KR101460285B1 - Device and method for levelling strip - Google Patents

Abstract

And a plurality of upper rolls and lower rolls arranged at intervals in an alternating manner along the progress line of the rolled steel sheet so as to perform more effective flattening of the post-rolled steel sheet and uniform plastic bending in the thickness direction And the upper roll and the lower roll form a pair of at least two rolls, respectively.

Description

Technical Field [0001] The present invention relates to a rolled steel plate correcting apparatus and a calibrating method,

The present invention relates to a steel plate correcting apparatus. More particularly, the present invention relates to a rolling steel plate calibrating apparatus and a calibrating method for calibrating a flatness of a rolled steel sheet and a uniform plastic bending process.

Generally, in the thick plate process, all products with different steel types, thicknesses and widths are produced in one line. Depending on the thickness of the rolled steel plate, the thickness of the material (thickness: ~ 15mm) (Thickness: 40mm or more).

The rolled steel sheet is produced by heating, rolling, cooling and calibrating. After reheating the hot slab or material, it is rolled to the desired size and cooled to obtain the desired material. Through this process, residual stress due to plastic deformation and quenching occurs in the steel sheet, and the plate shape becomes uneven, so that the shape of the plate is flattened in the calibration process and the internal residual stress is reduced.

The shape defect and the residual stress which can not be removed in the inline calibration process are calibrated offline once again, and the final product is completed. The off-line calibration facility is larger than the on-line calibration facility because the high temperature (200 ~ 700?) Steel plate is applied online and the low temperature (less than 200?) Steel plate is calibrated offline.

The roller calibrator of the conventional thick plate process is arranged so that a plurality of rolls are arranged in an up and down zig-zag manner irrespective of hot or cold and the vertical gap between the upper and lower rolls is set smaller than the thickness of the steel sheet, have.

At this time, the bending amount (upper roll reduction amount) is set to be large in order to make a uniform residual stress at the entrance side of the calibrator, and the bending amount is made zero by making the vertical roll interval equal to the thickness of the steel sheet .

In recent years, rolled steel sheet has been used in cold rolled and cold rolled conditions to increase the strength of rolled steel sheets. The demand for architectural or marine structures has increased, and the thickness of rolled steel sheets has increased to more than 100mm. to be.

Therefore, there is an increasing demand for effective restraining of high-strength post material with a limited residual capacity due to drastic increase in residual stress due to severe rolling and cooling conditions.

Conventional calibrators are capable of calibrating design thicknesses of all thicknesses from a base material to a backing material. However, in practice, the calibration effect is good only in a heavy material region and the calibration effect is not large in a material of a material or a material of a rear material.

This is because the curvature of the material is a function of the diameter of the roll, the roll pitch, and the amount of indentation when the material is subjected to a bending deformation by the calibrator roll. In the conventional calibrator, the roll diameter and pitch are fixed, This is because the diameter and pitch of the rolls optimized for thickness are used. Generally, in the case of a parquet material, it is known that a large curvature (a small radius of curvature) is advantageous for calibration, and conversely, a rear curved material has a small curvature (a large radius of curvature).

In order to solve the above problem, a calibrating device comprising a calibrator using various roll sizes, a small roll calibrator and a large roll calibrator has been proposed. However, the calibrating device has a drawback in that it is difficult to apply to a post material calibrating.

Particularly, as the thickness of the material becomes thicker on the bending mechanism of the steel sheet, the roll diameter and the roll pitch must be increased, resulting in a facility problem that the size of the equipment and the reduction capacity must be increased.

In addition, in the conventional apparatus, stress concentration occurs at a point where a roll and a material come into contact with each other when a large pressing force is applied, thereby causing a problem of surface quality in which press-in flaws are generated by rolls on the surface of the steel sheet, .

Accordingly, there is provided a rolling steel plate calibrating apparatus and a calibrating method which are capable of performing more effective flattening of the post-material-rolled steel plate and uniform plastic bending in the thickness direction.

Also provided is a rolling steel plate calibrating device and a calibrating method which are capable of applying a uniform plastic deformation to a post-material rolled steel sheet under a limited facility capability without additional facilities.

The present invention also provides a rolling steel plate calibrating device and a calibrating method which are capable of uniformly applying a bending load to the surface of a steel plate, thereby preventing a failure in press-fitting of the steel plate surface due to a concentrated load.

This calibrating apparatus includes a plurality of upper rolls and lower rolls arranged at intervals in an alternating manner up and down along the progress line of the rolled steel sheet, and the upper roll and the lower roll may each have a structure in which at least two rolls form a pair .

This calibration method is a method in which a rolled steel sheet subjected to a rolling process is advanced along a calibrating device in which upper rolls and lower rolls constituting a set of at least two rolls are arranged alternately up and down along the progress line, And is subjected to a plastic bending process.

The distance between the two rolls in the upper roll or the lower roll may be within 10% of the roll diameter.

The pair of rolls in the upper roll or the lower roll may have a structure in which the height with respect to the progress line is different from each other.

The rolls disposed in front of the pair of rolls in the upper roll or the lower roll along the rolling direction of the rolled steel plate may have a relatively larger height apart from the progress line than the rolls disposed at the rear side.

The height difference between the two inter-roll progress lines in the upper roll or the lower roll may be within 2 mm.

Wherein the backup roll is biased toward the roll disposed at the rear side along the rolling direction of the steel sheet at the center of the two rolls paired in the upper roll or the lower roll .

The calibrating device may be set to a value that satisfies a plastic deformation rate of 80% or more by the following formula in the amount of reduction of the upper roll or the lower roll at the inlet side.

이고, here,

ego,

δ = indentation amount, L = roll pitch, YS = yield strength, E = elastic modulus, t = steel sheet thickness, and YR = plastic strain.

The amount of the reduction can be linearly decreased from the inlet side of the calibrating device to the outlet side.

The rolled steel sheet may be rolled material.

According to the present embodiment as described above, an excellent correction effect can be obtained for the post material.

In addition, since a long bending pitch and a large rolling reduction amount can be provided through the roll arrangement structure, the plastic deformation can be uniformly given in the thickness direction during calibrating the rolled steel sheet after high strength and the residual stress in the plate can be minimized.

In addition, since the reduction load can be reduced as compared with the conventional apparatus, the facility capability can be maximized without increasing the facility capacity.

In addition, it is possible to prevent indentation failure on the surface of the steel sheet, to improve the surface quality of the product, and to improve the productivity by lowering the defect rate.

1 is a schematic view showing a progress line for calibrating a rolled steel plate according to the present embodiment.
Fig. 2 is a schematic view showing a calibration roll structure of a rolling steel plate calibrating device according to the present embodiment.
3 is a schematic view showing a calibration roll moving structure of the rolling steel plate calibrating device according to the present embodiment.
Fig. 4 is a schematic view showing a calibrated roll arrangement structure of a rolled steel plate calibrating device according to the present invention.
Fig. 5 is a chart showing the internal residual stress of the steel plate after calibration in comparison with the calibration device of the present embodiment and the conventional structure.
6 is a chart showing a comparison between the load generated on the calibrating roll in the calibrating device according to the present embodiment and the conventional structure.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Wherever possible, the same or similar parts are denoted using the same reference numerals in the drawings.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms as used herein include plural forms as long as the phrases do not expressly express the opposite meaning thereto. Means that a particular feature, region, integer, step, operation, element and / or component is specified, and that other specific features, regions, integers, steps, operations, elements, components, and / And the like.

All terms including technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Predefined terms are further interpreted as having a meaning consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or very formal meanings unless defined otherwise.

1 is a schematic view showing a progress line for calibrating a rolled steel plate according to the present embodiment.

As shown in Fig. 1, the rolled steel sheet has a heating section 100 for heating the slab, a rolled section 200 for rolling the slab, a rolling section for rolling the rolled section, And is commercialized through the calibration apparatus 10.

The orthodontic appliance 10 includes a plurality of calibrating rolls arranged in a zigzag arrangement arranged at an interval alternately up and down along the progress line of the rolled steel strip. The calibrating roll comprises an upper roll (20) arranged on the upper part of the progress line and a lower roll (21) arranged on the lower part.

The calibrating roll is set so that the distance between the upper roll 20 and the lower roll 21 is set to be smaller than the thickness of the rolled steel plate so that the rolling bending in the vertical direction is sequentially performed on the rolled steel plate moved therebetween.

The orthodontic appliance 10 of the present embodiment has a structure in which a material is thicker than a thickness of 40 mm in a rolled steel sheet after being rolled.

2, the calibrating apparatus of the present embodiment includes a plurality of upper rolls 20 and lower rolls 21 spaced apart in the vertical direction along the progress line of the rolled steel sheet, The roll 20 and the lower roll 21 each have a structure in which at least two rolls form a pair. The set may be composed of two rolls or two or more rolls, and in the case of this embodiment, two rolls are paired.

2, two pairs of rolls are arranged side by side along the progress line to form an upper roll 20, and two rolls which are also paired in the lower part of the progress line are arranged side by side, Roll 21 as shown in Fig.

2 for the upper roll 20 and the lower roll 21, a roll disposed on the front side along the proceeding line of the rolled steel sheet proceeding from the left to the right is referred to as the front roll 22 ) And the roll disposed at the rear side is referred to as a rear roll 24.

By configuring the upper roll 20 and the lower roll 21 as two pairs of rolls in this way, a longer bending pitch and a larger rolling reduction amount can be applied than when a bending load is applied to the after-rolled steel sheet.

In other words, when applying a bending load to the rolled steel sheet, all six rolls act like three conventional rolls. The load can be distributed to a larger number of rolls. Further, two rolls with smaller diameters act like rolls with a larger diameter, so that the bending pitch can be made longer when the steel sheet is bent, and a larger amount of rolling reduction can be applied. Therefore, uniform plastic deformation can be applied to the post material in the width direction under the facility capability of the orthodontic appliance.

In this embodiment, the front roll 22 and the back roll 24 are of the same diameter.

The diameter of the front roll and the back roll is smaller than 280 ~ 320mm which is mainly used in the calibration of the heavy material, and since the two rolls serve as one large roll, the diameter of more than half of 280 ~ 320mm , 140 mm or more. The pitch (L in FIG. 3) between the upper roll and the lower roll should be 350 mm or more when the diameter of the front roll is 280 mm in order to ensure the clearance between the upper and lower rolls.

3, the distance D between the front roll 22 and the rear roll 24 forming a pair in the upper roll 20 or the lower roll 21 is smaller than the distance D between the front roll 22 and the rear roll 22. [ May be less than 10% of the diameter of the outer diameter (24). As the distance D between the front roll 22 and the rear roll 24 becomes closer to each other, the space efficiency of the correcting device increases. If the interval exceeds the 10% range, the facility becomes large and the space efficiency decreases.

2 and 4, the calibrator 10 includes a backup roll 30 (not shown) coupled to the upper roll 20 and the lower roll 21 to support the upper roll 20 and the lower roll 21, ).

The calibrating roll of the calibrator is of elongated shape. Therefore, when a wide-width high-strength rolled steel sheet having a length of about 4 m is rolled down, a bending deformation occurs at the center of the calibrating roll in a convex shape in the width direction, and the correction in the width direction becomes uneven due to such deformation. To prevent this, a back-up roll is installed on the backside of the calibrating roll to support the widthwise bending of the calibrating roll.

The backup roll 30 has a function of transferring the loads of the upper roll 20 and the lower roll 21 to the frame and the upper roll 20 and the lower roll 21 to secure the cross- (32).

In the present embodiment, as shown in FIG. 2, the backup roll has a structure in which three backup rolls are supported by the upper roll 20 and the lower roll 21, respectively. The three back-up rolls are in turn respectively installed in the front roll 22, between the front roll 22 and the back roll 24, and in the rear roll 24, respectively. A backup roll disposed in the middle of the three backup rolls abuts both the front roll 22 and the rear roll 24 to support the two rolls. Hereinafter, the backup roll contacting both the front roll 22 and the rear roll 24 is referred to as an intermediate backup roll 32. [

Here, this calibrating device is capable of uniformly distributing a bending load to the front roll 22 and the rear roll 24 when the steel plate is bent.

4, the front roll 22 and the rear roll 24, which form a pair in the upper roll 20 or the lower roll 21, . The height to the progress line is the distance away from the pass line to the extent that the steel plate is retracted back from the pass line through which it passes. As the roll moves away from the line of advance, the height increases and the amount of indentation decreases.

In this embodiment, of the front roll 22 and the rear roll 24, the rolls arranged at the front along the rolling direction of the rolled steel plate are further away from the progress line than the rolls disposed at the rear, and the height is relatively large .

Thus, the front roll 22 and the rear roll 24 are arranged in a stepped manner with different heights relative to the progress line. The difference in height between the front roll 22 and the back roll 24 can be determined by the geometric bending shape of the steel sheet due to the pitch between the front roll 22 and the rear roll 24. [ In the present embodiment, the height difference may be within 2 mm. When the height difference between the front roll 22 and the rear roll 24 exceeds 2 mm, the bending load is not uniformly distributed.

The front roll 22 and the rear roll 24 come into uniform contact with the steel plate when the steel plate is in the stopped state when the steel plate is bent. However, when the actual steel sheet is conveyed at a constant speed, the bending shape is slightly pushed back, so that when the front roll 22 and the rear roll 24 are at the same position, the rear roll 24 is hardly in contact with the steel sheet In the front roll 22.

Therefore, as shown in Fig. 4, the front roll 22 is retracted from the pass line more than the rear roll 24, so that the two rolls are uniformly subjected to the down-load.

At this time, the intermediate backup roll 32 which supports both the front roll 22 and the rear roll 24 among the backup rolls should be biased toward the rear roll 24 from the center of the two rolls. As a result, the intermediate rolls 32 and the front rolls 22 are opened so that the front rolls 22 are retracted backwardly from the pass lines rather than the rear rolls 24.

On the other hand, in the present apparatus, two front rollers 22 and two rear rollers 24 act like one roll having a large diameter. To achieve this, the pressing force in the thickness direction Can be set.

It is known that the amount of bending at the mouth side is preferably set so that the plastic working ratio is at least 80% in the steel plate thickness direction. The plastic working rate is expressed by the thickness ratio of how deep the plastic zone occurs in the thickness direction of the steel sheet during bending.

Firing rate (%) = (firing area thickness / thickness of coating material) x 100 - (1)

Thus, in this embodiment, the reduction amount can be set to a value satisfying the plastic strain of 80% or more by the following equation (2).

--------------- 식 (2)

--------------- Equation (2)

here,

δ = indentation amount, L = roll pitch, YS = yield strength, E = elastic modulus, t = steel sheet thickness, and YR = plastic strain.

3, the lower roll 21 defines a distance between the lower surface of the upper roll 20 and the upper surface of the upper roll 20 with reference to the surface of the upper surface of the roll in parallel with the upper surface of the roll. Through the above equation (2), the reduction amount at which the plastic deformation ratio becomes 80% or more can be obtained. The value thus obtained is the minimum value of the input reduction amount of the calibration apparatus.

The press-in amount is set so as to decrease linearly with respect to each roll from the side of the calibrator to the side of the calibrator. The amount of indentation at the exit side shall be zero. For example, if the inlet press-in amount is 3 mm, the press-in amounts of the second, third, and fourth rolls toward the outlet can be set to 2 mm, 1 mm, and 0 mm.

Hereinafter, the operation of the present embodiment will be described with reference to FIGS. 5 and 6 in comparison with a comparative example.

Fig. 5 is a result of numerical analysis of the residual stress in the steel sheet after calibration by applying a conventional calibrating device and a calibrating device of the present embodiment to a post material of a general steel material having a thickness of 45 mm.

In the case of the comparative example, the calibration roll diameter is 280 mm and the pitch is 300 mm.

In the embodiment, the diameter of the front roll and the rear roll is 280 mm, the pitch between the front roll and the rear roll is 280 mm, the pitch between the upper roll and the lower roll is 350 mm, and the step between the front roll and the rear roll is 0.2 mm. The indentation amount was 2 mm for the comparative example, and 24 mm for the example. In the graph, the horizontal axis represents the magnitude of the residual stress, (+) value is the tensile residual stress, and (-) value is the compressive residual stress. The vertical axis represents the distance in the thickness direction of the steel sheet.

As shown in Fig. 5, in both the comparative example and the example, the tensile and compressive residual stress due to the up-and-down bending exist on both surfaces. Comparing the distribution of the residual stress, It can be confirmed that it is getting lower (closer to 0).

When the peak values of the residual stresses were compared according to the thickness positions (upper, middle, and lower), in the comparative example, the residual stress peaks at the upper surface and the center of the steel sheet exceeded the allowable value of 150 Mpa. However, Showing good residual stress levels.

6 shows a simulation result of the load generated on the calibrating roll when the aluminum steel plate is calibrated.

In FIG. 6, the diameter of the rolls was 60 mm in both Comparative Examples and Examples. In the comparative example, a total of 13 correction rolls were used, and the roll pitch was 70 mm. In the case of the embodiment, the pitch between the front roll and the rear roll was 70 mm, and the pitch between the upper roll and the lower roll was 100 mm. The load generated on the calibrating roll was simulated when the aluminum (A5052) steel plate with a thickness of 12 mm and a width of 100 mm was calibrated with a reduction amount of 1 mm through each calibrator.

In FIG. 6, the comparative example shows a load value at a third position on the entrance side, and a first position roll in the embodiment. The horizontal axis of the graph in Fig. 6 is the time during which the steel sheet passes through the calibrator. It can be seen that in the case of the same reduction in the amount of 1 mm, the calibration load of the embodiment is lowered to about half (125 to 60 tons) compared with the comparative example.

This means that when the calibration apparatus of the comparative example and the example is designed with the same load capacity, the calibrator of the embodiment can give a double indentation amount, which is more advantageous in the correction of the post material.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Of course.

10: calibrating device 20: upper roll
21: Lower roll 22: Front roll
24: rear roll 30: backup roll
32: Intermediate backup roll

Claims (10)

A calibration roll for calibrating the shape of the rolled steel sheet in contact with the rolled steel sheet; and a backup roll for supporting the calibrating roll in contact with the calibrating roll, wherein the calibrating rolls are arranged at intervals Wherein the upper roll and the lower roll which are in contact with the rolled steel sheet and constitute the calibration roll form a pair of at least two rolls each having a plurality of upper rolls and lower rolls. The method according to claim 1,
Wherein an interval between two pairs of rolls in the upper roll or the lower roll is within 10% of the roll diameter. The method according to claim 1,
Wherein the two rolls forming the pair in the upper roll or the lower roll have different heights with respect to the progress line. The method of claim 3,
Wherein the roll disposed in front of the pair of rolls in the upper roll or the lower roll along the rolling direction of the rolled steel plate has a height greater than that of the roll disposed in the backward direction and has a relatively large height. 5. The method of claim 4,
Wherein the height difference between the two inter-roll progress lines in the upper roll or the lower roll is within 2 mm. 6. The method according to any one of claims 1 to 5,
Wherein the backup roll is biased toward a roll disposed at a rear side along the rolling direction of the rolled steel plate at the center of two pairs of rolls in the upper roll or the lower roll. The method according to claim 6,
Wherein the calibrating device is set to a value satisfying a plastic deformation rate of 80% or more according to the following expression (2) in the amount of reduction of the upper roll or the lower roll at the entrance side.

-------------- Equation (2)
隆 = indentation amount,
L = roll pitch,
YS = yield strength,
E = modulus of elasticity,
t = steel sheet thickness,
YR = plastic strain 8. The method of claim 7,
Wherein the reduction amount linearly decreases from an inlet side of the calibrating device toward an outlet side. 9. The method of claim 8,
Wherein the rolled steel sheet is a rolled steel sheet. And a back-up roll supporting the calibrating roll in contact with the calibrating roll, wherein the upper roll and the lower roll form a pair of at least two rolls alternately up and down along the progress line, A rolling steel plate subjected to a rolling process along a calibrating device, and a rolling steel plate passing through each of the sets of rolls in order to perform a plastic bending process.

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