JP5581784B2 - Sizing press operation method - Google Patents

Description

  The present invention relates to a method of operating a hot width reduction press (sizing press) of a slab (slab) after continuous casting in a steel manufacturing process.

In a steel manufacturing process, when a slab (slab) manufactured by continuous casting is hot-plate rolled, it is applied to a front end portion (also referred to as a front portion) and a rear end portion (also referred to as a tail portion) of the steel sheet after rolling. An abnormal shape portion (referred to as crop) occurs, which is a problem in steel plate production. In order to avoid this crop, the width of the front part and tail part of the slab is narrowed and formed by a slab width reduction pre-forming press using a sizing press and a sizing mill (width reduction rolling device using a vertical roll). (For example, Patent Document 1)
This sizing press is for pressing a steel sheet under an intermittent impact load, and it is necessary to manage the maximum impact load so as not to exceed the allowable load of the equipment from the viewpoint of equipment protection. Therefore, comprehensive judgment is made based on pressing conditions such as rolling reduction and material conditions such as slab temperature, the maximum load is predicted, and the pressing conditions are initially set (set up) so that they do not exceed the allowable load of the sizing press device. It was.

JP 2008-272807 A

In predicting the load, the deformation amount (slab feed amount), deformation speed, etc. are usually used as pressing conditions, and the slab temperature, slab material properties, etc. are used as material conditions. be able to.
P = Kmp × Hsp × Qp × Lp Equation 1
Where P = Expected press load
Kmp = deformation resistance (from Misaka equation)
Hsp = average slab thickness
Qp = rolling force function
Lp = die contact projection length.

  However, in actual operation, the slab temperature cannot be accurately grasped because there is an oxide film on the slab surface. Also, since the outside of the slab cools rapidly, the internal temperature that affects the deformation resistance cannot be measured with high accuracy. For this reason, the accuracy of predicting material properties deteriorates, and the accuracy of deformation resistance deteriorates. Further, since the positioning accuracy of the slab is affected by slip or the like, it causes variation in the mold contact projection length corresponding to the press area. For these reasons, the accuracy of predicting the press load is deteriorated. As shown in FIG. 4 showing the distribution of the difference between the predicted press load value and the actual value, the maximum difference between the predicted value and the actual value is ± 5 MN. Therefore, in setting the actual press conditions, the press load has to be kept low in consideration of this difference. Therefore, the amount of reduction in one press (this is called a pass) is reduced, the number of presses is increased, and productivity is deteriorated. This is a bottleneck in the process and is an obstacle to optimization of the entire manufacturing process.

As a method for avoiding this, a method for determining a slab reduction condition has been proposed as in Patent Document 1. However, even with this method, since the setting of material conditions and pressing conditions is a prerequisite, a process for setting pressing conditions has been proposed, but from the viewpoint of improving the accuracy of predicted loads, an essential solution has been reached. Not in.
Also, because of the structure of the sizing press device, the press load becomes an intermittent impact load, and it is not a process with constant load addition such as rolling, extrusion molding, or pultrusion molding. Is different.

  Therefore, the present invention has an object to improve the accuracy of the predicted press load of the sizing press, which is realized by a simple method that can be used even at an actual site, and is used for efficient use of the sizing press. The goal is to improve productivity.

  As a result of intensive studies to solve the above problems, the present inventors have corrected the subsequent press load predicted value based on the actual value of the press load in the initial stage (or the first) pass, thereby improving the accuracy. It was found that a high press load can be predicted. That is, in the temperature measurement of the slab itself, there are many errors and it is difficult to measure accurately. However, while one slab is pressed by a series of width reductions with a sizing press, it takes about 5 minutes at most. Focused on little change. And it discovered that a press load prediction with high precision could be performed by correcting the subsequent press load prediction value based on the actual value of the press load in the initial stage (or the first pass). As a result, it was found that the prediction accuracy of deformation resistance based on temperature measurement error / accuracy and temperature variation can be improved.

Furthermore, in the slab conveyance, it was also found that the slip is suppressed and the conveyance error can be greatly reduced by sandwiching and conveying with a pinch roll instead of the conventional roll conveyance. As a result, the conventional roll conveyance has an error of ± 50 mm with respect to the conveyance amount of about 280 mm, but the pinch roll conveyance has an error of about ± 2 mm, and the error is actually reduced to 1/25. Thereby, the precision of the mold contact projection length can be increased, and as a result, the precision of the press load prediction value is improved.
This invention is made | formed based on such knowledge, The place made into the summary is as follows.

(1) In a method of pressing a steel slab with a sizing press machine, the ratio of those obtained based on the press load actual value and the press load predicted value corresponding to the press load actual value calculated from the formula (1). Is used as a correction coefficient, and a predicted load load value in subsequent passes is calculated using an expression obtained by multiplying expression (1) by the correction coefficient, and pressing under a width is performed by setting a pressing condition of a sizing press device. The operation method of the sizing press equipment for steel slabs.
P = Kmp × Hsp × Qp × Lp (1)
Here, P = expected press load, Kmp = deformation resistance, Hsp = average slab thickness, Qp = rolling force function, Lp = die contact projection length.

  (2) The method for operating a steel slab sizing press apparatus according to (1), wherein the sizing press apparatus is a sizing press apparatus that conveys the slab by a pinch roll.

(3) The correction coefficient is a ratio of those obtained based on the actual press load value of the first pass and the predicted press load value corresponding to the actual press load value of the first pass calculated from Equation (1). operation method for sizing press apparatus steel slab according to (1) or (2) that there is.

(4) The press corresponding to the press load actual value of a plurality of passes continuous from the first pass and the press load actual value of the plurality of passes continuous from the first pass calculated from the equation (1). The operation method of the sizing press apparatus for steel slabs according to (1) or (2) , wherein the ratio is obtained based on the predicted load value .

  The present invention increases the press load prediction accuracy of the sizing press and increases the amount of rolling reduction at one time, thereby reducing the required number of presses and enabling an efficient operation of the sizing press apparatus.

It is a figure which shows the outline | summary of a sizing press apparatus. It is a figure explaining the method of the width reduction press by a sizing press apparatus. It is a figure which shows transition of the prediction press load for every pass of the sizing press in the Example of this invention, and a performance press load. FIG. 3A shows the predicted press load and the actual press load of the comparative example. FIG. 3B shows the predicted press load and the actual press load of the embodiment of the present invention. FIG.3 (c) shows the Example when not using pinch roll conveyance. It is a figure which shows distribution of the difference of an estimated load and a performance load.

  An outline of the sizing press apparatus is shown in FIG. The molds 11 and 12 provided in the sizing press device 19 are substantially trapezoidal in plan view. Here, the slab 10 heated and held at about 900 ° C. to 1200 ° C. in the heating furnace stops at a predetermined position. The molds 11 and 12 have pressing portions 20 and 21 parallel to the side surface of the slab 10 and inclined portions 22 and 23 provided so as to be connected to the pressing portion 20.21. The distance between the opposing inclined parts 22 and 23 is installed so that it may become narrow gradually in the conveyance direction of the slab 10. As shown in FIG. Although not shown in the drawings, in an actual sizing press, a mold having an inclined portion connected in reverse to the pressing portions 20 and 21 in the steel plate conveying direction is above or below the molds 11 and 12. Is placed on top of each other. This is because the former mold presses the front part of the steel plate and the latter mold presses the tail part of the steel plate under a width.

  Ends of cylinder rods 26 and 27 constituting the width adjusting devices 24 and 25 are attached to the bases of the molds 11 and 12. The cylinder rods 26 and 27 can be reciprocated in the width direction of the slab 10 via the worm gear by rotating the width adjusting devices 24 and 25, and the distance between the opposing molds 11 and 12 can be adjusted. It has become.

  Further, main crank devices 30 and 31 are connected to the base end portions of the cylinders 28 and 29 at the base portions of the width adjusting devices 24 and 25, and the molds 11, 12 is pushed out, and a reduction force is applied to the slab 10. When the cranks 30 and 31 having eccentric shafts are rotated, the piston rods 28 and 29 are pushed out, and the molds 11 and 12 are pushed out in conjunction therewith, so that intermittent impact force is applied to the slab 10. become.

  The slab 10 is sandwiched between pinch rolls 34 and 35. Usually, the slab 10 is conveyed by a table roller (not shown) that supports the lower surface of the slab 10 in contact, but when pressed under a width, the slab 10 can be moved by pinch rolls 34 and 35. It has become.

  Next, the method of the width reduction press will be described. FIG. 2 is a plan view of the half of the mold 11 side from the center line of the slab 10. FIG. 2A shows a preformed state. In the pre-molding, the slab 10 is stopped, and the mold 11 is pressed with a width reduction so as to push the mold 11 into the slab 10. Preliminary forming is completed when it is reduced to a predetermined width.

Next, as shown in FIG. 2 (b), the slab 10 is moved and stopped by a fixed distance (feed amount), and the mold 11 is subjected to a width reduction press (one pass) to make the slab 10 a predetermined width. . This operation is repeated until a predetermined length in the longitudinal direction of the slab 10 reaches a predetermined width.
At this time, the length of the contact between the mold 11 and the slab 10 in one pass under the width reduction is defined as the mold contact projection length. That is, the sum of the contact length between the inclined portion 22 of the mold 11 and the slab 10 and the feed amount of the slab 10 in one pass is the mold contact projection length.

Next, how to obtain the predicted press load value according to the present invention will be described. The above formula can be used to predict the press load. To explain again, the load prediction formula is as follows.
P = Kmp × Hsp × Qp × Lp Equation 1
Where P = Expected press load
Kmp = deformation resistance (from Misaka equation)
Hsp = average slab thickness
Qp = rolling force function
Lp = die contact projection length.

  In addition, Shida's formula and the like are generally used among those skilled in the art for the deformation resistance, but the prediction formula is not particularly limited. In any case, the items necessary for the Misaka equation greatly affect the press load, so the Misaka equation will be described as an example.

  Consider the above four items necessary for predicting the press load. Of these, the average slab thickness is determined by the slab shape. Further, since the rolling force function is obtained from the deformation amount and the deformation speed, it is obtained from the rolling condition of the sizing press.

  As described above, the mold contact projection length is the length when the contact portion between the slab and the mold is viewed in plan, the length where the inclined portion of the mold contacts the slab, and the feed amount of the slab in one pass. Is the die contact projection length. As described above, if there is an error in the slab feed amount, the accuracy of the mold contact projection length is deteriorated.

Since the press load is obtained by multiplying these items, the press load is regarded as a function of the slab temperature and the feed amount. That is, if the accuracy of the slab temperature and the feed amount is good, the accuracy of the press load is increased.
With regard to the slab feed amount, the positioning accuracy of the slab feed can be increased by measures such as reducing the slip and increasing the control accuracy of the transport system. As described above, the normal feed amount is about 250 mm to 350 mm (may exceed 400 mm). Normally, the slab 10 is transported by a transport roller that contacts and supports the slab 10 from the lower surface. However, since the slab 10 is only contact-supported, slip is likely to occur. Actually, a positioning error of ± 50 mm occurs for a feed amount of 280 mm, and it is considered that the cause is mainly slip.

There are several ways to prevent slipping, but various investigations have shown that pinch rolls sandwich the slab up and down, apply a rolling force that does not slip, and move the slab without causing positioning errors. The slab could be transported well. For example, for a feed amount of 280 mm, the positioning error can be 2 mm. This is considered to be caused by wear of the pinch roll diameter. The positioning error can be further reduced by taking measures such as controlling the pinch roll diameter and increasing the control accuracy of the transport system such as feedback control from roll rotation.
As described above, since the positioning accuracy is improved, the feed amount accuracy is improved, and as a result, the error of the mold contact projection length can be reduced.

  As an example, when the one-side width reduction amount (one-side press amount) is 200 mm and the feed amount is 280 mm, the predetermined mold contact projection length is about 700 mm. However, in the movement by the conventional conveyance roll, the error is about 7% (± 50 mm), but when moved by a pinch roll, it is drastically reduced to about 0.3% (± 2 mm). That is, the error given to the press load can be reduced to about 1/25 only by carrying with the pinch roll.

  Finally, the deformation resistance that has the greatest influence is examined. Deformation resistance greatly depends on material properties, and material properties depend on components and material temperature. Since the components are known, as a result, in the pressing of the same slab, the deformation resistance is grasped as a function of temperature. As described above, the slab exiting the heating furnace has an oxide film on the surface, temperature measurement at a high temperature around 1000 ° C., and internal temperature that greatly affects deformation resistance cannot be measured directly. Therefore, it is difficult to measure the temperature that affects the physical properties of the material and it cannot be measured accurately.

  Therefore, the inventors paid attention to the temperature change of the slab during the pressing process of the sizing press, and performed a simulation on the change of the internal temperature of the slab. As a result, it was found that the surface temperature of the slab extracted from the heating furnace at 1000 ° C. decreased by about 30 ° C. in about 5 minutes considering the sizing press working time, but the internal temperature hardly changed. In other words, during the sizing press process, the slab internal temperature affecting the material characteristics hardly changed, and it was found that there is no problem even if the same material characteristics are considered in a series of press processes.

  Next, it is difficult to improve the accuracy of temperature measurement due to problems such as measurement technology and measurement environment. However, as described above, if the material characteristics during a series of press work do not change, the predicted load of a certain pass is compared with the actual load, and the predicted load of the next pass is corrected based on the result. The error can be absorbed, and the deformation resistance can be accurately predicted as a whole without considering the temperature measurement accuracy. As a result, the accuracy of the predicted press load can be increased.

Therefore, in the present invention, when calculating the predicted press load, the above-described equation (Equation 1) is multiplied by the correction coefficient G and predicted by the following equation.
P = Kmp × Hsp × Qp × Lp × G Equation 2
Where P = Expected press load
Kmp = deformation resistance (from Misaka equation)
Hsp = average slab thickness
Qp = rolling force function
Lp = die contact projection length
G = correction coefficient.

A correction method will be described. For example, when the actual load in a certain path is P1a and the predicted load is P1e, the ratio between the actual load and the predicted load can be used as a correction coefficient.
G = P1a / P1e
By substituting this G into Equation 2, the predicted load P2e for the next pass can be calculated. That is, in order to calculate the predicted load of the initial stage pass (the first pass or a series of passes including the first pass), the deformation resistance Kmp, the average slab thickness Hsp, the rolling force function Gp, and the mold contact projection length Lp are set and predicted. The load P0e is calculated, then the actual press load P0a of the initial stage pass is measured, the correction coefficient G is calculated therefrom, and the path after the next stage (including the second pass or the first pass is included by Equation 2 A predicted load of a series of passes after the series of presses) is calculated and set as a press condition of the sizing press apparatus.

  Needless to say, the method of obtaining the correction coefficient G is not limited to the above-described example (the ratio between the predicted load and the actual load). In short, it is a correction factor that is obtained by comparing the predicted press load in the previous pass with the actual press load, and by correcting the predicted press load in the next pass, it is possible to cancel the error in temperature measurement. The press load can be predicted well.

As described above, with regard to the method of predicting the press load, the improvement in positioning accuracy by pinch roll conveyance of the slab and the correction of the subsequent pass by comparing the predicted press load of the previous pass with the actual press load cancels the poor temperature measurement accuracy. I explained that. It is desirable to realize these simultaneously, but it is effective to implement either one. In particular, the correction based on the prediction / result comparison in the previous pass is a simple but highly effective measure that does not require any special equipment.
Next, examples of the present invention will be described.

With the same steel type (using slabs having the same casting conditions), a press (Example) in which the present invention was implemented and a press (Comparative Example) in which the present invention was not performed were continuously performed. The predicted press load at this time was compared with the actual press load. The sizing press conditions are as follows.
Steel type: 980 MPa high-tensile steel plate Slab temperature during sizing press (measured value): 1050 ° C
Rolling amount: 300mm
Conveyance amount (feed amount): 280mm
Conveyance method: Conveyance by pinch roll Correction coefficient: The ratio of the first actual press load to the predicted press load, and the same correction coefficient was applied to all subsequent passes.

  FIG. 3A shows the predicted press load and the actual press load of the comparative example. In the comparative example, since the actual press load is determined from the predicted press load in consideration of equipment maintainability, the actual press load is reduced, and a total of 24 passes are required to obtain a desired reduction width.

On the other hand, FIG. 3B shows the predicted press load and the actual press load of the embodiment of the present invention. Excluding the initial deviation, the predicted load and the actual load were almost the same in all passes, and it was confirmed that the prediction was performed with very high accuracy.
Therefore, the actual press load can be increased, and only 15 passes in total are required to obtain a desired reduction width, and 9 passes can be reduced. This was confirmed to correspond to a 37% productivity improvement in terms of the time required for the sizing press.

  FIG.3 (c) shows the Example when not using pinch roll conveyance on the same conditions as the above. It was confirmed that the difference between the predicted value and the actual value was smaller than that of the comparative example. However, it can be seen that the difference between the predicted value and the actual value is larger than in the example in which the pinch roll conveyance is applied.

At this time, a total of 20 passes were required to obtain a desired reduction width, and it was confirmed that the productivity was equivalent to an improvement of 15%.
Next, the difference between the predicted press load and the actual press load between one month before application and one month after application of the present invention is investigated, and the distribution of the difference is shown in FIG. Since it is a total for one month, the influence of the steel type and the difference in pressing conditions such as the rolling width are rounded up and averaged. As can be seen from FIG. 4, there was a variation over ± 5 MN before the application of the present invention (that is, conventional), but it was confirmed that the variation was about ± 2 MN after the application of the present invention. That is, it was confirmed that the accuracy of the predicted press load was remarkably improved.

  As mentioned above, although this invention has been demonstrated, the aspect of this invention is not limited to the aspect shown by description.

  The present invention can be used for a sizing press for rolling steel sheets in the steel industry.

DESCRIPTION OF SYMBOLS 10 Slab 11,12 Mold 19 Sizing press apparatus 20,21 Press part 22,23 Inclination part 24,25 Width adjustment apparatus 26,27 Cylinder rod 28,29 Cylinder 30,31 Crank apparatus 34 (Upper side) Pinch roll 35 (Lower Side) Pinch roll

Claims (4)

In the method of width-pressing steel slabs with a sizing press machine, the correction factor is the ratio obtained based on the actual press load value and the predicted press load value corresponding to the actual press load value calculated from Equation (1). As shown in FIG. 1 , the steel is characterized in that the predicted load value in the subsequent passes is calculated using the formula obtained by multiplying the formula (1) by the correction coefficient, and the pressing is performed under the width reduction by setting the pressing conditions of the sizing press device. Operation method of slab sizing press equipment.
P = Kmp × Hsp × Qp × Lp (1)
Here, P = expected press load, Kmp = deformation resistance, Hsp = average slab thickness, Qp = rolling force function, Lp = die contact projection length.   The method of operating a sizing press apparatus for a steel slab according to claim 1, wherein the sizing press apparatus is a sizing press apparatus that conveys the slab by a pinch roll. The correction coefficient is the ratio of those obtained based on the press load actual value of the first pass and the press load predicted value corresponding to the press load actual value of the first pass calculated from the equation (1). The operation method of the sizing press apparatus of the steel slab of Claim 1 or 2 characterized by the above-mentioned. The correction coefficient is a press load predicted value corresponding to a press load actual value of a plurality of passes continuous from the first pass and a press load actual value of a plurality of passes continuous from the first pass calculated from the equation (1). The method of operating a sizing press apparatus for steel slabs according to claim 1 or 2 , wherein the ratio is obtained based on the above.

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