Method for reducing the production of rotten steel in the rolling process of threaded steel

Abstract

The application discloses a method for reducing the generation of rotten steel of threaded steel in a rolling process. The method comprises the following steps: a refining process: a temperature drop detection device is arranged to detect the temperature drop of molten steel in a refining furnace; if the temperature drop is lower than or higher than 0.5-1.5 DEG C / min, the molten steel is subjected to temperature rising treatment through an automatic control system; if the temperature drop is within 0.5-1.5 DEG C / min, the molten steel is made to leave the station and enter a continuous casting process through the automatic control system; and the continuous casting process: after the molten steel is solidified and crystallized in a crystallizer, a square billet is obtained; and when the crystallizer pulling speed is adjusted, the single adjustment pulling speed is less than 0.3 m / min, and the time interval of the continuous adjustment pulling speed is greater than or equal to 30 s. According to the embodiment of the application, the generation of rotten steel of threaded steel in the rolling process can be reduced, and the production efficiency is improved.

Description

Technical Field

[0001] This application belongs to the field of metallurgical technology, and in particular relates to a method for reducing the generation of scrap steel during the rolling process of rebar. Background Technology

[0002] With the rapid development of the steel industry, factories are becoming increasingly strict in controlling the production costs of rebar, which has led to increasing attention being paid to the rolling process of rebar.

[0003] If the billet cracks in the center during the rolling process, it will block the rolling passes, thus affecting rolling efficiency and increasing production costs. Summary of the Invention

[0004] This application provides a method for reducing the occurrence of scrap steel during the rolling process of rebar, which can reduce the number of times scrap steel is generated during the rolling process and improve production efficiency.

[0005] This application provides a method for reducing the generation of scrap steel during the rolling process of rebar, including an automated control system and a casting and rolling process. The casting and rolling process includes a refining process, a continuous casting process, and a bar forming process. In the refining process, a temperature drop detection device is installed to detect the temperature drop of the molten steel in the refining furnace. If the temperature drop is less than 0.5 ℃ / min or greater than 1.5 ℃ / min, the molten steel is heated by the automated control system. If the temperature drop is within 0.5-1.5 ℃ / min, the molten steel is discharged from the station and enters the continuous casting process by the automated control system. In the continuous casting process, the molten steel is solidified and crystallized in a crystallizer to obtain a billet. When adjusting the crystallizer speed, the automated control system controls the single speed adjustment to be less than 0.3 m / min, and the time interval for continuous speed adjustments to be ≥30 s. In the bar forming process, the billet is processed by rolls and a flying shear to obtain rebar.

[0006] In any embodiment of this application, during the refining process, the superheat of the molten steel exiting the station is greater than 45°C.

[0007] In any embodiment of this application, during the refining process, if the temperature drop is less than 0.5 ℃ / min or more than 1.5 ℃ / min, the temperature rises to 1555-1580 ℃.

[0008] In any embodiment of this application, during the refining process, the superheat of the molten steel at the station exit is 40-56 ℃.

[0009] In any embodiment of this application, the casting speed is adjusted to 0.20-0.30 m / min in a single continuous casting process.

[0010] In any embodiment of this application, the casting speed is adjusted to 0.20-0.22 m / min in a single continuous casting process.

[0011] In any embodiment of this application, the time interval for continuously adjusting the casting speed in the continuous casting process is 30-36 s.

[0012] In any embodiment of this application, the time interval for continuously adjusting the casting speed in the continuous casting process is 32-36 s.

[0013] In any embodiment of this application, in the continuous casting process, the billet is a 165mm*165mm billet.

[0014] The method for reducing scrap steel generated during the rolling process of rebar in this application embodiment can effectively ensure that the scrap steel in the molten steel is completely melted in the refining process, and can reduce the amount of slag in the continuous casting process, thereby reducing the number of times the rebar is scrapped and improving production efficiency. Detailed Implementation

[0015] To better understand the above-mentioned objectives, features, and advantages of this application, the solution of this application will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0016] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of this application, and not all embodiments.

[0017] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0018] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0019] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0020] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0021] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0022] Unless otherwise specified, this application uses conventional testing methods or testing methods recommended by the instrument.

[0023] Continuous casting is a core process in modern steel production. Its complex operating conditions, influenced by various uncertainties such as steel composition, temperature, operating conditions, equipment status, and casting abnormalities, result in significant unpredictable fluctuations in the continuous casting process. For example, if a heat arrives at the continuous casting machine prematurely or late, a time disturbance occurs, leading to "casting interruptions" or excessively long waiting times for molten steel in the ladle, causing a drop in steel temperature and severely impacting the continuous casting machine's efficiency and billet quality. Currently, when time disturbances occur, the existing method involves dispatchers manually adjusting the continuous casting machine's settings based on the disturbance, determining the adjusted casting speed, and then the machine operator checks the water meter to set the cooling water volume accordingly.

[0024] When the casting speed fluctuates significantly, the slag droplets flowing from the submerged entry nozzle of the crystallizer split into an upward and downward flow after reaching the narrow face of the crystallizer. If the slag droplets cannot return to the slag and are instead carried into the depths of the molten steel pool or captured by the solidified billet shell, they will be drawn into the molten steel, causing slag entrapment. When the interval between speed adjustments is too short, it will exacerbate the fluctuations in the crystallizer surface caused by the previous speed adjustment, resulting in slag entrapment.

[0025] This application improves production efficiency by adding a temperature drop detection device in the refining process to ensure that the scrap steel in the molten steel is completely melted; and by specifying the time interval between single and continuous speed adjustments in the continuous casting process to reduce slag entrapment and the number of scrap steel pieces in rebar.

[0026] Methods to reduce the production of scrap steel during the rolling process of rebar. A method for reducing scrap steel generation during rebar rolling includes an automated control system and a casting and rolling process. The casting and rolling process includes a refining process, a continuous casting process, and a bar forming process. In the refining process, a temperature drop detection device is installed to monitor the temperature drop of the molten steel in the refining furnace. If the temperature drop is less than 0.5 ℃ / min or greater than 1.5 ℃ / min, the molten steel is heated by the automated control system. If the temperature drop is within 0.5-1.5 ℃ / min, the molten steel is discharged from the furnace and enters the continuous casting process by the automated control system. In the continuous casting process, the molten steel is solidified in a crystallizer to obtain a billet. When adjusting the crystallizer casting speed, the automated control system controls the single speed adjustment to be less than 0.3 m / min, and the time interval for continuous speed adjustments to be ≥30 s. In the bar forming process, the billet is processed by rolls and a flying shear to obtain rebar. The automated control system includes a basic automation system and a secondary process control system. The basic automation system mainly consists of a PLC (Programmable Logic Controller) and a DCS (Distributed Control System). It collects instrument data and equipment status signals for logic control and loop control of the equipment (control of switching quantities and loop control of continuously measurable simple physical parameters, such as temperature, pressure, and flow), and transmits the data and signals to the secondary process control system. In addition, the basic automation system receives the setpoint data from the secondary process control system and controls the equipment to achieve the control objectives based on this data. The secondary process control system refers to the higher-level functional part of the automation control system, used to implement more complex control functions. For example, target hit control in the manufacturing processes of finished and semi-finished products in steel production, such as the thickness control of coils in a hot rolling mill, and the final chemical composition and final temperature control of molten steel in a steelmaking converter, requires the use of mathematical models in the secondary process control system to significantly improve the hit rate of the control objectives. Temperature drop refers to the decrease in temperature per unit time. When scrap steel melts in molten steel, the temperature of the molten steel drops significantly because melting is an endothermic process. Therefore, the temperature drop of the molten steel can be used to detect the degree of melting of the scrap steel. Within this range, the time interval between single and continuous speed adjustments can reduce slag entrapment in continuous casting and decrease the frequency of broken rebar. In the bar milling process, rolls and flying shears need to be replaced and maintained regularly. If the rolls are working normally but the flying shear requires maintenance, production should not be carried out during the flying shear maintenance period due to production schedule constraints.

[0027] In some embodiments, during the refining process, the superheat of the molten steel leaving the station is greater than 45 °C. Superheat refers to the difference between the test temperature of the molten steel leaving the station and the liquidus line. The liquidus line generally refers to the temperature at the intersection of the solid and liquid states of molten steel. To ensure the accuracy of the temperature test, the molten steel temperature at the station needs to be tested once before soft blowing and once after soft blowing, with the temperature difference between the two tests being less than 5 °C.

[0028] In some embodiments, during the refining process, if the temperature drop is less than 0.5 °C / min or more than 1.5 °C / min, the temperature rises to 1555-1580 °C. At this temperature, unmelted scrap steel can be remelted.

[0029] In some embodiments, during the refining process, the superheat of the molten steel exiting the station is 40-56 °C. This range of superheat ensures continuous casting castability and stabilizes the production schedule.

[0030] In some embodiments, the casting speed is adjusted to 0.20-0.30 m / min per cycle during the continuous casting process. Adjusting the casting speed within this range can reduce slag entrapment during continuous casting, thereby reducing the number of times the rebar is damaged.

[0031] In some embodiments, during the continuous casting process, the single-time casting speed adjustment is 0.20-0.22 m / min. Adjusting the casting speed within this range reduces slag entrapment during continuous casting, thereby reducing the frequency of broken rebar. In some embodiments, during the continuous casting process, the time interval for continuous speed adjustment is 30-36 s. This time interval also reduces slag entrapment during continuous casting, further reducing the frequency of broken rebar.

[0032] In some embodiments, the time interval for continuously adjusting the casting speed during the continuous casting process is 32-36 seconds. Within this range, adjusting the casting speed continuously can reduce slag entrapment during continuous casting, thereby reducing the number of times the rebar is damaged.

[0033] In some embodiments, the billet in the continuous casting process is a 165mm*165mm square billet. A six-strand continuous casting machine is used for casting and rolling.

[0034] Example 1 Refining process: The scrap steel and the molten steel that has been initially refined in a converter, open hearth furnace or electric furnace are transferred to the refining furnace for refining. The temperature of the molten steel is raised to 1560 ℃. After soft blowing for three minutes, the temperature is measured again at 1556 ℃. The temperature difference between the two measurements is 4 ℃. The temperature drop of the molten steel is 1.3 ℃ / min, and the superheat is 49 ℃, so that the molten steel can be discharged from the station.

[0035] Continuous casting process: After molten steel enters the ladle, it passes through the tundish and the crystallizer to obtain a square billet. When adjusting the casting speed in the crystallizer, the single change in casting speed is 0.3 m / min, and the interval between changes in casting speed is 30 s.

[0036] Bar stock processing: The billet is rolled and sheared to obtain rebar.

[0037] Tests showed that the rebar rolling process went smoothly and the finished product had no surface defects.

[0038] Table 1 Specific process parameters for Example 1 Example 2 The experimental steps were the same as in Example 1, except that the specific process parameters were changed to obtain rebar.

[0039] Tests showed that the rebar rolling process went smoothly and the finished product had no surface defects.

[0040] Table 2 Specific process parameters for Example 2 Example 3 The experimental steps were the same as in Example 1, except that the specific process parameters were changed to obtain rebar.

[0041] Tests showed that the rebar rolling process went smoothly and the finished product had no surface defects.

[0042] Table 3 Specific process parameters for Example 3 Example 4 The experimental steps were the same as in Example 1, except that the specific process parameters were changed to obtain rebar.

[0043] Tests showed that the rebar rolling process went smoothly and the finished product had no surface defects.

[0044] Table 4 Specific process parameters for Example 4 Example 5 The experimental steps were the same as in Example 1, except that the specific process parameters were changed to obtain rebar.

[0045] Tests showed that the rebar rolling process went smoothly and the finished product had no surface defects.

[0046] Table 5 Specific process parameters for Example 5 Example 6 The experimental steps were the same as in Example 1, except that the specific process parameters were changed to obtain rebar.

[0047] Tests showed that the rebar rolling process went smoothly and the finished product had no surface defects.

[0048] Table 6 Specific process parameters for Example 6 Example 7 The experimental steps were the same as in Example 1, except that the specific process parameters were changed to obtain rebar.

[0049] Tests showed that the rebar rolling process went smoothly and the finished product had no surface defects.

[0050] Table 7 Specific process parameters for Example 7 As can be seen from the above seven examples, by controlling the refining temperature, changing the continuous casting speed, and maintaining the bar mill equipment, the rate of scrap steel can be effectively reduced and production efficiency improved.

[0051] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A method for reducing the generation of scrap steel during the rolling process of rebar, comprising an automated control system and a casting and rolling process, wherein the casting and rolling process includes a refining process, a continuous casting process, and a bar forming process, characterized in that, Refining process: A temperature drop detection device is installed to detect the temperature drop of molten steel in the refining furnace. If the temperature drop is less than 0.5 ℃ / min or more than 1.5 ℃ / min, the molten steel is heated through the automatic control system to a temperature of 1555-1580 ℃. If the temperature drop is within 0.5-1.5 ℃ / min, the molten steel is discharged from the station and enters the continuous casting process through the automatic control system. The superheat of the molten steel at the station is 40-56 ℃. Continuous casting process: After the above molten steel is solidified and crystallized in a crystallizer, a square billet is obtained. When adjusting the crystallizer casting speed, the automatic control system controls the single adjustment of the casting speed to be less than 0.3 m / min and the time interval of continuous adjustment of the casting speed to be ≥30 s. Bar stock processing: The above-mentioned billet is processed by rolling mills and flying shears to obtain rebar.

2. The method according to claim 1, characterized in that, In the continuous casting process, the casting speed is adjusted to 0.20-0.22 m / min per cycle.

3. The method according to claim 1, characterized in that, In the continuous casting process, the time interval for continuously adjusting the casting speed is 30-36 seconds.

4. The method according to claim 1 or 2, characterized in that, In the continuous casting process, the time interval for continuously adjusting the casting speed is 32-36 seconds.

5. The method according to claim 1, characterized in that, In the continuous casting process, the billet is a 165mm × 165mm billet.

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