Method for heat treatment of iron-nickel based alloy cast blanks

Abstract

The application relates to a heat treatment method of an iron-nickel-based alloy casting blank, which comprises the following steps: controlling a red delivery temperature to be between 800-900 DEG C, and feeding the obtained iron-nickel-based alloy casting blank into a homogenizing furnace; heating the homogenizing furnace to 1250-1280 DEG C at a heating speed of 80-100 DEG C / h, and performing first heat preservation on the iron-nickel-based alloy casting blank in the homogenizing furnace according to the thickness of the iron-nickel-based alloy casting blank; controlling the homogenizing furnace to be cooled to 1180-1200 DEG C, performing second heat preservation on the iron-nickel-based alloy casting blank in the homogenizing furnace according to the content of Cr and Mo in the iron-nickel-based alloy casting blank; and performing furnace cooling and air cooling treatment on the iron-nickel-based alloy casting blank. The heat treatment method of the iron-nickel-based alloy casting blank can obtain an iron-nickel-based alloy casting blank with high corrosion resistance, and can meet the corrosion resistance requirement of carbon capture, utilization and storage technology.

Description

Technical Field

[0001] This invention belongs to the field of billet heat treatment technology, specifically relating to a heat treatment method for iron-nickel based alloy billets. Background Technology

[0002] Carbon capture, utilization, and storage (CCUS) refers to technologies that separate carbon dioxide from industrial processes, energy use, or the atmosphere for utilization or storage. This technology can mitigate global climate change and is a crucial means of achieving carbon neutrality. The carbon capture stage in CCUS often involves the treatment of acidic gases (such as carbon dioxide and hydrogen sulfide) and corrosive media. Therefore, the related equipment requires materials with stringent overall corrosion resistance. Since iron-nickel-based alloys such as N08825 offer a significantly better corrosion resistance / cost balance than corrosion-resistant alloys like N06625 and 904L, current technologies typically use iron-nickel-based alloys such as N08825 to manufacture key equipment for flue gas treatment and acid gas absorption.

[0003] N08825 is a high-Ti iron-nickel-based alloy with a Cr-Ni-Mo-Cu composition system, containing over 65% Ti. This characteristic makes it prone to elemental segregation at the austenite grain boundaries during solidification of the N08825 iron-nickel-based alloy, leading to a sharp deterioration in the corrosion resistance of the nearby matrix. Traditional homogenization processes can eliminate this elemental segregation, but due to the high degree of elemental segregation in N08825 iron-nickel-based alloy, precipitates such as σ and Ni3Ti formed at the center of the billet thickness are difficult to completely dissolve back into the matrix. These residual precipitates will remain in the alloy during subsequent hot and cold working of the billet, and in severe cases, may even cause the final product to fail to meet corrosion resistance requirements. Summary of the Invention

[0004] To address all or part of the aforementioned problems, the present invention aims to provide a heat treatment method for iron-nickel-based alloy billets. The iron-nickel-based alloy billets obtained by the heat treatment method of the present invention have high corrosion resistance and can meet the corrosion resistance requirements of carbon capture, utilization and storage technologies.

[0005] According to one aspect of the present invention, a heat treatment method for iron-nickel-based alloy ingots is provided, comprising: The red-feeding temperature is controlled between 800-900℃, and the obtained iron-nickel-based alloy billet is fed into a homogenizing furnace. The homogenizing furnace is heated to 1250-1280℃ at a heating rate of 80-100℃ / h, and the iron-nickel-based alloy billet in the homogenizing furnace is held at the first temperature according to the thickness of the iron-nickel-based alloy billet. The homogenizing furnace is cooled to 1180-1200℃, and the iron-nickel-based alloy billet in the homogenizing furnace is subjected to secondary heat preservation according to the Cr and Mo content in the iron-nickel-based alloy billet; and, The iron-nickel-based alloy billet is subjected to furnace cooling and air cooling treatment.

[0006] Furthermore, before the obtained iron-nickel-based alloy billet is fed into the homogenizing furnace at the controlled red-feed temperature between 800-900℃, the method further includes: treating the iron-nickel-based alloy with an electric furnace / alloy melting furnace + AOD + LF + continuous casting process, or an electric furnace / alloy melting furnace + VOD + AOD + LF + continuous casting process, to obtain a continuously cast billet; and cutting the continuously cast billet into segments online to obtain the iron-nickel-based alloy billet.

[0007] Furthermore, the homogenizer is a bogie-type homogenizer.

[0008] Furthermore, the step of heating the homogenizing furnace to 1250-1280℃ at a heating rate of 80-100℃ / h, and performing an initial heat preservation on the iron-nickel-based alloy billet in the homogenizing furnace according to the thickness of the iron-nickel-based alloy billet, specifically involves heating the homogenizing furnace to 1250-1280℃ at a heating rate of 80-100℃ / h, and performing an initial heat preservation on the iron-nickel-based alloy billet. The heat preservation time for the initial heat preservation is equal to the thickness of the iron-nickel-based alloy billet divided by 10 times a first coefficient, where the first coefficient is a temperature coefficient related to the iron-nickel-based alloy.

[0009] Furthermore, the first coefficient is equal to 4 millimeters per hour.

[0010] Furthermore, the step of controlling the homogenizing furnace to cool down to 1180-1200℃ and performing secondary heat preservation on the iron-nickel-based alloy billet in the homogenizing furnace according to the Cr and Mo content in the iron-nickel-based alloy billet specifically involves: controlling the homogenizing furnace to cool down to 1180-1200℃ and performing secondary heat preservation on the iron-nickel-based alloy billet, wherein the heat preservation time of the secondary heat preservation is equal to the sum of the first and second terms, the first term is equal to 100 times the percentage content of Cr in the iron-nickel-based alloy multiplied by the second coefficient, and the second term is equal to 100 times the percentage content of Mo in the iron-nickel-based alloy multiplied by the third coefficient, wherein the second coefficient and the third coefficient are temperature coefficients related to the iron-nickel-based alloy.

[0011] Furthermore, the second coefficient is equal to 1.5 hours, and the third coefficient is equal to 1.2 hours.

[0012] Furthermore, the furnace cooling and air cooling treatment of the iron-nickel-based alloy billet further includes: after the secondary heat preservation, controlling the iron-nickel-based alloy billet to cool to 900-950°C in the homogenizing furnace at a cooling rate of 50-80°C / h, and then controlling the iron-nickel-based alloy billet to be air-cooled to room temperature after exiting the furnace.

[0013] Furthermore, the iron-nickel-based alloy is N08825 iron-nickel-based alloy.

[0014] As can be seen from the above technical solution, the heat treatment method for iron-nickel based alloy castings provided by the present invention has the following beneficial effects: The method of this invention employs online hot-feeding of continuously cast billets and a two-stage homogenization process, while matching corresponding heating, holding and cooling parameters. This effectively promotes the dissolution of precipitates in the billet back into the alloy matrix, resulting in a cast iron-nickel alloy billet with virtually no residual precipitates. The resulting cast iron-nickel alloy billet has high corrosion resistance, which meets the corrosion resistance requirements of carbon capture, utilization and storage technologies. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a heat treatment method for an iron-nickel-based alloy billet according to an embodiment of the present invention. Detailed Implementation

[0016] To better understand the purpose, structure, and function of this invention, a heat treatment method for an iron-nickel-based alloy billet according to the present invention will be described in further detail below with reference to the accompanying drawings.

[0017] like Figure 1 As shown, this invention illustrates a heat treatment method for an iron-nickel-based alloy billet, comprising the following steps: Step S001: Control the red-feeding temperature between 800-900℃ and send the obtained iron-nickel based alloy billet into a homogenizing furnace, such as a bogie-type homogenizing furnace. Step S002: Heat the homogenizing furnace to 1250-1280℃ at a heating rate of 80-100℃ / h. After heating, hold the iron-nickel-based alloy billet in the homogenizing furnace for the first time according to the thickness of the iron-nickel-based alloy billet. Step S003: Control the homogenizing furnace temperature to 1180-1200℃. After cooling, perform a second heat preservation on the iron-nickel-based alloy billet in the homogenizing furnace according to the Cr and Mo content in the billet; and, Step S004: Perform furnace cooling and air cooling treatment on the iron-nickel based alloy billet.

[0018] Regarding the iron-nickel-based alloy billet in step S001, which is obtained by cutting a continuously cast billet, that is, before the iron-nickel-based alloy billet is fed into the homogenizing furnace after controlling the red-feeding temperature between 800-900°C in step S001, the method of this embodiment further includes: processing the iron-nickel-based alloy using an electric furnace / alloy melting furnace + AOD + LF + continuous casting process, or an electric furnace / alloy melting furnace + VOD + AOD + LF + continuous casting process, to obtain a continuously cast billet; and cutting the continuously cast billet into segments online to obtain the iron-nickel-based alloy billet.

[0019] That is, before step S001, the iron-nickel-based alloy needs to be processed using either an electric furnace / alloy melting furnace + AOD + LF + continuous casting or an electric furnace / alloy melting furnace + VOD + AOD + LF + continuous casting to obtain a continuously cast billet. After obtaining the continuously cast billet, it needs to be cut into segments online to obtain iron-nickel-based alloy billets. For the obtained iron-nickel-based alloy billets, this embodiment of the invention utilizes the residual heat of the iron-nickel-based alloy billet to hot-feed it into a bogie-type soaking furnace. The hot-feeding temperature is controlled between 800-900℃, specifically, for example, 800℃, 820℃, 840℃, 860℃, 880℃, or 900℃. This embodiment of the invention can effectively reduce the precipitation degree of the billet core during cooling to a low level, providing favorable conditions for subsequent homogenization treatment. Regarding the hot-feeding temperature...

[0020] In step S002, the homogenizing furnace is heated to 1250-1280℃ at a heating rate of 80-100℃ / h. After heating, the iron-nickel-based alloy billet in the homogenizing furnace is held for the first time according to the thickness of the iron-nickel-based alloy billet. Specifically, the homogenizing furnace is heated to 1250-1280℃ at a heating rate of 80-100℃ / h, and then the iron-nickel-based alloy billet is held for the first time. The holding time of the first time is equal to the thickness of the iron-nickel-based alloy billet divided by 10 times the first coefficient, where the first coefficient is a temperature coefficient related to the iron-nickel-based alloy.

[0021] In specific implementation, the heating rate in step S002 is, for example, 80℃ / h, 85℃ / h, 90℃ / h, 95℃ / h, or 100℃ / h; the homogenizing furnace is heated to 1250℃, 1255℃, 1260℃, 1265℃, 1270℃, 1275℃, or 1280℃ according to the corresponding heating rate. For the initial holding time, the holding time is related to the thickness of the iron-nickel-based alloy billet and the first coefficient related to temperature of the iron-nickel-based alloy. Specifically, the initial holding time is set as t1, the thickness of the iron-nickel-based alloy billet is T, and the first coefficient is k1. Then t1 = T / 10k1, where T is in mm, t1 is in h, and k1 is in mm / h. Regarding the first coefficient, based on numerous experimental results of iron-nickel-based alloys, k1 = 4 mm / h is calculated and derived.

[0022] Regarding step S002: By rapidly heating to the high-temperature range and controlling the holding time according to the thickness of the iron-nickel-based alloy billet, the remelting rate of the precipitates that have already precipitated in the core of the billet can be effectively accelerated, while preventing severe oxidation of the billet surface.

[0023] In step S003, the homogenizing furnace is cooled to 1180-1200℃. After cooling, the iron-nickel-based alloy billet in the homogenizing furnace is subjected to secondary heat preservation according to the Cr and Mo content in the iron-nickel-based alloy billet. Specifically, the homogenizing furnace is cooled to 1180-1200℃, and the iron-nickel-based alloy billet is subjected to secondary heat preservation. The heat preservation time of the secondary heat preservation is equal to the sum of the first and second items. The first item is equal to 100 times the percentage content of Cr in the iron-nickel-based alloy multiplied by the second coefficient, and the second item is equal to 100 times the percentage content of Mo in the iron-nickel-based alloy multiplied by the third coefficient. The second and third coefficients are temperature coefficients related to the iron-nickel-based alloy.

[0024] Specifically, after the initial heat treatment, for example, the homogenizing furnace is cooled down to 1180℃, 1190℃, or 1200℃. After cooling down to the corresponding temperature, the iron-nickel-based alloy billet in the homogenizing furnace is subjected to a second heat treatment. The time of the second heat treatment is related to the percentage content of Cr and Mo in the iron-nickel-based alloy, as well as the second and third coefficients. The second and third coefficients are temperature coefficients related to the iron-nickel-based alloy. Specifically, if the second heat treatment time is set to t2, the percentage content of Cr in the iron-nickel-based alloy is w(Cr), the percentage content of Mo in the iron-nickel-based alloy is w(Mo), the second coefficient is k2, and the third coefficient is k3, then t2 = 100 w(Cr) k2 + 100 w(Mo) k3. The unit of t2 is h, and the units of k2 and k3 are h. For the second coefficient, k2 = 1.5h was calculated and derived based on a large number of experimental results. For the third coefficient, k3 = 1.2h was calculated and derived based on a large number of experimental results.

[0025] For step S003: The time for the second heat treatment is determined based on the content of the precipitated phase forming elements Cr and Mo, ensuring that the precipitate can be fully dissolved back into the matrix.

[0026] Specifically, step S004, which involves furnace cooling and air cooling of the iron-nickel alloy billet, involves cooling the iron-nickel alloy billet to 900-950°C in a homogenizing furnace at a cooling rate of 50-80°C / h after the second heat treatment. Then, the iron-nickel alloy billet is air-cooled to room temperature after exiting the furnace.

[0027] Specifically, regarding the cooling process, for example, the cooling rate of furnace cooling is 50℃ / h, 55℃ / h, 60℃ / h, 65℃ / h, 70℃ / h, 75℃ / h, or 80℃ / h. For example, furnace cooling cools the iron-nickel-based alloy billet to 900℃, 910℃, 920℃, 930℃, 940℃, or 950℃. After the iron-nickel-based alloy billet is cooled to the corresponding cooling temperature, it is taken out of the furnace and air-cooled to room temperature.

[0028] For step S004: the use of furnace cooling and air cooling methods further suppresses the precipitation of the precipitated phase during the cooling process.

[0029] In this embodiment of the invention, the iron-nickel based alloy is N08825 iron-nickel based alloy, and its standard composition control range is shown in Table 1 below: Table 1: Standard Composition Control Range (wt / %) of N08825 Iron-Nickel Based Alloy

[0030] The method of this invention employs online hot-feeding of continuously cast billets and a double-step homogenization process, while matching corresponding heating, holding and cooling parameters. This effectively promotes the dissolution of precipitates in the billet back into the alloy matrix, resulting in a cast iron-nickel alloy billet with virtually no residual precipitates. The resulting cast iron-nickel alloy billet has high corrosion resistance, which meets the corrosion resistance requirements of carbon capture, utilization and storage technologies.

[0031] The heat treatment method for iron-nickel based alloy billets of the present invention will be described in detail below through examples. Experimental methods not specified in the examples shall be performed according to conventional methods or product instructions.

[0032] The elemental composition of the iron-nickel based alloys in the following embodiments is shown in Table 2: Table 2. Iron-nickel based alloy composition (wt / %) in each embodiment

[0033] Example 1: A continuous casting billet of iron-nickel based alloy was obtained using an electric furnace + AOD + LF + continuous casting process. The thickness of the billet was 160 mm, and its actual composition is shown in Table 2. After the billet was cut into sections online, it was fed into a bogie-type homogenizer at a hot-feeding temperature of 800°C. The billet was heated to 1280°C in the homogenizer at a heating rate of 100°C / h and held for 4 hours. Then it was cooled to 1200°C and held for 34.5 hours. After the holding period, the billet was cooled to 950°C in the homogenizer at a cooling rate of 50°C / h and then air-cooled to room temperature.

[0034] Example 2: A continuous casting billet of iron-nickel based alloy was obtained using an alloy melting furnace + AOD + LF + continuous casting process. The thickness of the billet was 180 mm, and its actual composition is shown in Table 2. After the billet was cut into sections online, it was sent into a bogie-type homogenizer at a hot-feeding temperature of 860°C. The billet was heated to 1260°C in the homogenizer at a heating rate of 90°C / h and held for 4.5 h. Then it was cooled to 1180°C and held for 37.2 h. After the holding period, the billet was cooled to 920°C in the homogenizer at a cooling rate of 70°C / h and then air-cooled to room temperature.

[0035] Example 3: A continuous casting billet of iron-nickel based alloy was obtained using an electric furnace + VOD + AOD + LF + continuous casting process. The billet thickness was 200 mm, and its actual composition is shown in Table 2. After the continuous casting billet was cut into sections online, it was sent into a bogie-type homogenizing furnace at a hot-feeding temperature of 900°C. The billet was heated to 1250°C in the homogenizing furnace at a heating rate of 80°C / h and held for 5 hours. Then it was cooled to 1190°C and held for 38.1 hours. After the holding period, the billet was cooled to 900°C in a soaking furnace at a cooling rate of 80°C / h and then air-cooled to room temperature.

[0036] The results of observing the internal structure of the cast slabs obtained in Examples 1-3 are shown in Table 3 below. The results of intergranular corrosion and pitting corrosion tests on the cast slab obtained in Example 1, which was hot-rolled and cold-rolled to prepare a 3mm cold plate, are shown in Table 3 below. The results of intergranular corrosion and pitting corrosion tests on the cast slab obtained in Example 2, which was hot-rolled and cold-rolled to prepare a 3.3mm cold plate, are shown in Table 3 below. The results of intergranular corrosion and pitting corrosion tests on the cast slab obtained in Example 3, which was hot-rolled and cold-rolled to prepare a 3.5mm cold plate, are shown in Table 3 below. Intergranular corrosion was detected using the ASTM G28A method, which involves immersing the obtained cold plate in a boiling ferric sulfate and 50% sulfuric acid solution for 120 hours. Pitting corrosion was detected using the ASTM G48A method, which involves immersing the obtained cold plate in a 6% ferric chloride solution at a constant temperature (22°C) for 72 hours.

[0037] Table 3. Corrosion resistance of the iron-nickel based alloys of Examples 1-3 and the N08825 iron-nickel based alloy.

[0038] As shown in Table 3, the billets obtained in Examples 1-3 of the present invention do not have obvious precipitates compared with the N08825 billets of the prior art; the corrosion rate and intergranular corrosion depth of the cold plates obtained in Examples 1-3 of the present invention by the ASTM G28A method are significantly less than those of the N08825 cold plates of the prior art; the corrosion rate of the cold plates obtained in Examples 1-3 of the present invention by the ASTM G48A method is significantly less than that of the N08825 cold plates of the prior art.

[0039] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by those skilled in the art to which this invention pertains.

[0040] Furthermore, the terms "a," "two," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly defined.

[0041] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A heat treatment method for an iron-nickel-based alloy cast billet, characterized in that, include The red-feeding temperature is controlled between 800-900℃, and the obtained iron-nickel-based alloy billet is fed into a homogenizing furnace. The homogenizing furnace is heated to 1250-1280℃ at a heating rate of 80-100℃ / h. After heating, the iron-nickel-based alloy billet in the homogenizing furnace is held at the first temperature according to the thickness of the iron-nickel-based alloy billet. The homogenizing furnace is cooled to 1180-1200℃. After cooling, the iron-nickel-based alloy billet in the homogenizing furnace is subjected to secondary heat preservation according to the Cr and Mo content in the billet. The iron-nickel-based alloy billet is subjected to furnace cooling and air cooling treatment.

2. The heat treatment method for iron-nickel-based alloy ingots according to claim 1, characterized in that, Before the obtained iron-nickel-based alloy billet is fed into the homogenizing furnace at a controlled red-feeding temperature between 800-900℃, the method further includes: treating the iron-nickel-based alloy with an electric furnace / alloy melting furnace + AOD + LF + continuous casting process, or an electric furnace / alloy melting furnace + VOD + AOD + LF + continuous casting process, to obtain a continuously cast billet; and cutting the continuously cast billet into segments online to obtain the iron-nickel-based alloy billet.

3. The heat treatment method for iron-nickel-based alloy ingots according to claim 1, characterized in that, The homogenizer is a bogie-type homogenizer.

4. The heat treatment method for iron-nickel-based alloy ingots according to claim 1, characterized in that, The process of heating the homogenizing furnace to 1250-1280℃ at a heating rate of 80-100℃ / h, and then performing an initial heat preservation on the iron-nickel-based alloy billet in the homogenizing furnace according to the thickness of the iron-nickel-based alloy billet, specifically involves heating the homogenizing furnace to 1250-1280℃ at a heating rate of 80-100℃ / h, and then performing an initial heat preservation on the iron-nickel-based alloy billet after heating. The heat preservation time for the initial heat preservation is equal to the thickness of the iron-nickel-based alloy billet divided by 10 times a first coefficient, where the first coefficient is a temperature coefficient related to the iron-nickel-based alloy.

5. The heat treatment method for iron-nickel-based alloy ingots according to claim 4, characterized in that, The first coefficient is equal to 4 millimeters per hour.

6. The heat treatment method for iron-nickel-based alloy ingots according to claim 1, characterized in that, The specific steps of controlling the homogenizing furnace to cool down to 1180-1200℃ and then performing a secondary heat preservation on the iron-nickel-based alloy billet in the homogenizing furnace according to the Cr and Mo content in the iron-nickel-based alloy billet are as follows: controlling the homogenizing furnace to cool down to 1180-1200℃, performing a secondary heat preservation on the iron-nickel-based alloy billet after cooling down, and the heat preservation time of the secondary heat preservation is equal to the sum of the first and second items. The first item is equal to 100 times the percentage content of Cr in the iron-nickel-based alloy multiplied by the second coefficient, and the second item is equal to 100 times the percentage content of Mo in the iron-nickel-based alloy multiplied by the third coefficient. The second coefficient and the third coefficient are temperature coefficients related to the iron-nickel-based alloy.

7. The heat treatment method for iron-nickel-based alloy ingots according to claim 6, characterized in that, The second coefficient is equal to 1.5 hours, and the third coefficient is equal to 1.2 hours.

8. The heat treatment method for iron-nickel-based alloy ingots according to claim 1, characterized in that, The furnace cooling and air cooling treatment of the iron-nickel-based alloy billet further includes: after the secondary heat preservation, controlling the iron-nickel-based alloy billet to cool to 900-950°C in the homogenizing furnace at a cooling rate of 50-80°C / h, and then controlling the iron-nickel-based alloy billet to be air-cooled to room temperature after exiting the furnace.

9. The heat treatment method for iron-nickel-based alloy ingots according to claim 1, characterized in that, The iron-nickel based alloy is N08825 iron-nickel based alloy.

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