A method for setting a rolling force ramp of a continuous annealing and skin-pass mill

Abstract

The application discloses a rolling force slope setting method of a continuous annealing and skin pass mill, wherein a slope setting, a difference between a lower limit of an elongation setting value and an actual elongation value, a rolling force of a welding seam and a preset rolling force of a current coil are taken as setting inputs of a slope generator; the slope setting is determined according to a yield strength σ s of the strip steel; different slope settings are set according to different conditions; when the welding seam is located at a specified position of an inlet of the continuous annealing and skin pass mill, the slope generator starts a rolling force falling calculation process; and when the welding seam is located at a specified position of an outlet of the continuous annealing and skin pass mill, the slope generator starts a rolling force rising calculation process. The application can guarantee the elongation index of the continuous annealing product and the surface quality of the continuous annealing product.

Description

TECHNICAL FIELD

[0001] The present application relates to strip rolling technology, more particularly, to a rolling force slope setting method of a continuous annealing and skin pass mill. BACKGROUND

[0002] The continuous annealing unit is an important key processing line in the cold rolling production equipment, which combines the main processes of degreasing, annealing furnace, skin pass, finishing and other cold rolling production together to become a continuous and efficient sheet production line. Due to the particularity of the process, the continuous annealing unit directly determines the product variety and quality, and is the core unit of the cold rolling production. The continuous annealing and skin pass mill is an important equipment located at the outlet section of the continuous annealing unit, which rolls the strip after recrystallization annealing with a small deformation to eliminate the yield platform, control the shape, and achieve the surface quality requirements of the rolling equipment.

[0003] The elongation of the strip is an important process index of the continuous annealing and skin pass mill. Under the condition of constant tension, the elongation of the strip is ensured to meet the standard by adjusting the rolling force. The traditional elongation control method of the continuous annealing and skin pass mill realizes the elongation to meet the standard by changing the rolling force setting. Due to the complex and variable specifications of the strip in the continuous annealing production line, the fixed rolling force setting change process will cause the surface quality problem of the strip, and the most typical surface quality defect is the skin pass flower.

[0004] Patent No. CN104107837A introduces a rolling force setting method when the weld passes through the skin pass mill. The rolling force setting of this patent uses a fixed slope to increase, which can control the elongation of the strip. Patent No. CN1923391A and Patent No. CN105251780A introduce two kinds of skin pass mill elongation feedback control methods. Patent No. CN103962390A introduces a comprehensive setting method of rolling force and tension. Patent Nos. CN103302108A, CN110170535A, CN108704939A, CN101216695A and CN102294364A respectively introduce the calculation method of the pre-set rolling force of the skin pass mill under different production conditions. The above patents mainly consider the influence of the skin pass mill rolling force setting on the elongation of the strip, and fail to fully consider the influence of the rolling force setting change on the surface quality of the skin pass strip.

[0005] The existing process layout of the continuous annealing and skin pass mill is shown in Figure 1 The inlet tension roller 1 and the outlet tension roller 2 respectively apply tension T0 and T1 to the strip 3, and the continuous annealing and skin pass mill 4 applies rolling force P to the strip 3 through the push-up oil cylinder 5. The strip 3 is elongated by the combined action of the rolling force P and the tension T0, T1, that is, the elongation of the strip is controlled. The traditional elongation control method of the continuous annealing and skin pass mill is shown in Figure 2As shown, when the weld 6 reaches a certain position at the inlet of the continuous annealing and skin pass mill 4, the rolling force set value of the continuous annealing and skin pass mill 4 is lowered to the weld rolling force, so as to ensure the weld 6 to pass through the continuous annealing and skin pass mill 4 smoothly, and when the weld 6 reaches a certain position at the outlet of the continuous annealing and skin pass mill 4, the rolling force set value is gradually raised to the preset rolling force of the current coil. In Figure 2 the ramp generator 7 prevents the rolling force set value from changing too fast, and when the rolling force set value reaches the preset rolling force of the current coil, the elongation feedback is put into the additional rolling force. In the conventional elongation control method of the continuous annealing and skin pass mill, the slope of the ramp generator is set as a fixed value. In actual production, the steel grade of the strip steel changes a lot, and the rolling force set value with a larger fixed slope will cause the surface of the strip steel of some steel grades to have skin pass defects, and the rolling force set value with a smaller fixed slope will cause the elongation to be inconsistent with the length being too long. In addition, the continuous annealing and skin pass operator sets the preset rolling force of the current coil to be smaller for the reason of stabilizing the plate, which will also cause the elongation to be inconsistent with the length being too long. SUMMARY

[0006] In view of the above defects in the prior art, the purpose of the present application is to provide a rolling force slope setting method of a continuous annealing and skin pass mill, which can ensure the elongation index of the continuous annealing product and the surface quality of the continuous annealing product.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] A rolling force slope setting method of a continuous annealing and skin pass mill:

[0009] The slope setting, the difference between the elongation set value lower limit and the actual elongation value, the weld rolling force and the preset rolling force of the current coil are taken as the setting input of the ramp generator;

[0010] The slope setting is according to the yield strength σ s Different slopes are set for different settings;

[0011] When the weld is located at a specified position at the inlet of the continuous annealing and skin pass mill, the ramp generator starts the descending calculation process of the set rolling force;

[0012] When the weld is located at a specified position at the outlet of the continuous annealing and skin pass mill, the ramp generator starts the ascending calculation process of the set rolling force.

[0013] Preferably, the slope setting ΔP is calculated as follows:

[0014]

[0015] In formula (1), σ min is the lower limit of the yield strength of the strip steel; σ max is the upper limit of the yield strength of the strip steel; ΔP minto set the lower limit of the rolling force slope; ΔP max to set the upper limit of the rolling force slope.

[0016] Preferably, the ramp generator starts the calculation of the set rolling force as follows:

[0017] S1, calculate the set rolling force P set_new = P set_old - ΔP old (2)

[0018] In formula (2), P set_old is the set rolling force before the calculation is started, including the set rolling force of the previous coil and the additional rolling force fed back by the elongation rate; ΔP old is the slope size of the previous coil;

[0019] S2, judge whether the set rolling force P set_new at the current time is less than the rolling force P b across the weld, if yes, go to step S3, if no, end;

[0020] S3, adjust the set rolling force P set_new at the current time to be equal to the rolling force P b across the weld.

[0021] Preferably, if the weld is not located at the specified position at the inlet of the continuous annealing and skin pass mill, judge whether the weld is located between the specified position at the inlet of the continuous annealing and skin pass mill and the continuous annealing and skin pass mill, if yes, continue to execute steps S1 to S3, if no, end.

[0022] Preferably, the ramp generator starts the calculation of the set rolling force as follows:

[0023] S1, calculate the set rolling force P set_new = P b + ΔP new (3)

[0024] In formula (3), P b is the rolling force across the weld; ΔP new is the slope size of the current coil;

[0025] S2, judge whether the set rolling force P set_new at the current time is greater than the preset set rolling force P pre of the current coil, if yes, go to step S3, if no, end;

[0026] S3, adjust the set rolling force P set_new at the current time to be equal to the preset set rolling force P pre of the current coil.

[0027] Preferably, if the weld is not located at the specified position of the exit of the continuous annealing and skin pass mill, then it is determined whether the weld is located between the specified position of the exit of the continuous annealing and skin pass mill and the continuous annealing and skin pass mill, if not, then the process is ended, if yes, then it is determined again whether the actual value of the elongation ε act - lower limit of the set value of the elongation ε set_min is greater than or equal to 0, if yes, then the process is ended, if not, then the steps S1 to S3 are continuously executed.

[0028] The rolling force slope setting method of the continuous annealing and skin pass mill provided by the present application uses the actual value of the elongation and sets different setting values of the change of the rolling force, which not only can obtain good elongation index, but also can ensure the surface quality of the continuous annealing products of different steel grades. The method can be applied to the rolling force slope setting method of other continuous annealing units in China, which has good application prospect. Different continuous annealing units can set different setting values of the change of the rolling force according to different products of the unit, which avoids the possibility of the surface quality problem such as skin pass flower after the skin pass of the strip. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a schematic diagram of the process arrangement of the existing continuous annealing and skin pass mill;

[0030] Figure 2 is a schematic diagram of the principle of the elongation control of the existing continuous annealing and skin pass mill;

[0031] Figure 3 is a schematic diagram of the principle of the rolling force slope setting method of the present application;

[0032] Figure 4 is a schematic diagram of the process of the calculation of the decrease of the setting rolling force in the rolling force slope setting method of the present application;

[0033] Figure 5 is a schematic diagram of the process of the calculation of the increase of the setting rolling force in the rolling force slope setting method of the present application. DETAILED DESCRIPTION

[0034] In order to better understand the above technical solutions of the present application, the technical solutions of the present application are further explained below in combination with the drawings and embodiments.

[0035] In combination with Figure 3 the schematic diagram shown, the rolling force slope setting method of the continuous annealing and skin pass mill provided by the present application is as follows:

[0036] The slope setting, the difference between the lower limit of the set value of the elongation and the actual value of the elongation, the rolling force when passing the weld and the preset rolling force of the current coil are used as the setting input of the slope generator 7;

[0037] The slope specifically refers to the magnitude of the set rolling force that the slope generator 7 increases or decreases in each control cycle. In the rolling force slope setting method of this invention, the slope setting is based on the yield strength σ of the strip 3. s Different settings utilize different slope ratios to ensure that the strip elongation and surface quality meet all standards. The slope ratio ΔP is calculated as follows:

[0038]

[0039] In formula (1), σ min σ is the lower limit of the yield strength of strip steel 3; max ΔP represents the upper limit of the yield strength of strip 3; min To set the lower limit of the rolling force slope; ΔP max To set the upper limit of the rolling force slope.

[0040] Combination Figure 4 As shown, when the weld is located at the designated position at the entrance of the continuous annealing leveling machine 3, the ramp generator 7 initiates the calculation process for the descent of the set rolling force. The specific calculation process is as follows:

[0041] S1. Calculate the set rolling force P at the current moment. set_new =P set_old -ΔP old (2)

[0042] In formula (2), P set_old The rolling force setting before starting the calculation includes the setting rolling force of the previous coil and the additional rolling force output by the elongation feedback; ΔP old The slope of the previous volume;

[0043] S2. Determine the current set rolling force P. set_new Is it less than or equal to the weld seam rolling force P? b If yes, proceed to step S3; otherwise, end.

[0044] S3, Adjust the current setting rolling force P set_new Equal to the rolling force P through the weld seam b .

[0045] If the weld is not located at the designated entrance position of the continuous annealing leveling machine 3, then determine whether the weld is located between the designated entrance position of the continuous annealing leveling machine 3 and the continuous annealing leveling machine 3. If yes, continue to execute steps S1 to S3; otherwise, end.

[0046] Combination Figure 5As shown, when the weld is located at the designated exit position of the continuous annealing leveling machine 3, the ramp generator 7 initiates the calculation process for the rise of the set rolling force. The existing ramp generator does not consider the change in the actual value of the elongation. The rolling force ramp setting method considers the change in the actual value of the elongation. The specific calculation process is as follows:

[0047] S1. Calculate the set rolling force P at the current moment. set_new =P b +ΔP new (3)

[0048] In formula (3), P b For the over-weld rolling force; ΔP new The slope of the current volume;

[0049] S2. Determine the current set rolling force P. set_new Is it greater than or equal to the current roll's preset rolling force P? pre If yes, proceed to step S3; otherwise, end.

[0050] S3, Adjust the current setting rolling force P set_new Equal to the current roll preset rolling force P pre .

[0051] If the weld is not located at the designated exit position of the continuous annealing leveling machine 3, then determine whether the weld is located between the designated exit position of the continuous annealing leveling machine 3 and the continuous annealing leveling machine 3. If not, the process ends; if so, then determine the actual elongation value ε. act - Lower limit of elongation setting value ε set_min If the value is greater than or equal to 0, the process ends; otherwise, the process continues from step S1 to step S3.

[0052] In step 3 of the calculation process for the descent of the set rolling force when the ramp generator 7 starts, and in step 3 of the calculation process for the ascent of the set rolling force when the ramp generator 7 starts, the control program performs a calculation every certain period of time, and the calculated P at the current moment is... set_new It will be saved, and when the calculation is performed again in the next moment, the P calculated in the previous moment will be used. set_new Extracted and transformed into P set_old Then used to calculate P at the next time step. set_new .

[0053] Example 1

[0054] In this embodiment 1, the control cycle of the ramp generator 7 is 100ms, that is, the calculation of the set rolling force is performed every 100ms; the lower limit of yield strength σ min =200MPa corresponds to the lower limit of the set rolling force slope ΔP min =300KN; Upper limit of yield strength σmax =800MPa corresponds to the upper limit of the set rolling force slope ΔP max =600KN; Rolling force P through the weld seam b =800KN.

[0055] According to the direction of movement of strip 3, the yield strength of strip 3 before the weld is 400MPa, and the yield strength of strip 3 after the weld is 600MPa.

[0056] Based on the yield strength of the strip 3 before the weld, the slope of the previous coil of strip 3 can be obtained:

[0057]

[0058] Based on the yield strength of strip 3 after the weld, the slope of the current coiled strip 3 is obtained:

[0059]

[0060] When the weld reaches a certain position at the entrance of the continuous annealing leveling machine 3, assuming the rolling force setting value P at this time... set_old =3000KN, ramp generator 7 starts calculation. After six times as Figure 4 The calculation process yields the new set rolling force P. set_new =800KN;

[0061] When the weld reaches a certain position at the exit of the continuous annealing leveling machine 3, the ramp generator 7 begins calculation. Assume the current coil has a preset rolling force P. pre =2500KN, due to the rolling force P passing through the weld. b =800KN after four times Figure 5 The calculation process yields the new set rolling force P. set_new =2500KN; if the third time is like Figure 5 After calculation, ε act -ε set_min ≥0.0, to obtain the new set rolling force P set_new =800 + 500 × 3 = 2300 kN.

[0062] Example 2

[0063] In this embodiment 2, the control cycle of the ramp generator 7 is 100ms, that is, the calculation of the set rolling force is performed every 100ms; the lower limit of yield strength σ min =200MPa corresponds to the lower limit of the set rolling force slope ΔP min =300KN; Upper limit of yield strength σ max =800MPa corresponds to the upper limit of the set rolling force slope ΔP max =600KN; Rolling force P through the weld seam b= 800 KN.

[0064] According to the movement direction of the strip 3, the yield strength of the strip 3 before the weld is 500 MPa, and the yield strength of the strip 3 after the weld is 300 MPa.

[0065] According to the yield strength of the strip before the weld, the slope size of the current coil of strip is obtained:

[0066]

[0067] According to the yield strength of the strip after the weld, the slope size of the current coil of strip is obtained:

[0068]

[0069] When the weld reaches a certain position at the inlet of the continuous annealing and skin-pass mill 3, it is assumed that the rolling force setting value P set_old = 2400 KN at this time, and the ramp generator 7 starts to calculate. After four calculation processes as shown in the following formula: Figure 4 , the new setting rolling force P set_new = 800 KN is obtained;

[0070] When the weld reaches a certain position at the outlet of the continuous annealing and skin-pass mill 3, the ramp generator 7 starts to calculate. It is assumed that the current coil of strip is preset with a rolling force P pre = 2000 KN, and the rolling force P b = 800 KN after passing the weld. After four calculation processes as shown in the following formula: Figure 5 , the new setting rolling force P set_new = 2500 KN is obtained; if ε act - ε set_min ≥ 0.0 after the third calculation as shown in the following formula: Figure 5 , the new setting rolling force P set_new = 800 + 350 x 3 = 1850 KN is obtained.

[0071] It can be seen that, in the continuous annealing production, when the rolling force setting change speed is fast, the qualified length of the elongation rate can be improved, but the surface of some steel strips may have skin-pass defects. Based on the above reasons, different rolling force settings are considered to be set for different steel grades, and the rolling force setting change speed is reduced for the steel grades which are prone to skin-pass after skin-pass, so as to reduce the possibility of occurrence of the surface quality problem of the strip.

[0072] Those skilled in the art should understand that the above embodiments are only used to illustrate the present application, and are not used as a limitation of the present application, and as long as the changes and modifications of the above described embodiments are within the spirit and principles of the present application, they will fall within the scope of the claims of the present application.

Claims

1. A method for setting the rolling force slope of a continuous annealing leveling machine, characterized in that: The slope setting, the difference between the lower limit of the elongation setting value and the actual elongation value, the rolling force through the weld, and the current coil preset rolling force are used as the setting inputs for the slope generator. The slope is set based on the yield strength σ of the strip. s Different settings require different slope settings; When the weld is located at the designated position at the entrance of the continuous annealing leveling machine, the ramp generator initiates the calculation process for the descent of the set rolling force; When the weld is located at the designated exit position of the continuous annealing leveling machine, the ramp generator initiates the calculation process for the rise of the set rolling force. The slope setting ΔP is calculated as follows: In formula (1), σ min σ represents the lower limit of the yield strength of the strip steel; max This represents the upper limit of the yield strength of the strip steel. ΔP min To set the lower limit of the rolling force slope; ΔP max To set the upper limit of the rolling force slope.

2. The method for setting the rolling force slope of a continuous annealing leveling machine according to claim 1, characterized in that, The calculation process for the descent of the set rolling force when the ramp generator is activated is as follows: S1. Calculate the set rolling force P at the current moment. set_new =P set_old -ΔP old (2) In formula (2), P set_old The rolling force setting before starting the calculation includes the setting rolling force of the previous coil and the additional rolling force output by the elongation feedback; ΔP old The slope of the previous volume; S2. Determine the current set rolling force P. set_new Is it less than the over-weld rolling force P? b If yes, proceed to step S3; otherwise, end. S3, Adjust the current setting rolling force P set_new， Make it equal to the rolling force P through the weld. b .

3. The method for setting the rolling force slope of a continuous annealing leveling machine according to claim 2, characterized in that, If the weld is not located at the designated entrance position of the continuous annealing leveling machine, then determine whether the weld is located between the designated entrance position of the continuous annealing leveling machine and the continuous annealing leveling machine. If yes, continue to execute steps S1 to S3; otherwise, end.

4. The method for setting the rolling force slope of a continuous annealing leveling machine according to claim 1, characterized in that, The calculation process for the rise of the set rolling force when the ramp generator is activated is as follows: S1. Calculate the set rolling force P at the current moment. set_new =P b +ΔP new (3) In formula (3), P b For the over-weld rolling force; ΔP new The slope of the current volume; S2. Determine the current set rolling force P. set_new Is it greater than the current roll's preset rolling force P? pre If yes, proceed to step S3; otherwise, end. S3, Adjust the current setting rolling force P set_new Make it equal to the current roll's preset rolling force P pre .

5. The method for setting the rolling force slope of a continuous annealing leveling machine according to claim 4, characterized in that, If the weld is not located at the designated exit position of the continuous annealing leveling machine, then it is determined whether the weld is located between the designated exit position of the continuous annealing leveling machine and the continuous annealing leveling machine. If not, the process ends; if so, then the actual elongation value ε is determined. act - Lower limit of elongation setting value ε set_min If the value is greater than or equal to 0, the process ends; otherwise, the process continues from step S1 to step S3.

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