阅读说明：本技术 一种热轧带钢边部遮挡区间确定方法、遮挡方法及控制系统 (Hot-rolled strip steel edge shielding interval determining method, shielding method and control system ) 是由 赵志毅 王文广 费爱庚 杨孝鹤 薛润东 艾矫健 于 2021-08-25 设计创作，主要内容包括：本发明实施例提供一种热轧带钢边部遮挡区间确定方法,一种热轧带钢边部遮挡区间确定方法,包括以下步骤：1)获取冷却过程中所述带钢在宽度方向上的内应力演变规律；2)基于所述内应力演变规律设定边部遮挡区间。本发明从板宽方向不同位置的内应力演变规律出发,提出在相变应力大于热应力的区域实施边部遮挡,减缓相变进程,从而减少边部的相对膨胀量,减小相变应力,降低板宽方向内应力分布的不均匀性,改善边浪缺陷。(The embodiment of the invention provides a method for determining an edge shielding interval of hot-rolled strip steel, which comprises the following steps: 1) acquiring an internal stress evolution law of the strip steel in the width direction in the cooling process; 2) and setting an edge shielding interval based on the internal stress evolution rule. According to the invention, from the internal stress evolution law of different positions in the board width direction, edge shielding is implemented in the area where the phase change stress is greater than the thermal stress, and the phase change process is slowed down, so that the relative expansion amount of the edge is reduced, the phase change stress is reduced, the nonuniformity of the internal stress distribution in the board width direction is reduced, and the edge wave defect is improved.)

1. A method for determining an edge shielding section of hot-rolled strip steel comprises the following steps: 1) acquiring an internal stress evolution law of the strip steel in the width direction in the cooling process; 2) and setting an edge shielding interval based on the internal stress evolution rule.

2. The method according to claim 1, wherein in the step 2), the shielding region is a region where the phase change stress is greater than the thermal stress.

3. The method according to claim 2, wherein when there are a plurality of sections where the phase change stress is greater than the thermal stress, the sections where the phase change stress is greater than the thermal stress are merged to obtain the shielding section.

4. A hot-rolled strip steel edge shielding method comprises the following steps: 1) acquiring temperature parameters of the strip steel in the cooling process; 2) selecting a characteristic position based on the temperature parameter; 3) acquiring an internal stress evolution law of the strip steel in the width direction in the cooling process; 4) and setting an edge shielding interval based on the internal stress evolution rule, and selecting a shielding width based on the characteristic position.

5. The method according to claim 4, wherein in the step 4), the shielding region is a region where the phase change stress is greater than the thermal stress.

6. The method according to claim 5, wherein when there are a plurality of sections where the phase change stress is greater than the thermal stress, the sections where the phase change stress is greater than the thermal stress are merged to obtain the shielding section.

7. The method of claim 6, the characteristic locations comprising one or more of the following: the center position, the edge position, the start fluctuation position of the finish rolling temperature, the start fluctuation position of the coiling temperature, the maximum temperature drop position in the laminar cooling process and one or more supplement positions are inserted according to the space between the positions.

8. The method according to any one of claims 4 to 7, wherein in the step 3), an internal stress evolution law of the strip steel at a characteristic position in the width direction during the cooling process is obtained.

9. The method according to claim 4, wherein in the step 4), the distance from the edge part to the position where the coiling temperature starts to fluctuate in the width direction of the strip is taken as the shielding width.

10. A control system for shielding the edge of hot-rolled strip steel comprises a temperature measuring system, a temperature control system and a control system, wherein the temperature measuring system is used for measuring temperature parameters of the strip steel in the cooling process;

the memory is used for storing internal stress evolution rules of different strip steel materials under different process parameters;

the controller is used for receiving the temperature parameters transmitted by the temperature measuring system and selecting a characteristic position to determine the shielding width; based on the input strip steel material and the input process parameters, a corresponding internal stress evolution rule is called, and an edge shielding interval is determined;

and the execution mechanism is used for receiving the shielding width and the shielding interval data output by the controller and executing shielding operation.

Technical Field

The invention relates to the field of hot-rolled strip steel, in particular to a method for determining an edge shielding interval of hot-rolled strip steel and a shielding method.

Background

Cooling water flows to the edge of the steel plate in the laminar cooling process of the hot-rolled strip steel, so that the cooling speed of the edge region in the width direction of the plate is higher than that of the middle region, and the temperature field distribution in the width direction of the plate is uneven in the laminar cooling process. In addition, the initial temperature difference at the finish rolling outlet (high middle part and low edge part of finish rolling temperature) is also one of the causes of uneven distribution of the temperature field in the width direction of the sheet. The uneven distribution of the temperature field can lead to uneven distribution of thermal stress on one hand; on the other hand, the phase transformation and the non-uniform phase transformation occur at different times, thereby causing the phase transformation stress to be unevenly distributed. Under the coupling action of uneven thermal stress and phase change stress, uneven internal stress distribution can be finally generated in the width direction of the steel plate, so that edge wave defects can be generated on the steel plate, and the quality and the application of products are influenced.

To solve the problem of uneven cooling in the laminar cooling process, researchers at the present stage propose to adopt an edge shielding technology to realize uneven cooling control. Chinese patent CN 110860565 a proposes to realize accurate control of symmetrical shielding of the edge of the strip steel by detecting the transverse temperature distribution of the strip steel and adjusting the transverse position of the edge shielding mechanism. In addition, chinese patent CN 110270598A proposes a laminar cooling edge shielding device and a control method thereof, which solves the problem of uneven cooling distribution in the strip steel width direction of a laminar cooling system by adjusting the spray area of cooling water in the strip steel width direction. The edge shielding technique disclosed in the present application mainly relates to equipment, and has few details about implementation methods and principles, and is basically considered from the aspect of reducing non-uniformity of temperature distribution. The uneven distribution of the temperature is only a surface physical phenomenon, and the root cause of the edge wave defect is uneven internal stress distribution of 'middle drawing and edge pressing' in the width direction of the steel plate.

Disclosure of Invention

The invention aims to provide a method for determining an edge shielding section of hot-rolled strip steel and a shielding method aiming at the problems. Starting from the internal stress evolution law of different positions in the board width direction, edge shielding is implemented in the area where the phase change stress is larger than the thermal stress, and the phase change process is slowed down, so that the phase change non-timeliness is improved, the non-uniformity of the internal stress distribution in the board width direction is reduced, and the edge wave defect is improved.

The first aspect of the embodiment of the invention provides a method for determining an edge shielding interval of a hot-rolled strip steel, which comprises the following steps: 1) acquiring an internal stress evolution law of the strip steel in the width direction in the cooling process; 2) and setting an edge shielding interval based on the internal stress evolution rule.

According to the method for determining the edge shielding section of the hot-rolled strip steel, provided by the embodiment of the invention, according to the mechanism that the strip steel generates the edge waves, the method for determining the edge shielding section by adopting the internal stress evolution is provided, so that the accurate positioning of the shielding section is realized, compared with the mode that the shielding area is controlled by detecting the transverse temperature distribution of the strip steel in the prior art, the temperature distribution of the whole cooling area is omitted, the shielding section is determined by combining the internal stress evolution, the theoretical basis is provided for the shielding area as the support, and the edge wave defect is greatly improved.

In a possible implementation manner, in the step 2), the shielding region is a region where the phase change stress is greater than the thermal stress.

In a possible implementation manner, when there are a plurality of sections where the phase change stress is greater than the thermal stress, the sections where the phase change stress is greater than the thermal stress are merged to obtain the shielding section.

The second aspect of the embodiment of the invention provides a hot-rolled strip steel edge shielding method, which comprises the following steps: 1) acquiring temperature parameters of the strip steel in the cooling process; 2) selecting a characteristic position based on the temperature parameter; 3) acquiring an internal stress evolution law of the strip steel in the width direction in the cooling process; 4) and setting an edge shielding interval based on the internal stress evolution rule, and selecting a shielding width based on the characteristic position.

The invention provides a hot-rolled strip steel edge shielding method, which comprises the steps of obtaining a temperature curve along the width direction during finish rolling and coiling, selecting a characteristic position based on the temperature curve, and selecting a shielding width from the characteristic position; in addition, according to the mechanism that the strip steel generates edge waves, an internal stress evolution method is adopted to determine the edge shielding interval, so that specific shielding parameters of the edges of the hot-rolled strip steel are realized.

In a possible implementation manner, in the step 4), the shielding region is a region where the phase change stress is greater than the thermal stress.

In a possible implementation manner, when there are a plurality of sections where the phase change stress is greater than the thermal stress, the sections where the phase change stress is greater than the thermal stress are merged to obtain the shielding section.

In one possible implementation, the feature locations include one or more of the following: the center position, the edge position, the start fluctuation position of the finish rolling temperature, the start fluctuation position of the coiling temperature, the maximum temperature drop position in the laminar cooling process and one or more supplement positions are inserted according to the space between the positions.

In a possible implementation manner, in the step 3), an internal stress evolution law of the strip steel at the characteristic position in the width direction in the cooling process is obtained.

In a possible implementation manner, in the step 4), a distance from a winding temperature start fluctuation position in the strip width direction to an edge portion is used as the shielding width.

The third aspect of the invention provides a control system for edge shielding of hot-rolled strip steel, which comprises a temperature measurement system, a control system and a control system, wherein the temperature measurement system is used for measuring temperature parameters of the strip steel in a cooling process;

the memory is used for storing internal stress evolution curves of different strip steel materials under different process parameters;

the controller is used for receiving the temperature parameters transmitted by the temperature measuring system and selecting a characteristic position to determine the shielding width; based on the input strip steel material and the input process parameters, a corresponding internal stress evolution curve is taken, and an edge shielding interval is determined;

and the execution mechanism is used for receiving the shielding width and the shielding interval data output by the controller and executing shielding operation.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a temperature field distribution diagram of a low-alloy high-strength hot-rolled strip steel along a width direction according to an embodiment of the invention;

FIG. 2 is a graph showing the evolution of internal stress during laminar cooling at different positions in the width direction of a plate according to an embodiment of the present invention;

FIG. 3 is a stress inflection point for the location No. 2 in FIG. 2;

FIG. 4 shows stress inflection points at position No. 3 in FIG. 2;

FIG. 5 shows stress inflection points at location No. 4 in FIG. 2;

FIG. 6 shows stress inflection points at position 5 in FIG. 2;

FIG. 7 is a schematic diagram of an embodiment of edge masking;

fig. 8 is a schematic structural diagram of a control system according to an embodiment of the present invention.

Icon: 1-a temperature measurement system; 2-a memory; 3-an input terminal; 4-a controller; 5-an actuator.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

In the present example, low-alloy high-strength hot-rolled steel strip was used as an object of the present invention. The chemical composition of the steel grade is shown in Table 1.

TABLE 1 chemical composition of low-alloy high-strength hot-rolled strip

As shown in fig. 1, a distribution diagram of a temperature field in a plate width direction detected in an actual production process of a low-alloy high-strength hot-rolled strip steel, in which a horizontal axis represents a dimension in the strip steel width direction and a vertical axis represents a temperature; the curve with dots represents the finish rolling temperature, the curve with triangles represents the coiling temperature, and the curve with "x" represents the temperature drop during laminar cooling, i.e. the difference between the finish rolling temperature and the coiling temperature. In order to prevent data distortion and convenience in acquiring data in an actual production process, a certain size of edge trimming may be performed from the edge of the temperature field curve as an actual edge position of the steel plate, and in this embodiment, a trimming of 10mm is preferably performed as the actual edge position of the steel plate, that is, a position No. 5 in fig. 1 is performed as the steel plate edge. As can be seen from FIG. 1, the finishing temperature at the center (position No. 0) in the width direction of the steel plate is about 890 ℃, the finishing temperature starts to decrease at a position +/-585 mm from the center of the steel plate, namely position No. 3, the finishing temperature at the edge (position No. 5) is about 790 ℃, and the finishing temperature is relatively uniformly distributed in the range between the positions No. 3 in the width direction of the steel plate, namely in the range of 1170 mm; the coiling temperature at the center in the width direction of the steel sheet, i.e., position No. 0, was about 568 ℃, the coiling temperature at positions-370 mm (position No. 1') and 312mm (position No. 1) from the center of the steel sheet began to decrease, and the coiling temperature at position No. 5 was about 350 ℃. For the sake of convenience of examination, the temperature field in the steel sheet width direction was considered to be symmetrically distributed, and therefore position No. 1' was omitted, and position No. 1 was taken as a characteristic position representing the start of the decrease in the coiling temperature in the steel sheet width direction. The coiling temperature is distributed uniformly in the range of 682mm at the center of the steel sheet in the width direction, namely the range between the position No. 1' and the position No. 1. As can be seen from the curve with an "x" in FIG. 1, the position where the temperature drop in the width direction of the steel sheet is the largest is about + -663 mm from the center (position No. 4).

It should be noted that the present embodiment employs a conventional laminar cooling process, but the method of the present invention can also be applied to a turbulent cooling process; in the cooling process of the hot-rolled strip steel, the temperature field is asymmetric to the center of the strip steel, and the abandoned position No. 1' is adopted to facilitate the data processing, and the position No. 1 is taken as a characteristic position; however, in the actual operation process, an asymmetric position algorithm can be adopted as long as the selected characteristic position is a specific position, wherein the specific position is an edge part, a temperature drop starting position, a temperature difference maximum position, a central position and the like; the internal stress evolution curve in this embodiment is an expression form of an internal stress evolution law, and other expression modes such as a cloud chart can also be adopted.

In this embodiment, the characteristic positions may include one or more of the following positions: the position 0 is the center position of the steel plate, the position 1 is the position where the coiling temperature starts to decrease, the position 3 is the position where the finish rolling temperature starts to decrease, the position 4 is the position where the temperature drop is the largest in the laminar cooling process, and the position 5 is the edge position of the steel plate. To increase the data sampling, one or more common locations may be inserted at the more widely spaced locations, and in this embodiment, preferably one common location, i.e., location No. 2, is inserted, where location No. 2 is the common location of the selected increased temperature field distribution data point. Since the position 0 and the position 1 belong to the range of the uniform temperature field and the temperature data of the position 0 and the position 1 are the same, any one of the position 0 and the position 1 can be selected, so that the total number of the 6 regions representing the temperature field distribution in the width direction of the steel plate is 6, and only the 5 regions of the temperature field distribution need to be analyzed.

According to field production data, the length of a laminar cooling area is 103m, the speed of a steel plate passing through a laminar cooling section is 6m/s, the laminar cooling time of each area of the steel plate is about 17s, the low-alloy high-strength hot-rolled strip steel can be considered to be approximately uniform cooling of the whole process due to the fact that nozzles in the laminar cooling process are fully opened, and the average cooling speed of each area can be calculated by combining the temperature drop of each area. The temperature field data of the positions 1-5 in fig. 1 are used as the process parameters of the internal stress evolution test, and the specific process parameter setting conditions are shown in table 2.

TABLE 2 Process parameters for the internal stress evolution test

Fig. 2 is a graph showing the evolution of internal stress at different positions in the width direction of the sheet during laminar cooling, wherein the horizontal axis is a time axis, and the vertical axis is internal stress, and since the temperature data of the position 0 and the position 1 are the same, one of the two positions can be selected for analysis. In the laminar cooling process, the material can generate phase change, and because the specific volume of phase change products such as ferrite, bainite and the like is larger than that of austenite, the volume can expand in the phase change process, and phase change stress in the compression direction is generated in the material; in addition, as the temperature decreases, the volume shrinks due to the thermal expansion and contraction effect, and thermal stress in the stretching direction is generated. The internal stress level in the layer cooling stage is a result of the coupling of thermal stress and phase change stress. As can be seen from fig. 2, the internal stress at position No. 1 generally has a gradual increase trend, and the internal stress curves at positions 2 to 5 each show a trend of increasing, decreasing and then increasing. The stress curve is reversely changed because the compressive stress generated by the phase change expansion can counteract the tensile stress of cooling shrinkage, the thermal stress is equal to the phase change stress at the inflection point, the descending of the stress curve indicates that the phase change stress at the moment is greater than the thermal stress, and then the curve continuously ascends to indicate that the thermal stress is greater than the phase change stress.

FIGS. 3 to 6 are graphs for analysis of inflection points at positions 2 to 5. From FIGS. 3 to 6, the intervals in which the stress curves of the 2-5 positions are reduced are respectively 3.59 to 12.35s, 7.48 to 11.22s, 8.21 to 13.02s and 5.87 to 11.04s, and the results are 3.59 to 13.02s when the four intervals are merged. The total laminar flow length was 103m, and the steel plate speed was 6m/s, so that the shielding was started at 21.54m from the layer cold start end and stopped at 78.12 m from the layer cold start end, and the shielding length was 56.58 m. The range from the cold start end of the layer can be controlled within 20-23 m during the implementation, and the shielding interval in the rolling direction is controlled within 55-58 m. The uniform range of the finish rolling temperature of the middle area in the width direction of the steel plate is larger than the coiling temperature, the coiling temperature begins to fall at the position No. 1, the distance between the position No. 1 and the edge part is 468mm, the shielding width can be shielded according to the width of 470mm during implementation, and the width of unilateral shielding of the steel plate is 470 mm. The invention uses the fluctuation coefficient delta of the internal stress of the edge part and the middle part of the steel plate in the width direction to express the nonuniformity of the internal stress in the width direction of the steel plate, as shown in the formula (1).

Wherein, delta is the fluctuation coefficient of the internal stress of the edge part and the middle part of the steel plate in the width direction, and sigma₁Is the internal stress of the edge, σ₀Is the internal stress of the middle portion. The smaller δ is, the smaller the unevenness of stress in the plate width direction is.

FIG. 7 is a schematic diagram of an edge shield implementation. The practical effects are shown in table 3.

TABLE 3 internal stress distribution inhomogeneity of strip steel under old and new process

The old method is to realize the accurate control of the symmetrical shielding of the edge of the strip steel by detecting the transverse temperature distribution of the strip steel and adjusting the transverse position of the edge shielding mechanism.

It is understood that, in the above embodiment, when determining the internal stress evolution law in the cooling process, the stress evolution law of the characteristic position is preferably used to determine the occlusion interval; however, the shielding interval is not determined according to the stress evolution rule of the characteristic position, but the accuracy of the shielding interval is reduced, but the same function, namely the edge wave defect is improved. Therefore, when determining the occlusion interval and the occlusion width, the two calculation processes may be related or unrelated.

Another embodiment of the invention provides a control system for edge shielding of hot-rolled strip steel, which comprises a temperature measuring system 1, a control system and a control system, wherein the temperature measuring system is used for measuring temperature parameters in the cooling process of the strip steel; the storage 2 is used for storing internal stress evolution laws of different strip steel materials under different process parameters; the controller 3 is used for receiving the temperature parameters transmitted by the temperature measuring system and selecting characteristic positions to determine the shielding width based on the temperature parameters; based on the strip steel material and the process parameters input by the input end 4, a corresponding internal stress evolution law is taken to determine an edge shielding interval; and the executing mechanism 5 is used for receiving the shielding width and the shielding interval data output by the controller and executing shielding operation.

It should be noted that the temperature parameters include the distribution of the finish rolling temperature and the distribution of the coiling temperature in the width direction of the strip, the temperature change of the strip during the cooling process, and the like. The technological parameters include the speed of the steel plate passing through the cooling section, the finish rolling temperature, the coiling temperature, the temperature in the cooling process and the like.

The algorithm of the controller 3 is various, the first is as shown in the above embodiment, by acquiring the characteristic position in the temperature parameter, the internal stress evolution law of the characteristic position is retrieved from the memory to obtain the shielding section; the other method is that the controller 3 obtains the temperature change of the strip steel surface in the cooling process of the strip steel from the temperature measuring system 1 to obtain the cooling speed, and the corresponding internal stress evolution law is called in the memory to obtain the shielding interval based on the finish rolling temperature, the coiling temperature and the cooling speed. The input end 4 of the memory can input corresponding strip steel materials, components or other process parameters such as cooling water flow rate and the like through a mouse and a keyboard.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to 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.