Seamless line pipe with outer diameter of 508 mm for underwater oil and gas development and manufacturing method of seamless line pipe

Abstract

The invention relates to the field of offshore oil and gas development and seamless pipe manufacturing, and discloses a seamless line pipe with the outer diameter of 508 mm for underwater oil and gas development and a manufacturing method of the seamless line pipe. The seamless line pipe with the outer diameter of 508 mm is obtained through electric furnace steelmaking, 508 PQF continuous rolling, thermal refining and machining processes, the outer diameter of 508 mm is achieved, the wall thickness is larger than 28 mm, the strength is high, the hardness is low, and the overall-length and whole-circumference performance uniformity is achieved; the tensile strength is greater than 545 MPa, the transverse and longitudinal performance difference is less than or equal to 50 MPa, the low longitudinal strength difference is less than or equal to 80 MPa, the hardness is less than or equal to 220 HV10 under the condition that the tensile strength is greater than 545 MPa, and the low-temperature performance at-39 DEG C meets the requirements that the impact energy is greater than 200 J, the shear ratio is greater than or equal to 85%, and the CTOD value is greater than

Description

Technical Field

[0001] The invention relates to the field of marine oil and gas development and seamless pipe manufacturing, and in particular to a 508mm outer diameter seamless pipeline pipe for underwater oil and gas development and a manufacturing method thereof. Background Art

[0002] With the continuous deepening of offshore oil and gas field exploration and exploitation, offshore oil and gas has been exploited from conventional water depth (less than 300m) to deep water (300-1500m) and ultra-deep water (greater than 1500m), and the difficulty of exploitation has gradually increased, and the demand for high-performance pipelines has also increased day by day. As oil and gas exploitation moves towards the deep sea, the demand for pipelines with high strength, high toughness, high dimensional accuracy and corrosion resistance has increased.

[0003] The existing technology for producing 508mm outer diameter and wall thickness ≥25.4mm pipelines is mainly produced through hot rolling, hot expansion, oblique rolling and rotary expansion or cold drawing. The mechanical properties and corrosion resistance cannot meet the requirements of offshore pipe applications. Faced with the growing demand for product upgrades and quality improvements, achieving high dimensional accuracy and high performance of large-diameter seamless pipelines is a key common problem that advanced steel pipe companies at home and abroad urgently need to solve. It is mainly reflected in: 1) The commonly used traditional hot expansion process can no longer meet the requirements of dimensional accuracy, and a better rolling process is needed to achieve high dimensional accuracy. 2) Ordinary quenching methods cannot meet the requirements of performance uniformity, and there are large performance differences in the length direction. 3) It is necessary to develop higher strength seamless pipelines. Through patent and literature searches, it was found that 508mm deep-sea marine acidic environment high-strength seamless long-distance pipelines have not been reported.

[0004] Therefore, it is necessary to develop a 508mm outer diameter seamless pipeline pipe for underwater oil and gas development and a manufacturing method thereof. Summary of the invention

[0005] In order to solve the shortcomings of the prior art, the present invention provides a 508mm outer diameter seamless pipeline for underwater oil and gas development and a manufacturing method thereof. By improving the whole process control, a high degree of matching of the billet-tube rolling dimensional accuracy is achieved, and a seamless pipeline with a wall thickness greater than 28mm, high strength, low temperature and corrosion resistance is prepared, which can meet the requirements of oil and gas transportation in underwater oil and gas development of 800m and above in the deep sea.

[0006] The present invention is achieved through the following technical solutions:

[0007] On the one hand, the present invention provides a 508mm outer diameter seamless pipeline for underwater oil and gas development, the chemical components of which are calculated by mass percentage: C: 0.045-0.11wt%, Si: 0.25-0.60wt%, Mn: 1.30-1.70wt%, P: ≤0.012wt%, S: ≤0.003wt%, Al: 0.020-0.060wt%, Cr: 0.05-0.15wt%, Mo: 0.11-0.20wt%, Nb: 0.015-0.03wt%, Cu: 0.01-0.06wt%, Ni: 0.05%-0.20wt%, V: 0.025-0.05wt%, Ti:

[0008] 0.01-0.04wt%, B≤0.0005wt%, [H]≤2ppm, CEpcm:0.16-0.22wt%,

[0009] CE IIW :0.34-0.39wt%, CEpcm=C+Si / 30+Mn / 20+Cu / 20+Ni / 60+Cr / 20+Mo / 15+V / 10+5B, CE IIW =C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15, the remainder being Fe and inevitable impurities.

[0010] Furthermore, the structure of the seamless line pipe contains 20% to 50% ferrite, 50% to 80% tempered bainite, a grain size of ≥8, a banded structure of ≤3, and an inclusion level of ≤1.5.

[0011] Furthermore, the seamless pipeline achieves an outer diameter of 508 mm, a wall thickness of >28 mm, high strength and low hardness, uniform performance over the entire length and circumference, a transverse and longitudinal performance difference of ≤50 MPa, a low longitudinal strength difference of ≤80 MPa, and a hardness of ≤220 HV10 when the strength is greater than 545 MPa. The low temperature performance at -39°C satisfies the impact energy greater than 200 J, the shear ratio ≥85%, and the CTOD value ≥1.0 mm.

[0012] Another aspect of the present invention provides a method for manufacturing the above-mentioned 508 mm outer diameter seamless pipeline for underwater oil and gas development, comprising the following steps:

[0013] (1) Smelting of Φ500mm cross-section continuous casting round billets: The raw materials are refined by short-process EAF electric furnace and LF ladle furnace, alloy materials are added to adjust the composition, VD high vacuum treatment (high vacuum time is greater than 10min, soft blowing time is greater than 30min), wire feeding (Ca wire>50m / furnace), inert gas protection casting, double-station electromagnetic stirring, high-temperature straightening, and cast into 500mm continuous casting round billets on a continuous casting machine to obtain 500mm cross-section continuous casting round billets; the outer diameter tolerance of the continuous casting round billet is ±3.0mm, the ovality is ≤12.5mm, the curvature per meter should be ≤4mm, and the total curvature should be ≤0.4%L.

[0014] (2) Φ508PQF continuous rolling unit: The low segregation 500mm cross-section continuous casting round billet is heated in a ring furnace for 8 to 14 hours, and then pierced at a piercing temperature of 1000-1230°C. The outer diameter of the rough tube is controlled at 583-588mm. Then, the 508PQF unit is continuously rolled with a wall thickness accuracy of -7%-+10%t, a sizing and phosphorus removal pressure greater than 7-25MPa, and cold straightening to obtain a rolled steel pipe with a length greater than 12.5m and an outer diameter of 508mm.

[0015] (3) Large-diameter heat treatment: The rolled steel pipe is placed in a walking-beam high-temperature furnace for heating, the temperature control range is 850℃~950℃, the holding time is greater than 40min, high-pressure water is used for dephosphorization, quenching and water cooling, and tempering in a walking-beam low-temperature furnace, the temperature control range is 600℃~690℃, the holding time is greater than 45min, high-pressure water is used for dephosphorization, high-temperature heat straightening, and the heat straightening temperature is 500-650℃ to obtain seamless pipelines;

[0016] (4) Pipe end processing: For the ends whose inner diameter range is smaller than the tolerance requirement, internal sizing is performed, and the sizing rate is ≤0.015.

[0017] Furthermore, the dual-process electromagnetic stirring includes crystallizer electromagnetic stirring and terminal electromagnetic stirring, the crystallizer electromagnetic stirring frequency is 1-3 Hz, the current is 130-180A, the terminal electromagnetic stirring frequency is 5-8 Hz, the current is 300-400A.

[0018] Furthermore, the pressure of high-pressure water dephosphorization in step (3) is 7-25 MPa.

[0019] Furthermore, the smelting raw materials include molten iron, pig iron and scrap steel, and the alloy materials include ferrosilicon, ferromanganese, ferrovanadium, ferronickel, ferromolybdenum and ferroniobium.

[0020] Description of the main chemical components of the formulated steel grades:

[0021] C: It is the basic element of carbon manganese steel. Considering the influence of carbon content on the strength, toughness and welding performance of steel and the cost, electric furnace smelting with a carbon content lower than 0.045% will be difficult to achieve and will increase the cost of raw materials. If the carbon content is too high, it will reduce the low-temperature toughness and CTOD performance. Therefore, the content is within the range of 0.045-0.11wt%.

[0022] Si: One of the common elements in steel. The affinity of silicon to oxygen is second only to aluminum and titanium, and stronger than manganese, chromium and vanadium. Therefore, in the steelmaking process, it is used as a reducing agent and deoxidizer, so the Si content is controlled at 0.25wt% to 0.60wt%.

[0023] Al: It has a great affinity with oxygen and nitrogen. Its main function in steel is to deoxidize and nitrogenate, and refine grains. Therefore, the Al content is controlled at 0.020wt% to 0.060wt%.

[0024] Mn: It is the basic element of carbon manganese steel. Taking into account its influence on the strength, toughness and welding performance of steel and its cost, if Mn is too low, the cost will increase, and if Mn is too high, segregation will easily occur. Therefore, its content is limited to the range of 1.30-1.70wt%.

[0025] Nb: microalloying element. If the Nb content is too low, it cannot fully play its role in grain refinement. If it is too high, it is easy to cause rolling defects and increase costs. Considering the comprehensive surface quality and cost, the content is limited to between 0.015 and 0.030wt%.

[0026] V: microalloying element, precipitation strengthening and grain refining effects. If the V content is too low, it cannot fully play its role in grain refining, and if it is too high, it will increase the cost. Considering the comprehensive performance and cost, the V content is limited to between 0.025 and 0.05wt%.

[0027] Ni: alloying element, improves the low-temperature impact toughness of the material. Too low Ni content cannot significantly improve the toughness, while too high Ni content will increase production costs. Considering comprehensive performance and cost, its content is limited to between 0.05 and 0.20 wt%.

[0028] Mo: alloying element, improves the strength and corrosion resistance of thick-walled tubes. Too low a content will not improve the hardenability enough, while too high a content will increase production costs. Considering the comprehensive performance and cost, its content is limited to between 0.11 and 0.20 wt%.

[0029] Cr: alloying element, improves the strength of the material, thus ensuring the performance of large-diameter thick-walled pipes. If the content is too low, the strength increase is limited, and if the content is too high, it is easy to produce a structure that reduces low-temperature toughness. Therefore, its content is limited to between 0.05 and 0.15wt%.

[0030] Ti: micro alloying element, improves the thermoplasticity of the material and improves the surface quality of the 500mm round billet. If the Ti content is too low, it cannot produce fine grains and improve thermoplasticity. If the Ti content is too high, it is easy to produce TiN inclusions and reduce toughness. Therefore, its content is limited to between 0.01 and 0.04wt%.

[0031] As for other elements N, O and H, which are gas elements in steel, their contents are controlled in a low range considering welding performance and mechanical properties, and the maximum contents are not allowed to exceed N≤0.0120wt%, O≤0.0040wt% and H≤0.0002wt%.

[0032] Cu: Residual alloying element, beneficial to impact toughness and corrosion resistance, but considering the cost and contribution of carbon equivalent, its content is limited to between 0.010 and 0.060 wt % for comprehensive cost considerations.

[0033] P, S: P and S are harmful impurity elements, and their content should be reduced as much as possible. However, the cost of steelmaking cannot be ignored, and it is best to stipulate that P ≤ 0.012wt% and S ≤ 0.003wt%.

[0034] The advantages and positive effects of the present invention are:

[0035] The present invention strictly controls the element ratio, especially the CEpcm is between 0.16 and 0.22 wt%. IIW At 0.34-0.39wt%, combined with improvements to the entire process of smelting, rolling and heat treatment, a 508mm outer diameter high-dimensional precision seamless pipeline that meets the requirements of underwater oil and gas development in the deep sea of ​​800m and above is prepared. The prepared seamless pipeline has an outer diameter of 508mm, a wall thickness of >28mm, high strength and low hardness, uniformity of performance over the entire length and circumference, a transverse and longitudinal performance difference of ≤50MPa, a low longitudinal strength difference of ≤80MPa, and a tensile strength of greater than 545MPa, a hardness of ≤220HV10, and low-temperature performance of -39°C meets the requirements of impact energy greater than 200J, shear ratio ≥85%, and CTOD value ≥1.0mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The metallographic structure diagram of the seamless steel pipe prepared in Example 1;

[0037] Figure 2 This is the yield strength distribution diagram of the 508 mm outer diameter seamless line pipe of Example 1;

[0038] Figure 3 This is the hardness distribution diagram of the inner, middle and outer sides of the 508 mm outer diameter seamless pipeline of Example 1;

[0039] Figure 4This is the impact energy distribution diagram of the 508 mm outer diameter seamless pipeline of Example 1. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further described below in conjunction with embodiments so that those skilled in the art can better understand the present invention, but the present invention is not limited thereto.

[0041] Example 1

[0042] A 508mm outer diameter seamless pipeline for underwater oil and gas development, with a specification of Φ508mmx31.8mm, and chemical components in mass percentage: C 0.084wt%, Si 0.24wt%, Mn 1.30wt%, P: 0.012wt%, S: 0.003wt%, Al: 0.023wt%, Cr: 0.12wt%, Mo: 0.11wt%, Nb: 0.024wt%, Cu 0.06wt%, Ni: 0.12wt%, V: 0.04wt%, Ti: 0.010wt%, B: 0.0003wt%, CEpcm: 0.18wt%, CE IIW :0.37wt%, the balance being Fe and unavoidable impurities.

[0043] The method for manufacturing the above-mentioned 508 mm outer diameter seamless line pipe for underwater oil and gas development comprises the following steps:

[0044] (1) Smelting of Φ500mm cross-section continuous casting round billet: The corresponding raw materials are prepared according to the above-mentioned element ratios, and the raw materials are refined by short-process EAF electric furnace and LF ladle furnace, and alloy materials are added to adjust the composition, high vacuum treatment, air-breaking wire feeding treatment, soft blowing weak stirring treatment for 40 minutes, feeding calcium wire, titanium wire, Al wire, and ladle furnace temperature control for continuous casting. The whole process of inert gas protection casting is controlled to control the superheat at 35°C, and enters the 4-stream crystallizer through the tundish. The crystallizer is electromagnetically stirred at 2Hz and the current is 150A. The end electromagnetic stirring is 7Hz and the current is 350A. The straightening temperature is 950°C. Finally, a 500mm cross-section continuous casting round billet is obtained, which is cooled by stack cooling for 24 hours to obtain a low-segregation 500mm cross-section continuous casting round billet: the maximum outer diameter is 501mm, the minimum outer diameter is 499mm, the ovality is 2mm, the curvature per meter should be 1.5mm, and the total curvature is 5mm.

[0045] (2) Φ508PQF continuous rolling unit: The low segregation 500mm cross-section continuous casting round billet is heated in a 51m middle diameter walking beam annular furnace, and natural gas is used as the medium for 7-stage gradient heating, with a temperature range of 850℃-1080℃-1220℃-1270℃-1300℃-1280℃-1260℃. The furnace time is controlled at 10 hours, and the heating is uniform to achieve the best rolling state. A two-roller oblique rolling tapered roller piercing machine is used for piercing. The piercing continuous casting round billet temperature is 1000℃, the rough pipe outer diameter is 583-588mm, the wall thickness is 48mm, and the head is 445mm. A three-roller limited mandrel PQF continuous rolling pipe mill 50 is used. 8PQF continuous rolling unit, mandrel 462.9mm, system computer sets rolling target wall thickness 32.15mm, wall thickness tolerance control range -6.2%t~9%t, length 13.43 meters, high-pressure water dephosphorization pressure 10MPa before continuous rolling to ensure surface quality, high-pressure water dephosphorization 8.5MPa before sizing, first through three tube stripping machines and then two sizing machines for rolling, control the outer diameter of the steel pipe within the range of ±5%D, step-type cooling bed, the cooled steel pipe is cut to length, the length of the head and tail is 900mm, the pipe end is cut obliquely to 1.6mm, the cut length is 12.292 meters, and the three rotating rollers are cold straightened to achieve a full-length curvature of 5mm. Surface inspection is carried out using leakage magnetic flaw detection, the outer surface is horizontal and vertical, the flaw detection level is F2, and there are no defects. Qualified rolled steel pipes are obtained;

[0046] (3) The rolled steel pipe is placed in a walking beam high temperature furnace for heating at 930°C, holding time for 60 min, dephosphorization with 8MPa high pressure water, quenching and water cooling, tempering in a walking beam low temperature furnace at 650°C, holding time for 55 min, dephosphorization with 8MPa high pressure water, high temperature hot straightening, hot straightening temperature of 600°C, to obtain seamless pipelines. Pipe end processing: For the ends with an inner diameter range less than the tolerance requirement, internal sizing is performed, and the sizing rate is ≤0.015.

[0047] The metallographic structure of the Φ508.00mmx31.8mm seamless pipeline prepared in Example 1 is as follows Figure 1 The organizational composition of the prepared seamless line pipe is shown in Table 1, and the mechanical properties are shown in Table 2.

[0048] Example 2

[0049] A 508mm outer diameter seamless pipeline for underwater oil and gas development, with a specification of Φ508.00mmx34.9mm, chemical composition weight percentage Wt%: C: 0.076, Si 0.29, Mn1.32, P: 0.009, S: 0.002, Al: 0.025%, Cr: 0.12, Mo: 0.127, Nb: 0.03, Cu 0.06, Ni: 0.17, V: 0.05, Ti: 0.018, B: 0.0004, CEpcm: 0.18, CEIIW :0.37, the balance is Fe and unavoidable impurities. The rolling specification is 508mmx34.9mm.

[0050] The preparation method is the same as that of Example 1, except that the rolled steel pipe is placed in a walking beam high temperature furnace for heating at 940°C for 60 minutes, dephosphorized with 8MPa high pressure water, quenched and water cooled, tempered in a walking beam low temperature furnace at 670°C for 55 minutes, dephosphorized with 8MPa high pressure water, and hot straightened at 650°C to obtain a seamless line pipe. Pipe end processing: internal sizing is performed on the end whose inner diameter range is less than the tolerance requirement, and the sizing rate is ≤0.015.

[0051] The Φ508.00mmx34.9mm seamless pipeline prepared in Example 2 was subjected to performance testing. The organizational composition of the seamless pipeline is shown in Table 1, and the mechanical performance indicators are shown in Table 2.

[0052] Comparative Example 1

[0053] The only difference from Example 1 is that the rolled steel pipe is placed in a walking-beam high-temperature furnace for heating at a temperature of 840°C and a holding time of 60 min, dephosphorized with 8 MPa high-pressure water, quenched and water-cooled, tempered in a walking-beam low-temperature furnace at a temperature of 670°C and a holding time of 55 min, dephosphorized with 8 MPa high-pressure water, and hot straightening at a temperature of 550°C to obtain a seamless pipeline.

[0054] Comparative Example 2

[0055] The only difference from Example 1 is that the rolled steel pipe is placed in a walking-beam high-temperature furnace for heating at a temperature of 980°C and a holding time of 60 min, dephosphorized with 8 MPa high-pressure water, quenched and water-cooled, tempered in a walking-beam low-temperature furnace at a temperature of 670°C and a holding time of 55 min, dephosphorized with 8 MPa high-pressure water, and hot straightening at a temperature of 550°C to obtain a seamless pipeline.

[0056] Comparative Example 3

[0057] The only difference from Example 1 is that the rolled steel pipe is placed in a walking-beam high-temperature furnace for heating at a temperature of 930°C and a holding time of 60 minutes, dephosphorized with 8MPa high-pressure water, quenched and water-cooled, tempered in a walking-beam low-temperature furnace at a temperature of 700°C and a holding time of 55 minutes, dephosphorized with 8MPa high-pressure water, and hot straightening at a temperature of 550°C to obtain a seamless pipeline.

[0058] The organization composition of the seamless pipes prepared in Comparative Examples 1 to 3 is shown in Table 1. The mechanical performance indicators are shown in Table 2

[0059] Table 1 Organization composition of seamless line pipe

[0060] Example F B Back Ribbon Grain size Inclusion Example 1 40％ 60％ 2.0 9 A, B, C, D less than 1.0 Example 2 30％ 70％ 1.0 9 A, B, C, D less than 1.0 Comparative Example 1 70％ 30％ 3.0 8.5 A, B, C, D less than 1.0 Comparative Example 2 20％ 80％ 2.5 7.5 A, B, C, D less than 1.5 Comparative Example 3 60％ 40％ 2.0 9 A, B, C, D less than 2.0

[0061] Table 2 Mechanical properties

[0062]

[0063] Using the technology in this paper, more than 9,000 steel pipes with a specification of 508mmx31.8mm have been produced. The yield strength, hardness and impact energy of most steel pipe ends have been statistically analyzed. The distribution diagram of the actual measurement data is shown in the figure below. Figure 2 , Figure 3 and Figure 4 . Figure 2 This is the yield strength distribution diagram of 508mm outer diameter seamless pipeline; Figure 3 This is the hardness distribution diagram of the seamless pipeline with an outer diameter of 508 mm inside and outside. Figure 4 This is the impact energy distribution diagram of 508mm outer diameter seamless pipeline.

[0064] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept, which all belong to the protection scope of the present invention.

Claims

1. A 508mm outer diameter seamless line pipe for underwater oil and gas development, characterized in that: The chemical composition is calculated by mass percentage: C: 0.045-0.11wt%, Si: 0.25-0.60wt%, Mn: 1.30-1.70wt%, P: ≤0.012wt%, S: ≤0.003wt%, Al: 0.020-0.060wt%, Cr: 0.05-0.15wt%, Mo: 0.11-0.20wt%, Nb: 0.015-0.03wt%, Cu: 0.01-0.06wt%, Ni: 0.05%-0.20wt%, V: 0.025-0.05wt%, Ti: 0.01-0.04wt%, B≤0.0005wt%, [H]≤2ppm, CEpcm: 0.16-0.22wt%, CE IIW :0.34-0.39wt%, CEpcm=C+Si / 30+Mn / 20+Cu / 20+Ni / 60+Cr / 20+Mo / 15+V / 10+5B, CE IIW =C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15, the remainder being Fe and inevitable impurities.

2. The seamless line pipe according to claim 1, characterized in that The structure of the seamless line pipe contains 20% to 50% ferrite, 50% to 80% tempered bainite, a grain size of ≥8, a banded structure of ≤3, and an inclusion level of ≤1.

5.

3. The seamless line pipe according to claim 1, characterized in that The seamless pipeline has an outer diameter of 508 mm, a wall thickness of >28 mm, high strength and low hardness, uniform performance over the entire length and circumference, a transverse and longitudinal performance difference of ≤50 MPa, a low longitudinal strength difference of ≤80 MPa, and a hardness of ≤220 HV10 while achieving a tensile strength greater than 545 MPa. The low temperature performance at -39°C satisfies the requirements of impact energy greater than 200 J, shear ratio ≥85%, and CTOD value ≥1.0 mm.

4. The method for manufacturing a seamless line pipe according to any one of claims 1 to 3, characterized in that: The steps include: (1) Smelting of Φ500mm cross-section continuous casting round billets: The raw materials are refined by short-process EAF electric furnace and LF ladle furnace, alloy materials are added to adjust the composition, VD high vacuum treatment, wire feeding, inert gas protection casting, double-station electromagnetic stirring, high-temperature straightening, and cast into 500mm continuous casting round billets on a continuous casting machine to obtain low-segregation 500mm cross-section continuous casting round billets; (2) Φ508PQF continuous rolling unit: The low segregation 500mm cross-section continuous casting round billet is heated in a ring furnace, pierced after heating, the piercing temperature is 1000-1230°C, and then 508PQF unit continuous rolling, sizing, cold straightening, to obtain a rolled steel pipe with a length greater than 12.5m and an outer diameter of 508mm; (3) Large-diameter heat treatment: The rolled steel pipe is placed in a walking-beam high-temperature furnace for heating, the temperature control range is 850℃~950℃, the holding time is greater than 40min, high-pressure water is used for dephosphorization, quenching and water cooling, and tempering in a walking-beam low-temperature furnace, the temperature control range is 600℃~690℃, the holding time is greater than 45min, high-pressure water is used for dephosphorization, high-temperature heat straightening, and the heat straightening temperature is 500-650℃ to obtain seamless pipelines; (4) Pipe end processing: For the ends whose inner diameter range is smaller than the tolerance requirement, internal sizing is performed, and the sizing rate is ≤0.

015.

5. The manufacturing method according to claim 4, characterized in that: The dual-process electromagnetic stirring includes crystallizer electromagnetic stirring and terminal electromagnetic stirring. The crystallizer electromagnetic stirring frequency is 1-3 Hz, the current is 130-180 A, and the terminal electromagnetic stirring frequency is 5-8 Hz, the current is 300-400 A.

6. The manufacturing method according to claim 4, characterized in that: The pressure of high-pressure water dephosphorization in step (3) is 7-25 MPa.

7. The manufacturing method according to claim 4, characterized in that: The smelting raw materials include molten iron, pig iron and scrap steel, and the alloy materials include ferrosilicon, ferromanganese, ferrovanadium, ferronickel, ferromolybdenum and ferroniobium.

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