Method for controlling head slipping in coiling process of narrow-specification strip steel

Abstract

The invention relates to the technical field of hot-rolled strip steel, in particular to a method for controlling head slipping in the coiling process of narrow-specification strip steel, which comprises the steps of cooling process and pinch roll control optimization, layer water outflow time sequence control and strip head watering. A pinch roll steel biting signal is delayed by 1-2 s, a winding drum on-load signal is sent, and the pressure of a first circle of a wrapper roll is increased to 20-25 Mpa; a row of purging reverse spraying water for the contact position of strip steel and a guide ruler lining plate is additionally arranged above a pinch roll of a coiling machine, the position of the head of the strip steel on a roller way is determined, it is ensured that the strip threading speed is smaller than 11.6 m / s, and the shrinkage value, the pre-expansion value and the full expansion value of a coiling block are controlled to be 725 + / -0.5 mm, 760 + / -0.5 mm and 770 + / -0.5 mm respectively; the problem of head slipping in the strip steel curling process is effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of hot-rolled strip steel, and in particular to a method for controlling head slippage in a coiling process of a narrow-gauge strip steel. Background Art

[0002] Most of the production of hot-rolled strip mills adopts continuous coil production, and coiling is the last key process of hot-rolled strip process. The production status of the coiler directly affects the production capacity of the finishing mill and affects the smooth progress of the next process. The coiler is a complex system integrating electrical mechanical control and transmission, and works in harsh environments such as impact vibration, high temperature, water, and iron oxide. Therefore, there is a phenomenon of reel slippage in the actual coiling process, which will cause the steel coil to produce steamed bun coils, poor coiling and loose coils, etc., which not only affects the appearance of the product, but also directly affects the surface quality of the product. For example, the surface of the steel coil with poor coiling will form point-shaped bruises. In order to meet the product qualification, it must be processed on the sub-coiling line to increase the cost. Severe slippage may even cause steel jamming, causing the entire production line to stop production. Summary of the invention

[0003] The present invention provides a method for controlling head slippage during the coiling process of narrow-gauge strip steel, which is particularly suitable for strip steel with a specification of 800-1100 mm, a rolling yield strength of more than 420 MPa and a thickness greater than 4.0 mm, and effectively eliminates the problem of head slippage during the coiling process of the strip steel.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for controlling head slippage during coiling of narrow-gauge strip steel, comprising:

[0006] 1) Cooling process and pinch roller control optimization:

[0007] Control the timing of laminar water discharge, and use the method of watering the head to increase the temperature of the incoming material head. The head of the 30-40 meter strip is heated by 30-40℃, which reduces the head hardness and makes it easier for the strip head to be formed in the reel.

[0008] The pinch roller bite signal is delayed by 1 to 2 seconds to send the reel load signal;

[0009] Increase the first circle pressure of the auxiliary winding roller to 20-25 MPa;

[0010] 2) Auxiliary roll step control:

[0011] Add a row of reverse water sprays above the coiler pinch rollers to purge the contact position between the strip and the guide liner. The purge direction is opposite to the running direction of the strip, so that the water sprayed by the last group of headers for laminar cooling is brought into the coiler to cool and shrink the coil.

[0012] When the strip head leaves the final stand of the finishing mill, start tracking the strip head on the output roller. Calculate the tracking distance based on the strip speed, determine the position of the strip head on the roller, and ensure that the strip threading speed is less than 11.6 m / s.

[0013] The expansion and contraction positions of the roll are dynamically controlled to compensate for the wear of the roll. The roll contraction, pre-expansion and full expansion values ​​are controlled at 725±0.5mm, 760±0.5mm and 770±0.5mm respectively.

[0014] Furthermore, the water outflow timing of the control layer is to reduce the water outflow of the last three groups to 1.1-1.2 m 3 / s, and perform distributed cooling.

[0015] Furthermore, the distributed cooling is to set up an odd array of water outlets, and at the same time, the last three groups of header nozzles are to discharge water in an area 150 to 200 mm away from the edge of the steel plate.

[0016] Furthermore, the length of the strip head and the heating temperature of the incoming material head are in a positive linear relationship with a slope of 1.

[0017] Furthermore, a row of reverse water sprays for blowing on the contact position between the strip and the guide lining is added above the coiler pinch roller, and 6 to 8 through holes are opened on the guard plate at the entrance of the coiler pinch roller, and a water manifold is arranged in each through hole. The angle of the water nozzle of the water manifold is 30 to 50 degrees in the opposite direction of the running direction of the strip, and the water curtain sprayed by the water nozzle is fan-shaped.

[0018] Further, the tracking distance is calculated according to the strip speed to determine the position of the strip head on the roller table, specifically including:

[0019] V=Ti×t / (GD 2 / 375) / (π×D) (1)

[0020]

[0021] Where ρ is the specific gravity of the strip (7.8×10 -3 kg / m 3 );D is the initial diameter of the roll, unit is mm; D 0 is the diameter of the reel after the change, in mm; V is the speed of the strip head in m / s, Ti is the moment of inertia in kg / m 2 ; t is time, unit is s, G is gravity constant, unit is N / kg.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1) Use the method of watering the head to increase the temperature of the incoming material head, reduce the deformation resistance of the hot head, and make the head easy to bend and form;

[0024] 2) By adjusting the advance rate of the auxiliary roll, that is, the delay of the pinch roll biting signal, the load signal is prevented from coming late or not coming;

[0025] 3) Increasing the pressure of the first circle of the auxiliary roll increases the bending moment to make the steel plate bend and deform smoothly;

[0026] 4) By adding reverse water spray above the pinch roller of the coiler, excessive cooling water is prevented from entering the coiler to generate steam, and the threading speed is also reduced, so that the auxiliary coiling roller responds promptly and avoids slipping;

[0027] 5) The present invention effectively eliminates the problem of head slippage during the strip curling process, avoids quality problems on the product surface due to slippage, reduces steel jamming and production stoppage accidents on the production line, and improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the skipping control of the auxiliary winding roller of the present invention.

[0029] Figure 2 It is a schematic diagram of the head velocity tracking calculation of the present invention.

[0030] Figure 3 It is a schematic diagram of the head speed tracking calculation curve of the present invention. DETAILED DESCRIPTION

[0031] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings:

[0032] The coiling process of the coiler is completely controlled by a computer. After the finishing mill group is networked and communicated, the data transmitted from the second level, including the specifications rolled by the last stand of the finishing mill: width and thickness, rolling speed, calculate the preset roll gap of the upper and lower pinch rolls, the reel, the pressure of the auxiliary roll, etc. At the same time, the hot metal detector beside the roller is used to detect the position of the strip on the roller. When the pinch roll has a pressure signal, the laser detector behind the pinch roll detects it at the same time, and the auxiliary roll prepares for jumping. After the strip is wound around once, when the head of the strip reaches the first group of auxiliary rolls, it quickly jumps outward, passes the head, and then quickly presses back, and performs constant position and constant pressure alternating control. When the head of the strip reaches the second and third groups of auxiliary rolls, the jump step is the same as above, so that the strip can be wound tighter, until the jump step reaches the set 10 to 15 turns and automatically opens, and the jump step ends. The action of the reel is when the actual current of the reel is less than the set current, LOAD When the ON signal comes, the reel expands, making the strip more tightly wound.

[0033] When rolling harder steel grades or thick specifications, since the bending moment of the coiling rolls on the strip is not sufficient to bend the strip into shape, the strip cannot be wound tightly. Also, since the reel current cannot meet the condition of i ≤ |i_set - i_actual|, the reel load signal does not come or comes late, and the reel cannot be over-expanded in time, which further increases the tendency of slipping.

[0034] Under normal coiling conditions, the strip starts to skip steps after one turn. On the one hand, when the laser is blocked by water vapor or the tracking is abnormal, etc., and the coiling rolls skip steps in advance, the roll gap of the coiling rolls increases, causing the head of the strip not to be wound tightly and resulting in slipping. On the other hand, during coiling, the exit speed of the finishing mill is too high, so that the threading speed of the coiler is too fast, and the response speed of the coiling rolls cannot keep up, thus causing slipping.

[0035] A method for controlling the head slipping during the coiling process of narrow-specification strips according to the present invention includes:

[0036] 1) Optimization of the cooling process and pinch roll control:

[0037] Control the timing of the laminar flow water outlet, and use the method of watering the strip head to increase the temperature of the incoming material head. According to the material process system of production, reduce the water output of the last 3 groups in the secondary model from 1.5 m 3 / s to 1.2 m 3 / s, and adopt a dispersed cooling method, that is: generally, there are 15 groups of laminar flow headers in a hot rolling production line, and the odd-numbered groups are set to discharge water, which can avoid a large amount of water from concentrating and vaporizing on the strip surface, which is not conducive to the subsequent removal of surface water. At the same time, improve the nozzle form of the last 3 groups of headers, and only allow water to be discharged in the area 150 - 200 mm away from the edge;

[0038] Raise the temperature of the strip head by 35 °C for 35 meters of the strip. The length of the strip head and the temperature rise of the incoming material head have a positive linear relationship with a slope of 1. The purpose is that the head cooling rate is high and martensite is easily formed. Heating is to reduce the head hardness, make it easy to form in the reel, reduce the hot-state head deformation resistance, and make the head easy to bend and form.

[0039] Delay the sending of the reel load signal by 1 - 2 s for the pinch roll biting signal, thereby avoiding the late or non-arrival of the load signal.

[0040] Increase the pressure of the first turn of the coiling rolls to 24 MPa, so that the bending moment increases, and the steel plate can be bent and deformed smoothly. It is necessary to ensure that the pressure is between 20 - 25 MPa. Excessive pressure is easy to produce a tower shape.

[0041] 2) Coiling roll skip step control:

[0042] Add a row of reverse water sprays above the coiler pinch rollers for blowing and cleaning the contact position between the strip and the guide liner: 6 through holes are opened on the guard plate at the entrance of the coiler pinch rollers, and a water header is arranged in each through hole. The water nozzle angle of the water header is 45° to the opposite direction of the strip running, and the water curtain sprayed from the nozzle is fan-shaped. The water curtain has fan-shaped blowing on the contact position between the middle and both sides of the strip and the guide liner to avoid too much cooling water being brought into the coiler to generate steam; the reverse water spray is above the archway at the entrance of the coiler, and the blowing direction is opposite to the running direction of the strip. The purpose is to bring the water sprayed by the last group of headers for laminar cooling into the coiler, so that the reel is cooled and contracted, and the axial thermal expansion is inconsistent.

[0043] See Figure 1 The automatic step-jump control of the auxiliary winding roller is to minimize the indentation left by the head of the strip on the steel coil during the coiling process. The head indentation is caused by the contact between the head of the strip and the auxiliary winding roller. The specific principle of AJC automatic step-jump control is as follows: the auxiliary winding roller jumps before the head of the strip reaches the auxiliary winding roller (starting the position control based on the step-given position). When the head of the strip leaves the position of the auxiliary winding roller, the auxiliary winding roller falls and resumes pressure control (AFC). The step-jump timing and pressure control timing are completed according to the strip head tracking function.

[0044] From the moment the strip head leaves the last stand of the finishing mill, the strip head on the output roller starts to be tracked: the tracking distance is calculated through the strip speed to determine the position of the strip head on the roller. The strip head tracking is used for short-stroke control of the coiler side guide plate, roll load signal detection conditions and other control functions to ensure that the strip threading speed is less than 11.6 m / s; when the finishing rolling threading speed is higher than 11.6 m / s, the head will fold upward due to the fast speed, and the coiling temperature of materials with a yield strength of more than 420 MPa is between 550-600°C. If the speed is too fast, the temperature control accuracy cannot be guaranteed, and it will generally exceed the upper limit, resulting in low final performance.

[0045] The calculation of the tracking distance according to the strip speed and determination of the position of the strip head on the roller table specifically includes the following contents:

[0046] V=Ti×t / (GD 2 / 375) / (π×D) (3)

[0047]

[0048] Where ρ is the specific gravity of the strip (7.8×10 -3 kg / m 3 );D is the initial diameter of the roll, unit is mm; D 0 is the diameter of the reel after the change, in mm; V is the speed of the strip head in m / s, Ti is the moment of inertia in kg / m 2; t is time, unit is s, G is gravity constant, unit is N / kg.

[0049] The drum speed changes when the coiler is coiling steel. In order to maintain accurate strip tension control, the acceleration and deceleration torque must be calculated based on the drum's rotational inertia. The drum's rotational inertia also changes with the coiling diameter. This shortens the acceleration time when the drum starts and controls the drum speed when the tail stops, as well as other similar problems. In the following cases, in order to achieve speed control, the drum motor torque is given to the maximum value. When the drum speed accelerates from 0 to the standby speed after a certain period of time, the tail stop control begins (the strip leaves the coiler's pinch roller) until the tail stop is completed.

[0050] See Figure 2 In order to improve the tracking accuracy, some calibration points are set for the strip head and tail tracking to correct the tracking data. The sensors used for tracking correction are: HMD5001, HMD5002, HMD5003. The pre-coil width meter is not used for tracking correction because the high temperature meter signal response accuracy is insufficient.

[0051] See Figure 3 (1) When the finishing mill is not rolling or the car is not turning and the coiler is not coiling steel, it runs at a fixed low speed of 250 mpm;

[0052] (2) When the finishing mill is turning under rolling conditions and the coiler is unloaded (regardless of whether the finishing mill is biting steel), the coiler runs at a speed ahead of the finishing mill;

[0053] (3) After the coiler is loaded and before the deceleration point, the K roller runs at the synchronous speed with the finishing mill (the speed of the finishing mill is memorized after the steel is thrown), and the speed of the coiler is ahead of the K roller;

[0054] (4) After the finishing mill throws steel, the coiler starts to decelerate at the deceleration point;

[0055] (5) After the tail of the roll is positioned and adjusted, the roll stops.

[0056] In view of the influence of roll wear, online dynamic adjustment is carried out to accurately adjust the position of roll expansion and contraction to compensate for the wear of the roll, so that the roll contraction, pre-expansion and full expansion values ​​are controlled at 725mm, 760mm and 770mm respectively, which are within the required equipment accuracy range.

[0057] The above embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the above embodiments. The methods used in the above embodiments are conventional methods unless otherwise specified.

Claims

1. A method for controlling head slippage during coiling of narrow-gauge strip steel, characterized in that: include: 1) Cooling process and pinch roller control optimization: Control the timing of laminar water discharge, and use the method of watering the head to increase the temperature of the incoming material head. The head of the 30-40 meter strip is heated by 30-40℃, which reduces the head hardness and makes it easier for the strip head to be formed in the reel. The pinch roller bite signal is delayed by 1 to 2 seconds to send the reel load signal; Increase the first circle pressure of the auxiliary winding roller to 20-25 MPa; 2) Auxiliary roll step control: Add a row of reverse water sprays above the coiler pinch rollers to purge the contact position between the strip and the guide liner. The purge direction is opposite to the running direction of the strip, so that the water sprayed by the last group of headers for laminar cooling is brought into the coiler to cool and shrink the coil. When the strip head leaves the final stand of the finishing mill, start tracking the strip head on the output roller. Calculate the tracking distance based on the strip speed, determine the position of the strip head on the roller, and ensure that the strip threading speed is less than 11.6 m / s. The expansion and contraction positions of the roll are dynamically controlled to compensate for the wear of the roll. The roll contraction, pre-expansion and full expansion values ​​are controlled at 725±0.5mm, 760±0.5mm and 770±0.5mm respectively.

2. A method for controlling head slippage during coiling of narrow-gauge strip steel according to claim 1, characterized in that: The control of laminar flow water outflow timing is to reduce the water outflow of the last three groups to 1.1-1.2m 3 / s, and perform distributed cooling.

3. A method for controlling head slippage during coiling of narrow-gauge strip steel according to claim 2, characterized in that: The distributed cooling is to set an odd array of water outlets, and at the same time, the last three groups of header nozzles are to discharge water in an area 150 to 200 mm away from the edge of the steel plate.

4. A method for controlling head slippage during coiling of narrow-gauge strip steel according to claim 1, characterized in that: The length of the strip head and the heating temperature of the incoming material head are in a positive linear relationship with a slope of 1.

5. The method for controlling head slippage during coiling of narrow-gauge strip steel according to claim 1, characterized in that: The method of adding a row of reverse water sprays for blowing on the contact position between the strip and the guide lining plate above the coiler pinch roller is to open 6 to 8 through holes at the upper guard plate position of the coiler pinch roller entrance, and a water manifold is arranged in each through hole. The angle of the water nozzle of the water manifold is 30 to 50 degrees in the opposite direction of the strip running, and the water curtain sprayed by the water nozzle is fan-shaped.

6. A method for controlling head slippage during coiling of narrow-gauge strip steel according to claim 1, characterized in that: The calculation of the tracking distance according to the strip speed and determination of the position of the strip head on the roller table specifically includes the following contents: V=Ti×t / (GD 2 / 375) / (π×D) (1) Where ρ is the specific gravity of the strip (7.8×10 -3 kg / m 3 ); D is the initial diameter of the roll, in mm; D0 is the diameter of the roll after the change, in mm; V is the speed of the strip head in m / s, Ti is the moment of inertia in kg / m 2 ; t is time, unit is s, G is gravity constant, unit is N / kg.

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