Withdrawal and straightening machine arrangement method based on light and heavy combined pressing technology

Abstract

The invention provides a tension leveler arrangement method based on a light-heavy combined pressing technology, which belongs to the technical field of continuous casting and comprises the following steps of: determining a pressing interval corresponding to the pulling speed of each working condition of the light-heavy combined pressing technology; and the withdrawal and straightening machine is arranged under the condition that the minimum number of press-down rollers are arranged in the press-down intervals corresponding to the drawing speeds of all the working conditions. The problem that in the prior art, an effective scheme for reducing the number of withdrawal and straightening machines on the premise of meeting the requirement of a pressing process is lacked for arrangement of the withdrawal and straightening machines applied to light and heavy combined pressing can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of continuous casting, and more specifically, to a method for arranging a straightening machine based on a light-heavy combined pressing technology. Background Art

[0002] The continuous casting solidification end reduction technology is an effective technical means to improve the core defects of the billet, and has been widely studied and applied in various billet types. In the past decade, although the light reduction technology at the end of solidification is still being studied and applied, it has gradually developed into heavy reduction (or large reduction) technology, in order to obtain better billet core quality and improve the final product performance.

[0003] At present, the understanding and application of heavy reduction technology are still different, but from the perspective of guiding theory and practical application, heavy reduction technology can be roughly divided into three categories: (1) single-roll heavy reduction, using heavy reduction as an independent technology; (2) increasing the total reduction amount on the basis of light reduction; (3) a combination of light and heavy reduction, using light reduction in the front to improve segregation and heavy reduction in the back to "weld" shrinkage holes and improve the density of the ingot. However, no matter which heavy reduction method is used, the design criteria for the layout of the reduction straightening machine are not given.

[0004] The existing layout of the press-down straightening machine continues the design of light press-down, and no effective solution that can be relied on is given in terms of mechanism and improvement effect. Generally, it is given from the following perspectives: From the process perspective, the roller spacing of the press-down straightening machine is required to be as small as possible, such as 600-800mm. It is believed that a small roller spacing is conducive to continuous press-down and continuous action. However, no feasible design annotations are given. From the equipment perspective, the strength of the straightening machine, the layout of the transmission, the size of the cylinder diameter, the hoisting, etc. should be considered. The roller spacing is generally slightly larger, such as 0.95-1.6m. In principle, the greater the required press-down force, the larger the straightening machine frame, and the larger the roller spacing arrangement; the arrangement of the arc and straightening area requires a slightly larger roller spacing because the extraction space of the straightening machine should be considered. Therefore, at present, the roller spacing is determined by the comprehensive process and equipment, but the design limit is not given from the guiding principle, so as to achieve a reasonable integration of process and equipment.

[0005] As mentioned above, currently, in the prior art, the arrangement of the straightening machine for independent application of light and heavy combination pressing is considered from the perspective of the comprehensive roller spacing of the process and equipment, and its formation is similar to convention, and no design limit is given from the guiding principle. Therefore, for the arrangement of the straightening machine for independent application of light and heavy combination pressing, there is a lack of an effective solution to reduce the number of straightening machines while meeting the pressing process requirements. Summary of the invention

[0006] In view of the above problems, the purpose of the present invention is to provide a method for arranging a straightening machine based on a light-heavy combined pressing technology, so as to solve the problem in the prior art that the arrangement of straightening machines for light-heavy combined pressing applications lacks an effective solution to reduce the number of straightening machines while meeting the pressing process requirements.

[0007] The present invention provides a method for arranging a tension and leveling machine based on a light-heavy combined pressing-down technology, comprising the following steps:

[0008] Determine the compression range corresponding to the pulling speed of each working condition of the light and heavy combined compression technology; wherein the compression range is the range from the starting position of the compression range to the ending position of the compression range;

[0009] The tensioning and straightening machine is arranged to ensure that a preset minimum number of pressure rollers are arranged in the pressure-reducing range corresponding to the pulling speed of each working condition.

[0010] In addition, a preferred solution is that the method for determining the starting position of the pressing interval includes:

[0011] The starting position of the depression interval is obtained according to the starting position of the preset center solid phase ratio standard interval.

[0012] In addition, a preferred solution is that the method for determining the end position of the depressible interval includes:

[0013] According to the end position of the preset center solid phase ratio standard interval, the end position of the pressing interval is obtained;

[0014] The end position of the depressible interval is determined according to the end position of the depressing interval and the preset adjustable depressing length.

[0015] In addition, a preferred solution is that the preset central solid phase ratio standard interval is 0.3 to 1.0.

[0016] In addition, a preferred solution is that the determining the end position of the depressible interval according to the end position of the depressing interval and the preset adjustable depressing length comprises:

[0017] The depressible interval end position is obtained by adding the depressing interval end position to the preset adjustable depressing length.

[0018] In addition, a preferred solution is that the preset adjustable pressing length is 0.3 to 1.0 m.

[0019] In addition, a preferred solution is that the condition of ensuring that a preset minimum number of pressing rollers are arranged in the pressing interval corresponding to the pulling speed of each working condition, and arranging the straightening machine includes:

[0020] According to the end position of the depression interval and the start position of the depression interval corresponding to the pulling speed of each working condition of the light-heavy combined depression technology, the length of the depression interval corresponding to the pulling speed of each working condition is determined;

[0021] Determine the spacing of the pressing rollers in the pressing section corresponding to the pulling speed of each working condition according to the length of the pressing section corresponding to the pulling speed of each working condition and the preset minimum number of pressing rollers;

[0022] The tensioning and straightening machine is arranged based on the spacing between the pressing rollers in the pressing range corresponding to the pulling speed in each working condition.

[0023] In addition, a preferred solution is that, after arranging the tensioning and straightening machine, the condition of ensuring that a preset minimum number of pressing rollers are arranged in the pressing interval corresponding to the pulling speed of each working condition is further included:

[0024] During the execution of the light and heavy combined pressing process, when the number of pressing rollers arranged in the pressing interval corresponding to the selected working condition pulling speed is greater than the number of pressing rollers required to execute the pressing process, the number of pressing rollers required to execute the pressing process is selected from the side close to the end position of the pressing interval to execute the pressing process.

[0025] In addition, a preferred solution is that in the process of determining the possible reduction range corresponding to the pulling speed of each working condition of the light and heavy combined reduction technology,

[0026] The corresponding depression intervals of the working condition pulling speeds are determined in order from small to large. The larger the working condition pulling speed, the larger the corresponding depression interval, and the larger the spacing between the depression rollers when the straightening machine is arranged.

[0027] In addition, a preferred solution is that the preset minimum number is 3 to 5.

[0028] It can be seen from the above technical scheme that the method for arranging a straightening machine based on the light-heavy combined pressing technology provided by the present invention first determines the pressing range corresponding to the pulling speed of each working condition of the light-heavy combined pressing technology; then ensures that a preset minimum number of pressing rollers are arranged in the pressing range corresponding to the pulling speed of each working condition, and arranges the straightening machine, so as to obtain a scheme with the least arrangement of straightening machines on the basis of satisfying the process effect, and effectively solves the problem of lack of design standards for maximizing the spacing between rollers of straightening machines in the prior art, and inability to obtain the limit design boundary to ensure the pressing effect. The present invention avoids the fuzzy requirements for equipment that the smaller the roller spacing is, the better, which is recognized in the prior art, and achieves quantitative design. While ensuring the pressing effect, the least arrangement of straightening machines is used, thereby effectively reducing the cost of heavy pressure equipment, and then greatly reducing the overall cost of production.

[0029] In order to achieve the above and related purposes, one or more aspects of the present invention include the features that will be described in detail later. The following description and the accompanying drawings describe some exemplary aspects of the present invention in detail. However, these aspects indicate only some of the various ways in which the principles of the present invention can be used. In addition, the present invention is intended to include all these aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] By referring to the following description in conjunction with the accompanying drawings, and with a more complete understanding of the present invention, other objects and results of the present invention will become more apparent and easily understood.

[0031] Figure 1 The present invention is a flow chart of a method for arranging a tension and straightening machine based on a light and heavy combined pressing technology according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In the following description, for the purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. However, it is apparent that these embodiments may also be implemented without these specific details.

[0033] In view of the problem that the above-mentioned prior art lacks an effective solution to reduce the number of straightening machines while meeting the requirements of the press-down process, a method for arranging straightening machines based on a combination of light and heavy press-down technology is proposed.

[0034] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0035] In order to illustrate the arrangement method of the tension and leveling machine based on the light and heavy combined pressing technology provided by the present invention, Figure 1 The flowchart of the method for arranging a tension and leveling machine based on the light-heavy combined pressing technology according to an embodiment of the present invention is shown.

[0036] like Figure 1 As shown, the method for arranging a tension and leveling machine based on the light-heavy combined pressing technology provided by the present invention comprises the following steps:

[0037] Step S1, determining the possible compression interval corresponding to the pulling speed of each working condition of the light and heavy combined compression technology; wherein the possible compression interval is the interval from the starting position of the compression interval to the ending position of the possible compression interval.

[0038] Specifically, in the reduction process of the light-heavy combined reduction technology, the steel type and the pulling speed used for the ingot are different under different working conditions. For the same steel type, different pulling speeds will also lead to different reduction ranges. Therefore, it is necessary to comprehensively consider the reduction ranges corresponding to the pulling speeds under different working conditions. That is, comprehensively consider the reduction ranges corresponding to different steel types and different pulling speeds.

[0039] As a preferred solution of the present invention, the method for determining the starting position of the pressing interval includes:

[0040] The starting position of the depression interval is obtained according to the starting position of the preset center solid phase ratio standard interval.

[0041] Specifically, according to the starting value of the preset center solid phase ratio standard interval and the working condition pulling speed, the temperature model in the prior art can be used to calculate the starting position of the reduction interval corresponding to the working condition pulling speed. Since the temperature model is a commonly used technology in this field, it is not described in detail. In the technical solution of the present invention, it is only necessary to understand that, using the temperature model, according to the starting value of the preset center solid phase ratio standard interval, the starting position of the reduction interval under each working condition pulling speed can be calculated.

[0042] As a preferred solution of the present invention, a method for determining the end position of the depressible interval includes:

[0043] According to the end position of the preset center solid phase ratio standard interval, the end position of the pressing interval is obtained;

[0044] The end position of the depressible interval is determined according to the end position of the depressing interval and the preset adjustable depressing length.

[0045] Specifically, according to the end value of the preset center solid phase ratio standard interval and the working condition pulling speed, the temperature model in the prior art can be used to calculate the end position of the pressing interval corresponding to the working condition pulling speed. Considering that the currently popular light-heavy combination technology can still be pressed after solidification (that is, fs=1.0), a preset adjustable pressing length is given, that is, based on the calculated or theoretically obtained end position of the pressing interval, the preset adjustable pressing length is increased to determine the end position of the pressing interval.

[0046] As a preferred embodiment of the present invention, the preset central solid phase ratio standard range is 0.3 to 1.0.

[0047] As a preferred solution of the present invention, according to the end position of the pressing interval and the preset adjustable pressing length, determining the end position of the pressing interval includes:

[0048] The end position of the depressible interval is obtained by adding the end position of the depressing interval to the preset adjustable depressing length.

[0049] As a preferred solution of the present invention, the preset adjustable pressing length is 0.3-1.0 m.

[0050] Specifically, the preset center solid phase ratio standard interval and the preset adjustable pressure reduction length are obtained based on experimental verification and are given values ​​in the technical solution of the present invention.

[0051] It should be noted that: in the technical solution of the present invention, the above-mentioned method of determining the compressible range corresponding to the pulling speed of each working condition of the light and heavy combined pressing technology is not unique, and the compressible range corresponding to the pulling speed of different working conditions can also be determined through experience or experiments in actual operations. There are many ways in the art to determine the compressible range corresponding to the pulling speed of each working condition. As long as the compressible range corresponding to the pulling speed of each working condition required in the technical solution can be obtained, the present invention does not make any special limitation on this.

[0052] Step S2, arranging the tensioning and straightening machine to ensure that a preset minimum number of pressing rollers are arranged in the pressing interval corresponding to the pulling speed of each working condition.

[0053] Specifically, in the prior art, for the light-heavy combined pressing technology, the layout of the straightening machine is determined by the comprehensive consideration of the process and equipment, but similar to the convention, no limit standard for the integration of the two is given. It is generally believed that the smaller the roller spacing, the better, and the requirements for the equipment are vague. Based on this, the present invention provides a solution that can use the least arrangement of straightening machines on the basis of ensuring the process requirements, that is, to ensure that the minimum number of pressing rollers are arranged in the pressing interval corresponding to the pulling speed of each working condition, and arrange the straightening machine.

[0054] As a preferred solution of the present invention, to ensure that a preset minimum number of pressing rollers are arranged in the pressing interval corresponding to the pulling speed of each working condition, the arrangement of the straightening machine includes:

[0055] According to the end position of the compression interval and the start position of the compression interval corresponding to the pulling speed of each working condition of the light and heavy combined compression technology, the length of the compression interval corresponding to the pulling speed of each working condition is determined;

[0056] Determine the spacing of the reduction rollers in the reduction interval corresponding to the pulling speed of each working condition according to the length of the reduction interval corresponding to the pulling speed of each working condition and the preset minimum number of reduction rollers;

[0057] The tensioning and straightening machine is arranged based on the spacing between the press-down rollers in the press-down range corresponding to the pulling speed in each working condition.

[0058] Specifically, the length of the depression interval corresponding to the pulling speed of each working condition is calculated in turn, that is, the distance from the end position of the depression interval to the starting position of the depression interval, and then the corresponding depression roller spacing is determined according to the preset minimum number of depression rollers, so that the straightening machine is arranged according to the depression roller spacing.

[0059] As a preferred solution of the present invention, after the tensioning and leveling machine is arranged, it is ensured that a preset minimum number of pressure rollers are arranged in the pressure-reducing interval corresponding to the pulling speed of each working condition, and the following is further included:

[0060] During the execution of the combined light and heavy pressing process, when the number of pressing rollers arranged in the pressing interval corresponding to the selected working condition pulling speed is greater than the number of pressing rollers required to execute the pressing process, the number of pressing rollers required to execute the pressing process is selected from the side close to the end position of the pressing interval to execute the pressing process.

[0061] Specifically, when the reduction process is executed, according to the "farthest principle", that is, when there are reduction-straightening machines with more than the minimum number of reductions in the reduction range under a specific pulling speed, the reduction process is executed by selecting reduction rollers with the number of reduction rollers required for the reduction process from the side close to the end position of the reduction range.

[0062] As a preferred solution of the present invention, in the process of determining the pressing range corresponding to the pulling speed of each working condition of the light and heavy combined pressing technology,

[0063] The corresponding depression intervals of the working condition pulling speeds are determined in order from small to large. The larger the working condition pulling speed, the larger the corresponding depression interval, and the larger the spacing between the depression rollers when the straightening machine is arranged.

[0064] Specifically, based on the solidification characteristics, as the pulling speed increases, the reduction range increases, so the spacing between the reduction rollers can be appropriately increased.

[0065] As a preferred solution of the present invention, the preset minimum number is 3 to 5.

[0066] Specifically, the preset minimum number in the present invention is 3 to 5, and this solution is verified based on actual experiments.

[0067] By first determining the possible reduction interval corresponding to the pulling speed of each working condition of the light and heavy combined reduction technology; and then ensuring that a preset minimum number of reduction rollers are arranged in the possible reduction interval corresponding to the pulling speed of each working condition, the straightening machine is arranged, so as to obtain a solution with the least arrangement of straightening machines on the basis of satisfying the process effect, and effectively solving the problem of lack of maximization design standards for the roller spacing of the straightening machine in the prior art and inability to obtain the limit design boundary to ensure the reduction effect. The present invention avoids the fuzzy requirement for equipment that the roller spacing is as small as possible, which is recognized in the prior art, and achieves quantitative design. While ensuring the reduction effect, the straightening machine is arranged with the least arrangement, thereby effectively reducing the equipment cost of heavy pressure equipment, and then greatly reducing the overall production cost.

[0068] In order to better explain in detail the arrangement method of the tension and leveling machine based on the light and heavy combined pressing technology provided by the present invention, an example is given as follows:

[0069] Example 1

[0070] Taking a 165X165mm billet casting machine of a steel plant as an example, the main steel type produced by the casting machine is 82B. Therefore, the layout of the straightening machine is carried out according to the solidification history of 82B steel, and the light and heavy combination pressing technology is used. The pressing range standard is the center solid phase ratio of 0.3-1.0, and the adjustable pressing length is 0.6m. Based on this, the parameter data of the pressing range corresponding to the pulling speed of each working condition are calculated as shown in Table 1.

[0071]

[0072] Table 1

[0073] According to the parameter data of the compression range corresponding to the pulling speed of each working condition in Table 1, the arrangement process of the pulling and straightening machine provided by the present invention is as follows:

[0074] The preset minimum number of press-down rollers is set to 5. According to the condition that the minimum number of press-down rollers is satisfied within the press-down interval, the positions of the 1# to 5# press-down straightening machines are designed based on the minimum press-down interval of 2.2m / min. It is necessary to have 5 straightening machines within 13.0-16.8m, and the spacing between the press-down rollers needs to be kept basically 0.9m. On this basis, the pulling speed is increased successively, and the following straightening machines are arranged respectively according to the condition that the minimum number of press-down rollers is satisfied within the press-down interval. The arrangement of the straightening machine that finally satisfies the condition that the minimum number of press-down rollers is satisfied within the press-down interval under all working conditions is shown in Table 2. While satisfying the pulling speeds of 2.5m / min and 2.6m / min, the spacing between the press-down rollers can be appropriately increased as the working speed increases, so as to minimize the number of straightening machines. Among them, the straightening machine in the embodiment of the present invention adopts a single-roller straightening machine, that is, a straightening machine with a pair of press-down rollers.

[0075] Roller No. Position of tensioning and straightening machine (m) Roller spacing (m) 1# 13.0 / 2# 13.9 0.9 3# 14.8 0.9 4# 15.7 0.9 5# 16.6 0.9 6# 17.5 0.9 7# 18.4 0.9 8# 19.4 1.0

[0076] Table 2

[0077] The method for arranging the straightening machines provided by the present invention is used to arrange the straightening machines, which is a scheme for using the least arrangement of straightening machines on the basis of satisfying the process effect, which is beneficial to reducing the equipment cost under heavy pressure and greatly reducing the comprehensive cost of production.

[0078] On the basis of arranging the straightening machine by the straightening machine arrangement method provided by the present invention, the spacing between the press-down rollers can be reduced, similar to the smaller the better, but the equipment cost will be greatly increased. If the roller spacing is reduced, it is obvious that there will be more than the minimum number of straightening machines in the press-down interval under specific pulling speed conditions. At this time, the process can be executed according to the "farthest principle". That is, in the process of executing the light and heavy combined press-down process, when the number of press-down rollers arranged in the press-down interval corresponding to the selected working speed is greater than the number of press-down rollers required for the press-down process, the press-down process is performed by selecting the number of press-down rollers required for the press-down process from the side close to the end position of the press-down interval.

[0079] The embodiment of the present invention only considers one main steel grade. In the specific engineering design, other steel grades need to be considered, so comprehensive processing is required.

[0080] The arrangement method of the straightening machine provided by the present invention mainly considers the process requirements, which is conducive to simplifying the equipment. At the same time, it is also necessary to consider and optimize other conditions on the equipment, such as hoisting, straightening, dragging the billet, etc.

[0081] It should be noted that this embodiment is only for the purpose of explaining in detail the practical application of the method for arranging a straightening machine based on the light-heavy combined pressing technology provided by the present invention, and does not limit the technical solution provided by the present invention.

[0082] It can be seen from the above specific implementation methods that the method for arranging a straightening machine based on the light-heavy combined pressing technology provided by the present invention first determines the pressing range corresponding to the pulling speed of each working condition of the light-heavy combined pressing technology; then ensures that a preset minimum number of pressing rollers are arranged in the pressing range corresponding to the pulling speed of each working condition, and arranges the straightening machine, so as to obtain a solution with the least arrangement of straightening machines on the basis of satisfying the process effect, and effectively solves the problem of lack of design standards for maximizing the spacing between straightening machine rollers in the prior art, and inability to obtain the limit design boundary to ensure the pressing effect. The present invention avoids the fuzzy requirements for equipment that the smaller the roller spacing is, the better, which is recognized in the prior art, and achieves quantitative design. While ensuring the pressing effect, the least arrangement of straightening machines is used, thereby effectively reducing the cost of heavy pressure equipment, and then greatly reducing the overall cost of production.

[0083] As described above with reference to the accompanying drawings, the arrangement method of the straightening machine based on the light-heavy combined pressing technology proposed in the present invention is described by way of example. However, those skilled in the art should understand that various improvements can be made to the arrangement method of the straightening machine based on the light-heavy combined pressing technology proposed in the present invention without departing from the content of the present invention. Therefore, the protection scope of the present invention should be determined by the content of the attached claims.

Claims

1. A method for arranging a tension and leveling machine based on a light and heavy combined press-down technology, characterized in that: The steps include: Determine the compression range corresponding to the pulling speed of each working condition of the light and heavy combined compression technology; wherein the compression range is the range from the starting position of the compression range to the ending position of the compression range; The tensioning and straightening machine is arranged to ensure that a preset minimum number of pressure rollers are arranged in the pressure-reducing range corresponding to the pulling speed of each working condition.

2. The method for arranging a tension and leveling machine based on the light-heavy combined pressing technology according to claim 1 is characterized in that: The method for determining the starting position of the pressing interval includes: The starting position of the depression interval is obtained according to the starting position of the preset center solid phase ratio standard interval.

3. The method for arranging a tension and leveling machine based on the light-heavy combined pressing technology according to claim 1 is characterized in that: The method for determining the end position of the depressible interval includes: According to the end position of the preset center solid phase ratio standard interval, the end position of the pressing interval is obtained; The end position of the depressible interval is determined according to the end position of the depressing interval and the preset adjustable depressing length.

4. The method for arranging a tension and leveling machine based on the light-heavy combined pressing technology according to claim 2 or 3 is characterized in that: The preset central solid phase ratio standard range is 0.3 to 1.

0.

5. The method for arranging a tension and leveling machine based on the light-heavy combined pressing technology according to claim 3 is characterized in that: Determining the end position of the depressible interval according to the end position of the depressing interval and the preset adjustable depressing length includes: The depressible interval end position is obtained by adding the depressing interval end position to the preset adjustable depressing length.

6. The method for arranging a tension and leveling machine based on the light-heavy combined pressing technology according to claim 3 or 5 is characterized in that: The preset adjustable pressing length is 0.3-1.0m.

7. The method for arranging a tension and leveling machine based on the light-heavy combined pressing technology according to claim 1 is characterized in that: The arrangement of the tensioning and straightening machine to ensure that the minimum number of pressure rollers are arranged in the pressure-reducing interval corresponding to the pulling speed of each working condition includes: According to the end position of the depression interval and the start position of the depression interval corresponding to the pulling speed of each working condition of the light-heavy combined depression technology, the length of the depression interval corresponding to the pulling speed of each working condition is determined; Determine the spacing of the pressing rollers in the pressing section corresponding to the pulling speed of each working condition according to the length of the pressing section corresponding to the pulling speed of each working condition and the preset minimum number of pressing rollers; The tensioning and straightening machine is arranged based on the spacing between the pressing rollers in the pressing range corresponding to the pulling speed in each working condition.

8. The method for arranging a tension and leveling machine based on the light-heavy combined pressing technology according to claim 1 is characterized in that: After the tensioning and leveling machine is arranged under the condition of ensuring that a preset minimum number of pressure rollers are arranged in the pressure-reducing interval corresponding to the pulling speed of each working condition, the method further includes: During the execution of the light and heavy combined pressing process, when the number of pressing rollers arranged in the pressing interval corresponding to the selected working condition pulling speed is greater than the number of pressing rollers required to execute the pressing process, the number of pressing rollers required to execute the pressing process is selected from the side close to the end position of the pressing interval to execute the pressing process.

9. The method for arranging a tension and leveling machine based on the light-heavy combined pressing technology according to claim 1 is characterized in that: In the process of determining the possible reduction range corresponding to the pulling speed of each working condition of the light and heavy combined reduction technology, The corresponding depression intervals of the working condition pulling speeds are determined in order from small to large. The larger the working condition pulling speed, the larger the corresponding depression interval, and the larger the spacing between the depression rollers when the straightening machine is arranged.

10. The method for arranging a tension and leveling machine based on the light-heavy combined pressing technology according to any one of claim 1, characterized in that: The preset minimum number is 3 to 5.

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