High-precision ultra-thin h-shaped steel production method and system

Abstract

This invention discloses a high-precision ultra-thin H-beam production method and system, applicable to H-beams with web and / or flange thickness ≤ 8 mm. The billet is heated to 1200℃-1250℃, rough-rolled 3-11 times, exiting at 1050±20℃, and finish-rolled 9-11 times with a reduction rate of 8%-15%, and a flange-to-web reduction ratio of 0.8-1.2. During finish rolling, tension fluctuation is controlled to ≤ ±1.5% using a dynamic tension model, with segmented linear tension compensation at the beginning and end, and closed-loop control ensuring the web-to-flange temperature difference is ≤ 30℃. The final rolling temperature at the end of finish rolling is Ar3+20℃-40℃, employing atomized cooling for the flanges and laminar flow cooling for the web, with a cooling intensity ratio of 0.7-0.9 and a cooling rate of 10-15℃ / s to air cooling below 650℃. The system includes a roughing mill with AGC and axial rolls, a universal finishing mill, an infrared temperature measurement array (accuracy ±5℃), a distributed cooling nozzle group, and a microstructure detection unit. This invention achieves web and flange thickness deviations ≤0.5mm, grain size differences ≤1 grade, pearlite content deviation ≤5%, and lamellar spacing ≤0.4μm.

Description

Technical Field

[0001] This invention belongs to the technical field of hot-rolled H-beams and relates to a high-precision ultra-thin H-beam production method and system. Background Technology

[0002] H-beams are an economical and efficient profile with optimized cross-sectional area distribution and a reasonable strength-to-weight ratio, named for their "H"-shaped cross-section. Due to the right-angled arrangement of the web and flanges, H-beams exhibit excellent bending resistance in all directions, are easy to construct, have low cost, and are lightweight. They are widely used in high-rise building curtain wall framing, commercial trailer bottom beams, and photovoltaic supports. Compared to welded H-beams, hot-rolled H-beams offer higher overall strength, bending resistance, stability, and fatigue life. They also boast a more efficient production process, better quality consistency, lower overall life-cycle cost, lower resource utilization, and higher recyclability, meeting environmental and energy-saving requirements. With the rapid development of the construction, manufacturing, and new energy industries, the demand for ultra-thin H-beams with web and flange thicknesses ≤8mm is increasing. Their lightweight and high-strength characteristics make them invaluable in high-end applications.

[0003] However, the production of ultra-thin H-beams faces multiple technical challenges. Traditional hot-rolled H-beam production processes have the following significant problems when producing ultra-thin H-beams with web and flange thicknesses ≤8mm: First, due to the small web and flange thickness of ultra-thin H-beams, heat dissipation is rapid, resulting in a large temperature difference between the web and flange during rolling (usually exceeding 50℃), leading to inconsistent deformation and making it difficult to control the thickness deviation between the web and flange within 0.5mm. In traditional processes, the flange-to-web reduction ratio lacks precise control, often resulting in excessively thin flanges or excessively thick webs, affecting product dimensional accuracy and consistency. Second, insufficient temperature control during rolling leads to uneven temperature fields between roughing and finishing stages, resulting in differences in microstructure properties. Grain size deviations typically exceed grade 2, pearlite content deviations are as high as 10% or more, and lamellar spacing is often greater than 0.5μm, making it difficult to meet the requirements of high-end applications for mechanical properties and microstructure uniformity.

[0004] Furthermore, traditional processes have limitations in tension control. Tension fluctuations between continuous rolling mills are significant (typically exceeding ±3%), lacking a dynamic adjustment mechanism. This is especially true in the transition zones at the beginning and end of the rolled piece, where the absence of effective tension compensation strategies leads to defects such as out-of-tolerance deviations and wavy bends, reducing yield. Regarding cooling processes, traditional production often employs a single cooling method (such as laminar flow cooling), failing to differentiate the heat dissipation characteristics of the flanges and web. The cooling intensity ratio is not optimized, making it difficult to balance the demands of rapid flange heat dissipation and uniform web cooling, further exacerbating microstructure inhomogeneity. Summary of the Invention

[0005] In view of this, the purpose of this invention is to overcome the defects of low dimensional accuracy, uneven microstructure and poor production stability in the production of ultra-thin H-beams in the prior art, and to provide a high-precision production method and system for ultra-thin H-beams, which is applicable to H-beams with web and flange thickness ≤ 8 mm, and achieves high-precision production with web and flange thickness deviation ≤ 0.5 mm, grain size difference ≤ 1 grade, pearlite content deviation ≤ 5%, and pearlite lamellar spacing ≤ 0.4 μm.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A high-precision ultra-thin H-beam production method is applicable to H-beams with web and / or flange thickness ≤ 8mm. The billet is heated to 1200℃-1250℃ and then rough rolled 3-11 times. The exit temperature of the rough rolling is controlled at 1050±20℃. Then, it is finished rolled 9-11 times. The single-pass reduction rate is controlled at 8%-15%, and the flange to web reduction ratio is controlled at 0.8-1.2.

[0008] During the finishing rolling process, the tension between the continuous rolling mills is adjusted in real time according to the thickness deviation using a dynamic tension model, with a tension fluctuation range of ≤±1.5%, and segmented linear tension compensation is adopted in the transition zone between the head and tail. At the same time, the temperature difference between the web and flange of the H-beam is kept ≤30℃ by a temperature compensation device and a closed-loop control system. Temperature control adopts atomized cooling of the flange and laminar flow cooling of the web, and the cooling intensity ratio of the flange to the web is controlled at 0.7 to 0.9.

[0009] At the end of the finishing rolling process, the final rolling temperature is controlled at 20℃-40℃ above the Ar3 phase transformation point. After cooling to below 650℃ at a cooling rate of 10℃ / s-15℃ / s, the H-beam is air-cooled. The resulting H-beam has a grain size difference of ≤1 grade between the web and flange, a pearlite content deviation of ≤5%, and a pearlite lamellar spacing of ≤0.4μm.

[0010] Furthermore, in the continuous finishing rolling process, the reduction amount per pass is distributed as follows: the first 3 passes complete 40% to 50% of the total reduction amount, the middle passes complete 30% to 40%, and the last 3 passes complete the remaining 10% to 20%, ultimately ensuring that the total reduction amount is 100%.

[0011] Furthermore, the dynamic tension control adopts a micro-tension deviation dynamic control model, and the model formula is as follows:

[0012] Δh=K·(T 头 -T 尾 )·e -t / τ

[0013] Where Δh is the thickness deviation, K is the material coefficient, and T 头 and T The tail represents the tension at the head and tail, τ is the time constant, and t is time.

[0014] Furthermore, piecewise linear tension compensation is adopted in the transition zone between the beginning and end of the workpiece. The tension increase rate is 1.5 kN / m for the first 5 meters of the workpiece, and the decrease rate is 2 kN / m for the last 5 meters. The mathematical model is as follows:

[0015]

[0016] Among them, T base The reference tension is set according to the type and size of the steel; L is the length of the steel.

[0017] Furthermore, the mapping relationship between the single-pass reduction rate and temperature compensation is as follows: for every 1% increase in the single-pass reduction rate, the temperature rise of the rolled piece is compensated by 2℃ to 4℃.

[0018] Furthermore, when the final rolling temperature is >900℃, an upper limit cooling rate of 15℃ / s is adopted, and the cooling rate is reduced by 1℃ / s to 3℃ / s for every 50℃ decrease in temperature.

[0019] Furthermore, the thickness deviation of the web and flange of the H-beam produced by the method is ≤0.5mm.

[0020] A rolling system for realizing the above-mentioned high-precision ultra-thin H-beam production method includes a roughing mill with automatic roll gap control and axial roll shifting device and a universal finishing continuous rolling mill equipped with tension detection and control device.

[0021] A temperature compensation device and a closed-loop control system are installed at the finishing mill inlet; infrared temperature measuring arrays are installed at the finishing mill outlet, finishing mill inlet, finishing mill outlet and cooling zone inlet to measure the surface temperature of the web and flanges.

[0022] The universal finishing continuous rolling mill is equipped with a distributed cooling nozzle group between itself and the cooling bed. The distributed cooling nozzle group includes laminar flow nozzles and atomizing nozzles, which are used for laminar flow cooling of the web and atomizing cooling of the flanges, respectively.

[0023] Furthermore, the roughing mill is a four-roll reversible roughing mill with a roll shifting amount of ±3mm; the accuracy of the infrared temperature measurement array reaches ±5℃ or the absolute value of the measurement deviation is ≤5℃; the nozzle spacing in the distributed cooling nozzle group is 30~80mm.

[0024] Furthermore, it also includes an online or offline microstructure detection unit for detecting grain size and pearlite structure.

[0025] The beneficial effects of this invention are as follows:

[0026] This invention overcomes the shortcomings of existing technologies in the production of ultra-thin H-beams (web and flange thickness ≤ 8mm) by optimizing rolling pass allocation, dynamic tension control, zoned temperature regulation, and precise microstructure control, combined with an advanced rolling system. This results in significant technological advancements. The beneficial effects of this invention are detailed below from several aspects:

[0027] 1. High-precision dimensional control, with thickness deviation consistently within 0.5mm.

[0028] By optimizing the rolling pass allocation (3-11 passes for roughing, 9-11 passes for finishing, single-pass reduction rate of 8%-15%, flange to web reduction ratio of 0.8-1.2) and dynamic tension control (tension fluctuation ≤ ±1.5%, segmented linear tension compensation at the beginning and end, increasing rate of 1.5 kN / m for the first 5 meters, and decreasing rate of 2 kN / m for the last 5 meters), this invention significantly improves the dimensional accuracy of ultra-thin H-beams.

[0029] 2. Effectively balances the temperature difference between the web and the flange, reducing deformation inconsistencies.

[0030] This invention effectively solves the problem of excessive temperature difference between the web and flange caused by rapid heat dissipation in ultra-thin H-beams by using zoned temperature control (roughing exit temperature 1050±20℃, temperature difference in finishing stage ≤30℃) and differentiated cooling (fog cooling for flanges, laminar flow cooling for web, cooling intensity ratio 0.7-0.9).

[0031] 3. Excellent microstructure uniformity, meeting the needs of high-end applications.

[0032] By precisely controlling the final rolling temperature (20℃-40℃ above the Ar3 phase transformation point) and the post-rolling cooling rate (10-15℃ / s to air cooling after reaching below 650℃), this invention achieves excellent microstructure properties with a web and flange grain size difference of ≤1 grade, pearlite content deviation of ≤5%, and pearlite lamellar spacing of ≤0.4μm. This significantly improves the uniformity and mechanical properties of the microstructure, meeting the requirements of high-rise buildings and photovoltaic supports for high strength and toughness.

[0033] 4. Advanced rolling system improves production stability and control precision

[0034] The rolling system employed in this invention includes a four-high reversible roughing mill with automatic roll gap control (AGC) and axial roll shifting device (roll shifting amount ±3mm), a universal finishing continuous rolling mill equipped with tension detection and control devices, an infrared temperature measurement array (accuracy ±5℃), a distributed cooling nozzle group (spacing 30-80mm), and an online / offline microstructure detection unit. Compared with traditional systems (temperature measurement accuracy >±10℃, single cooling nozzle), the system of this invention precisely controls the roll gap through AGC and roll shifting device, ensures tension stability through dynamic tension model and head and tail tension compensation, achieves precise temperature and cooling control through infrared temperature measurement array and distributed nozzles, and supports real-time process optimization through the microstructure detection unit. These hardware supports significantly improve the stability and control accuracy of the production process and reduce process fluctuations.

[0035] 5. Significantly reduces defects, improves yield and batch stability.

[0036] By employing a dynamic tension control model, axial roll shifting control (AGC), head and tail tension compensation, zoned temperature control, and optimized rolling procedures, this invention significantly reduces defects such as head and tail deviations and wavy bends in rolled products, thereby improving the yield and batch stability of ultra-thin H-beams. In traditional processes, the head and tail deviation lengths often reach several meters, and wavy bends affect product straightness. The segmented linear tension compensation and closed-loop temperature control of this invention effectively shorten the head and tail deviation areas. Furthermore, the optimized cooling process and microstructure control reduce performance fluctuations caused by uneven microstructure, ensuring batch-to-batch quality consistency. This makes it particularly suitable for high-end applications with stringent quality requirements, such as photovoltaic brackets and high-rise buildings.

[0037] 6. Synergistic optimization of process and temperature compensation

[0038] This invention establishes a mapping relationship between single-pass reduction rate and temperature compensation (temperature rise compensation of 2℃-4℃ for every 1% increase in reduction rate, claim 5), as well as dynamic adjustment rules for final rolling temperature and cooling rate (cooling rate of 15℃ / s when final rolling temperature > 900℃, decreasing by 1-3℃ / s for every 50℃ decrease). These measures ensure coordinated control of heat and deformation during rolling, avoiding insufficient temperature due to excessive reduction or abnormal microstructure caused by improper cooling.

[0039] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0040] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0041] Figure 1 This is a schematic diagram of the rolling system in this invention.

[0042] Figure reference numerals: 1-Roughing mill; 2-Temperature compensation device and closed-loop control system; 3-Finishing continuous rolling mill; 4-Tension detection and control device; 5-Distributed cooling nozzle group. Detailed Implementation

[0043] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0044] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0045] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0046] Please see Figure 1 The rolling system used in this invention includes:

[0047] (1) Four-roll reversible roughing mill with AGC function 1: Automatic roll gap control (AGC) precisely controls the roll gap in the roughing stage and is equipped with an axial roll shifting device, with a shifting amount of up to ±3mm.

[0048] (2) Finishing continuous rolling mill 3: includes 4-6 universal rolling mills, with tension detection and control devices 4 between each mill stand to achieve dynamic micro-tension control.

[0049] (3) Temperature compensation device and closed-loop control system 2: set near the entrance of the finishing mill to accurately compensate for the low temperature of the flange or web.

[0050] (4) Infrared temperature measurement array with an accuracy of ±5℃: It is mainly arranged in key positions such as the finishing mill exit, finishing mill entrance, finishing mill exit and cooling zone entrance. It has multi-point temperature measurement capability and can simultaneously measure the surface temperature of the web and flange.

[0051] (5) Distributed cooling nozzle group 5: set after finishing rolling and before cooling bed. The nozzle types include laminar flow and atomizing, and are independently configured and adjusted according to the web and flange areas.

[0052] A method for producing high-precision ultra-thin H-beams includes the following steps:

[0053] (1) Heating: The steel billet is transported to a heating furnace and heated to about 1200℃;

[0054] (2) Rough rolling: The heated billet is transported to rough rolling mill 1. The temperature is controlled at around 1050℃ during rolling, and the number of passes is controlled at 3 to 11 depending on the billet.

[0055] (3) Finishing: The rough-rolled product obtained in step (2) is fed into the finishing mill for 9 to 11 passes. The reduction amount is distributed according to the following principles:

[0056] (1) The first three passes complete 40% to 50% of the total reduction in finishing rolling.

[0057] (2) The intermediate passes complete 30% to 40% of the total reduction in finishing rolling.

[0058] (3) The last three passes complete 10% to 20% of the total reduction in finishing rolling.

[0059] Temperature control during the rolling process mainly includes:

[0060] (1) In step 3, the temperature difference between the web and the flange is required to be ≤30℃. When the temperature difference at the entry point of the finishing mill is detected to be greater than 30℃, a temperature compensation device is used to compensate for the lower temperature, and a closed-loop control system is used to maintain the required temperature difference target.

[0061] (2) Differentiated cooling control is used in steps 2 and 3: the flange area adopts atomized cooling (with greater cooling intensity), the web area adopts laminar flow cooling (with relatively uniform cooling), and the ratio of flange cooling intensity to web cooling intensity (i.e., cooling intensity ratio) is controlled at 0.7-0.9 to balance the need for faster heat dissipation of the flange.

[0062] Tension control in the finishing rolling process mainly includes:

[0063] (1) A dynamic tension model is established between the continuous finishing rolling mills. This model adjusts the rolling tension value in real time based on the thickness deviation detected online. The dynamic control model for micro-tension deviation is as follows:

[0064] Δh=K·(T 头 -T 尾 )·e -t / τ

[0065] Where Δh is the thickness deviation, K is the material coefficient, and T 头 and T The tail represents the tension at the head and tail, τ is the time constant, and t is time.

[0066] (2) A segmented linear tension compensation strategy is adopted at the beginning and end of the rolled piece (approximately 10 meters each). In the first 5 meters of the transition zone, the tension is gradually increased to the set value at an increment rate of 1.5 kN / m. In the last 5 meters of the transition zone, the tension is gradually decreased to the set value at a decrease rate of 2 kN / m to reduce the out-of-tolerance length at the beginning and end. The mathematical model is as follows:

[0067]

[0068] Among them, T base The reference tension is set according to the type and size of the steel; L is the length of the steel.

[0069] The organizational control requirements are as follows:

[0070] (1) The final rolling temperature is strictly controlled within the range of 20℃ to 40℃ above the Ar3 phase transformation point to ensure that the austenite region completes the main deformation, which is conducive to refining the grains.

[0071] (2) Post-rolling cooling: After rolling, the steel is rapidly cooled to below 650℃ at a high cooling rate of 10℃ / s to 15℃ / s. When the final rolling temperature is >900℃, the upper limit of the cooling rate of 15℃ / s is adopted. When the final rolling temperature is ≤900℃, the corresponding cooling rate decreases by 1℃ / s to 3℃ / s from the upper limit for every 50℃ decrease in the final rolling temperature. The purpose is to obtain ideal phase transformation structure and properties at different final rolling temperatures.

[0072] (3) After cooling to below 650°C, the steel is air-cooled to room temperature on a cooling bed.

[0073] (4) The finished web and flange parts should meet the following requirements: grain size difference not exceeding grade 1 (ASTM E112), pearlite content ≤5%, and pearlite lamellar spacing ≤0.4μm.

[0074] Among them, the reduction amount of each pass and the temperature compensation in the finishing rolling process have the following mapping relationship: when the reduction rate of each pass increases by 1%, the corresponding temperature rise compensation of 2℃ to 4℃ for the rolled piece needs to be carried out in the rolling process or in the pre-rolling heating / temperature compensation.

[0075] Example 1

[0076] The method of this invention is used to produce HW150×150×5×5 H-beams:

[0077] (1) The roughing rolling process consists of 6 passes, with a billet heating temperature of 1250℃ and a roughing mill exit temperature of 1070℃ (within the target range of 1050±20℃). The reduction rate per pass is approximately 11%.

[0078] (2) There are 11 finishing rolling passes, and the flange web reduction ratio is controlled at 1.0. The reduction is distributed as follows: 46% finishing rolling reduction is completed in the first 3 passes, 38% in the middle 5 passes, and 16% in the last 3 passes. The reduction rate per pass is controlled at 10%.

[0079] (3) When the temperature difference at the entry point of the finishing mill is 25℃ (slightly lower for the flange), the heating device is activated to heat the flange to the set point, and closed-loop control is implemented. The final rolling temperature is controlled at Ar3+30℃ (approximately 860℃).

[0080] (4) The parameters of the micro-tension model are set as follows: K is taken as an empirical value of 1.5, τ is taken as 0.8 seconds, and the tension fluctuation is within ±1.2%. The head and tail are compensated according to the strategy (tension increase rate of 1.5kN / m in the first 5 meters and decrease rate of 2kN / m in the last 5 meters).

[0081] (5) The flanges are cooled by atomization (strength ratio 0.85), and the web is cooled by laminar flow. The final rolling temperature is 860℃ (>850℃), and the temperature is cooled to 620℃ at the upper limit cooling rate of 15℃ / s before being air-cooled on a cooling bed.

[0082] (6) The actual thicknesses of the web and flange were 5.05 mm and 5.00 mm, respectively (deviation <0.5 mm). The grain size of the web was grade 10.5 and that of the flange was grade 10 (difference 0.5 grade). The pearlite content of the web was 62% and that of the flange was 65% (difference 3%). The interlamellar spacing was approximately 0.12 μm.

[0083] Example 2

[0084] The production of HM298×149×5.5×8 H-section steel has a flange thickness of 8mm and a relatively thin web of only 5.5mm, requiring coordinated deformation.

[0085] (1) Rough rolling: 5 passes (total reduction rate 75%), billet temperature 1070℃, exit temperature 1050℃.

[0086] (2) Finishing rolling: 9 passes (total reduction rate 45%), reduction distribution: the first 3 passes complete 50% of the total reduction (flange thinning), the middle 3 passes complete 35% of the total reduction (web plate co-thinning), and the last 3 passes complete 15% of the total reduction (finishing). Flange / web plate reduction ratio: 1.2 for the first 3 passes (flange preferential thinning), and 0.9 for the last 3 passes (stress balancing).

[0087] (3) Tension control: Micro-tension model parameters: K = 1.2, τ = 1.0s. The measured tension fluctuation is within ±1.4%. Head and tail tension compensation is the same as in Example 1.

[0088] (4) Temperature control: Temperature difference at the entry point of the finishing mill: 22℃ (controllable by natural heat dissipation), no supplementary heating was triggered. Final rolling temperature: 840℃ (Ar3≈805℃, satisfying Ar3+35℃).

[0089] (5) Cooling process: The flanges are mist-cooled and the web is layer-cooled, with a strength ratio of 0.85. The final rolling temperature is 840℃, the cooling rate is 12℃ / s, and the temperature is reduced to 640℃ before air cooling.

[0090] (6) Finished product: Dimensional accuracy: web 5.52mm, flange 8.05mm (flange deviation 0.05mm). Microstructure: web grain size reaches grade 10, flange is grade 9.5. The pearlite content of the web is 65%, the flange is 63% (deviation 2%); the interlamellar spacing is 0.14μm.

[0091] Example 3

[0092] The HL550×220×6×12H steel is produced with a flange thickness of 12mm, but the web thickness is only 6mm.

[0093] (1) The roughing rolling passes are 8 (total reduction rate 80%), the billet temperature is 1060℃, and the exit temperature is 1030℃.

[0094] (2) There are 11 finishing rolling passes (total reduction rate 50%). The reduction is distributed as follows: the first 3 passes complete 42% (mainly web thinning), the middle 5 passes complete 38% (flange thinning), and the last 3 passes complete 20% (finishing). The flange / web reduction ratio is maintained at 0.9 throughout the process (to avoid web overload).

[0095] (3) Tension control: The micro-tension model parameters are selected as K=1.6 and τ=0.9s. Head and tail compensation are effective, and the tension fluctuation is within ±1.1%.

[0096] (4) Temperature control: The temperature difference at the entry point of the finishing mill is 33℃ (the flange dissipates heat more slowly than the web), triggering the heating device to heat the web, and controlling the closed loop until the temperature difference is ≤25℃. The final rolling temperature is 870℃, Ar3≈830℃, satisfying Ar3+40℃.

[0097] (5) The cooling process is as follows: the flanges are cooled in sections (to avoid overcooling), the web is cooled by misting, and the strength ratio is 0.7. The final rolling temperature is 870℃, the cooling rate is 15℃ / s, and the temperature is cooled to 620℃ before air cooling.

[0098] (6) Final product dimensions and microstructure: The web thickness is 6.02 mm, the flange thickness is 12.2 mm, and the dimensional accuracy meets the requirements. The web microstructure has a grain size of 10.5, a pearlite content of 64%, and a lamellar spacing of 0.12 μm (meeting the requirement of ≤0.15 μm).

[0099] The above embodiments demonstrate that by optimizing rolling passes, dynamic tension control, zoned temperature regulation, and precise microstructure control, combined with an advanced rolling system, the present invention successfully achieves high-precision production with web and flange thickness deviation ≤0.5mm, grain size difference ≤1 grade, pearlite content deviation ≤5%, and lamellar spacing ≤0.4μm. This significantly improves the yield and batch stability of ultra-thin H-beams and is suitable for high-end applications such as high-rise buildings and photovoltaic brackets.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-precision ultra-thin H-beam production method, applicable to H-beams with web and / or flange thickness ≤ 8mm, characterized in that: After heating the billet to 1200℃-1250℃, rough rolling is performed in 3-11 passes, with the exit temperature of the rough rolling mill controlled at 1050±20℃. Then, finish rolling is performed in 9-11 passes, with the single-pass reduction rate controlled at 8%-15% and the flange to web reduction ratio controlled at 0.8-1.

2. During the finishing rolling process, the tension between the continuous rolling mills is adjusted in real time according to the thickness deviation using a dynamic tension model, with a tension fluctuation range of ≤±1.5%, and segmented linear tension compensation is adopted in the transition zone between the head and tail. At the same time, the temperature difference between the web and flange of the H-beam is kept ≤30℃ by a temperature compensation device and a closed-loop control system. Temperature control adopts atomized cooling of the flange and laminar flow cooling of the web, and the cooling intensity ratio of the flange to the web is controlled at 0.7~0.

9. At the end of the finishing rolling stage, the final rolling temperature is controlled at 20℃-40℃ above the Ar3 phase transformation point. After cooling to below 650℃ at a cooling rate of 10℃ / s-15℃ / s, it is air-cooled. The resulting H-beam has a grain size difference of ≤1 grade between the web and the flange, a pearlite content deviation of ≤5%, and a pearlite lamellar spacing of ≤0.4μm. The dynamic tension model adopts a micro-tension deviation dynamic control model, and the model formula is as follows: Where Δh is the thickness deviation, K is the material coefficient, and T 头 and T 尾 Here, τ represents the tension at the beginning and end of the circuit, t represents the time constant, and t represents time. The transition zone between the beginning and end adopts piecewise linear tension compensation. The tension increase rate for the first 5 meters of the billet is 1.5 kN / m, and the decrease rate for the last 5 meters is 2 kN / m. The mathematical model is as follows: Among them, T base The reference tension is set according to the type and size of the steel; L is the length of the steel.

2. The method for producing high-precision ultra-thin H-beams according to claim 1, characterized in that: In continuous finishing rolling, the reduction per pass is distributed as follows: the first 3 passes complete 40% to 50% of the total reduction, the middle passes complete 30% to 40%, and the last 3 passes complete the remaining 10% to 20%, ultimately ensuring that the total reduction is 100%.

3. The method for producing high-precision ultra-thin H-beams according to claim 1, characterized in that, The mapping relationship between the single-pass reduction rate and temperature compensation is as follows: for every 1% increase in the single-pass reduction rate, the temperature rise of the rolled piece is compensated by 2℃~4℃.

4. The method for producing high-precision ultra-thin H-beams according to claim 1, characterized in that: When the final rolling temperature is >900℃, the upper limit cooling rate is 15℃ / s. For every 50℃ decrease in the final rolling temperature, the corresponding cooling rate decreases by 1℃ / s to 3℃ / s.

5. The method for producing high-precision ultra-thin H-beams according to claim 1, characterized in that, The thickness deviation of the web and flange of the H-beam produced by the method is ≤0.5mm.

6. A rolling system for implementing the high-precision ultra-thin H-beam production method according to any one of claims 1-5, characterized in that, This includes roughing mills with automatic roll gap control and axial roll shifting devices, and universal finishing continuous rolling mills equipped with tension detection and control devices; A temperature compensation device and a closed-loop control system are installed at the finishing mill inlet; infrared temperature measuring arrays are installed at the finishing mill outlet, finishing mill inlet, and cooling zone inlet to measure the surface temperature of the web and flanges. The universal finishing continuous rolling mill is equipped with a distributed cooling nozzle group between itself and the cooling bed. The distributed cooling nozzle group includes laminar flow nozzles and atomizing nozzles, which are used for laminar flow cooling of the web and atomizing cooling of the flanges, respectively.

7. The rolling system according to claim 6, characterized in that, The roughing mill is a four-roll reversible roughing mill with a roll shifting amount of ±3mm; the infrared temperature measurement array has an accuracy of ±5℃; and the nozzle spacing in the distributed cooling nozzle group is 30~80mm.

8. The rolling system according to claim 6, characterized in that, It also includes online or offline microstructure detection units for detecting grain size and pearlite structure.

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