CN111471898B - Low-expansion high-temperature alloy and preparation process thereof - Google Patents
Low-expansion high-temperature alloy and preparation process thereof Download PDFInfo
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- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 146
- 239000000956 alloy Substances 0.000 title claims abstract description 146
- 238000002360 preparation method Methods 0.000 title claims abstract description 8
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 19
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 19
- 238000010438 heat treatment Methods 0.000 claims description 77
- 238000005096 rolling process Methods 0.000 claims description 32
- 238000001816 cooling Methods 0.000 claims description 31
- 230000032683 aging Effects 0.000 claims description 25
- 238000004090 dissolution Methods 0.000 claims description 15
- 229910052782 aluminium Inorganic materials 0.000 claims description 14
- 229910052719 titanium Inorganic materials 0.000 claims description 14
- 229910052748 manganese Inorganic materials 0.000 claims description 11
- 238000004321 preservation Methods 0.000 claims description 9
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 238000000137 annealing Methods 0.000 claims 1
- 238000005496 tempering Methods 0.000 claims 1
- 238000005728 strengthening Methods 0.000 abstract description 21
- 239000000463 material Substances 0.000 abstract description 12
- 229910001566 austenite Inorganic materials 0.000 abstract description 5
- 239000002131 composite material Substances 0.000 abstract description 5
- 239000006104 solid solution Substances 0.000 abstract description 4
- 101000912561 Bos taurus Fibrinogen gamma-B chain Proteins 0.000 abstract description 3
- 238000001556 precipitation Methods 0.000 abstract description 3
- 229910001005 Ni3Al Inorganic materials 0.000 abstract description 2
- 239000011651 chromium Substances 0.000 description 36
- 229910052804 chromium Inorganic materials 0.000 description 11
- 239000013078 crystal Substances 0.000 description 9
- 230000003647 oxidation Effects 0.000 description 9
- 238000007254 oxidation reaction Methods 0.000 description 9
- 230000007797 corrosion Effects 0.000 description 7
- 238000005260 corrosion Methods 0.000 description 7
- 229910052758 niobium Inorganic materials 0.000 description 7
- 229910052726 zirconium Inorganic materials 0.000 description 6
- 239000010963 304 stainless steel Substances 0.000 description 5
- 229910000589 SAE 304 stainless steel Inorganic materials 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 238000003723 Smelting Methods 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 230000006698 induction Effects 0.000 description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 230000035882 stress Effects 0.000 description 3
- 238000005336 cracking Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 229910000601 superalloy Inorganic materials 0.000 description 2
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- 239000010883 coal ash Substances 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C19/00—Alloys based on nickel or cobalt
- C22C19/03—Alloys based on nickel or cobalt based on nickel
- C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
- C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
- C22C19/056—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 10% but less than 20%
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C30/00—Alloys containing less than 50% by weight of each constituent
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/10—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
- B21B2003/001—Aluminium or its alloys
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/004—Dispersions; Precipitations
Abstract
A low-expansion high-temperature alloy and a preparation process thereof adopt a solid solution and precipitation composite strengthening mode to ensure that the alloy has good high-temperature strength and structural stability, and simultaneously, the high W, Mo content in the alloy ensures that the alloy still has an extremely low thermal expansion coefficient above 800 ℃. The material obtained according to the invention consists of austenite, Ni3Al (gamma '), grain boundary M6C and M23C6 type carbide, wherein the volume fraction of the intragranular gamma' strengthening phase reaches more than 40%, and the volume fraction of the grain boundary carbide is not less than 15%. The alloy has good structure stability, and no harmful phase is separated out after the alloy is exposed for 1000 hours at the temperature of 800-850 ℃.
Description
Technical Field
The invention belongs to the field of high-temperature alloy, and particularly relates to a low-expansion high-temperature alloy and a preparation process thereof, which are particularly suitable for thick-wall parts such as ultra-supercritical unit blades, rotors, bolts, valves and the like, hydrogen production conversion furnaces, high-temperature gas cooled reactor key parts and the like which are used for a long time under the working condition of high temperature and low stress.
Background
The material is generally required to have good high-temperature strength and oxidation/corrosion resistance during high-temperature service, so that the excellent service life of the material is guaranteed. Such as superheater/reheater in the thermal power industry, ethylene cracking furnace tubes in the petrochemical industry, and the like. Wherein, the superheater/reheater generally requires materials with excellent high-temperature endurance strength, good oxidation resistance and good coal ash corrosion resistance; cracking furnace tubes generally require materials to have excellent oxidation resistance and coking and carburizing capabilities at high temperatures, and also require good high-temperature durable strength properties. Therefore, the performance requirements of the high-temperature components on the alternative materials are different due to different service working conditions of the high-temperature components. Under the condition of high-temperature service, the thick-wall part has high requirements on high-temperature fatigue performance, stress relaxation and the like of the material due to the poor heat transfer performance of the material, the limitation of factors such as a geometric structure and the like besides performance requirements on strength, corrosion and the like. Particularly, materials such as rotors and bolts are generally required to have a low thermal expansion coefficient, so that a component can be ensured to generate a small internal stress in the service period, and the service life of the material under a high-temperature condition is further improved.
To ensure a low thermal expansion coefficient, the chromium content of the superalloy is generally controlled to a low range, and the content of W, Mo and other elements is increased. However, chromium has the characteristics of strengthening grain boundaries, improving corrosion/oxidation resistance of the alloy and the like, so that the content of the chromium is ensured to be not too low as much as possible. In addition, although the element W, Mo has a solid solution strengthening effect, its solubility is low and the strengthening effect is not obvious, and it is not guaranteed that the alloy obtains a stable structure and achieves high strength by alloying alone. Therefore, the thermal expansion coefficient of the alloy is reduced by adjusting the contents of elements such as Cr, W, Mo and the like in the alloy, and meanwhile, the corrosion resistance, oxidation resistance, strength performance and the like of the alloy are greatly influenced.
Disclosure of Invention
The invention aims to provide a low-expansion high-temperature alloy and a preparation process thereof.
In order to achieve the above purpose, the invention adopts the technical scheme that:
a low expansion high temperature alloy comprises the following elements by mass percent: c: less than or equal to 0.05 percent, Cr: 15-18%, Co: 10-15%, Mn: less than or equal to 0.5 percent, Si: less than or equal to 0.5 percent, Nb: 0.1-0.5%, Mo: 8.5-10%, W: 1.0-3.5%, Ti: 4-4.5%, Al: 3-4%, B: less than or equal to 0.003 percent, Zr: less than or equal to 0.03 percent, and the balance being Ni.
A preparation process of a low-expansion high-temperature alloy comprises the following steps:
1) high-temperature rolling: heating the alloy to 10-50 ℃ above the gamma' dissolving temperature for high-temperature rolling, and controlling the deformation of each pass not to exceed 15% and the total deformation not less than 50%; the alloy comprises the following elements in percentage by mass: c: less than or equal to 0.05 percent, Cr: 15-18%, Co: 10-15%, Mn: less than or equal to 0.5 percent, Si: less than or equal to 0.5 percent, Nb: 0.1-0.5%, Mo: 8.5-10%, W: 1.0-3.5%, Ti: 4-4.5%, Al: 3-4%, B: less than or equal to 0.003 percent, Zr: less than or equal to 0.03 percent, and the balance being Ni;
2) high-temperature aging treatment: heating the alloy after high-temperature rolling to 950-1020 ℃, preserving heat for 0.5-1.0 h, then continuously heating to 10-50 ℃ below the gamma' dissolving temperature along with the furnace, preserving heat for 3-5 h, and cooling to room temperature after completion;
3) and (3) low-temperature aging treatment: heating the alloy subjected to high-temperature aging treatment to Cr23C6Keeping the temperature below the dissolution temperature of 200 ℃ and 250 ℃ for 10-16 hours, then air cooling, and then heating to Cr23C6The temperature is kept below the dissolving temperature by 100 ℃ and 150 ℃ for 3 to 8 hours.
The further improvement of the invention is that in the step 1), the next rolling is carried out after the furnace returning and the heat preservation are carried out after the deformation of each pass is finished.
The further improvement of the invention is that in the step 1), the temperature of the furnace returning and heat preservation after the deformation of each pass is 1120-1160 ℃, and the time is 15-20 min.
The further improvement of the invention is that in the step 2), the heating rate does not exceed 10 ℃/min in the alloy high-temperature aging treatment process.
The further improvement of the invention is that in the step 3), the alloy after high-temperature aging treatment is heated to Cr at a heating rate of not less than 60 ℃/min23C6Keeping the temperature below the dissolution temperature of 200 ℃ and 250 ℃ for 10-16 hours, then air cooling, and heating to Cr at a heating rate of not less than 60 ℃/min23C6Keeping the temperature for 3-8 hours in the range of 100-150 ℃ below the dissolution temperature and then cooling in air.
Compared with the prior art, the invention has the following beneficial effects: the alloy has a low coefficient of thermal expansion, and has good corrosion/oxidation resistance and high-temperature strength. The content of Cr element is improved on the premise of ensuring lower thermal expansion coefficient of the alloy by controlling the addition amount of Al, Ti and other elements and controlling the size and shape of precipitated phase. Meanwhile, the strength performance of the alloy is improved by adding W, Mo with a certain content in a solid solution and precipitation composite strengthening mode. Finally, the high-temperature alloy with stable structure, low thermal expansion coefficient, good corrosion/oxidation resistance and high-temperature strength performance is obtained.
Drawings
FIG. 1 is a photograph of the structure of the alloy of example 1;
FIG. 2 is the morphology of the gamma' -strengthening phase of the alloy in example 1;
FIG. 3 is a photograph of the structure of the alloy of example 1 after 1000 hours of thermal exposure at 850 ℃;
FIG. 4 is a graph of the morphology of the gamma prime strengthening phase of the alloy of example 1 after 1000 hours of thermal exposure at 850 ℃;
FIG. 5 shows the results of the thermal expansion coefficient test of the alloy of example 1
FIG. 6 is a photograph of the structure of the alloy of example 2;
FIG. 7 shows the morphology of the gamma' -strengthening phase of the alloy in example 2.
Detailed Description
The present invention will be described in further detail with reference to examples.
The low-expansion high-temperature alloy comprises the following elements in percentage by mass: c: less than or equal to 0.05 percent, Cr: 15-18%, Co: 10-15%, Mn: less than or equal to 0.5 percent, Si: less than or equal to 0.5 percent, Nb: 0.1-0.5%, Mo: 8.5-10%, W: 1.0-3.5%, Ti: 4-4.5%, Al: 3-4%, B: less than or equal to 0.003 percent, Zr: less than or equal to 0.03 percent, and the balance being Ni.
The alloy as-cast structure consists of four phases of intragranular austenite, primary gamma' and grain boundary M6C and M23C6 type carbide, wherein the volume fraction of the grain boundary carbide is not less than 15 percent;
the preparation process of the low-expansion high-temperature alloy comprises the following steps of:
1) high-temperature rolling: heating the alloy to 10-50 ℃ above the gamma' dissolving temperature for high-temperature rolling, wherein the total deformation is not less than 50%; in the rolling process, a 304 stainless steel sheath with the thickness of 0.5-1.0mm is adopted outside the alloy ingot to slow down the temperature reduction rate after the alloy ingot is taken out of the furnace, the deformation amount of each pass is controlled not to exceed 15%, and the next pass of rolling is carried out after the alloy ingot is subjected to remelting and heat preservation for 15-20min after the deformation is finished.
2) High-temperature aging treatment: heating the rolled alloy to 950-1020 ℃ along with the furnace, preserving heat for 0.5-1.0 h, then continuously heating the alloy along with the furnace to 10-50 ℃ below the gamma' dissolving temperature, preserving heat for 3-5 h, and cooling the alloy to room temperature in air after the completion; the temperature rise rate along with the furnace in the high-temperature aging treatment process of the alloy is not more than 10 ℃/min, the average grain size of the alloy after the high-temperature aging treatment is up to 70-100 mu m, and the volume fraction of gamma' phase in the grain is 10-15%.
3) And (3) low-temperature aging treatment: heating the alloy to Cr23C6Keeping the temperature below the dissolution temperature of 200 ℃ and 250 ℃ for 10-16 hours, then air cooling, and then heating to Cr23C6Keeping the temperature for 3-8 hours in the range of 100-150 ℃ below the dissolving temperature and then cooling in air. The alloy heating rate is not lower than 60 ℃/min during the low-temperature aging of the alloy, the volume fraction of the gamma' strengthening phase in the crystal after the aging is finished reaches more than 40%, and the volume fraction of the grain boundary carbide is not lower than 15%. The gamma 'in the crystal is in a cubic shape, and the size of the gamma' is about 200 nm and 300 nm.
The alloy has compressive yield strengths of 730 MPa, 450 MPa, 320MPa or more at 800 deg.C, 850 deg.C and 900 deg.C after heat treatment, and has thermal expansion coefficients of 14.2, 14.5 and 14.8 x 10 under three temperature conditions-6K-1. In addition, the alloy has good structural stability, and no harmful phase is precipitated after the alloy is subjected to thermal exposure for 1000 hours at 800-850 ℃.
Example 1
The alloy ensures a certain Cr content to ensure the oxidation resistance, improves elements such as W, Mo, Al, Ti and the like, and promotes the alloy to obtain high strength and low thermal expansion coefficient by a composite strengthening mode. Smelting the alloy by using a vacuum induction furnace, wherein the obtained alloy comprises the following components in percentage by mass: c: 0.04%, Cr: 16%, Co: 15%, Mn: 0.3%, Si: 0.2%, Nb: 0.5%, Mo: 9.0%, W: 3.0%, Ti: 4.5%, Al: 3.0%, B: 0.002%, Zr: 0.02% and the balance of Ni.
Heating the alloy to 20 ℃ above the gamma' dissolving temperature for high-temperature rolling, wherein the total deformation is 50%; in the rolling process, a 304 stainless steel sheath with the thickness of 1.0mm is adopted outside the alloy ingot to slow down the temperature reduction rate after the alloy ingot is discharged from the furnace, the deformation of each pass is controlled not to exceed 15%, and the alloy ingot is subjected to next rolling after the alloy ingot is subjected to remelting and heat preservation for 20min after the deformation is finished.
And (3) heating the rolled alloy to 950 ℃ along with the furnace at the speed of 10 ℃/min, preserving heat for 0.5 hour, then continuously heating the alloy along with the furnace to below the gamma' dissolving temperature by 30 ℃, preserving heat for 4 hours, and cooling the alloy to room temperature in air after the reaction is finished. Heating the alloy to Cr at a heating rate of 60 ℃/min23C6Keeping the temperature below the dissolution temperature of 200 ℃ for 16 hours, then air cooling, and then heating to Cr23C6Keeping the temperature below the dissolving temperature by 100 ℃ for 8 hours, and then cooling in air.
Fig. 1 and 2 show the structure photograph and the γ 'strengthening phase morphology of the alloy, in which austenite and uniformly distributed γ' form the inside of the crystal, and M6C and M23C6 type carbides exist in the grain boundaries. Wherein, the volume fraction of the gamma' strengthening phase in the crystal reaches more than 40 percent, and the volume fraction of the grain boundary carbide is not less than 15 percent. The alloy prepared by the process has good structure stability, the grain size is 70-100 mu m, the gamma' in the crystal is in a cubic shape, and the size is about 200-300 nm.
FIGS. 3 and 4 are photographs of the structure and the morphology of the gamma prime strengthening phase of the alloy after 1000 hours of heat exposure at 850 ℃. Therefore, the alloy has good structure stability, and no harmful phase is precipitated during heat exposure. The gamma prime strengthening phase spheroidizes, but its size does not appear to grow significantly.
FIG. 5 shows the results of the thermal expansion coefficient test of the alloy, and it can be seen that the thermal expansion coefficients of the alloy at 800 deg.C, 850 deg.C and 900 deg.C are 14.15, 14.38, 14.57 x 10-6K-1. The coefficient of thermal expansion of the alloy is relatively low compared to most superalloys.
Example 2
The alloy ensures a certain Cr content to ensure the oxidation resistance, improves elements such as W, Mo, Al, Ti and the like, and promotes the alloy to obtain high strength and low thermal expansion coefficient by a composite strengthening mode. Smelting the alloy by using a vacuum induction furnace, wherein the obtained alloy comprises the following components in percentage by mass: c: 0.04%, Cr: 16%, Co: 15%, Mn: 0.3%, Si: 0.2%, Nb: 0.5%, Mo: 9.0%, W: 3.0%, Ti: 4.0%, Al: 4.0%, B: 0.002%, Zr: 0.02% and the balance of Ni.
Heating the alloy to 30 ℃ above the gamma' dissolving temperature for high-temperature rolling, wherein the total deformation is 50%; in the rolling process, a 304 stainless steel sheath with the thickness of 1.0mm is adopted outside the alloy ingot to slow down the temperature reduction rate after the alloy ingot is discharged from the furnace, the deformation amount of each pass is controlled not to exceed 15%, and the alloy ingot is returned to the furnace and kept warm for 15% after the deformation is finished to be rolled for the next pass.
And (3) heating the rolled alloy to 1000 ℃ along with the furnace at the speed of 10 ℃/min, preserving the heat for 0.5-1.0 hour, then continuously heating along with the furnace to 20 ℃ below the gamma' dissolving temperature, preserving the heat for 4 hours, and cooling the alloy to room temperature in air after the completion. Heating the alloy to Cr at a heating rate of 60 ℃/min23C6Keeping the temperature below the dissolution temperature of 250 ℃ for 16 hours, then air cooling, and then heating to Cr23C6Keeping the temperature below the dissolving temperature by 150 ℃ for 8 hours, and then cooling in air.
Fig. 6 and 7 show the structure photograph and the γ 'strengthening phase morphology of the alloy, in which austenite and uniformly distributed γ' form the inside of the crystal, and M6C and M23C6 type carbides exist in the grain boundaries. Wherein, the volume fraction of the gamma' strengthening phase in the crystal reaches more than 40 percent, and the volume fraction of the grain boundary carbide is not less than 15 percent. The alloy prepared by the process has good structure stability, the grain size is 70-100 mu m, the gamma' in the crystal is in a cubic shape, and the size is about 200-300 nm.
Example 3
1) High-temperature rolling: heating the alloy to 50 ℃ above the gamma' dissolving temperature for high-temperature rolling, controlling the deformation of each pass not to exceed 15%, returning to the furnace after the deformation of each pass is completed, keeping the temperature at 1160 ℃ for 15min, and then performing the next pass of rolling, wherein the total deformation is not lower than 50%; the alloy comprises the following elements in percentage by mass: c: 0.05%, Cr: 15%, Co: 10%, Mn: 0.1%, Si: 0.4%, Nb: 0.1%, Mo: 8.5%, W: 1.0%, Ti: 4%, Al: 3%, B: 0.003%, Zr: 0.01 percent, and the balance of Ni;
2) high-temperature aging treatment: heating the alloy rolled at high temperature to 950 ℃ at a heating rate of 10 ℃/min, preserving heat for 1.0 hour, then continuously heating the alloy at the heating rate of 10 ℃/min to 10 ℃ below the gamma' dissolving temperature along with the furnace, preserving heat for 5 hours, and cooling to room temperature after finishing;
3) and (3) low-temperature aging treatment: heating the alloy subjected to high-temperature aging treatment to Cr at a heating rate of not less than 60 ℃/min23C6Keeping the temperature below the dissolution temperature within 200 ℃ for 16 hours, then air-cooling, and then heating to Cr at a heating rate of not less than 60 ℃/min23C6Keeping the temperature for 8 hours below the dissolution temperature within the range of 100 ℃ and then cooling in air.
Example 4
1) High-temperature rolling: heating the alloy to 40 ℃ above the gamma' dissolving temperature for high-temperature rolling, controlling the deformation of each pass not to exceed 15%, returning to the furnace after the deformation of each pass is completed, preserving the heat at 1120 ℃ for 20min, and then carrying out the next pass of rolling, wherein the total deformation is not lower than 50%; the alloy comprises the following elements in percentage by mass: c: 0.01%, Cr: 16%, Co: 12%, Mn: 0.2%, Si: 0.3%, Nb: 0.2%, Mo: 9%, W: 2.0%, Ti: 4.5%, Al: 4%, B: 0.001%, Zr: 0.03 percent, and the balance being Ni;
2) high-temperature aging treatment: heating the alloy rolled at the high temperature at the heating rate of 5 ℃/min to 1020 ℃, preserving the heat for 0.5 hour, then continuously heating the alloy at the heating rate of 5 ℃/min to the temperature which is 50 ℃ below the gamma' dissolving temperature along with the furnace, preserving the heat for 3 hours, and cooling the alloy to the room temperature after the completion;
3) and (3) low-temperature aging treatment: heating the alloy subjected to high-temperature aging treatment to Cr at a heating rate of not less than 60 ℃/min23C6Keeping the temperature below the dissolution temperature within 250 ℃ for 10 hours, then air-cooling, and then heating to Cr at a heating rate of not less than 60 ℃/min23C6Keeping the temperature below the dissolution temperature within 150 ℃ for 3 hours, and then cooling in air
Example 5
1) High-temperature rolling: heating the alloy to 10 ℃ above the gamma' dissolving temperature for high-temperature rolling, controlling the deformation of each pass not to exceed 15%, returning to the furnace after the deformation of each pass is completed, preserving the heat at 1150 ℃ for 17min, and then carrying out the next pass of rolling, wherein the total deformation is not lower than 50%; the alloy comprises the following elements in percentage by mass: c: 0.02%, Cr: 18%, Co: 15%, Mn: 0.5%, Si: 0.5%, Nb: 0.3%, Mo: 10%, W: 3.5%, Ti: 4.2%, Al: 3% and the balance of Ni;
2) high-temperature aging treatment: heating the alloy rolled at high temperature to 970 ℃ at the heating rate of 3 ℃/min, preserving heat for 0.6 hour, then continuously heating the alloy at the heating rate of 3 ℃/min to a temperature which is 30 ℃ below the gamma' dissolving temperature along with the furnace, preserving heat for 4 hours, and cooling to room temperature after the completion;
3) and (3) low-temperature aging treatment: heating the alloy subjected to high-temperature aging treatment to Cr at a heating rate of not less than 60 ℃/min23C6Keeping the temperature below the dissolution temperature within 230 ℃ for 14 hours, then air-cooling, and then heating to Cr at a heating rate of not less than 60 ℃/min23C6Comparative example 1 air cooling after 5 hours of heat preservation at 130 ℃ below the dissolution temperature
Smelting the alloy by using a vacuum induction furnace, wherein the obtained alloy comprises the following components in percentage by mass: c: 0.04%, Cr: 16%, Co: 15%, Mn: 0.3%, Si: 0.2%, Nb: 0.5%, Mo: 9.0%, W: 3.0%, Ti: 4.5%, Al: 3.0%, B: 0.002%, Zr: 0.02% and the balance of Ni.
Heating the alloy to 20 ℃ above the gamma' dissolving temperature for high-temperature rolling, wherein the total deformation is 50%; in the rolling process, a 304 stainless steel sheath with the thickness of 1.0mm is adopted outside the alloy ingot to slow down the temperature reduction rate after the alloy ingot is discharged from the furnace, the deformation of each pass is controlled not to exceed 15%, and the alloy ingot is subjected to next rolling after the alloy ingot is subjected to remelting and heat preservation for 20min after the deformation is finished.
And (3) heating the rolled alloy to 950 ℃ along with the furnace at the speed of 10 ℃/min, preserving heat for 0.5 hour, then continuously heating the alloy along with the furnace to below the gamma' dissolving temperature by 30 ℃, preserving heat for 4 hours, and cooling the alloy to room temperature in air after the reaction is finished. Heating the alloy to Cr at a heating rate of 60 ℃/min23C6The temperature is 100 ℃ below the dissolving temperature, and the air cooling is carried out after the heat preservation is carried out for 2 hours.
Comparative example 2
Smelting the alloy by using a vacuum induction furnace, wherein the obtained alloy comprises the following components in percentage by mass: c: 0.04%, Cr: 16%, Co: 15%, Mn: 0.3%, Si: 0.2%, Nb: 0.5%, Mo: 9.0%, W: 3.0%, Ti: 4.5%, Al: 3.0%, B: 0.002%, Zr: 0.02% and the balance of Ni.
Heating the alloy to 20 ℃ above the gamma' dissolving temperature for high-temperature rolling, wherein the total deformation is 50%; in the rolling process, a 304 stainless steel sheath with the thickness of 1.0mm is adopted outside the alloy ingot to slow down the temperature reduction rate after the alloy ingot is discharged from the furnace, the deformation of each pass is controlled not to exceed 15%, and the alloy ingot is subjected to next rolling after the alloy ingot is subjected to remelting and heat preservation for 20min after the deformation is finished.
And (3) heating the rolled alloy to 950 ℃ along with the furnace at the speed of 10 ℃/min, preserving heat for 0.5 hour, then continuously heating the alloy along with the furnace to below the gamma' dissolving temperature by 30 ℃, preserving heat for 4 hours, and cooling the alloy to room temperature in air after the reaction is finished. Heating the alloy to Cr at a heating rate of 60 ℃/min23C6Keeping the temperature below the dissolution temperature of 200 ℃ for 8 hours, then air cooling, and then heating to Cr23C6Keeping the temperature below the dissolving temperature for 2 hours at 100 ℃ and then cooling in air.
Table 1 shows the results of comparing the compressive yield strengths of the alloy of example 1 and the comparative example at 800-900 ℃, and it can be seen that the alloy of example 1 has good high-temperature yield strengths as the compressive yield strengths of not less than 730 MPa, 450 MPa and 320MPa at 800 ℃, 850 ℃ and 900 ℃ after heat treatment. The comparative example alloy was not sufficiently aged and the gamma' -strengthening phase was not sufficiently precipitated, so that the high-temperature strength was relatively low.
TABLE 1 alloy high temperature compressive yield strength
The invention is developed aiming at the requirements of high-temperature and high-stress long-term service working conditions such as steam turbine rotors, blades and the like in the industries of thermal power, nuclear power and the like on extremely high strength, low thermal expansion coefficient and the like of materials. The alloy is ensured to have good high-temperature strength and structural stability by adopting a solid solution and precipitation composite strengthening mode, and meanwhile, the high W, Mo content in the alloy ensures that the alloy still has an extremely low thermal expansion coefficient above 800 ℃. The material obtained according to the invention consists of austenite, Ni3Al (gamma '), grain boundary M6C and M23C6 type carbide, wherein the volume fraction of the intragranular gamma' strengthening phase reaches more than 40%, and the volume fraction of the grain boundary carbide is not less than 15%. The alloy prepared by the process has good structure stability, the grain size is 70-100 mu m, the gamma' in the crystal is in a cubic shape, and the size is about 200-300 nm. The alloy has compressive yield strengths of 730 MPa, 450 MPa, 320MPa or more at 800 deg.C, 850 deg.C and 900 deg.C after heat treatment, and has thermal expansion coefficients of 14.2, 14.5 and 14.8 x 10 under three temperature conditions-6K-1. In addition, the alloy has good structural stability, and no harmful phase is precipitated after the alloy is subjected to thermal exposure for 1000 hours at 800-850 ℃.
Claims (5)
1. A preparation process of a low-expansion high-temperature alloy is characterized by comprising the following steps of:
1) high-temperature rolling: heating the alloy to 10-50 ℃ above the gamma' dissolving temperature for high-temperature rolling, and controlling the deformation of each pass not to exceed 15% and the total deformation not less than 50%; the alloy comprises the following elements in percentage by mass: c: less than or equal to 0.05 percent, Cr: 15-18%, Co: 10-15%, Mn: less than or equal to 0.5 percent, Si: less than or equal to 0.5 percent, Nb: 0.1-0.5%, Mo: 8.5-10%, W: 1.0-3.5%, Ti: 4-4.5%, Al: 3-4%, B: less than or equal to 0.003 percent, Zr: less than or equal to 0.03 percent, and the balance being Ni;
2) high-temperature aging treatment: heating the alloy after high-temperature rolling to 950-1020 ℃, preserving heat for 0.5-1.0 h, then continuously heating to 10-50 ℃ below the gamma' dissolving temperature along with the furnace, preserving heat for 3-5 h, and cooling to room temperature after completion;
3) and (3) low-temperature aging treatment: heating the alloy subjected to high-temperature aging treatment to Cr23C6Keeping the temperature below the dissolution temperature of 200 ℃ and 250 ℃ for 10-16 hours, then air cooling, and then heating to Cr23C6The temperature is 100 ℃ and 150 ℃ below the dissolving temperature for 3-8 hours.
2. The process for preparing the low-expansion high-temperature alloy according to claim 1, wherein in the step 1), the next rolling is carried out after the tempering and the heat preservation after the deformation of each pass is finished.
3. The process for preparing a low-expansion high-temperature alloy as claimed in claim 1, wherein the temperature for the annealing after the deformation of each pass is 1120-1160 ℃ for 15-20min in step 1).
4. The process for preparing a low-expansion high-temperature alloy according to claim 1, wherein in the step 2), the heating rate is not more than 10 ℃/min during the high-temperature aging treatment of the alloy.
5. The process for preparing a low-expansion high-temperature alloy as claimed in claim 1, wherein in the step 3), the alloy subjected to high-temperature aging treatment is heated to Cr at a heating rate of not less than 60 ℃/min23C6Keeping the temperature below the dissolution temperature of 200 ℃ and 250 ℃ for 10-16 hours, then air cooling, and heating to Cr at a heating rate of not less than 60 ℃/min23C6Keeping the temperature for 3-8 hours in the range of 100-150 ℃ below the dissolving temperature and then cooling in air.
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