Method for overcoming broken edge defect of high-aluminum high-strength steel

Abstract

The invention relates to a method for overcoming the broken edge defect of high-aluminum high-strength steel, and belongs to the technical field of steel rolling. The method comprises the steps that a plate blank with target chemical components is obtained; the narrow face of the plate blank is subjected to machine cleaning treatment, so that defect inheritance is avoided, and a machine-cleaned plate blank is obtained; sequentially heating and rolling the machine-cleaned plate blank to obtain hot-rolled strip steel; and the hot-rolled strip steel is subjected to ultra-fast cooling and coiling in sequence, and a high-aluminum high-strength steel finished product is obtained. Through the comprehensive method of component optimization, slab machine cleaning and hot rolling process optimization, the technical problem of the broken edge defect of the high-aluminum high-strength steel is solved, through the combined action of the measures, the edge quality of the high-aluminum high-strength steel is effectively improved, and the requirement of downstream users for the high quality of strip steel products is met.

Description

Technical Field

[0001] This application relates to the field of steel rolling technology, and in particular to a method for solving the edge breakage defect in high-alumina high-strength steel. Background Technology

[0002] High-alumina high-strength steel, a type of cold-rolled duplex steel with an aluminum content of 0.5% to 1%, occupies an important position in steel materials due to its unique mechanical properties and broad application prospects. However, precisely because of its special chemical composition and processing characteristics, high-alumina steel generally faces the quality problem of hot-rolled edge breakage during production. This problem not only seriously affects the surface quality of the steel, but also brings many inconveniences in subsequent processing and use.

[0003] The occurrence of edge chipping defects in hot-rolled steel is mainly due to the brittle fracture of the edge structure during the hot rolling process of high-alumina steel, which is susceptible to various factors. These influencing factors include, but are not limited to, the control of steel composition, the quality of the slab, the parameter settings of the hot rolling process, and the selection of cooling methods. Severe edge chipping defects can lead to strip breakage after cold rolling, causing production interruption and significantly increasing costs. While minor edge chipping defects may not directly cause strip breakage during cold rolling, they leave burrs on the steel surface. These burrs are prone to detachment in the subsequent continuous annealing furnace, forming periodic burr defects, which seriously affect the surface quality of high-grade automotive steel and other high-end products, reducing their market competitiveness.

[0004] To avoid quality problems caused by edge chipping defects, the traditional practice is to trim the edges during pickling and rolling to remove the defective portions. However, this approach not only increases production costs but also reduces yield, making it less than optimal for modern steel companies that prioritize high-efficiency production and maximum resource utilization. In recent years, with the continuous advancement of steel rolling technology and the increasing demands of downstream users, more and more users are opting for burr-edge rolling or other processing methods, requiring strip steel to possess excellent edge quality. Therefore, solving the problem of edge chipping defects in high-alumina steel has become a pressing technical challenge for the steel industry. Summary of the Invention

[0005] This application provides a method for solving edge defects in high-alumina high-strength steel, in order to address the following technical problem: how to improve the edge quality of high-alumina high-strength steel.

[0006] This application provides a method for solving the edge chipping defect in high-alumina high-strength steel, the method comprising:

[0007] A slab with the target chemical composition is obtained;

[0008] The narrow face of the slab is machine-cleaned to avoid the inheritance of defects, resulting in a machine-cleaned slab.

[0009] The machine-cleaned slab is sequentially heated and rolled to obtain hot-rolled strip steel;

[0010] The hot-rolled strip steel is sequentially subjected to ultra-fast cooling and coiling to obtain high-aluminum high-strength steel finished product.

[0011] The target chemical composition, by mass fraction, includes: N ≤ 0.005%, Ti: 0.018%–0.025%, and Al: 0.5%–1%.

[0012] Optionally, the cleaning depth of the machine cleaning process is 2mm to 3mm.

[0013] Optionally, the heating includes a first heating section, a second heating section, and a heat spreader section, wherein the excess air coefficient of the second heating section and the heat spreader section is 0.95 to 1.05.

[0014] Optionally, the starting temperature of the second stage is 1040℃~1160℃, and the ending temperature of the second stage is 1240℃~1270℃.

[0015] Optionally, during the finishing rolling stage of the rolling process, the interstand cooling water is shut off.

[0016] Optionally, the final rolling temperature is 910℃~930℃.

[0017] Optionally, the cooling rate of the ultra-fast cooling is 70℃ / s to 100℃ / s, and the outlet temperature of the ultra-fast cooling is 700℃ to 760℃.

[0018] Optionally, the furnace exit temperature after heating is 1260℃~1280℃.

[0019] Optionally, the winding temperature is 500℃~540℃.

[0020] Optionally, the edge chipping defect rate of the high-aluminum high-strength steel finished product is ≤3%.

[0021] The technical solutions provided in this application have the following advantages compared with the prior art:

[0022] This application provides a method for solving the edge chipping defect in high-alumina high-strength steel. The method includes: obtaining a slab with a target chemical composition; performing machine cleaning on the narrow face of the slab to avoid defect inheritance, obtaining a machine-cleaned slab; sequentially heating and rolling the machine-cleaned slab to obtain hot-rolled strip steel; and sequentially subjecting the hot-rolled strip steel to ultra-fast cooling and coiling to obtain the finished high-alumina high-strength steel product. By controlling the nitrogen (N) content in the slab and adding a certain amount of Ti, Ti combines with N to form TiN, preventing the formation of AlN precipitates by combining N and Al elements in the third brittle zone, thus preventing brittle cracking and edge breakage defects. The narrow face of the slab is machine-cleaned to eliminate slab defects such as longitudinal cracks, preventing these defects from being inherited in subsequent processing and causing hot-rolled edge breakage. In the hot rolling process, the secondary heating section and the soaking section maintain an appropriate reducing or weakly oxidizing atmosphere to prevent minor cracks on the narrow face of the slab from further oxidation and aggravation during high-temperature heating. The final rolling temperature is controlled to prevent the hot-rolled ends from entering the third brittle zone, thus preventing brittle cracking and edge breakage. The water between the finishing mill stands is shut off to prevent localized overcooling at the edges, which can lead to edge breakage. An ultra-fast cooling mode is adopted for rapid cooling to avoid further AlN precipitation in the delaminated area, thereby reducing edge breakage defects. This application solves the technical problem of edge defects in high-alumina high-strength steel through a comprehensive approach of composition optimization, slab mill cleaning, and hot rolling process optimization. These measures work together to effectively improve the edge quality of high-alumina high-strength steel and meet the high-quality requirements of downstream users for strip steel products. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A flowchart illustrating a method for resolving edge chipping defects in high-alumina, high-strength steel, provided in an embodiment of this application;

[0026] Figure 2 The edge quality diagram provided for Comparative Example 1 of this application;

[0027] Figure 3 This is an edge quality diagram provided for Embodiment 1 of this application. Detailed Implementation

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

[0029] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1 to 6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "comprise" as used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0030] Figure 1 This is a flowchart illustrating a method for resolving edge chipping defects in high-alumina, high-strength steel, as provided in an embodiment of this application.

[0031] Please see Figure 1 This application provides a method for solving the edge chipping defect in high-aluminum high-strength steel, the method comprising:

[0032] S1. Obtain a slab with the target chemical composition;

[0033] First, the target chemical composition is determined based on the characteristics of high-aluminum, high-strength steel and production requirements. Particular attention is paid to controlling the nitrogen (N) and titanium (Ti) content, as these are crucial for avoiding edge chipping defects.

[0034] In some embodiments, the target chemical composition, by mass fraction, includes: N ≤ 0.005%, Ti: 0.018%–0.025%, and Al: 0.5%–1%.

[0035] Because nitrogen (N) can combine with aluminum (Al) in high-aluminum, high-strength steel to form AlN precipitates, these precipitates can lead to brittle fracture within the third brittle range of steel (650℃~850℃), resulting in edge chipping defects. By controlling the mass fraction of N to ≤0.005%, AlN precipitation can be significantly reduced, thereby lowering the risk of edge chipping defects. For example, the mass fraction of N can be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, etc.

[0036] By controlling the mass fraction of Ti between 0.018% and 0.025%, Ti can preferentially combine with N to form TiN precipitates, thereby preventing N from combining with Al to form AlN. This not only reduces the possibility of brittle cracking but also improves the toughness and strength of the steel. For example, the mass fraction of Ti can be 0.018%, 0.019%, 0.020%, 0.021%, 0.022%, 0.023%, 0.024%, 0.025%, etc.

[0037] Al is one of the main alloying elements in high-aluminum, high-strength steel, and its mass fraction has a significant impact on the steel's properties. While adding Al can improve the strength and corrosion resistance of steel, an Al mass fraction exceeding 1% can lead to increased brittleness and processing difficulties. By controlling the Al mass fraction between 0.5% and 1%, the high strength and other properties of the steel can be guaranteed while avoiding brittle cracking problems caused by an Al mass fraction exceeding 1%. For example, the Al mass fraction can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc.

[0038] S2. The narrow face of the slab is machine-cleaned to avoid the inheritance of defects, resulting in a machine-cleaned slab.

[0039] Mechanical cleaning is a process of cleaning the narrow face of a slab to remove surface defects such as longitudinal cracks. During this process, specialized machinery is used to clean the narrow face of the slab, with the cleaning depth typically controlled within a certain range to ensure effective removal of surface defects while avoiding over-cleaning that could damage the slab's quality.

[0040] In some embodiments, the cleaning depth of the machine cleaning process is 2mm to 3mm.

[0041] In this embodiment, by performing machine cleaning on the narrow face of the slab and controlling the cleaning depth between 2mm and 3mm, defects such as longitudinal cracks on the narrow face of the slab can be prevented from being inherited by the hot rolling process during subsequent processing, thereby reducing the generation of edge breakage defects. After the machine cleaning is completed, the narrow face of the slab is visually inspected to ensure that it is clean, free of cracks, inclusions, and other defects. For example, the cleaning depth of the machine cleaning can be 2mm, 2.2mm, 2.4mm, 2.6mm, 2.8mm, 3mm, etc.

[0042] S3. The machine-cleaned slab is heated and rolled sequentially to obtain hot-rolled strip steel;

[0043] In some embodiments, the heating includes a primary heating section, a secondary heating section, and a homogenizing section, wherein the excess air coefficient of the secondary heating section and the homogenizing section is 0.95 to 1.05.

[0044] In steel rolling processes, "heating includes three stages: preheating, secondary heating, and soaking." These stages refer to the three phases of temperature control the slab undergoes in the heating furnace. Specifically: The first stage (preheating stage) primarily heats the slab initially, gradually raising its temperature from room temperature to the target temperature. The goal of this stage is to avoid thermal stress cracking caused by rapid temperature rise and to lay the foundation for subsequent high-temperature heating. The second stage (main heating stage) is the core heating stage, heating the slab to the target temperature through high-temperature heating. After the second stage, maintaining a high temperature ensures temperature homogenization within the slab, eliminating temperature gradients. This stage ensures that the temperature difference between the slab core and surface is ≤20℃, providing uniform microstructure conditions for subsequent rolling.

[0045] The excess air coefficient is the ratio of the actual air supplied during combustion to the theoretically required air, used to characterize the oxidation / reduction state of the combustion atmosphere. When the excess air coefficient = 1, it means that the actual air supply equals the theoretical air supply required for complete fuel combustion, achieving an ideal stoichiometric ratio. When the coefficient < 1 (e.g., 0.95), the air supply is insufficient, forming a reducing atmosphere, which easily produces incomplete combustion products such as CO. When the coefficient > 1 (e.g., 1.2), there is excess air, forming a strongly oxidizing atmosphere, which can lead to excessive oxidation of the metal surface. In the embodiments of this application, by controlling the excess air coefficient of the second heating section and the soaking section between 0.95 and 1.05, it is possible to ensure that an appropriate reducing or weakly oxidizing atmosphere is maintained in the heating furnace. This atmosphere helps to reduce the oxidation of the steel billet during the heating process, especially preventing the further oxidation and aggravation of minor narrow-face crack defects in the billet during high-temperature heating. Controlling the excess air coefficient also helps prevent brittle cracking of steel billets due to excessive oxidation during heating, especially for high-alumina, high-strength steels that are sensitive to composition and process conditions. Appropriate control of the heating atmosphere is crucial to avoiding brittle cracking and edge chipping defects. For example, the excess air coefficients for the secondary heating section and the soaking section can be 0.95, 0.97, 0.99, 1.01, 1.03, 1.05, etc.

[0046] In some embodiments, the starting temperature of the second stage is 1040°C to 1160°C, and the ending temperature of the second stage is 1240°C to 1270°C.

[0047] The gradient design of the initial temperature (1040℃~1160℃) and final temperature (1240℃~1270℃) of the second heating stage ensures the uniformity of temperature distribution in the slab during heating. This temperature range promotes uniform recrystallization of the internal structure of the slab and avoids abnormally coarse grains caused by local overheating. By controlling the final temperature of the second heating stage at 1240℃~1270℃, combined with a reducing atmosphere (excess air coefficient 0.95~1.05), the degree of oxidation of the narrow face of the slab in the high-temperature section can be effectively reduced. This prevents the original slight cracks in the slab from further expanding under oxidation, thereby preventing the formation of chipped edges due to crack aggravation in the hot-rolled edge. For example, the starting temperature of the second stage can be 1040℃, 1060℃, 1080℃, 1100℃, 1120℃, 1140℃, 1160℃, etc.; the ending temperature of the second stage can be 1240℃, 1245℃, 1250℃, 1255℃, 1260℃, 1265℃, 1270℃, etc.

[0048] In some embodiments, the furnace exit temperature after heating is 1260°C to 1280°C.

[0049] First, a furnace temperature range of 1260℃ to 1280℃ helps ensure that the steel reaches an ideal heating state upon exiting the furnace, laying a solid foundation for the subsequent rolling process. Precise control of the exit temperature allows for a more uniform internal structure of the steel, improving its overall performance. Second, a furnace temperature within this range helps prevent overheating or undercooling during the heating process. Overheating can lead to adverse changes in the steel's internal structure, such as coarse grains and decreased performance; while undercooling may result in insufficient heating, affecting subsequent rolling. Therefore, controlling the exit temperature within 1260℃ to 1280℃ helps ensure the heating quality of the steel. For example, the furnace exit temperatures could be 1260℃, 1265℃, 1270℃, 1275℃, or 1280℃.

[0050] In some implementations, the interstand cooling water is shut off during the finishing rolling stage of the rolling process.

[0051] In the hot-rolled strip steel production process, inter-stand cooling water refers to the cooling water spray system installed between the stands of the finishing mill, mainly used to control the temperature distribution of the strip steel during the rolling process. Specifically, the inter-stand cooling water system adjusts the temperature gradient during the rolling process by spraying cooling water onto the strip steel surface, avoiding excessively high local temperatures that could lead to material performance deterioration. Its on / off state directly affects the cooling rate of the strip steel edges. In this embodiment, if the inter-stand cooling water is turned on during the finishing rolling stage, it may cause the local temperature of the strip steel edges to be too low. Since high-alumina high-strength steel is very sensitive to temperature, especially within its third brittle range (650℃~850℃), local overcooling at the edges can easily cause brittle cracking, thus forming edge breakage defects. Turning off the inter-stand cooling water can effectively avoid this problem, ensure uniform temperature at the strip steel edges, and reduce the occurrence of edge breakage defects. In addition, the presence of cooling water between the racks may cause the steel strip surface to react with the cooling water, resulting in oxidation or decarburization. These phenomena can damage the surface quality and internal properties of the steel strip. Turning off the cooling water between the racks can reduce the occurrence of these adverse reactions and protect the original properties of the steel strip.

[0052] In some embodiments, the final rolling temperature is 910°C to 930°C.

[0053] The third brittle range for high-alumina high-strength steel is 650-850℃. Within this temperature range, the plasticity of high-alumina high-strength steel decreases sharply, while its crack susceptibility increases significantly. Since the edge temperature of hot-rolled steel is 40℃-60℃ lower than the center temperature, if the final rolling temperature is below 910℃, the actual edge temperature may fall into the brittle range, leading to brittle cracking caused by AlN precipitates and resulting in edge chipping defects. By increasing the final rolling temperature to 910℃-930℃, it can be ensured that the post-rolling temperature of the hot-rolled edge remains above the upper limit of the brittle range, reducing the risk of cracking. For example, the final rolling temperature can be 910℃, 915℃, 920℃, 925℃, 930℃, etc.

[0054] S4. The hot-rolled strip steel is subjected to ultra-fast cooling and coiling in sequence to obtain high-aluminum high-strength steel finished product;

[0055] Through ultra-rapid cooling and coiling, high-alumina high-strength steel hot-rolled strip completes its final processing. The ultra-rapid cooling step, by rapidly lowering the strip temperature, helps prevent further AlN precipitation in the delaminated region, thus reducing brittle cracking and edge chipping defects. The coiling step, conducted at a suitable temperature, ensures the finished strip possesses excellent microstructure and mechanical properties. The close coordination of these two steps is crucial for achieving high-quality high-alumina high-strength steel products.

[0056] In some embodiments, the cooling rate of the ultra-fast cooling is 70°C / s to 100°C / s, and the outlet temperature of the ultra-fast cooling is 700°C to 760°C.

[0057] During the cooling process of high-alumina high-strength steel, if the cooling rate is slower than 70℃ / s, aluminum (Al) and nitrogen (N) easily combine to form brittle AlN precipitates. This leads to increased edge brittleness of the steel and consequently, edge chipping defects. By controlling the ultra-rapid cooling rate to 70℃ / s–100℃ / s, the steel temperature can be rapidly reduced, shortening the residence time of the steel in the temperature range where AlN is easily precipitated. This effectively reduces the formation of AlN precipitates and lowers the risk of edge chipping defects. Secondly, at a cooling rate of 70℃ / s–100℃ / s, the austenitic transformation of the steel is more uniform, and the grains are refined. This is beneficial for improving the strength and hardness of the steel, while also improving its toughness and plasticity. For high-alumina high-strength steel, which has high performance requirements, a refined microstructure is key to obtaining excellent mechanical properties. At cooling rates below 70℃ / s, the microstructure transformation of steel may be uneven, leading to significant performance differences. However, using ultra-fast cooling rates of 70℃ / s to 100℃ / s ensures a more uniform microstructure transformation during cooling, reducing performance variations and improving the overall quality of the steel. Ultra-fast cooling means that steel can pass through the cooling zone more quickly, thereby shortening the production cycle and increasing production efficiency, which is of great significance to modern steel companies pursuing high-efficiency production. For example, ultra-fast cooling rates can be 70℃ / s, 75℃ / s, 80℃ / s, 85℃ / s, 90℃ / s, 95℃ / s, and 100℃ / s. Setting the ultra-fast cooling outlet temperature to 700℃ to 760℃, combined with a coiling temperature of 500℃ to 540℃, allows the steel to quickly pass through the third brittle temperature range (650℃ to 850℃), reducing microstructural stress caused by temperature gradients at the edges. For example, the outlet temperature of the ultra-fast cooling can be 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, etc.

[0058] In some embodiments, the winding temperature is 500°C to 540°C.

[0059] Coiling temperature is a key process parameter in the production of hot-rolled strip steel. It refers to the temperature at which the strip steel enters the coiler for coiling after rolling and cooling. Its core function is to optimize the microstructure (such as suppressing AlN precipitation), mechanical properties, and surface quality of the strip steel by controlling the cooling rate and material phase transformation behavior. In the embodiments of this application, for high-alumina high-strength steel, a coiling temperature of 500℃ to 540℃ helps to obtain an ideal microstructure, thereby meeting the requirements of high strength and good toughness. For example, the coiling temperature can be 500℃, 510℃, 520℃, 530℃, 540℃, etc.

[0060] In some embodiments, the chipping defect rate of the high-aluminum high-strength steel finished product is ≤3%.

[0061] Edge breakage rate is a quantitative indicator that measures the frequency of quality defects in the edge of hot-rolled high-alumina high-strength steel coils. Specifically, it refers to the percentage of steel coils with defects such as brittle cracking, burrs, or localized detachment in the hot-rolled edge out of the total production. This indicator directly reflects the effectiveness of process control; the lower the value, the more stable the edge quality. This application's embodiments, through a comprehensive method of composition optimization, slab mill cleaning, and hot rolling process optimization, control the edge breakage rate of high-alumina high-strength steel to below 3%, significantly improving product quality stability and ensuring that the product will not experience breakage or detachment due to edge breakage during use, thereby enhancing product reliability and durability. For example, the edge breakage rate of the finished high-alumina high-strength steel product can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0062] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national / industry standards; if there is no corresponding national / industry standard, they are performed according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0063] This application provides a method for solving the edge chipping defect in high-alumina high-strength steel, including the following steps:

[0064] A slab with the target chemical composition is obtained;

[0065] The narrow face of the slab is machine-cleaned to avoid the inheritance of defects, resulting in a machine-cleaned slab.

[0066] The machine-cleaned slab is sequentially heated and rolled to obtain hot-rolled strip steel;

[0067] The hot-rolled strip was sequentially subjected to ultra-rapid cooling and coiling to obtain high-alumina, high-strength steel products. The influence of different process parameters (final rolling temperature, ultra-rapid cooling rate, etc.) on the defect rate was verified using the controlled variable method. Specific process parameters are shown in Table 1.

[0068] Table 1. Specific process parameters for the embodiments and comparative examples.

[0069] process point Example 1 Example 2 Example 3 Comparative Example 1 mass fraction of N 0.0020％ 0.0043％ 0.0035％ 0.0089％ Mass fraction of Ti 0.018％ 0.024％ 0.022％ 0.002％ mass fraction of Al 0.6％ 0.95％ 0.5％ 0.6％ Machine cleaning depth 3mm 2.4mm 2.8mm 0 Atmosphere in the second heating section and the homogenization section 0.98 1 1.01 1.2 The second stage starts at temperature 1060℃ 1140℃ 1110℃ 1000℃ The final temperature of the second stage 1240℃ 1270℃ 1260℃ 1280℃ Furnace temperature 1260℃ 1270℃ 1280℃ 1300℃ Final rolling temperature 930℃ 910℃ 920℃ 880℃ Inter-rack cooling water closure closure closure F1-F3: Turn on 30% of the rack-to-rack cooling water. Ultra-fast cooling speed 78℃ / s 85℃ / s 90℃ / s 40℃ / s Ultra-fast cooling outlet temperature 750℃ 730℃ 720℃ 840℃ winding temperature 510℃ 520℃ 530℃ 600℃

[0070] The high-alumina, high-strength steel products obtained in the examples and comparative examples were tested and calculated to obtain the edge chipping defect rate. The specific method is as follows:

[0071] Sampling is performed on the edges of the strip steel, and edge defects are identified through visual inspection or automated surface inspection equipment.

[0072] Define thresholds for judging edge defects such as size and depth based on industry standards or internal quality specifications.

[0073] Edge breakage rate = (number of defective samples / total number of inspected samples) × 100%.

[0074] See Table 2 for the edge chipping defect rate.

[0075] Table 2

[0076] Case Edge breakage rate Example 1 ≤2％ Example 2 ≤3％ Example 3 ≤3％ Comparative Example 1 ≥55％

[0077] As shown in Tables 1 and 2, the process parameters of the embodiments are within the required range of the present invention. The high-aluminum high-strength steel finished products prepared have a broken edge defect rate of ≤3% and good edge quality. Compared with the broken edge defect rate of ≥55% in Comparative Example 1, a significant quality improvement has been achieved, which greatly improves the product qualification rate and market competitiveness.

[0078] Appendix Figure 2-3 Detailed explanation:

[0079] Figure 2 The edge quality diagram provided for Comparative Example 1 of this application; Figure 3 The image shows the edge quality of the hot-rolled coil as provided in Embodiment 1 of this application. As can be seen from the comparison, the edge quality of the hot-rolled coil is significantly improved by the method provided in this application.

[0080] Furthermore, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0081] Traditionally, high-alumina, high-strength steel has had to undergo acid rolling and edge trimming due to edge breakage, resulting in a reduced yield. This invention addresses this edge breakage defect, enabling the production of high-alumina steel without edge trimming or with reduced trimming width. This improves raw material utilization and yield, while lowering production costs.

[0082] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A method for solving the edge chipping defect in high-alumina high-strength steel, the method comprising: A slab with the target chemical composition is obtained; The narrow face of the slab is machine-cleaned to avoid the inheritance of defects, resulting in a machine-cleaned slab. The machine-cleaned slab is sequentially heated and rolled to obtain hot-rolled strip steel; The hot-rolled strip steel is sequentially subjected to ultra-fast cooling and coiling to obtain high-aluminum high-strength steel finished product. The target chemical composition, by mass fraction, includes: N ≤ 0.005%, Ti: 0.018%–0.025%, and Al: 0.5%–1%.

2. The method according to claim 1, characterized in that, The cleaning depth of the machine cleaning process is 2mm to 3mm.

3. The method according to claim 1, characterized in that, The heating process includes a primary heating section, a secondary heating section, and a homogenization section. The excess air coefficients of the secondary heating section and the homogenization section are both 0.95 to 1.

05.

4. The method according to claim 3, characterized in that, The starting temperature of the second stage is 1040℃~1160℃, and the ending temperature of the second stage is 1240℃~1270℃.

5. The method according to claim 1, characterized in that, During the finishing rolling stage of the rolling process, the cooling water between the stands is shut off.

6. The method according to claim 1, characterized in that, The final rolling temperature is 910℃~930℃.

7. The method according to claim 1, characterized in that, The cooling rate of the ultra-fast cooling is 70℃ / s to 100℃ / s, and the outlet temperature of the ultra-fast cooling is 700℃ to 760℃.

8. The method according to claim 1, characterized in that, The furnace exit temperature after heating is 1260℃~1280℃.

9. The method according to claim 1, characterized in that, The winding temperature is 500℃~540℃.

10. The method according to claim 1, characterized in that, The chipping defect rate of the high-aluminum high-strength steel finished product is ≤3%.

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