WO2018062749A1 - Apparatus for manufacturing steel plate having excellent isotropy, and steel plate manufactured using same - Google Patents

Abstract

An apparatus for manufacturing a steel plate having excellent isotropy according to an embodiment of the present invention comprises: a rolling mill that has a plurality of rolling stands for pressing cast pieces; and a controller that is connected to the rolling mill so as to control the speed of the rolling mill at which a cast piece is pulled through the rolling stands, pressed and discharged, wherein the controller can control the rolling mill using the speed of the rolling mill at which the metal substance of the cast piece pressed by any one of the rolling stands is re-crystallised, and then transferred to the next rolling stand.

Description

Steel sheet manufacturing apparatus excellent in isotropy and steel sheet produced thereby

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

Slab (slab), which is a kind of slab made through the continuous casting process, is transferred to a hot rolling mill and heated above a predetermined temperature in a heating furnace to secure a temperature for rolling.

The slab extracted from the furnace is rolled through several stages in a roughing mill to secure the desired thickness of the rolled bar, depending on the thickness of the final product, and then the product thickness in the finishing mill. Final rolling is made to ensure.

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, and the slabs extracted from the furnace are used to secure the temperature at each position of the process set according to the characteristics of the product. The temperature of the material is controlled by means of cooling and heating.

In particular, in the final finishing mill, rolling is performed at a certain speed or more in order to secure the entry temperature and exit temperature of the finishing mill and ensure high productivity.

The product produced by the conventional rolling method is rolled again in the next rolling stand before the metal structure such as grain (grain) stretched in the rolling direction at the exit of the rolling stand according to the high rolling speed is recrystallized.

The product produced in this way has anisotropy which shows some difference in material properties in rolling direction and width direction.

The anisotropy of such a material is not a problem in general purpose products, but when deep drawing processing such as forming a cup shape is required, earrings occur and defects are formed in the product.

If this earing phenomenon is severe, it can not be used as a molded product is a cause of lowering the error rate of the product.

Therefore, there has been a need for a study on a steel sheet manufacturing apparatus excellent in isotropy and a steel sheet produced thereby for solving the above problems.

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus for producing a steel sheet excellent in isotropy and a steel sheet produced thereby, which can prevent an earing problem in forming a product and improve an error rate.

The steel sheet manufacturing apparatus excellent in isotropy according to an embodiment of the present invention is connected to the rolling mill and a rolling mill having a plurality of rolling stands for pressing the cast steel, the rolling speed is discharged by being pressed after the cast steel is introduced into the rolling stand And a controller that adjusts the controller, wherein the controller can adjust the mill at a rolling speed that is transferred to the next rolling stand after the metallographic structure of the pressed slab is recrystallized.

In addition, the rolling mill of the steel sheet manufacturing apparatus excellent in isotropy according to an embodiment of the present invention includes a roughing mill located on the exit side of the machine and a finishing mill located on the exit side of the roughing mill, the controller, the finishing mill It can be connected to adjust the rolling speed of the finishing mill.

In addition, the controller of the steel sheet manufacturing apparatus excellent in isotropy according to an embodiment of the present invention may be characterized by adjusting the rolling speed of the finishing mill to satisfy the following formula.

15.5 <(t × v) / {(n−1) × d} <30.8

Where t is the thickness of the cast steel (mm), v is the feed speed (m / min) of the cast steel, n is the number of rolling stands included in the finishing mill, and d is the distance (m) between neighboring rolling stands. .

In addition, the finishing mill of the steel sheet manufacturing apparatus excellent in isotropy according to an embodiment of the present invention, the number of the rolling stand (n) is provided with 3 to 7, the distance (d) between the adjacent rolling stand is 3 It is provided in ~ 6.5m, the controller may be characterized in that to adjust the rolling speed of the finishing mill to satisfy the following formula.

360 <t × v <715

In addition, the steel sheet manufacturing apparatus excellent in isotropy according to an embodiment of the present invention is provided with a player for producing a cast and a plurality of rolling stands provided on the exit side of the machine to receive the cast from the machine, and to roll the cast It includes a rolling mill, the rolling mill is provided with a roughing mill located on the exit side of the machine and the finishing mill located on the exit side of the roughing mill, it may be characterized by satisfying the following formula.

15.5 <(t × v) / {(n−1) × d} <30.8

Where t is the thickness of the cast steel (mm), v is the feed speed (m / min) of the cast steel, n is the number of rolling stands included in the finishing mill, and d is the distance (m) between neighboring rolling stands. .

In addition, the steel sheet manufacturing apparatus excellent in isotropy according to an embodiment of the present invention may be characterized in that the continuous casting is carried out by transferring the cast steel produced in the playing machine to the rolling mill without cutting.

In addition, the isotropic steel sheet according to another embodiment of the present invention may be manufactured by a steel sheet manufacturing apparatus excellent in the isotropic property.

In addition, 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 intermediate portion therebetween form uniformly isotropic characteristics.

The steel sheet manufacturing apparatus and the steel sheet produced by the excellent isotropic property of the present invention may have an advantage that can increase the isotropy by reducing the anisotropy for the steel sheet produced by rolling the cast.

Furthermore, it can also have the advantage of ensuring material uniformity with isotropy.

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

More specifically, by reducing the earing phenomenon occurring during deep drawing molding, such as cup shape, it is possible to prevent the problem caused by the defect of the molded product to have an advantage that can increase the error rate of the product.

1 is a front view showing a steel sheet manufacturing apparatus excellent in isotropy of the present invention.

Figure 2 is a front view showing a controller and a rolling mill in the steel sheet manufacturing apparatus excellent in isotropy of the present invention.

Figure 3 is a graph showing the speed range in the finishing mill for ensuring isotropy in the steel sheet manufacturing apparatus excellent in isotropy of the present invention.

Figure 4 is a graph showing a comparison of the ear ring forming height according to the prior art and the steel sheet manufacturing apparatus excellent in isotropy of the present invention.

Hereinafter, with reference to the drawings will be described in detail a specific embodiment of the present invention. However, the spirit of the present invention is not limited to the embodiments presented, and those skilled in the art who understand the spirit of the present invention may deteriorate other inventions or the present invention by adding, modifying, or deleting other elements within the scope of the same idea. Another embodiment to be included within the scope of the invention can be easily proposed, but it will also be included within the scope of the invention.

In addition, the components with the same functions within the scope of the same idea shown in the drawings of each embodiment will be described using the same reference numerals.

The present invention relates to a steel sheet manufacturing apparatus excellent in isotropy and a steel sheet produced thereby, the steel sheet manufacturing apparatus excellent in the isotropic property of the present invention and the steel sheet produced thereby reduces the anisotropy (anisotropy) for the steel sheet produced by rolling the slab And increase isotropy, it is possible to increase product productivity by preventing a reduction in the error rate due to anisotropy.

That is, by reducing the earing phenomenon that occurs during deep drawing molding such as cup shape, it is possible to prevent the problem caused by the defect of the molded product to have the advantage of increasing the error rate of the product.

Specifically, Figure 1 is a front view showing a steel sheet manufacturing apparatus excellent in isotropy of the present invention, referring to this, a steel sheet manufacturing apparatus excellent in isotropy according to an embodiment of the present invention a plurality of rolling stands for pressing the slab (R And a controller 30 connected to the rolling mill 20 and the rolling mill 20 to adjust the rolling speed at which the cast steel is pressurized and discharged after being introduced into the rolling stand R. 30, the rolling speed is transferred to the next rolling stand (Rn), such as the n-th and the like after the metal structure of the slab pressed in any one of the rolling stand (Rn-1), such as the n-1th The rolling mill 20 may be adjusted. Here, n is the number of rolling stands R included in the rolling mill 20.

In other words, in order to reduce the anisotropy and increase the isotropy of the rolled slab, after the slab is deformed by pressing the slab in one of the rolling stand (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 to control the cast to press the next rolling stand (Rn).

Here, the recrystallization of the metal structure means recrystallization by the formation of a new nucleus after deformation of the metal structure by pressing, and in some cases, may include a process of grain growth according to the growth of the new nucleus.

Since the new nucleus is formed while maintaining isotropy, the new nucleus is prevented from decreasing isotropy due to anisotropy of the previous metal crystal.

The rolling mill 20 may serve to produce a rolled steel sheet by pressing a slab. To this end, the rolling mill 20 may be pressed while passing the cast between the rolling roll pair, it may be provided with a plurality of rolling stands (R) provided with such a roll roll pair.

In addition, the rolling mill 20 is a rough rolling mill 21 for rolling to a medium thickness before producing the cast steel rolled to the final thickness of the provided slab, and the intermediate thickness (t) in the rough rolling mill 21 It may be provided with a finishing mill (22) for producing the cast slab pressed into a rolled steel sheet of the final thickness again.

In other words, the rolling mill 20 of the steel sheet manufacturing apparatus excellent in isotropy according to an embodiment of the present invention, the crude rolling mill 21 and the crude rolling mill 21 located on the exit side of the player 10 is located A finishing mill 22 is provided, and the controller 30 is connected to the finishing mill 22 to adjust a rolling speed of the finishing mill 22.

Here, the roughing mill 21 is located on the exit side of the player 10 to be described later, receives the cast produced by the player 10 to perform a rolling operation, the finishing mill 22 is the roughing mill Located at the exit side of 21, receiving the cast steel subjected to the rolling operation in the roughing mill 21 is subjected to rolling to perform a rolling operation for producing a final rolled steel sheet product.

In particular, the number n of the rolling stands R provided to the roughing mill 21 and the finishing mill 22 may be adjusted according to characteristics such as the material of the rolled steel sheet produced, and the tank in the entire installation. 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, and the secured rolling stands. In the number of (R), the number n actually used for driving is the number n of rolling stands R provided by the roughing mill 21 or the finishing mill 22.

In addition, since the isotropy of the finally produced rolled steel sheet is determined by the rolling speed in the finishing mill 22, the controller 30 adjusts the rolling speed of the rolling stand R to the finishing mill 22. It is desirable to provide for adjustment.

The controller 30 serves to adjust the rolling speed of the rolling mill 20, thereby improving the isotropy to reduce the anisotropy of the rolled steel sheet.

That is, the controller 30 performs rolling by pressing the slab in one rolling stand Rn-1, and then recrystallization of the metal structure of the slab is finished before pressing the slab again in the next rolling stand Rn. By controlling the rolling stand R at a rolling speed, isotropy can be improved.

The reason that the isotropy is improved by performing the next rolling after the recrystallization of the metal texture of the cast steel is completed by the rolling speed control as described above is that if the next rolling is performed before the metal structure is recrystallized, the recrystallization isotropy which is a basic characteristic of the metal structure Because you do not realize.

In other words, the metal structure that loses isotropy because the recrystallization is not completed is formed as an anisotropic crystal even when the strain is accelerated at the next pressing and does not have time to recover the isotropy.

In order to further improve the isotropy of the cast steel by the more precise control of the rolling mill 20, the controller 30 is the distance (d) between the rolling stand (R), the number of the rolling stand (R) (n) ) And the thickness (t) of the cast can be controlled by adding a variable. Detailed description thereof will be described later with reference to FIGS. 2 to 4.

In addition, the steel sheet manufacturing apparatus excellent in isotropy according to an embodiment of the present invention includes a player 10 for producing a cast, and is provided to the mouth of the rolling mill 20 to deliver the produced cast steel to the rolling mill 20. Endless continuous casting (rolling) can be carried out.

In other words, the steel sheet manufacturing apparatus excellent in isotropy according to an embodiment of the present invention is provided on the player 10 for producing a cast steel and the exit side of the player 10 receives the cast steel from the player 10, the cast steel And a rolling mill 20 having a plurality of rolling stands for rolling the rolling mill, wherein the rolling mill 20 is located at the roughing mill 21 and the roughing mill 21 at the exit side of the player 10. The finishing mill 22 may be provided, and the following formula may be satisfied.

15.5 <(t × v) / {(n−1) × d} <30.8

Where t is the thickness of the cast steel (mm), v is the feed rate (m / min) of the cast steel, n is the number of rolling stands included in the finishing mill 22, d is the distance between neighboring rolling stands ( m).

In addition, the steel sheet manufacturing apparatus having excellent isotropy according to an embodiment of the present invention may be characterized in that the continuous casting is carried out by transferring the cast steel produced in the player 10 to the rolling mill 20 without cutting. .

Thus, in the present invention, in order to prevent problems such as plate breaking, twisting, etc. of the cast during the rolling process can be carried out by continuous continuous rolling.

In other words, the problem of plate breaking and twisting of the slab is a problem occurring at the front end or the rear end of the cut slab, so that it is configured to perform continuous rolling to perform rolling with a continuous slab rather than the cut slab. .

Here, the player 10 may serve to produce cast steel from molten steel through a casting process. That is, the player 10 supplies molten steel from the tundish to the mold, and the supplied molten steel forms a cast steel while losing heat, and the cast steel is formed by a segment roll and a pinch roll. Guided and moved can be supplied to the rolling mill 20 to be described later.

2 is a front view showing the controller 30 and the rolling mill 20 in the steel sheet manufacturing apparatus excellent in isotropy of the present invention, Figure 3 is a finishing mill 22 for ensuring isotropy in the steel sheet manufacturing apparatus excellent in isotropy of the present invention Figure 4 is a graph showing a speed range in, Figure 4 is a graph showing a comparison of the earring forming height according to the prior art and the steel sheet manufacturing apparatus excellent in the isotropic property of the present invention.

2 to 4, the controller 30 of the steel sheet manufacturing apparatus excellent in isotropy according to an embodiment of the present invention, characterized in that to adjust the rolling speed of the rolling mill 20 to satisfy the following formula: You can do

15.5 <(t × v) / {(n−1) × d} <30.8

Where t is the thickness of the cast steel (mm), v is the feed rate of the cast steel (m / min), n is the number of rolling stands included in the finishing mill, d is the distance between neighboring rolling stands (R) ( m).

In particular, the feed rate (v) of the cast steel is the supply speed of the cast steel in the first rolling stand (R1) to enter the first cast, the speed corresponding to the rolling speed of the first rolling stand (R1).

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

When such a formula is satisfied, the steel sheet produced by rolling can ensure isotropy. In addition, material uniformity can be secured together with isotropy.

In other words, if the upper limit of 30.8 is exceeded in the above formula, the rolled steel sheet isotropic is not secured, so an upper limit must be secured, and if the lower limit is smaller than 15.5, material uniformity falls, so a lower limit must be secured.

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

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

First, Table 1 below shows that the thickness (t) of the cast steel, the number (n) of the rolling stand, the distance (d) between the rolling stand is fixed, and the injection speed (v) of the cast steel was changed to confirm the isotropy.

Thickness of cast steel (mm)	Casting speed of cast steel (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, fixing the thickness (t) of the cast steel, the feed rate (v) of the cast steel, change the number of the rolling stand (n), the distance (d) between the rolling stand to check whether or not isotropic It was.

Thickness of cast steel (mm)	Casting speed of cast steel (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 of cast steel (mm)	Casting speed of cast steel (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 of cast steel (mm)	Casting speed of cast steel (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

As such, it can be confirmed that isotropy and material uniformity are secured when the equation is satisfied.

On the other hand, the range of the rolling speed at the inlet side of the finishing mill 22 controlled by the controller 30 according to the variation in 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 10mm, it can be seen that the minimum speed of about 36m / min and the maximum speed of about 72m / min should be controlled.

The control by the controller 30 as described above is performed when the number of rolling stands R is five and the distance d between the rolling stands R is limited to about 5.8 mm. It is possible to control to produce an isotropic steel sheet by controlling the thickness t and the feed rate v of the cast steel.

That is, the rolling mill 20 of the steel sheet manufacturing apparatus excellent in isotropy according to an embodiment of the present invention, the number (n) of the rolling stand (R) is provided with 3 to 7, the adjacent rolling stand (R) The distance (d) is provided in 3 ~ 6.5m, the controller 30 may be characterized by adjusting the rolling speed of the rolling mill 20 to satisfy the following formula.

360 <t × v <715

The control range by the injection speed (v) of the cast steel and the thickness (t) of the cast steel may be determined as the mass flow of the cast steel passing through the rolling mill 20 in another aspect. In other words, the steel sheet produced while controlling the lower limit of the mass flow rate passing through the rolling mill 20 at 360 mm · m / min and the upper limit at 715 mm · m / min can maintain the isotropic property.

For example, if the thickness (t) of the slab flowing into the mouth of the rolling mill 20 is 16mm and the injection speed (v) of the slab is 60m / min, the mass flow rate is 960, which is out of the suggested range, thereby ensuring isotropy. However, if the thickness (t) of the cast steel is 16 mm and the feed rate (v) of the cast steel is 36 m / min, the mass flow rate is 576, so that the steel sheet with the isotropic property can be produced. Will be.

In addition, in order to ensure the isotropy of the steel sheet, when controlling the rolling mill 20, the temperature of the cast steel should be supplied in a state provided limited to a temperature suitable for performing rolling.

For example, when the controller 30 controls the finishing mill 22, the temperature of the cast steel supplied to the inlet side of the finishing mill 22 is preferably maintained at about 950 to 1100 ° C. The temperature of the rolled steel sheet discharged is maintained at about 700 ~ 900 ℃ is preferably discharged.

Thus, the steel sheet produced by the steel sheet manufacturing apparatus excellent in isotropy of the present invention can be secured isotropic.

That is, the isotropic steel sheet according to another embodiment of the present invention may be manufactured by a steel sheet manufacturing apparatus excellent in the isotropic property.

In order to confirm such isotropy, reference may be made to FIG. 4. FIG. 4 is a result of observing an earing phenomenon when a deep drawing is performed using a steel sheet produced according to the prior art and a steel sheet produced according to the present invention. to be.

Referring to FIG. 4, the steel sheet produced by the present invention has a uniform earring formation height at each position in the circumferential direction of the molding during the deep drawing, but the depth of the earring formation when the deep drawing of the steel sheet according to the prior art is performed. It can be seen that the unevenness causes severe mold defects.

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

In addition, 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 intermediate portion therebetween form uniformly isotropic characteristics.

In other words, the above-described isotropic steel sheet manufacturing apparatus transfers the slabs produced in the player 10 to the rolling mill 20 without cutting, and performs continuous continuous rolling, even after finally being discharged to the cut steel sheet, the steel sheet Since is manufactured continuously, even if finally cut, it can be provided so that the isotropic properties at the front end, the rear end, and the intermediate part between the front end and the rear end are uniformly formed.

Claims (8)

1. A rolling mill having a plurality of rolling stands for rolling the cast steel; And

   A controller connected to the rolling mill to adjust a rolling speed at which the cast steel is rolled and discharged after being introduced into the rolling stand;

   Including;

   The controller is excellent in isotropic steel sheet manufacturing apparatus for adjusting the rolling mill at a rolling speed that is transferred to the next rolling stand after the metal structure of the rolled slab in any one of the rolling stand is recrystallized.
2. The method of claim 1,

   The rolling mill includes a roughing mill located on the exit side of the player and a finishing mill located on the exit side of the roughing mill,

   The controller is connected to the finishing mill is steel plate manufacturing apparatus excellent in isotropy, characterized in that for adjusting the rolling speed of the finishing mill.
3. The method of claim 2,

   The controller is an excellent steel sheet manufacturing apparatus, characterized in that for adjusting the rolling speed of the finishing mill to satisfy the following formula.

   15.5 <(t × v) / {(n−1) × d} <30.8

   Where t is the thickness of the cast steel (mm), v is the feed speed (m / min) of the cast steel, n is the number of rolling stands included in the finishing mill, and d is the distance (m) between neighboring rolling stands. .
4. The method of claim 2,

   The finishing mill, the number of the rolling stand (n) is provided in 3 to 7, the distance (d) between neighboring rolling stands is provided in 3 to 6.5m,

   The controller is an excellent steel sheet manufacturing apparatus, characterized in that for adjusting the rolling speed of the finishing mill to satisfy the following formula.

   360 <t × v <715

   Where t is the thickness (mm) of the cast steel and v is the feed rate (m / min) of the cast steel.
5. A player for producing cast steel; And

   A rolling mill provided on the exit side of the player to receive the cast steel from the player and having a plurality of rolling stands for rolling the cast steel;

   Including;

   The rolling mill includes a roughing mill located on the exit side of the player and a finishing mill located on the exit side of the roughing mill,

   Steel sheet manufacturing apparatus excellent in isotropy characterized by satisfying the following formula.

   15.5 <(t × v) / {(n−1) × d} <30.8

   Where t is the thickness of the cast steel (mm), v is the feed speed (m / min) of the cast steel, n is the number of rolling stands included in the finishing mill, and d is the distance (m) between neighboring rolling stands. .
6. The method of claim 5,

   The steel sheet manufacturing apparatus excellent in isotropy characterized in that the continuous rolling is carried out by transferring the cast steel produced in the machine to the rolling mill without cutting.
7. An isotropic steel sheet manufactured with a steel sheet manufacturing apparatus having excellent isotropy according to any one of claims 1 to 6.
8. The method of claim 7, wherein

   The isotropic steel sheet is an isotropic steel sheet, characterized in that the front end portion, the rear end portion and the intermediate portion therebetween form uniformly isotropic properties.

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