High-strength high-corrosion-resistant alloy and preparation method thereof

Abstract

This invention discloses a high-strength, high-corrosion-resistant alloy and its preparation method, belonging to the field of corrosion-resistant alloy technology. It solves the problem that existing iron-nickel-based corrosion-resistant alloys cannot meet the high strength and high corrosion resistance requirements of oil well pipe materials. The high-strength, high-corrosion-resistant alloy comprises, by mass percentage: C≤0.03%, 27.0%<Cr≤29.0%, 29.5%<Ni≤32.5%, 0.08%<N≤0.20%, 0.10%<W≤1.00%, Mn≤1.0%, 3.0%<Mo≤4.0%, 1.0%<Cu≤1.4%, Si≤1.0%, P≤0.03%, S≤0.03%; the balance being Fe and unavoidable trace impurities. The high-strength, high-corrosion-resistant alloy of this invention exhibits excellent tensile strength, yield strength, hardness, and corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of corrosion-resistant alloy technology, and in particular to a high-strength, high-corrosion-resistant alloy and its preparation method. Background Technology

[0002] Materials for oil well tubing have undergone several generations of development, including martensitic stainless steel, duplex stainless steel, iron-nickel-based corrosion-resistant alloys, and corrosion-resistant alloys. Martensitic stainless steel can only be used in shallow oil and gas wells containing CO2; duplex stainless steel can be used in oil and gas wells where H2S and CO2 coexist; however, iron-nickel-based alloys and nickel-based alloys are needed as materials for oil well tubing in harsh environments with high temperature, high pressure, and high acidity partial pressure. However, with the increasing depth of oil and gas field development, higher temperatures, pressures, and corrosive media concentrations place more stringent demands on oil well tubing materials, especially their mechanical properties. Traditional iron-nickel-based corrosion-resistant alloys cannot meet the requirements for steel grades above 125ksi, and cannot meet the service environment of oil and gas fields with high depth and high acidity concentrations (temperature ≥175℃, CO2 partial pressure ≥3.5MPa, H2S partial pressure ≥3.5MPa). Therefore, how to provide a high-strength, highly corrosion-resistant alloy has become an urgent problem to be solved. Summary of the Invention

[0003] In view of the above, the present invention aims to provide a high-strength, high-corrosion-resistant alloy and its preparation method, in order to solve the problem that existing iron-nickel-based corrosion-resistant alloys cannot meet the high strength and high corrosion resistance requirements of oil well pipe materials.

[0004] The objective of this invention is mainly achieved through the following technical solutions:

[0005] On one hand, the present invention provides a high-strength, high-corrosion-resistant alloy, the composition of which, by mass percentage, comprises: C≤0.03%, 27.0%<Cr≤29.0%, 29.5%<Ni≤32.5%, 0.08%<N≤0.20%, 0.10%<W≤1.00%, Mn≤1.0%, 3.0%<Mo≤4.0%, 1.0%<Cu≤1.4%, Si≤1.0%, P≤0.03%, S≤0.03%; the balance being Fe and unavoidable trace impurities.

[0006] Furthermore, the composition of the high-strength, high-corrosion-resistant alloy, by mass percentage, can be: 0.009% ≤ C ≤ 0.02%, 27.3% ≤ Cr ≤ 28.8%, 30.0% ≤ Ni ≤ 32.0%, 0.10% ≤ N ≤ 0.20%, 0.50% ≤ W ≤ 1.00%, 0.10% ≤ Mn ≤ 0.50%, 3.2% ≤ Mo ≤ 4.0%, 1.05% ≤ Cu ≤ 1.4%, 0.10% ≤ Si ≤ 0.8%, P ≤ 0.03%, S ≤ 0.03%, with the balance being Fe and unavoidable trace impurities.

[0007] Furthermore, the microstructure of the high-strength, high-corrosion-resistant alloy contains no precipitates or inclusions.

[0008] This invention also provides a method for preparing the above-mentioned high-strength, high-corrosion-resistant alloy, comprising:

[0009] Step 1: Prepare the raw materials according to the mass percentage of each component of the high-strength, high-corrosion-resistant alloy, and then melt the steel.

[0010] Step 2: The ingot is prepared by using an electric furnace + argon-oxygen decarburization ladle refining + electroslag remelting method;

[0011] Step 3: Heat the ingot and hold it at that temperature for homogenization.

[0012] Step 4: After the ingot is heated and removed from the furnace, it is immediately forged into round steel using a high-speed forging machine.

[0013] Step 5: Perform water cooling treatment on the round steel.

[0014] Step 6: Heat the round steel and keep it warm;

[0015] Step 7: After the round steel is heated and removed from the furnace, it is immediately hot-extruded to obtain a rough tube;

[0016] Step 8: The rough tube is cold rolled to obtain a finished high-strength, high-corrosion-resistant alloy.

[0017] Furthermore, in step 3, the ingot is heated to 1180℃~1220℃ and held for 18~23 hours.

[0018] Furthermore, in step 4, the initial forging temperature of the high-speed forging mill is controlled to be 1140℃~1180℃.

[0019] Furthermore, in step 4, the final forging temperature of the high-speed forging mill is controlled to be 900℃~950℃.

[0020] Furthermore, in step 5, the forged round steel is controlled to undergo water cooling within 60 seconds.

[0021] Furthermore, in step 6, the heat preservation temperature is controlled at 1200℃~1220℃, and the heat preservation time is more than 5 hours.

[0022] Furthermore, in step 7, the extrusion ratio is controlled to be 10-20.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] a) The high-strength, high-corrosion-resistant alloy of the present invention ensures good tensile strength, yield strength, hardness, and corrosion resistance by precisely controlling the content of each component; for example, increasing the mass percentage of nitrogen element ensures good tensile strength, yield strength, hardness, and corrosion resistance; increasing the content of w element ensures improved wear resistance, strength, and corrosion resistance; and reducing the content of Ni and Mo elements ensures lower material costs.

[0025] (b) The preparation method of the high-strength, high-corrosion-resistant alloy of the present invention reduces the generation of harmful precipitates and inclusions by precisely controlling the composition, and combines this with measures such as lowering the initial forging temperature and precisely controlling the final forging temperature to ensure that the alloy of the present invention will not crack during forging; by reducing the number of cold rolling passes and reducing the amount of cold rolling deformation, the alloy of the present invention reduces damage to equipment during cold rolling. The method of the present invention is simple, causes little damage to equipment, is economical and feasible, and is suitable for large-scale industrial production.

[0026] c) The high-strength, high-corrosion-resistant alloy of the present invention has good tensile strength, yield strength, hardness and corrosion resistance; for example, the tensile strength reaches 980 MPa or more (e.g. 989-1060 MPa), the yield strength reaches 940 MPa or more (e.g. 940-1010 MPa), the Brinell hardness is 315-350 HBW, there is no tendency for intergranular corrosion, no stress corrosion cracking, and the average corrosion rate is less than 0.0022 mm / a (e.g. 0.0015-0.0022 mm / a).

[0027] d) The high-strength, high-corrosion-resistant alloy of the present invention has low content of alloying elements such as Ni and Mo, resulting in low cost and achieving excellent performance of high strength and high corrosion resistance at low cost.

[0028] Other features and advantages of the invention will be set forth in the following description, 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, claims, and drawings. Attached Figure Description

[0029] 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.

[0030] Figure 1 This is a microstructure diagram of the high-strength, high-corrosion-resistant alloy from Example 1;

[0031] Figure 2 This is a microstructure diagram of the high-strength, high-corrosion-resistant alloy from Example 2;

[0032] Figure 3 This is a microstructure diagram of the high-strength, high-corrosion-resistant alloy from Example 3;

[0033] Figure 4 This is a microstructure diagram of the high-strength, high-corrosion-resistant alloy from Example 4;

[0034] Figure 5 This is a microstructure diagram of the high-strength, high-corrosion-resistant alloy from Example 5;

[0035] Figure 6 This is a microstructure diagram of Comparative Example 1;

[0036] Figure 7 This is a microstructure diagram of Comparative Example 2;

[0037] Figure 8 This is a microstructure diagram of Comparative Example 3. 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 high-strength, high-corrosion-resistant alloy, the composition of which, by mass percentage, comprises: C≤0.03%, 27.0%<Cr≤29.0%, 29.5%<Ni≤32.5%, 0.08%<N≤0.20%, 0.10%<W≤1.00%, Mn≤1.0%, 3.0%<Mo≤4.0%, 1.0%<Cu≤1.4%, Si≤1.0%, P≤0.03%, S≤0.03%; the balance being Fe and unavoidable trace impurities.

[0040] The following details the function and dosage selection of the components contained in this invention:

[0041] C: In the high-strength, high-corrosion-resistant alloy of this invention, the main role of C is to maintain an ultra-low carbon state to ensure corrosion resistance. Simultaneously, C, as an interstitial element, can enhance strength. Excessive C content will exacerbate Cr content issues. 23 The precipitation of C6-type carbides reduces corrosion resistance. Therefore, this invention limits the C content to C≤0.030%.

[0042] Nitrogen (N): In the high-strength, high-corrosion-resistant alloy of this invention, nitrogen (N) not only acts as an interstitial element alongside carbon (C) to enhance strength, but also strongly forms and stabilizes the austenite phase region, thus improving corrosion resistance. However, nitrogen only has a beneficial effect on corrosion resistance when it exists in a solid solution state; conversely, if it appears as a precipitated phase, it will affect mechanical properties and corrosion resistance. Excessive nitrogen content will exacerbate the precipitation of Cr₂N-type nitrides, reducing mechanical properties and corrosion resistance, while insufficient nitrogen content will fail to guarantee the required strength. Therefore, this invention limits the nitrogen content to 0.08% < N ≤ 0.20%.

[0043] Cr: In the alloy of this invention, the main role of Cr is to improve corrosion resistance and increase the saturated solubility of N. Cr, Mo, and N elements work together to improve corrosion resistance. However, excessive Cr will exacerbate corrosion problems. 23 The precipitation of C6-type carbides, Cr2N-type nitrides, and Cr-rich σ-phase intermetallic compounds reduces mechanical properties and corrosion resistance. Too low a Cr content will reduce the saturated solubility of N. Therefore, this invention limits the Cr content to 27.0% < Cr ≤ 29.0%.

[0044] Ni: In the alloy of this invention, Ni mainly acts as an element that strongly forms and stabilizes the austenite phase region, expands the area of ​​the austenite phase region, improves processing performance, and reduces the tendency of σ phase precipitation. Too high a Ni content will increase production costs, while too low a Ni content will reduce the stability of the austenite phase region and reduce microstructure properties. Therefore, this invention limits the Ni content to 29.5% < Ni ≤ 32.5%.

[0045] W: In the alloy of this invention, W mainly improves wear resistance and increases service life. At the same time, a small amount of W can also improve strength and corrosion resistance. Excessive W will exacerbate the precipitation of Laves phase and affect toughness. Therefore, this invention limits the W content to 0.10% < W ≤ 1.0%.

[0046] Mn: In the alloy of this invention, the stabilizing effect of Mn on the austenite phase region is replaced by N. The Mn content is reduced to below 1.0% to avoid the formation of manganese sulfide and increase corrosion resistance. Therefore, the Mn content is limited to Mn≤1.0% in this invention.

[0047] Mo: In the alloy of this invention, Mo mainly improves corrosion resistance. According to the pitting corrosion equivalent formula: PREN = Cr% + 3.3Mo% + 16N, Mo, Cr, and N elements synergistically improve corrosion resistance. Too much Mo will reduce the area of ​​the austenite phase region and increase the tendency for σ phase precipitation. Too little Mo will reduce corrosion resistance. Therefore, this invention limits the Mo content to 3.0% < Mo ≤ 4.0%.

[0048] Cu: In the iron-nickel-based corrosion-resistant alloy of the present invention, Cu mainly improves corrosion resistance and increases work hardening tendency. The improvement of corrosion resistance by Cu is matched by that of Mn, and the improvement of work hardening tendency by Cu is matched by that of Ni. Too low Cu content can easily cause cracking during cold working. Therefore, the present invention limits the Cu content to 1.0% < Cu ≤ 1.4%.

[0049] To further improve the overall performance of the above-mentioned high-strength and high-corrosion-resistant alloy, the composition of the above-mentioned high-strength and high-corrosion-resistant alloy, by mass percentage, can be: 0.009%≤C≤0.02%, 27.3%≤Cr≤28.8%, 30.0%≤Ni≤32.0%, 0.10%≤N≤0.20%, 0.50%≤W≤1.00%, 0.10%≤Mn≤0.50%, 3.2%≤Mo≤4.0%, 1.05%≤Cu≤1.4%, 0.10%≤Si≤0.8%, P≤0.03%, S≤0.03%, with the balance being Fe and unavoidable trace impurities.

[0050] This invention also provides a method for preparing the above-mentioned high-strength, high-corrosion-resistant alloy, comprising:

[0051] Step 1: Prepare the raw materials according to the mass percentage of each component of the high-strength, high-corrosion-resistant alloy, and then melt the steel.

[0052] Step 2: The ingot is prepared by using an electric furnace + argon-oxygen decarburization ladle refining + electroslag remelting method;

[0053] Step 3: Heat the ingot and hold it at that temperature for homogenization.

[0054] Step 4: After the ingot is heated and removed from the furnace, it is immediately forged into round steel using a high-speed forging machine.

[0055] Step 5: Perform water cooling treatment on the round steel.

[0056] Step 6: Heat the round steel and keep it warm;

[0057] Step 7: After the round steel is heated and removed from the furnace, it is immediately hot-extruded to obtain a rough tube;

[0058] Step 8: The rough tube is cold rolled to obtain a finished high-strength, high-corrosion-resistant alloy.

[0059] Specifically, in step 3 above, the purpose of heating and holding the ingot is to eliminate harmful precipitates while ensuring good microstructure uniformity. Considering that excessively high holding temperature can lead to overheating and reduced performance, excessively long holding time can increase production costs, and excessively low holding temperature and short holding time can affect the elimination of precipitates and fail to guarantee the microstructure uniformity of the electroslag ingot, the ingot is heated to 1180℃~1220℃ and held for 18~23h.

[0060] Specifically, in step 4 above, if the initial forging temperature of the high-speed forging machine is too high, it will increase the risk of ingot cracking, and if it is too low, it will damage the forging equipment; therefore, the initial forging temperature of the high-speed forging machine should be controlled at 1140℃~1180℃.

[0061] Specifically, in step 4 above, if the final forging temperature of the high-speed forging machine is too high, it will increase the number of forging passes, increase costs, and reduce the uniformity of the microstructure; if it is too low, it will damage the forging equipment and even cause forging cracks. Therefore, the final forging temperature of the high-speed forging machine should be controlled at 900℃~950℃.

[0062] Specifically, in step 4 above, the round steel bar is a cylinder with an end face diameter of 200-360mm.

[0063] Specifically, in step 5 above, the forged round steel needs to be water-cooled immediately. If the interval is too long, recrystallization will occur. If the water cooling time is too long, the core grains will be abnormal. Therefore, the forged round steel should be water-cooled within 60 seconds, and the water cooling time should be more than 10 minutes, for example, 10 to 20 minutes.

[0064] Specifically, in step 6 above, heating and holding the round steel bar at this temperature aims to reduce the temperature difference between the surface and the core. Considering that excessively high holding temperatures can lead to overheating and prolonged holding times increase costs, while excessively low holding temperatures and short holding times result in a temperature difference between the surface and core, reducing the uniformity of the microstructure during hot extrusion, the holding temperature is controlled at 1200℃~1220℃, and the holding time is at least 5 hours, for example, 5~10 hours.

[0065] Specifically, in step 7 above, if the extrusion ratio of the hot-extruded rough tube is too high, the outer diameter tolerance and ovality are likely to exceed the tolerance; if it is too low, it will increase the cost of subsequent cold rolling. Therefore, the extrusion ratio should be controlled at 10-20.

[0066] Specifically, in step 8 above, if the total deformation of cold rolling is too large, it will damage the cold rolling equipment and reduce the cold rolling production efficiency; if the total deformation of cold rolling is too small, the mechanical properties will not meet the requirements. Therefore, the total deformation of cold rolling should be controlled between 45% and 65%.

[0067] Specifically, in step 8 above, too many deformation passes in cold rolling reduce cold rolling production efficiency. Therefore, the number of deformation passes in cold rolling should be controlled to 1 to 2.

[0068] Specifically, the microstructure of the aforementioned high-strength, high-corrosion-resistant alloys contains no precipitates or inclusions. The presence of precipitates reduces hot workability, increases the risk of forging cracks, and also reduces corrosion resistance.

[0069] Specifically, the aforementioned high-strength, high-corrosion-resistant alloys have uniform grains and no mixed grains.

[0070] The high-strength, high-corrosion-resistant alloy of the present invention ensures good tensile strength, yield strength, hardness, and corrosion resistance by precisely controlling the content of each component. For example, increasing the mass percentage of nitrogen ensures good tensile strength, yield strength, hardness, and corrosion resistance; increasing the content of w content improves wear resistance, strength, and corrosion resistance; and reducing the content of Ni and Mo results in lower material costs.

[0071] The method for preparing the high-strength, high-corrosion-resistant alloy of this invention reduces the generation of harmful precipitates and inclusions by precisely controlling the composition, and combines this with lowering the initial forging temperature and precisely controlling the final forging temperature to ensure that the alloy will not crack during forging. Furthermore, reducing the number of cold rolling passes and the amount of cold rolling deformation minimizes damage to equipment during cold rolling. The method of this invention is simple, causes minimal damage to equipment, is economical, and suitable for large-scale industrial production.

[0072] The high-strength, high-corrosion-resistant alloy of the present invention has good tensile strength, yield strength, hardness, and corrosion resistance; for example, the tensile strength reaches above 980 MPa (e.g., 989-1060 MPa), the yield strength reaches above 940 MPa (e.g., 940-1010 MPa), the Brinell hardness is 315-350 HBW, there is no tendency for intergranular corrosion, no stress corrosion cracking, and the average corrosion rate is below 0.0022 mm / a (e.g., 0.0015-0.0022 mm / a).

[0073] The high-strength, high-corrosion-resistant alloy of this invention has low content of alloying elements such as Ni and Mo, resulting in low cost and achieving excellent performance of high strength and high corrosion resistance at low cost.

[0074] Examples 1-5

[0075] The advantages of precise control over the composition and process parameters of the alloy of the present invention will be demonstrated below with specific embodiments and comparative examples.

[0076] The present invention provides a high-strength, high-corrosion-resistant alloy and its preparation method. The chemical composition of the embodiments is shown in Table 1.

[0077] The preparation method of Example 1 includes:

[0078] Step 1: Prepare the raw materials according to the mass percentage of each component of the high-strength, high-corrosion-resistant alloy, and then melt the steel.

[0079] Step 2: The ingot is prepared by using an electric furnace + argon-oxygen decarburization ladle refining + electroslag remelting method;

[0080] Step 3: Heat the ingot to 1190℃ and hold for 20 hours;

[0081] Step 4: After the ingot is heated and removed from the furnace, it is immediately forged by a high-speed forging machine to obtain round steel. The initial forging temperature of the high-speed forging machine is 1140℃, and the final forging temperature is 930℃. The round steel is a cylinder with an end diameter of 302mm.

[0082] Step 5: Cool the round steel bars with water for 60 seconds, and the water cooling time is 20 minutes.

[0083] Step 6: Heat the round steel to 1200℃ and keep it at that temperature for 7 hours;

[0084] Step 7: After the round steel is heated and removed from the furnace, it is immediately hot-extruded to obtain a rough tube with an extrusion ratio of 15.

[0085] Step 8: The rough tube is cold rolled to obtain a finished high-strength, high-corrosion-resistant alloy; the cold rolling process involves 2 deformation passes and the total deformation is 55%.

[0086] The preparation method of Example 2 includes:

[0087] Step 1: Prepare the raw materials according to the mass percentage of each component of the high-strength, high-corrosion-resistant alloy, and then melt the steel.

[0088] Step 2: The ingot is prepared by using an electric furnace + argon-oxygen decarburization ladle refining + electroslag remelting method;

[0089] Step 3: Heat the ingot to 1210℃ and hold for 19 hours;

[0090] Step 4: After the ingot is heated and removed from the furnace, it is immediately forged by a high-speed forging machine to obtain round steel. The initial forging temperature of the high-speed forging machine is 1160℃, and the final forging temperature is 950℃. The round steel is a cylinder with an end diameter of 269mm.

[0091] Step 5: Cool the round steel bars with water for 60 seconds, and the water cooling time is 18 minutes.

[0092] Step 6: Heat the round steel to 1200℃ and keep it at that temperature for 6 hours;

[0093] Step 7: After the round steel is heated and removed from the furnace, it is immediately hot-extruded to obtain a rough tube with an extrusion ratio of 18.

[0094] Step 8: The rough tube is cold rolled to obtain a finished high-strength, high-corrosion-resistant alloy; the cold rolling process involves one deformation pass and the total deformation is 45%.

[0095] The preparation method of Example 3 is the same as that of Example 1, except that:

[0096] Step 3: Heat the ingot to 1210℃ and hold for 22 hours;

[0097] Step 4: The initial forging temperature is 1180℃, the final forging temperature is 950℃, and the round steel is a cylinder with an end face diameter of 248mm.

[0098] The preparation method of Example 4 is the same as that of Example 1, except that:

[0099] Step 4: The initial forging temperature is 1180℃, the final forging temperature is 900℃, and the round steel is a cylinder with an end face diameter of 340mm.

[0100] Step 6: Heat the round steel to 1220℃ and keep it at that temperature for 9 hours;

[0101] Step 8: The rough tube is cold rolled to obtain a finished high-strength, high-corrosion-resistant alloy; the cold rolling process involves 2 deformation passes and the total deformation is 65%.

[0102] The preparation method of Example 5 is the same as that of Example 2, except that:

[0103] Step 3: Heat the ingot to 1200℃ and hold for 22 hours;

[0104] Step 7: After the round steel is heated and removed from the furnace, it is immediately hot-extruded to obtain a rough tube with an extrusion ratio of 20.

[0105] Step 8: The rough tube is cold rolled to obtain a finished high-strength, high-corrosion-resistant alloy; the cold rolling process consists of one deformation pass and a total deformation of 50%.

[0106] The microstructure of the high-strength, high-corrosion-resistant alloy of the present invention is shown in Table 2 below. Figure 1 This is a microstructure diagram of the high-strength, high-corrosion-resistant alloy from Example 1; Figure 2 This is a microstructure diagram of the high-strength, high-corrosion-resistant alloy from Example 2; Figure 3 This is a microstructure diagram of the high-strength, high-corrosion-resistant alloy from Example 3; Figure 4 This is a microstructure diagram of the high-strength, high-corrosion-resistant alloy from Example 4; Figure 5 This is a microstructure diagram of the high-strength, high-corrosion-resistant alloy from Example 5; Figure 6 This is a microstructure diagram of Comparative Example 1; Figure 7 This is a microstructure diagram of Comparative Example 2; Figure 8 The image shows the microstructure of Comparative Example 3. As can be seen from the image, the high-strength, high-corrosion-resistant alloy of this invention has no precipitates or inclusions in its microstructure. The microstructure of the comparative example shows obvious precipitates.

[0107] The main performance test results of the high-strength, high-corrosion-resistant alloy of the embodiments of the present invention are shown in Table 3.

[0108] Table 1 Chemical composition, wt%

[0109]

[0110]

[0111] Table 2 Microstructure

[0112] serial number Precipitated phase Inclusions Example 1 none none Example 2 none none Example 3 none none Example 4 none none Example 5 none none Comparative Example 1 5% precipitated phase none Comparative Example 2 22% precipitated phase none Comparative Example 3 18% precipitated phase none

[0113] Table 3 shows some performance test results.

[0114]

[0115]

[0116] It should be noted that the present invention conducted uniform corrosion, C-type ring stress corrosion and intergranular corrosion tests. The standards referenced for the tests are shown in Table 4 below, the corrosion-related parameters are shown in Table 5 below, and the corrosion results are shown in Table 3 above.

[0117] Table 4 Standards for Test Reference

[0118] Test number Test Project Test methods 1 Uniform corrosion JB / T 7901 2 Type C Circular Stress Corrosion NACE 0177 3 Intergranular corrosion ASTM A262

[0119] Table 5 Uniform Corrosion and Stress Corrosion Media

[0120] Test medium 25% (mass fraction) NaCl solution Temperature (°C) 175±5 CO2 partial pressure (MPa) 3.5 H2S (MPa) 3.5 Time (h) 720 Loading stress 90% YSmin

[0121] The inventors conducted extensive experimental research during the research process, and some poorly performing solutions are now presented as comparative examples.

[0122] Comparative Example 1

[0123] This comparative example provides a corrosion-resistant alloy, the composition of which is shown in Table 1 above. The preparation method is the same as that in Example 1, and will not be repeated here.

[0124] Comparative Example 2

[0125] This comparative example provides a corrosion-resistant alloy, the composition of which is shown in Table 1 above. The preparation method is the same as that in Example 5, and will not be repeated here.

[0126] Comparative Example 3

[0127] This comparative example provides a corrosion-resistant alloy, the composition of which is shown in Table 1 above. The preparation method is generally the same as that in Example 1, except that:

[0128] Step 3: Heat the ingot to 900℃ and hold for 7 hours;

[0129] Step 8: The rough tube is cold rolled to obtain a finished high-strength, high-corrosion-resistant alloy; the cold rolling process involves 2 deformation passes and the total deformation is 60%.

[0130] The organization and properties of the comparative examples are shown in Tables 2 and 3 above.

[0131] 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 high-strength, high-corrosion-resistant alloy, characterized in that, The high-strength, high-corrosion-resistant alloy comprises, by mass percentage: C ≤ 0.03%, 27.0% < Cr ≤ 29.0%, 29.5% < Ni ≤ 32.5%, 0.08% < N ≤ 0.20%, 0.10% < W ≤ 1.00%, Mn ≤ 1.0%, 3.0% < Mo ≤ 4.0%, 1.0% < Cu ≤ 1.4%, Si ≤ 1.0%, P ≤ 0.03%, S ≤ 0.03%; the balance being Fe and unavoidable trace impurities. The preparation method of the high-strength, high-corrosion-resistant alloy includes: Step 1: Prepare the raw materials according to the mass percentage of each component of the high-strength, high-corrosion-resistant alloy, and then melt the steel. Step 2: The ingot is prepared by using an electric furnace + argon-oxygen decarburization ladle refining + electroslag remelting method; Step 3: Heat the ingot and hold it at that temperature for homogenization. Step 4: After the ingot is heated and removed from the furnace, it is immediately forged into round steel using a high-speed forging machine. Step 5: Perform water cooling treatment on the round steel. Step 6: Heat the round steel and keep it warm; Step 7: After the round steel is heated and removed from the furnace, it is immediately hot-extruded to obtain a rough tube; Step 8: The rough tube is cold-rolled to obtain a finished high-strength, high-corrosion-resistant alloy. In step 3, the ingot is heated to 1180℃~1220℃ and held for 18~23 hours.

2. The high-strength, high-corrosion-resistant alloy according to claim 1, characterized in that, The composition of the high-strength, high-corrosion-resistant alloy, by mass percentage, is as follows: 0.009%≤C≤0.02%, 27.3%≤Cr≤28.8%, 30.0%≤Ni≤32.0%, 0.10%≤N≤0.20%, 0.50%≤W≤1.00%, 0.10%≤Mn≤0.50%, 3.2%≤Mo≤4.0%, 1.05%≤Cu≤1.4%, 0.10%≤Si≤0.8%, P≤0.03%, S≤0.03%, with the balance being Fe and unavoidable trace impurities.

3. The high-strength, high-corrosion-resistant alloy according to claim 1 or 2, characterized in that, The microstructure of the high-strength, high-corrosion-resistant alloy contains no precipitates or inclusions.

4. A method for preparing a high-strength, high-corrosion-resistant alloy according to any one of claims 1 to 3, characterized in that, include: Step 1: Prepare the raw materials according to the mass percentage of each component of the high-strength, high-corrosion-resistant alloy, and then melt the steel. Step 2: The ingot is prepared by using an electric furnace + argon-oxygen decarburization ladle refining + electroslag remelting method; Step 3: Heat the ingot and hold it at that temperature for homogenization. Step 4: After the ingot is heated and removed from the furnace, it is immediately forged into round steel using a high-speed forging machine. Step 5: Perform water cooling treatment on the round steel. Step 6: Heat the round steel and keep it warm; Step 7: After the round steel is heated and removed from the furnace, it is immediately hot-extruded to obtain a rough tube; Step 8: The rough tube is cold rolled to obtain a finished high-strength, high-corrosion-resistant alloy.

5. The preparation method according to claim 4, characterized in that, In step 3, the ingot is heated to 1180℃~1220℃ and held for 18~23 hours.

6. The preparation method according to claim 4, characterized in that, In step 4, the forging temperature of the high-speed forging machine is controlled to be 1140℃~1180℃.

7. The preparation method according to claim 4, characterized in that, In step 4, the final forging temperature of the high-speed forging machine is controlled to be 900℃~950℃.

8. The preparation method according to claim 4, characterized in that, In step 5, the forged round steel is controlled to undergo water cooling within 60 seconds.

9. The preparation method according to claim 4, characterized in that, In step 6, the heat preservation temperature is controlled at 1200℃~1220℃, and the heat preservation time is more than 5 hours.

10. The preparation method according to any one of claims 4 to 9, characterized in that, In step 7, the extrusion ratio is controlled to be 10-20.

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