Feedforward control method for deviation of strip steel in sendzimir method hot galvanizing unit furnace

Abstract

The invention relates to the technical field of cold rolling, in particular to a feedforward control method for in-furnace strip steel deviation of a sendzimir method hot galvanizing unit. A plate shape I value and a wave height allowable value are set based on the steel grade and the width; setting a furnace area tension coefficient and actual tension based on the steel grade and thickness; setting a furnace roller convexity value based on the steel grade and thickness; and the parameters are preset in a control system and executed before the strip steel enters the furnace. According to the method, a plate shape-tension-roll convex collaborative parameter spectrum covering the CQ, DQ and DDQ full levels and the 0.3-2.5 mm full thickness is established for the first time, and active defense of deviation source reduction, roll attaching stable matching and self-correction grading construction is achieved. Under the condition that equipment investment is not newly increased, zero deviation of the strip steel in the furnace is achieved, the hidden danger of strip breakage is eliminated, quality, efficiency and intrinsic safety are remarkably improved, and the industrial popularization value is extremely high.

Description

Technical Field

[0001] This invention relates to the field of cold rolling technology, specifically to a feedforward control method for strip deviation in a Sendzimir hot-dip galvanizing unit. Background Technology

[0002] The Sendzimir process for continuous hot-dip galvanizing is one of the mainstream production methods for wide, high-quality hot-dip galvanized steel sheets. The key feature of this process is that the cold-rolled strip first enters an open-flame heating section (oxidation furnace) before the reducing atmosphere annealing furnace, where it is directly heated by a gas flame. This process aims to burn off residual rolling oil on the strip surface and to induce controlled oxidation, forming a thin, dense iron oxide film. This film is then reduced to pure iron in the reduction section, resulting in excellent coating adhesion. The advantages of this method are: the strip temperature upon entering the zinc pot is higher than the zinc bath temperature, significantly reducing the heat load on the zinc pot and extending its lifespan; simultaneously, the generation of zinc ash and dross is greatly reduced, zinc consumption decreases, the aluminum content in the zinc bath is more easily controlled, and the uniformity of the coating quality is improved.

[0003] However, in actual production, hot-dip galvanizing units based on the Sendzimir process have long faced a common technical problem—strip deviation in the furnace.

[0004] Due to variations in product width, thickness, yield strength, and incoming material shape, strip steel often deviates from the unit's centerline during operation in the furnace area, shifting laterally towards the operating or transmission side. Slight deviation leads to uneven contact between the strip and the furnace rolls, resulting in quality defects such as uneven coating thickness and surface scratches. Severe deviation directly causes secondary accidents such as strip scraping against the furnace wall, folding, and breakage. Particularly noteworthy is the high-risk operation involved in handling strip breakage accidents within the furnace, including the shutdown and restoration of energy media in the furnace area, furnace cooling and heating, and personnel entry into confined spaces. These operations pose significant safety hazards, and a single accident often results in downtime losses of several hours to over ten hours, severely restricting unit operating rates and production cost control.

[0005] There have been relevant technological explorations in the industry to address the problem of strip deviation in the furnace.

[0006] For example, Chinese patent application CN112446130A discloses a "Strip Deviation Simulation System and Control Method for Annealing Furnaces in Continuous Hot-Dip Galvanizing Units". This method acquires process parameters and strip material data for each process segment, sets sampling points, calculates the deviation factor and deviation amount for each sampling point, calculates the correction amount for sampling points exceeding critical values, and summarizes the correction amounts for each process segment to pre-adjust the correction roller cylinder. This scheme focuses on deviation prediction and dynamic correction based on real-time sampling data, falling under the category of feedback control or feedforward pre-adjustment. Its implementation relies on the accuracy of the correction roller actuator and simulation model, and it corrects existing deviation trends rather than actively avoiding deviation at the process source.

[0007] For example, Chinese invention patent CN108802749B, authorized by patent number CN108802749B, provides a "method for measuring the deviation of strip steel in the air knife section of continuous hot-dip galvanizing." This method sets up a laser rangefinder and a linear slide module in the air knife section. By detecting the transverse and normal positions of the strip steel, it calculates the deviation and adjusts the air knife position and straightening rollers accordingly. This invention focuses on the detection and real-time correction of deviation in the air knife section. Its technical contribution lies in improving the accuracy of the measurement method, but it does not address the personalized design and feedforward setting of furnace process parameters, nor does it propose a systematic solution for the special furnace conditions of the Sendzimir process open-flame heating section.

[0008] In summary, existing technologies mainly exhibit the following characteristics: (1) Delayed control timing: mostly detection, feedback or dynamic adjustment after deviation occurs, lacking proactive pre-set mechanism before production; (2) Single control method: focusing on single factor adjustment (such as the action of the correction roller and the position of the air knife), without forming a coordinated control of multiple process parameters; (3) Failure to differentiate steel grades / specifications: A differentiated process parameter system was not established for different grades such as CQ, DQ, and DDQ, as well as for different width and thickness specifications, resulting in a "one-size-fits-all" approach with insufficient applicability. Summary of the Invention

[0009] To overcome the shortcomings of existing technologies, this invention provides a feedforward control method for strip deviation in a Sendzimir hot-dip galvanizing unit. Without increasing equipment investment or changing the existing mechanical structure of the furnace area, this method effectively controls strip deviation from the source of process parameter design.

[0010] To achieve the above objectives, the present invention employs the following technical solution: A feedforward control method for strip misalignment in a Sendzimir hot-dip galvanizing unit specifically includes the following steps: Step 1: Before the cold-rolled strip enters the furnace area of ​​the Sendzimir hot-dip galvanizing unit, obtain the steel grade and specification information of the strip; Step 2: Based on the steel grade and width specifications, set the cold-rolled strip shape control target, which includes the allowable value of I value and the allowable value of single-sided wave height; Step 3: Based on the steel grade and thickness specifications, set the furnace zone tension coefficient, and determine the actual tension value of the strip running in the furnace zone according to the furnace zone tension coefficient; the furnace zone tension coefficient is the ratio of the unit cross-sectional area tension value of the strip running in the furnace zone to the material yield strength of the strip. Step 4: Based on the steel grade and thickness specifications, set the furnace roll crown value; Step 5: The process parameters set in Steps 2 to 4 are preset in the unit control system so that the strip steel has the process conditions that match the current product specifications before entering the furnace area, and the process parameters are executed during continuous production to achieve feedforward control of strip steel deviation in the furnace.

[0011] Furthermore, in step 2: the steel grade includes CQ grade, DQ grade and DDQ grade; the width specification is divided into three ranges: 900~1100mm, 1100~1200mm and 1200~1550mm; CQ grade strip: When the width is 900~1100mm, the I value is ≤12 and the wave height on one side is ≤6mm; when the width is 1100~1200mm, the I value is ≤9 and the wave height on one side is ≤5mm; when the width is 1200~1550mm, the I value is ≤7 and the wave height on one side is ≤5mm. DQ grade strip: When the width is 900~1100mm, the I value is ≤8 and the wave height on one side is ≤4mm; when the width is 1100~1200mm, the I value is ≤7 and the wave height on one side is ≤3mm; when the width is 1200~1550mm, the I value is ≤6 and the wave height on one side is ≤3mm. DDQ grade strip: When the width is 900~1100mm, the I value is ≤7 and the wave height on one side is ≤2mm; when the width is 1100~1200mm, the I value is ≤6 and the wave height on one side is ≤2mm; when the width is 1200~1550mm, the I value is ≤5 and the wave height on one side is ≤2mm.

[0012] Furthermore, in step 3: the steel grade includes CQ grade, DQ grade and DDQ grade; the thickness specification is divided into three ranges: 0.3~0.5mm, 0.5~1.6mm and 1.6~2.5mm; CQ grade strip steel: When the thickness is 0.3~0.5mm, the furnace zone tension coefficient is 0.38~0.48; when the thickness is 0.5~1.6mm, the furnace zone tension coefficient is 0.45~0.50; when the thickness is 1.6~2.5mm, the furnace zone tension coefficient is 0.50~0.52. DQ grade strip steel: When the thickness is 0.3~0.5mm, the furnace zone tension coefficient is 0.47~0.52; when the thickness is 0.5~1.6mm, the furnace zone tension coefficient is 0.35~0.40; when the thickness is 1.6~2.5mm, the furnace zone tension coefficient is 0.40~0.42. DDQ grade strip: When the thickness is 0.3~0.5mm, the furnace zone tension coefficient is 0.52~0.63; when the thickness is 0.5~1.6mm, the furnace zone tension coefficient is 0.25~0.30; when the thickness is 1.6~2.5mm, the furnace zone tension coefficient is 0.32~0.36.

[0013] Furthermore, in step 4: the steel grade includes CQ grade, DQ grade and DDQ grade; the thickness specification is divided into three ranges: 0.3~0.5mm, 0.5~1.6mm and 1.6~2.5mm; CQ grade strip steel: When the thickness is 0.3~0.5mm, the furnace roll crown value is 400~450μm; when the thickness is 0.5~1.6mm, the furnace roll crown value is 450~500μm; when the thickness is 1.6~2.5mm, the furnace roll crown value is 500~600μm. DQ grade strip: When the thickness is 0.3~0.5mm, the furnace roll crown value is 350~400μm; when the thickness is 0.5~1.6mm, the furnace roll crown value is 400~450μm; when the thickness is 1.6~2.5mm, the furnace roll crown value is 450~500μm. DDQ grade strip: When the thickness is 0.3~0.5mm, the furnace roll crown value is 300~350μm; when the thickness is 0.5~1.6mm, the furnace roll crown value is 350~400μm; when the thickness is 1.6~2.5mm, the furnace roll crown value is 400~450μm.

[0014] Furthermore, the strip shape control target, furnace zone tension coefficient, and furnace roll crown value set in steps 2, 3, and 4 constitute a set of mutually matched collaborative control parameters. The strip shape control target is used to suppress the lateral tension difference caused by incoming strip waviness defects; the furnace zone tension coefficient is used to provide the longitudinal traction force required for the strip to adhere to the rolls; and the furnace roll crown value is used to provide the self-correcting recovery force when the strip deviates. These three sets of parameters are set collaboratively within their respective ranges to jointly suppress strip deviance within the furnace. In step 5, the preset process parameters are executed differently for each coil of strip based on its specifications, achieving feedforward control without adding furnace zone correction equipment or modifying the furnace roll mechanical structure.

[0015] Furthermore, when the strip is CQ grade, with a width of 1000~1150mm and a thickness of 0.3~0.5mm, the I value is set to ≤9, the wave height to ≤5mm, the tension coefficient to 0.38~0.48, and the furnace roll crown to 400~450μm; when the strip is DQ grade, with a width of 1050~1160mm and a thickness of 0.45~0.8mm, the I value is set to ≤7, the wave height to ≤3mm, the tension coefficient to 0.35~0.47, and the furnace roll crown to 350~422μm; when the strip is DDQ grade, with a width of 1080~1120mm and a thickness of 0.48~1.2mm, the I value is set to ≤6, the wave height to ≤2mm, the tension coefficient to 0.25~0.52, and the furnace roll crown to 329~466μm.

[0016] Compared with existing methods, the beneficial effects of the present invention are: 1. By controlling the strip shape in stages, the steering torque is eliminated at its mechanical source, significantly reducing the driving force for strip misalignment. The essence of strip misalignment is the steering torque generated by the lateral tension difference. Existing technologies lack specific restrictions on the incoming strip shape, and wide-specification and deep-drawing strips frequently misalign due to excessive wave height. This invention sets differentiated I values ​​(≤5~12) and wave height limits (≤2~6mm) for CQ, DQ, and DDQ grades and a width range of 900~1550mm, strictly controlling the lateral tension difference below the critical misalignment value.

[0017] The wavy side extends longer and has relaxed tension, while the straight side has concentrated tension, forming a steering torque. This invention eliminates the source of torque at its mechanical origin by strictly controlling the wave height.

[0018] As shown in Table 4, under stringent specifications such as CQ grade width of 1350mm and wave height of 4mm (≤5), and DDQ grade width of 1380mm and wave height of 1mm (≤2), no deviation occurred during the production process. The deviation sensitivity of wide-specification and deep-drawing grade strip steel was precisely matched, eliminating the need for online adjustment mechanisms and reducing the source of risk solely through pre-setting the incoming material quality.

[0019] 2. By designing steel grade-thickness classifications based on tension coefficients, a quantitative match between longitudinal traction force and material strength is established, breaking through the empirical inertia of "thin and low" and "thick and high".

[0020] Existing technologies use coarse tension settings, which can easily cause thin gauges to vibrate and deviate, while thick gauges may experience increased edge stress due to excessive tension, leading to hidden deviations. This invention defines a furnace zone tension coefficient (tension per unit cross-sectional area / yield strength) and establishes a differentiated coefficient system for the entire thickness range of 0.3~2.5mm and for all CQ, DQ, and DDQ grades.

[0021] Too low tension leads to insufficient friction and strip slack; too high tension amplifies the lateral tension difference and exacerbates edge stress. This invention achieves stable tension constraint without amplification through coefficient grading.

[0022] Thin-gauge DDQ strip (0.3~0.5mm) uses a high coefficient of 0.52~0.63. Example 7 (0.48mm, tension coefficient 0.58, convexity 329μm) operates smoothly without deviation, breaking the empirical inertia of "thin gauges must have low tension," and the swaying of thin strips is effectively suppressed. Medium-thickness DDQ strip (0.5~1.6mm) uses a low coefficient of 0.25~0.30. Example 8 (1.2mm, tension coefficient 0.28, convexity 466μm) actively reduces tension to half the conventional empirical level, and deviation is zero, verifying the key technological breakthrough of the counterintuitive setting of "thickness reduction and thinness increase." CQ and DQ grades establish a conventional gradient where the coefficient increases with thickness. The tension coefficients of Examples 1~6 (thickness 0.35~2.0mm) are all within the range of this invention, and the deviation is zero, forming a tension setting spectrum covering the entire product range.

[0023] 3. By matching the steel grade and thickness according to the furnace roll crown, a self-correcting capability is constructed and artificial waviness is avoided.

[0024] Existing technologies often use fixed values ​​or single curves for furnace roll crown. Excessive crown in deep-drawing strips can induce mid-section waviness, while excessive crown in thin strips can lead to overstretching in the middle. This invention is based on the self-correcting principle of "running towards the larger end," setting crown according to steel grade and thickness: CQ grade 400~600μm, DQ grade 350~500μm, DDQ grade 300~450μm, with crown decreasing as the steel grade increases.

[0025] When the strip deviates, the edge of the strip contacts the tapered area of ​​the roller surface, and the wrap angle and winding radius change, generating a reverse restoring force. If the convexity is too small, the correction is insufficient; if the convexity is too large, additional extension occurs in the middle, creating a mid-wave.

[0026] The DDQ grade uses a lower crown (300~450μm). Examples 7~9 (DDQ, thickness 0.48~1.8mm, crown 329~481μm) showed no deviation or mid-wave defects, achieving "weak correction and low stress"; the lower limit of crown was used for thinner specifications and the upper limit of crown was used for thicker specifications. Examples 1 (0.35mm, crown 420μm) and 3 (2.0mm, crown 521μm) operated stably, matching the adaptability of strip steel of different stiffness to the roll surface curve, and stably adhering to the roll across the entire thickness range.

[0027] 4. The three parameters of plate shape, tension and roll convexity work together to build a proactive defense closed loop of "source reduction - process suppression - end compensation" to achieve zero deviation across all varieties.

[0028] This invention is not a simple superposition of the three factors, but rather a collaborative control system constructed through the inherent physical correlation between parameters. Comparative experiments (Table 5) fully verify its non-obviousness. Single parameter optimization cannot completely eliminate deviation (deviation 18-35 times / 100 rolls), only when the strip shape, tension, and roll convexity are preset according to the graded collaborative rules of this invention, deviation and strip breakage are completely eliminated. The nine examples in Table 4 covering all levels of CQ, DQ, and DDQ, widths of 900-1550mm, and thicknesses of 0.3-2.5mm, showed no deviation during the production process. Deviation control has been upgraded from a reactive "case-by-case" approach to a standardized feedforward operation across the entire product line.

[0029] 5. Without adding any new hardware equipment, the technology can be promoted at low cost and with high applicability by redesigning process parameters instead of investing in equipment.

[0030] Existing technologies for solving deviation problems typically rely on hardware modifications such as adding correction rollers, laser rangefinders, and servo adjustment mechanisms. A single set of these modifications can easily cost over a million yuan, and are subject to space constraints in the furnace area, resulting in long modification cycles and significant implementation difficulties. This invention, however, relies entirely on existing furnace roller grinding capabilities, existing tension control systems, and existing plate shape detection methods. It requires no new equipment and does not alter the mechanical structure of the furnace area; its technical effectiveness stems entirely from the redefinition of process parameter rules. Detailed Implementation

[0031] This invention discloses a feedforward control method for strip misalignment in a Sendzimir process hot-dip galvanizing unit. Those skilled in the art can refer to this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0032] I. Overview of the Mechanism of the Technical Solution of the Invention This invention is based on a systematic analysis of the strip deviation mechanism in the furnace of a Sendzimir hot-dip galvanizing unit, identifying strip shape, tension, and furnace roll crown as the three core control elements, with the following mechanism of action: 1. Plate shape control mechanism The shape of cold-rolled steel sheets is a crucial factor affecting deviance in the furnace. For cold-rolled steel sheets operating in the furnace zone of a continuous hot-dip galvanizing unit, the wavy side actually extends longer and tends to relax more under tension; while the straighter or shorter side bears greater tension. This lateral tension difference generates a turning moment in the strip during furnace operation, causing it to deviate from the ideal centerline and drift towards the side with less tension (usually the wavy side). Therefore, strictly controlling the shape of incoming cold-rolled steel is a vital prerequisite for ensuring stable and efficient production on the galvanizing line. This invention, through graded limits on the I-value (shape index) and the allowable value of the wavy height on one side, controls the lateral tension difference below the critical deviation value, eliminating the turning moment at its mechanical source.

[0033] 2. Tension control mechanism In Sendzimir hot-dip galvanizing units, the scientific design of furnace zone tension is the core means to suppress strip deviation. A reasonable tension setting provides stable longitudinal traction to the strip through the tensioning rollers, ensuring it adheres tightly to the furnace rollers and forming an effective constraint, thereby resisting lateral movement caused by factors such as poor strip shape. If the tension is too low, the friction between the strip and the furnace rollers is insufficient, causing the strip to loosen easily and weakening its ability to correct shape defects (such as edge waviness), making deviation highly likely. Conversely, if the tension is too high, although it can enhance stability, it will amplify the original shape defects of the strip: for example, it will exacerbate local stress at the edge waviness, causing uneven lateral tension distribution, which in turn generates a torque that pushes the strip towards the waviness side, inducing deviation. At the same time, excessively high tension also increases the risk of strip breakage and furnace roller damage.

[0034] This invention introduces the concept of furnace zone tension coefficient, defined as the ratio of tension value per unit cross-sectional area to the material's yield strength. This invention considers product grade and thickness specifications to be key factors influencing tension design; that is, the furnace zone tension coefficient primarily depends on the steel grade and thickness specifications, while the width specification only affects the actual tension setting value based on this coefficient. For thin and thick strip steel, tension fluctuations have a more significant impact on deviation; therefore, their furnace zone tension coefficients are optimized separately, forming a counterintuitive setting system of "thickness reduction, thinness increase".

[0035] 3. Furnace Roller Convexity Control Mechanism In Sendzimir hot-dip galvanizing units, the roll profile is a key and proactive technique for controlling strip misalignment. Its core principle lies in compensating for or correcting the lateral misalignment trend of the strip through precisely designed roll surface profiles (such as crown, taper, or special curves). When strip misalignment occurs, its edge contacts a tapered area of ​​different roll diameters. This immediately changes the wrap angle and winding radius of the strip on that roll. Based on the principle of "running towards the larger end," a restoring force is generated at the contact point, causing the strip to move in the opposite direction, thus automatically pulling the strip back to the center position, achieving a self-correcting function.

[0036] Insufficient crowning results in inadequate self-correcting capability; excessive crowning leads to overstretching in the middle of the strip and loosening at the edges, inducing artificial waviness and ultimately damaging the strip shape. This invention classifies and matches the furnace roll crowning according to different steel grades and thicknesses, especially using a lower crowning for deep-drawing grade (DDQ) strip to avoid secondary strip shape defects caused by the self-correcting process.

[0037] 4. Three-parameter synergistic mechanism The strip shape control target, furnace zone tension coefficient, and furnace roll crown value described in this invention are not set in isolation, but rather constitute a set of mutually matched and coordinated control parameters. Strip shape control is used to suppress the lateral tension difference caused by incoming strip waviness defects, eliminating the turning torque at the source; tension control is used to provide the longitudinal traction force required for the strip to adhere to the rolls, suppressing the expansion of defects in the furnace; furnace roll crown is used to provide the self-correcting and restoring force when the strip deviates, forming end-of-line compensation. The three form an active defense closed loop of "source reduction - process suppression - end-of-line compensation". If any single parameter is out of the coordinated range, it is impossible to independently achieve stable control of all varieties and specifications.

[0038] II. Specific Implementation Methods for Plate Shape Control Targets This invention sets graded control targets for the shape of cold-rolled incoming materials based on steel grade and width specifications, specifically including allowable I-values ​​and allowable single-sided wave heights, as shown in Table 1.

[0039] Table 1. Requirements for the shape of cold-rolled steel sheets of various steel grades The basis for setting the strip shape control targets shown in Table 1 is as follows: wide-gauge strips, due to their large transverse span, are more prone to accumulating transverse tension differences, requiring stricter strip shape limits; deep-drawing grade (DDQ) strips have low yield strength and high elongation, making them highly sensitive to waviness defects, therefore, the waviness height on one side is strictly controlled to ≤2mm. These limits are critical values ​​for deviation control verified through extensive industrial testing, while ensuring the yield of the cold rolling process.

[0040] III. Specific Implementation Methods for Furnace Zone Tension Coefficient This invention proposes the concept of furnace zone tension coefficient, which is defined as the ratio of tension value per unit cross-sectional area to the yield strength of the material. The tension coefficient φ satisfies: φ=T / (σs·A), where T is the actual tension of the strip (N), σs is the yield strength of the strip (MPa), and A is the cross-sectional area of ​​the strip (mm²). 2 ).

[0041] The present invention sets the furnace zone tension coefficient in a graded manner according to the steel grade and thickness specification, as shown in Table 2.

[0042] Table 2 Design Table of Tension Coefficient in Furnace Area The principle behind setting the tension coefficient as shown in Table 2 is as follows: (1) CQ grade strip: The tension coefficient gradually increases with the increase of thickness. For thin specifications (0.3~0.5mm), it is 0.38~0.48; for medium-thick specifications (0.5~1.6mm), it is 0.45~0.50; and for thick specifications (1.6~2.5mm), it is 0.50~0.52. This gradient is consistent with the physical law that the stiffness of CQ grade strip increases with the increase of thickness and requires higher tension to maintain roll adhesion.

[0043] (2) DQ grade strip: For thin specifications (0.3~0.5mm), a higher coefficient of 0.47~0.52 is adopted to suppress thin strip vibration; for medium and thick specifications (0.5~1.6mm), the coefficient is reduced to 0.35~0.40, while for thick specifications (1.6~2.5mm), it rises to 0.40~0.42. The mechanism is that the yield strength of DQ grade strip is lower than that of CQ grade. If the medium and thick specifications are subjected to excessive tension, the edge waviness area will be overstretched, implicitly amplifying the transverse tension difference; therefore, the tension is actively reduced to "relax" the edge stress and avoid the cause of deviation.

[0044] (3) DDQ grade strip: The tension coefficient setting of this category in this invention exhibits a significant counterintuitive characteristic. For thin specifications (0.3~0.5mm), a high coefficient of 0.52~0.63 is adopted. The technical logic is that thin deep-drawing steel has extremely weak rigidity and is prone to swaying under high-speed operation. It is necessary to rely on high tension to force the rollers to maintain track stability. Moreover, the yield strength of DDQ grade is low, and the absolute tension value corresponding to the high tension coefficient is still within the safe range. For medium and thick specifications (0.5~1.6mm), a low coefficient of 0.25~0.30 is adopted. The technical logic is that the rigidity of the strip itself in this thickness range is sufficient to maintain the running trajectory. Excessive tension will seriously amplify the edge stress and induce deviation. Therefore, the tension is actively reduced to 1 / 2 of the conventional experience level to eliminate the turning torque caused by uneven tension. For thick specifications (1.6~2.5mm), a medium-low coefficient of 0.32~0.36 is adopted to balance rigidity support and stress control.

[0045] IV. Specific Implementation Methods for Furnace Roller Crown The present invention sets the furnace roll crown value in grades according to steel grade and thickness specifications, as shown in Table 3.

[0046] Table 3. Design of Furnace Roller Convexity The principle of setting the furnace roller crown shown in Table 3: (1) Steel grade dimension: The crown value decreases as the steel grade increases. CQ grade crown is 400~600μm, DQ grade is 350~500μm, and DDQ grade is 300~450μm. The mechanism is that: deep drawing grade (DDQ) strip has a high elongation and is sensitive to the curvature of the roll surface. Excessive crown is prone to forming additional elongation in the middle of the strip, resulting in a mid-wave. This invention reduces crown to exchange "weak correction" for "low stress" and avoids secondary strip shape defects caused by the self-correction process.

[0047] (2) Thickness Specification Dimension: The lower limit of convexity is used for thin specifications, and the upper limit of convexity is used for thick specifications. Taking CQ grade as an example, 400~450μm is used for 0.3~0.5mm, 450~500μm for 0.5~1.6mm, and 500~600μm for 1.6~2.5mm. The mechanism is that: thin specifications of strip steel have weak stiffness, and excessive convexity will lead to excessive stretching in the middle of the strip steel; thick specifications of strip steel have strong stiffness, and a larger convexity is required to provide sufficient self-correcting restoring torque. This setting matches the adaptability of strip steel with different stiffness to the roll surface curve, and realizes stable roll contact operation across the entire thickness range.

[0048] V. Specific Application Examples To verify the effectiveness of the technical solution of this invention, an industrial test was conducted on a Sendzimir process continuous hot-dip galvanizing unit in the cold rolling mill of Ansteel Co., Ltd. The unit has a furnace zone length of approximately 180m, 48 furnace rolls, and is equipped with tension closed-loop control and online grinding capability for furnace roll crown. Nine typical strip steel specifications from three grades (CQ, DQ, and DDQ) were selected, and feedforward presets were performed according to the parameter ranges set in Tables 1, 2, and 3, recording the deviation during production. Specific implementation parameters and operating results are shown in Table 4.

[0049] Table 4. Specific embodiments and operating results of the present invention The above nine sets of embodiments cover three major levels: CQ, DQ, and DDQ, with a width ranging from 900 to 1550 mm and a thickness ranging from 0.3 to 2.5 mm. After the preset parameters of the method of this invention, no furnace deviation occurred during the production process. This result fully demonstrates that the plate shape-tension-roller convexity graded collaborative preset system established by this invention successfully elevates furnace deviation control from a reactive "case-by-case" approach to a standardized feedforward operation covering the entire product range.

[0050] VI. Comparative Test Examples To verify the inventiveness and significant technical effect of the present invention, comparative examples were selected on the same production line. Comparative example 1 adopted the deviation simulation and correction pre-adjustment method disclosed in CN112446130A; comparative example 2 adopted the original "empirical method" parameter setting of the production line (without following the hierarchical coordination rules of the present invention); comparative example 3 only adopted the plate shape control of the present invention, without adjusting the tension and roll protrusion; comparative example 4 only adopted the tension control of the present invention, without optimizing the plate shape and roll protrusion; comparative example 5 only adopted the roll protrusion control of the present invention, without optimizing the plate shape and tension.

[0051] Each comparative example was compared with Example 7 of the present invention (DDQ grade, 1080mm×0.48mm) of the same specifications. The deviation judgment standard was: the deviation of the distance between the edge of the strip and the furnace wall exceeded ±15mm as deviation.

[0052] Table 5. Comparative test results of the examples and comparative examples. Comparative test results show that single-parameter optimization cannot completely eliminate deviation. Only when plate shape, tension, and roll protrusion are preset with feedforward according to the hierarchical synergistic rules of this invention can zero deviation operation in the furnace be achieved. This comparative test further confirms the non-obviousness and significant technical advancement of the three-parameter synergistic control system of this invention.

[0053] VII. Industrial Application Effects The technical solution of this invention has been fully implemented in the continuous hot-dip galvanizing unit of the cold rolling mill at Ansteel Co., Ltd. Post-application statistics show: Unplanned downtime caused by furnace misalignment decreased by 92%, furnace strip breakage accidents were eliminated, and zinc coating defects caused by edge scraping of strip steel were eliminated; the transverse coating thickness difference was reduced to ±1.5g / m. 2 Within 100%; unit operating rate increased by 5.2%; furnace roller grinding cycle extended by 30%.

[0054] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A feedforward control method for strip misalignment in a Sendzimir hot-dip galvanizing unit, characterized in that, Specifically, the following steps are included: Step 1: Before the cold-rolled strip enters the furnace area of ​​the Sendzimir hot-dip galvanizing unit, obtain the steel grade and specification information of the strip; Step 2: Based on the steel grade and width specifications, set the cold-rolled strip shape control target, which includes the allowable value of I value and the allowable value of single-sided wave height; Step 3: Based on the steel grade and thickness specifications, set the furnace zone tension coefficient, and determine the actual tension value of the strip running in the furnace zone according to the furnace zone tension coefficient; the furnace zone tension coefficient is the ratio of the unit cross-sectional area tension value of the strip running in the furnace zone to the material yield strength of the strip. Step 4: Based on the steel grade and thickness specifications, set the furnace roll crown value; Step 5: The process parameters set in Steps 2 to 4 are preset in the unit control system so that the strip steel has the process conditions that match the current product specifications before entering the furnace area, and the process parameters are executed during continuous production to achieve feedforward control of strip steel deviation in the furnace.

2. The feedforward control method for strip misalignment in a Sendzimir hot-dip galvanizing unit according to claim 1, characterized in that, In step 2: The steel grades include CQ, DQ, and DDQ. The width specifications are divided into three ranges: 900~1100mm, 1100~1200mm, and 1200~1550mm. CQ grade strip: When the width is 900~1100mm, the I value is ≤12 and the wave height on one side is ≤6mm; when the width is 1100~1200mm, the I value is ≤9 and the wave height on one side is ≤5mm; when the width is 1200~1550mm, the I value is ≤7 and the wave height on one side is ≤5mm. DQ grade strip: When the width is 900~1100mm, the I value is ≤8 and the wave height on one side is ≤4mm; when the width is 1100~1200mm, the I value is ≤7 and the wave height on one side is ≤3mm; when the width is 1200~1550mm, the I value is ≤6 and the wave height on one side is ≤3mm. DDQ grade strip: When the width is 900~1100mm, the I value is ≤7 and the wave height on one side is ≤2mm; when the width is 1100~1200mm, the I value is ≤6 and the wave height on one side is ≤2mm; when the width is 1200~1550mm, the I value is ≤5 and the wave height on one side is ≤2mm.

3. The feedforward control method for strip misalignment in a Sendzimir hot-dip galvanizing unit according to claim 1, characterized in that, In step 3: The steel grades include CQ, DQ, and DDQ. The thickness specifications are divided into three ranges: 0.3~0.5mm, 0.5~1.6mm, and 1.6~2.5mm. CQ grade strip steel: When the thickness is 0.3~0.5mm, the furnace zone tension coefficient is 0.38~0.48; when the thickness is 0.5~1.6mm, the furnace zone tension coefficient is 0.45~0.50; when the thickness is 1.6~2.5mm, the furnace zone tension coefficient is 0.50~0.

52. DQ grade strip steel: When the thickness is 0.3~0.5mm, the furnace zone tension coefficient is 0.47~0.52; when the thickness is 0.5~1.6mm, the furnace zone tension coefficient is 0.35~0.40; when the thickness is 1.6~2.5mm, the furnace zone tension coefficient is 0.40~0.

42. DDQ grade strip: When the thickness is 0.3~0.5mm, the furnace zone tension coefficient is 0.52~0.63; when the thickness is 0.5~1.6mm, the furnace zone tension coefficient is 0.25~0.30; when the thickness is 1.6~2.5mm, the furnace zone tension coefficient is 0.32~0.

36.

4. The feedforward control method for strip misalignment in a Sendzimir hot-dip galvanizing unit according to claim 1, characterized in that, In step 4: The steel grades include CQ, DQ, and DDQ. The thickness specifications are divided into three ranges: 0.3~0.5mm, 0.5~1.6mm, and 1.6~2.5mm. CQ grade strip: When the thickness is 0.3~0.5mm, the furnace roll crown value is 400~450μm; when the thickness is 0.5~1.6mm, the furnace roll crown value is 450~500μm. When the thickness is 1.6~2.5mm, the furnace roll crown value is 500~600μm; DQ grade strip: When the thickness is 0.3~0.5mm, the furnace roll crown value is 350~400μm; When the thickness is 0.5~1.6mm, the furnace roll crown value is 400~450μm; When the thickness is 1.6~2.5mm, the furnace roll crown value is 450~500μm; DDQ grade strip: When the thickness is 0.3~0.5mm, the furnace roll crown value is 300~350μm; when the thickness is 0.5~1.6mm, the furnace roll crown value is 350~400μm; when the thickness is 1.6~2.5mm, the furnace roll crown value is 400~450μm.

5. A feedforward control method for strip misalignment in a Sendzimir hot-dip galvanizing unit according to claim 2 or 3, characterized in that, When the strip steel is CQ grade, 1000~1150mm wide, and 0.3~0.5mm thick, the following settings are made: I value ≤9, wave height ≤5mm, tension coefficient 0.38~0.48, and furnace roll crown 400~450μm; When the strip is of DQ grade, with a width of 1050~1160mm and a thickness of 0.45~0.8mm, the following settings are made: I value ≤7, wave height ≤3mm, tension coefficient 0.35~0.47, and furnace roll crown 350~422μm; When the strip is DDQ grade, 1080~1120mm wide, and 0.48~1.2mm thick, the following settings are made: I value ≤6, wave height ≤2mm, tension coefficient 0.25~0.52, and furnace roll crown 329~466μm.

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