Centrifugal compressor impeller material for high-temperature high-partial-pressure acidic wet hydrogen sulfide working condition and preparation method thereof

Abstract

The invention discloses a centrifugal compressor impeller material for a high-temperature high-partial-pressure acidic wet hydrogen sulfide working condition and a preparation method thereof. The material comprises the following components: C, Si, Mn, P, S, Cr, Ni, Mo, Cu, Nb, V, N and the balance of Fe and inevitable impurities. The preparation method comprises the following steps: mixing the components in proportion, smelting and casting to obtain a primary steel ingot; then secondary smelting and pouring are conducted, and a secondary steel ingot is obtained; then electroslag remelting is carried out, and a tertiary steel ingot, namely a blank, is obtained; forging the blank in an austenite single-phase region, and air-cooling to room temperature after forging to obtain a forge piece; then, the forge piece is subjected to annealing heat treatment after forging, finally, solid solution heat treatment and aging heat treatment are sequentially conducted, and preparation of the martensitic precipitation hardening stainless steel material is completed. Through cooperation of raw material component setting, equivalent control and temperature setting in the preparation process, the impeller material has the advantages of high corrosion resistance, low cost and high strength.

Description

[0001] Technical Solution

[0002] The invention belongs to the technical field of centrifugal compressors, and in particular relates to an impeller material for a centrifugal compressor under high-temperature and high-partial-pressure acidic wet hydrogen sulfide working conditions and a preparation method thereof. Background Art

[0003] A centrifugal compressor is a mechanical device that compresses various process gases or mixed gases in the radial centrifugal direction to increase their pressure. A centrifugal compressor consists of a rotor, a stator, etc. The impeller and other parts form the rotor in a matching relationship with the main shaft.

[0004] The impeller is a key component of a centrifugal compressor. Gas is sucked in from the center of the impeller and flows along the impeller channel (the channel between the impeller blades) to the outer edge of the impeller. When the compressor is working, the high-speed rotating impeller works on the gas, causing the gas to gain energy, increase pressure and speed, and convert kinetic energy into pressure energy. When the impeller is working, the loads it bears mainly include rotating centrifugal force, shaft vibration force and aerodynamic force. The centrifugal force will cause the impeller to produce greater static stress, and the aerodynamic force and shaft vibration force will cause the impeller blades to vibrate, thereby causing the blades to produce greater alternating stress. Therefore, centrifugal compressors often use high-strength, high-ductility forged martensitic stainless steel materials.

[0005] When steel parts work in wet hydrogen sulfide media, hydrogen atoms generated by wet hydrogen sulfide corrosion penetrate into the steel and dissolve in the lattice, causing embrittlement. Under the action of applied tensile stress or residual stress, parts will crack without warning, which is stress corrosion. The factors that affect the rate of hydrogen sulfide stress corrosion mainly include working temperature and wet hydrogen sulfide partial pressure. The higher the working temperature and the higher the wet hydrogen sulfide partial pressure, the greater the probability of stress corrosion and the worse the impact of the accident. Ways to prevent wet hydrogen sulfide stress corrosion include: lowering the impeller operating temperature, reducing the wet hydrogen sulfide partial pressure in the gas, and selecting materials that are resistant to hydrogen sulfide stress corrosion. Among them, the impeller operating temperature and the wet hydrogen sulfide partial pressure are often parameters given by the system process. Therefore, selecting suitable materials is an important method to prevent wet hydrogen sulfide stress corrosion.

[0006] According to the general industry standard API 617 "Axial flow, centrifugal compressors and expanders - compressors", the materials of centrifugal compressor parts under wet hydrogen sulfide working conditions shall comply with NACE MR 0175 "Metallic materials for oilfield equipment resistant to sulfide stress corrosion cracking and stress corrosion cracking". According to NACE MR 0175, when used as any equipment or component, the maximum partial pressure of wet hydrogen sulfide of martensitic stainless steel at the temperature of the mining environment should be ≤10KPa and the pH value should be ≥3.5; when used as compressor components, S41000, S41500, S42400 martensitic stainless steel forging materials and S17400, S15500, S45000 martensitic precipitation hardening stainless steel forging materials with hardness and heat treatment system requirements are given. The maximum partial pressure of hydrogen sulfide and pH value of these limited materials at the mining environment temperature are not limited. The maximum temperature in the above mining environment is 150℃. Therefore, for centrifugal compressor parts operating in acidic media with an operating temperature of more than 150°C and a maximum partial pressure of wet hydrogen sulfide of more than 10KPa, there are no martensitic stainless steel or martensitic precipitation hardening stainless steel forging materials available, and very expensive precipitation hardening nickel-based alloys need to be used.

[0007] Existing impeller materials for centrifugal compressors working under high temperature and high partial pressure acidic wet hydrogen sulfide conditions include precipitation hardened nickel-based alloys. Since precipitation hardened nickel-based alloys are special alloys formed by adding various alloy elements such as chromium, molybdenum, niobium, cobalt, aluminum, and titanium to nickel and iron as the base, while having excellent strength and stress corrosion resistance and other properties, they have disadvantages such as high material cost, great processing difficulty, and limited parts forming methods. Summary of the invention

[0008] In order to overcome the deficiencies of the above-mentioned prior art, the object of the present invention is to provide a centrifugal compressor impeller material for high-temperature and high-partial-pressure acidic wet hydrogen sulfide working conditions and a preparation method thereof, by controlling the content of the main components in the material, especially the content of nickel, chromium, carbon, molybdenum, manganese, niobium, copper, and nitrogen elements, and then controlling the nickel equivalent, chromium equivalent, and pitting equivalent, to lay a good foundation for meeting the high stress and wet hydrogen sulfide stress corrosion of the impeller; by controlling the heat treatment system, uniform tempered martensite and a certain content of austenite are obtained, and the ferrite content is controlled below 1%, thereby ensuring high strength and high toughness of the material and meeting the strength and stress corrosion requirements of the impeller.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

[0010] A centrifugal compressor impeller material for high temperature and high partial pressure acidic wet hydrogen sulfide working conditions, wherein the chemical composition thereof comprises, by mass percentage: C: 0.03-0.05%, Si: 0.2-0.5%, Mn: 0.3-0.8%, P≤0.025%, S≤0.015%, Cr: 12.0-14.0%, Ni: 5.5-7.0%, Mo: 0.8-1.5%, Cu: 1.5-2.2%, Nb: 0.4-0.8%, V≤0.05%, N≤0.04%, and the rest are Fe and unavoidable impurities, and P, S, V and N are not 0;

[0011] Among them, the Ni equivalent is 8-10, the Cr equivalent is 15-18.5, and the pitting corrosion equivalent is 15.5-19; the Ni equivalent represents the total content of austenite forming elements, Ni equivalent = Ni + Co + 0.5Mn + 0.3Cu + 25N + 30C; the Cr equivalent represents the total content of ferrite forming elements, Cr equivalent = Cr + 1.5Mo + 2Si + 1.75Nb + 5V + 5.5Al + 1.5Ti + 0.75W; the pitting corrosion equivalent represents the tolerance to pitting corrosion, pitting corrosion equivalent = Cr + 3.3Mo + 16N.

[0012] A centrifugal compressor impeller material for high temperature and high partial pressure acidic wet hydrogen sulfide working conditions, wherein the chemical composition thereof comprises, by mass percentage: C: 0.03-0.045%, Si: 0.3-0.5%, Mn: 0.3-0.6%, P≤0.015%, S≤0.01%, Cr: 12.5-14.0%, Ni: 5.5-6.5%, Mo: 1.0-1.35%, Cu: 1.7-2.1%, Nb: 0.5-0.75%, V≤0.05%, N≤0.04%, and the rest are Fe and unavoidable impurities, and P, S, V and N are not 0;

[0013] Among them, the Ni equivalent is 8.3-9.5, the Cr equivalent is 16-18, and the pitting corrosion equivalent is 16.5-19; the Ni equivalent represents the total content of austenite forming elements, Ni equivalent = Ni + Co + 0.5Mn + 0.3Cu + 25N + 30C; the Cr equivalent represents the total content of ferrite forming elements, Cr equivalent = Cr + 1.5Mo + 2Si + 1.75Nb + 5V + 5.5Al + 1.5Ti + 0.75W; the pitting corrosion equivalent represents the tolerance to pitting corrosion, pitting corrosion equivalent = Cr + 3.3Mo + 16N.

[0014] A method for preparing an impeller material for a centrifugal compressor under high temperature and high partial pressure acidic wet hydrogen sulfide conditions comprises the following steps:

[0015] Step 1, by mass percentage, 0.03-0.05%, Si: 0.2-0.5%, Mn: 0.3-0.8%, P≤0.025%, S≤0.015%, Cr: 12.0-14.0%, Ni: 5.5-7.0%, Mo: 0.8-1.5%, Cu: 1.5-2.2%, Nb: 0.4-0.8%, V≤0.05%, N≤0.04%, the rest being Fe and unavoidable impurities, and P, S, V and N are not 0; mix to obtain a mixed raw material;

[0016] Step 2, smelting and casting the mixed raw material obtained in step 1 through an electric furnace to obtain a primary steel ingot;

[0017] Step 3, performing secondary smelting and casting on the primary steel ingot obtained in step 2 under vacuum to obtain a secondary steel ingot;

[0018] Step 4, electroslag remelting the secondary steel ingot obtained in step 3 to obtain a tertiary steel ingot, i.e., a billet;

[0019] Step 5, forging the blank obtained in step 4 in an austenite single phase region, and air cooling to room temperature after forging to obtain a forging; the initial forging temperature in the austenite single phase region is 1150-1200° C., the final forging temperature is 800-900° C., the blank is subjected to at least three upsetting and three stretching in the austenite single phase region, and the forging ratio is 6-8;

[0020] Step 6, performing post-forging annealing heat treatment on the forging obtained in step 5 at a temperature of 640-670° C.;

[0021] Step 7, performing solution heat treatment and aging heat treatment on the forging obtained in step 6 in sequence to complete the preparation of the martensitic precipitation hardening stainless steel material;

[0022] Solution heat treatment includes: entering the furnace below 250°C, heating to 1020-1060°C, holding for 0.5-2h, and oil cooling to below 150°C after exiting the furnace;

[0023] Aging heat treatment includes: entering the furnace below 350°C, heating to 600-630°C, keeping warm for 4-8 hours, and air cooling to below 150°C after being taken out of the furnace.

[0024] A method for preparing an impeller material for a centrifugal compressor under high temperature and high partial pressure acidic wet hydrogen sulfide conditions comprises the following steps:

[0025] Step 1, the chemical composition includes, by mass percentage, C: 0.03-0.045%, Si: 0.3-0.5%, Mn: 0.3-0.6%, P≤0.015%, S≤0.01%, Cr: 12.5-14.0%, Ni: 5.5-6.5%, Mo: 1.0-1.35%, Cu: 1.7-2.1%, Nb: 0.5-0.75%, V≤0.05%, N≤0.04%, and the rest is Fe and unavoidable impurities, and P, S, V and N are not 0; mixing to obtain a mixed raw material;

[0026] Step 2, smelting and casting the mixed raw material obtained in step 1 through an electric furnace to obtain a primary steel ingot;

[0027] Step 3, performing secondary smelting and casting on the primary steel ingot obtained in step 2 under vacuum to obtain a secondary steel ingot;

[0028] Step 4, electroslag remelting the secondary steel ingot obtained in step 3 to obtain a tertiary steel ingot, i.e., a billet;

[0029] Step 5, forging the blank obtained in step 4 in an austenite single phase region, and air cooling to room temperature after forging to obtain a forging; the initial forging temperature in the austenite single phase region is 1150-1200° C., the final forging temperature is 800-900° C., the blank is subjected to at least three upsetting and three stretching in the austenite single phase region, and the forging ratio is 6-8;

[0030] Step 6, performing post-forging annealing heat treatment on the forging obtained in step 5 at a temperature of 640-670° C.;

[0031] Step 7, performing solution heat treatment and aging heat treatment on the forging obtained in step 6 in sequence to complete the preparation of the martensitic precipitation hardening stainless steel material;

[0032] Solution heat treatment includes: entering the furnace below 250°C, heating to 1020-1060°C, holding for 0.5-2h, and oil cooling to below 150°C after exiting the furnace;

[0033] Aging heat treatment includes: entering the furnace below 350°C, heating to 600-630°C, keeping warm for 4-8 hours, and air cooling to below 150°C after being taken out of the furnace.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The impeller material of the present invention controls the chromium equivalent, nickel equivalent and pitting equivalent by limiting the content of each raw material component, especially the content of nickel, chromium, carbon, molybdenum, manganese, niobium, copper and nitrogen, thereby obtaining a uniform and fine tempered martensitic structure and dispersed phase, thereby improving the stress corrosion resistance of the impeller material to high temperature and high partial pressure acidic wet hydrogen sulfide. In addition, the impeller material of the present invention belongs to martensitic precipitation hardening stainless steel, which is an extension of the martensitic precipitation hardening stainless steel material of the centrifugal compressor impeller under acidic wet hydrogen sulfide working conditions with an operating temperature of ≤180°C and a maximum partial pressure of hydrogen sulfide of ≤100KPa. Its mechanical properties are equivalent to those of N07718 precipitation hardening nickel-based alloy material, and its cost is much lower than that of N07718 precipitation hardening nickel-based alloy material (about one third of N07718), which meets the stress requirements of the centrifugal compressor impeller while improving the economy of the precipitation hardening nickel-based alloy material.

[0036] 2. Based on the existing S17400, S15500, and S45000 martensitic precipitation hardening stainless steel materials, the present invention optimizes the raw material composition and its manufacturing process through repeated experiments and verifications, combined with theoretical research and the use environment of impeller materials, and obtains a new type of stress corrosion-resistant stainless steel material, which is suitable for the impeller of a centrifugal compressor under high temperature and high partial pressure acidic wet hydrogen sulfide stress corrosion conditions. It can effectively solve the problems of poor stress corrosion resistance and short service life of the current martensitic precipitation hardening stainless steel material for centrifugal compressor impellers under high temperature and high partial pressure acidic wet hydrogen sulfide conditions, and at the same time, it has the advantages of high strength and economy.

[0037] 3. The preparation method of the present invention, through the coordination of raw material composition setting, equivalent control, and temperature setting during the preparation process, makes the impeller material have strong corrosion resistance, low cost and high strength.

[0038] In summary, the present invention combines theoretical research and the use environment requirements of impeller parts, and optimizes the forging process and heat treatment process based on equivalent control of the content of key elements in the raw materials, thereby obtaining an ideal material microstructure, and obtaining a new martensitic precipitation hardening stainless steel material suitable for centrifugal compressor impellers under high temperature and high partial pressure acidic wet hydrogen sulfide stress corrosion conditions. Compared with precipitation hardened nickel-based alloys, this material has the advantages of low material cost, easy processing, good applicability, high strength, strong economy, and a variety of optional forming methods such as welding and integral processing of parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is the test result of stress corrosion test of three parallel specimens in four-point bending test at 180℃ and hydrogen sulfide partial pressure of 800KPa, among which: Figure 1 (a) before cleaning, Figure 1 (b) After cleaning.

[0040] Figure 2 is the metallographic structure of the material of the present invention after solution aging, wherein: Figure 2 (a) is 100 times the solid solution aging metallographic structure, Figure 2 (b) is the 200 times solution aging metallographic structure.

[0041] Figure 3 This is the hydrogen sulfide stress corrosion crack morphology at room temperature with a hydrogen sulfide partial pressure of 800KPa, where: Figure 3 (a) is the macroscopic morphology, Figure 3 (b) is the metallographic structure of the crack extension zone.

[0042] Figure 4 This is the fracture morphology of the impact specimen at room temperature with a hydrogen sulfide partial pressure of 800KPa, where: Figure 4 (a) is the macroscopic morphology, Figure 4 (b) is the SEM morphology of the source region. Figure 4 (c) is the SEM morphology of the extended area. Figure 4 (d) is the scanning electron microscope morphology of the fracture area.

[0043] Figure 5 It is the macroscopic view of hydrogen sulfide stress corrosion cracking specimen at room temperature and hydrogen sulfide partial pressure of 500KPa, among which, Figure 5 (a) is the macroscopic morphology, Figure 5 (b) is the SEM morphology of the extended area. Figure 5 (c) is the scanning electron microscope morphology of the fracture area. DETAILED DESCRIPTION

[0044] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0045] The existing technology is to determine the material and strength design requirements for the impeller of a centrifugal compressor for high-temperature (>150°C) and high-partial-pressure (>10KPa) acidic wet hydrogen sulfide working conditions based on the compressor operating conditions (operating medium temperature, hydrogen sulfide partial pressure, etc.) and the usual results of impeller stress calculation.

[0046] The present invention aims to solve the technical problem that when selecting materials for centrifugal compressor impellers under high temperature (>150°C) and high partial pressure (>10KPa) acidic wet hydrogen sulfide working conditions, S41000, S41500, S42400 martensitic stainless steels and S17400, S15500, S45000 martensitic precipitation hardening stainless steel forging materials have low costs but poor resistance to high temperature and high partial pressure acidic wet hydrogen sulfide stress corrosion performance, and precipitation hardening nickel-based alloy materials have excellent resistance to high temperature and high partial pressure acidic wet hydrogen sulfide stress corrosion performance but extremely high costs. The present invention provides a centrifugal compressor impeller material for resistance to high temperature and high partial pressure acidic wet hydrogen sulfide stress corrosion and a preparation method thereof.

[0047] The present invention provides a method for preparing an impeller material for a centrifugal compressor under high temperature and high partial pressure acidic wet hydrogen sulfide conditions, comprising the following steps:

[0048] 1. Smelting

[0049] The raw materials are weighed according to the aforementioned chemical composition and their weight percentages, the mixed raw materials are smelted and cast in an electric furnace to obtain a primary steel ingot, the primary steel ingot is subjected to secondary smelting and casting in a vacuum state to obtain a secondary steel ingot, the secondary steel ingot is electroslag remelted to obtain a tertiary steel ingot as a billet.

[0050] 2. Forging and post-forging heat treatment

[0051] The three-stage steel ingot as the blank is forged in the austenite single phase region and air-cooled to room temperature after forging to obtain the forging. The initial forging temperature in the austenite single phase region is 1150-1200°C, the final forging temperature is 800-900°C, at least three upsetting and three drawing are performed, and the forging ratio is 6-8.

[0052] After forging, annealing is performed at 640-670°C.

[0053] 3.Performance heat treatment

[0054] The forgings are subjected to solution heat treatment and aging heat treatment to complete the preparation of the martensitic precipitation hardened stainless steel impeller material.

[0055] Specifically, the solution heat treatment is to put the steel into the furnace at a temperature below 250°C, heat it to 1020-1060°C, keep it at this temperature for 0.5-2 hours, and then oil cool it to below 150°C after it is taken out of the furnace. Specifically, the aging heat treatment is to put the steel into the furnace at a temperature below 350°C, heat it to 600-630°C, keep it at this temperature for 4-8 hours, and then air cool it to below 150°C after it is taken out of the furnace.

[0056] Example 1

[0057] A method for preparing an impeller material for a centrifugal compressor under high temperature and high partial pressure acidic wet hydrogen sulfide conditions comprises the following steps:

[0058] 1. Ingredients

[0059] Step 1: Prepare the ingredients according to the following composition by mass percentage:

[0060] C: 0.05%, Si: 0.45%, Mn: 0.8%, P: 0.02%, S: 0.012%, Cr: 12%, Ni: 5.5%, Mo: 0.9%, Cu: 1.6%, Nb: 0.4%, V: 0.01%, N: 0.04%, and the rest being Fe and inevitable impurities, are mixed to obtain a mixed raw material;

[0061] Step 2, smelting and casting the mixed raw material obtained in step 1 through an electric furnace to obtain a primary steel ingot;

[0062] Step 3, performing secondary smelting and casting on the primary steel ingot obtained in step 2 under vacuum to obtain a secondary steel ingot;

[0063] Step 4, electroslag remelting the secondary steel ingot obtained in step 3 to obtain a tertiary steel ingot as a billet.

[0064] The smelting, casting and pouring processes for obtaining primary steel ingots, secondary steel ingots and tertiary steel ingots can be adjusted according to actual conditions.

[0065] 2. Forging and post-forging heat treatment

[0066] Step 5, forging the three steel ingots used as blanks in step 4 in the austenite single phase region, and air cooling to room temperature after forging to obtain forgings; wherein the initial forging temperature in the austenite single phase region is 1200° C., the final forging temperature is 800° C., the blank is subjected to at least three upsetting and three drawing in the austenite single phase region, and the forging ratio is 8;

[0067] Step 6, annealing and cooling the forged part at 640° C. after forging in step 5;

[0068] 3.Performance heat treatment

[0069] Step 7, performing solution heat treatment and aging heat treatment on the forging obtained in step 6 to complete the preparation of the martensitic precipitation hardened stainless steel impeller material;

[0070] The specific solution heat treatment is as follows: put into the furnace at 250°C, heat to 1030°C, keep warm for 1h, and oil cool to 130°C after leaving the furnace;

[0071] The specific aging heat treatment is as follows: enter the furnace at 300°C, heat to 605°C, keep warm for 4 hours, and air cool to 130°C after exiting the furnace.

[0072] Example 2

[0073] A method for preparing an impeller material for a centrifugal compressor under high temperature and high partial pressure acidic wet hydrogen sulfide conditions comprises the following steps:

[0074] 1. Ingredients

[0075] Step 1: Prepare the ingredients according to the following composition by mass percentage:

[0076] C: 0.03%, Si: 0.5%, Mn: 0.55%, P: 0.018%, S: 0.015%, Cr: 13%, Ni: 6%, Mo: 0.8%, Cu: 2%, Nb: 0.55%, V: 0.035%, N: 0.03%, and the rest being Fe and inevitable impurities, are mixed to obtain a mixed raw material;

[0077] Step 2, smelting and casting the mixed raw material obtained in step 1 through an electric furnace to obtain a primary steel ingot;

[0078] Step 3, performing secondary smelting and casting on the primary steel ingot obtained in step 2 under vacuum to obtain a secondary steel ingot;

[0079] Step 4, electroslag remelting the secondary steel ingot obtained in step 3 to obtain a tertiary steel ingot as a billet.

[0080] The smelting, casting and pouring processes for obtaining primary steel ingots, secondary steel ingots and tertiary steel ingots can be adjusted according to actual conditions.

[0081] 2. Forging and post-forging heat treatment

[0082] Step 5, forging the three steel ingots used as blanks in step 4 in the austenite single phase region, and air cooling to room temperature after forging to obtain forgings; wherein the initial forging temperature in the austenite single phase region is 1180° C., the final forging temperature is 800° C., the blank is subjected to at least three upsetting and three drawing in the austenite single phase region, and the forging ratio is 6;

[0083] Step 6, annealing and cooling the forged piece after forging in step 5 at 660° C.;

[0084] 3.Performance heat treatment

[0085] Step 7, performing solution heat treatment and aging heat treatment on the forging obtained in step 6 to complete the preparation of the martensitic precipitation hardened stainless steel impeller material;

[0086] The specific solution heat treatment is as follows: put into the furnace at 150°C, heat to 1060°C, keep warm for 0.7h, and oil cool to 145°C after leaving the furnace;

[0087] The specific aging heat treatment is as follows: entering the furnace at 350°C, heating to 615°C, keeping the temperature for 6 hours, and air cooling to 135°C after exiting the furnace.

[0088] Example 3

[0089] A method for preparing an impeller material for a centrifugal compressor under high temperature and high partial pressure acidic wet hydrogen sulfide conditions comprises the following steps:

[0090] 1. Ingredients

[0091] Step 1: Prepare the ingredients according to the following composition by mass percentage:

[0092] C: 0.035%, Si: 0.3%, Mn: 0.3%, P: 0.015%, S: 0.005%, Cr: 14%, Ni: 6.5%, Mo: 1.4%, Cu: 2.1%, Nb: 0.7%, V: 0.04%, N: 0.01%, and the rest being Fe and inevitable impurities, are mixed to obtain a mixed raw material;

[0093] Step 2, smelting and casting the mixed raw material obtained in step 1 through an electric furnace to obtain a primary steel ingot;

[0094] Step 3, performing secondary smelting and casting on the primary steel ingot obtained in step 2 under vacuum to obtain a secondary steel ingot;

[0095] Step 4, electroslag remelting the secondary steel ingot obtained in step 3 to obtain a tertiary steel ingot as a billet.

[0096] The smelting, casting and pouring processes for obtaining primary steel ingots, secondary steel ingots and tertiary steel ingots can be adjusted according to actual conditions.

[0097] 2. Forging and post-forging heat treatment

[0098] Step 5, forging the three steel ingots used as blanks in step 4 in the austenite single phase region, and air cooling to room temperature after forging to obtain forgings; wherein the initial forging temperature in the austenite single phase region is 1160° C., the final forging temperature is 850° C., the blank is subjected to at least three upsetting and three drawing in the austenite single phase region, and the forging ratio is 7;

[0099] Step 6, annealing and cooling the forged part in step 5 at 665°C;

[0100] 3.Performance heat treatment

[0101] Step 7, performing solution heat treatment and aging heat treatment on the forging obtained in step 6 to complete the preparation of the martensitic precipitation hardened stainless steel impeller material;

[0102] The specific solution heat treatment is as follows: put into the furnace at 200°C, heat to 1040°C, keep warm for 1h, and oil cool to 145°C after leaving the furnace;

[0103] The specific aging heat treatment is as follows: enter the furnace at 250°C, heat to 625°C, keep warm for 6 hours, and air cool to 145°C after exiting the furnace.

[0104] Example 4

[0105] A method for preparing an impeller material for a centrifugal compressor under high temperature and high partial pressure acidic wet hydrogen sulfide conditions comprises the following steps:

[0106] 1. Ingredients

[0107] Step 1: Prepare the ingredients according to the following composition by mass percentage:

[0108] C: 0.045%, Si: 0.25%, Mn: 0.7%, P: 0.02%, S: 0.008%, Cr: 13.5%, Ni: 7%, Mo: 1.3%, Cu: 1.6%, Nb: 0.6%, V: 0.015%, N: 0.02%, and the rest being Fe and inevitable impurities, are mixed to obtain a mixed raw material;

[0109] Step 2, smelting and casting the mixed raw material obtained in step 1 through an electric furnace to obtain a primary steel ingot;

[0110] Step 3, performing secondary smelting and casting on the primary steel ingot obtained in step 2 under vacuum to obtain a secondary steel ingot;

[0111] Step 4, electroslag remelting the secondary steel ingot obtained in step 3 to obtain a tertiary steel ingot as a billet.

[0112] The smelting, casting and pouring processes for obtaining primary steel ingots, secondary steel ingots and tertiary steel ingots can be adjusted according to actual conditions.

[0113] 2. Forging and post-forging heat treatment

[0114] Step 5, forging the three steel ingots used as blanks in step 4 in the austenite single phase region, and air cooling to room temperature after forging to obtain a forging; wherein the initial forging temperature in the austenite single phase region is 1200° C., the final forging temperature is 880° C., the blank is subjected to at least three upsetting and three drawing in the austenite single phase region, and the forging ratio is 8;

[0115] Step 6, annealing and cooling the forged part at 650° C. after forging in step 5;

[0116] 3.Performance heat treatment

[0117] Step 7, performing solution heat treatment and aging heat treatment on the forging obtained in step 6 to complete the preparation of the martensitic precipitation hardened stainless steel impeller material.

[0118] The specific solution heat treatment is as follows: put into the furnace at 180°C, heat to 1050°C, keep warm for 1h, and oil cool to 135°C after leaving the furnace;

[0119] The specific aging heat treatment is as follows: enter the furnace at 230°C, heat to 630°C, keep warm for 5 hours, and air cool to 125°C after exiting the furnace.

[0120] Example 5

[0121] A method for preparing an impeller material for a centrifugal compressor under high temperature and high partial pressure acidic wet hydrogen sulfide conditions comprises the following steps:

[0122] 1. Ingredients

[0123] Step 1: Prepare the ingredients according to the following composition by mass percentage:

[0124] C: 0.05%, Si: 0.4%, Mn: 0.5%, P: 0.01%, S: 0.006%, Cr: 13%, Ni: 6%, Mo: 1.1%, Cu: 2.2%, Nb: 0.8%, V: 0.03%, N: 0.04%, and the rest being Fe and inevitable impurities, are mixed to obtain a mixed raw material;

[0125] Step 2, smelting and casting the mixed raw material obtained in step 1 through an electric furnace to obtain a primary steel ingot;

[0126] Step 3, performing secondary smelting and casting on the primary steel ingot obtained in step 2 under vacuum to obtain a secondary steel ingot;

[0127] Step 4, electroslag remelting the secondary steel ingot obtained in step 3 to obtain a tertiary steel ingot as a billet.

[0128] The smelting, casting and pouring processes for obtaining primary steel ingots, secondary steel ingots and tertiary steel ingots can be adjusted according to actual conditions.

[0129] 2. Forging and post-forging heat treatment

[0130] Step 5, forging the three steel ingots used as blanks in step 4 in the austenite single phase region, and air cooling to room temperature after forging to obtain a forging; wherein the initial forging temperature in the austenite single phase region is 1160° C., the final forging temperature is 830° C., the blank is subjected to at least three upsetting and three drawing in the austenite single phase region, and the forging ratio is 6;

[0131] Step 6, annealing and cooling the forged part at 650° C. after forging in step 5;

[0132] 3.Performance heat treatment

[0133] Step 7, performing solution heat treatment and aging heat treatment on the forging obtained in step 6 to complete the preparation of the martensitic precipitation hardened stainless steel impeller material;

[0134] The specific solution heat treatment is as follows: put into the furnace at 220℃, heat to 1040℃, keep warm for 1.2h, and oil cool to 125℃ after leaving the furnace;

[0135] The specific aging heat treatment is as follows: entering the furnace at 320°C, heating to 620°C, keeping the temperature for 7 hours, and air cooling to 100°C after exiting the furnace.

[0136] Example 6

[0137] A method for preparing an impeller material for a centrifugal compressor under high temperature and high partial pressure acidic wet hydrogen sulfide conditions comprises the following steps:

[0138] 1. Ingredients

[0139] Step 1: Prepare the ingredients according to the following composition by mass percentage:

[0140] C: 0.045%, Si: 0.5%, Mn: 0.4%, P: 0.012%, S: 0.01%, Cr: 13%, Ni: 5.5%, Mo: 1.1%, Cu: 1.8%, Nb: 0.5%, V: 0.01%, N: 0.04%, and the rest being Fe and inevitable impurities, are mixed to obtain a mixed raw material;

[0141] Step 2, smelting and casting the mixed raw material obtained in step 1 through an electric furnace to obtain a primary steel ingot;

[0142] Step 3, performing secondary smelting and casting on the primary steel ingot obtained in step 2 under vacuum to obtain a secondary steel ingot;

[0143] Step 4, electroslag remelting the secondary steel ingot obtained in step 3 to obtain a tertiary steel ingot as a billet.

[0144] The smelting, casting and pouring processes for obtaining primary steel ingots, secondary steel ingots and tertiary steel ingots can be adjusted according to actual conditions.

[0145] 2. Forging and post-forging heat treatment

[0146] Step 5, forging the three steel ingots used as blanks in step 4 in the austenite single phase region, and air cooling to room temperature after forging to obtain forgings; wherein the initial forging temperature in the austenite single phase region is 1200° C., the final forging temperature is 800° C., the blank is subjected to at least three upsetting and three drawing in the austenite single phase region, and the forging ratio is 6;

[0147] Step 6, annealing and cooling the forged part at 640° C. after forging in step 5;

[0148] 3.Performance heat treatment

[0149] Step 7, performing solution heat treatment and aging heat treatment on the forging obtained in step 6 to complete the preparation of the martensitic precipitation hardened stainless steel impeller material;

[0150] The specific solution heat treatment is as follows: put into the furnace at 250°C, heat to 1030°C, keep warm for 1h, and oil cool to 130°C after leaving the furnace;

[0151] The specific aging heat treatment is as follows: enter the furnace at 300°C, heat to 605°C, keep warm for 4 hours, and air cool to 130°C after exiting the furnace.

[0152] Example 7

[0153] A method for preparing an impeller material for a centrifugal compressor under high temperature and high partial pressure acidic wet hydrogen sulfide conditions comprises the following steps:

[0154] 1. Ingredients

[0155] Step 1: Prepare the ingredients according to the following composition by mass percentage:

[0156] C: 0.03%, Si: 0.45%, Mn: 0.6%, P: 0.01%, S: 0.005%, Cr: 13.5%, Ni: 6%, Mo: 1.3%, Cu: 2%, Nb: 0.65%, V: 0.035%, N: 0.03%, and the rest being Fe and inevitable impurities, are mixed to obtain a mixed raw material;

[0157] Step 2, smelting and casting the mixed raw material obtained in step 1 through an electric furnace to obtain a primary steel ingot;

[0158] Step 3, performing secondary smelting and casting on the primary steel ingot obtained in step 2 under vacuum to obtain a secondary steel ingot;

[0159] Step 4, electroslag remelting the secondary steel ingot obtained in step 3 to obtain a tertiary steel ingot as a billet.

[0160] The smelting, casting and pouring processes for obtaining primary steel ingots, secondary steel ingots and tertiary steel ingots can be adjusted according to actual conditions.

[0161] 2. Forging and post-forging heat treatment

[0162] Step 5, forging the three steel ingots used as blanks in step 4 in the austenite single phase region, and air cooling to room temperature after forging to obtain forgings; wherein the initial forging temperature in the austenite single phase region is 1180° C., the final forging temperature is 850° C., the blank is subjected to at least three upsetting and three drawing in the austenite single phase region, and the forging ratio is 7;

[0163] Step 6, annealing and cooling the forged piece after forging in step 5 at 660° C.;

[0164] 3.Performance heat treatment

[0165] Step 7, performing solution heat treatment and aging heat treatment on the forging obtained in step 6 to complete the preparation of the martensitic precipitation hardened stainless steel impeller material;

[0166] The specific solution heat treatment is as follows: put into the furnace at 200°C, heat to 1040°C, keep warm for 1h, and oil cool to 145°C after leaving the furnace;

[0167] The specific aging heat treatment is as follows: entering the furnace at 250°C, heating to 625°C, keeping the temperature for 6 hours, and air cooling to 145°C after exiting the furnace.

[0168] Example 8

[0169] A method for preparing an impeller material for a centrifugal compressor under high temperature and high partial pressure acidic wet hydrogen sulfide conditions comprises the following steps:

[0170] 1. Ingredients

[0171] Step 1: Prepare the ingredients according to the following composition by mass percentage:

[0172] C: 0.035%, Si: 0.3%, Mn: 0.3%, P: 0.015%, S: 0.007%, Cr: 14%, Ni: 6%, Mo: 1.25%, Cu: 2.1%, Nb: 0.7%, V: 0.04%, N: 0.01%, and the rest being Fe and inevitable impurities, are mixed to obtain a mixed raw material;

[0173] Step 2, smelting and casting the mixed raw material obtained in step 1 through an electric furnace to obtain a primary steel ingot;

[0174] Step 3, performing secondary smelting and casting on the primary steel ingot obtained in step 2 under vacuum to obtain a secondary steel ingot;

[0175] Step 4, electroslag remelting the secondary steel ingot obtained in step 3 to obtain a tertiary steel ingot as a billet.

[0176] The smelting, casting and pouring processes for obtaining primary steel ingots, secondary steel ingots and tertiary steel ingots can be adjusted according to actual conditions.

[0177] 2. Forging and post-forging heat treatment

[0178] Step 5, forging the three steel ingots used as blanks in step 4 in the austenite single phase region, and air cooling to room temperature after forging to obtain forgings; wherein the initial forging temperature in the austenite single phase region is 1160° C., the final forging temperature is 800° C., the blank is subjected to at least three upsetting and three drawing in the austenite single phase region, and the forging ratio is 8;

[0179] Step 6, annealing and cooling the forged part at 650° C. after forging in step 5;

[0180] 3.Performance heat treatment

[0181] Step 7, performing solution heat treatment and aging heat treatment on the forging obtained in step 6 to complete the preparation of the martensitic precipitation hardened stainless steel impeller material;

[0182] The specific solution heat treatment is as follows: put into the furnace at 150°C, heat to 1060°C, keep warm for 0.7h, and oil cool to 140°C after leaving the furnace;

[0183] The specific aging heat treatment is as follows: enter the furnace at 350°C, heat to 615°C, keep warm for 6 hours, and air cool to 135°C after exiting the furnace.

[0184] Experimental analysis

[0185] (1) Strength and toughness index

[0186]

[0187] (2) Stress corrosion performance test

[0188] With reference to GB / T 4157-2017 "Laboratory Test Method for Resistance of Metals to Sulfide Stress Cracking and Stress Corrosion Cracking in Hydrogen Sulfide Environments", the E-four-point bending test was used to evaluate the SSC resistance at a specified temperature (180°C), hydrogen sulfide partial pressure (100KPa), and 85%, 90%, 95%, and 100% yield strength stress loading. After the 720-hour test, three parallel specimens without cleaning corrosion products were observed. Figure 1 (a), then clean the corrosion products and observe them with a stereo microscope after magnification 10 times. Figure 1 (b), the results show that no cracks are found on all surfaces.

[0189] The beneficial effects brought about by the technical solution of the present invention (the effects brought about by each component or step or proved by experimental data): The present invention determines the centrifugal compressor impeller material and its preparation method for high temperature (>150°C) and high partial pressure (>10KPa) acidic wet hydrogen sulfide working conditions, which meet the design requirements of centrifugal compressor impeller materials under special harsh working conditions.

[0190] (3) Stress corrosion and metallographic structure

[0191] Stress corrosion is a failure phenomenon caused by the combined action of static stress (mainly tensile stress) and corrosion on materials, mechanical parts or components. It is the result of the combined action of stress and electrochemical corrosion. Therefore, the main factors affecting stress corrosion are medium characteristics, stress conditions, and chemical composition and organization of materials. Among them, medium characteristics and stress conditions are external factors, and material chemical composition and organization are internal factors. For materials, chemical composition determines the metallographic structure, that is, the metallographic structure is the determining factor affecting stress corrosion. After heat treatment, this material obtains a mixed structure of one or more of martensite, austenite and ferrite. Among them, ferrite will undergo selective corrosion, so its content must be strictly controlled. If the ferrite content is too high, the toughness of the material will decrease, thereby affecting its resistance to stress corrosion. Austenite is mainly residual austenite and reverse transformation austenite in the process of martensite transformation. The solubility of hydrogen in these austenite structures is high, making austenite a strong hydrogen trap. At the same time, the hydrogen diffusion rate in austenite is low, which hinders the diffusion and aggregation of hydrogen in the steel structure and reduces the stress corrosion sensitivity of the material. The uniform tempered martensite structure is beneficial to the resistance to hydrogen sulfide stress corrosion. After the solid solution aging heat treatment, the material of the present invention obtains a uniform mixed structure of tempered martensite and a certain amount of austenite, and the ferrite content is 0. Figure 2 shown.

[0192] (4) Role of key chemical elements

[0193] Stress corrosion follows the slip-dissolution mechanism (also known as the protective film destruction theory), that is, tensile stress causes dislocations to move out of the surface, forming microcracks and destroying the surface passivation film. At the same time, stress concentration reduces the anode potential, accelerates metal dissolution, and forms pits, which expands the microcracks. When the microcracks expand to a certain extent, a new passivation film will form on the surface. The formation and destruction of the passivation film repeat until the microcracks reach a critical size and quickly become unstable, leading to brittle fracture. Therefore, in a stress corrosion environment, the corrosion resistance of the material is very important.

[0194] Ni equivalent means that austenite forming elements include Ni, C, Mn, Cu, N, etc. Cr equivalent means that ferrite forming elements include Cr, Mo, Si, Nb, V, Ti, etc. Pitting equivalent means that pitting corrosion resistance elements include Cr, Mo, N, etc. The above-mentioned Ni equivalent, Cr equivalent and pitting equivalent settings can improve the stress corrosion resistance of the impeller material and ensure the material strength through the interaction of each element, laying the foundation for meeting the design and use requirements.

[0195] In the impeller material composition of the present invention, the main function of the Cr element is corrosion resistance. When the Cr content is greater than 10%, the corrosion resistance of the steel will be greatly improved, and a passivation film can be formed to effectively slow down the corrosion rate. The dispersed phase of Cr is a strong trap for hydrogen, which can reduce the stress corrosion sensitivity. At the same time, Cr is also a representative ferrite forming element, and the Cr content needs to be determined and controlled. The Ni element is a representative austenite stabilizing element, which can enhance the corrosion resistance of the material. At the same time, it is beneficial for the impeller material to have excellent toughness and ductility and reduce stress concentration. The Mn element is an element that expands and stabilizes austenite, and can promote the segregation of harmful elements such as P and S to the grain boundary, so that the harmful elements segregated at the grain boundary and the hydrogen ions generated by wet hydrogen sulfide interact to cause hydrogen-induced intergranular fracture. Therefore, reducing the Mn content can improve the material's stress corrosion resistance. The Mo element can form a dispersed precipitate with the S element to reduce the solid solution sulfur content, and can also hinder the segregation of the impurity element P to reduce the probability of hydrogen-induced intergranular fracture. At the same time, the dispersed phase of Mo is a strong trap for hydrogen, which can reduce the stress corrosion sensitivity. P and S are impurity elements, and their contents should be minimized to improve toughness and corrosion resistance. Cu and N are austenite-forming and stabilizing elements, which significantly increase material strength while enhancing local corrosion resistance, so their contents need to be determined and controlled. Si and Nb can improve the material's resistance to intergranular corrosion, and V can refine grains. They are both ferrite-forming elements, so their contents need to be determined and controlled. C is an element that expands the austenite region, and its content should be controlled below 0.08% to ensure corrosion resistance.

[0196] In summary, various raw material components work together to form the raw materials of the impeller material of the present invention, and the proportions of various raw materials are also complementary to each other.

[0197] The composition of the impeller material of the present invention is not a simple combination of elements, nor can it be obtained by a simple single test. It is determined by fully considering the applicable working conditions of the material, through repeated tests and practical verification, combined with theoretical research. Therefore, the impeller material not only needs to meet the above-mentioned composition requirements, but also the Ni equivalent, Cr equivalent and pitting equivalent must meet the conditions.

[0198] (5) Test cases where stress corrosion occurred and did not occur under other test conditions

[0199] like Figure 3 As shown, the three-point bending beam notch specimen was placed in a 5.0% NaCl + 0.5% glacial acetic acid solution, the test temperature was room temperature, and the hydrogen sulfide partial pressure was 800KPa. Figure 3 It can be seen that the crack initiates from the root of the notch of the specimen. Figure 3(a) After the crack initiates, it propagates forward in the form of transgranular cleavage. There is an obvious bifurcation phenomenon during the propagation process. At the crack tip, more bifurcations occur, and secondary cracks appear around the crack. Figure 3 (b).

[0200] (6) Stress corrosion research case

[0201] Stress corrosion test specimen:

[0202] like Figure 4 As shown, 5.0% NaCl + 0.5% glacial acetic acid solution is added to the autoclave, and the evaporation of the solution is used to form a humid gas phase environment. The three-point bending beam notch specimen is placed in the gas phase environment, and the hydrogen sulfide partial pressure is 800KPa. Figure 4 It can be seen that the fracture surface of the fractured specimen is flat and there is no obvious plastic deformation on the fracture surface, which is a brittle fracture. Figure 4 (a) The microstructure of the crack initiation site is mainly cleavage fracture, and there are slip features on the cleavage plane, which has the characteristics of quasi-cleavage fracture. Figure 4 (b) The microstructure of the extended area is a typical cleavage fracture, and obvious secondary cracking can be observed on the cleavage surface. Figure 4 (c) The microstructure of the fracture zone is mainly cleavage fracture, and there are dimples on the cleavage surface. Figure 4 (d).

[0203] Samples without stress corrosion:

[0204] like Figure 5 As shown, the three-point bending beam notch specimen was placed in a 5.0% NaCl + 0.5% glacial acetic acid solution, the test temperature was room temperature, the hydrogen sulfide partial pressure was 500KPa, and the test time was 720 hours. Figure 5 It can be seen that there are obvious signs of corrosion on the surface of the sample, the notch is smooth, and no cracks are found at the root of the notch.

[0205] (7) Forging cost

[0206] this material N07718 precipitation hardening nickel-based alloy 90-120 yuan / kg 330-380 Yuan / kg

Claims

1. A centrifugal compressor impeller material for high temperature and high partial pressure acidic wet hydrogen sulfide working conditions, characterized in that: The chemical composition includes, by mass percentage, C: 0.03-0.05%, Si: 0.2-0.5%, Mn: 0.3-0.8%, P≤0.025%, S≤0.015%, Cr: 12.0-14.0%, Ni: 5.5-7.0%, Mo: 0.8-1.5%, Cu: 1.5-2.2%, Nb: 0.4-0.8%, V≤0.05%, N≤0.04%, and the rest are Fe and unavoidable impurities, and P, S, V and N are not 0; Among them, the Ni equivalent is 8-10, the Cr equivalent is 15-18.5, and the pitting corrosion equivalent is 15.5-19; the Ni equivalent represents the total content of austenite forming elements, Ni equivalent = Ni + Co + 0.5Mn + 0.3Cu + 25N + 30C; the Cr equivalent represents the total content of ferrite forming elements, Cr equivalent = Cr + 1.5Mo + 2Si + 1.75Nb + 5V + 5.5Al + 1.5Ti + 0.75W; the pitting corrosion equivalent represents the tolerance to pitting corrosion, pitting corrosion equivalent = Cr + 3.3Mo + 16N.

2. The impeller material for centrifugal compressors used in high temperature and high partial pressure acidic wet hydrogen sulfide working conditions according to claim 1, characterized in that: The chemical composition includes, by mass percentage, C: 0.03-0.045%, Si: 0.3-0.5%, Mn: 0.3-0.6%, P≤0.015%, S≤0.01%, Cr: 12.5-14.0%, Ni: 5.5-6.5%, Mo: 1.0-1.35%, Cu: 1.7-2.1%, Nb: 0.5-0.75%, V≤0.05%, N≤0.04%, and the rest is Fe and unavoidable impurities, and P, S, V and N are not 0; Among them, the Ni equivalent is 8.3-9.5, the Cr equivalent is 16-18, and the pitting corrosion equivalent is 16.5-19; the Ni equivalent represents the total content of austenite forming elements, Ni equivalent = Ni + Co + 0.5Mn + 0.3Cu + 25N + 30C; the Cr equivalent represents the total content of ferrite forming elements, Cr equivalent = Cr + 1.5Mo + 2Si + 1.75Nb + 5V + 5.5Al + 1.5Ti + 0.75W; the pitting corrosion equivalent represents the tolerance to pitting corrosion, pitting corrosion equivalent = Cr + 3.3Mo + 16N.

3. A method for preparing a centrifugal compressor impeller material for high temperature and high partial pressure acidic wet hydrogen sulfide working conditions, characterized in that: The following steps are involved: Step 1, by mass percentage, 0.03-0.05%, Si: 0.2-0.5%, Mn: 0.3-0.8%, P≤0.025%, S≤0.015%, Cr: 12.0-14.0%, Ni: 5.5-7.0%, Mo: 0.8-1.5%, Cu: 1.5-2.2%, Nb: 0.4-0.8%, V≤0.05%, N≤0.04%, the rest being Fe and unavoidable impurities, and P, S, V and N are not 0; mix to obtain a mixed raw material; Step 2, smelting and casting the mixed raw material obtained in step 1 through an electric furnace to obtain a primary steel ingot; Step 3, performing secondary smelting and casting on the primary steel ingot obtained in step 2 under vacuum to obtain a secondary steel ingot; Step 4, electroslag remelting the secondary steel ingot obtained in step 3 to obtain a tertiary steel ingot, i.e., a billet; Step 5, forging the blank obtained in step 4 in an austenite single phase region, and air cooling to room temperature after forging to obtain a forging; the initial forging temperature in the austenite single phase region is 1150-1200° C., the final forging temperature is 800-900° C., the blank is subjected to at least three upsetting and three stretching in the austenite single phase region, and the forging ratio is 6-8; Step 6, performing post-forging annealing heat treatment on the forging obtained in step 5 at a temperature of 640-670° C.; Step 7, performing solution heat treatment and aging heat treatment on the forging obtained in step 6 in sequence to complete the preparation of the martensitic precipitation hardening stainless steel material; Solution heat treatment includes: entering the furnace below 250°C, heating to 1020-1060°C, holding for 0.5-2h, and oil cooling to below 150°C after exiting the furnace; Aging heat treatment includes: entering the furnace below 350°C, heating to 600-630°C, keeping warm for 4-8 hours, and air cooling to below 150°C after being taken out of the furnace.

4. The method for preparing a centrifugal compressor impeller material for high temperature and high partial pressure acidic wet hydrogen sulfide working conditions according to claim 3, characterized in that: The following steps are involved: Step 1, the chemical composition includes, by mass percentage, C: 0.03-0.045%, Si: 0.3-0.5%, Mn: 0.3-0.6%, P≤0.015%, S≤0.01%, Cr: 12.5-14.0%, Ni: 5.5-6.5%, Mo: 1.0-1.35%, Cu: 1.7-2.1%, Nb: 0.5-0.75%, V≤0.05%, N≤0.04%, and the rest is Fe and unavoidable impurities, and P, S, V and N are not 0; mixing to obtain a mixed raw material; Step 2, smelting and casting the mixed raw material obtained in step 1 through an electric furnace to obtain a primary steel ingot; Step 3, performing secondary smelting and casting on the primary steel ingot obtained in step 2 under vacuum to obtain a secondary steel ingot; Step 4, electroslag remelting the secondary steel ingot obtained in step 3 to obtain a tertiary steel ingot, i.e., a billet; Step 5, forging the blank obtained in step 4 in an austenite single phase region, and air cooling to room temperature after forging to obtain a forging; the initial forging temperature in the austenite single phase region is 1150-1200° C., the final forging temperature is 800-900° C., the blank is subjected to at least three upsetting and three stretching in the austenite single phase region, and the forging ratio is 6-8; Step 6, performing post-forging annealing heat treatment on the forging obtained in step 5 at a temperature of 640-670° C.; Step 7, performing solution heat treatment and aging heat treatment on the forging obtained in step 6 in sequence to complete the preparation of the martensitic precipitation hardening stainless steel material; Solution heat treatment includes: entering the furnace below 250°C, heating to 1020-1060°C, holding for 0.5-2h, and oil cooling to below 150°C after exiting the furnace; Aging heat treatment includes: entering the furnace below 350°C, heating to 600-630°C, keeping warm for 4-8 hours, and air cooling to below 150°C after being taken out of the furnace.

5. The method for preparing a centrifugal compressor impeller material for high temperature and high partial pressure acidic wet hydrogen sulfide working conditions according to claim 3, characterized in that: The following steps are involved: Step 1: Prepare the ingredients according to the following composition by mass percentage: C: 0.05%, Si: 0.45%, Mn: 0.8%, P: 0.02%, S: 0.012%, Cr: 12%, Ni: 5.5%, Mo: 0.9%, Cu: 1.6%, Nb: 0.4%, V: 0.01%, N: 0.04%, and the rest being Fe and inevitable impurities, are mixed to obtain a mixed raw material; Step 2, smelting and casting the mixed raw material obtained in step 1 through an electric furnace to obtain a primary steel ingot; Step 3, performing secondary smelting and casting on the primary steel ingot obtained in step 2 under vacuum to obtain a secondary steel ingot; Step 4, electroslag remelting the secondary steel ingot obtained in step 3 to obtain a tertiary steel ingot as a billet; Step 5, forging the three steel ingots used as blanks in step 4 in the austenite single phase region, and air cooling to room temperature after forging to obtain forgings; wherein the initial forging temperature in the austenite single phase region is 1200° C., the final forging temperature is 800° C., the blank is subjected to at least three upsetting and three drawing in the austenite single phase region, and the forging ratio is 8; Step 6, annealing and cooling the forged part at 640° C. after forging in step 5; Step 7, performing solution heat treatment and aging heat treatment on the forging obtained in step 6 to complete the preparation of the martensitic precipitation hardened stainless steel impeller material; The specific solution heat treatment is as follows: put into the furnace at 250°C, heat to 1030°C, keep warm for 1h, and oil cool to 130°C after leaving the furnace; The specific aging heat treatment is as follows: enter the furnace at 300°C, heat to 605°C, keep warm for 4 hours, and air cool to 130°C after exiting the furnace.

6. The method for preparing a centrifugal compressor impeller material for high temperature and high partial pressure acidic wet hydrogen sulfide working conditions according to claim 3, characterized in that: The following steps are involved: Step 1: Prepare the ingredients according to the following composition by mass percentage: C: 0.03%, Si: 0.5%, Mn: 0.55%, P: 0.018%, S: 0.015%, Cr: 13%, Ni: 6%, Mo: 0.8%, Cu: 2%, Nb: 0.55%, V: 0.035%, N: 0.03%, and the rest being Fe and inevitable impurities, are mixed to obtain a mixed raw material; Step 2, smelting and casting the mixed raw material obtained in step 1 through an electric furnace to obtain a primary steel ingot; Step 3, performing secondary smelting and casting on the primary steel ingot obtained in step 2 under vacuum to obtain a secondary steel ingot; Step 4, electroslag remelting the secondary steel ingot obtained in step 3 to obtain a tertiary steel ingot as a billet; Step 5, forging the three steel ingots used as blanks in step 4 in the austenite single phase region, and air cooling to room temperature after forging to obtain forgings; wherein the initial forging temperature in the austenite single phase region is 1180° C., the final forging temperature is 800° C., the blank is subjected to at least three upsetting and three drawing in the austenite single phase region, and the forging ratio is 6; Step 6, annealing and cooling the forged piece after forging in step 5 at 660° C.; Step 7, performing solution heat treatment and aging heat treatment on the forging obtained in step 6 to complete the preparation of the martensitic precipitation hardened stainless steel impeller material; The specific solution heat treatment is as follows: put into the furnace at 150°C, heat to 1060°C, keep warm for 0.7h, and oil cool to 145°C after leaving the furnace; The specific aging heat treatment is as follows: entering the furnace at 350°C, heating to 615°C, keeping the temperature for 6 hours, and air cooling to 135°C after exiting the furnace.

7. The method for preparing a centrifugal compressor impeller material for high temperature and high partial pressure acidic wet hydrogen sulfide working conditions according to claim 3, characterized in that: The following steps are involved: Step 1: Prepare the ingredients according to the following composition by mass percentage: C: 0.035%, Si: 0.3%, Mn: 0.3%, P: 0.015%, S: 0.005%, Cr: 14%, Ni: 6.5%, Mo: 1.4%, Cu: 2.1%, Nb: 0.7%, V: 0.04%, N: 0.01%, and the rest being Fe and inevitable impurities, are mixed to obtain a mixed raw material; Step 2, smelting and casting the mixed raw material obtained in step 1 through an electric furnace to obtain a primary steel ingot; Step 3, performing secondary smelting and casting on the primary steel ingot obtained in step 2 under vacuum to obtain a secondary steel ingot; Step 4, electroslag remelting the secondary steel ingot obtained in step 3 to obtain a tertiary steel ingot as a billet; Step 5, forging the three steel ingots used as blanks in step 4 in the austenite single phase region, and air cooling to room temperature after forging to obtain forgings; wherein the initial forging temperature in the austenite single phase region is 1160° C., the final forging temperature is 850° C., the blank is subjected to at least three upsetting and three drawing in the austenite single phase region, and the forging ratio is 7; Step 6, annealing and cooling the forged part in step 5 at 665°C; Step 7, performing solution heat treatment and aging heat treatment on the forging obtained in step 6 to complete the preparation of the martensitic precipitation hardened stainless steel impeller material; The specific solution heat treatment is as follows: put into the furnace at 200°C, heat to 1040°C, keep warm for 1h, and oil cool to 145°C after leaving the furnace; The specific aging heat treatment is as follows: enter the furnace at 250°C, heat to 625°C, keep warm for 6 hours, and air cool to 145°C after exiting the furnace.

8. The method for preparing a centrifugal compressor impeller material for high temperature and high partial pressure acidic wet hydrogen sulfide working conditions according to claim 3, characterized in that: The following steps are involved: Step 1: Prepare the ingredients according to the following composition by mass percentage: C: 0.045%, Si: 0.25%, Mn: 0.7%, P: 0.02%, S: 0.008%, Cr: 13.5%, Ni: 7%, Mo: 1.3%, Cu: 1.6%, Nb: 0.6%, V: 0.015%, N: 0.02%, and the rest being Fe and inevitable impurities, are mixed to obtain a mixed raw material; Step 2, smelting and casting the mixed raw material obtained in step 1 through an electric furnace to obtain a primary steel ingot; Step 3, performing secondary smelting and casting on the primary steel ingot obtained in step 2 under vacuum to obtain a secondary steel ingot; Step 4, electroslag remelting the secondary steel ingot obtained in step 3 to obtain a tertiary steel ingot as a billet; Step 5, forging the three steel ingots used as blanks in step 4 in the austenite single phase region, and air cooling to room temperature after forging to obtain a forging; wherein the initial forging temperature in the austenite single phase region is 1200° C., the final forging temperature is 880° C., the blank is subjected to at least three upsetting and three drawing in the austenite single phase region, and the forging ratio is 8; Step 6, annealing and cooling the forged part at 650° C. after forging in step 5; Step 7, performing solution heat treatment and aging heat treatment on the forging obtained in step 6 to complete the preparation of the martensitic precipitation hardened stainless steel impeller material. The specific solution heat treatment is as follows: put into the furnace at 180°C, heat to 1050°C, keep warm for 1h, and oil cool to 135°C after leaving the furnace; The specific aging heat treatment is as follows: enter the furnace at 230°C, heat to 630°C, keep warm for 5 hours, and air cool to 125°C after exiting the furnace.

9. The method for preparing a centrifugal compressor impeller material for high temperature and high partial pressure acidic wet hydrogen sulfide working conditions according to claim 4, characterized in that: The following steps are involved: Step 1: Prepare the ingredients according to the following composition by mass percentage: C: 0.045%, Si: 0.5%, Mn: 0.4%, P: 0.012%, S: 0.01%, Cr: 13%, Ni: 5.5%, Mo: 1.1%, Cu: 1.8%, Nb: 0.5%, V: 0.01%, N: 0.04%, and the rest being Fe and inevitable impurities, are mixed to obtain a mixed raw material; Step 2, smelting and casting the mixed raw material obtained in step 1 through an electric furnace to obtain a primary steel ingot; Step 3, performing secondary smelting and casting on the primary steel ingot obtained in step 2 under vacuum to obtain a secondary steel ingot; Step 4, electroslag remelting the secondary steel ingot obtained in step 3 to obtain a tertiary steel ingot as a billet; Step 5, forging the three steel ingots used as blanks in step 4 in the austenite single phase region, and air cooling to room temperature after forging to obtain forgings; wherein the initial forging temperature in the austenite single phase region is 1200° C., the final forging temperature is 800° C., the blank is subjected to at least three upsetting and three drawing in the austenite single phase region, and the forging ratio is 6; Step 6, annealing and cooling the forged part at 640° C. after forging in step 5; Step 7, performing solution heat treatment and aging heat treatment on the forging obtained in step 6 to complete the preparation of the martensitic precipitation hardened stainless steel impeller material; The specific solution heat treatment is as follows: put into the furnace at 250°C, heat to 1030°C, keep warm for 1h, and oil cool to 130°C after leaving the furnace; The specific aging heat treatment is as follows: enter the furnace at 300°C, heat to 605°C, keep warm for 4 hours, and air cool to 130°C after exiting the furnace.

10. The method for preparing a centrifugal compressor impeller material for high temperature and high partial pressure acidic wet hydrogen sulfide working conditions according to claim 4, characterized in that: The following steps are involved: Step 1: Prepare the ingredients according to the following composition by mass percentage: C: 0.03%, Si: 0.45%, Mn: 0.6%, P: 0.01%, S: 0.005%, Cr: 13.5%, Ni: 6%, Mo: 1.3%, Cu: 2%, Nb: 0.65%, V: 0.035%, N: 0.03%, and the rest being Fe and inevitable impurities, are mixed to obtain a mixed raw material; Step 2, smelting and casting the mixed raw material obtained in step 1 through an electric furnace to obtain a primary steel ingot; Step 3, performing secondary smelting and casting on the primary steel ingot obtained in step 2 under vacuum to obtain a secondary steel ingot; Step 4, electroslag remelting the secondary steel ingot obtained in step 3 to obtain a tertiary steel ingot as a billet; Step 5, forging the three steel ingots used as blanks in step 4 in the austenite single phase region, and air cooling to room temperature after forging to obtain forgings; wherein the initial forging temperature in the austenite single phase region is 1180° C., the final forging temperature is 850° C., the blank is subjected to at least three upsetting and three drawing in the austenite single phase region, and the forging ratio is 7; Step 6, annealing and cooling the forged piece after forging in step 5 at 660° C.; Step 7, performing solution heat treatment and aging heat treatment on the forging obtained in step 6 to complete the preparation of the martensitic precipitation hardened stainless steel impeller material; The specific solution heat treatment is as follows: put into the furnace at 200°C, heat to 1040°C, keep warm for 1h, and oil cool to 145°C after leaving the furnace; The specific aging heat treatment is as follows: entering the furnace at 250°C, heating to 625°C, keeping the temperature for 6 hours, and air cooling to 145°C after exiting the furnace.

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