A control method for reducing the tail breakage rate of hot-rolled thin-gauge strip steel

Abstract

The application discloses a control method for reducing tail breakage rate of hot-rolled thin-gauge strip steel, and relates to the field of steel rolling. The control method for reducing tail breakage rate of hot-rolled thin-gauge strip steel comprises the following steps: when the rolling force range of the first four stands is in a first preset range, the plastic rigidity of the corresponding stand is controlled to be in a second preset range; and when the rolling force range of the last three stands is in a third preset range, the plastic rigidity of the corresponding stand is controlled to be in a fourth preset range. The control method for reducing tail breakage rate of hot-rolled thin-gauge strip steel can improve the stability in the tail breakage process and meet the rapid adjustment of the tail shape by automatically leveling when the strip steel tail passes through each stand, and solves the problem of tail breakage in the hot-rolled thin-gauge strip steel rolling process.

Description

Technical Field

[0001] This application relates to the field of steel rolling, and more specifically, to a method for controlling the tail breakage rate of hot-rolled thin strip steel. Background Technology

[0002] The thin slab continuous casting and rolling production line (CSP production line) is more conducive to the production of thin materials than conventional hot rolling due to its process characteristics. At the same time, driven by "acid-cooling", the market potential of thin-gauge hot-rolled pickled steel is huge.

[0003] Controlling the strip profile at the tail end is a key challenge in the production of thin-gauge pickled steel. Strip breakage at the tail end directly affects rolling stability, causing strip fragments to adhere to the work rolls, damaging them and leading to subsequent surface defects. In severe cases, this can result in reduced pulling speed, breakage, interrupted casting, roll spalling, and roll breakage. This is especially true when finishing mills produce strips with a thickness ≤2.0mm. During strip throwing, the centerline of the tail end deviates from the centerline during the stabilization period, causing the strip tail to deviate during thin-gauge rolling. This leads to tail-end slippage, breakage, and strip breakage, severely impacting the stability and continuity of finishing mill rolling. Summary of the Invention

[0004] The purpose of this application is to provide a control method for reducing the tail breakage rate of hot-rolled thin strip steel. By automatically leveling the strip tail as it passes through each stand, the stability of the tail steel throwing process can be improved and the tail plate shape can be quickly adjusted, thus solving the problem of tail breakage during the rolling process of hot-rolled thin strip steel.

[0005] This application is implemented as follows:

[0006] This application provides a method for controlling the tail breakage rate of hot-rolled thin strip steel, including the following steps:

[0007] When the rolling force ranges of the first stand, second stand, third stand, and fourth stand are 0-5000KN, 5000-10000KN, 10000-15000KN, 15000-20000KN, 20000-25000KN, 25000-30000KN, 30000-35000KN, and 35000-40000KN, control the first stand... The plastic stiffnesses of the second, third, and fourth frames are 1235-1351 KN / mm, 1352-1417 KN / mm, 1418-1464 KN / mm, 1465-1500 KN / mm, 1501-1530 KN / mm, 1531-1556 KN / mm, 1557-1587 KN / mm, and 1588-1620 KN / mm, respectively.

[0008] When the rolling force range of the fifth, sixth, and seventh stands is 0-4000KN, 4000-8000KN, 8000-12000KN, 12000-16000KN, 16000-20000KN, and 20000-24000KN, the plastic stiffness of the fifth, sixth, and seventh stands is controlled to be 1159-1270KN / mm, 1271-1334KN / mm, 1335-1380KN / mm, 1381-1415KN / mm, 1416-1444KN / mm, and 1445-1480KN / mm, respectively.

[0009] In some alternative implementations, the first stand is controlled to quickly open the roll gap when the tail of the strip reaches the roll gap, and the minimum rolling force when the first stand triggers the quick opening is 5000KN, the minimum activation ratio of the quick opening circuit control valve corresponding to the first stand is 50%, the maximum activation ratio of the quick opening circuit control valve corresponding to the first stand is 150%, and the minimum roll gap change when the first stand triggers the quick opening is 0.05mm.

[0010] In some alternative implementations, when the first stand rapidly opens the roll gap as the tail of the strip reaches the roll gap, the roll gap automatic control correction gain factor of the first stand is set to 2.05.

[0011] In some alternative implementations, when the first stand is controlled to quickly open the roll gap as the tail of the strip reaches the roll gap, the maximum distance between the first stand and the tail of the strip is 1.5m.

[0012] In some alternative implementations, the second stand is controlled to quickly open the roll gap when the tail of the strip reaches the roll gap, and the minimum rolling force when the second stand triggers the quick opening is 5000KN, the minimum activation ratio of the quick opening circuit control valve corresponding to the second stand is 80%, the maximum activation ratio of the quick opening circuit control valve corresponding to the second stand is 175%, and the minimum roll gap change when the second stand triggers the quick opening is 0.05mm.

[0013] In some alternative implementations, when the second stand rapidly opens the roll gap as the tail of the strip reaches the roll gap, the roll gap automatic control correction gain factor of the second stand is set to 2.

[0014] In some alternative implementations, when the second stand is controlled to quickly open the roll gap as the tail of the strip reaches the roll gap, the maximum distance between the second stand and the tail of the strip is 1m.

[0015] In some alternative implementations, the short-stroke opening of the inlet guide plates of the second, third, fourth, fifth, sixth, and seventh racks are 30mm, 30mm, 30mm, 70mm, 100mm, and 150mm, respectively.

[0016] In some alternative implementations, the short-stroke lengths of the inlet guide plates for the second, third, fourth, fifth, sixth, and seventh racks are 5m, 5m, 10m, 12m, 18m, and 25m, respectively.

[0017] The beneficial effects of this application are as follows: The control method for reducing the tail breakage rate of hot-rolled thin strip steel provided by this application can improve the stability of the tail steel throwing process and meet the rapid adjustment of the tail plate shape by automatically leveling the tail steel as it passes through each stand. It can assist or replace the operator's manual leveling, avoid ineffective leveling caused by visual errors, solve the problem of tail breakage in the rolling process of hot-rolled thin strip steel, improve the quality of strip steel and reduce the amount of scrap and defective products. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The strip tail profiles at the exits of the first and second stands after the quick opening of the mill tail are shown in the example of the control method for reducing the tail breakage rate of hot-rolled thin strip provided in the embodiments of this application.

[0020] Figure 2 To illustrate the control method for reducing the tail breakage rate of hot-rolled thin strip steel provided in the embodiments of this application, the strip tail section diagrams at the exits of the first and second stands after the quick opening of the mill tail are generated. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0022] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0023] This application provides a control method for reducing the tail breakage rate of hot-rolled thin strip steel. The method involves adjusting the first stand F1, second stand F2, third stand F3, fourth stand F4, fifth stand F5, sixth stand F6, and seventh stand F7 in a rolling mill, each equipped with upper and lower rolls. The method specifically includes the following steps:

[0024] Step 1: Quick opening of the tail section of the rolling mill, as shown in Table 1 below:

[0025] The first stand F1 of the control mill rapidly opens the roll gap when the tail of the strip reaches the roll gap, and the minimum rolling force when the first stand F1 triggers the quick opening is 5000KN, the minimum activation ratio of the quick opening circuit control valve corresponding to the first stand F1 is 50%, the maximum activation ratio of the quick opening circuit control valve corresponding to the first stand F1 is 150%, the minimum roll gap change when the first stand F1 triggers the quick opening is 0.05mm, the roll gap automatic control correction gain coefficient of the first stand F1 is 2.05, and the maximum distance from the tail of the strip when the first stand F1 triggers the quick opening is 1.5m.

[0026] The second stand F2 of the control mill rapidly opens the roll gap when the tail of the strip reaches the roll gap, and the minimum rolling force when the second stand F2 triggers the quick opening is 5000KN, the minimum activation ratio of the quick opening circuit control valve corresponding to the second stand F2 is 80%, the maximum activation ratio of the quick opening circuit control valve corresponding to the second stand F2 is 175%, the minimum roll gap change when the second stand F2 triggers the quick opening is 0.05mm, the roll gap automatic control correction gain coefficient of the second stand F2 is 2, and the maximum distance from the tail of the strip when the second stand F2 triggers the quick opening is 1m.

[0027] Table 1. Parameters for quick-opening at the tail of the rolling mill

[0028]

[0029] The quick opening at the tail of the rolling mill is designed to reduce uneven elongation of the strip tail. It acts on the front stands, namely the first stand F1 and the second stand F2. After determining the rolling force, the H-AGC cylinder roll gap is quickly opened when the strip tail reaches the roll gap of the corresponding stand. This reduces the impact of the rolling force on the shape of the strip tail, shortens the uneven elongation of the strip tail, reduces the ineffective adjustment when the strip is thrown at the tail of the rear stand, and thus reduces the breakage rate of the strip tail under untensioned conditions.

[0030] Step 2: Automatic leveling at the tail of the rolling mill, as shown in Table 2 below;

[0031] When the rolling force ranges of the first stand F1, the second stand F2, the third stand F3, and the fourth stand F4 are 0-5000KN, 5000-10000KN, 10000-15000KN, 15000-20000KN, 20000-25000KN, 25000-30000KN, 30000-35000KN, and 35000-40000KN, the rolling force of the first stand F4 is controlled. 1. The plastic stiffness of the second frame F2, the third frame F3, and the fourth frame F4 are 1235-1351KN / mm, 1352-1417KN / mm, 1418-1464KN / mm, 1465-1500KN / mm, 1501-1530KN / mm, 1531-1556KN / mm, 1557-1587KN / mm, and 1588-1620KN / mm, respectively;

[0032] When the rolling force ranges of the fifth stand F5, the sixth stand F6, and the seventh stand F7 are 0-4000KN, 4000-8000KN, 8000-12000KN, 12000-16000KN, 16000-20000KN, and 20000-24000KN, the plastic stiffness of the fifth stand F5, the sixth stand F6, and the seventh stand F7 are controlled to be 1159-1270KN / mm, 1271-1334KN / mm, 1335-1380KN / mm, 1381-1415KN / mm, 1416-1444KN / mm, and 1445-1480KN / mm, respectively.

[0033] Table 2 Automatic Leveling Parameters at the Tail of the Rolling Mill

[0034]

[0035]

[0036] Automatic leveling at the tail of the rolling mill is a function developed to improve stability during the tail-end strip throwing process and to assist or replace manual leveling by operators. It operates after the strip is thrown from the front stand, i.e., when the front stand is out of tension. It uses the difference in pressure head force on both sides of the stand before strip throwing as a reference, and takes values ​​from a static parameter table to meet the needs of rapid adjustment of the strip shape at the tail. The plastic stiffness characterizes the change in rolling force caused by each millimeter of horizontal adjustment. Static data is collected to show the relationship between leveling and rolling force changes during daily production. In other words, the amount of automatic leveling required at the tail end during the rolling and throwing stage to balance the change in rolling force difference on both sides is calculated based on the static table.

[0037] Step 3: Short-stroke control of the mill inlet guide plate, as shown in Table 3 below;

[0038] The short-stroke opening of the inlet guide plates of the second frame F2, the third frame F3, the fourth frame F4, the fifth frame F5, the sixth frame F6, and the seventh frame F7 are 30mm, 30mm, 30mm, 70mm, 100mm, and 150mm, respectively; the short-stroke length of the inlet guide plates of the second frame F2, the third frame F3, the fourth frame F4, the fifth frame F5, the sixth frame F6, and the seventh frame F7 are 5m, 5m, 10m, 12m, 18m, and 25m, respectively.

[0039] Table 3 Short-stroke control parameters for mill inlet guide plates

[0040] Short-stroke opening of the inlet guide plate (mm) 30 30 30 70 100 150 Short stroke length (m) of the inlet guide plate 5 5 10 12 18 25

[0041] Short-stroke control at the tail of the rolling mill is designed to reduce the scraping of the strip tail against the mill stand inlet guide plate during the strip throwing process. The strip tail typically extends unevenly on both sides, which can lead to contact and scraping with the mill stand inlet guide plate. This scraping can cause deformation such as edge folding and tearing of the strip tail. After the strip tail deforms and enters the mill stand roll gap, it can lead to strip breakage and folding. Therefore, by appropriately increasing the short stroke at the tail of the rolling mill, contact between the strip tail and the mill stand inlet guide plate can be avoided, thus effectively preventing additional deformation at the tail of the rolling mill.

[0042] The control method for reducing the tail breakage rate of hot-rolled thin strip provided in this application controls the rapid opening of the mill tail. When the strip is rolled to the tail end for steel throwing, the opening process of the HGC cylinder's thickness closed-loop control is relatively slow when it reaches the tail end of the strip. The rolling force can cause the tail end of the strip to be thinner and longer, resulting in a large extension. This extension will continue to lengthen in the subsequent stands, which has an adverse effect on rolling stability. Therefore, by confirming the parameters of the rapid opening of the tail end of the mill stand, the rapid response of the HGC cylinder in the first stand F1 and the second stand F2 during the tail steel throwing process is ensured, reducing the tail extension of the strip and the ineffective adjustment of subsequent stands.

[0043] The reason why the automatic leveling of the tail of the rolling mill is controlled in this embodiment is that poor strip shape during steel throwing can cause the tail of the strip to deviate from the rolling center line. The manual adjustment speed is 0.07mm per press, while through the development and optimization of the automatic leveling of the tail of the strip, the speed of automatic leveling can reach more than 20 times that of manual leveling, which plays a key role in correcting the strip shape at the tail of the strip. At the same time, the automatic leveling adopts pure rolling force closed-loop technology to avoid ineffective leveling caused by visual errors.

[0044] The reason for controlling the short stroke of the tail of the inlet guide plate of the rolling mill stand in this embodiment is to reduce or eliminate the deformation caused by the tail of the strip contacting the inlet guide plate before entering the roll gap during the strip throwing process, so as to avoid the occurrence of folding and rolling after abnormal deformation enters the roll gap, reduce roll mark quality problems, and reduce roll wear loss caused by abnormal roll changing.

[0045] The features and performance of the control method for reducing the tail breakage rate of hot-rolled thin strip steel of this application are further described in detail below with reference to embodiments.

[0046] Example 1

[0047] This application provides a method for controlling the tail breakage rate of hot-rolled thin strip steel. When producing SPHC-B strip steel with a specification of 1.2mm×1219mm, the tail opening of the rolling mill, the automatic leveling of the tail of the rolling mill, and the short stroke of the tail of the rolling mill stand inlet guide plate are adjusted according to Tables 4, 5 and 6 respectively. No tail breakage problem of strip steel occurred throughout the year of production.

[0048] Table 4 shows the adjustment of the quick-opening parameters at the tail of the rolling mill in Example 1.

[0049]

[0050]

[0051] Table 5. Automatic leveling parameters at the tail of the rolling mill in Example 1.

[0052]

[0053] Table 6. Short-stroke control parameters of the mill inlet guide in Example 1.

[0054]

[0055] Example 2

[0056] This application provides a method for controlling the tail breakage rate of hot-rolled thin strip steel. When producing Q235B strip steel with a specification of 1.4mm×1250mm, the quick opening of the mill tail, the automatic leveling of the mill tail, and the short stroke of the mill stand inlet guide plate tail are adjusted according to Tables 7, 8 and 9 respectively. No strip tail breakage problem occurred throughout the year of production.

[0057] Table 7 shows the adjustment of the quick-opening parameters at the tail of the rolling mill in Example 2.

[0058]

[0059] Table 8 Automatic leveling parameters at the tail of the rolling mill in Example 2 (Table 8)

[0060]

[0061] Table 9 Short-stroke control parameters of the mill inlet guide in Example 2

[0062]

[0063] Example 3

[0064] This application provides a method for controlling the tail breakage rate of hot-rolled thin strip steel. When producing Q235B strip steel with a specification of 1.8mm×1500mm, the tail opening of the rolling mill, the automatic leveling of the tail of the rolling mill, and the short stroke of the tail of the rolling mill stand inlet guide plate are adjusted according to Tables 10, 11 and 12 respectively. No tail breakage problem of strip steel occurred throughout the year of production.

[0065] Table 10 shows the adjustment of the quick-opening parameters at the tail of the rolling mill in Example 3.

[0066]

[0067] Table 11 Automatic leveling parameters at the tail of the rolling mill in Example 3

[0068]

[0069] Table 12 Short-stroke control parameters of the mill inlet guide in Example 3

[0070]

[0071] Example 4

[0072] This application provides a method for controlling the tail breakage rate of hot-rolled thin strip steel. When producing Q235B strip steel with a specification of 1.5mm×1500mm, the quick opening of the mill tail, the automatic leveling of the mill tail, and the short stroke of the mill stand inlet guide plate tail are adjusted according to Tables 13, 14, and 15 respectively. No strip tail breakage problem occurred throughout the year of production.

[0073] Table 13 shows the adjustment of the quick-opening parameters at the tail of the rolling mill in Example 4.

[0074]

[0075] Table 14 Automatic leveling parameters at the tail of the rolling mill in Example 4

[0076]

[0077] Table 15 Short-stroke control parameters of the mill inlet guide in Example 4

[0078]

[0079] Example 5

[0080] This application provides a method for controlling the tail breakage rate of hot-rolled thin strip steel. When producing SPA-H strip steel with a specification of 1.5mm×1175mm, the quick opening of the mill tail, the automatic leveling of the mill tail, and the short stroke of the mill stand inlet guide plate tail are adjusted according to Tables 16, 17, and 18 respectively. No strip tail breakage problem occurred throughout the year of production.

[0081] Table 16 shows the adjustment of the quick-opening parameters at the tail of the rolling mill in Example 5.

[0082]

[0083] Table 17 Automatic leveling parameters at the tail of the rolling mill in Example 5

[0084]

[0085] Table 18 Short-stroke control parameters for the mill inlet guide in Example 5

[0086]

[0087] Example 6

[0088] This application provides a method for controlling the tail breakage rate of hot-rolled thin strip steel. When producing SAE1006 strip steel with a specification of 2.0mm×1214mm, the quick opening of the mill tail, the automatic leveling of the mill tail, and the short stroke of the mill stand inlet guide plate tail are adjusted according to Tables 19, 20, and 21 respectively. No strip tail breakage problem occurred throughout the year of production.

[0089] Table 19 shows the adjustment of the quick-opening parameters at the tail of the rolling mill in Example 6.

[0090]

[0091] Table 20 Automatic leveling parameters at the tail of the rolling mill in Example 6

[0092]

[0093] Table 21 Short-stroke control parameters for the mill inlet guide in Example 6

[0094]

[0095]

[0096] Example 7

[0097] This application provides a method for controlling the tail breakage rate of hot-rolled thin strip steel. When producing Q345B strip steel with a specification of 1.8mm×1500mm, the quick opening of the mill tail, the automatic leveling of the mill tail, and the short stroke of the mill stand inlet guide plate tail are adjusted according to Tables 22, 23, and 24 respectively. No strip tail breakage problem occurred throughout the year of production.

[0098] Table 22 shows the adjustment of the quick-opening parameters at the tail of the rolling mill in Example 7.

[0099]

[0100] Table 23 Automatic leveling parameters at the tail of the rolling mill in Example 7

[0101]

[0102] Table 24 Short-stroke control parameters for the mill inlet guide in Example 7

[0103]

[0104] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A method for controlling the rate of tail-end breakage in hot-rolled thin strip steel, characterized in that, Includes the following steps: When the rolling force range of the first stand, second stand, third stand, and fourth stand is within the range of 0-5000KN, 5000-10000KN, 10000-15000KN, 15000-20000KN, 20000-25000KN, 25000-30000KN, 30000-35000KN, and 35000-40000KN, the first stand, second stand, and fourth stand are controlled... The plastic stiffness ranges of the frame, the third frame, and the fourth frame are 1235-1351 KN / mm, 1352-1417 KN / mm, 1418-1464 KN / mm, 1465-1500 KN / mm, 1501-1530 KN / mm, 1531-1556 KN / mm, 1557-1587 KN / mm, and 1588-1620 KN / mm, respectively. When the rolling force range of the fifth, sixth, and seventh stands is 0-4000KN, 4000-8000KN, 8000-12000KN, 12000-16000KN, 16000-20000KN, and 20000-24000KN, the plastic stiffness of the fifth, sixth, and seventh stands is controlled to be 1159-1270KN / mm, 1271-1334KN / mm, 1335-1380KN / mm, 1381-1415KN / mm, 1416-1444KN / mm, and 1445-1480KN / mm, respectively.

2. The control method for reducing the tail breakage rate of hot-rolled thin strip steel according to claim 1, characterized in that, The first stand is controlled to quickly open the roll gap when the tail of the strip reaches the roll gap, and the minimum rolling force when the first stand triggers the quick opening is 5000KN, the minimum activation ratio of the quick opening circuit control valve corresponding to the first stand is 50%, the maximum activation ratio of the quick opening circuit control valve corresponding to the first stand is 150%, and the minimum roll gap change when the first stand triggers the quick opening is 0.05mm.

3. The control method for reducing the tail breakage rate of hot-rolled thin strip steel according to claim 2, characterized in that, When the first frame is controlled to quickly open the roll gap when the tail of the strip reaches the roll gap, the roll gap automatic control correction gain coefficient of the first frame is set to 2.

05.

4. The control method for reducing the tail breakage rate of hot-rolled thin strip steel according to claim 2, characterized in that, When the first frame is controlled to quickly open the roll gap when the tail of the strip reaches the roll gap, the maximum distance between the first frame and the tail of the strip when the quick opening is triggered is 1.5m.

5. The control method for reducing the tail breakage rate of hot-rolled thin strip steel according to claim 1, characterized in that, The second stand is controlled to quickly open the roll gap when the tail of the strip reaches the roll gap, and the minimum rolling force when the second stand triggers the quick opening is 5000KN, the minimum activation ratio of the quick opening circuit control valve corresponding to the second stand is 80%, the maximum activation ratio of the quick opening circuit control valve corresponding to the second stand is 175%, and the minimum roll gap change when the second stand triggers the quick opening is 0.05mm.

6. The control method for reducing the tail breakage rate of hot-rolled thin strip steel according to claim 5, characterized in that, When the second frame is controlled to quickly open the roll gap when the tail of the strip reaches the roll gap, the roll gap automatic control correction gain coefficient of the second frame is set to 2.

7. The control method for reducing the tail breakage rate of hot-rolled thin strip steel according to claim 5, characterized in that, When the second frame is controlled to quickly open the roll gap when the tail of the strip reaches the roll gap, the maximum distance between the second frame and the tail of the strip when the quick opening is triggered is 1m.

8. The method for controlling the rate of tail-end breakage of hot-rolled thin strip steel according to claim 1, characterized in that, The short-stroke opening of the inlet guide plates of the second frame, the third frame, the fourth frame, the fifth frame, the sixth frame and the seventh frame are controlled to be 30mm, 30mm, 30mm, 70mm, 100mm and 150mm respectively.

9. The method for controlling the tail breakage rate of hot-rolled thin strip steel according to claim 1, characterized in that, The short-stroke lengths of the inlet guide plates of the second frame, the third frame, the fourth frame, the fifth frame, the sixth frame, and the seventh frame are 5m, 5m, 10m, 12m, 18m, and 25m, respectively.

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