CN112845584B

CN112845584B - Method for effectively controlling longitudinal shearing, splitting and side bending of hot-rolled strip steel

Info

Publication number: CN112845584B
Application number: CN202110007181.0A
Authority: CN
Inventors: 刘亮; 张鹏武; 袁金; 张扬; 陶文哲; 王立新; 赵江涛
Original assignee: Wuhan Iron and Steel Co Ltd
Current assignee: Wuhan Iron and Steel Co Ltd
Priority date: 2021-01-05
Filing date: 2021-01-05
Publication date: 2022-08-26
Anticipated expiration: 2041-01-05
Also published as: CN112845584A

Abstract

The invention discloses a method for effectively controlling longitudinal shearing, splitting and side bending of hot-rolled strip steel, which comprises the following steps: 1) smelting molten steel according to steel components and continuously casting the molten steel into a hot rolled plate blank; 2) heating the hot rolled plate blank; 3) rolling: a) rough rolling: the width of the hot-rolled plate blank is adjusted through a vertical roller or a fixed-width press, and the thickness of the hot-rolled plate blank is thinned for multiple passes through a flat roller; b) finish rolling: and increasing the positive roll shifting stroke to 100-150 mm through F1-F4 in the front rolling stage, and increasing the positive roll bending force to 150-250 t through F1-F4 for rolling until the convexity of the hot rolled plate blank is reduced to a convexity target value. The invention can reduce the actual convexity of the strip steel to the utmost extent, achieve the purpose of reducing the transverse thickness difference of the steel plate, ensure that the longitudinal extension length on the cross section tends to be equal everywhere in the process of rolling the billet, thereby controlling the longitudinal shearing, splitting and side bending of the hot rolled strip steel.

Description

Method for effectively controlling longitudinal shearing, splitting and side bending of hot-rolled strip steel

Technical Field

The invention belongs to the field of steel manufacturing, and particularly relates to a method for effectively controlling longitudinal shearing, splitting and side bending of hot-rolled strip steel.

Background

The lateral bending occurs in the steel plate longitudinal shearing and splitting process, the original internal stress balance of the steel plate is actually broken by external force, and the external expression form of new balance is achieved after the internal stress is released, thus essentially belonging to the internal stress problem category.

At present, whether the internal stress distribution of a steel plate is uniform or not is generally considered in the hot continuous rolling industry and mainly depends on the temperature uniformity in the rolling and laminar cooling processes. Based on the current situation and cognition, the internal stress control means is conservative in the hot-rolled strip steel manufacturing process, and the uniform distribution of the internal stress is ensured only by controlling the temperature uniformity of each link in the strip steel rolling process and the intact function precision of cooling system equipment; and the main task of reducing the internal stress of the strip steel is finished in a finishing stage (generally, the disordered internal stress in the strip steel gradually reaches balance by adopting the modes of finishing multi-pass straightening, pressure leveling and the like). With the improvement of the strength grade of the steel product, the bottleneck of eliminating the internal stress by the finishing method is more and more obvious; when the yield strength is improved to more than 450MPa, the traditional finishing process has poor effect and becomes a common problem in the industry at present.

In the industry of commercial vehicle girders and automobile rims, internal stress is released after hot-rolled strip steel is longitudinally sheared and split, and strips at two side parts are bent. After the material is punched or rolled, the material sheet has large lateral bending amount, so that finished parts such as automobile beams, rims and the like are scrapped, and the concrete conditions are as follows:

slitting and slitting side bend

As shown in fig. 1, the hot rolled steel coil is split into strips by splitting (taking the example that the strip steel is split into 3 strips equally by longitudinal shearing), and in the normal longitudinal shearing process, the middle strip is straight, and the two side strips are bent to one side of the edge within a certain length range. If the side bars are used as raw materials for roll forming and commercial vehicle girder steel is manufactured, the side bending value exceeds the standard, and a finished girder is scrapped, as shown in fig. 2.

Note: in fig. 1 and 2, Δ L1 and Δ L2 respectively represent the amount of bending of the two side bars, and Δ L represents the amount of bending of the girder.

Uneven butt welding of rims

As shown in fig. 3, after the side strips are cut into strip-shaped material sheets with a length of about 1m, when the side strips are used for manufacturing wheel rims and ring butt welding is performed, the welded sections are dislocated, and the problem of uneven butt welding is caused, so that rim parts are scrapped.

Analyzing the branch side bending principle:

1) analysis of the cause of lateral bending

As shown in fig. 4, the hot rolled steel coil is cut into 3 pieces, and after the steel coil is synchronously wound into a narrow coil, the middle strip is shorter than the two side strips. Therefore, the stress state of the middle part of the steel coil is tensile stress and the stress state of one side of the two sides close to the middle part is compressive stress in the steel coil state (before splitting). As shown in fig. 5, after the steel coil is split, the tensile stress of the middle strip disappears, the elastic deformation of the material is recovered, and the length of the material is shortened; the pressure stress of the side strip of the edge part close to the middle side disappears, the elastic deformation of the material is recovered, and the material has the phenomenon of length elongation, so that the side strip bends towards one side of the edge part where the side strip is located.

In conclusion, the uneven internal stress distribution of the cross section of the steel coil is released when slitting is carried out, and is the root cause of the slitting and lateral bending problem.

2) Cause analysis of nonuniform stress of steel coil cross section

In the production of hot continuous rolling strip steel, under the influence of bending deflection and roll shape abrasion of a finish rolling working roll in the rolling process, the roll gap of an actual working roll is slightly convex and has certain 'medium thickness' (convexity), as shown in figure 6; the convexity of the finished product of the common hot rolled plate is between 50 and 100 mu m according to the plate thickness; the thicker the steel plate, the greater the convexity. Because the billet is provided with a certain convexity in the rolling process, the longitudinal extension length of the cross section of the strip steel is different at each position, so that the difference exists between the internal stress of each adjacent point of the cross section of the strip steel, and the internal stress is released after the strip steel is longitudinally sheared and split. The larger the convexity is, the larger the difference value of the internal stress of each adjacent point of the cross section is, and the more obvious the side bending phenomenon caused by the release of the internal stress is.

In order to make the internal stress distribution of the cross section of the steel coil uniform, the longitudinal extension length of the cross section tends to be equal everywhere in the billet rolling process, so that the thickness difference of the cross section needs to be reduced as much as possible in the billet rolling process.

In view of the above, there is a need for a method for effectively minimizing the difference in the transverse thickness of hot rolled strip.

Disclosure of Invention

The invention aims to provide a method for effectively controlling the longitudinal shearing, splitting and side bending of hot rolled strip steel, which achieves the aim of reducing the transverse thickness difference of a steel plate by reducing the actual convexity of the strip steel to the maximum extent, so that the longitudinal extension length of the cross section tends to be equal everywhere in the billet rolling process, thereby controlling the longitudinal shearing, splitting and side bending of the hot rolled strip steel, namely manufacturing a high-precision transverse thickness difference hot rolled plate by taking the minimum convexity as a realizing means.

Definition of convexity: the difference between the thickness of the center line of the cross section of the strip steel and the average thickness of the two sidesThe thickness of the hem part is taken as a value of 40mm or 25mm from the hem part. As shown in FIG. 7, when X1 and X5 are at positions 25mm from the respective side portions, the thickness thereof is represented by H _X1 、H _X5 Represents; if X2 and X4 are 40mm away from the respective side, the thickness is H _X2 、H _X4 Represents; if X3 is the central line position of the strip steel, the thickness at the central line position is H _X3 Represents; then the convexity:

as shown in fig. 7, L1, L2, and L3 are schematic diagrams of transverse thickness curves of 3-coil steel respectively, and the transverse thickness difference of the steel strip is reduced along with the reduction of the convexity of the steel plate.

The technical scheme adopted by the invention is as follows:

a method for effectively controlling the longitudinal shearing, splitting and side bending of hot rolled strip steel comprises the following steps:

1) smelting molten steel according to steel components and continuously casting the molten steel into a hot rolled plate blank;

2) heating the hot-rolled plate blank;

3) rolling: a) rough rolling: the width of the hot-rolled plate blank is adjusted through a vertical roller or a fixed-width press, and the thickness of the hot-rolled plate blank is thinned for multiple passes through a flat roller; b) finish rolling: adjusting the positive roll shifting stroke of the front-stage working rolls F1-F4 in finish rolling to 100-150 mm, and adjusting the positive roll bending force of the front-stage working rolls F1-F4 in finish rolling to 150-250 t for rolling until the convexity of the hot-rolled plate blank is reduced to a convexity target value (the convexity target is-20-30 mu m);

according to the scheme, in the step 3) a), the thickness of the hot-rolled intermediate billet is controlled to be 30-45 mm.

According to the scheme, the finish rolling temperature is controlled to be 850-900 ℃.

According to the scheme, the finish rolling adopts a CVC, a CVC-Plus roll shape or a small negative roll shape.

According to the scheme, before rolling, a smaller convexity target value is set in a four-stage manufacturing management system of a computer; after the head of the hot-rolled strip steel is threaded, detecting and calculating the convexity value (real-time convexity) of the hot-rolled strip steel through an instrument detection system; automatically comparing the real-time convexity with a convexity target value; and the plate shape closed-loop control system converts the comparison result into a control parameter through model calculation, transmits the control parameter to the primary system for execution, and continuously and dynamically adjusts the roll bending parameters of each frame.

According to the scheme, the smaller convexity target value in the step 3) is-20-10 μm.

The invention has the beneficial effects that: the front sections F1-F4 are adopted for finish rolling to increase the positive roll shifting stroke to 100-150 mm, the positive roll shape area superposition of the working rolls is fully utilized, and the 'medium thickness' is greatly reduced while the strip steel is thinned;

the bending deflection and the roll shape abrasion of a finish rolling working roll are counteracted by increasing the bending deflection of the F1-F4 to 150-250 t through the positive bending roll, so that the medium thickness of the strip steel is reduced;

the finish rolling temperature is controlled to be 850-900 ℃, and the higher temperature is beneficial to controlling plastic deformation and the cross section profile of the strip steel;

the invention starts from the source of internal stress generation and the rolling principle, reduces the transverse thickness difference of the steel plate in the rolling process to ensure that the longitudinal extension length of the rolled billet tends to be equal everywhere, the internal stress difference value of each adjacent point of the cross section of the strip steel approaches to 0, and the internal stress release basically does not occur after the strip steel is longitudinally sheared and split, thereby effectively avoiding the occurrence of the lateral bending problem.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a schematic view of the hot rolled coil undergoing sidewise bending of the two strips during splitting;

FIG. 2 is a schematic side-turn illustration of a commercial vehicle frame;

FIG. 3 is a schematic view of a rim butt weld misalignment;

FIG. 4 is a schematic view of a hot rolled steel coil slit into 3 narrow strips;

FIG. 5 is a schematic diagram of the stress distribution and longitudinal shearing splitting of the cross section of a hot rolled steel coil;

FIG. 6 is a schematic view of the cross-sectional thickness profile of a hot rolled steel coil;

FIG. 7 is a schematic view of 3 rolls of steel strip with different cross-sectional thickness differences;

FIG. 8 is a schematic view of the structure of the CVC roll form;

FIG. 9 is a schematic view of a finish rolling flow;

FIG. 10 is a graph of the finish rolling work rolls of preceding stages F1-F4;

FIG. 11 is a graph of rear F5-F7 finish rolling work rolls;

FIG. 12 is a graph of the results of a 700MP grade girder steel cross sectional profile measurement.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

1) on the premise of ensuring that a hot continuous rolling finishing mill group can stably pass through a plate, a smaller convexity target value (generally set to be-20-30 mu m, preferably-20-10 mu m) is set in a four-stage manufacturing management system of a computer;

2) smelting molten steel according to steel components and continuously casting the molten steel into a hot rolled plate blank;

3) heating the plate blank by a heating furnace according to the set target heating time and the target extraction temperature;

4) rough rolling: the width of a hot-rolled plate blank (intermediate blank) is adjusted by a vertical roll or a fixed-width press, and the thickness of the intermediate blank is thinned for multiple passes by a flat roll; in order to reduce the convexity to the maximum extent in the subsequent finish rolling stage, the thickness of the intermediate blank should be reduced as much as possible and is generally controlled to be 30-45 mm;

5) finish rolling: in order to ensure that the working rolls F1-F4 finish crown control and reduce the crown to the maximum extent at the front stage of finish rolling, the finish rolling temperature FT7 of finish rolling is set to be higher as much as possible and is generally controlled to be 850-900 ℃; in the strategy of controlling the plate profile, the positive roll shifting stroke of the front-stage working rolls F1-F4 in finish rolling is increased to 100-150 mm, and the positive roll bending force of the front-stage working rolls F1-F4 in finish rolling is increased to 150-250 t, so that the convexity of the strip steel is reduced to the range preliminarily preset by a model. After the head of the hot-rolled plate blank is threaded, detecting the convexity value of the hot-rolled strip steel through an instrument detection system; comparing the convexity value with a target value, and feeding back a comparison result to a plate-shaped closed-loop control system; and the plate-shaped closed-loop control system controls the primary system to continuously and dynamically adjust the roll bending parameters of each frame according to the comparison result until the convexity is accurately controlled to be in a convexity target range (-20-30 mu m).

In the rolling process, the CVC or CVC-Plus roll shape and the small negative roll shape can be matched for use, so that a better crown reduction effect is obtained.

Example 1

Take the finished product number WL700(700MPa grade number) for manufacturing the commercial vehicle beam, the specification is 8.0 × 1360 × C (mm) as an example.

1) Before the production of hot continuous rolling feeding, a convexity target value is preset to be 10 micrometers in a four-stage manufacturing management system of a computer (the convexity target value is set to be as low as possible under the premise of ensuring that a finishing mill group can stably pass through a plate).

2) And smelting molten steel according to steel components and continuously casting the molten steel into a hot rolled plate blank.

3) Heating the plate blank in a step-by-step heating furnace of a hot continuous rolling production line, wherein the total heating time is 180 minutes, and the extraction temperature of the steel blank is 1300 ℃.

4) Starting rolling:

rough rolling: adjusting the width of the intermediate blank by a vertical roller or a width-fixing press, and reducing the thickness of the hot-rolled plate blank by a flat roller for multiple passes, wherein the outlet temperature (RT2) of rough rolling is 1080 ℃; in order to minimize the crown in the subsequent finish rolling stage, the thickness of the hot rolled slab should be reduced as much as possible, in this example 45 mm.

Finish rolling: the computer four-stage manufacturing management system issues a preset convexity target value (10 mu m) to the hot continuous rolling three-stage machine system to complete data receiving and auditing, and then continues to issue to the computer two-stage model system and issues to the computer one-stage control system to execute. In order to ensure that crown control is achieved and the crown is minimized in the stands (F1-F4) at the front end of the finish rolling, the finish rolling temperature (FT7) should be set as high as possible, in this case at 860 ℃.

The present example uses a CVC-Plus roll profile, i.e., 5 roll profiles; the strong convexity regulating and controlling capability of the CVC-Plus roll shape is fully utilized, and the limit small convexity control of the high-strength steel thick plate is realized.

Assuming the origin of coordinates is taken at the left center of the roll, as shown in FIG. 10, the radial coordinate y0(x) of the CVC roll form can be expressed as a fifth order polynomial:

for the upper work roll of the rolling mill, the 5-degree CVC roll shape function (radius function) y _t0 (x) Can be represented by the general formula:

y _t0 (x)＝R ₀ +a ₁ x+a ₂ x ² +a ₃ x ³ +a ₄ x ⁴ +a ₅ x ⁵ (1)

when the roll is moved axially by a distance s (the direction shown in the figure is positive), the roll shape function of the upper roll is y _ts (x) Is composed of

y _ts (x)＝y _t0 (x-s) (2)

According to the antisymmetry of the upper and lower working rolls in the CVC technology, the roll shape function of the lower roll is as follows:

y _b0 (x)＝y _t0 (b-x)

in the scheme, in a 2250mm hot continuous rolling unit, CVC-Plus roll shapes are configured at front sections F1-F4 (as shown in figure 10), and CVC roll shapes are configured at rear sections F5-F7 (as shown in figure 11), and the following process structures and parameters are adopted for design:

TABLE 1 finish rolling F1-F4 work roll form factor

Parameter(s)	A1	A2	A3	A4	A5
						Coefficient value of	0.335286E-02	-0.310650E-05	0.820197E-09	0.100000E-25	0.100000E-25

TABLE 2 finish rolling F5-F7 work roll form factor

TABLE 3 finish rolling F1-F7 work roll bending and roll shifting setting

Rack	F1	F2	F3	F4	F5	F6	F7
								Amount of roll shifting (mm)	145	53	20	21	30	37	-12
Roller force (t)	220	160	160	160	140	150	140

TABLE 4 finish rolling F1-F7 load distribution and exit thickness settings

Rack	F1	F2	F3	F4	F5	F6	F7
								Load distribution	0.55	0.59	0.5	0.45	0.38	0.3	0.24
Outlet thickness (mm)	30.705	19.162	14.392	11.816	9.912	8.795	8.027

During finish rolling, roll bending and roll shifting are preset according to the roll bending and roll shifting amount shown in the table 3, load distribution and outlet thickness setting are carried out according to the table 4, and after the head is threaded, an instrument detection system carries out continuous detection and calculation; and comparing the convexity set value with the calculated value and feeding back the convexity set value to the plate shape closed loop control system, and continuously and dynamically adjusting the roll bending parameters of each rack by the primary system according to the output result calculated by the plate shape closed loop system until the rolling process is finished.

5) And cooling the strip steel to 600 ℃ by a laminar cooling system, and conventionally coiling the strip steel for standby.

In this example, the steel coil was uncoiled and the cross-sectional thickness at each 20m position of the head and tail of the rolled steel was measured, and the cross-sectional profile was plotted as shown in fig. 12, and the crown was calculated to be 8 μm and 15 μm, respectively.

Through the actual measurement of longitudinal shearing and splitting, the length difference value of the left strip, the middle strip and the right strip is less than 5 mm; the measured value of the lateral bending amount of the left side edge strip is 2mm/10m, and the measured value of the lateral bending amount of the right side edge strip is 2mm/10 m; the 2 side strips are used for rolling a commercial vehicle crossbeam with the length of 11.512m, and the side bending amount of the crossbeam is less than or equal to 3 mm. The steel coil produced by managing the thickness difference of the cross section by adopting the conventional convexity (70-100 mu m) has the length difference value of the left strip, the middle strip and the right strip of the longitudinal shearing strip edge strip which is generally larger than 100 mm; the average level of the side bending amount is 13mm/10m, a commercial vehicle girder with the length of 11.512m is rolled by side strips of the edge part, and the side bending amount of the girder reaches 10-15 mm. By comparison, the lateral bending control level obtained by the embodiment is far beyond the conventional control means.

Example 2

Take the finished product number RCL380 for producing the wheel rim, the specification is 2.1 multiplied by 1270 multiplied by C (mm) as an example.

1) Before the production of hot continuous rolling feeding, a convexity target value is preset to be 30 micrometers in a four-stage manufacturing management system of a computer (the convexity target value is set to be as low as possible under the premise of ensuring that a finishing mill group can stably pass through a plate).

3) Heating the plate blank in a stepping heating furnace of a hot continuous rolling production line, wherein the total heating time is 150 minutes, and the extraction temperature of the steel blank is 1280 ℃.

4) Rolling:

rough rolling: the width of the intermediate billet is adjusted by a vertical roller or a fixed width press, the thickness of the intermediate billet is reduced by a plurality of passes by a flat roller, and the rough rolling outlet temperature (RT2) is 1090 ℃. In order to reduce the convexity to the maximum extent in the subsequent finish rolling stage, the thickness of the intermediate billet should be reduced as much as possible, 36mm in this embodiment.

In order to ensure that crown control is completed and the crown is minimized in the stands (F1-F4) at the front end of the finish rolling, the finish rolling temperature (FT7) should be set as high as possible, in this example 880 ℃. The computer four-stage manufacturing management system issues a preset convexity target value (30 micrometers) to a hot continuous rolling three-stage machine system to complete data receiving and auditing, and then continues to issue to a computer two-stage model system to perform comprehensive calculation of parameters such as roll wear, roll thermal expansion coefficient, rolling pressure, roll deflection, roll bending amount, roll shifting position and the like, gives a preset positioning parameter of equipment, and issues to a computer one-stage control system to execute.

In this embodiment, in a 2250mm hot continuous rolling mill train, CVC-Plus roll shapes are configured at front sections F1 to F4 (see fig. 10), and CVC roll shapes are configured at rear sections F5 to F7 (see fig. 11), and the flow and parameter design of fig. 9 is adopted:

TABLE 5 finish rolling F1-F7 work roll bending and roll shifting setting

Frame	F1	F2	F3	F4	F5	F6	F7
								Amount of roll shifting (mm)	120	60	25	23	30	33	15
Roller force (t)	180	140	120	120	120	120	110

TABLE 6 finish rolling F1-F7 load distribution and exit thickness settings

Rack	F1	F2	F3	F4	F5	F6	F7
								Load distribution	0.55	0.55	0.5	0.427	0.361	0.272	0.214
Outlet thickness (mm)	19.114	9.977	5.750	3.936	2.965	2.370	2.103

Presetting the roll bending and roll shifting amount shown in table 5 during finish rolling, carrying out load distribution and outlet thickness setting according to a graph 6, and continuously detecting and calculating by an instrument detection system after the head is threaded; and comparing the convexity set value with the calculated value and feeding back the convexity set value to the plate shape closed loop control system, and continuously and dynamically adjusting the roll bending parameters of each rack by the primary system according to the output result calculated by the plate shape closed loop system until the rolling process is finished.

5) And cooling the strip steel to 570 ℃ through a laminar cooling system, and coiling the strip steel conventionally for standby.

In this embodiment, the steel coil is uncoiled and the cross-sectional thickness of each 20m position of the head and tail of the steel rolling is measured, and the convexity is respectively calculated to be 25 μm and 33 μm. In the embodiment, the length difference value of the left strip, the middle strip and the right strip of the steel coil is actually measured by longitudinally shearing and splitting the steel coil and is less than 50 mm; the measured value of the left side edge side bending amount is 5mm/10m, and the measured value of the right side edge side bending amount is 6mm/10 m. The 2 side strips are cut into rim material pieces with the length of 1272mm, rim butt welding and rolling are carried out, and the problem of uneven butt joint of welding seams is not found. The steel coil produced by managing the thickness difference of the cross section by adopting the conventional convexity (50-60 mu m) is subjected to the actual measurement of the length difference values of the left strip, the middle strip and the right strip by longitudinal shearing and splitting, which is between 200 and 300 mm; the average level of side bending of the edge strips is 11mm/10m, the butt welding of the rim material sheets has the problem of uneven butt joint of welding seams, and the dislocation is about 2-3 mm. By comparison, it is found that the lateral bending control of the embodiment is significantly higher than the conventional level.

The above 2 examples merely exemplify the use of CVC-Plus roll form as one means of achieving the goal of extreme low crown, and there are actually many ways of achieving this goal. The invention takes the limit small convexity as an implementation means to manufacture the high-precision transverse thickness difference hot rolled plate and effectively control the longitudinal shearing, splitting and side bending. In the invention, the target range of the convexity (C40) for controlling the strip-dividing side bending of the hot-rolled strip steel is-20-30 mu m. According to different thicknesses of finished products, the convexity target is controlled to be as close to 0 mu m as possible on the premise of ensuring the stability of finish rolling; generally, the principle that the convexity target is smaller when the thickness of the finished product is larger, and the convexity target is larger when the thickness of the finished product is smaller is followed, but the maximum thickness of the finished product should not exceed 30 mu m; the plank allows a certain negative convexity to occur.

The method is carried out in a conventional hot continuous rolling production line, but is also suitable for a continuous casting and rolling production line (CSP or ESP for short).

It will be appreciated that modifications and variations are possible to those skilled in the art in light of the above teachings, and it is intended to cover all such modifications and variations as fall within the scope of the appended claims.

Claims

1. A method for effectively controlling longitudinal shearing, splitting and side bending of hot rolled strip steel is characterized by comprising the following steps:

2) heating the hot-rolled plate blank;

3) rolling: a) rough rolling: adjusting the width of the hot-rolled plate blank by using a vertical roll or a fixed-width press, and reducing the thickness of the hot-rolled plate blank by using a flat roll for multiple passes, wherein the thickness of the hot-rolled plate blank is controlled to be 30-36 mm; b) finish rolling: adjusting the positive roll shifting stroke of the front-stage working rolls F1-F4 in finish rolling to 100-150 mm, and increasing the positive roll bending force of the front-stage working rolls F1-F4 in finish rolling to 150-250 t for rolling until the convexity of the hot-rolled plate blank is reduced to a convexity target value;

before rolling, setting a smaller convexity target value in a four-stage computer manufacturing management system, wherein the smaller convexity target value is-20-30 mu m; after the head of the hot-rolled strip steel is threaded, detecting and calculating the real-time convexity of the hot-rolled strip steel through an instrument detection system; automatically comparing the real-time convexity with a convexity target value; and the plate shape closed-loop control system converts the comparison result into a control parameter through model calculation, transmits the control parameter to the primary system for execution, and continuously and dynamically adjusts the roll bending parameters of each frame.

2. The method for effectively controlling the slitting, splitting and side bending of the hot-rolled strip steel as claimed in claim 1, wherein the method comprises the following steps: and the finish rolling temperature is controlled to be 850-900 ℃.

3. The method for effectively controlling the slitting and side bending of the hot-rolled strip steel as claimed in claim 1, wherein the finish rolling adopts CVC, CVC-Plus roll shape or small negative roll shape.

4. The method for effectively controlling the slitting, splitting and side bending of the hot-rolled strip steel as claimed in claim 1, wherein the method comprises the following steps: the smaller convexity target value in the step 3) is-20-10 μm.