JPH10180428A - Method for cutting off cast slab in continuous casting of steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the casting capacity by executing rolling reduction only to a cutting-off scheduled position of a cast slab until the center part of the cast slab finishes solidification, mutually press-sticking the inner surface of the solidified shell of the cast slab, enclosing molten core at the downstream side and quickly cutting off. SOLUTION: Molten steel Me supplied into a mold 3 from a ladle 1 through a tundish 2 is cooled with the mold 3 and made to the cast slab 5 while forming the solidified shell inner surface 8. The cast slab 5 is drawn out through a secondary cooling zone 4 while straight extending with pinch rolls 6 in the condition of remaining the molten core in the inner part of the cast slab 5. When the cutting-off scheduled position P of the cast slab 5 reaches a press 7, the rolling reduction is locally executed to the cast slab 5 in the vertical direction with the press 7 and the solidified shell inner surfaces 8 are mutually press-stuck and the molten core 9 at the downstream side is enclosed. When the scheduled position P reaches a shearing machine 10, the cast slab 5 is cut off at the scheduled position P to make the cast slab 11 enclosing the molten core. The cast slab 5 can cut off without waiting till completing the solidification.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously casting steel, and more particularly to a method for improving casting efficiency.

[0002]

2. Description of the Related Art When a steel slab is manufactured by a continuous casting method, the slab is usually solidified to a center and then cut into a predetermined length to obtain a slab. As is well known, the casting efficiency is expressed by equation (1) for a square cross section. Pc = 4ρk ² sL (1) Pc; Casting efficiency (Kg / min) ρ; Density of steel (Kg / m ³ ) k; Solidification constant (m / min ^0.6) ) S; Shape factor (approximately 1.3 for a square) L; Machine length (length from casting surface to solidification completion position,
m) The casting efficiency Pc is limited by the machine length L and depends on the solidification coefficient k related to the cooling strength. Incidentally, the cross-sectional dimension of the slab is irrelevant. The maximum casting efficiency is obtained at a drawing speed at which the solidification of the central part is completed just before cutting within a proper cooling condition. Therefore, if more efficiency is required, the captain L
There has been a major problem in that remodeling to increase the number of strands or increase in the number of strands is required.

[0003] In the special continuous casting method disclosed in Japanese Patent Application Laid-Open No. 5-321096, the casting efficiency is dramatically increased as compared with the conventional method, and is expressed by equation (2). Pn = 4ρk ² L (2 / α-1) (2) α; solidified shell thickness ratio (solidified shell thickness / length from surface to center)

In this casting method, a nearly vertically cast slab is formed into an arc shape and a semicircle before the center portion solidifies, and furthermore, a static iron pressure height corresponding to atmospheric pressure (about 1.4 m) from the casting surface.
By pulling upward beyond the above, a hollow slab of a vacuum core is obtained. In order to obtain a steel slab having a predetermined size, prior to cutting, press rolling to a solid and forming rolling are required. Therefore, there is a problem that the equipment becomes very expensive.

[0005]

SUMMARY OF THE INVENTION The present invention is intended to solve such a conventional problem, and it is easy to improve casting efficiency by devising a slab cutting step which is a final step of continuous casting. To provide a way to obtain

[0006]

Means for Solving the Problems In order to achieve the above object, a first aspect of the present invention is to cut a slab into a steel slab in a continuous casting method of steel until the center of the slab is solidified. The slab is rolled down only near the scheduled cutting position of the slab, the inner surfaces of the solidified shells are pressed or welded together, the molten core on the downstream side is closed, and then the molten core is cut immediately. Is a method of cutting a continuous cast slab.

According to a second aspect of the present invention, a nearly vertically cast slab is formed into an arc and a semicircle before the center solidifies, and furthermore, a static iron pressure height (about 1) corresponding to atmospheric pressure from the casting surface. In a continuous casting method of steel in which a hollow slab is formed by drawing upward beyond 0.4 m), when the slab is cut into a slab, the slab is reduced only in the vicinity of the expected cutting position of the slab. This is a method for cutting a continuous cast slab, wherein the inner surfaces of the solidified shell are pressed or welded to each other to form a vacuum core-enclosed steel piece by closing the vacuum core on the downstream side and then cutting.

In the third aspect of the present invention, when the first and second aspects of the invention are implemented, the step of pressing or closely welding the inner surfaces of the solidified shell and the step of cutting the slab have both the functions of pressing and cutting. This is a method for cutting a continuous cast slab, wherein the slab is processed almost simultaneously by one shearing machine.

[0009]

The present invention will be described below with reference to the drawings. FIG. 1 is a schematic side view illustrating a continuous casting machine embodying the first invention, and FIG. 2 is a schematic side view illustrating a continuous casting machine embodying the second invention.
It is a schematic side view which illustrates the slab cutting machine which implements the invention of FIG.

In FIG. 1, molten steel Me supplied from a ladle 1 to a mold 3 via a tundish 2 is cooled by the mold 3 to form a slab 5 while forming a solidified shell. The slab 5 is drawn through the secondary cooling zone 4 while being stretched by a pinch roll 6 while leaving the molten core inside the slab 5. When the scheduled cutting position P on the slab 5 reaches the part of the press 7 installed downstream of the pinch roll 6, the press 7 operates to locally place the slab 5 vertically and sandwich the point P back and forth. And the inner surfaces 8 of the solidified shell are pressed against each other to close the molten core 9 on the downstream side. When the point P reaches the part of the shearing machine 10 installed immediately downstream of the press 7, the slab 5 is cut at the point P to become a molten core-enclosed steel slab 11. Fused core enclosed steel slab 11
Is supplied directly to the next step of hot rolling directly or through a holding furnace.

In the above configuration, the casting efficiency is naturally (1)
According to the formula, the meaning of the captain differs from that of the conventional system. That is, in the present invention, the solidification completion point shifts downstream substantially in proportion to the drawing speed without being limited by the installation position of the cutting device, and accordingly, the effective machine length also increases. The casting efficiency Pm can be easily obtained by equation (3). Pm = ρD ² V (3) ρ; steel density (Kg / m ³ ) D; slab side dimension (m) V; drawing speed (m / min) It is proportional to the drawing speed V and becomes V / Vcmax times as compared with the conventional method. Here, Vcmax is the maximum drawing speed of the conventional method limited by the design machine length (the length from the casting surface to the cutting device). To improve the efficiency, it is necessary to give due consideration to the problems of work and quality, but the faster the speed, the better.

With respect to the apparatus for bringing the inner surfaces of the solidified shell into pressure contact with each other, various mechanisms such as a forging machine, a roll-opening-type rolling mill, and a pinch roll having a rolling-down function can be considered in addition to the illustrated press. Of course, consideration should be given to preventing the occurrence of internal cracks and the ability to follow the slab pull-out during pressure welding.

Regarding the method of enclosing the molten core, as illustrated, the solidified shell inner surfaces of the slab having the molten core may be pressed against each other by pressing, but the pressing is performed immediately before the solidified shell inner surfaces of the slab are pressed against each other. There is also a method of stopping and enclosing the welding by the subsequent solidification progress. In this case, both the reduction force and the reduction amount are reduced, and the problem associated with the reduction is reduced.

With respect to the apparatus and method for cutting a slab, a gas fusing machine can be used in addition to the shearing machine illustrated. In the former case, the constricted portion of the slab is sheared, so that the blade mold needs to be devised. However, since the pressing is further advanced, the encapsulation is extremely good. Regarding the installation position of the cutting device, the optimum position is different depending on whether a welding method is employed or a close welding method is employed depending on the method of sealing the molten core. In the latter case, a certain interval is required from the pressing part to the cutting part.

The second invention will be described with reference to FIG. First
In the same manner as in the invention, the slab 5 passes through the secondary cooling zone 4 and remains in a molten core inside the slab 5 while being pinched by a pinch roll 6 and a guide roll 12 to form an arc and exceeds a semicircle and further from the casting surface. It is pulled upward beyond the static iron pressure height (about 1.4 m) equivalent to the atmospheric pressure. By doing so, a hollow cast piece 14 in which the inside of the solidified shell is vacuum is obtained. The slab is stretched by a straightening roll 15 after being raised to ３ yen. A press 7 arranged at a position holding a cavity on the slab withdrawal trajectory locally lowers the slab 5 vertically at the scheduled cutting position P on the slab 5 and sandwiches the point P back and forth to solidify the shell. Inner surface 8
Are pressed against each other to close the vacuum core 13 on the downstream side. P
When the point reaches the part of the shearing machine 10 installed downstream of the press 7, the slab 5 is cut at the point P, and the vacuum core enclosed steel slab 16
Becomes

In the above configuration, the casting efficiency is as described in
In this case, an extremely high value is obtained, which is completely equivalent to the above-described expression (2) presented in -321096.

On the other hand, in Japanese Unexamined Patent Publication No. Hei 5-321096, a pressure rolling mill is required to make the hollow slab 14 into a solid slab in the course of drawing locus, and a forming and rolling mill is also required to make a steel slab of a predetermined size. . The present invention does not require these expensive equipment.

The device for bringing the inner surfaces of the solidified shells into pressure contact with each other is the same as that of the first invention, and therefore the description is omitted.

With respect to the method of enclosing the vacuum core, the inner surfaces of the solidified shells of the slab having the vacuum core may be pressed against each other by pressing as shown in the example, but other portions holding the molten core, for example, as shown in FIG. There is also a method of reducing the pressure at the point Q and stopping the amount immediately before the inner surfaces of the solidified shell are pressed against each other, and enclosing the encapsulation for subsequent welding by the progress of solidification.

The apparatus and method for cutting a slab are the same as in the first invention.

Next, the third invention will be described. If the diameter of the molten core is sufficiently smaller than the outside diameter of the slab, the inner surface of the solidified shell can be simply and reliably pressed at the part immediately before and after the cut surface by cutting with a normal shearing machine even if there is no prior pressure welding treatment. , Is welded and the molten core is enclosed. On the other hand, when the molten core becomes large, the solidified shell is deformed so as to be crushed with normal shearing with the progress of shearing, and proceeds in both pressure welding and welding, but does not completely block the cut surface. As the slab is separated, the molten steel flows out due to the large static iron pressure. Therefore, prior pressure welding is indispensable.

FIG. 3 shows an example in which pressing and cutting are processed by one shearing machine. The reduction shearing machine 21 is arranged so as to penetrate the slab 5, and follows the slab pulling-out drive when operated by the bogie mechanism 22. Crimping
The point of the simultaneous processing of cutting is four dies 23, 24, 25, and 26 which move forward and backward at right angles to the slab axial direction, and operate them individually and by a predetermined amount to perform pressing and cutting functions. Hydraulic cylinders 23C, 24C, 25C, 26C
Consists of When the cutting signal is input, the dies 23, 24,
25 and 26 move forward by a predetermined distance and press down the slab 5 from above and below, so that constriction occurs and the inner surface 8 of the solidified shell comes into pressure contact. Next, when the dies 23 and 25 are kept as they are and the dies 24 and 26 are lowered with the slab interposed therebetween, the slab 5 is smoothly cut by the blades 27 and 28. In this way, a molten core-enclosed steel slab can be produced by one shearing machine. In the case of a vacuum core enclosed steel slab, the same shearing machine can be used. When the end of the slab is squeezed into a shell shape, the crushing property during rolling is improved, and the rolling yield at the end is also improved. It is natural to devise the mold shape and sliding direction according to the slab cross-sectional shape in order to optimize the end shape and press-contact, and to facilitate the cutting process, and it is easy for those skilled in the art to explain. Omitted.

FIG. 4 shows an embodiment of the third invention in which the size of the molten core is relatively medium. The reduction shearing machine 21 includes a fixed mold 29 having blades 27 and 28 attached thereto and a sliding mold 30, respectively.
Is provided, and when the sliding die 30 moves forward, shearing of the slab 5 proceeds by the blades 27 and 28 of both the dies,
In the anvil parts 31 and 32, only the slab 5
Light reduction progresses while sandwiching. In this way,
Simultaneous processing of cutting is performed.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A steel bar of the steel type SS41 is trial-produced by an existing curved continuous casting machine for billets. The conditions, curvature radius 5 m, PIC 12m, mold cross-sectional dimension 140mm square, the drawing speed 2.6 m / min _o cutting method using the diagonal shear, about the cut surface before and after the upper blade mounting dies 5
A 0 mm anvil part is temporarily provided, and it is reduced by about 15 mm when cutting. Roll 2 minutes and 5 minutes after cutting. As a comparison condition, a maximum drawing speed of 2.0, which is conventionally known empirically, is used.
Take m / min.

The test results are described below. Under the conventional conditions, the peripheral portion of the cut surface is smooth and the central portion has a wavy shape. However, in the high-speed casting of the test, the central portion is incandescent and has a large and severe waving. However, there is no outflow of molten steel. In the rolling for about 2 minutes after cutting, the semi-solid metal flowed out from the end face of the billet rear end, and there was no problem in the rolling after 5 minutes. The above test proved that the molten core was encapsulated, and that normal rolling was possible by properly holding and equalizing the molten core-enclosed steel slab.

[0026]

According to the present invention, in the first invention, in ordinary continuous casting, the drawing speed is set excessively beyond the limit of the machine length. Are pressed against each other, so that the molten steel does not flow out during cutting. Therefore, the casting efficiency increases in proportion to the drawing speed. As an additional effect, the slab is sent to the next rolling step while maintaining the molten core, so that energy can be saved by both reheating and soaking of the slab and rolling power.

In the second invention, the prior art forms a hollow slab once by a slab drawing trajectory of 3/4 yen, then press-rolls to a solid, forms and rolls to a predetermined cross-sectional dimension, and cuts the steel slab. On the other hand, in the present invention, since only the portion to be cut of the slab is cut down in advance and the vacuum core is sealed after cutting,
Expensive pressure rolling equipment and forming rolling equipment are not required. The effect of the dramatic improvement in the casting efficiency of the prior art is exhibited as it is.

In the third invention, the sealing of the molten core or the vacuum core by pressing the inner surface of the solidified shell and the cutting of the slab can be simultaneously processed by one reduction shearing machine.
The second invention can be implemented with relatively simple and inexpensive equipment.
By narrowing the shape of both ends of the slab by devising the shapes of the blade and the die of the shearing machine, it is possible to improve the humidification in rolling and the rolling yield.

[0022]

[Brief description of the drawings]

FIG. 1 is a schematic side view illustrating a continuous casting facility for carrying out a first invention.

FIG. 2 is a schematic side view illustrating a continuous casting facility for implementing the second invention.

FIG. 3 is a schematic side view illustrating a slab cutter for implementing the third invention;

FIG. 4 is a schematic side view illustrating a slab cutter similarly embodying the third invention.

[Explanation of symbols]

1: Ladle 2: Tundish 3: Mold 4: Secondary cooling zone 5: Slab 6: Pinch roll
7: Press 8: Inner surface of solidified shell 9: Melt core 10: Shearing machine
11: molten core enclosed steel slab 12: guide roll 13: vacuum core 14 hollow cast slab 15: straightening roll 16: vacuum core encapsulated steel slab 21: reduction shearing machine 2
2: Bogie mechanism 23, 24, 25, 26: Mold 23C, 24C, 25C, 26C: Hydraulic cylinder
27, 28: Blade 29: Fixed die 30: Sliding die 31, 32: Anvil part Me: Molten steel P: Scheduled cutting position on slab Q: Example of press installation site

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[Procedure amendment]

[Submission date] April 10, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0003

[Correction method] Change

[Correction contents]

[0003] In a special continuous casting in Japanese Application flat 5-321096, casting efficiency is drastically increased and as compared with the conventional method, as shown in equation (2). Pn = 4ρk ² L (2 / α-1) (2) α; solidified shell thickness ratio (solidified shell thickness / length from surface to center)

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

[0017] On the other hand, pressure rolling mill for a solid cast piece in the course of the trajectory pulling the hollow slab 14 in Japanese Application flat 5-321096 further molding mill for a steel slab of predetermined dimensions required Become. The present invention does not require these expensive equipment.

Claims (3)

[Claims] When a slab is cut into a slab in a continuous casting method of steel, the slab is reduced only in the vicinity of a cutting position of the slab until the center of the slab is solidified by solidifying the solidified shell. A method of cutting a continuous cast slab, wherein inner surfaces are pressed or welded to each other, a molten core on the downstream side is confined, and the molten core is cut immediately to form a molten core-enclosed steel slab. 2. A substantially vertically cast slab is formed into an arc and a semi-circle before the center portion solidifies, and a static iron pressure height (approximately 1.4 m) corresponding to atmospheric pressure is further increased from the casting surface. In continuous casting of steel that forms a hollow slab by pulling it over and over, when cutting the slab to make a slab, the slab is pressed down only in the vicinity of the expected cutting position of the slab and the inner surface of the solidified shell A method of cutting a continuous cast slab, comprising pressing and near-welding each other to form a vacuum core-enclosed steel piece by closing a vacuum core on the downstream side and then cutting. 3. The method according to claim 1, wherein the step of pressing or closely welding the inner surfaces of the solidified shell to each other and the step of cutting the slab are performed almost simultaneously by one shearing machine having both functions of pressing and cutting. The method according to claim 2.