crater end by some method using a roll, a mold, or the like. Idea-based methods have been proposed. For example, there are the following methods.

Japanese Unexamined Patent Publication No. 63-252655 (casting method under light pressure) By increasing the amount of secondary cooling water sprayed onto the surface of the slab, the surface temperature of the final solidified portion of the slab is maintained at a temperature of 700 to 800 ° C. Range to suppress bulging between rolls by increasing the thickness of the solidified shell, and further, by applying a rolling force with a strain rate of 0.2 to 0.4% per minute to the slab with a light rolling roll group. It blocks the flow of molten steel and prevents center segregation.

Japanese Unexamined Patent Publication No. 61-42460 (continuous casting method) A dendrite is cut by molten steel flow using an electromagnetic stirrer or an ultrasonic wave applying device installed on the upstream side of the solidification completion point and equiaxed near the crater end. After the crystal zone is formed, a large reduction of 3 mm or more is applied by a pair of reduction rolls arranged at one place immediately before the solidification completion point to forcibly form the solidification completion point and generate internal cracks. The central segregation is eliminated.

JP-A-178355 (continuous casting method) The roll gap in the thickness direction of the slab of the guide rolls arranged immediately below the mold in the drawing direction is gradually increased to cause bulging, thereby increasing the thickness of the slab slab. 2 to the short side of the mold
By increasing the crater end angle to 3 times, the concentrated molten steel can be floated and diffused. Then, by performing a light reduction with a small diameter roll group near the crater end, the concentrated molten steel can be prevented from falling and the center segregation can be prevented. Is being prevented.

In any of these methods, in the structure of the conventional roll segment device, as described above, the pressing force and the reduction amount can be easily adjusted in the light reduction casting with respect to changes in the steel type, the slab width, the casting speed, etc. However, there is a problem that the desired effect cannot be obtained due to the bending of the roll and the frame during the reduction for preventing the center segregation.

The present invention has been made to solve the above-mentioned problems, and its object is to reduce the pressing force and the amount of reduction with respect to changes in casting steel type, casting speed, and slab size during light reduction casting. The roll of the continuous casting machine can change the pressure easily and quickly, and can efficiently reduce only the unsolidified portion in the bulging roll reduction method with a relatively small reduction load, and effectively reduce the center segregation. To provide a segment device.

[0014]

DISCLOSURE OF THE INVENTION The present invention is a roll segment apparatus comprising a plurality of roll pairs arranged in a frame in a continuous casting direction from just below the mold in the cast strip withdrawing direction. It is characterized in that it is divided into a plurality of sections (preferably three sections), and each of these divided rolls is provided with a lifting mechanism (hydraulic cylinder, motor / screw mechanism, etc.) so that each of the divided rolls can be lifted and lowered individually. Such a dividing / elevating roll type roll segment device is used from immediately below the mold to the subsequent stage of the complete solidification point of the slab, that is, the guide roll group, the pressing roll group,
It may be applied to all of the pinch rolls or may be applied only to the reduction rolls.

Further, this roll segment device is provided with a control system for detecting the ascending / descending position of each divided roll and controlling the ascending / descending mechanism of each divided roll based on the ascending / descending position detection signal, enabling remote automatic operation. To do. A stepping cylinder, an operating transformer, a magnetic scale (magnet scale), a pulse generator, a pulse pickup, or the like can be used as a position detector that detects the vertical position of each divided roll.

Further, in the control system, each divided roll in each segment roll (a group of guide rolls, a group of reduction rolls, etc.) has a central portion in the width direction of the cast piece (unsolidified portion of the cast piece) and both ends (solidified portion) in the width direction of the cast piece. The vertical movement amount of each divided roll in each segment roll is automatically controlled so that different pressing force or reduction amount can be applied by and.

Further, in the control system, the interval in the thickness direction of the slab of the segment rolls arranged immediately below the mold in the drawing direction is gradually increased in the slab drawing direction to forcibly bulge the slab center. Immediately before the completion point of the freezing point, the amount of reduction of the segment rolls is controlled so as to reduce the bulging by the pair of segment rolls.
Specifically, the roll interval in the thickness direction of the slab in the guide roll group is gradually increased to generate bulging at a position where the solid fraction (fs) at the center of the slab is 0.1 or less. The maximum thickness of 5-100 from the length of the short side of the mold
mm thick, and 5 mm or more per pair (5 mm to 3 mm) by one or a plurality of pairs of reduction rolls immediately before the completion point of solidification.
A large reduction of 0 mm) is given.

In the roll segment apparatus for continuous casting, the lower segment frame is usually fixed to the foundation to serve as a reference side, and the upper segment frame is movable. Only the upper segment roll serves as a dividing / elevating roll. Is preferred. The lower segment roll may be a single integral / fixed roll or a split / elevation roll.

[0019]

With the above-described structure, the divided rolls in each roll segment device are automatically moved up and down by the elevating mechanism and the position detector during the light reduction casting to give a predetermined light reduction amount. Even if the casting steel type, casting speed, and slab size are changed during casting, the pressing force and the reduction amount can be changed easily and quickly.

In continuous casting for preventing center segregation,
The divided rolls of each roll segment device are automatically set to gradually increase the roll interval in the bulging zone, and are gradually set to gradually reduce the bulging part in the next reduction zone, and a relatively small reduction is performed. The large reduction effectively acts on the unsolidified portion of the slab by the load, whereby the center segregation can be remarkably reduced even to the semi-micro segregation without causing a negative segregation zone. At the same time,
Each split roll is automatically pressed with different pressing force and reduction amount at the center of the slab width direction and at both ends of the slab width direction, and only the required drawing force is applied at the slab coagulation part at both ends of the slab width direction. Can be applied, in the slab non-solidified portion of the slab width direction central portion, it is possible to apply the appropriate amount of reduction necessary for large reduction, like the structure of the conventional roll segment device roll and frame It is possible to efficiently reduce only the unsolidified bulging portion with a relatively small-sized device, and it is possible to effectively eliminate the center segregation.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to an embodiment shown in the drawings. This is an example applied to a curved type continuous casting machine for steel slabs, and FIG. 1 shows an example of a roll segment device according to the present invention. 2 (a),
(B) shows a state in which forced bulging is generated by the roll segment device in FIG. 1 and a state in which the bulging is pressed down at the final stage of solidification. FIG. 3 shows an entire continuous casting machine for carrying out continuous casting using the roll segment device according to the present invention.

In FIG. 3, the molten steel poured into the mold 1 by a ladle, a tundish, and a dipping nozzle forms a solidified shell 2a on the surface of the slab 2 by the primary cooling by the water-cooled mold 1 and the subsequent guide. Solidification is promoted by secondary cooling in the roll group 3 with spray water,
The slab 2 is pulled out while being guided and supported by the guide roll group 3, the pressing roll group 4, and the pinch roll group 5 while holding the unsolidified portion 2b therein.

In such a continuous casting machine, in the present invention, each roll segment device 10 in the guide roll group 3, the reduction roll group 4, and the pinch roll group 5 of FIG. 3 has a structure as shown in FIG. If necessary, the electromagnetic stirrer 6 is installed in the guide roll group 3 at an appropriate position before the solidification point of the slab (see FIG. 3).

In the curved continuous casting machine shown in FIG. 3, the lower segment frame 11 on the outer side of the curve is fixedly arranged on the foundation to serve as the reference side, and the upper segment frame 12 on the inner side of the curve is cast so that the roll gap can be adjusted. As shown in FIG. 1, each upper segment roll 14 arranged in a predetermined number below the upper segment frame 12 in the slab drawing direction is divided into three in the slab width direction. , The divided central roll 14A and the end rolls 14B and 14C at both ends are lifted and lowered by a hydraulic cylinder 15A.
・ 15B and 15C can be moved up and down independently.

Lifting hydraulic cylinders 15A, 15B, 15
A position detector 16 such as a magnetic scale including a detector 16a attached to the cylinder body and a scale 16b attached to a piston rod is attached to C, and the detection signal is input to the control device 17.

The hydraulic pressure control unit 18 is controlled by the control device 17.
By controlling each of the lifting cylinders 15A, 15B, and 15C individually to operate the central roll 14A and the end roll 1.
By 4B and 14C, different pressing force and reduction amount are applied to the central portion (unsolidified portion) in the width direction of the slab and both ends (solidified portion) in the width direction of the slab.

The lower segment frame 11 and the upper segment frame 12 are connected by connecting columns (posts) 19 at their four corners, and a pair is installed in the width direction of the slab at the center of the upper segment frame 12 in the drawing direction. The position of the upper segment frame 12 is adjusted with respect to the lower segment frame 11 by the frame elevating hydraulic cylinder 20, whereby the upper and lower roll intervals are initially set according to the thickness of the slab. In each of the lifting hydraulic cylinders 15A, 15B, and 15C, the cylinder body is fixed to the upper surface of the upper segment frame 12 via the mounting member 21, and the support bracket 2 is attached to the tip of the piston rod.
2 is attached, and each divided roll 15 is attached to this support bracket 22 via a roll chock 23.

Further, the control device 17 is provided with a CPU, processing software, etc., and cast steel type, casting speed, slab size (thickness, width) input from a process computer or the like.
Based on the above, the ascending / descending amount by the ascending / descending cylinders 15A, 15B, and 15C in each roll segment device 10 is calculated, and the result of this calculation is compared with the detection value of each position detector 16 to perform feedback control, Elevating cylinders 15A-1 in the roll segment device 10
Automatically controls the pressing force and amount of reduction by 5B and 15C. The end rolls 14B and 14C have a pressing force so that only the necessary pulling force is obtained, and the central roll 14
In A, the pressing force or the reduction amount is set so that the bulging is properly maintained or a large reduction amount described later for reducing the center segregation is obtained.

When performing light reduction casting, each roll segment device 10 controls the lifting cylinders 15A, 15B and 15C so that the light reduction amount per pair of the lower and upper rolls 13 and 14 becomes a predetermined amount. To do. Cast steel type
Even if the casting speed and the slab size (thickness / width) are changed midway, it is possible to respond easily and quickly.

When performing continuous casting by bulging / rolling roll reduction to reduce center segregation, it is performed as follows.

(1) After adjusting the position of the upper segment frame 11 according to the thickness of the cast piece, the intervals between all the upper and lower rolls 13 and 14 are initialized, and then the upper and lower rolls 13 of the guide roll group 3 are set. The bulging zone Z ₁ is formed when the solid phase ratio (fs) of the central portion of the cast slab 2 is within the range of 0.1 by gradually increasing the interval of 14. In particular,
When the roll interval in the slab thickness direction immediately below the mold is α,
The roll interval β at the end of the bulging zone Z ₁ is α
+ (20 to 100) mm (see FIG. 3).

Here, the reason that the range of the bulging zone Z _{1 is} the region where the (fs) at the center of the slab has a solid fraction of 0.1 or less is to prevent deterioration of center segregation due to bulging at the end of solidification. . That is, when the bulging was carried out at a position where the solid fraction in the center of the slab was larger than 0.1, the concentrated molten steel was sucked in, and the segregation and the porosity were locally deteriorated. Is.
Further, if the roll interval β is less than α + 20 mm, the unsolidified region to be rolled down by the rolling roll group 4 described later is insufficient, and if it is greater than α + 100 mm, it is necessary to prevent the occurrence of internal cracks in the bulging zone Z ₁ . It becomes difficult to set the roll interval.

Furthermore, such upper and lower rolls 13
・ At the same time as gradually increasing the interval of 14 in the slab drawing direction, as shown in FIG.
The central roll 14A of the end roll 14B
Increase above C. As a result, the end rolls 14B and 14C that are pressed against the solidified portion of the slab can apply only the required predetermined drawing force to the slab 2, and the central roll 14A that is pressed against the unsolidified portion of the slab prevents bulging. It can be controlled easily and properly.

(2) Next, before the solidification completion point of the slab 2,
That is, ₂ in each of the pair of upper and lower rolls in the reduction zone Z ₂ .
A large reduction of 0 mm or more is applied to reduce the bulging. By pressing down the bulging component with the pressing roll group 3 in the vicinity of the solidification completion point of the slab, the solidification interface becomes a compressive stress field, so that the solidification interface is not cracked and the central part of The center segregation including the semi-micro segregation is effectively improved by a relatively simple equipment without forming a negative segregation zone.

In the conventional roll reduction method, it is considered that the reduction amount cannot be more than a certain value because of the fear of cracking at the solidification interface by increasing the reduction amount. Although it was limited to a light reduction that compensates for the reduction, if the amount of reduction is further increased, the solidification interface becomes an extension state, but it is rather compressed because it is constrained in the casting direction in terms of stress,
Almost no cracks occur.

At this time, it was experimentally clarified that the required amount of reduction per pair of upper and lower rolls is 20 mm or more, and it is not always necessary to forcibly form the solidification completion point.

A considerable amount of rolling force is required for rolling down to the point where the solidification completion point is forcibly formed, and especially for large slabs, the rolling down device for that purpose is too large to be industrially practical. Therefore, in order to reduce the diameter of the pressing roll and downsize the pressing device, it is preferable to perform the pressing so that the solidification completion point is not forcibly formed.

According to the bulging-roll reduction method of the present invention, since the bulging portion in the bulging zone is reduced, it is not necessary to plastically deform the solidified portions at both ends of the slab having a large deformation resistance by the reduction, and the center segregation occurs. From the viewpoint of prevention, the position of the unsolidified portion that needs to be rolled down can be exposed by bulging, and that portion can be effectively rolled down, and a large reduction is effectively applied to the unsolidified portion with a relatively small rolling load. Can be made.

Further, according to the dividing / elevating rolls of the present invention, in the pressing roll group 4, the end rolls 14B and 14C at both ends of the upper roll 14 are pressed against the solidified portions at both ends of the cast slab, and the central roll 14A ends. The central roll 14A is gradually lowered from the state in which it is raised above the partial rolls 14B and 14C so that the rolling amount of each central roll 14A is 20 mm or more, and the bulging portion is gradually reduced. As a result, the end roll 14B pressed against the solidified portion of the slab
14C makes it possible to apply only the required predetermined drawing force to the slab 2, and the central roll 14A can efficiently reduce only the unsolidified part of the slab.

This bulging is a phenomenon that occurs only in the slab where the static pressure of molten steel acts and there is an unsolidified portion. Due to the flow of the unsolidified portion and variations in secondary cooling, the unsolidified portion, That is, the bulging may not always be in the center of the slab width direction. In this case, the unsolidified portion in the widthwise center of the slab is locally rolled down by a camel crown roll (a stepped roll having a large diameter roll portion in the center in a protruding shape) (JP-A-61-161). In Japanese Patent No. 132247), the unsolidified position and the position of the large-diameter roll portion do not coincide with each other, which causes a problem that the reduction position cannot be properly maintained. Further, a local depression causes a recess to be formed on the surface of the slab, which causes a surface flaw of the product in the subsequent rolling step. On the other hand, in the present invention, since it is a flat roll, only the non-solidified region can be effectively reduced, and the surface flaw of the product can be prevented.

(3) The solidified structure at the center of the slab 2 is usually
Although it has a columnar crystal structure, equiaxed crystals may be generated in the central portion by adding electromagnetic stirring by the electromagnetic stirring device 6 before the solidification completion point. In the case of a columnar crystal structure, the effect of locally improving segregation may be reduced by bridging, whereas in the case of an equiaxed crystal structure, molten steel flow is likely to occur due to rolling and local accumulation of concentrated molten steel is prevented. To be done. As a method of generating equiaxed crystals, it is not always necessary to use electromagnetic stirring, for example, a method of applying ultrasonic waves to a slab via a roll may be used, and in addition to low-temperature casting and casting in a mold in consideration of operation. It may be added with steel wire.

Next, specific numerical examples will be described.
This is an example of using the roll segment device 10 of FIG. 1 in the continuous casting machine of FIG. 3, and is shown in Table 1 (A),
Continuous casting was performed under the three conditions of (B) and (C). In the case of the conventional method (A) in which the central part of the slab is made equiaxed by electromagnetic stirring without bulging, and then the roll is subjected to large rolling reduction, bulging is performed by 20 mm and the central part of the slab is made equiaxed by electromagnetic stirring. In the case of the present invention (B) in which large roll reduction is performed, 100 mm bulging was performed, and after the central portion of the slab was made to be an equiaxed crystal by electromagnetic stirring, the case of the present invention (C) in which large roll reduction was performed was compared.

[0043]

[Table 1]

For evaluation, the produced slab was cut at a cross section perpendicular to the casting direction, a test piece was sampled from the center of the slab in the thickness direction, and the surface of this sample was divided into meshes having a roughness of 200 μm. The average concentration of [P] in the steel was investigated, and the segregation degree was investigated by comparing with the [P] concentration Po of the mother molten steel. FIG. 4A shows the maximum segregation degree (P / Po) max of [P] as a result of this segregation degree examination. Further, FIG. 4B shows the relationship between the semi-macro segregated grain size and the number of segregated grains in the case where (P / Po) is 3 or more.

As is apparent from FIG. 4, in Examples B and C of the present invention, the bulge was not solidified by performing appropriate bulging at an appropriate position to expose the unsolidified region and further applying a reduction by a roll. The reduction in the area can be effectively performed, and the center segregation is significantly improved as compared with Comparative Conventional Example A.

[0046]

As described above, in the roll segment device according to the present invention, the segment roll is divided into a plurality of pieces in the width direction of the cast piece, and the divided rolls are individually automatically raised and lowered by the elevating mechanism and the position detector. Since different pressing forces and different amounts of reduction can be applied to the widthwise central portion and both end portions, the following effects are achieved.

(1) When performing light reduction casting or the like, even if the casting steel type, casting speed, or slab size is changed, the pressing force and the reduction amount can be changed easily and quickly, resulting in work efficiency and production. It is possible to significantly improve the property and reduce the cost.

(2) In continuous casting to reduce center segregation,
By the bulging roll reduction method, a large reduction can be effectively applied to the unsolidified portion with a relatively small reduction load,
Furthermore, the split rolls can efficiently reduce only the unsolidified portion without the conventional roll or frame deflection, and can significantly reduce the central segregation to the semi-micro segregation without causing a negative segregation zone. .

(3) The apparatus can be downsized as compared with the conventional large-pressure reduction roll method, and since only the necessary parts are reduced by the dividing rolls, the elevating mechanism can be downsized and the equipment can be relatively inexpensive. it can.

[Brief description of drawings]

FIG. 1 is a front view showing an example of a roll segment device of a continuous casting machine according to the present invention.

2 (a) is a front view showing a state in which forced bulging is generated in the roll segment device of FIG. 1, (b).
[Fig. 3] is a front view showing a state in which bulging is pressed down at the end of coagulation.

FIG. 3 is a vertical cross-sectional view showing an entire continuous casting machine for carrying out continuous casting using roll segments according to the present invention.

FIG. 4 (a) is a graph comparing macro segregation between a conventional method and the present invention, and FIG. 4 (b) is a graph comparing semi-macro segregation between the conventional method and the present invention.

FIG. 5 shows a roll segment of a conventional continuous casting machine,
(A) is a side view and (b) is a front view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Mold 2 ... Cast piece, 2a ... Solidified shell, 2b ... Unsolidified part 3 ... Guide roll group 4 ... Reduction roll group 5 ... Pinch roll group 6 ... Electromagnetic stirrer 10 ... Roll segment device 11 ... Lower segment frame 12 ... Upper segment frame 13 ... Lower segment roll 14 ... Upper segment roll 14A ... Central roll, 14B, 14C ... End roll 15 ... Lifting hydraulic cylinder 16 ... Position detector 17 ... Control device 18 ... Hydraulic control unit

Claims (4)

[Claims] 1. A roll segment device comprising a plurality of roll pairs arranged in a frame in a continuous direction from a position immediately below a mold in a cast strip withdrawing direction, wherein a segment roll is divided into a plurality of pieces in the width direction of the cast piece, and each of these divisions is divided. A roll segment device for a continuous casting machine, wherein each roll is provided with an elevating mechanism so that each divided roll can be individually elevated. 2. A roll segment device for a continuous casting machine according to claim 1, further comprising: a control system for detecting an ascending / descending position of each divided roll and controlling an ascending / descending mechanism of each divided roll based on the ascending / descending position detection signal. A roll segment device for a continuous casting machine, which is characterized by being provided. 3. The roll segment apparatus for a continuous casting machine according to claim 2, wherein the control system is configured such that each division roll of each segment roll has different pressing force at the center portion in the width direction of the cast piece and at both ends in the width direction of the cast piece. A roll segment device for a continuous casting machine, characterized in that the vertical movement amount of each divided roll in each segment roll is automatically controlled so that a reduction amount can be applied. 4. The roll segment device for a continuous casting machine according to claim 3, wherein the control system gradually changes the interval in the thickness direction of the cast pieces of the segment rolls arranged in the pulling direction from directly below the mold in the cast drawing direction. The continuous casting machine is characterized in that the central part of the slab is forcibly bulging and the rolling amount of the segment rolls is controlled so as to roll down the bulging by at least one pair of segment rolls just before the freezing point completion point. Roll segment equipment.