US20180161837A1

US20180161837A1 - Continuous casting and rolling method and continuous casting and rolling apparatus

Info

Publication number: US20180161837A1
Application number: US15/578,520
Authority: US
Inventors: Young-Ju KO; Jea-Sook CHUNG; Suk-Cheol SONG; Kyeong-Mi PARK; Yong-Seok Cho; Young-Sup Shim
Original assignee: Posco Co Ltd
Current assignee: Posco Holdings Inc
Priority date: 2015-06-03
Filing date: 2015-09-18
Publication date: 2018-06-14
Also published as: JP2018516757A; WO2016195169A1; CN107666973A; CN107666973B; JP6511163B2; KR20160142931A; KR101736573B1

Abstract

Provided is a continuous casting and rolling method, which includes: a continuous casting operation of producing a slab; and a rolling operation of pressing the slab after a front end portion of the slab passes a first rolling stand into which the front end portion of the slab, which is provided as a continuous body to the slab produced in the continuous casting operation, initially enters.

Description

TECHNICAL FIELD

The present disclosure relates to a continuous casting and rolling method and to a continuous casting and rolling apparatus, and more particularly, to an invention for preventing a problem in which a slab moves backwards during a process of performing continuous casting and rolling.

BACKGROUND ART

A process of performing rolling using a high temperature slab solidified in a continuous caster is widely used at present, because equipment costs and operating costs are lower than a process according to the related art.
In addition, while continuous casting and rolling are continuously undertaken, it is also possible to carry out a discontinuous process in which rolling can be carried out separately from the continuous casting, described in Korean Patent Application Laid-open Publication No. 1990-7001437, in detail.
In other words, each of a continuous rolling mode, in which a continuous casting process and a rolling process are continuously performed, and a discontinuous rolling mode, in which the continuous casting process and the rolling process are discontinuously performed, may be carried out.
Here, FIG. 1 illustrates an apparatus 1′ capable of performing continuous rolling. When a slab 2′, having a constant thickness, is produced in a continuous caster 10′, the slab 2′ is rolled in a rolling mill 20′. Additionally, the slab 2′ is heated by a heater 40′ and is then rolled. The slab 2′, in which rolling is finished, is cut by a cutter 30′ and wound by a winder, so that a product is produced therefrom.
However, here, when a front end portion of the slab 2′ preceding the slab 2′, discharged from the continuous caster 10′, is input into the rolling mill 20′ and is reduced, the front end portion of the slab 2′ is input and reduced without tension, so a problem in which backward force in a direction of the continuous caster 10′ may occur.
This backward force may affect a level of a surface of molten steel in the continuous caster 10′, and may affects the entirety of equipment, so there may be limitations in securing product quality.
Thus, there has been a need for research into a continuous casting and rolling method and a continuous casting and rolling apparatus able to solve the above-mentioned problem.

DISCLOSURE

Technical Problem

An aspect of the present disclosure may provide a continuous casting and rolling method and a continuous casting and rolling apparatus, capable of preventing a problem in which a slab moves backwards when a front end portion of the slab, produced in a continuous caster, is input into a rolling mill.

Technical Solution

According to an aspect of the present disclosure, a continuous casting and rolling method includes: a continuous casting operation of producing a slab; and a rolling operation of reducing the slab after a front end portion of the slab passes a first rolling stand into which the front end portion of the slab, which is provided as a continuous body with the slab produced in the continuous casting operation, initially enters.
In the rolling operation, the slab is reduced, after the front end portion of the slab passes a rolling mill, a group of a plurality of rolling stands including the first rolling stand.
The rolling operation includes: an inputting operation of passing the front end portion of the slab through the first rolling stand, which is open; a supporting operation of allowing a pair of rolling rolls, provided in the first rolling stand after the front end portion of the slab passes the first rolling stand, to be in close contact with the slab; and a reducing operation of reducing the slab with the second rolling stand, when the front end portion of the slab enters a second rolling stand provided after the first rolling stand.
The rolling operation includes: an inputting operation of passing the front end portion of the slab through the first rolling stand, which is open; a reducing operation of reducing the slab with the second rolling stand, when the front end portion of the slab enters a second rolling stand provided after the first rolling stand; and a buffering operation of moving a pair of rolling rolls provided in the first rolling stand upwardly or downwardly, or moving a pair of pinch rolls provided in an inlet of the first rolling stand upwardly or downwardly, when a portion of the slab, having been reduced, moves backwards to the first rolling stand.
In the rolling operation, a pair of rolling rolls, provided in each of a plurality of rolling stands including the first rolling stand, sequentially roll the slab while a distance is gradually reduced in a direction of progress of the slab.
A continuous casting and rolling apparatus includes: a continuous caster for producing a slab; and a rolling mill located at an outlet of the continuous caster, and having a plurality of rolling stands including a first rolling stand into which a front end portion of the slab, provided as a continuous body with the slab produced in the continuous caster, initially enters, wherein the rolling mill is provided to reduce the slab after the front end portion of the slab passes the first rolling stand.
The rolling mill includes: a support point determining sensor provided at an outlet of the first rolling stand, and sensing the front end portion of the slab; and a reducing point determining sensor provided in an inlet of a second rolling stand provided after the first rolling stand, and sensing the front end portion of the slab.

Advantageous Effects

According to an exemplary embodiment in the present disclosure, in a continuous casting and rolling method and a continuous casting and rolling apparatus, when a front end portion of a slab is rolled, the slab may be prevented from moving backwards.
Thus, there is an advantage that a level of a surface of molten steel in a continuous caster may be stabilized and an influence on other apparatuses may be prevented.
Thus, continuity in a process of continuous casting and rolling may be ensured, and a quality of a rolled product to be produced may be improved.

DESCRIPTION OF DRAWINGS

FIG. 1 is a view illustrating a continuous casting and rolling apparatus according to the related art.

FIG. 2 is a side view illustrating a continuous casting and rolling apparatus according to an exemplary embodiment.

FIG. 3 is a side view illustrating an example of a case in which a front end portion of a slab is input into a rolling mill in a continuous casting and rolling apparatus according to an exemplary embodiment.

FIG. 4 is a side view illustrating another example of a case in which a front end portion of a slab is input into a rolling mill in a continuous casting and rolling apparatus according to an exemplary embodiment.

FIG. 5 is a flow diagram illustrating a continuous casting and rolling method according to an exemplary embodiment.

FIG. 6 is a flow diagram illustrating one example of a rolling operation in a continuous casting and rolling method according to an exemplary embodiment.

FIG. 7 is a flow diagram illustrating another example of a rolling operation in a continuous casting and rolling method according to an exemplary embodiment.

BEST MODE FOR INVENTION

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Meanwhile, the spirit of the present invention is not limited to the suggested embodiments, and those skilled in the art to which the present invention pertains could easily suggest a further retrogressive invention or another embodiment which falls within the spirit of the present invention through the addition, modification, and deletion of another component without departing from the spirit of the present invention.
In the following description, components having the same function within the same scope illustrated in the drawings of the embodiments are illustrated using the same reference numerals.
A continuous casting and rolling method and a continuous casting and rolling apparatus 1 according to an exemplary embodiment relate to the invention for preventing a problem in which a slab 2 moves backwards during a process of performing continuous casting and rolling.
In other words, according to the continuous casting and rolling method and the continuous casting and rolling apparatus 1 according to an exemplary embodiment, when a front end portion 2 a of the slab 2 is rolled, the slab 2 is prevented from moving backwards, so a level of molten metal of a continuous caster 10 is stabilized and an effect on other devices is prevented. Thus, continuity of a process for continuous casting and rolling may be ensured and a quality of a rolled product having been produced may be improved.
In detail, FIG. 2 is a side view illustrating a continuous casting and rolling apparatus 1 according to an exemplary embodiment. Referring thereto, a continuous casting and rolling apparatus 1 according to another exemplary embodiment includes a continuous caster 10 of producing a slab 2, and a rolling mill 20 located at an outlet of the continuous caster 10, and having a plurality of rolling stands including a first rolling stand 21 into which a front end portion 2 a of the slab 2, which is provided as a continuous body with the slab 2 produced in the continuous caster 10, initially enters. The rolling mill 20 may be provided to reduce the slab 2 after the front end portion 2 a of the slab 2 passes the first rolling stand 21.
In addition, the rolling mill 20 of the continuous casting and rolling apparatus 1 according to another exemplary embodiment may include a support point determining sensor 23 provided at an outlet of the first rolling stand 21, and sensing the front end portion 2 a of the slab 2, and a reducing point determining sensor 24 provided in an inlet of a second rolling stand 22 provided after the first rolling stand 21, and sensing the front end portion 2 a of the slab 2.
In other words, as a configuration for solving a problem, in which backward force is generated while a thickness of the slab 2 is reduced, when the front end portion 2 a of the slab 2 is reduced, the continuous caster 10, the rolling mill 20, and the like are proposed.
The continuous caster 10 may serve to produce the slab 2 from molten steel through a casting process. In other words, the continuous caster 10 supplies molten steel from a tundish to a mold, and the slab 2 is formed from the molten steel, having been supplied, while a certain amount of heat is removed therefrom. The slab 2 is guided by a segment roll and a pinch roll, moves, and is supplied to the rolling mill 20, which will be described later.
However, as the continuous caster 10 produces the slab 2, depending on a solidification rate of the molten steel, there may be limitations in controlling a production speed. In this case, producing a product by continuously receiving the slab 2 produced in the continuous caster 10 and reducing the slab using the rolling mill 20 which will be described later is limited in terms of speed.
However, as an average temperature of the slab 2 discharged from the continuous caster 10 is high, there is an advantage in which a temperature required during a rolling operation in the rolling mill 20 may be secured, to a certain extent.
The rolling mill 20 may serve to produce a rolled steel sheet by receiving the slab 2 produced in the continuous caster 10 and reducing the slab. To this end, the rolling mill 20 may allow the slab 2 to pass between a pair of rolling rolls and to be reduced, and a rolling stand to which the pair of rolling rolls are provided may be provided in plural.
Here, when the slab 2 produced in the continuous caster 10 is continuously received, and reducing is performed by the rolling mill 20, while tension is not maintained, of the front end portion 2 a of the slab 2 is input into the first rolling stand 21, an initial rolling stand, so backward force causing the slab to move toward the continuous caster 10 may be generated.
In other words, when the slab 2 is reduced, while a thickness of the slab 2 is reduced, a length is increased. An elongated portion is provided while a length is increased in a direction of progress of the slab 2. However, an elongated portion may be provided while a length is increased in an opposite direction to the direction of progress of the slab 2, so a problem in which backward force causing the slab 2 to move toward the continuous caster 10 may occur.
In order to solve the problem described above, in an exemplary embodiment, after the front end portion 2 a of the slab 2 passes the first rolling stand 21, reducing with respect to the slab 2 is performed, so backward force may be prevented from being exerted on the slab 2.
In other words, the slab 2 passing the first rolling stand 21 is pushed by other rolling stands such as the second rolling stand 22 provided after the first rolling stand 21, and the like. Thus, when the front end portion 2 a of the slab 2 in which tension is not maintained is reduced, a portion of the slab 2, located after the front end portion 2 a, supports that the slab 2 is pushed backwards.
In other words, a portion of the front end portion 2 a of the slab 2, a free end which is not fixed, moves forward in a direction of progress of the slab 2 in order to accommodate a portion in which a length is increased due to reducing, and portions located after the front end portion 2 a of the slab 2 reduced and held by the rolling stands, functioning as a fixed end, may not accommodate a portion of the slab 2, in which a length is increased, but may support that the slab 2 is pushed backwards.
Moreover, the rolling mill 20 includes the support point determining sensor 23, the reducing point determining sensor 24, and the like, thereby further increasing efficiency of preventing backward force from being generated when the front end portion 2 a of the slab 2 is reduced.
In other words, so that the first rolling stand 21 is provided to perform only a role of supporting that the slab 2 moves backwards, in addition to a role of reducing, for a period of time, the first rolling stand includes the support point determining sensor 23 and the reducing point determining sensor 24.
In other words, it is advantageous to perform reducing with respect to the slab 2 at a point as early as possible in order to improve yield percentage. In this regard, in order to perform a reducing operation from a point in which the front end portion 2 a of the slab 2 is input into the second rolling stand 22, the support point determining sensor 23 and the reducing point determining sensor 24 are included.
The support point determining sensor 23 is a sensor, provided at an outlet of the first rolling stand 21, discharging the slab 2 from the first rolling stand 21, and sensing a point at which the front end portion 2 a of the slab 2 passes the first rolling stand 21.
Here, when the support point determining sensor 23 senses the front end portion 2 a of the slab 2, a pair of rolling rolls 21 a provided in the first rolling stand 21 are provided to be in close contact with the slab 2, thereby preventing the slab 2 from being pushed backwards.
Thereafter, when the reducing point determining sensor 24 senses the front end portion 2 a of the slab 2, reducing is performed and a rolling operation is then performed.
The reducing point determining sensor 24 is a sensor, provided in an inlet of the second rolling stand 22, in which the slab 2 enters the second rolling stand 22, and sensing a point in which the front end portion 2 a of the slab 2 enters the second rolling stand 22.
Here, when the reducing point determining sensor 24 senses the front end portion 2 a of the slab 2, the second rolling stand 22 allows the slab 2 to be reduced, thereby performing a rolling operation.
In detail, in this case, the first rolling stand 21 is in close contact with the slab 2 to support that the slab 2 is pushed backwards. Thus, a portion of the slab 2, in which a length is increased when the slab is reduced in the second rolling stand 22, is provided to move forward without being pushed backwards.
In addition, the continuous casting and rolling apparatus 1 according to an exemplary embodiment may further include a cutter 30, a heater 40, and the like, and a continuous casting and rolling process may be performed.
Here, the heater 40 serves to heat the slab 2 when a temperature of the slab 2 does not reach a temperature for rolling, before the slab 2, produced and provided in the continuous caster 10, is supplied to the rolling mill 20.
The cutter 30 may serve to cut the slab 2, or may be provided to cut the slab 2 as needed in a middle portion of the continuous casting and rolling apparatus 1, in order to discharge a product finished by reducing the slab 2.
FIG. 5 is a flow diagram illustrating a continuous casting and rolling method according to an exemplary embodiment. Referring to this, a continuous casting and rolling method according to an exemplary embodiment may include a continuous casting operation of producing the slab 2, and a rolling operation or reducing the slab 2 after the front end portion 2 a of the slab 2 passes the first rolling stand 21 into which the front end portion 2 a of the slab 2, which is provided as a continuous body with the slab 2 produced in the continuous casting operation, initially enters.
In addition, in the rolling operation of the continuous casting and rolling method according to an exemplary embodiment, the rolling mill 20, a group of a plurality of rolling stands including the first rolling stand 21 allows the slab 2 to be reduced, after the front end portion 2 a of the slab 2 passes.
In addition, in the rolling operation of the continuous casting and rolling method according to an exemplary embodiment, a pair of rolling rolls, provided in each of a plurality of rolling stands, including the first rolling stand 21, allow the slab 2 to be sequentially rolled, while a distance is gradually reduced in a direction of progress of the slab 2.
In other words, when the front end portion 2 a of the slab 2 is reduced, in order to prevent a problem in which backward force is generated while a thickness of the slab 2 is reduced is prevented from occurring, a continuous casting operation and a rolling operation are proposed.
The continuous casting operation is an operation of producing the slab 2 by the continuous caster 10, and molten steel is received and the slab 2 is formed by continuous casting. In this case, the rolling operation is performed as the front end portion 2 a of the slab 2, generated at the beginning of the continuous casting operation, is input into the rolling mill 20.
The rolling operation is an operation of producing a rolled steel sheet product by receiving the slab 2 produced in the continuous casting operation and reducing the slab.
Here, at the beginning of performing reducing with respect to the slab 2, as the front end portion 2 a of the slab 2 is input into the first rolling stand, an initial rolling stand, while tension is not maintained, a problem in which backward force, causing the slab to move toward the continuous caster, is generated, is described previously.
In an exemplary embodiment, in order to solve the problem described above, in the rolling operation, after the front end portion 2 a of the slab 2 passes through the first rolling stand 21, reducing with respect to the slab 2 is performed, in order to prevent backward force of the slab 2 from being generated.
In other words, the slab 2 passing through the first rolling stand 21 is pushed by other rolling stands such as the second rolling stand 22 provided after the first rolling stand 21, and the like. Thus, when the front end portion 2 a of the slab 2 in which tension is not maintained is reduced, while a portion of the slab 2, located after the front end portion 2 a, supports that the slab 2 is pushed backwards, a rolling operation is performed.
In this regard, the rolling operation is performed so that a portion of the front end portion 2 a of the slab 2, a free end which is not fixed, moves forward in a direction of progress of the slab 2 in order to accommodate a portion in which a length is increased due to reducing, and portions located after the front end portion 2 a of the slab 2 pushed by the rolling stands function as a fixed end to support a portion of the slab 2 in which a length is increased.
Moreover, when reducing with respect to the slab 2 is performed after the front end portion 2 a of the slab 2 is discharged from the rolling mill 20, while reducing with respect to the front end portion 2 a of the slab 2 is not performed, only reducing with respect to a portion located after the front end portion 2 a of the slab 2 is performed. Thus, reducing is performed with respect to the slab 2 while tension is maintained, so a problem in which the slab 2 is pushed backwards due to reducing may be prevented.
In addition, sequential rolling with respect to the front end portion 2 a of the slab 2 is performed. Thus, when the slab 2 is reduced, backward force may be prevented from occurring in the slab 2.
In other words, in a plurality of rolling stands included in the rolling mill 20, a distance between a pair of rolling rolls is provided to be gradually reduced in a direction of progress of the slab 2. Thus, sequential rolling is performed with respect to the slab 2, so the slab 2 maybe prevented from moving backwards.
(a) through (d) of FIG. 3 are side views illustrating one example of a case in which the front end portion 2 a of the slab 2 is input into the rolling mill 20 in the continuous casting and rolling apparatus 1 according to an exemplary embodiment, and FIG. 6 is a flow diagram illustrating one example of a rolling operation in a continuous casting and rolling method according to an exemplary embodiment.
Here, (a) of FIG. 3 illustrates a state before the front end portion 2 a of the slab 2 enters the rolling mill 20, (b) of FIG. 3 illustrates an inputting operation, a state in which the front end portion 2 a of the slab 2 enters the first rolling stand 21, (c) of FIG. 3 illustrates a state in which a supporting operation is performed as the front end portion 2 a of the slab 2 passes the first rolling stand 21, and (d) of FIG. 3 illustrates a reducing operation in which the front end portion 2 a of the slab 2 enters the second rolling stand 22 to be reduced.
Referring to (a) through (d) of FIG. 3 and FIG. 6, the rolling operation of a continuous casting and rolling method according to an exemplary embodiment includes an inputting operation of allowing the front end portion 2 a of the slab 2 to pass through the first rolling stand 21, which is open, a supporting operation of allowing the pair of rolling rolls 21 a provided in the first rolling stand 21 after the front end portion 2 a of the slab 2 passes the first rolling stand 21 to be in close contact with the slab 2, and a reducing operation of reducing the slab 2 by the second rolling stand 22, when the front end portion 2 a of the slab 2 enters the second rolling stand 22 provided after the first rolling stand 21.
In other words, as one example of a specific operation of the rolling operation, an inputting operation, a supporting operation, a reducing operation, and the like may be sequentially provided.
The inputting operation is an operation of allowing the front end portion 2 a of the slab 2 to pass while the first rolling stand 21 is open. In other words, when reducing with respect to the front end portion 2 a of the slab 2 is performed from the first rolling stand 21, the slab 2 is not prevented from moving backwards. Thus, the pair of rolling rolls are positioned while a distance between the pair of rolling rolls 21 a provided in the first rolling stand is set to be greater than a thickness the slab 2.
The supporting operation is an operation of preventing backward force from being generated by supporting the slab 2 when the slab 2 is reduced in a subsequent reducing operation.
In other words, after the front end portion 2 a of the slab 2 passes the first rolling stand 21, the pair of rolling rolls 21 a, provided in the first rolling stand 21, are provided to be in close contact with the slab 2, so the slab 2 is held thereby and is not pushed backwards.
In this case, a case in which the pair of rolling rolls 21 a are in close contact with the slab 2 refers to that the pair of rolling rolls are provided to move in a direction of a position of the slab 2 with applied force sufficient to hold the slab 2 rather than applied force sufficient to reduce the slab 2.
In other words, a width of the pair of rolling rolls 21 a provided in the first rolling stand 21 may be provided to a degree corresponding to a thickness of the slab 2.
The reducing operation is an operation of performing a rolling operation by reducing the slab 2 using a pair of rolling rolls provided in the second rolling stand 22, when the front end portion 2 a of the slab 2 enters the second rolling stand 22.
In this case, the applied force with which the pair of rolling rolls of the second rolling stand 22 reduces the slab 2 may not be greater than a force with which the first rolling stand 21 reduces the slab 2 as described previously, and a distance between the pair of rolling rolls of the second rolling stand 22 may be smaller than a distance between a pair of rolling rolls provided in the first rolling stand 21.
As described above, a portion in which a length is increased and which is generated by reducing the slab 2 in the reducing operation moves not backward but forward due to supporting operation.
FIG. 4 is a side view illustrating another example of a case in which the front end portion 2 a of the slab 2 is input into the rolling mill 20 in the continuous casting and rolling apparatus 1 according to an exemplary embodiment, and FIG. 7 is a flow diagram illustrating another example of a rolling operation in a continuous casting and rolling method according to an exemplary embodiment.
Referring to FIGS. 4 and 7, the rolling operation of a continuous casting and rolling method according to an exemplary embodiment includes an inputting operation of allowing the front end portion 2 a of the slab 2 to pass through the first rolling stand 21, which is open, a reducing operation of reducing the slab 2 by the second rolling stand 22, when the front end portion 2 a of the slab 2 enters the second rolling stand 22 provided after the first rolling stand 21, and a buffering operation of allowing a pair of rolling rolls 21 a provided in the first rolling stand 21 to move upwardly or downwardly, or allowing a pair of pinch rolls provided to an inlet of the first rolling stand to move upwardly or downwardly, when a portion of the slab 2, having been reduced, moves backwards to the first rolling stand 21.
In other words, as another example of a specific operation of the rolling operation, an inputting operation, a reducing operation, a buffering operation, and the like may be sequentially provided.
The inputting operation is an operation of allowing the front end portion 2 a of the slab 2 to pass while the first rolling stand 21 is open, and is the same as described above.
The reducing operation is an operation of operating a rolling operation by reducing the slab 2 by a pair of rolling rolls provided in the second rolling stand 22, when the front end portion 2 a of the slab 2 enters the second rolling stand 22.
In this case, as the slab 2 is reduced, depending on a thickness of the slab 2, having been reduced, the slab 2 is increased. Thus, a portion in which a length is increased may be generated. The portion in which a length is increased may include not only a portion moving forward in a direction in which the slab 2 enters the rolling mill 20, but also a portion moving backwards in a direction of the continuous caster 10.
The portion, moving backwards, is counterbalanced by a buffering operation which will be described later, so it is prevented from affecting the continuous caster 10, and the like.
The buffering operation is an operation of absorbing backward force generated in the reducing operation. In other words, the slab 2 is moved by the pair of rolling rolls 21 a, provided in a rolling stand, in a direction perpendicular to a direction in which the slab enters the rolling mill 20, so a portion in which a length is increased and which is generated in the reducing operation may be accommodated.
Here, the region in the direction perpendicular thereto refers to a region in an upward direction or in a downward direction of a direction in which the slab 2 enters the rolling mill 20.
Similarly, in the buffering operation, pinch rolls are provided separately from the pair of rolling rolls 20 a. Thus, it is not the rolling rolls 20 a that are moved in the region in a perpendicular direction, but the pinch rolls. Thus, a portion in which a length is increased and which is generated in the reducing operation may be accommodated.

Claims

1. A continuous casting and rolling method, comprising:

a continuous casting operation of producing a slab; and

a rolling operation of reducing the slab after a front end portion of the slab passes a first rolling stand into which the front end portion of the slab, which is provided as a continuous body with the slab produced in the continuous casting operation, initially enters.

2. The continuous casting and rolling method of claim 1, wherein, in the rolling operation, the slab is reduced, after the front end portion of the slab passes a rolling mill, a group of a plurality of rolling stands including the first rolling stand.

3. The continuous casting and rolling method of claim 1, wherein the rolling operation includes:

an inputting operation of passing the front end portion of the slab through the first rolling stand, which is open;

a supporting operation of allowing a pair of rolling rolls, provided in the first rolling stand after the front end portion of the slab passes the first rolling stand, to be in close contact with the slab; and

a reducing operation of reducing the slab with the second rolling stand, when the front end portion of the slab enters a second rolling stand provided after the first rolling stand.

4. The continuous casting and rolling method of claim 1, wherein the rolling operation includes:

a reducing operation of reducing the slab with the second rolling stand, when the front end portion of the slab enters a second rolling stand provided after the first rolling stand; and

a buffering operation of moving a pair of rolling rolls provided in the first rolling stand upwardly or downwardly, or moving a pair of pinch rolls provided in an inlet of the first rolling stand upwardly or downwardly, when a portion of the slab, having been reduced, moves backwards to the first rolling stand.

5. The continuous casting and rolling method of claim 1, wherein, in the rolling operation, a pair of rolling rolls, provided in each of a plurality of rolling stands including the first rolling stand, sequentially roll the slab while a distance is gradually reduced in a direction of progress of the slab.

6. A continuous casting and rolling apparatus, comprising:

a continuous caster for producing a slab; and

a rolling mill located at an outlet of the continuous caster, and having a plurality of rolling stands including a first rolling stand into which a front end portion of the slab, which is provided as a continuous body with the slab produced in the continuous caster, initially enters,

wherein the rolling mill is provided to reduce the slab after the front end portion of the slab passes the first rolling stand.

7. The continuous casting and rolling apparatus of claim 6, wherein the rolling mill includes:

a support point determining sensor provided at an outlet of the first rolling stand, and sensing the front end portion of the slab; and

a reducing point determining sensor provided in an inlet of a second rolling stand provided after the first rolling stand, and sensing the front end portion of the slab.