Hot-rolled pipeline steel strip with high fracture toughness for straight-seam HFW welding pure hydrogen conveying pipeline and manufacturing method of hot-rolled pipeline steel strip

Abstract

The invention discloses a hot-rolled pipeline steel strip with high fracture toughness for a straight seam HFW welding pure hydrogen conveying pipeline and a manufacturing method of the hot-rolled pipeline steel strip. The hot-rolled pipeline steel strip comprises the following chemical components in percentage by mass: 0.03-0.06% of C, 0.05-0.20% of Si, 0.50-0.80% of Mn, 0.005-0.008% of Nb, 0.010-0.020% of Ti, 0.020-0.030% of Alt, less than or equal to 0.010% of P, less than or equal to 0.0020% of S, less than or equal to 2ppm of H, less than or equal to 30ppm of O, less than or equal to 50ppm of N and the balance of Fe and inevitable impurities. The hot-rolled pipeline steel strip has high fracture toughness.

Description

Technical Field

[0001] The present invention belongs to the field of metallurgical material technology, and specifically relates to a hot-rolled pipeline steel strip with strong fracture toughness for straight-seam HFW welded pure hydrogen transmission pipeline and a manufacturing method thereof. The present invention is based on the needs of HFW straight-seam welded pipes for long-distance and large-diameter transmission of pure hydrogen. The material provided is easy to weld and resistant to hydrogen embrittlement. It is mainly used in hydrogen pipeline transportation with a thickness specification of 10 to 16.0 mm. The implementation of the method provided by the present invention expands the forming methods of hydrogen transmission pipelines, improves the reliability and safety of hydrogen transmission pipeline operation, and provides strong support for the high-quality development of hydrogen energy in my country. Background Art

[0002] As my country continues to promote energy transformation and the "dual carbon" goal, the proportion of renewable energy in my country's energy structure has increased year by year. Hydrogen energy, as a large-scale, long-term energy storage solution, can provide a bottom line guarantee for intermittent renewable energy such as wind and solar. Compared with the self-discharge of batteries and the evaporation and dissipation of water, hydrogen, as a stable chemical, is more suitable for long-term storage, and is therefore more suitable for long-term energy storage across seasons.

[0003] Pipeline hydrogen transportation has extremely high economic value in realizing the development of the hydrogen energy industry and promoting the efficient use of energy, and is an important part of accelerating the realization of the energy transformation strategy. However, the forming method of straight seam high frequency HFW welded pipe is an efficient pipe making process, which is known for its advantages such as high welding efficiency, excellent weld quality and short weld. At the same time, the compatibility of hydrogen medium and steel pipeline is a prerequisite for the safe application of pipeline hydrogen transportation. The core of the present invention is to provide a method for preparing hot-rolled pipeline steel strip for HFW welded pipelines with good hydrogen compatibility with hydrogen medium, which is of great significance to the realization of large-scale pipeline transportation of hydrogen.

[0004] Patent document CN 116676538 A discloses "a kind of steel for hydrogen-doped natural gas pipeline and its preparation method", whose composition design system is C (0.02% to 0.05%), Si (0.20% to 0.30%), Mn (0.80% to 1.00%), P (≤0.008%), S (≤0.002%), Cr (0.10% to 0.15%), Nb (0.030% to 0.050%), Ti (0.015% to 0.020%), Al (0.025% to 0.040%), and the rest is Fe. The heating temperature of the ingot is 1200 to 1250°C, the start rolling temperature of the finishing rolling is 830 to 850°C, the final rolling temperature of the finishing rolling is 770 to 810°C, the cooling rate is 10 to 20°C / s, and the final cooling temperature is 400 to 450°C, which belongs to the TMCP process for medium and thick plates. The present invention is directed to preparing hydrogen pipeline steel strip products by using a 2250mm hot rolling mill TMCP process.

[0005] Patent document CN 116851485 A discloses "a kind of steel for hydrogen pipeline and its preparation method", which mainly introduces the production process of medium and thick plates for hydrogen pipelines, including heating of steel billets - rough rolling (including longitudinal rolling) - finishing rolling - pre-straightening - hot straightening, and controlling the deformation temperature and deformation system of each process to obtain steel for hydrogen pipelines. The chemical composition design of the product is not disclosed, which belongs to the medium and thick plate TMCP process. The present invention is aimed at preparing hydrogen pipeline steel strip products by 2250mm hot rolling unit TMCP process.

[0006] Patent document CN 117965857 A discloses "a high-strength pipeline steel plate suitable for hydrogen pipelines and a manufacturing method thereof". The process is to perform rough rolling and finish rolling on the ingot to obtain a finished rolled steel plate; the steel plate is cooled by differential cooling rates on the upper and lower surfaces, the upper surface of the steel plate is cooled by high-flow water spraying, and the lower surface is cooled by compressed air, spray cooling or natural cooling in the air, the cooling rate of the upper surface is greater than the cooling rate of the lower surface, and therefore, the strength of the upper surface of the steel plate is greater than the strength of the lower surface. The high-strength pipeline steel plate has strength differences along the thickness direction, the upper part of the steel plate has high strength, and the wall thickness of the pipeline is reduced; the lower part of the steel plate has low strength, and the influence of the transport medium hydrogen on the brittleness and fatigue life of the material is reduced, which not only ensures the pressure bearing capacity of the high-strength material, but also reduces the harmfulness of the hydrogen medium. It belongs to the TMCP process for medium and thick plates. The present invention is directed to the TMCP process of a 2250mm hot rolling unit to prepare hydrogen pipeline steel strip products. Summary of the invention

[0007] Based on the above technical background, through the controlled rolling and controlled cooling control technology of ultra-pure steel smelting, continuous casting and hot rolling, the product is obtained with equiaxed low-stress ferrite as the main and granular pearlite as the auxiliary structure through the post-rolling segmented cooling control strategy, and fine grain strengthening is used as the main measure to ensure strength and toughness, so as to achieve the low yield ratio control of the product, which helps to reduce the sensitivity of the steel strip material to hydrogen embrittlement. Based on this product control strategy, a manufacturing method for hot-rolled pipeline steel strip suitable for straight seam HFW welding pure hydrogen transmission pipeline is invented. The product composition design system is (0.03-0.06%) C-(0.05-0.20%) Si-(0.50-0.80%) Mn-(0.005-0.008%) Nb-(0.010-0.020%) Ti-P(≤0.010%)-S(≤0.0015%)-Fe, H≤2ppm, O≤30ppm, N≤50ppm. The rolling adopts the controlled cooling process of 2250mm hot rolling unit (slab heating-rough rolling-finishing rolling-layer cooling-coiling). The mechanical properties of the product meet the requirements of yield strength: ≥295MPa, tensile strength: ≥435MPa, elongation A 50:40~45%, yield strength ratio ≤0.70; -30℃ impact performance meets AKv2≥335J (full size); -30℃ drop hammer performance (DWTT) SR≥90%; the sum of non-metallic inclusions (A+B+C+D) inclusions ≤1.5 level, grain size ≥10 level. Hydrogen compatibility of pipe body, base material and weld in 6.3MPa hydrogen environment: under smooth sample testing conditions, slow strain (2*10 -5 s -1 ) The tensile test shows that the material hydrogen embrittlement sensitivity index is ≤15%; fatigue life is ≥300,000 times; and the hydrogen corrosion resistance HIC (crack length rate (CLR), crack thickness rate (CTR) and crack sensitivity rate (CSR) are all zero) is good. The product can safely serve in long-distance hydrogen pipelines. The production process is relatively simple and executable, the product cost is relatively economical, and it is suitable for stable batch production of enterprises.

[0008] The specific technical solutions of the present invention are as follows:

[0009] In one aspect, the present invention provides a hot-rolled pipeline steel strip for straight seam HFW welded pure hydrogen transportation pipeline with strong fracture toughness, wherein the chemical composition thereof is as follows by mass percentage: C 0.03-0.06%, Si 0.05-0.20%, Mn 0.50-0.80%, Nb0.005-0.008%, Ti 0.010-0.020%, Alt 0.020-0.030%, P≤0.010%, S≤0.0020%, H≤2ppm, O≤30ppm, N≤50ppm, and the remainder is Fe and unavoidable impurities;

[0010] The hot rolled pipeline steel strip has a -30°C drop weight performance (DWTT) SR ≥ 90%;

[0011] The manufacturing method of the hot-rolled pipeline steel strip includes the following processes: a smelting and continuous casting process and a rolling process; wherein:

[0012] The rolling process is as follows: slab heating - high-pressure water descaling - fixed width press - E1R1 roughing mill rolling - E2R2 roughing mill rolling - flying shear - high-pressure water descaling - F1-F7 finishing mill rolling - encrypted laminar flow segmented cooling - coiling;

[0013] The encrypted laminar segmented cooling adopts two-stage cooling. The front stage adopts centralized cooling (cooling rate: 30-40℃ / s) to reach the intermediate temperature of 720℃, and waits for 5±2s. The second stage adopts evacuation cooling (cooling rate 15-25℃ / s) to achieve a coiling temperature of 540-560℃.

[0014] In some embodiments, the chemical composition of the hot-rolled pipeline steel strip is calculated by mass percentage as follows: C 0.04%-0.05%, Si 0.08%-0.15%, Mn 0.65%-0.75%, Nb 0.007%-0.008%, Ti 0.010%-0.015%, Alt 0.020-0.030%, P≤0.008%, S≤0.0015%, H≤2ppm, O≤25ppm, N≤50ppm, and the rest is Fe and unavoidable impurities.

[0015] In some embodiments, the mechanical properties of the hot-rolled pipeline steel strip meet the following requirements: yield strength: ≥295 MPa, tensile strength: ≥435 MPa, elongation A 50 : 40~45%, yield strength ratio ≤0.70; -30℃ impact performance meets AKv2≥335J (full size); the sum of non-metallic inclusions (A+B+C+D) inclusions ≤1.5 level, grain size ≥10 level.

[0016] In some embodiments, the hydrogen compatibility of the pipe body, base material and weld of the hot-rolled pipeline steel in a 6.3 MPa hydrogen environment is as follows: under smooth sample testing conditions, slow strain (2*10 -5 s -1 ) The tensile test shows that the material's hydrogen embrittlement sensitivity index is ≤15%; fatigue life is ≥300,000 times; and the hydrogen corrosion resistance HIC (crack length rate (CLR), crack thickness rate (CTR) and crack sensitivity rate (CSR) are all zero) performance is good.

[0017] Another aspect of the present invention provides a method for manufacturing a hot-rolled pipeline steel strip, characterized in that the manufacturing method comprises the following processes: a smelting and continuous casting process and a rolling process.

[0018] In some embodiments, the smelting and continuous casting process is: molten iron → KR desulfurization → converter steelmaking → LF refining → RH degassing → slab continuous casting;

[0019] The converter smelting uses KR pre-desulfurized hot metal, and after smelting, ferrosilicon and ferromanganese are used for deoxidation alloying. Ferroniobium is added at the end of LF alloying, and ferrotitanium is added at the end of RH. The molten steel is stirred with argon blowing throughout the process; the vacuum degree is ≤2mbar, the deep vacuum time is ≥10min, and the superheat ΔT is 30~40℃.

[0020] In some embodiments, the rolling process is: slab heating - high-pressure water descaling - fixed width press - E1R1 roughing mill rolling - E2R2 roughing mill rolling - flying shear - high-pressure water descaling - F1-F7 finishing mill rolling - encrypted laminar flow segmented cooling - coiling - pallet transportation system - warehouse stacking slow cooling - sampling and inspection;

[0021] The slab heating temperature is 1200±20℃; the heating time is 180~240min; the rough rolling mode is 1+5, 3+3 or 3+5; the intermediate slab thickness range is 35~50mm; the finishing rolling start temperature is ≤1040℃; the finishing rolling final temperature is 820~850℃, and two-stage cooling is adopted. The front stage adopts centralized cooling (cooling rate: 30~40℃ / s) to reach the intermediate temperature of 720℃, wait for 5±2s, and the second stage adopts evacuation cooling (cooling rate 15~25℃ / s) to achieve a coiling temperature of 540~560℃.

[0022] The beneficial effects of the present invention are as follows: the present invention provides a C-Si-Mn-Nb-Ti microalloying design and a method for preparing raw material pipeline steel of straight seam HFW welded pipe for high pressure (6.3MPa) pure hydrogen transmission pipeline in service by controlled rolling and controlled cooling of 2250mm hot rolling mill, and the key measures include extremely low P and S control, ultra-pure steel smelting control and segmented laminar cooling control, so that the product has good strength and toughness, low yield ratio, easy weldability and good hydrogen compatibility. The production practice of 2250mm hot rolling production line has been achieved, which has good promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The slow strain tensile property curve of a smooth sample of a hot-rolled pipeline steel strip obtained in Example 1 under a hydrogen environment is shown.

[0024] Figure 2 The side morphology of the fracture surface of the smooth sample of the hot-rolled pipeline steel strip obtained in Example 1 is shown (a: 3-6.3 MPa nitrogen; b: 6-6.3 MPa hydrogen). DETAILED DESCRIPTION

[0025] The purpose of the present invention is to achieve through the following measures:

[0026] A hot-rolled steel strip for straight seam HFW welded pipe with a composition of C-Si-Mn-Nb-Ti is designed. The design idea of ​​the material composition is to use the synergistic effect of solid solution strengthening elements Mn and Si and fine grain strengthening, fine grain strengthening element Nb, and precipitation strengthening element Ti to jointly improve the material's strength, toughness, weldability and hydrogen embrittlement resistance.

[0027] The smelting and continuous casting process is: molten iron → KR desulfurization → converter steelmaking → LF refining → RH degassing → slab continuous casting. KR pre-desulfurized molten iron is used for converter smelting. After smelting, ferrosilicon and ferromanganese are used for deoxidation alloying. Ferroniobium is added at the end of LF alloying, and ferrotitanium is added at the end of RH. Argon is blown and stirred during the whole process of molten steel; vacuum degree ≤2mbar, deep vacuum time ≥10min, superheat ΔT: 30~40℃.

[0028] Material composition control: C content is controlled at 0.03% to 0.06% (preferably 0.04% to 0.05%) to ensure a certain solid solution strengthening effect, reduce band segregation, and improve welding quality; Si content is controlled at 0.05% to 0.20% (preferably 0.08% to 0.15%) to increase the strength of ferrite and improve material strength; Mn content is controlled at 0.50% to 0.80% (preferably 0.65% to 0.75%), which is a solid solution strengthening element and improves material strength, but an increase in content will reduce the plasticity and welding performance of steel, and its Mn / Si ratio is controlled in the range of 4 to 6; Nb content is controlled at 0.005% to 0.008% (preferably 0.007% to 0.008%) to refine the grains and improve the impact strength of steel The impact toughness can be increased and its brittle transition temperature can be reduced, which is beneficial to the welding performance; the Ti content is controlled at 0.010% to 0.020% (preferably 0.010% to 0.015%), and the TiC second phase is dispersed and precipitated in the coiled state of the steel strip to improve the strength of the material. The TiN precipitated at high temperature is beneficial to the refinement of the weld structure and the improvement of the welding performance; the P content is controlled at ≤0.010% (preferably ≤0.008%), which is a harmful element and needs to be effectively controlled, causing the plasticity and impact toughness to be significantly reduced; the S content is controlled at ≤0.002% (preferably ≤0.0015%), which is a harmful element and needs to be effectively controlled, which can significantly increase the tendency of hydrogen sulfide corrosion resistance; the gas in the steel is controlled to be H≤2ppm, O≤30ppm, and N≤50ppm.

[0029] The rolling process is: slab heating - high-pressure water descaling - fixed width press - E1R1 roughing mill rolling - E2R2 roughing mill rolling - flying shear - high-pressure water descaling - F1~F7 finishing mill rolling - encrypted laminar flow segmented cooling - coiling - pallet transportation system - warehouse stacking slow cooling - sampling and inspection. The slab heating temperature is 1200±20℃; heating time is 180~240min; rough rolling mode adopts 1+5, 3+3 or 3+5; intermediate billet thickness range: 35~50mm; finishing rolling start temperature ≤1040℃; finishing rolling final rolling temperature is 820~850℃, and two-stage cooling is adopted. The front stage adopts centralized cooling (cooling rate: 30~40℃ / s) to reach the intermediate temperature of 720℃, wait for 5±2s, and the second stage adopts evacuation cooling (cooling rate 15~25℃ / s) to achieve a coiling temperature of 540~560℃.

[0030] Material purification and homogenization control: Ultra-pure material control and structural uniformity control are the basis for ensuring that the material has good resistance to hydrogen embrittlement. Through the smelting and double refining process, the product non-metallic inclusions A, B, C, D levels are ≤1.0, and the sum of non-metallic inclusion levels is ≤1.5. The structural grain size is ≥10, and the core-surface structural grain level difference is ≤2.

[0031] Specifically, the manufacturing method of the hot-rolled pipeline steel strip includes the following processes:

[0032] 1. Material smelting

[0033] 1.1 Composition design: The composition design scheme is carried out according to the thickness of the hot-rolled steel strip product of hydrogen pipeline steel, as shown in Table 1.

[0034] Table 1: Composition design (mass percentage)

[0035]

[0036] 1.2 Converter smelting: The pretreated molten iron (S≤0.002%) enters the converter, where oxygen is blown for decarburization and the temperature is raised. In the later stage of smelting, ferrosilicon and ferromanganese are added for deoxidation and alloying. The P and S components are controlled to prevent overoxidation of the molten steel and the amount of steel tapping is controlled to prevent slag from entering the molten steel. The tapping temperature is 1600-1650℃, and the converter tapping has [P]≤0.013% and [S]≤0.006%.

[0037] 1.3 Refining outside the furnace: LF+RH full-process argon blowing process is adopted, a good reducing atmosphere is maintained during the refining process, Al wire is used for deoxidation, LF is used to add ferromanganese for alloying, RH vacuum treatment (vacuum degree ≤ 2mbar, deep vacuum time ≥ 10min), ferroniobium and ferrotitanium are added for alloying in the later stage, and calcium treatment is carried out after completion.

[0038] 1.4 Slab continuous casting: Molten steel superheat ΔT: 30~40℃, casting speed controlled at 0.90~1.10m / min. Equipped with dynamic soft reduction technology, straightening temperature ≥920℃. The head and tail slabs are converted into products for other purposes and are not used for hydrogen pipeline steel.

[0039] 1.5 Full nitrogen control: N≤50ppm in the tundish of molten steel, scrap ratio≤15%, converter tapping temperature≥1600℃, bottom blowing argon stirring in the converter, bottom blowing stirring mode with argon and nitrogen switching alternately cannot be used. The ladle is emptied with argon, argon is used to purge the tundish for ≥10min before continuous casting and heat exchange to exhaust the air in the ladle, and when the tundish pours 30t, the argon blowing tube is removed to reduce nitrogen absorption by molten steel, and argon blowing is used to protect the casting during the normal casting process.

[0040] 2. Controlled rolling and controlled cooling process

[0041] The ingot is heated in a walking-beam heating furnace (the heating process is shown in Table 2). The rough rolling adopts single-stand R1 and R2 reciprocating rolling. The rough rolling modes adopted are 1+5, 3+3 and 3+5. The finishing rolling adopts F1~F7 continuous rolling process. The specific controlled rolling and controlled cooling process is shown in Table 3.

[0042] Table 2: Billet heating system

[0043]

[0044] Table 3: Rolling system

[0045]

[0046] 3. Example Analysis

[0047] 3.1 According to the above smelting technical requirements, the hot-rolled pipeline steel strip with the following composition is smelted. The specific composition is shown in Table 4 below.

[0048] Table 4: Chemical composition of each example (mass percentage: %)

[0049]

[0050] 3.2 According to the above composition design and hot rolling process, the mechanical properties of the product are shown in Table 5. The hydrogen embrittlement resistance test of the hot-rolled pipeline steel strip obtained in Example 1 is based on GB / T 34542.2-2018 "Hydrogen Storage and Transportation System Part 2: Test Method for Compatibility of Metallic Materials with Hydrogen Environment", and the results are shown in Tables 6 and Figure 1-2 As shown, Figure 1 This is the slow strain tensile property curve of the hot-rolled pipeline steel strip in Example 1 under hydrogen environment. Figure 2 The side morphology of the fracture surface of the smooth sample of the hot-rolled pipeline steel strip in Example 1 (a: 3-6.3MPa nitrogen; b: 6-6.3MPa hydrogen). The hydrogen sulfide corrosion cracking performance (HIC) index of the hot-rolled pipeline steel strip obtained in Examples 1-3 is shown in Table 7. The test adopts solution A (5wt% NaCl+0.5wt% CH3COOH).

[0051] Table 5: Properties of hot-rolled pipeline steel strips in various examples

[0052]

[0053] Table 6: Hydrogen embrittlement resistance of hot-rolled pipeline steel strip of Example 1

[0054]

[0055] Table 7: Example HIC performance

[0056]

[0057] 3.3 The metallographic structure of the product is mainly polygonal ferrite, supplemented by pearlite, with a grain size of more than 10 levels, and the grain size difference between the core and surface organizations is ≤ 2 levels.

[0058] In summary, the invented material has good strength, toughness and resistance to hydrogen embrittlement, and can be promoted and applied in large quantities in the field of pure hydrogen transportation of medium and low pressure pipeline natural gas, providing broad space for the application of hydrogen energy.

[0059] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A hot-rolled pipeline steel strip for a straight seam HFW welded pure hydrogen transportation pipeline with strong fracture toughness, characterized in that: The chemical composition of the hot-rolled pipeline steel strip is calculated by mass percentage as follows: C 0.03-0.06%, Si 0.05-0.20%, Mn 0.50-0.80%, Nb 0.005-0.008%, Ti 0.010-0.020%, Alt 0.020-0.030%, P≤0.010%, S≤0.0020%, H≤2ppm, O≤30ppm, N≤50ppm, and the rest is Fe and unavoidable impurities; The hot rolled pipeline steel strip has a -30°C drop weight performance (DWTT) SR ≥ 90%; The manufacturing method of the hot-rolled pipeline steel strip includes the following processes: a smelting and continuous casting process and a rolling process; wherein: The rolling process is as follows: slab heating - high-pressure water descaling - fixed width press - E1R1 roughing mill rolling - E2R2 roughing mill rolling - flying shear - high-pressure water descaling - F1-F7 finishing mill rolling - encrypted laminar flow segmented cooling - coiling; The encrypted laminar segmented cooling adopts two-stage cooling. The front stage adopts centralized cooling (cooling rate: 30-40℃ / s) to reach the intermediate temperature of 720℃, and waits for 5±2s. The second stage adopts evacuation cooling (cooling rate 15-25℃ / s) to achieve a coiling temperature of 540-560℃.

2. The hot rolled pipeline steel strip according to claim 1, characterized in that: The chemical composition of the hot-rolled pipeline steel strip is calculated by mass percentage as follows: C 0.04%-0.05%, Si 0.08%-0.15%, Mn 0.65%-0.75%, Nb0.007%-0.008%, Ti 0.010%-0.015%, Alt 0.020-0.030%, P≤0.008%, S≤0.0015%, H≤2ppm, O≤25ppm, N≤50ppm, and the rest is Fe and unavoidable impurities.

3. The hot rolled pipeline steel strip according to claim 1 or 2, characterized in that: The mechanical properties of the hot-rolled pipeline steel strip meet the following requirements: yield strength: ≥295MPa, tensile strength: ≥435MPa, elongation A 50 : 40~45%, yield strength ratio ≤0.70; -30℃ impact performance meets AKv2≥335J (full size); the sum of non-metallic inclusions (A+B+C+D) inclusions ≤1.5 level, grain size ≥10 level.

4. The hot rolled pipeline steel strip according to any one of claims 1 to 3, characterized in that: Hydrogen compatibility of the pipe body, base material and weld of the hot-rolled pipeline steel in a 6.3MPa hydrogen environment: under smooth sample testing conditions, slow strain (2*10 - 5 s -1 ) The tensile test shows that the material's hydrogen embrittlement sensitivity index is ≤15%; fatigue life is ≥300,000 times; and the hydrogen corrosion resistance HIC (crack length rate (CLR), crack thickness rate (CTR) and crack sensitivity rate (CSR) are all zero) performance is good.

5. The method for manufacturing the hot rolled pipeline steel strip according to any one of claims 1 to 4, characterized in that: The manufacturing method comprises the following processes: a smelting and continuous casting process and a rolling process.

6. The manufacturing method according to claim 5, characterized in that: The smelting and continuous casting process is: molten iron → KR desulfurization → converter steelmaking → LF refining → RH degassing → slab continuous casting; The converter smelting uses KR pre-desulfurized hot metal, and after smelting, ferrosilicon and ferromanganese are used for deoxidation alloying. Ferroniobium is added at the end of LF alloying, and ferrotitanium is added at the end of RH. The molten steel is stirred with argon blowing throughout the process; the vacuum degree is ≤2mbar, the deep vacuum time is ≥10min, and the superheat ΔT is 30~40℃.

7. The manufacturing method according to claim 5 or 6, characterized in that: The rolling process is as follows: slab heating - high-pressure water descaling - fixed width press - E1R1 roughing mill rolling - E2R2 roughing mill rolling - flying shear - high-pressure water descaling - F1-F7 finishing mill rolling - encrypted laminar flow segmented cooling - coiling - pallet transportation system - warehouse stacking slow cooling - sampling and inspection; The slab heating temperature is 1200±20℃; the heating time is 180~240min; the rough rolling mode is 1+5, 3+3 or 3+5; the intermediate slab thickness range is 35~50mm; the finishing rolling start temperature is ≤1040℃; the finishing rolling final temperature is 820~850℃, and two-stage cooling is adopted. The front stage adopts centralized cooling (cooling rate: 30~40℃ / s) to reach the intermediate temperature of 720℃, wait for 5±2s, and the second stage adopts evacuation cooling (cooling rate 15~25℃ / s) to achieve a coiling temperature of 540~560℃.

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