KR101786388B1 - Manufacturing apparatus and method for steel sheet superior in isotropy and steel sheet being manufactured thereof - Google Patents

Abstract

A steel sheet manufacturing apparatus having excellent isotropy according to an embodiment of the present invention includes a rolling mill having a plurality of rolling stands for pressing a steel strip and a rolling mill connected to the rolling mill, Wherein the controller is capable of adjusting the rolling mill at a rolling speed which is then transferred to the rolling stand after the metallic structure of the pressed cast steel is recrystallized in either rolling stand.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel sheet manufacturing apparatus having excellent isotropy and a steel sheet produced by the method.

The present invention relates to a steel sheet manufacturing apparatus excellent in isotropy and a steel sheet produced thereby.

The slab, which is a kind of cast steel produced through the continuous casting process, is transferred to a hot rolling mill and then heated to a certain temperature or higher in the furnace to secure the temperature for rolling.

The slabs extracted from the furnace are rolled through several stages in a roughing mill to obtain the thickness of the target rolling bar according to the thickness of the final product, The final rolling is performed.

At this time, each product is cut into slab units in the continuous casting process according to the weight of the final product and transferred to the hot rolling mill. The slabs extracted from the heating furnace are heated in order to secure the temperature at each position of the process The material temperature is controlled by methods such as cooling and heating.

Especially, in the final finishing mill, rolling is performed at a constant speed or more in order to ensure the inlet temperature and outlet temperature of the finishing mill and ensure high productivity.

The product produced by the conventional rolling method is rolled in the next rolling stand before the metal structure such as grain drawn in the rolling direction from the rolling stand is recrystallized at a high rolling speed.

The product thus produced has anisotropy which is different from the material properties in the rolling direction and width direction.

Such anisotropy of the material is not a problem in a general purpose product, but in the case of deep drawing, such as forming a cup shape, an earring occurs and a product molding defect occurs.

In the case where such earing phenomenon is severe, the molded product can not be used, which causes a decrease in the product yield rate.

Therefore, it is necessary to study a steel sheet manufacturing apparatus having excellent isotropy for solving the above-mentioned problems and a steel sheet produced thereby.

An object of the present invention is to provide a steel sheet manufacturing apparatus having excellent isotropy capable of preventing a problem of earing at the time of forming a product and thereby improving a yield rate, and a steel sheet produced thereby.

A steel sheet manufacturing apparatus having excellent isotropy according to an embodiment of the present invention includes a rolling mill having a plurality of rolling stands for pressing a steel strip and a rolling mill connected to the rolling mill, Wherein the controller is capable of adjusting the rolling mill at a rolling speed which is then transferred to the rolling stand after the metallic structure of the pressed cast steel is recrystallized in either rolling stand.

Further, the rolling mill of the steel plate producing apparatus excellent in isotropy according to an embodiment of the present invention includes a rough rolling mill positioned on the exit side of the casting mill and a finishing mill located on the side of the rough rolling mill, So that the rolling speed of the finishing mill can be adjusted.

Further, the controller of the steel plate manufacturing apparatus having excellent isotropy according to the embodiment of the present invention may be characterized in that the rolling speed of the finishing mill is adjusted so as to satisfy the following expression.

15.5 < (t x v) / {(n-1) x d} < 30.8

Where t is the thickness of the cast steel in millimeters, v is the casting speed in m / min, n is the number of rolling stands in the finishing mill and d is the distance between neighboring rolling stands .

Further, in the above-mentioned finishing mill of the steel plate producing apparatus excellent in isotropy according to the embodiment of the present invention, the number (n) of rolling stands is provided as five, and the distance d between neighboring rolling stands is 5.8 m And the controller adjusts the rolling speed of the finishing mill so as to satisfy the following expression.

360 < t x v < 715

In addition, the steel sheet manufacturing apparatus having excellent isotropy according to an embodiment of the present invention includes a performance machine for producing a cast steel, and a plurality of rolling stands provided on the exit side of the performance machine for receiving the cast steel from the performance machine and rolling the cast steel Wherein the rolling mill has a rough rolling mill located on the exit side of the casting mill and a finishing mill located on the side of the rough rolling mill and satisfies the following equation.

15.5 < (t x v) / {(n-1) x d} < 30.8

Where t is the thickness of the cast steel in millimeters, v is the casting speed in m / min, n is the number of rolling stands in the finishing mill and d is the distance between neighboring rolling stands .

In addition, the steel sheet manufacturing apparatus having excellent isotropy according to an embodiment of the present invention is characterized in that the cast steel produced in the casting machine is conveyed to the rolling mill without cutting to perform continuous continuous rolling.

In addition, the isotropic steel sheet according to another embodiment of the present invention can be manufactured by the steel sheet manufacturing apparatus having excellent isotropy.

Further, the 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 middle portion therebetween are uniformly formed with isotropic characteristics.

The steel sheet producing apparatus having excellent isotropy of the present invention and the steel sheet produced therefrom can have an advantage of increasing the isotropy by reducing the anisotropy of the steel sheet produced by rolling the steel sheet.

Furthermore, it is possible to obtain an advantage of securing material uniformity in addition to isotropy.

Accordingly, it is possible to prevent the reduction of the error rate due to the anisotropy and increase the product productivity.

More specifically, it is possible to prevent a problem caused by defects of a molded product by reducing the easing phenomenon occurring during deep drawing forming such as a cup shape, and thus it is possible to increase the error rate of the product.

1 is a front view showing a steel sheet manufacturing apparatus having excellent isotropy according to the present invention.
2 is a front view showing a controller and a rolling mill in a steel sheet manufacturing apparatus having excellent isotropy according to the present invention.
3 is a graph showing the speed range in a finishing mill for ensuring isotropy in a steel sheet manufacturing apparatus having excellent isotropy according to the present invention.
4 is a graph showing the comparison of the height of earrings formed by the prior art steel sheet manufacturing apparatus according to the present invention.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventive concept. Other embodiments falling within the scope of the inventive concept may readily be suggested, but are also considered to be within the scope of the present invention.

The same reference numerals are used to designate the same components in the same reference numerals in the drawings of the embodiments.

The present invention relates to a steel sheet producing apparatus having excellent isotropy and a steel sheet produced by the method. The steel sheet producing apparatus of the present invention having excellent isotropy and the steel sheet produced thereby reduce the anisotropy of a steel sheet produced by rolling a steel sheet And it is possible to increase the isotropy, so that it is possible to prevent the decrease in the rate of error due to the anisotropy and to increase the productivity of the product.

That is, by reducing the easing phenomenon that occurs during deep drawing molding such as a cup shape, it is possible to prevent a problem caused by defects of a molded product, and to have an advantage that a product error rate can be increased.

1 is a front view showing a steel sheet manufacturing apparatus having excellent isotropy according to the present invention. Referring to FIG. 1, the steel sheet producing apparatus having excellent isotropy according to an embodiment of the present invention includes a plurality of rolling stands R , And a controller (30) connected to the rolling mill (20) for adjusting the rolling speed of the rolling mill (R) after it is drawn into the rolling stand (R) After the metal structure of the cast steel which has been pressed by one of the n-1 th rolling stands Rn-1 is recrystallized, the steel plate 30 is rotated at the rolling speed, which is transmitted to the next rolling stand Rn, And adjusting the rolling mill (20). 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 cast steel to be rolled and to increase the isotropy, the cast steel is pressed in one of the rolling stands Rn-1 during the rolling operation in the plurality of rolling stands R, After the recrystallization of the metal structure of the cast steel is finished, the cast steel is controlled to be pressurized in the next rolling stand Rn.

Here, the recrystallization of the metal structure means recrystallization due to the formation of new nuclei after deformation of the metal structure by pressurization, and in some cases may include a process of crystal growth due to the growth of new nuclei.

Since the formation of the new nucleus is maintained while maintaining the isotropy, the isotropic property due to the increase of the anisotropy of the former metal crystal is prevented.

The rolling mill 20 can function to produce a rolled steel sheet by rolling down a cast steel. For this purpose, the rolling mill 20 can be rolled while passing the slabs through a pair of rolling rolls, and a plurality of rolling stands R provided with such rolling roll pairs can be provided.

The rolling mill 20 is provided with a roughing mill 21 for rolling at a medium thickness before being produced into a finished rolled steel sheet product having a final thickness reduced to a final thickness, ) To produce a rolled steel sheet having a final thickness again.

In other words, the rolling mill 20 of the steel sheet manufacturing apparatus having excellent isotropy according to the embodiment of the present invention is provided with a rough rolling mill 21 located on the exit side of the continuous casting machine 10 and a rough rolling mill 21 located on the exit side of the rough rolling mill 21 And a finishing mill 22, and the controller 30 is connected to the finishing mill 22 to adjust the rolling speed of the finishing mill 22.

Here, the roughing mill 21 is located on the exit side of a sequencer 10 to be described later, receives the casting produced by the milling machine 10, performs a rolling operation, and the finishing mill 22 is connected to the roughing mill 10, The rolling mill is located on the exit side of the rolling mill 21 and receives the rolling casting from the rough rolling mill 21 to perform a rolling operation to produce a final rolled steel plate product.

In particular, the number n of the rolling stands R provided in the rough rolling mill 21 and the finishing mill 22 can be adjusted according to the characteristics of the material of the rolled steel sheet to be produced, The number of rolling stands R secured by the rolling mill 21 or the finishing mill 22 is not the number of rolling stands R provided by the roughing mill 21 or the finishing mill 22, The number n actually used in the driving in the number of rolling mills R becomes the number n of the rolling stands R provided by the roughing mill 21 or the finishing mill 22.

In addition, since the isotropy of the rolled steel sheet 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 to the finishing mill 22 It is desirable to provide the control.

The controller 30 adjusts the rolling speed of the rolling mill 20, thereby improving the anisotropy of reducing the anisotropy of the rolled steel sheet.

That is, the controller 30 finishes the recrystallization of the metal structure of the cast steel before the steel strip is rolled in the next rolling stand Rn after pressing the cast steel in one rolling stand Rn-1 to perform rolling By controlling the rolling stands R at the rolling speed, the isotropy can be improved.

The reason why the isotropy is improved by performing the next rolling after the recrystallization of the metal structure of the cast steel is completed by such rolling speed control is that when the next rolling is performed before the metal structure is recrystallized, the recrystallization isotropy It is because it does not realize it.

That is, the metal structure having lost the isotropy due to the incomplete recrystallization is formed of anisotropic crystals because the deformation accelerates further when it is next pressed and the time for recovering the isotropy can not be secured.

The controller 30 controls the distance d between the rolling stands R and the number n of the rolling stands R so as to further improve the isotropy of the casting by controlling the rolling mill 20. [ ) And the thickness of the cast steel (t) as variables. A detailed description thereof will be described later with reference to Figs. 2 to 4. Fig.

The apparatus for manufacturing a steel sheet having excellent isotropy according to an embodiment of the present invention includes a casting machine 10 for producing a cast steel and being provided at the entrance of the rolling mill 20 and delivering the produced cast steel to the rolling mill 20 To perform endless continuous casting and rolling.

In other words, a steel plate manufacturing apparatus having excellent isotropy according to an embodiment of the present invention is provided with a caster 10 for producing a cast steel, and a casting machine 10 provided on the exit side of the caster 10 for receiving the cast steel from the castor 10, And a rolling mill (20) having a plurality of rolling stands for rolling the rolling mill (20). The rolling mill (20) comprises a rough rolling mill (21) And a finishing rolling mill (22), and can satisfy the following expressions.

15.5 < (t x v) / {(n-1) x d} < 30.8

Where n is the number of rolling stands included in the finishing mill 22 and d is the distance between neighboring rolling stands (in millimeters) m).

The apparatus for manufacturing a steel plate having excellent isotropy according to an embodiment of the present invention is characterized in that the cast steel produced in the casting machine 10 is conveyed to the rolling mill 20 without cutting to perform continuous continuous rolling .

As described above, the present invention can be carried out by continuous continuous rolling in order to prevent problems such as plate breaking and twisting of the cast steel during the rolling process.

In other words, since the problem of plate breaking or kinking of the casting is a problem occurring at the front end or the rear end of the casting casting, it is configured to perform continuous cast rolling in which rolling is performed on a continuous casting, .

Here, the performance device 10 may serve to produce a cast steel from molten steel through a casting process. That is, the casting machine 10 supplies molten steel from the tundish to the casting mold, and the supplied molten steel is stripped of heat to form a casting. The casting is performed by a segment roll and a pinch roll Guided and moved and fed to a rolling mill 20 to be described later.

FIG. 2 is a front view showing a controller 30 and a rolling mill 20 in a steel sheet manufacturing apparatus having excellent isotropy according to the present invention. FIG. 3 is a top view showing a finishing mill 22 for securing isotropy in a steel sheet manufacturing apparatus having excellent isotropy, FIG. 4 is a graph showing a comparison of the height of earrings formed by the prior art steel sheet manufacturing apparatus according to the present invention.

2 to 4, the controller 30 of the steel plate manufacturing apparatus having excellent isotropy according to an embodiment of the present invention is characterized in that the rolling speed of the rolling mill 20 is adjusted so as to satisfy the following equation .

15.5 < (t x v) / {(n-1) x d} < 30.8

Where n is the number of rolling stands included in the finishing mill, d is the distance between neighboring rolling stands R (in millimeters) m).

Particularly, the feeding speed v of the cast steel is a feeding speed of the cast steel in the first rolling stand R1 in which the cast steel first enters, and corresponds to the rolling speed of the first rolling stand R1.

In other words, in addition to controlling the feed rate v associated with the rolling speed of the rolling stand R, in order to reduce the anisotropy of the rolling mill and increase the isotropy, The distance d, the number n of the rolling stands R included in the finishing mill 22 and the thickness t of the cast steel can be controlled as variables.

When such a formula is satisfied, the steel sheet produced by rolling can secure isotropy. In addition, material uniformity can be ensured along with isotropy.

In other words, if the upper limit of 30.8 is exceeded, the upper limit of the rolled steel sheet is not ensured. If the lower limit is less than 15.5, the uniformity of the material is lowered.

Here, the material uniformity is caused by the difference in grain size in the thickness direction, which is caused by the low rolling temperature, and the low rolling temperature is affected by the low rolling speed.

In addition, the experimental data for deriving the above equation to derive the isotropy are as follows. Here, O represents a state in which isotropy or material uniformity is completely ensured, DELTA represents a boundary where isotropy or material uniformity is ensured, and X represents a state in which isotropy or material uniformity is not ensured at all.

First, the thickness (t) of the cast steel, the number of rolling stands (n), and the distance (d) between the rolling stands were fixed and the isotropic properties were confirmed by varying the casting speed (v).

Thickness (mm) Feeding speed (m / min) Number of Rolling Stands Distance between rolling stands (m) Isotropic Material uniformity

25

12.0



5








5.8




O X 14.4 O △ 20.0 O O 28.6 △ O 32.0 X O

15

20.0 O X 24.0 O △ 33.3 O O 47.7 △ O 53.3 X O

Tables 2 to 3 below show the relationship between the number of rolling stands (n) and the distance between the rolling stands (d) by fixing the thickness t of the cast steel and the casting speed v of the cast steel, Respectively.

Thickness (mm) Feeding speed (m / min) Number of Rolling Stands Distance between rolling stands (m) Isotropic Material uniformity



15




20
4



5



O O 5 O △ 6 O X
33
4 X O 5 O O 6 O O
53
4 X O 5 X O 6 X O

Thickness (mm) Feeding speed (m / min) Number of Rolling Stands Distance between rolling stands (m) Isotropic Material uniformity



15




20
4



5.5



O O 5 O X 6 O X
33
4 △ O 5 O O 6 O O
53
4 X O 5 X O 6 O O

Thickness (mm) Feeding speed (m / min) Number of Rolling Stands Distance between rolling stands (m) Isotropic Material uniformity



15




20
4



6



O O 5 O X 6 O X
33
4 O O 5 O O 6 O △
53
4 X O 5 X O 6 O O

Thus, it can be confirmed that the isotropy and the material uniformity are secured when the above formula is satisfied.

On the other hand, the range of the rolling speed on the inlet side of the finishing mill 22 controlled by the controller 30 according to the variation of the thickness t of the cast steel is shown in the graph of Fig. That is, when the thickness t of the two pieces is about 10 mm, it can be confirmed that the minimum speed should be controlled to about 36 m / min and the maximum speed 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 m, It is possible to control to produce an isotropic steel sheet by controlling the thickness t of the sheet and the feeding speed v of the sheet.

That is, in the rolling machine 20 of the steel plate manufacturing apparatus having excellent isotropy according to the embodiment of the present invention, the number n of the rolling stands R is provided as five, and the number of the rolling stands R The distance d is provided at 5.8 m, and the controller 30 adjusts the rolling speed of the rolling mill 20 so as to satisfy the following equation.

360 < t x v < 715

The control range of the casting speed v and the control range of the thickness t of the cast steel may be determined by the mass flow of the casting passing through the rolling mill 20 on the other side. That is, the steel sheet produced can control the isotropic property while controlling the lower limit value of the mass flow rate passing through the rolling mill 20 to 360 mm · m / min and controlling the upper limit value to 715 mm · m / min.

For example, if the thickness t of the casting slab entering the inlet side of the rolling mill 20 is 16 mm and the feed rate v of the casting slab is 60 m / min, the mass flow rate becomes 960, (T) of the cast steel is 16 mm and the casting speed (v) of cast steel is 36 m / min, the mass flow rate is 576, which is included within the range shown. It will be.

In order to secure the isotropy of the steel sheet, when the rolling mill 20 is controlled, the temperature of the cast steel must be supplied in a state of being limited to a temperature suitable for performing rolling.

For example, when the controller 30 controls the finishing mill 22, it is preferable that the temperature of the finishing mill supplied to the inlet of the finishing mill 22 is provided to be maintained at about 950 to 1100 ° C. At this time, The temperature of the discharged rolled steel sheet is preferably maintained at about 700 to 900 ° C and discharged.

As described above, the steel sheet produced by the steel sheet manufacturing apparatus having excellent isotropy of the present invention can secure isotropy.

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

FIG. 4 is a graph showing the results of earing phenomenon observed when a deep drawing is performed using a steel sheet produced by the conventional technique and a steel sheet produced by the present invention. FIG. to be.

Referring to FIG. 4, the steel sheet produced by the present invention has uniform earing heights at respective positions in the circumferential direction of the molded article during deep drawing. However, when the conventional steel sheet is subjected to deep drawing, It can be seen that the unevenness is serious and the molding defects are generated.

That is, it can be seen that the isotropy of the steel sheet produced by the present invention is superior to that of the prior art.

Further, the 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 middle portion therebetween are uniformly formed with isotropic characteristics.

In other words, even if the above-described steel sheet manufacturing apparatus having excellent isotropy transfers the cast steel produced in the above-described continuous casting machine 10 to the rolling mill 20 without cutting to perform continuous continuous rolling, and finally discharged to the cutting steel plate, The rear end portion and the isotropic characteristic at the middle portion between the front end portion and the rear end portion can be uniformly formed even if the end portion is cut off.

10: Player 20: Rolling machine
21: rough rolling machine 22: finishing mill
30: Controller

Claims (8)

delete A casting machine for producing a cast steel;
A rolling mill having a plurality of rolling stands for receiving and rolling a cast steel produced in the machine, the rolling mill having a roughing mill located on the exit side of the mill and a finishing mill positioned on the side of the roughing mill; And
A controller coupled to the rolling mill to adjust a rolling speed at which the rolling mill is rolled after being drawn into the rolling stand;
/ RTI &gt;
The controller controls the rolling speed to be transferred to the next rolling stand after completion of recrystallization by formation of new nuclei after finishing of the bobbled metal structure rolled in either rolling stand or after completion of recrystallization by nucleation and grain growth, And the rolling speed of the finishing mill is adjusted so as to satisfy the following expression.
15.5 < (t x v) / {(n-1) x d} &lt; 30.8
Where t is the thickness of the cast steel in millimeters, v is the casting speed in m / min, n is the number of rolling stands in the finishing mill and d is the distance between neighboring rolling stands . delete 3. The method of claim 2,
The finishing mill is provided with five (n) of the rolling stands, the distance (d) between neighboring rolling stands being provided at 5.8 m,
Wherein the controller adjusts the rolling speed of the finishing mill so as to satisfy the following equation.
360 < t x v < 715
Where t is the thickness of the cast steel in mm and v is the casting speed in m / min. delete 3. The method of claim 2,
Wherein the cast steel produced in the casting machine is conveyed to the rolling mill without cutting to perform continuous continuous rolling. An isotropic steel sheet produced by a steel sheet manufacturing apparatus having excellent isotropy according to any one of claims 2, 4 and 6. 8. The method of claim 7,
Wherein the isotropic steel sheet has isotropic properties uniformly in the front end portion, the rear end portion and the intermediate portion therebetween.

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