Method for suppressing plate flaws in midship plate

Abstract

The application discloses a kind of middle plate ship plate plate line defect inhibition method, belong to steel rolling process technical field.The method is established based on the principle of gradient temperature control of finished product thickness, fixed finish rolling pass number and the timing scale strategy matched with rolling deformation law, realize the systematic inhibition of middle plate ship plate plate line defect.It includes: according to the thickness of finished steel plate, set intermediate blank water cooling end point temperature;In finish rolling stage, adopt fixed pass number to carry out rolling;And only after specific odd pass, carry out high-pressure water scale removal.The method realizes the matching control of different thickness steel plate in temperature drop characteristic and oxide scale stripping characteristic, effectively prevents the generation of surface plate line defect, makes finished plate line qualified rate significantly improve.

Description

Technical Field

[0001] This invention belongs to the field of steel rolling technology, specifically relating to a method for suppressing plate texture defects in medium plate shipbuilding. Background Technology

[0002] Currently, in the production of medium-plate shipbuilding, the commonly used methods for controlling plate marks (indentation of iron oxide scale) defects mainly include: Optimize the heating process: Reduce the formation of primary iron oxide scale by controlling the temperature of each section of the heating furnace.

[0003] Enhanced descaling: Increase the pressure of high-pressure water descaling before rough rolling and finish rolling to remove surface iron oxide scale.

[0004] Water cooling is used: the intermediate billet is cooled rapidly between the roughing and finishing mills to shorten the residence time in the critical temperature range and reduce the growth of recycled iron oxide scale.

[0005] Chinese Patent Application No. 202411309271.5 discloses a method for preventing water ripples on the surface of Q960E steel plates. The method involves processing the slab sequentially through rough rolling, water cooling, oscillating and warming, and finish rolling. Specifically, in the water cooling process, the water volume is 900-1000 m³ / h. 3 The water pressure is 0.1~0.2 MPa, and the water cooling rate is 2~3℃ / s. In the swing-and-warming process, the swing-and-warming time is 150~210 s, and the swing-and-warming cooling method is natural air cooling. This achieves the cooling of the intermediate billet to a fixed low temperature, such as 800-820℃.

[0006] Existing technologies often focus on improving single aspects of the process, lacking systematic coordination. This leads to the following drawbacks: 1. Inadequate Temperature Control: Existing water-cooling processes typically set a fixed target cooling temperature, failing to consider the significant differences in temperature drop rates and deformation requirements for steel plates of varying thicknesses during subsequent finishing rolling. For thin steel plates, excessively low cooling endpoint temperatures may lead to insufficient temperatures in the later stages of finishing rolling, affecting rolling stability and plate shape. For thick steel plates, excessively high cooling endpoint temperatures are insufficient to effectively suppress iron oxide scale growth (for thick steel plates, if the cooling endpoint temperature is too high (e.g., >920℃), the intermediate billet will remain in the 800-1000℃ zone of intense iron oxide scale formation for too long, resulting in relatively thick regenerated iron oxide scale even with water-cooling, burdening subsequent finishing rolling descaling).

[0007] 2. Inefficient descaling strategy: Descaling operations are mostly initiated based on experience, which may result in blind spots in cleaning and fail to accurately match the rolling deformation pattern (i.e., which passes after which iron oxide scale is most easily removed).

[0008] 3. Insufficient synergy: The improvement of the above-mentioned individual methods has failed to form a systematic process combination. There is a lack of linkage between the measures, and there is a bottleneck in the effect of suppressing board texture defects, making it difficult to achieve a breakthrough improvement in the pass rate.

[0009] This invention provides a method for suppressing defects in medium-plate shipboard patterns, particularly concerning how to improve product qualification rates. Summary of the Invention

[0010] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention provides a method for suppressing defects in medium-grain ship plates, with the purpose of improving product qualification rate.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is: a method for suppressing plate texture defects in medium-plate shipbuilding, comprising: (1) Gradient temperature control: The intermediate billet after rough rolling is cooled by a water-cooling device. Among them, the corresponding temperature control strategy is determined based on the target thickness of the finished product: When the target thickness of the finished product is less than the first preset thickness value, the intermediate billet is not water-cooled and is allowed to cool naturally to the rolling temperature. When the target thickness of the finished product is equal to the first preset thickness value, the surface of the intermediate billet is cooled to keep the surface temperature of the intermediate billet at a level not higher than the first preset upper limit value. When the target thickness of the finished product is greater than the first preset thickness value but not more than the second preset thickness value, the surface of the intermediate billet is cooled so that the surface temperature of the intermediate billet is controlled within the second preset temperature range. When the target thickness of the finished product is greater than the second preset thickness value, the surface of the intermediate billet is cooled to keep the surface temperature of the intermediate billet within the third preset temperature range. The different temperature ranges are used to balance the temperature drop characteristics and oxide scale formation characteristics of steel plates of different thicknesses during the finishing rolling process, so as to suppress plate texture defects. (2) Fixed-pass finishing rolling: The intermediate billet is finished rolling with a fixed total number of passes to ensure the stability and repeatability of rolling deformation; (3) Sequential descaling: During the finishing rolling process, the high-pressure water descaling device is turned on only after the preset odd number of rolling passes to descale the surface of the rolled piece.

[0012] The method improves the surface texture defects of finished steel plates by adjusting the intermediate billet water cooling temperature, the finishing rolling pass setting, and the descaling sequence.

[0013] The first preset thickness value is 8mm, and the second preset thickness value is 12mm.

[0014] The first preset temperature upper limit is 990℃.

[0015] The second preset temperature range is 920 to 950°C.

[0016] The third preset temperature range is 880–920°C.

[0017] The fixed number of finishing passes is no less than 7 passes.

[0018] The odd-numbered lanes include lanes 1, 3, 5, 7, and 9.

[0019] The temperature control strategy also includes: When the target thickness of the finished product is less than the first preset thickness value, the intermediate billet is not subjected to water cooling, and it is allowed to cool naturally to the rolling temperature.

[0020] The present invention also provides a medium-plate shipboard, which is prepared by the aforementioned method for suppressing defects in the medium-plate shipboard pattern.

[0021] The method for suppressing plate texture defects in medium-grain ship plates of the present invention has the following advantages compared with the prior art: 1. Highly targeted: By linking the final temperature of water cooling to the thickness of the finished product, the system optimizes the temperature control for thinner specifications which cool faster and thicker specifications which cool slower, achieving differentiated and precise control.

[0022] 2. High stability: A fixed rolling strategy of at least 7 passes is adopted to ensure stable deformation and stress distribution, and to reduce random fluctuations in plate shape and grain.

[0023] 3. High cleaning efficiency: The odd-numbered-pass sequential descaling strategy ensures that the oxide scale is removed during the most fragile stage, effectively preventing residue from being pressed into the surface.

[0024] 4. Collaborative optimization: Gradient temperature control, fixed pass count, and sequential descaling form a multi-dimensional synergistic system of thermal behavior, deformation behavior, and surface condition, which greatly improves the pass rate of plate texture. Attached Figure Description

[0025] This manual includes the following figures, which illustrate the following: Figure 1 This is a flowchart of the method for suppressing plate texture defects in shipbuilding plates according to the present invention; Figure 2 These are the experimental data from the examples and comparative examples; Figure 3 This is a schematic diagram of the water-cooled device. The markings in the diagram are: 1. Upper water spray pipe; 2. Lower water spray pipe; 3. Main water supply pipe. Detailed Implementation

[0026] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solutions of the present invention, and to facilitate its implementation.

[0027] It should be noted that in the following embodiments, the terms "first," "second," and "third" do not represent an absolute distinction in structure and / or function, nor do they represent the order of execution; they are merely for the convenience of description.

[0028] Firstly, such as Figure 1 As shown, this embodiment of the invention provides a method for suppressing plate texture defects in medium-grain ship plates, including: (1) Gradient temperature control: The intermediate billet after rough rolling is cooled by a water-cooling device. Among them, the corresponding temperature control strategy is determined based on the target thickness of the finished product: When the target thickness of the finished product is less than the first preset thickness value, the intermediate billet is not water-cooled and is allowed to cool naturally to the rolling temperature. When the target thickness of the finished product is equal to the first preset thickness value, the surface of the intermediate billet is cooled to keep the surface temperature of the intermediate billet at a level not higher than the first preset upper limit value. When the target thickness of the finished product is greater than the first preset thickness value but not more than the second preset thickness value, the surface of the intermediate billet is cooled so that the surface temperature of the intermediate billet is controlled within the second preset temperature range. When the target thickness of the finished product is greater than the second preset thickness value, the surface of the intermediate billet is cooled to keep the surface temperature of the intermediate billet within the third preset temperature range. Different temperature ranges are used to balance the temperature drop characteristics and oxide scale formation characteristics of steel plates of different thicknesses during the finishing rolling process, so as to suppress plate texture defects. (2) Fixed-pass finishing rolling: The intermediate billet is finished rolling with a fixed total number of passes to ensure the stability and repeatability of rolling deformation; (3) Sequential descaling: During the finishing rolling process, the high-pressure water descaling device is turned on only after the preset odd number of rolling passes to descale the surface of the rolled piece, so as to achieve precise and efficient cleaning.

[0029] Specifically, this invention provides a systematic solution, the core of which is to correlate the final water cooling temperature of the intermediate billet with the target thickness of the finished steel plate, and to match it with fixed finishing rolling passes and optimized descaling sequence. The method improves surface defects in the finished steel plate by adjusting the water cooling temperature of the intermediate billet, the finishing rolling passes, and the descaling sequence. The coordinated control of the three process parameters—gradient temperature control, fixed passes, and sequential descaling—achieves a match between the surface temperature gradient and the oxide scale state during finishing rolling, thereby significantly reducing the surface defect rate of the finished steel plate. Through this coordinated control system, the pass rate for surface defects in the finished steel plate is greatly improved.

[0030] In this embodiment of the invention, during the gradient temperature control step, a water-cooling device is used to cool the intermediate billet after rough rolling. The target cooling temperature is not a fixed value, but is precisely set according to the target thickness of the finished steel plate.

[0031] In this embodiment of the invention, the temperature control strategy further includes: When the target thickness of the finished product is less than the first preset thickness value, the intermediate billet is not subjected to water cooling, but is allowed to cool naturally to the rolling temperature. Natural cooling retains heat and avoids rolling stress cracks caused by excessively low rolling temperatures, while also reducing abnormal oxide scale formation caused by over-cooling.

[0032] In this embodiment of the invention, the first preset thickness value is 8mm and the second preset thickness value is 12mm.

[0033] In this embodiment of the invention, the first preset temperature upper limit is 990℃. The second preset temperature range is 920~950℃. The third preset temperature range is 880~920℃.

[0034] In this embodiment of the invention, if the target thickness of the finished product is <8mm, it still has a good surface effect without temperature control.

[0035] For thinner specifications with a target thickness of 8 mm, the surface temperature of the intermediate billet is cooled to a higher range of <990°C. This design aims to retain sufficient rolling heat for thin specifications that cool rapidly, preventing the finishing mill tail temperature from becoming too low.

[0036] For thinner specifications with a target thickness of <8 to <12 mm, the surface temperature of the intermediate billet is cooled to a higher range of 920 to 950°C. This design aims to retain sufficient rolling heat for thin specifications that cool rapidly, preventing the temperature at the tail of the finishing roll from becoming too low.

[0037] For thicker specifications with a target thickness >12mm, the surface temperature of the intermediate billet is cooled to a lower range of 880~920℃. This design aims to take advantage of the slower temperature drop of thicker specifications, ensuring rapid passage through the dangerous zone of iron oxide scale formation through a lower final temperature, and also helps to reduce the cross-sectional temperature difference before finishing rolling.

[0038] The temperature control strategy described above addresses the contradictory needs of thin-gauge paper, which experiences rapid temperature drop and requires the retention of rolling heat, and thick-gauge paper, which experiences slow temperature drop and requires strong suppression of iron oxide scale, thus achieving differentiated and precise control.

[0039] like Figure 3 As shown in this embodiment of the invention, the water-cooling device mainly includes a high-pressure water supply system and a jet manifold system. The high-pressure water supply system and the jet manifold system are connected. The high-pressure water supply system provides a stable and continuous high-pressure water (the pressure can typically reach tens of megapascals) to the jet manifold system. The high-pressure water supply system mainly includes components such as a high-pressure water pump and a main water supply pipe 3. The jet manifold system mainly includes an upper water spray pipe 1 and a lower water spray pipe 2. Nozzles, such as spiral nozzles, are installed on the upper water spray pipe 1 and the lower water spray pipe 2 to break the high-pressure water into a uniform and dense water curtain or water mist, ensuring that it can penetrate the vapor film on the surface of the steel plate and achieve efficient heat exchange. The height of the upper water spray pipe 1 is greater than the height of the lower water spray pipe 2. The upper water spray pipe 1 is located above the rolling line, and multiple upper water spray pipes 1 are arranged side by side to spray cooling water onto the intermediate billet below. The lower water spray pipe 2 is located below the rolling line and can spray cooling water onto the intermediate billet above. The upper water spray pipe 1 and the lower water spray pipe 2 are connected to the main water supply pipe 3 through water supply branch pipes.

[0040] In this embodiment of the invention, in the finishing rolling step, the fixed number of finishing rolling passes is not less than 7 passes, such as 7 passes, 8 passes or 9 passes.

[0041] Preferably, the total number of rolling passes in the finishing rolling stage is fixed at 9 passes. This provides a stable and repeatable deformation environment for the entire finishing rolling process, eliminates the process uncertainty caused by pass fluctuations, and further consolidates the defect suppression effect.

[0042] In this embodiment of the invention, when the fixed number of finishing rolling passes is 9, the odd-numbered passes in the sequential descaling process include passes 1, 3, 5, 7, and 9. During the finishing rolling process, the high-pressure water descaling device is not activated throughout the entire process, but only after specific odd-numbered passes, i.e., the high-pressure water descaling device is activated in passes 1, 3, 5, 7, and 9 to clean the surface of the rolled piece. Setting odd-numbered passes, especially the first few, is typically a critical pass with a large deformation, where the surface iron oxide scale is most easily broken and peeled off. This strategy ensures efficient cleaning at the optimal time, avoiding uneven results caused by indiscriminate descaling.

[0043] Traditional descaling can suffer from problems such as improper timing (e.g., descaling during even-numbered passes when the oxide scale is already firmly attached) or over-descaling. The advantage of sequential descaling lies in its use of high-pressure water descaling only in odd-numbered passes (passes 1, 3, 5, 7, and 9). This precisely matches the critical point of oxide scale formation. After odd-numbered passes, the oxide scale has just formed and its adhesion is relatively weak, resulting in the highest removal efficiency. This completely prevents the oxide scale from being carried into subsequent rolling processes (oxide scale pressed into the slab surface is a major direct cause of slab texture defects). This avoids process fluctuations caused by ineffective descaling, while ensuring that descaling is done thoroughly and on time, clearing obstacles for subsequent rolling.

[0044] The above-mentioned method for suppressing plate grain defects in medium-grain ship plates has the following advantages: 1. Significantly improved plate texture pass rate: The plate texture pass rate has been steadily increased from approximately 48% in the traditional process to over 96%. This is because "gradient temperature control" inhibits the formation of harmful iron oxide scale at the source, "sequential descaling" achieves efficient removal at the optimal time, and "fixed passes" ensure the stability of the process.

[0045] 2. Enhanced product quality stability: A standardized and replicable advanced process has been developed, reducing reliance on operator experience and making the production of high-quality ship plates controllable and predictable.

[0046] Secondly, embodiments of the present invention also provide a medium-plate shipboard, which is prepared using the above-mentioned method for suppressing defects in medium-plate shipboard patterns.

[0047] Comparative Example 1 like Figure 2 As shown, Comparative Example 1 is a traditional process, which uses air cooling and waiting for the temperature to rise, conventional rolling passes, and conventional descaling without any specific temperature control strategy. The qualified rate of the 14mm thick specification is only 48%, indicating that a large amount of oxide scale is generated and unevenly adhered during the air cooling process of the thick specification, which is the main cause of plate texture defects.

[0048] Comparative Example 2 like Figure 2 As shown, in Comparative Example 2, a conventional number of passes was used, and only some descaling timing was optimized. The pass rate was only 63% - indicating that an irregular number of passes will lead to uneven rolling deformation, mismatch between the timing of oxide scale removal and the deformation rhythm, and a large number of defects will still remain.

[0049] Comparative Example 2 only descaling is performed in passes 1, 5, and 9, lacking the critical removal nodes in passes 3 and 7. As a result, oxide scale easily adheres to these passes and is pressed into the slab, leading to a yield of only 63%. Example

[0050] like Figure 2As shown in this embodiment, for 14mm thick medium-plate ship plates, the final temperature of water cooling is precisely controlled at 890℃ within the range of 880~920℃. This meets the requirements of slow temperature drop and strong suppression of oxide scale in thicker plates, laying the foundation for subsequent processes. Furthermore, a fixed 9-pass process ensures that the deformation process of each slab is completely consistent, providing a stable process rhythm for sequential descaling and ensuring precise synchronization between oxide scale removal and rolling deformation. This is a key design feature that achieves a yield rate exceeding 90%.

[0051] Specifically, an odd number of descaling passes (1, 3, 5, 7, 9) are used to achieve efficient removal at the points where the oxide scale adhesion is weakest, avoiding problems such as oxide scale residue and indentation. This is one of the main reasons why the pass rate of Example 1 jumped to 93%. Example

[0052] like Figure 2 As shown, in this embodiment, for 10mm thick medium-thickness ship plates, the final temperature of water cooling is precisely controlled at 935℃ within the range of 920~950℃. This matches the characteristics of thinner plates, which experience rapid temperature drop and need to retain rolling heat, demonstrating the precise adaptability of gradient temperature control to different thicknesses. Furthermore, using a fixed 9 passes ensures that the deformation process of each slab is completely consistent, providing a stable process rhythm for sequential descaling and ensuring precise synchronization between oxide scale removal and rolling deformation. This is a key design feature that achieves a yield rate exceeding 90%. Specifically, odd-numbered descaling passes (1, 3, 5, 7, 9) are used to achieve efficient removal at the weakest point of oxide scale adhesion, avoiding oxide scale residue and indentation. This is also one of the main reasons why the yield rate in Example 2 jumped to 91%.

[0053] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution; or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A method for suppressing plate grain defects in medium-grain ship plates, characterized in that, include: (1) Gradient temperature control: The intermediate billet after rough rolling is cooled by a water-cooling device. Among them, the corresponding temperature control strategy is determined based on the target thickness of the finished product: When the target thickness of the finished product is less than the first preset thickness value, the intermediate billet is not water-cooled and is allowed to cool naturally to the rolling temperature. When the target thickness of the finished product is equal to the first preset thickness value, the surface of the intermediate billet is cooled to keep the surface temperature of the intermediate billet at a level not higher than the first preset upper limit value. When the target thickness of the finished product is greater than the first preset thickness value but not more than the second preset thickness value, the surface of the intermediate billet is cooled so that the surface temperature of the intermediate billet is controlled within the second preset temperature range. When the target thickness of the finished product is greater than the second preset thickness value, the surface of the intermediate billet is cooled to keep the surface temperature of the intermediate billet within the third preset temperature range. (2) Fixed-pass finishing rolling: The intermediate billet is finished rolled with a fixed total number of passes; (3) Sequential descaling: During the finishing rolling process, the high-pressure water descaling device is turned on only after the preset odd number of rolling passes to descale the surface of the rolled piece.

2. The method for suppressing plate texture defects in medium-grain ship plates according to claim 1, characterized in that, The first preset thickness value is 8mm, and the second preset thickness value is 12mm.

3. The method for suppressing plate grain defects in medium-plate shipbuilding as described in claim 1 or 2, characterized in that, The first preset temperature upper limit is 990℃.

4. The method for suppressing plate grain defects in medium-plate shipbuilding according to any one of claims 1 to 3, characterized in that, The second preset temperature range is 920 to 950°C.

5. The method for suppressing plate grain defects in medium-plate shipbuilding according to any one of claims 1 to 3, characterized in that, The third preset temperature range is 880–920°C.

6. The method for suppressing plate grain defects in medium-plate shipbuilding according to any one of claims 1 to 5, characterized in that, The fixed number of finishing passes is no less than 7 passes.

7. The method for suppressing plate grain defects in medium-plate shipbuilding as described in claim 6, characterized in that, The odd-numbered lanes include lanes 1, 3, 5, 7, and 9.

8. The method for suppressing plate texture defects in medium-plate shipbuilding according to any one of claims 1 to 7, wherein the temperature control strategy further includes: When the target thickness of the finished product is less than the first preset thickness value, the intermediate billet is not subjected to water cooling, and it is allowed to cool naturally to the rolling temperature.

9. A type of medium-sized shipboard, characterized in that, It is prepared using the method for suppressing plate texture defects in medium-sized ship plates as described in any one of claims 1 to 8.

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