Flexible h-shaped steel with different grades of yield strength of flange under same component and production method and application thereof

Abstract

This invention provides flexible H-beams with different flange yield strengths of the same composition, their production methods, and applications. Compared with existing technologies, this invention achieves superior comprehensive mechanical properties by using a reasonable and economical chemical composition ratio, strict heating temperature and time, large reduction in the billet stage to break the columnar structure and dynamic recrystallization behavior of the billet, cooling and rolling the flanges in the vertical rolling pass (BD stage) to increase deformation penetration and further refine the grains, and using reasonable inter-pass reduction distribution and temperature-controlled rolling in the universal stage. This results in hot-rolled H-beams with excellent comprehensive mechanical properties, a thickness ≤40mm, and yield strengths of 275MPa and 235MPa on both flanges, with multiple flexible grades. The hot-rolled H-beams produced by this technical solution meet the requirements for different yield strengths and weldability of the upper and lower flanges of H-beams.

Description

Technical Field

[0001] This invention belongs to the field of steel rolling production technology, and more specifically, relates to the preparation of flexible H-beams with different grades of flange thickness ≤40mm and flange yield strength of 275MPa and 235MPa under the same steel composition, as well as the production methods and applications. Background Technology

[0002] Steel structures offer advantages such as light weight, aesthetic appeal, short construction periods, and environmental friendliness, leading to their widespread application in various fields of modern construction engineering, including large-span structures, super high-rise steel structures, large-span industrial plants, large stadiums, viaducts, and long-span bridges. Steel structures must withstand loads in both vertical and horizontal directions; members bearing lateral loads and bending moments are called bending members. Bending members often also bear shear forces while bearing bending moments. In steel structures, bending members are generally referred to as beams. Hot-rolled H-beams possess superior mechanical properties. Due to their biaxially symmetric cross-section, their centroid and shear center coincide, reducing lateral deformation and improving overall stability under lateral loads. Combined with relatively simple manufacturing processes, hot-rolled H-beams are widely used in steel structures.

[0003] The design of flexural members requires ensuring the flexural stiffness and shear strength of the cross-section, while also considering the overall stability of the member, the local stability of the compression flange, and the local stability of the web. Furthermore, flexural members must have sufficient stiffness to ensure that their deformation during operation remains within acceptable limits.

[0004] H-beams are favored by various industries due to their high structural strength, larger section modulus compared to I-beams, and the ability to save 10% to 15% of metal under the same load conditions. They also offer flexible and diverse design styles; for the same beam height, the span of a steel structure can be 50% larger than that of a concrete structure, allowing for more flexible building layouts. Furthermore, their lighter weight compared to concrete structures reduces structural internal forces, simplifies foundation requirements, simplifies construction, and lowers costs.

[0005] In existing technologies, hot-rolled H-beams generally have upper and lower flanges with the same cross-section and thickness. Patent CN 103422610 A, published on December 4, 2013, discloses a "compression flange reinforced H-beam or I-beam." Its disclosed technical solution increases stiffeners, improving the buckling resistance and compressive stiffness of the compression flange portion of the compression flange reinforced H-beam or I-beam. Secondly, it reduces the cross-section of the tension flange, thereby reducing the functional redundancy of the tension flange. Furthermore, the compression flange reinforced H-beam or I-beam, as a whole, reflects the scientific and economical use of materials, compensating for the deficiencies of existing compression flanges and achieving a balanced performance of overall tensile, compressive, and shear resistance. This method mainly achieves tensile, compressive, and shear resistance by reducing the lower flange cross-section and increasing stiffeners, but this requires additional stiffeners, increasing costs. Summary of the Invention

[0006] The purpose of this invention is to provide a flexible H-beam with different flange yield strengths under the same composition and its production method. Through composition design, by utilizing fine grain strengthening, precipitation strengthening, phase transformation strengthening and solid solution strengthening mechanisms, flexible hot-rolled H-beams with different grades and excellent comprehensive mechanical properties are obtained, with flange thickness ≤40mm, yield strength of 275MPa on one flange and 235MPa on the other flange.

[0007] Another objective of this invention is to provide an application of flexible H-beams with different flange yield strengths of the same composition for use in the construction field.

[0008] The specific technical solution of this invention is as follows:

[0009] The present invention provides flexible H-beams with different flange yield strengths of the same composition. The flexible H-beams have a yield strength ≥275MPa, a tensile strength of 410MPa~540MPa, and an elongation ≥22% on one flange, and a yield strength ≥235MPa, a tensile strength of 370MPa~500MPa, and an elongation ≥26% on the other flange.

[0010] The flange of the flexible H-beam with a flange yield strength ≥275MPa has a ferrite + pearlite multiphase structure, and the ferrite grain size grade is ≥8.0.

[0011] The flange of the flexible H-beam with a flange yield strength ≥235MPa has a ferrite + pearlite multiphase structure, and the ferrite grain size is ≥7.5.

[0012] The flange thickness of the flexible H-beams with different flange yield strengths of the same composition is ≤40mm.

[0013] The two flanges of the H-beam are the same size;

[0014] The flexible H-beams with different flange yield strengths of the same composition include the following components by mass percentage:

[0015] C: 0.13%–0.20%, Si: 0.20%–0.35%, Mn: 1.20%–1.40%, P: ≤0.040%, S: ≤0.040%, with the remainder being Fe and unavoidable impurities.

[0016] This invention strictly controls the content of impurity elements such as P and S. The content of each component is controlled as follows:

[0017] C: 0.13%~0.20%. As a basic element in steel, C plays a very important role in improving the strength of steel. In order to obtain higher strength and reduce the difficulty of removing C in steelmaking, the lower limit is set at 0.13%. Excessive C content will seriously deteriorate the plasticity, toughness and weldability of steel, so the upper limit is set at 0.20%.

[0018] Si: 0.20%~0.35%. An appropriate amount of Si can play a strong solid solution strengthening role. Si is also an important reducing and deoxidizing element in the steelmaking process. In order to obtain higher strength, the lower limit is set at 0.20%, but the Si content cannot be too high. Studies have shown that excessive Si content will accelerate high-temperature delamination, reduce toughness and resistance to lamellar tearing, and easily generate red iron oxide scale on the surface of steel, affecting the surface quality of the product. The upper limit is set at 0.35%.

[0019] Mn: 1.20%~1.40%. Mn is a strengthening element in steel, which can improve the strength and hardenability of steel. In order to ensure the strength of steel, the lower limit is set at 1.20%. However, the Mn content cannot be too high. If it is too high, the feasibility of billet segregation will increase significantly, which will have an adverse effect on the formability of steel. The upper limit is set at 1.40%.

[0020] P and S, as impurity elements, can adversely affect the plasticity, toughness, and weldability of steel and should be strictly controlled. Considering the difficulty of controlling these elements in steelmaking, in actual production, P should be controlled at ≤0.040% and S at ≤0.040%.

[0021] The present invention provides a method for producing flexible H-beams with different flange yield strengths of the same composition, comprising the following process flow:

[0022] Converter smelting → Argon blowing refining → Continuous casting of irregular billets → Billet heating → BD section vertical rolling pass secondary flange cooling and rolling → Universal rolling → Air cooling.

[0023] The converter smelting process involves a steel flow time of ≥3 minutes. In the early stage of tapping, a carbon raiser is added based on the carbon content at the converter endpoint for pre-deoxidation.

[0024] The argon blowing refining process involves bottom blowing inert argon gas during smelting to remove dissolved gases and suspended non-metallic inclusions from the steel, purifying the molten steel, and then continuously casting it into billets.

[0025] The billet is heated by placing the irregularly shaped billet into a heating furnace and heating it to 1180℃~1220℃ for 80min~120min to ensure that the alloying elements are fully dissolved, while avoiding overheating and excessive coarsening of austenite grains.

[0026] The aforementioned method of using secondary flange cooling rolling in the BD section vertical rolling mill for billet preparation specifically involves:

[0027] The initial rolling temperature during the roughing stage is controlled at 1150℃~1180℃, and the final rolling temperature is controlled at above 1000℃.

[0028] Preferably, for flanges with a flange yield strength ≥275MPa, during the rough rolling stage, the reduction rate per pass is controlled at 12% to 14% in the temperature range of 1150℃ < temperature ≤1180℃; the reduction rate per pass is controlled at 22% to 27% in the temperature range of 1100℃ < temperature ≤1150℃; and the reduction rate per pass is controlled at 23% to 30% in the temperature range of 1050℃ < temperature ≤1100℃, with the total reduction rate of the billet controlled at over 50%.

[0029] Preferably, flanges with a flange yield strength ≥ 235 MPa are rolled at a temperature < 1150℃ during the rough rolling stage.

[0030] In the temperature range of ≤1180℃, the reduction rate per pass is controlled at 12% to 20%; in the temperature range of 1100℃ < temperature ≤1150℃, the reduction rate per pass is controlled at 18% to 30%; in the temperature range of 1050℃ < temperature ≤1100℃, the reduction rate per pass is controlled at 20% to 25%, and the total reduction rate of the billet is controlled at over 50%.

[0031] In the initial billet rolling process, the secondary flange cooling rolling method using the BD section vertical rolling pass is employed.

[0032] In the temperature range of 1150℃ < temperature ≤ 1180℃, the reduction rate of the flange pass for flanges with a flange yield strength ≥ 275MPa is less than the reduction rate of the flange pass for flanges with a flange yield strength ≥ 235MPa.

[0033] In the temperature range of 1100℃ < temperature ≤ 1150℃, the reduction rate of the flange pass for flanges with a flange yield strength ≥ 275MPa shall not be greater than the reduction rate of the flange pass for flanges with a flange yield strength ≥ 235MPa.

[0034] In the temperature range of 1050℃ < temperature ≤ 1100℃, the reduction rate of the flange pass for flanges with a flange yield strength ≥ 275MPa is greater than that of flanges with a flange yield strength ≥ 235MPa.

[0035] This stage is within the austenite recrystallization temperature range. The deformation per pass must be greater than the upper limit of the critical recrystallization deformation to ensure complete recrystallization. The reduction rate per pass in different temperature ranges is controlled to ensure that the austenite recrystallization percentage in each pass reaches more than 50%. Through large rolling deformation and repeated recrystallization of austenite, the austenite grains are continuously refined, so that the ferrite grain size of the final product reaches grade 7.5 or above, meeting the final comprehensive mechanical property requirements of the product.

[0036] After rough rolling, hot-rolled H-beams do not need to wait for warming and can directly enter the universal rolling mill for rolling. The remaining deformation of the billet is completed in this stage. The final rolling temperature of the flange side with a flange yield strength ≥275MPa is controlled below 930℃; the final rolling temperature of the flange side with a flange yield strength ≥235MPa is controlled below 950℃.

[0037] Preferably, in the universal rolling process, for flanges with a flange yield strength ≥275MPa, the reduction per pass is controlled at 10%–14% in the temperature range of 1000℃ < temperature ≤1050℃. This stage is two-phase rolling, and a deformation of more than 10% can improve strength and form a weak crystal texture with minimal separation. In the temperature range of 930℃ < temperature ≤1000℃, the reduction per pass is controlled at 25%–35%; in the temperature range below 930℃, the reduction per pass is controlled at 12%–15%, and the billet reduction per pass in this stage is controlled at over 55%.

[0038] Preferably, in the universal rolling process, for flanges with a flange yield strength ≥235MPa, the reduction per pass is controlled at 12%–18% in the temperature range of 1000℃ < temperature ≤1050℃. This stage is a two-phase rolling process, where a deformation of more than 10% can improve strength and form a weak crystal texture with minimal separation. In the temperature range of 950℃ < temperature ≤1000℃, the reduction per pass is controlled at 20%–30%; in the temperature range below 950℃, the reduction per pass is controlled at 12%–15%, and the billet reduction rate in this stage is controlled at over 55%.

[0039] The universal rolling process:

[0040] In the temperature range of 1000℃ < temperature ≤ 1050℃, the flange pass reduction rate for flanges with a yield strength ≥ 275MPa is less than that for flanges with a yield strength ≥ 235MPa.

[0041] The reduction rate per pass for flanges with a flange yield strength ≥ 275 MPa in the temperature range of 930℃ < temperature ≤ 1000℃ is greater than that for flanges with a flange yield strength ≥ 235 MPa in the temperature range of 950℃ < temperature ≤ 1000℃.

[0042] The reduction rate of a flange with a yield strength ≥ 275 MPa in the temperature range below 930℃ is equal to the reduction rate of a flange with a yield strength ≥ 2375 MPa in the temperature range below 950℃.

[0043] This stage falls within the non-recrystallization temperature range of austenite. In this temperature range, austenite recrystallization does not occur. The cumulative deformation caused by low temperature and high pressure elongates the austenite grains, forming numerous deformation bands and dislocations within the grains. The increased grain boundary area raises the austenite nucleation density, further refining the grain size, improving the steel's strength and toughness. The numerous crystallographic defects generated within the deformed austenite provide nucleation sites for ferrite phase transformation, leading to ferrite grain refinement. Simultaneously, the elongated austenite and the numerous deformation bands and dislocations provide ample landing sites for the precipitation of carbonitride second-phase particles. The stored energy formed under low temperature and high pressure also provides sufficient kinetic energy for the precipitation of carbonitride second-phase particles.

[0044] The universal rolling process utilizes a selective cooling system between the universal stands to precisely control the temperature changes of the rolled piece. For flanges with a yield strength ≥275MPa, the nozzles are fully open with a water pressure of 0.2MPa~0.5MPa; for flanges with a yield strength ≥235MPa, the nozzles are closed. Combined with the reduction designed in the rolling procedure, the H-beams are subjected to the set deformation within the corresponding temperature range to ensure the final product performance.

[0045] Universally rolled H-beams are air-cooled on a cooling bed.

[0046] This invention provides an application of flexible H-beams with different flange yield strengths of the same composition in the construction field.

[0047] The inventors discovered that because the flanges in the tensile zone do not require consideration of buckling, while the flanges in the compressive zone do require consideration of both buckling and stiffness, it is not economical and scientifically sound to design the upper and lower flanges with identical cross-sections (especially since the flanges in the compression zone are also designed as flat plates). In load-bearing tests, most failures occur at the loading point or mid-span, with the upper flange under compression buckling first, leading to increased deflection of the steel beam, causing local buckling of the web, and ultimately resulting in buckling or overturning torsional deformation and failure of the entire steel beam. This principle illustrates that the upper and lower flanges of H-beams or corrugated H-beams should have larger geometric cross-sections or higher strength; otherwise, the compressive flange will become the weakest point in the entire steel beam structure and will fail first. To meet design requirements, high-strength H-beams or increased flange thickness and cross-section are necessary, but this leads to insufficient utilization of material properties, resulting in disadvantages such as low economy, inadequate stiffness, and increased weight.

[0048] When the chemical composition and size of the billet are constant, traditional rolling processes are difficult to achieve the requirements of this invention. The design concept of this invention mainly involves a reasonable and economical chemical composition ratio, strict heating temperature and time, large reduction in the initial rolling stage to break up the columnar structure and dynamic recrystallization behavior of the billet, cooling and reducing the flange temperature in the vertical rolling pass (BD stage) to increase deformation penetration and further refine the grains, and finally, through reasonable reduction distribution and temperature-controlled rolling in the universal stage, achieving hot-rolled H-beams (MF hot-rolled H-beams) with excellent comprehensive mechanical properties, a thickness ≤40mm, and yield strengths of 275MPa and 235MPa on both flanges, and multiple flexibility levels. By reasonably distributing the reduction amount and controlling the temperature in each pass, deformation is avoided within the austenite recrystallization temperature range, thus increasing deformation penetration. Specifically, it employs a reasonable chemical composition, strict heating temperature and time, large reduction during billet opening, cooling rolling of the flanges in the BD section vertical rolling pass, and universal temperature-controlled rolling process. By reasonably allocating the reduction amount and controlling the temperature in each pass, deformation is avoided within the recrystallization temperature range of austenite, deformation penetration is increased, and deformation within the austenite recrystallization temperature range is increased to further refine the grain size.

[0049] Developing hot-rolled H-beams to replace welded H-beams meets environmental protection requirements. To address the aforementioned challenges and facilitate billet production in steel mills, this invention utilizes the same steel composition and different rolling processes to produce hot-rolled H-beams with varying degrees of flexibility in the upper and lower flanges (referred to as MF hot-rolled H-beams). Compared to existing technologies, this invention, while considering cost and quality, produces H-beams with the same steel composition, featuring flange thickness ≤40mm, upper flange yield strength ≥275MPa, tensile strength 410MPa~540MPa, elongation ≥22%, and lower flange yield strength ≥235MPa, tensile strength 370MPa~500MPa. This paper describes a rolling process for hot-rolled H-beams with various flexibility grades, including those with a strength of 0 MPa and an elongation of ≥26%. The process employs a rational and economical chemical composition ratio, controlled inter-pass reduction, and universal temperature-controlled rolling, improving the performance of the rolled product. Utilizing fine-grain strengthening, precipitation strengthening, and phase transformation strengthening mechanisms, the flange side microstructure at 235 MPa is a ferrite + pearlite multiphase structure with a ferrite grain size of ≥7.5, and the flange side microstructure at 275 MPa is also a ferrite + pearlite multiphase structure with a ferrite grain size of ≥8.0. Hot-rolled H-beams produced using this technology meet the requirements for different yield strengths and weldability of the upper and lower flanges. Detailed Implementation

[0050] The present invention will be further described below with reference to specific embodiments.

[0051] Taking the yield strength of the upper flange of an H-beam ≥275MPa and the yield strength of the lower flange ≥235MPa as an example, the following description is provided.

[0052] Examples 1 to 3

[0053] Flexible H-beams with different flange yield strengths of the same composition include the following elements by mass percentage: see Table 1 below. The remainder not shown in Table 1 are Fe and unavoidable impurity elements.

[0054] Comparative Examples 1 to 4

[0055] H-beams include the following elements by mass percentage: see Table 1 below for details. The remainder not shown in Table 1 are Fe and unavoidable impurity elements.

[0056] Table 1. List of chemical composition values ​​(wt%) for each embodiment and comparative example of the present invention.

[0057]

[0058]

[0059] Note that H300×300×12×12 refers to the height, width, web thickness, and flange thickness, respectively.

[0060] The production methods of H-beams in the above embodiments and comparative examples include the following process flow:

[0061] Converter smelting → Argon blowing refining → Continuous casting of irregularly shaped billets → Billet heating → BD section vertical rolling mill secondary flange cooling and rolling → Universal rolling → Air cooling. Details are as follows:

[0062] The converter smelting process involves a steel flow time of ≥3 minutes. In the early stage of tapping, a carbon raiser is added based on the carbon content at the converter endpoint for pre-deoxidation.

[0063] The argon blowing refining process involves bottom blowing inert argon gas during smelting to remove dissolved gases and suspended non-metallic inclusions from the steel, purifying the molten steel, and then continuously casting it into billets.

[0064] The billet is heated by placing the irregularly shaped billet into a heating furnace and heating it to 1180℃~1220℃ for 80min~120min to ensure that the alloying elements are fully dissolved, while avoiding overheating and excessive coarsening of austenite grains.

[0065] The aforementioned method of using secondary flange cooling rolling in the BD section vertical rolling mill for billet preparation specifically involves:

[0066] The initial rolling temperature during the roughing stage is controlled at 1150℃~1180℃, and the final rolling temperature is controlled at above 1000℃.

[0067] For flanges with a yield strength ≥275MPa, during the rough rolling stage, the reduction rate per pass is controlled at 12%–14% in the temperature range of 1150℃ ≤ 1180℃; in the temperature range of 1100℃ ≤ 1150℃, the reduction rate per pass is controlled at 22%–27%; and in the temperature range of 1050℃ ≤ 1100℃, the reduction rate per pass is controlled at 23%–30%, with the total reduction rate of the billet controlled at over 50%.

[0068] Preferably, flanges with a flange yield strength ≥ 235 MPa are rolled at a temperature < 1150℃ during the rough rolling stage.

[0069] In the temperature range of ≤1180℃, the reduction rate per pass is controlled at 12% to 20%; in the temperature range of 1100℃ < temperature ≤1150℃, the reduction rate per pass is controlled at 18% to 30%; in the temperature range of 1050℃ < temperature ≤1100℃, the reduction rate per pass is controlled at 20% to 25%, and the total reduction rate of the billet is controlled at over 50%.

[0070] After rough rolling, hot-rolled H-beams do not need to wait for warming and can directly enter the universal rolling mill for rolling. The remaining deformation of the billet is completed in this stage. The final rolling temperature of the flange side with a flange yield strength ≥275MPa is controlled below 930℃; the final rolling temperature of the flange side with a flange yield strength ≥235MPa is controlled below 950℃.

[0071] The universal rolling process, where flanges with a yield strength ≥275MPa are rolled in the temperature range of 1000℃ < temperature ≤1050℃, with a reduction rate controlled at 10%–14% per pass, is a two-phase rolling process. A deformation of more than 10% can improve strength and form a weak crystal texture with minimal segregation. In the range of 930℃ < temperature...

[0072] In the temperature range of ≤1000℃, the reduction rate per pass is controlled at 25% to 35%; in the temperature range below 930℃, the reduction rate per pass is controlled at 12% to 15%, and the billet reduction rate in this stage is controlled at more than 55%.

[0073] The universal rolling process, for flanges with a yield strength ≥235MPa, involves a reduction rate of 12%–18% per pass within the temperature range of 1000℃ < temperature ≤1050℃. This stage is a two-phase rolling process, where a deformation of more than 10% can improve strength and form a weak crystal texture with minimal segregation. Within the temperature range of 950℃ < temperature...

[0074] In the temperature range of ≤1000℃, the reduction rate per pass is controlled at 20% to 30%; in the temperature range below 950℃, the reduction rate per pass is controlled at 12% to 15%, and the billet reduction rate in this stage is controlled at more than 55%.

[0075] The universal rolling process utilizes a selective cooling system between the universal stands to precisely control the temperature changes of the rolled piece. For flanges with a yield strength ≥275MPa, the nozzles are fully open with a water pressure of 0.2MPa~0.5MPa; for flanges with a yield strength ≥235MPa, the nozzles are closed. Combined with the reduction designed in the rolling procedure, the H-beams are subjected to the set deformation within the corresponding temperature range to ensure the final product performance.

[0076] Universally rolled H-beams are air-cooled on a cooling bed.

[0077] The process parameters for each embodiment and comparative example production process are controlled as shown in Tables 2 and 3 below.

[0078] Table 2. Main process parameters of BD roughing for each embodiment and comparative example.

[0079]

[0080]

[0081] Table 3. Main process parameters of universal finishing rolling for each embodiment and comparative example.

[0082]

[0083] The performance testing of the H-beams produced in Examples 1 to 3 and Comparative Examples 1 to 4 was carried out in accordance with GB / T 11263 standard, and the specific details are shown in Table 4.

[0084] Table 4. Performance of H-beams produced in various embodiments and comparative examples of the present invention.

[0085]

[0086]

[0087] It should be noted that Comparative Examples 2 and 3 used the chemical composition of the present invention, with values ​​taken within the defined range, and the process used was existing technology; Comparative Example 1 did not use the chemical composition of the present invention, and the process used was existing technology; Comparative Example 4 used the chemical composition of the present invention and different rolling processes for the upper and lower flanges, but the parameters did not meet the requirements of the present invention. The performance of Comparative Examples 1-4 does not meet the performance requirements of the present invention.

[0088] This invention provides a method for producing hot-rolled H-beams (MF hot-rolled H-beams) with varying flexibility grades (≤40mm flange thickness, yield strengths of 275MPa and 235MPa on both flanges) using the same steel composition. It employs a rational chemical composition, heating regime, and rolling process. In particular, by strictly controlling heating temperature and time, adjusting the reduction between passes, using cooling rolling of the flanges in the BD section vertical rolling pass, and selective cooling and temperature control rolling between stands in the universal section, the uniformity of the rolled product's performance across the entire cross-section is improved. Utilizing fine-grain strengthening, precipitation strengthening, phase transformation strengthening, and solid solution strengthening mechanisms, hot-rolled H-beams with excellent comprehensive mechanical properties, a thickness ≤40mm, and yield strengths of 275MPa and 235MPa on both flanges, are obtained with varying flexibility grades.

[0089] The above-described detailed description of the production method of hot-rolled H-beams with different flexibility grades, including flange thickness ≤40mm, upper flange yield strength ≥275MPa, tensile strength 410MPa~540MPa, elongation ≥22%, lower flange yield strength ≥235MPa, tensile strength 370MPa~500MPa, and elongation ≥26%, under the same steel composition, is illustrative rather than limiting. Several embodiments can be listed according to the defined scope. Therefore, changes and modifications without departing from the overall concept of the present invention should be within the protection scope of the present invention.

Claims

1. Flexible H-beams with different flange yield strengths of the same composition, characterized in that, The flexible H-beam has a yield strength ≥275MPa, a tensile strength of 410MPa~540MPa, and an elongation ≥22% on one flange, and a yield strength ≥235MPa, a tensile strength of 370MPa~500MPa, and an elongation ≥26% on the other flange. The flexible H-beam comprises the following components by weight percentage: C: 0.13%~0.20%, Si: 0.20%~0.35%, Mn: 1.20%~1.40%, P: ≤0.040%, S: ≤0.040%, with the remainder being Fe and unavoidable impurities; The production method of the flexible H-beam includes the following process flow: Converter smelting → Argon blowing refining → Continuous casting of irregular billets → Billet heating → BD section vertical rolling pass secondary flange cooling and rolling → Universal rolling → Air cooling; For flanges with a yield strength ≥275MPa, during the rough rolling stage, the reduction rate per pass is controlled at 12%–14% in the temperature range of 1150℃ < temperature ≤1180℃; 22%–27% in the temperature range of 1100℃ < temperature ≤1150℃; and 23%–30% in the temperature range of 1050℃ < temperature ≤1100℃, with the total reduction rate of the billet controlled above 50%. After rough rolling, hot rolling... H-beams are directly rolled into a universal rolling mill, with the final rolling temperature controlled below 930℃. During the universal rolling stage, in the temperature range of 1000℃ < temperature ≤ 1050℃, the reduction rate per pass is controlled at 10% to 14%; in the temperature range of 930℃ < temperature ≤ 1000℃, the reduction rate per pass is controlled at 25% to 35%; and in the temperature range below 930℃, the reduction rate per pass is controlled at 12% to 15%, with the billet reduction rate controlled above 55% during this stage. For flanges with a yield strength ≥235MPa, during the rough rolling stage, the reduction rate per pass is controlled at 12%–20% in the temperature range of 1150℃ < temperature ≤1180℃; 18%–30% in the temperature range of 1100℃ < temperature ≤1150℃; and 20%–25% in the temperature range of 1050℃ < temperature ≤1100℃, with the total reduction rate of the billet controlled above 50%. After rough rolling, hot rolling… H-beams are directly rolled into a universal rolling mill, with the final rolling temperature controlled below 950℃. During the universal rolling stage, in the temperature range of 1000℃ < temperature ≤ 1050℃, the reduction rate per pass is controlled at 12% to 18%; in the temperature range of 950℃ < temperature ≤ 1000℃, the reduction rate per pass is controlled at 20% to 30%; and in the temperature range below 950℃, the reduction rate per pass is controlled at 12% to 15%, with the billet reduction rate controlled above 55% during this stage. In the universal rolling process, the flange-side nozzles with a flange yield strength ≥275MPa are fully open, and the water pressure is 0.2MPa~0.5MPa; the flange-side nozzles with a flange yield strength ≥235MPa are closed.

2. The flexible H-beam with different flange yield strengths of the same composition according to claim 1, characterized in that, The flange of the flexible H-beam with a flange yield strength ≥275MPa has a ferrite + pearlite multiphase structure, and the ferrite grain size grade is ≥8.

0. The flange of the flexible H-beam with a flange yield strength ≥235MPa has a ferrite + pearlite dual phase structure, with a ferrite grain size of ≥7.

5.

3. A method for producing flexible H-beams of the same composition with different flange yield strengths as described in claim 1 or 2, characterized in that, The production method includes the following process flow: Converter smelting → Argon blowing refining → Continuous casting of irregular billets → Billet heating → BD section vertical rolling pass secondary flange cooling and rolling → Universal rolling → Air cooling; For flanges with a yield strength ≥275MPa, during the rough rolling stage, the reduction rate per pass is controlled at 12%–14% in the temperature range of 1150℃ < temperature ≤1180℃; 22%–27% in the temperature range of 1100℃ < temperature ≤1150℃; and 23%–30% in the temperature range of 1050℃ < temperature ≤1100℃, with the total reduction rate of the billet controlled above 50%. After rough rolling, hot rolling... H-beams are directly rolled into a universal rolling mill, with the final rolling temperature controlled below 930℃. During the universal rolling stage, in the temperature range of 1000℃ < temperature ≤ 1050℃, the reduction rate per pass is controlled at 10% to 14%; in the temperature range of 930℃ < temperature ≤ 1000℃, the reduction rate per pass is controlled at 25% to 35%; and in the temperature range below 930℃, the reduction rate per pass is controlled at 12% to 15%, with the billet reduction rate controlled above 55% during this stage. For flanges with a yield strength ≥235MPa, during the rough rolling stage, the reduction rate per pass is controlled at 12%–20% in the temperature range of 1150℃ < temperature ≤1180℃; 18%–30% in the temperature range of 1100℃ < temperature ≤1150℃; and 20%–25% in the temperature range of 1050℃ < temperature ≤1100℃, with the total reduction rate of the billet controlled above 50%. After rough rolling, hot rolling… H-beams are directly rolled into a universal rolling mill, with the final rolling temperature controlled below 950℃. During the universal rolling stage, in the temperature range of 1000℃ < temperature ≤ 1050℃, the reduction rate per pass is controlled at 12% to 18%; in the temperature range of 950℃ < temperature ≤ 1000℃, the reduction rate per pass is controlled at 20% to 30%; and in the temperature range below 950℃, the reduction rate per pass is controlled at 12% to 15%, with the billet reduction rate controlled above 55% during this stage. In the universal rolling process, the flange-side nozzles with a flange yield strength ≥275MPa are fully open, and the water pressure is 0.2MPa~0.5MPa; the flange-side nozzles with a flange yield strength ≥235MPa are closed.

4. The production method according to claim 3, characterized in that, In the universal rolling process, during the universal rolling stage, the reduction rate of flanges with a flange yield strength ≥275MPa is less than that of flanges with a flange yield strength ≥235MPa in the temperature range of 1000℃ < temperature ≤1050℃; the reduction rate of flanges with a flange yield strength ≥275MPa in the temperature range of 930℃ < temperature ≤1000℃ is greater than that of flanges with a flange yield strength ≥235MPa in the temperature range of 950℃ < temperature ≤1000℃; and the reduction rate of flanges with a flange yield strength ≥275MPa in the temperature range below 930℃ is equal to that of flanges with a flange yield strength ≥2375MPa in the temperature range below 950℃.

5. The production method according to claim 3, characterized in that, The billet is heated by entering a heating furnace and being heated to 1180℃~1220℃ for 80min~120min.

6. The production method according to claim 3, characterized in that, The secondary flange of the BD section vertical rolling mill is cooled and rolled, with the initial rolling temperature controlled at 1150℃~1180℃ and the final rolling temperature controlled at above 1000℃.

7. The production method according to claim 3, characterized in that, In the initial billet rolling process, the secondary flange cooling rolling method using the BD section vertical rolling pass is employed. In the temperature range of 1150℃ < temperature ≤ 1180℃, the reduction rate of the flange pass for flanges with a flange yield strength ≥ 275MPa is less than the reduction rate of the flange pass for flanges with a flange yield strength ≥ 235MPa. In the temperature range of 1100℃ < temperature ≤ 1150℃, the reduction rate of the flange pass for flanges with a flange yield strength ≥ 275MPa shall not be greater than the reduction rate of the flange pass for flanges with a flange yield strength ≥ 235MPa. In the temperature range of 1050℃ < temperature ≤ 1100℃, the reduction rate of the flange pass for flanges with a flange yield strength ≥ 275MPa is greater than that of flanges with a flange yield strength ≥ 235MPa.

8. The application of a flexible H-beam with different flange yield strengths of the same composition as described in claim 1 or 2, characterized in that, Used in the construction field.

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