A kind of iron-nickel-cobalt alloy without martensitic phase transformation and preparation method thereof

Abstract

The invention provides an iron-nickel-cobalt alloy without martensitic phase transformation and a preparation method, belonging to the field of alloy preparation. The alloy comprises the following chemical components: Ni: 27% to 28%, Co: 17.5% to 18%, Mo: 0.01% to 0.1%, Mn: 0.5% to 0.8%, C: 0.015% to 0.025%, N: 0.01% to 0.02%, Cu: 0.1% to 0.15%, Cr: 0.1% to 0.3%, Fe and inevitable impurities. By rationally designing the chemical composition of the iron-nickel-cobalt alloy, the stability of austenite can be improved under the premise of strictly controlling the content of trace alloy elements, and an expansion alloy without martensitic phase transformation at low temperature can be obtained by subsequent treatment without significantly sacrificing the expansion coefficient. Thus, the martensitic phase transformation of the iron-nickel-cobalt alloy is completely suppressed without sacrificing its expansion coefficient.

Description

Technical Field

[0001] The present application relates to the technical field of alloy preparation, and in particular to an iron-nickel-cobalt alloy without martensitic phase transformation and a preparation method thereof. Background Art

[0002] Iron-nickel-cobalt expansion alloy has special expansion properties and excellent low-temperature toughness. It is mainly used as a sealing material in electric vacuum components, especially in the low-temperature field. It has a wide range of application value.

[0003] Since the iron-nickel-cobalt alloy is prone to undergo martensitic transformation at low temperatures, which in turn affects its expansion coefficient, generates internal stress in the seal, causes poor sealing quality, and even causes parts damage, its organizational stability should be strictly controlled at the use temperature, that is, the content of martensite should be strictly controlled. In the industrial production of iron-nickel-cobalt alloy, it is usually difficult to avoid the martensitic transformation of the alloy at low temperatures. After composition regulation, the martensitic transformation can be achieved only in local locations or completely suppressed at low temperatures of -70°C, but its expansion performance is highly sensitive to the composition, and suppressing the production of martensite will cause changes in the expansion coefficient. The causes of the martensitic transformation of iron-nickel-cobalt alloy at low temperatures, especially the causes and control methods of the martensitic transformation in local locations, have not been reported in detail. How to completely suppress the martensitic transformation without sacrificing its expansion coefficient is a difficulty in the stable production of iron-nickel-cobalt alloy for sealing in low temperature environments. Summary of the invention

[0004] The present application provides an iron-nickel-cobalt alloy without martensitic phase transformation and a preparation method thereof, so as to solve the following technical problem: how to completely suppress the martensitic phase transformation of the iron-nickel-cobalt alloy without sacrificing its expansion coefficient.

[0005] In a first aspect, the present application provides an iron-nickel-cobalt alloy without martensitic transformation, wherein the iron-nickel-cobalt alloy comprises the following chemical components, by mass fraction: Ni: 27%~28%, Co: 17.5%~18%, Mo: 0.01%~0.1%, Mn: 0.5%~0.8%, C: 0.015%~0.025%, N: 0.01%~0.02%, Cu: 0.1%~0.15%, Cr: 0.1%~0.3%, Fe and unavoidable impurities.

[0006] Optionally, the iron-nickel-cobalt alloy has no martensitic phase transformation after cryogenic treatment.

[0007] Optionally, within the range of room temperature to 400°C, the expansion coefficient of the iron-nickel-cobalt alloy is 4.7×10 -6 / ℃~4.8×10 -6 / ℃.

[0008] In a second aspect, the present application provides a method for preparing the iron-nickel-cobalt alloy according to any one embodiment of the first aspect, the method comprising:

[0009] Obtaining an alloy ingot of the chemical composition by vacuum induction melting;

[0010] Determining whether the size of the alloy ingot meets a preset size;

[0011] If the conditions are met, subjecting the alloy ingot to a first heat treatment in a hydrogen atmosphere to obtain an iron-nickel-cobalt alloy;

[0012] If not, the alloy ingot is forged, hot rolled and subjected to a second heat treatment to obtain an iron-nickel-cobalt alloy.

[0013] Optionally, the first heat treatment includes the following parameters: temperature of 1180°C to 1200°C and holding time of 5 hours.

[0014] Optionally, the forging includes the following parameters: heating temperature of 1230°C to 1290°C, holding time of 1h to 2h, forging ratio of 16 to 18, and final forging temperature ≥800°C.

[0015] Optionally, the hot rolling includes the following parameters: a heating temperature of 1250° C. to 1280° C. and a holding time of 30 min to 40 min.

[0016] Optionally, the hot rolling also includes the following parameters: rolling deformation is 80% to 90%, and the final rolling temperature is ≥800°C.

[0017] Optionally, the second heat treatment includes the following parameters: heating temperature is 1180°C~1200°C, and holding time is 1h.

[0018] Optionally, the pouring temperature of the alloy ingot is 1380°C~1400°C.

[0019] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0020] The present application provides an iron-nickel-cobalt alloy without martensitic transformation, which includes the following chemical components by mass fraction: Ni: 27%~28%, Co: 17.5%~18%, Mo: 0.01%~0.1%, Mn: 0.5%~0.8%, C: 0.015%~0.025%, N: 0.01%~0.02%, Cu: 0.1%~0.15%, Cr: 0.1%~0.3%, Fe and inevitable impurities. By rationally designing the chemical composition of the iron-nickel-cobalt alloy, each chemical component plays an important role and together constitutes the excellent properties of the alloy. At the same time, under the premise of strictly controlling the content of trace alloying elements, such as appropriate amounts of trace elements such as Mn, C, N, Cu and Cr, the stability of austenite can be improved, and an expansion alloy without martensitic transformation at low temperature can be obtained by using subsequent corresponding heat treatment methods or hot deformation processes combined with heat treatment without significantly sacrificing the expansion coefficient. Thereby, the martensitic phase transformation of the iron-nickel-cobalt alloy is completely suppressed without sacrificing its expansion coefficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0023] Figure 1 A schematic flow chart of a method for preparing an iron-nickel-cobalt alloy provided in an embodiment of the present application;

[0024] Figure 2 This is a microstructure photograph of the alloy ingot provided in Example 1 of the present application after cryogenic treatment;

[0025] Figure 3 This is a microstructure photograph of the iron-nickel-cobalt alloy after cryogenic treatment provided in Example 1 of the present application;

[0026] Figure 4 This is a microstructure photograph of the alloy ingot provided in Example 2 of the present application after cryogenic treatment;

[0027] Figure 5 This is a microstructure photograph of the iron-nickel-cobalt alloy after cryogenic treatment provided in Example 2 of the present application;

[0028] Figure 6 This is a microstructure photograph of the alloy ingot provided in Example 3 of the present application after cryogenic treatment;

[0029] Figure 7 This is a microstructure photograph of the iron-nickel-cobalt alloy after cryogenic treatment provided in Example 3 of the present application;

[0030] Figure 8 This is a microstructure photograph of the alloy ingot provided in Example 4 of the present application after cryogenic treatment;

[0031] Fig. 9 This is a microstructure photograph of the iron-nickel-cobalt alloy after deep cryogenic treatment provided in Example 4 of the present application. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0033] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0034] In addition, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plural" means two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc, or abc, where a, b, c can be single or plural, respectively.

[0035] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0036] The present application provides an iron-nickel-cobalt alloy without martensitic transformation. The iron-nickel-cobalt alloy includes the following chemical components, measured by mass fraction: Ni: 27%~28%, Co: 17.5%~18%, Mo: 0.01%~0.1%, Mn: 0.5%~0.8%, C: 0.015%~0.025%, N: 0.01%~0.02%, Cu: 0.1%~0.15%, Cr: 0.1%~0.3%, Fe and unavoidable impurities.

[0037] The design principle of the composition elements of the iron-nickel-cobalt alloy of this application:

[0038] Ni: Nickel is one of the key elements controlling the expansion coefficient in Fe-Ni-Co alloy. It works together with iron to make the expansion coefficient of the alloy as close as possible to that of certain non-metallic materials (such as silicon glass and ceramics), which is particularly important in sealing applications that require precise matching, such as electronic devices and sensors. At the same time, the addition of nickel also improves the stability of austenite, enabling it to maintain stability and reliability in various complex environments.

[0039] Co: Cobalt is one of the key elements affecting the stability of austenite. Its content range is very narrow, and a slight fluctuation in content can cause a large change in stability. In addition, Co is also one of the important elements affecting expansion properties. Therefore, precise control of Co content is the key to the design of this alloy.

[0040] Mo: Although the content of molybdenum is low, its strengthening effect on the alloy cannot be ignored. Molybdenum can refine the grain structure of the alloy and improve the strength and hardness of the alloy. At the same time, the addition of molybdenum also helps to improve the corrosion resistance of the alloy, especially in some harsh working environments, such as high temperature, high humidity or strong corrosive media.

[0041] Mn: Manganese is one of the commonly used alloying elements in Fe-Ni-Co alloys. An appropriate amount of manganese can improve the stability of austenite and inhibit the occurrence of martensitic phase transformation. At the same time, manganese can also enhance the strength and toughness of the alloy, which helps to improve the overall performance of the alloy.

[0042] C, N: Carbon and nitrogen usually exist in the form of interstitial atoms in alloys, and they have a significant effect on the microstructure and properties of the alloy. Appropriate amounts of carbon and nitrogen can stabilize the austenite phase and reduce the tendency of martensite transformation. However, too high a content may cause alloy embrittlement, so its content needs to be strictly controlled.

[0043] Cu: Copper also has the function of stabilizing austenite in iron-nickel-cobalt alloy and can also improve the corrosion resistance of the alloy.

[0044] Cr: Chromium is one of the important elements in alloys to improve corrosion resistance. It can form a dense oxide film on the surface of the alloy to prevent the intrusion of oxygen and other corrosive media, thereby protecting the alloy matrix from corrosion. At the same time, chromium can also promote the passivation process of the alloy, making it easier for the alloy to form a stable passivation film under certain conditions, further improving its corrosion resistance. In addition, a small amount of Cr can also improve the stability of austenite and inhibit martensitic phase transformation at low temperatures.

[0045] Therefore, the present application rationally designs the chemical composition of the iron-nickel-cobalt alloy, and the chemical composition plays an important role respectively, and together constitutes the excellent performance of the alloy. At the same time, under the premise of strictly controlling the content of trace alloy elements, such as appropriate amounts of trace elements such as Mn, C, N, Cu and Cr, the stability of austenite can be improved, and an expansion alloy without martensitic phase transformation at low temperature can be obtained by using subsequent corresponding heat treatment methods or thermal deformation processes combined with heat treatment without significantly sacrificing the expansion coefficient. Exemplarily, the mass fraction of Ni can be 27%, 27.1%, 27.2%, 27.4%, 27.6%, 27.8%, 28%, etc., the mass fraction of Co can be 17.5%, 17.6%, 17.7%, 17.8%, 17.9%, 18%, etc., the mass fraction of Mo can be 0.01%, 0.02%, 0.04%, 0.06%, 0.08%, 0.1%, etc., the mass fraction of Mn can be 0.5%, 0.6%, 0.7%, 0.8%, etc., and the mass fraction of C can be The mass fraction of N can be 0.01%, 0.012%, 0.014%, 0.016%, 0.018%, 0.020%, 0.022%, 0.024%, 0.025%, etc. The mass fraction of Cu can be 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, etc. The mass fraction of Cr can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, etc.

[0046] In some embodiments, the iron-nickel-cobalt alloy has no martensitic transformation after cryogenic treatment.

[0047] In some embodiments, within the range of room temperature to 400° C., the expansion coefficient of the iron-nickel-cobalt alloy is 4.7×10 -6 / ℃~4.8×10 -6 / ℃.

[0048] The present invention obtains an expansion coefficient of 4.7×10 by rationally designing the chemical composition and heat treatment process of the iron-nickel alloy. -6 / ℃~4.8×10 -6 / ℃, the iron-nickel-cobalt alloy has the advantages of good thermal matching, high stability, and excellent mechanical properties. These advantages make the alloy widely used in many fields such as glass-metal sealing, electric vacuum devices, aerospace, etc., and play an important role. For example, the expansion coefficient of the iron-nickel-cobalt alloy can be 4.7×10 -6 / ℃、4.72×10 -6 / ℃、4.74×10 -6 / ℃、4.76×10 -6 / ℃、4.78×10 -6 / ℃、4.8×10 -6 / ℃, etc.

[0049] Figure 1 A schematic flow chart of a method for preparing an iron-nickel-cobalt alloy provided in an embodiment of the present application.

[0050] See also Figure 1 The present application provides a method for preparing the iron-nickel-cobalt alloy described in any one of the above embodiments, the method comprising:

[0051] S101, obtaining an alloy ingot having the chemical composition through vacuum induction melting;

[0052] In some embodiments, the casting temperature of the alloy ingot is 1380°C to 1400°C.

[0053] In the production process of alloy ingots, the pouring temperature has an important influence on the microstructure and properties of the alloy. Limiting the pouring temperature of the alloy ingot to 1380℃~1400℃ can ensure that the alloy has good fluidity during solidification, which is conducive to the uniform distribution of elements in the melt, thereby reducing the occurrence of microsegregation. At the same time, the appropriate pouring temperature can also promote grain refinement. Exemplarily, the pouring temperature of the alloy ingot can be 1380℃, 1385℃, 1390℃, 1395℃, 1400℃, etc.

[0054] S102, determining whether the size of the alloy ingot meets a preset size;

[0055] S103a, if satisfied, subjecting the alloy ingot to a first heat treatment in a hydrogen atmosphere to obtain an iron-nickel-cobalt alloy;

[0056] In some embodiments, the first heat treatment includes the following parameters: temperature of 1180° C. to 1200° C., and holding time of 5 hours.

[0057] In the production process of alloy ingots, the pouring temperature and subsequent heat treatment process have an important influence on the microstructure and properties of the alloy. Under the premise of limiting the pouring temperature of the alloy ingot to 1380℃~1400℃, the temperature of the first heat treatment is limited to 1180℃~1200℃ and the holding time is 5h, so that high temperature and long time annealing can be used. Through high temperature and long time annealing, the atomic diffusion and redistribution process inside the alloy can be accelerated, making the alloy structure more uniform, thereby effectively inhibiting the martensitic phase transformation that occurs in local positions during subsequent low temperature treatment or use. At the same time, high temperature annealing can also promote the release of residual stress that may exist in the alloy, further improving the stability and service life of the alloy. In addition, high temperature annealing can not only inhibit martensitic phase transformation, but also optimize the microstructure of the alloy through atomic diffusion and recrystallization processes. For example, defects such as dendrite segregation, shrinkage cavities and shrinkage porosity generated during the casting process can be eliminated or alleviated. The optimized microstructure usually has a more uniform grain size and fewer internal defects, which helps to improve the mechanical properties, processing properties and corrosion resistance of the alloy. For example, the temperature of the first heat treatment may be 1180° C., 1185° C., 1190° C., 1195° C., 1200° C., etc.

[0058] S103b. If not satisfied, the alloy ingot is forged, hot rolled and subjected to a second heat treatment to obtain an iron-nickel-cobalt alloy.

[0059] In some embodiments, the forging includes the following parameters: heating temperature is 1230°C to 1290°C, holding time is 1h to 2h, forging ratio is 16 to 18, and final forging temperature is ≥800°C.

[0060] The use of a large forging ratio during forging means that the alloy undergoes a large plastic deformation during the forging process. This deformation will break the coarse grains and dendrites in the original cast structure and refine them, thereby increasing the grain boundary area and providing more channels for the diffusion of elements. At the same time, the deformation heat and mechanical energy during the forging process will also promote the diffusion of alloy elements, especially at grain boundaries and defects, which helps to reduce the uneven distribution of elements on a microscopic scale. Exemplarily, the heating temperature for forging can be 1230°C, 1240°C, 1250°C, 1260°C, 1270°C, 1280°C, 1290°C, etc., the holding time can be 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, etc., the forging ratio can be 16, 16.5, 17, 17.5, 18, etc., and the final forging temperature can be 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, etc.

[0061] In some embodiments, the hot rolling includes the following parameters: the heating temperature is 1250° C. to 1280° C., and the holding time is 30 min to 40 min.

[0062] Optionally, the hot rolling also includes the following parameters: rolling deformation is 80% to 90%, and the final rolling temperature is ≥800°C.

[0063] Hot rolling deformation can further refine the grain structure of the alloy, while introducing more dislocations and defects, which are conducive to the rapid diffusion of elements. At the same time, hot rolling can also improve the plastic processing properties of the alloy and provide a good foundation for subsequent heat treatment. Exemplarily, the heating temperature of hot rolling can be 1250°C, 1255°C, 1260°C, 1265°C, 1270°C, 1275°C, 1280°C, etc., the holding time is 30min, 32min, 34min, 36min, 38min, 40min, etc., the rolling deformation can be 80%, 82%, 84%, 86%, 88%, 90%, etc., and the final rolling temperature can be 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, etc.

[0064] In some embodiments, the second heat treatment includes the following parameters: a heating temperature of 1180° C. to 1200° C. and a holding time of 1 hour.

[0065] High temperature annealing is a key step to achieve rapid homogenization of alloy composition. At high temperature, the diffusion rate of alloying elements increases significantly, and uniform distribution of elements in a large range can be achieved in a short time. The annealing process can also effectively eliminate the internal stress generated by the alloy during forging and hot rolling, and reduce the local martensitic phase transformation induced by stress concentration. At the same time, through high temperature annealing, the microstructure of the alloy can be further optimized, such as reducing segregation at grain boundaries and promoting recrystallization, thereby improving the mechanical properties and stability of the alloy. At the same time, as mentioned above, through the combined effects of large forging ratio, hot rolling deformation and high temperature annealing, the composition of the alloy is rapidly homogenized. This reduces the possibility of local martensitic phase transformation induced by uneven composition. In addition, internal stress is eliminated during annealing, reducing the formation of local martensite caused by stress concentration. By optimizing the microstructure and component distribution of the alloy, the phase transformation conditions of the alloy can also be changed, making it more inclined to form a stable phase structure rather than a metastable phase such as martensite. Illustratively, the heating temperature of the second heat treatment may be 1180° C., 1185° C., 1190° C., 1195° C., 1200° C., or the like.

[0066] In summary, under the premise of limiting the pouring temperature of the alloy ingot to 1380℃~1400℃, the composition can be quickly homogenized through a large forging ratio combined with hot rolling deformation and subsequent high-temperature annealing, ultimately suppressing the local martensite formation of the Fe-Ni-Co alloy.

[0067] The product prepared by the method for preparing the iron-nickel-cobalt alloy is the above-mentioned iron-nickel-cobalt alloy. The chemical composition and microstructure of the iron-nickel-cobalt alloy prepared by the method for preparing the iron-nickel-cobalt alloy can refer to the above-mentioned embodiment. Since the method for preparing the iron-nickel-cobalt alloy adopts part or all of the technical solutions of the iron-nickel-cobalt alloy embodiment, it at least has all the beneficial effects brought by the technical solutions of the iron-nickel-cobalt alloy embodiment, which will not be described one by one here.

[0068] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0069] Example 1

[0070] This embodiment provides a method for preparing an iron-nickel-cobalt alloy, the method comprising:

[0071] S111. Obtain an alloy ingot by vacuum induction melting; the pouring temperature of the alloy ingot is 1380° C., and the chemical composition of the alloy ingot is: 27% Ni, 18% Co, 0.01% Mo, 0.5% Mn, 0.015% C, 0.01% N, 0.1% Cu, 0.1% Cr, and the rest is Fe, all in weight percentage;

[0072] S112, determining whether the size of the alloy ingot meets the preset size;

[0073] S113. If the size of the alloy ingot meets the preset size, the alloy ingot is heat treated in a hydrogen atmosphere. The heat treatment process is: heating the furnace to 1180°C and keeping it warm for 5 hours to obtain a low-temperature iron-nickel-cobalt alloy without martensitic phase transformation. In the range of room temperature to 400°C, its expansion coefficient is 4.7×10 -6 / ℃.

[0074] Figure 2 This is a microstructure photograph of the alloy ingot provided in Example 1 of the present application after cryogenic treatment; Figure 3 This is a microstructure photo of the iron-nickel-cobalt alloy after cryogenic treatment provided in Example 1 of the present application. The alloy ingot before heat treatment was placed at -70°C for 4 hours and then placed at room temperature. The microstructure photo is as follows Figure 2 As shown, the heat-treated iron-nickel-cobalt alloy was placed at -70°C for 4 hours and then placed at room temperature. The microstructure of the alloy is shown in FIG. Figure 3 As shown. Figure 2 and Figure 3By comparison, it can be seen that the structure of the alloy ingot has obvious martensitic phase transformation at low temperature, while the structure of the iron-nickel-cobalt alloy has no martensitic phase transformation at low temperature. Therefore, the heat treatment process of this embodiment can effectively suppress the occurrence of martensitic phase transformation at local positions at low temperature.

[0075] Example 2

[0076] This embodiment provides a method for preparing an iron-nickel-cobalt alloy, the method comprising:

[0077] S121. Obtain an alloy ingot by vacuum induction melting; the pouring temperature of the alloy ingot is 1400° C. The chemical composition of the alloy ingot is: 28% Ni, 17.5% Co, 0.1% Mo, 0.8% Mn, 0.025% C, 0.02% N, 0.15% Cu, 0.3% Cr, and the rest is Fe, all in weight percentage;

[0078] S122, determining whether the size of the alloy ingot meets the preset size;

[0079] S123. If the size of the alloy ingot meets the preset size, the alloy ingot is heat treated in a hydrogen atmosphere. The heat treatment process is: heating the furnace to 1200°C and keeping it warm for 5 hours to obtain a low-temperature iron-nickel-cobalt alloy without martensitic phase transformation. In the range of room temperature to 400°C, its expansion coefficient is 4.72×10 -6 / ℃.

[0080] Figure 4 This is a microstructure photograph of the alloy ingot provided in Example 2 of the present application after cryogenic treatment; Figure 5 This is a microstructure photo of the iron-nickel-cobalt alloy after cryogenic treatment provided in Example 2 of the present application. The alloy ingot before heat treatment was placed at -70°C for 4 hours and then placed at room temperature. The microstructure photo is as follows Figure 4 As shown, the heat-treated iron-nickel-cobalt alloy was placed at -70°C for 4 hours and then placed at room temperature. The microstructure of the alloy is shown in FIG. Figure 5 As shown. Figure 4 and Figure 5 By comparison, it can be seen that the structure of the alloy ingot has obvious martensitic phase transformation at low temperature, while the structure of the iron-nickel-cobalt alloy has no martensitic phase transformation at low temperature. Therefore, the heat treatment process of this embodiment can effectively suppress the occurrence of martensitic phase transformation at local positions at low temperature.

[0081] Example 3

[0082] This embodiment provides a method for preparing an iron-nickel-cobalt alloy, the method comprising:

[0083] S131. Obtain an alloy ingot by vacuum induction melting; the pouring temperature of the alloy ingot is 1390° C., and the chemical composition of the alloy ingot is: 27% Ni, 17.8% Co, 0.05% Mo, 0.6% Mn, 0.02% C, 0.018% N, 0.07% Cu, 0.08% Cr, and the rest is Fe, all in weight percentage;

[0084] S132, determining whether the size of the alloy ingot meets the preset size;

[0085] S133. If the size of the alloy ingot does not meet the preset size, the alloy ingot is forged, hot rolled and heat treated in sequence. The specific forging process is: 1230℃ for 2h, forging ratio is 16, and final forging temperature is 850℃; hot rolling process is: 1250℃ for 30min, rolling deformation is 90%, and final rolling temperature is 820℃; the subsequent heat treatment process is: 1180℃ for 1h to obtain a low-temperature iron-nickel-cobalt alloy without martensitic phase transformation. In the range of room temperature to 400℃, its expansion coefficient is 4.8×10 -6 / ℃.

[0086] Figure 6 This is a microstructure photograph of the alloy ingot provided in Example 3 of the present application after cryogenic treatment; Figure 7 This is a microstructure photo of the iron-nickel-cobalt alloy after cryogenic treatment provided in Example 3 of the present application. The alloy ingot before heat treatment was placed at -70°C for 4 hours and then placed at room temperature. The microstructure photo is as follows Figure 6 As shown, the heat-treated iron-nickel-cobalt alloy was placed at -70°C for 4 hours and then placed at room temperature. The microstructure of the alloy is shown in FIG. Figure 7 As shown. Figure 6 and Figure 7 By comparison, it can be seen that the structure of the alloy ingot has obvious martensitic phase transformation at low temperature, while the structure of the iron-nickel-cobalt alloy has no martensitic phase transformation at low temperature. Therefore, the heat treatment process of this embodiment can effectively suppress the occurrence of martensitic phase transformation at local positions at low temperature.

[0087] Example 4

[0088] This embodiment provides a method for preparing an iron-nickel-cobalt alloy, the method comprising:

[0089] S141. Obtain an alloy ingot by vacuum induction melting; the pouring temperature of the alloy ingot is 1400° C. The chemical composition of the alloy ingot is: 27.5% Ni, 17.8% Co, 0.1% Mo, 0.6% Mn, 0.02% C, 0.01% N, 0.1% Cu, 0.3% Cr, and the rest is Fe, all in weight percentage;

[0090] S142, determining whether the size of the alloy ingot meets the preset size;

[0091] S143. If the size of the alloy ingot does not meet the preset size, the alloy ingot is forged, hot rolled and heat treated in sequence. The specific forging process is: 1290℃ for 1h, forging ratio is 18, and final forging temperature is 880℃; hot rolling process is: 1280℃ for 40min, rolling deformation is 80%, and final rolling temperature is 900℃; the subsequent heat treatment process is: 1200℃ for 1h to obtain a low-temperature iron-nickel-cobalt alloy without martensitic phase transformation. In the range of room temperature to 400℃, its expansion coefficient is 4.7×10 -6 / ℃.

[0092] Figure 8 This is a microstructure photograph of the alloy ingot provided in Example 4 of the present application after cryogenic treatment; Fig. 9 This is a microstructure photo of the iron-nickel-cobalt alloy after cryogenic treatment provided in Example 4 of the present application. The alloy ingot before heat treatment was placed at -70°C for 4 hours and then placed at room temperature. The microstructure photo is as follows Figure 8 As shown, the heat-treated iron-nickel-cobalt alloy was placed at -70°C for 4 hours and then placed at room temperature. The microstructure of the alloy is shown in FIG. Fig. 9 As shown. Figure 8 and Fig. 9 By comparison, it can be seen that the structure of the alloy ingot has obvious martensitic phase transformation at low temperature, while the structure of the iron-nickel-cobalt alloy has no martensitic phase transformation at low temperature. Therefore, the heat treatment process of this embodiment can effectively suppress the occurrence of martensitic phase transformation at local positions at low temperature.

[0093] In addition, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0094] In the embodiments of the present invention, under the premise of strictly controlling the content of trace alloying elements, such as appropriate amounts of trace elements such as Mn, C, N, Cu and Cr, the stability of austenite can be improved, and the controllable range of the expansion coefficient can be ensured. The appropriate melting and casting temperature is selected to effectively control the microsegregation of elements. The subsequent high-temperature and long-term annealing can effectively inhibit the occurrence of martensitic phase transformation in local positions at low temperatures, or the composition can be quickly homogenized through a large forging ratio combined with hot rolling deformation and subsequent high-temperature annealing, thereby ultimately inhibiting the formation of local martensite.

[0095] In the embodiment of the present invention, the preparation method of the iron-nickel-cobalt alloy provided has a simple implementation process and can simultaneously realize the control of the expansion coefficient, thereby realizing stable production in industry.

[0096] In the embodiment of the present invention, within the range of room temperature to 400°C, the expansion coefficient of the iron-nickel-cobalt alloy is 4.7×10 -6 / ℃~4.8×10 -6 / ℃.

[0097] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. An iron-nickel-cobalt alloy without martensitic transformation, characterized in that: The iron-nickel-cobalt alloy comprises the following chemical components by mass fraction: Ni: 27%-28%, Co: 17.5%-18%, Mo: 0.01%-0.1%, Mn: 0.5%-0.8%, C: 0.015%-0.025%, N: 0.01%-0.02%, Cu: 0.1%-0.15%, Cr: 0.1%-0.3%, Fe and inevitable impurities; the iron-nickel-cobalt alloy has no martensitic phase transformation after cryogenic treatment, and the cryogenic treatment condition is -70°C for 4 hours and then placed at room temperature; within the range of room temperature to 400°C, the expansion coefficient of the iron-nickel-cobalt alloy is 4.7×10 -6 / ℃~4.8×10 -6 / ℃.

2. A method for preparing the iron-nickel-cobalt alloy according to claim 1, characterized in that: The method comprises: Obtaining an alloy ingot having the chemical composition through vacuum induction melting; Determining whether the size of the alloy ingot meets a preset size; If the conditions are met, subjecting the alloy ingot to a first heat treatment in a hydrogen atmosphere to obtain an iron-nickel-cobalt alloy; If not, the alloy ingot is forged, hot rolled and subjected to a second heat treatment to obtain an iron-nickel-cobalt alloy.

3. The method according to claim 2, characterized in that The first heat treatment includes the following parameters: temperature is 1180°C-1200°C, and holding time is 5h.

4. The method according to claim 2, characterized in that: The forging includes the following parameters: heating temperature is 1230°C to 1290°C, holding time is 1h to 2h, forging ratio is 16 to 18, and final forging temperature is ≥800°C.

5. The method according to claim 2, characterized in that: The hot rolling includes the following parameters: the heating temperature is 1250° C. to 1280° C., and the holding time is 30 min to 40 min.

6. The method according to claim 5, characterized in that The hot rolling also includes the following parameters: rolling deformation is 80% to 90%, and the final rolling temperature is ≥800°C.

7. The method according to claim 2, characterized in that The second heat treatment includes the following parameters: heating temperature is 1180°C~1200°C, and holding time is 1h.

8. The method according to claim 2, characterized in that: The pouring temperature of the alloy ingot is 1380°C to 1400°C.

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