Method for controlling camber in steel plate rolling process

Abstract

The invention relates to the technical field of steel rolling, in particular to a camber control method in a steel plate rolling process, which comprises the following steps of: adopting the rolling reduction of 1-35mm in the first 1-3 passes of finish rolling, and controlling the actual value of the rolling reduction to be 1-35mm according to the strength difference of steel grades in the actual rolling process; the rolling force of the last two passes is 4000-5000t, the rolling force is within 85% of the set requirement, the rolling speed is set to be 4-5m / s, a sliding plate on the side edge of a working roller bearing box adopts a wedge-shaped gasket of 1-3mm, the gap of a memorial archway is controlled to be 1.5-2.2 mm, and the rolling force of 5000t is used for carrying out a bounce test on a rack; the roll gap tilting value is adjusted in advance; according to the control method, the plate shape defects such as wave shape, camber and frame scraping easily generated during rolling of the thin steel plate with the width of 3600 mm or above can be overcome, the yield of the steel plate is increased, and the rolling spot rate is reduced.

Description

Technical Field

[0001] This invention relates to the field of steel rolling technology, and in particular to a method for controlling the sickle bend during the rolling process of steel plates. Background Technology

[0002] The camber angle has consistently been a bottleneck for improving output and quality control in the 5500mm thick plate production area. The size and degree of camber directly affect spot market indicators and can lead to more frequent operational accidents, slowing down the production pace and impacting output. Severe camber can even cause frame scraping, triggering operational accidents. To address this issue, operators can reduce the size and degree of camber by adjusting the reduction amount, rolling passes, and rolling speed. Comprehensive prediction can eliminate operational hazards and non-conforming rates at the outset. Ensuring contract fulfillment rates and building a high-quality brand are crucial for enhancing market competitiveness.

[0003] To improve the control of camber in ultra-thin and ultra-wide steel plates, the current common method is to use two parameters, unit rolling force and reduction rate, as boundary conditions for pass allocation. This results in unreasonable pass roll gaps and rolling forces, poor overall rectangularity of the steel plate, unsatisfactory camber control, and low success rate. This method wastes a lot of production time, causes many accidents, and is costly, which is not conducive to mass production.

[0004] Chinese patent CN102688884 discloses a rolling process for steel plates of extreme specifications using a 2800mm double-stand medium-thick plate mill; Chinese patent CN102962253 discloses a rolling process for 5mm steel plates; and Chinese patent CN101259482 discloses a rolling process for 6mm steel plates. All three patent documents employ a single-fire rolling process with multiple rolling passes. The drawbacks include increased temperature drop, which is detrimental to steel plate shape and temperature control. Furthermore, the steel plate width is relatively small, with the width of the rolled blank slab ≤2800mm, directly impacting the product's application areas.

[0005] Chinese patent CN102825065 discloses a rolling method for wide and thin steel plates. This invention uses a double-stand rolling mill to roll wide and thin steel plates and uses a single-fire forming process. The selected billet is relatively thick, and there are many rolling passes, which increases the temperature drop and is not conducive to plate shape and temperature control. At the same time, due to the large billet size and multiple-length rolling, the steel plate is too wide, the temperature drops quickly, the temperature uniformity of the plate is poor, the temperature difference is large, and it is easy to cause uneven performance of the steel plate.

[0006] Chinese patent CN1019513745 discloses a method for rolling wide and thin plates using a thick plate mill. The current steel plate thickness is 6mm. It adopts a two-fire forming process, uses PVPC, and controls the AGC function to solve the problem of unstable plate shape and performance during the production of wide and thin steel plates. Its shortcomings are: the method of pressing and stacking the plates after slitting the sub-plates seriously affects the delivery schedule of the steel plates; the widening is placed in the billet opening stage, and there is no widening during the second-fire rolling, which easily leads to poor transverse properties of the steel plates.

[0007] None of the aforementioned patents offer solutions to address the common shape defects such as waviness, camber, and scraping that arise during the rolling of thin steel plates with widths exceeding 3600 mm. Therefore, developing a rolling process for thin steel plates to produce stable, ultra-wide steel plates with uniform shape and performance is of great significance for the production of heavy and wide plate products. Summary of the Invention

[0008] This invention provides a method for controlling camber during steel plate rolling, which can solve the problems of plate shape defects such as waviness, camber, and scraping that are easily generated when rolling thin steel plates with a width of 3600 mm or more, thereby improving the steel plate yield and reducing the rolling spot rate.

[0009] To achieve the above objectives, the present invention employs the following technical solution:

[0010] A method for controlling camber during steel plate rolling includes the following:

[0011] 1) Reduction adjustment: The reduction is 1-35mm in the first 1-3 passes of finishing rolling. In the actual rolling process, the actual reduction is controlled between 1-35mm according to the strength difference of steel grade; to ensure that the overall rolling force decreases, and the rolling force of the last two passes is 4000-5000t.

[0012] 2) Pass adjustment: Under the premise of ensuring the process, there should be no waiting for the temperature to rise in the pass, and the rolling force should be within 85% of the set requirement;

[0013] 3) Speed ​​adjustment: The rolling speed is set to 4-5 m / s.

[0014] Furthermore, it also includes:

[0015] 1) Ensure that the width of the archway is relatively consistent from top to bottom, use 1-3mm wedge-shaped shims on the side slide of the working roller bearing box, and control the gap between the archways to 1.5-2.2mm;

[0016] 2) To address the issue of inconsistent stiffness on both sides of the rolling mill, a 5000t rolling force is used to conduct a bounce test on the stand after each roll change. Based on the roll gap deviation on both sides during the bounce test, the roll gap tilt value is adjusted in advance.

[0017] Furthermore, it also includes controlling the roundness of the finishing mill, keeping its roundness index between 0 and 0.3 mm.

[0018] Furthermore, the adjustment of the roll gap tilt value ensures that the roll gap in the final pass is between 2.5 and 40 mm.

[0019] Furthermore, in the aforementioned pass adjustment, the pass control for a single-stand finishing mill is 6 to 22 load passes, and the pass control for a double-stand finishing mill is 6 to 8 load passes for roughing and 7 to 11 load passes for finishing.

[0020] Furthermore, the steel plate is a steel plate with a width of 3600mm or more and a specification of 5-8mm.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1) Using wedge-shaped shims can temporarily alleviate the phenomenon of inconsistent gap between the lower support roll and the stand of the finishing mill, thereby reducing the phenomenon of cross rolls during the rolling process, and also reducing the positional deviation of the HGC cylinder on the same side.

[0023] 2) Mitigating the swaying of the support rollers caused by the archway by controlling the gap between the archways;

[0024] 3) By conducting a bounce test on the stand, the roll gap tilt value can be adjusted in advance, thereby reducing roll gap deviation during the rolling process;

[0025] 4) By adjusting the bottom and speed, the rolling process is stabilized, reducing the formation of camber.

[0026] 5) The sickle-shaped curve caused the proportion of sickle-shaped products in the spot inventory to decrease from 64.6% to 28.2%, while the overall yield of steel plates increased by 0.22%.

[0027] 6) Based on the existing production line equipment and process conditions, without increasing equipment investment and production costs, reducing the risk of equipment damage, and improving the steel plate yield, stable rolling of ultra-thin and ultra-wide limit specification steel plates has been achieved. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating the sickle-shaped bend in the steel plate caused by the large gap between the rolling mills as described in this invention.

[0029] Figure 2 This is a schematic diagram of the gap between the steel plates described in this invention.

[0030] Figure 3 This is a schematic diagram of the roll swaying during the rolling process described in this invention.

[0031] In the diagram: 1. Steel plate; 2. Upper work roll; 3. Lower work roll; 4. Mill exit gate; 5. Mill entrance gate; 6. Gap; 7. Work roll bearing housing. Detailed Implementation

[0032] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0033] This invention discloses a method for controlling camber during steel plate rolling, suitable for rolling thin steel plates with a width of 3600mm or more. The specific control method is as follows:

[0034] Factors that cause camber during rolling include equipment factors, operational reasons, and management reasons.

[0035] 1. Equipment factors:

[0036] The main reasons include severe wear on the archway windows and inconsistent rigidity of the archways on both sides of the rolling mill.

[0037] Currently, the stand window of the finishing mill is severely worn, and the gap between the work roll bearing housing 7 and the stand is large. This causes significant deviations in the inlet and outlet positions of the HGC cylinder during rolling, resulting in inconsistent roll gaps on both sides. Meanwhile, see... Figure 2 Because the gaps 6 between the work roll bearing housing 7 and the mill exit gate 4 and the mill entrance gate 5 are large, see Figure 1 and Figure 3 During the rolling process, the upper work roll 2 and the lower work roll 3 will cross, which is very easy to cause sickle bending. The actual measured data of the finishing mill archway window, directly measuring the width of the archway window and the width of the work roll bearing box 7, clearly shows that both the lower work roll bearing box and the finishing mill archway are flared, wider at the top and narrower at the bottom, with a difference of more than 1mm in the upper and lower gaps. The gap 6 between the lower support roll and the archway after the rolls are loaded is measured with a feeler gauge. The measurement results show that the gap on the transmission side is significantly smaller than that on the operating side, but the trend on both sides is basically the same, with the upper gap being larger and the lower gap being smaller.

[0038] In addition, the inconsistent stiffness on both sides of the rolling mill is another major cause of camber. The inconsistent stiffness (arches, roll system, etc.) on both sides of the finishing mill results in a roll gap deviation of about 0.6mm between the drive side and the operating side when the rolling force reaches 65,000KN. This deviation is related to factors such as the stiffness of the arches on both sides and the stiffness of the entire roll system. Currently, the arch stiffness data in the system is a curve, not a curve for each arch. Therefore, the deviation of the roll gap on both sides is related to the rolling force and is not a constant value.

[0039] Control measures:

[0040] (1) The support roll slide plate uses a 3mm wedge-shaped shim. The wedge-shaped shim can temporarily alleviate the phenomenon of inconsistent gap between the support roll and the archway of the finishing mill, thereby reducing the phenomenon of cross rolls during the rolling process, and also reducing the position deviation of the HGC cylinder on the same side.

[0041] (2) During the annual maintenance period, the mill archway is welded to ensure that the upper and lower widths of the archway are relatively consistent and the gap between the archway is controlled at 1.5 to 2.2 mm to reduce the problem of support roller swaying caused by the archway.

[0042] (3) In response to the inconsistent stiffness on both sides of the rolling mill, after each roll change, a rolling force of 5000t is used to conduct a bounce test on the stand, and the roll gap tilt value is adjusted in advance based on the roll gap deviation on both sides during the bounce test. The adjustment of the roll gap tilt value makes the roll gap of the last pass 2.5 to 4mm, thereby reducing the roll gap deviation during the rolling process.

[0043] 2. Operational reasons: Different shifts have different operating habits, and the level of camber control also varies. Judging from the feedback of the operators of each shift on the shearing line, the control method with the highest level of camber control is to manually center the steel plate during the finishing rolling stage to ensure that the center line of steel plate 1 is consistent with the center line of the roller table. The control process of rolling passes, reduction rate, rolling force and corresponding rolling speed is more reasonable. This operating method can effectively control camber.

[0044] Control methods:

[0045] (1) Control the roundness of the finishing mill to 0-0.3mm;

[0046] (2) Reduction adjustment: The principle of pass allocation is to use a large reduction in the first 1 to 3 passes of finishing rolling, that is, to limit it to 35mm. In the actual rolling process, the actual value is controlled between 25 and 35mm according to the strength difference of steel grade. The reduction adjustment adopts segmented control. As the number of rolling passes decreases, the reduction decreases synchronously to ensure that the overall rolling force decreases. The rolling force of the last two passes is more reasonable at 4000 to 5000t.

[0047] (3) Pass adjustment: It is completed by using the reduction rate and rolling force limit conditions. Under the premise of ensuring the process, there should be no waiting for the temperature of the pass. The rolling force should be within 85% of the set requirement. The pass control of a single stand finishing mill is 6 to 22 load passes, and the pass control of a double stand finishing mill is 7 load passes for roughing and 9 load passes for finishing.

[0048] (4) Speed ​​adjustment: When the rolling temperature is too high, the deformation resistance is low, and high-speed rolling is possible. There are few cases of large rolling force deviation. However, when the rolling temperature is too low (calculated temperature below 880℃), the deformation resistance is high. If the rolling speed is too fast, the rolling force deviation will be large, the HGC working stroke will fluctuate greatly, and the rolling will be unstable. At this time, we set the rolling speed to 4-5m / s.

[0049] 3. Management reasons: Currently, it is impossible to strictly distinguish between short and narrow dimensions caused by camber and rolled short or narrow dimensions. First, there is no effective means of monitoring camber from the end of rolling to the end of cutting. Second, due to factors such as the width ratio, insufficient width at the beginning and end of the steel plate is easily confused with camber and is not easy to distinguish. Third, different operators have different criteria for judging camber. Therefore, there is currently no accurate data on the quantity of dimensional items caused by camber.

[0050] Work measures:

[0051] (1) Advance the PSG repair work to provide a strong guarantee for the accurate measurement of sickle bend data;

[0052] (2) Unify the criteria for determining sickle bends so as to reflect the current situation of sickle bends as accurately as possible.

[0053] The following embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified, the methods used in the following embodiments are conventional methods.

[0054] Example 1:

[0055] The steel billet is 200*1450*3320mm, and the produced steel plate is 7*3980*34560mm. The specific control method is as follows:

[0056] 1. After calibration, the roundness index of the finishing mill is 0.131, and the gap between the rollers is controlled within 0.18. Rolls with a rolling cycle of 1800t are selected for production scheduling.

[0057] 2. The calibrated rolling force was increased to 5000t, and the bending force was incorporated into the rolling force calculation, thus obtaining the accurate corresponding value of rolling force and roll gap. The roll gap was calibrated using 1000 tons, the mill stiffness was calibrated using 2000 tons, and the roll gap was calibrated again using 1000 tons of rolling force after the stiffness was calibrated.

[0058] 3. Heating regime control: The heating process is executed at the upper limit of the process, the total furnace time is 4.5 hours, the heat soaking temperature is 1260℃, the high temperature section is 80 minutes, and the heat soaking is controlled at 60 minutes;

[0059] 4. Reduction adjustment: Segmented control is adopted. As the number of rolling passes decreases, the reduction decreases synchronously. The reduction of the last pass is controlled within 1.2mm to ensure that the roll gap of the last pass is above 3.5mm. Under the premise of ensuring the process, there is no waiting for the temperature of the pass. The rolling conditions are within 75% of the mill capacity.

[0060] 5. Pass adjustment: The single-stand finishing mill controls 10 load passes, and the double-stand finishing mill controls 6 load passes. The final goal is to control the finishing temperature above 880℃.

[0061] 6. Speed ​​adjustment: Low-speed bite and high-speed rolling are adopted. The acceleration and rolling speed are set reasonably. The acceleration is controlled at 1.5m / s and the rolling speed is controlled at 4.5m / s, which is ideal for the plate shape and rolling success rate.

[0062] By changing the shape of the slide plate, we achieved a gap between the archway and the work roll slide plate of 1.6 to 1.9 mm, achieving the best range ever. The rolling of the case variety has been effectively controlled in terms of sickle bend, and the spot stock of this variety has been halved, from the original spot stock ratio of 61% to the current 30%, which can reach the leading level in the industry.

Claims

1. A method for controlling camber during steel plate rolling, characterized in that, Includes the following: 1) Reduction adjustment: The reduction is 1-35mm in the first 1-3 passes of finishing rolling. In the actual rolling process, the actual reduction is controlled between 1-35mm according to the strength difference of steel grade; to ensure that the overall rolling force decreases, and the rolling force of the last two passes is 4000-5000t. 2) Pass adjustment: Under the premise of ensuring the process, there should be no waiting for the temperature to rise in the pass, and the rolling force should be within 85% of the set requirement; 3) Speed ​​adjustment: The rolling speed is set to 4-5 m / s.

2. The method for controlling camber during steel plate rolling according to claim 1, characterized in that, Also includes: 1) Ensure that the width of the archway is relatively consistent from top to bottom, use 1-3mm wedge-shaped shims on the side slide of the working roller bearing box, and control the gap between the archways to 1.5-2.2mm; 2) To address the issue of inconsistent stiffness on both sides of the rolling mill, a 5000t rolling force is used to conduct a bounce test on the stand after each roll change. Based on the roll gap deviation on both sides during the bounce test, the roll gap tilt value is adjusted in advance.

3. The method for controlling camber during steel plate rolling according to claim 1, characterized in that, It also includes controlling the roundness of the finishing mill, keeping its roundness index between 0 and 0.3 mm.

4. The method for controlling camber during steel plate rolling according to claim 1, characterized in that, The adjusted roll gap tilt value is such that the roll gap for the final pass is between 2.5 and 40 mm.

5. The method for controlling camber during steel plate rolling according to claim 1, characterized in that, In the aforementioned pass adjustment, the pass control for a single-stand finishing mill is 6 to 22 load passes, and the pass control for a double-stand finishing mill is 6 to 8 load passes for roughing and 7 to 11 load passes for finishing.

6. The method for controlling camber during steel plate rolling according to claim 1, characterized in that, The steel plate is a steel plate with a width of 3600mm or more and a specification of 5-8mm.

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