High-strength high-nitrogen iron-nickel-based corrosion-resistant alloy and preparation method thereof

Abstract

This invention discloses a high-strength, high-nitrogen iron-nickel-based 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-nitrogen iron-nickel-based corrosion-resistant alloy comprises, by mass percentage: C≤0.015%, 25.0%<Cr≤27.0%, 28.5%<Ni≤29.5%, 0.20%<N≤0.45%, Mn≤1.0%, 2.0%<Mo≤3.0%, 0.6%<Cu≤1.0%, Si≤1.0%, P≤0.03%, S≤0.01%; the balance being Fe and unavoidable trace impurities. The high-strength, high-nitrogen iron-nickel-based 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-nitrogen iron-nickel-based corrosion-resistant alloy and its preparation method. Background Technology

[0002] With economic development, the demand for oil and natural gas is increasing, necessitating greater exploitation of deep, harsh-environment oil and gas fields. Iron-nickel-based corrosion-resistant alloys, as the primary material for oil well casings used in harsh environments, possess high Cr and Ni content, making them highly resistant to corrosion in Cl- environments. - While exhibiting strong resistance to both uniform and localized corrosion in acidic media with high H2S content, it also maintains good mechanical properties. However, with the increasing depth of oil and gas field extraction, higher temperatures, pressures, and concentrations of corrosive media place more stringent demands on oil well pipe materials, especially their mechanical properties. Traditional iron-nickel-based corrosion-resistant alloys are insufficient to meet the requirements of steel grades above 125ksi, and can only improve strength by increasing cold rolling deformation or by directly using nickel-based alloys with better alloy content as substitutes. The former greatly increases the wear and tear on cold rolling equipment, while the latter is far more expensive than iron-nickel-based alloys. Therefore, how to provide a low-cost, high-strength 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-nitrogen iron-nickel-based 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-nitrogen iron-nickel-based corrosion-resistant alloy, wherein the components of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy, by mass percentage, include: C≤0.015%, 25.0%<Cr≤27.0%, 28.5%<Ni≤29.5%, 0.20%<N≤0.45%, Mn≤1.0%, 2.0%<Mo≤3.0%, 0.6%<Cu≤1.0%, Si≤1.0%, P≤0.03%, S≤0.01%; the balance being Fe and unavoidable trace impurities.

[0006] Furthermore, the composition of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy, by mass percentage, can be: 0.012%≤C≤0.015%, 26.0%≤Cr≤27.0%, 28.6%≤Ni≤29.5%, 0.22%≤N≤0.45%, 0.1%≤Mn≤0.9%, 2.2%≤Mo≤3.0%, 0.7%≤Cu≤1.0%, 0.1%≤Si≤0.5%, P≤0.03%, S≤0.01%; the balance being Fe and unavoidable trace impurities.

[0007] Furthermore, the microstructure of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy contains no precipitated phases or inclusions.

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

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

[0010] Step 2: Ingots are prepared by pressure induction melting followed by electroslag remelting;

[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 the finished high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy.

[0017] Furthermore, in step 3, the ingot is heated to 1160℃~1200℃ and held for 18~22h.

[0018] Furthermore, in step 4, the initial forging temperature of the high-speed forging mill is controlled to be 1100℃~1140℃.

[0019] Furthermore, in step 4, the final forging temperature of the high-speed forging mill is controlled to be 830℃~900℃.

[0020] Furthermore, in step 6, the heat preservation temperature is controlled at 1180℃~1200℃, and the heat preservation time is 5~6h.

[0021] Furthermore, in step 7, the extrusion ratio is controlled to be 8-10.

[0022] Furthermore, in step 8, the total deformation of cold rolling is controlled to be 30% to 45%.

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

[0024] a) The high-strength, high-nitrogen iron-nickel-based 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 manganese (Mn) increases the saturated solubility of nitrogen in the alloy, expanding and stabilizing the austenite phase region; reducing the content of carbon (C) and sulfur (S) reduces the generation of harmful precipitates and inclusions; and reducing the content of nitrogen (Ni) and molybdenum (Mo) ensures lower material costs.

[0025] (b) The preparation method of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy of the present invention reduces the generation of harmful precipitates and inclusions by precisely controlling the composition, and by combining this with lowering the initial forging temperature and precisely controlling the final forging temperature, ensures that the alloy of the present invention will not crack during forging. Furthermore, by reducing the number of cold rolling passes and the amount of cold rolling deformation, the alloy of the present invention minimizes damage to equipment during cold rolling. Compared with existing multi-pass, large-deformation cold rolling methods, the method of the present invention is simple, causes less damage to equipment, is economical, and suitable for large-scale industrial production.

[0026] c) The high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy of the present invention has good tensile strength, yield strength, hardness and corrosion resistance; for example, the tensile strength reaches 1090 MPa or more (e.g., 1094 to 1180 MPa), the yield strength reaches 1040 MPa or more (e.g., 1042 to 1110 MPa), the Brinell hardness is 350 to 385 HBW, there is no tendency for intergranular corrosion, no stress corrosion cracking, and the average corrosion rate is less than 0.002 mm / a (e.g., 0.0016 to 0.002 mm / a).

[0027] d) The high-strength, high-nitrogen iron-nickel-based 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 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 The microstructure of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy of Example 1 is shown in the diagram.

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

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

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

[0034] Figure 5 This is a microstructure diagram of the high-strength, high-nitrogen iron-nickel-based 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-nitrogen iron-nickel-based corrosion-resistant alloy. The composition of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy, by mass percentage, includes: C≤0.015%, 25.0%<Cr≤27.0%, 28.5%<Ni≤29.5%, 0.20%<N≤0.45%, Mn≤1.0%, 2.0%<Mo≤3.0%, 0.6%<Cu≤1.0%, Si≤1.0%, P≤0.03%, S≤0.01%; 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 iron-nickel-based corrosion-resistant alloy of this invention, the main role of carbon is to maintain an ultra-low carbon state to ensure corrosion resistance. The strength-enhancing effect of carbon as an interstitial element is replaced by nitrogen. Excessive carbon content will exacerbate Cr... 23The precipitation of C6-type carbides reduces corrosion resistance. Therefore, this invention limits the C content to C≤0.015%.

[0042] Nitrogen (N): In the iron-nickel-based corrosion-resistant alloy of this invention, nitrogen not only acts as an interstitial element, replacing carbon (C) to enhance strength, but also acts as an element that 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 in the form of 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; conversely, insufficient nitrogen content will fail to guarantee the required strength. Therefore, this invention limits the nitrogen content to 0.20% < N ≤ 0.45%.

[0043] Cr: In the iron-nickel-based corrosion-resistant alloy of this invention, the main role of Cr is to improve corrosion resistance and increase the saturated solubility of N. According to the pitting corrosion equivalent formula: PREN = Cr% + 3.3Mo% + 16N, the effect of Cr in improving corrosion resistance can be replaced by Mo and N. However, excessive Cr will exacerbate corrosion. 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 25.0% < Cr ≤ 27.0%.

[0044] Ni: In the iron-nickel-based corrosion-resistant alloy of the present 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 the microstructure properties. Therefore, the present invention limits the Ni content to 28.5% < Ni ≤ 29.5%.

[0045] Mn: In the iron-nickel-based corrosion-resistant alloy of the present 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 present invention limits the Mn content to Mn≤1.0%.

[0046] Mo: In the iron-nickel-based corrosion-resistant alloy of the present invention, the main function of Mo is to improve the corrosion resistance. According to the pitting corrosion equivalent formula: PREN = Cr% + 3.3Mo% + 16N, the effect of Mo on improving corrosion resistance is 3.3 times that of Cr. If the Mo content is too high, it will reduce the area of ​​the austenite phase region and increase the tendency of σ phase precipitation. If the Mo content is too low, it will reduce the corrosion resistance. Therefore, the present invention limits the Mo content to 2.0% < Mo ≤ 3.0%.

[0047] 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 0.6% < Cu ≤ 1.0%.

[0048] To further improve the overall performance of the above-mentioned high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy, the composition of the above-mentioned high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy, by mass percentage, can be: 0.012%≤C≤0.015%, 26.0%≤Cr≤27.0%, 28.6%≤Ni≤29.5%, 0.22%≤N≤0.45%, 0.1%≤Mn≤0.9%, 2.2%≤Mo≤3.0%, 0.7%≤Cu≤1.0%, 0.1%≤Si≤0.5%, P≤0.03%, S≤0.01%; the balance being Fe and unavoidable trace impurities.

[0049] This invention also provides a method for preparing the above-mentioned high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy, comprising:

[0050] Step 1: Prepare the raw materials according to the mass percentage of each component of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy, and then smelt the steel.

[0051] Step 2: Ingots are prepared by pressure induction melting followed by electroslag remelting;

[0052] Step 3: Heat the ingot and hold it at that temperature for homogenization.

[0053] 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.

[0054] Step 5: Perform water cooling treatment on the round steel.

[0055] Step 6: Heat the round steel and keep it warm;

[0056] Step 7: After the round steel is heated and removed from the furnace, it is immediately hot-extruded to obtain a rough tube;

[0057] Step 8: The rough tube is cold rolled to obtain the finished high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy.

[0058] 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 temperatures can lead to overheating and reduced performance, while excessively long holding times increase production costs, and excessively low holding temperatures and short holding times can affect the elimination of precipitates and compromise the microstructure uniformity of the ingot, the ingot is heated to 1160℃~1200℃ and held for 18~22 hours.

[0059] 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 1100℃~1140℃.

[0060] 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 830℃~900℃.

[0061] Specifically, in step 4 above, the round steel bar is a cylinder with an end face diameter of 200-250mm.

[0062] 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 15 minutes.

[0063] 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 of the bar. Considering that excessively high holding temperatures can easily 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 of the round steel bar, reducing the uniformity of the microstructure during hot extrusion, the holding temperature is controlled at 1180℃~1200℃, and the holding time is 5~6 hours.

[0064] 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 8 to 10.

[0065] 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 efficiency of cold rolling production; 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 at 30% to 45%.

[0066] Specifically, in step 8 above, too many deformation passes in cold rolling reduce cold rolling production efficiency. Therefore, the deformation passes in cold rolling should be controlled to be 1.

[0067] Specifically, the microstructure of the aforementioned high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy contains no precipitates or inclusions. The presence of precipitates reduces hot working properties, increases the risk of forging cracks, and also reduces corrosion resistance.

[0068] Specifically, the aforementioned high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy has uniform grains and no mixed crystals.

[0069] The high-strength, high-nitrogen iron-nickel-based 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 manganese (Mn) increases the saturated solubility of nitrogen in the alloy, expanding and stabilizing the austenite phase region; reducing the content of carbon (C) and sulfur (S) reduces the formation of harmful precipitates and inclusions; and reducing the content of nitrogen (Ni) and molybdenum (Mo) ensures lower material costs.

[0070] The preparation method of the high-strength, high-nitrogen iron-nickel-based 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. Furthermore, by reducing the number of cold rolling passes and the amount of cold rolling deformation, the alloy of the present invention minimizes damage to equipment during cold rolling. Compared with existing multi-pass, large-deformation cold rolling methods, the method of the present invention is simple, causes less damage to equipment, is economical and feasible, and is suitable for large-scale industrial production.

[0071] The high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy of the present invention has good tensile strength, yield strength, hardness and corrosion resistance; for example, the tensile strength reaches above 1090 MPa (e.g., 1094-1180 MPa), the yield strength reaches above 1040 MPa (e.g., 1042-1110 MPa), the Brinell hardness is 350-385 HBW, there is no tendency for intergranular corrosion, no stress corrosion cracking, and the average corrosion rate is below 0.002 mm / a (e.g., 0.0016-0.002 mm / a).

[0072] The high-strength, high-nitrogen iron-nickel-based 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 at low cost.

[0073] Examples 1-5

[0074] 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.

[0075] The present invention provides a high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy and its preparation method. The chemical composition of the embodiments is shown in Table 1.

[0076] The preparation method of Example 1 includes:

[0077] Step 1: Prepare the raw materials according to the mass percentage of each component of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy, and then smelt the steel.

[0078] Step 2: Ingots are prepared by pressure induction melting followed by electroslag remelting;

[0079] Step 3: Heat the ingot to 1200℃ and hold for 20 hours;

[0080] 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 1100℃, and the final forging temperature is 900℃. The round steel is a cylinder with an end face diameter of 249mm.

[0081] Step 5: Cool the round steel bars with water for 60 seconds, and the water cooling time is 15 minutes.

[0082] Step 6: Heat the round steel to 1200℃ and keep it at that temperature for 5 hours;

[0083] 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 8.

[0084] Step 8: The rough tube is cold rolled to obtain a finished high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy; the cold rolling process consists of one deformation pass and a total deformation of 35%.

[0085] The preparation method of Example 2 includes:

[0086] Step 1: Prepare the raw materials according to the mass percentage of each component of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy, and then smelt the steel.

[0087] Step 2: Ingots are prepared by pressure induction melting followed by electroslag remelting;

[0088] Step 3: Heat the ingot to 1170℃ and hold for 22 hours;

[0089] 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 1120℃, and the final forging temperature is 850℃. The round steel is a cylinder with an end face diameter of 220mm.

[0090] Step 5: Cool the round steel bars with water for 60 seconds, and the water cooling time is 12 minutes.

[0091] Step 6: Heat the round steel to 1180℃ and keep it at that temperature for 5 hours;

[0092] 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 10.

[0093] Step 8: The rough tube is cold rolled to obtain a finished high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy; the cold rolling process consists of one deformation pass and a total deformation of 40%.

[0094] The preparation method of Example 3 is the same as that of Example 1, except that:

[0095] Step 3: Heat the ingot to 1180℃ and hold for 18 hours;

[0096] Step 4: The initial forging temperature is 1110℃, the final forging temperature is 900℃, and the round steel is a cylinder with an end face diameter of 242mm.

[0097] Step 8: The rough tube is cold rolled to obtain a finished high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy; the cold rolling process consists of one deformation pass and the total deformation is 45%.

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

[0099] Step 8: The rough tube is cold rolled to obtain a finished high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy; the cold rolling deformation is done in one pass and the total deformation is 30%.

[0100] The preparation method of Example 5 is the same as that of Example 2, except that:

[0101] Step 8: The rough tube is cold rolled to obtain a finished high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy; the cold rolling process consists of one deformation pass and a total deformation of 35%.

[0102] The microstructure of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy of the present invention is shown in Table 2 below. Figure 1 The microstructure of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy of Example 1 is shown in the diagram. Figure 2 This is a microstructure diagram of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy from Example 2; Figure 3 This is a microstructure diagram of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy of Example 3; Figure 4 This is a microstructure diagram of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy from Example 4; Figure 5 This is a microstructure diagram of the high-strength, high-nitrogen iron-nickel-based 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-nitrogen iron-nickel-based corrosion-resistant alloy of this invention has no precipitates or inclusions in its microstructure. The microstructure of the comparative example shows obvious precipitates.

[0103] The main performance test results of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy of the embodiments of the present invention are shown in Table 3.

[0104] Table 1 Chemical composition, wt%

[0105]

[0106]

[0107] Table 2 Microstructure

[0108] 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 4% precipitated phase none Comparative Example 3 12% precipitated phase none

[0109] Table 3 shows some performance test results.

[0110]

[0111]

[0112] 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, and the corrosion-related parameters are shown in Table 5 below.

[0113] Table 4 Standards for Test Reference

[0114] Test number Experimental Project Test methods 1 Uniform corrosion JB / T 7901 2 Type C Circular Stress Corrosion NACE 0177 3 Intergranular corrosion ASTM A262

[0115] Table 5 Uniform Corrosion and Stress Corrosion Media

[0116] 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

[0117] The inventors conducted extensive experimental research during the research process, and some poorly performing solutions are now presented as comparative examples.

[0118] Comparative Example 1

[0119] 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 3, and will not be repeated here.

[0120] Comparative Example 2

[0121] 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.

[0122] Comparative Example 3

[0123] 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:

[0124] Step 3: Heat the ingot to 1100℃ and hold for 8 hours.

[0125] The organization and properties of the comparative examples are shown in Tables 2 and 3 above.

[0126] 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-nitrogen iron-nickel-based corrosion-resistant alloy, characterized in that, The high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy comprises, by mass percentage: C ≤ 0.015%, 25.0% < Cr ≤ 27.0%, 28.5% < Ni ≤ 29.5%, 0.20% < N ≤ 0.45%, Mn ≤ 1.0%, 2.0% < Mo ≤ 3.0%, 0.6% < Cu ≤ 1.0%, Si ≤ 1.0%, P ≤ 0.03%, S ≤ 0.01%; the balance being Fe and unavoidable trace impurities. The preparation method of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy includes: Step 1: Prepare the raw materials according to the mass percentage of each component of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy, and then smelt the steel. Step 2: Ingots are prepared by pressure induction melting followed by electroslag remelting; 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 the finished high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy. In step 3, the ingot is heated to 1160℃~1200℃ and held for 18~22h.

2. The high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy according to claim 1, characterized in that, The composition of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy, by mass percentage, is as follows: 0.012%≤C≤0.015%, 26.0%≤Cr≤27.0%, 28.6%≤Ni≤29.5%, 0.22%≤N≤0.45%, 0.1%≤Mn≤0.9%, 2.2%≤Mo≤3.0%, 0.7%≤Cu≤1.0%, 0.1%≤Si≤0.5%, P≤0.03%, S≤0.01%; the balance being Fe and unavoidable trace impurities.

3. The high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy according to claim 1, characterized in that, The microstructure of the high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy contains no precipitated phases or inclusions.

4. A method for preparing a high-strength, high-nitrogen iron-nickel-based 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-nitrogen iron-nickel-based corrosion-resistant alloy, and then smelt the steel. Step 2: Ingots are prepared by pressure induction melting followed by electroslag remelting; 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 the finished high-strength, high-nitrogen iron-nickel-based corrosion-resistant alloy.

5. The preparation method according to claim 4, characterized in that, In step 3, the ingot is heated to 1160℃~1200℃ and held for 18~22h.

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 1100℃~1140℃.

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 830℃~900℃.

8. The preparation method according to claim 4, characterized in that, In step 6, the heat preservation temperature is controlled at 1180℃~1200℃, and the heat preservation time is 5~6h.

9. The preparation method according to claim 4, characterized in that, In step 7, the extrusion ratio is controlled to be 8-10.

10. The preparation method according to any one of claims 4 to 9, characterized in that, In step 8, the total deformation of cold rolling is controlled to be 30% to 45%.

Images