Manufacturing method and application of hot rolled plate coil for 896MPa-grade shale gas well straight seam electric resistance welding casing pipe

Abstract

The invention discloses a manufacturing method and application of a hot rolled plate coil for an 896MPa-grade shale gas well straight seam electric resistance welding casing pipe, and relates to the technical field of oil casing pipes. According to the performance required by the hot rolled plate coil for the 896MPa-grade shale gas well straight seam electric resistance welding sleeve, required elements, the mass percent range of all the elements and manufacturing process window conditions are limited; according to limited manufacturing conditions, through material genetic engineering, the component design of the hot-rolled plate coil and the mechanical performance of the hot-rolled plate coil are calculated by adopting a first principle and a molecular dynamics principle; and manufacturing the hot-rolled plate coil according to the output result. According to the method, the traditional trial and error type material research and development process for component and performance optimization in a simulation experiment can be rapidly operated, large-system material simulation and rapid calculation are achieved, the material screening efficiency and the design level are improved, the components of the hot-rolled plate coil with target performance and the mechanical performance of the hot-rolled plate coil can be rapidly predicted, the material research and development time is shortened, and the research and development efficiency is improved. And the material research and development cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of petroleum casing, and in particular to a manufacturing method and application of a hot-rolled coil for a 896MPa-grade shale gas well straight seam resistance welded casing. Background Art

[0002] Shale gas development will become the main source of natural gas production in the future. Shale gas exploitation has the characteristics of long horizontal sections, long fracturing operation time and high pressure. The casing is subjected to long-term high-pressure cycle composite loads. Multi-stage fracturing of horizontal wells drives the uneven sliding of natural fractures and weak bedding planes in the formation, thereby increasing the risk of casing collapse and deformation. Therefore, shale gas well casing needs to have a high strength and toughness match. At present, high-strength oil casing mainly uses seamless steel pipes. The seamless steel pipe is formed by perforation forming, and it is difficult to control the precision of the pipe body size. Due to the particularity of its processing technology, the straight seam resistance welded casing has good uniformity of materials and geometric parameters. Compared with seamless pipes, it has a natural advantage of high anti-collision strength. Hot-rolled coils, as the raw material for the production of straight seam resistance welded casings, are the key to whether high-grade shale gas well straight seam resistance welded casings can be formed. The development of hot-rolled coils and their manufacturing methods suitable for the narrow process window conditions of high-grade straight seam resistance welded casings is an engineering problem for the development of high-performance casings for shale gas development. Traditional material research and development uses continuous trial and error experimental optimization of ingredients and processes, combined with continuous understanding of structure-performance relationships to obtain materials that meet performance indicators. This method not only consumes a lot of labor and material costs, but also takes a long time and has a relatively low success rate. Summary of the invention

[0003] In order to meet the requirements of properties required for preparing hot-rolled coils for 896MPa shale gas well casing and reduce resource waste, the present invention provides a method for manufacturing hot-rolled coils for 896MPa shale gas well straight seam electric resistance welded casing.

[0004] A method for manufacturing a hot-rolled coil for a 896MPa grade shale gas well straight seam electric resistance welded casing comprises the following steps:

[0005] Firstly, according to the required performance of hot-rolled coil for 896MPa grade shale gas well straight seam electric resistance welded casing, the required elements and the mass percentage range of each element, as well as the manufacturing process window conditions are defined;

[0006] Secondly, according to the limited manufacturing conditions, material genetic engineering is used to calculate the composition design and mechanical properties of the hot-rolled coil. The specific steps are as follows:

[0007] S1: The mass percentage of each element is used as the input of the first principle calculation and input into the calculation system. The first principle calculation is applied to pre-calculate the macroscopic characteristics and obtain the energy band and wave function characteristics of the system.

[0008] S2, using the system energy band and wave function characteristics as input, combined with the principle of molecular dynamics to calculate the mechanical properties of hot-rolled coils;

[0009] S3: judging whether the mechanical properties of the hot-rolled coil obtained in S2 meet the welding properties of the hot-rolled coil for 896MPa grade shale gas well straight seam resistance welding casing, if the welding properties are met, outputting the hot-rolled coil composition design and the mechanical properties of the hot-rolled coil; if the welding properties are not met, modifying the distribution ratio and returning to S1 until the welding properties are met, outputting the hot-rolled coil composition design and the mechanical properties of the hot-rolled coil;

[0010] Finally, the hot-rolled coil is manufactured according to the output hot-rolled coil composition design and the mechanical properties of the hot-rolled coil.

[0011] In the calculation system of material genetic engineering, the process flow is set as: coil forming-welding-quenching and tempering heat treatment.

[0012] When applying the first principle calculation to pre-calculate the macroscopic properties, the input of the first principle calculation is the mass percentage of C, Mn, Cr, Mo, Si and B; the carbon equivalent composition is used as a boundary condition, and the carbon equivalent is less than 0.5.

[0013] Mechanical properties include room temperature yield strength and toughness after hot rolling, weldability, and room temperature yield strength and toughness after quenching and tempering.

[0014] The required elements and the mass percentage range of each element are limited as follows: C: 0.12% ~ 0.22%, Mn: 1.0% ~ 1.6%, Cr: 0.4% ~ 0.6%, Mo: 0.3% ~ 0.5%, Si: 0.05% ~ 0.6%, B: 5 ~ 60PPM, and the rest is Fe and unavoidable impurities in the steel billet.

[0015] The process window conditions for manufacturing hot-rolled coils for 896MPa grade shale gas well straight seam resistance welded casing are as follows: during the high-temperature hot rolling process, the heating temperature of the heating furnace is 1170-1210°C, the final rolling temperature is controlled at 830-870°C, and the steel plate with a thickness of 10-13mm is obtained; after rolling, the steel plate is controlled to cool and then coiled, and the coiling temperature is 550-650°C.

[0016] The welding performance requirements of hot-rolled coils for 896MPa grade shale gas well straight seam resistance welded casing are as follows:

[0017] The yield strength is 300-600MPa, the elongation is ≥20%, the transverse impact energy is ≥40J at 0°C, the grain size conforms to ASTM E112 NO.9 or finer, and the banded structure is ≤3.0 grade.

[0018] The production process includes converter rough refining, refining outside the furnace, slab continuous casting, high temperature hot rolling and controlled cooling after rolling.

[0019] The production process includes converter rough refining, refining outside the furnace, slab continuous casting, high temperature hot rolling and controlled cooling after rolling. The specific operations are as follows:

[0020] Step 1: Put the steel into the furnace, and use argon for low-blowing in the converter and ladle; use ferrosilicon, metallic manganese, and low-carbon ferrochrome to fine-tune the composition during the refining process, deoxidize ferrosilicon powder and aluminum particles, and tap the steel after the temperature and composition are appropriate; the molten steel enters the crystallizer through the tundish, and is cooled through the fan-shaped section to form a cast slab;

[0021] Step 2: The cast slab containing the calculated chemical composition mass percentage is used as a hot-rolled slab, the initial continuous casting slab thickness is 230 mm, and during heating, the continuous casting slab is placed in a heating furnace for heating, and the furnace temperature of the continuous casting slab is controlled at 1170-1210° C., and the holding time is 1 hour;

[0022] Step 3: subjecting the continuously cast slab obtained in step 2 to seven-stand continuous rolling, with a cumulative deformation of ≥ 60%, and a final rolling temperature controlled at 830-870° C. to obtain a steel plate with a thickness of 10-13 mm;

[0023] Step 4: After the rolled steel plate is cooled, the coiling operation is performed, wherein the coiling temperature is 550-650°C, and gradient controlled cooling is adopted to ensure the toughness of the coil while reducing the formation of banded structure, thereby ensuring good processing performance of the coil.

[0024] A hot-rolled coil prepared by the above method is used for welding 896MPa-grade shale gas well casing. After the pipe is made by straight seam resistance welding process, the 896MPa-grade shale gas well casing with a yield strength of 900-960MPa and a Charpy impact energy of 130-220J can be obtained by tempering treatment.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention uses material genetic engineering, first principles and molecular dynamics principles to quickly run the traditional trial-and-error material development process of optimizing composition and performance in simulation experiments, realize large-system material simulation, fast calculation, improve material screening efficiency and design level, and can quickly predict the composition of target performance hot-rolled coils and the mechanical properties of hot-rolled coils, shorten the time for material development, and reduce the cost of material development; it also defines manufacturing conditions according to needs and narrows the scope of simulation experiments; and then undergoes process processing to obtain 896MPa-grade hot-rolled coils for straight seam resistance welding casing of shale gas wells that meet welding performance.

[0027] Furthermore, under specific limited manufacturing conditions, the hot-rolled coil for 896MPa grade shale gas well straight seam resistance welded casing needs to have lower yield strength and higher toughness, good cold formability and welding performance, and higher yield strength and toughness matching after quenching and tempering treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the following briefly introduces the drawings required for use in the embodiment:

[0029] Figure 1 The present invention is a flowchart of a method for manufacturing a hot-rolled coil;

[0030] Figure 2 Flow chart of genetic engineering of materials used in the present invention;

[0031] Figure 3 The metallographic structure diagram of the hot-rolled coil prepared in Example 1 of the present invention;

[0032] Figure 4 This is the metallographic structure diagram of the hot-rolled coil prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0033] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0034] like Figure 1 As shown, a method for manufacturing a hot-rolled coil for a 896MPa grade shale gas well straight seam resistance welded casing comprises the following steps:

[0035] First, according to the required performance of hot-rolled coil for 896MPa grade shale gas well straight seam resistance welded casing, the mass percentage of each required element is limited to the following range:

[0036] Including C: 0.12%~0.22%, Mn: 1.0%~1.6%, Cr: 0.4%~0.6%, Mo: 0.3%~0.5%, Si: 0.05%~0.6%, B: 5~60PPM, and the rest is Fe and unavoidable inclusions.

[0037] Carbon equivalent is the equivalent amount of carbon in metal materials recommended by the International Welding Institute. Controlling it within a smaller range is beneficial to reducing the heat affected zone of welding, improving the crack resistance and impact resistance of the weld, and ensuring the stability of weld quality and performance. The calculation method of carbon equivalent is as follows:

[0038] CE(IIW)=C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15

[0039] According to the design of alloy elements and their mass percentage, the carbon equivalent is controlled within 0.5.

[0040] The design principles of each alloy element and its mass percentage are as follows:

[0041] C is the most economical strengthening element. Adding C can significantly improve the strength of steel. However, for 896MPa grade hot-rolled coils for shale gas well casing, in order to ensure excellent toughness and welding performance, the C content is controlled at 0.12% to 0.22%.

[0042] Si plays a role of solid solution strengthening in steel, thereby improving the strength of hot-rolled coils, but too high Si content will affect the surface quality of the steel and damage its performance. Therefore, the Si content is controlled at 0.05% to 0.6% to meet the use requirements.

[0043] Mn can improve the strength of steel through solid solution strengthening, but too high Mn elements will cause center segregation of the material, which is not conducive to the processing performance of hot-rolled coils. Therefore, the Mn content is controlled at 1.00-1.50%.

[0044] The addition of Cr element will improve the atmospheric corrosion resistance of the material. In steel, the addition of Cr element with a mass percentage of > 0.3% is generally beneficial, but when the Cr element content is > 0.6%, the atmospheric corrosion resistance of the material is not significantly increased. Therefore, the Cr content is controlled at 0.4% to 0.6%.

[0045] Mo can play a role in solid solution strengthening and can also promote the formation of bainite, thereby achieving the effect of bainite phase transformation strengthening. Adding Mo within 5% can increase the bainite content and improve the high temperature yield strength of the material. When the content is greater than 5%, Mo usually begins to precipitate, so the Mo content is controlled at 0.3% to 0.5%.

[0046] The B element plays a role in increasing hardenability, improving density and hot rolling performance, and increasing strength. When the B element content exceeds 70PPM, the steel will easily become brittle, so the B element content is controlled at about 5-60PPM.

[0047] The process window conditions for manufacturing hot-rolled coils for 896MPa grade shale gas well straight seam resistance welded casing are as follows: during the high-temperature hot rolling process, the heating temperature of the heating furnace is 1170-1210℃, and the holding time is 1 hour to ensure uniform heating, promote austenite homogenization and sufficient solid solution of micro-alloy elements such as MO and Si in austenite, while also avoiding excessive coarsening of austenite grains; the final rolling temperature is 830-870℃ to avoid coarsening of austenite grains due to excessive final rolling temperature; the rolled steel plate is cooled and then coiled, where the coiling temperature is 550-650℃, and gradient controlled cooling is adopted to ensure the processing performance of the coil.

[0048] The 896MPa grade hot-rolled coil for straight seam resistance welded casing of shale gas wells meets the yield strength of 300-600MPa, elongation ≥20%, and transverse impact energy ≥40J at 0°C, which meets the requirements of room temperature asymptotic forming control of the coil; the grain size conforms to ASTME112NO.9 or finer, and the banded structure ≤3.0, which meets the requirements of welding stability and quality control.

[0049] The SEW process is adopted for pipe making, and the quenching is carried out by heating at a temperature of 860-920℃, holding for 25-50 minutes, internal spraying and external quenching, and heating at a temperature of 510-570℃, holding for 50-100 minutes, and tempering. The performance requirements of the shale gas well casing pipe yield strength of 900-960MPa and Charpy impact energy of 130-220J are guaranteed.

[0050] Secondly, according to the limited manufacturing conditions, after optimizing the composition through material genetic engineering, the composition design of the hot-rolled coil and the mechanical properties of the hot-rolled coil were obtained by calculation, thus achieving the welding performance of the hot-rolled coil for 896MPa-grade shale gas well straight seam resistance welding casing.

[0051] The calculation steps of material genetic engineering are as follows:

[0052] Step 1: Apply the first principle (KS-DFT) to predict and calculate the macroscopic properties. According to the basic idea of ​​KS-DFT, the solution of the density functional principle based on the numerical expression of carbon equivalent can be given by the following equation:

[0053]

[0054] in, is the Hamiltonian of the system, ψ is the wave function of the system, represents the reduced Planck constant, m is the mass of the system, is the Laplace gradient operator of the system in the rectangular coordinate system, is a commonly used central system potential function expression. For this calculation system, the process flow is: coil forming-welding-quenching and tempering heat treatment. The input of the first principle calculation is the content of each element (C, Mn, Cr, Mo, Si, B), the carbon equivalent composition is used as the boundary condition, and the carbon equivalent constraint value is less than 0.5. The Hamiltonian can be constructed according to the element proportion, and then the energy band and wave function characteristics can be calculated using the first principle, thereby predicting its mechanical properties.

[0055] Step 2: Combine the molecular dynamics principle to further calculate its macroscopic mechanical properties. For this calculation system, the input value can be the system energy band and wave function characteristics obtained by the first principle. The software can output macroscopic mechanical properties such as strength-toughness and tensile strength through a large number of step simulations. The basic principle of the molecular dynamics algorithm can be given by the following formula:

[0056]

[0057] Where m is the mass of the system, a is the acceleration of the system, and F(x(t)) is the function of the force acting on the system relative to the displacement. The Laplace operator operation representing potential energy. The core algorithm of molecular dynamics is to solve multiple differential equations like this and perform iterative operations to obtain the macroscopic mechanical properties of the system.

[0058] Step 3: Determine whether the calculation results of material genetic engineering meet the welding performance requirements of hot-rolled coils for 896MPa grade shale gas well straight seam resistance welding casing. If so, process treatment is performed; if not, the distribution ratio is modified for calculation until the welding performance requirements are met for process treatment.

[0059] like Figure 2 As shown, through material genetic engineering simulation calculation, the hot-rolled coil composition design, room-temperature yield strength and toughness after hot rolling, weldability, quenching and tempering heat treatment process and room-temperature yield strength and toughness after quenching and tempering are obtained, which serves the optimization and verification of the hot-rolled coil composition and manufacturing process, so that the component ratio matches the strength and toughness of the hot-rolled coil for 896MPa-grade shale gas well straight seam resistance welded casing and the narrow process window of plastic toughness of the welded pipe.

[0060] Finally, according to the output hot-rolled coil composition design and the mechanical properties of the hot-rolled coil, the process flow of manufacturing 896MPa grade hot-rolled coil for shale gas well straight seam resistance welding casing is as follows:

[0061] The process adopts a series of operations including converter rough refining, refining outside the furnace, slab continuous casting, high temperature hot rolling, and controlled cooling after rolling. The specific steps are as follows:

[0062] Step 1: Put the steel into the furnace, and use argon for low-blowing in the converter and ladle; use ferrosilicon, metallic manganese, and low-carbon ferrochrome to fine-tune the composition during the refining process, deoxidize ferrosilicon powder and aluminum particles, and tap the steel after the temperature and composition are appropriate; the molten steel enters the crystallizer through the tundish, and is cooled through the fan-shaped section to form a cast slab;

[0063] Step 2: The cast slab containing the calculated chemical composition mass percentage is used as a hot-rolled slab, wherein during heating, the continuous casting slab is placed in a heating furnace for heating, the furnace temperature of the continuous casting slab is controlled to be 1170-1210° C., and the initial continuous casting slab thickness is 230 mm;

[0064] Step 3: The continuous casting slab obtained in step 2 is subjected to seven-stand continuous rolling, with a cumulative deformation amount of ≥ 60%. By accumulating large deformation, the deformation band and dislocation density in the deformed austenite are increased, the phase deformation nucleus is increased, and the grain is refined. The final rolling temperature is controlled at 830-870°C to obtain a steel plate with a thickness of 10-13 mm;

[0065] The heating temperature of the heating furnace in the rolling process is 1170-1210° C., and the holding time is 1 hour to ensure uniform heating, promote austenite homogenization and sufficient solid solution of micro-alloy elements such as MO and Si in austenite, while also avoiding excessive coarsening of austenite grains; the final rolling temperature is 830-870° C. to avoid coarsening of austenite grains due to excessively high final rolling temperature.

[0066] Step 4: After the rolled steel plate is cooled, the coiling operation is performed, wherein the coiling temperature is 550-650°C, and gradient controlled cooling is adopted to ensure the toughness of the coil while reducing the formation of banded structure, thereby ensuring good processing performance of the coil.

[0067] A hot-rolled coil for 896MPa shale gas well straight seam electric resistance welded casing has a carbon equivalent of less than 0.5 and excellent welding performance. After being manufactured by SEW process, the 896MPa shale gas well casing with a yield strength of 900-960MPa and a Charpy impact energy of 130-220J can be obtained through appropriate quenching and tempering treatment.

[0068] Through the quenching treatment of heating temperature to 860-920℃, holding time for 25-50 minutes by internal spraying and tempering at 510-570℃, holding time for 50-100 minutes, the performance requirements of shale gas well casing pipe yield strength of 900-960MPa and Charpy impact energy of 130-220J are guaranteed.

[0069] The corresponding relationship between quenching time and tempering time ensures the feasibility of the actual working conditions of the production line; the lower limit of the tempering temperature of 510℃ is adopted to ensure the online smoothness of the actual production tempering process to the hot straightening process, and meet the temperature drop control requirements of the final minimum temperature (400℃) of hot straightening.

[0070] A hot-rolled coil for straight seam resistance welding casing of 896MPa shale gas wells is composed of the following components by mass percentage: C: 0.12% to 0.22%, Mn: 1.0% to 1.6%, Cr: 0.4% to 0.6%, Mo: 0.3% to 0.5%, Si: 0.05% to 0.6%, about 5 to 60PPM of B is added, the carbon equivalent is less than 0.5, and the rest is Fe and unavoidable inclusions. The process adopts a series of operations including converter rough refining, refining outside the furnace, slab continuous casting, high temperature hot rolling, and controlled cooling after rolling.

[0071] Example 1: Rolling 11.5mm 896MPa grade hot-rolled coil for straight seam resistance welding casing of shale gas wells

[0072] A steel billet composed of the following components in mass percentage: C: 0.17%, Si: 0.065%, Mn: 1.21%, Cr: 0.34%, Mo: 0.39%, B: 0.0020%, and the remainder being Fe and inevitable impurities;

[0073] The rationality of the component design is verified by calculation. First, the mass of each component is calculated according to the percentage coefficient, and the wave function characteristics of the system are obtained by using the first principles. Then, through molecular dynamics, the differential equation is solved according to the onlooker force of the system to predict the deformation resistance of the material within the elastic deformation range and the plastic deformation range, and the material yield strength and tensile strength of the component system are obtained to meet the design requirements.

[0074] The preparation steps are as follows:

[0075] The steel material is fed into the furnace, and argon is used for low-level blowing in the converter and ladle. During the refining process, ferrosilicon, metallic manganese, and low-carbon ferrochrome are used for fine-tuning of the composition. Ferrosilicon powder and aluminum particles are deoxidized, and the steel is tapped after the temperature and composition are appropriate. The molten steel enters the crystallizer through the tundish and is cooled through the fan-shaped section to form a cast slab.

[0076] The ingot slab containing the calculated chemical composition mass percentage is charged into a heating furnace for heating at a temperature of 1200°C. After being kept warm in the equalizing section for 1 hour, it is taken out of the furnace for rolling. The starting rolling temperature is 1200°C, the final rolling temperature is 850°C, the coiling temperature is 630°C, and the cooling is controlled after rolling at a cooling rate of 10°C / s to obtain a 11.5mm 896MPa grade hot-rolled coil for shale gas well straight seam resistance welded casing.

[0077] Figure 3 This is a metallographic structure photograph of the coil prepared in Example 1. The test method refers to GB / T 13298-2015.

[0078] The microstructure of the above-mentioned 11.5 mm 896 MPa grade hot-rolled coil for straight seam electric resistance welded casing for shale gas wells is ferrite + pearlite microstructure.

[0079] The mechanical properties of the hot-rolled coil for 11.5mm 896MPa grade shale gas well straight seam resistance welded casing are: at room temperature, Rm is 350MPa, elongation is 35%, transverse impact energy (0℃) is 60J, and banded structure is level 3.0.

[0080] Example 2: Rolling of 12.5mm 896MPa grade hot-rolled coil for straight seam resistance welding casing of shale gas wells:

[0081] A steel billet composed of the following components in mass percentage: C: 0.16%, Si: 0.064%, Mn: 1.5%, Cr: 0.45%, Mo: 0.42%, B: 0.0013%, and the remainder being Fe and inevitable impurities;

[0082] The rationality of the component design is verified by calculation. First, the mass of each component is calculated according to the percentage coefficient, and the wave function characteristics of the system are obtained by using the first principles. Then, through molecular dynamics, the differential equation is solved according to the onlooker force of the system to predict the deformation resistance of the material within the elastic deformation range and the plastic deformation range, and the material yield strength and tensile strength of the component system are obtained to meet the design requirements.

[0083] The preparation steps are as follows:

[0084] The steel material is fed into the furnace, and argon is used for low-level blowing in the converter and ladle. During the refining process, ferrosilicon, metallic manganese, and low-carbon ferrochrome are used for fine-tuning of the composition. Ferrosilicon powder and aluminum particles are deoxidized, and the steel is tapped after the temperature and composition are appropriate. The molten steel enters the crystallizer through the tundish and is cooled through the fan-shaped section to form a cast slab.

[0085] The ingot slab containing the calculated chemical composition mass percentage is charged into a heating furnace for heating at a temperature of 1150°C. After being kept in a uniform temperature section for 1 hour, it is taken out of the furnace for rolling. The starting rolling temperature is 1150°C, the final rolling temperature is 840°C, the coiling temperature is 580°C, and controlled cooling is performed after rolling at a cooling rate of 15°C / s to obtain a 12.5mm 896MPa grade hot-rolled coil for straight seam resistance welded casing of shale gas wells.

[0086] Figure 4 This is a metallographic structure photograph of the coil prepared in Example 2. The test method refers to GB / T 13298-2015.

[0087] The microstructure of the above-mentioned 12.5 mm 896 MPa grade hot-rolled coil for straight seam electric resistance welded casing for shale gas wells is ferrite + granular bainite microstructure, and the bainite content is about 43%.

[0088] The mechanical properties of the above-mentioned 12.5mm 896MPa grade hot-rolled coil for straight seam resistance welded casing of shale gas wells are: at room temperature, Rm is 550MPa, elongation is 21%, transverse impact energy (0°C) is 45J, and banded structure is level 2.5.

[0089] At room temperature, the mechanical properties of Example 1 and Example 2 are tested as shown in Table 1.

[0090] Table 1 Mechanical properties test results of examples at room temperature

[0091]

[0092] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art can still modify or make equivalent substitutions to the specific implementations of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention to be approved.

Claims

1. A method for manufacturing a hot-rolled coil for 896MPa grade shale gas well straight seam resistance welded casing, characterized in that: The following steps are involved: Firstly, according to the required performance of hot-rolled coil for 896MPa grade shale gas well straight seam electric resistance welded casing, the required elements and the mass percentage range of each element, as well as the manufacturing process window conditions are defined; Secondly, according to the limited manufacturing conditions, material genetic engineering is used to calculate the composition design and mechanical properties of the hot-rolled coil. The specific steps are as follows: S1: The mass percentage of each element is used as the input of the first principle calculation and input into the calculation system. The first principle calculation is applied to pre-calculate the macroscopic characteristics and obtain the energy band and wave function characteristics of the system. S2, using the system energy band and wave function characteristics as input, combined with the principle of molecular dynamics to calculate the mechanical properties of hot-rolled coils; S3: judging whether the mechanical properties of the hot-rolled coil obtained in S2 meet the welding properties of the hot-rolled coil for 896MPa grade shale gas well straight seam resistance welding casing, if the welding properties are met, outputting the hot-rolled coil composition design and the mechanical properties of the hot-rolled coil; if the welding properties are not met, modifying the distribution ratio and returning to S1 until the welding properties are met, outputting the hot-rolled coil composition design and the mechanical properties of the hot-rolled coil; Finally, the hot-rolled coil is manufactured according to the output hot-rolled coil composition design and the mechanical properties of the hot-rolled coil.

2. A method for manufacturing a hot-rolled coil for 896MPa grade shale gas well straight seam electric resistance welded casing according to claim 1, characterized in that: In the calculation system of material genetic engineering, the process flow is set as: coil forming-welding-quenching and tempering heat treatment.

3. The method for manufacturing a hot-rolled coil for 896MPa grade shale gas well straight seam electric resistance welded casing according to claim 1, characterized in that: When applying the first principle calculation to pre-calculate the macroscopic properties, the input of the first principle calculation is the mass percentage of C, Mn, Cr, Mo, Si and B; the carbon equivalent composition is used as a boundary condition, and the carbon equivalent is less than 0.

5.

4. The method for manufacturing a hot-rolled coil for 896MPa grade shale gas well straight seam electric resistance welded casing according to claim 1, characterized in that: Mechanical properties include room temperature yield strength and toughness after hot rolling, weldability, and room temperature yield strength and toughness after quenching and tempering.

5. The method for manufacturing a hot-rolled coil for 896MPa grade shale gas well straight seam electric resistance welded casing according to claim 1, characterized in that: The required elements and the mass percentage range of each element are limited as follows: C: 0.12% ~ 0.22%, Mn: 1.0% ~ 1.6%, Cr: 0.4% ~ 0.6%, Mo: 0.3% ~ 0.5%, Si: 0.05% ~ 0.6%, B: 5 ~ 60PPM, and the rest is Fe and unavoidable impurities in the steel billet.

6. The method for manufacturing a hot-rolled coil for 896MPa grade shale gas well straight seam electric resistance welded casing according to claim 1, characterized in that: The process window conditions for manufacturing hot-rolled coils for 896MPa grade shale gas well straight seam resistance welded casing are as follows: during the high-temperature hot rolling process, the heating temperature of the heating furnace is 1170-1210°C, the final rolling temperature is controlled at 830-870°C, and the steel plate with a thickness of 10-13mm is obtained; after rolling, the steel plate is controlled to cool and then coiled, and the coiling temperature is 550-650°C.

7. The method for manufacturing a hot-rolled coil for 896MPa grade shale gas well straight seam electric resistance welded casing according to claim 1, characterized in that: The welding performance requirements of hot-rolled coils for 896MPa grade shale gas well straight seam resistance welded casing are as follows: The yield strength is 300-600MPa, the elongation is ≥20%, the transverse impact energy is ≥40J at 0°C, the grain size conforms to ASTME112 NO.9 or finer, and the banded structure is ≤3.

0.

8. The method for manufacturing a hot-rolled coil for 896MPa grade shale gas well straight seam electric resistance welded casing according to claim 1, characterized in that: The production process includes converter rough refining, refining outside the furnace, slab continuous casting, high temperature hot rolling and controlled cooling after rolling.

9. The method for manufacturing a hot-rolled coil for 896MPa grade shale gas well straight seam electric resistance welded casing according to claim 8, characterized in that: The production process includes converter rough refining, refining outside the furnace, slab continuous casting, high temperature hot rolling and controlled cooling after rolling. The specific operations are as follows: Step 1: Put the steel into the furnace, and use argon for low-blowing in the converter and ladle; use ferrosilicon, metallic manganese, and low-carbon ferrochrome to fine-tune the composition during the refining process, deoxidize ferrosilicon powder and aluminum particles, and tap the steel after the temperature and composition are appropriate; the molten steel enters the crystallizer through the tundish, and is cooled through the fan-shaped section to form a cast slab; Step 2: The cast slab containing the calculated chemical composition mass percentage is used as a hot-rolled slab, the initial continuous casting slab thickness is 230 mm, and during heating, the continuous casting slab is placed in a heating furnace for heating, and the furnace temperature of the continuous casting slab is controlled at 1170-1210° C., and the holding time is 1 hour; Step 3: subjecting the continuously cast slab obtained in step 2 to seven-stand continuous rolling, with a cumulative deformation of ≥ 60%, and a final rolling temperature controlled at 830-870° C. to obtain a steel plate with a thickness of 10-13 mm; Step 4: After the rolled steel plate is cooled, the coiling operation is performed, wherein the coiling temperature is 550-650°C, and gradient controlled cooling is adopted to ensure the toughness of the coil while reducing the formation of banded structure, thereby ensuring good processing performance of the coil.

10. A hot-rolled coil prepared according to the method according to any one of claims 1 to 9 is used for welding 896 MPa grade shale gas well casing, characterized in that: After the pipe is made by the straight seam electric resistance welding process, the 896MPa grade shale gas well casing with a yield strength of 900-960MPa and a Charpy impact energy of 130-220J can be obtained through tempering treatment.

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