Method for controlling temperature uniformity of cross section of hot rolled strip steel

Abstract

The invention relates to a method for controlling the temperature uniformity of the cross section of hot-rolled strip steel, which is characterized in that a plurality of laminar cooling temperature control groups corresponding to the width of the strip steel are arranged at the starting end of laminar cooling, the edges of upper spray headers in the laminar cooling temperature control groups are blocked to form trapezoidal cooling areas, and the gradual expansion direction of the trapezoidal cooling areas is consistent with the rolling reverse direction of the strip steel; and in the cooling process, a layer cooling temperature control group is correspondingly input according to the width of the strip steel. According to the invention, the layer cooling temperature control group adopts trapezoidal cooling, so that the temperature of the edge part of the strip steel is more uniform, the influence on the product quality due to larger stress difference or strength difference between the edge part of the strip steel and the central area is avoided, and the layer cooling input group can be automatically selected according to different strip steel widths; and the defect that nozzle plugs need to be frequently assembled and disassembled on site when the width is changed is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of strip rolling, and particularly relates to a method for controlling the cross-sectional temperature uniformity of hot-rolled strip steel. Background Art

[0002] The edge of the hot-rolled strip steel is far from the central part, and it is difficult for the central temperature to reach the edge through heat conduction, which results in a more obvious temperature drop at the edge compared to the central part. At the same time, affected by the downward spraying of laminar cooling, the sprayed water column will flow onto the edge of the strip steel. Therefore, the temperature change at the edge of the hot-rolled strip steel is relatively drastic, affecting the cross-sectional temperature uniformity and causing adverse effects on the quality and shape of the strip steel edge.

[0003] The existing patent CN110064667B discloses a method for laminar cooling of steel plates, including: obtaining the real-time finishing rolling temperature of the steel plate; correcting the real-time finishing rolling temperature according to the corresponding relationship between the thickness of the steel plate and the temperature of the steel plate; calculating the opening quantity and position of the cooling headers in the laminar cooling equipment according to the corrected finishing rolling temperature; opening the corresponding cooling headers according to the calculated opening quantity and position of the cooling headers to cool the steel plate; according to the selection of the opening quantity and position of the cooling headers in the laminar cooling equipment, the cooling uniformity of the steel plate can be improved, and thus the shape of the plate can be improved; the calculating the opening quantity and position of the cooling headers in the laminar cooling equipment according to the corrected finishing rolling temperature includes: subtracting the preset target final cooling temperature from the finishing rolling temperature to obtain the cooling temperature drop; dividing the cooling temperature drop by the preset target cooling rate to obtain the cooling time of the steel plate; multiplying the cooling time by the roll speed to obtain the cooling zone distance; dividing the cooling zone distance by the length of a single group of headers to obtain the opening quantity of the cooling headers in the laminar cooling equipment; and looking up the opening position in the configuration table of the preset header quantity and header position through the opening quantity of the cooling headers. The existing patent mainly focuses on the longitudinal temperature control of steel plates and does not consider the transverse temperature drop. Since the temperature drop at the edge of the strip steel is greater than that at the central part, the cooling rates at the edge and the middle of the strip steel are different, and the cooling rate at the edge is fast, resulting in uneven transverse cooling and affecting the shape quality and mechanical properties of the product. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for controlling the cross-sectional temperature uniformity of hot-rolled strip steel, so as to reduce the functional fluctuation of the strip steel on the entire cross-section and at the same time reduce the shape defects caused by excessive cooling rate at the edge.

[0005] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0006] A method for controlling the temperature uniformity of the cross-section of hot-rolled strip. At the starting end of laminar cooling, multiple sets of laminar cooling temperature control groups corresponding to the strip width are set. The edges of the upper spray headers in the laminar cooling temperature control groups are blocked to form a trapezoidal cooling zone. The gradually expanding direction of the trapezoidal cooling zone is consistent with the rolling direction of the strip. During the cooling process, the laminar cooling temperature control groups are put into use according to the strip width.

[0007] The blocking method of the upper spray headers in the laminar cooling temperature control groups specifically includes the following steps:

[0008] Step 1: Calculate the temperature drop of each upper spray header in the central area of the strip according to the formula T0 = (T1 - T2) ÷ N; where: T0 is the temperature drop in the central area of the strip; T1 is the finishing rolling temperature; T2 is the coiling temperature; N is the number of longitudinally put-in upper spray headers.

[0009] Step 2: Calculate the temperature difference ΔT between the edge and the central area of the strip at the laminar cooling outlet. The edge of the strip refers to the width within the range of 200 - 300 mm outside the cross-section of the strip. ΔT = coiling temperature - average temperature of the strip edge.

[0010] Step 3: Calculate the number of columns of upper spray headers that need to be blocked longitudinally according to the formula N1 = ΔT ÷ T0.

[0011] Step 4: Block the nozzles on both sides of the upper spray headers corresponding to the upper limit strip width in each laminar cooling temperature control group. First, block all the nozzles of the upper spray headers outside the strip width. Secondly, block the nozzles on both sides of the upper spray headers within the strip width according to the number of columns of upper spray headers that need to be blocked calculated in Step 3. The blocking method is: the single-side blocking width of the first column of upper spray headers is consistent with the width range for detecting the strip edge temperature. Along the rolling direction of the strip, block the nozzles on both sides of the upper spray headers of other columns in a gradually expanding manner.

[0012] The laminar cooling temperature control groups include 1# laminar cooling temperature control group, 2# laminar cooling temperature control group, 3# laminar cooling temperature control group, and 4# laminar cooling temperature control group, corresponding to strip widths W ≤ 1300 mm; 1300 mm < W ≤ 1500 mm; 1500 mm < W ≤ 1800 mm; W > 1800 mm respectively.

[0013] Compared with the existing technology, the beneficial effects of the present invention are:

[0014] The laminar cooling temperature control groups of the present invention adopt trapezoidal cooling, which can make the temperature of the strip edge more uniform, avoid large stress differences or strength differences between the strip edge and the central area, and affect the product quality. Moreover, the present invention can automatically select the laminar cooling input group according to different strip widths, avoiding the disadvantages of frequent on-site loading and unloading of nozzle blocking when changing the width.

[0015] On the premise of ensuring the basic mechanical properties of hot-rolled strip steel, this application reduces the temperature drop at the edges and improves the temperature uniformity in the cross-sectional direction of the hot-rolled strip steel during the cooling process. The temperature difference across the strip steel can be controlled within 5°C. It avoids the problems of large differences in product performance across the cross-section of the strip caused by excessive cooling rates and cooling intensities at the edges and the deterioration of the strip shape due to cooling stress. It optimizes the strip shape of high-strength or wide-width products. Description of the Drawings

[0016] Figure 1 It is a schematic diagram of plugging the upper spray header for the present invention. Detailed Embodiments

[0017] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "a plurality" is more than two.

[0018] Unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0019] A method for controlling the temperature uniformity across the cross-section of hot-rolled strip steel, in which multiple groups of laminar cooling temperature control groups corresponding to the width of the strip steel are arranged at the starting end of laminar cooling. The edges of the upper spray headers in the laminar cooling temperature control groups are plugged to form a trapezoidal cooling zone. The gradually expanding direction of the trapezoidal cooling zone is consistent with the rolling direction of the strip steel, and the laminar cooling temperature control groups are put into use according to the width of the strip steel during the cooling process.

[0020] The plugging method of the upper spray headers in the laminar cooling temperature control groups specifically includes the following steps:

[0021] Step 1: Calculate the temperature drop of each upper spray header in the center area of the strip according to the formula T0 = (T1 - T2) ÷ N; where: T0 is the temperature drop in the center area of the strip; T1 is the finishing temperature; T2 is the coiling temperature; N is the number of longitudinal upper spray headers.

[0022] Step 2: Calculate the temperature difference ΔT between the strip edge and the center area at the laminar cooling outlet. The strip edge refers to the width within the range of 200 - 300 mm outside the cross-section of the strip. ΔT = coiling temperature - average temperature of the strip edge.

[0023] Step 3: Calculate the number of rows of upper spray headers to be blocked longitudinally according to the formula N1 = ΔT ÷ T0.

[0024] Step 4: Block the nozzles at both side edges of the upper spray headers corresponding to the upper limit strip width within each laminar cooling temperature control group. First, block all the nozzles of the upper spray headers outside the strip width. Second, block the nozzles at both side edges of the upper spray headers within the strip width according to the number of rows of upper spray headers to be blocked calculated in Step 3. The blocking method is: the single-side edge blocking width of the first row of upper spray headers is the same as the width range for detecting the strip edge temperature. Along the strip rolling direction, block the nozzles at both side edges of the other rows of upper spray headers in an expanding manner. As Figure 1 shown.

[0025] The laminar cooling temperature control groups mentioned above include the 1# laminar cooling temperature control group, 2# laminar cooling temperature control group, 3# laminar cooling temperature control group, and 4# laminar cooling temperature control group, corresponding to strip widths W ≤ 1300 mm; 1300 mm < W ≤ 1500 mm; 1500 mm < W ≤ 1800 mm; 1800 mm < W ≤ 2000 mm respectively.

[0026] The preferred embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept scope of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention. Additionally, it should be noted that in the above specific embodiments, the various specific technical features described can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention does not separately describe various possible combination methods. Furthermore, any combination can be made between different embodiments of the present invention as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

[0027] To make the objectives, technical solutions and technical effects of the present invention clearer, the technical solutions in the embodiments of the present invention will now be described clearly and completely. However, the embodiments described below are only some embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art in combination with the embodiments of the present invention without making creative efforts fall within the scope of protection of the present invention.

[0028] Embodiment

[0029] In a certain steel mill, there are a total of 22 laminar cooling units in the laminar cooling zone. Each unit has 10 upper spray headers, and each upper spray header has 56 nozzles. When cooling hot-rolled strip steel, 5 units, that is, 50 headers, are put into use. The finishing rolling temperature is 860 °C, the coiling temperature is 600 °C, and the average temperature of the strip edge at the outlet of the laminar cooling is 550 °C (the strip edge range is 0 - 300 mm outside the single side of the strip).

[0030] A method for controlling the temperature uniformity of the cross-section of hot-rolled strip steel includes:

[0031] Set 4 laminar cooling temperature control units at the starting end of the laminar cooling zone, specifically including the 1# laminar cooling temperature control unit, the 2# laminar cooling temperature control unit, the 3# laminar cooling temperature control unit, and the 4# laminar cooling temperature control unit, corresponding to strip widths W ≤ 1300 mm; 1300 mm < W ≤ 1500 mm; 1500 mm < W ≤ 1800 mm; 1800 mm < W ≤ 2000 mm respectively.

[0032] The plugging method of the upper spray headers in each laminar cooling temperature control unit is specifically as follows:

[0033] 1) Calculate the temperature drop T0 of each upper spray header in the central area of the strip: T0 = (T1 - T2) ÷ N = (860 °C - 600 °C) ÷ 50 headers = 5.2 °C;

[0034] 2) Calculate the temperature difference ΔT between the strip edge and the central area: ΔT = 860 °C - 550 °C = 310 °C;

[0035] 3) Calculate the number of upper spray header rows N1 that need to be plugged longitudinally: N1 = ΔT ÷ T0 = 50 °C ÷ 5.2 °C = 10 rows;

[0036] 4) 1# laminar cooling temperature control unit: Plug all the nozzles of the upper spray headers outside the width of 1300 mm; within the width of 1300 mm, the plugging width of the single side of the first row of upper spray headers is 300 mm, and along the strip rolling direction, the nozzles on both sides of the other 9 rows of upper spray headers are plugged in a gradually expanding manner.

[0037] 2# Layer Cooling Temperature Control Group: Completely block all the nozzles of the upper spray header outside a width of 1500 mm; within a width of 1500 mm, the single-side edge blocking width of the first row of the upper spray header is 300 mm, and along the strip rolling direction, block the nozzles on both side edges of the other 9 rows of the upper spray header in a gradually expanding manner.

[0038] 3# Layer Cooling Temperature Control Group: Completely block all the nozzles of the upper spray header outside a width of 1800 mm; within a width of 1800 mm, the single-side edge blocking width of the first row of the upper spray header is 300 mm, and along the strip rolling direction, block the nozzles on both side edges of the other 9 rows of the upper spray header in a gradually expanding manner.

[0039] 4# Layer Cooling Temperature Control Group: Completely block all the nozzles of the upper spray header outside a width of 2000 mm; within a width of 2000 mm, the single-side edge blocking width of the first row of the upper spray header is 300 mm, and along the strip rolling direction, block the nozzles on both side edges of the other 9 rows of the upper spray header in a gradually expanding manner.

[0040] When the hot-rolled steel plate is cooled:

[0041] When the strip width W ≤ 1300 mm, put into the 1# layer cooling temperature control group and 4 groups of normal layer cooling; after detection, the measured average temperature within 300 mm of the edge is 596 °C, which is basically the same as the temperature in the central area.

[0042] When 1300 mm < W ≤ 1500 mm; put into the 2# layer cooling temperature control group and 4 groups of normal layer cooling; after detection, the measured average temperature within 300 mm of the edge is 597 °C, which is basically the same as the temperature in the central area.

[0043] When 1500 mm < W ≤ 1800 mm; put into the 3# layer cooling temperature control group and 4 groups of normal layer cooling; after detection, the measured average temperature within 300 mm of the edge is 595 °C, which is basically the same as the temperature in the central area.

[0044] When 1800 mm < W ≤ 2000 mm; put into the 4# layer cooling temperature control group and 4 groups of normal layer cooling; after detection, the measured average temperature within 300 mm of the edge is 596 °C, which is basically the same as the temperature in the central area.

[0045] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and deformations can be made to these embodiments without departing from the principles and basic spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for controlling the temperature uniformity of the cross-section of hot-rolled strip steel, characterized in that, At the starting end of laminar cooling, multiple sets of laminar cooling temperature control groups corresponding to the strip width are arranged. The edges of the upper spray headers in the laminar cooling temperature control groups are blocked to form a trapezoidal cooling zone. The gradually expanding direction of the trapezoidal cooling zone is consistent with the rolling direction of the strip. During the cooling process, the laminar cooling temperature control groups are put into use according to the strip width.

2. The method for controlling the temperature uniformity of the cross-section of hot-rolled strip according to claim 1, characterized in that, The method for blocking the upper spray headers in the laminar cooling temperature control group specifically includes the following steps: Step 1: Calculate the temperature drop of each upper spray header in the central area of the strip according to the formula T0 = (T1 - T2) ÷ N; where: T0 is the temperature drop in the central area of the strip; T1 is the finishing rolling temperature; T2 is the coiling temperature; N is the number of longitudinally put-in upper spray headers. Step 2: Calculate the temperature difference ΔT between the edge and the central area of the strip at the laminar cooling outlet. The strip edge refers to the width within the range of 200 - 300 mm outside the cross-section of the strip. ΔT = coiling temperature - average temperature of the strip edge. Step 3: Calculate the number of columns of upper spray headers that need to be blocked longitudinally according to the formula N1 = ΔT ÷ T0. Step 4: Block the nozzles on both sides of the upper spray headers corresponding to the upper limit strip width in each laminar cooling temperature control group. First, block all the nozzles of the upper spray headers outside the strip width. Second, block the nozzles on both sides of the upper spray headers within the strip width according to the number of columns of upper spray headers that need to be blocked calculated in Step 3. The blocking method is: the single-side blocking width of the first column of upper spray headers is consistent with the width range for detecting the strip edge temperature. Along the rolling direction of the strip, block the nozzles on both sides of the upper spray headers of other columns in a gradually expanding manner.

3. The method for controlling the cross-sectional temperature uniformity of hot-rolled strip according to claim 1, characterized in that, The laminar cooling temperature control groups include the 1# laminar cooling temperature control group, 2# laminar cooling temperature control group, 3# laminar cooling temperature control group, and 4# laminar cooling temperature control group, corresponding to strip widths W ≤ 1300 mm; 1300 mm < W ≤ 1500 mm; 1500 mm < W ≤ 1800 mm; W > 1800 mm respectively.

Images