High-strength low-temperature-resistant anti-fatigue large-specification electric power angle steel and preparation method thereof

Abstract

The invention relates to the technical field of angle steel, and provides high-strength low-temperature-resistant anti-fatigue large-specification electric angle steel which is composed of the following components in percentage by mass: 0.12%-0.18% of C, 0.2%-0.5% of Si, 1.6%-1.61% of Mn, 0.86%-0.92% of Cr, 0.5%-0.8% of Ni, 0.22%-0.29% of Mo, 0.08%-0.165% of V, 0.04%-0.06% of Nb, 0.03%-0.035% of Ti, 0.2%-0.3% of Cu, less than or equal to 0.015% of P, less than or equal to 0.005% of S, less than or equal to 0.008% of N, less than or equal to 0.003% of O and the balance of Fe and inevitable impurities. According to the technical scheme, the problem that the electric angle steel in the related technology is difficult to meet high strength, low temperature resistance and fatigue resistance at the same time is solved.

Description

Technical Field

[0001] This invention relates to the field of angle steel technology, specifically to a high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel and its preparation method. Background Technology

[0002] With the development of power grid construction, ultra-high voltage (UHV) transmission lines are increasingly extending into extreme environments such as high altitudes and high latitudes. The complex operating conditions in these areas, including low temperatures, strong winds, and snow, place stringent demands on the structural stability and load-bearing reliability of transmission towers. As the core load-bearing component of these towers, the performance of large-diameter power angle steel directly determines the long-term safe operation of the power grid. Therefore, higher standards are being set for the comprehensive performance of large-diameter power angle steel: it must not only possess high strength to withstand extreme loads, but also excellent toughness at extreme low temperatures, and long-life fatigue resistance, comprehensively ensuring the stable operation of the UHV power grid in extreme environments.

[0003] Existing power angle steel is mostly made of ordinary carbon structural steel or low-alloy high-strength steel. However, there are significant technical shortcomings: First, improving the strength of power angle steel easily leads to a decrease in low-temperature toughness. This is because increasing strength often relies on strengthening solid solution and increasing precipitates, but at low temperatures, this hinders plastic deformation and amplifies brittleness, resulting in decreased low-temperature toughness. Second, improving low-temperature toughness easily sacrifices fatigue resistance. This is because improving low-temperature toughness usually requires adding toughening elements, reducing strengthening phases, or lowering strength, which weakens the crack resistance barrier, making cracks in the power angle steel more likely to initiate and propagate, thus sacrificing fatigue resistance. Currently, a technical system that can synergistically improve strength, low-temperature toughness, and fatigue resistance has not yet been formed. Therefore, developing a high-strength, low-temperature resistant, and fatigue-resistant large-size power angle steel is key to solving the construction problems of ultra-high voltage transmission lines in extremely low-temperature regions, and is of great significance for ensuring national energy security and reducing project costs. Summary of the Invention

[0004] This invention proposes a high-strength, low-temperature resistant, and fatigue-resistant large-size power angle steel, which solves the problem that large-size power angle steel in related technologies cannot simultaneously meet the requirements of high strength, low-temperature resistance, and fatigue resistance.

[0005] The technical solution of the present invention is as follows: This invention proposes a high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel, which is composed of the following components by mass percentage: C 0.12%~0.18%, Si 0.2%~0.5%, Mn 1.6%~1.61%, Cr 0.86%~0.92%, Ni 0.5%~0.8%, Mo 0.22%~0.29%, V 0.08%~0.165%, Nb 0.04%~0.06%, Ti 0.03%~0.035%, Cu 0.2%~0.3%, P≤0.015%, S≤0.005%, N≤0.008%, O≤0.003%, with the balance being Fe and unavoidable impurities; the mass content of Mn, Cr, Mo, Ti, and V satisfies the relationship: 13≤(Mn+Cr+Mo) / (Ti+V)≤26.

[0006] As a further technical solution, the mass contents of Mn, Cr, Mo, Ti, and V satisfy the relationship: (Mn+Cr+Mo) / (Ti+V)=23.

[0007] As a further technical solution, the mass content of Mo, V and Ti satisfies the relationship: 11≤(Mo+V) / Ti≤13.

[0008] As a further technical solution, the mass content of Mo, V and Ti satisfies the relationship: (Mo+V) / Ti=11.67.

[0009] This invention also proposes a method for preparing high-strength, low-temperature resistant, and fatigue-resistant large-size power angle steel, which includes the following steps: S1. After the converter steel is refined by LF to obtain the target composition, it is degassed under vacuum and continuously cast to obtain the billet; S2. The billet is hot-rolled, cooled, and heat-treated to obtain high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel.

[0010] As a further technical solution, the continuous casting includes the following steps: the molten steel after vacuum degassing is injected into the crystallizer for primary cooling, then pulled out and enters the secondary cooling zone for secondary atomized cooling to obtain the billet; The specific water volume for the secondary aerosol cooling is 1.2~1.5L / kg.

[0011] As a further technical solution, the hot rolling process involves sequential heat treatment, rough rolling, and finish rolling. The heat treatment consists of a preheating section, a heating section, and a soaking section; The temperature of the preheating section is 500~800℃, and the preheating time is 1.5~2h; The temperature of the heating section is 800~1100℃, and the heating time is 2~2.5h; The temperature of the heat exchange zone is 1180~1220℃, and the heat exchange period is 2.5~3h.

[0012] As a further technical solution, the initial rolling temperature of the roughing process is 1100~1200℃, and the final rolling temperature is 1050~1100℃.

[0013] As a further technical solution, the initial rolling temperature of the finishing rolling process is 950~1000℃, and the final rolling temperature is 820~850℃.

[0014] As a further technical solution, in step S2, the cooling is performed sequentially by water cooling, first air cooling, and second air cooling; the cooling rates of the first air cooling and the second air cooling are different. The water cooling process involves reducing the temperature to 650°C at a rate of 15-20°C / s.

[0015] As a further technical solution, the first air cooling is to cool down to 450°C at a rate of 3~5°C / s.

[0016] As a further technical solution, the second air cooling method involves cooling to 200°C at a rate of 1~2°C / s and holding at that temperature for 2~3 hours.

[0017] As a further technical solution, the heat treatment process includes quenching, tempering, and cooling in sequence. The quenching process includes heating, holding, and water quenching; the heating is performed at 880~920℃; the holding time is 1~1.2 min / mm. During water quenching, the temperature is first cooled to 400°C at a rate of 50-60°C / s, and then cooled to 150°C at a rate of 30-40°C.

[0018] In this invention, during water quenching, the material is first cooled to 400°C at a rate of 50-60°C / s, and then further cooled to 150°C at a rate of 30-40°C. This improves the yield strength and tensile strength of the large-size power angle steel. Cooling at 50-60°C / s inhibits the transformation of austenite to pearlite or ferrite, promoting the transformation of austenite into fine, high-density martensite. This type of structure possesses extremely high strength and hardness, providing a strength foundation for the material. Then, cooling at 30-40°C / s reduces the significant structural stress caused by excessive temperature differences across the cross-section, effectively preventing quenching cracks and ensuring material integrity. Furthermore, this cooling rate allows the initially formed martensite to undergo slight self-tempering, releasing some internal stress. This improvement in stress state and the formation of the multiphase structure further enhance the yield strength and tensile strength of the large-size power angle steel.

[0019] As a further technical solution, the tempering temperature is 580~620℃, and the tempering holding time is 1.2~1.5min / mm.

[0020] The working principle and beneficial effects of this invention are as follows: This invention achieves a synergistic improvement in the strength, low-temperature resistance, and fatigue resistance of large-size power angle steel by limiting the proportional relationship between five elements: Mn, Cr, Mo, Ti, and V. Mn, Cr, and Mo work together to strengthen the steel through solid solution: Mn enhances the matrix strength, laying the foundation for load-bearing capacity; Cr improves the stability of the microstructure at low temperatures, preventing a decrease in toughness under extreme conditions; Mo delays carbide coarsening, ensuring long-term strength stability, while also refining fatigue band spacing and extending crack propagation paths to improve fatigue resistance; Ti and V are key refining and precipitation strengthening elements. V forms VC and disperses to achieve precipitation strengthening, while Ti forms carbonitrides to refine grains, and simultaneously fixes N to form TiN, preventing it from forming harmful phases with Mo and V, thus ensuring the effectiveness of each element. By limiting the ratio to 16 ≤ (Mn + Cr + Mo) / (Ti + V) ≤ 35, this invention ensures a synergistic balance between different strengthening mechanisms. If the ratio is below 16, the solid solution strengthening of Mn, Cr, and Mo is insufficient, making it difficult to meet the high strength load-bearing requirements. Furthermore, the fatigue resistance of Mo is weakened, while the relative strength of Ti and V may lead to excessive precipitation, which in turn reduces toughness. If the ratio is above 35, the solid solution strengthening of Mn, Cr, and Mo is excessive, which can easily cause microstructure embrittlement. In addition, the relative deficiency of Ti and V will weaken the grain refinement and precipitation strengthening effects, failing to effectively hinder dislocation movement and crack propagation. This ratio range ensures that the solid solution strengthening of Mn, Cr, and Mo is synergistically enhanced with the refinement and precipitation strengthening of Ti and V. Ultimately, this allows the power angle steel to simultaneously meet the core requirements of high strength load-bearing capacity, low-temperature toughness, and fatigue resistance in the extreme environment of ultra-high voltage, providing a reliable guarantee for the long-term safe operation of the power grid. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1 A high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel is composed of the following components by mass percentage: C 0.12%, Si 0.2%, Mn 1.61%, Cr 0.91%, Ni 0.5%, Mo 0.24%, V 0.09%, Nb 0.04%, Ti 0.03%, Cu 0.2%, P 0.008%, S 0.003%, N 0.004%, O 0.001%, with the balance being Fe and unavoidable impurities; the value of (Mn+Cr+Mo) / (Ti+V) is 23; the value of (Mo+V) / Ti is 11. A method for preparing high-strength, low-temperature resistant, and fatigue-resistant large-size power angle steel includes the following steps: S1. After the converter steel is refined by LF to obtain the target composition, it is degassed under vacuum and continuously cast to obtain the billet; S2. The billet undergoes heat treatment, rough rolling, finish rolling, and cooling. It is heated to 880℃ and held for 1.2 min / mm. After holding, it is water quenched and then tempered at 580℃ for 1.5 min / mm. After tempering, it is naturally air-cooled to room temperature at a rate of 2℃ / s to obtain high-strength, low-temperature resistant, fatigue-resistant, large-size electric angle steel. Continuous casting includes the following steps: after vacuum degassing, molten steel is injected into a crystallizer for primary cooling, then pulled out and enters a secondary cooling zone for secondary atomized cooling (the specific water volume for secondary atomized cooling is 1.2 L / kg) to obtain a billet. The continuous casting process is carried out at a casting speed of 0.7 m / min. The heat treatment consists of a preheating section, a heating section, and a soaking section, performed sequentially. The temperature of the preheating section is 500℃, and the preheating time is 2 hours. The temperature of the heating section is 800℃, and the heating time is 2.5 hours. The temperature of the soaking section is 1180℃, and the soaking time is 3 hours. The initial rolling temperature for rough rolling was 1100℃, and the final rolling temperature was 1050℃; the total reduction rate was 50%. The initial rolling temperature for finishing rolling was 950℃, and the final rolling temperature was 820℃; the total reduction rate was 50%. The cooling process after finishing rolling involves sequential water cooling, first air cooling, and second air cooling. Water cooling section: temperature is reduced to 650℃ at a rate of 15℃ / s; first air cooling: temperature is reduced to 450℃ at a rate of 3℃ / s; second air cooling: temperature is reduced to 200℃ at a rate of 1℃ / s, and held for 2 hours. During water quenching, the temperature is first cooled to 400℃ at a rate of 50℃ / s, and then cooled to 150℃ at a rate of 30℃.

[0023] Example 2 A high-strength, low-temperature resistant, and fatigue-resistant large-size power angle steel is composed of the following components by mass percentage: C 0.15%, Si 0.3%, Mn 1.61%, Cr 0.91%, Ni 0.7%, Mo 0.24%, V 0.09%, Nb 0.05%, Ti 0.03%, Cu 0.25%, P 0.0012%, S 0.004%, N 0.006%, O 0.002%, with the balance being Fe and unavoidable impurities; the value of (Mn+Cr+Mo) / (Ti+V) is 23; the value of (Mo+V) / Ti is 11. A method for preparing high-strength, low-temperature resistant, and fatigue-resistant large-size power angle steel includes the following steps: S1. After the converter steel is refined by LF to obtain the target composition, it is degassed under vacuum and continuously cast to obtain the billet; S2. The billet undergoes heat treatment, rough rolling, finish rolling, and cooling. It is heated to 900℃ and held for 1.1 min / mm. After holding, it is water quenched and then tempered at 600℃ for 1.3 min / mm. After tempering, it is naturally air-cooled to room temperature at a rate of 2℃ / s to obtain high-strength, low-temperature resistant, fatigue-resistant, large-size electric angle steel. Continuous casting includes the following steps: after vacuum degassing, molten steel is injected into a crystallizer for primary cooling, then pulled out and enters a secondary cooling zone for secondary air mist cooling (the specific water volume for secondary air mist cooling is 1.4 L / kg) to obtain a billet. The continuous casting process is carried out at a casting speed of 0.7 m / min. The heat treatment consists of a preheating section, a heating section, and a soaking section, performed sequentially. The temperature of the preheating section is 700℃, and the preheating time is 1.8 hours. The temperature of the heating section is 950℃, and the heating time is 2.3 hours. The temperature of the soaking section is 1200℃, and the soaking time is 2.7 hours. The initial rolling temperature for rough rolling was 1150℃, and the final rolling temperature was 1070℃; the total reduction rate was 50%. The initial rolling temperature for finishing rolling was 970℃, and the final rolling temperature was 830℃; the total reduction rate was 50%. The cooling process after finishing rolling involves sequential water cooling, first air cooling, and second air cooling. Water cooling section: temperature is reduced to 650℃ at a rate of 18℃ / s; first air cooling: temperature is reduced to 450℃ at a rate of 4℃ / s; second air cooling: temperature is reduced to 200℃ at a rate of 2℃ / s, and held for 3 hours. During water quenching, the temperature is first cooled to 400℃ at a rate of 50℃ / s, and then cooled to 150℃ at a rate of 30℃.

[0024] Example 3 A high-strength, low-temperature resistant, and fatigue-resistant large-size power angle steel is composed of the following components by mass percentage: C 0.18%, Si 0.5%, Mn 1.61%, Cr 0.91%, Ni 0.8%, Mo 0.24%, V 0.09%, Nb 0.06%, Ti 0.03%, Cu 0.3%, P 0.015%, S 0.005%, N 0.008%, O 0.003%, with the balance being Fe and unavoidable impurities; the value of (Mn+Cr+Mo) / (Ti+V) is 23; the value of (Mo+V) / Ti is 11. A method for preparing high-strength, low-temperature resistant, and fatigue-resistant large-size power angle steel includes the following steps: S1. After the converter steel is refined by LF to obtain the target composition, it is degassed under vacuum and continuously cast to obtain the billet; S2. The billet undergoes heat treatment, rough rolling, finish rolling, and cooling. It is heated to 920℃ and held for 1.2 min / mm. After holding, it is water quenched and then tempered at 620℃ for 1.2 min / mm. After tempering, it is naturally air-cooled to room temperature at a rate of 3℃ / s to obtain high-strength, low-temperature resistant, fatigue-resistant, large-size electric angle steel. Continuous casting includes the following steps: after vacuum degassing, molten steel is injected into a crystallizer for primary cooling, then pulled out and enters a secondary cooling zone for secondary air mist cooling (the specific water volume for secondary air mist cooling is 1.5 L / kg) to obtain a billet. The continuous casting process is carried out at a casting speed of 0.7 m / min. The heat treatment consists of a preheating section, a heating section, and a soaking section, performed sequentially. The temperature in the preheating section is 800℃, and the preheating time is 1.5 hours. The temperature in the heating section is 1100℃, and the heating time is 2 hours. The temperature in the soaking section is 1220℃, and the soaking time is 2.5 hours. The roughing process involved an initial rolling temperature of 1200℃ and a final rolling temperature of 1100℃; the total reduction rate was 50%. The initial rolling temperature for the finishing rolling process is 1000℃, and the final rolling temperature is 850℃; the total reduction rate is 50%. The cooling process after finishing rolling involves sequential water cooling, first air cooling, and second air cooling. Water cooling section: temperature is reduced to 650℃ at a rate of 20℃ / s; first air cooling: temperature is reduced to 450℃ at a rate of 5℃ / s; second air cooling: temperature is reduced to 200℃ at a rate of 2℃ / s, and held for 3 hours. Quenching processes include heating, heat preservation, and water quenching; During water quenching, the temperature is first cooled to 400℃ at a rate of 50℃ / s, and then cooled to 150℃ at a rate of 30℃.

[0025] Example 4 The difference between this embodiment and Embodiment 2 is only that the high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel is composed of the following components by mass percentage: C 0.15%, Si 0.3%, Mn 1.6%, Cr 0.86%, Ni 0.7%, Mo 0.22%, V 0.165%, Nb 0.05%, Ti 0.035%, Cu 0.25%, P 0.0012%, S 0.004%, N 0.006%, O 0.002%, with the balance being Fe and unavoidable impurities; the value of (Mn+Cr+Mo) / (Ti+V) is 13.4; and the value of (Mo+V) / Ti is 11.

[0026] Example 5 The difference between this embodiment and Embodiment 2 is only that the high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel is composed of the following components by mass percentage: C 0.15%, Si 0.3%, Mn 1.6%, Cr 0.92%, Ni 0.7%, Mo 0.25%, V 0.08%, Nb 0.05%, Ti 0.03%, Cu 0.25%, P 0.0012%, S 0.004%, N 0.006%, O 0.002%, with the balance being Fe and unavoidable impurities; the value of (Mn+Cr+Mo) / (Ti+V) is 25.18; and the value of (Mo+V) / Ti is 11.

[0027] Example 6 The difference between this embodiment and Embodiment 2 is only that the high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel is composed of the following components by mass percentage: C 0.15%, Si 0.3%, Mn 1.61%, Cr 0.86%, Ni 0.7%, Mo 0.29%, V 0.09%, Nb 0.05%, Ti 0.03%, Cu 0.25%, P 0.0012%, S 0.004%, N 0.006%, O 0.002%, with the balance being Fe and unavoidable impurities; the value of (Mn+Cr+Mo) / (Ti+V) is 23; the value of (Mo+V) / Ti is 12.67.

[0028] Example 7 The difference between this embodiment and Embodiment 2 is only that the high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel is composed of the following components by mass percentage: C 0.15%, Si 0.3%, Mn 1.6%, Cr 0.9%, Ni 0.7%, Mo 0.26%, V 0.09%, Nb 0.05%, Ti 0.03%, Cu 0.25%, P 0.0012%, S 0.004%, N 0.006%, O 0.002%, with the balance being Fe and unavoidable impurities; the value of (Mn+Cr+Mo) / (Ti+V) is 23; the value of (Mo+V) / Ti is 11.67.

[0029] Example 8 The only difference between this embodiment and Embodiment 2 is that during water quenching, the temperature is first cooled to 400°C at a rate of 55°C / s, and then cooled to 150°C at a rate of 35°C.

[0030] Example 9 The only difference between this embodiment and Embodiment 2 is that during water quenching, the temperature is first cooled to 400°C at a rate of 60°C / s, and then cooled to 150°C at a rate of 40°C.

[0031] Example 10 The only difference between this embodiment and Embodiment 2 is that during water quenching, the temperature is first cooled to 400°C at a rate of 35°C / s, and then cooled to 150°C at a rate of 55°C.

[0032] Example 11 The only difference between this embodiment and Embodiment 2 is that the water quenching is performed at a rate of 55°C / s to 150°C.

[0033] Comparative Example 1 The only difference between this comparative example and Example 2 is that the high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel is composed of the following components by mass percentage: C 0.15%, Si 0.3%, Mn 1.61%, Cr 0.91%, Ni 0.7%, V 0.09%, Nb 0.05%, Ti 0.03%, Cu 0.25%, P 0.0012%, S 0.004%, N 0.006%, O 0.002%, with the balance being Fe and unavoidable impurities.

[0034] Comparative Example 2 The only difference between this comparative example and Example 2 is that the high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel is composed of the following components by mass percentage: C 0.15%, Si 0.3%, Mn 1.61%, Cr 0.91%, Ni 0.7%, Mo 0.24%, Nb 0.05%, Ti 0.03%, Cu 0.25%, P 0.0012%, S 0.004%, N 0.006%, O 0.002%, with the balance being Fe and unavoidable impurities.

[0035] Comparative Example 3 The only difference between this comparative example and Example 2 is that the high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel is composed of the following components by mass percentage: C 0.15%, Si 0.3%, Mn 1.61%, Cr 0.91%, Ni 0.7%, Mo 0.24%, V 0.09%, Nb 0.05%, Cu 0.25%, P 0.0012%, S 0.004%, N 0.006%, O 0.002%, with the balance being Fe and unavoidable impurities.

[0036] Test case The high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steels prepared in Examples 1-11 and Comparative Examples 1-3 were tested according to the following methods: 1. Yield strength, elongation after fracture, tensile strength, and reduction of area: The yield strength, elongation after fracture, tensile strength, and reduction of area of ​​the sample shall be tested according to the test methods specified in GB / T 228.1-2021 "Metallic materials, tensile testing—Part 1: Tests at room temperature". According to Method A, the test rate for yield strength is 0.002 s. -1 The test rate for elongation after fracture and tensile strength was 0.002 s. -1 The test results are shown in Tables 1 and 2 below; 2. Low-temperature impact energy: The impact energy of the sample at -40℃ and -60℃ was tested according to the test method specified in GB / T 229-2020 "Metallic Materials Charpy Pendulum Impact Test Method". The sample was a standard impact specimen: 10mm×10mm×55mm. The test results are shown in Table 3 below. 3. Fatigue resistance: Fatigue tests were conducted according to GB / T 3075-2008 "Method for controlling axial force in fatigue testing of metallic materials" (stress ratio R=0.1, loading frequency 10Hz, maximum stress 400MPa). The test results are shown in Table 4 below. 4. Corrosion resistance: Neutral salt spray test (5% NaCl solution, temperature 35℃, relative humidity 95%) was conducted according to GB / T 10125-2021 "Civilized Atmosphere Corrosion Test Salt Spray Test". The sample size was 150mm×70mm×1mm. At the same time, the atmospheric exposure corrosion rate for 1 year was tested (exposure environment: Qingdao marine atmosphere). The test results are shown in Table 5 below. Table 1 Performance test results of Examples 1-7 and Comparative Examples 1-3

[0037] As shown in Table 1, the yield strength, tensile strength, elongation after fracture, and reduction of area of ​​Examples 1-7 are all higher than those of Comparative Examples 1-3. This indicates that by limiting the ratio of Mn, Cr, Mo, Ti, and V to 16≤(Mn+Cr+Mo) / (Ti+V)≤35, the present invention improves the yield strength, tensile strength, elongation after fracture, and reduction of area of ​​large-size power angle steel.

[0038] Table 2 Performance test results of Examples 2 and 8-11

[0039] The yield strength and tensile strength of Examples 2 and 8-9 are higher than those of Examples 10-11, indicating that the present invention further improves the yield strength and tensile strength of large-size power angle steel by limiting the cooling rate during water quenching.

[0040] Table 3 Performance test results of Examples 1-2, Example 7, and Comparative Examples 1-3

[0041] The impact energy at -40℃ and -60℃ of Examples 1-2 and Example 7 are higher than those of Comparative Examples 1-3, and the brittle quasi-transformation temperature of Examples 1-2 and Example 7 is lower than that of Comparative Examples 1-3. This indicates that the present invention improves the low-temperature toughness of large-size power angle steel by limiting the ratio of Mn, Cr, Mo, Ti, and V to 16≤(Mn+Cr+Mo) / (Ti+V)≤35.

[0042] Table 4. Fatigue resistance test results of Examples 1-2, Example 7, and Comparative Examples 1-3

[0043] The fatigue life and fatigue strength of Examples 1-2 and Example 7 are higher than those of Comparative Examples 1-3, and the fatigue crack propagation rate of Examples 1-2 and Example 7 is lower than that of Comparative Examples 1-3. This shows that by limiting the ratio of Mn, Cr, Mo, Ti and V to 16≤(Mn+Cr+Mo) / (Ti+V)≤35, the present invention improves the excellent fatigue resistance of large-size power angle steel.

[0044] Table 5. Corrosion resistance test results of Examples 1-3 and Comparative Examples 1-2

[0045] The time it took for red rust to appear and the 1-year atmospheric corrosion rate in the neutral salt spray test of Examples 1-3 were slower than those in Comparative Examples 1-2, indicating that the large-size power angle steel of the present invention has excellent corrosion resistance.

[0046] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel, characterized in that, The high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel is composed of the following components by mass percentage: C 0.12%~0.18%, Si 0.2%~0.5%, Mn 1.6%~1.61%, Cr 0.86%~0.92%, Ni 0.5%~0.8%, Mo 0.22%~0.29%, V 0.08%~0.165%, Nb 0.04%~0.06%, Ti 0.03%~0.035%, Cu 0.2%~0.3%, P≤0.015%, S≤0.005%, N≤0.008%, O≤0.003%, with the balance being Fe and unavoidable impurities; the mass content of Mn, Cr, Mo, Ti, and V satisfies the relationship: 13≤(Mn+Cr+Mo) / (Ti+V)≤26.

2. The high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel according to claim 1, characterized in that, The mass contents of Mo, V, and Ti satisfy the following relationship: 11 ≤ (Mo + V) / Ti ≤ 13.

3. A method for preparing a high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel, used to prepare the high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel according to any one of claims 1-2, characterized in that, Includes the following steps: S1. After the converter steel is refined by LF to obtain the target composition, it is degassed under vacuum and continuously cast to obtain the billet; S2. The billet is hot-rolled, cooled, and heat-treated to obtain high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel.

4. The method for preparing a high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel according to claim 3, characterized in that, The continuous casting includes the following steps: the molten steel after vacuum degassing is injected into the crystallizer for primary cooling, then pulled out and enters the secondary cooling zone for secondary atomized cooling to obtain a billet; The specific water volume for the secondary aerosol cooling is 1.2~1.5L / kg.

5. The method for preparing a high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel according to claim 3, characterized in that, The hot rolling process involves sequential heat treatment, rough rolling, and finish rolling. The heat treatment consists of a preheating section, a heating section, and a soaking section; The temperature of the preheating section is 500~800℃, and the preheating time is 1.5~2h; The temperature of the heating section is 800~1100℃, and the heating time is 2~2.5h; The temperature of the heat exchange zone is 1180~1220℃, and the heat exchange period is 2.5~3h.

6. The method for preparing a high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel according to claim 3, characterized in that, In step S2, the cooling process involves sequential water cooling, first air cooling, and second air cooling; the cooling rates of the first air cooling and the second air cooling are different. The water cooling process involves reducing the temperature to 650°C at a rate of 15-20°C / s.

7. The method for preparing a high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel according to claim 6, characterized in that, The first air cooling is to cool down to 450°C at a rate of 3~5°C / s.

8. The method for preparing a high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel according to claim 6, characterized in that, The second air cooling process involves cooling the temperature to 200°C at a rate of 1~2°C / s and holding it at that temperature for 2~3 hours.

9. The method for preparing a high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel according to claim 3, characterized in that, The heat treatment process consists of quenching, tempering, and cooling in sequence. The quenching process includes heating, holding, and water quenching; the heating is performed at 880~920℃; the holding time is 1~1.2 min / mm. During water quenching, the temperature is first cooled to 400°C at a rate of 50-60°C / s, and then cooled to 150°C at a rate of 30-40°C.

10. The method for preparing a high-strength, low-temperature resistant, fatigue-resistant, large-size power angle steel according to claim 9, characterized in that, The tempering temperature is 580~620℃, and the tempering time is 1.2~1.5min / mm.

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