Reverse adjusting method for intermediate roll of HC series rolling mill

Abstract

The invention relates to an HC series rolling mill intermediate roll reverse adjustment method, which comprises the following steps: 1) before dynamic specification change, according to the strip steel specification span before and after specification change, reducing the roll bending value of an intermediate roll and increasing the roll bending value of a working roll; (2) during dynamic specification changing, welding seams of strip steel of two specifications enter a roll gap, and a middle roll is subjected to UC-amp; automatic axial positioning is carried out according to the value, the middle roller has no convexity highest point, no obvious wave shape is generated in the whole axial positioning process of the middle roller, and only slight wave shapes caused by rolling force fluctuation after welding are generated; 3) finishing dynamic specification changing, and performing UC-amp; the value is reset, axial positioning of the middle roller is completed, the wave shape condition stably fluctuates within the range of 0-3I, and at the moment, the middle roller bending value and the working roller bending value are restored to preset values. The method has the advantages that double-side waves of the strip head during dynamic specification changing are effectively avoided, the strip shape quality is guaranteed, and the relative length difference is effectively reduced.

Description

Technical Field

[0001] The invention belongs to the field of cold-rolled plate and strip production, and in particular relates to a reverse adjustment method for an intermediate roll of an HC series rolling mill suitable for dynamically changing specifications of cold-rolled plate and strip. Background Art

[0002] The poor plate shape caused by the dynamic specification change of UCM, CVC, CVC+ mills (HC series mills) is the "congenital" technical defect of all HC series mills. Common means of dynamic specification change include: cooling of roller segment points, roller tilting, increasing positive bending roller value, optimization of rolling procedures (rolling speed, tension, and pressure reduction system), and mainly controlling the transverse thickness difference (except tension). It only plays an auxiliary control role for straightness, and tension control has a certain risk of strip breakage.

[0003] Deficiencies of existing technology:

[0004] 1. Increase the bending value of the working roll and the intermediate roll: For the edge waves caused by dynamic variable specifications, conventional control methods at home and abroad adopt increasing the positive bending of IMR and WR to expand the bending effect of the roll. However, it not only fails to improve the edge waves, but also aggravates the severity of the wave shape and causes an increase in the roll tightening rate.

[0005] 2. Speed ​​optimization: Its essence is to improve the transverse thickness difference. By improving the friction coefficient between the roller and the strip, the faster the rolling speed, the smaller the friction coefficient, the smaller the rolling force, and the thinning of the edge will also be improved. However, if the speed is too fast, the amount of emulsion brought in will increase, which will also lead to the phenomenon of "over-lubrication". This is also one of the factors causing the stand mill to slip, making rolling difficult.

[0006] 3. Tension control: It is one of the commonly used means of plate shape control. In fact, it is to improve the flatness, but it improves the flatness by adjusting the stretching amount of the strip. This adjustment method is the most direct and obvious among all conventional methods, but it has a certain risk factor and can easily cause the strip to break. This depends on whether the composition of the steel is uniform, whether there are problems with the edge quality, etc. Therefore, tension cannot be used as the main means of plate shape control, but can only be used as an additional means for auxiliary control.

[0007] 4. Emulsion point cooling control: The cooling characteristics of the emulsion are used to spray the local position of the roll to control the local high point of the roll, and finally control the roll gap shape and improve the transverse thickness difference. Although this method can accurately control the thermal expansion of the local position of the roll and finely optimize the plate shape, it has two major disadvantages: First, there is a large lag in the plate shape control process in the data collection, transmission, control, feedback, comparative calculation, compensation, execution of the injection valve station and the expected cooling time of the plate shape meter at the last stand exit. Second, the purpose of segmented point cooling is to change the temperature of the roll, adjust and reduce the local high point of the roll caused by thermal expansion to achieve roll shape control. When the actual plate shape abnormality is not caused by the thermal deformation of the roll, the last stand plate shape meter collects the actual plate shape abnormality data, and automatically performs point cooling, which will eventually lead to the abnormal superposition effect of poor flatness, increase the plate shape defects, and make control more difficult. Therefore, it can only be put into use at the last stand exit.

[0008] 5. Optimize the reduction rate: It is only effective for the normal control of the plate shape during the coiling process. It has no targeted improvement effect on the poor plate shape caused by instantaneous changes in rolling force, tension, thickness and specifications.

[0009] The above-mentioned plate shape control methods are only suitable for production process control. Under normal circumstances, they are auxiliary control of transverse thickness difference (except tension control methods). When the specifications are changed dynamically, due to the lag of the pressing mechanism and the detection, data collection and calculation feedback also require a certain amount of time, the problem of poor plate shape before and after the weld when the specifications are changed dynamically is a problem that domestic and foreign steel companies or research institutions have always needed to solve. Summary of the invention

[0010] The purpose of the present invention is to provide a method for reversely adjusting the intermediate rolls of an HC series rolling mill, so as to solve the problem of poor head shape (double-sided waves) when the specifications of cold-rolled strip steel are dynamically changed, and to effectively avoid the generation of dynamic lateral resistance.

[0011] To achieve the above object, the present invention is implemented through the following technical solutions:

[0012] A method for reversely adjusting the intermediate roll of an HC rolling mill comprises the following steps:

[0013] 1) Before dynamic specification change, reduce the intermediate roll bending value and increase the working roll bending value according to the strip specification span before and after specification change;

[0014] 2) When the specification is changed dynamically, the welds of the two specifications of the strip steel enter the roll gap, and the intermediate roll is automatically axially positioned according to the UC-& value. The intermediate roll has no highest point of convexity, and no obvious wave shape is generated during the entire process of axial positioning of the intermediate roll. There is only a slight wave shape caused by the fluctuation of rolling force behind the weld;

[0015] 3) After the dynamic specification change is completed, the UC-& value is reset, the axial positioning of the intermediate roll is completed, and the wave shape is stabilized in the range of 0 to 3I. At this time, the intermediate roll bending value and the working roll bending value are restored to the preset values.

[0016] In step 1), the yield strength of the strip steel is greater than 440 MPa, the total reduction ratio is greater than 73%, and the rolling outlet thickness is less than 0.65 mm.

[0017] In step 2), when the second specification strip is within 1 meter from the head and the IMR intermediate roller moves 1%, the I value is 12. As the rolling length gradually increases, when it reaches 49 meters from the strip head and the IMR intermediate roller moves 97%, the I value becomes 0.

[0018] The width difference between the two specifications of the strip steel is within 300 mm.

[0019] In step 3), the axial positioning of the intermediate roll is completed according to the width of the narrow strip and the UC-& value.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The method of the present invention effectively avoids leading double-sided waves when the specifications are dynamically changed, ensures the quality of the board shape, and effectively reduces the relative length difference.

[0022] 2. The flatness quality of the strip head at the rear of the weld of two specifications of strip steel has been improved, and the length of the poor flatness area at the head and tail of the strip steel has been greatly shortened, and the length range has been controlled from about 40m to less than 20m.

[0023] 3. The method of the present invention can avoid the waste caused by the inability to roll and the open rack discharge due to the bad shape of the dynamically variable specification plate, and improve the yield rate.

[0024] 4. The method of the present invention avoids roller tightening caused by dynamic specification change (wide material connected to narrow material), reduces roller consumption and saves production costs.

[0025] 5. Reduce the time for changing rollers and dealing with broken belts due to dynamic specification changes (wide material connected to narrow material), and improve the unit operation rate and hourly output. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the principle of the reverse regulation method before dynamic specification change.

[0027] Figure 2 It is a schematic side view of the rolling mill before dynamically changing specifications using the reverse adjustment method.

[0028] Figure 3 It is a top view schematic diagram of the rolling mill before dynamically changing specifications using the reverse adjustment method.

[0029] Figure 4 It is a schematic diagram of the principle of dynamically changing specifications using the reverse regulation method.

[0030] Figure 5 It is a schematic side view of the rolling mill when the specifications are dynamically changed using the reverse adjustment method.

[0031] Figure 6 It is a top view schematic diagram of the rolling mill when the specifications are dynamically changed using the reverse adjustment method.

[0032] Figure 7 It is a schematic diagram of the principle after the reverse regulation method dynamically changes specifications.

[0033] Figure 8 It is a schematic side view of the rolling mill after the dynamic specification change by the reverse adjustment method is completed.

[0034] Fig. 9 It is a top view schematic diagram of the rolling mill after the dynamic specification change by the reverse adjustment method is completed.

[0035] Fig.10 It is a schematic diagram of the principle of the conventional control method before dynamic specification change.

[0036] Fig.11 It is a schematic side view of the rolling mill before the conventional control method dynamically changes the specifications.

[0037] Fig.12 It is a top view schematic diagram of the rolling mill before the conventional control method dynamically changes the specifications.

[0038] Fig.13 This is a schematic diagram of the principle of the conventional control method when the specifications are dynamically changed.

[0039] Fig.14 It is a schematic diagram of the side view of the rolling mill when the specifications are dynamically changed using the conventional control method.

[0040] Fig.15 It is a top view schematic diagram of the rolling mill when the specifications are dynamically changed using the conventional control method.

[0041] Fig.16 This is a schematic diagram of the principle of the conventional control method after dynamic specification change is completed.

[0042] Fig.17 It is a schematic side view of the rolling mill after dynamic specification change using the conventional control method.

[0043] Fig.18 This is a top view schematic diagram of the rolling mill after the dynamic specification change is completed using the conventional control method.

[0044] Fig.19 It is a visual data analysis chart.

[0045] Fig. 20 This is a comparison chart of the control principles of conventional control method and reverse regulation method.

[0046] Fig.21 This is the measured curve of the plate shape meter with the plate head position of 1m using the conventional control method.

[0047] Fig. 22 This is the measured curve of the plate shape meter with the plate head position of 15m using the conventional control method.

[0048] Fig.23 This is the measured curve of the plate shape meter with the plate head position of 35m using the conventional control method.

[0049] Fig.24 This is the measured curve of the plate shape meter with the plate head position of 49m under the conventional control method.

[0050] Fig.25 It is the measured curve of the plate shape meter with the plate head position of 1m using the reverse adjustment method.

[0051] Fig.26 It is the measured curve of the plate shape meter with the plate head position of 15m using the reverse adjustment method.

[0052] Fig. 27 It is the measured curve of the plate shape meter with the plate head position of 35m using the reverse adjustment method.

[0053] Fig.28 This is the measured curve of the plate shape meter with the plate head position of 49m using the reverse adjustment method.

[0054] In the figure: 1-strip steel 2-working roll 3-intermediate roll 4-support roll 5-roll system 6-edge wave 7-highest point of positive bending convexity of lower intermediate roll 8-increase intermediate roll bending value 9-increase working roll bending value 10-decrease intermediate roll bending value 11-highest point of positive bending convexity of upper intermediate roll 12-intermediate roll bending value restores to set value 13-working roll bending value restores to set value. DETAILED DESCRIPTION

[0055] The present invention is described in detail below in conjunction with the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0056] Example

[0057] Take wide strip becoming narrow strip as an example, that is, DC51D+Z, 3.5×1450mm strip connected to DC51D+Z, 3.5×1200mm strip.

[0058] The method for reverse adjustment of the intermediate roll of the HC rolling mill comprises the following steps:

[0059] 1) Before dynamically changing specifications, see Figure 1-Figure 3 ;

[0060] When the tail of the wide steel strip approaches the roll gap before dynamic specification change, the intermediate roll bending value is reduced from the original preset value of 35t (ton force) to 25t, so that the intermediate roll shape is parallelized to avoid the highest point of the intermediate roll crown. The working roll bending is increased from the original 25t to 40t to avoid the change of the roll gap shape caused by the fluctuation of the rolling force during dynamic specification change.

[0061] The operation of increasing the working roll bending can be determined according to the specific situation. Except for the yield strength > 440 MPa, the total reduction rate > 73%, and the rolling outlet thickness < 0.65 mm, this operation is not required in other cases. In this stage, the operation of increasing the working roll bending only takes into account the poor plate shape caused by the fluctuation of rolling force during dynamic specification change, which has nothing to do with the axial shifting of the intermediate roll and the bending roll compensation.

[0062] 2) When changing specifications dynamically, see Figure 4-Figure 6 ;

[0063] Phenomenon: The weld enters the roll gap, the narrow steel strip begins to be bitten into the roll gap, the dynamic specification change process begins, the intermediate roll automatically performs axial positioning according to the UC-& value, the intermediate roll has no convexity peak point, and no obvious wave shape (double-sided wave) is generated during the entire process of axial positioning of the intermediate roll, only slight wave shape caused by rolling force fluctuation after the weld. In this process, when the strip head is 1 meter and the IMR intermediate roll moves 1%, the I value is 12. As the rolling length gradually increases, when the DC51D+Z, 3.5×1200mm strip head is 49 meters and the IMR intermediate roll moves 97%, the I value is 0. .

[0064] Among them, due to the different extensions of each point in the transverse direction of the strip (width direction), the degree of warping is also different. L represents the original rolled length. The difference between each transverse point and the original rolled length is ΔL. ΔL / L represents the shape value of the longitudinal strip. The shape value is in units of I, which is the I unit value of the wave shape detection of the tension shape meter. 1I is equivalent to a relative length difference of 10 -5 Internationally, the method of expressing the flatness of plates and strips is generally the I unit, which is defined as the change in plate shape caused by a strain difference of 0.001% or 1 / 100000 between adjacent parts of the strip. That is, when the edge of a 1000mm long rolled strip is extended to 1000.01mm, the plate shape difference between the middle and the edge is called 1I unit (Unit), represented by the symbol I or IU.

[0065] The weld enters the roll gap, the narrow strip head begins to be bitten into the roll gap, and the dynamic specification change process begins. The intermediate roll automatically adjusts its position (axial movement) according to the UC-& value to avoid the highest point of the positive convexity of the intermediate roll and make the intermediate roll shape straight. During the entire axial movement of the intermediate roll, the longitudinal flow of metal particles does not produce dynamic lateral resistance, avoiding the appearance of wave shape. The wave shape data of different strip head positions in this process are detailed in Table 1.

[0066] 3) Dynamic specification change is completed, see Figure 7-Figure 9 ;

[0067] UC-& value is reset. At this time, the axial positioning of the intermediate roll is completed, and the wave shape fluctuates stably within the range of 0 to 3I. At this time, the intermediate roll bending value and the working roll bending value are restored to the preset values ​​to prepare for normal plate shape control.

[0068] The axial positioning of the intermediate roll is completed according to the width of the narrow strip and the UC-& value. The UC-& value is the distance from the current strip edge where the diameter of the intermediate roll changes. This distance does not change continuously, but remains unchanged after setting.

[0069] Comparative Example

[0070] Take wide plate to narrow plate as an example, that is, DC51D+Z, 3.5×1450mm strip steel connects to DC51D+Z, 3.5×1200mm strip steel.

[0071] Conventional control methods include:

[0072] 1) Before dynamically changing specifications, see Figure 10-12 In order to avoid the sudden change of rolling force caused by the change of strip width and the lag of the bending roller hydraulic cylinder during dynamic specification change, which leads to the generation of instantaneous convex roll gap, and finally causes the wavy edge of the narrow strip head, before the weld between the wide strip and the narrow strip enters the rolling mill, when the tail of the wide strip is close to the roll gap (when the strip in the roll gap is the tail of the wide strip), the intermediate roll bending value and the working roll bending value are increased. The intermediate roll bending value is increased from the original setting value of 25t to 35t, and the working roll bending value is increased from the original 23t to 33t.

[0073] 2) When changing specifications dynamically, see Figure 13-Figure 15 , the weld enters the roll gap, the narrow steel strip begins to be bitten by the roll gap, and the dynamic specification change process begins. The intermediate roller automatically adjusts its position (axial movement) according to the UC-& value. At this time, the highest point of the positive bend convexity of the intermediate roller acts on the narrow steel strip for the first time, and the narrow steel strip first appears double-sided waves. As the rolling process continues, the length of the rolled steel plate gradually increases, and the upper and lower intermediate rollers gradually move relative to each other in the axial direction. The highest point of the convexity of the intermediate roller also gradually moves relative to each other. The wave shape of the rolled steel plate gradually shrinks from the initial strip edge wave to the rib, and its visible wave shape gradually decreases. In this process, when the strip head is 1 meter and the IMR intermediate roller moves 1%, the I value is 25. As the rolling length gradually increases, when the strip head is 49 meters and the IMR intermediate roller moves 97%, the I value is 4. The wave shape data for different strip head positions in this process are shown in Table 1.

[0074] During dynamic specification change, the intermediate roller makes relative axial displacement, which causes the highest point of the positive bending convexity of the intermediate roller (the highest point of deflection) to act on the two sides of the narrow steel plate strip head adjacent to the weld at the first time, first causing double-sided waves on the strip head (the roll gap value corresponding to the highest point of the positive bending convexity of the intermediate roller is relatively smaller than that of other parts of the roll gap, which greatly reduces the positive bending efficiency of the working roller and destroys the ideal parallel roll gap); since the axial positioning of the intermediate roller requires a certain time (affected by the low-speed rolling weld) and a certain strip rolling length, as the rolling length increases, the highest point of the positive bending convexity of the intermediate roller moves relative to each other (the upper and lower intermediate rollers move 125mm relative to each other at the same speed at the same time), resulting in the longitudinal flow of the metal particles of the strip, which will be affected by the roller shape and maneuverability of the intermediate roller and produce lateral dynamic resistance. Finally, the wave shape is gradually reduced from the edge of the narrow steel plate strip head adjacent to the weld to the rib of the narrow strip away from the weld until the intermediate roller positioning is completed.

[0075] 3) Dynamic specification change is completed, see Figure 16-Figure 18 , UC-& value is reset, at this time, the axial positioning of the middle roller is completed, the highest point of its positive bending convexity acts on the narrow steel plate rib, and the wave shape returns to normal value (that is, stable at about 4 units of I). After the dynamic specification change is completed, the axial positioning of the middle roller is completed, the dynamic lateral resistance to the longitudinal flow of the strip metal particles disappears, and the plate shape returns to normal value.

[0076] Table 1 Control effect of embodiments and comparative examples

[0077]

[0078]

[0079] As shown in Table 1, Fig.19 As shown in Table 1, the control effect of the conventional control method (comparative example) is compared with the control effect of the method of the present invention (embodiment). Under different belt head positions and intermediate roller movement positioning conditions, the degree of different double-sided waves is different. According to the visualization data analysis generated in Table 1, Fig.19 As shown, there are two curves a and b in the data analysis diagram. Curve a is the control effect of conventional bending roll, and the lower one is the comparison of the control change value of the reverse adjustment method. At this time, the ambient temperature remains unchanged, the rolling speed remains unchanged, and the roll gap conversion function and the buckling point are only affected by the strip width and the axial movement of the intermediate roll bending convexity. Under conventional control, as the movement of the intermediate roll increases, the wave height gradually decreases and tends to be stable. Curve b is the control effect of the reverse adjustment method. After the reverse adjustment method is adopted, due to the change of the positive convexity of the intermediate roll bending roll, its wave height is basically in a low and flat state.

[0080] See Figure 21-Figure 28, are the actual curve samples collected by the shape meter curves of the present embodiment and the comparative example when the lead position is 1m, 15m, 35m and 49m. When the conventional control means and control method are adopted: when the lead position is 1m, I unit is 25; when the lead position is 15m, I unit is 17; when the lead position is 35m, I unit is 14; when the lead position is 49m, I unit is 4. When the reverse adjustment method is adopted: when the lead position is 1m, I unit is 12; when the lead position is 15m, I unit is 4; when the lead position is 35m, I unit is 2; when the lead position is 49m, I unit is 0.

[0081] In addition, in the reverse adjustment method of the intermediate roll of the HC series rolling mill, the reduction in the intermediate roll bending value is related to the difference in strip specification span before and after the weld and the difference in strip yield strength, see Table 2.

[0082] Table 2 Example HC series rolling mill intermediate roll reverse adjustment method

[0083]

[0084] From Table 2, it can be seen that the width difference of the two specifications of strip steel is within 300mm, and the yield strength difference is within 400MPa. Other parameters of the strip steel must also meet the yield strength of the strip steel>440MPa, the total reduction rate>73%, and the rolling outlet thickness<0.65mm.

Claims

1. A method for reverse adjustment of the intermediate roll of an HC rolling mill, It is characterized in that The following steps are involved: 1) Before dynamic specification change, reduce the intermediate roll bending value and increase the working roll bending value according to the strip specification span before and after specification change; 2) When the specification is changed dynamically, the welds of the two specifications of the strip steel enter the roll gap, and the intermediate roll is automatically axially positioned according to the UC-& value. The intermediate roll has no highest point of convexity, and no obvious wave shape is generated during the entire process of axial positioning of the intermediate roll. There is only a slight wave shape caused by the fluctuation of rolling force behind the weld; 3) After the dynamic specification change is completed, the UC-& value is reset, the axial positioning of the intermediate roll is completed, and the wave shape is stabilized in the range of 0 to 3I. At this time, the intermediate roll bending value and the working roll bending value are restored to the preset values.

2. A method for reversely adjusting the intermediate roll of a HC rolling mill according to claim 1, It is characterized in that In step 1), the yield strength of the strip steel is greater than 440 MPa, the total reduction ratio is greater than 73%, and the rolling outlet thickness is less than 0.65 mm.

3. A method for reversely adjusting the intermediate roll of a HC rolling mill according to claim 1, It is characterized in that In step 2), when the second specification strip is within 1 meter from the head and the IMR intermediate roller moves 1%, the I value is 12. As the rolling length gradually increases, when it reaches 49 meters from the strip head and the IMR intermediate roller moves 97%, the I value becomes 0.

4. A method for reversely adjusting the intermediate roll of a HC rolling mill according to claim 1, It is characterized in that The width difference between the two specifications of the strip steel is within 300 mm.

5. A method for reversely adjusting the intermediate roll of a HC rolling mill according to claim 1, It is characterized in that In step 3), the axial positioning of the intermediate roll is completed according to the width of the narrow strip and the UC-& value.

Images