Strip steel coating baking quality online evaluation method and strip steel coating baking control method

Abstract

According to the on-line evaluation method for the baking quality of the strip steel coating, on-line evaluation of the baking quality of the strip steel coating is completed on the basis of on-line monitoring of the displacement of the strip steel in the baking process, and the invention further discloses a strip steel coating baking control method. And feedback adjustment on the power of the burner is established according to the actual displacement of the strip steel coating in the baking process. According to the on-line evaluation method for the baking quality of the strip steel coating and the baking control method for the strip steel coating, the on-line evaluation method not only can realize on-line evaluation, but also can establish timely regulation and control on the baking power of the subsequent strip steel coating according to the evaluation result, so that the automation degree is high; according to the strip steel coating baking control method, feedback control compared with previous open-loop control is established, so that the baking power can be regulated and controlled in real time according to actual conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of drying magnesium oxide coating on the surface of steel strip in the production of oriented silicon steel, and specifically relates to an online evaluation method for the baking quality of steel strip coating and a method for controlling the baking of steel strip coating. Background Art

[0002] The magnesium oxide isolation coating of oriented silicon steel is a very important process in the production of silicon steel. The drying process has an important influence on the quality of the isolation coating finally generated. Excellent magnesium oxide coating quality is the prerequisite for obtaining oriented silicon steel products with excellent surface quality and excellent magnetic properties. Insufficient baking or excessive baking will cause serious quality defects. In addition to a large amount of unreacted water, the magnesium oxide slurry coated on the surface of the strip also contains chemical water and free water combined with magnesium oxide. Among them, the chemical water is Mg(OH)2, which is formed by the combination of magnesium oxide and water in the form of a primary valence bond. When heated to 350-450℃ in a high-temperature furnace, Mg(OH)2 decomposes and releases water. Free water is water combined with magnesium oxide by van der Waals force to form MgO·H2O, which can be removed by desiccant or physical means. The main purpose of baking the magnesium oxide coating is to remove the water and free water that are not involved in the hydration reaction in the magnesium oxide wet film.

[0003] The requirements of magnesium oxide wet film at different stages of the entire baking process are as follows: for the initial stage of coating baking, the process requires a large amount of concentrated energy to ensure the drying operation in a short time; that is, to quickly evaporate at least a specified percentage of water within a short specified time after the coating is completed, which is called the rapid water removal stage. The relatively later stage of baking is the coating curing stage. After at least a specified percentage of water in the wet film is removed, this stage is mainly to ensure that the board temperature of the substrate remains stable at above 200°C to prevent the large amount of water vapor contained in the gas in the furnace from being absorbed by the cured wet film again. That is, while continuing to remove residual water, consolidate the drying effect of the first stage.

[0004] The current evaluation scheme for wet film baking effect usually adopts the method of measuring the plate temperature of wet film after baking, or measuring the water content in wet film after baking, and then comparing it with the target required by the product to evaluate whether the expected effect is achieved. The basic control of drying used in current large-scale production is: according to experience, the corresponding initial power is set in advance according to different thicknesses and types of coatings, and then several burners are arranged along the axial direction of the furnace shell above and below the strip running channel line, and the heat radiated by the burners is used to evaporate the water in the strip surface coating.

[0005] The shortcomings of the above evaluation method are: since the drying effect is evaluated by the design of equipment configuration to ensure the drying process and the final result, it is impossible to predict and evaluate whether the magnesium oxide wet film is carried out in accordance with the drying process requirements of rapid water removal in the initial stage of drying and consolidation of the drying effect in the later stage of drying as mentioned above. Because when the speed, specifications, and wet film thickness of the product change, the furnace section corresponding to the rapid water removal stage in the drying process may move backward in the axial direction of the drying device. In this case, the above drying effect evaluation method for the final plate temperature or final moisture content still shows that the expected effect has been achieved. But in fact, due to the backward shift of the rapid water removal stage and the insufficient time of the consolidation stage, the final product quality will be defective.

[0006] The invention application with application number: CN201210474942.4 discloses "a method for establishing an infrared spectrum measurement model for the moisture content of a steel strip surface coating". The method first determines the measurement wavelength of the moisture content of the coating sample and calibrates the infrared spectrum absorption value, determines the measurement area of ​​the coating sample, the infrared spectrum acquisition method, and the number of infrared spectrum acquisitions, and uses chemical methods and infrared measurements to measure the moisture content of multiple coating samples. Regression calculation is used for multiple measurement values ​​to obtain one or more regression linear curves of the infrared spectrum measurement of the moisture content of the steel strip surface coating, and verifies the infrared spectrum measurement accuracy of the curve to obtain an infrared spectrum measurement model that can reflect the moisture content of the steel strip surface coating.

[0007] The invention application with application number: CN202110852462.6 discloses "a method for controlling the baking quality of magnesium oxide coating for producing oriented silicon steel". By adding a set of online plate temperature meters that can move in the transverse direction of the strip above the strip at the outlet of the baking furnace, the baking furnace state is monitored based on the online plate temperature detection value, and a baking output power control system is established for real-time adjustment. Summary of the invention

[0008] The purpose of the present invention is to provide an online evaluation of the baking quality of the steel strip coating and a feedback control of the baking power of the steel strip coating.

[0009] In order to achieve the above technical objectives, the present invention provides an online evaluation method for the baking quality of a steel strip coating and a steel strip coating baking control method, and the technical scheme thereof is specifically as follows:

[0010] The invention discloses an online evaluation method for the baking quality of a steel strip coating. The online evaluation method is based on the online monitoring of the water discharge of the steel strip coating during the baking process.

[0011] Further,

[0012] The online monitoring of the water discharge of the steel strip coating during the baking process consists of two parts: online monitoring of the water discharge of the steel strip coating in the rapid water removal furnace section and online monitoring of the water discharge of the steel strip coating in the coating curing furnace section.

[0013] Further,

[0014] The "online monitoring of the water discharge of the steel strip coating during the baking process" is specifically as follows: an exhaust pipe is arranged beside the burner, and a flow monitor and a dew point monitor are respectively arranged on the exhaust pipe, and the water discharge is calculated based on the gas flow monitored in each exhaust pipe and the monitored dew point value.

[0015] Further,

[0016] The water discharge of the steel strip coating in the rapid water removal furnace section is determined according to the following formula:

[0017]

[0018] in,

[0019] Hi=H i1 +H i2 +H i3 ,

[0020]

[0021] In the above formula,

[0022] Hm: the amount of water discharged from the current strip coating in the rapid water removal furnace section, unit: g;

[0023] c k : The drainage capacity coefficient of the current strip coating, which is related to the coating properties;

[0024] c k-1 : Drainage capacity coefficient of the previous coil coating, related to the coating properties;

[0025] c k+1 : The drainage capacity coefficient of the coating of the last coil of strip steel, which is related to the coating properties;

[0026] H i1 : The amount of water discharged from the coating of the current strip by the i-th exhaust pipe from the time when the head of the strip arrives at the furnace inlet to the time when the head of the strip arrives at the end of the rapid water removal furnace section, unit: g;

[0027] H i2 : The amount of water discharged from the coating of the current strip by the i-th exhaust pipe from the time when the head of the strip arrives at the end of the rapid water removal furnace section to the time when the tail of the strip arrives at the furnace inlet, unit: g;

[0028] H i3: The amount of water discharged from the coating of the current strip by the i-th exhaust pipe from the tail to the furnace inlet to the tail to the end of the rapid water removal furnace section, unit: g;

[0029] i: Serial number of the exhaust pipe of the rapid water removal furnace section;

[0030] m: the total number of exhaust pipes set in the rapid water removal furnace section;

[0031] Fi: flow rate per unit time in the exhaust pipe, unit: m 3 / s,

[0032] L 1 : length of the rapid water removal furnace section, unit: m;

[0033] L 3 : Strip length, unit: m;

[0034] V: Strip running speed, unit: m / s;

[0035] ρ: water vapor density, unit: g / m 3 ,

[0036] d: moisture content, unit: g / kg.

[0037] Further,

[0038] The water discharge of the steel strip coating in the coating curing furnace section is determined according to the following formula:

[0039]

[0040] in,

[0041] Hi=H i1 +H i2 +H i3 ,

[0042]

[0043] In the above formula,

[0044] Hn: The current water discharge of the steel strip coating in the coating curing furnace section, unit: g;

[0045] c k : The drainage capacity coefficient of the current strip coating, which is related to the coating properties;

[0046] c k-1 : Drainage capacity coefficient of the previous coil coating, related to the coating properties;

[0047] c k+1 : The drainage capacity coefficient of the coating of the last coil of strip steel, which is related to the coating properties;

[0048] Hi1 : The amount of water discharged from the coating of the current coil by the i-th exhaust pipe from the time when the head reaches the beginning of the coating curing furnace section to the time when the head reaches the furnace outlet, unit: g;

[0049] H i2 : The amount of water discharged from the coating of the current strip extracted by the i-th exhaust pipe from the time when the head of the strip reaches the furnace outlet to the time when the tail of the strip reaches the beginning of the coating curing furnace section, unit: g;

[0050] H i3 : The amount of water discharged from the current strip coating by the i-th exhaust pipe from the time when the tail of the strip reaches the beginning of the coating curing furnace section to the time when the tail of the strip reaches the furnace outlet, unit: g;

[0051] i: Serial number of the exhaust pipe of the coating curing furnace section;

[0052] n: the total number of exhaust pipes set up in the coating curing furnace section;

[0053] Fi: flow rate per unit time in the exhaust pipe, unit: m 3 / s;

[0054] L 1 : length of the rapid water removal furnace section, unit: m;

[0055] L 2 : Length of coating curing furnace section, unit: m;

[0056] L 3 : Strip length, unit: m;

[0057] V: Strip running speed, unit: m / s;

[0058] ρ: water vapor density, unit: g / m 3 ,

[0059] d: moisture content, unit: g / kg.

[0060] Further,

[0061] When the water discharge of the strip in the rapid water removal furnace section exceeds the upper limit of the set interval, it is judged that the baking power is too large and the baking is excessive;

[0062] When the water discharge of the strip in the rapid water removal furnace section is lower than the lower limit of the set interval, it is judged that the baking power is too small and the baking is insufficient;

[0063] When the water discharge of the strip in the rapid water removal furnace section falls within the set range, the baking quality is judged to be qualified;

[0064] When the water discharge of the strip in the coating curing furnace section falls within the set range, the baking quality is judged to be qualified, otherwise it is judged to be abnormal.

[0065] Further,

[0066] The setting range of the rapid water removal furnace section discharge volume is:

[0067]

[0068] The setting range of the water discharge of the coating curing furnace section is:

[0069]

[0070] In the above formula,

[0071] S: overflow rate of theoretical moisture content of each coil per unit time, unit: g / s;

[0072] V: strip speed, unit: m / s;

[0073] L 1 : length of the rapid water removal furnace section, unit: m;

[0074] L 2 : Length of coating curing furnace section, unit: m;

[0075] L 3 : Strip length, unit: m;

[0076] k 1 , k 2 , k 3 , k 4 :Adjustment coefficient, and satisfy 0.75≤k 1 <k 2 ≤0.85, 0.05≤k 3 <k 4 ≤0.25.

[0077] Further,

[0078] The flow rate value per unit time Fi in the exhaust pipe used to be substituted into the formula of each period is represented by the average value of the flow monitor in this period;

[0079] The moisture content d substituted into the formula for each time period is represented by the average value of the dew point monitor within that time period.

[0080] Further,

[0081] The moisture content d at each collection time is determined based on the corresponding collected dew point value through the following formula:

[0082] d = 3.703 + 0.286 × D + 9.164 × 10 -3 ×D 2 +1.446×10 -4 ×D3 +1.741×10 -6 ×D 4 +5.195×10 -8 ×D 5

[0083] In the above formula,

[0084] d: moisture content, unit: g / kg;

[0085] D: Detection value of dew point meter, ℃.

[0086] A method for controlling baking of a steel strip coating,

[0087] Feedback regulation of the burner power is established by monitoring the actual water discharge of the strip coating during the baking process.

[0088] Further,

[0089] The feedback regulation is composed of feedback regulation of the rapid water removal furnace section and feedback regulation of the coating curing furnace section.

[0090] Further,

[0091] An exhaust pipe is set beside the burner, and a flow monitor and a dew point monitor are respectively set on the exhaust pipe. The drainage volume is calculated based on the gas flow and dew point values ​​monitored in each exhaust pipe.

[0092] The feedback adjustment of the rapid water removal furnace section accordingly includes the following steps:

[0093] S11: Calculate the amount of water that is drawn into each exhaust pipe from the time when the head of the current strip arrives at the furnace inlet to the time when the tail of the strip arrives at the end of the rapid water removal furnace section;

[0094] S12: summing up the water discharge of each exhaust pipe, and then comparing the calculated result with the theoretical water discharge. If the water discharge is greater than the theoretical water discharge, the baking power of the next roll of steel strip is reduced; if the water discharge is less than the theoretical water discharge, the baking power of the next roll of steel strip is increased; otherwise, the existing power is maintained.

[0095] The feedback adjustment of the coating curing furnace section accordingly includes the following steps:

[0096] S21: Calculate the amount of water that is drawn into each exhaust pipe from the time when the head of the current strip arrives at the beginning of the coating curing furnace section to the time when the tail of the strip arrives at the furnace outlet;

[0097] S22: summing up the water discharge of each exhaust pipe, and then comparing the calculated result with the theoretical water discharge. If it is greater than the theoretical water discharge, the baking power of the next roll of strip steel is reduced; if it is less than the theoretical water discharge, the baking power of the next roll of strip steel is increased; otherwise, the existing power is maintained.

[0098] Further,

[0099] The theoretical water discharge used to compare with the actual discharge of the rapid water removal furnace section and the theoretical water discharge used to compare with the actual discharge of the coating curing furnace section are both interval values.

[0100] The theoretical water discharge range used for comparison with the actual water discharge of the rapid water removal furnace section is:

[0101]

[0102] The theoretical water discharge range used to compare with the actual water discharge of the coating curing furnace section is:

[0103]

[0104] In the above formula,

[0105] S: overflow rate of theoretical moisture content of each coil per unit time, unit: g / s;

[0106] V: strip speed, unit: m / s;

[0107] L 1 : length of the rapid water removal furnace section, unit: m;

[0108] L 2 : Length of coating curing furnace section, unit: m;

[0109] L 3 : Strip length, unit: m;

[0110] k 1 , k 2 , k 3 , k 4 :Adjustment coefficient, and satisfy 0.75≤k 1 <k 2 ≤0.85, 0.05≤k 3 <k 4 ≤0.25.

[0111] Further,

[0112] The drainage volume of each exhaust pipe installed in the rapid water removal furnace section is determined according to the following formula:

[0113] Hi=H i1 +Hi2 +H i3 ,in,

[0114]

[0115] In the above formula,

[0116] c k : The drainage capacity coefficient of the current strip coating, which is related to the coating properties;

[0117] c k-1 : Drainage capacity coefficient of the previous coil coating, related to the coating properties;

[0118] c k+1 : The drainage capacity coefficient of the coating of the last coil of strip steel, which is related to the coating properties;

[0119] H i1 : The amount of water discharged from the coating of the current strip by the i-th exhaust pipe from the time when the head of the strip arrives at the furnace inlet to the time when the head of the strip arrives at the end of the rapid water removal furnace section, unit: g;

[0120] H i2 : The amount of water discharged from the coating of the current strip by the i-th exhaust pipe from the time when the head of the strip arrives at the end of the rapid water removal furnace section to the time when the tail of the strip arrives at the furnace inlet, unit: g;

[0121] H i3 : The amount of water discharged from the coating of the current strip by the i-th exhaust pipe from the tail to the furnace inlet to the tail to the end of the rapid water removal furnace section, unit: g;

[0122] i: Serial number of the exhaust pipe of the rapid water removal furnace section;

[0123] m: the total number of exhaust pipes set in the rapid water removal furnace section;

[0124] Fi: flow rate per unit time in the exhaust pipe, unit: m 3 / s,

[0125] L 1 : length of the rapid water removal furnace section, unit: m;

[0126] L 3 : Strip length, unit: m;

[0127] V: Strip running speed, unit: m / s;

[0128] ρ: water vapor density, unit: g / m 3 ,

[0129] d: moisture content, unit: g / kg.

[0130] Further,

[0131] The drainage volume of each exhaust pipe installed in the coating curing furnace section is determined according to the following formula:

[0132] Hi=H i1 +H i2 +H i3 ,in,

[0133]

[0134] In the above formula,

[0135] c k : The drainage capacity coefficient of the current strip coating, which is related to the coating properties;

[0136] c k-1 : Drainage capacity coefficient of the previous coil coating, related to the coating properties;

[0137] c k+1 : The drainage capacity coefficient of the coating of the last coil of strip steel, which is related to the coating properties;

[0138] H i1 : The amount of water discharged from the current steel strip coating by the i-th exhaust pipe from the time when the head reaches the beginning of the coating curing furnace section to the time when the head reaches the furnace outlet, unit: g;

[0139] H i2 : The amount of water discharged from the coating of the current strip extracted by the i-th exhaust pipe from the time when the head of the strip reaches the furnace outlet to the time when the tail of the strip reaches the beginning of the coating curing furnace section, unit: g;

[0140] H i3 : The amount of water discharged from the current strip coating by the i-th exhaust pipe from the time when the tail of the strip reaches the beginning of the coating curing furnace section to the time when the tail of the strip reaches the furnace outlet, unit: g;

[0141] i: Serial number of the exhaust pipe of the coating curing furnace section;

[0142] Fi: flow rate per unit time in the exhaust pipe, unit: m 3 / s;

[0143] L 1 : length of the rapid water removal furnace section, unit: m;

[0144] L 2 : Length of coating curing furnace section, unit: m;

[0145] L 3 : Strip length, unit: m;

[0146] V: Strip running speed, unit: m / s;

[0147] ρ: water vapor density, unit: g / m 3 ,

[0148] d: moisture content, unit: g / kg.

[0149] Further,

[0150] The flow rate value per unit time Fi in the exhaust pipe used to be substituted into the formula of each period is represented by the average value of the flow monitor in this period;

[0151] The moisture content d substituted into the formula for each time period is represented by the average value of the dew point monitor within that time period.

[0152] Further,

[0153] The moisture content d at each collection time is determined based on the corresponding collected dew point value through the following formula:

[0154] d = 3.703 + 0.286 × D + 9.164 × 10 -3 ×D 2 +1.446×10 -4 ×D 3 +1.741×10 -6 ×D 4 +5.195×10 -8 ×D 5

[0155] In the above formula,

[0156] d: moisture content, unit: g / kg;

[0157] D: Detection value of dew point meter, ℃.

[0158] The present invention provides an online evaluation method for the baking quality of a steel strip coating and a steel strip coating baking control method, wherein the online evaluation method can not only realize online evaluation, but also establish timely regulation of the subsequent baking power of the steel strip coating according to the evaluation results, and has a high degree of automation; the steel strip coating baking control method therein establishes feedback control compared to the previous open-loop control, so that the baking power can be regulated in real time according to actual conditions.

[0159] In summary, the online evaluation method for the baking quality of steel strip coating and the steel strip coating baking control method of the present invention can not only ensure that the overall water discharge reaches the target requirement, but also more accurately control the water vapor discharge at each stage of the baking process, ensuring that each stage of the magnesium oxide wet film drying process is carried out in accordance with the target requirements, thereby improving the drying quality and product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0160] Figure 1It is a schematic diagram of the length of the rapid water removal furnace section, the length of the coating curing furnace section and the length of the strip steel in the present invention;

[0161] Figure 2 It is a step sequence diagram of feedback regulation of the rapid water removal furnace section in the strip coating baking control method of the present invention;

[0162] Figure 3 It is a step sequence diagram of feedback regulation of the coating curing furnace section in the strip coating baking control method of the present invention. DETAILED DESCRIPTION

[0163] Below, an online evaluation method for the baking quality of a steel strip coating and a method for controlling the baking of a steel strip coating of the present invention are further specifically described according to the accompanying drawings and specific implementation methods of the specification.

[0164] The basic idea of ​​an online evaluation method for the baking quality of a strip coating in the technical solution is: by setting an exhaust pipe beside the burner, and setting a flow monitor and a dew point monitor on the exhaust pipe respectively, the drainage volume is calculated and established based on the gas flow monitored in each exhaust pipe and the dew point value monitored. The drainage volume is calculated for the drainage volume of the strip coating in the rapid dehydration furnace section and the drainage volume of the strip coating in the coating curing furnace section. When the drainage volume of the strip coating in the rapid dehydration furnace section exceeds the upper limit of the set interval, it is determined that the baking power is too large and the baking is excessive; when the drainage volume of the strip coating in the rapid dehydration furnace section is lower than the lower limit of the set interval, it is determined that the baking power is too small and the baking is insufficient; when the drainage volume of the strip coating in the rapid dehydration furnace section falls into the set interval, it is determined that the baking quality is qualified; when the drainage volume of the strip coating in the coating curing furnace section falls into the set interval, it is determined that the baking quality is qualified, otherwise it is determined to be abnormal.

[0165] The basic idea of ​​a strip coating baking control method of the present technical solution is: by monitoring and calculating the actual water discharge of the strip coating during the baking process, the feedback adjustment of the burner power in the rapid water removal furnace section and the feedback adjustment in the coating curing furnace section are established. The monitoring and calculation of the actual water discharge are specifically as follows: an exhaust pipe is set beside the burner, and a flow monitor and a dew point monitor are set on the exhaust pipe respectively, and the water discharge is calculated based on the gas flow monitored in each exhaust pipe and the monitored dew point value. The feedback adjustment of the rapid water removal furnace section is shown in FIG. Figure 2, including the following steps: S11: Calculate the water volume of the current strip that is drawn into each exhaust pipe from the time when the head of the strip reaches the furnace entrance to the time when the tail of the strip reaches the end of the rapid water removal furnace section; S12: Add the water volume of each exhaust pipe, and then compare the calculated result with the theoretical water output. If it is greater than the theoretical water output, the baking power of the next roll of strip is reduced; if it is less than the theoretical water output, the baking power of the next roll of strip is increased, otherwise the current power is maintained. Among them, the feedback adjustment of the coating curing furnace section, see Figure 3 , including the following steps: S21: calculating the water discharge amount of the current strip steel drawn into each exhaust pipe from the time when the head of the strip steel arrives at the beginning of the coating curing furnace section to the time when the tail of the strip steel arrives at the furnace outlet; S22: summing up the water discharge amount of each exhaust pipe, and then comparing the calculated result with the theoretical water discharge amount, when it is greater than the theoretical water discharge amount, the baking power of the next roll of strip steel is reduced, and when it is less than the theoretical water discharge amount, the baking power of the next roll of strip steel is increased, otherwise the existing power is maintained.

[0166] In the above, the theoretical water output used to compare with the actual water output of the rapid water removal furnace section and the theoretical water output used to compare with the actual water output of the coating curing furnace section are both interval values.

[0167] The theoretical water discharge range used for comparison with the actual water discharge of the rapid water removal furnace section is:

[0168]

[0169] The theoretical water discharge range used to compare with the actual water discharge of the coating curing furnace section is:

[0170]

[0171] In the formula,

[0172] S: overflow rate of theoretical moisture content of each coil per unit time, unit: g / s;

[0173] V: strip speed, unit: m / s;

[0174] L 1 : length of the rapid water removal furnace section, unit: m;

[0175] L 2 : Length of coating curing furnace section, unit: m;

[0176] L 3 : Strip length, unit: m;

[0177] k 1 , k 2 , k 3 , k4 :Adjustment coefficient, and satisfy 0.75≤k 1 <k 2 ≤0.85, 0.05≤k 3 <k 4 ≤0.25.

[0178] In the above, both the online evaluation method for strip coating baking quality and the strip coating baking control method are based on first dividing the furnace length into a rapid water removal furnace section and a coating curing furnace section. Figure 1 Then, the drainage volume of the coating baking of each coil of steel strip is statistically analyzed in the rapid dewatering furnace section and the coating curing furnace section respectively, and finally the drainage volume is compared with the theoretical value.

[0179] The furnace length is divided into a rapid dewatering furnace section and a coating curing furnace section based on the baking process requirements. Since the baking process requires a set percentage of baking dewatering to be completed within a set period of time after coating, this process time requirement is mapped to the furnace length according to the strip running speed to form a rapid dewatering furnace section and a coating curing furnace section; thus, a more accurate evaluation can be established for each process section according to the drainage of the rapid dewatering furnace section and the drainage of the coating curing furnace section, and regulation can be established based on the evaluation; this mapping is dynamic, that is, the actual division of the corresponding length can be carried out according to its actual needs to form a rapid dewatering furnace section and a coating curing furnace section that are consistent with the actual situation. The drainage of each roll of strip in the rapid dewatering furnace section and the coating curing furnace section is completed based on the exhaust pipe, flow detector, and dew point meter as described above. Whether it is online evaluation or feedback regulation established based on the drainage, it is completed by comparing the respective drainage with the respective set theoretical intervals mentioned above. The following focuses on the determination process of the drainage of each roll of strip in the rapid dewatering furnace section and the coating curing furnace section:

[0180] The basic setting of existing baking is: the burners at the upper and lower positions of the same length of the furnace shell form a pair, and each pair of burners used for drying is designed with a separate power adjustment system to adjust the power of each pair of burners.

[0181] This technical solution arranges the exhaust pipe on the basis of the existing burner arrangement structure. The gas in the furnace of the drying device is extracted from the exhaust pipe through the fan. A gas flow detector and a gas dew point detector are set on each exhaust pipe to detect the flow rate and dew point value of the gas extracted from each exhaust pipe. i represents the exhaust pipe number. Considering the complex situation in the furnace, the exhaust pipe is densely arranged in the rapid water removal furnace section, that is, a corresponding exhaust pipe is set beside each burner, and sparsely arranged in the coating curing furnace section, that is, an exhaust pipe is set every multiple burners. The overflow flow rate of the theoretical moisture content of each roll of strip in unit time mentioned above is determined according to the moisture content W in the coating of each roll of strip, the product speed V and the product length L; and the moisture content W in the coating of each roll of strip is determined according to the mass ratio concentration P (%) of the coating solute and water of each variety and specification of the strip, the thickness H of the coating wet film after drying, and the surface area S of the product roll. Both the online evaluation and feedback control of this technical solution are performed according to the usual L2 and L1, wherein L1 is used to obtain the collected signal and issue the mechanical action execution instruction, and L2 is used to calculate and complete the evaluation and judgment or complete the control according to the data uploaded by L1; or the data calculation and processing are placed in L1.

[0182] The calculation of the drainage volume of each exhaust pipe of the rapid dewatering furnace section is based on dividing the strip into three sections for separate statistics and finally adding them up. The timing starts from the time when the head of each strip reaches the furnace inlet and ends when the tail of each strip reaches the end of the rapid dewatering furnace section. Specifically:

[0183] Hi=H i1 +H i2 +H i3 ,in,

[0184]

[0185] In the above formula,

[0186] c k : The drainage capacity coefficient of the current strip coating is related to and determined by the coating properties;

[0187] c k-1 : The drainage capacity coefficient of the coating of the previous coil of strip steel, which is related to the coating properties and determined by the coating properties;

[0188] c k+1 : The drainage capacity coefficient of the coating of the last coil of steel strip is related to the coating properties and is determined by the coating properties;

[0189] H i1 : The amount of water discharged from the coating of the current strip by the i-th exhaust pipe from the time when the head of the strip arrives at the furnace inlet to the time when the head of the strip arrives at the end of the rapid water removal furnace section, unit: g;

[0190] H i2 : The amount of water discharged from the coating of the current strip by the i-th exhaust pipe from the time when the head of the strip arrives at the end of the rapid water removal furnace section to the time when the tail of the strip arrives at the furnace inlet, unit: g;

[0191] H i3 : The amount of water discharged from the coating of the current strip by the i-th exhaust pipe from the tail to the furnace inlet to the tail to the end of the rapid water removal furnace section, unit: g;

[0192] i: Serial number of the exhaust pipe of the rapid water removal furnace section;

[0193] m: the total number of exhaust pipes set in the rapid water removal furnace section;

[0194] Fi: flow rate per unit time in the exhaust pipe, unit: m 3 / s,

[0195] L 1 : length of the rapid water removal furnace section, unit: m;

[0196] L 3 : Strip length, unit: m;

[0197] V: Strip running speed, unit: m / s;

[0198] ρ: water vapor density, unit: g / m 3 ,

[0199] d: moisture content, unit: g / kg.

[0200] The statistics of the total water discharge of the rapid water removal furnace section are completed by adding up the water discharge of each exhaust pipe.

[0201] Among them, the three time periods in the above formula are calculated separately for each exhaust pipe, among which as well as The values ​​within the two time periods take into account the duration issue, and in practice an empirical value can also be used instead.

[0202] Similarly, the drainage volume of each exhaust pipe of the coating curing furnace section is based on the statistics of the strip steel divided into three sections, and finally the sum is completed. The timing starts from the head of each strip steel reaching the beginning of the coating curing furnace section, and ends when the tail of each strip steel reaches the outlet of the coating curing furnace section. Specifically:

[0203] Hi=H i1 +H i2 +H i3 ,in,

[0204]

[0205] In the above formula,

[0206] c k : The drainage capacity coefficient of the current strip coating, determined by the coating properties;

[0207] c k-1 : Drainage capacity coefficient of the previous coil coating, determined by the coating properties;

[0208] c k+1 : The drainage capacity coefficient of the coating of the last coil of strip steel, determined by the coating properties;

[0209] H i1 : The amount of water discharged from the current steel strip coating by the i-th exhaust pipe from the time when the head reaches the beginning of the coating curing furnace section to the time when the head reaches the furnace outlet, unit: g;

[0210] H i2 : The amount of water discharged from the coating of the current strip extracted by the i-th exhaust pipe from the time when the head of the strip reaches the furnace outlet to the time when the tail of the strip reaches the beginning of the coating curing furnace section, unit: g;

[0211] H i3 : The amount of water discharged from the current strip coating by the i-th exhaust pipe from the time when the tail of the strip reaches the beginning of the coating curing furnace section to the time when the tail of the strip reaches the furnace outlet, unit: g;

[0212] i: Serial number of the exhaust pipe of the coating curing furnace section;

[0213] Fi: flow rate per unit time in the exhaust pipe, unit: m 3 / s;

[0214] L 1 : length of the rapid water removal furnace section, unit: m;

[0215] L 2 : Length of coating curing furnace section, unit: m;

[0216] L 3 : Strip length, unit: m;

[0217] V: Strip running speed, unit: m / s;

[0218] ρ: water vapor density, unit: g / m 3 ,

[0219] d: moisture content, unit: g / kg.

[0220] The total drainage volume of the coating curing furnace section is calculated by adding up the drainage volume of each exhaust pipe. still Both are considered as one-half, because the thickness and type of the coating before and after baking remain basically unchanged. Unless there is a change, the proportion will be confirmed according to the actual situation.

[0221] In the above, the flow value Fi per unit time in the exhaust pipe used to be substituted into the formula of each time period is represented by the average value of the flow monitor in the corresponding time period; the moisture content d used to be substituted into the formula of each time period is represented by the average value of the dew point monitor in the corresponding time period.

[0222] The moisture content d at each collection time is determined based on the corresponding collected dew point value through the following formula:

[0223] d = 3.703 + 0.286 × D + 9.164 × 10 -3 ×D 2 +1.446×10 -4 ×D 3 +1.741×10 -6 ×D 4 +5.195×10 -8 ×D 5

[0224] In the above formula,

[0225] d: moisture content, unit: g / kg;

[0226] D: Detection value of dew point meter, ℃.

Claims

1. An online evaluation method for the baking quality of a steel strip coating, characterized in that: Based on the online monitoring of the water discharge of the strip coating during the baking process, the online evaluation of the baking quality of the strip coating is completed.

2. The online evaluation method for baking quality of steel strip coating according to claim 1 is characterized in that: The online monitoring of the water discharge of the steel strip coating during the baking process consists of two parts: online monitoring of the water discharge of the steel strip coating in the rapid water removal furnace section and online monitoring of the water discharge of the steel strip coating in the coating curing furnace section.

3. The online evaluation method for the baking quality of a steel strip coating according to claim 2 is characterized in that: The "online monitoring of the water discharge of the steel strip coating during the baking process" is specifically as follows: an exhaust pipe is arranged beside the burner, and a flow monitor and a dew point monitor are respectively arranged on the exhaust pipe, and the water discharge is calculated based on the gas flow and dew point values ​​monitored in each exhaust pipe.

4. The method for online evaluation of the baking quality of a steel strip coating according to claim 3, characterized in that: The water discharge of the steel strip coating in the rapid water removal furnace section is determined according to the following formula: in, Hi=H i1 +H i2 +H i3 , In the above formula, Hm: the amount of water discharged from the current strip coating in the rapid water removal furnace section, unit: g; c k : The drainage capacity coefficient of the current strip coating, which is related to the coating properties; c k-1 : Drainage capacity coefficient of the previous coil coating, related to the coating properties; c k+1 : The drainage capacity coefficient of the coating of the last coil of strip steel, which is related to the coating properties; H i1 : The amount of water discharged from the coating of the current strip by the i-th exhaust pipe from the time when the head of the strip arrives at the furnace inlet to the time when the head of the strip arrives at the end of the rapid water removal furnace section, unit: g; H i2 : The amount of water discharged from the coating of the current strip by the i-th exhaust pipe from the time when the head of the strip arrives at the end of the rapid water removal furnace section to the time when the tail of the strip arrives at the furnace inlet, unit: g; H i3 : The amount of water discharged from the coating of the current strip by the i-th exhaust pipe from the tail to the furnace inlet to the tail to the end of the rapid water removal furnace section, unit: g; i: Serial number of the exhaust pipe of the rapid water removal furnace section; m: the total number of exhaust pipes set in the rapid water removal furnace section; Fi: flow rate per unit time in the exhaust pipe, unit: m 3 / s, L1: length of the rapid water removal furnace section, unit: m; L3: Strip length, unit: m; V: Strip running speed, unit: m / s; ρ: water vapor density, unit: g / m 3 , d: moisture content, unit: g / kg.

5. The method for online evaluation of the baking quality of a steel strip coating according to claim 3, characterized in that: The water discharge of the steel strip coating in the coating curing furnace section is determined according to the following formula: in, Hi=H i1 +H i2 +H i3 , In the above formula, Hn: The current water discharge of the steel strip coating in the coating curing furnace section, unit: g; c k : The drainage capacity coefficient of the current strip coating, which is related to the coating properties; c k-1 : Drainage capacity coefficient of the previous coil coating, related to the coating properties; c k+1 : The drainage capacity coefficient of the coating of the last coil of strip steel, which is related to the coating properties; H i1 : The amount of water discharged from the coating of the current coil by the i-th exhaust pipe from the time when the head reaches the beginning of the coating curing furnace section to the time when the head reaches the furnace outlet, unit: g; H i2 : The amount of water discharged from the coating of the current strip extracted by the i-th exhaust pipe from the time when the head of the strip reaches the furnace outlet to the time when the tail of the strip reaches the beginning of the coating curing furnace section, unit: g; H i3 : The amount of water discharged from the current strip coating by the i-th exhaust pipe from the time when the tail of the strip reaches the beginning of the coating curing furnace section to the time when the tail of the strip reaches the furnace outlet, unit: g; i: Serial number of the exhaust pipe of the coating curing furnace section; n: the total number of exhaust pipes set up in the coating curing furnace section; Fi: flow rate per unit time in the exhaust pipe, unit: m 3 / s; L1: length of the rapid water removal furnace section, unit: m; L2: length of coating curing furnace section, unit: m; L3: Strip length, unit: m; V: Strip running speed, unit: m / s; ρ: water vapor density, unit: g / m 3 , d: moisture content, unit: g / kg.

6. The method for online evaluation of the baking quality of a steel strip coating according to claim 2, characterized in that: When the water discharge of the strip in the rapid water removal furnace section exceeds the upper limit of the set interval, it is judged that the baking power is too large and the baking is excessive; When the water discharge of the strip in the rapid water removal furnace section is lower than the lower limit of the set interval, it is judged that the baking power is too small and the baking is insufficient; When the water discharge of the strip in the rapid water removal furnace section falls within the set range, the baking quality is judged to be qualified; When the water discharge of the strip in the coating curing furnace section falls within the set range, the baking quality is judged to be qualified, otherwise it is judged to be abnormal.

7. The method for online evaluation of the baking quality of steel strip coating according to claim 6, characterized in that: The setting range of the rapid water removal furnace section discharge volume is: The setting range of the water discharge of the coating curing furnace section is: In the above formula, S: overflow rate of theoretical moisture content of each coil per unit time, unit: g / s; V: strip speed, unit: m / s; L1: length of the rapid water removal furnace section, unit: m; L2: length of coating curing furnace section, unit: m; L3: Strip length, unit: m; k1, k2, k3, k4: adjustment coefficients, and satisfy 0.75≤k1<k2≤0.85, 0.05≤k3<k4≤0.

25.

8. The method for online evaluation of the baking quality of a steel strip coating according to claim 4 or 5, characterized in that: The flow rate value per unit time Fi in the exhaust pipe, which is substituted into the formula of each period, is represented by the average value of the flow monitor in this period; The moisture content d substituted into the formula for each time period is represented by the average value of the dew point monitor within that time period.

9. The method for online evaluation of the baking quality of steel strip coating according to claim 8, characterized in that: The moisture content d at each collection time is determined based on the corresponding collected dew point value through the following formula: d=3.703+0.286×D+9.164×10 -3 ×D 2 +1.446×10 -4 ×D 3 +1.741×10 -6 ×D 4 +5.195×10 -8 ×D 5 In the above formula, d: moisture content, unit: g / kg; D: Detection value of dew point meter, ℃.

10. A method for controlling the baking of a steel strip coating, characterized in that: Feedback regulation of the burner power is established by monitoring the actual water discharge of the strip coating during the baking process.

11. A method for controlling baking of a steel strip coating according to claim 10, characterized in that: The feedback regulation is composed of feedback regulation of the rapid water removal furnace section and feedback regulation of the coating curing furnace section.

12. A method for controlling baking of a steel strip coating according to claim 11, characterized in that: An exhaust pipe is set beside the burner, and a flow monitor and a dew point monitor are respectively set on the exhaust pipe. The drainage volume is calculated based on the gas flow and dew point values ​​monitored in each exhaust pipe. The feedback adjustment of the rapid water removal furnace section accordingly includes the following steps: S11: Calculate the amount of water that is drawn into each exhaust pipe from the time when the head of the current strip arrives at the furnace inlet to the time when the tail of the strip arrives at the end of the rapid water removal furnace section; S12: summing up the water discharge of each exhaust pipe, and then comparing the calculated result with the theoretical water discharge. If the water discharge is greater than the theoretical water discharge, the baking power of the next roll of steel strip is reduced; if the water discharge is less than the theoretical water discharge, the baking power of the next roll of steel strip is increased; otherwise, the existing power is maintained. The feedback adjustment of the coating curing furnace section accordingly includes the following steps: S21: Calculate the amount of water that is drawn into each exhaust pipe from the time when the head of the current strip arrives at the beginning of the coating curing furnace section to the time when the tail of the strip arrives at the furnace outlet; S22: summing up the water discharge of each exhaust pipe, and then comparing the calculated result with the theoretical water discharge. If it is greater than the theoretical water discharge, the baking power of the next roll of strip steel is reduced; if it is less than the theoretical water discharge, the baking power of the next roll of strip steel is increased; otherwise, the existing power is maintained.

13. A method for controlling baking of a steel strip coating according to claim 11, characterized in that: The theoretical water discharge used to compare with the actual discharge of the rapid water removal furnace section and the theoretical water discharge used to compare with the actual discharge of the coating curing furnace section are both interval values. The theoretical water discharge range used for comparison with the actual water discharge of the rapid water removal furnace section is: The theoretical water discharge range used to compare with the actual water discharge of the coating curing furnace section is: In the above formula, S: overflow rate of theoretical moisture content of each coil per unit time, unit: g / s; V: strip speed, unit: m / s; L1: length of the rapid water removal furnace section, unit: m; L2: length of coating curing furnace section, unit: m; L3: Strip length, unit: m; k1, k2, k3, k4: adjustment coefficients, and satisfy 0.75≤k1<k2≤0.85, 0.05≤k3<k4≤0.

25.

14. A method for controlling baking of a steel strip coating according to claim 11, characterized in that: The drainage volume of each exhaust pipe installed in the rapid water removal furnace section is determined according to the following formula: Hi=H i1 +H i2 +H i3 ,in, In the above formula, c k : The drainage capacity coefficient of the current strip coating, which is related to the coating properties; c k-1 : Drainage capacity coefficient of the previous coil coating, related to the coating properties; c k+1 : The drainage capacity coefficient of the coating of the last coil of strip steel, which is related to the coating properties; H i1 : The amount of water discharged from the coating of the current strip by the i-th exhaust pipe from the time when the head of the strip arrives at the furnace inlet to the time when the head of the strip arrives at the end of the rapid water removal furnace section, unit: g; H i2 : The amount of water discharged from the coating of the current strip by the i-th exhaust pipe from the time when the head of the strip arrives at the end of the rapid water removal furnace section to the time when the tail of the strip arrives at the furnace inlet, unit: g; H i3 : The amount of water discharged from the coating of the current strip by the i-th exhaust pipe from the tail to the furnace inlet to the tail to the end of the rapid water removal furnace section, unit: g; i: Serial number of the exhaust pipe of the rapid water removal furnace section; m: the total number of exhaust pipes set in the rapid water removal furnace section; Fi: flow rate per unit time in the exhaust pipe, unit: m 3 / s, L1: length of the rapid water removal furnace section, unit: m; L3: Strip length, unit: m; V: Strip running speed, unit: m / s; ρ: water vapor density, unit: g / m 3 , d: moisture content, unit: g / kg.

15. The method for controlling baking of a steel strip coating according to claim 11, characterized in that: The drainage volume of each exhaust pipe installed in the coating curing furnace section is determined according to the following formula: Hi=H i1 +H i2 +H i3 ,in, In the above formula, c k : The drainage capacity coefficient of the current strip coating, which is related to the coating properties; c k-1 : Drainage capacity coefficient of the previous coil coating, related to the coating properties; c k+1 : The drainage capacity coefficient of the coating of the last coil of strip steel, which is related to the coating properties; H i1 : The amount of water discharged from the current steel strip coating by the i-th exhaust pipe from the time when the head reaches the beginning of the coating curing furnace section to the time when the head reaches the furnace outlet, unit: g; H i2 : The amount of water discharged from the coating of the current strip extracted by the i-th exhaust pipe from the time when the head of the strip reaches the furnace outlet to the time when the tail of the strip reaches the beginning of the coating curing furnace section, unit: g; H i3 : The amount of water discharged from the current strip coating by the i-th exhaust pipe from the time when the tail of the strip reaches the beginning of the coating curing furnace section to the time when the tail of the strip reaches the furnace outlet, unit: g; i: Serial number of the exhaust pipe of the coating curing furnace section; Fi: flow rate per unit time in the exhaust pipe, unit: m 3 / s; L1: length of the rapid water removal furnace section, unit: m; L2: length of coating curing furnace section, unit: m; L3: Strip length, unit: m; V: Strip running speed, unit: m / s; ρ: water vapor density, unit: g / m 3 , d: moisture content, unit: g / kg.

16. A method for controlling baking of a steel strip coating according to claim 14 or 15, characterized in that: The flow rate value per unit time Fi in the exhaust pipe, which is substituted into the formula of each period, is represented by the average value of the flow monitor in this period; The moisture content d substituted into the formula for each time period is represented by the average value of the dew point monitor within that time period.

17. A method for controlling baking of a steel strip coating according to claim 16, characterized in that: The moisture content d at each collection time is determined based on the corresponding collected dew point value through the following formula: d=3.703+0.286×D+9.164×10 -3 ×D 2 +1.446×10 -4 ×D 3 +1.741×10 -6 ×D 4 +5.195×10 -8 ×D 5 In the above formula, d: moisture content, unit: g / kg; D: Detection value of dew point meter, ℃.

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