460 mpa-grade extra-thick hot-rolled h-shaped steel and production method therefor

Abstract

A 460 MPa-grade extra-thick hot-rolled H-shaped steel and a production method therefor. The 460 MPa-grade extra-thick hot-rolled H-shaped steel comprises components C: 0.10-0.20%, Si: 0.30-0.50%, Mn: 0.8% -1.50%, P ≤ 0.015%, S ≤ 0.005%, Nb: 0.010-0.050%, V: 0.040% -0.100%, Ti: 0.006% -0.020%, Cr: 0.10% -0.30%, N: 0.0060% -0.0120%, and the balance of Fe and inevitable impurities, 0.35% ≤ C+Mn / 6 ≤ 0.45%, and 0.060% ≤ Nb+V ≤ 0.130%. In production, after blanks are continuously cast, a blank slow cooling area is provided so as to slowly cool a pull-out blank pile by means of a specific process, and subsequently controlled rolling and controlled cooling are carried out, thereby solving difficulties in producing extra-thick high-strength hot-rolled H-shaped steel, and allowing for low components and excellent performance.

Description

A 460MPa grade extra-thick hot-rolled H-shaped steel and its production method

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on November 27, 2023, with application number 202311592693.3 and invention name “A 460MPa grade extra-thick hot-rolled H-beam and its production method”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention belongs to the technical field of hot-rolled H-shaped steel production, and more particularly relates to a 460MPa grade extra-thick hot-rolled H-shaped steel and a production method thereof. Background Art

[0003] Extra-thick hot-rolled H-beam refers to hot-rolled H-beam with a flange thickness greater than 60mm. When producing extra-thick hot-rolled H-beam, due to the influence of its production equipment and related technologies, super-large special-shaped billets with a flange thickness of 150mm-210mm are usually used as billets. The quality control of the casting of such special-shaped billets is much more difficult than that of small and medium-sized special-shaped billets, resulting in large fluctuations in the mechanical properties of the finished extra-thick hot-rolled H-beam products.

[0004] In addition, as the flange thickness of hot-rolled H-shaped steel products increases, it is more difficult to improve the mechanical properties of the products due to the thickness effect. Currently, the yield strength of extra-thick hot-rolled H-shaped steel with flange thickness greater than 60mm is mainly 355MPa, and the 460MPa grade is temporarily blank.

[0005] With the increasing construction of super-high-rise buildings, long-span bridges, and large venues, 460MPa-grade extra-thick hot-rolled H-beams will become a key material for their supporting structures. As can be seen from the above, extra-thick, high-strength hot-rolled H-beams have broad application prospects, but their related production technology is still lacking. Therefore, to address the shortcomings of existing technologies, it is urgent to develop a set of key production technologies for this type of product.

[0006] Patent publication number CN 104630625 A, published on May 20, 2015, discloses a low-temperature-resistant hot-rolled H-beam and its production method. The chemical composition of the hot-rolled H-beam is (by weight): C: 0.07-0.10%, Si: 0.2-0.4%, Mn: 1.30-1.60%, P ≤ 0.020%, S ≤ 0.015%, V: 0.015-0.070%, Ti: 0.010-0.030%, with the balance being Fe and unavoidable impurities. The production method includes converter smelting, LF furnace refining, continuous casting, and rolling. The H-beam produced by this invention has a structure of polygonal ferrite and pearlite, and a yield strength of 350-450 MPa. This patented rolling process utilizes conventional methods, with chemical composition designed to achieve a post-rolling yield strength of 450 MPa, an elongation greater than 22%, and a -40°C V-shaped impact energy greater than 200 J. This inventive method is suitable for the production of high-strength, low-temperature-resistant, hot-rolled H-beams less than 40 mm in diameter, but is not suitable for the production of extra-thick, 460 MPa-grade hot-rolled H-beams greater than 60 mm in diameter.

[0007] The patent with publication number CN 110016611 A, published on July 16, 2019, discloses a weather-resistant and low-temperature-resistant hot-rolled H-shaped steel with a yield strength of 355 MPa. The mass percentage of its chemical composition includes: C: 0.08%~0.14%, Si: 0.35%~0.50%, Mn: 1.00%~1.15%, P≤0.020%, S≤0.015%, Cr: 0.40%~0.50%, Cu: 0.30%~0.40%, Ni: 0.30%~0.40%, Nb: 0.03%~0.05%, Al: 0.020%~0.040%, and the rest is Fe and impurities, with a total mass fraction of 100%. The patent also discloses a method for producing weather-resistant and low-temperature-resistant hot-rolled H-beams with a yield strength of 355 MPa using 280mm×380mm rectangular billets. The patent successfully develops weather-resistant hot-rolled H-beams with good low-temperature toughness using rectangular billets. This inventive method adds 0.30-0.40% Ni, 0.40%-0.50% Cr, and 0.30%-0.40% Cu. The resulting hot-rolled H-beams have good weather resistance and low-temperature toughness, but their strength level is only 355 MPa, making them unsuitable for the production of extra-thick hot-rolled H-beams over 60mm and 460 MPa.

[0008] The patent with publication number CN 108642381 A published on October 12, 2018 discloses a hot-rolled high-toughness low-temperature-resistant H-shaped steel with a yield strength of 460 MPa and a preparation method thereof. The H-beam covered by this patent adopts a composite microalloying composition containing nitrogen. Its chemical composition by weight is as follows: C: 0.03% to 0.07%, Si≤0.3%, Mn: 1.20% to 1.40%, Nb: 0.015% to 0.030%, V: 0.10% to 0.15%, Ti: 0.015% to 0.025%, Ni: 0.25% to 0.45%, Cr: 0.30% to 0.50%, Als: 0.01% to 0.06%, N: 0.010% to 0.023%, P≤0.015%, S≤0.010%, O≤0.004%, and the remainder is Fe and unavoidable impurities. This allows the H-beam to achieve a strength of 460 MPa or higher on a conventional hot-rolled H-beam mill while also achieving high toughness. After rolling, its yield strength can reach 460 MPa, tensile strength can reach 600 MPa, and elongation can reach 18% or more; the longitudinal impact energy at -40°C can reach 100 J. This inventive method adds 0.015% to 0.030% Nb, 0.10% to 0.15% V, 0.015% to 0.025% Ti, 0.25% to 0.45% Ni, and 0.30% to 0.50% Cr, achieving a strength level of 460 MPa and a longitudinal impact energy of 100 J at -40°C. However, its composition design is costly and economical, making it unsuitable for practical industrial production.

[0009] Patent publication number CN 103966507 A, published on August 6, 2014, discloses a 275 MPa yield strength, ultra-thick, low-temperature-resistant, hot-rolled H-beam and its production method. Flange thicknesses range from 26 mm to 35 mm. The chemical composition, by weight, is as follows: C: 0.12% to 0.17%, Si: 0.10% to 0.30%, Mn: 0.90% to 1.40%, P ≤ 0.02%, S ≤ 0.015%, V: 0.01% to 0.03%, Ti: 0.005% to 0.020%, with the remainder being iron and unavoidable impurities. The mechanical properties and -20°C longitudinal impact energy of the 275 MPa yield strength ultra-thick, low-temperature-resistant, hot-rolled H-beam provided by this invention fully meet the technical requirements for 275 MPa ultra-thick, low-temperature-resistant, hot-rolled H-beam. The hot-rolled H-shaped steel produced by this method has a thickness of 26 to 35 mm and a strength level of 275 MPa. It is not suitable for the production of extra-thick hot-rolled H-shaped steel with a thickness of more than 60 mm and a strength level of 460 MPa.

[0010] Patent publication number CN 109972042 A, published on July 5, 2019, discloses a low-temperature, corrosion-resistant H-beam with a yield strength of 800 MPa and a method for its preparation. The chemical composition, by mass percentage (%), is as follows: C: 0.10-0.20; Si: 0.20-0.40; Mn: 1.20-1.60; Ni: 0.2-0.4; Cr: 0.2-0.6; V: 0.06-0.10; Nb: 0-0.04; Ti: 0.01-0.02; N: 100-150 ppm, P ≤ 0.020, S ≤ 0.020, with the remainder being Fe and unavoidable impurities. The preparation process involves billeting, followed by hot rolling, followed by quenching and tempering. The hot rolling temperature is 1180-1150°C, and the final rolling temperature is 800-890°C. The quenching temperature is 900°C, with a cooling rate of 30-100°C / s. The tempering temperature is 450-600°C. The resulting H-beam has a yield strength of 800 MPa or higher, a tensile strength of 860-940 MPa, an elongation of 14.0°C or higher, and a low-temperature impact strength of 50 J or higher at -20°C. While this method can produce hot-rolled H-beams with a yield strength of up to 800 MPa, the use of a tempering process undoubtedly increases production costs.

[0011] Patent publication number CN 103938079 A, ​​published on July 23, 2014, discloses a low-compression-ratio, ultra-thick, low-temperature-resistant hot-rolled H-beam and its production method. The H-beam consists of the following chemical composition by weight: C: 0.11-0.19%, Si: 0.15-0.30%, Mn: 1.30-1.55%, P ≤ 0.02%, S ≤ 0.008%, Ti: 0.008-0.020%, V: 0.015-0.055%, with the remainder being Fe and unavoidable impurities. The production method includes smelting in a converter or electric furnace, LF refining, continuous casting of a beam blank with full protection, heating, rolling, and cooling. The resulting low-temperature hot-rolled H-beam has a flange thickness of approximately 35 mm, a compression ratio of 2.5 < 3.0, and good surface quality. The average longitudinal impact energy at -20°C is over 150 J, suggesting broad market application prospects. The maximum flange width of the hot-rolled H-beam produced by this method is 35mm, the minimum compression ratio is 2.5, and the flange thickness is less than 60mm. Therefore, this method is not suitable for the production of extra-thick hot-rolled H-beams of 460MPa grade with a thickness of more than 60mm.

[0012] Therefore, it is very necessary to provide a low-cost, high-performance 460MPa grade extra-thick hot-rolled H-shaped steel.

[0013] Summary of the Invention

[0014] The purpose of the present invention is to provide a 460MPa grade extra thick hot rolled H-beam and its production method, by optimizing the composition and matching the process parameters, to obtain a hot rolled H-beam with a flange thickness of 60-140mm, and the yield strength R eH The tensile strength is between 466 and 493 MPa, the tensile strength is between 613 and 680 MPa, the elongation is between 22.0 and 26.5%, and the impact value at -20°C is between 78 and 106 J. It solves the production difficulties of ultra-thick high-strength hot-rolled H-beams and has low composition and excellent performance.

[0015] The specific technical solutions of the present invention are as follows:

[0016] A 460MPa grade extra-thick hot-rolled H-beam, comprising the following components in percentage by mass:

[0017] C: 0.10-0.20%, Si: 0.30-0.50%, Mn: 0.8%-1.50%, P≤0.015%, S≤0.005%, Nb: 0.010-0.050%, V: 0.040%-0.100%, Ti: 0.006%-0.020%, Cr: 0.10%-0.30%, N: 0.0060%-0.0120%, and the rest are Fe and unavoidable impurities.

[0018] The composition of the 460MPa grade extra-thick hot-rolled H-beam satisfies the following: 0.35%≤C+Mn / 6≤0.45%;

[0019] The composition of the 460MPa grade extra-thick hot-rolled H-beam satisfies: 0.060%≤Nb+V≤0.130%;

[0020] The above formula ensures sufficient strength and toughness. A low C+Mn / 6 ratio will result in a low carbon equivalent. This weakens the solid solution strengthening effect of C and Mn in the steel, negatively impacting the steel's strength and potentially making it difficult to meet strength requirements. Excessive C+Mn / 6 content affects the steel's weldability, resulting in poor weldability. C: 0.10-0.20%, Mn: 0.8%-1.50%, and 0.35% ≤ C+Mn / 6 ≤ 0.45%. To ensure sufficient strength and good weldability, a combined addition of Nb and V is more effective. Adding Nb alone improves toughness but has limited strengthening effects. Adding V alone has a good strengthening effect but limited toughness improvements. A low total Nb+V ratio results in insufficient strength and toughness. A high total, especially with a high Nb content, significantly reduces the steel's high-temperature ductility and makes cracking more likely during production. In order to ensure sufficient strength and toughness and guarantee the surface quality of the steel, Nb: 0.010~0.050%, V: 0.040%~0.100%, and 0.060%≤Nb+V≤0.130%.

[0021] In the calculation formula, the index value of each element = the content of the element in the steel × 100.

[0022] Preferably, the Nb content of the 460MPa-grade extra-thick hot-rolled H-beam should be controlled between 0.020% and 0.040%. Nb within this range can prevent the growth of prior austenite grains during the heating process, thereby refining the ferrite grain size and improving the strength and toughness of the steel. A Nb content that is too low is detrimental to the strength and toughness of the steel, while a Nb content that is too high is detrimental to the plasticity of the steel.

[0023] Preferably, the V content of the 460MPa grade extra-thick hot-rolled H-beam should be controlled between 0.060% and 0.100% to ensure better precipitation strengthening after rolling. Too low a V content is detrimental to the strength of the steel, while too high a V content is detrimental to the toughness of the steel.

[0024] Preferably, the Ti content of the 460MPa grade extra-thick hot-rolled H-beam should be controlled at 0.008% to 0.015%. Ti is more refractory than Nb and V during the heating process of the ingot, and its ability to inhibit the original austenite grain size is more significant. At the same time, the fine precipitates of Ti after rolling can more significantly pin dislocations, playing a higher strengthening role. In addition, Nb precipitates usually precipitate along the Ti precipitates, which can achieve soft phase encapsulation of hard phases, thereby effectively improving the toughness of the steel. If the Ti content is too low, the Ti precipitates are too few, which is not conducive to strength. If the Ti content is too high, the precipitates are too large, which is not conducive to the plasticity and toughness of the steel.

[0025] Preferably, the nitrogen content of the 460 MPa grade extra-thick hot-rolled H-beam should be controlled between 0.0080% and 0.0100% to ensure that sufficient fine and uniform carbonitrides are formed with Nb, V, and Ti. Furthermore, nitrogen can also appropriately improve the hardenability of the steel. A nitrogen content that is too low will not form sufficient carbonitrides of Nb, V, and Ti, making the microalloying element less effective. A high nitrogen content can easily lead to cracking.

[0026] Preferably, the Cr content of the 460MPa grade extra-thick hot-rolled H-beam should be controlled at 0.20% to 0.30% to increase the hardenability of the steel after rolling. Too low a Cr content is detrimental to the strength of the steel, while too high a Cr content is detrimental to the plasticity and toughness of the steel.

[0027] The flange structure of the 460MPa grade extra-thick hot-rolled H-shaped steel is as follows: the surface layer of 2mm is tempered bainite; the core is ferrite + pearlite, the ferrite area accounts for 80±2%, the pearlite area accounts for 20±2%, and the grain size is ≥8.0.

[0028] The flange thickness of the 460MPa grade extra-thick hot-rolled H-beam is 60-140mm;

[0029] The yield strength R of the 460MPa grade extra thick hot rolled H-beam eH 466~493MPa, tensile strength 613~680MPa, elongation 22.0~26.5%, -20℃ impact value is 78~106J.

[0030] The present invention provides a production method for 460MPa grade extra-thick hot-rolled H-shaped steel, comprising the steps of: casting, drawing, stack cooling, reheating, controlled rolling and controlled cooling;

[0031] The flange thickness of the casting billet is 180 to 210 mm;

[0032] The stack cooling time t d >5 hours, effectively reducing the hydrogen content in the billet and preventing hydrogen accumulation, which would result in low or even unacceptable elongation.

[0033] Preferably, the stack cooling time t d The temperature T before the billet enters the cooling zone d There is a relationship between The temperature of the cold zone after the billet leaves the pile T c Controlled at 400~500℃, stack cooling time t d Controlled within >5 hours. The temperature T before the billet enters the cooling zone d Generally, it is 900-1300℃. If the cooling time is too short, it is not conducive to the diffusion of hydrogen and the tensile properties of steel. If the cooling time is too long, it is not conducive to production efficiency.

[0034] Stack cooling time t d The unit is hour, h; the temperature T before the billet enters the cooling zone d The unit is ℃; when calculating with the above formula, just substitute the data before the above unit into the formula.

[0035] The heating process is to send the billet after stack cooling into a heating furnace for heating, with the heating time controlled at 120min-180min and the temperature in the furnace controlled at 1200℃-1250℃; the temperature out of the furnace is 1200℃-1250℃;

[0036] Preferably, the heating time should be controlled within 130 min to 150 min. If the heating time is too short, the carbonitrides of Nb, V, and Ti cannot be completely melted in the austenite, and the unmelted second phase particles tend to be too large when precipitated after rolling, which has no obvious contribution to the mechanical properties and may even be harmful. If the heating time is too long, the original austenite grain size tends to grow, which is detrimental to the mechanical properties of the product.

[0037] The heating temperature of the present invention should be controlled at 1200°C to 1250°C. If the heating temperature is too low, the carbonitrides of Nb, V, and Ti cannot be completely melted in the austenite, and the unmelted second phase particles are likely to be too large when precipitated after rolling, which has no obvious contribution to the mechanical properties and may even be harmful. If the heating temperature is too high, the original austenite grain size is likely to grow, which is detrimental to the mechanical properties of the product.

[0038] The controlled rolling and controlled cooling comprises a universal rolling stage after the cogging stage;

[0039] In the universal rolling stage, the flange cooling device should be turned on in the 1st to 4th passes to control the cooling of the flange, with a flange cooling rate of 15°C / s to 30°C / s, and the temperature after cooling controlled at 960°C to 980°C; wherein, the second pass of the universal rolling adopts temperature-controlled rolling, i.e., the web rolling temperature is controlled at 900°C to 950°C.

[0040] After the universal rolling stage is completed, controlled cooling is carried out after rolling. A rapid cooling device is used for cooling. The cooling temperature is controlled at 900℃~950℃, the flange cooling rate is 30℃ / s~50℃ / s, and the surface temperature of the steel after controlled cooling is controlled at 400℃~500℃.

[0041] Preferably, the flange cooling rate for the 1st to 4th passes is controlled at 20°C / s to 25°C / s. If the cooling rate is too high, the rolling pressure will be too high, the equipment loss will be large, and if the cooling rate is too low, it will not be conducive to improving the mechanical properties of the steel.

[0042] Preferably, the starting rolling temperature of the second pass of universal rolling should be controlled at 920℃~940℃. If the starting rolling temperature is too low, it will lead to excessive rolling pressure and cause great damage to the equipment. If the starting rolling temperature is too high, it will be detrimental to grain refinement and the mechanical properties of the steel.

[0043] Preferably, the cooling start temperature is controlled at 910°C to 930°C. If the cooling start temperature is too low, it will be detrimental to the strength and toughness of the steel. If the cooling start temperature is too high, it will be detrimental to the toughness of the steel.

[0044] Preferably, during controlled cooling after rolling, the cooling rate should be controlled at 35°C / s to 45°C / s, and the surface temperature of the steel after controlled cooling should be controlled at 430°C to 460°C. The temperature after controlled cooling is the autotempering temperature of the extra-thick H-beam. If this temperature is too low, the toughness of the steel will be adversely affected. If this temperature is too high, both the strength and toughness of the steel will be adversely affected.

[0045] After controlled rolling and controlled cooling, the product is placed on the cooling bed and cooled naturally. The heat in the core is gradually transferred to its subsurface and surface layers, so that the subsurface and surface metals after controlled cooling are self-tempered, thereby improving their mechanical properties.

[0046] Compared with existing technologies, the present invention utilizes a specific composition design during the steelmaking process to achieve a finer and more uniform grain size in the billet. After continuous casting, a billet slow cooling zone is established to perform a specific slow cooling process on the pulled, stacked billets, effectively diffusing hydrogen from the billet interior. A specific controlled rolling and controlled cooling process is employed in the rolling zone. When the present invention method is used to produce hot-rolled H-shaped steel with a flange thickness of 60-140 mm, the product achieves a yield strength ReH of 466-493 MPa, a tensile strength of 613-680 MPa, an elongation of 22.0-26.5%, and a -20°C impact strength of 78-106 J. The metallographic structure of the product is shown in Figure 2, showing that the surface layer is tempered bainite; the core is ferrite + pearlite, with a grain size of 8.0, and the tensile specimen fracture surface is free of white spots. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] FIG1 is a schematic diagram of the stack cooling of the profiled blanks of the present invention; conventional stack cooling, with windbreak walls equipped with heat-insulating cotton at the bottom, top and surrounding areas, and the blanks are naturally cooled slowly in the stack cooling area;

[0048] FIG2 is a metallographic structure of hot-rolled H-beam produced by the present invention;

[0049] FIG3 is a fracture surface of a hot-rolled H-beam tensile test specimen, where a is obtained by adopting the method of the present invention, and b is obtained by not adopting the method of the present invention. DETAILED DESCRIPTION

[0050] The following is a further detailed description of the specific embodiments of the present invention through the description of implementation examples:

[0051] Example 1-Example 5

[0052] A 460 MPa grade extra-thick hot-rolled H-shaped steel comprises the following components in mass percentage: as shown in Table 1, and the remainder not shown in Table 1 is Fe and unavoidable impurities.

[0053] Comparative Example 1-Comparative Example 2

[0054] A 460 MPa grade extra-thick hot-rolled H-shaped steel comprises the following components in mass percentage: as shown in Table 1, and the remainder not shown in Table 1 is Fe and unavoidable impurities.

[0055] Table 1 Composition and content of H-beams in various embodiments and comparative examples (wt%)

[0056] The above embodiments and comparative examples are produced according to the following method: after the casting billet is drawn, the billet is pile-cooled; reheated, controlled rolling and controlled cooling;

[0057] After the casting is drawn, the billet is pile-cooled for a cooling time of >5 hours. Preferably, the cooling time t d The temperature T before the billet enters the cooling zoned There is a relationship between The temperature of the cold zone after the billet leaves the pile T c Controlled at 400~500℃, stack cooling time t d Control> 5 hours. The temperature T before the billet enters the cooling zone d Generally, it is 900-1300℃. The billet after stack cooling is sent to the heating furnace for heating. The heating time is controlled at 120min~180min, and the temperature in the furnace is controlled at 1200℃~1250℃; the furnace discharge temperature is 1200℃~1250℃, and there are no special requirements for the specific process in the billet opening stage; in the universal rolling stage, the flange cooling device should be turned on for the 1st to 4th passes to control the cooling of the flange, with a cooling rate of 15℃ / s~30℃ / s, and the temperature after cooling is controlled at 960~980℃; the second pass of universal rolling adopts temperature-controlled rolling, that is, the web rolling temperature is controlled at 900℃~950℃. After the universal rolling process is completed, controlled cooling should be carried out after rolling, and a rapid cooling device should be used for cooling. The cooling start temperature is controlled at 900℃~950℃, the cooling rate is 30℃ / s~50℃ / s, and the surface temperature of the steel after controlled cooling is controlled at 400℃~500℃. The parameters of each embodiment and comparative example are specifically controlled according to Table 2.

[0058] Table 2 Main process parameters of each embodiment and comparative example

[0059] The properties of H-beam produced according to the above method are shown in Table 3. Sampling and sample preparation are in accordance with GB / T 2975, tensile test is carried out in accordance with GB / T 228.1, and impact test is carried out in accordance with GB / T 229.

[0060] Table 3 Main properties of each embodiment and comparative example

[0061] The underlined data above are data that do not meet the requirements of the present invention.

[0062] When hot-rolled H-beams with flange thicknesses of 60-140 mm are produced using the method of the present invention, the product exhibits a yield strength (ReH) of 466-493 MPa, a tensile strength of 613-680 MPa, an elongation of 22.0-26.5%, and a -20°C impact strength of 78-106 J, as shown in Table 1. The metallographic structure of the product is shown in Figure 2, which shows a surface layer composed of tempered bainite; a core composed of ferrite + pearlite with a grain size of 8.0. The tensile specimen fracture surface exhibits no white spots, as shown in Figure 3(a). Hot-rolled H-beams with flange thicknesses of 140 mm, produced without the method and apparatus of the present invention, exhibit yield strength (ReH) of 398-502 MPa, a tensile strength of 568-730 MPa, an elongation of 20.0-24.5%, and a -20°C impact strength of 22-101 J, as shown in Table 1. There are fisheye-shaped white spots on the fracture surface of the tensile specimen of the product, as shown in Figure 3 (b).

Claims

1. A 460MPa grade extra thick hot rolled H-beam, characterized in that: The 460MPa grade extra thick hot rolled H-beam comprises the following components in mass percentage: C: 0.10~0.20%, Si: 0.30~0.50%, Mn: 0.8%~1.50%, P≤0.015%, S≤0.005%, Nb: 0.010~0.050%, V: 0.040%~0.100%, Ti: 0.006%~0.020%, Cr: 0.10%~0.30%, N: 0.0060%~0.0120%, and the rest are Fe and unavoidable impurities.

2. The 460MPa grade extra thick hot rolled H-beam according to claim 1, characterized in that: The composition of the 460MPa grade extra-thick hot-rolled H-shaped steel satisfies: 0.35%≤C+Mn / 6≤0.45%.

3. The 460MPa grade extra thick hot rolled H-beam according to claim 1 or 2, characterized in that: The composition of the 460MPa grade extra-thick hot-rolled H-shaped steel satisfies: 0.060%≤Nb+V≤0.130%.

4. A method for producing 460MPa grade extra thick hot rolled H-beam according to any one of claims 1 to 3, characterized in that: The production method comprises the steps of: stack cooling the cast billet after billet drawing; reheating, controlled rolling and controlled cooling.

5. The production method according to claim 4, characterized in that: The stack cooling time t d >5 hours.

6. The production method according to claim 4, characterized in that: Pile cooling time t d The temperature T before the billet enters the cooling zone d Relationship The temperature of the billet before entering the cooling zone is T d 900-1300℃.

7. The production method according to claim 4, characterized in that: The heating is to send the stack-cooled billet into a heating furnace for heating, the heating time is controlled within 120min-180min, the temperature in the furnace is controlled within 1200°C-1250°C; the temperature out of the furnace is 1200°C-1250°C.

8. The production method according to claim 4, characterized in that: The controlled rolling and controlled cooling is followed by a universal rolling stage.

9. The production method according to claim 8, characterized in that: In the universal rolling stage: the flange cooling device should be turned on in the 1st to 4th passes to control the cooling of the flange, and the flange cooling rate is 15°C / s to 30°C / s; the second pass of universal rolling adopts temperature-controlled rolling, and its web rolling temperature is controlled at 900°C to 950°C.

10. The production method according to claim 8 or 9, characterized in that: After the universal rolling process is completed, controlled cooling is carried out after rolling. A rapid cooling device is used for cooling. The start cooling temperature is controlled at 900℃~950℃, the cooling rate is 30℃ / s~50℃ / s, and the surface temperature of the steel after controlled cooling is controlled at 400℃~500℃.

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