A method for producing a super low coiling temperature abrasion resistant steel

Abstract

The application discloses a method for producing ultra-low coiling temperature wear-resistant steel, and specifically comprises the following steps: S1, a rough rolling machine to a air cooling section of a finishing rolling machine, a heat preservation cover is arranged on an intermediate conveying roller way between the rough rolling machine and the finishing rolling machine to reduce the loss of temperature; S2, a finishing rolling section, by limiting the acceleration of the finishing rolling machine, the acceleration is reduced, thereby increasing the time of the strip steel in the cooling area, and the uniformity of the cooling temperature is achieved; S3, an ultra-fast cooling section, by adjusting the cooling water amount to improve the temperature drop of the ultra-fast cooling section, the strip steel realizes rapid cooling in the high temperature zone of the ultra-fast cooling section, the process temperature is reduced from the finish rolling temperature 850 DEG C to 400 DEG C, and the transformation of the structure and performance is realized; S4, the laminar flow cooling area is slowly cooled to the process coiling temperature 200 DEG C, and the structure and performance of the strip steel are stabilized. Through the combination control mode of the above processes, the performance requirements of the wear-resistant steel are achieved, and the method for low-cost production of the ultra-low coiling temperature wear-resistant steel is realized.

Description

Technical Field

[0001] This invention relates to the field of strip cooling technology, specifically a method for producing wear-resistant steel with ultra-low coiling temperature. Background Technology

[0002] In the hot rolling process, the process of setting the strip coiling temperature depends on the amount of alloying elements in the slab and the level of cooling control to achieve the ideal strip microstructure and properties, thereby enabling the development and mass production of special steel grades, such as wear-resistant steel with a coiling temperature of 200℃ after cooling.

[0003] Typically, improving the microstructure and properties of a product is achieved by adding alloying elements in the previous process, but this increases manufacturing costs significantly. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method for producing wear-resistant steel with ultra-low coiling temperature. By developing a medium-pressure cooling control mode and cooling strategy, and optimizing the speed control method of the finishing mill, the speed deviation of the strip at the beginning and end of the finishing mill is kept within the cooling control requirements. The ultra-fast cooling zone rapidly cools the strip to 400°C in the high-temperature section, and then cools it to the required coiling temperature of 200°C in the laminar flow zone, thus meeting the performance requirements of the wear-resistant steel after cooling and achieving the technical objective of low-cost production of wear-resistant steel.

[0005] To achieve the above-mentioned technical objectives, the present invention employs the following technical means:

[0006] A method for producing wear-resistant steel with ultra-low coiling temperature comprises four sections along the strip rolling direction on a rolling line: an air-cooling section from the roughing mill to the finishing mill, a finishing section, an ultra-rapid cooling section, and a laminar flow cooling section. The method specifically includes the following steps:

[0007] S1. In the air-cooling section from the roughing mill to the finishing mill, a heat insulation cover is installed on the intermediate conveyor roller table between the roughing mill and the finishing mill to reduce temperature loss.

[0008] S2. In the finishing mill section, by limiting the acceleration of the finishing mill, the acceleration is reduced, thereby increasing the time the strip spends in the cooling zone and achieving uniform cooling temperature.

[0009] S3. In the ultra-fast cooling section, the temperature drop of the ultra-fast cooling section is increased by adjusting the cooling water volume, so that the strip steel can be rapidly cooled in the high-temperature zone in the ultra-fast cooling section, and the process temperature is reduced from the final rolling temperature of 850℃ to 400℃±30℃, thereby realizing the transformation of microstructure and properties.

[0010] S4. The strip is cooled to the process coiling temperature of 200℃ through a laminar flow cooling zone to stabilize the microstructure and properties of the strip.

[0011] In step S1, the insulation cover ensures that the temperature difference between the head and tail of the strip is reduced to between 30°C and 40°C before finishing rolling.

[0012] In step S2, the finishing mill includes multiple finishing mill stands arranged sequentially along the strip running direction. The rolling acceleration of the finishing mill is limited to no more than 0.03% by controlling the speed of the rolls on different finishing mill stands.

[0013] Step S3 is as follows:

[0014] To develop an ultra-fast medium-pressure cooling control method, firstly, a new medium-pressure control program for the primary water treatment pump station is added. Secondly, the secondary model determines the type of steel. If it is wear-resistant steel, a medium-pressure mode is selected. Finally, the primary automation controls the number of valves opened and the water volume. The pump station adjusts the frequency of the variable frequency pump to achieve the required water output based on the given water volume.

[0015] Meanwhile, the cooling mode adopts a front-end cooling method.

[0016] A first high-temperature gauge for detecting the surface temperature of the strip after roughing is installed after the roughing mill;

[0017] A second high-temperature gauge for detecting the surface temperature of the steel strip before finishing rolling is provided before the finishing rolling section;

[0018] A third high-temperature gauge for detecting the surface temperature of the strip after final rolling is installed before the ultra-fast cooling section;

[0019] A fourth high-temperature gauge is installed between the ultra-fast cooling section and the laminar flow cooling section to detect the surface temperature of the strip after ultra-fast cooling;

[0020] A fifth pyrometer for detecting the winding temperature is provided after the laminar flow cooling section.

[0021] Beneficial effects:

[0022] First, this invention utilizes an ultra-fast medium-pressure cooling control method. Through primary automation control, it controls the number of valves opened and the water volume. The pump station adjusts the frequency of the variable frequency pump to achieve the required water output based on the given water volume. Simultaneously, the cooling mode employs a front-end cooling method, enabling the strip steel to achieve rapid cooling in the high-temperature zone of the ultra-fast cooling section. The process temperature is reduced from 850℃ to 400℃, resulting in a transformation of the microstructure and properties. This achieves the goal of replacing metal with water, thereby realizing the low-cost production of ultra-low curling temperature wear-resistant steel.

[0023] Second, the speed control of the finishing mill. As the temperature of the strip changes, the mill speed will accelerate. The lower the temperature, the greater the acceleration, which is not conducive to cooling control. By limiting the acceleration of the finishing mill, the acceleration can be reduced, thereby increasing the time of the strip in the cooling zone and achieving uniform cooling temperature. However, limiting the acceleration will cause the temperature drop at the tail of the strip to increase, and the load during the finishing mill rolling will increase, which can easily cause overcurrent tripping.

[0024] Third, based on the increased temperature drop at the tail of the strip after speed limiting, an insulation cover is used on the conveyor roller table between the roughing mill and the finishing mill to reduce the temperature drop when rolling this type of steel. The temperature difference between the head and tail is reduced from the original 80-90℃ to 40℃, thereby changing the risk of overcurrent tripping of the finishing mill and achieving stable rolling.

[0025] By combining and controlling the above processes, and rationally controlling the settings of each process, ultra-low temperature wear-resistant steel was successfully produced, its microstructure and properties were effectively improved, and the performance requirements of wear-resistant steel were met, thus achieving low-cost production of wear-resistant steel. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the steel strip and cooling line of the present invention;

[0027] Figure 2 This is a schematic diagram of the air-cooling section from the roughing mill to the finishing mill of the present invention;

[0028] Figure 3 This is a schematic diagram of the finishing mill section structure of the present invention;

[0029] Figure 4 This is a schematic diagram of the ultrafast cooling section and laminar flow cooling section of the present invention;

[0030] Among them, 1 is the roughing mill; 2 is the first pyrometer; 3 is the insulation cover; 4 is the second pyrometer; 5 is the finishing mill; 6 is the third pyrometer; 7 is the ultra-fast cooling section; 8 is the fourth pyrometer; 9 is the laminar flow cooling section; and 10 is the fifth pyrometer. Detailed Implementation

[0031] A method for producing wear-resistant steel with ultra-low coiling temperature is proposed. This method addresses the issue of the head section failing to cool to the process coiling temperature of 200℃ by developing an ultra-fast, medium-pressure cooling control system; it also solves the problem of temperature rise after acceleration at the tail section by adjusting the finishing mill rolling speed; and it addresses the instability caused by high rolling force at the tail section during finishing mill rolling by controlling the temperature drop between the roughing and finishing mills. Through systematic research, a control method suitable for the production of ultra-low temperature wear-resistant steel has been developed. The specific steps are as follows:

[0032] First, develop an ultra-fast cold medium-pressure cooling control method. First, add a primary and water treatment pump station medium-pressure control program. Second, the secondary model judges according to the steel type. If it is wear-resistant steel, the medium-pressure mode selection is given. Finally, the primary automatic control controls the number of valves opened and the water volume. The pump station adjusts the frequency of the variable frequency pump to achieve the output of water volume by giving the water volume.

[0033] Meanwhile, the cooling mode adopts a front-end cooling method, which enables the strip steel to be rapidly cooled in the high-temperature zone in the ultra-fast cooling section, reducing the process temperature from 850℃ to 400℃, thereby achieving the transformation of the microstructure and properties and realizing the goal of replacing gold with water.

[0034] Secondly, the speed control of the finishing mill is crucial. As the strip temperature changes, the mill speed will accelerate accordingly. The lower the temperature, the greater the acceleration, which is not conducive to cooling control. By limiting the acceleration of the finishing mill, the acceleration can be reduced, thereby increasing the time the strip spends in the cooling zone and achieving uniform cooling temperature. However, limiting the acceleration will cause the temperature drop at the tail of the strip to increase, which will increase the load during the finishing mill rolling and easily cause overcurrent tripping.

[0035] Third, reduce the temperature drop between the roughing mill and the finishing mill.

[0036] Due to the increased temperature drop at the tail of the strip after speed limiting, an insulation cover is used on the conveyor roller table between the roughing mill and the finishing mill to reduce the temperature drop when rolling this type of steel. The temperature difference between the head and tail is reduced from the original 80-90℃ to 40℃, thereby changing the risk of overcurrent tripping of the finishing mill and achieving stable rolling.

[0037] Figure 2 It is an intermediate conveyor roller table between V2DT and FET. Under normal circumstances, the temperature drop of the strip head and tail is 80-90℃. The tail end relies on the acceleration set by the finishing mill to ensure rolling stability. However, due to the relatively short effective cooling length of the laminar flow cooling in this invention, the strip time in the cooling zone is reduced after high acceleration, and the tail temperature shows an upward trend. It is impossible to guarantee the microstructure and properties of the wear-resistant steel tail end. Therefore, in order to reduce the aggravation of the tail temperature drop, an insulation cover is used on the intermediate conveyor roller table to reduce temperature loss and ensure that the head and tail temperature difference is 40℃ to ensure the rolling stability of the finishing mill.

[0038] Optimize the acceleration control of the finishing mill to provide a prerequisite for cooling.

[0039] The present invention will be further described in conjunction with specific embodiments:

[0040] The hot rolling production process in a certain factory begins with heating the slab in a furnace, followed by rolling on a roughing mill and a finishing mill, then cooling in a cooling zone, and finally coiling into coils using a coiler. When rolling wear-resistant steel with ultra-low coiling temperatures, the key challenge lies in adjusting the cooling zone settings. When the cooling zone valves are fully open to maximize cooling capacity, a holistic approach considering the preceding processes is necessary; otherwise, the ultra-low coiling temperature of the wear-resistant steel will not meet control requirements. This production line has developed the following optimization scheme through research:

[0041] On the intermediate roller table between the roughing mill and the finishing mill, heat insulation covers are used to reduce the temperature drop at the tail of the strip. The temperature at the tail of the strip can be increased by 40-50°C, which reduces the increase in rolling load and speed at the tail of the finishing mill.

[0042] Under the premise of meeting the final rolling process temperature, the acceleration of the finishing rolling is adjusted from the original 0.07% to 0.03% to reduce the change in acceleration and increase the time of the strip in the cooling zone, thus providing a good prerequisite for cooling control.

[0043] The control mode of the cooling zone is optimized by developing a medium-pressure cooling mode. Specifically, the set pressure and water volume of the secondary model system are used to control the opening of the valves in the primary automation field. The primary automation then provides real-time frequency increase to the ultra-fast cooling pumps to adjust the water volume. Simultaneously, three ultra-fast cooling pumps are activated in the medium-pressure cooling mode to increase the water volume. At the same time, the cooling mode adopts a front-end cooling method, which allows the strip steel to be rapidly cooled in the high-temperature section through the ultra-fast cooling zone, reducing the process temperature from 850℃ to 400℃, thereby changing the microstructure and properties and achieving the goal of replacing metal with water. Then, the strip steel is cooled slowly to the process coiling temperature of 200℃ through the laminar flow cooling zone, stabilizing the microstructure and properties of the strip steel.

[0044] By combining and controlling the above processes, and rationally controlling the settings of each process, ultra-low temperature wear-resistant steel was successfully produced, and its microstructure and properties were effectively improved, meeting the performance requirements of wear-resistant steel. This demonstrated a successful method for producing wear-resistant steel through ultra-low temperature cooling control.

Claims

1. A method for producing wear-resistant steel with ultra-low coiling temperature, comprising four sections along the strip rolling direction on a rolling line: an air-cooling section from a roughing mill to a finishing mill, a finishing section, an ultra-fast cooling section, and a laminar flow cooling section, characterized in that... Specifically, the following steps are included: S1. In the air-cooling section from the roughing mill to the finishing mill, a heat insulation cover is installed on the intermediate conveyor roller table between the roughing mill and the finishing mill to reduce temperature loss. S2. In the finishing mill section, by limiting the acceleration of the finishing mill, the acceleration is reduced, thereby increasing the time the strip spends in the cooling zone and achieving uniform cooling temperature. S3. In the ultra-fast cooling section, the temperature drop of the ultra-fast cooling section is increased by adjusting the cooling water volume, so that the strip steel can be rapidly cooled in the high-temperature zone in the ultra-fast cooling section, and the process temperature is reduced from the final rolling temperature of 850℃ to 400℃±30℃, thereby realizing the transformation of microstructure and properties. S4. The strip steel is cooled to the process coiling temperature of 200℃ through the slow cooling method of the laminar flow cooling section to stabilize the microstructure and properties of the strip. In step S1, the insulation cover ensures that the temperature difference between the head and tail of the strip is reduced to between 30°C and 40°C before finishing rolling. In step S2, the finishing mill includes multiple finishing mill stands arranged sequentially along the strip running direction. The rolling acceleration of the finishing mill is limited to no more than 0.03% by controlling the speed of the rolls on different finishing mill stands. Step S3 specifically involves developing an ultra-fast medium-pressure cooling control method. First, a new medium-pressure control program for the primary water treatment pump station is added. Second, the secondary model determines the type of steel. If it is wear-resistant steel, a medium-pressure mode selection is given. Finally, the primary automation controls the number of valves opened and the water volume. The pump station adjusts the frequency of the variable frequency pump to achieve the required water output based on the given water volume. At the same time, the cooling mode adopts a front-end cooling method. A first high-temperature gauge for detecting the surface temperature of the strip after roughing is installed after the roughing mill; A second high-temperature gauge for detecting the surface temperature of the strip before finishing rolling is provided before the finishing rolling section; A third high-temperature gauge for detecting the surface temperature of the strip after final rolling is installed before the ultra-fast cooling section. A fourth high-temperature gauge is installed between the ultra-fast cooling section and the laminar flow cooling section to detect the surface temperature of the strip after ultra-fast cooling; A fifth pyrometer for detecting the winding temperature is installed after the laminar flow cooling section.

Images