A method for stopping a continuous annealing furnace to prevent oxidation of a furnace roller

Abstract

A shutdown control method for preventing oxidation of furnace rollers in a continuous annealing furnace includes the following steps: S1: Starting from the shutdown time, the dew point value during the period from the dew point drop to the target temperature is discretely acquired; S2: Based on the dew point value of each discrete acquisition point, the corresponding hydrogen concentration is calculated under the constraint of the oxidation energy limit value during normal production; S3: Based on the calculation, the corresponding hydrogen concentration within the time period of two adjacent discrete acquisition points is controlled, thereby establishing a shutdown control cycle that dynamically controls the hydrogen concentration in the furnace according to the change of dew point value. This invention's shutdown control method for preventing oxidation of furnace rollers in a continuous annealing furnace, based on the anti-oxidation threshold of the carbon rollers and the oxidation energy situation in the furnace during hydrogen shutdown, selects to simultaneously reduce the hydrogen content during the dew point drop process, ensuring that the oxidation energy of the furnace atmosphere is within a safe range, reducing hydrogen consumption, and greatly improving the production efficiency of the continuous operation line.

Description

Technical Field

[0001] This invention belongs to the field of continuous annealing heat treatment technology, and specifically relates to a shutdown control method for preventing oxidation of furnace rollers in a continuous annealing furnace. Background Technology

[0002] Continuous annealing is the final process step in the production of cold-rolled electrical steel, determining its magnetic and mechanical properties. To fully utilize micro-tension annealing to improve the magnetic properties of the final product, horizontal annealing furnaces are generally used for cold-rolled electrical steel. In horizontal annealing furnaces, the rollers are arranged horizontally and parallel. During production, the strip steel runs on the rollers inside the furnace. To prevent scratching the strip steel, graphite carbon sleeve rollers are generally used in electrical steel annealing furnaces. These carbon sleeve rollers consist of a steel roller core and a graphite carbon sleeve, which are fixed together with a special steel key. During operation, the roller core drives the carbon sleeve. The steel strip is in direct contact with the graphite sleeve. Graphite is relatively soft, has a low coefficient of friction with the strip steel, and also possesses lubricating properties, making it difficult to scratch or abrade the strip steel even during operation due to relative sliding.

[0003] However, ordinary graphite materials have weaknesses such as easy oxidation in high-temperature and oxidizing atmospheres and poor wear resistance, thus requiring special treatment. Generally, the surface of carbon sleeve rollers is treated with impregnation of different components to improve their oxidation resistance. Carbon sleeve rollers are divided into two main categories according to the different impregnation treatments: P-treated and M-treated. P-treated rollers use inorganic salt impregnants (semi-permeation process), while M-treated rollers use SiC impregnants (full permeation process). The impregnation process is particularly important in carbon sleeve production, as it helps to increase the product's density and reduce porosity, increase its mechanical strength, electrical conductivity, and thermal conductivity. Impregnation with antioxidant impregnating agents significantly improves the oxidation resistance of the graphite carbon sleeve.

[0004] For annealing furnaces used in cold-rolled electrical steel, the furnace length is typically 300-350 meters, with over 200 carbon sleeve rolls installed. During normal production, the high-temperature section of the furnace is circulated with a protective atmosphere having a high dew point of around 60-80°C and a temperature exceeding 800°C. This atmosphere has strong oxidizing properties. To prevent the carbon sleeves from oxidizing, the atmosphere also contains approximately 75% hydrogen as a reducing protective gas. Under these conditions, the impregnated carbon sleeve rolls can be used normally for more than 12 months. However, when the unit needs to be shut down for cooling, to ensure the carbon sleeves do not oxidize, the dew point must first be lowered to below 0°C. Only after the oxidizing atmosphere inside the furnace has weakened can the hydrogen supply be stopped and cooling continue. This causes the following problems:

[0005] 1. When the unit is shut down, the dew point drops below 0°C for 3-4 hours. During this period, it is necessary to ensure a continuous hydrogen flow of 500-700 m3 / h into the annealing furnace to prevent the furnace rollers from being oxidized, resulting in a huge waste of energy.

[0006] 2. After the dew point inside the furnace drops below 0°C, nitrogen gas is continuously purged into the furnace to reduce the hydrogen concentration inside the furnace to a safe range below 4%. The entire purging process takes 2-3 hours. The entire furnace shutdown process takes a long time, which limits the capacity of continuous production lines.

[0007] Invention application CN200910011962.6 discloses "a method for controlling and treating nodule formation on the bottom roller of a carbon jacket furnace." This method utilizes effective preventative measures to reduce the likelihood of nodule formation, including controlling the brushing current of the brush roller to reduce the use of severely oxidized strips, adjusting appropriate furnace pressure, dew point, and hydrogen content according to different process speeds and temperatures, periodically adjusting the furnace roller speed to reduce the speed difference between the furnace roller and the strip, and controlling the heating and cooling rates during steel quality changes. Furthermore, different treatment methods are used for different nodule states, significantly reducing processing time.

[0008] The invention application with application number CN 201210357687.5 discloses "a method for controlling nodule formation on the bottom rollers of a carbon jacket furnace". The method involves preventing transition steel coils from entering the furnace if their running speed in the high-temperature furnace is ≥60m / min, or if their surface oxidation is severe or they have been run 15 times. It also involves controlling the oil and iron content of the alkaline washing solution and adjusting the furnace roller speed according to the strip temperature to ensure the linear speed of the furnace rollers matches that of the strip. Furthermore, it involves alternating production of high and low grades, with each high-grade production run not exceeding two days, and reducing the furnace tension during high-grade production. The overall air-fuel ratio in the non-oxidizing furnace is controlled at 0.92-0.98, the furnace gas dew point in the carbon jacket section is 30-35℃, the hydrogen content in the soaking furnace is 16-20%, and the furnace temperature of the corresponding section of the carbon jacket with nodule formation is reduced by 30℃ to disrupt the nodule formation conditions. Summary of the Invention

[0009] To address the above problems, this invention provides a shutdown control method for preventing oxidation of furnace rollers in a continuous annealing furnace, the specific technical solution of which is as follows:

[0010] A shutdown control method for preventing oxidation of furnace rollers in a continuous annealing furnace, characterized by comprising the following steps:

[0011] S1: Starting from the furnace shutdown time, the dew point value is discretely obtained during the period when the dew point drops to the target temperature.

[0012] S2: Based on the dew point values ​​at each discrete acquisition point, calculate the corresponding hydrogen concentration under the constraint of the oxidation energy limit during normal production.

[0013] S3: Based on the calculation, the corresponding hydrogen concentration is controlled within the time period of two adjacent discrete acquisition points, and a shutdown control cycle is established to dynamically control the hydrogen concentration in the furnace according to the change of dew point value.

[0014] A shutdown control method for preventing oxidation of furnace rollers in a continuous annealing furnace according to the present invention is characterized in that:

[0015] The oxidation energy value during normal production is represented by a fitting function determined based on two variables: dew point value and hydrogen concentration value.

[0016] The oxidation energy value is the limit value for normal production when the dew point value in the fitting function is the maximum value set for the dew point in the historical product process, and the hydrogen concentration value is the minimum value set for the hydrogen concentration in the historical product process.

[0017] A shutdown control method for preventing oxidation of furnace rollers in a continuous annealing furnace according to the present invention is characterized in that:

[0018] The fitting function is:

[0019] P=0.127+0.002×DP-0.187×Ch,

[0020] When DP = DP max And Ch = Ch min At that time, the corresponding P value is the oxidation energy limit value during normal production;

[0021] In the formula,

[0022] P: Oxidation energy;

[0023] DP: Protective atmosphere dew point value, unit: °C;

[0024] Ch: Hydrogen concentration in the protective atmosphere;

[0025] DP max The maximum dew point setting in the historical product manufacturing process, in °C;

[0026] Ch min The minimum hydrogen concentration set in the historical product process.

[0027] A shutdown control method for preventing oxidation of furnace rollers in a continuous annealing furnace according to the present invention is characterized in that:

[0028] The control of the corresponding hydrogen concentration at the two discrete acquisition points within the time period was achieved by purging with nitrogen.

[0029] A shutdown control method for preventing oxidation of furnace rollers in a continuous annealing furnace according to the present invention is characterized in that:

[0030] The aforementioned "discrete acquisition of dew point values ​​during the period when the dew point drops to the target temperature" is based on real-time detection by a dew point detector.

[0031] A shutdown control method for preventing oxidation of furnace rollers in a continuous annealing furnace according to the present invention is characterized in that:

[0032] The aforementioned "discrete acquisition of dew point values ​​during the period when the dew point drops to the target temperature" is based on historical dew point acquisition.

[0033] A shutdown control method for preventing oxidation of furnace rollers in a continuous annealing furnace according to the present invention is characterized in that:

[0034] The flow rate of nitrogen gas is determined by the following formula:

[0035] C h =C0×e (-Qt / V) ,

[0036] In the formula,

[0037] C h : Hydrogen concentration in the furnace after purging for time t;

[0038] C0: Unit of hydrogen concentration in the furnace at a time before time t;

[0039] Q: Flow rate of the purging gas, unit: m³ 3 / h;

[0040] t: The time interval between two discrete acquisition points, in hours (h).

[0041] V: Furnace volume, unit: m³ 3 .

[0042] A shutdown control method for preventing oxidation of furnace rollers in a continuous annealing furnace according to the present invention is characterized in that:

[0043] When controlling the corresponding hydrogen concentration during two discrete acquisition point time periods by purging with nitrogen, the oxidation energy in the furnace is also calculated in real time according to a set calculation frequency, and the calculation results are compared with a set threshold.

[0044] When the calculation result is greater than or equal to the set threshold, nitrogen gas supply is stopped; otherwise, nitrogen gas supply continues or is restarted.

[0045] A shutdown control method for preventing oxidation of furnace rollers in a continuous annealing furnace according to the present invention is characterized in that:

[0046] The set threshold is determined based on the oxidation energy limit value during normal production, specifically as follows:

[0047] P T =P max ×k,

[0048] P T : The set threshold;

[0049] P max Oxidation energy limit during normal production;

[0050] k: Safety factor.

[0051] A shutdown control method for preventing oxidation of furnace rollers in a continuous annealing furnace according to the present invention is characterized in that:

[0052] When the flow rate of the purging gas is greater than or equal to 600 m³ / h 3 When / h, K takes the value 0.995-1;

[0053] When the flow rate of the purging gas is less than 600 m³ / h 3 When / h, K takes the value of 0.99-0.995.

[0054] A shutdown control method for preventing oxidation of furnace rollers in a continuous annealing furnace according to the present invention is characterized in that:

[0055] The target temperature for dew point reduction is determined by the following formula:

[0056] 0.127 + 0.0020 × X - 0.187 × 0.04 ≤ Pmax;

[0057] In the formula,

[0058] X: Target value for dew point reduction, unit: °C;

[0059] Pmax: Oxidation energy limit during normal production.

[0060] This invention discloses a shutdown control method for preventing oxidation of furnace rolls in a continuous annealing furnace. The method involves fitting two variables: historical dew point and hydrogen concentration values. An oxidation energy value, characterized by these two variables, is established through fitting. Simultaneously, the maximum oxidation energy value (i.e., the oxidation energy limit value mentioned above) is determined based on the historical maximum dew point and minimum hydrogen concentration values. Then, under the constraint of the oxidation energy limit value, segmented control of the hydrogen concentration is established during the period when the dew point decreases to the target value. This ensures that the hydrogen concentration remains at a low level while preventing oxidation of the furnace rolls. This reduces hydrogen consumption during shutdown and eliminates the need for nitrogen purging after the hydrogen concentration drops below a safe level, allowing the hydrogen concentration to quickly reach below the safe range of 4%. This significantly improves the shutdown efficiency of the continuous unit and increases production capacity. Attached Figure Description

[0061] Figure 1 This is a schematic diagram of the control steps of the present invention. Detailed Implementation

[0062] The following is a detailed description of a shutdown control method for preventing oxidation of furnace rollers in a continuous annealing furnace according to the present invention, based on the accompanying drawings and specific embodiments.

[0063] like Figure 1 The method for controlling the shutdown of a continuous annealing furnace to prevent oxidation of the furnace rollers, as shown, includes the following steps:

[0064] S1: Starting from the furnace shutdown time, the dew point value is discretely obtained during the period when the dew point drops to the target temperature.

[0065] S2: Based on the dew point values ​​at each discrete acquisition point, calculate the corresponding hydrogen concentration under the constraint of the oxidation energy limit during normal production.

[0066] S3: Based on the calculation, the corresponding hydrogen concentration is controlled within the time period of two adjacent discrete acquisition points, and a shutdown control cycle is established to dynamically control the hydrogen concentration in the furnace according to the change of dew point value.

[0067] in,

[0068] The oxidation energy value during normal production is represented by a fitting function determined based on two variables: dew point value and hydrogen concentration value.

[0069] The oxidation energy value is the limit value for normal production when the dew point value in the fitting function is the maximum value set for the dew point in the historical product process, and the hydrogen concentration value is the minimum value set for the hydrogen concentration in the historical product process.

[0070] in,

[0071] The fitting function is:

[0072] P=0.127+0.002×DP-0.187×Ch,

[0073] When DP = DP max And Ch = Ch min At that time, the corresponding P value is the oxidation energy limit value during normal production;

[0074] In the formula,

[0075] P: Oxidation energy;

[0076] DP: Protective atmosphere dew point value, unit: °C;

[0077] Ch: Hydrogen concentration in the protective atmosphere;

[0078] DP max The maximum dew point setting in the historical product manufacturing process, in °C;

[0079] Ch minThe minimum hydrogen concentration set in the historical product process.

[0080] in,

[0081] The control of the corresponding hydrogen concentration at the two discrete acquisition points within the time period was achieved by purging with nitrogen.

[0082] in,

[0083] The aforementioned "discrete acquisition of dew point values ​​during the period when the dew point drops to the target temperature" is based on real-time detection by a dew point detector or on historical dew point data.

[0084] in,

[0085] The flow rate of nitrogen gas is determined by the following formula:

[0086] C h =C0×e (-Qt / V) ,

[0087] In the formula,

[0088] C h : Hydrogen concentration in the furnace after purging for time t;

[0089] C0: Unit of hydrogen concentration in the furnace at a time prior to time t;

[0090] Q: Flow rate of the purging gas, unit: m³ 3 / h;

[0091] t: The time interval between two discrete acquisition points, in hours (h).

[0092] V: Furnace volume, unit: m³ 3 .

[0093] in,

[0094] When controlling the corresponding hydrogen concentration during two discrete acquisition point time periods by purging with nitrogen, the oxidation energy in the furnace is also calculated in real time according to a set calculation frequency, and the calculation results are compared with a set threshold.

[0095] When the calculation result is greater than or equal to the set threshold, nitrogen gas supply is stopped; otherwise, nitrogen gas supply continues or is restarted.

[0096] in,

[0097] The set threshold is determined based on the oxidation energy limit value during normal production, specifically as follows:

[0098] P T =P max ×k,

[0099] PT : The set threshold;

[0100] P max Oxidation energy limit during normal production;

[0101] k: Safety factor.

[0102] in,

[0103] When the flow rate of the purging gas is greater than or equal to 600 m³ / h 3 When / h, K takes the value 0.995-1;

[0104] When the flow rate of the purging gas is less than 600 m³ / h 3 When / h, K takes the value of 0.99-0.995.

[0105] in,

[0106] The target temperature for dew point reduction is determined according to the following formula (i.e., at maximum oxidation energy, the corresponding dew point temperature after the hydrogen concentration reaches 4% or below is the target temperature):

[0107] 0.127 + 0.0020 × X - 0.187 × 0.04 ≤ Pmax;

[0108] In the formula,

[0109] X: Target value for dew point reduction, unit: °C;

[0110] Pmax: Oxidation energy limit during normal production.

[0111] Working process and principle

[0112] The present invention provides a shutdown control method for preventing oxidation of furnace rollers in a continuous annealing furnace, which is achieved through the following annealing furnace structure and steps:

[0113] 1. Calculate the oxidation energy value inside the annealing furnace based on the dew point and hydrogen concentration parameters of the protective atmosphere. The calculation method is as follows:

[0114] P = 0.127 + 0.0020 * DP - 0.187 * Ch (Equation 1)

[0115] Where P is the maximum oxidation energy of the furnace atmosphere, DP is the dew point value of the protective atmosphere (°C), and C h To maintain the hydrogen concentration in the protective atmosphere, this formula is an expression fitted based on historical data.

[0116] 2. During normal production, the dew point and hydrogen concentration of the protective atmosphere introduced into different sections of the furnace vary depending on the product being produced. When using (Equation 1) to calculate the oxidation energy in the furnace, DP is taken as the maximum value DP set for the dew point in all product processes.max C h The value is the minimum hydrogen concentration setting C in all product processes. hmin The calculated result P max This represents the maximum oxidation energy value within the annealing furnace.

[0117] 3. Starting from the shutdown time, the dew point value is discretely obtained during the period when the dew point drops to the target temperature (the target temperature is determined based on the hydrogen concentration reaching 4% under the oxidation energy limit, i.e.: 0.127 + 0.0020 × X - 0.187 × 0.04 ≤ Pmax; Note: the target temperature setting here is only for monitoring purposes. In practice, due to errors at various points, the target temperature and the hydrogen concentration reaching 4% may not be reached at the same time. In this case, the hydrogen concentration reaching 4% should be used as the criterion for stopping the operation). (Discrete acquisition can be based on historical dew point curves.) Alternatively, it can be based on real-time detection by a dew point detector. When based on real-time detection, subsequent monitoring and control are lagging controls, and the corresponding values ​​will be adaptively adjusted according to actual conditions (the technical solution still serves the technical objective). After determining the corresponding hydrogen concentration based on the dew point values ​​at each discrete point, pure nitrogen is introduced into the furnace through the nitrogen injection port to purge the protective atmosphere inside the furnace (the purging goal is to reduce the hydrogen concentration to 4%; simultaneously, during the purging process, the real-time dew point value and the oxidation energy value calculated from the corresponding hydrogen concentration must not exceed the limit). The nitrogen flow rate is based on C. h =C0×e (-Qt / V) Determine, in the formula, V(m) 3 C is the furnace volume, C0 is the hydrogen concentration in the furnace at the previous discrete acquisition point, and C h Let Q(m) be the hydrogen concentration in the furnace after time t. 3 / h) represents the flow rate of the purging gas, and t(h) represents the time interval between two discrete acquisition points; during the purging process, C is also used as a reference. h =C0*e (-Qt / V) Calculate the hydrogen concentration C in the furnace in real time. h And according to C h The oxidation energy P of the furnace atmosphere is calculated using the actual dew point value DP detected by the dew point detector and the dew point value. When P ≥ P... max If ×k, then the shut-off valve of the nitrogen injection pipeline is cut off through the electrical interlock procedure, stopping the supply of pure nitrogen. If P <P max If ×k is applied, then pure nitrogen gas will be continuously or restarted through the nitrogen injection port. K is a safety factor, related to the flow rate of the purging gas Q, where Q ≥ 600m³. 3 When the value is / h, K takes the value of 0.995-1, and Q < 600m. 3 When / h, K takes the value of 0.99-0.995.

[0118] The control logic of this technical solution is as follows: the maximum oxidation energy value in the furnace under normal production process conditions is used as the maximum oxidation energy threshold that the carbon roller can withstand. During furnace shutdown, as the normal dew point of the atmosphere decreases towards the target dew point, the corresponding hydrogen concentration is determined based on the dew point values ​​of discrete acquisition points, thereby determining the purge nitrogen flow rate within the time period of two adjacent discrete acquisition points. Simultaneously, based on the purge nitrogen flow rate, purge time, and hydrogen concentration index before shutdown, the furnace hydrogen concentration is calculated in real time, and the oxidation energy of the furnace atmosphere is calculated in real time based on this value. By comparing the result with the maximum oxidation energy threshold, the purge nitrogen is controlled to stop or supply, ensuring that during the shutdown process, while the dew point and hydrogen concentration are reduced simultaneously, the oxidation energy value of the furnace atmosphere is always below the maximum oxidation energy value that the carbon roller can withstand.

[0119] This invention has been implemented in a continuous annealing line at Baosteel. Taking the shutdown process of this continuous annealing line as an example: a section of the furnace is 1m high, 1.3m wide, and 172m long. The furnace volume is V = 223.6m³. During normal production, the process hydrogen concentration and atmosphere dew point values ​​in the furnace for various products produced by this annealing line are shown in the table below:

[0120] Process Classification Dew point setting (°C) Hydrogen concentration setting Product Process 1 50 0.5 Product Process 2 55 0.55 Product Process 3 55 0.5

[0121] Then DP max =55℃, Ch min =0.5, C0=0.5, calculate P max =0.1435. The maximum flow rate of purging nitrogen in the annealing furnace of this unit is designed to be 1000 m³ / h. 3 / h, K is 0.995.

[0122] After the furnace shutdown operation begins, the target dew point value inside the furnace is set to 25℃. Simultaneously, pure nitrogen is introduced through the nitrogen injection port inside the furnace to purge the protective atmosphere; the amount of nitrogen used for purging is Q = 1000m³. 3 / h. And according to C h =C0×e (-Qt / V) Calculate the hydrogen concentration C in the furnace after time t from the start of purging. h And according to C h The oxidation energy P of the furnace atmosphere is calculated using the actual dew point value DP detected by the dew point detector and the P value. When P ≥ P... max If ×K=0.1427, the shut-off valve of the nitrogen injection pipeline will be cut off through the electrical interlocking procedure to stop the supply of pure nitrogen. If P<0.1427, the supply of pure nitrogen through the nitrogen injection port will be maintained or restarted.

[0123] This invention discloses a shutdown control method for preventing oxidation of furnace rolls in a continuous annealing furnace. The method involves fitting two variables: historical dew point and hydrogen concentration values. An oxidation energy value, characterized by these two variables, is established through fitting. Simultaneously, the maximum oxidation energy value (i.e., the oxidation energy limit value mentioned above) is determined based on the historical maximum dew point and minimum hydrogen concentration values. Then, under the constraint of the oxidation energy limit value, segmented control of the hydrogen concentration is established during the period when the dew point decreases to the target value. This ensures that the hydrogen concentration remains at a low level while preventing oxidation of the furnace rolls. This reduces hydrogen consumption during shutdown and eliminates the need for nitrogen purging after the hydrogen concentration drops below a safe level, allowing the hydrogen concentration to quickly reach below the safe range of 4%. This significantly improves the shutdown efficiency of the continuous unit and increases production capacity. In summary, the present invention provides a shutdown control method for preventing oxidation of furnace rollers in a continuous annealing furnace. Based on the oxidation threshold of the carbon roller and the oxidation energy in the furnace during hydrogen shutdown, the method selects to simultaneously reduce the hydrogen content during the dew point reduction process, ensuring that the oxidation energy of the furnace atmosphere is within a safe range, reducing hydrogen consumption, and greatly improving the production efficiency of the continuous operation line.

Claims

1. A method of stopping a continuous annealing furnace to prevent oxidation of the rolls, characterized by It comprises the following steps: S1: from the moment of stopping the furnace, the dew point value of the period of dew point falling to the target temperature is acquired discretely, S2: according to the dew point value of each discrete acquisition point, the corresponding hydrogen concentration is calculated with the oxidation energy limit value in normal production as the constraint condition, S3: according to the calculation, the control of the corresponding hydrogen concentration in the period of adjacent two discrete acquisition points is formed, and the stopping control rhythm of dynamically controlling the hydrogen concentration in the furnace along with the change of the dew point value is established, The oxidation energy value in normal production is represented by a fitting function determined based on two variables of the dew point value and the hydrogen concentration value; When the dew point value in the fitting function takes the maximum value set for the dew point in the historical product process, and the hydrogen concentration value takes the minimum value set for the hydrogen concentration in the historical product process, the oxidation energy value is the oxidation energy limit value in normal production, The fitting function is: P = 0.127 + 0.002 × DP - 0.187 × Ch, When DP = DP max and Ch = Ch min , the corresponding P value is the oxidation energy limit value in normal production; In the formula, P: oxidation energy value; DP: dew point value of the protective atmosphere, unit: ℃; Ch: hydrogen concentration of the protective atmosphere; DP max : maximum value of the set point for the dew point in the historical product process, unit: °C; Ch min : minimum value set for hydrogen concentration in historical product process, The control of the corresponding hydrogen concentration in the period of two discrete acquisition points is carried out by purging with nitrogen, When the corresponding hydrogen concentration in the period of two discrete acquisition points is controlled by purging with nitrogen, the oxidation energy in the current furnace is also calculated in real time according to the set calculation frequency, and the calculation result is compared with the set threshold value, When the calculation result is greater than or equal to the set threshold value, the nitrogen purging is stopped; Otherwise, continue or re-purge nitrogen.

2. The stopping control method for preventing the oxidation of the furnace roller of the continuous annealing furnace according to claim 1, characterized in that: The "discrete acquisition of the dew point value in the period of dew point falling to the target temperature" is acquired according to the real-time detection of the dew point detector.

3. The method of claim 1, wherein the method further comprises: determining a temperature of the workpiece; and determining a temperature of the workpiece at the end of the workpiece's travel through the furnace. The "discrete acquisition of the dew point value in the period of dew point falling to the target temperature" is based on the historical dew point acquisition.

4. The method of claim 1, wherein the method further comprises: determining a temperature of the furnace; and determining a temperature of the furnace roll. The flow rate of the purging nitrogen is determined according to the following formula: C h = C0x e (-Qt / V) , In the formula, C h : hydrogen concentration in the hearth after purging for t time; C0: hydrogen concentration in the furnace hearth at the time before t; Q: flow rate of the blowoff gas, unit: m 3 / h; t: period between two discrete acquisition points, unit: h; V: furnace volume, unit: m 3 .

5. The stopping control method for preventing the oxidation of the furnace roller of the continuous annealing furnace according to claim 1, characterized in that: The set threshold value is determined according to the oxidation energy limit value in normal production, specifically: P T = P max x k, P r : set threshold value; P max : Oxidation energy limit value at normal production; k: safety factor.

6. A continuous annealing furnace anti-roller oxidation shutdown control method according to claim 5, characterized in that: when the flow rate of the purge gas is greater than or equal to 600 m 3 / h, k takes a value of 0.995-1; When the flow rate of the purge gas is less than 600 m 3 / h, k takes a value of 0.99-0.

995.

7. The method of claim 1, wherein the method further comprises: determining a temperature of the workpiece; and determining a temperature of the workpiece at the end of the workpiece's travel through the furnace. The target temperature of dew point falling is determined according to the following formula: 0.127 + 0.0020 x X - 0.187 x 0.04 < P max In the formula, X: target value of dew point falling, unit: ℃; P max : Oxidation energy limit value at normal production.

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