High-V hot-rolled H-shaped steel and web longitudinal crack control production method thereof

Abstract

According to the high-V hot-rolled H-shaped steel and the web longitudinal crack control production method thereof, V in the components ranges from 0.100% to 0.140%, the equipment precision and technological parameters are precisely controlled through cooperation of the procedures of desulfurization, converter treatment, argon station treatment, continuous casting, hot rolling and the like, particularly, the water quality of soft water of a crystallizer is improved, and the performance of casting powder is optimized, so that the requirement for high mechanical performance is met, and meanwhile the production cost is lowered. And the crack grinding rate of the high-V hot-rolled H-shaped steel web is greatly reduced, and the product quality meets the design requirement of a large building project. According to mechanical properties of the product, the yield strength ReL is not lower than 450 MPa, the tensile strength Rm is not lower than 550 MPa, the ductility A is not lower than 18%, and the KV2 longitudinal impact energy is not lower than 50 J under the condition of 0 DEG C. After the high-V hot-rolled H-shaped steel casting blank is scalped, the longitudinal crack detection of the web is less than or equal to 40mm / m, the longitudinal crack detection incompatibility ratio of the rolled web is less than or equal to 4.0%, and the reject ratio caused by the longitudinal crack of the web is less than or equal to 0.3%.

Description

Technical Field

[0001] The invention belongs to the technical field of hot-rolled H-shaped steel, and in particular relates to a high-V hot-rolled H-shaped steel and a production method for controlling longitudinal cracks in the web thereof. Background Art

[0002] Large H-beam products, due to their high mechanical performance requirements, utilize VN alloys to enhance the strength of hot-rolled H-beams. The V content in the molten steel can reach over 0.100%, making them challenging to produce and subject to high quality control risks. These H-beam products are primarily used in large-scale construction projects. However, this high V content can easily lead to longitudinal cracks in the web of the ingot. Furthermore, since high-V hot-rolled H-beam blanks require the addition of over 0.100% V for alloying, the high V content is adjusted using VN alloys, resulting in nitrogen content exceeding 120 ppm. Nitrogen is a crack-sensitive element in steel, and can easily cause longitudinal cracks in the ingot during the mold shell formation process. Furthermore, during the hot rolling process of the ingot on large H-beam production lines, longitudinal cracks in the ingot can be transferred to the finished H-beam product, resulting in noticeable longitudinal cracks in the web. Minor cracks can be eliminated through grinding, but this affects the surface aesthetics of the hot-rolled H-beam product. Severe cracks are considered scrap.

[0003] The main problems with existing products are that the longitudinal crack detection rate of the web of high-V hot-rolled H-shaped steel ingot after peeling is ≥100mm / m, the proportion of unqualified longitudinal crack detection of the web after rolling is ≥10.0%, and the proportion of scrap caused by longitudinal cracks in the web is ≥0.6%. The high web crack grinding rate and scrap rate increase production costs, reduce product quality, and seriously affect the brand image and market competitiveness of H-shaped steel.

[0004] At present, only a few steel companies in China have the ability to stably produce high-V hot-rolled H-shaped steel. The problem of longitudinal cracks in the web is an industry problem in this field and has not been solved. There are even fewer reports on research on controlling longitudinal cracks in the web of high-V hot-rolled H-shaped steel. Reducing the longitudinal crack defects of high-V hot-rolled H-shaped steel is still in the research and exploration stage. Summary of the Invention

[0005] The purpose of the present invention is to provide a production method for controlling longitudinal cracks in the web of high-V hot-rolled H-shaped steel and the same. By coordinating the processes of desulfurization, converter, argon station, continuous casting and hot rolling, the equipment accuracy and process parameters are precisely controlled. In particular, by improving the quality of soft water in the crystallizer and optimizing the performance of the protective slag, while meeting the high mechanical performance requirements, the crack grinding rate of the web of the high-V hot-rolled H-shaped steel is greatly reduced, and the product quality meets the design requirements of large-scale construction projects.

[0006] The specific technical solutions of the present invention are as follows:

[0007] A high-V hot-rolled H-shaped steel comprises the following chemical components in weight percentage: C: 0.12% to 0.20%; Si: 0.30% to 0.60%; Mn: 1.10% to 1.60%; P≤0.030%; S≤0.030%; V: 0.100% to 0.140%; N: 120 to 260 ppm, with the remainder being iron and unavoidable impurities.

[0008] The composition of the high-V hot-rolled H-shaped steel also satisfies: carbon equivalent CEV≤0.48%, and the calculation formula of carbon equivalent is CEV(%)=C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15.

[0009] The specifications of the high-V hot-rolled H-shaped steel are: height × width × web thickness × flange thickness: 630mm × 200mm × 13mm × 20mm;

[0010] The mechanical properties of the high V hot rolled H-beam require a yield strength R eL ≥450MPa, tensile strength R m ≥550MPa, elongation A ≥18%, KV2 longitudinal impact energy ≥50J at 0℃; the scrap ratio due to longitudinal cracks in the web ≤0.3%.

[0011] The longitudinal crack detection rate of the web of the high-V hot-rolled H-shaped steel after casting is ≤40mm / m, and the unqualified ratio of the longitudinal crack detection rate of the web after rolling is ≤4.0%.

[0012] The invention provides a production method for controlling longitudinal cracks in the web of high-V hot-rolled H-shaped steel, which comprises desulfurization, converter smelting, argon blowing station, continuous casting and hot rolling.

[0013] In the desulfurization step, KR molten iron pretreatment is used for S removal. When the S content of the molten iron is ≤0.030%, only slag skimming treatment is required, and the slag skimming bright surface is ≥80%. When the S content of the molten iron is >0.030%, KR desulfurization and slag skimming are required. The target S content of the molten iron after desulfurization is ≤0.020%, and the slag skimming bright surface is ≥80%.

[0014] During the converter smelting, the converter tapping temperature is controlled at 1620° C. to 1660° C., the converter tapping C is ≥ 0.07%, the converter tapping P is ≤ 0.030%, the converter tapping S is ≤ 0.030%, and the converter tapping composition is adjusted to the target control range.

[0015] The argon blowing station starts blowing argon from the bottom of the converter during the steel-making process. The temperature of the molten steel is measured after entering the argon blowing station. The argon blowing time is ≥ 6 minutes. After ensuring that the composition is uniformly controlled, samples are taken to test the composition. If the composition does not meet the standard requirements, alloy fine-tuning is performed.

[0016] During the continuous casting, the mold soft water quality requirements are: nitrite content 300-500 mg / L, soft water turbidity ≤ 5 NTU; mold protection slag 1.4-1.8 Pa.s / 1300 ° C, and mold soft water flow 180-260 m 3 / h, the secondary cooling section is divided into 1 to 5 sections, and the secondary cooling water volume is 0.4 to 1.0 l / kg.

[0017] Furthermore, in the continuous casting, copper plates are used for casting for ≤500 furnaces, and the number of uses of the sector support section 1, support section 2 and support section 3 are all ≤500 furnaces. The crystallizer copper plate is used less frequently, which can avoid wear of the crystallizer coating and taper deformation caused by excessive use; strictly controlling the number of uses of the sector can avoid the roller spacing becoming larger and the sector rollers being stuck, thereby preventing the billet from experiencing bulging, concaving and other dimensional deformations, deterioration of internal quality, and a high proportion of longitudinal cracks in the web. During the pouring process, the nozzle insertion depth is controlled at 70 to 110 mm, and when pouring begins, the steel liquid level in the middle package is quickly raised to ≥12 tons before pouring begins. This can control the stability of the crystallizer flow field and avoid slag rolling during the pouring process, which causes the billet quality to fail to meet the rolling requirements and flange cracking problems. In order to reduce the longitudinal cracks on the web of V-shaped hot-rolled H-shaped steel blanks, a control mode matching the drawing speed and secondary cooling water weak cooling is adopted. The continuous casting speed range of the continuous casting machine is 0.65-1.05m / min, the superheat control range is 15-30℃, and the total pressure control range of the secondary cooling water is 10.0-13.0bar.

[0018] After continuous casting, high-V hot-rolled H-beam special-shaped blanks are obtained after fire cutting, and the special-shaped blanks of the high-V hot-rolled H-beam of the present invention are obtained. Before each hot rolling production, the web of the ingot is subjected to a peeling inspection to determine the web crack index of the ingot. The obtained high-V hot-rolled H-beam special-shaped blank has a web longitudinal crack ratio of ≤4.0%, and the web longitudinal crack detection after the ingot is peeled is ≤40mm / m. The special-shaped blank is rolled to obtain high-strength high-V hot-rolled H-beam that meets the web crack grinding rate standard requirement.

[0019] The cross-sectional specifications of the high-V hot-rolled H-beam steel profile blank are 750mm × 450mm × 120mm × 75mm for height × width × web thickness × flange thickness. The production of high-V hot-rolled H-beam steel billets places stringent requirements on the cooling process and mold slag properties during the continuous casting process. By adopting the process described in the present invention, the web grinding rate of large H-beam steel after hot rolling is reduced from ≥10.0% to below 4%, and the scrap rate due to longitudinal web cracks is ≤0.3%. This significantly improves the yield rate and quality of the product, effectively reducing production costs and enhancing market competitiveness.

[0020] The obtained continuous casting ingots: low-magnification detection analysis shows that the central porosity is ≤1.0, the central segregation is ≤1.0, the corner cracks are ≤1.0, and there are no quality problems such as subcutaneous cracks, middle cracks, central cracks and subcutaneous bubbles.

[0021] The hot rolling is carried out by controlling the heating furnace temperature to be ≥1200°C, the heating time to be ≥140min, and the rolling process to be performed in 5 passes, wherein the rolling temperature of the first pass is ≤1000°C, the rolling temperature of the third pass is ≤980°C, the rolling temperature of the fifth pass is ≤930°C, and the rolling speed is ≤3.0m / s; during the rolling process, the cooling water of the lower web of the universal section is all turned on, the side nozzles, the upper nozzles and the lower nozzles are all turned on, and the cooling water flow rate is 400-800m 3 / h, with a rolling pressure of 4-8MN. By matching the rolling temperature, speed, and cooling process, a stable rolling process is ensured, which can improve minor internal defects in the ingot. Appropriate rolling and cooling processes can refine grains and enhance mechanical properties. Excessive temperatures, rapid rolling speeds, and uneven cooling can lead to amplified internal defects during the rolling of high-V hot-rolled H-beam profiles, increasing the occurrence of longitudinal cracks in the web and increasing the wear rate of high-V hot-rolled H-beam products, failing to meet the requirement of a web longitudinal crack wear rate of ≤4.0%.

[0022] The specifications of the produced high-V hot-rolled H-beam are: height × width × web thickness × flange thickness: 630 mm × 200 mm × 13 mm × 20 mm. To reduce the proportion of longitudinal cracks in the web after rolling, strict requirements are placed on the cooling process and mold slag properties during the continuous casting process. If production is not carried out in accordance with the various processes required by the present invention, the grinding rate of the web of the heavy H-beam after hot rolling will exceed 10.0%, failing to meet production cost and quality control requirements.

[0023] The design ideas of the present invention are as follows:

[0024] C: Increasing the strength and hardness of steel increases, while reducing plasticity and toughness. On the basis of ensuring strength, reducing the carbon content is beneficial to improving the toughness and cold working properties of steel. Therefore, the present invention controls the C content to 0.12% to 0.20%.

[0025] Si: Properly increasing the silicon content in the special-shaped blank is beneficial to the comprehensive mechanical properties of the steel and increases the corrosion resistance of the steel. The present invention controls the Si content to be 0.30% to 0.60%.

[0026] Mn: An important alloying element that increases the strength of hot-rolled H-shaped steel products and improves toughness. It can be infinitely dissolved in Fe, and while increasing the strength of the steel, has relatively little effect on plasticity. The present invention controls the Mn content to 1.10% to 1.60%.

[0027] P: It has strong solid solution strengthening and work hardening effects, but it segregates severely in steel, increasing the cold brittleness of the steel and making it susceptible to acid corrosion. Therefore, the phosphorus content of high-V hot-rolled H-beam should be ≤0.030%. For high-V hot-rolled H-beam with higher quality requirements, the phosphorus content in the steel should be ≤0.025%.

[0028] S: Sulfur is a harmful impurity element that causes steel to become hot brittle and rust. Therefore, the sulfur content of high-V hot-rolled H-beams should be ≤ 0.030%. For large-scale construction projects with high design service life requirements, the sulfur content of high-V hot-rolled H-beams should be ≤ 0.025%.

[0029] V: Its primary function in steel is to refine grains. Through the dispersion and precipitation of carbonitrides and solid solution of V, it significantly improves the steel's strength and toughness. Therefore, adding a VN alloy to increase the V content in steel and ensuring a certain N content is beneficial for improving the strength of the finished high-V hot-rolled H-beam. Because the high-V hot-rolled H-beam produced by the present invention has high strength requirements and a V content of 0.100-0.140%, defects such as longitudinal cracks in the web are easily generated during the continuous casting of the beam blanks. This results in high web grinding and scrap rates, impacting production cost control.

[0030] N: With the increase of nitrogen content, the strength of steel can be significantly improved, while the plasticity is reduced, especially the toughness is significantly reduced, the weldability is deteriorated, and the cold brittleness is aggravated; at the same time, the aging tendency and cold brittleness and hot brittleness are increased, which damages the welding performance and cold bending performance of steel. The present invention adopts VN alloy to increase V, and the N content in the molten steel will also increase, and eventually VN particles will be formed inside the steel and dispersed in the steel, which will inhibit the growth of grains during heating and hot rolling, and play a role of dispersion strengthening. The increase in N content improves the mechanical properties, but at the same time, it will cause longitudinal cracks in the web of the ingot during the continuous casting and shrinkage process, which will be transmitted to the hot rolling process, causing the problem of longitudinal cracks in the web during the rolling process. The present invention requires that the N content be controlled at 120 to 260 ppm, which plays a strengthening role while meeting the requirement of reducing the grinding rate of web cracks.

[0031] The present invention adopts high-V alloying composition design, and refines the steelmaking, argon station and continuous casting processes according to the user's design requirements for the mechanical properties and internal quality of H-shaped steel. In particular, the continuous casting adopts a matching control mode of pulling speed and secondary cooling water weak cooling. The continuous casting machine continuous casting pulling speed range is 0.65~1.05m / min, the superheat control range is 15~30℃, the secondary cooling water total pressure control range is 10.0~13.0bar, the soft water quality requirements are nitrite content 300mg / L~500mg / L, soft water turbidity ≤5NTU, and the crystallizer protective slag is 1.4~1.8Pa.s / 1300℃, which reduces the proportion of longitudinal cracks in the web of high-V hot-rolled H-shaped steel. After heating and rolling in the heating furnace of the large H-shaped steel production line, the mechanical properties required yield strength R eL Not less than 450MPa, tensile strength R m The strength is not less than 550MPa, the elongation A is not less than 18%, and the KV2 is not less than 50J at 0°C. The high-V hot-rolled H-beam provided by the present invention has been tested and the grinding ratio of web longitudinal cracks is ≤4.0%, meeting the low-cost and high-quality production requirements of large H production lines.

[0032] Compared with the existing technology, the high-V hot-rolled H-beam and its web longitudinal crack control production method provided by the present invention adopt near-net-shape special-shaped blank rolling, and the specifications of the special-shaped blank casting are 750mm×450mm×120mm×75mm in height×width×web thickness×flange thickness respectively. Through the coordination of desulfurization, converter, argon station, continuous casting and hot rolling, the equipment accuracy and process parameters are precisely controlled to solve the problem of high longitudinal crack ratio of high-V hot-rolled H-beam products and meet the high-quality development requirements of large H-beam products. Compared with the existing technology, the present invention adopts high-V alloying design, according to the requirements of large-scale construction project design for the mechanical properties and internal quality of hot-rolled H-beam, to obtain the mechanical properties required yield strength R eL Not less than 450MPa, tensile strength R m Products with a strength of no less than 550MPa, an elongation A of no less than 18%, and a KV2 longitudinal impact energy of no less than 50J at 0°C. The web longitudinal crack detection rate of high-V hot-rolled H-beam ingots after peeling is ≤40mm / m, the unqualified rate of web longitudinal crack detection after rolling is ≤4.0%, and the scrap rate due to web longitudinal cracks is ≤0.3%. The surface quality and mechanical properties of high-V hot-rolled H-beams meet architectural design and market standards. The present invention reduces the grinding rate and scrap rate of web longitudinal cracks, which can reduce production costs. The surface quality and mechanical properties meet architectural design and market standards, improving the quality and market competitiveness of H-beam products. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The web of the high V hot-rolled H-beam ingot of Example 1 was peeled and inspected for cracks;

[0034] Figure 2 For comparative example 1, a 20 cm long crack was found in the web of the high V hot-rolled H-beam ingot after peeling. DETAILED DESCRIPTION

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0036] Example 1-Example 6

[0037] A high-V hot-rolled H-beam comprises the following chemical components in weight percentage: as shown in Table 1, and the balance not shown in Table 1 is Fe and unavoidable impurities.

[0038] Comparative Example 1-Comparative Example 2

[0039] A high-V hot-rolled H-beam comprises the following chemical components in weight percentage: as shown in Table 1, and the balance not shown in Table 1 is Fe and unavoidable impurities.

[0040] Table 1 Composition control of each embodiment and comparative example (wt%; N unit ppm)

[0041]

[0042]

[0043] The production method for controlling longitudinal cracks in the web of high-V hot-rolled H-shaped steel in each embodiment and comparative example includes desulfurization in a desulfurization station, converter smelting, argon blowing station, continuous casting and hot rolling.

[0044] In the desulfurization step, KR molten iron pretreatment is used for S removal. When the S content of the molten iron is ≤0.030%, only slag skimming treatment is required, and the slag skimming bright surface is ≥80%. When the S content of the molten iron is >0.030%, KR desulfurization and slag skimming are required. The target S content of the molten iron after desulfurization is ≤0.020%, and the slag skimming bright surface is ≥80%.

[0045] In the converter smelting, a converter is used for steelmaking, and auxiliary materials and alloys such as refined slag, lime, ferroaluminum, medium carbon ferromanganese and ferrosilicon are added at one time during the tapping process. The converter tapping temperature is controlled at 1620° C. to 1660° C., the converter tapping C is ≥0.07%, the converter tapping P is ≤0.030%, the converter tapping S is ≤0.030%, and the converter tapping composition is adjusted to a target control range.

[0046] The argon blowing station starts the converter tapping process by blowing argon from the bottom. The temperature of the molten steel is measured after entering the argon blowing station. The argon blowing time is ≥6 minutes to ensure that the molten steel composition is evenly controlled. Samples are taken to measure the molten steel composition before leaving the station. When the composition does not meet the design requirements, alloy fine-tuning is performed.

[0047] During the continuous casting, the mold soft water quality requirements are: nitrite content 300-500 mg / L, soft water turbidity ≤ 5 NTU; mold protection slag 1.4-1.8 Pa.s / 1300 ° C, and mold soft water flow 180-260 m 3 / h, the secondary cooling section is divided into 1 to 5 sections, and the secondary cooling water volume is 0.4 to 1.0 l / kg.

[0048] Furthermore, in the continuous casting, copper plates are used for casting for ≤500 furnaces, and the number of uses of the sector support section 1, support section 2 and support section 3 are all ≤500 furnaces. The crystallizer copper plate is used less frequently, which can avoid wear of the crystallizer coating and taper deformation caused by excessive use; strictly controlling the number of uses of the sector can avoid the roller spacing becoming larger and the sector rollers being stuck, thereby preventing the billet from experiencing bulging, concaving and other dimensional deformations, deterioration of internal quality, and a high proportion of longitudinal cracks in the web. During the pouring process, the nozzle insertion depth is controlled at 70 to 110 mm, and when pouring begins, the steel liquid level in the middle package is quickly raised to ≥12 tons before pouring begins. This can control the stability of the crystallizer flow field and avoid slag rolling during the pouring process, which causes the billet quality to fail to meet the rolling requirements and flange cracking problems. In order to reduce the longitudinal cracks on the web of hot-rolled H-beam steel blanks, a control mode matching the casting speed and secondary cooling water weak cooling is adopted. The continuous casting casting speed range of the continuous casting machine is 0.65-1.05m / min, the superheat control range is 15-30℃, and the secondary cooling water total pressure control range is 10.0-13.0bar.

[0049] After continuous casting, high V hot-rolled H-shaped steel profile blanks are obtained through fire cutting, thus obtaining the high V hot-rolled H-shaped steel profile blanks of the present invention.

[0050] The cross-sectional specifications of the high-V hot-rolled H-beam steel profile blank are: height × width × web thickness × flange thickness: 630mm × 200mm × 13mm × 20mm. The production of high-V hot-rolled H-beam steel billets places stringent requirements on the cooling process and mold slag properties during the continuous casting process. By employing the process described in the present invention, the web grinding rate of heavy H-beam steel after hot rolling is reduced from ≥10.0% to below 4%, significantly improving the product yield and quality, effectively reducing production costs and enhancing market competitiveness.

[0051] The hot rolling is carried out by controlling the heating furnace temperature to be ≥1200°C, the heating time to be ≥140min, and the rolling process to be performed in 5 passes, wherein the rolling temperature of the first pass is ≤1000°C, the rolling temperature of the third pass is ≤980°C, the rolling temperature of the fifth pass is ≤930°C, and the rolling speed is ≤3.0m / s; during the rolling process, the cooling water of the lower web of the universal section is all turned on, the side nozzles, the upper nozzles and the lower nozzles are all turned on, and the cooling water flow rate is 400-800m 3 / h, with a rolling pressure of 4-8MN. By matching the rolling temperature, speed, and cooling process, a stable rolling process is ensured, which can improve minor internal defects in the ingot. Appropriate rolling and cooling processes can refine grains and enhance mechanical properties. Excessive temperatures, rapid rolling speeds, and uneven cooling can lead to amplified internal defects during the rolling of high-V hot-rolled H-beam profiles, increasing the occurrence of longitudinal cracks in the web and increasing the wear rate of high-V hot-rolled H-beam products, failing to meet the requirement of a web longitudinal crack wear rate of ≤4.0%.

[0052] The specifications of the produced high-V hot-rolled H-beam are: height × width × web thickness × flange thickness: 630 mm × 200 mm × 13 mm × 20 mm. To reduce the proportion of longitudinal cracks in the web after rolling, strict requirements are placed on the cooling process and mold slag properties during the continuous casting process. If production is not carried out in accordance with the various processes required by the present invention, the grinding rate of the web of the heavy H-beam after hot rolling will exceed 10.0%, failing to meet production cost and quality control requirements.

[0053] The main production process parameters of each embodiment and comparative example are shown in Table 2.

[0054] Table 2 shows the main production process parameters of each embodiment and comparative example.

[0055]

[0056] The high V hot-rolled H-beam products produced from heavy-duty profiled blanks through post-processing were statistically analyzed for web longitudinal crack repair rates and scrap rates for the examples and comparative examples. The results for the produced V hot-rolled H-beams are shown in Table 3.

[0057] Table 3 Performance control of high V hot-rolled H-beam in various embodiments and comparative examples

[0058]

[0059]

[0060] The high-V hot-rolled H-beam special-shaped blanks produced using Examples 1 to 6 above are of excellent quality and have a good surface. Low-magnification analysis shows that the central porosity is ≤1.0, the central segregation is ≤1.0, and the corner cracks are ≤1.0. There are no quality problems such as subcutaneous cracks, intermediate cracks, central cracks, and subcutaneous bubbles. The special-shaped blanks produced using the present invention are subjected to heating furnace, hot rolling, controlled cooling, and finishing processes to produce high-V hot-rolled H-beam finished products with mechanical properties such as yield strength ReL ≥450 MPa, tensile strength Rm ≥550 MPa, elongation A not less than 18%, and KV2 not less than 50 J at 0°C. Crack testing of the web of the high-V hot-rolled H-beam shows that the web crack grinding rate is reduced to less than 4.0%, and the web crack scrap rate is reduced to less than 0.30%, with significant improvement in web crack indicators.

[0061] The high V hot-rolled H-shaped steel blanks produced by the above comparative examples 1 to 2 are of excellent quality and good surface. The low-power detection analysis shows that the center porosity is ≤1.5, the center segregation is ≤1.0, the corner crack is ≤1.5, and there are no quality problems such as subcutaneous cracks, middle cracks, center cracks and subcutaneous bubbles. The high V hot-rolled H-shaped steel products produced by the comparative example are subjected to the heating furnace, hot rolling, controlled cooling and finishing processes. The composition and process of comparative example 1 do not meet the requirements, and the yield strength R eL , tensile strength R mand KV2 cannot meet the mechanical performance design requirements under 0℃ conditions; the composition and process of Example 2 do not meet the requirements, resulting in the elongation not meeting the design requirements, and the web longitudinal crack grinding rate and scrap rate are high, which does not meet the low-cost H-beam design requirements.

[0062] The underlined data do not meet the requirements of the present invention.

[0063] The above embodiments are described to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A high V hot rolled H-beam, characterized in that: The high V hot-rolled H-beam comprises the following chemical components in weight percentage: C: 0.12% to 0.20%; Si: 0.30% to 0.60%; Mn: 1.10% to 1.60%; P≤0.030%; S≤0.030%; V：0.100％～0.140％； N: 120-260 ppm, the balance is iron and inevitable impurities.

2. The high V hot-rolled H-beam according to claim 1, characterized in that: The specifications of the high-V hot-rolled H-shaped steel are height×width×web thickness×flange thickness: 630mm×200mm×13mm×20mm.

3. The high V hot rolled H-beam according to claim 1, characterized in that: The mechanical properties of the high V hot rolled H-beam require a yield strength R eL ≥450MPa, tensile strength R m ≥550MPa, elongation A≥18%, KV2 longitudinal impact energy ≥50J at 0℃.

4. A method for controlling longitudinal cracks in the web of high-V hot-rolled H-beam according to any one of claims 1 to 3, characterized in that: The production method includes desulfurization, converter smelting, argon blowing station, continuous casting and hot rolling.

5. The production method according to claim 4, characterized in that In the desulfurization step, KR molten iron pretreatment is used to remove sulfur, and the target sulfur content of the molten iron after desulfurization is ≤0.020%.

6. The production method according to claim 4, characterized in that During the converter smelting, the converter tapping temperature is controlled at 1620° C. to 1660° C., and the converter tapping C is ≥0.07%.

7. The production method according to claim 4, characterized in that During the continuous casting, the soft water quality of the crystallizer requires a nitrite content of 300 to 500 mg / L; and the crystallizer protection slag is 1.4 to 1.8 Pa.s / 1300°C.

8. The production method according to claim 4 or 7, characterized in that The proportion of longitudinal cracks on the web of the high-V hot-rolled H-shaped steel special-shaped billet obtained after continuous casting is ≤4.0%, and the longitudinal crack detection on the web after the billet is peeled is ≤40mm / m.

9. The production method according to claim 4, characterized in that During the hot rolling and cooling process, the cooling water flow rate is controlled at 400-800m 3 / h, rolling pressure 4~8MN.

10. The production method according to claim 4 or 9, characterized in that After hot rolling, the scrap ratio due to longitudinal cracks in the web is ≤0.3%.

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