A production method for solving transverse cracks at the end of 130mm square cross-section 3SP steel continuous casting billets

Abstract

A production method for solving the problem of transverse cracks at the ends of 130mm square cross-section 3SP steel continuous casting billets is disclosed. This method includes converter primary refining, continuous casting, and billet inspection processes. The generation of transverse cracks at the ends of the 130mm square cross-section continuous casting billets is suppressed by controlling key process parameters in the converter charging process, the deoxidation and alloying process at tapping, and the continuous casting process. In the converter process, when smelting 3SP steel, ladles with low sulfur content (S) are selected, requiring the charging molten iron [S] to be ≤0.030%, and the molten steel [S] to be ≤0.022% after converter primary refining. In the converter deoxidation and alloying process, the [Mn] content of the molten steel is controlled to be ≥0.55%, ensuring an Mn / S ratio ≥25, and the tapping temperature is 1650℃-1680℃. In the continuous casting process, the tundish baking temperature is ≥1050℃, the superheat during continuous casting is controlled to be 20℃-35℃, the electromagnetic stirring current in the crystallizer is 200-250A, the frequency is 2.5-4HZ, the casting speed is controlled to be 2.9-3.5m / min, and the specific water content is controlled to be 1.2-1.4L / kg. This invention effectively suppresses the generation of transverse cracks at the ends of continuously cast billets and improves the internal quality and overall yield of the billets by optimizing the key process parameters of the converter and continuous casting processes.

Description

Technical Field

[0001] This invention relates to the field of metallurgical methods, and in particular to a production method for solving transverse cracks at the ends of 130mm square cross-section 3SP steel continuous casting billets. Background Technology

[0002] 3SP steel grade small square billets (130mm square continuous casting billets) are heat-sensitive billet shapes, prone to transverse cracks at the billet ends during production. Furthermore, after the ends are cut off, these transverse cracks tend to extend into the billet. Such defects severely affect the billet's appearance and can lead to delamination and surface defects in subsequent rolling processes, ultimately impacting the product's mechanical properties and safety in use.

[0003] Therefore, there is an urgent need for an effective production method to suppress the generation of transverse cracks at the ends of 130 square section 3SP steel continuous casting billets. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a production method for solving the problem of transverse cracks at the end of 130 square cross-section 3SP steel continuous casting billets. This method effectively suppresses the generation of transverse cracks at the end of the continuous casting billets by optimizing the key process parameters of the converter and continuous casting processes, thereby improving the internal quality of the billets and the overall yield.

[0005] The technical problem to be solved by the present invention is achieved through the following technical solution. The present invention is a production method for solving the problem of transverse cracks at the end of 130 square cross-section 3SP steel continuous casting billets. The method includes converter primary refining, continuous casting and billet inspection processes. The generation of transverse cracks at the end of 130 square cross-section continuous casting billets is suppressed by controlling the key process parameters of the molten iron entering the converter, the deoxidation and alloying of the tapped steel and the continuous casting process. In the converter process, when smelting 3SP steel, a ladle with low sulfur content is selected. The molten iron entering the furnace is required to have [S] ≤ 0.030%, and the molten steel after primary refining in the converter has [S] ≤ 0.022%. During the converter deoxidation and alloying process, the molten steel has [Mn] ≥ 0.55%, ensuring that the Mn / S ratio is ≥ 25, and the tapping temperature is 1650℃-1680℃. In the continuous casting process, the tundish baking temperature is ≥1050℃, the superheat during continuous casting is controlled at 20℃-35℃, the electromagnetic stirring current of the crystallizer is 200-250A, the frequency is 2.5-4HZ, the casting speed is controlled at 2.9-3.5m / min, and the specific water content is controlled at 1.2-1.4L / kg. The inspection process includes online infrared detection and low-magnification inspection of the billet, real-time monitoring of shrinkage defects and feedback on process compliance.

[0006] The technical problem to be solved by the present invention can also be further achieved through the following technical solution: For the production method of solving the transverse crack at the end of the 130 square section 3SP steel continuous casting billet described above, in this method, the chemical composition and mass percentage of 3SP are as follows: C: 0.14~0.22%, Si: 0.15~0.30%, Mn: 0.40~0.70%, P≤0.045%, S≤0.045%, with the balance being Fe and unavoidable impurities.

[0007] 3. The production method for solving the transverse crack at the end of a 130 square cross-section 3SP steel continuous casting billet according to claim 1, characterized in that: in the converter process, the molten iron [S] entering the furnace is ≤0.028%, and the molten steel [S] after primary refining in the converter is ≤0.020%.

[0008] The technical problem to be solved by the present invention can also be further achieved through the following technical solution: For the production method of solving the transverse crack at the end of the 130 square section 3SP steel continuous casting billet described above, in the converter process, during the converter deoxidation and alloying process, the [Mn] of the molten steel is controlled to be ≥0.60%, and the Mn / S ratio is guaranteed to be ≥28.

[0009] The technical problem to be solved by the present invention can also be further achieved by the following technical solution: For the production method of solving the transverse crack at the end of the 130 square section 3SP steel continuous casting billet described above, the baking temperature of the tundish in the continuous casting process is ≥1100℃.

[0010] The technical problem to be solved by the present invention can also be further achieved by the following technical solution: For the production method of solving the transverse crack at the end of the 130 square section 3SP steel continuous casting billet described above, in the continuous casting process, the superheat is controlled at 25℃-30℃.

[0011] The technical problem to be solved by the present invention can also be further realized by the following technical solution: For the production method of solving the transverse crack at the end of the 130 square section 3SP steel continuous casting billet as described above: In the continuous casting process, the electromagnetic stirring current of the crystallizer is 220-240A and the frequency is 2.8-3.5HZ.

[0012] The technical problem to be solved by the present invention can also be further achieved by the following technical solution: For the production method of solving the transverse crack at the end of the 130 square section 3SP steel continuous casting billet described above, the casting speed is controlled at 3.2-3.3m / min in the continuous casting process.

[0013] The technical problem to be solved by the present invention can also be further achieved through the following technical solution: For the production method of solving the transverse crack at the end of the 130 square section 3SP steel continuous casting billet described above, the specific water content in the continuous casting process is controlled at 1.3L / kg.

[0014] The technical problem to be solved by the present invention can also be further achieved through the following technical solutions: For the production method of solving the transverse crack at the end of the 130 square section 3SP steel continuous casting billet described above, in the inspection process, the online infrared detection device is equipped with a multispectral analysis module to monitor the surface temperature distribution of the billet and the possible types and locations of defects in real time; the low-magnification inspection of the billet adopts a digital image analysis system to perform quantitative analysis of the internal quality of the billet and automatically feed the analysis results back to the production control system to adjust the production parameters.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention selects molten iron ladles with low sulfur content (S), requiring the molten iron entering the furnace to have a sulfur content (S) of ≤0.030% and the molten steel after primary refining in the converter to have a sulfur content (S) of ≤0.022%, which effectively reduces the sulfur content in the billet and reduces the generation of transverse cracks; 2. In the converter deoxidation and alloying process of this invention, the [Mn] content of the molten steel is controlled to be ≥0.55%, and the Mn / S ratio is guaranteed to be ≥25, which further improves the crack resistance of the billet; 3. This invention controls the baking temperature of the tundish in the continuous casting process to ≥1050℃ and the superheat in the continuous casting process to be controlled at 20℃-35℃, which effectively improves the solidification conditions of the billet and enhances the internal quality of the billet. 4. The present invention uses an electromagnetic stirring current of 200-250A and a frequency of 2.5-4HZ in the crystallizer to increase equiaxed crystal nuclei and improve the crack resistance of the cast billet.

[0016] 5. This invention uses a casting speed control of 2.9-3.5 m / min and a water content control of 1.2-1.4 L / kg. By using high superheat and high casting speed combined with medium-high water content, the billet temperature is increased, the conditions for the formation of transverse cracks in the core of the billet are weakened, and the generation of transverse cracks at the end of the continuously cast billet is suppressed. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] A production method for solving the problem of transverse cracks at the ends of 130 cubic meter cross-section 3SP steel billets is proposed. This method involves ensuring the Mn / S ratio of the molten steel is ≥25, controlling the continuous casting speed at 2.9-3.5 m / min, and adjusting and optimizing the specific water content to 1.2 kg-1.4 L / kg. Specifically: 1. Chemical composition control 3SP steel has specific chemical composition and mass percentage requirements, specifically: C: 0.14~0.22%, Si: 0.15~0.30%, Mn: 0.40~0.70%, P≤0.045%, S≤0.045%, with the balance being Fe and unavoidable impurities; Carbon (C) is an important element affecting the strength and hardness of steel; Silicon (Si) can improve the elastic limit, yield strength and fatigue resistance of steel; Manganese (Mn) can not only improve the strength and hardness of steel, but also effectively deoxidize and desulfurize, and improve the hot working performance of steel; Phosphorus (P) and Sulfur (S) are harmful elements, and their content needs to be strictly controlled to avoid adverse effects on the performance of steel.

[0019] 2. Production process Converter primary refining process: Selection of molten iron: Select molten iron ladle with low sulfur content for converter, requiring the molten iron to be charged with [S] ≤ 0.030%, because sulfur (S) is one of the main elements that cause hot brittleness of steel. During continuous casting, it is easy to agglomerate at the grain boundaries, reducing the grain boundary bonding force and thus causing transverse cracks. Selecting low-sulfur molten iron can reduce the sulfur content at the source, laying the foundation for subsequent control of sulfur content in molten steel.

[0020] Sulfur content control in molten steel after primary refining: After primary refining in the converter, the sulfur content in the molten steel is ≤0.022%. Through the blowing process in the converter, the sulfur content in the molten steel is further reduced, thereby reducing the adverse effects of sulfur on the properties of the steel.

[0021] Deoxidation and alloying process: During the converter deoxidation and alloying process, the [Mn] content in the molten steel is controlled to be ≥0.55%, ensuring an Mn / S ratio ≥25. Manganese has a strong affinity for sulfur, forming manganese sulfide (MnS) inclusions. When the Mn / S ratio reaches a certain value, the manganese sulfide inclusions are spherical, minimizing their adverse effects on steel properties. Simultaneously, manganese can improve the strength and toughness of the steel, enhance its hot working properties, and effectively inhibit the formation of transverse cracks. Furthermore, the tapping temperature is controlled at 1650℃-1680℃. A suitable tapping temperature facilitates the smooth operation of subsequent continuous casting processes, ensuring the fluidity of the molten steel and the quality of casting.

[0022] Continuous casting process: Tundish baking: The tundish baking temperature is ≥1050℃. A higher tundish baking temperature can reduce the contamination of the molten steel by the refractory material on the inner wall of the tundish, while ensuring the temperature stability of the molten steel in the tundish. This avoids the segregation of steel composition and changes in solidification characteristics caused by temperature fluctuations, which would affect the quality of the cast billet.

[0023] Superheat control during continuous casting: The superheat during continuous casting is controlled between 20℃ and 35℃. Appropriate superheat can ensure good solidification of molten steel in the crystallizer and avoid excessive superheat leading to a thin billet shell that is prone to cracking; it also avoids excessive superheat leading to poor fluidity of molten steel that affects the smooth progress of casting.

[0024] Electromagnetic stirring in the crystallizer: Electromagnetic stirring is used in the crystallizer with a current of 200-250A and a frequency of 2.5-4HZ. Electromagnetic stirring can generate forced convection in the molten steel in the crystallizer, increase equiaxed crystal nuclei, refine the grain structure, and improve the crack resistance of the billet. The equiaxed crystal structure is isotropic, which can effectively prevent crack propagation and reduce the generation of transverse cracks.

[0025] Casting speed control: The casting speed should be controlled between 2.9 and 3.5 m / min. A suitable casting speed can ensure the solidification time and rate of the billet in the crystallizer, allowing the billet shell to grow uniformly and avoiding excessively thin shells due to excessive casting speed, which can easily lead to cracks; it also avoids low production efficiency and over-solidification of the billet due to excessively slow casting speed, which increases the risk of crack formation.

[0026] Water content control: The water content should be controlled between 1.2-1.4 L / kg. Utilizing high superheat and high casting speed combined with a medium-to-high water content can increase the billet temperature and weaken the conditions for transverse crack formation in the billet core. A suitable water content ensures uniform cooling of the billet in the secondary cooling zone, preventing excessive internal stress due to uneven cooling, which can lead to transverse cracks.

[0027] Inspection procedures for cast billets: The inspection process includes online infrared detection and low-magnification inspection of the cast billet. Online infrared detection can monitor the temperature distribution and shrinkage defects on the surface of the cast billet in real time, promptly identifying problems in the production process and providing feedback on process compliance. Low-magnification inspection of the cast billet involves observing its microstructure at low magnification to check for defects such as cracks and segregation, assessing the internal quality of the cast billet. The combination of these two inspection methods allows for comprehensive and accurate monitoring of the cast billet quality, ensuring that the produced cast billets meet quality requirements.

[0028] 3. Examples Example 1, Raw material preparation: Select a ladle with molten iron [S]=0.028% for converter smelting.

[0029] Converter primary refining: The process is carried out according to the normal converter blowing process, and the tapping temperature is controlled at 1660℃. After the converter primary refining, the molten steel [S] = 0.020%.

[0030] Deoxidation alloying: During the deoxidation alloying process, an appropriate amount of ferromanganese is added to make the molten steel [Mn] = 0.58%, at which point the Mn / S ratio = 29.

[0031] Continuous casting process: Casting begins after the intermediate ladle reaches a baking temperature of 1060℃.

[0032] The superheat during the continuous casting process is controlled at 25℃.

[0033] The electromagnetic stirring current of the crystallizer is set to 220A and the frequency is 3HZ.

[0034] The pulling speed is controlled at 3.0 m / min.

[0035] The water content should be controlled at 1.3L / kg.

[0036] Ingot inspection: Online infrared detection showed that the surface temperature distribution of the ingot was uniform and no obvious shrinkage cavities were found. Low-magnification inspection of the ingot showed that the internal structure was uniform and no transverse cracks or other defects were found, indicating that the ingot quality was good.

[0037] Example 2, Raw material preparation: A ladle with molten iron [S] = 0.025% was selected for converter smelting.

[0038] Converter primary refining: The tapping temperature is controlled at 1670℃. After converter primary refining, the molten steel [S] = 0.018%.

[0039] Deoxidation and alloying: Adding ferromanganese to adjust the composition of molten steel so that [Mn] = 0.60% and Mn / S ratio = 33.3.

[0040] Continuous casting process: Casting is carried out after the intermediate ladle reaches a baking temperature of 1070℃.

[0041] The superheat during the continuous casting process is controlled at 30℃.

[0042] The electromagnetic stirring current of the crystallizer is set to 240A and the frequency is 3.5HZ.

[0043] The pulling speed is controlled at 3.2 m / min.

[0044] The specific water content is controlled at 1.35L / kg.

[0045] Ingot inspection: Online infrared detection showed that the ingot surface quality was good, with no abnormal temperature fluctuations or shrinkage cavities. Low-magnification inspection of the ingot showed that the ingot had a high proportion of equiaxed grains, a dense structure, and no defects such as transverse cracks, meeting product quality requirements.

[0046] 4. Product Standards and Testing Methods The 3SP product standard of this invention refers to GB / T702-2017, which specifies the technical requirements for the dimensions, shape, weight, and permissible deviations of hot-rolled steel bars. The product performance testing method standard refers to GB / T222, used to determine the chemical composition of steel. The low-magnification testing standards for cast billets refer to YB / T2011 and YB / T153, which involve inspecting the internal defects of the cast billets and evaluating their quality through methods such as low-magnification acid immersion tests.

[0047] In summary, this invention effectively solves the problem of transverse cracks at the ends of 130mm square cross-section 3SP steel continuous casting billets by comprehensively optimizing key process parameters in the converter and continuous casting processes. This improves the internal quality of the billets and the overall yield, resulting in significant economic and social benefits. The embodiments also verify the feasibility and effectiveness of this production method, providing reliable technical support for actual production.

Claims

1. A production method for solving transverse cracks at the end of 130mm square cross-section 3SP steel continuous casting billets, characterized in that: This method includes converter primary refining, continuous casting, and billet inspection processes. It suppresses the generation of transverse cracks at the ends of 130mm square cross-section continuous casting billets by controlling key process parameters of molten iron entering the converter, deoxidation and alloying of tapped steel, and continuous casting processes. In the converter process, when smelting 3SP steel, a ladle with low sulfur content is selected. The molten iron entering the furnace is required to have [S] ≤ 0.030%, and the molten steel after primary refining in the converter has [S] ≤ 0.022%. During the converter deoxidation and alloying process, the molten steel has [Mn] ≥ 0.55%, ensuring that the Mn / S ratio is ≥ 25, and the tapping temperature is 1650℃-1680℃. In the continuous casting process, the tundish baking temperature is ≥1050℃, the superheat during continuous casting is controlled at 20℃-35℃, the electromagnetic stirring current of the crystallizer is 200-250A, the frequency is 2.5-4HZ, the casting speed is controlled at 2.9-3.5m / min, and the specific water content is controlled at 1.2-1.4L / kg. The inspection process includes online infrared detection and low-magnification inspection of the billet, real-time monitoring of shrinkage defects and feedback on process compliance.

2. The production method for solving the transverse crack at the end of a 130mm square cross-section 3SP steel continuous casting billet according to claim 1, characterized in that: In this method, the chemical composition and mass percentage of 3SP are as follows: C: 0.14-0.22%, Si: 0.15-0.30%, Mn: 0.40-0.70%, P≤0.045%, S≤0.045%, with the balance being Fe and unavoidable impurities.

3. The production method for solving the transverse crack at the end of a 130mm square cross-section 3SP steel continuous casting billet according to claim 1, characterized in that: In the converter process, the molten iron [S] entering the furnace is ≤0.028%, and the molten steel [S] after primary refining in the converter is ≤0.020%.

4. The production method for solving the transverse crack at the end of a 130mm square cross-section 3SP steel continuous casting billet according to claim 1, characterized in that: In the converter process, during the converter deoxidation and alloying process, the [Mn] content in the molten steel is controlled to be ≥0.60%, ensuring that the Mn / S ratio is ≥28.

5. The production method for solving the transverse crack at the end of a 130mm square cross-section 3SP steel continuous casting billet according to claim 1, characterized in that: In the continuous casting process, the tundish baking temperature is ≥1100℃.

6. The production method for solving the transverse crack at the end of a 130mm square cross-section 3SP steel continuous casting billet according to claim 1, characterized in that: In the continuous casting process, the superheat is controlled at 25℃-30℃.

7. The production method for solving the transverse crack at the end of a 130mm square cross-section 3SP steel continuous casting billet according to claim 1, characterized in that: In the continuous casting process, the electromagnetic stirring current of the crystallizer is 220-240A, and the frequency is 2.8-3.5HZ.

8. The production method for solving the transverse crack at the end of a 130mm square cross-section 3SP steel continuous casting billet according to claim 1, characterized in that: In the continuous casting process, the casting speed is controlled at 3.2-3.3 m / min.

9. The production method for solving the transverse crack at the end of a 130mm square cross-section 3SP steel continuous casting billet according to claim 1, characterized in that: In the continuous casting process, the specific water content is controlled at 1.3 L / kg.

10. The production method for solving the transverse crack at the end of a 130mm square cross-section 3SP steel continuous casting billet according to claim 1, characterized in that: During the inspection process, the online infrared detection device is equipped with a multispectral analysis module to monitor the surface temperature distribution of the billet and the types and locations of possible defects in real time; the low-magnification inspection of the billet adopts a digital image analysis system to perform quantitative analysis of the internal quality of the billet and automatically feed the analysis results back to the production control system to adjust production parameters.