JP2019529116A - Steel sheet manufacturing apparatus excellent in isotropic property and steel sheet manufactured thereby - Google Patents

Abstract

An apparatus for producing a steel sheet having excellent isotropy according to an embodiment of the present invention includes a rolling mill having a plurality of rolling stands for rolling a slab, and after the slab is drawn into the rolling stand. A controller that controls a rolling speed that is rolled and discharged, and the controller controls the rolling mill after the recrystallization of the metal structure of the slab pressed by any of the rolling stands. It can control by the rolling speed sent to a rolling stand.

Description

  The present invention relates to a steel plate manufacturing apparatus excellent in isotropic property and a steel plate manufactured thereby.

  A slab, which is a kind of slab made through a continuous casting process, is transferred to a hot rolling plant and then heated to a certain temperature or higher in a heating furnace in order to secure a temperature for rolling. .

  The slab delivered from the heating furnace was rolled through several stages in a roughing mill to ensure the target rolled bar thickness according to the final product thickness. Thereafter, final rolling is performed in order to ensure the thickness of the product with a finishing mill.

  At this time, according to the weight of the final product, each product is cut in slab units in the continuous casting process, transferred to the hot rolling mill, and the slab sent from the heating furnace is set according to the product characteristics In order to secure the temperature at each position in the processed process, the temperature of the material is controlled by a method such as cooling or heating.

  In particular, in the final finish rolling mill, rolling is performed at a constant speed in order to secure the inlet side temperature and the outlet side temperature of the finish rolling mill and to ensure high productivity.

  Conventionally, a product produced at a high rolling speed is moved from the exit side of the rolling stand to the next rolling stand before the metallographic structure such as grain stretched in the rolling direction is recrystallized. And rolled again.

  The product thus produced has anisotropy with slightly different physical properties in the direction of rolling of the material and in the width direction.

  The anisotropy of the material is not a problem for general purpose products, but an ear phenomenon occurs when deep drawing processing such as forming a cup shape is required. , Leading to the occurrence of product molding defects.

  When this ear phenomenon is severe, it may not be used as a molded product, which causes a reduction in the actual yield of the product.

  Therefore, it has become necessary to study a steel sheet manufacturing apparatus excellent in isotropy for solving the above-described problems and a steel sheet manufactured thereby.

  An object of the present invention is to provide a steel sheet manufacturing apparatus that is excellent in isotropy, and that can improve the actual yield by preventing a problem that an ear phenomenon occurs during product forming, and a steel sheet manufactured thereby. It is to be.

  An apparatus for producing a steel sheet having excellent isotropy according to an embodiment of the present invention includes a continuous casting machine for producing a slab, a rolling machine having a plurality of rolling stands for rolling the slab, and the rolling machine. A controller for controlling a rolling speed until the slab is drawn into the rolling stand and then rolled and sent out, and the controller rolls the rolling mill at any of the rolling stands. It is possible to control the rolling speed to be sent to the next rolling stand after the metal structure of the cast slab is recrystallized.

  Further, the rolling mill in the steel sheet manufacturing apparatus excellent in isotropy according to one embodiment of the present invention includes a roughing mill positioned on the outlet side of the continuous casting machine and a finish positioned on the outlet side of the roughing mill. A rolling mill, and the controller is connected to the finishing mill and can control a rolling speed of the finishing mill.

In addition, the controller in the steel sheet manufacturing apparatus excellent in isotropy according to one embodiment of the present invention can control the rolling speed of the finish rolling mill so as to satisfy the following mathematical formula. .
15.5 <(t × v) / {(n−1) × d} <30.8 [Formula (1)]
Here, t is the thickness of the slab (mm), v is the casting speed of the slab (m / min), n is the number of rolling stands included in the finish rolling mill, and d is between adjacent rolling stands. Distance (m).

In addition, in the finish rolling mill in the steel sheet manufacturing apparatus excellent in isotropic property according to an embodiment of the present invention, the number (n) of the rolling stands is 3 to 7, and the distance d between the adjacent rolling stands is d. Is provided at 3 to 6.5 m, and the controller controls the rolling speed of the finish mill to satisfy the following mathematical formula.
360 <t × v <715 [Formula (2)]

In addition, a steel sheet manufacturing apparatus excellent in isotropy according to an embodiment of the present invention is provided on a continuous casting machine for manufacturing a slab, and on the outlet side of the continuous casting machine. A rolling mill provided with a plurality of rolling stands for receiving the delivery and rolling the slab, wherein the rolling mill is located on the outlet side of the continuous casting machine, and the outlet side of the rough rolling mill And a finish rolling mill located at a position satisfying the following mathematical formula.
15.5 <(t × v) / {(n−1) × d} <30.8 [Formula (1)]
Here, t is the thickness of the slab (mm), v is the casting speed of the slab (m / min), n is the number of rolling stands included in the finish rolling mill, and d is between adjacent rolling stands. Distance (m).

  In addition, the steel sheet manufacturing apparatus excellent in isotropy according to an embodiment of the present invention performs continuous continuous rolling by sending the slab manufactured by the continuous casting machine to the rolling mill without cutting. Features.

  In addition, an isotropic steel sheet according to another embodiment of the present invention can be manufactured using a steel sheet manufacturing apparatus having excellent isotropic properties.

  In addition, an isotropic steel sheet according to another embodiment of the present invention may be characterized in that all of the front end portion, the rear end portion, and the intermediate portion therebetween exhibit uniform isotropic characteristics.

  The isotropic steel sheet manufacturing apparatus of the present invention and the steel sheet manufactured thereby can increase the isotropic property by reducing the anisotropy of the steel sheet manufactured by rolling the slab. Can have the advantage of being able to.

  Moreover, it can have an advantage that isotropy and material uniformity can be ensured.

  Thereby, the effect that the productivity of a product can be improved by preventing the fall of the actual yield resulting from anisotropy can be show | played.

  More specifically, it has the advantage that the actual yield of the product can be increased by reducing the ear phenomenon that occurs during deep drawing such as the cup shape, thereby preventing problems caused by defects in the molded product. Can have.

It is a front view which shows the manufacturing apparatus of the steel plate excellent in the isotropy of this invention. It is a front view which shows the control machine and rolling mill in the manufacturing apparatus of the steel plate excellent in the isotropy of this invention. It is a graph which shows the speed range in the finish rolling mill for ensuring isotropy in the manufacturing apparatus of the steel plate excellent in the isotropy of this invention. It is a graph which compares and shows the formation height of the ear | edge by the manufacturing apparatus of the steel plate excellent in the isotropic property of this invention, and a prior art.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.
However, the idea of the present invention is not limited to the presented embodiments, and those skilled in the art who understand the idea of the present invention can step back through adding, changing, or deleting other components within the scope of the same idea. Other embodiments included in the scope of the idea of the present invention or the present invention can be easily proposed. However, this is also included in the scope of the idea of the present invention.

  Moreover, the same component which has a function within the range of the same thought shown by drawing of each Example is demonstrated using the same referential mark.

  The present invention relates to a steel plate manufacturing apparatus having excellent isotropy and a steel plate manufactured thereby, and the steel plate manufacturing apparatus having high isotropy according to the present invention and the steel plate manufactured thereby are cast. In order to reduce anisotropy and increase the isotropic property of a steel sheet produced by rolling a piece, by preventing a decrease in the actual yield due to anisotropy, Product productivity can be improved.

  That is, by reducing the ear phenomenon that occurs during deep drawing such as a cup shape, it is possible to prevent problems caused by defects in the molded product and increase the actual yield of the product. .

FIG. 1 is a front view showing a steel sheet manufacturing apparatus excellent in isotropic property according to the present invention.
As shown in FIG. 1, a steel sheet manufacturing apparatus excellent in isotropy according to an embodiment of the present invention is connected to a rolling mill 20 including a plurality of rolling stands R for pressing a slab, and the rolling mill 20. A controller 30 that controls the rolling speed until the slab is drawn into the rolling stand R and then pressed and discharged, and the controller 30 moves the rolling mill 20 to any one of the n−1th ones. The rolling structure is adjusted to a rolling speed at which the metal structure of the slab pressed by the rolling stand Rn-1 is recrystallized and then moved to the next n-th rolling stand Rn. Here, n is the number of rolling stands R included in the rolling mill 20.

  In other words, in order to reduce the anisotropy of the rolled slab and increase the isotropy, the slab is pressed by one of the rolling stands Rn-1 during the rolling operation at the plurality of rolling stands R. After the slab is deformed, when the recrystallization of the metal structure of the slab is completed, the slab is controlled to be pressurized by the next rolling stand Rn.

  Here, the recrystallization of the metal structure means recrystallization by forming new nuclei after deformation of the metal structure by pressurization. In some cases, a process of crystal grain growth accompanying the growth of new nuclei can be included.

  Since the formation of such new nuclei is formed while maintaining isotropy, it prevents a decrease in isotropicity due to an increase in anisotropy of conventional metal crystals.

  The rolling mill 20 can produce a rolled steel sheet by pressing the slab. For this purpose, the rolling mill 20 can be pressed while passing a slab between a pair of rolling rolls, and a plurality of rolling stands R provided with the pair of rolling rolls can be provided.

  The rolling mill 20 includes a rough rolling mill 21 that performs rolling to an intermediate thickness before producing the final rolled steel sheet product obtained by pressing the provided slab to a final thickness, and an intermediate thickness using the rough rolling mill 21. And a finish rolling mill 22 for producing a rolled steel sheet having a final thickness from the slab pressed down.

  That is, the rolling mill 20 in the steel sheet manufacturing apparatus excellent in isotropy according to one embodiment of the present invention is positioned on the exit side of the continuous casting machine 10 and on the exit side of the rough rolling machine 21. And a finisher 22, and the controller 30 is connected to the finisher 22 and controls the rolling speed of the finisher 22.

  Here, the rough rolling mill 21 is located on the exit side of the continuous casting machine 10 to be described later, and receives a slab manufactured by the continuous casting machine 10 and performs a rolling operation. Further, the finish rolling mill 22 is located on the exit side of the rough rolling mill 21 and is pressed to receive a cast slab that has been rolled by the rough rolling mill 21 and rolled to produce a final rolled steel sheet product. Do work.

  In particular, the number (n) of rolling stands R provided to the roughing mill 21 and the finish rolling mill 22 can be adjusted according to characteristics such as the material of the rolled steel sheet to be produced. However, in all facilities, the number of rolling stands R secured by the rough rolling mill 21 or the finishing rolling mill 22 is not the number of rolling stands R provided by the rough rolling mill 21 or the finishing rolling mill 22 but secured rolling stands. Of the number of R, the number (n) used for actual driving is the number (n) of rolling stands R provided by the roughing mill 21 or the finish rolling mill 22.

  Furthermore, since the isotropy of the rolled steel sheet that is finally produced is determined by the rolling speed in the finishing mill 22, the controller 30 controls the rolling speed of the rolling stand R in the finishing mill 22. It is preferable.

  The controller 30 plays a role of controlling the rolling speed of the rolling mill 20. Thereby, isotropy can be improved by reducing the anisotropy of the rolled steel plate.

  That is, the controller 30 presses the slab at one of the rolling stands Rn-1 and performs rolling, and then presses the rolling stand R on the slab before pressing the slab again at the next rolling stand Rn. Isotropicity can be improved by controlling the rolling speed to complete recrystallization of the metal structure.

  As described above, after the recrystallization of the metal structure of the slab is completed by controlling the rolling speed, the isotropic property is improved by performing the next rolling before the metal structure is recrystallized. This is because recrystallization isotropy that is a basic characteristic of the metal structure cannot be realized.

  That is, the recrystallization is not completed, and the metal structure that has lost its isotropic property is further deformed at the next pressing, and it becomes impossible to secure time for recovering the isotropic property, and a more anisotropic crystal is formed. Will be.

  In order to further improve the isotropy of the slab by more precise control of the rolling mill 20, the controller 30 includes the distance d between the rolling stands R, the number of rolling stands R (n), and the thickness of the slab. The length t can be further controlled as a variable. A more detailed description of this will be described later with reference to FIGS.

  Further, the steel sheet manufacturing apparatus with excellent isotropy according to an embodiment of the present invention manufactures a slab, provides it to the entrance side of the rolling mill 20, and sends the manufactured slab to the rolling mill 20. By including 10, continuous continuous casting (rolling continuous casting and rolling) can be performed.

In other words, the steel sheet manufacturing apparatus with excellent isotropy according to an embodiment of the present invention is provided on a continuous casting machine 10 for producing a cast piece and an outlet side of the continuous casting machine 10. A rolling mill 20 having a plurality of rolling stands for receiving the pieces and rolling the slab. The rolling mill 20 includes a rough rolling mill 21 located on the exit side of the continuous casting machine 10 and a rough rolling mill 21. And a finish rolling mill 22 located on the exit side of the above, which satisfies the following mathematical formula.
15.5 <(t × v) / {(n−1) × d} <30.8 [Formula (1)]
Here, t is the thickness of the slab (mm), v is the casting speed of the slab (m / min), n is the number of rolling stands included in the finish rolling mill, and d is between adjacent rolling stands. Distance (m).

  And the manufacturing apparatus of the steel plate excellent in isotropy by one Example of this invention is characterized by sending the continuous slab by sending to the rolling mill 20 without cut | disconnecting the slab manufactured with the continuous casting machine 10. And

  Thus, the present invention can be performed by continuous rolling in order to prevent problems such as plate breakage and twisting of the slab during the rolling process.

  In other words, since the plate breakage or twist of the slab is a problem that occurs at the front end portion or the rear end portion of the cut slab, the present invention rolls with a continuous slab instead of a cut slab. It is configured to perform continuous continuous rolling.

  Here, the continuous casting machine 10 can play a role of producing a slab from molten steel through a casting process. That is, the continuous casting machine 10 supplies molten steel from the tundish to the mold, and the supplied molten steel is deprived of heat and forms a slab. The slab is guided and moved by a segment roll and a pinch roll, and can be supplied to the rolling mill 20 described later.

  FIG. 2 is a front view showing the controller 30 and the rolling mill 20 in the steel sheet manufacturing apparatus excellent in isotropic property of the present invention, and FIG. FIG. 4 is a graph showing a speed range in a finish rolling mill for ensuring the directivity, and FIG. 4 is a graph showing a comparison of the isotropic height of the steel plate manufacturing apparatus according to the present invention and the ear forming height according to the prior art. It is.

As shown in FIG. 2 to FIG. 4, the controller 30 in the steel sheet manufacturing apparatus excellent in isotropic property according to one embodiment of the present invention controls the rolling speed of the rolling mill 20 so as to satisfy the following mathematical formula. It is characterized by.
15.5 <(t × v) / {(n−1) × d} <30.8 [Formula (1)]
Here, t is the thickness of the slab (mm), v is the casting speed of the slab (m / min), n is the number of rolling stands included in the finish rolling mill, and d is between adjacent rolling stands. Distance (m).

  In particular, the casting speed v of the slab is a slab supply speed in the first rolling stand R1 where the slab first enters, and is a speed corresponding to the rolling speed of the first rolling stand R1.

  That is, in order to reduce the anisotropy of the rolled slab and increase the isotropy, in addition to controlling the slab loading speed v related to the rolling speed of the rolling stand R, the rolling stand R The distance d between them, the number (n) of rolling stands R included in the finish rolling mill 22, and the thickness t of the slab can be added and controlled as variables.

  When satisfy | filling this numerical formula, the steel plate manufactured by rolling can ensure isotropy. Furthermore, isotropy and material uniformity can be ensured.

  In other words, when the upper limit of 30.8 of the formula (1) is exceeded, the isotropic property of the rolled steel sheet is not ensured. Therefore, an upper limit needs to be secured. Moreover, when it becomes smaller than the lower limit of 15.5, the material uniformity decreases. Therefore, a lower limit needs to be secured.

  Here, the deterioration of the material uniformity occurs due to a difference in grain size in the thickness direction and a low rolling temperature. That is, the low rolling temperature is affected by the low rolling speed.

  Experimental data for deriving a mathematical formula that ensures isotropicity is as follows. Here, O indicates a state in which isotropic or material uniformity is completely secured, Δ indicates a boundary where isotropic or material uniformity is ensured, and x indicates isotropic or material uniform. This indicates a state in which no sex is ensured.

  First, Table 1 below shows an isotropic state while fixing the thickness t of the slab, the number of rolling stands (n), the distance d between the rolling stands, and changing the casting speed v of the slab. Is.

Table 2 and Table 3 below show the isotropic state while fixing the thickness t of the slab and the casting speed v of the slab, and changing the number of rolling stands (n) and the distance d between the rolling stands. It has been confirmed.

  Thus, it can be confirmed that the isotropic property and the material uniformity are ensured when the above mathematical formula (1) is satisfied.

  On the other hand, the graph of FIG. 3 shows the range of rolling speeds on the entry side of the finish rolling mill 22 controlled by the controller 30 as the slab thickness t changes. That is, when the thickness t of the slab is about 10 mm, it can be confirmed that the minimum speed must be controlled to about 36 m / min and the maximum speed must be controlled to about 72 m / min.

  When the number (n) of the rolling stands R is five and the distance d between the rolling stands R is limited to about 5.8 mm, the controller 30 has a thickness t of the rolled slab and a casting It is possible to control the isotropic steel sheet to be manufactured by controlling the charging speed v of the piece.

That is, the rolling mill 20 in the steel sheet manufacturing apparatus with excellent isotropy according to an embodiment of the present invention is provided with 3 to 7 rolling stands R (n), and the distance d between adjacent rolling stands R is d. Is provided at 3 to 6.5 m, the controller 30 controls the rolling speed of the rolling mill 20 so as to satisfy the following formula (2).
360 <t × v <715 [Formula (2)]

  The control range based on the slab charging speed v and the slab thickness t can be determined from the mass flow rate of the slab passing through the rolling mill 20 in another aspect. That is, the steel sheet manufactured while controlling the lower limit of the mass flow rate passing through the rolling mill 20 to 360 mm & mdot / min and the upper limit to 715 mm · m / min can maintain isotropic characteristics. .

  As an example, when the thickness t of the slab flowing into the entrance side of the rolling mill 20 is 16 mm and the casting speed v of the slab is 60 m / min, the mass flow rate becomes 960 and the control range is increased. Therefore, a steel sheet that cannot ensure isotropy is produced. On the other hand, when the thickness t of the slab is 16 mm and the charging speed v of the slab is 36 m / min, the mass flow rate is 576 and is included in the control range, so that the isotropic property is obtained. Secured steel sheet can be manufactured.

  Moreover, when controlling the rolling mill 20 in order to ensure the isotropy of the steel plate, the temperature of the slab must be supplied while being maintained at an appropriate temperature for rolling. .

  As an example, when the controller 30 controls the finishing mill 22, it is preferable that the temperature of the slab supplied to the entrance side of the finishing mill 22 is maintained at about 950 to 1100 ° C. At this time, the rolled steel sheet discharged to the outlet side is preferably maintained at about 700 to 900 ° C. and discharged.

  Thus, the steel plate manufactured by the steel plate manufacturing apparatus excellent in isotropy according to the present invention ensures isotropic properties.

  That is, an isotropic steel sheet according to another embodiment of the present invention can be manufactured using the steel sheet manufacturing apparatus having excellent isotropy.

  In order to confirm the securing of such isotropy, reference can be made to FIG. FIG. 4 is a result of observing the phenomenon of ears when deep drawing is performed using a steel plate manufactured by the prior art and a steel plate manufactured by the present invention.

  As shown in FIG. 4, the steel plate manufactured according to the present invention has a uniform ear formation height in each circumferential direction of the molded product during deep drawing, but the steel plate manufactured according to the prior art. When deep drawing is performed, it is confirmed that the formation height of the ears is extremely uneven and a molding defect is generated.

  That is, it can be seen that the steel sheet manufactured according to the present invention is superior in isotropy compared to the prior art.

  In addition, an isotropic steel sheet according to another embodiment of the present invention may be characterized in that the front end portion, the rear end portion, and the intermediate portion therebetween all exhibit isotropic characteristics.

  That is, after the continuous continuous rolling is performed by the above-described steel sheet manufacturing apparatus having excellent isotropy sent to the rolling mill 20 without cutting the slab manufactured by the continuous casting machine 10, the steel sheet is finally cut. Even if discharged as a steel sheet, the steel sheet is continuously manufactured. As a result, even if it is finally cut, the isotropic characteristics at the front end portion, the rear end portion, and the intermediate portion between the front end portion and the rear end portion can be uniformly shown and provided.

Claims (8)

A continuous casting machine for producing slabs;
A rolling mill comprising a plurality of rolling stands for rolling the slab;
A controller connected to the rolling mill, for controlling the rolling speed at which the slab is rolled and fed out after being drawn into the rolling stand;
Including
The controller controls the rolling mill at a rolling speed delivered to the next rolling stand after the metal structure of the slab rolled at any of the rolling stands is recrystallized, etc. Steel sheet manufacturing equipment with excellent directivity. The rolling mill includes a rough rolling mill located on the exit side of the continuous casting machine, and a finish rolling mill located on the exit side of the rough rolling mill,
The said control machine is connected with the said finishing mill, and controls the rolling speed of the said finishing mill, The manufacturing apparatus of the steel plate excellent in isotropic of Claim 1 characterized by the above-mentioned. The said control machine controls the rolling speed of the said finish rolling mill so that the following numerical formula may be satisfy | filled, The manufacturing apparatus of the steel plate excellent in isotropic of Claim 2 characterized by the above-mentioned.
15.5 <(t × v) / {(n−1) × d} <30.8 [Formula (1)]
Here, t is the thickness of the slab (mm), v is the casting speed of the slab (m / min), n is the number of rolling stands included in the finish rolling mill, and d is between adjacent rolling stands. Distance (m). The finishing mill is provided with 3 to 7 rolling stands (n), and a distance d between adjacent rolling stands of 3 to 6.5 m,
The said control machine controls the rolling speed of the said finish rolling mill so that the following numerical formula may be satisfy | filled, The manufacturing apparatus of the steel plate excellent in isotropic of Claim 2 characterized by the above-mentioned.
360 <t × v <715 [Formula (2)]
Here, t is the thickness (mm) of the slab, and v is the casting speed (m / min). A continuous casting machine for producing slabs;
A rolling mill provided on the exit side of the continuous casting machine, comprising a plurality of rolling stands for receiving the slab from the continuous casting machine and rolling the slab;
Including
The rolling mill includes a rough rolling mill located on the exit side of the continuous casting machine, and a finish rolling mill located on the exit side of the rough rolling mill,
An apparatus for producing a steel sheet excellent in isotropy characterized by satisfying the following mathematical formula.
15.5 <(t × v) / {(n−1) × d} <30.8 [Formula (1)]
Here, t is the thickness of the slab (mm), v is the casting speed of the slab (m / min), n is the number of rolling stands included in the finish rolling mill, and d is between adjacent rolling stands. Distance (m).   6. The apparatus for producing a steel sheet with excellent isotropic property according to claim 5, wherein continuous cast rolling is performed by cutting a slab produced by the continuous casting machine to the rolling mill without cutting.   An isotropic steel sheet manufactured by the steel sheet manufacturing apparatus excellent in isotropic property according to any one of claims 1 to 6.   The isotropic steel sheet according to claim 7, wherein the isotropic steel sheet uniformly exhibits isotropic characteristics at a front end portion, a rear end portion, and an intermediate portion therebetween.

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