Iron-nickel alloy for heat exchangers and method for producing the same

Abstract

An iron-nickel alloy for heat exchanger contains the following components in percentage by mass: Cr 14.5-23.5%, Ni 40-52%, C 0.12-0.45%, W 5.5-8%, Al 0.8-3%, B≤0.06%, Si≤0.6%, Mn≤0.7%, Pm≤0.26%, Yb≤0.15%, Lu≤0.15%, S≤0.05%, P≤0.05%, and the balance of Fe. The component design of the iron-nickel alloy is reasonable, which can effectively hinder the oxidation of the alloy at high temperature, effectively resist the initiation of thermal cracks, prolong the service life of the iron-nickel alloy, reduce the material cost, and show good economic benefits.

Description

Technical Field

[0001] This invention relates to the field of alloy materials technology, and in particular to an iron-nickel alloy for heat exchangers and its preparation method. Background Technology

[0002] A heat exchanger is a device that transfers some of the heat from a hot fluid to a cold fluid; it is also called a heat exchanger. Heat exchangers play a vital role in chemical, petroleum, power, food, and many other industrial production processes. Their main functions are heat transfer, temperature control, energy conservation and emission reduction, fluid handling, and equipment protection. The core function of a heat exchanger is heat transfer, achieving the effective utilization and control of heat energy. A long service life of a heat exchanger not only reduces equipment costs but, more importantly, is a prerequisite for its long-term stable operation.

[0003] At high temperatures, heat exchanger materials are prone to oxidation, leading to oxidative damage and reducing their service life. During heat transfer, the temperatures encountered by these materials are complex, variable, and cyclical, easily inducing thermal fatigue cracks and causing fatal damage. The stronger the high-temperature resistance of the heat exchanger material, the wider its application range and the longer its service life. Therefore, heat exchanger materials operating in complex high-temperature environments must possess excellent high-temperature oxidation and thermal fatigue resistance.

[0004] Currently, materials commonly used to manufacture heat exchangers include nickel alloys, titanium alloys, and stainless steel. However, these materials have insufficient performance under ultra-high temperature conditions of 1000℃. Therefore, it is necessary to provide an iron-nickel alloy for heat exchangers and its preparation method. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by providing an iron-nickel alloy for heat exchangers and its preparation method, thereby at least partially solving the problems of the prior art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] On the one hand, an iron-nickel alloy for heat exchangers comprises, by mass percentage, the following components: Cr 14.5–23.5%, Ni 40–52%, C 0.12–0.45%, W 5.5–8%, Al 0.8–3%, B ≤0.06%, Si ≤0.6%, Mn ≤0.7%, Pm ≤0.26%, Yb ≤0.15%, Lu ≤0.15%, S ≤0.05%, P ≤0.05%, with the balance being Fe.

[0008] In a further embodiment, the iron-nickel alloy used in the heat exchanger comprises, by mass percentage, the following components: Cr 16.5–17.3%, Ni 47.5–48.5%, C 0.3–0.42%, W 6.4–7%, Al 2.4–2.8%, B 0.01–0.015%, Si 0.3–0.5%, Mn 0.4–0.5%, Pm 0.22–0.24%, Yb 0.1–0.14%, Lu 0.1–0.14%, S 0.005–0.03%, P 0.015–0.05%, with the balance being Fe.

[0009] Preferably, the iron-nickel alloy used in the heat exchanger comprises, by mass percentage: Cr 17-17.3%, Ni 48-48.5%, C 0.3-0.42%, W 6.4-7%, Al 2.4-2.8%, B 0.014-0.015%, Si 0.3-0.5%, Mn 0.4-0.5%, Pm 0.22-0.24%, Yb 0.1-0.12%, Lu 0.1-0.12%, S 0.005-0.03%, P 0.03-0.05%, with the balance being Fe.

[0010] On the other hand, the preparation method of the iron-nickel alloy used in the above-mentioned heat exchanger includes the following steps:

[0011] Step 1: Smelting

[0012] First, steel, nickel plate and ferrotungsten are added to a non-vacuum coreless induction furnace. After they are completely melted, low-carbon ferrochrome, high-carbon ferrochrome and sponge titanium are added for refining. Then aluminum lime is added for deoxidation. Finally, boron powder, lutetium, promethium and ytterbium are added and kept warm to obtain the casting liquid.

[0013] Step 2: Casting and Molding

[0014] The casting liquid is poured into the ingot mold and cooled to room temperature to obtain the cast part;

[0015] Step 3: Solution treatment

[0016] The cast part is placed in a heating furnace for solution treatment to obtain a preform;

[0017] Step 4: Time-sensitive processing

[0018] The preformed part is placed in a heat treatment furnace for aging treatment to obtain the iron-nickel alloy for heat exchangers.

[0019] In a further embodiment, in step one, the refining time is 8–12 minutes; the heat preservation temperature is 1600–1630°C, and the heat preservation time is 18–24 minutes.

[0020] As a preferred option, the non-vacuum coreless induction furnace uses electromagnetic induction heating during the melting process. It has no carbon electrodes, thus preventing carbon buildup. A high power of 200–250 kW is applied during melting to rapidly melt the material, reducing oxidation and gas absorption in the molten metal and improving efficiency. In the preparation of the casting liquid, after the steel, nickel plate, and ferrotungsten have melted, low-carbon ferrochrome and high-carbon ferrochrome are added for refining. This refining process effectively reduces element loss and helps improve the performance of the alloy material. After refining for a period of time, aluminum lime is added to the molten metal for deoxidation. Finally, boron powder and rare earth elements are added to obtain a casting liquid of excellent quality.

[0021] In a further embodiment, in step two, the casting liquid is discharged from the furnace at a rate of 1600–1630°C before pouring; the pouring into the ingot mold also includes cooling to room temperature to obtain a cast part.

[0022] In a further embodiment, step three, the solution treatment step, is as follows: the cast part is placed in a heating furnace and heated to 1150-1180°C at a heating rate of 5-10°C / min, and held at this temperature for 1.5-2 hours; then the temperature is lowered to 1020-1050°C and held at this temperature for 1.5-2 hours, and then air-cooled to room temperature to obtain the preform.

[0023] Preferably, in step three, the heating rate is: 10℃ / min for temperatures below 1000℃, and 5℃ / min for temperatures above 1000℃.

[0024] In a further proposed solution, step four, the timeliness processing steps, are as follows:

[0025] The preform is placed in a heat treatment furnace and heated to 850-870°C at a heating rate of 10°C / min. It is then held at this temperature for 6-7 hours and air-cooled to room temperature to obtain the iron-nickel alloy for heat exchangers.

[0026] Preferably, in step four, the temperature of the heat treatment furnace is ≤100℃ before the preform is placed into the heat treatment furnace.

[0027] On the other hand, a heat exchanger is made from the aforementioned iron-nickel alloy used in heat exchangers.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The iron-nickel alloy for heat exchangers provided by the present invention, through the strengthening effect of four elements (nickel, iron, chromium and tungsten), the grain boundary strengthening effect of trace elements (carbon and boron), and the beneficial effect of rare earth elements in terms of oxidation performance and thermal fatigue performance, ensures that the iron-nickel alloy of the present invention has good hardness, wear resistance and toughness in high temperature environment.

[0030] 2. The iron-nickel alloy used in the heat exchanger of this invention can operate stably for a long time at 1000℃, and its oxidation resistance at 1000℃ for 100 hours is 0.1 g·m⁻². -2 ·h -1 Within a certain range, it reaches the level of complete oxidation resistance; after 20 thermomechanical fatigue tests at 1000℃-20℃, no cracks were produced, demonstrating excellent high-temperature oxidation and thermal fatigue performance.

[0031] 3. The iron-nickel alloy used in the heat exchanger of the present invention can effectively inhibit the oxidation of the alloy at high temperatures and can also effectively resist the initiation of hot cracks, thus extending the service life of the iron-nickel alloy and reducing material costs, demonstrating good economic benefits. Attached Figure Description

[0032] Figure 1 This is a scanning electron microscope (SEM) image of the preform 1 prepared in Embodiment 1 of the present invention.

[0033] Figure 2 This is a scanning electron microscope (SEM) micrograph (1000x) of the iron-nickel alloy for heat exchangers prepared in Example 1 of this invention.

[0034] Figure 3 This is a scanning electron microscope (SEM) image (100x) of the iron-nickel alloy for heat exchangers prepared in Example 1 of this invention. Detailed Implementation

[0035] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following description is merely an exemplary illustration of the scope of protection of the present invention, and those skilled in the art can make various changes and modifications to the invention based on the disclosed content, which should also fall within the scope of protection of the present invention.

[0036] A heat exchanger is a device that transfers some of the heat from a hot fluid to a cold fluid. At high temperatures, heat exchanger materials are prone to oxidation, causing oxidative damage and reducing their lifespan. During heat transfer, the temperatures the heat exchanger materials come into contact with are complex, variable, and cyclical, easily inducing thermal fatigue cracks and causing fatal damage. The stronger the high-temperature resistance of the heat exchanger material, the wider its application range and the longer its service life. Currently, heat exchanger materials generally include nickel alloys, titanium alloys, and stainless steel, but these materials have insufficient performance under ultra-high temperature conditions of 1000℃.

[0037] This invention utilizes the strengthening effects of four elements—nickel, iron, chromium, and tungsten—the grain boundary strengthening effect of trace elements such as carbon and boron, and the beneficial effects of rare earth elements on oxidation performance and thermal fatigue performance. Through rational design, it ensures the long-term stable operation of iron-nickel alloys at 1000℃.

[0038] To address the aforementioned problems, embodiments of the present invention provide an iron-nickel alloy for heat exchangers, comprising the following components by mass percentage: Cr 14.5–23.5%, Ni 40–52%, C 0.12–0.45%, W 5.5–8%, Al 0.8–3%, B≤0.06%, Si≤0.6%, Mn≤0.7%, Pm≤0.26%, Yb≤0.15%, Lu≤0.15%, S≤0.05%, P≤0.05%, with the balance being Fe.

[0039] In a further embodiment, the iron-nickel alloy used in the heat exchanger comprises, by mass percentage, the following components: Cr 16.5–17.3%, Ni 47.5–48.5%, C 0.3–0.42%, W 6.4–7%, Al 2.4–2.8%, B 0.01–0.015%, Si 0.3–0.5%, Mn 0.4–0.5%, Pm 0.22–0.24%, Yb 0.1–0.14%, Lu 0.1–0.14%, S 0.005–0.03%, P 0.015–0.05%, with the balance being Fe.

[0040] Preferably, the iron-nickel alloy used in the heat exchanger comprises, by mass percentage: Cr 17-17.3%, Ni 48-48.5%, C 0.3-0.42%, W 6.4-7%, Al 2.4-2.8%, B 0.014-0.015%, Si 0.3-0.5%, Mn 0.4-0.5%, Pm 0.22-0.24%, Yb 0.1-0.12%, Lu 0.1-0.12%, S 0.005-0.03%, P 0.03-0.05%, with the balance being Fe.

[0041] In the iron-nickel alloy used in the heat exchanger of the present invention, the boron powder is selected as high-purity boron powder with a mass percentage purity of 99.9%. Boron can usually play a role in strengthening grain boundaries in the alloy, which is beneficial to improving the high-temperature strength of the alloy. The addition of carbon mainly affects the type, quantity and size of carbide precipitation, thereby improving the strengthening of the alloy. In addition, the enhancement performance of rare earth elements in terms of oxidation performance and thermal fatigue performance ensures that the iron-nickel alloy of the present invention has good oxidation resistance and fatigue resistance at a high temperature of 1000℃.

[0042] This invention also provides a method for preparing an iron-nickel alloy for heat exchangers, comprising the following steps:

[0043] Step 1: Smelting

[0044] First, steel, nickel plate and ferrotungsten are added to a non-vacuum coreless induction furnace for smelting. After all the materials are completely melted, low-carbon ferrochrome and high-carbon ferrochrome are added for refining. Then, aluminum lime is added for deoxidation. Finally, boron powder, lutetium powder, promethium and ytterbium are added and kept warm to obtain the casting liquid.

[0045] Step 2: Casting and Molding

[0046] The casting liquid is poured into the ingot mold and cooled to room temperature to obtain the cast part;

[0047] Step 3: Solution treatment

[0048] The cast part is placed in a heating furnace for solution treatment to obtain preform 1;

[0049] Step 4: Time-sensitive processing

[0050] The preform 1 is placed in a heat treatment furnace for aging treatment to obtain the iron-nickel alloy for heat exchangers.

[0051] As a preferred option, the non-vacuum coreless induction furnace uses electromagnetic induction heating during the melting process. It has no carbon electrodes, thus preventing carbon buildup. A high power of 200–250 kW is applied during melting to rapidly melt the material, reducing oxidation and gas absorption in the molten metal and improving efficiency. In the preparation of the casting liquid, after the steel, nickel plate, and ferrotungsten have melted, low-carbon ferrochrome and high-carbon ferrochrome are added for refining. This refining process effectively reduces element loss, improving the alloy material and thus enhancing the high-temperature oxidation resistance and thermal fatigue resistance of the nickel-iron alloy. After refining for a period, aluminum lime is added to the molten metal for deoxidation. Finally, boron powder and rare earth elements are added to obtain a casting liquid of excellent quality.

[0052] In this embodiment of the invention, nickel plate is selected, Q345C steel and carbon ferrochrome are selected from FeCr60C8.0 grade, low carbon ferrochrome are selected from FeCr50C0.1 grade, and ferrotungsten is selected from ferrotungsten 85 grade.

[0053] In a further embodiment, in step one, the refining time is 8–12 minutes; the heat preservation temperature is 1600–1630°C, and the heat preservation time is 18–24 minutes.

[0054] In a further embodiment, in step two, the casting liquid is discharged from the furnace at a rate of 1600-1630°C before pouring; the pouring into the ingot mold also includes cooling to room temperature to obtain a cast part.

[0055] In a further embodiment, step three, the solution treatment step, is as follows: heating to 1150-1180℃ at a heating rate of 5-10℃ / min, holding at this temperature for 1.5-2 hours; then cooling to 1020-1050℃ and holding at this temperature for 1.5-2 hours, and air cooling to room temperature to obtain a preform.

[0056] Preferably, in step three, the heating rate is: 10℃ / min for temperatures below 1000℃, and 5℃ / min for temperatures above 1000℃.

[0057] This invention selects to first perform a solution treatment on the cast part at a high temperature, and then perform a second solution treatment at a lower temperature. Compared with a single solution treatment, the segmented solution treatment of this invention is more conducive to the re-precipitation of fine and uniformly distributed strengthening phases during subsequent aging, eliminating the stress caused by cold and hot working, thereby improving the high-temperature oxidation resistance and thermal fatigue resistance of nickel-iron alloys.

[0058] In a further proposed solution, step four, the timeliness processing steps, are as follows:

[0059] The temperature is increased to 850-870℃ at a rate of 10℃ / min, and held at this temperature for 6-7 hours. Then it is air-cooled to room temperature to obtain the iron-nickel alloy for heat exchangers.

[0060] Preferably, in step four, the temperature of the heat treatment furnace is ≤100℃ before the preform is placed into the heat treatment furnace.

[0061] This invention produces an iron-nickel alloy using a non-vacuum coreless induction furnace melting, casting, solution treatment, and aging treatment method. Through the strengthening effect of four elements (nickel, iron, chromium, and tungsten), the grain boundary strengthening effect of trace elements (carbon and boron), and the beneficial effects of rare earth elements on oxidation performance and thermal fatigue performance, the resulting material can operate stably for a long time at 1000℃ and exhibits excellent oxidation performance and thermal fatigue resistance at 1000℃.

[0062] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all chemical reagents used in the embodiments of the present invention are obtained through conventional commercial means.

[0063] Examples 1-5 and Comparative Examples 1-6

[0064] An iron-nickel alloy for heat exchangers has the composition shown in Table 1 below. The iron-nickel alloy is prepared by the following method:

[0065] Step 1: Smelting

[0066] First, steel, nickel plate and ferrotungsten are added to a non-vacuum coreless induction furnace. After they are completely melted, low carbon ferrochrome and high carbon ferrochrome are added and refined for 12 minutes to melt them. Then aluminum lime is added for deoxidation. Finally, boron powder, lutetium, promethium and ytterbium are added and kept at 1620℃ for 24 minutes to obtain the casting liquid.

[0067] Step 2: Casting and Molding

[0068] The temperature of the casting liquid is controlled at 1620℃. The casting liquid is poured into the ingot mold and cooled to room temperature to obtain the cast part.

[0069] Step 3: Solution treatment

[0070] First, the temperature is increased to 1000℃ at a rate of 10℃ / min, then increased to 1180℃ at a rate of 5℃ / min, and held at this temperature for 2 hours; then the temperature is decreased to 1050℃ and held for 2 hours, and then air-cooled to room temperature to obtain preform 1.

[0071] Step 4: Time-sensitive processing

[0072] The preform 1 is placed in a heat treatment furnace and heated to 870°C at a rate of 10°C / min. It is then held at this temperature for 7 hours and then air-cooled to room temperature to obtain the iron-nickel alloy for the heat exchanger.

[0073] Table 1

[0074]

[0075] The difference between Comparative Example 7 and Example 2 is that the metal material in this comparative example was added simultaneously.

[0076] The difference between Comparative Example 8 and Example 2 is that the solution treatment step in this comparative example is as follows: the cast part is placed in a heating furnace and heated to 1180°C at a rate of 10°C / min, and held at this temperature for 4 hours, and then air-cooled to room temperature to obtain a preform.

[0077] The difference between Comparative Example 9 and Example 2 is that the solution treatment step in this Comparative Example is as follows:

[0078] First, the temperature is increased to 1000℃ at a rate of 10℃ / min, then increased to 1180℃ at a rate of 5℃ / min, and held at this temperature for 4 hours to obtain the preform.

[0079] The difference between Comparative Example 10 and Example 2 is that the solution treatment step in this comparative example is as follows: the cast part is placed in a heating furnace, heated to 1050°C at a rate of 10°C / min and held for 4 hours, and then air-cooled to room temperature to obtain a preform.

[0080] Experimental Example 1

[0081] The microstructure of the cast parts and the iron-nickel alloy for heat exchangers prepared in Example 1 was analyzed using field emission scanning electron microscopy. The results are as follows: Figures 1 to 3 As shown.

[0082] As shown in the figure, compared to the microstructure of the cast part ( Figure 1 ), iron-nickel alloy for heat exchangers ( Figure 2 and Figure 3 The microstructure of the iron-nickel alloy used in heat exchangers is more uniform, and the alloy's strength and overall performance are further improved. The precipitated phases in the microstructure of the iron-nickel alloy are mainly secondary carbides M6C and M... 23 C6 contains two types of carbides with small size and very high stability, which is very beneficial to the thermal fatigue performance of the material; the appropriate amount of carbide precipitation ensures the high-temperature strength of the material; the addition of rare earth elements improves the bonding of the oxide film and enhances the high-temperature oxidation performance of the material, thereby improving the high-temperature performance and service life of the heat exchanger.

[0083] Experimental Example 2

[0084] High temperature antioxidant properties

[0085] High-temperature oxidation tests were conducted using an SX-G04133 muffle furnace. Following the test standard (HB 5258-2000), the iron-nickel alloys prepared in the above examples and comparative examples underwent a continuous 100-hour high-temperature oxidation resistance test at 1000℃. The results are shown in Table 2.

[0086] Table 2

[0087]

[0088]

[0089] As shown in the table, the oxidation rate of the nickel-iron alloy prepared by this invention is 0.1 g / m³ at 1000℃ for 100 hours. 2 Within h, according to the standard, the antioxidant performance of this invention at a high temperature of 1000℃ has reached the level of complete antioxidant.

[0090] The results of Comparative Examples 1-6 show that promethium, ytterbium, and lutetium have a synergistic effect, and the simultaneous addition of all three elements helps to significantly improve the high-temperature oxidation resistance of the alloy. The oxidation rates of Comparative Examples 8-10 are significantly higher than those of the Examples, indicating that the solution treatment conditions have a significant impact on the high-temperature oxidation resistance of the alloy. Stepwise heat treatment and controlling the heating and cooling rates and holding time during the solution treatment process can help to significantly enhance the high-temperature oxidation resistance of the alloy.

[0091] Experimental Example 3

[0092] High-temperature thermal fatigue performance

[0093] High-temperature thermal fatigue performance tests were conducted using an SX-G04133 muffle furnace. The sample shape and dimensions were based on HB6660-1992. The iron-nickel alloys prepared in the above examples and comparative examples were heated to 1000℃, held for 10 min, and then quickly removed from the furnace and placed in water at 20℃. The mixture was then rapidly cooled to 20℃, and this cycle was repeated 20 times. The results are shown in Table 3.

[0094] Table 3

[0095] Example 1 no — Example 2 no — Example 3 no — Example 4 no — Example 5 no — Comparative Example 1 yes 0.0545 Comparative Example 2 yes 0.1364 Comparative Example 3 yes 0.0647 Comparative Example 4 yes 0.1143 Comparative Example 5 yes 0.0762 Comparative Example 6 yes 0.1351 Comparative Example 7 yes 0.0526 Comparative Example 8 yes 0.0747 Comparative Example 9 yes 0.0575 Comparative Example 10 yes 0.0838

[0096] As shown in the table, the iron-nickel alloy prepared by this invention did not develop any cracks after 20 consecutive cycles of thermal fatigue testing at 1000℃-20℃, demonstrating excellent thermal fatigue performance. Comparative Example 2 shows that the addition of promethium improved the thermal fatigue performance of the alloy; the results of Comparative Examples 1-6 show that promethium, ytterbium, and lutetium have a synergistic effect, which is beneficial to improving the thermal fatigue performance of the alloy; adding any one or two of promethium and lutetium on the basis of ytterbium addition can improve the thermal fatigue performance of the alloy, with the best thermal fatigue performance when all three elements are present simultaneously. It can also be seen that the rare earth element ytterbium has the most significant effect on improving the thermal fatigue performance of the alloy, followed by lutetium, while promethium has a relatively smaller impact on the thermal fatigue performance of the alloy.

[0097] The results of Comparative Example 7 indicate that stepwise loading of raw materials for smelting and casting is more beneficial to the thermal fatigue performance of the alloy. The results of Comparative Examples 8, 9, and 10 indicate that whether the heat treatment process is carried out in steps and the temperature conditions both have a significant impact on the alloy properties. Stepwise heat treatment and appropriate temperature conditions are conducive to the gradual dissolution of precipitated phases in the alloy microstructure, thereby improving the homogenization of the alloy microstructure and enhancing the high-temperature oxidation resistance and thermal fatigue performance of the alloy.

[0098] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. An iron-nickel alloy for heat exchangers, characterized in that, By mass percentage, it contains the following components: Cr 14.5–23.5%, Ni 40–52%, C 0.12–0.45%, W 5.5–8%, Al 0.8–3%, B ≤0.06%, Si ≤0.6%, Mn ≤0.7%, Pm 0.22–0.26%, Yb 0.1–0.15%, Lu 0.1–0.15%, S ≤0.05%, P ≤0.05%, with the balance being Fe; The preparation method of the iron-nickel alloy used in the heat exchanger includes: Step 1: Smelting First, steel, nickel plate and ferrotungsten are added to a non-vacuum coreless induction furnace. After they are completely melted, low-carbon ferrochrome and high-carbon ferrochrome are added for refining. Then, aluminum lime is added for deoxidation. Finally, boron powder, lutetium, promethium and ytterbium are added and the furnace is kept warm to obtain the casting liquid. Step 2: Casting and Molding The casting liquid is poured into the ingot mold and cooled to room temperature to obtain the cast part; Step 3: Solution treatment The cast part is placed in a heating furnace and heated to 1150-1180℃ at a heating rate of 5-10℃ / min, and held at this temperature for 1.5-2 hours; then cooled to 1020-1050℃ and held at this temperature for 1.5-2 hours, and then air-cooled to room temperature to obtain the preform. Step 4: Time-sensitive processing The preformed part is placed in a heat treatment furnace for aging treatment to obtain the iron-nickel alloy for heat exchangers.

2. The iron-nickel alloy for heat exchangers according to claim 1, characterized in that, By mass percentage, it contains the following components: Cr 16.5–17.3%, Ni 47.5–48.5%, C 0.3–0.42%, W 6.4–7%, Al 2.4–2.8%, B 0.01–0.015%, Si 0.3–0.5%, Mn 0.4–0.5%, Pm 0.22–0.24%, Yb 0.1–0.14%, Lu 0.1–0.14%, S 0.005–0.03%, P 0.015–0.05%, with the balance being Fe.

3. The iron-nickel alloy for heat exchangers according to claim 2, characterized in that, By mass percentage, it contains the following components: Cr 17–17.3%, Ni 48–48.5%, C 0.3–0.42%, W 6.4–7%, Al 2.4–2.8%, B 0.014–0.015%, Si 0.3–0.5%, Mn 0.4–0.5%, Pm 0.22–0.24%, Yb 0.1–0.12%, Lu 0.1–0.12%, S 0.005–0.03%, P 0.03–0.05%, with the balance being Fe.

4. The iron-nickel alloy for heat exchangers according to claim 1, characterized in that, In step one, the refining time is 8 to 12 minutes; the heat preservation temperature is 1600 to 1630°C; and the heat preservation time is 18 to 24 minutes.

5. The iron-nickel alloy for heat exchangers according to claim 1, characterized in that, In step three, the heating rate is: 10℃ / min for temperatures below 1000℃, and 5℃ / min for temperatures above 1000℃.

6. The iron-nickel alloy for heat exchangers according to claim 1, characterized in that, In step four, the timeliness processing steps are as follows: The preform is placed in a heat treatment furnace and heated to 850-870°C at a heating rate of 10°C / min. It is then held at this temperature for 6-7 hours and air-cooled to room temperature to obtain the iron-nickel alloy for heat exchangers.

7. The iron-nickel alloy for heat exchangers according to claim 6, characterized in that, Before the preform is placed into the heat treatment furnace, the temperature of the heat treatment furnace is ≤100℃.

8. A heat exchanger, characterized in that, It is prepared from the iron-nickel alloy for heat exchangers as described in any one of claims 1 to 3.

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