A 655MPa grade H2S stress corrosion resistant coil for oil casing and its manufacturing method

Abstract

This invention relates to the field of oil casing manufacturing technology, and more particularly to a 655MPa grade H2S stress corrosion resistant oil casing coil and its manufacturing method. The composition is as follows: C: 0.095%–0.13%, Si: 0.2%–0.4%, Mn: 0.9%–1.1%, P: ≤0.015%, S: ≤0.004%, Ti: 0.01%–0.03%, Cr: 0.10%–0.25%, V: 0.07%–0.10%, Mg: 0.001%–0.003%, Zr: 0.0006%–0.003%, Ni: 0.1%–0.3%, Als: 0.02%–0.05%, N: ≤0.008%, with the remainder being Fe and unavoidable elements. The final microstructure of the coiled steel is ferrite-bainite, with a ferrite volume fraction of less than 15%, Pcm of less than 0.21%, inclusion grades A / B / C / D below 1.0, sum grade of each inclusion below 1.5, and banded structure below 0.5. The steel grade in API SPEC 5CT is K55, and the impact energy at -20℃ is greater than 150J. It has high tensile strength, a lower yield strength ratio, better low-temperature toughness, and excellent resistance to SSC (susceptibility to brittle fracture) of oil well tubing, providing higher safety, and the alloy cost is moderate.

Description

Technical Field

[0001] This invention relates to the field of oil casing manufacturing technology, and in particular to a 655MPa grade H2S stress corrosion resistant oil casing coil and its manufacturing method. Background Technology

[0002] Oil casing is one of the most commonly used oilfield-specific pipe materials, used in large quantities and at high cost, and is an indispensable construction material in oil and gas field drilling and production operations. Compared with seamless pipe, HFW (high frequency welded) casing has significant advantages such as uniform wall thickness, high dimensional accuracy, good perforation performance, strong resistance to crushing, and low cost, and is gradually replacing traditional seamless steel pipe.

[0003] With the continuous increase in population, the growth in global energy demand is also becoming increasingly significant. Natural gas production has maintained a high-speed growth trend, and the corrosion and protection of oil casing has gradually become a major concern. The development of deep and ultra-deep wells is increasing, and oil extraction conditions are becoming increasingly harsh. In addition to low-molecular-weight alkanes and inert gases, oil and natural gas also contain CO2 and H2S. During the natural gas extraction process, the water content in natural gas increases, and H2S dissolves in the water film on the metal surface, forming a corrosive medium. This causes different types of corrosion in different parts of the downhole casing steel, making the service conditions of oil casing increasingly demanding. It requires not only excellent mechanical properties of oil casing steel but also good resistance to acid corrosion.

[0004] The coiled steel with a tensile strength of 655 MPa belongs to the K55 steel grade specified in API Spec 5CT. API Spec 5CT specifies that K55 grade steel has a yield strength between 379-552 MPa, a tensile strength ≥655 MPa, an elongation ≥20%, and an impact energy (Akv, 21℃, transverse) ≥20 J. For H2S stress corrosion resistance (SSC), samples subjected to 72% of the nominal yield strength load using method A solution according to NACE TM0177 should not crack after 720 hours. To ensure that the K55 straight seam welded oil casing requires resistance welding, good weldability and a low cold cracking sensitivity coefficient (Pcm) are required. To ensure impact and extrusion resistance, a certain level of impact toughness is necessary. To ensure HIC resistance, the fineness and uniformity of inclusions and microstructure need to be controlled. To ensure strength, certain alloys need to be added to refine the grain and provide hardenability.

[0005] Chinese patent document CN104357756A discloses "A straight-seam welded oil casing resistant to hydrogen sulfide stress corrosion and its manufacturing method." The composition includes: C: 0.08%-0.15%, Si: 0.15%-0.30%, Mn: 0.50%-1.00%, P≤0.010%, S≤0.0050%, Cr: 0.40%-0.65%, Ni≤0.25%, Mo: 0.30%-0.50%, Nb≤0.02%, V: 0.05%-0.10%, Zr: 0.0005%-0.01%, Al: 0.005%-0.01%, Ca: 0.001%-0.003%, B: 0.0005%-0.001%, RE: 0.001%-0.005%. The steel grade is 90ksi, which is C90 according to API standards. The production process involves ladle refining, RH furnace vacuum treatment, and continuous casting. The steel is then thermomechanically rolled into coils on a continuous rolling mill, processed into tubes via HFW (High-Temperature Winding), and finally tempered at high temperatures and then stress-relieved to obtain qualified steel pipes. However, due to the low C and Mn content and high strength requirements, large amounts of expensive alloying elements such as Mo, Ni, V, and Nb must be added, resulting in high alloy costs. Furthermore, the addition of Zr, Ca, B, and RE complicates the smelting process.

[0006] Chinese patent document CN102296233A discloses "Steel for High-Frequency Resistance Welding of Oil Casing and its Manufacturing Method". The composition includes C: 0.15%-0.35%, Si: 0.10%-0.60%, Mn: 0.30%-1.00%, P≤0.015%, S≤0.003%, Mo: 0.1%-0.5%, V: 0.03%-0.20%, Nb: 0.01%-0.05%, Ti: 0.01%-0.05%, Al: 0.01%-0.08%, Ca: 0.001%-0.005%, and B: 0.001%-0.003%. The steel grade is 80ksi, which is API standard N80. The product is produced through ladle refining, RH furnace vacuum treatment, and continuous casting. It is then thermomechanically rolled into plates and coils on a continuous rolling mill production line, and finally processed into qualified steel pipes through HFW pipe making and online weld normalizing treatment. However, the high carbon content results in poor HFW weldability and is detrimental to HIC performance; the high content of precious elements such as Mo, V, Nb, and Ti also increases the alloy cost.

[0007] In summary, ensuring that the coil with a tensile strength of 655MPa has high tensile strength, lower yield strength ratio, better low-temperature toughness, and excellent resistance to SSC (substantial fracture) to prevent brittle fracture of oil well tubing and provide higher safety, while also taking into account alloy costs, has become an urgent technical problem to be solved. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, this invention provides a 655MPa grade H2S stress corrosion resistant coiled steel sheet for oil well casing and its manufacturing method. It features high tensile strength, a lower yield strength ratio, better low-temperature toughness, and excellent SSC resistance, preventing brittle fracture of the oil well casing, thus providing higher safety, and the alloy cost is moderate.

[0009] To achieve the above objectives, the present invention employs the following technical solution:

[0010] A type of coiled steel sheet for oil casing with H2S stress corrosion resistance of 655MPa grade, the chemical composition of which is as follows by weight percentage:

[0011] C: 0.095%–0.13%, Si: 0.2%–0.4%, Mn: 0.9%–1.1%, P: ≤0.015%, S: ≤0.004%, Ti: 0.01%–0.03%, Cr: 0.10%–0.25%, V: 0.07%–0.10%, Mg: 0.001%–0.003%, Zr: 0.0006%–0.003%, Ni: 0.1%–0.3%, Als: 0.02%–0.05%, N: ≤0.008%, with the remainder being Fe and unavoidable elements.

[0012] The final microstructure of the coil is ferrite-bainite, with a ferrite volume fraction of less than 15%; Pcm less than 0.21%; inclusion grades A / B / C / D below 1.0; sum grade of each type below 1.5; and banded structure below 0.5. The steel grade in API SPEC 5CT is K55, and the impact energy at -20℃ is greater than 150J.

[0013] A method for manufacturing a coiled plate with 655MPa resistance to H2S stress corrosion in oil casing includes the following steps:

[0014] 1) Continuous casting in smelting:

[0015] Hot metal pretreatment.

[0016] Converter smelting is carried out through top blowing or a combination of top and bottom blowing.

[0017] Ladle refining, LF furnace light desulfurization treatment, and calcium treatment.

[0018] Slabs are continuously cast into slabs, and the continuous casting process employs electromagnetic stirring or dynamic light pressure.

[0019] 2) Rolling:

[0020] The continuously cast slab is heated to 1230-1270°C in a heating furnace and then subjected to thermomechanical rolling.

[0021] The roughing rolling temperature is 1000-1050℃, the finishing rolling temperature is 930-980℃, and the finishing rolling temperature is 880-930℃.

[0022] 3) Cooling:

[0023] The rolling process employs a two-stage cooling system: the first stage uses air cooling, while the second stage uses laminar flow cooling.

[0024] The starting temperature for air cooling followed by water cooling is 810–860℃, and the cooling rate is 7–13℃ / s.

[0025] 4) Winding:

[0026] After cooling, the product is wound up at a temperature of 550–600℃.

[0027] Compared with the prior art, the present invention has at least the following technical effects or advantages:

[0028] 1. This invention employs a low-carbon, magnesium-containing Cr-V-Ni composite design. C: 0.095%–0.13%, ensuring both material hardness and its weldability, plasticity, and impact toughness; Mg: 0.001%–0.003%, reducing oxygen and sulfur content and inclusions in the steel, purifying the molten steel; Cr: 0.10%–0.25%, improving tensile strength, giving the steel high strength and hardness, enhancing wear resistance, refining grain size, and reducing corrosion rate in high-temperature carbon dioxide environments, thus slowing down casing corrosion in oil wells and extending service life; V: 0.07%–0.10%, improving hardenability, effectively increasing tensile strength, reducing yield strength ratio, and refining grain size, thus benefiting low-temperature impact toughness; Ni: 0.10%–0.30%, allowing for a suitable reduction in carbon content in nickel-containing steel, thereby improving toughness and plasticity. It improves the fatigue properties of steel, reduces the steel's sensitivity to notches, and also has a certain degree of acid resistance, which is beneficial for resisting SSC (sulfate-sensitive steel).

[0029] 2. The addition of Mg to refine inclusions in this invention can effectively change the morphology and size of inclusions. Containing magnesium oxide, this structure is finely dispersed in the steel to form composite inclusions, which significantly improves corrosion resistance and enhances the performance and impact resistance of SSC.

[0030] 3. This invention's V-Cr composite exhibits superior SSC resistance. Vanadium shrinks the austenite phase region and is infinitely soluble in σ-iron, making it a strong carbide and nitride forming element. Its solid solution in austenite improves the hardenability of steel; its solid solution in ferrite provides strong solid solution strengthening, effectively increasing tensile strength and reducing the yield ratio. It also refines grain size, thus benefiting low-temperature impact toughness. Vanadium forms carbides with carbon, improving resistance to hydrogen corrosion under high temperature and pressure; chromium enhances strength through solid solution strengthening and grain refinement, and Cr, like Mn, can dissolve into solid solutions, thus increasing tensile strength. When chromium (Cr) dissolves into austenite, it increases the stability of supercooled austenite, shifts the C-curve to the right, improves the hardenability of steel, promotes bainite transformation, and gives steel high strength, hardness, and wear resistance. Simultaneously, Cr is a medium-sized carbide-forming element; among all carbides, chromium carbides are the finest, allowing for uniform distribution throughout the steel volume. It also hinders the movement of austenite grain boundaries and the growth of austenite grains, thus refining the grain size. Furthermore, chromium reduces the corrosion rate of steel in high-temperature carbon dioxide environments, slowing down the corrosion rate of casing in oil wells and extending its service life.

[0031] 4. The Pcm of this invention is below 0.231%, resulting in good weldability. Existing K55 weld metal generally uses a C content of over 0.20% and a Mn content of over 1.2%, with a Pcm close to 0.25%. When the Pcm value is greater than 0.25, the tendency for cold cracking increases significantly, and weldability decreases. The lower the Pcm, the better the weldability; this invention has a Pcm below 0.21%, resulting in excellent weldability.

[0032] 5. The present invention has moderate content of precious elements V and Ti, and moderate alloy cost.

[0033] 6. The roughing and finishing rolling temperature of this invention is 1000-1050℃, the finishing rolling temperature is 930-980℃, and the finishing rolling temperature is 880-930℃. This temperature range is conducive to the solid solution strengthening effect of Cr and V, and improves tensile strength; it also has a certain V and Ti precipitation strengthening effect, refines grain size, and improves tensile strength and toughness.

[0034] 7. This invention employs a two-stage cooling system after rolling: the first stage uses air cooling, and the second stage uses laminar flow cooling. The initial cooling temperature of the water cooling after air cooling is 810–860℃, and the cooling rate is 7–13℃ / s. At this cooling rate, the bainite and ferrite structures can be fully homogenized, improving the resistance to ferrite solidification (SSC). It can also reduce banded structures to below grade 0.5, significantly improving tensile strength, lowering the yield strength ratio, and simultaneously improving toughness and corrosion resistance.

[0035] 8. The present invention is cooled and then wound up at a temperature of 550-600°C. This temperature range is beneficial to the uniformity and refinement of the bainitic structure.

[0036] 9. The present invention employs ladle refining, LF furnace light desulfurization treatment, and calcium treatment to control inclusion morphology and improve the ductility, toughness, and cold bending performance of steel. The slab is continuously cast to produce a continuously cast slab. Continuous casting uses electromagnetic stirring or dynamic light reduction to improve the quality of the continuously cast slab. Detailed Implementation

[0037] This invention discloses a 655MPa-grade H2S stress corrosion resistant coiled steel plate for oil casing and its manufacturing method. Those skilled in the art can refer to this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0038] A type of coiled steel sheet for oil casing with H2S stress corrosion resistance of 655MPa grade, the chemical composition of which is as follows by weight percentage:

[0039] C: 0.095%–0.13%, Si: 0.2%–0.4%, Mn: 0.9%–1.1%, P: ≤0.015%, S: ≤0.004%, Ti: 0.01%–0.03%, Cr: 0.10%–0.25%, V: 0.07%–0.10%, Mg: 0.001%–0.003%, Zr: 0.0006%–0.003%, Ni: 0.1%–0.3%, Als: 0.02%–0.05%, N: ≤0.008%, with the remainder being Fe and unavoidable elements.

[0040] The final microstructure of the coil is ferrite-bainite, with a ferrite volume fraction of less than 15%; Pcm less than 0.21%; inclusion grades A / B / C / D below 1.0; sum grade of each type below 1.5; and banded structure below 0.5. The steel grade in API SPEC 5CT is K55, and the impact energy at -20℃ is greater than 150J.

[0041] Compared with existing technologies, this solution adopts a low-carbon magnesium-containing Cr-V-Ni composite design, which has high tensile strength, lower yield strength ratio, better low-temperature toughness, and excellent SSC resistance. Mg refines inclusions, which can effectively change the morphology and size of inclusions, which is beneficial to SSC performance and impact. Cr and V effectively improve tensile strength without significantly increasing yield strength, significantly reduce yield strength ratio, and improve SSC resistance. Pcm is less than 0.21%, and the weldability is good.

[0042] The following details the mechanism of action of each alloy component in this invention, where the percentage symbol % represents a weight percentage:

[0043] Carbon (C) is a carbide-forming element and the most effective element for ensuring strength. It improves hardenability and guarantees the material's strength and hardness. Only with sufficient carbon can enough carbon-rich retained austenite be formed and stabilized at room temperature, ultimately forming a small amount of uniform and fine M / A microstructure. If the carbon content is too low, the material's hardness cannot be guaranteed, resulting in poor threading performance. If the content is too high, it will affect the product's weldability, plasticity, and impact toughness. The optimal range is 0.095%-0.13%.

[0044] Si can dissolve in ferrite and austenite, playing a certain role in solid solution strengthening. It can significantly improve the hardness and tensile strength of steel, reduce the yield strength ratio, and improve fatigue strength and fatigue ratio. However, excessive content will significantly reduce the plasticity and toughness of steel. Its optimal range is 0.2%-0.4%.

[0045] Mn (manganese): Manganese has solid solution strengthening properties and can increase the stability of austenite, which is also beneficial to improving hardenability and effectively ensuring the strength of steel. Manganese and iron form a solid solution, increasing the hardness and strength of ferrite and austenite in steel. It is also a carbide-forming element, entering cementite and replacing some iron atoms. In steel, manganese lowers the critical transformation temperature, shifting the C-curve to the right and promoting bainite transformation. However, excessive manganese content can increase the tendency for center segregation in continuously cast billets, leading to an increase in banded structures in the steel plate. Ultimately, the steel plate will contain a certain amount of banded structures, increasing brittleness, reducing plasticity, and worsening corrosion resistance. Simultaneously, it readily forms MnS, which has a detrimental effect on HIC (high-temperature corrosion resistance). The optimal range for MnS is 0.9%-1.1%.

[0046] P, S, and N are unavoidable impurity elements in steel, and it is desirable to keep them as low as possible. However, excessively low levels will increase production costs. In this invention, P ≤ 0.015%, S ≤ 0.004%, and N ≤ 0.006%.

[0047] Titanium (Ti): Titanium is a strong nitrogen-fixing element. Adding approximately 0.015% Ti can form high-temperature stable, fine TiN precipitates during slab continuous casting. These fine TiN precipitates effectively prevent austenite grain growth during heating and significantly improve the toughness of the heat-affected zone during welding. Higher Ti content yields more TiC particles, increasing steel strength through strain-induced precipitation and phase transformation precipitation. Simultaneously, the precipitated TiC provides strong precipitation strengthening, ensuring minimal grain growth during subsequent normalizing heat treatment, thus guaranteeing the overall tube's strength meets J55 performance requirements. However, excessively high Ti content increases alloy cost. The optimal range is 0.01%-0.03%.

[0048] Cr: Chromium can improve strength through solid solution strengthening and grain refinement. Like Mn, Cr can dissolve into solid solutions, increasing tensile strength. When Cr dissolves into austenite, it increases the stability of supercooled austenite, shifting the C-curve to the right, improving hardenability, and promoting bainite transformation. This results in high strength and hardness in the steel, improving its wear resistance. Simultaneously, Cr is a moderate carbide-forming element; among all carbides, chromium carbides are the finest, uniformly distributed throughout the steel volume, hindering austenite grain boundary movement and grain growth, thus refining the grain size. Chromium also reduces the corrosion rate of steel in high-temperature carbon dioxide environments, slowing down casing corrosion in oil wells and extending service life. However, excessive chromium content significantly increases the brittle transition temperature, reduces elongation, and easily forms coarse carbides, leading to decreased toughness. The suitable range is 0.10%-0.25%.

[0049] Vanadium (V): Vanadium shrinks the austenite phase region, is infinitely soluble in ferrite, and is a strong carbide and nitride forming element. Its solution in austenite improves the hardenability of steel; its solution in ferrite has a very strong solid solution strengthening effect, effectively increasing tensile strength and reducing the yield ratio. It has a grain-refining effect, thus benefiting low-temperature impact toughness. Vanadium forms carbides with carbon, which improves resistance to hydrogen corrosion under high temperature and pressure. The suitable range is 0.07%-0.10%.

[0050] Mg: Magnesium has strong chemical reactivity and a strong affinity for oxygen and sulfur, making it an effective refining agent. It can reduce the oxygen and sulfur content and the number of inclusions in steel, purifying the molten steel. It can also significantly modify inclusions in steel, improving its properties. Trace amounts of magnesium can alter the quantity, type, size, and distribution of sulfides, carbides, and carbonitrides. Magnesium-treated inclusions are mixed phases, with magnesium oxides at their core. This structure is finely dispersed in the steel, forming composite inclusions that improve steel properties and corrosion resistance. The suitable range is 0.001%-0.003%.

[0051] Zr: Trace amounts of zirconium have deoxidizing, purifying, and grain-refining effects, and significantly modify inclusions, improving the low-temperature toughness of steel. When added in combination with Cr, it can significantly inhibit recrystallization of the alloy and improve its resistance to SSC corrosion. The optimal range is 0.0006%-0.003%.

[0052] Ni (Ni): Nickel and iron are infinitely soluble in solid matter. Nickel expands the austenite region of iron and is a major alloying element for the formation and stabilization of austenite. It lowers the critical transformation temperature, reduces the diffusion rate of elements in steel, and improves hardenability. It reduces the carbon content of eutectoid pearlite, its effect being second only to nitrogen and stronger than manganese, indirectly promoting bainite formation. The carbon content of nickel-containing steel can be appropriately reduced, thus improving toughness and plasticity. It improves the fatigue performance of steel and reduces its notch sensitivity. It also provides some acid resistance and is beneficial for resistance to HIC (high acid concentration). The suitable range is 0.10%-0.30%.

[0053] Als: Aluminum is a commonly used deoxidizer. Adding a small amount of aluminum to steel can refine the grains and improve impact toughness. The Al content of this invention is 0.02%-0.05%.

[0054] A method for manufacturing a 655MPa grade H2S stress corrosion resistant oil casing coil includes hot metal pretreatment, steelmaking, ladle refining and slab continuous casting, continuous casting billet reheating, rolling, cooling and coiling, specifically including the following steps:

[0055] 1) Continuous casting process:

[0056] Hot metal pretreatment, converter smelting – top blowing or top-bottom combined blowing, ladle refining, LF furnace light desulfurization treatment and calcium treatment to control inclusion morphology and improve the ductility, toughness and cold bending performance of steel.

[0057] Slabs are continuously cast into slabs – continuous casting employs electromagnetic stirring or dynamic light pressure to improve the quality of the slabs.

[0058] 2) Rolling and cooling process: The continuously cast slab is heated to 1230-1270℃ in a heating furnace and then subjected to thermomechanical rolling.

[0059] The roughing rolling temperature is 1000-1050℃, the finishing rolling temperature is 930-80℃, and the finishing rolling temperature is 880-930℃. This temperature range is conducive to the solid solution strengthening effect of Cr and V, which improves tensile strength. It also has a certain strengthening effect of V and Ti precipitation, which refines the grain size and improves tensile strength and toughness. The post-rolling cooling is two-stage, with the first stage using air cooling and the second stage using laminar flow cooling.

[0060] The initial cooling temperature after air cooling is 810–860℃, with a cooling rate of 7–13℃ / s. This cooling rate effectively homogenizes the bainite and ferrite microstructure, improving SSC resistance and reducing banded structures to below grade 0.5. This significantly increases tensile strength, lowers the yield strength ratio, and simultaneously enhances toughness and corrosion resistance. After cooling, coiling is performed at a temperature of 550–600℃, a temperature range conducive to the homogenization and refinement of the bainite microstructure.

[0061]

Example

[0062] A 655MPa-grade H2S stress corrosion resistant oil casing coil and its manufacturing method are described below:

[0063] Table 1 shows the chemical composition of the coils in the examples; Table 2 shows the heating, rolling, and cooling process parameters in the examples; and Table 3 shows the mechanical property test results of the examples.

[0064] Table 1 Chemical composition (wt%) of the examples

[0065]

[0066]

[0067] Table 2 Heating, Rolling, and Cooling Process Parameters

[0068]

[0069] Table 3 Mechanical and Corrosion Resistance Properties

[0070]

[0071] As can be seen from Tables 1-3, the 655MPa grade H2S stress corrosion resistant oil casing coil produced by adopting the composition design, rolling and coiling process of the present invention meets the requirements of API SPEC 5CT standard K55 grade mechanical properties and SSC resistance.

[0072] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for manufacturing a coiled plate with 655MPa-grade H2S stress corrosion resistance for oil casing, characterized in that, Its chemical composition by weight percentage is as follows: C: 0.095%–0.13%, Si: 0.2%–0.4%, Mn: 0.9%–1.1%, P: ≤0.015%, S: ≤0.004%, Ti: 0.01%–0.03%, Cr: 0.10%–0.25%, V: 0.07%–0.10%, Mg: 0.001%–0.003%, Zr: 0.0006%–0.003%, Ni: 0.22%–0.30%, Als: 0.02%–0.05%, N: ≤0.008%, Pcm less than 0.21%, the remainder being Fe and unavoidable elements; The final microstructure of the coil is ferrite-bainite, with a ferrite volume fraction of less than 15%; inclusions of type A / B / C / D are grade 1.0 or lower, the sum of each type is grade 1.5 or lower, and banded microstructure is grade 0.5 or lower. Specifically, the steps include the following: 1) Continuous casting in smelting: Ladle refining, LF furnace desulfurization treatment, and calcium treatment. Slabs are continuously cast into continuously cast billets, and the continuous casting process employs electromagnetic stirring or dynamic light reduction. 2) Rolling: The continuously cast slab is heated to 1230–1270°C and then subjected to thermomechanical rolling. The roughing rolling temperature is 1000-1050℃, the finishing rolling temperature is 930-980℃, and the finishing rolling temperature is 880-930℃. 3) Cooling: The rolling process employs a two-stage cooling system: the first stage uses air cooling, and the second stage uses laminar flow cooling. The starting temperature for air cooling followed by water cooling is 810–860℃, and the cooling rate is 7–13℃ / s. 4) Winding: After cooling, the product is wound up at a temperature of 590–600℃.

2. The method for manufacturing a 655MPa grade H2S stress corrosion resistant coiled plate for oil casing according to claim 1, characterized in that, The first step is that the converter smelting is carried out by top blowing or top-bottom combined blowing.

3. The method for manufacturing a 655MPa grade H2S stress corrosion resistant coiled plate for oil casing according to claim 1, characterized in that, The 2) continuously cast slab is heated to 1230-1270°C in a heating furnace.

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