CN108906885B - Method for hot rolling strip steel - Google Patents
Method for hot rolling strip steel Download PDFInfo
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- CN108906885B CN108906885B CN201810502396.8A CN201810502396A CN108906885B CN 108906885 B CN108906885 B CN 108906885B CN 201810502396 A CN201810502396 A CN 201810502396A CN 108906885 B CN108906885 B CN 108906885B
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- strip steel
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
- B21B2001/225—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length by hot-rolling
Abstract
The invention provides a hot rolling method of strip steel, which is used for a finishing mill and comprises the following steps: determining a target temperature for hot rolling the strip steel; determining the head length of the strip steel and a first compensation temperature relative to the target temperature, and determining the tail length of the strip steel and a second compensation temperature relative to the target temperature; controlling the finishing mill to perform temperature compensation on the head of the strip steel at the target temperature and the first hot rolling temperature, controlling the finishing mill to perform temperature control on the middle of the strip steel at the target temperature, and controlling the finishing mill to perform temperature compensation on the tail of the strip steel at the second hot rolling temperature. By adopting the technical scheme of the invention, the difference of longitudinal mechanical properties is eliminated, so that head and tail steel belts do not need to be cut off during continuous annealing production, the yield of the product is improved by about 0.4%, the accident rate is reduced, and the hourly output is improved.
Description
Technical Field
The invention relates to the technical field of metallurgy, in particular to a method for hot rolling strip steel.
Background
At present, the problem of uneven mechanical properties of the hot rolled strip steel in the length direction is generally existed after the hot rolled strip steel is curled at high temperature, the mechanical properties are shown in table 1 by taking the mark DC01 as an example, and the longitudinal mechanical properties of the strip steel at different positions are greatly different. The performance is unstable, so that problems are easy to occur in the punch forming process, and the subsequent forming process of the automobile steel cannot be met. In order to eliminate the difference of longitudinal performance, at least 20m long steel strips need to be cut from the head and the tail of the continuous annealing production line, on one hand, the product is greatly damaged, and on the other hand, the field operation is complicated, the small yield is influenced, and the production is easily influenced by accidents.
TABLE 1
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art or the related art.
To this end, one aspect of the present invention is to provide a method of hot rolling a steel strip.
In view of the above, the technical solution of the present invention provides a method for hot rolling a strip steel, which is used for a finishing mill, and includes: determining a target temperature for hot rolling the strip steel; determining the head length of the strip steel and a first compensation temperature relative to the target temperature, and determining the tail length of the strip steel and a second compensation temperature relative to the target temperature; and controlling the finishing mill to perform temperature compensation on the head of the strip steel by using the first compensation temperature, controlling the finishing mill to cool the middle of the strip steel by using the target temperature, and controlling the finishing mill to perform compensation on the tail of the strip steel by using the second compensation temperature, wherein the sum of the head length, the middle length and the tail length of the strip steel is the total length of the strip steel.
Further, the method of hot rolling a steel strip further comprises: and self-learning the heat exchange rate of the last target temperature and the last measured temperature of the strip steel to adjust the first compensation temperature, the target temperature and the second compensation temperature.
Further, before determining the head length of the strip steel and the first compensation temperature relative to the target temperature, and determining the tail length of the strip steel and the second compensation temperature relative to the target temperature, the method further includes: setting the head length of the strip steel and the first compensation temperature, setting the tail length of the strip steel and the second compensation temperature, measuring the mechanical property of the strip steel in the length direction after hot rolling, determining the head length of the strip steel and the first compensation temperature relative to the target temperature through historical data, and determining the tail length of the strip steel and the second compensation temperature relative to the target temperature.
One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:
after the head and tail of the strip steel are subjected to temperature compensation, the difference of longitudinal mechanical properties is eliminated, so that the head and tail strip steel does not need to be cut during continuous annealing production, the yield of the product is improved by about 0.4%, the accident rate is reduced, and the hourly output is improved.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 shows a schematic flow diagram of a method of hot rolling a strip according to one embodiment of the invention;
FIG. 2 is a schematic diagram showing a hot rolling temperature profile of a prior art method of hot rolling a steel strip;
FIG. 3 shows a statistical plot of the yield strength of a strip produced by a prior art method of hot rolling a strip;
FIG. 4 shows a prior art metallographic representation of the middle metallographic structure of DC01 for a hot rolled steel strip produced by the method of hot rolling steel strip;
FIG. 5 shows a metallographic structure plot of the DC01 tail of a strip produced by a prior art hot rolling strip process.
Detailed Description
So that the manner in which the above recited aspects, features and advantages of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflict.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described herein, and therefore the scope of the present invention is not limited by the specific embodiments disclosed below.
Example 1:
a method of hot rolling a steel strip as shown in fig. 1 for a finishing mill, comprising:
step S102, determining the head length and the first hot rolling temperature of the strip steel, and determining the tail length and the second hot rolling temperature of the strip steel;
step S104, controlling the finishing mill to heat the head of the strip steel at a first compensation temperature, controlling the finishing mill to cool the middle of the strip steel at a target temperature, controlling the finishing mill to heat the tail of the strip steel at a second compensation temperature,
wherein the sum of the head length, the middle length and the tail length of the strip steel is the total length of the strip steel.
Collecting and summarizing the performance data of the head and the tail of a continuous annealing automobile steel product DC01 produced by consistent cooling temperature of the head and the tail of the strip steel, and summarizing the data of the performance difference of the head, the tail and the middle steel strip by comparing the performance of the steel strip at the middle position of the product. The data prove that the steel strips of the automobile steel products, which are not produced by the method of the embodiment, have difference in the length direction, and the main rule is that the properties of the head steel strip and the tail steel strip are higher than those of the middle steel strip. The reason is that: under the normal condition of hot rolling production control, the temperature of the whole length of the strip steel fluctuates in a certain range around a target value, in the process of cooling to room temperature after coiling and coiling, the head and the tail of the strip steel are in contact with air, the cooling rate is higher than the cooling rate of the strip steel in a coil, the grain size of the head and the tail of the strip steel is smaller than the grain size of the middle part of the strip steel, the head and the tail have higher strength than the middle strip steel, so that the performance of the product in the length direction is uneven, and the defect of punching cracking can be seriously caused.
In the prior art, the hot rolling production adopts a conventional cooling mode, the head and the tail are not compensated by temperature, the hot rolling temperature curve is shown in figure 2,
as can be seen from fig. 2, the head and tail of the steel strip are controlled according to the target temperature, and the whole curve is produced according to the target temperature. Data of head and tail performance and middle performance of the steel strip product produced by using the cooling mode are collected, and specific data are shown in a figure 3.
It can be seen from the statistical results that the difference of the longitudinal performance of the strip steel products is finally caused due to the difference of the cooling speed of the hot coil. It is evident from the statistical data results in fig. 3 that the head and tail yield strength is generally higher than the mid-section yield strength.
The metallographic structure diagram of the middle part of the DC01 of the strip steel product is shown in figure 4, the metallographic structure diagram of the tail part of the DC01 of the strip steel product is shown in figure 5, the grain size rating of the metallographic structure of figure 4 is 9, the grain size rating of the metallographic structure of figure 5 is 10, and the yield strength is different due to the difference between the metallographic structure of the tail part and the metallographic structure of the middle part of the same coil of strip steel.
Therefore, in order to reduce the influence of the different cooling rates on the strip force properties, the strip was hot rolled using the method of this example. In the method of this embodiment, the target head and tail hot rolling temperatures are properly set at a certain length, and the target head and tail hot rolling temperatures are increased within the length range to eliminate the performance difference caused by the uneven cooling of the mechanical properties in the length direction of the later strip steel.
Taking the steel strip with the mark DC01 as an example, the set compensation temperature and length are shown in Table 2, the mechanical property is shown in Table 3,
TABLE 2
TABLE 3
As is clear from Table 3, the variation in the longitudinal mechanical properties was greatly reduced by the method of hot rolling the steel strip of the present example.
In the current hot rolled strip steel rolling process, when the head of a strip steel enters a finishing mill, a cooling temperature control model divides the strip steel into a plurality of controlled units at equal intervals in the length direction, the water quantity of each controlled unit is calculated by combining U-shaped cooling parameters and the heat exchange coefficient of the steel type, after the strip steel enters a layer cold state, the head position of the strip steel is obtained by calculating the speed of a layer cold roller way, the set value of the water quantity required by the controlled unit is calculated according to the collected measured temperature, the target required temperature and the heat exchange rate of the controlled unit, and a control system converts the set value of the water quantity into the number of water valves and sends the number of the water valves to an execution mechanism for actual control. And after the cooling process is finished, the cooling model performs regression calculation on the collected actually-measured temperature data and the number of the water valve switches to obtain the heat exchange coefficient of the strip steel. In the method of the embodiment, further, the model can take the measured temperatures of the three controlled units at the head, the middle and the tail of the strip steel to perform the self-learning of the heat exchange rate, so that the temperature control precision can be further improved, and the next strip steel can inherit the self-learning result of the heat exchange rate of the previous strip steel during calculation, so that the control precision is continuously improved.
Further, the method for determining the head length and the first compensation temperature, the tail length and the second compensation temperature comprises the following steps: setting the head length and the first compensation temperature of the strip steel, setting the tail length and the second compensation temperature of the strip steel, measuring the mechanical property of the hot-rolled strip steel in the length direction, continuously optimizing the setting of the head length, the first compensation temperature, the tail length and the second compensation temperature through summarizing historical data, and determining the head length of the strip steel, the first compensation temperature relative to the target temperature, the tail length of the strip steel and the second compensation temperature relative to the target temperature.
Example 2:
for the strip steel with the mark DC01, the head length, the first compensation temperature, the tail length and the second compensation temperature parameters set by the strip steel with different thicknesses are shown in the table 4:
TABLE 4
In the above table: delta TH1, compensating temperature of the head of the strip steel; LH 1: the length of the head of the strip steel; LH 2: transition length of the strip steel head; Δ TH 2: compensating the temperature at the tail of the strip steel; LT 1: the length of the tail of the strip steel; LT 2: transition length of the tail of the strip steel.
The transition length of the head of the strip steel is set to enable the hot rolling temperature of the head to be stably reduced to the target temperature of the middle, and the transition length of the tail of the strip steel is set to enable the hot rolling temperature of the middle to be stably increased to the target temperature of the tail.
The technical scheme of the invention is explained by combining the attached drawings, and through the technical scheme of the invention, the longitudinal mechanical property difference is eliminated after the head and tail temperature compensation of the strip steel, so that the head and tail strip steel does not need to be cut off during continuous annealing production, the product yield is improved by about 0.4 percent, the accident rate is reduced, and the hourly output is improved.
In the description herein, the description of the terms "one embodiment," "some embodiments," "specific embodiments," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (3)
1. A method of hot rolling a steel strip in a finishing mill, comprising:
determining a target temperature for hot rolling the strip steel;
determining the head length of the strip steel and a first compensation temperature relative to the target temperature, and determining the tail length of the strip steel and a second compensation temperature relative to the target temperature;
controlling the finishing mill to perform temperature compensation on the head of the strip steel at the first compensation temperature, controlling the finishing mill to cool the middle of the strip steel at the target temperature, controlling the finishing mill to perform temperature compensation on the tail of the strip steel at the second compensation temperature,
the sum of the head length, the middle length and the tail length of the strip steel is the total length of the strip steel.
2. The method of hot rolling steel strip as claimed in claim 1 further comprising: and self-learning the heat exchange rate of the last target temperature and the last measured temperature of the strip steel to adjust the first compensation temperature, the target temperature and the second compensation temperature.
3. The method of hot rolling the steel strip as claimed in claim 1 further comprising, prior to determining the head length of the steel strip and the first compensation temperature relative to the target temperature and determining the tail length of the steel strip and the second compensation temperature relative to the target temperature:
setting the head length of the strip steel and the first compensation temperature, setting the tail length of the strip steel and the second compensation temperature, measuring the mechanical property of the strip steel in the length direction after hot rolling, determining the head length of the strip steel and the first compensation temperature relative to the target temperature through historical data, and determining the tail length of the strip steel and the second compensation temperature relative to the target temperature.
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| CN115228929A (en) * | 2022-07-29 | 2022-10-25 | 广西广盛新材料科技有限公司 | Temperature control method and device for strip steel production, terminal equipment and storage medium |
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| JP5054369B2 (en) * | 2006-12-19 | 2012-10-24 | 株式会社日立製作所 | Winding temperature control device and control method |
| CN102601128B (en) * | 2011-01-24 | 2014-06-04 | 宝山钢铁股份有限公司 | Temperature difference control method for rolling pieces for steckel mill |
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