TW201330944A - Continuous annealing line cooling process parameter regulation method - Google Patents

Abstract

The invention relates to a continuous annealing line cooling process parameter regulation method, including the steps of: (a) providing a continuous annealing line gas cooling region to cool a steel strip, in which the continuous annealing line gas cooling region includes a plurality of sub-regions, each of the sub-regions includes a plurality of regularly-arranged nozzles, and any two adjacent nozzles are corresponding to a plurality of node points formed on the steel strip; (b) utilizing heat transfer coefficient of the nozzles and a thermal-resistance thermal-capacity expression of each node point to calculate temperature distribution of the steel strip located between the two nozzles associated with variation in time and taking temperature difference and temperature variation in a width direction of the steel strip as a target function; and (c) minimizing the target function to calculate wind temperature and air-rate of each sub-region.

Description

Continuous annealing line cooling process parameter control method

The invention relates to a method for regulating process parameters, in particular to a method for controlling the parameters of a continuous annealing line cooling process.

In the standard operation of the steel mill, the main function of the continuous annealing line air cooling zone is to cool the steel strip. Conventional steel strip continuous annealing line gas cooling zone usually has several sub-zones, and the steel strip temperature measuring point is generally located at the outlet of the air-cooling zone. Therefore, the cooling rate of the steel strip can only be calculated by dividing the inlet and outlet temperature difference by the elapsed time, and each sub-zone There is no certain standard for the wind temperature and air volume adjustment in the area. When the cooling fan capacity is attenuated or the cooling water flow rate and the inlet temperature change, the wind temperature and the air volume will be mutated, resulting in a misalignment of the cooling process parameters. When the cooling process parameters are out of alignment, it will not only affect the cooling rate of the steel strip in the sub-zone, but also the cooling process parameters of the sub-zones in the latter section will be biased, which may cause the cooling speed of the steel strip in the front section to be too fast and the cooling speed of the steel strip in the latter section. Too slow, seriously affecting the quality of the steel strip.

In view of this, it is necessary to provide an innovative and progressive continuous annealing line cooling process parameter control method to solve the above problems.

The invention provides a method for controlling a continuous annealing line cooling process parameter, the method comprising the steps of: (a) providing a continuous annealing line air cooling zone, wherein the continuous annealing line air cooling zone is for cooling a steel strip, the continuous annealing line The air-cooling zone has a plurality of sub-zones, each of which is provided with a plurality of regularly arranged nozzles, and any two adjacent nozzles correspond to a plurality of nodes on the steel strip; (b) heat transfer using the nozzles The coefficient and the thermal resistance-heat capacity calculation formula of each node calculate the temperature distribution of the steel strip with time between the two nozzles, and take the temperature difference and temperature change of the strip width direction as an objective function; and (c) minimize the The objective function calculates the wind temperature and air volume control values for each of the sub-zones.

The invention utilizes the calculation method of the transient heat transfer of the steel strip to calculate the temperature distribution of the steel strip cooling process, and takes the temperature difference of the strip width direction and the temperature change as the objective function, under the condition of satisfying the wire speed, the inlet temperature and the outlet temperature of the steel strip. The optimization method is used to obtain the wind temperature and air volume control values of the sub-zones, and the control values can be used to stably control the cooling rate of each sub-zone during the cooling process of the steel strip, thereby improving the quality of the steel strip.

Figure 1 is a flow chart showing the method for controlling the parameters of the continuous annealing line cooling process of the present invention. Fig. 2 is a view showing the structure of the continuous annealing line air-cooling zone of the present invention. Figure 3 shows a schematic view of the cooling of the steel strip of the present invention via an impinging jet. Figure 4 is a schematic view showing the relative positions of the nozzles on the nozzle and the steel strip of the present invention. Referring to step S11, FIG. 2 and FIG. 4 of FIG. 1 , a continuous annealing line air cooling zone 20 is provided. The continuous annealing line air cooling zone 20 is used for cooling a steel strip 30, and the continuous annealing line air cooling zone 20 There are a plurality of sub-areas 21, each of which is provided with a plurality of regularly arranged nozzles J, and any two adjacent nozzles J are corresponding to a plurality of nodes N on the steel strip 30, as shown in FIG. The embodiment is divided into 7 nodes N and connected to its neighbors by thermal resistance. In this embodiment, if the internal energy of the node N is expressed as a function of specific heat and temperature, its rate of change over time is approximately:

Where Δ E is the energy increment of the steel strip, Δ V is the volume element, Δτ is the time increment, T is the temperature, subscript i is the position index, superscript k is the time index, ρ is the steel strip density, c is the steel strip More than heat. In this embodiment, when the heat capacity C _i = ρ _i c _i Δ V _i is defined, the thermal resistance-heat capacity calculation formula of each node N is

The subscript i is the first position indicator, the subscript j is the second position indicator, and R _ij is the thermal resistance. In this embodiment, when the subscript j is a node on the steel strip, R _ij is the thermal resistance of the node on the node i and its adjacent steel strip, and the thermal resistance is expressed as R _{i +} = R _{i -} = Where e is the thermal conductivity of the steel strip, Δ W is the unit length of the length of the steel strip, Δ x is the joint spacing, t is the thickness of the steel strip; and when the subscript j is the convective environment, R _ij is the node i and its adjacent The thermal resistance of the convective environment is expressed as R _∞ = Where h is the thermal convection coefficient of the flow field.

Referring to step S12, FIG. 3 and FIG. 4 of FIG. 1 , the heat transfer coefficient of the nozzles J and the thermal resistance-heat capacity calculation formula of each node N are used to calculate the steel strip 30 between the two nozzles J. The temperature distribution of the change is taken as the objective function of the temperature difference and temperature change in the width direction of the largest sub-zone outlet strip. In this embodiment, the heat transfer coefficient of the nozzles J is used to calculate the heat convection coefficient h , and the calculation formula of the heat convection coefficient h is

Nu _stag =0.641 Re ^0.566 ( H/D ) ^-0.078 ,

_{^{Nu average = 0.993 Re 0.625 (H}} / D) -0.625 (s / D) -0.375,

Where e is the heat transfer coefficient of the steel strip, H is the nozzle height (mm), D is the nozzle diameter (mm), s is the nozzle spacing (mm), Nu _stag is the number of the _nappe of the impinging jet stagnation zone (Nusselt number), Nu _average The average number of nano-plugs for the impinging flow field. Moreover, in this embodiment, the temperature distribution of the steel strip can be obtained by calculating the thermal convection coefficient h and the thermal resistance-heat capacity calculation formula of each node N, and the expression of the objective function is

Where a and b are weight coefficients, l is the sub-area number, and s is the nozzle spacing.

Referring to step S13 and FIG. 2 of FIG. 1 , the objective function is minimized to calculate the wind temperature and air volume control values of each sub-area 21 . In this embodiment, the method for minimizing the objective function may be planned. Solve or rush diminishing.

The invention uses the numerical heat transfer method to calculate the temperature distribution of the cooling process of the steel strip, and takes the temperature difference and the temperature change in the width direction of the steel strip as the objective function, and uses the optimization method to satisfy the condition of the wire speed, the inlet temperature and the outlet temperature of the steel strip. The wind temperature and air volume control values of each sub-zone are obtained, and the control values can be used to stably control the cooling rate of each sub-zone during the cooling process of the steel strip, thereby improving the quality of the steel strip.

The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the scope of the present invention. The scope of the invention should be as set forth in the appended claims.

20. . . Continuous annealing line air cooling zone

twenty one. . . Subzone

30. . . Steel strip

D. . . Nozzle diameter

H. . . Nozzle height

J. . . nozzle

N. . . node

s. . . Nozzle spacing

1 is a flow chart showing a method for controlling a cooling annealing process parameter of the continuous annealing line of the present invention;

2 is a schematic view showing the structure of a continuous annealing line gas cooling zone of the present invention;

Figure 3 is a schematic view showing the cooling of the steel strip of the present invention via an impinging jet;

Figure 4 is a schematic view showing the relative positions of the nozzles on the nozzle and the steel strip of the present invention.

(no component symbol description)

Claims (9)

A continuous annealing line cooling process parameter control method comprises the following steps: (a) providing a continuous annealing line air cooling zone, wherein the continuous annealing line air cooling zone is used for cooling a steel strip, the continuous annealing line air cooling zone Having a plurality of sub-areas, each of the sub-areas is provided with a plurality of regularly arranged nozzles, and any two adjacent nozzles are corresponding to a plurality of nodes on the steel strip; (b) utilizing heat transfer coefficients of the nozzles and each The thermal resistance-heat capacity calculation formula of the node calculates the temperature distribution of the steel strip with time between the two nozzles, and takes the temperature difference and temperature change of the strip width direction as an objective function; and (c) minimizes the objective function The wind temperature and air volume control values for each sub-zone are calculated. The method of claim 1, wherein the thermal resistance-heat capacity equation of each node in step (b) is Where T is temperature, subscript i is the first position index, subscript j is the second position index, superscript k is the time index, Δτ is the time increment, R _ij is the thermal resistance, and C _i is the heat capacity. The method of claim 2, wherein when the subscript j is a node on the steel strip, R _ij is a thermal resistance of the node i and the node on the adjacent steel strip, and the thermal resistance is expressed by R _{i +} = R _{i -} = Where e is the heat transfer coefficient of the steel strip, Δ W is the unit length of the length of the steel strip, Δ x is the joint pitch, and t is the thickness of the steel strip. For the method of claim 2, wherein the subscript j is a convection environment, R _ij is the thermal resistance of the node i and its adjacent convection environment, and the thermal resistance is expressed as R _∞ = Where h is the thermal convection coefficient of the flow field, Δ W is the unit length of the length of the steel strip, and Δ x is the node spacing. The method of claim 4, wherein in the step (b), the heat transfer coefficients of the nozzles are used to calculate the heat convection coefficient h , and the heat convection coefficient h is calculated as Nu _stag =0.641 Re ^0.566 ( H/ ^{_{D) -0.078, Nu average = 0.993}} Re 0.625 (H / D) -0.625 (s / D) -0.375, Where e is the heat transfer coefficient of the steel strip, H is the nozzle height, D is the nozzle diameter, s is the nozzle spacing, Nu _stag is the Nusselt number of the impinging jet stagnation zone, and Nu _average is the average number of nano-plugs of the impinging flow field . The method of claim 5, wherein the temperature distribution of the steel strip in step (b) is obtained by calculating a thermal convection coefficient h and a thermal resistance-heat capacity calculation of each of the nodes. The method of claim 6, wherein the representation of the objective function in step (b) is Where a and b are weight coefficients, l is the sub-area number, and s is the nozzle spacing. The method of claim 1, wherein the method of minimizing the objective function in step (c) is a solution. The method of claim 1, wherein the method of minimizing the objective function in the step (c) is an emergency diminishing method.