IF Steel Substrate Strip Rough Rolling Exit Temperature Control Method

Abstract

This invention relates to a method for controlling the exit temperature of IF steel ribbed strip roughing mill, belonging to the technical field of control methods specifically applicable to metal rolling mills. The method involves setting up an oscillation zone between the R1 and R2 mills in an existing rolling production line, and setting up one pass for R1, seven passes for R2, and a no-pass for the final pass of R2. Using an existing temperature calculation model of the rolling production line, the method reads the inlet temperature of the strip in the oscillation zone during the sixth pass of R2, iteratively calculating the oscillation time, the temperature drop of the strip from the inlet of the oscillation zone before R2 to the exit of R2, and the exit temperature T1 of the strip at R2. By gradually bringing T1 closer to the production requirement of the target exit temperature T0 of the roughing mill at R2, the actual oscillation time is determined and oscillation is executed, thereby controlling the roughing mill exit temperature to reach the production-specified target exit temperature.

Description

Technical Field

[0001] This invention relates to a method for ensuring that the roughing mill exit temperature meets production requirements during IF steel rib rolling, and belongs to the technical field of control methods specifically applicable to metal rolling mills. Background Technology

[0002] IF steel slurry rolling process as follows Figure 1 As shown: The strip steel passes through the furnace front roller table, descaling box, and R1 mill for rolling, and then undergoes reversible rolling on the R2 reversible mill. After reversible rolling, it enters the hot coil box for coiling. After coiling in the hot coil box, it is uncoiled only after the hot coil box scraper is in place. After uncoiling, it enters the finishing mill for rolling. Thermometers are generally placed at the entrance and exit of the R2 mill and the entrance of the finishing mill. In the area from the heating furnace to the exit of the R1 mill (entrance of the R2 mill), due to environmental factors and iron oxide scale on the surface of the strip steel, accurate measurement is not possible, therefore thermometers are not installed. The rolling temperature requirements for IF steel strip are as follows: the furnace exit temperature is about 1120°C, the finishing mill inlet temperature is ≤840°C, and after roughing, the strip temperature drops by 280°C before the finishing mill inlet to achieve the required inlet temperature of ≤840°C. Therefore, the target exit temperature of the roughing mill must be controlled at ≤860°C (the temperature drop between the pyrometer at the R2 exit of the roughing mill and the pyrometer at the finishing mill inlet is usually about 20°C).

[0003] For rolling lines without water cooling equipment, to achieve significant temperature reduction, a swing zone is typically added between the R1 and R2 mills. The roughing mill rolling pattern is set to 1+7, with the last pass skipped (i.e., 1 pass in R1, 6 passes in R2, and the 7th pass in R2 skipped). After the strip has rolled 7 passes, air cooling and thermal radiation are used to achieve swing cooling in the swing zone. During swinging, the operator observes the thermometer at the R2 inlet or outlet and manually stops the swing once the required temperature is reached. However, this control method cannot reliably guarantee that the actual roughing mill exit temperature reaches the target roughing mill exit temperature.

[0004] A Chinese patent with publication number CN111250545A discloses a control system and method for reducing the over-thickness rate of oscillating steel coils. This system and method address the problem of excessive thickness at the finishing mill exit when the strip oscillates. The solution is to recalculate and adjust the finishing mill inlet temperature based on the oscillation time. However, this adjustment of the finishing mill inlet temperature is not intended to make the actual finishing mill inlet temperature close to the target finishing mill inlet temperature. It only aims to prevent the finishing mill exit from being over-thick based on the oscillation time, and cannot guarantee that the roughing mill exit temperature meets the standard.

[0005] Chinese patent CN103990653A discloses a method for ensuring the accuracy of the finishing mill inlet temperature. This method calculates the roughing mill outlet temperature T2 based on the furnace exit temperature T0, and then calculates the roughing mill outlet temperature T1 based on FTO and speed. According to the method's specification, with an iteration cycle of 300ms and an upper limit of 180 iterations, the maximum oscillation time is 54 seconds and the maximum temperature drop is 82°C. However, the general requirement for the overall temperature drop in roughing milling is around 130°C, which fails to meet the roughing mill outlet temperature requirements for IF steel production. Summary of the Invention

[0006] The technical problem to be solved by this invention is: how to achieve the target exit temperature of roughing in the rolling of IF steel basalt strip.

[0007] The technical solution proposed by this invention to solve the above-mentioned technical problems is: a method for controlling the exit temperature of IF steel rib strip roughing mill, involving two roughing mill stations R1 and R2 in the rolling production line and the existing temperature calculation model of the rolling production line, and performing the following steps:

[0008] S1. Set the roughing mode of one pass for R1 and seven passes for R2, and let the seventh pass of R2 pass empty. Set the swing zone between the R1 mill and the R2 mill, and enter the swing zone after the R2 mill completes the sixth pass to start calculating the swing time and swinging.

[0009] S2. Read the temperature calculation model and calculate the inlet temperature T of the strip in the swing zone in the sixth pass of R2. 入口 ;

[0010] S3. Calculate the exit temperature T1 of the strip at R2 using the following formula (1) iteratively.

[0011] T1 = T_inlet - T_temperature drop (1),

[0012] In equation (1), T1 is the outlet temperature of the strip at R2 calculated iteratively, and T_temperature drop is the temperature drop of the strip from the inlet of the pre-swinging zone of R2 to the outlet of R2, calculated according to equation (2).

[0013] Temperature drop T = W * t1(2),

[0014] In equation (2), W is the temperature drop per unit time of the strip from the inlet to the outlet of R2 in the swing zone before R2, calculated by the temperature calculation model, and t1 is the swing time of the current iteration calculated by the iterative calculation, which is expressed as in equation (3).

[0015] t1=t10+(T10-T0)*G, (3),

[0016] In equation (3), T10 is the exit temperature of the strip at R2 calculated in the previous iteration, T0 is the target exit temperature of the roughing mill at R2 specified in production, G is a coefficient in seconds / ℃, and t10 is the oscillation time calculated in the previous iteration.

[0017] The temperature drop and T1 are calculated iteratively from the initial value according to the oscillation time.

[0018] S4. Compare T1 calculated in each iteration with T0.

[0019] If |T1-T0|≥1, then repeat step S3;

[0020] If |T1-T0| < 1, then stop the calculation, output the swing time t1 calculated in the current iteration as the swing time of the strip entering the swing zone, and execute the swing.

[0021] The beneficial effects of this invention are as follows: By linking the temperature drop Ttemperature drop calculated at the R2 exit of the strip with the set oscillation time t1, that is, by associating the calculated exit temperature T1 of the strip at R2 with the oscillation time t1, the oscillation time is iteratively calculated from an initial value to T1 and compared with the target exit temperature T0 specified for roughing mill R2. When the difference between the calculated T1 and T0 is large, the calculation of t1 and T1 continues iteratively. When the calculated T1 and T0 are close, the calculation stops and the current calculated oscillation time is output as the time for the strip to enter oscillation and oscillation is executed. Therefore, in the IF steel slab rolling process, the strip can be oscillated between R1 and R2 with an oscillation time close to the target exit temperature T0 specified for roughing mill, thereby controlling the roughing mill exit (R2 exit) temperature to reach the target exit temperature T0 specified for roughing mill as much as possible.

[0022] Furthermore, as is known, W in equation (2) is calculated by the temperature calculation model according to equation (4).

[0023]

[0024] In equation (4), ρ is the density coefficient of the strip, Cp is the specific heat coefficient of the strip, V is the volume of the strip, and Q is the heat lost by radiation from the strip, calculated by the temperature calculation model according to equation (5).

[0025] Q=ε*A*σ(T 环境 -T 入口 (5)

[0026] In equation (5), ε is the thermal emissivity coefficient, A is the emissivity coefficient, σ is the Stefan-Boltzmann constant, and T 环境 It refers to the ambient temperature.

[0027] Furthermore, G in equation (3) is 0.05-0.15, and the initial value of the oscillation time is 0-180 seconds. Attached Figure Description

[0028] Figure 1 This is a layout diagram of the rolling production line equipment involved in the IF steel slab strip roughing exit temperature control method of the present invention. Detailed Implementation

[0029] Example

[0030] This embodiment describes a method for controlling the exit temperature of IF steel ribbed strip roughing mill, involving the Meigang 1422 hot rolling production line. The specifications of a certain IF steel ribbed strip being rolled are shown in Table 1 below. The rolling production line has two roughing mill stations, R1 and R2, and an existing temperature calculation model for the rolling production line is available.

[0031] Table 1

[0032]

[0033] The specific steps are as follows:

[0034] S1. Set up a roughing rolling mode with one pass for R1 and seven passes for R2, with the last pass of R2 (the seventh pass) skipped. Set the swing zone between the R1 and R2 mills, and start calculating the swing time and swinging after the R2 mill completes its sixth pass, as shown. Figure 1 As shown.

[0035] S2. Read the existing temperature calculation model of the rolling production line and calculate the inlet temperature T of the strip in the swinging region in the sixth pass of R2. 入口 It is 1040℃;

[0036] S3. Calculate the exit temperature T1 of the strip at R2 using the following formula (1) iteratively.

[0037] T1 = T 入口 -T 温降 (1),

[0038] In equation (1), T1 is the exit temperature of the strip at R2 calculated iteratively, and T_temperature drop is the temperature drop of the strip from the inlet to the outlet of the pre-R2 swing zone.

[0039] T 温降 =W*t1 (2),

[0040] In equation (2), W is the temperature drop of the strip from the inlet to the outlet of R2 in a fixed unit time, calculated by the existing temperature calculation model of the rolling production line. t1 is the oscillation time calculated in the current iteration, and the iterative calculation of t1 is expressed as in equation (3).

[0041] t1=t10+(T10-T0)*G, (3),

[0042] In equation (3), T0 is the target exit temperature of the roughing mill R2 specified for production, G is a coefficient in seconds / ℃, which is generally taken as 0.1; t10 is the oscillation time calculated in the previous iteration.

[0043] As is known, the existing temperature calculation model for the rolling production line calculates W according to the following formula (4).

[0044]

[0045] In equation (4), ρ is the density coefficient of the strip, Cp is the specific heat coefficient of the strip, V is the volume of the strip, and Q is the heat lost by radiation of the strip. As known, the temperature calculation model of the production line calculates Q according to the following equation (5).

[0046] Q=ε*A*σ(T 环境 -T 入口 (5)

[0047] In equation (5), ε is the thermal emissivity coefficient, A is the emissivity coefficient, σ is the Stefan-Boltzmann constant, and T 环境 It refers to the ambient temperature.

[0048] In this embodiment, W = 0.895℃ / second is calculated using the existing temperature calculation model of the rolling production line.

[0049] S4. Compare T1 calculated in each iteration with T0.

[0050] If |T1-T0|≥1, then repeat step S3;

[0051] If |T1-T0| < 1, then stop calculating the swing times t1 and T1, output the currently calculated swing time t1 as the time when the strip enters the swing, and execute the swing.

[0052] The following is a detailed explanation of steps S3 and S4. In this embodiment, the temperature drop T and T1 are calculated iteratively starting from the initial value of the oscillation time (0) as follows:

[0053] First calculation

[0054] The initial swing time = 0 seconds.

[0055] Temperature drop T = W * t1 = 0

[0056] T1 = T_inlet = 1040℃

[0057] Since 1040 is relatively large compared to 860, i.e., |1040-860|≥1, we continue the iterative calculation.

[0058] Second calculation

[0059] The previous iteration calculated the oscillation time t10 = the initial oscillation time = 0 seconds.

[0060] The oscillation time calculated in this iteration is t1 = 0 + (1040 - 860) * 0.1 = 18 seconds.

[0061] Temperature drop T = W * t1 = 0.895 * 18 = 16.11℃

[0062] T1 = T_inlet - T_temperature drop = 1040 - 16.11 = 1023.89℃

[0063] Since 1023.89 is relatively large compared to 860, i.e., |1023.89-860|≥1, we continue the iterative calculation.

[0064] Third calculation

[0065] The previous iteration calculated the oscillation time t10 = 18 seconds.

[0066] The oscillation time calculated in this iteration is t1 = 18 + (1023.89 - 860) * 0.1 = 34.39 seconds.

[0067] Temperature drop T = W * t1 = 0.895 * 34.39 ≈ 30.78℃

[0068] T1 = T_inlet - T_temperature drop = 1040 - 30.78 = 1009.22℃

[0069] Since 1009.22 is relatively large compared to 860, i.e., |1009.22-860|≥1, the iterative calculation continues;

[0070] Fourth calculation

[0071] The previous iteration calculated the oscillation time t10 = 34.39 seconds.

[0072] The oscillation time in this iteration is t1 = 34.39 + (1009.22 - 860) * 0.1 = 49.31 seconds.

[0073] Temperature drop T = W * t1 = 0.895 * 49.31 ≈ 44.13℃

[0074] T1 = T_inlet - T_temperature drop = 1040 - 44.13 = 995.87℃

[0075] Since 995.87 is significantly different from 860, i.e., |995.87-860| ≥ 1, the iterative calculation continues. Because subsequent iterative calculations are identical to the above, a detailed description is omitted. All iterative calculation results are shown in Table 2 below. The calculation continues until the fifty-seventh iteration, where the current swing time t1 = 200.06 seconds ≈ 200 seconds, and T1 = 860.94℃. Since |860.94-860| < 1 at this point, the calculation stops, and the currently calculated swing time of 200 seconds is output as the time for the strip to enter the swing phase, and the swing is then executed.

[0076] Table 2

[0077]

[0078]

[0079]

[0080] The iterative calculations of the oscillation time and the roughing mill (R2) exit temperature described above started from an initial oscillation time of 0 and were performed 57 times to determine the final oscillation time. The iterative process is lengthy. To simplify the calculations, it is practically possible to start the iterative calculations with an initial oscillation time of 100 seconds or 150 seconds, thus reducing the number of iterations. The initial oscillation time of 100 seconds or 150 seconds is based on empirical values.

[0081] The above description is merely a preferred embodiment of the present invention, but the present invention is not limited thereto. For example, 1) G can also take other values ​​within the range of 0.05-0.15; 2) the initial value of the oscillation time can take other values ​​within the range of 0-180 seconds. All equivalent substitutions or equivalent changes made to the concepts and technical solutions of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for controlling the exit temperature of IF steel rib strip roughing mill, involving two roughing mill stations R1 and R2 in the rolling production line and an existing temperature calculation model of the rolling production line, characterized in that... Perform the following steps: S1. Set the roughing mode of one pass for R1 and seven passes for R2, and skip the seventh pass of R2. Set the swing zone between the R1 mill and the R2 mill, and start swinging after the R2 mill completes the sixth pass. S2. Read the temperature calculation model and calculate the inlet temperature T of the strip in the swing zone in the sixth pass of R2. 入 mouth; S3. Calculate the exit temperature T1 of the strip at R2 using the following formula (1) iteratively. T1 = T_inlet - T_temperature drop (1), In equation (1), T1 is the outlet temperature of the strip at R2 calculated iteratively, and T_temperature drop is the temperature drop of the strip from the inlet of the pre-swinging zone of R2 to the outlet of R2, calculated according to equation (2). Temperature drop T = W * t1(2), In equation (2), W is the temperature drop per unit time of the strip from the inlet to the outlet of R2 in the swing zone before R2, calculated by the temperature calculation model, and t1 is the swing time of the current iteration calculated by the iterative calculation, which is expressed as in equation (3). t1=t10+(T10-T0)*G, (3), In equation (3), T10 is the exit temperature of the strip at R2 calculated in the previous iteration, T0 is the target exit temperature of the roughing mill at R2 specified in production, G is a coefficient in seconds / ℃, and t10 is the oscillation time calculated in the previous iteration. The temperature drop and T1 are calculated iteratively starting from the initial value according to the calculated oscillation time; S4. Compare T1 calculated in each iteration with T0. If |T1-T0|≥1, then repeat step S3; If |T1-T0| < 1, then stop the calculation, output the oscillation time t1 calculated in the current iteration as the time when the strip enters the oscillation, and execute the oscillation.

2. The method for controlling the exit temperature of IF steel ribbed strip roughing mill according to claim 1, characterized in that: The W is calculated according to the following formula (4), In equation (4), ρ is the density coefficient of the strip, Cp is the specific heat coefficient of the strip, V is the volume of the strip, and Q is calculated according to equation (5). Q=ε*A*σ(T 环境 -T 入口 ) (5) In equation (5), ε is the thermal emissivity coefficient, A is the emissivity coefficient, σ is the Stefan-Boltzmann constant, and T 环境 It refers to the ambient temperature.

3. The method for controlling the exit temperature of IF steel ferritic strip roughing mill according to claim 1 or 2, characterized in that: In the formula (3), G is taken as 0.05-0.15, and the initial value of the oscillation time is 0-180 seconds.

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