A temperature prediction method for continuous annealing water mist cooling process section

Abstract

The application discloses a continuous annealing water mist cooling process section temperature prediction method, comprising the following steps: obtaining process parameters and field feedback data of a water mist cooling section equipment; calculating the relationship between specific heat capacity, density and strip steel temperature; calculating the strip steel temperature after heat dissipation from the end point of the slow cooling section to the start point of the water mist cooling section; calculating the relationship between the heat exchange coefficient of the strip steel and the strip steel temperature in the water mist cooling process; calculating the cooling amount of the strip steel; calculating the heat exchange correction coefficient; calculating the actual heat exchange coefficient; calculating the temperature of the strip steel after passing through the water mist cooling section; and calculating the final temperature after heat dissipation from the end point of the water mist cooling section to the outlet of the unit. The application combines the water mist cooling equipment and utilizes the related knowledge of heat dissipation principle to predict the temperature change in the water mist cooling process, which is beneficial to effectively setting the cooling capacity of the water mist cooling equipment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of continuous annealing, and particularly relates to a temperature prediction method for a water mist cooling process section of continuous annealing. BACKGROUND

[0002] The water mist cooling equipment is applied to the fast cooling process section of the strip steel continuous annealing, and can meet the production requirement of ultra-high strength steel and has the advantage of fast cooling speed.

[0003] At present, there is no mature water mist cooling equipment at home and abroad, and the temperature regulation on site is only based on the production situation on site to adjust the number of spray beams and the opening degree of the nozzles to regulate the temperature, but this adjustment method has a certain hysteresis. SUMMARY

[0004] The present application aims to provide a method for predicting the temperature of the water mist cooling process section of the strip steel in the continuous annealing process, so as to well predict the temperature at the cooling end of the strip steel and facilitate the adjustment of the cooling capacity.

[0005] In order to achieve the above technical purpose, the present application adopts the following technical scheme: a temperature prediction method for a water mist cooling process section of continuous annealing, characterized in that it comprises the following steps:

[0006] (A) obtaining the process parameters and the on-site feedback data of the water mist cooling section equipment, including: the number n of the opened spray beams, the running speed v of the strip steel, the width B of the strip steel, the thickness h0 of the strip steel, the length l of the water mist cooling section, the mass flow density v of the cooling water s , the end temperature T sc1 of the strip steel in the slow cooling section, and the temperature T w of the cooling water.

[0007] (B) obtaining the relationship C p , ρ between the specific heat capacity, the density and the temperature of the strip steel by using the data obtained from the enthalpy-temperature curve.

[0008]

[0009] (C) calculating the temperature T1 of the strip steel after the heat dissipation from the end of the slow cooling section to the start of the water mist cooling section according to the relationship between the temperature drop and the natural heat dissipation, wherein k is the heat dissipation coefficient, ε is the blackness constant, and σ is the Boltzmann constant.

[0010]

[0011] (D) According to the principle of water mist cooling heat transfer, the heat transfer coefficient is measured to obtain the relationship between the heat transfer coefficient of the strip and the strip temperature during the water mist cooling process h c1 , where ΔT = TT w .

[0012]

[0013] (E) Due to the deviation of nozzle position and height in actual installation, the heat transfer coefficient obtained by theoretical calculation deviates from the actual production, thus affecting the accuracy of plate temperature prediction. The water mist heat transfer coefficient mechanism model is modified using the measured strip outlet temperature. According to the strip specifications and water mist parameters, the theoretical cooling amount Q of the strip is calculated. strip_cool , Actual cooling amount of strip Q WFC , where T fc1 is the measured value of strip temperature, C p0 , ρ0 is the specific heat capacity and density of the strip at the starting point of water mist cooling, C p1 , ρ1 is the specific heat capacity and density of the strip at the end point of water mist cooling.

[0014] Q strip_cool =(C p0 ρ0T fc1 -C p1 ρ1T1)h0Bv s

[0015]

[0016] (F) According to the theoretical cooling amount Q of the strip strip_cool , Actual cooling amount of strip Q WFC , calculate the heat transfer correction coefficient C hc :

[0017]

[0018] (G) Based on the heat transfer correction coefficient C obtained in (D) hc , calculate the actual heat transfer coefficient h c :

[0019] h c =C hc ·h c1

[0020] (H) In the water mist cooling section, according to the heat exchange principle, the temperature T2 of the strip after the water mist cooling section is calculated, where

[0021]

[0022] (I) Calculate the final temperature T0 of the water mist cooling section end point to the unit outlet after heat dissipation:

[0023]

[0024] Wherein, T2 is the temperature of the strip after the water mist cooling section, k is the heat dissipation coefficient, ε is the blackness constant, σ is the Boltzmann constant, C p is the specific heat capacity of the strip, ρ is the density of the strip, h0 is the thickness of the strip. T0 is the predicted temperature.

[0025] The beneficial effects of the present application are: using the method of the present application, before the strip enters the cooling section, the cooling end temperature can be predicted according to the operation of the water mist cooling equipment, and the cooling capacity of the water mist cooling equipment can be effectively set.

[0026] The application of the present application to the water mist cooling equipment of a certain continuous annealing unit rapid cooling section can improve the output of the unit and avoid the problem that the product does not reach the set temperature due to different cooling capacities. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a flow chart of the continuous annealing water mist cooling process temperature prediction method of the present application.

[0028] Figure 2 It is a water mist cooling process schematic diagram in the present application.

[0029] Figure 3 It is the predicted value and the measured value of the transverse distribution of the strip outlet temperature in Example 1 in the present application.

[0030] Figure 4 It is the predicted value and the measured value of the transverse distribution of the strip outlet temperature in Example 2 in the present application. DETAILED DESCRIPTION

[0031] In order to further illustrate the application process of the present application, taking the production performance of the water mist cooling process section of a certain continuous annealing production line as an example, the application of the present method in the field is described in detail.

[0032] Example 1

[0033] As Figure 1 shown, the continuous annealing water mist cooling process section temperature prediction method of the present application has the following implementation steps:

[0034] Step (A): Obtain the process parameters and on-site feedback data of the water mist cooling section equipment, including: the number of opened spray beams n = 2, the strip running speed v = 51 mm / min, the strip width B = 1227 mm, the strip thickness h0 = 1.4 mm, the water mist cooling section length l = 3500 mm, the cooling water mass flow density v s=50Kg / (m 2 ·s), the end temperature of the strip slow cooling section T sc1 =734℃, cooling water temperature T w =26℃.

[0035] Step (B): Using the data obtained from the enthalpy-temperature curve, obtain the specific heat capacity C p , the relationship between density ρ and strip temperature:

[0036]

[0037] Step (C): Based on the relationship between temperature drop and natural heat exchange, the temperature of the strip after heat dissipation from the end of the slow cooling section to the starting point of the water mist cooling section is calculated, where k is the heat dissipation coefficient, ε is the blackness constant, and σ is the Boltzmann constant.

[0038]

[0039] According to calculation, the strip temperature T1 is 733.661℃ after heat dissipation from the end of the slow cooling section to the starting point of the water mist cooling section.

[0040] Step (D): According to the water mist cooling heat transfer principle, the heat transfer coefficient is measured to obtain the relationship between the heat transfer coefficient of the strip and the strip temperature during the water mist cooling process h c1 , where ΔT = TT w .

[0041]

[0042] Calculated

[0043] Step (E): Due to the deviation of nozzle position and height in actual installation, the heat transfer coefficient obtained according to theoretical calculation deviates from the actual production, thus affecting the accuracy of plate temperature prediction. The water mist heat transfer coefficient mechanism model is modified using the measured strip outlet temperature. According to the strip specifications and water mist parameters, the theoretical cooling amount Q of the strip is calculated. strip_cool , Actual cooling amount of strip Q WFC , where T fc1 =140℃、C p0 , ρ0 is the specific heat capacity and density of the strip at the starting point of water mist cooling, C p1 , ρ1 is the specific heat capacity and density of the strip at the end point of water mist cooling.

[0044] Q strip_cool =(C p0 ρ0T fc1 -C p1 ρ1T1)h0Bv s

[0045]

[0046] Calculated Q strip_cool = 2.785 x 10 11 J, Q WFC = 3.2 x 10 11 J.

[0047] Step (F): According to the strip theoretical cooling amount Q strip_cool , the strip actual cooling amount Q WFC , the heat exchange correction coefficient C hc is calculated:

[0048]

[0049] Calculated C hc = 0.86.

[0050] Step (G): According to the heat exchange correction coefficient C hc obtained in step (D), the actual heat exchange coefficient h c is calculated:

[0051] h c = C hc · h c1

[0052] Calculated h = 0.86 x 0.5 = 0.43 W / m2K

[0053] Step (H): According to the heat exchange principle, the temperature T2 of the strip after passing through the water mist cooling section is calculated, wherein

[0054]

[0055] Calculated T2 = 136.82°C.

[0056] Step (I): The final temperature T0 after passing through the water mist cooling section and then passing through the heat dissipation at the exit of the unit is calculated:

[0057]

[0058] Calculated T0 = 135.634°C, and the calculation is completed; T0 is the predicted temperature at the end of cooling.

[0059] In this example, the strip water mist cooling process section temperature is predicted by theoretical calculation, and the actual measured temperature is compared to obtain Figure 3 the predicted value and the measured value of the transverse distribution of the strip exit temperature.

[0060] Example 2

[0061] As Figure 1As shown, the present application is a continuous annealing water mist cooling process segment temperature prediction method, the implementation steps are as follows:

[0062] Step (A): Obtain the process parameters and field feedback data of the water mist cooling segment equipment, including: the number of opened spray beams n = 2, the strip running speed v = 81 mm / min, the strip width B = 1233 mm, the strip thickness h0 = 1.5 mm, the water mist cooling segment length l = 3500 mm, the cooling water mass flow density v s = 35 Kg / (m 2 ·s), the strip slow cooling segment endpoint temperature T sc1 = 751℃, the cooling water temperature T w = 26℃.

[0063] Step (B): Using the data obtained from the enthalpy-temperature curve, the relationship between specific heat capacity C p , density p and strip temperature is obtained:

[0064]

[0065] Step (C): According to the relationship between temperature drop and natural heat dissipation, the strip temperature T1 after heat dissipation from the slow cooling segment endpoint to the water mist cooling segment starting point is calculated:

[0066]

[0067] The calculated strip temperature T1 after heat dissipation from the slow cooling segment endpoint to the water mist cooling segment starting point is 750.65℃.

[0068] Step (D): According to the water mist cooling heat exchange principle, the heat exchange coefficient is measured, and the relationship between the strip heat exchange coefficient and the strip temperature in the water mist cooling process h c1 is obtained, where ΔT = T-T w .

[0069]

[0070] The calculated

[0071] In step (E): Due to the deviation of nozzle position and height in actual installation, the deviation between the theoretically calculated heat exchange coefficient and the actual production affects the plate temperature prediction accuracy. The water mist heat exchange coefficient mechanism model is corrected using the measured outlet strip temperature. According to the strip specification parameters and water mist parameters, the strip theoretical cooling amount Q strip_cool , the strip actual cooling amount Q WFC is calculated, where T fc1 = 385℃, C p0 , p0 are the specific heat capacity and density of the strip at the water mist cooling starting point, C p1ρ1 is the specific heat capacity and density of the strip at the end of the water mist cooling.

[0072] Q strip_cool = (C p0 ρ0T fc1 - C p1 ρ1T1) h0Bv s

[0073]

[0074] Calculated Q strip_cool = 2.0993 x 10 11 J, Q WFC = 2.282 x 10 11 J.

[0075] In step (F): according to the theoretical cooling amount Q strip_cool of the strip, the actual cooling amount Q WFC of the strip, the heat exchange correction coefficient C hc is calculated:

[0076]

[0077] Calculated C hc = 0.92.

[0078] Step (G): according to the heat exchange correction coefficient C hc obtained in step (D), the actual heat exchange coefficient h c is calculated:

[0079] h c = C hc · h c1

[0080] Calculated

[0081] Step (H): according to the heat exchange principle, the temperature T2 of the strip after passing through the water mist cooling section is calculated, wherein

[0082]

[0083] Calculated T2 = 403.01 °C.

[0084] In step (I): the final temperature T0 after heat dissipation from the end of the water mist cooling section to the outlet of the unit is calculated:

[0085]

[0086] Calculated T0 = 402.4 °C, the calculation is completed; T0 is the predicted temperature at the end of the cooling.

[0087] The present example predicts the temperature of the strip water mist cooling process section by theoretical calculation, and compares the predicted value with the actual measured temperature to obtain Figure 4 The predicted value and the actual measured value of the transverse distribution of the strip outlet temperature.

[0088] The above content is only used to illustrate the technical solutions of the present application, and simple modifications or equivalent replacements of the technical solutions of the present application by those skilled in the art do not deviate from the essence and scope of the technical solutions of the present application.

Claims

1. A method for predicting the temperature of a continuous water mist cooling process section, characterized in that: The process includes the following steps: (A) Obtain the process parameters and on-site feedback data of the water mist cooling section equipment, including: number of open spray beams n, strip running speed v, strip width B, strip thickness h0, water mist cooling section length l, cooling water mass flow density v s , the end temperature of the strip slow cooling section T sc1 , cooling water temperature T w ; (B) Using the strip enthalpy and temperature curve, and the strip density and temperature curve, the strip specific heat capacity C is fitted. p , Relationship between strip density ρ and strip temperature T: (C) According to the relationship between temperature drop and natural heat dissipation, the strip temperature T1 after heat dissipation from the end of the slow cooling section to the starting point of the water mist cooling section is calculated. Where k is the heat dissipation coefficient, ε is the blackness constant, and σ is the Boltzmann constant; (D) According to the principle of water mist cooling heat transfer, the heat transfer coefficient is measured to obtain the relationship between the heat transfer coefficient of the strip and the strip temperature during the water mist cooling process h c1 , Where, ΔT = TT w ; (E) Use the measured outlet strip temperature to modify the water mist heat transfer coefficient mechanism model; calculate the theoretical strip cooling amount Q according to the strip specifications and water mist parameters strip_cool , Actual cooling amount of strip Q WFC , Q strip_cool =(C p0 ρ0T fc1 -C p1 ρ1T1)h0Bv s Among them, T fc1 is the measured value of strip temperature, C p0 , ρ0 is the specific heat capacity and density of the strip at the starting point of water mist cooling, C p1 , ρ1 is the specific heat capacity and density of the strip at the end of water mist cooling; (F) According to the theoretical cooling amount Q of the strip strip_cool , Actual cooling amount of strip Q WFC , calculate the heat transfer correction coefficient C hc : (G) According to the heat transfer correction coefficient C obtained in step (D) hc , calculate the actual heat transfer coefficient h c : h c =C hc ·h c1 Among them, h c1 is the relationship between the heat transfer coefficient of the strip and the strip temperature during the water mist cooling process; (H) In the water mist cooling section, according to the heat exchange principle, the temperature T2 of the strip after the water mist cooling section is calculated. in, l is the length of the water mist cooling section, v is the running speed of the strip; (I) Calculate the final temperature T0 from the end of the water mist cooling section to the unit outlet after heat dissipation: Among them, T2 is the temperature of the strip after the water mist cooling section, k is the heat dissipation coefficient, ε is the blackness constant, σ is the Boltzmann constant, C p is the specific heat capacity of the strip, ρ is the density of the strip, and h0 is the thickness of the strip.

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