WO2020096391A1

WO2020096391A1 - Compress-reducing device

Info

Publication number: WO2020096391A1
Application number: PCT/KR2019/015105
Authority: WO
Inventors: 최정윤; 이형준; 김성연
Original assignee: 주식회사 포스코
Priority date: 2018-11-08
Filing date: 2019-11-07
Publication date: 2020-05-14
Also published as: KR20200053295A; KR102288411B1

Abstract

A compress-reducing device according to an embodiment of the present invention comprises a plurality of convex rolls which extend in the widthwise direction of a cast piece, have protrusions protruding outward from the outer circumferential surfaces thereof, and are arranged in a row in the lengthwise direction crossing the widthwise direction of the cast piece, respectively, wherein the protrusions of the plurality of convex rolls have different widths from each other, and the plurality of convex rolls are arranged so that the widths of the protrusions become narrower in a direction in which a solid fraction increases. Accordingly, according to an aspect of the present invention, a plurality of convex rolls are arranged so that the widths of protrusions are decreased in accordance with an increase in a solid fraction, and thus a sufficient compress-reducing force can be transferred to a non-solidified part. Therefore, the present invention can suppress or prevent a defect in a cast piece, that is, occurrence of a shrunk hole or segregation.

Description

Rolling-down device

The present invention relates to a pressing device, and more particularly, to a pressing device capable of suppressing or preventing the occurrence of defects in the inside of the cast iron.

In general, a continuous casting device is a device that injects molten steel into a mold and continuously draws molten steel reacted in the mold downward to produce cast pieces of various shapes such as slabs, blooms, billets, beam blanks, and the like.

Looking at the general configuration of such a continuous casting device, a tundish that temporarily receives and receives molten steel from a ladle, and a mold that initially injects molten steel through an immersion nozzle from the tundish and initially solidifies into a constant shape through primary cooling ( mold) and a cooling zone that performs a series of molding operations while completing the solidification by secondary cooling the cast steel drawn from the mold. The cast piece that has passed through the cooling zone is cut to a predetermined length, and then transferred to a collecting point.

Solidification proceeds from the surface toward the center, and unsolidified molten steel remains inside the casting until solidification is completed. Here, solidification shrinkage occurs, and voids and segregation may be formed inside the casting. have.

Since the voids and segregation significantly deteriorate the quality of the cast, in order to solve this, the cast is pressed with a pressing device equipped with a plurality of rolling rolls to suppress the occurrence of central segregation of the cast by reducing the residual voids.

On the other hand, as the cast becomes farther from the mold, in other words, the amount of uncoated steel inside decreases as it goes to the end of solidification, and its strength increases.

However, in the prior art, in rolling down the cast steel, regardless of a decrease in the amount of uncoagulated molten steel or an increase in strength of the cast steel, the cast steel was rolled using a flat roll having a constant diameter in the width direction. In this case, the unsolidified molten steel is not sufficiently depressed in the end of the solidification period with high strength. In other words, at the end of solidification, the pressing force applied from the flat roll is insufficient to suppress the occurrence of voids and segregation, and there is a problem that the quality of the cast steel is deteriorated.

To solve this problem, it is possible to improve the entire casting facility to increase the rolling-down force in the end of solidification, but for this, there is a problem that the cost for improvement is increased.

(Advanced technical literature)

(Patent Document 1) Korean Patent Publication 2012-0057315

The present invention provides a pressing device capable of suppressing or preventing the occurrence of segregation and shrinkage pores inside the cast iron.

The present invention provides a pressing device capable of increasing the pressing force applied to the cast piece.

The pressing device according to the embodiment of the present invention, each of which is formed to extend in the width direction of the cast piece, is provided with a protruding portion protruding outward on the outer circumferential surface, a plurality of convex rolls arranged in a longitudinal direction crossing the width direction of the cast piece Including, the protrusions of each of the plurality of convex rolls have different widths, and the plurality of convex rolls are arranged such that the width of the protrusions narrows toward the direction in which the solid phase rate of the cast piece increases.

The width of each projection of each of the plurality of convex rolls is equal to or greater than the width of the unsolidified portion of the cast piece on which each convex roll is disposed.

Each of the plurality of convex rolls is provided such that the center in the width direction of the protrusion is on a straight line with the center in the width direction of the non-solidified portion of the cast piece.

Three or more convex rolls are provided.

The plurality of convex rolls are installed in sections with a solid phase ratio of more than 0.6 and less than 1.0.

The plurality of convex rolls are installed in a section having a solid phase ratio of more than 0.6 and 0.9 or less.

On the upper and lower sides of the cast piece, the plurality of convex rolls are arranged in series in the extending direction of the cast piece.

Each is formed to extend in the width direction of the cast piece, and includes a plurality of flat rolls arranged in the longitudinal direction of the cast piece, and on either one of the upper and lower sides of the cast piece, the plurality of convex rolls extend in the direction of the cast piece In a row, the plurality of flat rolls are arranged in a row in the extending direction of the cast on the other side.

Each is formed to extend in the width direction of the cast piece, and includes a plurality of flat rolls arranged in the longitudinal direction of the cast piece, and arranged so that the convex roll and the flat roll are alternately repeated multiple times on each of the upper and lower sides of the cast piece. It is arranged so that the arrangement of the convex roll and the flat roll on the upper side of the cast piece and the arrangement of the convex roll and the flat roll on the lower side of the cast piece are staggered.

The plurality of convex rolls are disposed at the rear of the plurality of convex rolls so as to be located in a lower solid phase section than the solid phase ratio of the cast pieces, each of which is formed to extend in the width direction of the cast piece, the longitudinal direction of the cast piece It includes a plurality of flat rolls arranged in line.

The plurality of flat rolls are installed in sections having a solid phase ratio of 0.3 or more and 06 or less.

According to the embodiment of the present invention, a sufficient pressing force can be transmitted to the non-solidified portion by arranging a plurality of convex rolls so that the width of the protruding portion decreases as the solid phase rate increases. Therefore, it is possible to suppress or prevent the occurrence of defects inside the cast iron, that is, shrinkage holes and segregation.

In addition, as the pressing portion is pressed using a plurality of convex rolls having different widths, the pressing marks are formed more gently than in the prior art. Accordingly, it is possible to prevent the occurrence of surface defects, such as overlapping defects, during rolling of the cast, which is a subsequent process.

In addition, it is possible to increase the pressing force without taking a large cost of remodeling the entire casting facility, thereby reducing the cost of improving the facility.

1 is a view showing a casting equipment including a pressing device according to an embodiment of the present invention

Figure 2 is a conceptual diagram for explaining the uncoated portion of the cast

Figure 3 is a conceptual diagram for explaining the width of the non-solidified portion according to the solid phase rate

4 is a view showing a flat roll according to an embodiment of the present invention

5 is a view showing a convex roll according to an embodiment of the present invention

6 is a conceptual diagram for explaining the arrangement of a plurality of convex rolls according to an embodiment of the present invention according to the increase of the solid phase rate of the cast

7 is a conceptual diagram for explaining the arrangement of a plurality of flat rolls and a plurality of convex rolls according to an embodiment of the present invention according to the solid phase rate of the cast steel

8 is a conceptual diagram for explaining the arrangement of the convex roll in the vertical direction of the cast iron in the pressing device of the embodiment of the present invention

9 is a conceptual diagram for explaining the arrangement of the roll in the vertical direction of the cast piece in the pressing device according to the modification of the embodiment

10 is a graph showing the amount of reduction by the roll located at the end and the force applied from the driving device to achieve the amount of reduction.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, and only the present embodiments allow the disclosure of the present invention to be complete, and the scope of the invention to those skilled in the art is completely It is provided to inform you. The same reference numerals in the drawings refer to the same elements.

1 is a view showing a casting equipment including a pressing device according to an embodiment of the present invention. 2 is a conceptual diagram for explaining a non-coagulation part of a cast piece. 3 is a conceptual diagram for explaining the width of the non-solidified portion according to the solid-phase rate.

4 is a view showing a flat roll according to an embodiment of the present invention. 5 is a view showing a convex roll according to an embodiment of the present invention. 6 is a conceptual diagram for explaining the arrangement of a plurality of convex rolls according to an embodiment of the present invention according to an increase in the solid phase rate of a cast steel. 7 is a conceptual diagram for explaining the arrangement of a plurality of flat rolls and a plurality of convex rolls according to an embodiment of the present invention according to the solid phase ratio of the cast steel. 8 is a conceptual view for explaining the arrangement of the convex roll in the vertical direction of the cast steel in the rolling-down device of the embodiment of the present invention.

Referring to FIG. 1, the casting facility receives the molten steel and temporarily stores it in a tundish (10) for storing and temporarily storing it, and receives the molten steel stored in the tundish (10) in an open form to initially solidify in a predetermined shape ( It includes a solidification device (primary solidification) (mold) (20), solidification (secondary solidification) while moving the cast steel (S) drawn from the mold 20 in one direction, and a solidification device (4000) for pressing it down.

In addition, the casting equipment is located in front of the immersion nozzle 30 and the solidification device 4000 for supplying molten steel of the tundish 10 to the mold 20, a cutting machine for cutting the finished solid S (not shown) Poetry).

The tundish 10 is a means for supplying molten steel to the mold 20, and is a shape of a container having an inner space for receiving molten steel, and the outermost outer wall is formed of an iron shell, and the inner wall of the iron shell is protected by a refractory material.

The mold 20 has a hollow shape having upper and lower sides open and an internal space. In addition, the mold 20 has a shape in which the lower side is opened for continuous drawing of the primary solidified cast steel S therein, and the lower opening is closed by a dummy bar (not shown) before casting starts.

The coagulation device 4000 is located at the lower side of the mold 20 and is located in front of the guide device 4100 and the guide device 4100 for moving and cooling the cast piece S drawn from the mold 20, the cast piece And a pressing device 4200 for pressing the cast piece S while moving and cooling (S).

The guide device 4100 is positioned between the plurality of guide rolls 4110 and a plurality of guide rolls 4110 arranged from the lower side of the mold 20 to the front end of the pressing device 4200 and toward the cast piece S It includes an injection nozzle (not shown) for spraying coolant.

The plurality of guide rolls 4110 may include a plurality of drive rolls capable of self-rotating to move the cast piece S in one direction, and a plurality of rotation rolls rotatable by the force of the moving piece S.

On the other hand, the primary solidified from the mold 20 and drawn out (S) is secondary solidified by the cooling water injected while moving along the solidification device 4000. In this way, the solidification of the cast iron S proceeds from the surface of the cast iron S to the inner side, whereby the center of the cast iron S is solidified at the latest.

Here, the central part of the cast iron S is the center of the width direction (Y-axis direction) and the thickness direction of the cast steel S (crossing the X-axis direction) or the longitudinal direction (X-axis direction) of the cast steel S Z-axis direction) (see Fig. 2).

As described above, as the solidification proceeds from the surface of the cast iron S in the inner direction, the final solidification completion point of the cast steel S becomes the center of the cast steel.

Therefore, there is a molten steel (hereinafter, unsolidified molten steel) that has not yet solidified inside the region of the slab S that has not yet reached the completion position of solidification, where solidification shrinkage occurs, thereby causing central segregation and Voids can form.

In order to solve this problem, a rolling device 4200 is installed in front of the guide device 4100 to roll down the cast iron S, and more specifically, soft reduction.

On the other hand, as the above-mentioned, the casting S is solidified and cooled while passing through the solidification device 4000, so that the liquid amount inside the casting S increases from the lower side of the mold 20 toward the direction where the cutter (not shown) is located. (In other words, the amount of uncoated molten steel) decreases, and the amount of solid phase increases. In other words, the solid state rate increases as the area of the cast piece S adjacent to the cutter (not shown) increases.

The solid-phase rate is a value indicating how much unsolidified molten steel is contained in the cast steel, that is, the width (Y-axis direction) length (W _S ) of the cast steel (S) and the unsolidified molten steel in the cast steel (S). It can be expressed as a ratio of the width W (Y-axis direction) length W _L of the non-solidified portion LA (see FIGS. 2 and 3).

For example, when the solid phase rate is 0.3, when the width direction length W _{S of the} cast piece S is 1, the width W _L of the non-solidified portion in the entire width direction length W _S of the cast piece S is 1 ) Means 0.7 (70%) (see Fig. 3 (a)). As another example, that the solid phase ratio is 0.6 means that the width W _L of the non-solidified portion is 0.4 (40%) in the entire length W _S of the cast steel S (see FIG. 3 (b)). ). As another example, having a solid phase rate of 0.9 means that the width W _L of the non-solidified portion is 0.1 (10%) in the entire length W _S of the cast steel S (Fig. 3 (c). ) Reference).

And, the position at which the solid phase rate is 1.0 is the position in which the width W _L of the non-solidified portion LA becomes '0' in the entire width direction length W _S of the cast piece S, that is, there is no liquid amount. In other words, this is the location where the solidification is completed, and is usually referred to as the solidification completion point S _F (see FIG. 2).

As described above, as the cast piece S moves along the solidification device 4000, the solid state rate increases as cooling or solidification progresses. That is, as the solidification completion point S _F approaches, the length and thickness (the length in the Z-axis direction) of the solid portion SA increase in the width direction (the length in the Z-axis direction), and the width direction (in the Y-axis direction) of the liquid portion LA ) Length and thickness (Z-axis length) decrease.

And, as the solid phase rate increases, the strength increases by decreasing the liquid phase and increasing the solid phase. In addition, since the temperature of the cast steel S decreases as it approaches the solidification completion point S _F , the strength of the cast steel S increases.

As described above, since the strength increases as the area closer to the solidification completion point S _F increases, the deformation resistance due to pressing increases, so that the closer it is to the solidification completion point S _F , the greater the force is required. There is. In other words, a greater pressing force is needed.

On the other hand, even in a section in which the solid phase rate is less than 0.3, even if a pressing force is provided, it is difficult to press down because the surface of the cast steel S is not sufficiently solidified. Accordingly, even in the case where the solid phase rate is less than 0.3, the effect of suppressing the occurrence of shrinkage cavities and segregation may not be obtained, or cracks may be generated inside the cast.

Further, in the section where the solid phase rate is 0.3 or more and 0.6 or less (0.3 to 0.6), the surface of the cast steel is solidified to facilitate reduction, and sufficient unsolidified molten steel exists inside. In addition, the solid phase rate is 0.3 or more and 0.6 or less. In the section (0.3 to 0.6), since the temperature of the cast steel S is relatively high and the strength is low compared to the section with a solid phase ratio exceeding 0.6, it is possible to sufficiently reduce even with a small pressing force.

In addition, in the section where the solid phase rate exceeds 0.6, the amount of unsolidified molten steel is small, the solid phase amount is large, the temperature is low, and the strength of the cast steel (S) is high compared to a section having a solid phase rate of 0.3 or more and 0.6 or less. Accordingly, the deformation resistance of a section in which the solid phase rate exceeds 0.6 is larger than a section in which the solid phase rate is 0.3 or more and 0.6 or less. Therefore, in order to sufficiently reduce the unsolidified portion LA in a section in which the solid phase rate exceeds 0.6, a large force or a pressing force is required compared to a section in which the solid phase rate is 0.3 or more and 0.6 or less.

In addition, in a section where the solid phase rate exceeds 0.6, the strength tends to increase rapidly with an increase in the solid phase rate, and in the section where the solid phase rate exceeds 0.6, the rolling force is further increased toward the solidification completion point (S _F ). There is a need.

Therefore, the pressing device 4200 according to an embodiment of the present invention is pressed with a relatively small pressing force in a section having a solid phase rate of 0.3 or more and 0.6 or less, and a relatively large pressing force in a section having a solid phase rate exceeding 0.6. It is configured to be pressed.

In addition, the pressing device 4200 is configured to increase the pressing force toward the casting direction or solidification completion point in a section where the solid phase rate exceeds 0.6.

Hereinafter, a pressing device according to an embodiment will be described.

1, 4 to 8, the pressing device 4200, each of which is formed to extend in the width direction (Y-axis direction) of the cast piece (S) of the cast piece (S) in front of the guide roll (4110) A plurality of flat rolls 4210 arranged in series in the extension direction (X-axis direction) and each of which is formed to extend in the width direction (Y-axis direction) of the cast piece S, and thus the cast piece S in front of the plurality of flat rolls 4210 It includes a plurality of convex rolls 4220 arranged in a row in the extending direction (X-axis direction).

In addition, the pressing device 4200 includes an injection nozzle (not shown) that is located between the plurality of flat rolls 4210 and the convex rolls 4220 to spray cooling water into the cast piece S.

Each of the plurality of flat rolls 4210 and the plurality of convex rolls 4220 is provided on the upper and lower sides of the cast piece S, respectively. That is, on each of the upper side and the lower side of the cast piece S, a plurality of flat rolls 4210 are arranged in a row, and a plurality of convex rolls 4220 are arranged in a row in front of the last flat roll 4210.

The pressing device 4200 moves the upper flat roll 4210 and the lower flat roll 4210 closer to each other, and moves the upper convex roll 4220 and the lower convex roll 4220 closer to each other, thereby being positioned therebetween. It is a device for rolling down the cast piece S.

To this end, the pressing device 4200, the flat roll 4210 on the upper side of the cast steel S, so that the separation distance between the flat roll 4210 located on the upper side of the cast steel S and the flat roll 4210 located on the lower side is adjusted. A driving device (not shown) that can be moved up and down and rotated, and the upper side of the cast piece S so that the separation distance between the convex roll 4220 positioned on the upper side of the cast piece S and the convex roll 4220 located on the lower side is adjusted. It includes a driving device (not shown) that can move up and down and rotate the convex roll 4220 of.

The rolling-down device 4200 as described above, that is, the plurality of flat rolls 4210 and the plurality of convex rolls 4220 are arranged in a section in which the solid phase ratio is 0.3 or more and less than 1. Preferably, a plurality of flat rolls 4210 and a plurality of convex rolls 4220 are installed in a section having a solid phase ratio of 0.3 or more and 0.9 or less. Then, the flat roll 4210 or the convex roll 4220 is disposed according to the solid phase rate.

Hereinafter, the flat roll 4210 and the convex roll 4220 will be described in more detail.

4 and 7, the flat roll 4210 includes a roll member (hereinafter, a first roll member 4211) and a first roll member 4211 formed in the width direction (Y-axis direction) of the cast piece S It includes a rotating body (hereinafter, the first rotating body 4212) formed to protrude outward from both ends in the extending direction of).

The first roll member 4211 has a flat outer peripheral surface in a direction parallel to the width direction (Y-axis direction) of the cast piece S. That is, the first roll member 4211 has a shape in which the diameter of the cast piece S does not change in the width direction (Y-axis direction). In other words, the height of the outer circumferential surface parallel to the width direction (Y-axis direction) of the cast piece S does not change or is the same as the first roll member 4211 in the width direction (Y-axis direction) of the cast piece S.

In addition, the length of the first roll member 4211 in the width direction (Y-axis direction) may be greater than or equal to the length of the width direction (Y-axis direction) of the cast piece S.

The first rotating body 4212 may be installed to protrude outwardly from one end and the other end, which are both ends in the extending direction (Y-axis direction) of the first roll member 4211. A driving device (not shown) for applying a rotational driving force may be connected to the first rotating body 4212.

In addition, the first roll member 4211 and the first rotation body 4212 are driven by rotational power applied to the first rotation body 4212, so that the first rotation body 4212 and the first roll member 4211 are formed. It is installed mutually fastened or connected so that it can rotate together.

As described above, the flat roll 4210 as described above is installed in a section having a solid phase ratio of 0.3 or more and 0.6 or less. More specifically, in a section in which the solid phase rate is 0.3 or more and 0.6 or less, a plurality of flat rolls 4210 are arranged in the extending direction (X-axis direction) of the cast piece S on each of the upper and lower sides of the cast piece S.

In the section where the solid phase rate is 0.3 or more and 0.6 or less, sufficient unsolidified molten steel exists inside, and since the temperature of the cast steel S is relatively high, it is possible to sufficiently reduce even with a small pressing force.

Therefore, the unsolidified portion LA in a section having a solid phase ratio of 0.3 or more and 0.6 or less can be sufficiently reduced even with a flat roll 4210.

1, 5, and 6, the convex roll 4220 is in the outer peripheral surface F in a direction parallel to the width direction (Y-axis direction) of the cast iron S, and some regions protrude outward. . That is, the convex roll 4220 has a different diameter in the width direction (Y-axis direction) of the cast piece S, and is a region in which a relatively large diameter area protrudes.

Hereinafter, a region protruding outward from the outer circumferential surface F of the convex roll 4220 parallel to the width direction (Y-axis direction) of the cast piece S is referred to as a protrusion portion 4221a.

When explaining the configuration of the convex roll 4220 in more detail, it is formed to extend in the width direction (Y axis direction) of the cast piece S, and the outer peripheral surface F parallel to the width direction (Y axis direction) of the cast piece S A rotating member (hereinafter referred to as a protruding portion 4221a) is formed to protrude outward from both ends in the extending direction (Y-axis direction) of the roll member (hereinafter, the second roll member 4221) and the second roll member 4221. It includes a second rotating body (4222).

The second roll member 4221 is a shape in which a part of the region protrudes outward on the outer peripheral surface F parallel to the width direction (Y-axis direction) of the cast piece S. That is, in the second roll member 4221, the cast steel S has a different diameter in the width direction (Y-axis direction), the diameter of the center of the width direction is larger than other areas, and the area with a relatively large diameter is a protrusion ( 4221a). In other words, the outer circumferential surface F of the second roll member 4221 includes a protrusion 4221a that protrudes further outward.

Further, the width or the extended length (the length in the Y-axis direction) of the second roll member 4221 may be greater than or equal to the width (W _S ) (the length in the Y-axis direction) of the cast piece S.

It is preferable that the protruding portion 4221a is provided so that the center of its width direction (Y-axis direction) and the center of the width direction (Y-axis direction) of the cast piece S coincide. In addition, the width A of the protrusion (the length in the Y-axis direction) may be equal to or greater than the width W _L (the length in the Y-axis direction) of the non-solidified portion LA.

The second rotating body 4222 may be installed to protrude outwardly from one end and the other end, which are both ends in the extending direction (Y-axis direction) of the second roll member 4221. The second rotating body 4422 may be connected to a driving device that applies rotational driving force.

In addition, the second roll member 4221 and the second rotation body 4222 are driven by rotational power applied to the second rotation body 4222, so that the second rotation member 4422 and the second roll member 4221 are rotated. It is installed mutually fastened or connected so that it can rotate together.

On the other hand, in the section where the solid phase rate exceeds 0.6, the solid phase amount is higher than the section having a solid phase rate of 0.3 to 0.6, and the strength is high. Therefore, when the flat roll 4210 is used for pressing, the pressing force reaching the unsolidified portion is reduced. Insufficient, it is not possible to effectively lower the non-solidified portion LA.

However, in the case of the convex roll 4220, since the protrusion part 4121a is provided on a part of the outer circumferential surface F, the pressing force applied to the non-solidified part LA of the cast steel S compared to the flat roll 4210 is provided. Can be increased.

This, when the slab (S) is pressed by adjusting the interval so that the upper convex roll 4220 and the lower convex roll 4220 are closer, among the outer circumferential surfaces (F) of the upper and lower convex rolls 4220, the upper side This is because the separation distance between the protruding portion 4221a and the lower protruding portion 4221a is closer than other regions (see FIG. 8). Accordingly, among the outer circumferential surfaces F of the convex roll 4220, the pressing force exerted on the cast S region facing the protrusions 4221a and the pressing force applied to the cast S region facing the other outer circumferential surfaces F It is big compared to.

Therefore, a plurality of convex rolls 4220 are installed in a section requiring a large pressing force, that is, a section having a solid phase ratio of greater than 0.6 and less than 1.0. In the section where the solid phase ratio is greater than 0.6 and less than 1.0, at least three convex rolls 4220 are installed on the upper and lower sides of the cast piece S, respectively.

In addition, the width of the unsolidified portion LA decreases as the width W _L goes toward the solidification completion point S _F , and in the section where the solid phase rate exceeds 0.6, the strength of the cast steel S rapidly increases as the solid phase rate increases. Increase.

Accordingly, in the installation of a plurality of convex rolls 4220 in the extending direction of the cast piece S in a section where the solid phase rate is greater than 0.6 and less than 1.0, as shown in FIGS. 6 and 7, solidification completion point S _F The width A of the protrusion 4221a (the length in the Y-axis direction) decreases toward the position. That is, in a plurality of convex rolls 4220, the widths A of each of the protrusions 4221a are all different, and in a section in which the solid phase ratio is greater than 0.6 and less than 1.0, the protrusions gradually go toward the solidification completion point S _F A plurality of convex rolls 4220 are installed so that the width A of 4221a (the length in the Y-axis direction) is small.

The convex roll 4220 as described above is disposed on each of the upper and lower sides of the cast piece S, as shown in FIG. 8. That is, a plurality of convex rolls 4220 are disposed on each of the upper and lower sides of the cast iron S of a section with a solid phase ratio of greater than 0.6 and less than 1.0, and the width A of the protrusion 4221a increases toward the solidification completion point S _F position. ) (The length in the Y-axis direction) is arranged to be small.

At this time, the protrusions 4221a of each of the plurality of convex rolls 4220 are preferably provided so that the center of the width direction (Y-axis direction) is located in line with the center of the width direction of the cast piece S.

In addition, the width A (the length in the Y-axis direction) of the protrusions 4221a of each of the plurality of convex rolls 4220 is the same as the width W _L of the non-solidified portion LA at the position where each is disposed. It is preferred, but is not limited to this, and may be large in length.

As described above, the width A of the protrusion 4221a (the length in the Y-axis direction) may be larger than the width W _{L of the} non-solidified portion LA, for example, of the non-solidified portion LA The width may be adjusted so that the difference between the width W _L and the width A of the protrusion 4221a is 5% or less of the width W _L of the non-solidified portion LA.

Thus, the installation of the convex roll 4220 having a narrower width A (the length in the Y-axis direction) of the protruding portion 4221a toward the solidification completion point S _F is the width A of the protruding portion 4221a ( The smaller the length in the Y-axis direction), the smaller the force applied or the area acting, and the same force exerted from the driving device has the effect of concentrating the force into the area of the cast steel S facing the protrusion 4221a. Because there is.

Accordingly, there is an effect of increasing the amount of reduction in which the area of the slab S facing the protrusion 4221a, that is, the unsolidified portion LA is pressed down.

As described above, the convex roll 4220 having a narrow width (A) (length in the Y-axis direction) of the protruding portion 4221a toward the solidification completion point S _F in a section in which the solid phase rate is greater than 0.6 and less than 1.0 is installed and reduced. By doing so, the unsolidified portion LA can be sufficiently lowered in a section where the solid phase ratio is greater than 0.6 and less than 1.0.

Therefore, it is possible to suppress or prevent the occurrence of shrinkage holes and segregation at the center of the cast piece S.

In addition, as the width A of the protrusions 4221a is reduced by using a plurality of convex rolls 4220 different from each other, the reduction marks are formed more slowly than in the prior art. Accordingly, it is possible to prevent the occurrence of surface defects, such as overlapping defects, during rolling of the cast, which is a subsequent process.

In addition, since the strength of the solid portion SA is stronger than that of the non-solidified portion LA and the strength of the solid portion SA is stronger in a section in which the solid phase ratio is greater than 0.6 and less than 1.0, a large pressing force is applied to the solid portion SA. In some cases, cracks may occur.

However, the width A (Y-axis length) of each of the protrusions 4221a of the plurality of convex rolls 4220 according to the embodiment is the width W _L of the non-solidified portion LA at the position where each is disposed. ), Or provided to have a predetermined length and is positioned corresponding to the non-solidified portion LA, so that a relatively small pressing force is applied to the solid portion SA compared to the non-solidified portion LA. Therefore, it is possible to suppress or prevent the occurrence of cracks in the solid phase.

9 is a conceptual view for explaining the arrangement of the convex roll in the vertical direction of the cast piece in the pressing device according to the modification of the embodiment.

In the above-described embodiment, it has been described that a plurality of convex rolls 4220 are installed on the upper and lower sides of the cast piece S, respectively.

However, the present invention is not limited thereto, and as shown in the modified example shown in FIG. 9, the convex roll 4220 may be disposed on the upper side of the cast piece S, and the flat roll 4210 may be disposed on the lower side. More specifically, in a section in which the solid phase ratio is greater than 0.6 and less than 1.0, a plurality of convex rolls 4220 are arranged in the extension direction of the cast piece S on the upper side of the cast piece S, and the lower side of the cast piece S A plurality of flat rolls 4210 may be arranged in the direction of extension of the cast piece (S). At this time, at least three or more convex rolls 4220 installed on the upper side of the cast piece S. In addition, a plurality of convex rolls 4220 are arranged on the upper side of the cast piece S, and the convex roll 4220 having a narrow width A of the protrusion toward the solidification completion point S _F is disposed.

In addition, although not shown, as shown in FIG. 9, the flat roll 4210 may be disposed on the upper side of the cast piece S, and the convex roll 4220 may be disposed on the lower side.

As another example, in the section where the solid phase rate is greater than 0.6 and less than 1.0, the convex roll 4220 and the flat roll 4210 may be alternately arranged in the extending direction of the cast piece S on the upper and lower sides of the cast piece S, respectively. have.

That is, in a section in which the solid phase rate is greater than 0.6 and less than 1.0, the convex roll 4220 and the flat roll 4210 are alternately installed and repeated multiple times on the upper side of the cast piece S, and the convex roll on the lower side of the cast piece S ( 4220) and the flat roll 4210 may be alternately installed to be repeated multiple times. At this time, the arrangement of the convex roll 4220 and the flat roll 4210 on the upper side of the cast piece S, and the arrangement of the convex roll 4220 and the flat roll 4210 on the lower side of the cast piece S may be arranged to be staggered. At this time, at least three or more convex rolls 4220 are installed on the upper and lower sides of the cast iron. Then, the plurality of convex rolls 4220 are disposed on each of the upper and lower sides of the cast piece S, and are arranged in such a manner that the width A of the protruding portion 4221a becomes narrower toward the solidification completion point S _F.

As in the above-described modified examples, in a section in which the solid phase ratio is greater than 0.6 and less than 1.0, the width A of the protrusions 4221a is narrowed in the extending direction of the cast steel S on the upper or lower surface of the cast steel S, By installing the flat roll 4210 on the upper side or the lower side of the cast piece S, it is possible to more effectively suppress the occurrence of overlapping flaws while improving the pressing force in the section where the solid phase rate is greater than 0.6 and less than 1.0 compared to the prior art.

Table 1 shows whether segregation occurred in the cast slab pressed by the method according to Comparative Examples and Examples.

In the first comparative example, in rolling down the cast S, a plurality of flat rolls were installed on each of the upper and lower sides of the cast in a section with a solid phase ratio of 0.3 or more and 0.9 or less, and the roll was pressed.

In the second comparative example and the embodiment, in rolling down the cast piece S, a plurality of flat rolls 4210 are installed on each of the upper and lower sides of the cast piece in a section with a solid phase rate of 0.3 or more and 0.6 or less, and the rolling phase is over 0.6, In a section of 0.9 or less, a plurality of convex rolls 4220 are installed on each of the upper and lower sides of the cast, and are pressed.

Here, the second comparative example is a case where the width A of the protrusions 4221a of the plurality of convex rolls 4220 in a section with a solid phase ratio of more than 0.6 and 0.9 or less is the same.

And, the embodiment is a case in which a plurality of convex rolls 4220 are disposed in a section with a solid phase ratio of more than 0.6 and 0.9 or less, so that the width A of the protrusion 4221a decreases toward the solidification completion point S _F.

The amount of rolling is a difference value between the thickness of the cast steel S before rolling down and the thickness of the casting S after rolling down.

구분division	압하량(mm)Rolling amount (mm)
제 1 비교예Comparative Example 1	16mm16 mm
제 2 비교예Comparative Example 2	25.5mm25.5mm
실시예Example	31mm31 mm

Referring to Table 1, in the case of the first comparative example, the rolling reduction amount was 16 mm, and contraction holes and segregation were clearly seen. In addition, in the second comparative example, the rolling reduction amount was 25.5 mm, which was increased compared to the first comparative example, and shrinkage holes and segregation occurred, but decreased compared to the first comparative example. Looking at the example, the rolling reduction amount was 31 mm. It can be seen that the increase was compared to the first and second comparative examples, and it was confirmed that the occurrence of shrinkage cavities and segregation was significantly improved compared to the first and second comparative examples.

From this, by pressing the slab S using the pressing device 4200 according to the embodiment, it is possible to increase the pressing amount so that the unsolidified portion LA is sufficiently pressed, thereby suppressing segregation and shrinkage hole generation. You can see that

FIG. 10 is a graph showing the amount of reduction by the roll located at the end of the test described in Table 1 and the force applied from the driving device to achieve the amount of reduction.

The last positioned roll is a roll installed at a position with a solid phase ratio of 0.9, which is a flat roll in the first comparative example and a convex roll in the second comparative example and the embodiment.

The force applied from the driving device was expressed as a ratio of the performance to the force capability that the driving device can exert maximum.

In the case of the first comparative example using only the flat roll 4210, the maximum force was required even with a small rolling reduction performance. In the case of the second comparative example using the flat roll 4210 and the convex roll 4220 having the same protruding portion 4221a width, the maximum force was required, but the amount of rolling reduction was increased compared to the first comparative example. That is, a larger amount can be reduced under the same force condition.

And, in the embodiment in which the convex roll 4220 is disposed such that the width of the flat roll 4210 and the protrusions 4221a is narrow, the proportion of performance is higher, despite more rolling reduction results than the first and second comparative examples. It was smaller than this maximum value. That is, it showed a higher rolling amount at a lower performance ratio than the first and second comparative examples.

Therefore, according to the rolling-down device 4200 according to the embodiment, it is possible to increase the rolling-down force without taking a large cost of remodeling the entire casting facility, thereby reducing the cost of improving the facility.

Claims

Each of which is formed to extend in the width direction of the cast piece, is provided with a protruding portion projecting outward on the outer circumferential surface, and includes a plurality of convex rolls arranged in the longitudinal direction crossing the width direction of the cast piece,

The protrusions of each of the plurality of convex rolls have different widths,

The pressing device in which the plurality of convex rolls are arranged such that the width of the protrusions becomes narrower as the solid phase rate of the cast piece increases.
The method according to claim 1,

The width of the protrusions of each of the plurality of convex rolls is equal to or greater than the width of the unsolidified portion of the cast piece on which each convex roll is disposed.
The method according to claim 1,

Each of the plurality of convex rolls, the pressing device is provided so that the center of the width direction of the protrusion is in line with the center of the width direction of the non-solidified portion of the cast piece.
The method according to claim 1,

The convex roll is provided with three or more pressing devices.
The method according to claim 4,

The plurality of convex roll is a rolling-down device that is installed in a section having a solid phase ratio greater than 0.6 and less than 1.0.
The method according to claim 5,

The plurality of convex roll is a rolling-down device that is installed in a section having a solid phase ratio of more than 0.6, 0.9 or less.
The method according to claim 5,

A rolling-down device in which the plurality of convex rolls are arranged in a row in the extending direction of the cast piece on each of the upper and lower sides of the cast piece.
The method according to claim 5,

Each is formed to extend in the width direction of the cast piece, and includes a plurality of flat rolls arranged in the longitudinal direction of the cast piece,

On either one of the upper and lower sides of the cast piece, the plurality of convex rolls are continuously arranged in the extension direction of the cast piece, and the plurality of flat rolls are continuously arranged in the extension direction of the cast piece on the other side. .
The method according to claim 5,

Each is formed to extend in the width direction of the cast piece, and includes a plurality of flat rolls arranged in the longitudinal direction of the cast piece,

On the upper and lower sides of the cast piece, the convex roll and the flat roll are alternately arranged to be repeated a plurality of times,

The rolling-down apparatus arrange | positioned so that the arrangement of the said convex roll and a flat roll in the upper side of the said casting, and the arrangement of the convex roll and a flat roll in the lower side of the said casting may be staggered.
The method according to any one of claims 1 to 9,

The plurality of convex rolls are disposed at the rear of the plurality of convex rolls, so that they are located in a lower solid phase section compared to the solid phase rate of the cast piece,

A pressing device comprising a plurality of flat rolls, each of which is formed to extend in the width direction of the cast piece and arranged in the longitudinal direction of the cast piece.
The method according to claim 10,

The plurality of flat rolls is a rolling-down device that is installed in a section having a solid phase ratio of 0.3 or more and 0.6 or less.