Hot-rolled H-shaped steel for construction with high toughness and method for manufacturing the same.

Abstract

The present invention belongs to the technical fields of steel smelting and rolling, and specifically relates to a hot-rolled H-shaped steel for construction with high strength and toughness and a manufacturing method thereof. The chemical components of the hot-rolled H-shaped steel are, in weight percent (wt%), C: 0.06-0.10, Si: ≦0.25, Mn: 0.8-1.30, P≦0.015, S≦0.008, Cu: 0.15-0.25, Cr: 0.25-0.60, Ni: 0.10-0.19, V: 0.01-0.03, Al: 0.01-0.03, RE: 0.009-0.019, As+Sn+Zn+Pb+Ca+Mg≦0.035, N≦0.008, T.[O]≦0.002, and the balance is Fe and unavoidable impurities. The present invention not only realizes weight reduction of steel for building structures, but also has good comprehensive performance such as good corrosion resistance, Z-direction performance, and low temperature toughness resistance, fully meeting the current engineering needs of steel for prefabricated building structures.

Description

Technical Field

[0001] [Cross-reference to Related Applications] This application claims priority based on Chinese Patent Application No. 202210851313.2 filed on July 20, 2022, and all the contents of this Chinese patent application are incorporated herein by reference. The present invention belongs to the fields of steelmaking technology and rolling forming technology. Specifically, it relates to a hot-rolled H-section steel for construction with high strength and toughness and a method for manufacturing the same.

Background Art

[0002] As the requirements for the quality of domestic construction projects gradually increase, higher requirements are being placed on the development of steel for building structures. In particular, in the area of prefabricated buildings, the country has successively introduced policies to widely promote them. Prefabricated buildings have technical advantages such as good seismic performance, low self-weight, high construction speed, high degree of industrialization, and high precast member prefabrication rate. The use of steel structures satisfies the natural assembly advantages, and the construction period has greater advantages compared to the conventional construction period. When the precast members in assembled steel structures are often made of steel, they belong to environmentally friendly building materials and are incomparably more environmentally friendly than concrete in terms of recycling and reuse, having advantages in environmental protection. The occupancy rate of domestic prefabricated buildings is significantly lower than that of foreign advanced countries. Therefore, in accordance with the requirements of application, economy, safety, ecology, and aesthetics, it is necessary to promote the innovation of building methods, greatly develop assembled concrete buildings and steel structure buildings, continuously improve the ratio of prefabricated buildings in newly built buildings, improve the performance and technical measures such as fire protection and corrosion prevention of steel structure buildings, expand the application of hot-rolled H-section steel, weathering steel, and fire-resistant steel, and promote the overall development of the core technologies and related industries of steel structure buildings.

[0003] Hot-rolled H-beams, as a primary material for building structures, demand higher requirements for their mechanical performance, corrosion resistance, fire resistance, and structural stability under various operating conditions. Among these, lamellar tear resistance is a crucial indicator, ensuring the safety and structural stability of building structural steel. Lamellar tear-resistant steel, also known as Z-direction steel, is primarily evaluated using the sectional shrinkage coefficient Z in tensile tests along the thickness direction of the steel plate. For steel materials exceeding 15mm in thickness, if tension or fatigue stress occurs along the plate thickness direction in the structural member, it is generally necessary to inspect the Z-direction lamellar tear resistance. In the case of general building structural steel sections, only the Z-direction performance index of the flange is required, and it is less common to propose a Z-direction performance index for the web plate. Therefore, to satisfy the needs of steel for prefabricated and high-rise buildings, a crucial indicator of overall lamellar tear resistance—namely, the Z-performance of both the flange and web plate—must simultaneously satisfy the requirements, and the difficulty increases with increasing thickness.

[0004] Patent application CN113564480A discloses a heavy, hot-rolled H-beam having Z-direction performance and a method for producing the same, wherein the hot-rolled H-beam contains the chemical components C, Si, Mn, Nb, Ti, N, B, and Als, with the remainder being iron and unavoidable impurities, and the production method includes steps such as molten iron pretreatment → converter smelting → argon gas blowing refining → RH → complete protective casting of beam blanks → stacking and slow cooling → rolling → post-rolling air cooling. This invention utilizes a combination strengthening method of phase transition + precipitation + fine grain by controlling the number of precipitated second-direction particles using a rational mixing ratio of components and process control, employing a bloc rolling + universal rolling + post-rolling air cooling process. The resulting large hot-rolled H-beam with a flange thickness of 80 mm or less has excellent toughness and Z-direction performance, with a Z-direction performance of 65-80%. Although this invention achieves strengthening through a bainite structure, the bainite is affected by the cooling rate, making it difficult to control and obtain a stable and uniform bainite structure, and there is no apparent yield phenomenon in the bainite steel.

[0005] Patent CN103334051B discloses hot-rolled H-shaped steel for construction having Z-direction performance and a method for producing the same. The invention obtains a steel grade with excellent Z-direction performance and mechanical performance by optimizing the smelting and rolling processes and strictly controlling the means for controlling product quality and the production process of the product. The chemical composition of the H-shaped steel is, in weight percent, C: 0.06%~0.18%, Si: 0.10%~0.25%, Mn: 0.90%~1.60%, V less than 0.10%, Nb less than 0.060%, Ti less than 0.030%, and the remainder being iron and unavoidable impurities.

[0006] Japanese Patent No. CN102418037B provides a hot-rolled H-shaped steel with lamellar tear resistance and a method for producing the same. The method for producing H-shaped steel according to the present invention involves deoxygenating silicon-killed steel by adding Si to the molten steel during the molten steel discharge process without using Al deoxygenation, thereby adjusting the Si content in the molten steel to 0.10% to 0.15% of the total weight of the molten steel. Then, at least one of Ti and Zr in a predetermined amount is added to the molten steel, and the Si content required for the steel type may be added during refining. The hot-rolled H-shaped steel according to the present invention has lamellar tear resistance and can satisfy the requirements for Z-direction performance in a certain thickness direction.

[0007] In the above-mentioned conventional technology, simple microalloying is unfavorable for improving the surface quality of the cast slab, severely limiting the improvement of toughness, and is prone to causing welding defects due to excessive carbon content, leading to increased load on the rolling mill, difficulty in controlling the curvature and head misalignment of the rolled members, and high requirements for the equipment, resulting in relatively low overall performance of H-shaped steel and dimensional acceptance rates of the finished product.

[0008] Currently, cooling control is a serious issue in the production of structural steel, as it consistently affects the uniformity of performance. Especially for thicker standard products, the difference in flange and web plate thickness dimensions is relatively large, and using a single cooling mode has a relatively significant impact on the final performance. This also affects the uniformity of Z-axis performance, resulting in relatively large differences that can compromise structural safety. How to solve this problem while balancing cost and efficiency remains a constant challenge in the industry. Some companies use ultrafast cooling systems, but these require relatively large investments and are not economically appropriate for a single product type where the need exists. Therefore, for structural steel products in buildings where overall Z-axis performance is required, it is necessary to design special cooling systems to satisfy the performance requirements. [Overview of the project] [Problems that the invention aims to solve]

[0009] To satisfy the needs of steel for prefabricated building structures, the present invention specially designs a cooling system to meet these needs. It provides hot-rolled H-shaped steel for building structures with high toughness, reaching a yield strength of 420 MPa grade, and excellent lamellar tear resistance, as well as a method for manufacturing the same. This steel product is suitable for use in the field of prefabricated building structural engineering, and both its web plate and flange have relatively high Z-direction performance, both exceeding the Z35 level. To achieve good Z-direction performance in the flange and web plate, the steel composition is designed in conjunction with the design, and a control device for temperature uniformity of the flange and web plate is added to the rolling process design. This achieves good impact toughness under low temperature conditions of -20°C, and features excellent corrosion resistance, weldability, and a low yield ratio, satisfying the application needs of hot-rolled H-shaped steel materials in steel building fields such as prefabricated building structures in general and cold regions. [Means for solving the problem]

[0010] To achieve the above objective, the proposed technical solution of the present invention has the following specific requirements.

[0011] This invention provides a 420 MPa grade hot-rolled H-shaped steel for construction, the H-shaped steel having the following chemical composition in weight percent (wt%): C: 0.06~0.10, Si: ≤0.25, Mn: 0.8~1.30, P ≤0.015, S ≤0.008, Cu: 0.15~0.25, Cr: 0.25~0.60, Ni: 0.10~0.19, V: 0.01~0.03, Al: 0.01~0.03, RE: 0.009~0.019, As + Sn + Zn + Pb + Ca + Mg ≤0.035, with the remainder being Fe and unavoidable impurities. During the smelting process, the gases in the steel are controlled to N ≤0.008 and T.[O] ≤0.002 in weight percent.

[0012] To reduce the yield ratio, a design using only a single microalloy of vanadium nitrogen alloy based on a low-carbon component design is employed, and its content is strictly controlled to mitigate the influence of precipitation strengthening on the yield strength, ultimately resulting in a yield ratio of ≤0.8 for the H-shaped steel. To improve low-temperature toughness and strictly control the number and size of inclusions, when modifying the inclusions by adding RE elements, it is preferable to control the content of other residual elements to As+Sn+Zn+Pb+Ca+Mg≤0.035.

[0013] The roles of each chemical element when added to the 420 MPa grade H-shaped steel for building structures, which has excellent overall lamellar tear resistance (Z-direction performance) as described in the present invention, are as follows.

[0014] In accordance with the strength requirements of a 420MPa grade carbon (C) steel, the low-carbon component design ensures that the structural steel has a certain low-temperature resistance, while also ensuring the formation of a certain pearlite structure to improve the yield ratio, thus meeting the needs of structural steel applications. After adding corrosion-resistant elements, it is possible to avoid the formation of abnormal structures such as Widmanstätten compared to the case of low-carbon content. In the case of beam blanks, the carbon content of the present invention is controlled to 0.06% to 0.10% considering structural performance and smelting costs, as it is easier to control cracks on the web plate in the transverse and longitudinal directions.

[0015] Silicon (Si): An appropriate amount of Si contributes to improved strength, while excessive Si content tends to form structures such as bainite. To avoid the impact on surface quality due to the generation of large amounts of Fe2SiO4 during the reheating process, the upper limit of the Si content is set to 0.25% or less, preferably 0.25% or less, and more preferably 0.20% or less.

[0016] Manganese (Mn): Manganese is a stable element of austenite and can significantly improve the hardenability of steel and increase its strength through solid solution strengthening. However, if present in excess, segregation is likely to occur, and differences in structure are relatively large. There are differences in the microstructure of different parts of thick structural steel used in buildings. Therefore, in order to ensure strength and avoid limiting hardenability and generating a large amount of abnormal structure, it is preferable to set the upper limit of the Mn content to 1.30%. Taking various factors into account, it is preferable to control the Mn content in the H-shaped steel of the present invention within the range of 0.8 to 1.30% and set the range to 1.0 to 1.20% based on the amount of VN alloy added in order to obtain a strength of 420 MPa grade.

[0017] Phosphorus (P): High phosphorus content can easily improve corrosion resistance, but excessive phosphorus can worsen low-temperature resistance at brittle grain boundaries. Therefore, the lower the phosphorus content, the better the effect, improving low-temperature toughness, and controlling P to 0.015% or less. Sulfur (S): When there is an excess of sulfur, sulfides such as MnS are easily formed, which can create a large amount of longitudinal MnS inclusions in different parts of the structural steel with a complex cross-section. This reduces low-temperature toughness, is detrimental to improving corrosion resistance, affects the sectional shrinkage rate, and thus affects the lamellar tear resistance of the steel. Therefore, S should be strictly controlled to ≤0.008%. Copper (Cu): Copper is a fundamental element that improves the corrosion resistance of steel. By promoting anodic passivation of steel, Cu can reduce the corrosion rate and is considered one of the commonly used elements in corrosion-resistant steel. When enriched in the rust layer, it can significantly improve the protective performance of the rust layer. To achieve the Cu enrichment effect in the rust layer, a Cu content of 0.20% or more is required. However, excessive Cu content is detrimental to the welding performance of structural steel for building structures and also makes copper embrittlement more likely. In the process of producing structural steel with lamellar tear resistance using irregularly shaped continuous casting slabs, cracks due to copper enrichment are likely to occur at the corners of the legs, seriously affecting the surface quality of the cast slab and resulting in low plasticity of the steel. In order to satisfy the requirements for corrosion resistance of structural steel for prefabricated building structures, the Cu content of this invention is controlled to 0.15-0.25%.

[0018] Nickel (Ni): Nickel is an effective element that improves the strength of steel through solid solution strengthening and enhances low-temperature toughness. At the same time, it can improve the high-temperature plasticity of steel during the continuous casting process, reducing the occurrence of surface defects in cast slabs. Ni plays a role in expanding the austenite region and improving hardenability, while also refining the pearlite lamellae and thus the pearlite, thus performing a fine-grain strengthening effect. In conjunction with the control ratio of Cu content, the steel of the present invention controls the Ni content within the range of 0.10 to 0.19%.

[0019] Chromium (Cr): Chromium is an element that improves hardenability and tempering stability, thereby contributing to increased steel strength, as well as improving the corrosion resistance of steel materials. When used in combination with Cu and Ni elements, it can significantly improve the corrosion resistance of steel. When the carbon content is relatively low, adding an appropriate amount of Cr can improve the hardness and strength of the steel, and also improve the corrosion resistance of structural steel. Adding too much chromium will reduce the toughness, weldability, and gas cutting performance of the material. In terms of microstructure control, too much Cr can affect the microstructure transition of the steel, leading to the formation of abnormal structures such as bainite. Considering the improvement of strength and corrosion resistance, this invention controls the chromium content to Cr: 0.25~0.60%.

[0020] Vanadium (V): Vanadium is one of the most commonly used and effective strengthening elements in microalloy steels. The role of vanadium is to influence the structure and performance of the steel by forming VN, V(CN), which primarily precipitates in the ferrite at austenite grain boundaries, refining the ferrite grains and thereby improving the material's strength and low-temperature toughness. Considering the greater impact of precipitation strengthening on yield strength and the resulting improvement in strength, V is added at 0.01-0.03%.

[0021] Rare Earth Elements: Rare earth elements purify and alter the steel structure, reducing pitting and intergranular corrosion. Solid-solution rare earth elements in steel improve the polarization resistance and self-corrosion potential of the steel matrix, contributing to improved corrosion resistance of the steel matrix. They also alter the microstructure of the rust layer, forming a highly adhesive, dense, and corrosion-resistant rust layer, thereby improving the corrosion resistance of high-strength weathering steel. Considering the addition of appropriate amounts of RE rare earth elements according to the modification needs of inclusions such as MnS, the selection range is set to RE: 0.009~0.019%. RE rare earth elements are one of the composite additive elements, and considering factors such as economy and cost performance, this application mainly uses lanthanum and cerium-based elements, which play the role of spherical inclusions.

[0022] Aluminum (Al): Al is used by adding it as a strong deoxidizing element in the process of manufacturing low-temperature steel. In order to reduce the oxygen content in the steel as much as possible, reduce the inclusion content, and ensure that excess aluminum can further form AlN precipitates with the nitrogen element in the steel after deoxidation, refine the austenite grain size during the heating and hot rolling processes. Therefore, as a deoxidizing element and a grain refinement strengthening element, the aluminum content is controlled within the range of 0.01 - 0.03%.

[0023] As, Sn, Zn, Pb, Ca, Mg: These have a relatively large impact on the low-temperature impact toughness as residual elements in the steel and also greatly affect the surface quality. Therefore, as elements that cannot be completely removed in the steel, their contents should be reduced as much as possible. Considering production practice, equipment capabilities, and cost control, the total amount of residual elements is controlled within the range of As + Sn + Zn + Pb + Ca + Mg ≦ 0.035.

[0024] Nitrogen (N): If the nitrogen content is excessive, it is likely to cause quality defects in the slab. At the same time, the alloying effect of VN should be ensured. Therefore, the present invention requires that the nitrogen content is 0.008% or less.

[0025] Oxygen (O): In order to avoid forming large-particle oxide inclusions and deteriorating the toughness and plasticity of the steel, in the present invention, it is necessary that the total oxygen content is T.[O] ≦ 0.0020%.

[0026] The H-shaped steel product of the present invention has good comprehensive mechanical properties, with a yield strength of ≧ 420 MPa, a tensile strength of ≧ 520 MPa, an elongation rate of ≧ 19%, a longitudinal impact energy at -20 °C of ≧ 5J, and is suitable for use in building structures in areas with low-temperature conditions. The web plate and flange have good Z-direction performance, and the cross-sectional shrinkage rate of both is ≧ 60%.

[0027] A method for manufacturing hot-rolled H-shaped steel suitable for application to building structures in the above different regions and having excellent lamellar tearing resistance mainly includes steps such as hot metal pretreatment → converter steelmaking → LF refining → RH refining → dressing of steel slab surface defects → casting of profiled continuous casting slab → reheating of steel slab by walking beam reheating furnace → descaling by high-pressure water → temperature-controlled rolling + controlled cooling → low-temperature leveling → cutting to size → collection and stacking, etc.

[0028] Smelt hot metal and steel scrap in a converter + refining furnace (LF + RH equipment), obtain a profiled continuous casting slab in the refining and continuous casting process, detect and clean the surface, and then enter the rolling forming process. First, put the steel slab into a walking beam reheating furnace for reheating to obtain an austenite structure of appropriate dimensions, perform rough rolling and finish rolling, and then roll and form, and control rolling and cooling during the rolling process. In addition, accurately control the temperature in the final pass of finish rolling, and use a developed special cooling device (for the cooling device, see Figure 1(a) for reference) to The web plate is horizontal H-shaped steel of Meet the requirement that the temperatures on both the upper and lower sides of the flange are approximately the same, ensure the compatibility of the Z-direction performance of the flange and web plates under uniform tissue conditions, and ensure the stability and safety of the structure when this product is adopted in prefabricated building structures.

[0029] The main processes of controlled rolling and cooling in the rolling process are to control the heating temperature at 1250 - 1300 °C, make the temperature of the final pass of rough rolling vary depending on dimensions between 1150 - 1050 °C, make the cumulative deformation rate 40% - 60%, and complete the rest in the finish rolling stage. After rough rolling, perform finish rolling with three stands, accurately control the final rolling temperature of finish rolling between 800 °C - 850 °C, completely transform the austenite structure into pearlite and ferrite, and achieve fine grain controlled rolling. The web plate is horizontal H-shaped steel of Since there is a temperature difference of 30 - 50 °C on both the upper and lower sides of the flange and web plate, in the last pass of finish rolling , established use the calculated cooling device to Flange spray water on the flange and web plate with nozzles , fumarolesIt precisely controls and cools, and responds based on the detected temperature difference. The flow Quantity control is performed. After cooling. Flange The temperature difference at the same location was reduced to within 10°C, and the temperature difference between the upper and lower surfaces of the web plate was reduced to within 5°C, thereby reducing the H-shaped steel of The Z-direction performance of the lunge and the entire web plate is ensured to be nearly identical. After finish rolling, the rolled member passes through a conveyor roller table, and the cooling rate is controlled using an insulating cover according to the ambient temperature, thus avoiding the impact on final performance due to significant fluctuations in ambient temperature across different seasons. After being removed from the finish rolling mill, it is naturally cooled in a low-temperature furnace, and the product temperature is... To 200-300℃ Descending Then The material is placed in a leveler for straightening. The specifications for the finished rolled material are that the flange thickness range is 15-50 mm. Sampling is performed at the flange and intermediate points of the web plate of the H-shaped steel to detect its mechanical properties. The tensile cross-sectional shrinkage rate in the Z direction of the flange and web plate of the H-shaped steel produced by the above process is measured. difference It is controlled to 5% or less.

[0030] Preferably, the 420 MPa grade hot-rolled H-shaped steel for prefabricated buildings with excellent lamellar tear resistance according to the present invention, its manufacturing method, and specific process control include the following two steps.

[0031] 1. Smelting process (1) Converter smelting The converter is controlled based on basic operations, and the main processes include strictly controlling the content of residual elements such as sulfur and arsenic in the molten iron in the blast furnace to suitably process the molten iron quality, reducing both arsenic and tin to less than 0.008%, setting the basicity of the finish slag in the converter to a range of 2.1 to 3.9, using slag stopping and molten steel discharge, and using deoxygenation and alloying with aluminum, manganese, and iron in the molten steel discharge process. In the molten steel discharge process, deoxygenators, ferrosilicon, metallic manganese, vanadium nitrogen alloy, niobium iron alloy, nickel plate, etc. are added in several stages to adjust the final converter composition to meet the requirements of the internal control objectives.

[0032] (2) Dual control of LF+RH in refining In the refining process, gases and inclusions are controlled by dual LF+RH control. LF is used to prepare the slag using calcium carbide, silicon-calcium-barium, and aluminum particles, and the top slag should be white or yellowish-white before being removed from the station. After bringing the slag into the station and taking the first sample, the oxygen level is controlled to [O] ≤ 20 ppm. RE is added before supplying calcium wire. Nitrogen bottom blowing is performed throughout the process according to process requirements, the soft blowing time is set to 20 minutes or more, the refining cycle is set to 30 minutes or more, and the molten steel temperature is controlled to 1600-1620°C at the end of LF refining to counteract the temperature drop during RH treatment. It is prohibited to "increase the temperature by adding aluminum to generate chemical heat" during RH treatment.

[0033] In RH smelting, the following processing modes are used, with a reflux time longer than 15 minutes and a pure degassing time longer than 5 minutes. After processing is complete, 200-250 m of calcium aluminum wire is supplied to each furnace, the soft blow time is set to 10 minutes or more, and the RH smelting cycle is controlled to 40-50 minutes.

[0034] Protective casting throughout the entire process means that argon seal protection is applied using a protective sleeve from the ladle to the intermediate container, the intermediate container is covered with a coating agent together with charred rice husks, argon seal protection is applied using an immersion nozzle from the intermediate container to the crystallizer, and the liquid surface of the crystallizer is covered with peritectic steel protective slag, preferably with the components of the peritectic steel protective slag being 25%≦SiO≦35%, 35%≦CaO≦45%, 1.90%≦MgO≦3.00%, and 3.00%≦Al2O3≦4.00% by weight percentage.

[0035] (3) Continuous casting In the continuous casting process, a fully protective casting process is used, a protective sleeve for the large ladle is utilized, a seal ring control is added, and the intermediate container uses a stopper container to cast the molten steel, improving efficiency by adjusting the drawing speed of the irregularly shaped continuous casting slabs. 0.7~0.9By setting the flow rate to m / min and controlling the superheating temperature to 20°C to 30°C or lower, it is possible to prevent the protective sleeve from becoming blocked. The refined molten steel is cast into three dimensional standards of near-net-shape cross-section beam blanks. Because the alloy content is relatively high, the beam blanks are slowly cooled after casting using heat-retaining holes, sand holes, or heat-retaining felt to avoid cracking on the surface.

[0036] 2. Rolling process (1)Heating The material is austenitized and uniformly heated in a heating furnace. The temperature during the heating and soaking stages is controlled to 1250-1300°C, and the heating time is 90-120 minutes. Then, it is removed from the furnace and rolled. High-temperature, short-time heating is used, and the process is controlled to homogenize and refine the austenite.

[0037] (2) Controlled rolling and controlled cooling A controlled rolling / controlled cooling process is used in large-scale production lines. The rough rolling process achieves die rolling primarily for shape, with fewer than 9 rolling passes, while the finish rolling process performs performance-controlled rolling, with fewer than 7 rolling passes. The final rolling temperature in the finish rolling is controlled to 800°C to 850°C. The cooling rails in the low-temperature furnace are maintained at a temperature of 400°C or higher, and the products are cooled slowly and simultaneously in the low-temperature furnace to prevent the cooling rate from being too fast and affecting the final performance. Once the product temperature drops to 200-300°C, it is placed in a leveler for straightening to ensure the integrity of the primary scale on the surface.

[0038] The present invention provides a cooling device for improving overall performance, which provides comprehensive cooling of the web plate and flange during the rolling process using a specially designed cooling device, which is mounted at the rear of the finishing rolling mill, and which comprises a plurality of spaced cooling liquid pipes 1 and a plurality of spaced cold air pipes 2, the cooling liquid pipes 1 being for cooling the flange. Web plate 8 is horizontal Hot-rolled H-shaped steel of Lunge 6 、7It is installed below and comprises a first flange pipe 4 parallel to the web plate and two sets of second flange pipes perpendicular to and communicating with the first flange pipe 4, with one flange corresponding to each set of second flange pipes, and each set of second flange pipes comprises two parallel lower flange pipes 5, and the lower flange pipe 5 of Lunge 6 、7 On the opposite side, multiple nozzles 3 for cooling the flange are installed, and the H-shaped steel of Lunge 6 、7 Both are placed between two parallel lower flange pipes 5, and the cold air pipe 2 is for cooling the web plate and has a convex shape. ,centre Lunge 6 、7 It is installed between and web plate 8. hand Multiple nozzles 3 for cooling the web plate 8 are installed in the cold air piping parallel to and adjacent to the web plate 8. is It fits the shape formed by the lunge and web plate. The cooling rate can be controlled by the thickness of the web plate and flange. ru. The cooling system is mounted at the rear of the finishing rolling mill and starts during the final pass of rolling, cooling the attached flanges and web plates individually. Figure 1 (a) Therefore, the coolant piping labeled 1 is for cooling the flange, and because the flange is thick, it is necessary to cool it with cooling water or another cooling medium depending on the cooling rate. The magnitude of the coolant flow rate is Flange After measuring the temperature difference using an online temperature measuring device, it is adjusted by nozzle 3. Since the thickness of the web plate is thinner than the flange, the need can be met by using cooling air. The cooling air piping indicated by reference numeral 2 is for cooling the web plate, and since the temperature difference between the upper and lower parts of the web plate is relatively small, cooling is achieved by appropriately adjusting the flow rate of cooling air in nozzle 3 as needed. ,centreThe temperature difference of the lunge is within the range of 5-10°C, and the temperature difference of the web plate is within the range of 3-6°C. This ensures uniformity of the structure and improves the Z-direction performance of the web plate and flange of structural steel for building construction. By combining the above apparatus with the design of vanadium microalloying, it is possible to meet the performance requirements for the final hot-rolled H-beam while ensuring that the Z-direction performance of both the web plate and flange reaches a relatively high level.

[0039] (3) Finishing process After the product rolls off the production line, surface and dimensional finishing treatments are performed. Samples are then taken during the finishing process to analyze the product's performance and ensure that the material's properties are accurate and reliable. [Effects of the Invention]

[0040] The advantages of the present invention compared to the prior art are as follows:

[0041] (1) By using a low-carbon + trace VN alloying + RE component design, it is simpler and more efficient than other alloying methods, reducing the occurrence rate of cast slab defects. (2) By controlling the low residual elements and impurity elements in the molten steel, it contributes to improving the plasticity and low-temperature toughness of the steel. (3) By adding a certain amount of RE elements, the inclusions in the steel are fine, which contributes to simultaneously improving the lamellar tear resistance of the flange and web plate. (4) By using a one-sided casting control technology for the beam blank, an Al deoxygenation process is realized, improving the cleanliness of the molten steel and avoiding the problem of the protective sleeve becoming blocked during the casting process. (5) A specially designed fountain device realizes a uniform cooling process for the web plate flange, improving the uniformity of the overall structure of the web plate flange, simultaneously controlling and improving lamellar tear resistance, and overall improving the toughness performance of the H-beam. (6) The yield strength of the H-shaped steel produced by the above process reaches a level of 420 MPa or higher, achieving weight reduction of structural steel for buildings, and possessing overall performance such as good corrosion resistance, Z-direction performance, and low-temperature toughness, fully satisfying the current engineering needs for prefabricated building structural steel. [Brief explanation of the drawing]

[0042] [Figure 1(a)] This is a plan view of a cooling system for the production of H-shaped steel according to the present invention. [Figure 1(b)] This is a three-dimensional structural diagram of a cooling equipment for the production of H-shaped steel according to the present invention. [Figure 2(a)] This is a microstructural diagram of the upper leg of the H-shaped steel obtained in Example 1 of the present invention. [Figure 2(b)] This is a microstructural diagram of the lower leg of the H-shaped steel obtained in Example 1 of the present invention. [Figure 2(c)] This is a microstructure diagram of the flange of an H-shaped steel obtained in Example 1 of the present invention. [Figure 3(a)] This is a microstructural diagram of the upper leg of the H-shaped steel obtained in Example 6 of the present invention. [Figure 3(b)] This is a microstructural diagram of the lower leg of the H-shaped steel obtained in Example 6 of the present invention. [Figure 3(c)] This is a microstructural diagram of the flange of an H-shaped steel obtained in Example 6 of the present invention. [Modes for carrying out the invention]

[0043] The present invention will be further explained below with reference to specific examples.

[0044] The present invention will be described in detail below. Table 1 is a list of the chemical components of each example and comparative example of the present invention, Table 2 is a list of the main process parameters of each example and comparative example of the present invention, and Table 3 is a list of the performance detections of each example and comparative example of the present invention.

[0045] Each embodiment of the present invention is manufactured according to the following steps.

[0046] In step (1), preferably, molten iron with low phosphorus, low sulfur, and low residual elements is placed in the furnace and then smelted in the converter, and the components and inclusions are controlled by dual LF+RH control, the temperature of the molten steel is controlled to 1600~1620°C at the end of LF refining to counteract the temperature drop of the molten steel during RH treatment by raising the temperature of the molten steel, it is forbidden to "raise the temperature by adding aluminum to generate chemical heat" during RH treatment, RH refining is performed using this treatment mode, the reflux time is made longer than 15 minutes, the pure degassing time is made longer than 5 minutes, after the treatment is completed, 200~250m of calcium aluminum wire is supplied to each furnace, the soft blow time is made longer than 10 minutes, and the RH refining cycle is controlled to 40~50 minutes.

[0047] Finally, the parts are continuously cast into beam blanks and divided into three material types according to the difference in flange thickness. The residual elements in the molten iron are strictly controlled to As+Sn+Zn+Pb+Ca+Mg≦0.035, and the casting superheating degree is set to 20 during the casting process. ~30 ℃ to Control, 0.7~0.9 Select one value from the m / min extraction speeds as a constant extraction speed, and set the straightening temperature to 850°C or higher.

[0048] In the rolling process of step (2), the material is reheated in a heating furnace to control the temperature to 1250-1300°C, the heating time is set to 90-120 minutes, and then it is removed from the furnace and rolled. A controlled rolling / controlled cooling process is used. The number of rolling passes in the rough rolling process (BD) is set to less than 9 passes, and the number of rolling passes in the finish rolling process (TM) is set to less than 7 passes. The final rolling temperature in the finish rolling is controlled to 800-850°C. The cooling rails in the low-temperature furnace are maintained at a temperature of 400°C or higher, and the products are cooled simultaneously and slowly in the low-temperature furnace for more than 15 minutes. When the temperature of the products drops to 200-300°C, they are placed in a leveler for straightening.

[0049] In the finishing process of step (3), after the product rolls off the line, surface and dimensional finishing treatments are performed, and samples are taken during the finishing process to analyze the product's performance.

[0050] [Table 1]

[0051] Refer to Table 2 for the main process parameters of smelting.

[0052] [Table 2]

[0053] Refer to Table 3 for specific process parameters of the continuous casting process.

[0054] [Table 3]

[0055] Table 4 lists the main process parameters for each example and comparative example of the present invention.

[0056] [Table 4]

[0057] Table 5 is a list of performance detections for each embodiment and comparative example of the present invention.

[0058] [Table 5] JPEG0007848244000006.jpg90170

[0059] The prototype products were sampled and performance tests were conducted. For the mechanical performance test, the sampling location for the H-shaped steel flange was one-third of the way from the edge to the core, and for the web plate, the sampling location was in the middle. The reference standard was BS EN ISO 377-1997 "Sampling location and preparation of mechanical performance test specimens," the reference standard for the yield strength, tensile strength, and elongation test methods was ISO 6892-1-2009 "Metallic materials: Room temperature tensile test method," and the reference standard for the impact energy test method was ISO 148-1 "Charpy impact test for metallic materials." The results are shown in Table 5. By comparison, it was found that the Z-direction performance of the H-shaped steel flange and web plate produced by the manufacturing method related to this patent is superior to that of the current patented product.

[0060] Any aspects of this invention that are not described in detail may be based on general technical knowledge in the art.

[0061] Finally, it should be noted that the above embodiments are merely for illustrating the technical concept of the present invention and do not limit it. Although the present invention has been described in detail with reference to the embodiments, as those skilled in the art will understand, any modification or equivalent substitution of the technical concept of the present invention will not depart from the spirit and scope of the technical concept of the present invention, and will all be included within the scope of the claims of the present invention. [Explanation of symbols]

[0062] 1 Coolant piping 2. Cold air piping 3 nozzles 4. First flange piping 5. Lower flange piping 6 centre Lunge 7 centre Lunge 8 Web Plates

Claims

1. A hot-rolled H-shaped steel for construction having high toughness, The chemical composition of the hot-rolled H-shaped steel is, in weight percent, C: 0.06-0.10%, Si: ≤0.25%, Mn: 0.8-1.30%, P ≤0.015%, S ≤0.008%, Cu: 0.15-0.25%, Cr: 0.25-0.60%, Ni: 0.10-0.19%, V: 0.01-0.03%, Al: 0.01-0.03%, RE: 0.009-0.019%, As + Sn + Zn + Pb + Ca + Mg ≤0.035%, N ≤0.008%, T. [O] ≤0.002%, with the remainder being Fe and unavoidable impurities. The hot-rolled H-shaped steel has a yield ratio of ≤0.8 in the Z direction (thickness direction) of the web plate and flange, a yield strength of ≥420 MPa, a tensile strength of ≥520 MPa, an elongation of ≥19%, a longitudinal impact energy of ≥50 J at -20°C, and a cross-sectional shrinkage rate of ≥60% in the thickness direction of both the web plate and flange. A hot-rolled H-shaped steel, characterized in that the sample is sampled in accordance with ISO 377, the yield strength, tensile strength and elongation are measured in accordance with ISO 6892-1, and the impact energy is measured in accordance with ISO 148-1.

2. A method for manufacturing an H-shaped steel according to Claim 1, This includes the smelting process in step (1), the rolling process in step (2), and the finishing process in step (3). In the smelting process of step (1) above, Converter smelting and LF+RH refining involves controlling the temperature of the molten steel to 1600-1620°C at the end of LF refining, increasing the recirculation time of RH refining to more than 15 minutes, and controlling the refining cycle to 40-50 minutes, and This includes continuous casting and, in sequence, In the rolling process of step (2) above, The heating and soaking stages are controlled to 1250-1300°C, the heating time is set to 90-120 minutes, and then the material is removed from the furnace and rolled. The process includes controlled rolling and controlled cooling, in which the final rolling temperature of the finish rolling is controlled to 800°C to 850°C, and in the final pass of the finish rolling, the web plate and flange are cooled individually by a cooling device so that the temperature difference between the upper and lower sides of the flange of the horizontal H-shaped steel is within 10°C and the temperature difference between the upper and lower surfaces of the web plate is within 5°C, and then they are further cooled and straightened simultaneously in a low-temperature furnace. Our manufacturing method

3. The manufacturing method according to claim 2, characterized in that, in step (1) above, the content of arsenic and tin in the converter smelting is both less than 0.008%, the basicity of the finish slag in the converter is in the range of 2.1 to 3.9, slag stopping and molten steel discharge are used, and deoxygenation and alloying with aluminum, manganese, and iron are used in the molten steel discharge process.

4. In the LF refining in step (1) above, RE is added before supplying the calcium wire, the soft blowing time is set to 20 minutes or more, and the refining cycle is set to 30 minutes or more. In RH refining, increase the pure degassing time to more than 5 minutes, and after processing is complete, supply 200-250 m of calcium aluminum wire to each furnace and set the soft blowing time to 10 minutes or more. Protective casting was performed throughout the entire process, the intermediate container was covered with a coating agent and carbide rice husks, argon seal protection was used with an immersion nozzle from the intermediate container to the crystallizer, the liquid surface of the crystallizer was covered with peritectic steel protective slag, and the components of the peritectic steel protective slag were 25% ≤ SiO ≤ 35%, 35% ≤ CaO ≤ 45%, 1.90% ≤ MgO ≤ 3.00%, and 3.00% ≤ Al ２ O ３ The manufacturing method according to claim 2, characterized in that the amount is ≤ 4.00%.

5. The manufacturing method according to claim 2, characterized in that the continuous casting process in step (1) uses a fully protected casting process, in which molten steel is cast using an intermediate container and a stopper container, the drawing speed of the irregularly shaped continuous casting slab is set to 0.7 to 0.9 m / min, and the degree of superheating is controlled to 20 to 30°C.

6. Step (2) further includes a rough rolling process, which achieves die rolling primarily focused on shape, where the temperature of the final pass of the rough rolling is between 1150 and 1050°C, the cumulative deformation rate is between 40% and 60%, and the number of rolling passes is less than 9. The manufacturing method according to claim 2, characterized in that, in the finishing rolling process, the number of rolling passes is made smaller than 7 passes, and when the temperature of the product drops to 200-300°C in a low-temperature furnace, it is placed in a leveler for straightening.

7. A cooling device used for cooling according to claim 2, The cooling device is mounted behind the finishing rolling mill, and the cooling device comprises a plurality of cooling liquid pipes arranged at intervals and a plurality of cold air pipes arranged at intervals. The aforementioned cooling liquid piping is for cooling the flange, and the web plate is installed below the flange of a horizontal hot-rolled H-shaped steel, and comprises a first flange piping parallel to the web plate and two sets of second flange piping perpendicular to and communicating with the first flange piping, with one flange corresponding to each set of second flange piping. Each set of the second flanged pipes comprises two parallel lower flanged pipes, and multiple nozzles for cooling the flanges are installed on the surfaces of the lower flanged pipes facing the flanges, with the flanges of the H-shaped steel placed between the two parallel lower flanged pipes. The cooling device is characterized in that the cold air piping is for cooling the web plate, is installed between the two sets of second flange piping, has a convex shape that follows the two sets of second flange piping and the lower surface of the web plate, and has multiple nozzles installed in the cold air piping parallel to and close to the web plate for cooling the web plate.

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