Strip threading method for finishing mill

Abstract

The present application discloses a strip threading method for a finishing mill. The method comprises: determining the second flow rate of each stand and the initial threading speed of each stand based on the secondary model of the hot rolling production line and the second flow rate balance principle; determining the high-speed threading speed of the first stand, determining the number of stands implementing high-speed threading, and constructing a high-speed threading model based on a preset speed increase ratio and the initial threading speed of the first stand; and determining the deceleration rate of the stand implementing high-speed threading based on the number of stands implementing high-speed threading and the high-speed threading speed of the first stand. The strip threading method for a finishing mill of the present application can increase the strip threading speed of the finishing mill, thereby increasing the output of the entire hot rolling production line.

Description

Technical Field

[0001] The present application relates to the technical field of steel rolling, and in particular to a strip threading method for a finishing mill. Background Art

[0002] In existing hot rolling models, the strip threading speed of the finishing mill is calculated by a secondary model based on parameters such as the strip process requirements, equipment production capacity, and the actual strip finishing entrance temperature. However, in actual production, the strip threading speed of the front stand is often about one-tenth of that of the last stand, because the strip between the stands of the finishing mill must meet the principle of second flow balance. The speed of the strip from the flying shear to entering the finishing mill usually needs to match the speed at which it enters the first stand, which prolongs the finishing entry time and also increases the pure rolling time of the finishing mill, resulting in an excessive temperature drop at the strip head, which is not conducive to the sampling self-learning of the secondary model and the stability of production. These problems have greatly restricted the improvement of the rolling speed of the finishing mill and affected the output of the entire hot rolling production line. Summary of the Invention

[0003] An embodiment of the present application provides a strip threading method for a finishing mill, which can increase the strip threading speed of the finishing mill, thereby increasing the output of the entire hot rolling production line.

[0004] An embodiment of the present application proposes a strip threading method for a finishing mill, comprising: determining the second flow rate of each rack and the initial threading speed of each rack based on a secondary model of a hot rolling production line and a second flow rate balance principle; determining the high-speed threading speed of the first rack, determining the number of racks implementing high-speed threading and constructing a high-speed threading model based on a preset speed increase ratio and the initial threading speed of the first rack; determining the deceleration rate of the rack implementing high-speed threading based on the number of racks implementing high-speed threading and the high-speed threading speed of the first rack.

[0005] According to one aspect of an embodiment of the present application, the step of determining the deceleration rate of each rack implementing high-speed threading according to the number of racks implementing high-speed threading and the high-speed threading speed of the first rack includes: before the first rack is loaded, the running speed of the strip head is the high-speed threading speed, after the first rack is loaded, the strip head is decelerated at a preset deceleration rate, and after the n-1th rack is loaded and before the nth rack is loaded, the strip head is decelerated to the final threading speed.

[0006] According to one aspect of an embodiment of the present application, the steps of determining the high-speed threading speed of the first frame, determining the number of frames for implementing high-speed threading, and constructing a high-speed threading model based on a preset speed increase ratio and the initial threading speed of the first frame include obtaining the maximum threading speed of the last frame, the minimum threading speed of the last frame, the maximum thickness of the intermediate billet, the minimum thickness of the intermediate billet, the maximum thickness of the finished product, and the minimum thickness of the finished product.

[0007] According to one aspect of an embodiment of the present application, the racks for implementing high-speed tape threading include a first rack, a second rack, a third rack, and a fourth rack.

[0008] According to one aspect of an embodiment of the present application, the steps of determining the high-speed threading speed of the first rack, determining the number of racks for implementing high-speed threading, and constructing a high-speed threading model based on a preset speed increase ratio and the initial threading speed of the first rack include constructing a speed factor setting model and confirming the first limit limit.

[0009] According to one aspect of an embodiment of the present application, constructing a speed factor setting model and confirming the first limit limit includes determining a high-speed threading coefficient using equations (1)-(4):

[0010] α=1+δ*β (1)

[0011]

[0012]

[0013]

[0014] Among them, W MAX The maximum width of the finished product, in mm, W set W is the set value of the finished product width in mm. MIN The minimum width of the finished product, in mm, H MAX The maximum thickness of the finished product, in mm, H SET H is the set value of the finished product thickness, in mm. MIN is the minimum thickness of the finished product, in mm, α is the multiplication gain coefficient of high-speed threading, in %, δ is the width factor of high-speed threading, in %, δ width is the width factor correction coefficient, unit is %, β is the thickness factor of high-speed threading, unit is %, β thick is the thickness factor correction coefficient, the unit is %, K is the high speed factor limit, the unit is %, is the high-speed threading coefficient, in %.

[0015] According to one aspect of an embodiment of the present application, the steps of determining the high-speed threading speed of the first rack, determining the number of racks to implement high-speed threading, and constructing a high-speed threading model based on a preset speed increase ratio and the initial threading speed of the first rack include performing a second limit limit check on the high-speed threading factor of the last rack, wherein the high-speed threading speed of the last rack is obtained by multiplying the normally set threading speed of the last rack by the high-speed threading coefficient.

[0016] According to one aspect of the embodiment of the present application, a second limit amplitude check is performed on the high-speed threading factor of the last rack using formula (5):

[0017]

[0018] In V F-last快速 ≤V F-last设定 In the case of the high-speed threading speed of the last rack is V F-last设定 ;

[0019] In V F-last快速 >V F-last最大 In the case of the high-speed threading speed of the last rack is V F-last最大 ;

[0020] Among them, V F-last快速 The high-speed threading speed of the last rack in high-speed threading mode is in m / s. V F-last设定 The normal setting threading speed of the last rack is m / s, V F-last最大 is the maximum threading speed of the last rack, in m / s. is the high-speed threading coefficient, in %.

[0021] According to one aspect of an embodiment of the present application, the steps of determining the high-speed threading speed of the first rack, determining the number of racks for implementing high-speed threading, and constructing a high-speed threading model based on a preset speed increase ratio and the initial threading speed of the first rack include performing a second limit limiting check on the high-speed threading factor of all racks.

[0022] According to one aspect of the embodiment of the present application, a second limit amplitude check is performed on the full-rack high-speed tape-through factor using formula (6):

[0023]

[0024] Among them, V Fi快速 is the high-speed threading speed of the i-th rack, in m / s, V F-last快速 The high-speed threading speed of the last rack in high-speed threading mode, in m / s, h Fi is the calculated thickness of the intermediate billet at the exit of the i-th rack, in mm, h F-last The calculated thickness of the intermediate billet at the final stand, in mm;

[0025] In V Fi快速 ≥V Fi最大 In the case of , the high-speed tape threading speed of the i-th rack is replaced by the maximum tape threading speed of the i-th rack, and the high-speed tape threading speed of the last rack is recalculated using formula (5).

[0026] The embodiment of the present application determines the high-speed threading speed of the first stand, determines the number of stands implementing high-speed threading, and constructs a high-speed threading model based on a preset speed increase ratio and the initial threading speed of the first stand, thereby increasing the threading speed of the finishing mill within the capacity of existing rolling mill equipment. In addition, the embodiment of the present application determines the deceleration rate of the stand implementing high-speed threading based on the number of stands implementing high-speed threading and the high-speed threading speed of the first stand, thereby increasing the head temperature of the strip, ensuring that the head temperature of the strip is within an appropriate range during the rolling process, thereby improving the threading stability, reducing the labor intensity of operators, and further increasing the threading speed of the strip in the finishing mill, thereby increasing the output of the entire hot rolling production line. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The features, advantages and technical effects of exemplary embodiments of the present application will be described below with reference to the accompanying drawings.

[0028] Figure 1 A schematic diagram of the strip running speed of the finishing mill strip threading method provided in an embodiment of the present application.

[0029] in:

[0030] 10. Flying shear shearing area; 20. Fine descaling area; 30. High-speed belt threading area; 40. Deceleration starting point; 50. Deceleration area; 60. Deceleration completion point; 70. Normal belt threading area. DETAILED DESCRIPTION

[0031] The features and exemplary embodiments of various aspects of the present application will be described in detail below. In the detailed description below, many specific details are set forth in order to provide a comprehensive understanding of the present application. However, it will be apparent to those skilled in the art that the present application can be implemented without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present application by illustrating examples of the present application. In the accompanying drawings and the following description, at least some of the well-known structures and technologies are not shown in order to avoid unnecessary ambiguity in the present application; and, for clarity, the sizes of some structures may be exaggerated. In addition, the features, structures, or characteristics described below may be combined in any suitable manner in one or more embodiments.

[0032] In this application, the terms "first", "second", etc. are used to distinguish similar objects, but are not used to describe a specific order or sequence.

[0033] It should be noted that the hot rolling production line in the embodiment of the present application includes a flying shear shearing process, a fine descaling process and a rolling process. The rolling time in the embodiment of the present application is the time required for the head of the strip to enter the first stand to the tail of the strip to exit the last stand. The rolling time can also be called the finishing rolling time. The rolling process refers to the process from the head of the strip entering the first stand to the tail of the strip exiting the last stand. The strip threading process in the embodiment of the present application refers to the process from the head of the strip entering the first stand to the head of the strip passing through the last stand.

[0034] The present application provides a strip threading method for a finishing mill, comprising:

[0035] According to the secondary model of the hot rolling production line and the principle of second flow balance, the second flow of each stand and the initial strip threading speed of each stand are determined;

[0036] According to the preset speed increase ratio and the initial threading speed of the first rack, the high-speed threading speed of the first rack is determined, the number of racks to be threaded at high speed is determined, and a high-speed threading model is constructed;

[0037] The deceleration rate of the rack implementing high-speed tape threading is determined according to the number of racks implementing high-speed tape threading and the high-speed tape threading speed of the first rack.

[0038] The embodiment of the present application determines the high-speed threading speed of the first stand, determines the number of stands implementing high-speed threading, and constructs a high-speed threading model based on a preset speed increase ratio and the initial threading speed of the first stand, thereby increasing the threading speed of the finishing mill within the capacity of existing rolling mill equipment. In addition, the embodiment of the present application determines the deceleration rate of the stand implementing high-speed threading based on the number of stands implementing high-speed threading and the high-speed threading speed of the first stand, thereby increasing the head temperature of the strip, ensuring that the head temperature of the strip is within an appropriate range during the rolling process, thereby improving the threading stability, reducing the labor intensity of operators, and further increasing the threading speed of the strip in the finishing mill, thereby increasing the output of the entire hot rolling production line.

[0039] The principle of second flow balance of strip steel means that the mass of steel strip passing through each rack per unit time is equal.

[0040] The calculation formula for the second flow rate of the strip steel may include: taking a certain frame in the rolling process, at this time the speed of the strip steel at the outlet of the frame is V, the thickness of the strip steel at the outlet of the frame in the hot state is H, and the width of the strip steel at the outlet of the frame in the hot state is W, and calculating the second flow rate m of the strip steel at the outlet of the frame according to m=V*H*W (Formula 1-1).

[0041] In some optional embodiments, the step of determining the deceleration rate of each rack implementing high-speed threading based on the number of racks implementing high-speed threading and the high-speed threading speed of the first rack may include setting the running speed of the strip head to the high-speed threading speed before the first rack is loaded, decelerating the strip head at a preset deceleration rate after the first rack is loaded, and decelerating the strip head to the final threading speed after the n-1 rack is loaded and before the n rack is loaded.

[0042] Figure 1 Schematic diagram of the strip running speed of the finishing mill strip threading method provided in the embodiment of the present application. When a 7-stand finishing mill is used for rolling, CS is a shearing machine, and the running speed of the strip in the flying shear shearing zone 10 is the flying shear shearing speed. FSB is a fine descaling machine, and the strip usually runs at a higher speed in the fine descaling zone 20, that is, under normal circumstances, the running speed of the strip in the fine descaling zone 20 is higher than the running speed of the strip in the high-speed threading zone 30. The 1st stand F1, the 2nd stand F2, the 3rd stand F3, the 4th stand F4, the 5th stand F5, the 6th stand F6 and the 7th stand F7 are all finishing stands, and the area where the finishing stands are located is the finishing zone, wherein the finishing zone can be divided into a high-speed threading zone 30, a deceleration starting point 40, a deceleration zone 50, a deceleration completion point 60 and a normal threading zone 70.

[0043] Depend on Figure 1 As can be seen, after the first stand is loaded, the strip runs at a high threading speed. Between the first and fourth stands, the strip runs at a preset deceleration rate, and then resumes normal threading speed until the strip head reaches the fourth stand. The term "loading" refers to the moment when the strip head enters a stand, or when the strip head bites into that stand. It can also be referred to as the moment when the pressure sensor in that stand detects that the rolling force exceeds the rolling threshold.

[0044] It should be noted that a frame implementing high-speed strip threading means that the strip threading speed in the frame is higher than its normal strip threading speed, or higher than its strip threading speed in the normal strip threading area 70. Unless otherwise specified, the strip speed refers to the speed of the strip head.

[0045] The preset speed increase ratio can be determined based on factors such as the actual production capacity of the rolling mill and the reaction time of the operator.

[0046] In some optional embodiments, the steps of determining the high-speed threading speed of the first frame, determining the number of frames for implementing high-speed threading, and constructing a high-speed threading model based on a preset speed increase ratio and the initial threading speed of the first frame may include obtaining the maximum threading speed of the last frame, the minimum threading speed of the last frame, the maximum thickness of the intermediate billet, the minimum thickness of the intermediate billet, the maximum thickness of the finished product, and the minimum thickness of the finished product.

[0047] Generally, when determining the number of racks for high-speed strip threading, it is also necessary to refer to the operator's reaction time so that the operator can adapt to the finishing mill strip threading method of the embodiment of the present application. The operator's reaction time can be determined according to his or her operating proficiency. For example, the operator's reaction time can be 0.5-1.5s.

[0048] The maximum value of the last stand threading speed, the minimum value of the last stand threading speed, the maximum value of the intermediate billet thickness, the minimum value of the intermediate billet thickness, the maximum value of the finished product thickness and the minimum value of the finished product thickness can all be determined based on the production capacity of the equipment in the production line and the reaction time of the operator.

[0049] The thickness of the intermediate billet in the embodiments of the present application refers to the thickness of the strip steel after rough rolling and before shearing.

[0050] For example, when a 7-stand finishing mill is used for rolling, the last stand is the 7th stand. In this case, the maximum strip threading speed of the last stand is 11.5 m / s, the minimum strip threading speed of the last stand is 1.8 m / s, the maximum intermediate bar thickness is 60 mm, the minimum intermediate bar thickness is 30 mm, the maximum finished product thickness is 25.4 mm, and the minimum finished product thickness is 1.4 mm.

[0051] In some optional embodiments, the racks for implementing high-speed threading may include a first rack, a second rack, a third rack, and a fourth rack.

[0052] The embodiment of the present application enables operators to adapt to the strip threading method of the finishing mill by setting the high-speed strip threading racks to the 1st to 4th racks, thereby improving the strip threading efficiency and increasing the output of the finishing mill within the scope of the existing finishing mill.

[0053] It should be noted that although the above determination of the number of stands for high-speed strip threading is based on the situation of using a 7-stand finishing mill for rolling, when the total number of finishing mills increases or decreases, the number of stands for high-speed strip threading can also be adaptively increased or decreased. The finishing mill in the embodiment of the present application can be a 7-stand four-high finishing mill.

[0054] In some optional embodiments, the steps of determining the high-speed threading speed of the first rack, determining the number of racks for implementing high-speed threading, and constructing a high-speed threading model based on a preset speed increase ratio and the initial threading speed of the first rack may include constructing a speed factor setting model and confirming a first limit limit.

[0055] The embodiment of the present application constructs a speed factor setting model and confirms the first limit limit, so that the temperature of the strip head is within an appropriate range during the rolling process, and the threading method is adapted to strips of different specifications, thereby achieving an increase in the threading speed of the finishing mill within the capacity of the existing rolling mill equipment.

[0056] In some optional embodiments, constructing the speed factor setting model and confirming the first limit limit may include determining the high-speed tape penetration coefficient through equations (1)-(4):

[0057] α=1+δ*β (1)

[0058]

[0059]

[0060]

[0061] Among them, W MAX The maximum width of the finished product, in mm, W set W is the set value of the finished product width in mm. MIN The minimum width of the finished product, in mm, H MAX The maximum thickness of the finished product, in mm, H SET H is the set value of the finished product thickness, in mm. MIN is the minimum thickness of the finished product, in mm, α is the multiplication gain coefficient of high-speed threading, in %, δ is the width factor of high-speed threading, in %, δ width is the width factor correction coefficient, unit is %, β is the thickness factor of high-speed threading, unit is %, β thick is the thickness factor correction coefficient, the unit is %, K is the high speed factor limit, the unit is %, is the high-speed threading coefficient, in %.

[0062] The value of is the minimum value of α and K. This process is the confirmation of the first limit limit. The confirmation of the first limit limit can make the strip threading speed in each frame within an appropriate range, thereby improving the quality of strip rolling and further improving the threading efficiency.

[0063] It should be noted that the width factor correction coefficient δ in the embodiment of the present application is width and thickness factor correction coefficient β thick are all known constants.

[0064] The high speed factor limit K in formula (4) can be determined according to the steel grade, the thickness of the finished product, and the width of the finished product. For example, when the steel grade is SPHC-A, the thickness of the finished product is 1.4-1.6 mm, and the width of the finished product is less than 1080 mm, or when 1080 mm ≤ the width of the finished product is less than 1180 mm, the value of the high speed factor limit K is 120%.

[0065] The high-speed threading limit factor K needs to be adjusted according to the hit rate of finishing rolling and self-learning status after the high-speed threading function is put into use for strips of various specifications, on the premise of meeting the operator's reaction time, equipment production capacity and process indicators.

[0066] In order to ensure the high-speed belt wear coefficient of the second flow balance principle The multiplication gain coefficient α of high-speed threading and the high-speed factor limit K are common to all racks.

[0067] In some optional embodiments, the steps of determining the high-speed threading speed of the first rack, determining the number of racks to implement high-speed threading, and constructing a high-speed threading model based on a preset speed increase ratio and the initial threading speed of the first rack may include performing a second limit limit check on the high-speed threading factor of the last rack, wherein the high-speed threading speed of the last rack is obtained by multiplying the normally set threading speed of the last rack by the high-speed threading coefficient.

[0068] In some optional embodiments, the second limit amplitude check of the high-speed tape-through factor of the last rack can be performed using formula (5):

[0069]

[0070] In V F-last快速 ≤V F-last设定 In the case of the high-speed threading speed of the last rack is V F-last设定 ;

[0071] In V F-last快速 >V F-last最大 In the case of the high-speed threading speed of the last rack is V F-last最大 ;

[0072] Among them, V F-last快速 The high-speed threading speed of the last rack in high-speed threading mode is in m / s. V F-last设定 The normal setting threading speed of the last rack is m / s, V F-last最大 is the maximum threading speed of the last rack, in m / s. is the high-speed threading coefficient, in %.

[0073] Unless otherwise specified, the high-speed threading speed refers to the high-speed threading speed of the rack in high-speed threading mode.

[0074] V F-last最大 It can be determined based on the production capacity of the equipment in the production line and the response time of the operator. For example, V F-last最大 is 11.5m / s.

[0075] For example, when the finishing process adopts a 7-stand finishing mill, V F-last快速 V F7快速 , V F-last设定 V F7设定 , V F-last最大 V F7最大 .

[0076] It should be noted that the speed in the embodiments of the present application is a linear speed.

[0077] The embodiment of the present application performs a second limit amplitude limit check on the high-speed threading factor of the last stand, so that the high-speed threading speed of the last stand can reach the maximum value without exceeding the maximum threading speed of the last stand, thereby increasing the threading speed of the last stand of the finishing mill within the capacity of existing equipment.

[0078] In some optional embodiments, the steps of determining the high-speed threading speed of the first rack, determining the number of racks implementing high-speed threading, and constructing a high-speed threading model based on a preset speed increase ratio and the initial threading speed of the first rack may include performing a second limit limiting check on the high-speed threading factor of all racks.

[0079] In some optional embodiments, the second limit limit check of the full-rack high-speed tape-through factor can be performed using formula (6):

[0080]

[0081] Among them, V Fi快速 is the high-speed threading speed of the i-th rack, in m / s, V F-last快速 The high-speed threading speed of the last rack in high-speed threading mode, in m / s, h Fi is the calculated thickness of the intermediate billet at the exit of the i-th rack, in mm, h F-last The calculated thickness of the intermediate billet at the final stand, in mm.

[0082] For example, when the finishing process adopts a 7-stand finishing mill, V F-last快速 V F7快速 , h F-last h F7 .

[0083] In some optional embodiments, at V Fi快速 ≥V Fi最大In the case of , the high-speed tape threading speed of the i-th rack is replaced by the maximum tape threading speed of the i-th rack, and the high-speed tape threading speed of the last rack is recalculated using formula (5).

[0084] The embodiment of the present application performs a second limit limit check on the high-speed threading factor of the entire frame, so that the high-speed threading speed of the entire frame can reach the maximum value without exceeding the maximum threading speed of its corresponding frame, thereby increasing the threading speed of the entire frame of the finishing mill within the capacity of the existing equipment.

[0085] For example, at V Fi快速 ≥V Fi最大 In the case of , the maximum threading speed of the i-th rack is used to replace the high-speed threading speed of the i-th rack. At this time, set α = V Fi最大 / V Fi设定 The recalculated α is substituted into formula (5) to calculate the high-speed threading speed of the last rack, and the second limit limit check is performed on the high-speed threading factor of the entire rack through formula (6).

[0086] In some optional embodiments, the step of determining the deceleration rate of each rack implementing high-speed threading based on the number of racks implementing high-speed threading and the high-speed threading speed of the first rack may include determining a deceleration rate reference rack based on the high-speed threading speed of the last rack.

[0087] For example, when a 7-stand finishing mill is used for rolling, the step of determining the deceleration rate of each stand implementing high-speed threading according to the number of stands implementing high-speed threading and the high-speed threading speed of the first stand may include calculating the deceleration rate of the high-speed threading using formulas (7)-(8):

[0088] FM=[-0.424*V F-last快速 +6.779] (7)

[0089] FM=LIMT(3,6) (8)

[0090] Where FM is the deceleration rate reference frame, V F-last快速 It is the high-speed threading speed of the 7th rack, in m / s.

[0091] It should be noted that formula (7) refers to rounding the calculation results, and formula (8) means that the value range of the deceleration rate completion frame is an integer in the range of 3-6. That is to say, when the number of finishing mills is 7, if the calculated deceleration rate reference frame is 7, the deceleration rate reference frame value is 6, and if the calculated deceleration rate reference frame is 1, the deceleration rate reference frame value is 3. If the calculated deceleration rate reference frame is in the range of 3-6, the deceleration rate reference frame value is the closest integer.

[0092] The deceleration rate reference rack is the deceleration completion rack, that is, the deceleration process needs to be completed before the strip head reaches this rack.

[0093] In some optional embodiments, the step of determining the deceleration rate of each rack performing high-speed threading based on the number of racks performing high-speed threading and the high-speed threading speed of the first rack may include obtaining the deceleration rate of the high-speed threading based on the high-speed threading speed of the rack that has completed deceleration, the set speed of the rack that has completed deceleration, and the distance between the racks.

[0094] In some optional embodiments, the step of determining the deceleration rate of each rack implementing high-speed threading according to the number of racks implementing high-speed threading and the high-speed threading speed of the first rack may include calculating the deceleration rate of the high-speed threading using formula (9):

[0095]

[0096] Among them L dec =L F3F4 -L F1_dis -L dis_F4

[0097] D FM快速 is the deceleration rate in m / s 2 , L F3F4 The distance between the third and fourth racks, in meters, L F1_dis The distance between the first rack and the deceleration completion point, in meters, L dis_F4 The distance between the deceleration completion point and the fourth rack, in meters, V FM Fast is the high-speed threading speed of the 4th rack, in m / s, V FM设定 It is the normal setting threading speed of the 4th rack, in m / s.

[0098] In D FM快速 >D FM最大 In the case of FM最大 At the same time, an alarm sign is sent to the secondary machine and the operator to remind them to reduce the high-speed threading coefficient. .

[0099] D FM最大 This can be determined based on the equipment limitations in the production line.

[0100] The "secondary machine" in the embodiments of the present application refers to a secondary control system or a process parameter control system.

[0101] The deceleration completion point is the position where the running speed of the strip reaches the normal operating speed. For example, when the deceleration is completed before the 4th rack, the distance from the 1st rack to the deceleration completion point refers to the distance from the center point of the 1st rack to the center point of the 4th rack.

[0102] It should be noted that the reduction rate between the reduction frames in the embodiment of the present application is a constant value.

[0103] The embodiment of the present application takes the finishing mill in the hot rolling production line as the research object, and based on the research on the finishing mill strip threading speed strategy, combined with a large amount of rolling data statistical analysis and field experiments, breaks through the limitations of conventional technology and proposes a finishing mill strip threading method that increases the finishing mill strip threading speed within the capacity of existing rolling mill equipment. It increases the head temperature of the strip, so that the head temperature of the strip is within a suitable range during the rolling process, thereby improving the threading stability and reducing the labor intensity of the operators. By optimizing the threading speed control strategy, the finishing mill strip threading method can be adapted to strips of different specifications, and the finishing mill strip threading speed can be increased, thereby improving the output and production efficiency of the entire hot rolling production line, which has a positive driving effect on the production of steel enterprises and provides a new solution for the sustainable development of the steel industry.

[0104] Example

[0105] The following examples more specifically describe the contents disclosed in the present application. These examples are intended to be illustrative only, as various modifications and variations within the scope of the contents disclosed in the present application will be apparent to those skilled in the art.

[0106] Examples 1-3

[0107] Examples 1-3 adopt the high-speed threading model of the present application.

[0108] In Examples 1-3, the multiplication gain coefficient is set to 15%. According to formulas (1)-(9), the racks for implementing high-speed threading are the 1st to 4th racks, the initial threading speed of F1, the initial threading speed of F7, the high-speed threading speed of F1, the high-speed threading speed of F7 and the deceleration rate are calculated and shown in Table 1.

[0109] Table 1

[0110]

[0111] Comparative Examples 1-3

[0112] Comparative Examples 1-3 use the conventional secondary model to calculate the tape threading speed of each rack.

[0113] Under the condition of the same strip threading speed, the rolling conditions of Examples 1-3 and Comparative Examples 1-3 were statistically analyzed and shown in Table 2.

[0114] Table 2

[0115]

[0116] Average pure rolling time of finishing rolling: the time required from the head of the strip entering the first stand to the tail of the strip exiting the last stand.

[0117] Average rolling rhythm: the time from the previous strip head passing through F1 to the next strip head entering F1.

[0118] Number of rolling blocks: The number of samples taken during the experimental study, which does not involve the rolling capacity of the finishing mill.

[0119] As can be seen from Table 2, by adopting the strip threading method of the finishing mill of the embodiment of the present application, the average pure rolling time of the finishing rolling of strips of different steel grades is reduced by 4.27s, and the strip threading speed of the finishing mill is increased, which can improve the output and production efficiency of the entire hot rolling production line.

[0120] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A strip threading method for a finishing mill, characterized in that: include: According to the secondary model of the hot rolling production line and the principle of second flow balance, the second flow of each stand and the initial strip threading speed of each stand are determined; The steps of determining the high-speed threading speed of the first rack, determining the number of racks for implementing high-speed threading, and constructing a high-speed threading model according to a preset speed increase ratio and an initial threading speed of the first rack, including obtaining a maximum threading speed of the last rack, a minimum threading speed of the last rack, a maximum thickness of the intermediate billet, a minimum thickness of the intermediate billet, a maximum thickness of the finished product, and a minimum thickness of the finished product; This step includes constructing a speed factor setting model and confirming the first limit limit; the construction of the speed factor setting model and confirming the first limit limit include determining the high-speed threading coefficient through equations (1)-(4): （1） （2） （3） φ = min(α, K) (4) Among them, W MAX The maximum width of the finished product, in mm, W set W is the set value of the finished product width in mm. MIN The minimum width of the finished product, in mm, H MAX The maximum thickness of the finished product, in mm, H SET H is the set value of the finished product thickness, in mm. MIN is the minimum thickness of the finished product, in mm, and α is the multiplication gain coefficient of high-speed threading, in %. δ is the width factor of high-speed tape threading, unit is %. δ width is the width factor correction coefficient, unit is %. β is the thickness factor of high-speed threading, unit is %. β thick is the thickness factor correction coefficient, unit is %, K is the high-speed factor limit, unit is %, φ is the high-speed threading coefficient, unit is % This step includes performing a second limit amplitude limit check on the high-speed tape threading factor of the last rack, wherein the high-speed tape threading speed of the last rack is obtained by multiplying the normal set tape threading speed of the last rack by the high-speed tape threading coefficient; the second limit amplitude limit check on the high-speed tape threading factor of the last rack is performed by formula (5): （5） exist In the case of , the high-speed threading speed of the last rack is ; exist In the case of , the high-speed threading speed of the last rack is ; in, The high-speed threading speed of the last rack in high-speed threading mode, in m / s. The normal setting threading speed of the last rack is m / s. is the maximum threading speed of the last rack, in m / s; φ is the high-speed threading coefficient, in %. The high-speed threading speed of the last rack is obtained by multiplying the normal threading speed of the last rack by the high-speed threading coefficient. The deceleration rate of the rack for high-speed threading is determined according to the number of the racks for high-speed threading and the high-speed threading speed of the first rack.

2. The strip threading method for a finishing mill according to claim 1, characterized in that: The step of determining the deceleration rate of each rack implementing high-speed threading according to the number of racks implementing high-speed threading and the high-speed threading speed of the first rack includes: before the first rack is loaded, the running speed of the strip head is the high-speed threading speed, after the first rack is loaded, the strip head is decelerated at a preset deceleration rate, and after the (n-1)th rack is loaded and before the (n)th rack is loaded, the strip head is decelerated to the final threading speed.

3. The strip threading method for a finishing mill according to claim 1, characterized in that: The racks for implementing high-speed tape threading include a first rack, a second rack, a third rack and a fourth rack.

4. The strip threading method for a finishing mill according to claim 1, characterized in that: The steps of determining the high-speed threading speed of the first rack based on the preset speed increase ratio and the initial threading speed of the first rack, determining the number of racks for implementing high-speed threading, and constructing a high-speed threading model include performing a second limit limit check on the high-speed threading factor of all racks.

5. The strip threading method for a finishing mill according to claim 4, characterized in that: The second limit amplitude check of the full-rack high-speed tape-through factor is performed using formula (6): （6） in, is the high-speed threading speed of the i-th rack, in m / s, The high-speed threading speed of the last rack in high-speed threading mode, in m / s. is the calculated thickness of the intermediate billet at the exit of the i-th rack, in mm, The calculated thickness of the intermediate billet at the final stand, in mm; exist In the case of , the high-speed tape threading speed of the i-th rack is replaced by the maximum tape threading speed of the i-th rack, and the high-speed tape threading speed of the last rack is recalculated using formula (5).

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