CN109772897B - Setting control method for improving full-length convexity and wedge-shaped precision of hot continuous rolling strip steel - Google Patents
Setting control method for improving full-length convexity and wedge-shaped precision of hot continuous rolling strip steel Download PDFInfo
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Abstract
A setting control method for improving the full-length convexity and wedge precision of hot continuous rolling strip steel is characterized in that the setting upper limit of a PC angle when a wedge is good is determined through the statistics of the setting range of the PC angle when the strip steel produced historically has good convexity and wedge, the control range of the PC angle and the roll bending force is reasonably distributed when the subsequent rolling strip steel is set according to the statistical result, the upper limit of the PC angle counted is used as the setting upper limit of the PC angle, and after the PC angle is set to be limited, the part with insufficient convexity control capability is compensated by the roll bending force, so that the convexity control precision is met, and the precision of the finish rolling outlet wedge control is ensured. The method overcomes the defect that the PC angle is singly used as a main convexity control means when the traditional PC rolling mill is set and controlled, and aims at the PC angle which is limited to be used maximally by different varieties and specifications, the convexity control precision requirement is met, the wedge generation probability is reduced, the convexity and wedge precision of a hot-rolled strip steel product are improved, and the quality of the hot-rolled strip steel product is improved.
Description
Technical Field
The invention relates to a hot-rolled strip steel production technology in the field of ferrous metallurgy production, in particular to a setting control method for improving the full-length convexity and wedge precision of hot continuous rolled strip steel.
Background
At present, in the production of strip steel of various iron and steel metallurgical production enterprises, one of the important indexes for measuring the quality of strip steel products is the strip shape, and the two general strip shape indexes are convexity and flatness, and with the increasing requirements on the quality of strip steel products in recent years, a part of high-precision strip steel also puts higher requirements on the wedge shape, wherein, as shown in fig. 1, the convexity and the wedge shape are defined as follows:
1. convexity definition:
C＝hc-(he1+he2)/2
2. wedge definition:
W＝he1-he2
in the figure, hc is the middle thickness of the cross section of the strip steel, and he1 and he2 are the thicknesses of two side parts of the cross section respectively.
The crown is also called as a strip lateral thickness difference, and refers to a thickness difference of a plate strip in the width direction. The requirements for the convexity of different hot rolled strip steel products are different, the requirement for the control of the convexity of a hot continuous rolling finishing mill group is to control the convexity to a target value under the condition of ensuring the flatness of the strip steel at a finishing rolling outlet, and the requirement for the control of a wedge is to control the wedge within a threshold value range under the condition of ensuring the convexity.
The long-time work experience of field operators shows that the main factors influencing the strip steel convexity in the hot continuous rolling production process are the mechanical convexity of a roller, the thermal convexity of the roller, the wear convexity of the roller and the transverse flow of the strip steel, which all cause the convexity change. The factors influencing the mechanical crown of the roller mainly include the original crown of the roller, the bending and elastic flattening of the roller caused by the rolling force, the transverse moving position of a plate shape control mechanism (such as CVC), the set amount of a PC angle, the shape change of a roller body caused by the set value of the bending force and the like, and the factors can bring about crown change, wherein the rolling force is the main factor influencing the crown change of the whole length of the strip steel, and the deformation of a roller system changes along with the change of the rolling force, so that the crown of the strip steel changes.
The main factor influencing the rolling force is the temperature, and the change of the temperature can directly cause the change of the rolling force, thereby influencing the outlet convexity of the strip steel. The hot crown of the roller, the wear crown of the roller and the crown caused by the transverse flow of the strip steel are physical processes, and under the condition that the general equipment condition is not changed, the values are all kept unchanged in the rolling process of the same steel.
The main control means of crown control of hot-rolled strip steel is set control, and the principle is that according to the rolling data (rolling force of each stand, contact arc length, outlet thickness of each stand, etc.) of current strip steel calculated by a finish rolling set calculation program (FSU), PDI data (target width, thickness, target crown, flatness), and roll data (diameter, crown, roll body length, etc. of the working roll and the supporting roll) provided by the roll management application program, the hot crown of the strip steel of each pass calculated by the hot crown calculation module, the wear crown data of the strip steel of each pass provided by the roll wear calculation module, the current PC angle and roll bending force value transmitted from the L1, the roll system deformation of each frame and the outlet crown of each frame are calculated by a series of models, thus, the set values of the plate shape control mechanisms of all the frames (the roll bending force, the PC angle or the CVC transverse moving position are optimized) are calculated, and the strip steel is ensured to meet the requirements of target convexity and flatness.
As shown in fig. 2, a schematic diagram of a PC (Pair Cross) rolling mill widely used in hot rolling production at present is shown, in which the crown is controlled by crossing rolls at a certain angle, and the larger the roll offset angle θ is, the stronger the crown control capability is. However, another problem is caused, because the strip steel cannot be accurately centered, the central line of the strip steel and the central line of the roller always have certain deviation, and because a certain angle exists between the roller axis of the PC rolling mill and the horizontal line, when the strip steel is not centered, the larger the deviation angle theta of the roller is, the larger the axial force along the strip steel axis is, the more serious the strip steel deviation is, the deviation of the strip steel can cause inconsistent pressing quantity of the two sides, and thus wedge-shaped strip steel is generated, that is, the larger the deviation angle theta of the roller is, the more serious the strip steel wedge-shaped strip steel is. It can be seen that there is a conflict between controlling the crown and controlling the wedge using the PC angle.
The reason for the above problem is that in the prior art, the traditional plate shape setting control uses simple convexity control as a control target, the wedge quality is never considered, for a PC rolling mill, a PC angle is used as a preferred control means, in the setting control, the control principle is to control the convexity by using the PC angle as much as possible, the roll bending force is used as little as possible, and the control strategy has the consequence that the convexity meets the standard and the wedge exceeds the standard.
In order to solve the problems, several hot continuous rolling strip steel wedge and convexity combined control technologies exist at present, and the technologies comprise the following steps:
1) an invention patent with patent number 201010230419.8, published on 2010, 07-20.A method and a system for automatically controlling the crown and/or wedge of a hot rolling tandem mill are disclosed, which relates to a method and a system for automatically controlling the crown and/or wedge (ASCC) of a hot rolling tandem mill, wherein the method and the system realize the full-automatic control of the crown (wedge) of a strip by establishing the feedback control of the bending of a working roll and the leveling of a roll gap of a finish rolling stand from a first stand to a last stand in the tandem mill, namely, after the wedge of the strip is detected by an ASCC model in the rolling process, the deviation is obtained by comparing the ASCC model with a target wedge, the deviation is corrected by utilizing the comprehensive operation and control means of the system, and a stepped adjustment method is established, thereby maximizing the response of the feedback control, correcting the wedge and the crown of the strip, ensuring the good flatness of a product, preventing the serpentine motion of the strip in each, the defect of single convexity control means in the prior art is eliminated, and the relation between convexity and flatness is comprehensively balanced.
The method can comprehensively control the wedge shape and the convexity, but the method is feedback control, the strip steel head does not move until reaching an outlet detection instrument of a finishing mill group, the strip steel head is not in a control range, and the convexity control execution mechanism is the bending force, and when the deviation is large, the required precision cannot be achieved by simply using the bending force due to the limitation of equipment capacity. The wedge is controlled by leveling the pressing mechanisms on the two sides of the frame, and similarly, when the wedge is large, the problem of capacity limitation of an actuating mechanism can be solved, and the head of the strip steel cannot be effectively controlled.
2) The invention discloses an invention patent 'heredity-based automatic control method for a strip steel wedge shape', with the patent application number of 201510275691.0, wherein the invention obtains an actually measured wedge shape value of the strip steel through the detection of a detector at the outlet of a rolling mill, and compares the actually measured wedge shape value of the strip steel with a wedge shape value threshold value to obtain a wedge shape deviation value; and then selecting a plurality of racks as wedge-shaped control racks, setting the efficiency coefficient of each wedge-shaped control rack, and calculating the wedge-shaped deviation value by combining the speed and the efficiency coefficient of the strip steel in the wedge-shaped control racks to obtain the single-side roll gap regulating quantity of the racks. The wedge-shaped regulating quantity of each frame is proportionally controlled based on the second flow balance principle, and the wedge-shaped of the hot-rolled finished product can be quickly and effectively controlled.
The invention is also a wedge feedback control, the adjusting mechanism is still the one-side roll gap of the finish rolling stand, only the wedge genetic coefficient is introduced, the wedge adjusting quantity distribution of the stands at the upstream is more reasonable, but the wedge control problem of the strip steel head is still not solved, and the convexity can not be controlled in a combined manner.
3) The invention relates to an automatic control method for camber and wedge of a hot-rolled strip roughing mill set, which is disclosed by the invention patent No. CN201010266910, and the invention mainly takes the actual values of rolling forces on two sides of an on-site roughing mill, the actual calculated values of roll gaps, bounce parameters on two sides of a rack and the like as input, and finally realizes the correction of camber and wedge by adjusting the roll gaps on one side or two sides of the mill after accurate calculation.
The scheme only adjusts the wedge at the outlet of the roughing mill, the hot rolled finished product also needs to be continuously rolled by a finish rolling frame, if the deviation of the strip steel of the finish rolling unit or the pressing of two sides is inconsistent, the finished product still has the possibility of poor wedge after rolling is finished, and the convexity cannot be simultaneously controlled.
The methods mainly improve the control precision of the convexity and the wedge through feedback control, but the measuring instrument used for the feedback control is positioned behind a finishing mill outlet frame, so that the measuring instrument has larger time lag and can only be used for the convexity and the wedge at the middle rear part of the strip steel. And when the convexity and wedge deviation is large, the required convexity and wedge precision targets cannot be achieved by completely depending on feedback control due to the capability of an actuating mechanism. Moreover, the above patents are directed to conventional mills and do not consider the characteristics of PC mills, i.e., the effect of the PC angle on the wedge shape.
In summary, the conventional setting control in the prior art only aims at the convexity precision, and the factors causing the wedge defect are not considered in the strip shape setting control, and in recent years, along with the increasing requirements of users on the wedge of the hot rolled strip, the quality of the wedge also needs to be considered in the setting control.
Disclosure of Invention
The invention provides a setting control method for improving the full-length convexity and wedge precision of hot continuous rolling strip steel, which is different from the prior art in that the characteristics of a PC rolling mill are fully considered, the influence of the PC angle on the wedge is considered in the process of setting the plate shape, the PC angle and the roll bending force are reasonably divided, the upper limit of the PC angle under the good condition of the wedge is firstly determined by analyzing historical rolling data, then the roll bending force is used for compensating the allowance of convexity control, the invention overcomes the defect that the PC angle is singly used as the main control means of the convexity in the setting control of the traditional PC rolling mill, reasonably distributes the control range of the PC angle and the roll bending force, limits the PC angle which is maximally used according to different varieties and specifications, and reduces the probability of wedge generation while meeting the requirement of the convexity control precision, meanwhile, the convexity and wedge precision of the hot rolled strip steel product are improved, and the product quality of the hot rolled strip steel is improved.
A setting control method for improving the full-length convexity and wedge precision of hot continuous rolling strip steel comprises a hot continuous rolling mill and a frame thereof, and comprises the following specific steps:
1) firstly, counting historical setting data of strip steel with good convexity and wedge shape:
the convexity is well defined as the strip steel convexity and the target value are within the deviation of +/-20 mu m, and the qualification rate is 100 percent;
the wedge shape is well defined as that the strip steel wedge shape is within +/-15 mu m deviation, and the qualification rate is 100 percent;
2) and 1) counting the set values of the PC angles of three racks F2, F3 and F4 of the hot continuous rolling mill, taking the PC angle of the strip steel with the highest proportion as the later set upper limit of the PC angle, and writing the counted upper limit of the PC angle into a PC angle upper limit data table with good convexity wedges.
3) Starting finish rolling plate shape presetting when the strip steel reaches a finish rolling front temperature measuring instrument, firstly, fixing the bending roll force to be the middle value of the bending roll force control range value through the plate shape presetting, then, calculating the set values of the PC angles of three frames F2, F3 and F4 which can reach the target convexity through a mathematical model, and then, checking whether the set value of the PC angle exceeds the upper limit of the PC angle with good convexity wedges of the frame counted in the step 2);
the purpose of the steps is that in the traditional PC rolling mill strip shape setting, when two convexity control mechanisms of a PC angle and a roll bending force are selected, the PC angle is generally used for controlling the convexity of the strip steel preferentially, the upper limit of the PC angle is generally set as the upper limit of mechanical capacity, the roll bending force is generally set as the middle value of a control range value, and when the set value of the PC angle exceeds a certain value, the strip steel is easy to deviate due to the action of lateral force, a wedge is generated, and wedge defect is caused. Therefore, if both good camber and wedge conditions are to be met, the range of PC angles that can be used must be limited, and the ability to reasonably use a portion of the roll bending to control camber.
4) If the set values of the PC angles of the three frames F2, F3 and F4 do not exceed the upper limit of the PC angle with good convexity wedge of the frame counted in the step 2), calculating the set values of the PC angles of F2, F3 and F4 which can reach the target convexity as final set values through a series of mathematical models, and outputting the PC angles and the roll bending force of each frame to a control system L1;
5) in the step 3), if the set values of the PC angles of the three frames F2, F3 and F4 exceed the upper limit of the PC angle with good convexity wedge of the frame counted in the step 2), taking the upper limit of the PC angle of the frames F2, F3 and F4 as the set value of the current PC angle, then recalculating the set value of the roll bending force, and finally calculating the final set values of the PC angle and the roll bending force and transmitting the final set values to the control system L1;
the design purposes of the step 4) and the step 5) are that the traditional hot continuous rolling mill provided with a PC rolling mill generally takes the PC angle as a primary control means when the plate shape is set and calculated, the roll bending force only makes up the deficiency of the convexity control capability when the PC angle reaches the limit of mechanical equipment, and whether the convexity reaches the standard or not is only considered when the setting is carried out.
The setting control method for improving the full-length convexity and the wedge precision of the hot continuous rolling strip steel is characterized in that the PC angle set values of F2, F3 and F4 capable of reaching the target convexity are calculated as final set values through a series of mathematical models in the step 4), and the method comprises the following specific steps:
2a) in the case of a hot finishing mill equipped with a PC rolling mill, there are two types of control mechanisms for controlling crown, PC angle and roll bending force, and it is impossible to solve two control amounts of PC angle and roll bending force, and it is necessary to fix one control amount and calculate the other control amount as a main control amount. During the first setting, selecting a fixed roll bending force, solving a PC angle when the target convexity is reached, wherein the control range of the PC angle is the maximum mechanical allowable control range of the PC angle, generally 0-1.5 degrees, and selecting a median value of a control domain for the fixed value of the roll bending force at the moment, namely:
in the formula:
i: a rack number;
Fb(i) i, calculating the roll bending force;
Fbmin(i) the method comprises the following steps The ith calculates the minimum value of the roll bending force;
Fbmax(i) the method comprises the following steps The ith calculates the maximum value of the roll bending force;
after the roll bending force is fixed, a PC angle set value theta (i) meeting the current convexity target is obtained;
2b) after the step 2a) is finished, reading the upper limit value of the PC angle which is pre-stored in the data table and can simultaneously meet the requirements of the convexity and the wedge according to the steel grade, the width grade and the thickness grade of the current rolled strip steel, comparing the upper limit value with the PC angle set value theta (i) calculated in the step 2a), and if any one frame PC angle calculated value is larger than the upper limit value of the PC angle which simultaneously meets the requirements of the convexity and the wedge, setting the PC angle set value of the frame as the upper limit value, and fixing. If the PC angle does not exceed the upper limit, the original value is kept unchanged, and the specific judgment mode is as follows:
if theta (i) ≧ thetamax(i) Then θ (i) is θmax(i)；
If theta (i)<θmax(i) Then θ (i) is θ (i);
in the formula:
θ (i): the calculated PC angle of the ith rack;
θmax(i) the method comprises the following steps The ith frame simultaneously meets the upper limit value of the PC angle required by convexity and wedge, and the upper limit value of the PC angle is read from a previous PC angle upper limit data table;
2c) after the PC angle obtained in the step 2b) is fixed, setting for the second time, and solving a roll bending force set value F meeting the convexity target requirement under the current PC angle setting within the maximum and minimum allowable range of the roll bending force machineb(i) After the second setting calculation is finished, the set value F of the bending force of each frame is solvedb(i) And the PC angle set value theta (i) is used as the final set value.
The setting control method for improving the full-length convexity and wedge precision of the hot continuous rolling strip steel is characterized in that historical setting data of the strip steel with good statistical convexity and wedge in the step 1) and the step 2) are used for obtaining the upper limit of the PC angle when the convexity and the wedge are good, wherein the data are classified firstly because the PC angle setting difference of the strip steel with various specifications is large, the classification principle is to classify and screen the data according to the steel type, the width grade and the thickness grade of the strip steel, an excellent sample is screened as the basis of statistical analysis, the sample is the basis of whether the statistical analysis is reasonable or not and must simultaneously meet the condition that the convexity and the wedge are good, the screening principle is that the definition of the good convexity is that the convexity and the target value of the strip steel are within the deviation of +/-20 mu m, the qualification rate is 100 percent, and the definition of the good wedge is that the wedge of the strip steel is within the deviation of +/-15 mu m, the qualification rate is 100%, and the two simultaneously satisfied strip steels are brought into an excellent sample statistical analysis database.
The setting control method for improving the full-length convexity and the wedge precision of the hot continuous rolling strip steel is characterized in that the two strip steels meeting the requirement at the same time are contained in an excellent sample statistical analysis database, specifically, the distribution of PC angles of the excellent samples is analyzed, the PC angle with 90% of the accumulative ratio is selected as the upper limit value of the PC angle setting, and the upper limit value of the PC angle setting of each frame counted is stored in a PC angle upper limit table according to the steel type, the width level and the thickness level for later setting and use.
The setting control method for improving the full-length convexity and the wedge-shaped precision of the hot continuous rolling strip steel has the following beneficial effects that:
1. the invention relates to a setting control method for improving the full-length convexity and wedge precision of hot continuous rolling strip steel, which solves the problems of the plate shape setting control of the existing hot continuous rolling PC rolling mill, overcomes the defect that the traditional plate shape setting control only takes a PC angle as a main control mechanism, controls the convexity by using a roll bending force when the convexity control capability is insufficient, and reasonably distributes the control ranges of the PC angle and the roll bending force;
2. the setting control method for improving the full-length convexity and the wedge-shaped precision of the hot continuous rolling strip steel limits the maximum used PC angle according to different varieties and specifications, thereby meeting the convexity control precision, reducing the probability of wedge generation, preventing the strip steel from deviating due to larger lateral force when the PC angle is larger, effectively improving the convexity and wedge-shaped control precision and improving the quality of hot rolling strip steel products.
Drawings
FIG. 1 is a schematic illustration of convexity and wedge definition;
FIG. 2 is a schematic diagram of a PC rolling mill;
FIG. 3 is a calculation flow chart of a setting control method for improving the full-length convexity and wedge precision of hot continuous rolling strip steel according to the invention;
FIG. 4 is a PC angle upper limit value statistical chart of the setting control method for improving the full-length convexity and wedge precision of the hot continuous rolling strip steel.
Detailed Description
The following describes a setting control method for improving the full-length convexity and wedge precision of hot continuous rolling strip steel in the invention with reference to the accompanying drawings and embodiments.
A setting control method for improving the full-length convexity and wedge precision of hot continuous rolling strip steel comprises a hot continuous rolling mill and a frame thereof, and comprises the following specific steps:
1) firstly, counting historical setting data of strip steel with good convexity and wedge shape:
the convexity is well defined as the strip steel convexity and the target value are within the deviation of +/-20 mu m, and the qualification rate is 100 percent;
the wedge shape is well defined as that the strip steel wedge shape is within +/-15 mu m deviation, and the qualification rate is 100 percent;
2) and 1) counting the set values of the PC angles of three racks F2, F3 and F4 of the hot continuous rolling mill, taking the PC angle of the strip steel with the highest proportion as the later set upper limit of the PC angle, and writing the counted upper limit of the PC angle into a PC angle upper limit data table with good convexity wedges.
3) Starting finish rolling plate shape presetting when the strip steel reaches a finish rolling front temperature measuring instrument, firstly, fixing the bending roll force to be the middle value of the bending roll force control range value through the plate shape presetting, then, calculating the set values of the PC angles of three frames F2, F3 and F4 which can reach the target convexity through a mathematical model, and then, checking whether the set value of the PC angle exceeds the upper limit of the PC angle with good convexity wedges of the frame counted in the step 2);
4) if the set values of the PC angles of the three frames F2, F3 and F4 do not exceed the upper limit of the PC angle with good convexity wedge of the frame counted in the step 2), calculating the set values of the PC angles of F2, F3 and F4 which can reach the target convexity as final set values through a series of mathematical models, and outputting the PC angles and the roll bending force of each frame to a control system L1;
5) in the step 3), if the set values of the PC angles of the three frames F2, F3 and F4 exceed the upper limit of the PC angle with good convexity wedge of the frame counted in the step 2), taking the upper limit of the PC angle of the frames F2, F3 and F4 as the set value of the current PC angle, then recalculating the set value of the roll bending force, and finally calculating the final set values of the PC angle and the roll bending force and transmitting the final set values to the control system L1;
in the step 4), the set values of the PC angles of F2, F3 and F4 which can reach the target convexity are calculated as final set values through a series of mathematical models, and the specific steps are as follows:
2a) in the case of a hot finishing mill equipped with a PC rolling mill, there are two types of control mechanisms for controlling crown, PC angle and roll bending force, and it is impossible to solve two control amounts of PC angle and roll bending force, and it is necessary to fix one control amount and calculate the other control amount as a main control amount. During the first setting, selecting a fixed roll bending force, solving a PC angle when the target convexity is reached, wherein the control range of the PC angle is the maximum mechanical allowable control range of the PC angle, generally 0-1.5 degrees, and selecting a median value of a control domain for the fixed value of the roll bending force at the moment, namely:
in the formula:
i: a rack number;
Fb(i) i, calculating the roll bending force;
Fbmin(i) the method comprises the following steps The ith calculates the minimum value of the roll bending force;
Fbmax(i) the method comprises the following steps The ith calculates the maximum value of the roll bending force;
after the roll bending force is fixed, a PC angle set value theta (i) meeting the current convexity target is obtained;
2b) after the step 2a) is finished, reading the upper limit value of the PC angle which is pre-stored in the data table and can simultaneously meet the requirements of the convexity and the wedge according to the steel grade, the width grade and the thickness grade of the current rolled strip steel, comparing the upper limit value with the PC angle set value theta (i) calculated in the step 2a), and if any one frame PC angle calculated value is larger than the upper limit value of the PC angle which simultaneously meets the requirements of the convexity and the wedge, setting the PC angle set value of the frame as the upper limit value, and fixing. If the PC angle does not exceed the upper limit, the original value is kept unchanged, and the specific judgment mode is as follows:
if theta (i) ≧ thetamax(i) Then θ (i) is θmax(i)；
If theta (i)<θmax(i) Then θ (i) is θ (i);
in the formula:
θ (i): the calculated PC angle of the ith rack;
θmax(i) the method comprises the following steps The ith frame simultaneously meets the upper limit value of the PC angle required by convexity and wedge, and the upper limit value of the PC angle is read from a previous PC angle upper limit data table;
2c) after the PC angle obtained in the step 2b) is fixed, setting for the second time, and solving a roll bending force set value F meeting the convexity target requirement under the current PC angle setting within the maximum and minimum allowable range of the roll bending force machineb(i) After the second setting calculation is finished, the set value F of the bending force of each frame is solvedb(i) And the PC angle set value theta (i) is used as the final set value.
The above process is shown in fig. 3.
The historical data of the strip steel with good statistical convexity and wedge in the step 1) and the step 2) is set to obtain the upper limit of the PC angle when the convexity and the wedge are good, wherein the data are classified according to the PC angle setting difference of the strip steel with various specifications, the classification principle is to classify and screen the data according to the steel type, the width grade and the thickness grade of the strip steel, an excellent sample is screened as the basis of statistical analysis, the sample is the basis of whether the statistical analysis is reasonable, the conditions of good convexity and wedge are required to be met at the same time, the screening principle is that the convexity is well defined to be within +/-20 mu m deviation of the strip steel convexity and a target value, the qualification rate is 100%, the wedge is well defined to be within +/-15 mu m deviation of the wedge strip steel, the qualification rate is 100%, and the strip steel which is met at the same time is brought into a statistical analysis database of the excellent sample.
The two simultaneously satisfied strip steels are brought into an excellent sample statistical analysis database, and the method specifically comprises the steps of analyzing the distribution of PC angles of an excellent sample, selecting the PC angle with the accumulative ratio of 90% as an upper limit value set by the PC angle, and storing the set upper limit value of the PC angle of each frame counted into a PC angle upper limit table according to steel types, width levels and thickness levels for later setting and use.
Examples
The setting control method for improving the full-length convexity and the wedge precision of the hot continuous rolling strip steel is applied to the plate shape setting control of a 1580 hot continuous rolling mill, and the unit equipment configuration is as follows 1:
| F1 | F2 | F3 | F4 | F5 | F6 | F7 | |
| model type | Common four rolls | PC rolling mill | PC rolling mill | PC rolling mill | Common four rolls | Common four rolls | Common four rolls |
| Bending force control range (kN) | 0～1200 | 0～1200 | 0～1200 | 0～1200 | 0～1200 | 0～1200 | 0～1200 |
| PC control Range (°) | -- | 0-1.5 | 0-1.5 | 0-1.5 | -- | -- | -- |
TABLE 1 Unit Equipment configuration Table
Specification of rolled strip steel, slab specification:
the thickness Hs is 230mm, the width Ws is 1250mm, the finished hot rolled strip specification finish rolling outlet thickness he is 2.61mm, the finish rolling outlet width we is 1220mm, and the target convexity Co is 30 μm.
The upper limit statistics for the PC angles for which the frames of specifications F2, F3, and F4 satisfy both good camber and good wedge are given in Table 2 below:
TABLE 2-Upper limit statistical Table of PC Angle
According to the statistical analysis in table 2 above, when the ratio is 90%, the upper limit of the calculated PC angle is:
| F2 | F3 | F4 |
| 0.85 | 0.7 | 0.5 |
the results of the first setting of the PC angle as the first crown adjustment means with the roll bending force fixed are as follows:
| F1 | F2 | F3 | F4 | F5 | F6 | F7 | |
| roller force (kN) | 1100 | 600 | 600 | 600 | 800 | 747 | 560 |
| PC angle (°) | -- | 0.875 | 0.85 | 0.43 | -- | -- | -- |
From the above results, it can be seen that the PC angles of F2 and F3 both have exceeded the upper limit, so the PC angles of F2 and F3 are fixed and the second setting is made with the following results:
| F1 | F2 | F3 | F4 | F5 | F6 | F7 | |
| roller force (kN) | 1100 | 775 | 985 | 600 | 800 | 747 | 560 |
| PC angle (°) | -- | 0.85 | 0.7 | 0.43 | -- | -- | -- |
From the above results, it can be seen that the bending force settings of F2 and F3 were changed after fixing the PC angles of F2 and F3.
In order to evaluate the effectiveness of the embodiment, the double-qualification rate data of the strip steel with the same specification in two months before and after the input of the setting control method for improving the full-length convexity and the wedge-shaped precision of the hot continuous rolling strip steel is counted, and the calculation formula is as follows:
the definition of the double qualified rate means that the length qualified rate of the strip steel simultaneously satisfies the convexity and the target value within the deviation of +/-20 mu m is 100 percent, and the definition of the good wedge shape is that the length qualified rate of the strip steel wedge within the deviation of +/-15 mu m is 100 percent. And if the convexity and the wedge are qualified at the same time, the strip steel is considered to be double-qualified. After the method is put into use, the proportion of the strip steel with the convexity and the wedge shape reaching the standard simultaneously is improved by 15 percent, and the convexity, particularly the wedge shape control precision is improved remarkably.
The invention relates to a setting control method for improving the full-length convexity and wedge precision of hot continuous rolling strip steel, which solves the problems of the plate shape setting control of the existing hot continuous rolling PC rolling mill, overcomes the defect that the traditional plate shape setting control only takes a PC angle as a main control mechanism, controls the convexity by using a roll bending force when the convexity control capability is insufficient, and reasonably distributes the control ranges of the PC angle and the roll bending force; the method limits the maximum PC angle for different varieties and specifications, thereby meeting the convexity control precision, reducing the probability of wedge-shaped occurrence, preventing the strip steel from deviating due to larger lateral force when the PC angle is larger, effectively improving the convexity and wedge-shaped control precision and improving the quality of hot-rolled strip steel products.
Claims (4)
1. A setting control method for improving the full-length convexity and wedge precision of hot continuous rolling strip steel comprises a hot continuous rolling mill and a frame thereof, and comprises the following specific steps:
1) firstly, counting historical setting data of strip steel with good convexity and wedge shape:
the convexity is well defined as the strip steel convexity and the target value are within the deviation of +/-20 mu m, and the qualification rate is 100 percent;
the wedge shape is well defined as that the strip steel wedge shape is within +/-15 mu m deviation, and the qualification rate is 100 percent;
2) step 1), counting the set values of the PC angles of three racks F2, F3 and F4 of the hot continuous rolling mill, taking the PC angle of the strip steel with the highest proportion as the later set upper limit of the PC angle, and writing the counted upper limit of the PC angle into a PC angle upper limit data table with good convexity wedges;
3) starting finish rolling plate shape presetting when the strip steel reaches a finish rolling front temperature measuring instrument, firstly, fixing the bending roll force to be the middle value of the bending roll force control range value through the plate shape presetting, then, calculating the set values of the PC angles of three frames F2, F3 and F4 which can reach the target convexity through a mathematical model, and then, checking whether the set value of the PC angle exceeds the upper limit of the PC angle with good convexity wedges of the frame counted in the step 2);
4) if the set values of the PC angles of the three frames F2, F3 and F4 do not exceed the upper limit of the PC angle with good convexity wedge of the frame counted in the step 2), calculating the set values of the PC angles of F2, F3 and F4 which can reach the target convexity as final set values through a series of mathematical models, and outputting the PC angles and the roll bending force of each frame to a control system L1;
5) and 3) if the set values of the PC angles of the three frames F2, F3 and F4 exceed the upper limit of the PC angle with good convexity wedge of the frame counted in the step 2), taking the upper limit of the PC angle of the frames F2, F3 and F4 as the set value of the current PC angle, recalculating the set value of the roll bending force, and transmitting the finally calculated PC angle and the roll bending force as final set values to the control system L1.
2. The setting control method for improving the full-length crown and wedge accuracy of the hot continuous rolling strip steel as claimed in claim 1, wherein the PC angle setting values of F2, F3 and F4 capable of achieving the target crown are calculated as final setting values through a series of mathematical models in the step 4), and the specific steps are as follows:
2a) for a hot finishing mill equipped with a PC rolling mill, two control mechanisms for controlling the crown are provided, namely a PC angle and a bending force, and solving two control quantities of the PC angle and the bending force is impossible, one control quantity must be fixed, the other control quantity is used as a main control quantity to calculate, when the control quantity is set for the first time, the fixed bending force is selected, and the PC angle reaching the target crown is solved, wherein the control range of the PC angle is the maximum mechanical allowable control range of the PC angle, generally 0-1.5 degrees, and the middle value of a control domain is selected according to the fixed value of the bending force, namely:
in the formula:
i: a rack number;
Fb(i) i, calculating the roll bending force;
Fbmin(i) the method comprises the following steps The ith calculates the minimum value of the roll bending force;
Fbmax(i) the method comprises the following steps The ith calculates the maximum value of the roll bending force;
after the roll bending force is fixed, a PC angle set value theta (i) meeting the current convexity target is obtained;
2b) after step 2a) is finished, reading the upper limit value of the PC angle which is pre-stored in a data table and can simultaneously meet the requirements of the convexity and the wedge according to the steel grade, the width grade and the thickness grade of the current rolled strip steel, comparing the upper limit value with the PC angle set value theta (i) calculated in step 2a), if any one rack PC angle calculated value is larger than the upper limit value of the PC angle which simultaneously meets the requirements of the convexity and the wedge, setting the PC angle set value of the rack as the upper limit value, fixing, and if the PC angle does not exceed the upper limit, keeping the original value unchanged, wherein the specific judgment mode is as follows:
if theta (i) ≧ thetamax(i) Then θ (i) is θmax(i)；
If theta (i)<θmax(i) Then θ (i) is θ (i);
in the formula:
θ (i): the calculated PC angle of the ith rack;
θmax(i) the method comprises the following steps The upper limit of the PC angle at which the ith frame meets both the convexity and wedge requirementsA value read from the previous PC angle ceiling data table;
2c) after the PC angle obtained in the step 2b) is fixed, setting for the second time, and solving a roll bending force set value F meeting the convexity target requirement under the current PC angle setting within the maximum and minimum allowable range of the roll bending force machineb(i) After the second setting calculation is finished, the set value F of the bending force of each frame is solvedb(i) And the PC angle set value theta (i) is used as the final set value.
3. The setting control method for improving the full-length convexity and wedge accuracy of the hot continuous rolling strip steel according to claim 1, characterized in that the historical setting data of the strip steel with good statistical convexity and wedge in the steps 1) and 2) is used for obtaining the PC angle upper limit when the convexity and wedge are good, wherein, because the PC angle setting difference of the strip steel with various specifications is large, the data must be classified firstly, the classification principle is to classify and screen the data according to the steel type, width grade and thickness grade of the strip steel, an excellent sample is screened as the basis of the statistical analysis, the sample is the basis of whether the statistical analysis is reasonable, the conditions of good convexity and wedge must be simultaneously satisfied, the screening principle is that the definition of good convexity is that the convexity and the target value of the strip steel are within the deviation of +/-20 μm, the qualification rate is 100%, and the definition of good wedge is that the wedge is within the deviation of +/-15 μm, the qualification rate is 100%, and the two simultaneously satisfied strip steels are brought into an excellent sample statistical analysis database.
4. The setting control method for improving the full-length crown and the wedge precision of the hot continuous rolling strip steel as claimed in claim 3, wherein the two strip steels meeting at the same time are included in the excellent sample statistical analysis database, which is characterized in that the distribution of PC angles of the excellent samples is analyzed, the PC angle with 90% of the cumulative proportion is selected as the upper limit value of the PC angle setting, and the statistical upper limit values of the PC angles of the frames are stored in the PC angle upper limit table according to the steel type, the width level and the thickness level for later setting and use.
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