High-performance anticorrosion non-magnetic drill collar and manufacturing method thereof

Abstract

The application discloses a kind of high-performance corrosion-resistant non-magnetic drill collar and manufacturing method thereof, belong to stainless steel material technical field, solve the problem that the organization uniformity of non-magnetic drill collar in prior art is poor, mechanical properties and stress corrosion resistance cannot be effectively improved simultaneously.The manufacturing method comprises: smelting molten steel;Preparation ingot;After ingot is discharged, it is forged into billet using fast forging machine;Billet is heated and kept warm;Using radial forging machine, billet is forged into intermediate billet;Intermediate billet is water cooled;After water cooling, intermediate billet is forged using radial forging machine for the second time, and after forging, air cooling obtains finished product billet;Finished product billet is straightened, drilled, reamed, bored, internally controlled rolled, shot blasted, and high-performance corrosion-resistant non-magnetic drill collar is obtained.The grain of the high-performance corrosion-resistant non-magnetic drill collar of the application is small and uniform, and the mechanical properties and corrosion resistance are excellent.

Description

Technical Field

[0001] This invention relates to the field of stainless steel materials technology, and in particular to a high-performance corrosion-resistant non-magnetic drill collar and its manufacturing method. Background Technology

[0002] The environment for offshore oil and gas exploration and extraction is significantly more complex than that on land, requiring exploration through areas rich in chloride ions (Cl). - The drilling rig, consisting of seawater and mud layers, also faces unique geological challenges in deep water, including variable formation pressures and strong ocean current stresses. These extreme conditions place more stringent demands on drilling tools, especially drill collars, particularly in terms of corrosion resistance.

[0003] Enhancing the corrosion resistance of non-magnetic drill collars is crucial for ensuring their long-term stable operation in harsh marine environments. Furthermore, in offshore drilling operations, magnetic measuring instruments play a vital role in geological guidance and wellbore trajectory control, and the non-magnetic nature and stability of non-magnetic drill collars, as the benchmark components for these precision measurements, are essential for ensuring the accuracy of measurement data. Once the drill collar undergoes magnetic changes due to corrosion, it directly weakens measurement accuracy, thereby threatening extraction efficiency and operational safety. Therefore, developing non-magnetic drill collars with higher corrosion resistance is not only necessary to address current challenges but also a significant driving force for technological innovation and industrial upgrading in offshore oil and gas extraction. Summary of the Invention

[0004] In view of the above, the present invention aims to provide a high-performance corrosion-resistant non-magnetic drill collar and its manufacturing method, in order to solve one of the following problems: the existing non-magnetic drill collars have poor microstructure uniformity, and their mechanical properties and stress corrosion resistance cannot be effectively improved at the same time.

[0005] The objective of this invention is mainly achieved through the following technical solutions:

[0006] This invention provides a method for manufacturing a high-performance corrosion-resistant non-magnetic drill collar, the method comprising the following steps:

[0007] Step 1: Melting molten steel;

[0008] Step 2: Prepare the ingot;

[0009] Step 3: After the ingot is taken out of the furnace, it is forged into steel billets using a high-speed forging machine;

[0010] Step 4: Heat and hold the steel billet at the desired temperature;

[0011] Step 5: Forge the steel billet into an intermediate billet using a radial forging machine;

[0012] Step 6: Perform water cooling treatment on the intermediate billet;

[0013] Step 7: The intermediate billet after water cooling is forged a second time using a radial forging machine, and then air-cooled to obtain the finished steel billet.

[0014] Step 8: The finished steel billet is straightened, drilled, enlarged, bored, internally controlled rolling, and shot peening to obtain a high-performance corrosion-resistant non-magnetic drill collar.

[0015] Furthermore, in step 2, the ingot is prepared using the method of electric furnace + AOD + LF + ingot casting + electroslag remelting.

[0016] Furthermore, in step 2, during LF smelting, the aluminum content in the molten steel is controlled to be between 0.025% and 0.035%.

[0017] Furthermore, in step 3, the forging temperature is controlled to be 1050℃~1200℃.

[0018] Furthermore, in step 4, the steel billet is heated to 1150℃~1200℃.

[0019] Furthermore, in step 5, the final forging temperature is controlled to be 890℃~910℃.

[0020] Furthermore, in step 7, the initial forging temperature for the secondary forging is 500℃~550℃.

[0021] Furthermore, in step 8, the straightening deviation must not exceed 2.5mm.

[0022] Furthermore, the composition of the high-performance corrosion-resistant non-magnetic drill collar, by mass percentage, is as follows: 18.30% ≤ Cr < 21.00%, 2.60% ≤ Mo ≤ 3.0%, 4.10% ≤ Ni ≤ 4.50%, 20.50% < Mn ≤ 22.00%, Si ≤ 0.4%, 0.015% < Nb ≤ 0.03%, P ≤ 0.025%, S ≤ 0.01%, C ≤ 0.02%, 0.80% < N ≤ 0.85%, with the balance being Fe and other unavoidable impurities.

[0023] The present invention also provides a high-performance corrosion-resistant non-magnetic drill collar, which is manufactured by the above-described manufacturing method.

[0024] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0025] The manufacturing method of the high-performance corrosion-resistant non-magnetic drill collar of this invention employs rapid forging followed by two radial forging processes, along with shot peening, and precisely controls the process parameters at each step to ensure that the non-magnetic drill collar has fine and uniform grains, achieving a good balance between mechanical properties and corrosion resistance. Furthermore, rapid forging followed by two radial forging processes offers advantages such as improved production efficiency, enhanced surface quality and precision, improved material properties, optimized process flow, and reduced production costs.

[0026] The manufacturing method of this invention ensures deoxidation effect and avoids AlN precipitation by precisely controlling the smelting process parameters, thereby further guaranteeing the excellent mechanical properties and corrosion resistance of the non-magnetic drill collar.

[0027] The manufacturing method of this invention, by precisely controlling the content of elements such as Mo, Ni, Mn, Cr, N, and Nb in the non-magnetic drill collar, can ensure that the non-magnetic drill collar has fine and uniform grains, and achieve a good match between mechanical properties and corrosion resistance.

[0028] The high-performance corrosion-resistant non-magnetic drill collar of the present invention has excellent mechanical properties, with a yield strength of 1150 MPa or more, for example, a yield strength of 1151 to 1200 MPa; a relative magnetic permeability of 1.0025 or less, for example, 1.0021 to 1.0025; the above-mentioned high-performance corrosion-resistant non-magnetic drill collar has excellent corrosion resistance, for example, stress corrosion life ≥1800h, and it passes the intergranular corrosion E method.

[0029] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of what is particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0030] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0031] Figure 1 This is a photograph of the grain size at 1 / 4*R of the non-magnetic drill collar of Embodiment 1 of the present invention;

[0032] Figure 2 This is a photograph of the grain size at 1 / 2*R of the non-magnetic drill collar of Embodiment 1 of the present invention;

[0033] Figure 3 This is a photograph of the grain size at 3 / 4*R of the non-magnetic drill collar of Embodiment 1 of the present invention;

[0034] Figure 4 This is a photograph of the grain size at 1 / 4*R of the non-magnetic drill collar of Comparative Example 5 of the present invention;

[0035] Figure 5 This is a photograph of the grain size at 1 / 2*R of the non-magnetic drill collar of Comparative Example 5 of the present invention;

[0036] Figure 6 This is a photograph of the grain size at 3 / 4*R of the non-magnetic drill collar of Comparative Example 5 of the present invention;

[0037] Figure 7This is a microstructure diagram of the non-magnetic drill collar of Comparative Example 2 of the present invention. Detailed Implementation

[0038] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of the present invention and, together with the embodiments of the present invention, serve to illustrate the principles of the present invention.

[0039] This invention provides a method for manufacturing a high-performance corrosion-resistant non-magnetic drill collar, comprising the following steps:

[0040] Step 1: Melting molten steel;

[0041] Step 2: Prepare the ingot;

[0042] Step 3: After the ingot is taken out of the furnace, it is forged into steel billets using a high-speed forging machine;

[0043] Step 4: Heat and hold the steel billet at the desired temperature;

[0044] Step 5: Forge the steel billet into an intermediate billet using a radial forging machine;

[0045] Step 6: Perform water cooling treatment on the intermediate billet;

[0046] Step 7: The intermediate billet after water cooling is forged a second time using a radial forging machine, and then air-cooled to obtain the finished steel billet.

[0047] Step 8: The finished steel billet is straightened, drilled, enlarged, bored, internally controlled rolling, and shot peening to obtain a high-performance corrosion-resistant non-magnetic drill collar.

[0048] Specifically, in step 2 above, the method of electric furnace + AOD + LF + ingot casting + electroslag remelting is used to prepare ingots, which has the advantages of high efficiency in raw material processing and refining, high quality in forming and solidification, and significant comprehensive advantages.

[0049] Specifically, in step 2 above, the tapping temperature of the electric furnace smelting is 1630–1660℃.

[0050] Specifically, in step 2 above, the target temperature for AOD smelting is set to 1670–1680℃. The N2 / Ar gas blowing system is as follows: during the oxidation period, argon can be blown if C ≤ 0.30%, and nitrogen is blown during reduction; the reducing slag system is CaO-SiO2-Al2O3-MgO, with a ratio of 45:20:30:5.

[0051] Specifically, in step 2 above, in order to ensure the deoxidation effect and at the same time avoid AlN precipitation as much as possible, the aluminum content in the molten steel is controlled between 0.025% and 0.035% during LF smelting.

[0052] Specifically, in step 3 above, after the ingot is taken out of the furnace, it is forged into a steel billet by a 4500-ton high-speed forging machine. The end diameter of the steel billet is actually calculated based on the size of the finished diameter forged steel billet and the final forging deformation.

[0053] Specifically, in step 3 above, the ingot is cold-loaded, and the surface of the ingot is inspected before loading into the furnace to confirm that there are no visible cracks, inclusions, or other surface defects.

[0054] Specifically, in step 3 above, considering that excessively high initial forging temperatures can lead to overheating or burning, while excessively low initial forging temperatures can easily cause cracks, excessively high final forging temperatures can result in coarse grains and defects, while excessively low final forging temperatures can make the forging process difficult, the initial forging temperature is controlled at 1050℃~1200℃, for example 1070℃, 1090℃, 1110℃, 1130℃, 1150℃, 1170℃, 1190℃, and the final forging temperature is controlled at 940℃~960℃, for example 940℃, 950℃, 960℃.

[0055] Specifically, step 4 above aims to promote the uniform diffusion of segregated elements. Considering that excessively high temperatures or prolonged holding times lead to coarse grains and a thicker oxide scale, while excessively low temperatures or short holding times result in insufficient element diffusion and uneven microstructure, the steel billet is heated to 1150℃~1200℃, for example, 1160℃, 1170℃, 1180℃, or 1190℃, and held for 1~4 hours, for example, 2 hours or 3 hours.

[0056] Specifically, in step 5 above, after the steel billet is heated, it is forged into an intermediate billet by a 1800-ton radial forging machine.

[0057] Specifically, in step 5 above, considering that excessively high final forging temperatures in radial forging mills can lead to coarse grains and defects, while excessively low final forging temperatures can cause difficulties in the forging process, the final forging temperature is controlled to be between 890℃ and 910℃, for example, 890℃, 900℃, or 910℃.

[0058] Specifically, in step 6 above, the surface temperature of the intermediate billet after water cooling is 600℃~650℃, for example 610℃, 620℃, 630℃, 640℃.

[0059] Specifically, in step 7 above, considering that excessively high temperatures during the secondary forging of the radial forging mill can easily lead to coarse grains and defects, while excessively low final forging temperatures result in high deformation resistance, the initial forging temperature of the secondary forging is controlled to be between 500℃ and 550℃, for example, 510℃, 520℃, 530℃, or 540℃.

[0060] Specifically, in step 7 above, considering that the stainless steel of the present invention can effectively improve yield strength by appropriately increasing the deformation amount during secondary forging in a radial forging mill, but excessive deformation amount will greatly reduce stress corrosion life, the inventors, after in-depth research and comprehensive consideration, have controlled the deformation amount of secondary forging to 10% to 12%, for example, 10%, 11%, or 12%.

[0061] Specifically, in step 8 above, the straightening deviation must not exceed 2.5mm.

[0062] Specifically, in step 8 above, the surface roughness of the boring hole is RA ≥ 1.6 μm.

[0063] Specifically, in step 8 above, the shot used for shot peening is a mixture of stainless steel shot with a particle size of 0.3 to 0.6 mm and a coverage rate of 200%.

[0064] Specifically, the composition of the above-mentioned high-performance corrosion-resistant non-magnetic drill collar, by mass percentage, is as follows: 18.30% ≤ Cr < 21.00%, 2.60% ≤ Mo ≤ 3.0%, 4.10% ≤ Ni ≤ 4.50%, 20.50% < Mn ≤ 22.00%, Si ≤ 0.4%, 0.015% < Nb ≤ 0.03%, P ≤ 0.025%, S ≤ 0.01%, C ≤ 0.02%, 0.80% < N ≤ 0.85%, with the balance being Fe and other unavoidable impurities.

[0065] The following provides a detailed explanation of the function and dosage selection of the components contained in this invention.

[0066] C is one of the alloying elements that strongly promotes the formation of austenite and expands the austenite phase region. However, due to its tendency to form carbides, it leads to chromium-depleted regions at grain boundaries, resulting in an increased susceptibility to grain boundary corrosion. However, when the C content of austenitic stainless steel is less than 0.02%, all C dissolves in austenite. Even when heated between 450°C and 850°C, "chromium-depleted regions" will not form at grain boundaries. Therefore, this invention controls C to ≤ 0.02%.

[0067] Cr is the main element for forming the passivation film, which can increase the pitting corrosion resistance of super austenitic stainless steel. Increasing the Cr content will make the passivation film more stable and improve its resistance to high-temperature oxidation. However, increasing the Cr content will promote the precipitation of intermetallic compounds such as σ phase and Laves phase, resulting in a decrease in the steel's plasticity and toughness, and at the same time impairing the steel's corrosion resistance. Taking all factors into consideration, this invention controls the Cr content to 18.30% ≤ Cr < 21.00%.

[0068] Ni is an austenitizing element; its addition can improve the stability of the passivation film in stainless steel and inhibit the formation of intermetallic phases (such as σ and χ phases). Due to the proper combination of Ni and Cr, the corrosion resistance of stainless steel can be significantly improved. Furthermore, Ni is the only element that improves resistance to transgranular stress corrosion in many media, but it is relatively expensive. Considering all factors, this invention controls the Ni content to 4.10% ≤ Ni ≤ 4.50%.

[0069] Nitrogen's austenite-forming stability is comparable to carbon, about 30 times that of Ni. Ni's properties are similar to those of carbon; it is a major element in the formation of interstitial phases, determined by its small atomic size and electronic structure. Ni atoms readily distribute uniformly in solid solutions due to their occupies octahedral interstitial positions. The interfacial energy between iron-based materials and nitrides is relatively low, making it easier for nitrides to form dispersed, fine reinforcing phases. Adding a small amount of Ni can significantly improve the mechanical properties and resistance to localized corrosion of steel. Adding a large amount of Ni improves the corrosion resistance, ensures the forgeability and toughness of steel, and increases strength. Furthermore, the addition of Ni causes Cr and Mo to accumulate in the passivation film on the stainless steel surface, improving the passivation ability of the steel. Ni can react with H in solution... + The reaction forms NH + It reacts with NH3 to increase the pH value in the micro-region, thus slowing down corrosion, and can also form NO3. - This process facilitates passivation and repassivation, and also allows for the formation of chromium-rich nitrides at the metal-passivation film interface, thereby improving the stability of the stainless steel passivation film and enhancing its corrosion resistance. Taking all factors into consideration, this invention controls N to be between 0.80% and 0.85%.

[0070] Mo can broaden the passivation range of austenitic stainless steel, enabling it to passivate earlier and improving its corrosion resistance in reducing media. This is mainly because molybdenum can form molybdates, which are anodic corrosion inhibitors, reducing anodic reactivity. In marine atmospheres, chromium (Cr) alone, even at a Cr content of 24%, is insufficient to effectively prevent stainless steel corrosion; Mo must be added. The formation of Mo in the passivation film is complex, with the inner layer containing Mo. 4+ Ions, with the outer layer containing Mo 6+ The formation of an ion-passivated film can prevent further corrosion of the substrate, especially in Cl... - When the passivation film is damaged, it can be rapidly regenerated, thereby improving the corrosion resistance of stainless steel. Taking all factors into consideration, this invention controls the content of Mo to be 2.60% ≤ Mo ≤ 3.00%.

[0071] Mn can increase the solubility of nitrogen in austenitic stainless steel, but Mn exists in the steel in the form of MnS, which leads to a decrease in resistance to chloride pitting corrosion and crevice corrosion. Taking all factors into consideration, this invention controls the content of Mn to be between 20.50% and 22.00%.

[0072] Nb plays a stabilizing role and can reduce the tendency of intergranular corrosion in welding materials. This is because Nb has a much greater affinity for C than Cr, preferentially combining with C to form NbC, thus preventing or reducing M 23 The formation of C6 prevents sensitized intergranular corrosion. The addition of a small amount of Nb in this invention refines the grains, thereby improving the problem of coarse or mixed grains in steel ingots. Taking all factors into account, this invention controls the Nb content to be between 0.015% and 0.03%.

[0073] Sulfur (S) is often considered a harmful element, affecting the hot plasticity of steel and reducing its corrosion resistance. This is mainly because MnS is easily soluble in acidic chloride solutions and often becomes a corrosion source. However, the addition of S can improve the machinability of stainless steel. This invention controls S to ≤0.01%.

[0074] P is generally considered a harmful impurity, which reduces the resistance to corrosion by nitric acid of various concentrations in both the solid solution and sensitized states. It is particularly detrimental in concentrated nitric acid and chromium-containing solutions. 6+ The susceptibility to intergranular corrosion in nitric acid and liquid phases with solid solutions is significantly enhanced. This invention controls P ≤ 0.025%.

[0075] Specifically, in order to further improve the overall performance of the above-mentioned high-performance corrosion-resistant non-magnetic drill collar, the composition of the above-mentioned high-performance corrosion-resistant non-magnetic drill collar by mass percentage is as follows: 18.5%≤Cr<21.00%, 2.65%≤Mo≤3.00%, 4.15%≤Ni≤4.50%, 20.60%<Mn≤22.00%, Si≤0.4%, 0.016%≤Nb≤0.029%, P≤0.025%, S≤0.01%, C≤0.02%, 0.81%≤N≤0.85%, with the balance being Fe and other unavoidable impurities.

[0076] The present invention also provides a high-performance corrosion-resistant non-magnetic drill collar, which is prepared by the above-described manufacturing method.

[0077] Specifically, the microstructure of the aforementioned high-performance corrosion-resistant non-magnetic drill collar is austenite, with fine and uniform grains. The grain size level is finer than 6, for example, the grain size is 6.5 to 7.5, and the difference in grain size level at different locations is within 1 level.

[0078] Specifically, the aforementioned high-performance corrosion-resistant non-magnetic drill collars possess excellent mechanical properties, with a yield strength exceeding 1150 MPa (e.g., 1151–1200 MPa); a relative magnetic permeability below 1.0025 (e.g., 1.0021–1.0025); and excellent corrosion resistance, with a stress corrosion life ≥1800 h and passing the intergranular corrosion E-method.

[0079] The manufacturing method of the high-performance corrosion-resistant non-magnetic drill collar of this invention employs rapid forging followed by two radial forging processes, along with shot peening, and precisely controls the process parameters at each step to ensure that the non-magnetic drill collar has fine and uniform grains, achieving a good balance between mechanical properties and corrosion resistance. Furthermore, rapid forging followed by two radial forging processes offers advantages such as improved production efficiency, enhanced surface quality and precision, improved material properties, optimized process flow, and reduced production costs.

[0080] The manufacturing method of this invention ensures deoxidation effect and avoids AlN precipitation by precisely controlling the smelting process parameters, thereby further guaranteeing the excellent mechanical properties and corrosion resistance of the non-magnetic drill collar.

[0081] The manufacturing method of this invention, by precisely controlling the content of elements such as Mo, Ni, Mn, Cr, N, and Nb in the non-magnetic drill collar, can ensure that the non-magnetic drill collar has fine and uniform grains, and achieve a good match between mechanical properties and corrosion resistance.

[0082] The high-performance corrosion-resistant non-magnetic drill collar of the present invention has excellent mechanical properties, with a yield strength of 1150 MPa or more, for example, a yield strength of 1151 to 1200 MPa; a relative magnetic permeability of 1.0025 or less, for example, 1.0021 to 1.0025; the above-mentioned high-performance corrosion-resistant non-magnetic drill collar has excellent corrosion resistance, for example, stress corrosion life ≥1800h, and it passes the intergranular corrosion E method.

[0083] The following specific embodiments and comparative examples demonstrate the advantages of precise control of the composition and process parameters of the high-performance corrosion-resistant non-magnetic drill collar of the present invention.

[0084] Examples 1-5 of the present invention provide a high-performance corrosion-resistant non-magnetic drill collar and a method for manufacturing the same. The chemical composition of the non-magnetic drill collars of Examples 1-5 is shown in Table 1.

[0085] The methods for preparing the steel in Examples 1-5 include:

[0086] Step 1: Melting molten steel;

[0087] Step 2: Prepare the ingot;

[0088] Step 3: After the ingot is taken out of the furnace, it is forged into steel billets using a high-speed forging machine;

[0089] Step 4: Heat and hold the steel billet at the desired temperature;

[0090] Step 5: Forge the steel billet into an intermediate billet using a radial forging machine;

[0091] Step 6: Perform water cooling treatment on the intermediate billet;

[0092] Step 7: The intermediate billet after water cooling is forged a second time using a radial forging machine, and then air-cooled to obtain the finished steel billet;

[0093] Step 8: The finished steel billet is straightened, drilled, enlarged, bored, internally controlled rolling, and shot peening to obtain a high-performance corrosion-resistant non-magnetic drill collar;

[0094] Specifically, in step 2, ingots are prepared using an electric furnace + AOD + LF + ingot casting + electroslag remelting method; the tapping temperature of the electric furnace melting is 1630-1660℃; the target temperature of the AOD melting is set at 1670-1680℃; the N2 / Ar gas blowing system is argon blowing during the oxidation period when C≤0.30%, and nitrogen blowing during reduction; the reducing slag system is CaO-SiO2-Al2O3-MgO, with a ratio of 45:20:30:5; during LF melting, the aluminum content in the molten steel is controlled at 0.03%.

[0095] Specifically, in step 8, the straightening deviation is less than 2.5 mm; the surface roughness of the boring hole is above 1.6 μm; and the shot used for shot peening is a mixture of stainless steel shot with a particle size of 0.3 to 0.6 mm and a coverage rate of 200%.

[0096] The specific process parameters of Examples 1-5 are shown in Table 2; the microstructure of the produced high-performance corrosion-resistant non-magnetic drill collar is shown in Table 3, and the main performance test results are shown in Table 4.

[0097] The grain size of different parts of the non-magnetic drill collar in Example 1 is as follows: Figures 1-3 As shown.

[0098] As can be seen from the results in Tables 3 and 4, the high-performance corrosion-resistant non-magnetic drill collar of the present invention has fine and uniform grains, for example, a grain size level finer than 6, such as a grain size of 6.5 to 7.5, with the grain size level difference between different locations within 1 level. The high-performance corrosion-resistant non-magnetic drill collar of the present invention exhibits excellent mechanical properties, with a yield strength exceeding 1150 MPa, for example, a yield strength of 1151 to 1200 MPa; and a relative magnetic permeability below 1.0025, for example, 1.0021 to 1.0025. The aforementioned high-performance corrosion-resistant non-magnetic drill collar also exhibits excellent corrosion resistance, for example, a stress corrosion life ≥1800 h, and passes the intergranular corrosion E-method.

[0099] Table 1 Chemical composition, wt%

[0100]

[0101]

[0102] Table 2 Specific Process Parameters

[0103]

[0104] Table 3 Grain size levels at different locations

[0105]

[0106]

[0107] Table 4 Performance

[0108]

[0109] The inventors conducted extensive experimental research during the research process, and some poorly performing solutions are now presented as comparative examples.

[0110] Comparative Example 1

[0111] This comparative example provides a non-magnetic drill collar and its preparation method. The overall steps of steps 1-2 of the preparation method are the same as those in Example 1. The difference is that in step 2, during LF melting, the aluminum content in the molten steel is 0.02%, and the composition of other elements is the same as in Example 1. The ingot cracked during forging. The reason for this is that the Al content was insufficient during LF melting, resulting in incomplete removal of O from the molten steel. The excessively high O content formed large inclusions, leading to cracking during forging.

[0112] Comparative Example 2

[0113] This comparative example provides a non-magnetic drill collar and its preparation method. The overall steps of the preparation method are the same as those in Example 1, except that in step 2, during LF melting, the aluminum content in the molten steel is controlled at 0.04%, while the composition of other elements is the same as in Example 1. The mechanical properties and corrosion resistance of Comparative Example 2 are poor. The reason for this is that the Al content is too high. Although the O content is low, AlN precipitates appear in the microstructure. Figure 7 This affects the corrosion resistance and mechanical properties of steel.

[0114] Comparative Example 3

[0115] This comparative example provides a non-magnetic drill collar and its preparation method. Its components are shown in Table 1 above, and the specific process parameters of the preparation method are shown in Table 2. Since shot peening was not performed, the corrosion resistance of this comparative example is poor.

[0116] Comparative Example 4

[0117] This comparative example provides a non-magnetic drill collar and its preparation method. Its components are shown in Table 1 above, and the specific process parameters of the preparation method are shown in Table 2. Since shot peening was not performed, the corrosion resistance of this comparative example is poor.

[0118] Comparative Example 5

[0119] This comparative example provides a non-magnetic drill collar and its preparation method. The composition is shown in Table 1 above, and the specific process parameters for the preparation method are shown in Table 2. Due to unsuitable composition, the microstructure of this comparative example has poor uniformity, and its corrosion resistance and mechanical properties are relatively poor. The grain size of different parts of the non-magnetic drill collar in this comparative example is shown below. Figures 4-6 As shown.

[0120] Comparative Example 6

[0121] This comparative example provides a non-magnetic drill collar and its preparation method. Its components are shown in Table 1 above, and the specific process parameters of the preparation method are shown in Table 2. Due to the unsuitable composition, the microstructure of this comparative example has poor uniformity, and its corrosion resistance and mechanical properties are poor.

[0122] Comparative Example 7

[0123] This comparative example provides a non-magnetic drill collar and its preparation method. Its composition is the same as that of Example 1. The specific process parameters of the preparation method are shown in Table 2. Due to some process parameters of the preparation method not meeting the requirements, the microstructure of this comparative example has poor uniformity, corrosion resistance and mechanical properties.

[0124] The microstructure and main performance test results of the comparative non-magnetic drill collars are shown in Tables 3-4 above.

[0125] 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 changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for manufacturing a high-performance corrosion-resistant non-magnetic drill collar, characterized in that, The high-performance corrosion-resistant non-magnetic drill collar comprises, by mass percentage: 18.30%≤Cr<21.00%, 2.60%≤Mo≤3.0%, 4.10%≤Ni≤4.50%, 20.50%<Mn≤22.00%, Si≤0.4%, 0.015%<Nb≤0.03%, P≤0.025%, S≤0.01%, C≤0.02%, 0.80%<N≤0.85%, with the balance being Fe and other unavoidable impurities; The manufacturing method includes the following steps: Step 1: Melting molten steel; Step 2: Prepare the ingot; Step 3: After the ingot is taken out of the furnace, it is forged into steel billets using a high-speed forging machine; Step 4: Heat and hold the steel billet at the desired temperature; Step 5: Forge the steel billet into an intermediate billet using a radial forging machine; Step 6: Perform water cooling treatment on the intermediate billet; Step 7: The intermediate billet after water cooling is forged a second time using a radial forging machine, and then air-cooled to obtain the finished steel billet. Step 8: The finished steel billet is straightened, drilled, enlarged, bored, internally controlled rolling, and shot peening to obtain a high-performance corrosion-resistant non-magnetic drill collar; In step 2, the ingot is prepared using an electric furnace + AOD + LF + ingot casting + electroslag remelting method; during LF melting, the aluminum content in the molten steel is controlled between 0.025% and 0.035%. In step 3, the initial forging temperature is controlled at 1050℃~1200℃; the final forging temperature is controlled at 940℃~960℃. In step 4, the steel billet is heated to 1150℃~1200℃; In step 5, the final forging temperature is controlled to be 890℃~910℃; In step 7, the initial forging temperature of the secondary forging is 500℃~540℃; the deformation amount of the secondary forging is controlled to be 10%~12%; In step 8, the shot used for shot peening is a mixture of stainless steel shot with a particle size of 0.3-0.6 mm. The microstructure of the high-performance corrosion-resistant non-magnetic drill collar is austenite with fine and uniform grains. The grain size is finer than level 6, and the difference in grain size between different locations is within level 1. The high-performance corrosion-resistant non-magnetic drill collar has a yield strength of over 1150 MPa, a relative permeability of less than 1.0025, and a stress corrosion life of ≥1800 h.

2. The manufacturing method according to claim 1, characterized in that, In step 3, the forging temperature is controlled to be 1070℃~1200℃.

3. The manufacturing method according to claim 1, characterized in that, In step 4, the steel billet is heated to 1160℃~1200℃.

4. The manufacturing method according to claim 1, characterized in that, In step 5, the final forging temperature is controlled to be 900℃~910℃.

5. The manufacturing method according to claim 1, characterized in that, In step 7, the initial forging temperature for the secondary forging is 510℃~540℃.

6. The manufacturing method according to any one of claims 1 to 5, characterized in that, In step 8, the straightening deviation shall not exceed 2.5 mm.

7. The manufacturing method according to any one of claims 1 to 5, characterized in that, The high-performance corrosion-resistant non-magnetic drill collar comprises, by mass percentage: 18.5%≤Cr<21.00%, 2.60%≤Mo≤3.0%, 4.10%≤Ni≤4.50%, 20.50%<Mn≤22.00%, Si≤0.4%, 0.015%<Nb≤0.03%, P≤0.025%, S≤0.01%, C≤0.02%, 0.80%<N≤0.85%, with the balance being Fe and other unavoidable impurities.

8. A high-performance, corrosion-resistant, non-magnetic drill collar, characterized in that, The high-performance corrosion-resistant non-magnetic drill collar is manufactured using the manufacturing method described in any one of claims 1 to 7.

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