CN111451295A - Cascade control method for controlling rolling warpage of billet - Google Patents
Cascade control method for controlling rolling warpage of billet Download PDFInfo
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- CN111451295A CN111451295A CN202010187543.4A CN202010187543A CN111451295A CN 111451295 A CN111451295 A CN 111451295A CN 202010187543 A CN202010187543 A CN 202010187543A CN 111451295 A CN111451295 A CN 111451295A
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Abstract
The invention relates to a cascade control method for controlling rolling warpage of small billets, which belongs to the technical field of steel rolling control and has the technical scheme that a descaling temperature difference control model is established in key steps of establishing an equation (P1-P2)/P1= k Δ T x kH (lambda 2-lambda 1)/lambda 2) of the opening of a descaling water adjusting valve, the heat conductivity coefficient of the billets, the slab thickness and the temperature difference of the upper and lower surfaces of the billets, and a second flow control model of a rolling mill is established in key steps of establishing an equation omega 1/omega 2= (R2(1+ β 1))/(R1(1+ β 2)) of the rotating speed of working rolls, the radius of the working rolls and the thermal expansion coefficient of the upper and lower surfaces of the billets.
Description
Technical Field
The invention relates to a cascade control method for controlling rolling warpage of a billet, belonging to the technical field of steel rolling control.
Background
In the billet rolling process, the head or tail of a rolled piece cannot advance linearly along a roller way after biting, and upward and downward bending and even bending with uncertain directions, namely warping, can occur.
The analysis of the reasons is that firstly, after the billet steel is discharged from the heating furnace, when the billet steel is conveyed by a roller way, the temperature of the upper surface and the lower surface is not uniform due to the processes of natural heat dissipation, descaling and the like, and the temperature difference is large; secondly, the head and the tail of the billet are close to the rolling mill in the rolling process, contact with the cooling water of the roller firstly, the temperature is obviously reduced, and the head and the tail are easier to reduce than the middle part of the billet, so that the temperature difference between the head and the tail and the middle part of the billet is obviously increased; and thirdly, the roll diameters or the rotating speeds of the upper working roll and the lower working roll are different, so that the second flow rates of metal on different surfaces of the steel billet are different in the steel biting process.
When the rolling warpage of the billet is obvious, the billet can be scraped and collided with a guide and a conveying roller way, and can be pushed against a roller water cooling pipeline and a detection instrument in serious cases, even accidents such as roller drilling, roller collision, runaway and the like occur.
Disclosure of Invention
The invention aims to provide a cascade control method for controlling rolling warpage of small billets, which is characterized in that a descaling temperature difference control model and a rolling mill second flow control model are established, and temperature difference and second flow cascade control are respectively carried out in a descaling stage and a rolling stage, so that the possible warpage in the rolling process of the small billets is avoided or reduced, the safety and controllability of the rolling process are ensured, the qualified product quality is ensured, and the problems in the background technology are effectively solved.
The invention has the technical scheme that the cascade control method for controlling the rolling warpage of the billet comprises the following steps of carrying out cascade control on the billets in different technological processes, and establishing a descaling temperature difference control model and a rolling mill second flow control model, wherein the descaling temperature difference control model comprises the following key steps of establishing an equation (P1-P2)/P1= k T x kH (lambda 2-lambda 1)/lambda 2) of the opening degree of a descaling water adjusting valve, the heat conductivity of the billet, the thickness of the slab and the temperature difference of the upper surface and the lower surface of the billet, and establishing a rolling mill second flow control model comprising (the key steps of establishing an equation omega 1/omega 2= (R2(1+ β 1)) (R1(1+ β 2)) of the rotating speed of a working roll, the radius of the working roll and the thermal expansion coefficient of the upper surface and the lower surface of the billet.
The second flow control model of the rolling mill comprises the following key steps of (in key steps of) adjusting the rotating speeds omega 1 and omega 2 of the working rolls in real time aiming at the temperature difference between the head and the tail of the billet and the middle part of the billet, setting the thermal expansion coefficients of the upper surface and the lower surface of the head of the billet to be β 1 and β 2, and setting the thermal expansion coefficients of the upper surface and the lower surface of the middle of the billet to be β 3 and β 4, and then having the following relation:
V1=S (1+β1)/t=ω1R1，V2=S (1+β2)/t=ω2R2；
V3=S (1+β3)/t=ω3R1，V4=S (1+β4)/t=ω4R1；
by calculation
∆ω1=（ω3-ω1）/ω1；
∆ω2=（ω4-ω2）/ω2；
Therefore, when the secondary system sets the rolling speed of any working roll at any moment, the real-time rolling speed of the upper working roll and the lower working roll at all moments can be calculated, and the metal second flow of the upper surface and the lower surface of the billet at all moments is ensured to be the same.
The invention has the beneficial effects that: the method comprises the steps of detecting the temperatures of the upper surface and the lower surface of a steel billet before descaling and before rolling through an instrument, establishing a descaling temperature difference control model and a rolling mill second flow control model which comprise parameters such as the temperature difference between the upper surface and the lower surface of the steel billet, the opening of a descaling water valve, the heat conductivity coefficient of the steel billet, the rotating speed of a working roll, the radius of the working roll, the thermal expansion coefficient of the steel billet and the like, and performing temperature difference and second flow cascade control respectively in a descaling stage and a rolling stage to ensure that the second flows of metal on the upper surface and the lower surface of the steel billet at all times are the same, so that the possible warping in the small steel billet rolling process is.
Drawings
FIG. 1 is a flow chart of the operation of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions of the embodiments of the present invention with reference to the drawings of the embodiments, and it is obvious that the described embodiments are a small part of the embodiments of the present invention, rather than all embodiments, and all other embodiments obtained by a person of ordinary skill in the art without creative work based on the embodiments of the present invention belong to the protection scope of the present invention.
A cascade control method for controlling rolling warpage of small billets comprises the following steps of carrying out cascade control on billets in different technological processes, establishing a descaling temperature difference control model and a rolling mill second flow control model, wherein the descaling temperature difference control model comprises the key steps of establishing an equation (P1-P2)/P1= k Δ T x kH (lambda 2-lambda 1)/lambda 2) of an opening degree of a descaling water adjusting valve, a billet heat conductivity coefficient, a slab thickness and a billet upper and lower surface temperature difference, establishing a rolling mill second flow control model, and establishing an equation omega 1/omega 2= (R2(1+ β 1))/(R1(1+ β 2)) of a working roll rotating speed, a working roll radius and a billet upper and lower surface thermal expansion coefficient.
The rolling mill second flow control model comprises the key steps of aiming at the temperature difference between the head and the tail of a steel billet and the middle part of the steel billet, adjusting the rotating speeds omega 1 and omega 2 of a working roller in real time, setting the thermal expansion coefficients of the upper surface and the lower surface of the head of the steel billet to be β 1 and β 2, setting the thermal expansion coefficients of the upper surface and the lower surface of the middle of the steel billet to be β 3 and β 4, and then having the following relation:
V1=S (1+β1)/t=ω1R1，V2=S (1+β2)/t=ω2R2；
V3=S (1+β3)/t=ω3R1，V4=S (1+β4)/t=ω4R1；
by calculation
∆ω1=（ω3-ω1）/ω1；
∆ω2=（ω4-ω2）/ω2；
Therefore, when the secondary system sets the rolling speed of any working roll at any moment, the real-time rolling speed of the upper working roll and the lower working roll at all moments can be calculated, and the metal second flow of the upper surface and the lower surface of the billet at all moments is ensured to be the same.
At present, the basic rolling process flows of a billet production line are descaling, cogging (rough rolling) and finish rolling of hot billets, and step-by-step control is carried out aiming at three reasons for causing the warping of the billets mentioned in different process flows and the background technology, so that the warping of the billets is avoided or reduced in the cogging (rough rolling) and finish rolling processes. The overall scheme is divided into two parts, wherein the two parts are in cascade control relationship:
1. aiming at the problem of large temperature difference between the upper part and the lower part of a hot steel blank possibly generated in the cogging and descaling process, a descaling temperature difference control model is established. The method comprises the following specific steps:
s01, installing two hot metal temperature detectors at the entrance of a descaler, respectively detecting the upper surface temperature T1 and the lower surface temperature T2 of the steel billet, and inputting the collected temperatures into a cogging (rough rolling) P L C system;
s02, inputting the collected temperature into a cogging (rough rolling) P L C system, and calculating the temperature difference Δ T between the upper surface and the lower surface of the billet by the cogging (rough rolling) P L C system;
s03 the descaler is provided with an upper row of nozzles and a lower row of nozzles, the upper surface and the lower surface of the billet are respectively sprayed, the descaling water flow is controlled by a pneumatic film valve, the pneumatic film valve is regulated by PI, and the opening degrees of the two pneumatic film valves are P1 and P2 respectively;
s04, the thermal conductivity coefficients lambda of the steel billet at different temperatures can be known through a CRC Handbook of Chemistry and Physics, and the thermal conductivity coefficients lambda 1 and lambda 2 corresponding to the upper and lower surface temperatures T1 and T2 are respectively searched;
s05, inputting the heat conductivity coefficients lambda 1 and lambda 2 into a cogging (rough rolling) P L C system to calculate the relationship between the heat conductivity coefficient and the opening degrees P1 and P2 of the pneumatic membrane valve, and according to a plurality of tests, (P1-P2)/P1= k (lambda 2-lambda 1)/lambda 2, k is a fine adjustment coefficient;
s06 fine-tuning the nozzle opening P2 according to the temperature difference Δ T and the billet thickness H, and the fine-tuning proportionality coefficient k = k∆TxkHObtaining the following proportional coefficient empirical table according to a plurality of tests;
TABLE 1 scale factor empirical table
S07, based on the opening P1 of the upper surface nozzle of the descaler, the opening P2 of the lower surface nozzle is calculated according to the proportional relation between the thermal conductivity and the opening of the pneumatic membrane valve in S05.
2. Aiming at the problems that the second flow of metal on different surfaces of a billet is different in the steel biting process due to the difference of the roll diameters of upper and lower working rolls in the rolling (cogging or finish rolling), the difference of the temperature between the upper and lower surfaces of the billet or the difference of the temperature between the head and the tail of the billet and the middle part of the billet, a second flow control model of a rolling mill is established. The method comprises the following specific steps:
s11, installing two hot metal temperature detectors at the inlet of a rolling mill, respectively detecting the upper surface temperature T11 and the lower surface temperature T12 of the billet, and inputting the collected temperatures into a cogging or finish rolling P L C system;
s12 inputting the collected temperature into the P L C system for cogging or finish rolling, calculating the temperature difference T between the upper surface and the lower surface of the billet by the P L C system for cogging or finish rollingBite type；
S13 it is known that the thermal expansion coefficient β of the steel billet under different temperature changes can be obtained through tests and table look-up, the thermal expansion coefficients β 1 and β 2 corresponding to the upper and lower surface temperatures T11 and T12 are looked up, and the difference between the upper and lower surface thermal expansion coefficients Δ β = β 1- β 2;
s14, acquiring the radius R1 and R2 information of the upper working roll and the lower working roll by a rolling mill secondary system, inputting the information into a cogging or finish rolling P L C system, and calculating the relation between the radius of the rolls and the speeds V1 and V2 of the upper working roll and the lower working roll, wherein V1/V2= (omega 1R 1)/(omega 2R2), omega 1 is the rotating speed of the upper rolls, and omega 2 is the rotating speed of the lower rolls;
s15, inputting thermal expansion coefficients β 1 and β 2 into a cogging or finish rolling P L C system, calculating the relation between the thermal expansion coefficients and linear speeds V1 and V2 of upper and lower working rolls, and knowing V1= S (1+ β 1)/t and V2= S (1+ β 2)/t according to the definition of the thermal expansion coefficients, wherein S is the moving distance of the billet without thermal expansion, and t is the constant moving time of the billet;
s16 combining the mathematical relationships in S14 and S15, the following equation can be obtained:
V1/V2= (ω1R1)/(ω2R2)= (1+β1)/ (1+β2)，
from this, ω 1/ω 2= (R2(1+ β 1))/(R1(1+ β 2));
s17, under the condition that the diameters of the upper and lower working rolls are different and the temperature difference exists between the upper and lower surfaces of the billet, the second flow rates of metal on the upper and lower surfaces of the billet are the same by adjusting the rotating speeds of the upper and lower working rolls through calculation of S16, so that the possibility of the billet warping is reduced.
S18, aiming at the temperature difference between the head and the tail of the billet and the middle part of the billet, the rotating speeds omega 1 and omega 2 of the working rolls are adjusted in real time, the thermal expansion coefficients of the upper surface and the lower surface of the head of the billet are set to be β 1 and β 2, the thermal expansion coefficients of the upper surface and the lower surface of the middle of the billet are set to be β 3 and β 4, and then the following relation formula is provided:
V1=S (1+β1)/t=ω1R1，V2=S (1+β2)/t=ω2R2；
V3=S (1+β3)/t=ω3R1，V4=S (1+β4)/t=ω4R1；
by calculation
∆ω1=（ω3-ω1）/ω1；
∆ω2=（ω4-ω2）/ω2。
Therefore, when the secondary system sets the rolling speed of any working roll at any moment, the real-time rolling speed of the upper working roll and the lower working roll at all moments can be calculated according to the invention, and the metal second flow of the upper surface and the lower surface of the billet at all moments is ensured to be the same.
Claims (2)
1. A cascade control method for controlling rolling warpage of small billets is characterized by comprising the following steps of carrying out cascade control on billets in different technological processes, and establishing a descaling temperature difference control model and a rolling mill second flow control model, wherein the descaling temperature difference control model comprises an equation (P1-P2)/P1= k Δ T x kH (lambda 2-lambda 1)/lambda 2) for establishing the opening of a descaling water adjusting valve, the heat conductivity of the billets, the thickness of the billets and the temperature difference of the upper surface and the lower surface of the billets, and the rolling mill second flow control model comprises an equation omega 1/omega 2= (R2(1+ β 1))/(R1(1+ β 2)) for establishing the rotating speed of working rolls, the radius of the working rolls and the thermal expansion coefficient of the upper surface and the lower surface of the billets.
2. The cascade control method for controlling rolling warpage of billets as claimed in claim 1, wherein the rolling mill second flow control model comprises the following relations for setting the thermal expansion coefficients of the upper and lower surfaces of the head of the billet to β 1 and β 2, and the thermal expansion coefficients of the upper and lower surfaces of the middle of the billet to β 3 and β 4 by adjusting the rotation speeds ω 1 and ω 2 of the work rolls in real time for the temperature difference between the head and the tail of the billet and the middle of the billet:
V1=S (1+β1)/t=ω1R1，V2=S (1+β2)/t=ω2R2；
V3=S (1+β3)/t=ω3R1，V4=S (1+β4)/t=ω4R1；
by calculation
∆ω1=（ω3-ω1）/ω1；
∆ω2=（ω4-ω2）/ω2；
Therefore, when the secondary system sets the rolling speed of any working roll at any moment, the real-time rolling speed of the upper working roll and the lower working roll at all moments can be calculated, and the metal second flow of the upper surface and the lower surface of the billet at all moments is ensured to be the same.
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| CN106903166A (en) * | 2017-03-21 | 2017-06-30 | 北京科技大学 | A kind of aluminum alloy plate materials asymmetrical rolling warpage forecast and the method for optimization |
| CN108838216A (en) * | 2018-06-29 | 2018-11-20 | 首钢京唐钢铁联合有限责任公司 | Control method for raising head of plate blank |
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Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3930847B2 (en) * | 2003-10-21 | 2007-06-13 | 新日本製鐵株式会社 | Thick plate rolling method |
| CN102601128A (en) * | 2011-01-24 | 2012-07-25 | 宝山钢铁股份有限公司 | Temperature difference control method for rolling pieces for steckel mill |
| CN103128106A (en) * | 2011-11-25 | 2013-06-05 | 宝山钢铁股份有限公司 | Control method for head warping or head down bending for heavy plate rolling |
| CN103920721A (en) * | 2013-01-11 | 2014-07-16 | 宝山钢铁股份有限公司 | Method for controlling strip steel head stability during hot rolling |
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