Method for controlling dynamic steel biting slipping of inlet rack of hot continuous rolling mill

Abstract

The invention discloses a method for controlling dynamic steel biting and slipping of an inlet rack of a hot continuous rolling mill. A lower working roller and a lower supporting roller are sequentially arranged below a rolling center of the hot continuous rolling mill, and an upper working roller and an upper supporting roller are sequentially arranged above the rolling center of the hot continuous rolling mill; the method comprises the steps that the distance between the top of a lower working roller and a rack bottom plate is elevation; a base plate adjusting area is arranged between the bottom of the lower supporting roller and a machine frame bottom plate, when the supporting roller is replaced to calculate a base plate, the elevation is lifted by 2-10 mm, and the head of the strip steel is tightly attached to the lower roller face to be gripped in when entering an inlet machine frame; the roller diameter range of F1 to F3 is 0-30 mm, the roller diameter range of F4 to F7 is 0-20 mm, and all the maximum roller diameters are applied to a rack F1, a rack F2 and a rack F3; setting roll gap + impact bounce = outlet thickness; all mechanical gaps are eliminated through zero-adjustment pre-pressing of a new roller; the clamping force of the pinch rollers to the strip steel is 5-20 kN, and meanwhile the rotating speed of the pinch rollers is matched and synchronous with the speed of the roller way. According to the invention, the dynamic biting slip of the inlet rack can be effectively reduced.

Description

Technical Field

[0001] The invention relates to the field of material control of a finishing rolling mill, and in particular to a dynamic steel biting and slipping method for an inlet frame of a hot rolling mill. Background Art

[0002] The finishing mill is the core equipment of the entire main rolling line. Its operation stability is directly related to the production capacity and quality level of the rolling line. The finishing mill has seven four-roll mills from F1 to F7. Each mill consists of upper and lower working rolls and upper and lower support rolls. In the daily production and rolling process, it usually appears at the entrance F1F2 rack. The thickness of the incoming intermediate billet of these two racks is large, and the relative reduction rate of the rack is much greater than that of the rear rack. In particular, the F1 rack is the first mill at the entrance. Due to the fluctuation of the incoming material thickness, the temperature of the incoming material head, the plate shape of the incoming material head, and the descaling water of the head, the probability of biting and slipping is the highest. At the same time, when the support rolls are used in the later stage, the roughness of the roll surface and the uneven wear of the roll diameter will make the slip phenomenon more and more serious. The consequence of the slip is that the incoming material cannot bite into the scrap steel normally, or even if it bites into it, the strip shape and dimensional accuracy will be abnormal, and the quality of the strip head cannot be guaranteed, resulting in greater losses. The frame slip also has a fatal impact on the main drive shaft, gearbox, reducer, and large motor of the equipment.

[0003] Problems and control measures of existing technologies

[0004] The existing 2050 finishing mill is basically the same as the existing hot rolling mills of domestic and foreign manufacturers. They are all four-roller continuous rolling mills. The support rolls are passively driven by the working rolls. Therefore, from the understanding and grasp of the situation, other manufacturers often encounter the phenomenon of dynamic steel biting and slipping of the front frame of the entrance. As for the current slip of the 2050 hot rolling mill, the causes and existing control methods are as follows:

[0005] 1. Once the front frame of the finishing rolling entrance frame slips and has difficulty biting into scrap steel or scrap steel occurs, the operator will reduce the thickness of the incoming intermediate billet to maintain production and reduce the frequency of frame slippage. However, this cannot completely solve the problem of frame slippage, but can only relatively control and reduce the frequency of slippage. The use of thinning the intermediate billet will cause a long rolling rhythm for a single piece of strip steel, affect the production capacity, affect the product compression ratio, and cause the internal mechanical properties to fail to meet the standards.

[0006] 2. Once the finishing rolling entrance frame slips and becomes difficult to bite into or scrap steel occurs, the operator will reduce the number of descaling passes at the head of the incoming material if the frame thinning of the intermediate billet still cannot eliminate the problem. Although this helps to control slippage, it will also reduce the surface quality of the strip head, causing the oxide scale to be pressed into the surface per unit length of the head, affecting product quality.

[0007] 3. Once the finishing rolling entrance stand slips and has difficulty biting into scrap steel, the operator will also reduce the load pressure of the stand on this basis. However, this method will also move the overall load backward, causing the oxide film on the roller surface of the rear stand to peel off due to the increased load, resulting in surface quality problems of the strip.

[0008] 4. Once the entrance frame of the finishing rolling mill slips and becomes difficult to bite into scrap steel, the operator will adjust other process parameters because the effect is not obvious after adjusting relevant measures, such as: increasing the head temperature of the incoming strip, increasing the threading speed, reducing the cooling water of the rolls, etc. However, these measures are taken after the fact, and it is difficult to find a solution to the slippage of the entrance frame from the source.

[0009] Therefore, once the finishing rolling entrance frame slips and has difficulty biting into scrap steel or scrap steel, even after the relevant operators can take immediate adjustment measures, uncertain slippage will still occur, and the machine can only be stopped to replace the support rolls or working rolls. This will disrupt the rolling line maintenance and roll replacement cycle, and the impact will be even greater.

[0010] The hot rolling entrance mill involved refers to the finishing rolling F1 stand. Mainly when the intermediate billet of the unit enters the finishing rolling mill, the entrance F1 stand often slips inexplicably. Once the stand slips, it may cause errors in the dynamic tracking of the strip, resulting in quality problems with the size and shape of the strip. In severe cases, it may cause serious scrap steel accidents due to the inconsistency between the dynamic tracking and the actual object. This phenomenon seriously troubles the normal production of the production line and has a huge impact on output, quality, cost and safety. It is necessary to find the cause of the frame biting the steel and the control method to ensure the safe and smooth operation of the production line. Summary of the invention

[0011] Therefore, the technical problem to be solved by the present invention is to provide a method for controlling the dynamic steel biting and slipping of the entrance frame of a hot rolling mill.

[0012] Through the analysis of the reasons for the multiple entrance frame slippages that have occurred in Baosteel's 2050 hot rolling mill over the years, and the repeated search for control solutions in field practice, combined with the theoretical analysis of frame slippage, through the principle control of the rolled piece biting into the roll, combined with the actual various working conditions on site, it is hoped that a control method for the dynamic biting slippage of the entrance frame can be finally found to control and solve the problem of slippage from the source, thus making up for the existing series of existing problems. The technical solution of the present invention is as follows:

[0013] A method for controlling dynamic steel biting and slipping of an entrance stand of a hot rolling mill, wherein the entrance stand comprises an F1 stand and an F2 stand, a lower working roll and a lower support roll are arranged below a rolling center of the hot rolling mill, and an upper working roll and an upper support roll are arranged above the rolling center; the method comprises the following steps:

[0014] The distance between the top of the lower working roll and the bottom plate of the frame is the elevation; a pad adjustment area is provided between the bottom of the lower support roll and the bottom plate of the frame. When the support roll is replaced and the pad is calculated, the elevation is raised by 2-10 mm so that the head of the strip is closely attached to the lower roll surface when entering the entrance frame;

[0015] During the use and replacement cycle of the support rollers, before replacing the support rollers, it is necessary to confirm the actual roller diameter size range of the working rollers of the current frames, so as to determine the matching roller diameter and pad thickness of the support rollers in this cycle, and ensure the actual available range of the working rollers of the corresponding frames within this cycle; the maximum roller diameter is the roller diameter of the new rollers leaving the factory, and the minimum roller diameter refers to the scrap roller diameter of the corresponding frame; within one cycle after the support rollers are replaced, the F1~F3 working rollers are based on the current maximum roller diameter, minus 0~30mm on the basis of the maximum roller diameter, and the F4~F7 working rollers are based on the current maximum roller diameter, minus 0~20mm on the basis of the maximum roller diameter, and the corresponding frames within this roller diameter range can be used; in the next replacement cycle, the roller diameter after wear and grinding in the previous cycle is the current maximum roller diameter, and within one cycle after the support rollers are replaced, the F1~F3 working rollers are based on the current maximum roller diameter, minus 0~30mm on the basis of the maximum roller diameter, and the F4~F7 working rollers are based on the current maximum roller diameter, minus 0~20mm on the basis of the maximum roller diameter; until the working rollers are worn to less than the scrap roller diameter. At the same time, during this cycle, relatively large roller diameters within the range of F1 to F3 are used on the F1 stand, followed by the F2 and F3 stands.

[0016] Roll gap setting, set roll gap + impact bounce = exit thickness; all mechanical gaps are eliminated by zero-adjusting pre-pressure of the new roll;

[0017] The roller conveys the strip into the rolling mill by relying on the rotating force of the roller and the rotating friction of the strip surface. The clamping force of the pinch rollers and the upper and lower pinch rollers on the strip is 5 to 20 kN. At the same time, the rotation speed of the pinch rollers is synchronized with the roller speed.

[0018] At present, the pad calculation is based on the diameter of the frame support roll + the diameter of the working roll equipped in this cycle to calculate the thickness of the pad to be added or subtracted. The rounding rule is used to confirm the required pad, which is also determined in combination with the standard specifications of the pads configured on site.

[0019] There are seven identical stands in the entrance, the first one is called F1, and the seventh one is called F7. The maximum diameter of new rolls of F1~F3 is 850mm, and the diameter of scrapped rolls is 765mm. The maximum diameter of new rolls of F4~F7 is 765mm, and the diameter of scrapped rolls is 685mm. The continuous rolling mill unit has seven stands, namely F1~F7, and the roll diameter range of F1~F3 refers to 0~30mm, and F4~F7 refers to 0~20mm. It means that after the roll diameter of the support roll used in this cycle is determined, the maximum to minimum range of the work roll diameter to be matched is 0~30mm and 0~20mm. For example, the maximum diameter of the new work rolls of F1~F3 is 850mm, and according to the allowed use range of 0-30mm, the roll diameter range used in this cycle is 850-820mm. After a period of use, the working rolls are worn, and the maximum working roll diameter is 840mm. The support rolls are adjusted with pads, but the working roll diameter matching range is still 0-30mm. Because the maximum roll diameter of all working rolls of the frame is only 840mm, according to the allowed use range of 0-30mm, the working roll diameter range of the frame is 840-810mm. After another cycle of use, due to wear, the maximum working roll diameter of the frame may become 830mm. In the next support roll replacement cycle, the use range is 0-30mm, that is, the maximum use is 830mm-30mm=800mm, and the use range is 830-800mm, and so on, until it is scrapped below 765mm. The scrapped roll diameter range is clear, F1~3 new rolls have a maximum of 850mm and are scrapped at 765mm. F4~7 new rolls have a maximum of 765mm and are scrapped at 685mm.

[0020] The diameter of the working rolls of the seven stands F1 to F7 changes dynamically with the tonnage of the rolled strip and they need to be sharpened on a grinder each time. Therefore, the so-called maximum diameter of the working rolls also changes dynamically (the maximum diameter of the new rolls mentioned in the text refers to the new rolls of 850mm from the manufacturer, and the minimum diameter of the working rolls mentioned refers to the scrapped roll diameter of 765mm).

[0021] Production line process specification: The replacement cycle of support rolls is generally controlled at about 1 month, for example, 20-40 days. Before replacing the support rolls, the actual roll diameter size range of the working rolls of each frame must be confirmed to determine the matching support roll diameter and pad thickness of this cycle, and ensure that the actual working roll available range of the corresponding frame is within this cycle. The working roll diameters of the seven frames F1 to F7 vary with the tonnage of rolled strip steel, and they need to be ground on the grinder each time. Therefore, the so-called maximum roll diameter of the working roll also changes dynamically (the maximum working roll diameter of the new roll described in the text refers to the new roll from the manufacturer, which is 850mm, and the minimum roll diameter of the working roll described refers to the scrap roll diameter of 765mm). After the replacement of the support rollers, within one cycle, the F1~F3 working rollers shall be based on the current maximum roller diameter, minus 0~30mm on the basis of the maximum roller diameter, and the 4~F7 working rollers shall be based on the current maximum roller diameter, minus 0~20mm on the basis of the maximum roller diameter. All the corresponding frames within this roller diameter range can be used. At the same time, within this cycle, the relatively large roller diameters within the range of F1~F3 shall be used on the F1 frame, followed by the F2 and F3 frames.

[0022] The roll gap is set according to the finished strip thickness and rack load distribution, and is set according to the spring equation of steel rolling process. The rack zero adjustment accuracy of F1~F3 upper and lower working rolls is 1500 tons, and F4~F7 is 1000 tons. The existing process of pre-pressing range is to statically press to 300 tons after the new working roll is replaced, and then transfer the dynamic pressure to 1500 tons of F1~3 racks and 1000 tons of F4~7 racks. The spring amount is calculated according to the hardness, specifications and other process parameters of the rolled product, and the computer automatically pre-calculates it. The working roll replacement cycle is generally replaced once for a rolling plan (the maximum mileage is less than 120KM, mainly determined by the planned structure process), and the support roll replacement cycle F1~3 is about 1 million tons in two months, and F4~7 is about 500,000 tons in one month.

[0023] Abnormal bounces are generally ignored. Even if a rack has abnormal bounces, the export target value of the finished rack is guaranteed after seven racks.

[0024] The roller conveyor conveys the strip into the rolling mill by relying on the rotating force of the roller and the rotating friction of the strip surface. The general process stipulates that the roller is fed in at a speed of 1 m / s, and the clamping force of the pinch rollers and the upper and lower pinch rollers on the strip is 5 to 20 kN. At the same time, the rotation speed of the pinch rollers is synchronized with the roller speed.

[0025] When the strip head of the entrance rack bites into the machine, the kinetic energy is affected by the different shapes of the strip head at that time, and the vertical force and horizontal force generated are different, which will cause the biting conditions to change and eventually lead to biting slippage.

[0026] The main consideration is to improve the bite angle of the strip entering the entrance frame. Since the irregular head of the strip needs to be cut off by flying shears before entering, most of the heads after shearing are upturned. If the rolling center line is low, the slightly upturned head will be pressed down by the upper roller and then sent into the roller gap at the moment of biting into the frame. This can easily cause difficulty in biting and cause slipping. Therefore, when replacing the support roller and calculating the pad, special consideration is given to raising the elevation for a certain distance. This solves the problem of unfavorable biting of the upturned head, and allows the strip head to bite close to the lower roller surface when entering the entrance frame. Such biting conditions are much better than biting conditions with low elevations, ensuring that the entrance frame is favorable for biting and preventing biting and slipping.

[0027] The cause of slippage is analyzed according to the bite angle conditions of the hot rolling mill rolls. For this purpose, adjustments are made to the use of the roll diameter of the entrance stand. The entrance stand is currently defined as two stands, F1 and F2. From the experience of stand slippage over the years, the first entrance stand has the highest probability of slippage. Therefore, we have made new regulations on the use of grinding roll roll diameters. Currently, the roll diameter range of F1 to 3 is 0 to 30 mm, and the roll diameter range of F4 to 7 is 0 to 20 mm. All maximum roll diameters are used in the F1 stand, followed by the F2F3 stands. A large working roll diameter is the most advantageous from the bite angle theory analysis, and can also minimize the probability of slippage in the entrance stand.

[0028] The basis for setting the roll gap is the bounce equation in the principle of steel rolling. The principle is to set the exit thickness requirement according to the frame, and the preset roll gap is the set roll gap + impact bounce = exit thickness, provided that all mechanical gaps are eliminated through zero adjustment and pre-pressure of the new roll. If the zero adjustment is inaccurate, there may be mechanical gaps that should be eliminated but are not actually eliminated, which are superimposed on the set roll gap value and ultimately cause exit thickness deviation.

[0029] This step puts forward higher requirements on the roll gap setting of the entrance frame. Once the roll gap setting is incorrect, the strip will suddenly change in bounce at the moment of biting, resulting in abnormal actual roll biting angle and slipping. Therefore, the zero adjustment accuracy of the frame is required to be higher. Once the zero adjustment rolling force and zero adjustment accuracy exceed the standard, it should be handled and resolved in time as a functional abnormality. At the same time, the inaccurate roll gap setting is related to the length of the support roll service life and the amount of wear, so the replacement cycle must be clearly stipulated to reduce the slipping caused by dynamic abnormal factors. Inaccurate roll gap setting mainly refers to the need for zero adjustment of the new roll when it is installed in the frame according to the process regulations, that is, through a certain pre-pressure, all the gaps between the frames are compacted to ensure that the pre-set embedded roll gap before rolling the strip is correct. When the strip enters the upper and lower rolls, the impact bounce amount is within the pre-calculated range, and the embedded roll gap is calculated in advance to avoid the abnormal change of the roll gap due to the unexpected error, which leads to slipping.

[0030] To ensure that the strip has enough kinetic energy when entering the entrance rack, the main factor affecting the strip's kinetic energy when entering the rack and biting the steel is that the entrance rack guide plate is seriously worn, causing the strip to be stuck in the excessively worn guide plate groove, increasing the running resistance of the strip and causing insufficient kinetic energy. At the same time, the driving force of the strip before biting into the rack is also the clamping force of the roller and the descaling pinch roller. Once the pushing force of these two aspects is insufficient, it will affect the kinetic energy of the entrance rack biting into the steel and cause the steel to slip at the moment of biting into the steel. This mainly puts higher requirements on the equipment precision management. If the strip slips when biting into the steel due to abnormal wear and deterioration of precision, it is a management error. Before the strip enters the entrance rack, the thrust of the conveying roller alone cannot meet the normal steel biting. It needs to be clamped by the descaling pinch roller and sent into the rack together to facilitate the entry rack biting into the steel and avoid slipping to the greatest extent.

[0031] Sufficient kinetic energy can be guaranteed by the hot rolling process conditions themselves, but due to various uncontrollable factors, the change in kinetic energy cannot meet the steel biting conditions and causes slippage. The speed of the strip entering the entrance frame is not a fixed value, but is constantly changing according to the different requirements of the rolled product steel type, specification, mechanical properties, etc., and is currently automatically realized by the L2 computer and the L1 control system. The pressure of the descaling pinch rollers is also automatically set according to the thickness and width specifications of the product. What we need to pay attention to is that the settings given by the computer are affected by other working conditions, resulting in the failure to meet the biting conditions. In the actual abnormal process, we can also check the set values ​​given by the computer and compare them with the actual curves stored in the basic automation.

[0032] According to a method for controlling dynamic steel biting and slipping of an entrance stand of a hot rolling mill of the present invention, preferably, the elevation is raised by 5-10 mm.

[0033] Preferably, during the use and replacement cycle of the support rollers, relatively large roller diameters within the range of F1 to F3 are used in the F1 frame, followed by the F2 and F3 frames.

[0034] According to a method for controlling dynamic steel biting and slipping of an entrance stand of a hot rolling mill of the present invention, preferably, in the roll gap setting, H0=H+P / K, H0--actual outlet thickness, H--set roll gap, P--rolling force, and K--mill stiffness coefficient.

[0035] According to a method for controlling dynamic steel biting and slipping of an entrance stand of a hot rolling mill of the present invention, preferably, the method also includes that when the strip is dynamically sheared during operation, the shearing speed of the flying shear is greater than the running speed of the strip; and the shearing speed of the flying shear is corrected every 3-8 days.

[0036] With regard to the relationship between the shape of the strip head after shearing and the biting and slipping, we have found through years of experience that there is a great relationship. Since the incoming strip steel of our production line is dynamically sheared during operation, the roller running speed does not match the shearing speed of the flying shear, which directly leads to the shape of the strip head after shearing. Because if the shearing speed of the flying shear is less than the running speed at the moment of shearing, the flying shear will bring the strip head when it returns to the waiting position after shearing, causing the heads of most of the strip steel to be upturned after shearing as mentioned above, which will be detrimental to the biting of the strip steel at the entrance rack, and the possibility of slipping will be greater. Therefore, we will adjust and verify the shearing speed of the flying shear every week to ensure that the shearing head does not hit the blade and try to ensure the flatness of the head shape after shearing. The main consideration is to provide the best possible head shape, which is conducive to the biting of the entrance rack. If the dynamic roller speed does not match the dynamic shearing speed, external factors will cause the strip head to warp or knock.

[0037] The shearing speed will not affect the slippage and the biting speed, but it will cause the head shape of the strip after shearing, and the upturn or downturn will affect the biting conditions. Furthermore, the shearing speed is 1 to 1.25 m / s. The shearing speed is determined by the process according to the shearing accuracy of the head and tail of the strip, and is generally matched with the roller conveying speed (1 to 1.25 m / s).

[0038] According to a method for controlling dynamic steel biting and slipping of an entrance stand of a hot rolling mill of the present invention, preferably, the method further comprises controlling the temperature of the head of the strip and the temperature of the middle of the billet in the heating furnace to be as consistent as possible.

[0039] Furthermore, the strip head refers to the first 8%-15% of the length of the strip.

[0040] The temperature control of the strip head mainly considers that the head of the incoming strip is easy to dissipate heat, resulting in a large temperature drop. At the same time, different furnaces have different heating temperatures for the strip. Therefore, we hope that the head temperature is as consistent as possible with the middle of the billet. Generally, our process controls the head high target temperature to be around 0 to 30 degrees, but this is not the main reason. In the actual production process, we can adjust the head shearing amount to ensure it, but we must also take into account the yield factor. At present, the longest billet in our production line furnace is controlled within 11.5 meters, and the head temperature is generally controlled at 1 to 1.5 meters.

[0041] Controlling the temperature of the strip head is also an important factor to ensure normal biting without slipping. If the descaling pass is reduced and the temperature is increased during the process, various quality problems will occur on the surface of the strip head. Even if the slipping is controlled, it will lead to various quality problems. In fact, it is a practice of picking up sesame seeds and dropping watermelons. It is an undesirable and helpless approach. Therefore, I have higher requirements for the head temperature control of the slab in the furnace to ensure that the strip does not slip due to too low temperature when biting into the entrance rack. Even if the head temperature is found to be low, the water consumption of the head can only be adjusted in the rough rolling area. The descaling in the finishing area cannot be reduced casually. The main thing is to balance the slipping and the surface quality of the strip head, which is more critical. In actual production, if the biting steel is caused by other comprehensive factors and the continuous slipping, it will be necessary to reduce the head descaling water method at the expense of a little quality to temporarily solve this abnormal continuous slipping. However, in this case, adjusting the process temperature immediately can solve it quickly.

[0042] It varies according to different specifications and requirements of different varieties. In addition, the line from the furnace to the finishing mill is 600 meters long. The process will vary greatly due to the influence of working conditions. Generally, the higher the temperature, the smoother the bite, and vice versa. Reducing descaling water is a necessary method of immediate temporary control and adjustment. Temperature control is mainly carried out in the heating furnace, and the temperature drop on the rolling line is mainly controlled by controlling speed and water consumption.

[0043] Beneficial Effects

[0044] 1) The present invention provides a method for controlling the dynamic steel biting and slipping of the entrance frame of a hot rolling mill. Without changing the structure of the peripheral equipment of the rolling mill, the method is optimized and improved mainly in terms of process control and equipment precision control according to the causes of the slipping, so that the occurrence of dynamic steel biting and slipping of the entrance frame can be controlled to the greatest extent.

[0045] 2) The present invention provides a method for controlling the dynamic steel biting and slipping of the entrance frame of a hot rolling mill, which basically does not increase the workload of the operator. It only requires the calculation and pre-adjustment of the pad for the entrance frame elevation before the support rollers of the unit are replaced to optimize and improve the rolling line elevation and the strip biting conditions, thereby controlling the occurrence of abnormal slipping caused by failure to meet the biting conditions.

[0046] 3) The present invention provides a method for controlling the dynamic steel biting and slipping of the entrance frame of a hot rolling mill. By analyzing the conditions for the strip biting, it is clear which factors will affect the biting, and by analyzing these conditions before, during and after the event, and taking practical improvement methods, the occurrence of the slipping problem caused by the biting of the entrance frame can be further controlled.

[0047] 4) The invention discloses a method for controlling the dynamic steel biting and slipping of the entrance frame of a hot rolling mill. After implementation, the problem of steel biting and slipping of the entrance frame has been basically solved. The invention patent technology analyzes and controls the frame biting conditions, and improves the roller biting angle conditions from the perspectives of the shape of the rolled piece head, resistance, and tightening push force, so as to reduce the dynamic biting and slipping. It has a great promotion and reference effect for the same hot rolling production line. It generates considerable economic benefits in terms of accident control, cost savings, and safety risk control. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is the 2050 hot rolling process flow chart.

[0049] Figure 2 This is a picture of the actual production strip buckle head.

[0050] Figure 3 This is the ideal strip bite diagram.

[0051] Figure 4 This is a schematic diagram of the difficulty in biting into the warped end of the strip.

[0052] Figure 5 Schematic diagram of the strip buckle head biting into the state.

[0053] Figure 6 Schematic diagram of the slightly warped head of the strip biting in.

[0054] Figure 7 Schematic diagram of abnormal bounce of the roll gap when the strip bites in.

[0055] Figure 8 Schematic diagram of the strip guide plate biting into one side.

[0056] Fig. 9 Schematic diagram of the strip pinch rollers feeding the strip into the bite steel. DETAILED DESCRIPTION

[0057] A method for controlling the dynamic steel biting and slipping of the entrance stand of a hot rolling mill, wherein the lower working roll and the lower support roll are arranged below the rolling center of the hot rolling mill, and the upper working roll and the upper support roll are arranged above the rolling center (see Figure 3 ); the method comprising:

[0058] The distance between the top of the lower working roll and the frame bottom plate is the elevation; a pad adjustment area is provided between the bottom of the lower support roll and the frame bottom plate (see Figure 5 ), when replacing the support roller calculation pad, raise the elevation by 2-10mm, so that the strip head can bite into the lower roller surface when entering the entrance frame;

[0059] In each backup roll replacement cycle, after confirming the reference roll diameter value, the use range of the roll diameter is: F1~F3 roll diameter wear range 0~30mm, F4~F7 roll diameter wear range 0~20mm; all maximum roll diameters are used in the F1 frame, followed by the F2 and F3 frames;

[0060] Roll gap setting, set roll gap + impact bounce = exit thickness; all mechanical gaps are eliminated by zero-adjusting pre-pressure of the new roll;

[0061] The roller conveys the strip into the rolling mill by relying on the rotating force of the roller and the rotating friction of the strip surface. The clamping force of the pinch rollers and the upper and lower pinch rollers on the strip is 5 to 20 kN. At the same time, the rotation speed of the pinch rollers is synchronized with the roller speed.

[0062] At present, the pad calculation is based on the diameter of the frame support roll + the diameter of the working roll equipped in this cycle to calculate the thickness of the pad to be added or subtracted. The rounding rule is used to confirm the required pad, which is also determined in combination with the standard specifications of the pads configured on site.

[0063] The process of the present invention is:

[0064] 001- Calculation and adjustment of roller diameter pad when replacing support roller: F1 lower support roller diameter is 1515.68mm, theoretical pad thickness is 57.16mm, actual pad thickness is 65mm (7.9mm more than calculated considering the inlet frame slip factor), F1 working roller diameter is 820~850mm.

[0065] 002-Rolled strip steel plan 118772600100, steel mark AP1056E5, steel grade specification \1277*3.99, heating furnace outlet temperature 1230 degrees, hardness group 01.

[0066] 003-During the production of this plan, the roll numbers and roll diameters of the seven-stand working rolls are as follows:

[0067] Finishing Rolling F1~F7 Roller Diameter and Roller Number Table

[0068] F1 F2 F3 F4 F5 F6 F7 Upper roller number 6605 6110 6525 9001 5512 5501 5523 Lower roller number 6606 6111 6115 9561 5513 5898 5525 Upper roller diameter 834.21 795.88 795.95 707.66 729.97 714.11 753.32 Lower roller diameter 833.96 795.76 796.11 707.61 729.75 714.31 753.24

[0069] 004- Rolling plan finishing rolling F1~F7 roll gap setting parameters:

[0070] Finishing mill F1~F7 parameter setting

[0071] frame thickness Roll gap Rolling force Reduction rate (%) speed Inlet temperature F1 24.61 23.94 24320 44.5 1.43 985 F2 14.15 13.62 22740 42.5 2.48 957 F3 9.65 9.19 18652 31.8 3.75 952 F4 6.81 6.18 15941 29.5 5.39 946 F5 5.15 4.36 13255 24.2 7.22 939 F6 4.14 3.9 11215 19.7 9.14 929 F7 3.61 3.99 8235 12.7 10.66 919

[0072] Figure 2 In the actual production process, it is generally difficult to ensure the ideal straight state of the head of the hot strip. The buckled head has a direct impact on whether the dynamic bite of the entrance rack is smooth, and it is also a key factor causing abnormal slippage of the entrance rack biting the steel.

[0073] Figure 3 In the actual production process, the state of the rolled piece we hope for is that the rolled piece is aligned with the rolling center line, the head shape is straight, the bite angle is in the best state, and the probability of dynamic bite slip is the lowest.

[0074] Figure 4 In the actual production process, due to the low rolling center line, the head of the workpiece contacts the upper working roll first, and the upper roll presses the head of the workpiece to bite into it, which is very easy to slip. This state has the highest probability of slipping in the actual production process.

[0075] Figure 5 In the actual production process, in order to facilitate the biting of the rolled piece and reduce the slipping phenomenon in Figure 4, we artificially raise the rolling center line by 5 to 10 mm when replacing the support roll. This ensures that the head of the rolled piece touches the lower roll first when biting, which can minimize the slipping phenomenon.

[0076] Figure 6 In the actual production process, when the elevation is fixed and cannot be adjusted, we try our best to control the head of the rolled piece to be slightly warped after shearing by the flying shear. This is also conducive to the bite of the rolled piece and can relatively reduce the occurrence of dynamic bite slippage.

[0077] Figure 7 In the actual production process, when other conditions remain unchanged, the rolling mill may experience abnormal bounce in the roll gap at the moment the workpiece bites due to inaccurate zero adjustment of the roll gap or other reasons. The normal bounce amount is S0, and the abnormal bounce amount is S1, and S1 is much larger than S0. In this case, slippage will generally occur.

[0078] Figure 8 In the actual production process, it is generally difficult for the incoming rolled pieces to run off the conveyor roller. The rolled pieces will basically enter the entrance frame along the guide plate on one side. At this time, if the guide plate lining is severely worn, the kinetic energy of the rolled pieces biting the steel will increase due to the wear and blockage resistance on one side, and slippage will also occur.

[0079] Fig. 9 In the actual production process, the kinetic energy of the incoming rolled piece when it is fed into the steel depends largely on the clamping force of the pinch rollers. If the descaling pinch rollers do not clamp the rolled piece tightly due to other reasons, the feeding kinetic energy will be greatly reduced, and slippage will occur when biting the steel.

Claims

1. A method for controlling the dynamic steel biting and slipping of the entrance stand of a hot rolling mill, wherein the entrance stand includes an F1 stand and an F2 stand, and is characterized in that: The hot rolling mill has a lower working roll and a lower support roll below the rolling center, and an upper working roll and an upper support roll above the rolling center; the method comprises: The distance between the top of the lower working roll and the bottom plate of the frame is the elevation; a pad adjustment area is provided between the bottom of the lower support roll and the bottom plate of the frame. When the support roll is replaced and the pad is calculated, the elevation is raised by 2-10 mm so that the head of the strip is closely attached to the lower roll surface when entering the entrance frame; During the use and replacement cycle of the support rollers, before replacing the support rollers, the actual roller diameter size range of the working rollers of the current racks must be confirmed to determine the matching roller diameter and pad thickness of the support rollers in this cycle, and ensure that the actual working roller range of the corresponding racks is available within this cycle; the maximum roller diameter is the roller diameter of the new rollers leaving the factory, and the minimum roller diameter refers to the scrap roller diameter of the corresponding rack; within one cycle after the support rollers are replaced, the F1~F3 working rollers are based on the current maximum roller diameter, minus 0~30mm on the basis of the maximum roller diameter, and the F4~F7 working rollers are based on the current maximum roller diameter, minus 0~20mm on the basis of the maximum roller diameter. The corresponding racks within this roller diameter range can be used; in the next replacement cycle, the roller diameter after wear and grinding in the previous cycle is the current maximum roller diameter, and within one cycle after the support rollers are replaced, the F1~F3 working rollers are based on the current maximum roller diameter, minus 0~30mm on the basis of the maximum roller diameter, and the F4~F7 working rollers are based on the current maximum roller diameter, minus 0~20mm on the basis of the maximum roller diameter; until the working rollers are worn to less than the scrap roller diameter; Roll gap setting, set roll gap + impact bounce = exit thickness; all mechanical gaps are eliminated by zero-adjusting pre-pressure of the new roll; The roller conveys the strip into the rolling mill by relying on the rotating force of the roller and the rotating friction of the strip surface. The clamping force of the pinch rollers and the upper and lower pinch rollers on the strip is 5 to 20 kN. At the same time, the rotation speed of the pinch rollers is synchronized with the roller speed.

2. A method for controlling dynamic steel biting and slipping of an entrance stand of a hot rolling mill according to claim 1, characterized in that: Raise the elevation by 5-10mm.

3. The method for controlling the dynamic steel biting and slipping of the entrance stand of a hot rolling mill according to claim 1, characterized in that: During the use and replacement cycle of the support rollers, relatively large roller diameters within the range of F1 to F3 are used on the F1 frame, followed by the F2 and F3 frames.

4. The method for controlling dynamic steel biting and slipping of the entrance stand of a hot rolling mill according to claim 1, characterized in that: In the roll gap setting, H0=H+P / K, H0--actual outlet thickness, H--set roll gap, P--rolling force, K--is the rolling mill stiffness coefficient.

5. The method for controlling dynamic steel biting and slipping of the entrance stand of a hot rolling mill according to claim 1, characterized in that: The method also includes that when the strip steel is dynamically sheared during operation, the shearing speed of the flying shear is greater than the running speed of the strip steel; and the shearing speed of the flying shear is corrected every 3-8 days.

6. A method for controlling dynamic steel biting and slipping of an entrance stand of a hot rolling mill according to claim 5, characterized in that: Shear speed 1~1.25 m / s.

7. The method for controlling dynamic steel biting and slipping of the entrance stand of a hot rolling mill according to claim 1, characterized in that: The method also includes controlling the temperature of the head of the strip and the temperature of the middle of the billet in the heating furnace to be as consistent as possible.

8. A method for controlling dynamic steel biting and slipping of an entrance stand of a hot rolling mill according to claim 7, characterized in that: The strip head refers to the first 8%-15% of the length of the strip.

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