A method for reducing the curvature of the ladle when rolling high-strength wide and thin plates with a wide and thick plate rolling mill

Abstract

The present invention discloses a method for reducing the curvature of high-strength wide and thin plates rolled by a wide and thick plate mill, comprising: (1) heating and temperature adjustment; (2) plan arrangement; (3) rolling reduction schedule arrangement; (4) controlled rolling adjustment; (5) pre-straightening and ACC water cooling; (6) hot straightening. The method of the present invention can quickly and effectively reduce the curvature of steel plates in the production process of high-strength wide and thin plates. The average monthly curvature incidence rate was reduced from 25.5% to 8%, and the effect was quite obvious.

Description

Technical Field

[0001] The invention relates to a steel plate rolling method, in particular to a method for reducing the curvature of a steel plate when a wide and thick plate rolling mill rolls a high-strength wide and thin plate. Background Art

[0002] In the prior art, due to the rapid temperature drop of the steel plate during the rolling process, and the large temperature drop difference between the longitudinal head, middle and tail and the transverse middle and edge of the steel plate, the final rolling temperature is controlled to be low, which can easily lead to unstable rolling state, plate shape problems such as wave shape, bend, sickle bend, etc., and affect the uniformity of the mechanical properties of the steel plate, which can easily lead to a significant reduction in the impact toughness of the middle part of the steel plate. In 2021, the wide plate plant will produce about 5,000 tons of wide thin plates with a thickness of ≤10mm per month, and the bend incidence rate is as high as 25%, that is, about 1,250 tons of wide thin plates bend each month. Not only is the plate shape abnormally wave-shaped during the rolling process, there is a risk of scrapping, but also the plate shape rescue cost of the subsequent process is increased, and other surface quality risks appear during the re-correction and rescue process, which also affects the fulfillment of the contract. The monthly plate shape rescue task is arduous and consumes a lot of manpower and material resources. The bend defect of the plate shape has become a heavy burden, and it is necessary to tackle and solve the control of the rolling plate shape. Summary of the invention

[0003] Purpose of the invention: The purpose of the invention is to provide a method for reducing the curvature of a wide and thick plate rolling mill when rolling high-strength wide thin plates.

[0004] Technical solution: The method provided by the present invention for reducing the curvature of the ladle when rolling high-strength wide and thin plates with a wide and thick plate rolling mill comprises the following steps:

[0005] (1) Heating and temperature adjustment: Make the feeding direction of the walking beam consistent with the width direction of the billet; control the billet heating temperature at 1200-1220°C, and the temperature uniformity is ≤10°C; set the target lower surface temperature of the steel tapping lower than the upper surface temperature; obtain uniformity of metal deformation by improving the uniformity of heating temperature, and consider the risk of warping during rolling, and set the target lower surface temperature of the steel tapping 25-45°C lower than the upper surface temperature.

[0006] (2) Planning: After the roll change, the second or third furnace will directly produce, the transition billets of similar width specifications shall not be less than 6 pieces, and the rolling roll tonnage shall not be greater than 1,000 tons;

[0007] (3) Rolling reduction schedule arrangement: mainly to reasonably optimize the reduction schedule, appropriately reduce the final pass reduction rate and rolling force, increase the second stage rolling temperature to reduce the rolling deformation resistance, and stabilize the rolling conditions to reduce plate shape fluctuations. During rolling, the cooling water of the input and output rollers of the mill is turned off; and the roller surface temperature is controlled by hot rolling and adjusting the cooling water volume of the working roll body, so that the surface temperature of the working roll is controlled between 45 and 60 ° C during the rolling process of the rolled piece.

[0008] Adopt the even-pass 10+1 rolling procedure, reduce one steel transfer to increase the rolling temperature, and control the upper limit of the second-stage rolling temperature between 1010-1030℃; under the premise of ensuring the rolling force ≥33000kN, the final pass of finishing rolling has a smaller rolling force, the final pass reduction rate of finishing rolling is ≤14%, FIN Late 90, and the final pass rolling force is 40000kN-45000kN; limit the CVC stroke between 55-100; limit the roll shifting value of the last three passes to 6, -23 and -43; the same specification reduction procedure ensures consistency;

[0009] (4) Control rolling adjustment: adopt effective control means and preventive measures during the rolling process to reduce the incidence of wave shape and sickle bending.

[0010] The thickness of the intermediate billet is controlled within 36mm-48mm, and the thickness of the intermediate billet of the same specification is ensured to be consistent; the temperature of the second stage rolling of the same specification is ensured to be consistent; according to the upper and lower working roll main motor transmission load allowable range and the roll gap control logic, the upper and lower roll speed ratio and the rolling line height are adjusted; when rolling to the second to last pass, the rolling temperature of this pass is controlled to be ≥880℃, and the rolling temperature of the last pass is ≥820℃, and the roll shifting value of these two passes is set value;

[0011] (5) Pre-straightening and ACC water cooling: Adjust the roll gap of the pre-straightening machine to improve the plate shape before cooling, which is conducive to uniform ACC water cooling and reducing plate shape changes. When pre-straightening the steel plate, manually intervene to reduce the roll gap distance and increase the bending roll force by 0.2;

[0012] (6) Hot straightening: Straightening temperature: After cooling, the ACC automatically and quickly passes through the straightening machine for high-temperature straightening to ensure that the straightening temperature is ≥580℃; Straightening passes and straightening force: Straightening passes ≥3, straightening force 1000-1500kN.

[0013] Furthermore, in the step (1), the target lower surface temperature of the steel tapping is set to be 25-45° C. lower than the upper surface temperature.

[0014] Furthermore, in step (4), the upper and lower roller speed ratio is adjusted to 1.00-1.10.

[0015] Furthermore, in step (4), the rolling line height is 805-815 mm.

[0016] Furthermore, in the step (5), manual intervention is performed to reduce the roll gap distance by 0.5-1.0 mm during pre-straightening of the steel plate.

[0017] The method of the present invention successfully realizes the rolling of wide and thin high-strength steel plates with a thickness of ≤10mm and a width of more than 3000mm by a 5000mm wide and thick plate mill through uniform high-temperature heating, roller profile and roller surface temperature control, optimization of rolling procedures, especially ensuring the stability of the last three rolling passes, CVC value limitation, and control of cooling plate profile, straightening model and process key points. The unevenness of the steel plate can be within 3mm / m, and the performance of the entire steel plate is uniform, especially the impact toughness requirement better meets the manufacturing requirements of steel structures such as bridges and buildings. The present invention relies on the existing equipment capacity and production capacity of the wide and thick plate plant, does not require additional equipment investment, and can achieve the goal of the present invention only through control of the production process, which can be achieved for most of the current wide and thick plate plants. The method of the present invention is particularly suitable for the mass production of high-strength wide and thin plates, has a high pass rate, and can effectively meet the growing market demand. After the implementation of the invention, the buckling of high-strength wide and thin steel plates with a thickness of ≤10mm was effectively controlled, and the average monthly buckling rate in January-March 2022 was reduced from 25.5% in 2021 to 8%, with a very obvious effect. 1. The cost of the warp correction process is calculated at 40 yuan / ton per ton. The wide and thick plate plant produces 5,000 tons of high-strength wide and thin plates per month. The economic benefits of reducing the buckling of thick plates from January to March 2022 are: (20.5%-8%)*5,000 tons / month*40 yuan*3 months=75,000 yuan. 2. Reasonable procedures are arranged and the roller shifting value of the last three passes is limited to avoid the unplanned incidence rate caused by abnormal wave shape and uncontrollable sickle bends of 0.10%. The unplanned correction is reduced to 0.001*5,000 tons / month*500 yuan / ton*3 months=7,500 yuan from January to March 2022.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following advantages: it can quickly and effectively reduce the curvature of steel plates during the production of high-strength wide thin plates. The average monthly curvature rate is reduced from 25.5% to 8%, and the effect is quite obvious. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of adjusting the control parameters of the PFC model;

[0020] Figure 2 Arrange a schematic diagram for the secondary rolling schedule;

[0021] Figure 3 This is a schematic diagram of the control parameter adjustment of the RFS model;

[0022] Figure 4 This is a schematic diagram of the setting values ​​for the last three bending passes of the rolling mill. DETAILED DESCRIPTION

[0023] Example 1

[0024] The method of this embodiment includes the following steps:

[0025] 1. Heating and temperature:

[0026] A walking beam heating furnace is used to make the feeding direction of the walking beam consistent with the width direction of the billet; the billet heating temperature is controlled between 1200-1220℃, and the temperature uniformity is ≤10℃; the uniformity of metal deformation is obtained by improving the uniformity of heating temperature, and the risk of warping during rolling is taken into consideration, and the target lower surface temperature of steel output is set 25-45℃ lower than the upper surface temperature.

[0027] 2. Plan Arrangement:

[0028] After the roll change, the second or third furnace shall go into production directly. There shall be no less than 6 transition billets of similar width specifications, and the tonnage of the rolling rolls shall not be greater than 1,000 tons.

[0029] 3. Rolling and pressing procedures:

[0030] The main purpose is to reasonably optimize the reduction procedure, appropriately reduce the final reduction rate and rolling force, increase the second-stage rolling temperature to reduce the rolling deformation resistance, and stabilize the rolling conditions to reduce plate shape fluctuations. During rolling, the cooling water of the input and output rollers of the rolling mill is turned off; and the roller surface temperature is controlled by hot rolling and adjusting the cooling water volume of the working roll body, so that the surface temperature of the working roll is controlled between 45-60℃ during the rolling process of the rolled piece.

[0031] 1. Adopt the even-pass 10+1 rolling procedure, steel transfer code 3, reduce one steel transfer to increase the rolling temperature, and control the upper limit of the second-stage rolling temperature between 1010-1030℃.

[0032] 2. Under the premise of ensuring the rolling force ≥33000kN (zero roll gap calibration force), the rolling force of the last pass of finishing rolling is relatively small, the reduction rate of the last pass of finishing rolling is ≤14% (pre-arrangement), FIN Late 90, and the rolling force of the last pass is 40000kN-45000kN.

[0033] 3. Limit the CVC stroke to between 55 and 100 to avoid the situation where the CVC stroke between passes is too long and the rolled piece is waiting for rolling to start, resulting in low steel temperature and uncontrolled plate shape.

[0034] 4. Limit the roll shifting values ​​in the last three passes (6, -23, -43) to avoid uncontrollable sickle bending caused by roll bounce in the rolled piece.

[0035] 5. The same specifications of pressing procedures ensure consistency.

[0036] 4. Control rolling adjustment: adopt effective control means and preventive measures during the rolling process to reduce the incidence of wave shape and sickle bend.

[0037] 1. The thickness of the intermediate billet is controlled at 36mm-48mm during rolling, and the thickness of the intermediate billets of the same specification is guaranteed to be consistent.

[0038] 2. Ensure that the second stage rolling temperature of the same specifications is consistent.

[0039] 3. Adjustment of buckle head: According to the allowable range of transmission load of the upper and lower working roll main motors and the roll gap control logic, the risk of buckle head flatness during rolling can be avoided by adjusting the upper and lower roll speed ratio (1.00-1.10) and the rolling line height (805-815mm).

[0040] 4. When rolling to the penultimate pass, control the rolling temperature of this pass to be ≥880℃, the rolling temperature of the last pass to be ≥820℃, and make the roll shifting values ​​of these two passes the set values.

[0041] 5. To control the final rolling temperature to ≤810℃, the rolling roller speed and the steel throwing roller speed can be adjusted to 5.0m / s

[0042] 5. Pre-straightening and ACC water cooling: Adjust the roller gap of the pre-straightening machine to improve the plate shape before cooling, which is conducive to uniform ACC water cooling and reduce plate shape changes.

[0043] 1. When pre-straightening the steel plate, manually intervene to reduce the roll gap by 0.5-1.0mm and increase the bending roll force by 0.2 to improve the straightening effect.

[0044] 2. Optimize the water ratio model (as shown in the following table) to improve the first-piece watering plate type hit rate and cooling plate type qualification rate.

[0045] Table 1 Water ratio parameter optimization

[0046]

[0047] 6. Hot straightening: Optimize the straightening process, increase the straightening temperature and straightening force for high-strength wide and thin plates, which can reduce deformation resistance and improve straightening effect.

[0048] 1. Straightening temperature: After cooling, the ACC will automatically and quickly pass through the straightening machine for high-temperature straightening to ensure that the straightening temperature is ≥580℃.

[0049] 2. Straightening passes and straightening force: straightening passes ≥ 3, straightening force 1000kN-1500kN.

Claims

1. A method for reducing the curvature of a wide and thick plate rolling mill when rolling high-strength wide thin plates, characterized in that: The steps include: (1) Heating and temperature adjustment: Make the feeding direction of the walking beam consistent with the width direction of the billet; control the billet heating temperature at 1200-1220°C, and the temperature uniformity is ≤10°C; set the target steel tapping lower surface temperature lower than the upper surface temperature; (2) Planning: After the roll change, the second or third furnace will directly produce, the transition billets of similar width specifications shall not be less than 6 pieces, and the rolling roll tonnage shall not be greater than 1,000 tons; (3) Rolling reduction schedule arrangement: adopt the even-pass 10+1 rolling schedule, reduce one steel transfer to increase the rolling temperature, and control the upper limit of the second-stage rolling temperature between 1010-1030℃; under the premise of ensuring the rolling force ≥33000kN, the final pass of finishing rolling has a smaller rolling force, the final pass reduction rate of finishing rolling is ≤14%, FIN Late 90, and the final pass rolling force is 40000kN-45000kN; limit the CVC stroke between 55-100; limit the roll shifting value of the last three passes to 6, -23 and -43; the same specification of reduction schedule ensures consistency; (4) Control rolling adjustment: The thickness of the intermediate billet is controlled within 36mm-48mm, and the thickness of the intermediate billets of the same specification is ensured to be consistent; the second stage rolling temperature of the same specification is ensured to be consistent; according to the upper and lower working roll main motor transmission load allowable range and the roll gap control logic, the upper and lower roll speed ratio and the rolling line height are adjusted; when rolling to the second to last pass, the rolling temperature of this pass is controlled to be ≥880℃, and the rolling temperature of the last pass is ≥820℃, and the roll shifting value of these two passes is set; (5) Pre-straightening and ACC water cooling: When pre-straightening the steel plate, manually intervene to reduce the roll gap distance and increase the bending roll force by 0.2; (6) Hot straightening: Straightening temperature: After cooling, the ACC automatically and quickly passes through the straightening machine for high-temperature straightening to ensure that the straightening temperature is ≥580℃; Straightening passes and straightening force: Straightening passes ≥3, straightening force 1000-1500kN.

2. The method for reducing the curvature of the ladle when rolling high-strength wide and thin plates by a wide and thick plate rolling mill according to claim 1, characterized in that: In the step (1), the target tapping lower surface temperature is set to be 25-45° C. lower than the upper surface temperature.

3. The method for reducing the curvature of the ladle when rolling high-strength wide and thin plates by a wide and thick plate rolling mill according to claim 1, characterized in that: In the step (4), the speed ratio of the upper and lower rollers is adjusted to 1.00-1.

10.

4. The method for reducing the curvature of the ladle when rolling high-strength wide and thin plates by a wide and thick plate rolling mill according to claim 1, characterized in that: The rolling line height in step (4) is 805-815 mm.

5. The method for reducing the curvature of the ladle when rolling high-strength wide thin plates by a wide and thick plate rolling mill according to claim 1, characterized in that: In the step (5), manual intervention is performed to reduce the roll gap distance by 0.5-1.0 mm during pre-straightening of the steel plate.

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