A method for heating a strip of steel

Abstract

This invention discloses a heating control method for strip steel, belonging to the field of strip steel annealing furnace heating technology, including the following steps: Based on the actual temperature Td of the strip steel located in the furnace chamber of the annealing furnace and the target annealing temperature T of the strip steel to be annealed... d0 The target temperature Tt of the furnace cavity is obtained by considering the width W, thickness d, and operating speed V. The actual temperature of the furnace cavity is subtracted from the target temperature Tt to obtain the difference ΔT. The heating power Pt of the heating tube of the annealing furnace is calculated based on the difference ΔT: Pt = P0 + kp × ΔT - (kp × ΔT × 1000) / Ti, where P0 ranges from 10 to 40, kp ranges from 0.1 to 10, and Ti ≤ 100. The heating tube is heated using the calculated heating power Pt. The heating method provided by this invention utilizes the actual temperature of the strip steel inside the furnace, the furnace temperature, and the dimensions and operating speed of the strip steel to be annealed outside the annealing furnace as the basis for calculation. This allows for timely adjustment of the heating power of the annealing furnace heating tube, resulting in rapid response and accurate temperature control.

Description

Technical Field

[0001] This invention belongs to the field of strip steel annealing furnace heating technology, specifically relating to a method for controlling the heating of strip steel. Background Technology

[0002] Non-oriented silicon steel is a key material for drive motors, a core component of new energy vehicles. Therefore, it is required to have good magnetic properties, and continuous annealing furnace is the most important process for achieving these properties. Continuous annealing furnace can heat-treat non-oriented silicon steel, thereby controlling the internal microstructure evolution to obtain the desired microstructure.

[0003] Currently, the annealing temperature of strip steel in the annealing furnace is controlled by detecting the temperature inside the furnace cavity, which cannot truly reflect the temperature of the strip steel itself. Furthermore, controlling the heating by the actual temperature of the strip steel will result in a lag in the strip steel temperature control, affecting the stability of the product. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a heating control method for strip steel, which can adjust the heating power of the annealing furnace heating tubes in a timely manner to meet the heating requirements of the strip steel about to enter the furnace. The method is rapid, the temperature control is accurate, and the magnetic property stability of non-oriented silicon steel products is improved.

[0005] The technical solution of the present invention is as follows: a method for controlling the heating of strip steel is provided, comprising the following steps: Based on the actual temperature T of the strip steel located in the annealing furnace chamber d The target annealing temperature T of the strip to be annealed d0 The target temperature T inside the furnace cavity is obtained by considering the width W, thickness d, and operating speed V. t ; The target temperature T t Subtract the actual temperature inside the furnace to obtain the difference ΔT; The heating power Pt of the heating tube in the annealing furnace is calculated based on the difference ΔT, specifically as follows: Pt = P0 + kp × △T - P0 ranges from 10 to 40, kp ranges from 0.1 to 10, and T... i ≤100; The heating element heats the object using the calculated heating power Pt.

[0006] In some embodiments, the target temperature T t Subtract the actual temperature of the furnace cavity, specifically including: Select the target temperature value T t The larger of the empirical values ​​for the temperature inside the furnace cavity is subtracted from the actual temperature inside the furnace cavity.

[0007] In some embodiments, the actual temperature T of the strip located in the annealing furnace is used as the basis for the determination. d The target annealing temperature T of the strip to be annealed d0 The target temperature T inside the furnace cavity is obtained by considering the width W, thickness d, and operating speed V. t Specifically, it includes: The actual temperature T of the strip steel located in the annealing furnace chamber d The target annealing temperature T of the strip to be annealed d0 Substituting the width W, thickness d, and running speed V into the formula To obtain the target temperature T inside the furnace cavity t ,in, It is 5.67 10 -8 w / (m²•k 4 ), 0 < ≤1, C p The value is 0.46 × 10³ J / (kg•℃), and the value of ρ is 7.8 × 10³ J / (kg•℃). 3 kg / m 3 .

[0008] In some embodiments, the running speed V of the strip is in the range of 100-180 m / min.

[0009] In some embodiments, the width W of the strip to be annealed is 750-1300 mm and the thickness d is 0.1-0.5 mm.

[0010] In some embodiments, the heating is performed in an annealing furnace, the annealing furnace comprising: The furnace body is provided with the furnace chamber and an inlet and an outlet communicating with the furnace chamber; The first heating tube group and the second heating tube group are each provided in multiples. The multiple first heating tube groups and the multiple second heating tube groups are arranged sequentially at intervals along the running direction of the strip. The first heating tube group and the second heating tube group each include two heating tubes arranged opposite each other located above and below the strip, respectively. The two heating tubes have the same power, and the power of the heating tubes decreases sequentially along the running direction of the strip.

[0011] In some embodiments, among two adjacent heating tubes along the length of the strip, the heating power of the heating tube closer to the outlet is 70-90% of the heating power of the heating tube closer to the inlet.

[0012] In some embodiments, the heating tubes of the plurality of first heating tube groups are all W-type radiant tubes, and the heating tubes of the plurality of second heating tube groups are all I-type radiant tubes.

[0013] In some embodiments, in the gap between any two adjacent W-shaped radiant tubes along the length direction of the strip, the gap near the inlet is smaller than the remaining gap near the outlet. In the gap between two adjacent Type I radiant tubes along the length of the strip, the gap closer to the inlet is smaller than the remaining gap closer to the outlet.

[0014] In some embodiments, the furnace is provided with thermocouples for detecting the temperature inside the furnace cavity.

[0015] The beneficial effects of the present invention include at least the following: The present invention provides a method for controlling the heating of strip steel, comprising the following steps: based on the actual temperature T of the strip steel located in the annealing furnace chamber... d The target annealing temperature T of the strip to be annealed d0 The target temperature T inside the furnace cavity is obtained by considering the width W, thickness d, and operating speed V. t The target temperature T t Subtract the actual temperature inside the furnace to obtain the difference ΔT; calculate the heating power Pt of the heating tube of the annealing furnace based on the difference ΔT, specifically: Pt = P0 + kp × ΔT - (kp × ΔT × 1000) / Ti, where P0 ranges from 10 to 40, kp ranges from 0.1 to 10, and Ti ≤ 100; the heating tube heats with the calculated heating power Pt. The heating method provided by this invention uses the actual temperature of the strip inside the furnace, the furnace temperature, and the dimensions and running speed of the strip to be annealed outside the annealing furnace as the basis for calculation. This allows for timely adjustment of the heating power of the annealing furnace heating tube to meet the heating requirements of the strip about to enter the furnace, resulting in rapid response and accurate temperature control, thus improving the magnetic property stability of non-oriented silicon steel products. Attached Figure Description

[0016] Figure 1 A schematic diagram of a heating control method for strip steel according to an embodiment is shown.

[0017] Figure 2 A schematic diagram illustrating the principle of strip steel operating in an annealing furnace according to an embodiment of this application is shown.

[0018] Figure 3 A schematic diagram of the structure of the annealing furnace used in the heating control method of this application embodiment is shown.

[0019] Figure label: 100-Furnace body, 210-Heating tube, 211-W-type radiant tube, 212-I-type radiant tube, 300-Furnace roller, 400-Strip steel. Detailed Implementation

[0020] To enable those skilled in the art to better understand this application, the technical solution of this application will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] Because the heat transfer process within the annealing furnace is complex, the temperature of the non-oriented silicon steel is the core of the entire annealing process. Precisely adjusting the furnace temperature to ensure the heating temperature of the non-oriented silicon steel is crucial. In existing technologies, the annealing temperature control in the heating furnace relies on feedback from the actual temperature of the strip. However, the strip moves within the annealing furnace at a certain rate; therefore, the temperature feedback is lagging. Adjusting the heating power of the furnace's heating tubes only after detecting that the strip temperature is too low or too high will still result in longer sections of strip failing to reach the target annealing temperature, causing fluctuations in the magnetic properties of the non-oriented silicon steel along its length.

[0022] This application provides a heating control method for strip steel, which at least to some extent improves the timeliness of annealing furnace heating temperature adjustment and improves the uniformity of magnetic properties of non-oriented silicon steel in the length direction.

[0023] Please combine Figure 1 The method for controlling the heating of strip steel provided in this application includes the following steps: S1, based on the actual temperature T of the strip steel located in the annealing furnace chamber. d The target annealing temperature T of the strip to be annealed d0 The target temperature T inside the furnace cavity is obtained by considering the width W, thickness d, and operating speed V. t ; The target annealing temperature for the strip steel is determined based on its composition and desired microstructure. At this temperature, the strip steel will achieve the desired microstructure after annealing. The actual temperature T of the strip steel inside the furnace is... d The actual temperature of the strip can be obtained using a pyrometer. Generally, the pyrometer is located at the end of the heating section. Therefore, the actual temperature T of the strip can be used alone. d The heating temperature is adjusted accordingly, but the strip temperature reacts lag-wise to disturbance deviations. The width W and thickness d of the strip to be annealed can be obtained by means of a width measuring instrument, thickness gauge, etc., or can be obtained from the previous process, such as the cold rolling process; this application does not impose any restrictions. The strip to be annealed is generally the strip that has not yet entered the heating section of the annealing furnace, i.e., the next coil to be annealed. The running speed V of the strip can be obtained from a speed measuring instrument. Generally, the running speed V of the strip is in the range of 100-180 m / min.

[0024] Specifically, the actual temperature T of the strip steel located in the annealing furnace is... d The target annealing temperature T of the strip to be annealed d0 Substituting the width W, thickness d, and running speed V into the formula To obtain the target temperature T inside the furnace cavityt In the formula, δ represents the Stephen Bolhertz constant, which is 5.67 × 10⁻⁶. -8 w / (m²•k⁴), εg represents emissivity, 0<εg≤1, Cp is the specific heat capacity at isobaric pressure, Cp is 0.46×10³ J / (kg•℃), ρ is the density, ρ takes the value of 7.8×10³ kg / m³, T d T d0 And T t The unit for all values ​​is K.

[0025] Based on the actual temperature T of the strip steel located in the annealing furnace chamber d The target annealing temperature T of the strip to be annealed d0 The target temperature T inside the furnace cavity is calculated from the width W, thickness d, and operating speed V. t More accurate, the target temperature T inside the furnace cavity t This is the target temperature value for the next coil of strip to be annealed, allowing for advance prediction of the temperature inside the annealing furnace to ensure that the heating temperature of the next coil of strip reaches the target annealing temperature. Changes in the specifications, surface emissivity, and speed of the strip to be annealed can cause temperature fluctuations within the furnace chamber, which in turn lead to changes in the strip temperature. Therefore, the target annealing temperature T of the strip to be annealed is considered. d0 Including the width W and thickness d can improve the accuracy of the results. Generally, the width of the strip to be annealed is 750-1300mm and the thickness is 0.1-0.5mm.

[0026] S2, Set the target temperature T t Subtract the actual temperature inside the furnace to obtain the difference ΔT; The target temperature T inside the furnace cavity t This allows for more accurate temperature control by determining whether to increase or decrease the heating power of the heating element. The actual temperature inside the furnace cavity can be obtained by measuring the atmosphere within the furnace cavity using a temperature sensor such as a thermocouple. Target temperature T t The target temperature T may be higher than the actual temperature inside the furnace cavity. t It may also be lower than the actual temperature inside the furnace cavity, so ΔT may be a positive or negative value.

[0027] To avoid the actual temperature T of the strip d Detection errors lead to a decrease in the target temperature T inside the furnace cavity. t Calculation errors occur; in other embodiments, the target temperature T is... t Subtracting the actual temperature of the furnace cavity specifically includes: selecting the target temperature value T. tSubtracting the actual temperature of the furnace cavity from the larger of the empirical temperature values ​​for the furnace body's inner cavity (ΔT) further improves the accuracy of temperature control and ensures uniform heat radiation. The empirical temperature values ​​for the furnace cavity are based on historical temperature data accumulated during production; that is, the temperature value of the furnace cavity at a certain heating power of the heating element. Similarly, the aforementioned larger value may be higher than or lower than the actual temperature of the furnace cavity; therefore, ΔT may be a positive or negative value.

[0028] S3. Calculate the heating power Pt of the heating tube in the annealing furnace based on the difference ΔT, specifically as follows: Pt = P0 + kp × △T - P0 is the base load, expressed as a percentage, representing the load of the heating element at the minimum flow rate required to prevent backfire (ensuring safety). It is the ratio of the heating element's power at this minimum flow rate to its rated power. P0 ranges from 10% to 40%. kp is a proportionality coefficient, expressed as % / K, ranging from 0.1% to 10% / K. i Let T be the integration time constant. i ≤100; for example, when the difference ΔT is -0.2K, P0 is 35%, kp is 8, and T i The value is 80, and the heating power Pt = 35 - 8 × 0.2 + (8 × 0.2 × 1000) / 80 = 53.4%. For example, when the difference ΔT is -0.2K, P0 is 38%, kp is 10, and T... i For example, when the difference ΔT is 0.2K, P0 is 30%, kp is 6, and T... i The value is 60, and the heating power Pt = 38 + 6 × 0.2 - (6 × 0.2 × 1000) / 60 = 19.2%. Therefore, at the target temperature T... t When the temperature is higher than the actual temperature inside the furnace cavity, the heating power of the heating tubes needs to be appropriately reduced to maintain the target temperature T. t When the temperature is lower than the actual temperature inside the furnace cavity, the heating power of the heating tubes needs to be appropriately increased.

[0029] S4. Control the heating tube to heat with the calculated heating power Pt.

[0030] Specifically, in combination Figure 2 Heating is carried out in an annealing furnace. Please refer to... Figure 3The annealing furnace includes a furnace body 100, a first heating tube group, and a second heating tube group. The furnace body 100 has a furnace chamber and an inlet and an outlet communicating with the furnace chamber. Multiple first and second heating tube groups are provided, both located in the heating section of the annealing furnace. The multiple first and second heating tube groups are arranged sequentially and at intervals from the inlet and outlet. Each first and second heating tube group includes two opposing heating tubes 210 located above and below the strip 400, respectively. The power of the two heating tubes 210 is... Similarly, the power of the heating tube 210 decreases sequentially from the inlet to the outlet. This results in a higher heating power near the inlet of the annealing furnace and a lower heating power near the outlet, which allows the strip 400 to have a faster heating rate in the heating section. When the strip 400 is non-oriented silicon steel, the faster heating rate results in less recrystallization and a faster nucleation rate. Nucleation can also occur in areas with lower energy storage. At this time, the recrystallization nucleation sites are relatively increased, and the preferred orientation of the nuclei is reduced, which improves the texture composition of the non-oriented silicon steel and thus improves its magnetic properties.

[0031] In some embodiments, the annealing furnace further includes a plurality of furnace rollers 300 for supporting and providing power for the running of the strip 400. The plurality of furnace rollers 300 are arranged sequentially at intervals along the running direction of the strip 400, and the furnace rollers 300 are located between the heating tube 210 below and the strip 400.

[0032] In some embodiments, among two adjacent heating tubes 210 along the length direction of the strip 400, the heating power of the heating tube 210 near the outlet is 70-90% of the heating power of the heating tube 210 near the inlet. Specifically, the heating power of each heating tube 210 in the first heating tube group is 100-180KW, and the heating power of each heating tube 210 in the second heating tube group is 30-60KW. This is coordinated with the running speed of the strip 400 to form a heating gradient and control the heating rate of the non-oriented silicon steel.

[0033] In some embodiments, the heating tubes 210 of the plurality of first heating tube groups are all W-type radiant tubes 211, and the heating tubes 210 of the plurality of second heating tube groups are all I-type radiant tubes 212. The heating area of ​​the W-type radiant tube 211 is larger than that of the I-type radiant tube 212, and its heating power is higher. The use of W-type radiant tubes 211 near the inlet of the heating tube 210 can provide a faster heating rate. Both the W-type radiant tube 211 and the I-type radiant tube 212 are prior art, and they are equipped with burners inside. Combustible gas, such as blast furnace gas, is used as fuel and is burned in the burners to generate heat, which is transferred to the atmosphere inside the furnace cavity through the heating tubes 210, and then the strip steel 400 is heated through heat transfer.

[0034] In some embodiments, in the gap between two adjacent W-shaped radiant tubes 211 along the length direction of the strip 400, the gap near the inlet is smaller than the remaining gap near the outlet. For example, in the first heating tube group composed of W-shaped radiant tubes 211, there are a total of 48 W-shaped radiant tubes 211, with two W-shaped radiant tubes 211 above and below forming a group, for a total of 24 groups. The gap between the first 12 groups is 2m, and the gap between the last 12 groups is 2.5m, so as to control the heating rate to 25-30℃ / S. In the gap between two adjacent I-type radiant tubes 212 along the length of the strip 400, the gap near the inlet is smaller than the remaining gap near the outlet. For example, in the second heating tube group composed of I-type radiant tubes 212, there are a total of 80 W-type radiant tubes 211. The upper and lower I-type radiant tubes 212 form a group, totaling 40 groups. The gap between the first 24 groups is 1m, and the gap between the last 16 groups is 2m, so as to control the heating rate at 8-15℃ / S. Preferably, the heating power of the heating tube 210 in the first heating tube group is 180KW, and the heating power of the heating tube 210 in the second heating tube group is 60KW.

[0035] The thermocouple used to detect the temperature inside the furnace cavity can be located between the first heating tube group and the second heating tube group.

[0036] After the heating power Pt is calculated, each heating tube 210 is heated with a certain heating power. For example, if the heating power Pt = 56%, then the number of burners opened by each heating tube 210 is 56% of the total number of its own burners.

[0037] The strip heating control method described in this application is stored in a controller as a computer program. This controller can adjust the strip heating control based on the actual temperature T of the strip located in the annealing furnace. d The target annealing temperature T of the strip to be annealed d0 Calculate the target temperature T inside the furnace cavity based on the width W, thickness d, and operating speed V. t The target temperature T t Subtract the actual temperature of the furnace cavity to obtain the difference ΔT; calculate the heating power Pt of the heating tube of the annealing furnace based on the difference ΔT; and control the heating tube to heat with the calculated heating power Pt.

[0038] The present invention provides a strip heating control method that uses the actual temperature of the strip inside the furnace, the furnace temperature, and the dimensions and running speed of the strip to be annealed outside the annealing furnace as the basis for calculation. It can adjust the heating power of the heating tubes of the annealing furnace in a timely manner to meet the heating requirements of the strip about to enter the furnace, so that the strip can quickly and accurately reach the target temperature, thereby improving the magnetic property stability of non-oriented silicon steel products. The present invention adopts a stepped heating tube arrangement for heating, which further improves the heating rate of non-oriented silicon steel and improves the timeliness.

[0039] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0040] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for controlling the heating of steel strip, characterized in that, Includes the following steps: The actual temperature T of the strip steel located in the annealing furnace chamber d The target annealing temperature T of the strip to be annealed d0 Substituting the width W, thickness d, and running speed V into the formula To obtain the target temperature T inside the furnace cavity t ,in, It is 5.67 10 -8 w / (m²•k 4 ), 0 < ≤1, C p The value is 0.46 × 10³ J / (kg•℃), and the value of ρ is 7.8 × 10³ J / (kg•℃). 3 kg / m 3 The target temperature T t Subtract the actual temperature inside the furnace to obtain the difference ΔT; The heating power Pt of the heating tube in the annealing furnace is calculated based on the difference ΔT, specifically as follows: Pt = P0 + kp × △T - P0 ranges from 10 to 40, kp ranges from 0.1 to 10, and T... i ≤100; The heating tube is controlled to heat the material using the calculated heating power Pt.

2. The method for controlling the heating of strip steel according to claim 1, characterized in that, The target temperature T t Subtract the actual temperature of the furnace cavity, specifically including: Select the target temperature value T t The larger of the empirical values ​​for the temperature inside the furnace cavity is subtracted from the actual temperature inside the furnace cavity.

3. The method for controlling the heating of strip steel according to claim 1, characterized in that, The running speed V of the strip is in the range of 100-180 m / min.

4. The method for controlling the heating of strip steel according to claim 1, characterized in that, The width W of the strip to be annealed is 750-1300mm, and the thickness d is 0.1-0.5mm.

5. The method for controlling the heating of strip steel according to any one of claims 1-4, characterized in that, The heating is carried out in an annealing furnace, which includes: The furnace body is provided with the furnace chamber and an inlet and an outlet communicating with the furnace chamber; The first heating tube group and the second heating tube group are each provided in multiples. The multiple first heating tube groups and the multiple second heating tube groups are arranged sequentially at intervals along the running direction of the strip. The first heating tube group and the second heating tube group each include two heating tubes arranged opposite each other located above and below the strip, respectively. The two heating tubes have the same power, and the power of the heating tubes decreases sequentially along the running direction of the strip.

6. The method for controlling the heating of strip steel according to claim 5, characterized in that, In two adjacent heating tubes along the running direction of the strip, the heating power of the heating tube closer to the outlet is 70-90% of the heating power of the heating tube closer to the inlet.

7. The method for controlling the heating of strip steel according to claim 5, characterized in that, The heating tubes of the multiple first heating tube groups are all W-type radiant tubes, and the heating tubes of the multiple second heating tube groups are all I-type radiant tubes.

8. The method for controlling the heating of strip steel according to claim 5, characterized in that, In the gap between any two adjacent W-shaped radiant tubes along the length of the strip, the gap closer to the inlet is smaller than the remaining gap closer to the outlet. In the gap between two adjacent Type I radiant tubes along the length of the strip, the gap closer to the inlet is smaller than the remaining gap closer to the outlet.

9. The method for controlling the heating of strip steel according to claim 5, characterized in that, The furnace chamber is equipped with thermocouples for detecting the temperature inside the furnace chamber.

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