A method for improving the service life of crystallizer nozzle

Abstract

The present application provides a method for improving the service life of a crystallizer nozzle, which relates to the field of metallurgical continuous casting technology and includes the following steps: Step 1: Initializing the pouring and nozzle protection system, and determining nozzle protection related parameters based on on-site process data; Step 2: Calculating the upward and downward changes in the nozzle protection system; Step 3: Enabling asymmetric trapezoidal wave control to adjust the upper limit of the liquid level; Step 4: Adjusting the lower limit of the liquid level; Step 5: Adjusting the recovery of the liquid level; Repeating steps 3, 4, and 5 until the crystallizer is stopped. The present invention achieves precise control of the nozzle slag line position and uniform erosion by adopting an asymmetric trapezoidal wave control model, effectively avoiding the ")" type uneven erosion problem, effectively extending the service life of the nozzle, increasing the number of continuous casting furnaces, and reducing the cost of refractory material consumption.

Description

Technical Field

[0001] The present application relates to the field of metallurgical continuous casting technology, and in particular to a method for improving the service life of a crystallizer nozzle. Background Art

[0002] In the continuous casting process, changing the slab water inlet is the most important step. The existing submerged water inlet is located between the tundish and the crystallizer. By controlling the flow state and injection speed of the molten steel, it can effectively prevent the secondary oxidation and splashing of the molten steel in the air, and can protect the stable operation of the casting system. However, during the continuous casting process, it is often corroded by the protective slag and molten steel, resulting in a shortened service life.

[0003] To extend the service life of submerged nozzles, steel mills currently use nozzle protection systems. These systems adjust the position of the nozzle's slag line within the mold, changing the contact area between the nozzle and the mold slag to achieve uniform erosion distribution. However, existing nozzle protection systems suffer from numerous technical drawbacks: their sinusoidal wave control model makes it difficult to avoid technical issues such as uneven nozzle erosion and a short service life. These technical limitations not only fail to achieve the desired goal of extending nozzle life, but can also cause quality issues such as slab cracking and steel leakage due to adhesion, posing process risks and economic losses to continuous casting production. Summary of the Invention

[0004] The present application is made in view of the above-mentioned problems, and its purpose is to provide a method for improving the service life of the crystallizer nozzle. An asymmetric trapezoidal wave control model is adopted to achieve precise control and uniform erosion of the nozzle slag line position, so that the nozzle slag line position changes uniformly, effectively avoiding the ")" type uneven erosion problem caused by the traditional sine wave. Compared with the sine wave control model, it can effectively extend the service life of the nozzle, increase the number of continuous casting furnaces, and reduce the refractory consumption cost.

[0005] Specifically, a first aspect of the present application provides a method for improving the service life of a crystallizer nozzle, comprising the following steps:

[0006] Step 1: Start pouring and initialize the nozzle protection system. Determine the nozzle protection offset value ±A, the overall downward offset value B of the asymmetric trapezoidal nozzle protection, and the nozzle protection period T based on the process data.

[0007] The nozzle protection period T needs to wait until the liquid level is amplified and is approximately a straight line, which is generally more than 120 minutes. The value of T needs to make the calculated value of [the smelting period of a furnace of molten steel (generally 40 minutes) × the number of pouring times and continuous pouring furnaces / nozzle protection period] as equal to an integer as possible to ensure that the nozzle slag line position is as evenly distributed as possible during the total production cycle.

[0008] Casting refers to the process of smoothly introducing refined molten steel from the tundish into the crystallizer for casting during the steel production process.

[0009] The mold is the core component of the continuous casting machine. Its primary function is to control the flow of molten steel and ensure a uniform shell during solidification. The flow pattern within the mold directly impacts the quality of the cast strand, including liquid level fluctuations, flow velocity distribution, and the flotation of inclusions. Uneven flow patterns or excessive liquid level fluctuations within the mold can lead to surface defects such as cracks and slag inclusions. The mold's design and operating parameters (such as taper and cooling water distribution) require careful adjustment to ensure a smooth solidification of the molten steel into a shell.

[0010] The submerged nozzle is located between the tundish and the crystallizer. By controlling the flow state and injection speed of the molten steel, it can effectively prevent the secondary oxidation and splashing of the molten steel in the air, and can protect the stable operation of the casting system.

[0011] Step 2: Calculate the upward and downward changes of the nozzle protection system, which are (AB) and (-(A+B)).

[0012] Step 3: Enable asymmetric trapezoidal wave control to adjust the upper limit of the liquid level;

[0013] Traditional sinusoidal vibration control improves the flow of molten steel and reduces breakouts and vibration marks by vibrating the mold up and down at a specific amplitude and frequency. However, sinusoidal vibration has limitations. For example, it is less effective at low casting speeds and cannot completely eliminate breakouts and vibration marks.

[0014] Step 4: Adjust the lower limit of the liquid level;

[0015] Step 5: Perform liquid level recovery adjustment;

[0016] Step 6: Repeat steps 3, 4, and 5 until the crystallizer is no longer in use.

[0017] Furthermore, the process data specifically include: the total range R of the liquid level detection system, the optimal point S% of linearity and the corrosion resistance area range of the nozzle.

[0018] The total range R of the liquid level detection system is related to the device of the detection system and is generally 150mm~200mm.

[0019] Furthermore, the optimal linearity point S% is the optimal point of measurement linearity of the liquid level detection system, which is generally 70% to 80% of the total range R of the liquid level detection system.

[0020] The best linearity of the liquid level detection system is generally 70%~80% of the total range R of the detection system, and the height from the copper tube mouth of the crystallizer is generally 80~100mm.

[0021] Furthermore, the nozzle protection offset value ±A is the offset of the actual molten steel moving up and down at the linearity optimal point S%, which needs to ensure that the upper and lower limit thresholds of the molten steel are still in the corrosion resistance area of ​​the nozzle.

[0022] The upper threshold of molten steel is S%×R+A, and the lower threshold is S%×RA. It is necessary to meet the upper and lower thresholds of the molten steel and still be in the erosion-resistant area of ​​the nozzle. The erosion-resistant area of ​​the nozzle is generally 60mm~180mm above the nozzle outlet. In order to make the quality of the steel billet more consistent, the steel mill generally controls the difference in nozzle insertion depth under different conditions (different nozzles, different furnace steel), and keeps the change range of the molten steel within 30mm. Therefore, the value of A is generally calculated as 2A+liquid slag layer thickness+liquid level fluctuation amplitude ≤30mm.

[0023] Furthermore, the overall downward offset value B of the asymmetric trapezoidal nozzle protection is the overall downward offset of the upper and lower limit thresholds after the asymmetric nozzle protection is enabled for the molten steel. The upper and lower limit thresholds of the molten steel after the offset must remain in the corrosion-resistant area of ​​the nozzle and erode the optimal linearity point S% as little as possible. The value range is 3mm~5mm.

[0024] The upper limit threshold of the molten steel after the shift is S%×R+AB, and the lower limit threshold of the molten steel after the shift is S%×R-(A+B). The upper and lower limit thresholds of the molten steel after the shift must still be within the corrosion-resistant area of ​​the nozzle.

[0025] Furthermore, the adjustment climbing time of the liquid level: upper limit holding time: lower limit holding time = 1: 0.9~1.1: 0.9~1.1.

[0026] Furthermore, the slope of the change in the molten steel level for adjusting the ramp time is (2A) / (T / 6).

[0027] Furthermore, the upper limit adjustment is specifically to use the linearity optimal point S% of the liquid level detection system plus the upward change as the upper limit threshold value A1 of the trapezoidal wave control liquid level, and adjust the liquid level to reach A1 within T / 18 time and maintain it for T / 3 time.

[0028] Furthermore, the lower limit adjustment is specifically to use the linearity optimal point S% of the liquid level detection system plus the downward change as the lower limit threshold A2 of the trapezoidal wave control liquid level, and adjust the liquid level to reach A2 within T / 6 time and maintain it for T / 3 time.

[0029] Furthermore, the recovery adjustment is specifically to adjust the liquid level to return to the optimal linearity point S% of the liquid level detection system within T / 9 time.

[0030] Furthermore, the upper limit of the liquid level cannot be higher than the upper limit alarm value of the system, and the lower limit of the liquid level cannot be lower than the lower limit alarm value of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present drawings or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present drawings. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0032] Figure 1 is a flow chart of the steps of the present invention;

[0033] Figure 2 A variation control diagram of an asymmetric trapezoidal wave control model according to an embodiment of the present invention;

[0034] Figure 3 Schematic diagram of nozzle erosion according to an embodiment of the present invention.

[0035] The purpose, features and advantages of this drawing will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is described and illustrated below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely used to explain this application and are not intended to limit this application. Based on the embodiments provided in this application, all other embodiments obtained by those of ordinary skill in the art without making any creative efforts are within the scope of protection of this application.

[0037] Obviously, the drawings described below are merely examples or embodiments of the present application. Those skilled in the art can, without inventive effort, apply the present application to other similar scenarios based on these drawings. Furthermore, it is also understood that, although the effort involved in such a development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, changes in design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as an insufficiency of the content disclosed in this application.

[0038] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0039] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0040] Unless otherwise specified, all steps of the present 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 may include steps (b) and (a) performed sequentially. For example, the method may further 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 may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0041] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0042] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0043] In order to better understand the solutions of the embodiments of the present application, some relevant terms and concepts that may be involved in the embodiments of the present application are first introduced below.

[0044] (1) The crystallizer is a device used to solidify molten steel in a continuous casting machine. It is usually a rectangular or cylindrical container with a cooling system inside. It controls the cooling intensity to affect the solidification rate of the molten steel and the shape of the ingot. The design and operating parameters of the crystallizer directly affect the surface quality and internal structure of the ingot. The main function is to control the flow state of the molten steel to ensure that the molten steel forms a uniform ingot shell during the solidification process. The flow state of the molten steel in the crystallizer directly affects the quality of the ingot, including the liquid level fluctuation, flow rate distribution and the floating of inclusions. If the flow field in the crystallizer is uneven or the liquid level fluctuation is too large, it may cause defects such as cracks and slag inclusions on the surface of the ingot.

[0045] (2) The submerged nozzle is an important channel connecting the tundish and the crystallizer. It is usually installed at the bottom of the tundish and inserted below the steel liquid level in the crystallizer. Its main function is to prevent secondary oxidation of the molten steel, control the flow rate of the molten steel when it enters the crystallizer, and promote the floating of inclusions in the molten steel. The design of the submerged nozzle includes its shape, size, material and insertion depth, etc. These factors will have a significant impact on the flow field and temperature field in the crystallizer. For example, the shape of the nozzle (such as straight hole, concave, convex, etc.) will affect the stability of the molten steel flow, while the insertion depth of the nozzle will affect the liquid level fluctuation and the occurrence of slag roll-up.

[0046] (3) Mold sine wave control refers to optimizing the quality of the ingot and improving production efficiency by controlling the waveform of the mold vibration to a sinusoidal wave during the continuous casting process. Sine wave vibration is a common form of vibration characterized by constant frequency and amplitude. It is typically used to reduce the depth and spacing of vibration marks on the surface of the ingot, thereby improving the surface quality of the ingot.

[0047] In this embodiment, Figure 1 As shown, a method for improving the service life of a crystallizer nozzle comprises the following steps:

[0048] Step 1: Start pouring and initialize the nozzle protection system. Determine the nozzle protection offset value ±A, the overall downward offset value B of the asymmetric trapezoidal nozzle protection, and the nozzle protection period T based on the on-site process data.

[0049] The nozzle protection period T needs to wait until the liquid level is amplified and is approximately a straight line, which is generally more than 120 minutes. The value of T needs to make the calculated value of [the smelting period of a furnace of molten steel (generally 40 minutes) × the number of pouring times and continuous pouring furnaces / nozzle protection period] as equal to an integer as possible to ensure that the nozzle slag line position is as evenly distributed as possible during the total production cycle.

[0050] Casting refers to the process of smoothly introducing refined molten steel from the tundish into the crystallizer for casting during the steel production process.

[0051] The mold is the core component of the continuous casting machine. Its primary function is to control the flow of molten steel and ensure a uniform shell during solidification. The flow pattern within the mold directly impacts the quality of the cast strand, including liquid level fluctuations, flow velocity distribution, and the flotation of inclusions. Uneven flow patterns or excessive liquid level fluctuations within the mold can lead to surface defects such as cracks and slag inclusions. The mold's design and operating parameters (such as taper and cooling water distribution) require careful adjustment to ensure a smooth solidification of the molten steel into a shell.

[0052] The submerged nozzle is located between the tundish and the crystallizer. By controlling the flow state and injection speed of the molten steel, it can effectively prevent the secondary oxidation and splashing of the molten steel in the air, and can protect the stable operation of the casting system.

[0053] Step 2: Calculate the upward and downward changes of the nozzle protection system, which are (AB) and (-(A+B)).

[0054] Step 3: Enable asymmetric trapezoidal wave control to adjust the upper limit of the liquid level;

[0055] Traditional sinusoidal vibration control improves the flow of molten steel and reduces breakouts and vibration marks by vibrating the mold up and down at a specific amplitude and frequency. However, sinusoidal vibration has limitations. For example, it is less effective at low casting speeds and cannot completely eliminate breakouts and vibration marks.

[0056] Step 4: Adjust the lower limit of the liquid level;

[0057] Step 5: Perform liquid level recovery adjustment;

[0058] Step 6: Repeat steps 3, 4, and 5 until the crystallizer is no longer in use.

[0059] Furthermore, the on-site process data specifically includes: the total range R of the liquid level detection system, the optimal point S% of linearity and the corrosion-resistant area range of the water outlet.

[0060] The total range R of the liquid level detection system is related to the device of the detection system, and is 180 mm in this embodiment.

[0061] Furthermore, the optimal linearity point S% is the optimal point of measurement linearity of the liquid level detection system, which is generally 70% to 80% of the total range R of the liquid level detection system.

[0062] In this embodiment, the best advantage of the measurement linearity of the liquid level detection system is that the total range R of the detection system is 75%, and the height from the copper tube mouth of the crystallizer is 100 mm.

[0063] Furthermore, the nozzle protection offset value ±A is the offset of the actual molten steel moving up and down at the linearity optimal point S%, which needs to ensure that the upper and lower limit thresholds of the molten steel are still in the corrosion resistance area of ​​the nozzle.

[0064] The upper threshold of molten steel is S%×R+A, and the lower threshold is S%×RA. It is necessary to meet the upper and lower thresholds of the molten steel and still be in the erosion resistance area of ​​the nozzle. The erosion resistance area of ​​the nozzle is 60mm~180mm above the nozzle outlet. In order to make the quality of the steel billet more consistent, the steel mill generally controls the difference in nozzle insertion depth under different conditions (different nozzles, different furnace steel) and keeps the change range of molten steel within 30mm. Therefore, the value of A is generally calculated as 2A+liquid slag layer thickness+liquid level fluctuation amplitude ≤30mm.

[0065] Furthermore, the overall downward offset value B of the asymmetric trapezoidal nozzle protection is the overall downward offset of the upper and lower limit thresholds after the asymmetric nozzle protection is enabled for the molten steel. The upper and lower limit thresholds of the molten steel after the offset must remain in the corrosion-resistant area of ​​the nozzle and erode the optimal linearity point S% as little as possible. In this embodiment, the value is 3mm.

[0066] The upper limit threshold of the molten steel after the shift is S%×R+AB, and the lower limit threshold of the molten steel after the shift is S%×R-(A+B). The upper and lower limit thresholds of the molten steel after the shift must still be within the corrosion-resistant area of ​​the nozzle.

[0067] Furthermore, the liquid level adjustment climbing time: upper limit holding time: lower limit holding time = 1:1:1.

[0068] Furthermore, the slope of the change in the molten steel level for adjusting the ramp time is (2A) / (T / 6).

[0069] Furthermore, the upper limit adjustment is specifically to use the linearity optimal point S% of the liquid level detection system plus the upward change as the upper limit threshold value A1 of the trapezoidal wave control liquid level, and adjust the liquid level to reach A1 within T / 18 time and maintain it for T / 3 time.

[0070] Furthermore, the lower limit adjustment is specifically to use the linearity optimal point S% of the liquid level detection system plus the downward change as the lower limit threshold A2 of the trapezoidal wave control liquid level, and adjust the liquid level to reach A2 within T / 6 time and maintain it for T / 3 time.

[0071] Furthermore, the recovery adjustment is specifically to adjust the liquid level to return to the optimal linearity point S% of the liquid level detection system within T / 9 time.

[0072] Furthermore, the upper limit of the liquid level cannot be higher than the upper limit alarm value of the system, and the lower limit of the liquid level cannot be lower than the lower limit alarm value of the system.

[0073] In this embodiment, the process conditions of the steel plant are that the thickness of the liquid slag layer is 6 mm, and the liquid level fluctuation range is ±3 mm (that is, the liquid level fluctuation amplitude is 6 mm). Therefore, A≤(30 mm–6 mm–6 mm) / 2 = 9 mm. In this embodiment, A is 9 mm, R=180 mm; S%=75%, T=60 min, ±A =±9 mm, B=3 mm, the upward change in liquid level height is A1=AB=6 mm, the downward change in liquid level height is A2=-(A+B)=-12 mm, the optimal linear point position of the molten steel is S%×R=135 mm, the upper limit threshold of the molten steel is S%×R+A=144 mm, and the lower limit threshold is S%×RA=126 mm. After the asymmetric nozzle protection is enabled, the upper and lower limit thresholds are shifted downward as a whole. After the shift, the upper limit threshold of the molten steel is S%×R+AB =141mm, the lower limit threshold after offset is S%×R-(A+B)=123mm, the variation control diagram of the asymmetric trapezoidal wave control model is as follows Figure 2 As shown, the erosion curve after the nozzle protection by the asymmetric trapezoidal wave control of this embodiment is as follows Figure 3 As shown, Figure 3 In the figure, the left side shows the actual erosion situation, the right side shows the ideal erosion situation, and the arrow is the position of the optimal point of linearity. Figure 3 It can be seen that the liquid level control is better, the slag line erosion is more uniform, and the erosion of the optimal linear point position of the liquid level detection system is reduced, making the liquid level control more accurate, reducing liquid level fluctuations and abnormal fluctuations, and achieving the effect of extending the service life of the nozzle.

[0074] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for increasing the service life of a crystallizer nozzle, characterized in that: The following steps are involved: Step 1: Start pouring and initialize the nozzle protection system. Determine the nozzle protection offset value ±A, the overall downward offset value B of the asymmetric trapezoidal nozzle protection, and the nozzle protection period T based on the process data. The nozzle protection offset value ±A is the offset of the actual molten steel moving up and down at the linear optimal point S%, which needs to ensure that the upper and lower limit thresholds of the molten steel are still in the corrosion resistance area of ​​the nozzle; The overall downward offset value B of the asymmetric trapezoidal nozzle protection is the overall downward offset of the upper and lower thresholds after the molten steel starts to use the asymmetric trapezoidal wave for nozzle protection. The offset upper and lower thresholds of the molten steel must remain in the corrosion-resistant area of ​​the nozzle and erode the linearity optimal point S% as little as possible. The value range is 3mm~5mm; The nozzle protection period T needs to make the calculated value of [the smelting period of a furnace of molten steel × the number of continuous pouring furnaces / nozzle protection period] an integer, which is more than 120 minutes; Step 2: Calculate the upward and downward changes of the nozzle protection system, which are (AB) and (-(A+B)), respectively, which are the upper and lower limits of the asymmetric trapezoidal wave change; Step 3: Enable asymmetric trapezoidal wave control to adjust the upper limit of the liquid level; The asymmetric trapezoidal wave control is to control the molten steel level according to the set asymmetric trapezoidal wave; The upper limit adjustment is specifically to use the linearity optimal point S% of the liquid level detection system plus the upward change as the upper limit threshold value A1 of the trapezoidal wave control liquid level, and adjust the liquid level to reach A1 within T / 18 time and maintain it for T / 3 time; Step 4: Adjust the lower limit of the liquid level; The lower limit adjustment is specifically to use the linearity optimal point S% of the liquid level detection system plus the downward change as the lower limit threshold A2 of the trapezoidal wave control liquid level, and adjust the liquid level to reach A2 within T / 6 time and maintain it for T / 3 time; Step 5: Perform liquid level recovery adjustment; The recovery adjustment specifically includes adjusting the liquid level to return to the optimal linearity point S of the liquid level detection system within T / 9; Step 6: Repeat steps 3, 4, and 5 until the crystallizer is no longer in use.

2. A method for improving the service life of a crystallizer nozzle according to claim 1, characterized in that: The process data specifically include: the total range R of the liquid level detection system, the optimal point S% of linearity and the corrosion resistance area range of the nozzle.

3. A method for improving the service life of a crystallizer nozzle according to claim 2, characterized in that: The optimal linearity point S% is 70% to 80% of the total range R of the liquid level detection system.

4. A method for increasing the service life of a crystallizer nozzle according to claim 1, characterized in that: The overall downward offset value B of the asymmetric trapezoidal nozzle protection ranges from 3 mm to 5 mm.

5. A method for increasing the service life of a crystallizer nozzle according to claim 1, characterized in that: The adjustment climbing time of the liquid level: upper limit holding time: lower limit holding time = 1: 0.9~1.1: 0.9~1.

1.

6. A method for increasing the service life of a crystallizer nozzle according to claim 5, characterized in that: The slope of the molten steel level change for adjusting the ramp time is (2A) / (T / 6).

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