Variable-frequency energy-saving control method for descaling in hot rolling and finish rolling

Abstract

The invention relates to a variable-frequency energy-saving control method for hot rolling and finish rolling descaling. The method comprises the steps of grouping the working frequencies of descaling motors, testing acceleration and deceleration, increasing the compensation amount, controlling actual working conditions and the like. According to the hot rolling and finish rolling descaling variable-frequency energy-saving control method provided by the invention, the frequency of a steel descaling motor with low pressure requirements is reduced, so that the descaling power consumption is reduced. The frequency of the descaling motor is greatly reduced in the interval time, and the energy-saving effect is obvious. And when the device is applied to a 1422 hot rolling production line site, more than 30% of electricity is saved per ton of steel under normal production conditions.

Description

Technical Field

[0001] The invention relates to a frequency conversion energy-saving control method for hot rolling finish rolling descaling, and belongs to the technical field of metal rolling. Background Art

[0002] At present, the hot rolling descaling system is gradually developing from a common descaling system for roughing and finishing rolling to a separate and nearby arrangement of roughing and finishing rolling, so as to reduce the pressure loss caused by long-distance transmission. The descaling water consumption of roughing rolling is pulsed, and the average consumption level is not high, but the stage consumption is very large. The descaling pressure fluctuation and descaling capacity can be reduced by increasing the capacity of the accumulator. The descaling consumption of finishing rolling is relatively stable. When rolling the same piece of steel strip, the descaling consumption is generally the same from the start of descaling to the end of descaling, and energy saving can be achieved through frequency conversion control. By utilizing the rolling interval time, frequency conversion technology can be used to save energy; generally, the descaling requirements of different varieties and specifications, including uses, are different, and the use of frequency conversion technology to adjust the descaling pressure can also save energy. However, in the prior art, the frequency conversion motor only runs at a high speed at a general industrial frequency in actual conventional finishing rolling, which wastes a lot of energy. Summary of the invention

[0003] The technical problem to be solved by the present invention is: to overcome the disadvantages of the above-mentioned technology and provide a descaling frequency conversion energy-saving control method which reduces the descaling power consumption in the rolling gap and the power waste when low descaling pressure is required.

[0004] In order to solve the above technical problems, the technical solution proposed by the present invention is: a frequency conversion energy-saving control method for hot rolling finishing descaling, comprising the following steps: (1) The working frequency of the descaling motor is divided into n groups from high to low. The working frequency of the descaling motor corresponding to the first group is the highest, which is 50Hz, and the working frequency of the descaling motor corresponding to the nth group is the lowest. The working frequency f of the descaling motor is selected according to the type and specification of the strip to be processed and the user's requirements. i , i=1,2,3…n; (2) Under normal working conditions, the maximum acceleration am1 of the descaling motor from the idle frequency to the maximum operating frequency of 50 Hz and the maximum deceleration am of the descaling motor from the maximum operating frequency of 50 Hz to the idle frequency 2 ;The unit of maximum acceleration and maximum deceleration is Hz / s; (3) Determine the actual acceleration a of the descaling motor 1 ; a 1 =k 1 *am 1 ; where k 1 is the acceleration safety factor; (4) Determine the actual deceleration a of the descaling motor 2 ; a 2 =k 2 *am2 ; where k 2 is the deceleration safety factor; (5) Calculate the theoretical acceleration time t of the descaling motor 1 ;t 1 =(f i -f 0 ) / a 1 ; where f i is the working frequency of the dephosphorization motor corresponding to the strip steel currently to be processed, f 0 is the idle frequency of the descaling motor; (6) Determine the actual acceleration time t of the descaling motor 0 ;t 0 =t 1 +k 3 ; where k 3 The first time margin; (7) Let the current time be t. When the current time t = 0, the time from the current time t to the start of descaling injection is T, then the current time t = Tt 0 The descaling motor accelerates at a 1 Accelerate until reaching f in step (5) i The frequency of post-maintenance work remains unchanged; The actual operating frequency f acceleration process of the descaling motor is: When t≤Tt 0 When f=max(f 0 , f i-1 ); When Tt 0 <t<Tk 3 When f=max(f 0 +a 1 *(t-T+t 0 ), f i-1 ); When t>Tk 3 When f=f i ; Where f is the actual operating frequency of the descaling motor, f i-1 The working frequency set for the descaling motor after the previous strip is processed and the descaling spray is turned off; (8) After the current strip to be processed is processed and the descaling spray is turned off, delay k 4 Seconds descaling motor starts with a 2 Decelerate, slow down to the lowest idle frequency f 0 Then keep the frequency unchanged; where k 4 is the time margin; The actual operating frequency f of the descaling motor deceleration process is: Assume the current time is t, at t=0, the descaling spray is turned off; When time t≤k 4 When f=f i ; When time t>k 4 When f=f i -a 2 *(tk 4 ), and f ≥ f 0 .

[0005] The above scheme is further improved in that: 1 and k 2 The value range is 0.9 to 0.95.

[0006] The above scheme is further improved in that: 3 and k 4 The value range is 0.5 seconds to 2 seconds.

[0007] The hot rolling finishing descaling frequency conversion energy-saving control method provided by the present invention reduces the descaling motor frequency due to the low pressure requirement, and the descaling power consumption is reduced. The descaling motor frequency is greatly reduced during the interval time, and the energy-saving effect is obvious. When applied to the 1422 hot rolling production line, under normal production conditions, more than 30% of electricity can be saved per ton of steel. Implementation

[0008] The hot rolling finishing descaling frequency conversion energy-saving control method of this embodiment takes the 1422 hot rolling production line finishing descaling box as an example. The maximum descaling pressure of the 1422 hot rolling finishing descaling box is 25MPa, the corresponding descaling motor frequency is 50Hz, the rated power is 3150KW, and the idle frequency is set to 20Hz.

[0009] The specific implementation methods are as follows: (1) According to the production line product outline, user needs and on-site verification, the descaling pressure configurations are 25MPa, 24MPa, 23MPa, 22MPa, 21MPa and 20MPa, and the corresponding descaling motor operating frequencies are 50Hz, 48.99Hz, 47.96Hz, 46.9Hz, 45.83Hz and 44.72Hz respectively.

[0010] (2) Under normal working conditions, the maximum acceleration am of the descaling motor in a stable state from the lowest idle frequency of 20Hz to the maximum frequency of 50Hz is tested. 1 4Hz / s; 50HZ to 20Hz maximum deceleration am 2 3.95Hz / s; (3) Determine the actual acceleration a of the descaling motor 1 ; a 1 =k 1 *am1 =3.75Hz / s; k1 is the acceleration safety factor, which is an empirical value used to adjust the margin of the actual production process. The value range is 0.9 to 0.95, and 0.9375 is taken here; (4) Determine the actual deceleration a of the descaling motor 2 ; a 2 =k 2 *am 2 =3.7Hz / s; where k 2 is the deceleration safety factor, which is an empirical value used to adjust the margin of the actual production process. Its value range is 0.9 to 0.95; here it is 0.9367; (5) According to actual needs, the descaling pressure of the strip to be processed is required to be 25 MPa, and the corresponding operating frequency of the descaling motor is 50 Hz. The theoretical acceleration time of the descaling motor is calculated as: t 1 ≈8 seconds; (6) Since in the previous step, t 1 The actual calculated value is 30 / 3.7=8.108… seconds. In order to simplify the calculation of the equipment, and the equipment cannot achieve extremely high data accuracy, a time margin is introduced to determine the actual acceleration time of the descaling motor. The time margin is an empirical value, usually ranging from 0.5 seconds to 2 seconds. Here, 1 second is selected in advance, which means that the actual acceleration time of the descaling motor is 9 seconds; By adjusting the acceleration and acceleration time from step (4) to step (6), it can be ensured that the descaling motor is accelerated from 20 Hz to 50 Hz within 9 seconds; (7) Before 9 seconds before the descaling spray is turned on, the descaling motor maintains an idle speed of 20 Hz. 9 seconds before the descaling spray is turned on, it starts to accelerate at an acceleration of 3.75 Hz / s. About 0.9 seconds before the descaling spray is turned on, the speed increases to 50 Hz and remains constant. Since the equipment may have processed a piece of steel strip before processing the current piece of steel strip, the time between the descaling start and the last descaling stop is relatively short, and the working frequency of the descaling motor may not be reduced to the idle frequency. Therefore, during the acceleration process, the frequency is determined. If the working frequency is higher than the idle frequency, the descaling will not be reduced, thereby further saving energy. (8) When the descaling injection is turned off, the time margin is increased in the same way. The time margin ranges from 0.5 to 2 seconds, and the value here is 1 second. The descaling motor starts to slow down from 3.7 Hz / s to the idle speed of 20 Hz and then remains unchanged.

[0011] This embodiment also has a special case. Since the time between the start of descaling and the last stop of descaling is extremely short, and the descaling motor has not dropped to the operating frequency required by the current strip, the descaling motor frequency is first decelerated and controlled as required by the previous strip, and then controlled as required by the current strip after decelerating to the operating frequency required by the current strip.

[0012] The present invention is not limited to the above embodiments. Any technical solution formed by equivalent replacement falls within the protection scope required by the present invention.

Claims

1. A hot rolling finishing descaling frequency conversion energy-saving control method, characterized in that: The steps include: (1) The working frequency of the descaling motor is divided into n groups from high to low. The working frequency of the descaling motor corresponding to the first group is the highest, which is 50Hz, and the working frequency of the descaling motor corresponding to the nth group is the lowest. The working frequency f of the descaling motor is selected according to the type and specification of the strip to be processed and the user's requirements. i , i=1,2,3…n; (2) Under normal working conditions, the maximum acceleration am1 of the descaling motor from the idle frequency to the maximum operating frequency of 50 Hz and the maximum deceleration am2 of the descaling motor from the maximum operating frequency of 50 Hz to the idle frequency are tested; the unit of the maximum acceleration and the maximum deceleration is Hz / s; (3) Determine the actual acceleration a1 of the descaling motor; a1=k1*am1; where k1 is the acceleration safety factor; (4) Determine the actual deceleration a2 of the descaling motor; a2=k2*am2; where k2 is the deceleration safety factor; (5) Calculate the theoretical acceleration time t1 of the descaling motor; t1 = (f i -f0) / a1; where f i is the working frequency of the dephosphorization motor corresponding to the strip steel currently to be processed, and f0 is the idle frequency of the descaling motor; (6) Determine the actual acceleration time t0 of the descaling motor; t0=t1+k3; where k3 is the first time margin; (7) Let the current time be t. When the current time is t=0, the time from the current time t to the start of the descaling spray is T. Then when the current time is t=T-t0, the descaling motor accelerates at an acceleration of a1 until it reaches f in step (5). i The frequency of post-maintenance work remains unchanged; The actual operating frequency f acceleration process of the descaling motor is: When t≤T-t0, f=max(f0,f i-1 ); When T-t0<t<T-k3, f=max(f0+a1*(t-T+t0), f i-1 ); When t > T - k3, f = f i ; Where f is the actual operating frequency of the descaling motor, f i-1 The working frequency set for the descaling motor after the previous strip is processed and the descaling spray is turned off; (8) After the current strip to be processed is processed and the descaling spray is turned off, the descaling motor starts to decelerate at a2 after a delay of k4 seconds, and after decelerating to the idle frequency f0 at the lowest, the frequency remains unchanged; k4 is the time margin; The actual operating frequency f of the descaling motor deceleration process is: Assume the current time is t, at t=0, the descaling spray is turned off; When time t≤k4, f=f i ; When time t>k4, f=f i -a2*(t-k4), and f≥f0.

2. The hot rolling and finishing descaling frequency conversion energy-saving control method according to claim 1 is characterized in that: The value range of k1 and k2 is 0.9 to 0.

95.

3. The hot rolling and finishing rolling descaling frequency conversion energy-saving control method according to claim 1 is characterized in that: The value range of k3 and k4 is 0.5 seconds to 2 seconds.