Buckling prevention device control method and width press equipment having buckling prevention device

Abstract

To provide a method for controlling a buckling preventive device, that can suppress abnormality caused by warping of slabs from progressing and also reduce quality defects of slab edge parts, and to provide width pressing equipment implementing the method.SOLUTION: In width pressing equipment including one or more pairs of buckling restraining rolls and a temperature measuring unit aligned in a vertical direction in a vicinity of a center in plate thickness of a slab, a method for controlling a buckling preventive device enables changing of application between fixed position control and constant pressure control of the buckling restraining rolls according to a difference between: a predicted thickness increase amount of the slab, calculated from a width pressing equipment entering temperature measured by the temperature measuring unit, when reducing a width of the slab intermittently; and a slab thickness increase amount prescribed on the basis of a width reduction amount, an initial slab width, and a steel type.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a buckling prevention device control method that can avoid progress abnormalities without causing quality defects in slabs (steel billets), and width press equipment having a buckling prevention device. Specifically, the present invention relates to a method for controlling rolls that prevent buckling of a slab when width reduction rolling (hereinafter simply referred to as "width reduction") is performed by intermittently pressing a steel billet from both sides in the width direction with a pair of dies while transporting the slab in the longitudinal direction. Note that the rolls may also be simply referred to as "buckling prevention rolls" or "buckling restraint rolls." The present invention also relates to width press equipment that performs the method. [Background technology]

[0002] In width press equipment for slabs, buckling easily occurs in the width direction of the slab during width reduction rolling. Buckling is a phenomenon in which the slab bends upward (convex) or downward (concave) during width reduction. Patent Document 1 discloses a width press equipment as a technology for suppressing the above-mentioned buckling phenomenon, which includes a die that performs width reduction of the material and a pair of upper and lower rolls that prevent buckling and presses both sides of the central portion of the material in the width direction at a position corresponding to the center of the die's longitudinal direction. Patent Document 1 also discloses a technology in which a pair of feed rollers and measuring rolls that can press the entire width of the material (slab) are provided at at least two locations on the inlet and outlet sides of the die, gripping the material during width reduction and preventing buckling or twisting of the material.

[0003] Furthermore, Patent Documents 2 to 4 disclose the installation of buckling restraint rolls whose vertical height positions are variable in order to prevent buckling of the slab. They also disclose a method of appropriately adjusting the vertical height positions of the buckling restraint rolls in consideration of slab deformation due to width reduction, in accordance with a predicted value of the amount of thickness increase at the leading edge and steady portion of the slab due to width reduction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-154810 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-248186 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-140056 [Patent Document 4] Japanese Patent Application Laid-Open No. 2010-110786 Summary of the Invention [Problem to be solved by the invention]

[0005] The conventional technology is a method to prevent buckling of the slab by adjusting the vertical height positions of the buckling restraint rolls according to the predicted value of the thickness increase at the leading edge and the steady part of the slab. However, if there is a discrepancy between the actual thickness increase and the predicted value, the position of the buckling prevention rolls becomes inappropriate, which causes the problem of abnormal progress due to slab warping.

[0006] In addition, the thickness increase at the leading edge and steady section of the slab is significantly affected by the temperature when the slab enters the width reduction device. However, there was a problem in that the predicted value of the thickness increase, which is predetermined based on the width reduction amount, initial slab width, and steel type, was insufficient in accuracy compared to the actual thickness increase.

[0007] The present invention aims to provide a buckling prevention device control method and width press equipment equipped with a buckling prevention device that can suppress progress abnormalities due to slab warping and reduce quality defects at the slab edge. [Means for solving the problem]

[0008] The inventors have conducted research to solve the above problems, and as a result have made the following findings.

[0009] When a large width reduction is required for a slab, especially one with a thickness of 200 mm or more, the width reduction load and thickness increase are both large, and the error in the predicted values ​​also increases. For this reason, due to concerns about slab warpage, the width reduction is limited during operation.

[0010] Furthermore, when intermittently reducing the width of a slab in a width press, if the anti-buckling rolls are only controlled at a fixed position, the pass line becomes unstable, and if only constant pressure control is used, problems arise with threading. As a result, it was found that progress abnormalities due to slab warping and quality deterioration of the slab edge area occur.

[0011] Therefore, we found that this problem can be solved by predicting the amount of thickness increase based on the slab temperature measured at the inlet side of the width press equipment, and varying the constant position control and constant pressure control depending on the difference between the width reduction amount, the initial slab width, and the plate thickness increase amount (slab thickness increase amount) predetermined by the steel type.

[0012] In particular, it was found that by performing hybrid control, which involves constant position control when the difference is small and constant pressure control when the difference is large, it becomes possible to suppress progress abnormalities caused by slab warping, and as a result, the amount of width reduction can also be increased.

[0013] The present invention was made based on the above findings, and the gist of the present invention is as follows. [1] A buckling prevention device control method in which, when a slab is intermittently width-reduced using width press equipment having one or more pairs of buckling restraint rolls in the vertical direction near the center of the slab's width and a temperature measurement unit, the fixed position control and constant pressure control of the buckling restraint rolls are varied based on the difference between the predicted slab thickness increase calculated from the slab's temperature at entry into the width press equipment measured by the temperature measurement unit and the slab thickness increase determined from the width reduction amount, initial slab width, and steel type. [2] A buckling prevention device control method described in [1], in which the predicted slab thickness increase is calculated using the width press equipment inlet temperature and the press load, width reduction, and initial slab width predicted from the width press equipment inlet temperature. [3] A buckling prevention device control method described in [1] or [2], in which, when the predicted slab thickness increase differs by 30% or more from the slab thickness increase determined from the width reduction, the initial slab width, and the steel type, the control method of one or more lower buckling restraint rolls is changed from the fixed position control to the constant pressure control. [4] A width press facility comprising a temperature measurement unit, a slab transport path, a pair of dies for width reduction of the slab, and a buckling prevention device, wherein the buckling prevention device comprises one or more pairs of buckling restraint rolls arranged in the vertical direction near the center of the plate width of the slab passing through the slab transport path, and a control mechanism, wherein the control mechanism comprises an evaluation means for evaluating the predicted slab thickness increase calculated from the width press facility entry temperature measured by the temperature measurement unit, and a change means for varying the fixed position control and constant pressure control of the buckling restraint rolls depending on the difference between the width reduction amount and the slab thickness increase amount specified by the initial slab width and steel type. [5] The width press equipment described in [4], wherein the evaluation means calculates the predicted slab thickness increase amount based on the width press equipment inlet temperature, the press load, width reduction amount, and initial slab width predicted from the width press equipment inlet temperature. [6] The width press equipment described in [4] or [5], wherein the change means changes the control method of one or more lower buckling restraint rolls from the fixed position control to the constant pressure control when the difference between the predicted slab thickness increase amount and the slab thickness increase amount determined from the width reduction amount, the initial slab width, and the steel type is 30% or more. [Effects of the Invention]

[0014] The present invention makes it possible to suppress progress abnormalities due to slab warpage, resulting in the effect of increasing the width reduction amount. Furthermore, by improving pass line accuracy, it is also possible to prevent the occurrence of slab edge seam defects. As a result, it is now possible to provide a more accurate buckling prevention technology for slabs with thicknesses of 200 mm to 400 mm, which was previously difficult to achieve, and this has extremely great industrial value. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic side view showing an example of a width press facility layout for implementing the present invention. [Figure 2] FIG. 2 is a diagram showing the amount of pass line deviation with respect to the number of presses in each method of controlling the lower buckling prevention roll according to the present invention. [Figure 3] FIG. 3 is a diagram showing the average value of pass line deviation in each control method for the lower buckling prevention roll according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be specifically described below with reference to the drawings showing embodiments thereof. Note that the present invention is not limited to the following embodiments. The components in the following embodiments include those that can be easily substituted by a person skilled in the art or those that are substantially the same.

[0017] FIG. 1 is a schematic side view showing an example of the layout of a width press facility embodying the present invention. The width press facility shown in FIG. 1 has a slab temperature measurement unit (1) on its inlet side. This temperature measurement unit (1) may be a known thermometer capable of measuring the temperature of a slab. From the inlet side of the facility, the facility includes an inlet table roll (2), a pair of inlet upper and lower pinch rolls (4, 3), and one or more pairs of upper and lower anti-buckling rolls #1 and #2 (6, 8, 5, 7). Furthermore, the facility includes a pair of dies (11) and a pair of exit upper and lower pinch rolls (10, 9). The inlet table roll (2), the inlet and exit pinch rolls (3, 4, 9, 10), the anti-buckling rolls #1 and #2 (5-8), and the die (11) can be known. The anti-buckling rolls #1 and #2 (5-8) and the control mechanism (13) together constitute a buckling prevention device. The control mechanism (13) comprises an evaluation means (15) and a change means (16). The evaluation means (15) calculates the predicted slab thickness increase, the width reduction, the initial slab width, and the slab thickness increase determined from the steel grade, and calculates the difference between these. The change means (16) has a function of changing the control of the buckling restraint rolls #1 and #2 (5 to 8) according to the results of the evaluation means (15). The control mechanism (13) may also comprise a known control device equipped with a computer, and the known control device may include a programmable logic controller (PLC).

[0018] Here, the buckling prevention device control method of the present invention will be described below.

[0019] In FIG. 1, a slab (12) is conveyed along a slab conveying path equipped with an inlet table roll (2) and pinch rolls (3, 4, 9, 10) in the slab travel direction indicated by the arrow in FIG. 1, and is intermittently reduced in width by a die (11). At the same time, the slab is generally restrained by buckling restraint rolls #1 and #2 (5-8). At this time, the buckling restraint rolls #1 and #2 (5-8) restrain the vicinity of the width center of the slab (12) from above and below. Note that the vicinity of the width center is a conventionally known restraint position optimal for preventing buckling, predicted based on the slab's thickening behavior when not restrained by the buckling restraint rolls #1 and #2 (5-8) during width reduction by the die (11), with the width center of the slab being the most preferable. In the buckling prevention device control method of the present invention, the buckling restraint rolls #1 and #2 (5-8) are controlled as follows.

[0020] First, the temperature of the slab (12) is measured by the temperature measuring unit (1) and transmitted as the width press equipment inlet temperature to the evaluation means (15) of the control mechanism (13). The surface temperature of the slab (12) is preferably measured, but if the central temperature of the slab (12) can be measured, the central temperature may also be used.

[0021] Next, the predicted slab thickness increase is calculated from the width press equipment entry temperature by the evaluation means (15). The predicted slab thickness increase is preferably calculated from the width press load, width reduction, and initial slab width predicted from the width press equipment entry temperature. More specifically, the influence of these parameters on the thickness increase may be investigated in advance through experiments or numerical calculations, and a known formulation may be prepared.

[0022] Next, the slab thickness increase amount defined from the width reduction amount, the initial slab width, and the steel type is calculated by the evaluation means (15). For the calculation of the slab thickness increase amount, the influence of these parameters on the thickness increase amount may be investigated in advance through experiments or numerical calculations, and a known formulation may be prepared.

[0023] For the above-mentioned known formulation, for example, equation (1) in Patent Document 3 can be used. ΔH=α(ΔW / WO)2×HO [mm] ···(1) Here, ΔH is the increase in thickness of the slab (width center) after width reduction, WO is the width of the slab before width reduction, ΔW is the width reduction amount, and HO is the thickness of the slab before width reduction.

[0024] The switching between fixed position control and constant pressure control is performed by a switching device (16) in response to the error between the predicted slab thickness increase, which is determined in advance based on the width reduction, initial slab width, and steel grade, and the predicted slab thickness increase, which is determined based on the slab temperature measured by the slab temperature measuring device. This hybrid control can alleviate the pass line stability issues inherent in fixed position control and the sheet threading issues inherent in constant pressure control. Here, fixed position control refers to controlling the positions of the lower buckling restraint rolls (5, 7) to predetermined positions. Constant pressure control refers to controlling the lower buckling restraint rolls (5, 7) so that the pressure applied to the slab is constant. The switching between fixed position control and constant pressure control can be performed by any known method, and the switching device (16) used for this purpose can also be a known method.

[0025] Furthermore, it is preferable that the difference between the predicted slab thickness increase calculated from the slab's temperature at the entry point to the width press equipment measured by the temperature measurement unit (1) and the slab thickness increase predetermined based on the width reduction, initial slab width, and steel type be less than 30%. If the difference is 30% or more, the control method for one or more lower buckling prevention rolls #1, 2 (5, 7) is constant pressure control. If the difference is less than 30%, the control method for one or more lower buckling prevention rolls #1, 2 (5, 7) is constant position control.

[0026] This type of control is particularly preferable when width reduction is performed on a slab (12) having a thickness of 200 mm or more. In this case, the lower anti-buckling rolls #1 and #2 (5, 7) are fixed at a position 20 mm or more below the pass line (14), and the predicted slab thickness increase, which is predicted from the temperature of the slab (12) entering the width press equipment, is shown to be reproducible within ±6 mm. This effect makes it possible to prevent progress abnormalities due to slab warping and suppress edge seams when width reduction is performed on material with a large width reduction. [Example]

[0027] In FIG. 1 , the pass line deviation, which is the deviation between the center of the slab (12) and the center of the die (11) (die core), was calculated for the following cases: The first case is when both the lower buckling prevention roll #1 (5) and the lower buckling prevention roll #2 (7) are controlled at fixed positions. The second case is when both the lower buckling prevention roll #1 (5) and the lower buckling prevention roll #2 (7) are controlled at constant pressure. The third case is when the lower buckling prevention roll #1 (5) is controlled at fixed positions and the lower buckling prevention roll #2 (7) is controlled at constant pressure. The first and second cases are conventional control methods, and the third case is the control method of the present invention. In the control methods of Examples 1 and 2, when the difference between the specified slab thickness increase and the predicted slab thickness increase obtained by the evaluation means was 20% or more and 30% or more, respectively, the control method of the lower buckling prevention roll was changed from fixed position control to constant pressure control before the start of slab width reduction. Figure 2 shows the amount of pass line deviation versus the number of presses for each control method for the lower buckling prevention rolls (5, 7). Note that "Hybrid" in Figure 2 refers to Example 2. It was confirmed that there was little variation in the amount of pass line deviation when the lower buckling prevention roll #1 (5) was controlled in a fixed position and the lower buckling prevention roll #2 (7) was controlled in a constant pressure. Figure 3 also shows the average value of pass line deviation for each control method for the lower buckling prevention rolls (5, 7). As in Figure 2, the present invention, which combines fixed position control and constant pressure control, showed the smallest variation in pass line deviation, and the amount of pass line deviation itself was also small. This prevented progress abnormalities due to slab warpage during width reduction and suppressed edge seams. It was found that Example 2, in which the control method for the lower buckling prevention rolls was changed from fixed position control to constant pressure control when the above-mentioned difference reached 30% or more, showed significantly less variation in the amount of pass line deviation than Example 1 (20%). [Explanation of symbols]

[0028] 1 Temperature measurement part 2 Incoming table roll 3. Entry side lower pinch roll 4. Upper pinch roll on the inlet side 5 Lower anti-buckling roll #1 6 Upper anti-buckling roll #1 7 Lower anti-buckling roll #2 8 Upper anti-buckling roll #2 9. Lower pinch roll on the exit side 10. Upper pinch roll on the exit side 11 Mold 12 Slabs 13 Control Mechanism 14 Pass Line 15 Evaluation tools 16. Change Methods

Claims

1. A buckling prevention device control method in which, when a slab is intermittently width-reduced using width press equipment having one or more pairs of buckling restraint rolls in the vertical direction near the center of the slab width and a temperature measurement unit, the method varies the fixed position control and constant pressure control of the buckling restraint rolls by controlling the difference between a predicted slab thickness increase calculated from the slab's temperature at entry into the width press equipment measured by the temperature measurement unit and a slab thickness increase determined from the width reduction amount, initial slab width, and steel type when the difference is smaller than a predetermined value, and by controlling the constant pressure control when the difference is larger than a predetermined value.

2. The buckling prevention device control method according to claim 1, wherein the predicted slab thickness increase is calculated from the width press equipment inlet temperature and the press load, width reduction amount, and initial slab width predicted from the width press equipment inlet temperature.

3. 3. A buckling prevention device control method according to claim 1, wherein when the predicted slab thickness increase differs by 30% or more from the slab thickness increase determined from the width reduction, the initial slab width, and the steel type, the control method for one or more lower buckling restraint rolls is changed from the fixed position control to the constant pressure control.

4. A width press facility comprising a temperature measuring unit, a slab conveying path, a pair of dies for width reduction of the slab, and a buckling prevention device; The buckling prevention device comprises one or more pairs of buckling restraint rolls arranged in the vertical direction near the center of the plate width of the slab passing through the slab conveying path, and a control mechanism; The control mechanism An evaluation means for evaluating a predicted slab thickness increase calculated from the slab width press equipment inlet temperature measured by the temperature measurement unit; and a change means for varying the fixed position control and constant pressure control of the buckling restraint rolls by performing fixed position control when the difference between the predicted slab thickness increase amount and the slab thickness increase amount determined from the width reduction amount, initial slab width, and steel type is smaller than a predetermined value, and performing constant pressure control when the difference is larger than a predetermined value.

5. The width press equipment according to claim 4, wherein the evaluation means calculates a predicted thickness increase of the slab based on the width press equipment inlet temperature, the press load, width reduction, and initial slab width predicted from the width press equipment inlet temperature.

6. 6. The width press equipment according to claim 4, wherein the changing means changes the control method of one or more lower buckling restraint rolls from the fixed position control to the constant pressure control when a difference between the predicted slab thickness increase amount and the slab thickness increase amount determined from the width reduction amount, the initial slab width, and the steel type is 30% or more.

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