A method for reducing the temperature difference between the head and tail of a directly rolled bloom

Abstract

The embodiment of the application provides a method for reducing the temperature difference between the head and tail of a directly rolled square billet, which comprises the following steps: during the direct rolling of the square billet, an 8-machine 8-flow mode is adopted to increase the drawing speed of the square billet to 4 m / s, so that the head cooling time of the square billet is shortened by 45 s; a high-temperature-resistant alloy ground roller is used to form an ejection roller way, two vertical heat preservation roller ways are symmetrically arranged along the two sides of the ejection roller way and taking the ejection roller way as the center, so that the head of the square billet is heat preserved by moving the heat preservation roller way during the passing of the square billet through the ejection roller way, and the tail of the square billet is cooled.

Description

Technical Field

[0001] This invention relates to the field of steel production, and in particular to a method for reducing the temperature difference between the head and tail of a straight-rolled square billet. Background Technology

[0002] To achieve better development, enterprises must keep pace with the national green and low-carbon development strategy. Direct rolling technology for bar and wire rod billets is one such green and low-carbon technology. Direct rolling technology refers to the rolling of billets (square billets) produced by continuous casting (or primary rolling) without reheating (or with only slight heating at the edges). Since reheating is unnecessary, it reduces energy consumption (coal gas, natural gas, etc.) and lowers carbon dioxide emissions, making it a highly energy-efficient and environmentally friendly measure. However, direct rolling technology still faces many problems. The most significant issue is the long production time for each continuously cast billet (square billet). The head is exposed to air first, resulting in a head temperature that is nearly 80°C lower than the tail temperature. This lower head temperature increases the mill load, and in some cases, the temperature may be too low to meet the requirements for direct rolling. Furthermore, the large temperature difference between the head and tail leads to uneven weight deviation and inconsistent performance of the finished bar, posing a risk of weight deviation or performance not meeting national standards. Currently, common methods for solving the temperature difference between the head and tail of straight-rolled square billets include electromagnetic induction heating at the head and heating at the head of tunnel furnaces. However, these measures not only require large investments, but also require additional heating, which consumes more energy and emits carbon dioxide. They cannot perfectly solve the problem of the temperature difference between the head and tail.

[0003] In the process of developing this invention, the applicant discovered at least the following problems in the prior art:

[0004] The process of reducing the temperature difference between the head and tail of continuously cast billets results in problems such as high investment, high energy consumption, and high carbon dioxide emissions. Summary of the Invention

[0005] This invention provides a method for reducing the temperature difference between the head and tail of a straight-rolled square billet, which solves the problems of high investment, high energy consumption, and high carbon dioxide emissions caused by reducing the temperature difference between the head and tail of a continuously cast square billet.

[0006] To achieve the above objectives, in one aspect, embodiments of the present invention provide a method for reducing the temperature difference between the head and tail of a straight-rolled square billet, comprising:

[0007] During the direct rolling of the billet, an 8-machine 8-flow mode is adopted to increase the drawing speed of the billet to 4 m / s, thereby shortening the cooling time of the billet head by 45 seconds.

[0008] The billet discharge roller track is composed of high-temperature alloy ground rollers. Two vertical heat-insulating roller tracks are symmetrically arranged on both sides of the billet discharge roller track with the billet discharge roller track as the center. During the passage of the billet through the billet discharge roller track, the heat-insulating roller tracks are moved to keep the head of the billet warm and dissipate heat from the tail of the billet.

[0009] Furthermore, the heat-insulating roller conveyor includes at least one vertical roller; the heat-insulating tracks on both sides of the billet discharge roller conveyor are relatively translated in the horizontal direction with the billet discharge roller conveyor as the center;

[0010] The method further includes: when the length of the billet entering the heat-insulating roller channel is less than a preset length, for each pair of opposite vertical rollers in the heat-insulating roller channels on both sides, after the head of the billet exceeds the vertical centerline of each of the opposite vertical rollers, the opposite vertical rollers are translated towards the centerline of the billet exit roller channel, and the translation is stopped when the channel width between the opposite vertical rollers is equal to the set width of the billet, so that the heat-insulating roller channels on both sides keep the billet warm;

[0011] Once the pre-set length of the billet enters the heat-insulating roller conveyor, the heat-insulating roller conveyors on both sides are reset to keep the head of the billet warm and dissipate heat from the tail of the billet.

[0012] Furthermore, the preset length is 2 / 3 of the length of the billet.

[0013] Furthermore, the method also includes: measuring the temperature distribution along the length of the entire billet, determining the head-to-tail temperature difference of the billet based on the temperature distribution, controlling the valve opening of the descaling tank based on the head-to-tail temperature difference, and using the descaling tank to cool the tail of the billet.

[0014] Furthermore, controlling the valve opening degree of the descaling tank according to the head-to-tail temperature difference includes: setting the valve opening degree of the descaling tank to 10% to 50% according to the head-to-tail temperature difference.

[0015] Furthermore, the heat-insulating roller conveyor is composed of refractory ceramic fibers and high-temperature resistant alloys.

[0016] Furthermore, the original number of machines and streams was 10 machines and 10 streams; the preset number of machines and streams was 8 machines and 8 streams.

[0017] The method includes: reducing the original 10 machines and 10 streams of the billet continuous casting machine on the production line to a preset 8 machines and 8 streams, so that the billet drawing speed is increased from 3.2 m / s to 4 m / s, and the head and tail temperature difference of the billet is reduced from the original 80 degrees Celsius to 60 degrees Celsius.

[0018] The billet discharge rollers are composed of high-temperature alloy rollers. Two vertical heat-insulating rollers are symmetrically arranged on both sides of the billet discharge rollers with the billet discharge rollers as the center. A hot metal detector is added at the head of the heat-insulating rollers to detect the position of the billet head. After detecting the billet signal, each heat-insulating roller moves inward to get closer to the billet. When 2 / 3 of the length of the billet passes the hot metal detector, the heat-insulating rollers return to their original position to accelerate the heat dissipation at the tail end and reduce the temperature difference between the head and tail from 60 degrees Celsius to 40 degrees Celsius.

[0019] A pyrometer is installed at the steel separator to measure the temperature distribution along the length of the entire billet. The temperature difference between the head and tail of the billet is determined based on the temperature distribution. The opening of the valve of the dephosphorization water tank is controlled at 10% to 50% based on the temperature difference between the head and tail of the billet, so as to reduce the temperature difference between the head and tail to within 30 degrees Celsius. The water pressure of the dephosphorization water tank is 1.0 to 1.2 MPa.

[0020] The above technical solutions have the following beneficial effects: by reducing the original large number of machines and flow rates to a preset relatively small number, using high-temperature alloy ground rollers, and increasing the number of heat-insulating rollers, the temperature difference between the head and tail of the billet is reduced. Based on the movable heat-insulating rollers, the head of the billet can be specifically heat-insulated and the tail can be cooled, further reducing the head-tail temperature difference; by using a descaling water tank to determine the head-tail temperature difference based on the temperature distribution of the billet, and by spraying heat to the tail in a targeted manner based on the head-tail temperature difference, the head-tail temperature difference is further reduced. Through the combination of one or more of the above methods, the continuously cast billet (square billet) better meets the direct rolling conditions, improves production efficiency, reduces energy consumption, reduces carbon dioxide emissions, reduces oxidation loss, reduces production costs, and avoids negative weight deviations or performance inconsistencies. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart of a method for reducing the temperature difference between the head and tail of a straight-rolled square billet, one of the embodiments of the present invention;

[0023] Figure 2 This is a schematic diagram of the position of the insulation roller table before the billet head enters the insulation roller table in one embodiment of the present invention.

[0024] Figure 3 This is a schematic diagram of the insulation roller conveyor moving to the insulation position when the billet head reaches the insulation roller conveyor in one embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of a square billet moving within a heat-insulating roller conveyor, where the vertical rollers of the heat-insulating roller conveyor move sequentially to the heat-insulating position, according to one embodiment of the present invention.

[0026] Figure 5 This is a schematic diagram showing the position of the insulation roller conveyor after the pre-set length of the billet enters the insulation roller conveyor and the roller conveyor resets, which is one embodiment of the present invention.

[0027] Explanation of reference numerals in the attached drawings: 1. Billet exit roller conveyor; 2. Square billet; 3. Insulation roller conveyor; 31. Vertical roller; 4. Insulation roller conveyor drive device. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] On one hand, embodiments of the present invention provide a method for reducing the temperature difference between the head and tail of a straight-rolled square billet, comprising:

[0030] Step S10: During the direct rolling of the billet, an 8-machine 8-flow mode is adopted to increase the drawing speed of the billet to 4 m / s, thereby shortening the cooling time of the head of the billet by 45 seconds and reducing the temperature difference between the head and tail of the billet by 20 degrees Celsius.

[0031] Step S11: Use high-temperature alloy ground rollers to form a billet discharge roller channel. Two vertical heat-insulating roller channels are symmetrically arranged on both sides of the billet discharge roller channel with the billet discharge roller channel as the center. During the billet discharge roller channel, the head of the billet is kept warm by moving the heat-insulating roller channels and the tail of the billet is cooled.

[0032] The length of the square billet is 12 meters;

[0033] Preferably, the heads of the heat-insulating rollers on both sides of the billet discharge roller are aligned with the heads of the billet discharge roller, and the length of the heat-insulating roller along the direction of the billet discharge roller is 12 meters.

[0034] The following is a specific embodiment of the present invention. Liuzhou Steel adopts a Nb microalloying strengthening process. Specifically, the chemical composition of the billet is as follows: C: 0.20%–0.24%, Si: 0.20%–0.35%, Mn: 1.05%–1.25%, Nb: 0.017%–0.027%; P≤0.035%; S≤0.035%. During continuous casting, the precipitation of Nb and N bonds easily leads to cracks in the billet. The higher the casting speed, the more severe the cracks caused by Nb and N bond precipitation. These cracks affect the surface quality of the finished steel reinforcement, resulting in defects such as scabs and cracks. When the original billet continuous casting machine used a 10-machine, 10-flow configuration, due to the influence of the rhythm of the preceding and following processes (e.g., the basic arc radius of the casting machine is 10 meters), with 10 machines and 10 flows, the billet cross-sectional size is 150mm×150mm~170mm×170mm (millimeters), and the fixed length is 9~12m (meters), hydraulic shear cutting is used. If the casting speed is too high, the amount of molten iron cannot keep up. Therefore, when using a 10-machine, 10-flow configuration, the maximum casting speed for billets can only reach 3.2 meters per second. It takes 225 seconds to cast a 12-meter billet (square billet), meaning the head of the billet (square billet) cools for 225 seconds longer than the tail, resulting in a significant temperature difference between the head and tail. While increasing the casting speed can reduce the head waiting time and thus the head temperature drop, in the 10-machine 10-flow mode, a casting speed exceeding 3.2 m / s will cause the molten iron quantity to lag behind the continuous casting rhythm. To address this, the inventors made further creative improvements. In direct rolling, the original number of machines and flow rates were reduced to an 8-machine 8-flow mode, allowing the casting speed to be increased to 4 m / s. Casting a 12-meter billet (square billet) only takes 180 seconds, reducing the head temperature drop time by 45 seconds and decreasing the head-to-tail temperature difference from 80℃ to 60℃. When the casting speed exceeds 4 m / s, the billet is prone to serious cracking defects and steel leakage accidents. Cracks in the billet will affect the surface quality of the finished steel bars, leading to defects such as scabs and cracks. Therefore, reducing the original number of machines and flow rates to an 8-machine 8-flow mode and increasing the casting speed to 4 m / s reduces the head-to-tail temperature difference and avoids steel leakage and cracking defects in the billet. The inventors analyzed the heat preservation measures of the billet discharge roller conveyor in the prior art and found that, because the infrared length measuring equipment is installed on the top of the plant, a heat preservation cover cannot be added to the first 2 meters of the billet discharge roller conveyor, while the continuous casting billet temperature is highest at this point, resulting in the fastest heat dissipation. Furthermore, the internal space of the heat preservation cover above the ground roller is large, and there are no baffles at both ends, allowing air to carry away a significant amount of heat through convection. Without other measures, the temperature difference between the beginning and end can only be reduced by about 10°C, which is not ideal. Additionally, using a water-cooled roller conveyor for the ground roller also removes some heat. Based on these findings, the inventors used a high-temperature resistant alloy ground roller in the embodiments of this invention to reduce heat loss from the ground roller; preferably, the high-temperature resistant alloy ground roller is a ZG45Cr28Ni48W5Si2 alloy, which is suitable for high-temperature working environments up to 1300°C.At the same time, vertical heat-insulating roller tracks are added on both sides of the billet discharge roller track. The length of the heat-insulating roller track along the billet discharge track (i.e., billet movement) is 12 meters, providing better heat preservation effect.

[0035] Furthermore, the heat-insulating roller conveyor includes at least one vertical roller; the heat-insulating tracks on both sides of the billet discharge roller conveyor are relatively translated in the horizontal direction with the billet discharge roller conveyor as the center;

[0036] The method further includes: when the length of the billet entering the heat-insulating roller channel is less than a preset length, for each pair of opposite vertical rollers in the heat-insulating roller channels on both sides, after the head of the billet exceeds the vertical centerline of each of the opposite vertical rollers, the opposite two vertical rollers are translated towards the centerline of the billet exit roller channel, and the translation is stopped when the channel width between the opposite two vertical rollers is equal to the set width of the billet, so that the heat-insulating roller channels on both sides keep the billet warm;

[0037] Once the pre-set length of the billet enters the heat-insulating roller conveyor, the heat-insulating roller conveyors on both sides are reset to keep the head of the billet warm and dissipate heat from the tail of the billet.

[0038] In some embodiments, when not heat-insulating, each vertical roller 31 of the heat-insulating roller conveyor 3 is located at the edges on both sides of the billet exit roller conveyor 1, i.e., the reset position. During heat-insulating, the heat-insulating roller conveyor 3 is translated towards the centerline of the billet exit roller conveyor 1 by the heat-insulating roller conveyor drive device 4, and the channel width between the heat-insulating roller conveyors is the set width of the billet (i.e., the heat-insulating position), so that the billet contacts the heat-insulating roller conveyor for heat preservation. The preset length of the billet is the preset length starting from the head of the billet. The purpose is to use the heat-insulating roller conveyor to heat the preset length portion starting from the head of the billet and to dissipate heat from the tail, so as to reduce the temperature difference between the head and tail of the billet. The specific value can be determined based on field tests or based on the temperature distribution of the billet. Figure 2 As shown, before the billet 2 reaches the corresponding vertical roller 31 of the heat-insulating roller conveyor 3, the corresponding vertical roller 31 of the heat-insulating roller conveyor 3 on both sides of the billet discharge roller conveyor 1 is in the reset position, that is, located at the edge of both sides of the billet discharge roller conveyor; as Figure 3 As shown, when the head of the billet 2 reaches a certain set of vertical rollers 31 on the heat-insulating roller conveyor 3 (a set of vertical rollers 31 refers to two vertical rollers 31 located at opposite positions on both sides of the billet exit roller conveyor), and exceeds the respective central axis position of the set of vertical rollers 31, the two vertical rollers 31 in that set translate towards the center line of the billet exit roller conveyor 1, and the translation stops when the channel width between the set of vertical rollers 31 is equal to the set width of the billet, thus achieving the desired result. Figure 4 As shown, during the forward movement of billet 2, the portion of the billet entering the heat-insulating roller conveyor 3 is heat-insulated near both sides of billet 2. Figure 5As shown, after the pre-set length starting from the head of the billet 2 enters the heat-insulating roller conveyor 3, the heat-insulating roller conveyor 3 separates and returns to the reset position under the drive of the heat-insulating roller conveyor drive device 4. Specifically, under the drive of the heat-insulating roller conveyor drive device 4, the vertical rollers 31 on both sides of the billet 2, which have undergone the aforementioned translation, separate and return to the reset position. At this time, the heat-insulating roller conveyor 3 no longer heats the billet 2, thereby achieving heat preservation for the pre-set length starting from the head of the billet 2, while leaving the remaining tail section uninsulated. This achieves heat preservation of the billet head and heat dissipation of the tail, controlling the temperature difference between the head and tail of the billet. The vertical roller 31 is moved inward to rest against the side of the billet only after the billet head exceeds the vertical central axis position of the corresponding vertical roller 31, in order to prevent the billet head from hitting the vertical roller 31.

[0039] The following is a specific embodiment of the present invention. When the original number of machines and flow rate of the billet continuous casting machine was 10 machines and 10 flow rates, the maximum casting speed of the billet could only reach 3.2 m / s due to the influence of the rhythm of the preceding and following processes. It would take 225 seconds to cast a 12-meter billet (square billet), that is, the head of the billet (square billet) would cool for 225 seconds longer than the tail. In order to reduce the waiting time at the head and reduce the temperature drop at the head, when direct rolling is required, the original number of machines and flow rate is reduced to the preset number of machines and flow rate, that is, the 8-machine 8-flow mode is adopted. The casting speed can be increased to 4 m / s (equivalent to the preset speed in this embodiment). It only takes 180 seconds to cast a 12-meter billet (square billet), reducing the head temperature drop time by 45 seconds, and the head-tail temperature difference is reduced from the original 80℃ to 60℃. The inventors analyzed the heat preservation measures of the billet discharge roller conveyor in the prior art and found that, because the infrared length measuring equipment is installed on the top of the plant, a heat preservation cover cannot be added to the first 2 meters of the billet discharge roller conveyor. At this point, the continuous casting billet temperature is highest, resulting in the fastest heat dissipation. Furthermore, the internal space of the heat preservation cover above the ground roller is large, and there are no baffles at both ends, allowing air to carry away a significant amount of heat through convection. Without other measures, the temperature difference between the front and rear ends can only be reduced by about 10°C, which is not ideal. Additionally, the use of a water-cooled roller conveyor for the ground roller also leads to heat loss. Based on these findings, in the embodiments of this invention, the inventors used high-temperature resistant alloy ground rollers to reduce heat loss from the ground rollers; simultaneously, 12-meter-long vertical heat preservation roller conveyors were added to both sides of the billet discharge roller conveyor to provide better heat preservation. A hot metal detector is added to the head of the heat-insulating roller conveyor to detect the position of the billet (square billet). After detecting the billet (square billet) signal, each heat-insulating roller conveyor moves inward to get closer to the billet (square billet). After the billet (square billet) passes the hot metal detector at its preset length, the heat-insulating roller conveyor returns to its original position, which accelerates heat dissipation at the tail end and can reduce the temperature difference between the head and tail from 60℃ to 40℃.

[0040] Furthermore, the preset length is 2 / 3 of the length of the billet.

[0041] In some embodiments, a hot metal detector is added to the head of the heat-insulating roller conveyor to detect the position of the billet (square billet). After detecting the billet (square billet) signal, each heat-insulating roller conveyor moves inward to get closer to the billet (square billet). After 2 / 3 of the billet (square billet) length has passed the hot metal detector, the heat-insulating roller conveyor returns to its original position, accelerating heat dissipation at the tail end. This effectively focuses on heat preservation of most of the billet (square billet) on the head side (2 / 3 of its length) and heat dissipation on a small portion (1 / 3 of its length) at the tail end, thereby further reducing the temperature difference between the head and tail.

[0042] Furthermore, the method also includes: measuring the temperature distribution along the length of the entire billet, determining the head-to-tail temperature difference of the billet based on the temperature distribution, controlling the valve opening of the descaling tank based on the head-to-tail temperature difference, and using the descaling tank to cool the tail of the billet.

[0043] The following describes a specific embodiment of the present invention. Due to equipment limitations, the rolling speed of the billet (square billet) on the No. 1 rolling mill is 0.20 m / s to 0.50 m / s, and the length of the billet (square billet) is 12 meters. Simple calculations show that the rolling time of the entire billet (square billet) is 30 to 60 seconds. Therefore, there is sufficient time to use the descaling water tank in front of the No. 1 rolling mill to cool the tail end, thereby further reducing the temperature at the tail end and minimizing the temperature difference between the head and tail. Specifically, a pyrometer can be installed at the steel separator to measure the temperature distribution along the length of the entire billet. Based on the temperature distribution, the temperature difference between the head and tail of the billet (square billet) can be determined. The water pressure in the descaling water tank is 1.0 to 1.2 MPa, and the valve opening of the descaling water tank is controlled at a preset opening degree according to the temperature difference between the head and tail of the billet (square billet) to reduce the temperature difference between the head and tail to within 30°C.

[0044] Furthermore, controlling the valve opening degree of the descaling tank according to the head-to-tail temperature difference includes: setting the valve opening degree of the descaling tank to 10% to 50% according to the head-to-tail temperature difference.

[0045] In some embodiments, the opening degree of the dephosphorization tank valve is controlled at a preset opening degree based on the temperature difference between the head and tail of the billet (square billet), which is 10% to 50%.

[0046] Furthermore, the heat-insulating roller conveyor is composed of refractory ceramic fibers and high-temperature resistant alloys.

[0047] In some embodiments, using refractory ceramic fibers and high-temperature alloys to form the insulation roller conveyor can provide better insulation performance and service life.

[0048] Furthermore, the original number of machines and streams was 10 machines and 10 streams; the preset number of machines and streams was 8 machines and 8 streams.

[0049] The method includes: reducing the original 10 machines and 10 streams of the billet continuous casting machine on the production line to a preset 8 machines and 8 streams, so that the billet drawing speed is increased from 3.2 m / s to 4 m / s, and the head and tail temperature difference of the billet is reduced from the original 80 degrees Celsius to 60 degrees Celsius, thereby reducing the head and tail temperature difference of the billet by 20 degrees Celsius.

[0050] The billet discharge rollers are composed of high-temperature alloy rollers. Two vertical heat-insulating rollers are symmetrically arranged on both sides of the billet discharge rollers with the billet discharge rollers as the center. A hot metal detector is added at the head of the heat-insulating rollers to detect the position of the billet head. After each heat-insulating roller detects the billet signal, it moves inward to get closer to the billet. When 2 / 3 of the length of the billet passes the hot metal detector, the heat-insulating rollers return to their original position to accelerate the heat dissipation at the tail end, so that the temperature difference between the head and tail ends is reduced from 60 degrees Celsius to 40 degrees Celsius, and the temperature difference between the head and tail ends of the billet is further reduced by 20 degrees Celsius.

[0051] A pyrometer is installed at the steel separator to measure the temperature distribution along the length of the entire billet. The temperature difference between the head and tail of the billet is determined based on the temperature distribution. The opening of the valve of the dephosphorization water tank is controlled at 10% to 50% based on the temperature difference between the head and tail of the billet, so as to reduce the temperature difference between the head and tail to within 30 degrees Celsius. The water pressure of the dephosphorization water tank is 1.0 to 1.2 MPa.

[0052] The embodiments of this invention have the following technical effects: by reducing the original large number of machines and flow rates to a preset relatively small number, using high-temperature alloy ground rollers, and adding heat-insulating roller conveyors, the temperature difference between the head and tail of the billet is reduced. Based on the movable heat-insulating roller conveyor, the head of the billet can be specifically heat-insulated and the tail can be cooled, further reducing the head-tail temperature difference; by using a descaling water tank to determine the head-tail temperature difference based on the temperature distribution of the billet, and by spraying heat to the tail in a targeted manner based on the head-tail temperature difference, the head-tail temperature difference is further reduced. Through the combination of one or more of the above methods, the continuously cast billet better meets the direct rolling conditions, improves production efficiency, reduces energy consumption, reduces carbon dioxide emissions, reduces oxidation loss, reduces production costs, and avoids negative weight deviations or performance defects.

[0053] The technical solutions of the present invention will be described in detail below with reference to specific application examples. For technical details not described in the implementation process, please refer to the relevant descriptions above.

[0054] This invention provides a method for reducing the temperature difference between the head and tail of a straight-rolled square billet, solving the problem of head-tail temperature difference, enabling the continuously cast square billet to better meet the conditions for straight rolling, improving production efficiency, reducing energy consumption, reducing carbon dioxide emissions, reducing oxidation loss, reducing production costs, and avoiding negative weight deviation or performance incompatibility.

[0055] The following is an illustration using a specific example:

[0056] When the billet continuous casting machine originally used a 10-machine, 10-strand configuration, the maximum casting speed of the billet could only reach 3.2 m / s due to the influence of the rhythm of the preceding and following processes. It would take 225 seconds to cast a 12-meter billet (square billet), meaning that the head cooled for 225 seconds longer than the tail. In order to reduce the waiting time at the head and reduce the temperature drop at the head, when direct rolling is required, the number of machines and strands is reduced to the preset 8-machine, 8-strand configuration. The casting speed can be increased to 4 m / s, and it only takes 180 seconds to cast a 12-meter billet (square billet). This reduces the head temperature drop time by 45 seconds, and the head-to-tail temperature difference is reduced from 80℃ to 60℃ (degrees Celsius).

[0057] Because the infrared length measuring equipment is installed on the roof of the factory, a heat insulation cover cannot be added to the 2 meters in front of the billet discharge roller, while the continuous casting billet temperature is highest at this point, resulting in the fastest heat dissipation. Furthermore, the internal space of the heat insulation cover above the ground roller is large, and there are no baffles at both ends, allowing air to carry away a significant amount of heat through convection. Without other measures, the temperature difference between the beginning and end can only be reduced by about 10°C, which is unsatisfactory. Using a water-cooled roller conveyor for the ground roller also carries away some heat. Therefore, this embodiment of the invention uses a high-temperature alloy ground roller to reduce heat loss. Simultaneously, 12-meter-long vertical, retractable heat-insulating rollers composed of refractory ceramic fibers and high-temperature alloys are added to both sides of the billet discharge roller conveyor. A hot metal detector is added to the head of each heat-insulating roller conveyor to detect the position of the billet (square billet). Each heat-insulating roller conveyor detects the billet (square billet) head to reduce the temperature difference between the beginning and end from 60°C to 40°C.

[0058] Due to equipment limitations, the rolling speed of the billet (square billet) on the No. 1 rolling mill is 0.20 m / s to 0.50 m / s, and the billet length is 12 meters. Simple calculations show that the rolling time for the entire billet is 30 to 60 seconds. Therefore, there is sufficient time to utilize the descaling water tank before the No. 1 rolling mill to cool the tail section, further reducing its temperature and minimizing the temperature difference between the head and tail. A pyrometer is installed at the steel separator to measure the temperature distribution along the length of the entire billet. The water pressure in the descaling water tank is 1.0 to 1.2 MPa, and the valve opening is controlled within 10% to 50% of the head-to-tail temperature difference, reducing the head-to-tail temperature difference to within 30°C.

[0059] The embodiments of this invention have the following technical effects: by reducing the original large number of machines and flow rates to a preset relatively small number of machines and flow rates, using high-temperature alloy ground rollers, and adding heat-insulating roller tracks, the temperature difference between the head and tail of the billet (square billet) is reduced. Based on the movable heat-insulating roller tracks, the head of the billet (square billet) can be specifically heat-insulated and the tail can be cooled, further reducing the head-tail temperature difference; by using a descaling water tank to determine the head-tail temperature difference based on the temperature distribution of the billet (square billet), and by spraying heat to the tail in a targeted manner based on the head-tail temperature difference, the head-tail temperature difference is further reduced. Through the combination of one or more of the above methods, the continuously cast square billet better meets the direct rolling conditions, improves production efficiency, reduces energy consumption, reduces carbon dioxide emissions, reduces oxidation loss, reduces production costs, and avoids negative weight deviations or performance defects.

[0060] The following is an illustration using another specific embodiment:

[0061] This invention provides a method for reducing the temperature difference between the head and tail of a straight-rolled square billet, comprising:

[0062] The specific process is as follows: blast furnace molten iron smelting → molten iron desulfurization pretreatment → converter molten steel smelting → billet continuous casting → rough rolling → intermediate rolling → finishing rolling mill → large cooling bed → fixed length cold shearing → small cooling bed → bundling, weighing, tagging, and warehousing;

[0063] During direct rolling, reduce the number of streams and increase the drawing speed per stream to over 4 m / s to reduce the head heat dissipation time;

[0064] High-temperature alloy ground rollers are used to reduce heat loss. At the same time, 12-meter-long vertical retractable heat-insulating rollers composed of refractory ceramic fibers and high-temperature alloys are added to both sides of the roller conveyor. A hot metal detector is added to the head of the heat-insulating roller to detect the position of the billet (square billet). After each heat-insulating roller detects the billet signal, it moves close to the billet. After 2 / 3 of the billet length has passed the hot metal detector, the heat-insulating roller returns to its original position to accelerate heat dissipation at the tail end.

[0065] The tail section is cooled by using the descaling water tank in front of the No. 1 rolling mill. The water pressure is 1.0 to 1.2 MPa. The valve opening is controlled at 10% to 50% according to the temperature difference between the head and tail of the billet, so as to reduce the temperature difference between the head and tail to within 30℃.

[0066] The embodiments of this invention have the following technical effects: by reducing the original large number of machines and flow rates to a preset relatively small number of machines and flow rates, using high-temperature alloy ground rollers, and adding heat-insulating roller tracks, the temperature difference between the head and tail of the billet (square billet) is reduced. Based on the movable heat-insulating roller tracks, the head of the billet (square billet) can be specifically heat-insulated and the tail can be cooled, further reducing the head-tail temperature difference; by using a descaling water tank to determine the head-tail temperature difference based on the temperature distribution of the billet (square billet), and by spraying heat to the tail in a targeted manner based on the head-tail temperature difference, the head-tail temperature difference is further reduced. Through the combination of one or more of the above methods, the continuously cast square billet better meets the direct rolling conditions, improves production efficiency, reduces energy consumption, reduces carbon dioxide emissions, reduces oxidation loss, reduces production costs, and avoids negative weight deviations or performance defects.

[0067] The following is an illustration using another specific embodiment:

[0068] This invention provides a method for reducing the temperature difference between the head and tail of a straight-rolled square billet, comprising:

[0069] When rolling non-directly, use a 10-machine 10-flow mode, and the drawing speed is determined according to the production situation. When rolling directly, reduce the number of flows and increase the drawing speed of each flow to more than 4 meters per second to reduce the head heat dissipation time.

[0070] High-temperature alloy rollers are used to reduce heat loss. At the same time, 12-meter-long vertical retractable heat-insulating rollers composed of refractory ceramic fibers and high-temperature alloys are added to both sides of the roller conveyor. A hot metal detector is added to the head of the heat-insulating roller conveyor to detect the position of the billet (square billet). After each heat-insulating roller conveyor detects the billet signal, it moves close to the billet. After 2 / 3 of the billet length has passed the hot metal detector, the heat-insulating roller conveyor returns to its original position to accelerate heat dissipation at the tail end.

[0071] The tail section is cooled by using the descaling water tank in front of the No. 1 rolling mill. The water pressure is 1.0 to 1.2 MPa, and the valve opening is controlled at 10% to 50% according to the temperature difference between the head and tail of the billet, so as to reduce the temperature difference between the head and tail to within 30℃.

[0072] The following is a data comparison between the process method of this invention embodiment and the original process method:

[0073] Examples 1-3 are the process methods of the present invention, and Comparative Examples 4-6 are the original process methods. The head, middle and tail temperatures and head and tail temperature differences after shearing of the continuously cast billet are shown in Table 1. After increasing the casting speed of each stream to more than 4 m / s, the extreme temperature difference of the billet (i.e. the difference between the highest and lowest temperatures of the entire billet) is reduced from about 80°C to about 60°C.

[0074] Examples 1-3 are the process methods of the present invention, and Comparative Examples 4-6 are the original process methods. The head, middle and tail temperatures at the steel separator are shown in Table 2. After installing the heat-insulating roller conveyor, the temperature difference of the steel billet is reduced from about 60°C to about 40°C.

[0075] Examples 1-3 are the process methods of the present invention, and Comparative Examples 4-6 are the original process methods. The head, middle and tail temperatures after dephosphorization are shown in Table 3. After cooling the tail with dephosphorization water, the temperature difference of the billet drops from about 40°C to about 30°C.

[0076] Examples 1-3 are the process methods of the present invention, and Comparative Examples 4-6 are the original process methods. The rolling temperatures at the beginning, middle and end are shown in Table 4. After cooling the tail end with dephosphorization water, the temperature difference of the billet is about 30℃.

[0077] Examples 1-3 are the process methods of the present invention, and Comparative Examples 4-6 are the original process methods. The negative deviation of the weight at the beginning, middle and end is shown in Table 5. After applying the method of the present invention, the temperature difference range of the billet is about 30℃, and the negative deviation range (i.e. the difference between the maximum and minimum negative deviation of the weight at the beginning, middle and end) is reduced from 1.8% to 0.2%.

[0078] Examples 1-3 are the process methods of the present invention, and Comparative Examples 4-6 are the original process methods. The yield strength of the head, middle and tail is shown in Table 6. After applying the method of the present invention, the temperature difference of the billet is about 30℃, and the strength difference (i.e. the difference between the maximum and minimum yield strength of the head, middle and tail) is reduced from 20MPa to 5MPa.

[0079] Table 1: Head, Middle and Tail Temperatures at the Hydraulic Shear in Each Embodiment

[0080] Example Temperature measurement point Head temperature / ℃ Central temperature / °C Tail temperature / °C Temperature range / ℃ Example 1 hydraulic shear 993 1025 1052 59 Example 2 hydraulic shear 997 1023 1055 58 Example 3 hydraulic shear 992 1027 1048 56 Comparative Example 4 hydraulic shear 950 996 1029 79 Comparative Example 5 hydraulic shear 954 1001 1033 79 Comparative Example 6 hydraulic shear 947 998 1032 85

[0081]

[0082]

[0083] Table 3: Head, middle and tail temperatures after phosphorus removal in each example

[0084] Example Temperature measurement point Head temperature / ℃ Central temperature / °C Tail temperature / °C Temperature range / ℃ Example 1 After the phosphorus removal tank 964 975 989 25 Example 2 After the phosphorus removal tank 968 971 992 24 Example 3 After the phosphorus removal tank 960 979 987 27 Comparative Example 4 After the phosphorus removal tank 920 954 990 70 Comparative Example 5 After the phosphorus removal tank 923 956 994 71 Comparative Example 6 After the phosphorus removal tank 919 952 993 74

[0085] Table 4: Head, Middle and Tail Rolling Temperatures in Each Embodiment

[0086] Example Temperature measurement point Head temperature / ℃ Central temperature / °C Tail temperature / °C Temperature range / ℃ Example 1 Before No. 2 rolling mill 957 968 974 17 Example 2 Before No. 2 rolling mill 961 966 981 20 Example 3 Before No. 2 rolling mill 954 963 979 25 Comparative Example 4 Before No. 2 rolling mill 916 946 978 62 Comparative Example 5 Before No. 2 rolling mill 920 949 980 60 Comparative Example 6 Before No. 2 rolling mill 915 941 976 61

[0087] Table 5: Negative Deviation of Head, Middle and Tail Weight in Each Embodiment

[0088]

[0089]

[0090]

[0091] As can be seen from Tables 1, 2, 3, 4, 5 and 6, the embodiments of the present invention can solve the problem of temperature difference between the head and tail, enabling the continuously cast billet to better meet the conditions for direct rolling, improve production efficiency, reduce energy consumption, reduce carbon dioxide emissions, reduce oxidation loss, reduce production costs, and avoid negative weight deviation or performance incompatibility.

[0092] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to the specific order or hierarchy described.

[0093] In the above detailed description, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features of the single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, wherein each claim stands alone as a preferred embodiment of the invention.

[0094] The disclosed embodiments have been described above to enable any person skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit and scope of this disclosure. Therefore, this 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.

[0095] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations falling within the scope of the appended claims. Furthermore, the term "comprising" as used in the specification or claims is used in a manner similar to the term "including." Additionally, the use of any term "or" in the specification of the claims is intended to mean "non-exclusive or."

[0096] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment 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 within the scope of protection of the present invention.

Claims

1. A method for reducing the temperature difference between the head and tail of a straight-rolled square billet, characterized in that, include: During the direct rolling of the billet, an 8-machine 8-flow mode is adopted to increase the drawing speed of the billet to 4 m / s, thereby shortening the cooling time of the billet head by 45 seconds. The billet discharge roller channel is composed of high-temperature alloy ground rollers. Two vertical heat-insulating roller channels are symmetrically arranged on both sides of the billet discharge roller channel with the billet discharge roller channel as the center. During the passage of the billet through the billet discharge roller channel, the heat-insulating roller channels are moved to keep the head of the billet warm and dissipate heat from the tail of the billet. The heat-insulating roller conveyor includes at least one vertical roller; the heat-insulating tracks on both sides of the billet discharge roller conveyor are relatively translated in the horizontal direction with the billet discharge roller conveyor as the center; The method further includes: when the length of the billet entering the heat-insulating roller channel is less than a preset length, for each pair of opposite vertical rollers in the heat-insulating roller channels on both sides, after the head of the billet exceeds the vertical centerline of each of the opposite vertical rollers, the opposite two vertical rollers are translated towards the centerline of the billet exit roller channel, and the translation is stopped when the channel width between the opposite two vertical rollers is equal to the set width of the billet, so that the heat-insulating roller channels on both sides keep the billet warm; Once the pre-set length of the billet enters the heat-insulating roller conveyor, the heat-insulating roller conveyors on both sides are reset to keep the head of the billet warm and dissipate heat from the tail of the billet.

2. The method for reducing the temperature difference between the head and tail of a straight-rolled square billet as described in claim 1, characterized in that, The preset length is 2 / 3 of the length of the billet.

3. The method for reducing the temperature difference between the head and tail of a straight-rolled square billet as described in claim 1, characterized in that, Also includes: The temperature distribution along the length of the entire billet is measured, the temperature difference between the head and tail of the billet is determined based on the temperature distribution, and the valve opening of the descaling water tank is controlled based on the head and tail temperature difference to cool the tail of the billet.

4. The method for reducing the temperature difference between the head and tail of a straight-rolled square billet as described in claim 3, characterized in that, The step of controlling the valve opening degree of the descaling tank according to the head-to-tail temperature difference includes: setting the valve opening degree of the descaling tank to 10% to 50% according to the head-to-tail temperature difference.

5. The method for reducing the temperature difference between the head and tail of a straight-rolled square billet as described in claim 1, characterized in that, The heat-insulating roller conveyor is composed of refractory ceramic fibers and high-temperature resistant alloys.

6. The method for reducing the temperature difference between the head and tail of a straight-rolled square billet as described in claim 1, characterized in that, The original number of machines and streams was 10 machines and 10 streams; the default number of machines and streams is 8 machines and 8 streams. The number of billet continuous casting machines on the production line was reduced from 10 machines and 10 streams to a preset 8 machines and 8 streams, so that the billet drawing speed was increased from 3.2 m / s to 4 m / s and the temperature difference between the head and tail of the billet was reduced from 80 degrees Celsius to 60 degrees Celsius. The billet discharge rollers are composed of high-temperature alloy rollers. Two vertical heat-insulating rollers are symmetrically arranged on both sides of the billet discharge rollers with the billet discharge rollers as the center. A hot metal detector is added at the head of the heat-insulating rollers to detect the position of the billet head. After detecting the billet signal, each heat-insulating roller moves inward to get closer to the billet. When 2 / 3 of the length of the billet passes the hot metal detector, the heat-insulating rollers return to their original position to accelerate the heat dissipation at the tail end and reduce the temperature difference between the head and tail from 60 degrees Celsius to 40 degrees Celsius. A pyrometer is installed at the steel separator to measure the temperature distribution along the length of the entire billet. The temperature difference between the head and tail of the billet is determined based on the temperature distribution. The opening of the valve of the dephosphorization water tank is controlled at 10% to 50% based on the temperature difference between the head and tail of the billet, so as to reduce the temperature difference between the head and tail to within 30 degrees Celsius. The water pressure of the dephosphorization water tank is 1.0 to 1.2 MPa.

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