Heavy H-shaped steel and manufacturing method of thick high-strength heavy H-shaped steel meeting flaw detection standard requirements

Abstract

The invention discloses heavy H-shaped steel and a manufacturing method of thick high-strength heavy H-shaped steel meeting flaw detection standard requirements. The heavy H-shaped steel comprises the following chemical components in percentage by weight: 0.10-0.25% of C; 0.30 to 0.70% of Si; 1.30% to 1.70% of Mn; p is less than or equal to 0.035%; s is less than or equal to 0.035%; 0.080% to 0.140% of V; the content of Nb is 0.010 to 0.060 percent; n < = 300 ppm; the carbon equivalent CEV is less than or equal to 0.50%, Mn / S is greater than or equal to 45, and Mn / Si is greater than or equal to 4; the processes of high-V micro-Nb alloying component design, refining steelmaking, external refining, continuous casting and the like are adopted, the produced thick-specification high-strength heavy H-shaped steel is subjected to an infrared flaw detection test, the indication length or width of a single defect meets the requirements that the width is smaller than 20 mm, the length is smaller than 50 mm, and the flaw detection performance is qualified.

Description

Technical Field

[0001] The invention belongs to the technical field of H-beams, and in particular relates to a heavy-duty H-beam and a manufacturing method of a thick-gauge high-strength heavy-duty H-beam that meets the requirements of flaw detection standards. Background Art

[0002] Thick-gauge high-strength heavy-duty H-beams are rolled from near-net-shape profiled billets. Due to the large cross-sectional specifications of heavy-duty H-beam profiled billets, such as height × width × web thickness × flange thickness = 1300mm × 510mm × 140mm × 180mm, improper control of steelmaking composition, temperature and continuous casting process can easily lead to defects such as looseness in the R corner area of ​​the billet and cracks inside the web.

[0003] After hot rolling, when producing thick products, due to the high strength, it is necessary to add about 0.10% of V and Nb elements for alloying. High V and high Nb components are prone to cause cracks in the billet during the production process. During the hot rolling process of thin-gauge heavy-duty H-shaped steel billets, under the condition of large compression ratio, defects such as looseness and cracks inside the billet can be welded, and the flaw detection performance can meet the standard requirements. The maximum allowable single defect indication length or width requirements for some heavy-duty H-shaped steels for large buildings in the flaw detection standard are: width ≤ 20mm, length ≤ 50mm.

[0004] However, when producing thick-gauge heavy-duty H-beam products with flange thickness ≥50mm, due to the small compression ratio of the profiled billet, the internal defects such as looseness and cracks of the billet are inherited to the heavy-duty H-beam products, and the heavy-duty H-beam produced will have a large number of unqualified flaw detection problems, making it impossible to use in large-scale construction projects. To solve the problems of looseness and cracks in the center of thick-gauge billets, the traditional method is to use end-stage electromagnetic stirring or light and heavy pressure reduction technology in continuous casting. This technology has been maturely used in the fields of square billets, round billets and slabs, but due to the complex cross-sectional structure of profiled billets, these technologies to solve defects such as looseness and cracks in the center of the billet are still blank in the field of heavy profiled billet production.

[0005] Currently, only a few foreign companies have the ability to produce heavy-duty H-beams, and there are few reports of heavy-duty H-beam products that can meet the requirements. There are currently no similar products produced in China. Improving the pass rate of heavy-duty H-beam flaw detection is still in the research and exploration stage.

[0006] Chinese patent CN 107876721A discloses a method for controlling cracks in the web of a profiled blank. The profiled blank continuous casting machine disclosed in the patent has a cross-sectional size of 295mm×205mm×85mm~430mm×300mm×85mm; the radius of the casting machine base arc is 9~12m; the secondary cooling zone includes three cooling zones, namely, the foot roll section, the secondary cooling zone section 1 and the secondary cooling zone section 2; the distance between the outlet of the casting blank support system and the meniscus of the crystallizer is 4~6m. The profiled blank produced by the patent belongs to the field of small H-beam.

[0007] The document "Principle Analysis and Measures for Non-conformity of NDT of Medium and Thick Plate Rolling Materials" proposes that the causes of non-conformity of NDT are hydrogen-induced cracks, central segregation of the ingot, internal inclusions of the ingot, and developed banded structure in the center of the ingot. This document mainly solves the problem of non-conformity of NDT of medium and thick plates.

[0008] The above-mentioned prior art is only limited to the field of casting machines and profiled blanks whose cross sections belong to small H-beams. The cross sections of small H-beams and heavy profiled blanks are quite different and belong to H-beam products of different grades. Summary of the invention

[0009] In order to solve the above technical problems, the present invention provides a heavy H-shaped steel and a manufacturing method of thick-gauge high-strength heavy-gauge H-shaped steel that meets the requirements of flaw detection standards, which solves the problem of thick-gauge high-strength heavy-gauge H-shaped steel products failing flaw detection, replaces traditional welded H-shaped steel products, and meets the design requirements of large-scale construction projects.

[0010] The technical solution adopted by the present invention is as follows:

[0011] The invention provides a heavy H-shaped steel, which comprises the following chemical components in weight percentage: C 0.10%-0.25%; Si 0.30%-0.70%; Mn 1.30%-1.70%; P≤0.035%; S≤0.035%; V0.080%-0.140%; Nb 0.010%-0.060%; N≤300ppm; H≤5.0ppm; the balance is iron and unavoidable impurities, wherein carbon equivalent CEV≤0.50%, Mn / S≥45, and Mn / Si≥4.

[0012] The heavy H-beam preferably comprises the following chemical compositions in weight percentage: C 0.14% to 0.22%; Si 0.35% to 0.65%; Mn 1.35% to 1.65%; P ≤ 0.032%; S ≤ 0.032%; V 0.085% to 0.120%; Nb 0.015% to 0.045%; N ≤ 260ppm, H ≤ 4.0ppm; the remainder is iron and unavoidable impurities, wherein the carbon equivalent CEV ≤ 0.48%.

[0013] The calculation formula of carbon equivalent is CEV(%)=C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15.

[0014] The metallographic structure of the heavy H-beam is ferrite, bainite and pearlite, wherein the grain size grade of ferrite is above 9.0, and the volume percentage of bainite and pearlite is not less than 22%.

[0015] The yield strength R of the heavy H-beam eL Not less than 400MPa, tensile strength Rm Not less than 500MPa, elongation A not less than 18%, KV2 not less than 27J at 0℃.

[0016] The present invention also provides a method for manufacturing thick-gauge high-strength heavy-duty H-shaped steel that meets the requirements of the flaw detection standard, the manufacturing method comprising the following steps: obtaining a heavy-duty special-shaped blank of the heavy-duty H-shaped steel of the present invention by smelting and continuous casting, and then rolling the heavy-duty special-shaped blank to obtain a thick-duty high-strength heavy-duty H-shaped steel that meets the requirements of the flaw detection standard;

[0017] Among them, in the continuous casting step, copper plates of ≤300 furnaces are used for casting, and the number of uses of sector support section 1, support section 2 and support section 3 are all ≤400 furnaces. Such crystallizer copper plates can avoid wear of the crystallizer coating and taper deformation caused by excessive use; and strict control of the number of uses of the sector segments can avoid the increase of the roller spacing and the jamming of the sector segment rollers, thereby preventing the billet from bulging, concaving and other external dimensional deformations, deterioration of internal quality, and the occurrence of billet flaw detection failures. The whole pouring process is protected by argon. The insertion depth of the nozzle is controlled at 80-120mm during the pouring process. When pouring starts, the liquid level of the molten steel in the middle package is quickly raised to ≥12 tons before pouring. This can control the stability of the crystallizer flow field and avoid slag rolling during the pouring process, which leads to the ingot quality not meeting the rolling requirements and the problem of flange cracking. In order to reduce the looseness of the R-angle center and the cracks in the web of the heavy-duty special-shaped billet, low drawing speed and secondary cooling water weak cooling mode control are adopted. The continuous casting speed range of the continuous casting machine is 0.40-0.70m / min, the superheat control range is 15-30℃, and the total pressure control range of the secondary cooling water is 10.0-13.0bar. After fire cutting, the heavy-duty special-shaped billet is obtained.

[0018] The argon protection during the entire pouring process refers to: blowing argon for protection during the ladle transfer process during pouring, blowing argon for protection during pouring in the ladle protection sleeve, and blowing argon for protection in the ladle of the heavy-duty special-shaped billet continuous casting machine before pouring. This can prevent the molten steel from being oxidized by contact with air, increase of inclusions inside the billet, and inclusion defects after hot rolling of the billet, which not only affects the product quality, but also leads to an increase in internal defects and non-compliance with NDT in severe cases.

[0019] The continuous casting speed of the continuous casting machine is preferably in the range of 0.45 to 0.65 m / min.

[0020] The cross-sectional specifications of the heavy-duty special-shaped blank are height×width×web thickness×flange thickness=1300mm×510mm×140mm×180mm; the meter weight of the heavy-duty special-shaped blank reaches 2.833t, which is the largest cross-sectional special-shaped blank unique in China.

[0021] In the rolling step, 5 passes are used, the rolling temperature of the first pass is ≤1000℃, the rolling temperature of the third pass is ≤980℃, the rolling temperature of the fifth pass is ≤960℃, and the rolling speed is ≤4.0m / s; during the rolling process, the cooling water of the lower belly plate of the universal section is all turned on, the side nozzle, the upper nozzle and the lower nozzle are all turned on, and the rolling pressure is ≥1.3MPa. By matching the rolling temperature, speed and cooling process, the rolling process is ensured to be stable, and the internal defects of the ingot are improved to a certain extent, and the grains can be refined and the mechanical properties can be improved. Excessive temperature, excessive rolling speed and uneven cooling will cause the internal defects of heavy-duty special-shaped billets to be amplified during rolling, and cracks will appear inside the heavy-duty H-beam, resulting in unqualified flaw detection of heavy-duty H-beam products.

[0022] The smelting process comprises the following steps in sequence: KR molten iron pretreatment desulfurization, converter smelting, and LF furnace refining.

[0023] In the KR molten iron pretreatment desulfurization step, the target S content of the molten iron after desulfurization is ≤0.010%, and the molten iron slag bright surface is ≥80%.

[0024] In the converter smelting step, the converter tapping temperature is controlled at 1600° C. to 1650° C., the converter tapping C is ≥ 0.07%, the converter tapping P is ≤ 0.030%, and the converter tapping S is ≤ 0.030%.

[0025] In the converter smelting step, argon is blown from the bottom of the converter at the beginning of the steel-making process, the temperature of the molten steel is measured after entering the argon blowing station, and the argon blowing time is ≥3 minutes.

[0026] In the LF furnace refining step, argon is blown at the bottom of the ladle, alloys are added according to the composition design requirements, argon is blown for 3 minutes to 10 minutes of strong stirring and temperature measurement and sampling are performed, and the steel is discharged after the composition and temperature meet the design requirements. The target time from refining entry to exit is ≤30 minutes, and the heating time is ≤15 minutes. The refining composition control requirements are Mn / S≥45, Mn / Si≥4, so as to avoid R-angle shrinkage holes and internal cracks in the web, which may lead to unqualified flaw detection of the finished heavy H-beam after hot rolling.

[0027] The specifications of the finished heavy H-beam are height×width×web thickness×flange thickness=600mm×476mm×100mm×140mm, and the weight per meter reaches 1299kg. It is the largest-specification special-shaped billet in China, and has strict requirements on the cooling process during the continuous casting process. If the production is not carried out according to the various processes required by the present invention, the qualified rate of the flaw detection of the heavy H-beam after hot rolling cannot meet the production standard requirements.

[0028] In the heavy H-beam provided by the present invention, the functions and controls of the components are as follows:

[0029] C: As the content increases, the strength and hardness of the steel increase, while the plasticity and toughness decrease. On the basis of ensuring the strength, reducing the carbon content is beneficial to improving the toughness and cold working performance of the steel, so the present invention controls the C content to 0.10% to 0.25%.

[0030] Si: Properly increasing the content of silicon in the heavy-duty 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 0.70%.

[0031] Mn: An important alloying element that improves the strength of heavy H-beam finished products and the toughness of heavy H-beams. It can be infinitely dissolved with Fe, and has a relatively small effect on plasticity while improving the strength of steel. When the Mn content exceeds 1.5%, it will promote the formation of bainite. In order to improve the rolling performance of heavy profiled blanks, the present invention requires Mn / S≥60 and Mn / Si≥4, which is conducive to reducing crack defects in the rolling process.

[0032] P: It has strong solid solution strengthening and work hardening effects, and segregates severely in steel, which increases the cold brittleness of the steel and makes the steel susceptible to acid corrosion. For heavy H-shaped steel with high quality requirements, the phosphorus content in the steel should be ≤0.035%.

[0033] S: The presence of sulfur causes steel to become hot and brittle and rust, and is a harmful impurity element. Therefore, the sulfur content of heavy H-beams should be ≤0.035%. For large-scale construction projects with high design service life requirements, the sulfur content of heavy H-beams should be ≤0.032%.

[0034] V and Nb: their main function in steel is to refine grains. Through the dispersion and precipitation of carbonitrides and the solid solution of Nb and V, the strength and toughness of steel are greatly improved. Therefore, adding two microalloying elements, Nb and V, to heavy-duty special-shaped blanks and ensuring a certain N content is beneficial to improving the strength of the finished heavy-duty H-shaped steel. Since the thick-gauge heavy-duty H-shaped steel produced by the present invention has high strength requirements, the total content of V+Nb reaches the range of 0.100-0.150%. The addition of high contents of V and Nb is prone to defects such as cracks during the continuous casting of heavy-duty special-shaped blanks, resulting in unsatisfactory flaw detection performance.

[0035] N: With the increase of nitrogen content, the strength of steel can be significantly improved, while plasticity, especially toughness, is significantly reduced, weldability is deteriorated, and cold brittleness is aggravated; at the same time, the aging tendency, cold brittleness and hot brittleness are increased, and the welding performance and cold bending performance of steel are damaged. The present invention adopts VN alloy to increase V, and the N content in molten steel will also increase, and VN will eventually be formed inside the steel, which inhibits grain growth and plays a role of dispersion strengthening. The increase of N content improves mechanical properties and causes cracking problems in the rolling process. The present invention requires that the N content be controlled to ≤300ppm, which plays a strengthening role while meeting the rolling requirements.

[0036] H: The most harmful element in steel. Hydrogen dissolved in steel can cause defects such as hydrogen embrittlement and white spots. Like oxygen and nitrogen, hydrogen has very low solubility in solid steel. It dissolves into molten steel at high temperatures and does not have time to escape during cooling, so it accumulates in the structure to form high-pressure fine pores, which sharply reduce the plasticity, toughness and fatigue strength of the steel. In severe cases, it can cause cracks and brittle fractures. In order to reduce the H content in steel, dry raw and auxiliary materials are used for production, and the casting is protected to avoid H increase in the continuous casting ladle. The present invention controls H≤5.0ppm.

[0037] The invention adopts high V and micro Nb alloying composition design, and according to the requirements of large-scale construction project design for the mechanical properties and internal quality of heavy H-shaped steel, refines the processes of steelmaking, refining outside the furnace and continuous casting, especially the continuous casting adopts low pulling speed and secondary cooling water weak cooling mode control, reduces the looseness of the R corner center and the web crack of the heavy special-shaped blank, and obtains the yield strength R required by the mechanical properties after rolling by the heavy universal rolling mill. eL Not less than 400MPa, tensile strength R m Not less than 500MPa, elongation A not less than 18%, KV2 not less than 27J at 0°C. The thick gauge high-strength heavy H-shaped steel provided by the present invention is tested by infrared flaw detection, and the length or width of a single defect indication meets the requirements: width <20mm, length <50mm, and it is a high-strength thick gauge flaw detection performance qualified product. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The metallographic structure diagram of the H-beam produced in Example 1; DETAILED DESCRIPTION

[0039] The invention provides a heavy H-shaped steel, which comprises the following chemical components in weight percentage: C 0.10%-0.25%; Si 0.30%-0.70%; Mn 1.30%-1.70%; P≤0.035%; S≤0.035%; V0.080%-0.140%; Nb 0.010%-0.060%; N≤300ppm; H≤5.0ppm; the balance is iron and unavoidable impurities, wherein carbon equivalent CEV≤0.50%, Mn / S≥45, and Mn / Si≥4.

[0040] The manufacturing method of the heavy H-beam is as follows:

[0041] 1) KR molten iron pretreatment desulfurization: Thick-gauge heavy H-beam products have certain requirements on the S content of molten iron. When the S content of molten iron exceeds 0.035%, the molten iron is pretreated at the KR desulfurization station before being added to the converter. The target S content of the molten iron after desulfurization is ≤0.010%, and the bright surface of the molten iron slag is ≥80%.

[0042] 2) Converter steelmaking: The converter is used for steelmaking. Auxiliary materials and alloys such as refined slag, lime, ferroaluminum, medium carbon ferromanganese and ferrosilicon are added once during the steelmaking process. The converter tapping temperature is controlled in the range of 1600℃ ~ 1650℃. 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.

[0043] 3) Argon station: Argon is blown from the bottom of the converter at the beginning of the steel-making process. The temperature of the molten steel is measured after it enters the argon blowing station. The argon blowing time is required to be ≥3 minutes. Samples are taken to measure the composition of the molten steel before leaving the station.

[0044] 4) LF furnace refining: argon is blown at the bottom of the ladle, and alloys such as ferrovanadium and ferroniobium are added according to the composition design requirements. Argon is blown for strong stirring for 3min to 10min and temperature is measured and sampled. The steel is discharged after the composition and temperature meet the design requirements. In order to control the increase in the content of N, O and H gas elements during the refining process, the target time from refining entry to exit is required to be ≤30min, and the heating time is ≤15min. The refining composition control requirements are Mn / S≥45, Mn / Si≥4.

[0045] 5) Continuous casting of heavy-duty special-shaped billet continuous casting machine: The present invention focuses on solving the low-quality problems such as looseness in the R-angle area of ​​heavy-duty special-shaped billets and cracks in the center of the web. It requires precise control of the precision of the continuous casting equipment and the production process. For the production of thick-gauge heavy-duty H-shaped steel billets, it is required to use ≤300 furnaces of copper plates for casting, and the number of times the fan-shaped support 1, support 2 and support 3 are used is ≤400 furnaces. During casting, argon is blown for protection during the transfer process of the large ladle, and the large ladle protection sleeve is blown for argon protection during casting. Before casting, the middle ladle of the heavy-duty special-shaped billet continuous casting machine is blown for argon protection. The nozzle insertion depth during the casting process is controlled at 80-120mm. When casting, the steel liquid level in the middle ladle is quickly raised to ≥12 tons to start casting. The continuous casting speed range of the heavy-duty special-shaped billet continuous casting machine is 0.40~0.70m / min, which is optimized to 0.45~0.65m / min. The casting is low-superheated, and the superheat control range is 15~30℃. The secondary cooling section adopts weak cooling control, and the total pressure control range of the secondary cooling water is 10.0~13.0bar. After fire cutting, the heavy-duty special-shaped billet with a cross-sectional specification of height×width×web thickness×flange thickness=1300mm×510mm×140mm×180mm is obtained. The meter weight of the heavy-duty special-shaped billet reaches 2.833t, which is the largest cross-sectional special-shaped billet unique in China.

[0046] 6) Hot rolling of thick-gauge heavy-duty H-beam: rolled by heavy-duty universal rolling mill, with 5 passes, the rolling temperature of the 1st pass ≤1000℃, the rolling temperature of the 3rd pass ≤980℃, the rolling temperature of the 5th pass ≤960℃, and the rolling speed ≤4.0m / s; during the rolling process, the cooling water of the lower belly plate of the universal section is fully opened, the side nozzle, upper nozzle and lower nozzle are all opened, and the rolling pressure is ≥1.3MPa.

[0047] The present invention is described in detail below with reference to the embodiments.

[0048] The composition control of Examples 1 to 7 and Comparative Examples 1 to 3 of the present invention is shown in Table 1, the process and ingot quality control results are shown in Table 2 and Table 3, and the mechanical properties and flaw detection results are shown in Table 4.

[0049] Table 1 Composition control of thick gauge high strength heavy H-beam (wt%; N and H in ppm)

[0050] Element C Si Mn P S V Nb N H CEV Example 1 0.18 0.45 1.52 0.030 0.027 0.098 0.038 228 3.7 0.45 Example 2 0.14 0.52 1.48 0.025 0.019 0.102 0.015 210 3.5 0.41 Example 3 0.19 0.36 1.60 0.022 0.029 0.110 0.045 236 3.1 0.48 Example 4 0.22 0.35 1.48 0.032 0.032 0.090 0.038 258 3.7 0.48 Example 5 0.19 0.48 1.45 0.018 0.030 0.094 0.040 243 4.0 0.45 Example 6 0.21 0.65 1.52 0.020 0.018 0.103 0.036 260 3.6 0.48 Example 7 0.21 0.54 1.47 0.023 0.027 0.105 0.035 255 3.9 0.48 Comparative Example 1 0.22 0.70 1.62 0.035 0.03 0.115 0.050 280 4.2 0.51 Comparative Example 2 0.21 0.30 1.49 0.038 0.039 0.085 0.014 258 3.7 0.48 Comparative Example 3 0.22 0.43 1.30 0.027 0.035 0.094 0.026 249 3.9 0.46

[0051] Table 2 Thick specification high strength heavy H-beam casting production process control

[0052]

[0053]

[0054] Table 3 Thick specification high strength heavy H-beam hot rolling production process control

[0055]

[0056] The mechanical properties of heavy-duty H-shaped steel products produced by post-processing of heavy-duty special-shaped blanks are required to meet the requirements of yield strength ReL not less than 400MPa, tensile strength Rm not less than 500MPa, elongation A not less than 18%, and KV2 not less than 27J under 0°C conditions. At the same time, infrared flaw detection tests are carried out on the R angle areas and webs of the embodiments and comparative examples.

[0057] Table 4 Thick specification high strength heavy H-beam performance control

[0058]

[0059]

[0060] The thick gauge high strength heavy-duty special-shaped blanks produced by the above-mentioned embodiments 1 to 7 have excellent quality and good surface. Low-power detection analysis shows that the center porosity is ≤1.0, the center segregation is ≤1.0, the corner crack is ≤1.0, and there are no quality problems such as subcutaneous cracks, middle cracks, center cracks and subcutaneous bubbles. The thick gauge high strength heavy-duty H-shaped steel products produced by the casting blanks manufactured by the present invention are subjected to heating furnace, hot rolling, controlled cooling and finishing processes, and obtain the yield strength R required by the mechanical properties. eL 460~490MPa, tensile strength R m560~600MPa, elongation A not less than 23%, KV2 not less than 75J at 0℃, thick-gauge high-strength heavy-duty H-shaped steel is tested by infrared flaw detection, and the length or width of a single defect indication meets the requirements: width <20mm, length <50mm, and it is a qualified product with high-strength thick-gauge flaw detection performance.

[0061] The thick-gauge, high-strength, heavy-duty special-shaped blanks produced by the above-mentioned comparative examples 1 to 3 have excellent quality and good surface. 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 heavy-duty H-shaped steel products produced by the comparative example are subjected to heating furnace, hot rolling, controlled cooling and finishing processes, and the yield strength R eL Not less than 400MPa, tensile strength R m Not less than 500MPa, elongation A not less than 17%, KV2 not less than 27J at 0℃. After infrared flaw detection, there are cracks with width > 20mm and length > 50mm in the R corner area and the middle of the web of thick-specification high-strength heavy H-shaped steel products, and the flaw detection fails.

[0062] The detailed description of a heavy H-beam and a method for manufacturing a thick-gauge high-strength heavy H-beam that meets the requirements of the flaw detection standards with reference to the above-mentioned embodiments is illustrative rather than restrictive, and several embodiments can be listed according to the limited scope. Therefore, changes and modifications without departing from the overall concept of the present invention should fall within the scope of protection of the present invention.

Claims

1. A heavy H-beam, characterized in that: The heavy H-beam includes the following chemical components in weight percentage: C 0.10% to 0.25%; Si 0.30% to 0.70%; Mn 1.30% to 1.70%; P ≤ 0.035%; S≤0.035%; V 0.080%~0.140%; Nb 0.010%~0.060%; N≤300ppm; H≤5.0ppm; The balance is iron and unavoidable impurities, among which carbon equivalent CEV≤0.50%, Mn / S≥45, and Mn / Si≥4.

2. The heavy H-beam according to claim 1, characterized in that: The metallographic structure of the heavy H-beam is ferrite, bainite and pearlite, wherein the grain size grade of ferrite is above 9.0, and the volume percentage of bainite and pearlite is not less than 22%.

3. The heavy H-beam according to claim 1, characterized in that: The yield strength R of the heavy H-beam eL Not less than 400MPa, tensile strength R m Not less than 500MPa, elongation A not less than 18%, KV2 not less than 27J at 0℃.

4. A method for manufacturing thick-gauge high-strength heavy-duty H-shaped steel that meets the requirements of flaw detection standards, characterized in that: The manufacturing method comprises the following steps: obtaining the heavy-duty H-beam blank as claimed in claim 1 through smelting and continuous casting, and then rolling the heavy-duty H-beam blank to obtain the thick-gauge high-strength heavy-duty H-beam meeting the requirements of the flaw detection standard; Among them, in the continuous casting step, copper plates of ≤300 furnaces are used for casting, and the fan-shaped segment support section 1, support section 2 and support section 3 are used ≤400 furnaces; argon protection is carried out throughout the casting process, the water nozzle insertion depth during the casting process is controlled at 80-120mm, and the steel liquid level in the middle package is quickly raised to ≥12 tons when pouring begins; the continuous casting speed range of the continuous casting machine is 0.40-0.70m / min; the superheat control range is 15-30℃; the total pressure control range of the secondary cooling water is 10.0-13.0bar; and heavy-duty special-shaped billets are obtained after fire cutting.

5. The manufacturing method according to claim 4, characterized in that: In the rolling step, five rolling passes are adopted, 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 ≤960°C, and the rolling speed is ≤4.0m / s; during the rolling process, the cooling water of the lower belly plate of the universal section is all turned on, the side nozzle, the upper nozzle and the lower nozzle are all turned on, and the rolling pressure is ≥1.3MPa.

6. The manufacturing method according to claim 4, characterized in that: The smelting process comprises the following steps in sequence: KR hot metal pretreatment desulfurization, converter smelting, LF furnace refining.

7. The manufacturing method according to claim 6, characterized in that: In the KR molten iron pretreatment desulfurization step, the target S content of the molten iron after desulfurization is ≤0.010%, and the molten iron slag bright surface is ≥80%.

8. The manufacturing method according to claim 6, characterized in that: In the converter smelting step, the converter tapping temperature is controlled at 1600° C. to 1650° C., the converter tapping C is ≥ 0.07%, the converter tapping P is ≤ 0.030%, and the converter tapping S is ≤ 0.030%.

9. The manufacturing method according to claim 6, characterized in that: In the converter smelting step, argon is blown from the bottom of the converter at the beginning of the steel-making process, the temperature of the molten steel is measured after entering the argon blowing station, and the argon blowing time is ≥3 minutes.

10. The manufacturing method according to claim 6, characterized in that: In the LF furnace refining step, argon is blown at the bottom of the ladle, alloys are added according to the composition design requirements, argon is blown for 3min to 10min of strong stirring and temperature measurement and sampling are performed, and the steel is discharged after the composition and temperature meet the design requirements. The target time from refining entry to exit is ≤30min, and the heating time is ≤15min; the refining composition control requirements are Mn / S≥45, Mn / Si≥4.

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