Technological lubrication method of hot continuous rolling unit in rolling process

Abstract

The invention belongs to the field of hot continuous rolling strip steel production processes, and particularly relates to a process lubricating method for a hot continuous rolling unit in the rolling process, which comprises the following steps of: determining a process lubricating oil proportion of each rack; collecting a head and tail cutting signal of a flying shear and an on-load signal of a rolling mill, and preparing an oil-water mixture based on the proportion of process lubricating oil; after an on-load signal of the F1 is triggered, an oil-water mixture is sprayed to a supporting roller of the F1, and the rotating supporting roller transmits the oil-water mixture to a working roller in contact with the supporting roller; after the on-load signals of F2, F3 and F4 are triggered, delaying for first preset time, and spraying an oil-water mixture onto a working roller of a rack; after an on-load signal of the F5 is triggered, delaying a second preset time and spraying an oil-water mixture onto a working roller of the F5; and when a tail cutting signal of the flying shear is triggered, the hot rolling oil valve is closed, and the oil-water mixture injection valve is closed after a third preset time is delayed after the tail cutting signal is triggered. The problem of slipping of the first rolling mill is completely eradicated.

Description

Technical Field

[0001] This invention belongs to the field of hot strip steel production technology, specifically relating to a process lubrication method for hot strip mills during the rolling process. Background Technology

[0002] In the hot strip rolling process, finishing mills typically employ process lubrication technology to reduce rolling forces, improve work roll surface quality, and extend roll changeover cycles. This technology involves spraying an oil-water mixture onto the roll surface, forming a lubricating film in the contact area between the roll and the strip, thereby reducing the coefficient of friction and optimizing the rolling process. This technology is primarily applied to the work rolls, and its effectiveness is influenced by factors such as rolling speed, rolling force, and lubricant spraying parameters; therefore, the lubrication strategy must be adjusted according to specific operating conditions.

[0003] Currently, the application of process lubrication technology for work rolls in hot continuous rolling mills has significant limitations. For example, when this technology is applied to the first stand of a continuous rolling mill, fluctuations in rolling force and unstable lubrication film formation can easily lead to slippage between the rolls and the strip, forcing production interruptions. When process lubrication is applied to the last stand, uneven lubrication film distribution can cause looper fluctuations and strip misalignment, affecting production stability. Existing technologies largely rely on static lubrication parameter settings or empirical tables, making it difficult to dynamically adapt to the rolling conditions of different stands. This limits the application scope of process lubrication, especially when multiple stands are operating simultaneously, making it impossible to balance rolling stability and lubrication effectiveness. Summary of the Invention

[0004] In response to the aforementioned technical problems in existing hot strip mill processes, such as unreasonable lubrication control, slippage of the first stand, fluctuations in rolling force, and poor surface quality of the rolls and strip, this invention provides a process lubrication method for hot strip mills during the rolling process. This invention primarily utilizes the coordinated setting of lubrication ratios for each stand by the primary and secondary control systems of the finishing mill. Stand F1 is indirectly lubricated through support rolls, F2-F4 undergo delayed spraying, and F5 undergoes separate delayed spraying. This effectively eliminates slippage of the first stand while simultaneously reducing rolling force and improving the surface quality of the rolls and strip.

[0005] The technical means employed in this invention are as follows:

[0006] A process lubrication method for a hot strip mill during the rolling process, the hot strip mill including a finishing mill, the finishing mill being equipped with a primary control system and a secondary control system, the method comprising the following steps: The secondary control system determines the process lubricant ratio for each stand based on the steel grade and the target thickness of the strip, and then transmits the process lubricant ratio to the primary control system. The primary control system acquires the head and tail cutting signals of the flying shear and the on-load signal of the rolling mill, and prepares an oil-water mixture based on the process lubricating oil ratio. When the on-load signal of the first stand F1 of the finishing mill is triggered, the oil-water mixture is sprayed onto the support roll of F1, and the rotating support roll transfers the oil-water mixture to the work roll in contact with it. When the on-load signal of the second to fourth stands of the finishing mill is triggered, the oil-water mixture is sprayed onto the work rolls of the stands after a first preset time delay. When the on-load signal of the fifth stand F5 of the finishing mill is triggered, the oil-water mixture is sprayed onto F5 after a second preset time delay. When the tail-cutting signal of the flying shear is triggered, the hot rolling oil valve is closed, and the oil-water mixture injection valve is closed after a third preset time delay after the tail-cutting signal is triggered.

[0007] Furthermore, the first preset time is 0 to 5 seconds, the second preset time is 1 to 5 seconds, and the third preset time is 8 to 12 seconds.

[0008] Furthermore, the 6th and 7th stands of the finishing mill, F6 and F7, are not lubricated.

[0009] Furthermore, for the 6th and 7th stands F6 and F7 of the finishing mill unit, the support rolls or work rolls of F6 and F7 are lubricated.

[0010] Furthermore, the oil-water mixture is sprayed onto the work roll or support roll of F5 after a second preset time delay.

[0011] Furthermore, the formula for calculating the proportion of process lubricating oil is as follows: Process lubricant ratio = basic ratio coefficient × alloy composition correction coefficient × thickness correction coefficient × mill adjustment coefficient + correction coefficient.

[0012] Furthermore, the basic proportional coefficient is determined by the surface quality requirement level. For ordinary surface requirements, the basic proportional coefficient is 2% to 7%; for higher surface requirements, the basic proportional coefficient is 7% to 12%; and for the highest surface requirements, the basic proportional coefficient is 12% to 30%. The alloy composition correction factor is determined by the manganese content. When the manganese content is ≤0.3%, the ratio correction factor is 0.95~1.2; when 0.3% < manganese content ≤0.5%, the ratio correction factor is 1~1.3; when the manganese content is greater than 0.5%, the ratio correction factor is 1.2~1.5. The thickness correction factor is determined by the target thickness of the strip. When 1.2mm ≤ target thickness of the strip < 2.5mm, the thickness correction factor is 1.2~1.5; when 2.5mm ≤ target thickness of the strip < 4.5mm, the thickness correction factor is 1~1.2; when the target thickness of the strip is ≥ 4.5mm, the corresponding thickness correction factor is 0.6~1. The mill adjustment coefficient is set according to different stand numbers. The mill adjustment coefficient corresponding to F1 mill is 0.95~1.05, the mill adjustment coefficient corresponding to F2 to F4 mills is 1~1.2, and the mill adjustment coefficient corresponding to F5 mill is 1~1.1.

[0013] Compared with the prior art, the present invention has the following advantages: 1. The partitioned collaborative lubrication architecture provided by the present invention solves the technical problem of slippage by combining indirect lubrication with the front support roll, delayed lubrication with the middle work roll, and no or no lubrication at the rear, thereby improving the investment rate of process lubrication technology and reducing the rolling force of the hot strip mill by 2% to 15% compared with the traditional method.

[0014] 2. The delayed injection control strategy provided by this invention effectively avoids high-temperature ablation and ensures the stability of strip threading by dynamically matching the rolling speed and temperature field of each stand.

[0015] 3. The method for setting the lubricating oil ratio provided by the present invention effectively improves the surface quality of strip steel by coordinating and matching with the rolling load of each stand and the characteristics of the steel grade.

[0016] Based on the above reasons, this invention can be widely promoted in fields such as hot-rolled strip steel. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic flowchart of a process lubrication method for a hot strip mill during the rolling process according to the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0020] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] like Figure 1 As shown, this invention provides a process lubrication method for a hot strip mill during the rolling process. The hot strip mill includes a finishing mill, which is equipped with a primary control system and a secondary control system. The method includes the following steps: S1. The secondary control system determines the proportion of process lubricating oil (also known as hot rolling oil) for each stand based on the steel grade and the target thickness of the strip, and then transmits the process lubricating oil proportion to the primary control system.

[0022] Among them, the first and second levels of the finishing mill have agreed on the transmission rules for special messages.

[0023] The formula for calculating the proportion of process lubricating oil is: Process lubricant ratio = basic ratio coefficient × alloy composition correction coefficient × thickness correction coefficient × mill adjustment coefficient + correction coefficient.

[0024] The basic proportion coefficient is determined by the surface quality requirement level. For ordinary surface requirements, the basic proportion coefficient is 2% to 7%; for higher surface requirements, the basic proportion coefficient is 7% to 12%; and for the highest surface requirements, the basic proportion coefficient is 12% to 30%.

[0025] The alloy composition correction factor is determined by the manganese content. When the manganese content is ≤0.3%, the ratio correction factor is 0.95~1.2; when 0.3% < manganese content ≤0.5%, the ratio correction factor is 1~1.3; when the manganese content is greater than 0.5%, the ratio correction factor is 1.2~1.5.

[0026] The thickness correction factor is determined by the target thickness of the strip. When 1.2mm ≤ target thickness of the strip < 2.5mm, the thickness correction factor is 1.2~1.5; when 2.5mm ≤ target thickness of the strip < 4.5mm, the thickness correction factor is 1~1.2; when the target thickness of the strip is ≥ 4.5mm, the corresponding thickness correction factor is 0.6~1.

[0027] The mill adjustment coefficient is set according to the different stand numbers. The mill adjustment coefficient corresponding to F1 mill is 0.95~1.05, the mill adjustment coefficient corresponding to F2 to F4 mills is 1~1.2, and the mill adjustment coefficient corresponding to F5 mill is 1~1.1.

[0028] S2. The primary control system collects the head and tail signals of the flying shear and the on-load signal of the rolling mill, and prepares an oil-water mixture based on the process lubricating oil ratio.

[0029] Specifically, after receiving the set data from the secondary level, the primary level starts the oil pump, water pump, and other supporting facilities according to certain logic, collects reliable signals from the rolling process, and uses reasonable rules to implement the mixing ratio requirements and injection start and stop issued by the secondary level. The mixing ratio of the process lubricating oil issued by the secondary level is accurately controlled by a dedicated metering device.

[0030] S3. When the on-load signal of the first stand F1 of the finishing mill is triggered, the oil-water mixture is sprayed onto the support roll of F1. The rotating support roll then transfers the oil-water mixture to the work roll in contact with it, thereby reducing the rolling force and improving the quality of the roll surface.

[0031] The finishing mill uses a combination of process lubrication to prevent slippage.

[0032] S4. When the on-load signal of the second to fourth stands of the finishing mill is triggered, the oil-water mixture is sprayed onto the work rolls of the stand after a first preset time delay, which can immediately reduce the mill force.

[0033] S5. When the on-load signal of the 5th stand F5 of the finishing mill is triggered, the oil-water mixture is sprayed onto F5 after a second preset time delay. Support roll lubrication technology or work roll lubrication technology can be used.

[0034] This invention employs differentiated delayed injection strategies for different stands, achieving a precise match between the timing of lubricant injection and the rolling conditions. Specifically, the strip temperature in the finishing mill stands (F2-F4) is extremely high. If the lubricant is injected too early, the base oil and additives in the oil film are prone to premature evaporation or carbonization (i.e., "burned off") under high temperatures, resulting in a significant reduction in lubrication efficiency when it reaches the roll gap. Conversely, if the injection is too late, an effective lubricating film cannot be established before the strip enters the mill. This invention, by setting a first preset time of 0-5 seconds, ensures that the oil-water mixture is injected onto the work roll surface within the optimal time window after the mill establishes a stable load and before the oil film fails due to excessive heat radiation from the strip. For the F5 stand, since it is located in the middle and rear of the finishing mill, the strip runs faster. Therefore, a longer second preset time of 1-5 seconds is set to compensate for the strip head threading time. This ensures that the lubricating oil acts on the roll gap just when the rolling force reaches its peak. This avoids the lubricating oil being burned by high temperature due to premature injection, and also prevents lubrication lag caused by late injection. This achieves synergistic optimization of the smooth reduction of rolling force and the surface quality of the strip.

[0035] S6. When the tail-cutting signal of the flying shear is triggered, the hot rolling oil valve is closed, and the oil-water mixture injection valve is closed after a third preset time delay after the tail-cutting signal is triggered.

[0036] Specifically, there is a certain distance between the flying shear tail and the rolling mill throwing the steel. Based on this distance, a delayed closing of the injection valve is adopted. Ideally, when the stand throws the steel, the hot rolling oil on the working roll surface of that stand is just burned by the high temperature of the slab. In actual control, it is generally earlier than the ideal state to avoid the accident of slippage and steel jamming when the next piece of steel bites the steel strip if there is lubricating oil residue on the roll surface.

[0037] S7. When the timing of the next piece of steel meets the above requirements, start and stop the process lubrication technology according to the timing.

[0038] As a preferred embodiment of the present invention, the first preset time is 0 to 5 seconds, the second preset time is 1 to 5 seconds, and the third preset time is 8 to 12 seconds.

[0039] This method also includes: for the 6th and 7th stands of the finishing mill, F6 and F7, no process lubrication is applied, or support roll lubrication or work roll lubrication is used.

[0040] Example 1 S1. The secondary control system determines the proportion of process lubricating oil (also known as hot rolling oil) for each stand based on the steel grade, target strip thickness, and target strip width, and then transmits the process lubricating oil proportion to the primary control system.

[0041] S2. The primary control system collects the head and tail signals of the flying shear and the on-load signal of the rolling mill, and prepares an oil-water mixture based on the process lubricating oil ratio.

[0042] S3. When the on-load signal of the first stand F1 of the finishing mill is triggered, the oil-water mixture is sprayed onto the support roll of F1. The rotating support roll then transfers the oil-water mixture to the work roll in contact with it, thereby reducing the rolling force and improving the quality of the roll surface.

[0043] S4. When the on-load signal of the second to fourth stands of the finishing mill is triggered, the oil-water mixture is immediately sprayed onto the work rolls of the stands, which can immediately reduce the mill force.

[0044] S5. When the on-load signal of the 5th stand F5 of the finishing mill is triggered, the oil-water mixture is sprayed onto the F5 support roll after a 1-second delay.

[0045] S6. No process lubrication shall be applied to the 6th and 7th stands (F6 and F7) of the finishing mill.

[0046] S7. When the tail-cutting signal of the flying shear is triggered, close the hot rolling oil valve, and close the oil-water mixture injection valve after a delay of 8 seconds after the tail-cutting signal is triggered.

[0047] S8. When the timing of the next piece of steel meets the above requirements, start and stop the process lubrication technology according to the timing.

[0048] The start and stop of the process lubrication system met the rolling sequence control requirements. The F1 mill had smooth steel biting without slippage or other issues affecting production. The strip threading process of the other mills was good. Each mill sprayed hot-rolling oil according to the set ratio. When process lubrication was activated, the rolling force of each mill decreased to varying degrees compared to when there was no process lubrication, which is beneficial for rolling thinner products. Taking 2.65mm low-carbon steel as an example, compared to the scheme of applying lubrication to the work rolls of all stands, the rolling force of the product decreased by 2%-8%, the roll surface quality was good, and there were no defects such as pitting on the strip surface that would affect its use.

[0049] Example 2 S1. The secondary control system determines the proportion of process lubricating oil (also known as hot rolling oil) for each stand based on the steel grade, target strip thickness, and target strip width, and then transmits the process lubricating oil proportion to the primary control system.

[0050] S2. The primary control system collects the head and tail signals of the flying shear and the on-load signal of the rolling mill, and prepares an oil-water mixture based on the process lubricating oil ratio.

[0051] S3. When the on-load signal of the first stand F1 of the finishing mill is triggered, the oil-water mixture is sprayed onto the support roll of F1. The rotating support roll then transfers the oil-water mixture to the work roll in contact with it, thereby reducing the rolling force and improving the quality of the roll surface.

[0052] S4. When the on-load signal of the second to fourth stands of the finishing mill is triggered, the oil-water mixture is sprayed onto the work rolls of the stand after a 5-second delay, which can immediately reduce the mill force.

[0053] S5. When the on-load signal of the 5th stand F5 of the finishing mill is triggered, the oil-water mixture is sprayed onto the F5 work roll after a 5-second delay, which can immediately reduce the mill force.

[0054] S6. No process lubrication shall be applied to the 6th and 7th stands (F6 and F7) of the finishing mill.

[0055] S7. When the tail-cutting signal of the flying shear is triggered, close the hot rolling oil valve, and close the oil-water mixture injection valve 12 seconds after the tail-cutting signal is triggered.

[0056] S8. When the timing of the next piece of steel meets the above requirements, start and stop the process lubrication technology according to the timing.

[0057] The start and stop of the process lubrication system met the rolling sequence control requirements. The F1 mill had smooth steel biting without slippage or other issues affecting production. The strip threading process of the other mills was good. Each mill sprayed hot-rolling oil according to the set ratio. When process lubrication was activated, the rolling force of each mill decreased to varying degrees compared to when there was no process lubrication. The effect was delayed compared to Example 1. Process lubrication also facilitated the rolling of thinner products. Taking 1.5mm container steel as an example, compared to the scheme of applying lubrication to the support rolls of all stands, the rolling force of the product decreased by 2%-15%, the roll surface quality was good, and there were no defects such as pitting on the strip surface that would affect its use.

[0058] Comparative Example 1 During the hot continuous rolling process, process lubrication is applied to the work rolls of all finishing mill stands (F1-F7). The lubricating medium is sprayed onto the roll surface through nozzles located on the inlet side of the work rolls, and is carried into the roll gap by the rotation of the roll surface to participate in rolling. Each stand sprays according to a fixed hot rolling oil flow rate ratio, without optimizing the flow rate for the functional differences of different stands.

[0059] While this traditional method can reduce the overall rolling load, it presents significant problems during the strip biting stage of the F1 mill. Due to the large reduction in the F1 mill, premature lubrication significantly reduces the friction coefficient between the rolls and the strip, making it highly susceptible to strip head slippage. In severe cases, this can lead to strip pile-up accidents, forcing the production line to shut down. Therefore, in actual production, to avoid frequent rolling accidents, most manufacturers are forced to disable the work roll lubrication function of the F1 mill for extended periods. This results in the rolls of this stand being rolled without lubrication, leading to rough roll surfaces, susceptibility to rust, shortened roll life, and increased roll consumption costs.

[0060] Comparative Example 2 In hot continuous rolling production, lubricating medium is mainly supplied by spraying it onto the support rolls or by employing a strategy of uniformly delaying the opening of all stands. The lubricating medium is sprayed onto the support roll surface through nozzles and indirectly transferred to the work rolls or rolling zone. To ensure that the middle and later stands (F3-F7) receive sufficient lubrication to reduce rolling force, a higher hot rolling oil flow rate is typically set, with minimal differences in flow rate between stands.

[0061] While this traditional method mitigates the slippage risk of the F1 mill to some extent, it introduces new problems. Due to the delayed lubrication activation, a significant portion of the strip head (typically 15-20 meters) remains unlubricated during rolling. This section experiences large fluctuations in rolling force, making the strip surface prone to defects such as scratches and pitting, leading to increased head and tail losses and a decreased yield. Furthermore, the use of a higher, uniform flow rate to ensure lubrication in the middle and later stands results in excessive oil consumption, failing to achieve economical oil utilization and leading to high oil costs per ton of steel.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process lubrication method for a hot strip mill during the rolling process, the hot strip mill comprising a finishing mill, the finishing mill being equipped with a primary control system and a secondary control system, characterized in that, The method includes the following steps: The secondary control system determines the process lubricant ratio for each stand based on the steel grade and the target thickness of the strip, and then transmits the process lubricant ratio to the primary control system. The primary control system acquires the head and tail cutting signals of the flying shear and the on-load signal of the rolling mill, and prepares an oil-water mixture based on the process lubricating oil ratio. When the on-load signal of the first stand F1 of the finishing mill is triggered, the oil-water mixture is sprayed onto the support roll of F1, and the rotating support roll transfers the oil-water mixture to the work roll in contact with it. When the on-load signal of the second to fourth stands of the finishing mill is triggered, the oil-water mixture is sprayed onto the work rolls of the stands after a first preset time delay. When the on-load signal of the fifth stand F5 of the finishing mill is triggered, the oil-water mixture is sprayed onto F5 after a second preset time delay. When the tail-cutting signal of the flying shear is triggered, the hot rolling oil valve is closed, and the oil-water mixture injection valve is closed after a third preset time delay after the tail-cutting signal is triggered.

2. The process lubrication method for hot strip mills during rolling according to claim 1, characterized in that, The first preset time is 0 to 5 seconds, the second preset time is 1 to 5 seconds, and the third preset time is 8 to 12 seconds.

3. The process lubrication method for hot strip mills during rolling according to claim 1, characterized in that, No lubrication is applied to the 6th and 7th stands (F6 and F7) of the finishing mill unit.

4. The process lubrication method for hot strip mills during rolling according to claim 1, characterized in that, For the 6th and 7th stands of the finishing mill, F6 and F7, the support rolls or work rolls of F6 and F7 are lubricated.

5. The process lubrication method for hot strip mills during rolling according to claim 1, characterized in that, The oil-water mixture is sprayed onto the work roll or support roll of F5 after a second preset time delay.

6. The process lubrication method for a hot strip mill during rolling according to claim 1, characterized in that, The formula for calculating the proportion of process lubricating oil is: Process lubricant ratio = basic ratio coefficient × alloy composition correction coefficient × thickness correction coefficient × mill adjustment coefficient + correction coefficient.

7. The process lubrication method for a hot strip mill during rolling according to claim 6, characterized in that, The basic proportional coefficient is determined by the surface quality requirement level. For ordinary surface requirements, the basic proportional coefficient is 2% to 7%; for higher surface requirements, the basic proportional coefficient is 7% to 12%; and for the highest surface requirements, the basic proportional coefficient is 12% to 30%. The alloy composition correction factor is determined by the manganese content. When the manganese content is ≤0.3%, the ratio correction factor is 0.95~1.2; when 0.3% < manganese content ≤0.5%, the ratio correction factor is 1~1.3; when the manganese content is greater than 0.5%, the ratio correction factor is 1.2~1.

5. The thickness correction factor is determined by the target thickness of the strip. When 1.2mm ≤ target thickness of the strip < 2.5mm, the thickness correction factor is 1.2~1.5; when 2.5mm ≤ target thickness of the strip < 4.5mm, the thickness correction factor is 1~1.2; when the target thickness of the strip is ≥ 4.5mm, the corresponding thickness correction factor is 0.6~1. The mill adjustment coefficient is set according to different stand numbers. The mill adjustment coefficient corresponding to F1 mill is 0.95~1.05, the mill adjustment coefficient corresponding to F2 to F4 mills is 1~1.2, and the mill adjustment coefficient corresponding to F5 mill is 1~1.1.

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