High-strength angle steel and production process thereof

Abstract

The invention relates to the field of alloy steel, and particularly discloses high-strength angle steel and a production process thereof. The high-strength angle steel comprises the following chemical components: C, Si, Mn, P, S, Al, Nb, V, Ti, N and Fe, wherein the ratio of (Nb mass percent / atomic weight + V mass percent / atomic weight + Ti mass percent / atomic weight) / (C mass percent / atomic weight + N mass percent / atomic weight) is 0.80-1.05; the preparation method comprises the following steps: heating a steel billet to 1000-1150 DEG C, carrying out hot rolling, and controlling the initial rolling temperature of finish rolling to 950-1000 DEG C; and then carrying out two-stage cooling: firstly, rapidly cooling to 750-800 DEG C at a speed of 15-25 DEG C / s, and then slowly cooling to 60-80 DEG C by a cooling bed in a stepping period of 4-6 s. And finally, straightening and fixed-length shearing are carried out. The high-strength angle steel has the advantages of being high in strength and good in structure uniformity.

Description

Technical Field

[0001] This application relates to the field of alloy steel, and more specifically, to a high-strength angle steel and its manufacturing process. Background Technology

[0002] Angle steel, as a classic steel profile, is widely used in the manufacture of steel structures such as houses, bridges, and towers due to its unique L-shaped cross-section, which has good bending resistance and convenient connection. It is one of the key components for bearing and transmitting loads, and its strength directly determines the safety and economy of the overall structure.

[0003] Currently, the production of conventional angle steel mainly relies on hot rolling processes. Existing technologies typically employ walking beam or pusher furnaces to heat the steel billet, followed by multiple rolling passes, and finally cooling, straightening, and shearing to obtain the finished product. However, these conventional methods have many shortcomings in terms of heating uniformity, continuity of rolling deformation, and control of the cooling process. For example, uneven temperature distribution in the furnace can easily lead to coarse and uneven internal structure of the steel billet; limited rolling passes and discontinuous deformation make it difficult to sufficiently refine the austenite grains; more importantly, the subsequent cooling process lacks precise control, and uneven cooling rates can easily lead to asynchronous phase transformations, resulting in uneven ferrite and pearlite microstructures and residual stress within the steel.

[0004] The limitations of the existing production processes mentioned above ultimately lead to problems such as poor internal structure uniformity and low grain size in angle steel products. This microstructural inhomogeneity directly becomes a weak link in the macroscopic mechanical properties of the material, severely restricting further improvements in its yield strength and tensile strength, and failing to meet the growing demand of modern building structures for high-strength and high-reliability angle steel. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a high-strength angle steel and its manufacturing process.

[0006] The first part of this application provides a high-strength angle steel using the following technical solution: A high-strength angle steel, the chemical composition of which, by mass percentage, comprises: C: 0.14%~0.18%, Si: 0.40%~0.55%, Mn: 1.35%~1.52%, P≤0.015%, S≤0.008%, Al: 0.020%~0.050%, Nb: 0.025%~0.040%, V: 0.050%~0.070%, Ti: 0.010%~0.025%, N: 0.0080%~0.0120%, with the balance being Fe; The ratio of (Nb mass percentage / atomic weight + V mass percentage / atomic weight + Ti mass percentage / atomic weight) / (C mass percentage / atomic weight + N mass percentage / atomic weight) is between 0.80 and 1.05.

[0007] By adopting the above technical solution, controlling the carbon content to 0.14%-0.18% ensures the optimal balance between matrix strength and toughness. Simultaneously, significantly reducing phosphorus and sulfur content to below 0.015% and 0.008% respectively significantly reduces grain boundary segregation and inclusions. Limiting the ratio of the total molar number of microalloying elements to the total molar number of carbon and nitrogen elements to the range of 0.80-1.05 ensures that the microalloying elements can achieve near-complete chemical stoichiometry with carbon and nitrogen atoms during subsequent hot working, thereby maximizing the formation of nanoscale composite carbonitride precipitates. This avoids the formation of coarse cementite due to excess carbon, which impairs toughness, and also prevents the waste of microalloying elements through solid solution, thus achieving optimal precipitation strengthening effect.

[0008] Secondly, this application provides a method for producing high-strength angle steel, comprising the following steps: Step 1: Heat the steel billet in a heating furnace to a homogenization temperature of 1000℃~1150℃; Step 2: The heated steel billet is rolled using a multi-pass continuous hot rolling process, wherein the initial rolling temperature of the finishing rolling stage is controlled at 950℃~1000℃. Step 3: The rolled material obtained in Step 3 is subjected to a first cooling and a second cooling in sequence; the first cooling rate is 15℃ / s~25℃ / s, and the cooling termination temperature is 750℃~800℃; the second cooling is natural cooling on the cooling bed with a step cycle of 4-6s, and the termination temperature is 60℃~80℃. Step 4: Straighten the cooled rolled material and cut it to a fixed length.

[0009] By employing the above technical solution, the steel billet is heated to 1000-1150℃ to allow microalloying elements such as Nb, V, and Ti to fully dissolve in austenite, providing the preconditions for subsequent precipitation strengthening. The finishing rolling temperature is controlled within the 950-1000℃ range to ensure rolling occurs in the non-recrystallization zone, effectively accumulating deformation energy and providing more sites for ferrite nucleation during phase transformation. A two-stage cooling mode is adopted: the first stage involves rapid cooling to 750-800℃ to inhibit grain growth, while the second stage involves slow cooling to 60-80℃ to ensure complete phase transformation, ultimately yielding a fine and uniform ferrite-pearlite microstructure.

[0010] Optionally, in step one, the steel billet is held at a homogenization temperature of 1000℃ to 1150℃ for more than 30 minutes.

[0011] By adopting the above technical solution, sufficient heat preservation time allows microalloying elements, especially niobium, to be completely dissolved in the austenitic matrix, avoiding the presence of undissolved large-sized carbonitrides, while promoting full deoxidation of aluminum, creating ideal initial microstructure conditions for subsequent controlled rolling and cooling processes.

[0012] Optionally, in step two, the final rolling temperature of the finishing rolling stage is controlled at 850℃~880℃.

[0013] By adopting the above technical solution, the temperature range is located between the lower limit of the non-recrystallization region of austenite and the upper limit of the phase transformation point. This ensures that crystal defects such as deformation bands and dislocations accumulated during the rolling process are preserved, providing a large number of nucleation sites for ferrite phase transformation, while also preventing the rolling process into the two-phase region from causing mixed crystal structure.

[0014] Optionally, in step three, the first cooling is achieved using a water-cooling method with water as the medium.

[0015] By adopting the above technical solution and utilizing the efficient heat exchange characteristics of water cooling, the temperature range sensitive to austenite grain growth can be rapidly skipped at a precise cooling rate of 15-25℃ / second, quickly reducing the rolled material temperature to 750-800℃. This forced cooling method effectively suppresses the migration of austenite grain boundaries, fixes the elongated austenite grains formed during rolling, and prepares the microstructure for subsequent phase transformation.

[0016] Optionally, in step three, during the initial stage of the second cooling, the average cooling rate of the rolled material in the temperature range of 650℃ to 700℃ is controlled to be no greater than 10℃ / s.

[0017] By adopting the above technical solution, the temperature range is located in the core range of ferrite phase transformation. The appropriate slow cooling rate provides sufficient atomic diffusion time for the precipitation of carbonitrides, which promotes the dispersion and precipitation of microalloying elements at the nanoscale, while ensuring the sufficiency of ferrite transformation and avoiding the generation of non-equilibrium structures such as bainite caused by excessively rapid cooling.

[0018] Optionally, in step four, the straightening process is performed when the temperature of the rolled material drops below 80°C.

[0019] By adopting the above technical solution, straightening is performed at a lower temperature, resulting in a higher yield strength of the material. This effectively eliminates the bending deformation generated during the cooling process of the rolled material and avoids excessive plastic deformation that may occur due to the low yield strength of the material during high-temperature straightening. At the same time, it helps to reduce the residual stress of the finished steel and improve dimensional stability.

[0020] Optionally, in step two, a single-pass reduction rate of not less than 60% is used for rolling during the roughing stage.

[0021] By adopting the above technical solution, the coarse dendritic structure and compositional segregation in the center of the cast steel billet can be effectively broken, significantly improving the density and uniformity of the core material. The massive plastic deformation can generate high-density deformation bands within the austenite grains. These deformation bands will become preferential sites for ferrite nucleation in subsequent processes, thereby significantly refining the final microstructure.

[0022] Optionally, in step three, the stepping cycle is dynamically adjusted according to the termination temperature of the second cooling: when the termination temperature is detected to be higher than 80°C, the stepping cycle is shortened to 4s; when the termination temperature is detected to be lower than 60°C, the stepping cycle is extended to 6s.

[0023] By adopting the above technical solution, when the temperature is detected to be higher than 80℃, the stepping cycle is automatically shortened to 4 seconds to accelerate the heat dissipation; when the temperature is lower than 60℃, it is extended to 6 seconds to slow down the cooling rate. This feedback control ensures that the final cooling temperature is always stable within the optimal range of 60-80℃ under different environmental conditions, ensuring the uniformity and stability of product performance and significantly improving the yield.

[0024] In summary, this application has the following beneficial effects: 1. Because this application adopts the “Nb-V-Ti-Al” composite microalloying system and precisely controls the atomic ratio of microalloying elements to carbon and nitrogen elements within the range of 0.80-1.05, it fundamentally ensures that near-ideal precipitation kinetics can be achieved in the subsequent hot working process, so that microalloying elements and carbon and nitrogen atoms can be fully combined to form nanoscale composite carbonitrides, maximizing the precipitation strengthening effect, while avoiding the formation of coarse phases that impair toughness due to excess carbon elements or the waste of microalloying elements, thus solving the problem of microstructure uniformity at the micro level.

[0025] 2. The preferred controlled rolling and cooling process parameters in this application effectively refine the grains and optimize the microstructure by controlling the austenite state and phase transformation process, thereby fully releasing the potential of the aforementioned composition design and transforming the composition advantages into stable and excellent macroscopic mechanical properties.

[0026] 3. The method of this application systematically matches the composition system with the process parameters and introduces a control mechanism based on the dynamic adjustment of the step cycle according to the termination temperature. This method not only ensures the high stability of the final product performance, but also effectively reduces the performance dispersion and dimensional defects caused by process fluctuations, significantly improves production efficiency and product yield, and realizes the efficient and stable industrial production of high-strength angle steel. Detailed Implementation

[0027] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0028] Example 1 A method for producing high-strength angle steel: In this embodiment, a qualified continuous casting billet is selected as the raw material, and its specific chemical composition is controlled by mass percentage as follows: Carbon (C): 0.16%; Silicon (Si): 0.48%; Manganese (Mn): 1.44%; Phosphorus (P): 0.012%; Sulfur (S): 0.005%; Aluminum (Al): 0.035%; Niobium (Nb): 0.032%; Vanadium (V): 0.060%; Titanium (Ti): 0.018%; Nitrogen (N): 0.0100%; Iron (Fe): Balance.

[0029] Calculate the atomic ratio of microalloying elements to carbon and nitrogen elements: (Nb / 93+V / 51+Ti / 48) / (C / 12+N / 14)≈0.935.

[0030] Step 1: The steel billet is fed into a walking beam furnace for heating at 1100℃ for 45 minutes to ensure that the microalloying elements are fully dissolved and the microstructure is homogenized.

[0031] Step Two: Controlled rolling was performed using an 18-stand continuous rolling mill. In the roughing stage, the billet underwent large deformation processing at a single-pass reduction rate of 65% within the temperature range of 1050-1150℃, effectively breaking down the original as-cast microstructure. In the finishing stage, the initial rolling temperature was precisely controlled at 950℃, and the final rolling temperature at 865℃. Through rolling deformation in the non-recrystallized austenite region, a large number of deformation bands and dislocations accumulated within the austenite grains, providing ample space for ferrite nucleation during subsequent phase transformation.

[0032] Step 3: Implement two-stage precise control cooling: The first stage employs a high-pressure water curtain for water cooling, rapidly cooling the rolled material from the final rolling temperature to 775℃ at a cooling rate of 20℃ / second. This rapid cooling process effectively inhibits austenite grain growth. The second stage involves transferring the rolled material to a walking beam cooling bed for natural cooling. The basic walking beam cycle is set to 5 seconds, and within the critical phase transformation temperature range of 650-700℃, the average cooling rate is controlled below 8℃ / second, ultimately cooling to a final temperature of 70℃. A dynamic adjustment mechanism is also established throughout the cooling process, monitoring the final cooling temperature in real time and adjusting the walking beam cycle accordingly. When the temperature is too high, the cycle is shortened to 4 seconds; when the temperature is too low, it is extended to 6 seconds, ensuring the stability of the cooling process.

[0033] Step Four: After the steel temperature drops below 70℃, a nine-roll straightener is used to straighten it under a straightening force of 520kN, which effectively eliminates the bending deformation of the steel and reduces residual stress. Finally, a cold shearing machine is used to cut the steel into pieces.

[0034] Example 2 A method for producing high-strength angle steel: The difference from Example 1 lies in the adjustment of the chemical composition ratio: Carbon (C): 0.18%; Niobium (Nb): 0.025%; Vanadium (V): 0.050%; Titanium (Ti): 0.010%; Nitrogen (N): 0.0080%; The remaining components are the same as in Example 1.

[0035] The calculated atomic ratio is approximately 0.81.

[0036] Example 3 A method for producing high-strength angle steel: The difference from Example 1 lies in the adjustment of the chemical composition ratio: Carbon (C): 0.14%; Niobium (Nb): 0.040%; Vanadium (V): 0.070%; Titanium (Ti): 0.025%; Nitrogen (N): 0.0120%; The remaining components are the same as in Example 1.

[0037] The calculated atomic ratio is approximately 1.04.

[0038] Example 4 A method for producing high-strength angle steel: The difference from Example 1 lies in the finishing rolling temperature parameters: Finishing rolling start temperature: 1000℃; Finishing rolling temperature: 865℃.

[0039] Example 5 A method for producing high-strength angle steel: The difference from Example 1 lies in the adjustment of cooling parameters. First-stage cooling rate: 25℃ / s; Second-stage step cycle: 4 seconds; Termination temperature: 60℃.

[0040] Example 6 A method for producing high-strength angle steel: the difference from Example 1 is that the single-pass reduction rate is 60%.

[0041] Example 7 A method for producing high-strength angle steel: The difference from Example 1 is that the dynamic adjustment function is cancelled, the stepping cycle is fixed at 5 seconds, and the termination temperature fluctuation range is 55-85℃.

[0042] Comparative Example 1 A manufacturing process for a high-strength angle steel: The difference from Example 1 lies in the adjustment of the alloy material ratio: Carbon (C): 0.12%; Niobium (Nb): 0.040%; Vanadium (V): 0.070%; Nitrogen (N): 0.0120%; No titanium (Ti) is added.

[0043] The calculated ratio is approximately 1.25.

[0044] Comparative Example 2 A preparation process for a high-strength angle steel: The difference from Example 1 is that titanium is not added to the alloy material, while the rest remains the same, and the ratio is calculated to be approximately 0.78.

[0045] Comparative Example 3 A process for preparing high-strength angle steel: The difference from Example 1 is that the initial rolling temperature of the finishing rolling is 920℃, and the final rolling temperature of the finishing rolling is 830℃.

[0046] Comparative Example 4 A manufacturing process for high-strength angle steel: The difference from Example 1 is that step three omits the first stage of water cooling and directly adopts natural cooling on a cooling bed, with a stepping cycle of 5 seconds and a termination temperature of 150°C.

[0047] Comparative Example 5 A manufacturing process for high-strength angle steel: The difference from Example 1 is that the cooling rate in the first stage of step three is 30℃ / s, and the cooling rate in the 650-700℃ range is 18℃ / s.

[0048] Detection methods 1. Mechanical property testing According to GB / T228.1 standard, the sampling is carried out on a universal testing machine. The sampling location is the middle of the long side of the L-shaped section of the angle steel. The specimen size is a round bar specimen with a gauge length of 50 mm and a diameter of 10 mm.

[0049] Test items: Yield strength (Rp0.2), tensile strength (Rm), elongation after fracture (A).

[0050] 2. Microstructure analysis Metallographic specimens were prepared from the cross-section of angle steel, including the long side, short side, and root. A 4% nitric acid alcohol solution was used as the etchant, and an optical microscope (OM) was employed for analysis.

[0051] Testing item: Grain size rating (according to GB / T6394).

[0052] 3. Uniformity test A Vickers hardness tester was used with a load of 10 kg. The test path was along the long side of the angle steel section → root → short side, with a spacing of 5 mm.

[0053] Uniformity index: ΔHV=(HVmax-HVmin) / HVavg×100%.

[0054] Table 1 Detection Data Grain size (grade) Yield strength (MPa) Tensile strength (MPa) Elongation (%) Hardness uniformity ΔHV (%) Example 1 9.5 395 545 24 4.2 Example 2 8.5 365 510 22 5.8 Example 3 9.0 385 535 23 4.8 Example 4 8.8 380 525 22 5.5 Example 5 9.2 405 550 21 6.2 Example 6 9.0 380 530 23 5.0 Example 7 8.5 375 520 22 7.8 Comparative Example 1 6.5 315 450 18 15.6 Comparative Example 2 7.0 345 485 20 12.4 Comparative Example 3 Mixed crystal 4-7 350 480 19 18.5 Comparative Example 4 6.5 300 430 15 22.3 Comparative Example 5 8.0* 420 565 12 25.1 As can be seen from Example 1 and Comparative Example 1, and in conjunction with Table 1, this application achieves microstructure refinement and performance optimization by precisely controlling the atomic ratio of microalloying elements to carbon and nitrogen elements within the range of 0.80-1.05. Example 1, using an optimized composition system (atomic ratio 0.935), obtained an ultrafine-grained microstructure of grade 9.5, a yield strength of 395 MPa, and excellent hardness uniformity of 4.2%. In contrast, Comparative Example 1, due to an unbalanced atomic ratio (1.25) and the absence of Ti, suffered from insufficient precipitation strengthening, resulting in coarse carbonitrides in the microstructure. Ultimately, it only achieved a coarse-grained microstructure of grade 6.5 and a yield strength of 315 MPa, with hardness uniformity deteriorating to 15.6%. This demonstrates that precise composition control is crucial for obtaining high-performance angle steel.

[0055] As can be seen from Example 1 and Comparative Example 2, and in conjunction with Table 1, the addition of Ti plays a crucial role in refining the grain size. Example 1, containing 0.018% Ti, achieved a fine grain structure of grade 9.5. Comparative Example 2, without the addition of Ti, although other components were the same as in Example 1, had a grain size of only grade 7.0, a yield strength reduced to 345 MPa, and a hardness uniformity decreased to 12.4%. This indicates that Ti effectively inhibits austenite grain growth by forming TiN particles, making it a key element in ensuring microstructure uniformity.

[0056] Combining Example 1 and Comparative Example 3 with Table 1, it can be seen that the finishing rolling temperature control is crucial for microstructure uniformity. Example 1, using a finishing rolling start temperature of 950℃ and a finishing rolling temperature of 865℃, obtained a uniform 9.5-grade grain structure. However, Comparative Example 3, using a finishing rolling start temperature of 920℃ and a finishing rolling temperature of 830℃, resulted in a mixed-grain structure of grades 4-7, a yield strength reduction to 350 MPa, and a deterioration in hardness uniformity to 18.5%. This indicates that rolling within a suitable temperature range is key to avoiding mixed-grain structures and ensuring uniform performance.

[0057] Combining Example 1 and Comparative Example 4 with Table 1, the necessity of a two-stage cooling regime can be seen. Example 1, employing a two-stage cooling process of rapid cooling followed by slow cooling, achieved excellent overall performance. However, Comparative Example 4 omitted the first stage of water cooling, relying solely on natural cooling, resulting in a coarsened microstructure (grade 6.5), a significant decrease in yield strength to 300 MPa, and a deterioration in hardness uniformity to 22.3%. This demonstrates the crucial role of a two-stage cooling regime in obtaining a fine and uniform microstructure.

[0058] Combining Example 1 and Comparative Example 5 with Table 1, it can be seen that proper control of the cooling rate is crucial for performance balance. Example 1, using a cooling rate of 20℃ / s, achieved a good match between strength and plasticity. However, Comparative Example 5, employing an excessively rapid cooling rate of 30℃ / s, while increasing the strength to 420MPa, resulted in a sharp decrease in elongation to 12% and a deterioration in hardness uniformity to 25.1%. This indicates that an excessively rapid cooling rate leads to a significant deterioration in plasticity, which is detrimental to the overall performance of the material.

[0059] Combining Examples 1 and 7 with Table 1, it can be seen that the dynamic adjustment mechanism is of great value in ensuring product stability. Example 1, employing dynamic cooling adjustment, achieved excellent performance stability (hardness uniformity of 4.2%). However, Example 7, by eliminating dynamic adjustment and using a fixed step cycle, resulted in fluctuations in the final cooling temperature, a decrease in hardness uniformity to 7.8%, and a significant reduction in performance stability. This demonstrates that the dynamic adjustment mechanism is a crucial guarantee for ensuring the stability of mass production.

[0060] As can be seen from Examples 1, 2, and 3, and Table 1, good performance can be obtained within the atomic ratio range of 0.80-1.05. Example 1 (ratio 0.935) exhibits the best performance. Although the performance of Examples 2 (ratio 0.81) and 3 (ratio 1.04) is slightly reduced, it is still significantly better than the comparative example. This demonstrates that the scope of the claims in this application is reasonably set, ensuring product performance within a relatively wide range of components.

[0061] Combining Examples 1, 4, and 5 with Table 1, it can be seen that the optimized combination of process parameters affects performance. Example 1, using median process parameters, achieved the best overall performance. Example 4, using a higher finishing rolling temperature, resulted in a slight decrease in performance; Example 5, using a faster cooling rate, improved strength but reduced plasticity. This indicates that by adjusting process parameters, product performance can be controlled within a certain range to meet different application requirements.

[0062] Combining Examples 1 and 6 with Table 1, it can be seen that the roughing reduction rate affects the microstructure refinement. Example 1, using a reduction rate of 65%, obtained a fine-grained microstructure of grade 9.5; Example 6, using a reduction rate of 60%, showed a slight decrease in grain size (grade 9.0), but it was still at a relatively high level. This indicates that a higher roughing reduction rate is beneficial for obtaining a finer microstructure, but a reduction rate of 60% is sufficient to meet the basic requirements.

[0063] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-strength angle steel, characterized in that, Its chemical composition, by mass percentage, includes: C: 0.14%~0.18%, Si: 0.40%~0.55%, Mn: 1.35%~1.52%, P≤0.015%, S≤0.008%, Al: 0.020%~0.050%, Nb: 0.025%~0.040%, V: 0.050%~0.070%, Ti: 0.010%~0.025%, N: 0.0080%~0.0120%, with the balance being Fe; The ratio of (Nb mass percentage / atomic weight + V mass percentage / atomic weight + Ti mass percentage / atomic weight) / (C mass percentage / atomic weight + N mass percentage / atomic weight) is between 0.80 and 1.

05.

2. A method for producing high-strength angle steel as described in claim 1, characterized in that, Includes the following steps: Step 1: Heat the steel billet in a heating furnace to a homogenization temperature of 1000℃~1150℃; Step 2: The heated steel billet is rolled using a continuous hot rolling process to obtain rolled material. The continuous hot rolling process includes roughing and finishing rolling, with the initial rolling temperature of the finishing rolling stage controlled between 950℃ and 1000℃. Step 3: The rolled material obtained in Step 3 is subjected to a first cooling and a second cooling in sequence; the first cooling rate is 15℃ / s~25℃ / s, and the cooling termination temperature is 750℃~800℃; the second cooling is natural cooling on the cooling bed with a step cycle of 4-6s, and the termination temperature is 60℃~80℃. Step 4: Straighten the cooled rolled material and cut it to a fixed length.

3. The method for producing high-strength angle steel according to claim 2, characterized in that, In step one, the steel billet is kept at a homogenization temperature of 1000℃ to 1150℃ for more than 30 minutes.

4. The method for producing high-strength angle steel according to claim 2, characterized in that, In step two, the final rolling temperature of the finishing rolling stage is controlled at 850℃~880℃.

5. The method for producing high-strength angle steel according to claim 2, characterized in that, In step three, the first cooling process uses water as the medium for water cooling.

6. The method for producing high-strength angle steel according to claim 2, characterized in that, In step three, during the initial stage of the second cooling, the average cooling rate of the rolled material in the temperature range of 650℃ to 700℃ is controlled to be no greater than 10℃ / s.

7. The method for producing high-strength angle steel according to claim 2, characterized in that, In step four, the straightening process is performed when the temperature of the rolled material drops below 80°C.

8. The method for producing high-strength angle steel according to claim 2, characterized in that, In step two, a single-pass reduction rate of not less than 60% is used for rolling during the roughing stage.

9. The method for producing high-strength angle steel according to claim 2, characterized in that, In step three, the stepping cycle is dynamically adjusted according to the termination temperature of the second cooling: when the termination temperature is detected to be higher than 80°C, the stepping cycle is shortened to 4s; when the termination temperature is detected to be lower than 60°C, the stepping cycle is extended to 6s.