KR20120054440A - Apparatus for adding reduction force of strip and method for continuous casting using the same - Google Patents

Abstract

PURPOSE: A slab reduction apparatus and a continuous casting method using the same are provided to easily press slab using a plurality of roll assemblies. CONSTITUTION: A slab reduction apparatus(1000) comprises first, second, and third roll assemblies(100,200,300) which press slab. The first roll assembly has a plurality of flat rolls(110). The second roll assembly has a plurality of first type convex rolls(210). The third roll assembly has a plurality of second type convex rolls(310) in which the width of a projected portion is smaller than the width of a projected portion of the first type convex roll.

Description

Apparatus for adding reduction force of strip and method for continuous casting using the same}

The present invention relates to a slab pressing apparatus and a continuous casting method. In particular, the present invention relates to a slab-pressing device and a continuous casting method using the slab to reduce the slab in a plurality of rolls are formed in different widths of the flat roll and the projection depending on the generator of the center segregation.

In general, the continuous casting device (hereinafter referred to as a 'cycle cycle') injects molten steel into the mold, and continuously draws the molten steel reacted in the mold to the lower side of the mold, thereby forming various shapes such as slabs, blooms, billets, beam blanks, and the like. It is a device for manufacturing cast iron.

Looking at the general configuration of such a machine with reference to Figure 1, the player is a ladle (ladle; 10) containing the molten steel (1) refined in the steelmaking process, and the molten steel (1) supplied from the ladle 10 temporarily stored Tundish 20 and drawing from mold 30 and mold 30 which inject molten steel 1 from the tundish 20 through the immersion nozzle and initially solidify to a constant shape through primary cooling. The cast slab 2 is cooled to secondary cooling to complete the solidification while performing a series of molding operations, including a cooling and apharine (40). The slab 2 that has passed through the cooling and pressing lines 40 is cut to a predetermined length and then transferred to a collection box or the like.

The cast piece 2 drawn out from the mold 30 includes a non-solidified molten steel portion flowing inside the cast piece 2 at the beginning of the drawing, so that solidification shrinkage occurs, thereby causing center segregation inside the cast piece 2. ) And central porosity could be formed. The center segregation and the central void greatly deteriorate the quality of the slab 2, and in order to solve this problem, a method of pressing the slab 2 with the roll apparatus at the end of the solidification of the slab 2 has been conventionally used.

By the way, conventionally, when the slab 2 is pressed by applying a flat roll having a constant diameter to a roll device provided in the Apharine 40 to lower the slab 2, solidification in the slab 2 is completed. Due to the rigidity of the part, there was a problem that it is difficult to effectively roll down the unsolidified molten steel. That is, in the case of using a flat roll to roll down the cast steel, a large pressing force is required to improve the center segregation and the center void, and thus, there is a problem in that the cost of the playing process is increased due to the improvement of the playing equipment. In addition, when the slab 2 is pressed down due to insufficient rolling force without improvement of the performance equipment, there is a problem that the quality of the slab 2 is deteriorated by causing an internal crack or the like.

In addition, in the related art, a slab 2 is pressed by applying a convex roll or a convex roll in which a protrusion narrower than the width of the slab 2 is formed on the roll apparatus provided in the Abharine 40. However, conventionally, as a plurality of convex rolls having the same protrusions, the slab 2 in which the solid fraction is changed is pressed down so that a large amount of reduction is applied to the slab 2, which causes the surface of the slab 2 to be recessed. There was a problem of causing surface defects such as overlap defects when rolling the slab 2 in a later step.

The present invention provides a slab pressing apparatus and a continuous casting method using the same.

The present invention provides a slab-pressing apparatus and a continuous casting method using the slab to reduce the slab in a plurality of rolls are formed in different widths of the flat roll and the roll projection according to the generator of the central segregation with different solid phase rate.

According to an embodiment of the present invention, a slab pressing apparatus includes: a first roll assembly including a plurality of flat rolls to press down a slab, a second roll assembly including a plurality of first type convex rolls to press down the slab; And a third roll assembly having a plurality of second type convex rolls having a width of the protrusion smaller than the width of the protrusion of the first type convex roll to press down the slab.

The first roll assembly may reduce the slab at the initial stage of the occurrence of the center segregation of the central solid phase of the slab is 0.1 to 0.4. The second roll assembly may reduce the slab to a central segregation generating medium in which the central solid phase of the slab is 0.3 to 0.6. The third roll assembly may reduce the slab at the end of the central segregation in which the central solid phase of the slab is 0.5 to 0.8.

The widths of the protrusions of the first type convex roll and the second type convex roll are greater than or equal to the width of the unsolidified molten steel with a solidity rate of 0.6 to 0.8 or less and less than or equal to the width of the unsolidified molten steel with a solidity of 1 or less. Is formed.

In addition, the continuous casting method according to an embodiment of the present invention is a combination of a plurality of flat rolls and a plurality of convex rolls in which the width of the central portion is reduced in the cast slab drawn out from the mold and the central solid phase ratio is changed as the time of central segregation occurs It is pushed down through the pressing apparatus.

In the initial stage of the occurrence of the center segregation of the central portion of the cast steel is 0.1 to 0.4 can be reduced to the plurality of flat rolls. In the middle segregation generating medium in which the central solid phase ratio of the slab is 0.3 to 0.6, the plurality of first type convex rolls may be reduced. At the end of the center segregation of the central solid phase of the slab is 0.5 to 0.8 can be reduced to a plurality of second convex roll having a protrusion width smaller than the width of the protrusion of the first type convex roll.

The slab is pressed so that the total reduction amount by the plurality of flat rolls and the plurality of convex rolls is 65 mm or less.

According to the slab pressing apparatus and the continuous casting method using the same according to the embodiments of the present invention, a plurality of roll assemblies each provided with a flat roll, a first type convex roll, a second type convex roll are aligned along the casting direction, and By using a plurality of roll assemblies to reduce the slab, it is possible to easily reduce the slab in which the central solid phase rate changes depending on the generation time of the central segregation. Therefore, the reduction force required for the improvement of the center segregation and the center void of the cast steel can be smoothly applied to the cast steel. In other words, it is possible to improve the quality of the cast without improving the performance of the playing equipment can reduce the cost of the playing process.

In addition, it is possible to prevent a large amount of reduction on the surface of the slab by pressing the slab with a convex roll having a different width of the projection according to the solid state ratio of the central portion of the slab. That is, the surface of the cast steel can be prevented from being recessed by the projections of the convex roll, thereby preventing the occurrence of cast defects when the cast steel is processed in a subsequent process.

Therefore, the cast steel which has the outstanding quality can be manufactured, and the productivity of a playing process can be improved.

1 is a view showing the configuration of a typical continuous casting device.
2 is a view showing the configuration of a slab pressing apparatus according to an embodiment of the present invention.
3 is a view showing the type of roll applied to the slab pressing apparatus shown in FIG.
4 is a view showing a pressed shape of the cast steel according to the shape of the protrusion of the convex roll.
FIG. 5 is a graph showing the facility performance under light pressure according to the solid state rate of cast steel; FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms, and only the embodiments of the present invention to complete the disclosure of the present invention, to those skilled in the art It is provided to fully inform the category. Wherein like reference numerals refer to like elements throughout.

2 is a view showing the configuration of a slab pressing apparatus according to an embodiment of the present invention, Figure 3 is a view showing the type of roll applied to the slab pressing apparatus shown in Figure 2, Figure 4 is a convex roll Fig. 5 is a view showing the reduced shape of the cast steel according to the shape of the protrusion, Figure 5 is a graph showing the capacity of the light pressure installation capacity according to the solid phase rate of the cast steel.

2 to 4, the slab pressing apparatus 1000 according to an embodiment of the present invention is provided with a plurality of flat roll (flat roll) 110, the center of the solid state of the slab 2 is 0.1 to 0.4 center A first roll assembly 100 for pressing down the slab 2 at the beginning of segregation, and a plurality of first-type convex rolls 210, each having a central solid phase ratio of 0.3 to 0.6. In the middle of the generation of segregation, the second roll assembly 200 for pressing down the slab 2 and the plurality of second convex rolls 310 are provided, and the central segregation of the slab 2 has a central solid phase of 0.5 to 0.8. The third roll assembly 300 for pressing the slab 2 is included in the. In addition, the first roll assembly 100, the second roll assembly 200, and the third roll assembly 300 are sequentially aligned along the casting direction (x direction). As described above, in the present embodiment, the slab pressing device 1000 capable of soft reduction is formed by combining one type of flat roll and two types of convex rolls. (Here, 'A to B' means 'A or more and B or less'.)

The solid phase rate of the slab 2, which is set in a different range depending on the generation time of the central segregation, can be obtained through repeated experiments. The solid phase rate is a numerical value indicating how much unsolidified molten steel is contained in the slab 2, and can be expressed as a ratio of the width length of the slab 2 to the width length of the unsolidified molten steel portion 1 '. . For example, a solid phase of 0.1 means that the interior of the cast steel 2 is filled with unsolidified molten steel, and a solid phase of 0.5 means that the solidified portion and the unsolidified portion of the cast steel 2 are the same. It means that it is formed to have a width length.

In the early stage of the occurrence of the central segregation, the slab 2 does not have a large reduction in rolling resistance when pressed due to the low solid state (0.1 to 0.4). Therefore, even when the slab 2 is pressed using the flat roll 110, a sufficient reduction force is transmitted to the non-solidified molten steel part 1 ′ formed inside the slab 2, thereby enabling effective reduction. In the case where the solid phase ratio is less than 0.1, the surface of the cast piece 2 cannot be solidified and is hard to be pressed down.

However, in the middle segregation occurrence period in which the solidity rate of the slab 2 is 0.3 to 0.6, the solidified shell is thickened inside the slab 2 and the width W _L of the unsolidified molten steel part 1 'is increased. Decreases. (Here, the solidified shell refers to the portion of the cast steel, except for the unsolidified molten steel portion.) Therefore, when the slab 2 is pressed using the flat roll 110, the unsolidified molten steel portion 1 'is reached. The reducing force is reduced so that the cast (2) can not be effectively reduced. Therefore, the convex rolls 210 and 310 in which protrusions are formed to apply sufficient pressing force to the unsolidified molten steel portion 1 'are used after the middle segregation period.

In addition, at the end of the central segregation in which the central solidification rate of the slab 2 is 0.5 to 0.8, the thickness of the solidified shell in the slab 2 becomes thicker (when the solidification ratio exceeds 0.5, the solidified portion becomes The width W _L of the unsolidified molten steel part 1 'at the end of solidification decreases rapidly in the range of several tens of millimeters. Therefore, at the end of the center segregation, the second type convex roll 310 having a narrower width W _R than the first type convex roll 210 so as to sufficiently transmit the pressing force to the center of the cast steel 2. This is used.

The types of rolls applied for rolling down the slab 2 according to the generation time of the central segregation having different ranges of solid phase ratios in the center of the slab 2 are summarized in Table 1 below.

When the central segregation occurs Solid phase Roll type Early segregation 0.1? 0.4 Flat roll Middle segregation period 0.3? 0.6 Convex Roll Type 1 Late segregation 0.5? 0.8 Type 2 Convex Roll

Referring to the above [Table 1], the solid phase rate has a different range depending on the classification of the central segregation time. At this time, the upper limit and the lower limit of the solid phase rate were to overlap the range so that the cast (2) can be continuously pressed down. That is, two kinds of rolls can be used in the range where a solid phase rate overlaps. (For example, when the solid phase rate is 0.3, the cast steel 2 may be pressed down on the flat roll 110 or the first type convex roll 210.)

Referring to FIG. 4, the convex roll applied to the slab pressing apparatus 1000 according to the present invention has a width W _R of the protruding portion having a width W _L1 of the unsolidified molten steel portion 1 ′ having a solid phase of 0.6 to 0.8 or less. ) Is greater than or equal to) and is formed to have a length within a range less than or equal to the width W _S of the unsolidified molten steel portion 1 ′ having a solid phase ratio of 1 or less. Further, the projected height h _R of the projected portion is 65 mm or less, so that the maximum amount of reduction that can be pressed into the projected portion is 65 mm.

Referring to [Table 2] below, the experimental results of the cast slab passing through the slab (2) through the slab pressing apparatus 1000 is as follows.

Experimental Example Roll type Rolling amount (mm) Rolling depth (mm) Central segregation V segregation Internal crack Overlap One Flat roll 0 0 4.0 3 0 Not occurring 2 30 0 1.5 2 One Not occurring 3 Convex Roll Type 1 30 30 1.0 One One Occur 4 65 65 0.5 0 3 Occur 5 Type 1 and Type 2 Convex Rolls 20 20 1.0 One 0 Not occurring 6 50 50 0.5 0 2 Occur 7 Flat rolls, type 1 and type 2 convex rolls 20 13 One One 0 Not occurring 8 30 20 0.5 0 0 Not occurring 9 50 25 0 0 0 Not occurring 10 60 30 0 One One Occur

For the above experiment, [C] 0.8% steel, cast steel 2 of 400 mm × 500 mm were tested, and the quality of the cast steel 2 and the occurrence of surface defects during the rolling of the post process were confirmed. .

Experimental Example 1 and Experimental Example 2 are applied to the flat roll 110 only, and reduced to a reduction amount of 30 mm and the case of the unrolled, and increasing the reduction amount, the central segregation is improved compared to the unpressed, but V piece The stone remained as it was, and a slight internal crack occurred.

Experimental Example 3 and Experimental Example 4 are experimental examples obtained by pressing only the first type convex roll 210 with a reduction amount of 30 mm and a reduction amount of 65 mm. Compared with the results of applying the flat roll 110 alone, the center segregation was excellent at 1.0 and 0.5 grades, respectively, and the V segregation level was very good at 1.0 and 0 grades, respectively. However, due to the large amount of reduction, the inner crack level was insufficient, and the excessive reduction depth h _B caused overlapping defects in the form of linear flaws during rolling in the post process.

Experimental Example 5 and Experimental Example 6 are experimental examples in which the first type convex roll 210 and the second type convex roll 310 are combined and pressed down with a reduction amount of 20 mm and a reduction amount of 50 mm. The type 1 convex roll 210 corresponding to the width W _L of the unsolidified molten steel 1 ′ of the cast steel 2 has a solid phase of 0.1 to 0.5, and the type 2 convex roll 310 is 0.5 to 0.8. The reduction was performed over the range of. As a result, the central segregation level was excellent, 1.0 and 0.5, respectively. Compared with the results of the first type convex roll 210 carried out in Experimental Example 3 and Experimental Example 4, in Experimental Example 5 and Experimental Example 6, the result of the central segregation similar to that of applying one type of convexroll with a small amount of rolling reduction is obtained. Could get However, when the amount of reduction was small (20 mm), V segregation remained, and when it was reduced by a large amount of reduction of 50 mm, internal cracks were generated, and overlapping flaws occurred during rolling in the subsequent step. Therefore, when a large amount of reduction is necessary to improve the internal quality of the center segregation and central void of the casting 2 by increasing the size of the casting 2, the slab 2 is reduced by a large amount of rolling reduction by using a convex roll alone or in combination. In this case, the quality of the center segregation is improved, but internal cracks are not necessarily prevented, and it is confirmed that defects occur in the product after rolling due to the deep and concave cast surface.

In the present invention, the reduction was carried out as in Experimental Example 7 to Experimental Example 10. That is, the flat roll 110 is applied at the beginning of the center segregation, the first type convex roll 210 is applied at the middle segregation period, and the second type convex roll 310 is applied at the end of the central segregation generation. Was carried out.

In Experimental Example 7, the total reduction amount was set to 20 mm, 7 mm reduction was performed on the flat roll 110, and 13 mm was reduced by the first type convex roll 210 and the second type convex roll 310. As a result, the center segregation was a good grade 1, but the V segregation remained. In addition, internal cracks and overlapping defects did not occur.

In Experimental Example 8, the total reduction amount was increased to 30 mm to reduce the thickness of 10 mm in the flat roll 110, and 20 mm was reduced in the first type convex roll 210 and the second type convex roll 310. In addition, Experimental Example 9 increased the total reduction amount to 50 mm, reduced 25 mm in the flat roll 110, and reduced 25 mm in the first type convex roll 210 and the second type convex roll 310. As a result, the level of center segregation and V segregation was very good at 0 grade, and no defect occurred even after the internal crack and rolling.

In Experimental Example 10, the total reduction amount was 60 mm, 30 mm was reduced on the flat roll 110, and 30 mm was reduced on the first type convex roll 210 and the second type convex roll 310. As a result, the level of central segregation was very good, with 0 grade, but due to the large amount of reduction, reverse V segregation occurred, resulting in lower V segregation level and internal cracking.

The graph shown in FIG. 5 is a graph which shows the result when the slab 2 was pressed under the conditions of Experimental Example 10. FIG. By applying the flat roll 110 and the two types of convex rolls 210 and 310, the facility capacity at the end of the solidification (solid state rate 0.8) is sufficiently reduced even with 75% facility capacity compared to the case where only the protrusion width is applied. It could be confirmed that it can be achieved.

(In this case, the rolling capacity is a percentage of the rolling reduction applied to achieve the indication during the rolling reduction divided by the maximum rolling reduction in percent, and the rolling reduction rate is the ratio of the reduction achieved to the indicated rolling reduction in percentage. This is the displayed number.)

As described above, according to the slab pressing apparatus and the continuous casting method using the same according to the embodiments of the present invention, a plurality of roll assemblies each provided with a flat roll, a first type convex roll, and a second type convex roll along a casting direction By aligning and using a plurality of such roll assemblies to press down the cast, it is possible to easily press down the cast having a central solid phase change in accordance with the generation time of the central segregation. Therefore, the reduction force required for the improvement of the center segregation and the center void of the cast steel can be smoothly applied to the cast steel. In other words, it is possible to improve the quality of the cast without improving the performance of the playing equipment can reduce the cost of the playing process. In addition, it is possible to prevent a large amount of reduction on the surface of the slab by pressing the slab with a convex roll having a different width of the projection according to the solid state ratio of the central portion of the slab. That is, the surface of the cast steel can be prevented from being recessed by the projections of the convex roll, thereby preventing the occurrence of cast defects when the cast steel is processed in a subsequent process. Therefore, the cast steel which has the outstanding quality can be manufactured, and the productivity of a playing process can be improved.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. Therefore, it will be apparent to those skilled in the art that the present invention may be variously modified and modified without departing from the spirit of the appended claims.

100: first roll assembly 110: flat roll
200: second roll assembly 210: first type convex roll
300: the third roll assembly 310: the second type convex roll
1000: cast steel pressing device

Claims (11)

A first roll assembly having a plurality of flat rolls to press down the cast piece;
A second roll assembly having a plurality of first type convex rolls to press down the slab;
A third roll assembly including a plurality of second type convex rolls having a width of a protrusion smaller than a width of the protrusion of the first type convex roll to press down the slab;
Cast rolling device comprising a. The method according to claim 1,
The first roll assembly,
A slab pressing apparatus for reducing the slab at the initial stage of the center segregation of the central solid phase of the slab is 0.1 to 0.4. The method according to claim 1,
The second roll assembly,
A slab pressing apparatus for reducing the slab in the center segregation generating middle portion of the central portion of the slab is 0.3 to 0.6. The method according to claim 1,
The third roll assembly,
A slab-pressing device for pressing the slab at the end of the center segregation occurrence of the central solid phase of the slab is 0.5 to 0.8. The method according to claim 1,
And the first roll assembly, the second roll assembly, and the third roll assembly are sequentially aligned along a casting direction. The method according to claim 1,
The widths of the protrusions of the first type convex roll and the second type convex roll are greater than or equal to the width of the unsolidified molten steel with a solidity rate of 0.6 to 0.8 or less and less than or equal to the width of the unsolidified molten steel with a solidity of 1 or less. Cast slab device formed. A continuous casting method in which a slab drawn from a mold and having a central solidity rate that changes as the time of occurrence of central segregation passes is passed through a rolling device in which a plurality of flat rolls and a plurality of convex rolls each having a smaller width of a protrusion are pressed. The method of claim 7,
A continuous casting method of pressing down with a plurality of flat rolls at the initial stage of the occurrence of the center segregation of the central solid phase of the cast steel is 0.1 to 0.4. The method of claim 7,
A continuous casting method of pressing down with a plurality of first type convex rolls in the center segregation generation medium of which the central solid phase ratio of the cast steel is 0.3 to 0.6. The method according to claim 9,
And a second type convex roll having a protrusion width smaller than the width of the protrusion of the first type convex roll at the end of the center segregation occurrence in which the central solid phase ratio of the cast steel is 0.5 to 0.8. The method of claim 7,
And the slab is pressed so that the total reduction amount by the plurality of flat rolls and the plurality of convex rolls is 65 mm or less.

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