A method for controlling the shape of a plate at the outlet of a continuous annealing water mist cooling process section

Abstract

The application discloses a kind of continuous annealing water mist cooling process section outlet plate shape control method, first obtain the process parameters and field feedback data of water mist cooling section equipment, determine the relationship of specific heat capacity, density and strip temperature, determine the relationship of strip heat exchange coefficient and strip temperature, calculate the actual cooling capacity of strip theoretical cooling capacity and, and the actual heat exchange coefficient of heat exchange correction coefficient;Then temperature adjustment quantity, adjusted cooling water mass flow density, adjusted nozzle opening are calculated in turn;Finally, the final plate shape of outlet is calculated and whether the plate shape distribution is up to standard is judged, and corresponding processing is carried out according to the judgment result.The application combines continuous annealing unit water mist cooling equipment, and adjusts strip deformation by temperature difference, specifically, the opening of each nozzle is adjusted to realize the accurate control of strip plate shape at the outlet of continuous annealing unit water mist cooling section, so as to ensure the quality and performance of finished strip, and reduce the instability of subsequent production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of water mist cooling in continuous annealing process, and particularly relates to a method for controlling the shape of a strip at the outlet of a water mist cooling process section in a continuous annealing unit. BACKGROUND

[0002] The water mist cooling process is the main method for cooling the strip in the rapid cooling section of a continuous annealing unit. The water mist cooling process can meet the requirements of the cooling rate of ultra-high strength steel. The distribution of the temperature of the strip during the cooling process not only affects the shape of the strip but also affects the uniformity of the properties of the product. The shape of the strip is an important evaluation criterion for the quality of the strip. When controlling the shape of the strip while ensuring the temperature of the strip, the change in the internal stress of the strip when the temperature of the strip decreases from high to low is utilized to control the temperature of the strip by adjusting the opening of the nozzles, so as to control the redistribution of the internal stress of the strip, which can effectively reduce the shape of the strip and ensure that the transverse distribution of the temperature does not cause the uniformity of the distribution of the properties of the strip.

[0003] The control of the temperature and the shape of the strip by the water mist cooling is mainly completed by the nozzles. The position of the spray beam, the number of the nozzles and the opening of the nozzles are used to control the distribution of the water flow, and then the temperature and the shape of the strip are adjusted. In order to ensure the uniformity of the temperature of the strip, the change in the temperature should be considered when adjusting the shape of the strip. The change in the difference in the opening of the nozzles on both sides of the strip should not cause the change in the total opening of the nozzles, otherwise the transverse non-uniformity of the temperature of the strip will occur, which will affect the uniformity of the distribution of the properties of the strip, and even other defects of the strip will occur.

[0004] A Chinese patent with the publication number CN115874040A and the title of a strip crown control method for a continuous annealing water mist cooling system discloses a method for adjusting the shape of the strip by the feedback of the shape value of the outlet shape gauge. The adjustment is relatively slow because the shape of the strip can only be adjusted step by step when the shape of the strip is too large. SUMMARY

[0005] The present application aims to provide a method for controlling the shape of the strip at the outlet of the water mist cooling process section of a continuous annealing unit, which can directly calculate the specific adjustment amount and further control the shape of the strip in combination with the feedback, while avoiding the non-compliance caused by the excessive deviation of the shape of the strip from the set value.

[0006] In order to achieve the above technical purpose, the present application adopts the following technical solution: a method for controlling the shape of the strip at the outlet of a water mist cooling process section, characterized in that it comprises the following steps:

[0007] (A) According to the arrangement of the water mist cooling section nozzle, the strip steel width direction is divided into units, a discrete model is established, and the strip steel is evenly divided into 5 zones in the width direction according to the distribution of the nozzle, denoted as region j, j = 1 ~ 5, there are eight rows of spray beams arranged longitudinally, denoted as i, i = 1 ~ 8, the same nozzles are arranged on the upper and lower surfaces of the strip steel, denoted as the upper surface as the alpha surface and the lower surface as the beta surface;

[0008] (B) Obtain the process parameters and field feedback data of the water mist cooling section equipment, including: the number of opened spray beams N, the opening degree K of the jth nozzle of the ith spray beam i,j , the strip steel running speed v, the strip steel width B, the strip steel thickness h0, the water mist cooling section length l, the strip steel water mist cooling section starting temperature T sc1 , the cooling water temperature T w , the upper limit of the cooling water mass flow density V smax , the distance between adjacent nozzles d, and the field process value ε; wherein the field process value ε represents the critical value for determining whether the plate shape meets the production requirements, which is related to the steel grade, incoming plate shape and annealing environment, and is set according to the actual situation.

[0009] (C) According to the strip steel specification, the effective nozzle number n corresponding to the strip steel is calculated:

[0010]

[0011] (D) According to the temperature distribution T j at the cooling outlet, the actual heat transfer coefficient h cj is calculated:

[0012]

[0013] Wherein, C p , ρ is the specific heat capacity and density of the strip steel,

[0014] (E) According to the heat transfer principle of water mist cooling, the heat transfer coefficient is measured to obtain the relationship between the heat transfer coefficient h c1j of the strip steel in the water mist cooling process and the cooling water mass flow density V s ,

[0015]

[0016] Wherein, ΔT = T-T w , a2, b, c are relationship coefficients;

[0017] (F) The heat transfer coefficient is corrected to obtain the correction coefficient C hcj , and the relationship between the heat transfer coefficient h cj ' of the strip steel in the actual water mist cooling process and the cooling water mass flow density is calculated:

[0018]

[0019] (G) measure the current strip shape value distribution l j , calculate the temperature adjustment requirement ΔT j , and calculate the temperature distribution T j ′ that should be reached after adjustment, wherein γ is the linear expansion coefficient:

[0020]

[0021] (H) according to (D), calculate the heat exchange coefficient h cj ′ of the strip required to meet the outlet temperature;

[0022] (I) according to (F), calculate the mass flow density V s ′ of the cooling water;

[0023]

[0024] (J) calculate the opening K i,j ′ after adjustment, and issue the opening data for adjustment:

[0025]

[0026] (K) collect the strip shape distribution l j ′ after adjustment after 30s, and calculate the strip shape distribution target function G(X):

[0027]

[0028] (L) determine whether the strip shape G(X)≤ε is true, if true, the calculation is ended, if not true, turn to (G).

[0029] The beneficial effects of the present application are: the method of the present application is designed for the purpose of meeting the metal organization standard of the strip outlet, and an outlet strip shape control method suitable for the water mist cooling process of the continuous annealing unit is designed, which greatly improves the control effect of the outlet strip shape of the water mist cooling section.

[0030] The present application is applied to the water mist cooling equipment of a certain continuous annealing unit, the strip deformation is adjusted by using the temperature difference, specifically, the specific adjustment amount is directly calculated, the opening of each nozzle is adjusted to realize the accurate control of the outlet strip shape of the water mist cooling section of the continuous annealing unit, which can effectively improve the finished strip quality and bring economic benefits to the enterprise. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is the general flow chart of the present application.

[0032] Figure 2It is a discrete model of the strip steel under the action of a single spray beam in the present invention.

[0033] Figure 3 This is a schematic diagram of the nozzles corresponding to the α and β sides of the steel strip on the water mist cooling equipment in the rapid cooling section of the present invention. DETAILED DESCRIPTION

[0034] In order to further illustrate the application process of the technology of the present invention, the production performance of the water mist cooling process section of a continuous annealing production line is taken as an example to explain in detail the application of this method in the field.

[0035] Example 1

[0036] like Figure 1 As shown, the present invention provides a method for controlling the plate shape in a continuous water mist cooling process section, and the implementation steps are as follows:

[0037] Step (A) constructs a discrete model of the steel strip under the action of double-sided spray beams, determines the number of nozzles acting on the steel strip, divides the steel strip into corresponding units according to the location of the nozzles, and evenly divides the steel strip into 5 zones in the width direction according to the distribution of the nozzles, denoted as zone j, j = 1 to 5. There are eight rows of spray beams arranged longitudinally, denoted as i, i = 1 to 8. The same nozzles are arranged on both the upper and lower surfaces of the steel strip, denoted as α surface and the lower surface as β surface. The nozzles on both sides of the steel strip adjust the temperature of the corresponding unit strip, thereby adjusting the strip shape caused by the temperature, such as Figure 2 .

[0038] Step (B) is to obtain the process parameters and on-site feedback data of the water mist cooling section equipment, including: the number of open spray beams M = 2, the opening degree of each spray beam nozzle K i,j See Table 1, strip running speed v = 51m / min, strip width B = 1248mm, strip thickness h0 = 1.1mm, water mist cooling section length l = 12000mm, strip water mist cooling section starting temperature T sc1 , cooling water temperature T w =26℃, upper limit of cooling water mass flow density V smax =60Kg / (m 2 ·s), the distance between adjacent nozzles d = 350 mm; the on-site process value ε = 10.

[0039] Table 1 Opening K of each nozzle in each spray beam after adjustment in Example 1 i,j '

[0040]

[0041] Note: 1 in Table 1 and Table 2 α , 2 α The two rows of spray beams that are opened correspond to the nozzles on the α surface of the strip; 1 β , 2 βThe nozzles corresponding to the strip β surface for the two rows of spray beams opened.

[0042] Step (C), according to the strip specification, calculate the effective nozzle number n corresponding to the strip:

[0043]

[0044] After calculation: n = 5.

[0045] According to the temperature distribution T of the cooling outlet j ={354, 359, 357, 359, 356}, the actual heat transfer coefficient h is calculated cj , where C p , ρ is the specific heat capacity and density of the strip,

[0046]

[0047] After calculation: h cj ={1283.519, 1256.668, 1267.36, 1256.668, 1272.73}.

[0048] Step (E), according to the heat transfer principle of water mist cooling, measure the heat transfer coefficient to obtain the theoretical heat transfer coefficient h c1j of the strip in the water mist cooling process:

[0049]

[0050] After calculation h c1j ={2053.631, 2010.669, 2027.776, 2010.669, 2036.368}.

[0051] Step (F), correct the heat transfer coefficient to obtain the correction coefficient C hcj , and calculate the relationship between the heat transfer coefficient h cj ′ of the strip in the actual water mist cooling process and the mass flow density of the cooling water:

[0052]

[0053] After calculation

[0054] Step (G), measure the current unit outlet plate shape value distribution l j ={5, 6, 10, 7, 5}(I), calculate the required temperature adjustment ΔT j , and calculate the temperature distribution T j ′ that should be reached after adjustment, where γ is the linear expansion coefficient:

[0055]

[0056] Calculated

[0057] ΔT j = {4.950495, 5.940594, 9.90099, 6.930693, 4.950495} °C

[0058] T j ' = {356.4752, 361.9703, 361.9505, 362.4653, 358.4752} °C.

[0059] Step (H), calculate the heat transfer coefficient h required to meet the outlet temperature cj ';

[0060] h cj ' = {2032.282, 1985.452, 1985.616, 1981.271, 2015.148}.

[0061] Step (I), according to (F) to calculate the mass flow density V of cooling water s ';

[0062] V s ' = {32.2, 35.13, 34.6, 35.28, 32.28}.

[0063] Step (J), calculate the adjusted opening K i,j ', and issue the opening data for adjustment:

[0064]

[0065] Table 2 Opening K of each nozzle in each spray beam after adjustment in Example 1 i,j '

[0066]

[0067] Step (K), collect the adjusted strip shape distribution l j ' = {3, 4, 7, 3, 2} (I), and calculate the strip shape distribution target function G(X):

[0068]

[0069] Calculated G(X) = 2.96.

[0070] Step (L), the strip shape distribution target function G(X) ≤ ε is established, and the calculation is completed.

[0071] Example 2:

[0072] AsFigure 1 The method for controlling the strip shape in the continuous annealing water mist cooling process section is shown in the following steps:

[0073] Step (A), a discrete model of the strip steel under the action of the double-sided spray beam is constructed, the number of nozzles acting on the strip steel is determined, the strip steel is divided into corresponding units according to the positions of the nozzles, the strip steel is evenly divided into five zones in the width direction of the strip steel, denoted as zone j, j = 1 ~ 5, there are eight rows of spray beams arranged longitudinally, denoted as i, i = 1 ~ 8, the same nozzles are arranged on the upper and lower surfaces of the strip steel, denoted as the upper surface α and the lower surface β. The temperature of the corresponding unit strip steel is adjusted by the nozzles on both sides of the strip steel, and then the strip shape caused by the temperature is adjusted, such as Figure 2 ;

[0074] Step (B), the process parameters and on-site feedback data of the water mist cooling section equipment are obtained, including: the number of opened spray beams M = 2, the opening degree K i,j of the nozzles of each spray beam, the running speed v = 91 m / min of the strip steel, the width B = 1248 mm of the strip steel, the thickness h0 = 1.2 mm of the strip steel, the length l = 12000 mm of the water mist cooling section, the upper limit V smax of the cooling water mass flow density = 60 Kg / (m 2 ·s), the distance d = 350 mm between adjacent nozzles; the starting temperature T sc1 of the strip steel in the water mist cooling section = 675℃, the cooling water temperature T w = 26℃; the on-site process value ε = 10.

[0075] Table 3 Opening degree K i,j of each nozzle in each spray beam of Example 2

[0076]

[0077] Note: In Table 3 and Table 4, 1 α , 2 α are the nozzles on the α surface of the strip steel corresponding to the two opened rows of spray beams; 1 β , 2 β are the nozzles on the β surface of the strip steel corresponding to the two opened rows of spray beams.

[0078] Step (C), according to the specifications of the strip steel, the effective number of nozzles n corresponding to the strip steel is calculated:

[0079]

[0080] After calculation: n = 5.

[0081] Step (D), according to the temperature distribution T j ={456, 458, 449, 454, 456} at the cooling outlet, the actual heat transfer coefficient h cjwhere C p ρ is the specific heat capacity and density of the strip,

[0082]

[0083] h cj = {1450.047, 1433.701, 1507.862, 1466.469, 1450.047}.

[0084] Step (E), according to the heat exchange principle of water mist cooling, the heat exchange coefficient is measured to obtain the heat exchange coefficient h c1j of the strip in the theoretical water mist cooling process:

[0085]

[0086] h c1j = {2334.575, 2308.258, 2427.658, 2361.015, 2334.575}.

[0087] Step (F), the heat exchange coefficient is corrected to obtain the correction coefficient C hcj , and the relationship between the heat exchange coefficient h cj ′ of the strip in the actual water mist cooling process and the mass flow density of the cooling water is calculated:

[0088]

[0089] Step (G), measure the current strip shape value distribution l j = {4, 2, -8, 5, 3} (I), calculate the required temperature adjustment ΔT j , and calculate the temperature distribution T j ′ that should be reached after adjustment, where γ is the linear expansion coefficient:

[0090]

[0091] After calculation

[0092] ΔT j = {3.960396, 1.980198, -7.92079, 4.950495, 2.970297} ℃

[0093] T j ′ = {457.9802, 458.9901, 445.0396, 456.4752, 457.4851} ℃.

[0094] Step (H), according to (D), calculate the heat exchange coefficient h cj ′ required to meet the outlet temperature;

[0095] h cj ′ = {1433.862, 1425.637, 1540.998, 1446.156, 1437.902}.

[0096] Step (I), calculate the mass flow density V of cooling water according to (F) s ′;

[0097] V s ′ = {29.5, 29.76, 31.02, 29.4, 29.5}.

[0098] Step (J), calculate the adjusted opening K i,j ′ see Table 4, and issue the opening data for adjustment:

[0099]

[0100] Table 4 Opening K of each nozzle in each spray beam after adjustment in Example 2 i,j ′

[0101]

[0102] Step (K), collect the adjusted strip shape distribution l j ′ = {3, 1, -3, 3, 1} (I), and calculate the strip shape distribution target function G(X):

[0103]

[0104] G(X) = 4.8 after calculation.

[0105] Step (L), the strip shape distribution target function G(X) ≤ ε is established, and the calculation is completed.

[0106] The above is only used to illustrate the technical solutions of the present application, and the simple modification or equivalent replacement of the technical solutions of the present application by those skilled in the art does not deviate from the essence and scope of the technical solutions of the present application.

Claims

1. A method for controlling the outlet plate shape of a continuous water mist cooling process section, characterized in that: The steps include: (A) The strip width is divided into units based on the arrangement of the nozzles in the water mist cooling section. A discrete model is established. The strip width is evenly divided into five zones based on the distribution of the nozzles, denoted as zone j, where j = 1 to 5. Eight rows of spray beams are arranged longitudinally, denoted as i, where i = 1 to 8. (B) Obtain the process parameters and on-site feedback data of the water mist cooling section equipment, including: the number of open spray beams N, the opening K of the jth nozzle of the i-th row spray beam i,j , strip running speed v, strip width B, strip thickness h0, water mist cooling section length l, strip water mist cooling section starting temperature T sc1 , cooling water temperature T w , cooling water mass flow density upper limit V smax , the distance d between adjacent nozzles, the on-site process value ε; where the on-site process value ε represents the critical value for determining whether the plate shape meets the production requirements, and is related to the steel type, incoming plate shape, and annealing environment, and is set according to actual conditions; (C) According to the strip steel specifications, calculate the effective number of nozzles n corresponding to the strip steel: (D) According to the temperature distribution T of the cooling outlet j , calculate the actual heat transfer coefficient h cj : Among them, C p , ρ is the specific heat capacity and density of the strip, (E) According to the principle of water mist cooling heat transfer, the heat transfer coefficient is measured to obtain the theoretical heat transfer coefficient h of the strip during water mist cooling. c1j and cooling water mass flow density V s Relationship: Where ΔT = TT w , a2, b, c are relationship coefficients; (F) Correct the heat transfer coefficient to obtain the correction coefficient C hcj , and calculate the heat transfer coefficient h of the strip during the actual water mist cooling process cj The relationship between ′ and cooling water mass flow density: (G) Measure the current unit outlet flatness value distribution l j , calculate the temperature ΔT required for adjustment j , and calculate the temperature distribution T that the outlet should reach after adjustment j ′, where γ is the linear expansion coefficient: (H) Based on (D), calculate the heat transfer coefficient h of the strip required to meet the outlet temperature cj '; (I) Calculate the mass flow density V of cooling water based on (F) s '; (J) Calculate the opening K after adjustment i,j ', and at the same time send the opening data for adjustment: (K) Collect the adjusted plate shape distribution l after adjusting for 30s j ′, and calculate the strip shape distribution objective function G(X): (L) Determine whether the plate shape G(X)≤ε is true. If so, the calculation ends. If not, go to (G).

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