A method for controlling the temperature difference between the head and tail of a rolled piece

Abstract

The embodiment of the present invention provides a method for controlling the temperature difference between the head and tail of a rolled piece, comprising: sequentially performing rough rolling, rough rolling controlled cooling, intermediate rolling, intermediate rolling controlled cooling, finishing rolling, and finishing rolling controlled cooling processes, and controlling the difference between the head temperature and the tail temperature of the rolled piece to ≤30°C; wherein, temperature measurement is performed in the rough rolling process, and a first temperature curve is generated according to the measurement result; the rough rolling controlled cooling process specifically comprises: setting a water nozzle on the outside of the rolled piece; selecting a water spraying starting position on the rolled piece; spraying water on the part after the water spraying starting position on the rolled piece through the water nozzle; and adjusting the water spraying intensity of each water nozzle in real time according to the temperature curve. Through the technical solution of the present invention, the temperature difference between the head and the tail of the rolled piece can be controlled within a reasonable range, so that the strength of the final rolled product is uniform, and the problem of poor consistency of strength between the head and the tail caused by excessive temperature difference between the head and the tail is eliminated.

Description

Technical Field

[0001] The invention relates to the technical field of steel production, and in particular to a method for controlling the temperature difference between the head and tail of a rolled piece. Background Art

[0002] Direct rolling of square billets without heating has become the current development direction of bar and wire production. In this process, the billet does not need to be reheated in a heating furnace and can directly enter the rolling mill for rolling, thereby improving efficiency and reducing production costs.

[0003] In the process of implementing the present invention, the inventors found that there are at least the following problems in the prior art:

[0004] Since the directly rolled ingot is not reheated in the heating furnace, the head of the ingot is produced first in the continuous casting machine and the tail is produced later. Therefore, the temperature of the head of the ingot is low and the temperature of the tail is high. As a result, there is a significant temperature difference between the head and tail of the rolled piece during the subsequent rolling process, which makes the mechanical strength of the head of the final product high and the strength of the tail low, affecting the stability of product quality. Therefore, how to control the temperature difference between the head and tail of the rolled piece within a reasonable range in the direct rolling of square billets without heating is a problem that needs to be solved. Summary of the invention

[0005] The embodiment of the present invention provides a method for controlling the temperature difference between the head and the tail of a rolled piece, so as to solve the problem of excessively large temperature difference between the head and the tail of the rolled piece in the existing direct rolling of square billets without heating.

[0006] To achieve the above-mentioned purpose, an embodiment of the present invention provides a method for controlling the temperature difference between the head and the tail of a rolled piece, comprising: sequentially performing rough rolling, rough rolling controlled cooling, intermediate rolling, intermediate rolling controlled cooling, finishing rolling, and finishing rolling controlled cooling processes, and controlling the difference between the head temperature and the tail temperature of the rolled piece to ≤30°C; wherein, temperature measurement is performed in the rough rolling process, and a first temperature curve is generated based on the measurement results; the rough rolling controlled cooling process specifically comprises: arranging a water nozzle on the outside of the rolled piece; selecting a water spraying starting position on the rolled piece; spraying water on the part of the rolled piece after the water spraying starting position through the water nozzle; and adjusting the water spraying intensity of each water nozzle in real time based on the temperature curve.

[0007] Furthermore, the temperature difference between the head and tail of the rolled piece is controlled within 20°C to 30°C:

[0008] Furthermore, the water spray heads are arranged on the outside of the rolled piece, specifically including: a plurality of water spray heads are evenly distributed along the direction of the billet feeding roller at four positions of the upper left, lower left, lower right and upper right of the outside of the rolled piece.

[0009] Furthermore, the selecting of the water spraying starting position on the rolled piece specifically includes: determining, according to the temperature curve, a position on the rolled piece that is 20° C. higher than the temperature of the head of the rolled piece as the water spraying starting position.

[0010] Furthermore, before the rough rolling controlled cooling process, the method further includes: designing the spray hole shape of each water nozzle to be a hollow rectangle.

[0011] Furthermore, temperature measurement is performed in the intermediate rolling process, and a second temperature curve is generated according to the measurement results; a water penetrator is used to adjust the temperature of the rolled piece in the intermediate rolling controlled cooling process, and the cooling control intensity of the intermediate rolling controlled cooling process is adjusted in real time according to the second temperature curve; temperature measurement is performed in the finishing rolling process, and a third temperature curve is generated according to the measurement results; a multi-stage cooling device is used to adjust the temperature of the rolled piece in the finishing rolling controlled cooling process, and the cooling control intensity of the finishing rolling controlled cooling process is adjusted in real time according to the third temperature curve.

[0012] Furthermore, the method for controlling the temperature difference between the head and tail of the rolled piece also includes: temperature measurement after finishing rolling and controlled cooling after finishing rolling; wherein, temperature measurement is performed in the temperature measurement process after finishing rolling, and a fourth temperature curve is generated according to the measurement results; the controlled cooling process after finishing rolling adopts a multi-stage cooler to adjust the temperature of the rolled piece, and the cooling control intensity of the controlled cooling process after finishing rolling is adjusted in real time according to the fourth temperature curve.

[0013] Furthermore, before the finishing rolling process, it also includes pre-finishing rolling and pre-finishing rolling controlled cooling processes; wherein, temperature measurement is performed in the pre-finishing rolling process, and a fifth temperature curve is generated according to the measurement results; the pre-finishing rolling controlled cooling process adopts a multi-stage nozzle to adjust the temperature of the rolled piece, and the controlled cooling intensity of the pre-finishing rolling controlled cooling process is adjusted in real time according to the fifth temperature curve.

[0014] The above technical solution has the following beneficial effects:

[0015] In the technical solution of the present invention, a multi-level cooling control device is set up during the rolling process, and in particular, a unique form of water nozzle is designed in the rough rolling section. All cooling control processes are based on the measured temperature trend line as a reference, thereby realizing real-time adjustment of temperature control at different positions on the rolled piece, effectively reducing the temperature difference between the head and tail of the rolled piece, thereby ensuring that the strength difference between the head and tail of the final finished product is also controlled within a reasonable range, greatly improving the stability of product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 Schematic diagram of the arrangement of water nozzles in the rough rolling controlled cooling process in an embodiment of the present invention;

[0018] Figure 2 Schematic diagram of the spray range of the water nozzle in the embodiment of the present invention (i.e. Figure 1 A-direction view in the figure);

[0019] Figure 3 Schematic diagram of the spray hole structure of the water spray head in the embodiment of the present invention;

[0020] Figure numbers: 1, ingot; 11, corner; 3, ingot conveying roller; 4, water nozzle; 41, spray hole; 42, rectangular water spray coverage area. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] An embodiment of the present invention provides a method for controlling the temperature difference between the head and tail of a rolled piece, comprising: sequentially performing rough rolling, rough rolling controlled cooling, intermediate rolling, intermediate rolling controlled cooling, finishing rolling, and finishing rolling controlled cooling processes, and controlling the difference between the head temperature and the tail temperature of the rolled piece to ≤30°C; wherein, temperature measurement is performed in the rough rolling process, and a first temperature curve is generated based on the measurement result; the rough rolling controlled cooling process specifically comprises: arranging a water nozzle on the outside of the rolled piece; selecting a water spraying starting position on the rolled piece; spraying water on the part of the rolled piece after the water spraying starting position through the water nozzle; and adjusting the water spraying intensity of each water nozzle in real time based on the temperature curve.

[0023] Since the tail temperature of the ingot is significantly higher than the head temperature, even after the treatment of eliminating the temperature difference between the head and tail of the ingot, the tail temperature of the rolled piece is still higher than the head temperature during the rolling stage, and the closer to the tail, the higher the temperature, resulting in inconsistent strength between the head and tail of the finished product. Therefore, in order to control the temperature difference between the head and tail of the rolled piece, the present application arranges a multi-layer cooling control device at each stage of rolling, and uses a specially designed water nozzle in the rough rolling controlled cooling process after rough rolling to cool the part with higher temperature in the middle and rear end of the rolled piece, so that its temperature tends to be consistent with the head temperature.

[0024] In order to reasonably control the temperature change, it is necessary to quantify and reasonably control the water output of the water nozzle. Therefore, before using the water nozzle for cooling, the surface temperature of the rolled piece must be measured first to obtain the actual temperature of each recording point, and a temperature curve reflecting the temperature change trend at different positions of the rolled piece is drawn according to the actual temperature of each recording point. After that, the temperature curve is input into the control system, so that the control system treats each point on the rolled piece differently according to the temperature curve, so that the higher the temperature, the greater the water output of the corresponding water nozzle, the greater the cooling amplitude, and the lower the temperature, the smaller the water output. In this way, the difference between the head temperature and the tail temperature of the rolled piece can be controlled within 30°C.

[0025] There are multiple temperature measurement points along the direction of the billet feeding roller, which are distributed at the corresponding positions in the rough rolling, intermediate rolling, pre-finishing rolling, finishing rolling and other processes. Each temperature measurement point is equipped with a pyrometer for temperature measurement, and the measured value is recorded at a predetermined time interval (for example, one number is recorded every 0.1S). After the measured value is transmitted to the control system (such as a computer, etc.), a temperature curve can be drawn based on multiple measured value data, and the temperature curve represents the current head-to-tail temperature difference of the rolled piece.

[0026] Furthermore, the temperature difference between the head and tail of the rolled piece is controlled within 20°C to 30°C:

[0027] In practical applications, it is difficult to achieve complete consistency between the head temperature and the tail temperature, nor is it necessary to achieve complete consistency. According to actual measurements and analysis, controlling the head and tail temperature difference at 20℃~30℃ can meet the process requirements.

[0028] Furthermore, the provision of water spray heads on the outside of the rolled piece specifically includes: distributing a plurality of water spray heads evenly along the direction of the billet feeding roller at four positions of the upper left, lower left, lower right and upper right of the outside of the rolled piece.

[0029] The arrangement of water nozzles in the rough rolling temperature control process is as follows: Figure 1 As shown, the length of the temperature adjustment device is equivalent to that of the ingot 1. A plurality of water spray heads 4 are arranged at an appropriate distance outside the rolled piece. These water spray heads 4 are arranged at the four corner points around the outside of the billet conveying roller 3. A bracket can be provided to fix the spray heads 4. In addition, it should be ensured that one water spray head 4 is arranged at each of the four corners of the same cross section of the rolled piece 1, that is, there are a total of four water spray heads 4 in the upper left, upper right, lower left, and lower right of the same cross section, and the water spray heads 4 should not be arranged directly below the ingot 1 to avoid being blocked by impurities dropped from the rolled piece 1. In the length direction of the billet conveying roller 3, the water spray heads 4 are evenly arranged, that is, four rows of spray heads are formed. The spacing between the spray heads in the same row is arranged in principle so that the sprayed water can completely cover the surface of the rolled piece 1. Since there are gaps between the rollers below and on the sides of the billet conveying roller 3, the water spray heads 4 located at the lower left and lower right can spray cooling water to the sides and bottom of the rolled piece 1.

[0030] Furthermore, selecting a water spraying start position on the rolled piece specifically includes: determining a position on the rolled piece that is 20° C. higher than the temperature of the head of the rolled piece as the water spraying start position according to the temperature curve.

[0031] In order to control the temperature difference between 20℃ and 30℃, before spraying water for cooling, a position 20℃ higher than the head temperature of the rolled piece 1 should be found as the starting position for water spraying according to the temperature curve generated in advance, and the part after this starting position for water spraying should be cooled.

[0032] Furthermore, before the rough rolling controlled cooling process, the method further includes: designing the spray hole shape of each water nozzle to be a hollow rectangle.

[0033] The spray hole 41 of the water spray head 4 should not be designed as a common round hole, but the spray hole 41 should be designed as a hollow rectangle (such as Figure 3 As shown), so that Figure 2 As shown, the protection range of the sprayed water is formed into a rectangular water spray coverage area 42 (the protection range of the ordinary round hole water outlet is circular). In this way, since the rolled piece 1 is a square billet, and the water nozzle 4 is arranged at the four corner points outside the rolled piece 1, the water nozzle 4 is located on the diagonal connecting line of the square cross section of the rolled piece 1; since the corner 11 of the rolled piece 1 is a two-dimensional heat transfer, its temperature drop rate is fast, so the water volume in the middle of the water spray coverage area 42 sprayed by the water nozzle 4 is small, and the water volume on both sides is large, which can avoid excessive temperature drop in the corner 11 of the rolled piece 1 and maintain the overall temperature uniformity of the rolled piece 1.

[0034] Furthermore, temperature measurement is performed in the intermediate rolling process, and a second temperature curve is generated based on the measurement results; a water penetrator is used to adjust the temperature of the rolled piece in the intermediate rolling controlled cooling process, and the cooling control intensity of the intermediate rolling controlled cooling process is adjusted in real time according to the second temperature curve; temperature measurement is performed in the finishing rolling process, and a third temperature curve is generated based on the measurement results; a multi-stage cooling device is used to adjust the temperature of the rolled piece in the finishing rolling controlled cooling process, and the cooling control intensity of the finishing rolling controlled cooling process is adjusted in real time according to the third temperature curve.

[0035] In the remaining controlled cooling process, even if other controlled cooling devices other than the aforementioned water nozzles are used, the controlled cooling amount should also be adjusted according to the corresponding temperature curve. Temperature measuring points are respectively set in the intermediate rolling stand and the finishing rolling stand, so that the corresponding temperature curves are generated in the intermediate rolling process and the finishing rolling process according to the temperature measurement results, and the corresponding temperature curves are used in the subsequent intermediate rolling controlled cooling process and the finishing rolling controlled cooling process for controlled cooling adjustment.

[0036] Furthermore, the method for controlling the temperature difference between the head and tail of the rolled piece also includes: temperature measurement after finishing rolling and controlled cooling process after finishing rolling; wherein, temperature measurement is performed in the temperature measurement process after finishing rolling, and a fourth temperature curve is generated based on the measurement results; the controlled cooling process after finishing rolling adopts a multi-stage cooler to adjust the temperature of the rolled piece, and the controlled cooling intensity of the controlled cooling process after finishing rolling is adjusted in real time based on the fourth temperature curve.

[0037] In some rolling production lines, in addition to rough rolling, intermediate rolling and finishing rolling, it is also necessary to perform controlled cooling treatment again after the finishing rolling controlled cooling process (i.e. controlled cooling after finishing rolling). At this time, it is also necessary to measure the temperature and generate a temperature curve, and then carry out the controlled cooling process after finishing rolling according to the temperature curve.

[0038] Furthermore, before the finishing rolling process, it also includes pre-finishing rolling and pre-finishing rolling controlled cooling processes; wherein, temperature measurement is performed in the pre-finishing rolling process, and a fifth temperature curve is generated according to the measurement results; the pre-finishing rolling controlled cooling process uses a multi-stage nozzle to adjust the temperature of the rolled piece, and the controlled cooling intensity of the pre-finishing rolling controlled cooling process is adjusted in real time according to the fifth temperature curve.

[0039] In some rolling production lines, pre-finishing rolling is required between intermediate rolling and finishing rolling. In this case, the temperature should be measured during the pre-finishing rolling process to generate a corresponding temperature curve, and then the pre-finishing rolling controlled cooling process should be carried out according to the temperature curve.

[0040] The following is a specific example to illustrate the temperature difference control method of the rolled piece head and tail of the present application:

[0041] 1. Design of rolling line: The rolling line is equipped with multi-level cooling control device during the rolling process.

[0042] Ordinary bar production line: 6 roughing mills + roughing controlled cooling device + 6 intermediate rolling mills + intermediate controlled cooling device + 4 finishing mills + finishing controlled cooling device + recovery section + temperature measuring device after finishing + 2 finishing mills + post-finishing controlled cooling device + recovery section + cooling bed (temperature measurement is carried out after the 4th stand of the roughing, intermediate and finishing mills, which can provide recovery time for the rolled piece before temperature measurement, make the surface temperature uniform, and avoid uneven surface temperature and overcooling of the rolled piece caused by the controlled cooling device, which affects the surface temperature measurement accuracy).

[0043] High-speed bar production line: 6 roughing mills + roughing controlled cooling device + 6 intermediate rolling mills + intermediate controlled cooling device + 6 pre-finishing mills + pre-finishing controlled cooling device + 4 finishing mills + finishing controlled cooling device + recovery section + temperature measuring device after finishing + 2 finishing mills + post-finishing controlled cooling device + recovery + cooling bed (temperature measurement after the 4th stand of the roughing, intermediate, pre-finishing and finishing mills, respectively, can provide recovery time for the rolled pieces before temperature measurement, make the surface temperature uniform, and avoid uneven surface temperature and surface overcooling of the rolled pieces caused by the controlled cooling device).

[0044] High-speed wire rod production line: 6 roughing mills + roughing controlled cooling device + 6 intermediate rolling mills + intermediate rolling controlled cooling device + 6 pre-finishing mills + pre-finishing controlled cooling device + recovery section + 8 finishing mills + finishing controlled cooling device + recovery section + temperature measuring device after finishing + 2 sizing mills + post-finishing controlled cooling device (temperature measurement is carried out after the 4th stand of roughing, intermediate and pre-finishing rolling and the 8th stand of the finishing mill, which can provide recovery time for the rolled piece before temperature measurement, make the surface temperature uniform, and avoid uneven surface temperature and surface overcooling of the rolled piece caused by the controlled cooling device).

[0045] 2. Draw temperature trend lines at each measuring point based on the temperature of the rolled piece at each measuring point. The cooling process after each measuring point of the rolling line adjusts the temperature of the rolled piece according to the temperature trend line to control the temperature difference between the head and the tail of the rolled piece. Based on the surface temperature trend line of the rolled piece, water spray cooling starts from the head of the rolled piece to the back, where the temperature is 20°C higher than the head. The higher the temperature, the greater the water spray intensity.

[0046] 3. Different controlled cooling devices are used in different positions: water nozzles are used in the rough rolling controlled cooling process, water piercers are used in the intermediate rolling controlled cooling process, multi-stage nozzles are used in the pre-finishing rolling controlled cooling process, and multi-stage controlled coolers are used in the finishing rolling controlled cooling process and the post-finishing rolling controlled cooling process.

[0047] Among them, water nozzles are used for controlled cooling of rough rolling: Since the rolled piece at the rough rolling outlet is large and there may be problems such as bending at the head, a cooling device (i.e. controlled cooling device) should be installed after the No. 1 flying shear. The cooling device here consists of multiple groups of water nozzles. There is one nozzle arranged at each of the four corners of the same cross section of the rolled piece, and there are four nozzles in the same cross section, which can prevent the nozzle located directly below from being blocked by the falling of the oxide scale of the ingot, thereby affecting its use. The shape of the water outlet of the nozzle is rectangular, and its coverage area is based on the four nozzles completely covering the surface of the rolled piece.

[0048] The controlled cooling of the intermediate rolling mill is a water piercer: Since the size of the rolled piece at the intermediate rolling mill outlet is also large, there may be problems such as bending at the head. Therefore, a cooling device (controlled cooling device) should be installed after the No. 2 flying shear. The cooling device uses a water piercer commonly used in bar rolling lines for cooling.

[0049] Pre-finishing rolling, finishing rolling mill and post-finishing rolling controlled cooling all use multi-stage controlled coolers (graded controlled cooling devices), and each position is composed of multiple small controlled cooling devices that can individually control the water volume.

[0050] In a specific measurement of rolling ordinary bars, the production line was arranged according to the aforementioned ordinary bar production line, the cross-section of the ingot was 165mm×165mm, the ingot length was 11m, the steel bar specification produced was 28mm, the length of the finished rolled piece after being placed on the cooling bed was 486m, and the temperature difference between the head and tail of the rolled piece was finally controlled to 25°C.

[0051] In the above detailed description, various features are grouped together in a single embodiment to simplify the disclosure. This method of disclosure should not be interpreted as reflecting an intention that the embodiments of the claimed subject matter require more features than are clearly stated in each claim. On the contrary, as reflected in the appended claims, the invention is in a state of having less than all the features of the disclosed individual embodiments. Therefore, the appended claims are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the invention.

[0052] The disclosed embodiments are described above to enable any person skilled in the art to implement or use the present invention. Various modifications of these embodiments are obvious to those skilled in the art, and the general principles defined herein may also be applied to other embodiments without departing from the spirit and scope of the present disclosure. Therefore, the present disclosure is not limited to the embodiments given herein, but is consistent with the broadest scope of the principles and novel features disclosed in this application.

[0053] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for controlling the temperature difference between the head and tail of a rolled piece, characterized in that: include: The rough rolling, rough rolling controlled cooling, intermediate rolling, intermediate rolling controlled cooling, finishing rolling, and finishing controlled cooling processes are sequentially performed to control the temperature difference between the head and tail of the rolled piece to be ≤30°C; Wherein, temperature measurement is performed in the rough rolling process, and a first temperature curve is generated according to the measurement result; The rough rolling controlled cooling process specifically includes: A water spray nozzle is arranged on the outside of the rolled piece; Select the water spraying starting position on the rolled piece; Spray water on the portion of the rolled piece after the water spraying start position through the water spraying head; adjusting the water spray intensity of each water nozzle in real time according to the first temperature curve; The method for controlling the temperature difference between the head and the tail of the rolled piece also includes: Performing temperature measurement in the intermediate rolling process and generating a second temperature curve according to the measurement result; The intermediate rolling controlled cooling process uses a water penetrator to adjust the temperature of the rolled piece, and the controlled cooling intensity of the intermediate rolling controlled cooling process is adjusted in real time according to the second temperature curve; Performing temperature measurement in the finishing rolling process and generating a third temperature curve according to the measurement result; The finishing rolling controlled cooling process uses a multi-stage controlled cooling device to adjust the temperature of the rolled piece, and the controlled cooling intensity of the finishing rolling controlled cooling process is adjusted in real time according to the third temperature curve; Temperature measurement after finishing rolling and controlled cooling process after finishing rolling; Wherein, temperature measurement is performed in the temperature measurement process after finishing rolling, and a fourth temperature curve is generated according to the measurement result; The post-finishing cooling process uses a multi-stage cooling device to adjust the temperature of the rolled piece, and the cooling intensity of the post-finishing cooling process is adjusted in real time according to the fourth temperature curve; Before the finishing rolling process, it also includes pre-finishing rolling and pre-finishing rolling controlled cooling process; Wherein, temperature measurement is performed in the pre-finishing rolling process, and a fifth temperature curve is generated according to the measurement result; The pre-finishing rolling controlled cooling process uses a multi-stage nozzle to adjust the temperature of the rolled piece, and the controlled cooling intensity of the pre-finishing rolling controlled cooling process is adjusted in real time according to the fifth temperature curve; The ordinary bar production line includes 6 roughing mills + roughing controlled cooling device + 6 intermediate rolling mills + intermediate controlled cooling device + 4 finishing mills + finishing controlled cooling device + recovery section + temperature measurement device after finishing + 2 finishing mills + post-finishing controlled cooling device + recovery section + cooling bed, and temperature measurement is carried out after the 4th stand of the roughing, intermediate and finishing mills respectively; The high-speed bar production line includes 6 roughing mills + roughing controlled cooling devices + 6 intermediate rolling mills + intermediate controlled cooling devices + 6 pre-finishing mills + pre-finishing controlled cooling devices + 4 finishing mills + finishing controlled cooling devices + recovery section + temperature measurement device after finishing + 2 finishing mills + post-finishing controlled cooling devices + recovery + cooling bed, and the temperature is measured after the 4th stand of the roughing, intermediate, pre-finishing and finishing mills respectively; The high-speed wire rod production line includes 6 roughing mills + roughing controlled cooling devices + 6 intermediate rolling mills + intermediate rolling controlled cooling devices + 6 pre-finishing mills + pre-finishing controlled cooling devices + recovery sections + 8 finishing mills + finishing controlled cooling devices + recovery sections + temperature measuring devices after finishing + 2 sizing mills + controlled cooling devices after finishing, and temperature measurements are taken after the 4th stand of roughing, intermediate rolling, pre-finishing and the 8th stand of the finishing mill.

2. The method for controlling the temperature difference between the head and the tail of a rolled piece according to claim 1, characterized in that: The temperature difference between the head and tail of the rolled piece is controlled at 20°C to 30°C.

3. The method for controlling the temperature difference between the head and the tail of a rolled piece according to claim 1, characterized in that: The water spray head is arranged on the outside of the rolled piece, specifically comprising: A plurality of water spray heads are evenly distributed along the direction of the billet feeding roller at four positions of the upper left, lower left, lower right and upper right of the outer side of the rolled piece.

4. The method for controlling the temperature difference between the head and the tail of a rolled piece according to claim 1, characterized in that: The step of selecting a water spraying starting position on the rolled piece specifically includes: According to the first temperature curve, a position on the rolling stock which is 20° C. higher than the temperature of the head of the rolling stock is determined as the water spraying starting position.

5. The method for controlling the temperature difference between the head and the tail of a rolled piece according to claim 1, characterized in that: Before the rough rolling controlled cooling step, the method further comprises: The shape of the spray hole of each water spray head is designed to be a hollow rectangle.

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