Hot-rolled steel strip with uniform internal stress and method for producing the same

Abstract

The application relates to a hot-rolled strip steel with uniform internal stress and a preparation method thereof, and belongs to the technical field of steel preparation; the method comprises the following steps: hot-rolling a casting blank; then, according to preset working conditions, controlling the opening and closing of water spraying on each side to perform laminar cooling, so that a finished strip steel is obtained; by designing a new hot-rolling laminar cooling section side water spraying use method, under the premise of guaranteeing the basic sealing water process function of the side water spraying, the total use quantity of the side water spraying is greatly reduced, so that the influence degree of the whole laminar cooling section side water spraying on the surface temperature of the strip steel is reduced, the uniformity of the temperature of the strip steel along the width direction after passing through the laminar cooling section is improved, and the control level of the organization, performance and internal stress of the hot-rolled strip steel product is improved.

Description

Technical Field

[0001] This application relates to the field of steel preparation technology, and in particular to a hot-rolled strip steel with uniform internal stress and its preparation method. Background Technology

[0002] Laminar flow cooling equipment is a standard configuration in hot strip mill production lines, located between the finishing mill and the coiler. Typically, about 20 sets are configured, forming a laminar flow cooling process section. Each set of laminar flow cooling manifolds consists of upper and lower sections, cooling the upper and lower surfaces of the strip respectively. Each upper and lower cooling manifold set contains multiple rows of individually controllable water-cooled manifolds. By designing different numbers and sequences of water-cooled manifolds, the cooling path and final microstructure and properties of the hot-rolled strip are controlled. Simultaneously, side spray nozzles are installed at the inlet and outlet of the laminar flow cooling section, as well as between adjacent sets of upper laminar flow cooling manifolds, to provide side-spray process water. The main function of the side spray is to blow away residual laminar water on the strip surface, preventing residual water from causing uncontrollable cooling, affecting temperature monitoring, and impacting cooling efficiency.

[0003] In actual hot rolling production, after the strip is cooled in the laminar flow cooling section, the temperature distribution along the width of the strip is uneven, with lower temperatures at the edges and localized low temperatures in the middle. This temperature distribution pattern causes changes in the microstructure, properties, and internal stress of the strip in the lower temperature areas, and in particular, the localized low temperatures in the middle can lead to significant residual internal stress. Summary of the Invention

[0004] This application provides a hot-rolled strip steel with uniform internal stress and a method for preparing the same, in order to improve the problem of residual internal stress generated by current preparation methods.

[0005] Through a comprehensive analysis of various process factors, such as the final rolling temperature distribution characteristics of strip steel, the cooling efficiency distribution characteristics of laminar cooling water along the width direction of strip steel, and the impact area of ​​laminar cooling side spray process water on the surface of strip steel, the inventors discovered that laminar cooling side spray process water is one of the key reasons for the non-uniform distribution of strip steel temperature along the width direction.

[0006] Therefore, the inventors intend to develop a method for using side-sprayed water in laminar flow cooling to reduce the impact of side-sprayed water on the surface temperature of strip steel, improve the uniformity of temperature distribution along the width direction of strip steel after laminar flow cooling, and thereby improve the microstructure, properties and internal stress uniformity of strip steel products.

[0007] In a first aspect, this application provides a method for preparing hot-rolled strip steel with uniform internal stress, the method comprising:

[0008] The hot-rolled strip is then subjected to laminar flow cooling to obtain the finished strip.

[0009] The opening and closing of the side spray water of each cooling manifold group in the laminar flow cooling system meets the preset operating conditions.

[0010] As an optional implementation, the method for determining the opening and closing of the side spray water of each cooling manifold assembly in the preset operating condition is as follows:

[0011] Let i be the sequence number of the upper cooling manifolds in each group of the laminar flow cooling section according to the running direction of the strip; n be the total number of groups of upper cooling manifolds; K i K represents the number of cooling manifolds actually opened in the upper cooling manifold of the i-th group; Mi denoted as the total number of cooling manifolds in the upper cooling manifold of the i-th group; 'a' is the residual water backflow sealing judgment coefficient; 'b' is the residual water secondary sealing judgment coefficient; 'C0' is the laminar flow cooling section inlet side spray opening / closing status, 1 represents open, 0 represents closed; C i This represents the on / off status of the side spray process water between the upper laminar cooling manifolds of the i-th group, where 1 represents on and 0 represents off; C n This indicates the on / off status of the water spray at the outlet side of the laminar flow cooling section; 1 represents on, and 0 represents off.

[0012] When i = 1, if K i ≤a×K Mi Let C0 = 0, c i =0; if a×K Mi <K i <b×K Mi Let C0 = 1, C i =1; if K i ≥b×K Mi Let C0 = 1, C i =1, C i+1 =1.

[0013] As an optional implementation, when 1 < i ≤ n-1, if 0 = K i-1 Then the following judgment is made: if K i ≤a×K Mi , making C i-1 =0, C i =0; if a×K Mi <K i <b×K Mi , making C i-1 =1, C i =1; if K i ≥b×K Mi , making C i-1 =1, C i =1, C i+1 =1; if 0 < K i-1 Then the following judgment is made: if 0 < K i <b×K Mi , making Ci-1 =0, C i =1; if a×K Mi <K i <b×K Mi , making C i-1 =0, C i =1, C i+1 =1.

[0014] As an optional implementation, when i = n, if 0 ≤ K i , making C i-1 =1, C n =1.

[0015] As an optional implementation, the residual water backflow sealing judgment coefficient α ranges from 0.1 to 0.3.

[0016] As an optional implementation, the residual water secondary sealing judgment coefficient b ranges from 0.6 to 0.8.

[0017] Secondly, this application provides a method for preparing hot-rolled strip steel with uniform internal stress, the method comprising:

[0018] According to the preset working conditions, the water spray on each side is controlled to perform laminar flow cooling on the hot-rolled strip steel to obtain the finished strip steel.

[0019] The method for determining the opening and closing of the side spray water of each cooling manifold assembly in the preset operating condition is as follows:

[0020] Let i be the sequence number of the upper cooling manifolds in each group of the laminar flow cooling section according to the running direction of the strip; n be the total number of groups of upper cooling manifolds; K i K represents the number of cooling manifolds actually opened in the upper cooling manifold of the i-th group; Mi denoted as the total number of cooling manifolds in the upper cooling manifold of the i-th group; 'a' is the residual water backflow sealing judgment coefficient; 'b' is the residual water secondary sealing judgment coefficient; 'C0' is the laminar flow cooling section inlet side spray opening / closing status, 1 represents open, 0 represents closed; C i This represents the on / off status of the side spray process water between the upper laminar cooling manifolds of the i-th group, where 1 represents on and 0 represents off; C n This indicates the on / off status of the water spray at the outlet side of the laminar flow cooling section; 1 represents on, and 0 represents off.

[0021] When i = 1, if K i ≤a×K Mi Let C0 = 0, C i =0; if a×K Mi <K i <b×K Mi Let C0 = 1, C i =1; if K i≥b×K Mi Let C0 = 1, C i =1, C i+1 =1;

[0022] When 1 < i ≤ n-1, if 0 = K i-1 Then the following judgment is made: if K i ≤a×K Mi , making C i-1 =0, C i =0; if a×K Mi <K i <b×K Mi , making C i-1 =1, C i =1; if K i ≥b×K Mi , making C i-1 =1, C i =1, C i+1 =1; if 0 < K i-1 Then the following judgment is made: if 0 < K i <b×K Mi , making C i-1 =0, C i =1; if a×K Mi <K i <b×K Mi , making C i-1 =0, C i =1, C i+1 =1;

[0023] When i = n, if 0 ≤ K i , making C i-1 =1, C n =1.

[0024] As an optional implementation, the residual water backflow sealing judgment coefficient 'a' ranges from 0.1 to 0.3; and / or

[0025] The residual water secondary sealing judgment coefficient b ranges from 0.6 to 0.8.

[0026] As an optional implementation, the order of determining the opening and closing of the side spray water of each cooling manifold group in the preset working condition is as follows: the upper cooling manifolds of each group in the laminar flow cooling section are arranged in ascending order of their serial numbers according to the running direction of the strip steel.

[0027] Thirdly, this application provides a hot-rolled strip steel with uniform internal stress, characterized in that the hot-rolled strip steel is prepared by the preparation method of hot-rolled strip steel with uniform internal stress described in the first or second aspect.

[0028] The technical solutions provided in this application have the following advantages compared with the prior art:

[0029] The method provided in this application embodiment, by designing a new method for using side spray water in the laminar flow cooling section of hot rolling, significantly reduces the total amount of side spray water used while ensuring the basic sealing effect of the side spray water process. This reduces the impact of the side spray water in the entire laminar flow cooling section on the surface temperature of the strip steel, improves the uniformity of the temperature distribution along the width direction of the strip steel after passing through the laminar flow cooling section, and is conducive to improving the control level of the microstructure, properties and internal stress of hot-rolled strip steel products. Attached Figure Description

[0030] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0031] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A flowchart illustrating the method provided in the embodiments of this application;

[0033] Figure 2 A comparison diagram of the strip temperature distribution along the width direction before and after application of the method provided in Embodiment 1 of this application;

[0034] Figure 3 A comparison diagram of the strip temperature distribution along the width direction before and after the application of the method provided in Embodiment 2 of this application. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0037] Through a comprehensive analysis of various process factors, such as the final rolling temperature distribution characteristics of strip steel, the cooling efficiency distribution characteristics of laminar cooling water along the width direction of strip steel, and the impact area of ​​laminar cooling side spray process water on the surface of strip steel, the inventors discovered that laminar cooling side spray process water is one of the key reasons for the non-uniform distribution of strip steel temperature along the width direction.

[0038] Therefore, the inventors intend to develop a method for using side-sprayed water in laminar flow cooling to reduce the impact of side-sprayed water on the surface temperature of strip steel, improve the uniformity of temperature distribution along the width direction of strip steel after laminar flow cooling, and thereby improve the microstructure, properties and internal stress uniformity of strip steel products.

[0039] like Figure 1 As shown in the embodiment of this application, a method for preparing hot-rolled strip steel with uniform internal stress is provided, the method comprising:

[0040] According to the preset working conditions, the water spray on each side is opened and closed to perform laminar flow cooling on the hot-rolled strip steel to obtain the finished strip steel.

[0041] The method for determining the opening and closing of the side spray water of each cooling manifold assembly in the preset operating condition is as follows:

[0042] Let i be the sequence number of the upper cooling manifolds in each group of the laminar flow cooling section according to the running direction of the strip; n be the total number of groups of upper cooling manifolds; K i K represents the number of cooling manifolds actually opened in the upper cooling manifold of the i-th group; Mi denoted as the total number of cooling manifolds in the upper cooling manifold of the i-th group; 'a' is the residual water backflow sealing judgment coefficient, ranging from 0.1 to 0.3; 'b' is the residual water secondary sealing judgment coefficient, ranging from 0.6 to 0.8; 'C0' is the laminar flow cooling section inlet side spray water opening and closing status, 1 represents open, 0 represents closed; C i This represents the on / off status of the side spray process water between the upper laminar cooling manifolds of the i-th group, where 1 represents on and 0 represents off; C n This indicates the on / off status of the water spray at the outlet side of the laminar flow cooling section; 1 represents on, and 0 represents off.

[0043] When i = 1, if K i ≤a×K Mi Let C0 = 0, C i =0; if a×K Mi <K i <b×K Mi Let C0 = 1, C i =1; if K i ≥b×K Mi Let C0 = 1, C i =1, C i+1 =1;

[0044] When 1 < i ≤ n-1, if 0 = K i-1 Then the following judgment is made: if K i ≤a×K Mi , making C i-1 =0, C i =0; if a×K Mi <K i <b×K Mi , making C i-1 =1, C i =1; if K i ≥b×K Mi , making C i-1 =1, C i =1, C i+1 =1; if 0 < K i-1 Then the following judgment is made: if 0 < K i <b×K Mi , making C i-1 =0, C i =1; if a×K Mi <K i <b×K Mi , making C i-1 =0, C i =1, C i+1 =1;

[0045] When i = n, if 0 ≤ K i , making C i-1 =1, C n =1.

[0046] In some embodiments, the order of determining the opening and closing of the side spray water of each cooling manifold group in the preset operating condition is as follows: The upper cooling manifolds of each group in the laminar flow cooling section are arranged in ascending order of their serial numbers according to the running direction of the strip steel. The specific calculation process is as follows:

[0047] Let i be the sequence number of the upper cooling manifolds in each group of the laminar flow cooling section according to the running direction of the strip; n be the total number of groups of upper cooling manifolds; K i K represents the number of cooling manifolds actually opened in the upper cooling manifold of the i-th group; Mi denoted as the total number of cooling manifolds in the upper cooling manifold of the i-th group; 'a' is the residual water backflow sealing judgment coefficient, ranging from 0.1 to 0.3; 'b' is the residual water secondary sealing judgment coefficient, ranging from 0.6 to 0.8; 'C0' is the laminar flow cooling section inlet side spray water opening and closing status, 1 represents open, 0 represents closed; C i This represents the on / off status of the side spray process water between the upper laminar cooling manifolds of the i-th group, where 1 represents on and 0 represents off; C n This indicates the on / off status of the water spray at the outlet side of the laminar flow cooling section; 1 represents on, and 0 represents off.

[0048] Let i = 1, and determine if K i ≤a×K Mi Let C0 = 0, C i =0; if a×K Mi <K i <b×K Mi Let C0 = 1, C i =1; if K i ≥b×K Mi Let C0 = 1, C i =1, C i+1 =1, where i is the sequence number of each group of upper cooling manifolds in the laminar flow cooling section according to the running direction of the strip, i = 1 to n; n is the total number of groups of upper cooling manifolds; K i K represents the number of cooling manifolds actually opened in the upper cooling manifold of the i-th group; Mi denoted as the total number of cooling manifolds in the upper cooling manifold of the i-th group; 'a' is the residual water backflow sealing judgment coefficient, ranging from 0.1 to 0.3; 'b' is the residual water secondary sealing judgment coefficient, ranging from 0.6 to 0.8; 'C0' is the laminar flow cooling section inlet side spray opening / closing status, 1 represents open, 0 represents closed; C i This represents the on / off state of the side spray process water between the upper laminar cooling manifolds of the i-th and i+1-th groups, where 1 represents on and 0 represents off.

[0049] The second step is to let i = i` + 1. If i ≤ n - 1, proceed to the third step. If i = n, proceed to the sixth step, where i` is the sequence number of the previous judgment.

[0050] The third step is to determine if 0 = K. i-1 Then proceed to step four; if 0 < K i-1 Then proceed to step five.

[0051] Fourth step, determine if K i ≤a×K Mi , making C i-1 =0, c i =1; if a×K Mi <K i <b×K Mi Let c i-1 =1, C i =1; if K i ≥b×K Mi , making C i-1 =1, c i =1, C i+1 =1; Return to step two.

[0052] Step 5: Determine if 0 < K i <b×K Mi , making C i-1 =0, C i=1; if a×K Mi <K i <b×K Mi , making C i-1 =0, c i =1, C i+1 =1; Return to step two.

[0053] Step 6: Determine if 0 < K i Let c i-1 =1, C n =1, end, where C n This indicates the on / off state of the water spray at the outlet of the laminar flow cooling section; 1 represents on and 0 represents off.

[0054] This method, by designing a new side-spraying water application method for the laminar flow cooling section of hot rolling, significantly reduces the total amount of side-spraying water used while ensuring the basic sealing effect of the side-spraying water process. This reduces the impact of the side-spraying water on the surface temperature of the strip steel in the entire laminar flow cooling section, improves the uniformity of the temperature distribution along the width direction of the strip steel after passing through the laminar flow cooling section, and is conducive to improving the control level of the microstructure, properties and internal stress of hot-rolled strip steel products.

[0055] Based on a general inventive concept, embodiments of this application also provide a hot-rolled strip steel with uniform internal stress, wherein the hot-rolled strip steel is prepared by the preparation method of hot-rolled strip steel with uniform internal stress as provided above.

[0056] The hot-rolled strip steel is prepared based on the above method. The specific steps of the method can be referred to the above embodiments. Since the steel adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0057] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0058] Example 1

[0059] The side-spray water opening and closing design method provided in this application was applied to a 2250 hot rolling line in a certain factory. This production line has 21 sets of laminar flow cooling manifolds in its laminar flow cooling section. Sets 1-4 each have 6 rows of individually controlled cooling manifolds, sets 5-19 each have 4 rows of individually controlled cooling manifolds, and sets 20 and 21 each have 8 rows of individually controlled cooling manifolds. In the production of a certain hot-rolled strip steel product with a width of 1500mm and a thickness of 3.0mm, the residual water backflow sealing judgment coefficient 'a' was set to 0.25, and the residual water secondary sealing judgment coefficient 'b' was set to 0.75. The comparison of the number of laminar flow cooling side-spray water units used before and after application is shown in the table below:

[0060]

[0061]

[0062] As shown in the table above, after designing the side spray system using the method provided in this application, the number of side spray systems put into operation is reduced from 15 to 5.

[0063] A comparison of the strip temperature distribution along the width direction before and after application is shown in the figure below. Figure 2 As shown in the figure, the temperature deviation at the local low temperature point decreased from about 35℃ to about 10℃, and the maximum temperature difference in the strip width direction decreased from about 90℃ to about 60℃.

[0064] Example 2

[0065] The side-spray water opening and closing design method provided in this application was applied to a 1580 hot rolling line in a certain factory. This production line has 21 sets of laminar flow cooling manifolds in its laminar flow cooling section. Sets 1-4 each have 6 rows of individually controlled cooling manifolds, sets 5-19 each have 4 rows of individually controlled cooling manifolds, and sets 20 and 21 each have 8 rows of individually controlled cooling manifolds. In the production of a certain hot-rolled strip steel product with a width of 1250mm and a thickness of 2.0mm, the residual water backflow sealing judgment coefficient 'a' was set to 0.25, and the residual water secondary sealing judgment coefficient 'b' was set to 0.75. The comparison of the number of laminar flow cooling side-spray water units used before and after application is shown in the table below:

[0066]

[0067] As shown in the table above, after designing the side spray system using the method provided in this application, the number of side spray systems put into operation is reduced from 17 to 5.

[0068] A comparison of the strip temperature distribution along the width direction before and after application is shown in the figure below. Figure 3 As shown in the figure, the temperature deviation at the local low temperature point decreased from about 40℃ to about 10℃, and the maximum temperature difference in the strip width direction decreased from about 90℃ to about 50℃.

[0069] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0070] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the orientation shown in the accompanying drawings. Furthermore, in the description of this application, the terms "comprising," "including," etc., mean "including but not limited to."

[0071] In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any actual relationship or order between these entities or operations. In this document, "and / or" describes the association between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c," or "at least one of a, b, and c," can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0072] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing hot-rolled strip steel with uniform internal stress, characterized in that, The method includes: The hot-rolled strip is then subjected to laminar flow cooling to obtain the finished strip. The opening and closing of the side spray water of each cooling manifold group of the laminar flow cooling meets the preset working conditions. The method for determining the opening and closing of the side spray water of each cooling manifold assembly in the preset operating condition is as follows: Let i be the sequence number of each group of upper cooling manifolds in the laminar flow cooling section according to the running direction of the strip steel; n is the total number of groups of upper cooling manifolds. The number of cooling manifolds actually opened in the upper cooling manifold of the i-th group; denoted as the total number of cooling manifolds in the upper cooling manifold of the i-th group; a is the residual water backflow sealing judgment coefficient; b is the residual water secondary sealing judgment coefficient. This indicates the on / off state of the water spray at the inlet side of the laminar flow cooling section; 1 represents on and 0 represents off. This represents the on / off status of the side spray process water between the upper laminar cooling manifolds of the i-th group, where 1 represents on and 0 represents off. This indicates the on / off status of the water spray at the outlet side of the laminar flow cooling section; 1 represents on, and 0 represents off. When i=1, if ,make =0、 ;like ,make , ;like ,make , , .

2. The method for preparing hot-rolled strip steel with uniform internal stress according to claim 1, characterized in that, When 1 < i ≤ n-1, if Then the following judgment is made: If ,make =0、 ;like ,make , ;like ,make , , ;like Then the following judgment is made: If ,make =0、 ;like ,make =0、 , .

3. The method for preparing hot-rolled strip steel with uniform internal stress according to claim 1, characterized in that, When i=n, ​​if ,make , .

4. The method for preparing hot-rolled strip steel with uniform internal stress according to claim 1, characterized in that, The residual water backflow sealing judgment coefficient 'a' ranges from 0.1 to 0.

3.

5. The method for preparing hot-rolled strip steel with uniform internal stress according to claim 1, characterized in that, The residual water secondary sealing judgment coefficient b ranges from 0.6 to 0.

8.

6. A method for preparing hot-rolled strip steel with uniform internal stress, characterized in that, The method includes: The billet is hot rolled, then According to the preset working conditions, the water spray on each side is opened and closed to carry out laminar flow cooling and obtain finished steel strip. The method for determining the opening and closing of the side spray water of each cooling manifold assembly in the preset operating condition is as follows: Let i be the sequence number of each group of upper cooling manifolds in the laminar flow cooling section according to the running direction of the strip steel; n is the total number of groups of upper cooling manifolds. The number of cooling manifolds actually opened in the upper cooling manifold of the i-th group; denoted as the total number of cooling manifolds in the upper cooling manifold of the i-th group; a is the residual water backflow sealing judgment coefficient; b is the residual water secondary sealing judgment coefficient. This indicates the on / off state of the water spray at the inlet side of the laminar flow cooling section; 1 represents on and 0 represents off. This represents the on / off status of the side spray process water between the upper laminar cooling manifolds of the i-th group, where 1 represents on and 0 represents off. This indicates the on / off status of the water spray at the outlet side of the laminar flow cooling section; 1 represents on, and 0 represents off. When i=1, if ,make =0、 ;like ,make , ;like ,make , , ; When 1 < i ≤ n-1, if Then the following judgment is made: If ,make =0、 ;like ,make , ;like ,make , , ;like Then the following judgment is made: If ,make =0、 ;like ,make =0、 , ; When i=n, ​​if ,make , .

7. The method for preparing hot-rolled strip steel with uniform internal stress according to claim 6, characterized in that, The residual water backflow sealing judgment coefficient 'a' ranges from 0.1 to 0.3; and / or The residual water secondary sealing judgment coefficient b ranges from 0.6 to 0.

8.

8. The method for preparing hot-rolled strip steel with uniform internal stress according to claim 6, characterized in that, The order of determining the opening and closing of the side spray water of each cooling manifold group in the preset working condition is as follows: the upper cooling manifolds of each group in the laminar flow cooling section are arranged in ascending order of the strip running direction.

9. A hot-rolled strip steel with uniform internal stress, characterized in that, The steel is prepared by the method for preparing hot-rolled strip steel with uniform internal stress as described in any one of claims 1 to 8.

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