Preparation method of heat-resistant alloy thin plate for high-temperature molten salt energy storage

Abstract

The invention relates to the technical field of materials, in particular to a preparation method of a heat-resistant alloy thin plate for high-temperature molten salt energy storage. According to the specific technical scheme, the preparation method of the heat-resistant alloy thin plate for high-temperature molten salt energy storage comprises the steps that heat-resistant alloy and aluminum are smelted, hot rolling cogging at the temperature of 1200 DEG C is conducted after smelting, rolling with the deformation being 60% is conducted, and a hot-rolled plate is obtained; and the hot-rolled plate is subjected to solution treatment, water quenching, grinding and rolling, and then the high-aluminum heat-resisting alloy plate is obtained. Compared with nickel-based alloy, the novel alloy thin plate provided by the invention is low in price, excellent in mechanical property and outstanding in corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of materials technology, specifically to a method for preparing a heat-resistant alloy thin sheet for high-temperature molten salt energy storage. Background Technology

[0002] Energy is the main battleground, and electricity is the main force. Building a new power system based on clean energy has become the main direction of the world's energy transition. Concentrated solar power (CSP) demonstrates significant low-carbon advantages and is undoubtedly an important component of renewable energy generation. Equipped with energy storage systems, CSP has better peak-shaving capabilities than coal-fired power, and its power quality is comparable to thermal power. Energy storage systems are a key component of CSP, and energy storage media are a crucial factor in these systems. Therefore, the construction and development of energy storage media are essential for the widespread application of CSP. Molten salt is the most widely used and mature energy storage medium in CSP. Molten carbonate salts, with their low melting point, wide operating temperature range, weak corrosiveness, and low vapor pressure, have become the preferred energy storage medium for CSP power plants. Currently, the energy storage medium used in CSP power plants both domestically and internationally is mainly ternary molten salt (Li₂CO₃-Na₂CO₃-K₂CO₃ (43.5:31.5:25.0 mol%).

[0003] However, in order to use advanced supercritical carbon dioxide Brayton power cycles with high thermal-to-electrical conversion efficiency, next-generation concentrated solar power plants require operating temperatures above 700°C. Such high temperatures would exacerbate the corrosion of materials by molten salt, and since the heat exchanger is one of the core components of the CSP system, it would be in full contact with the high-temperature molten salt. Therefore, it is crucial to develop a heat-resistant alloy sheet for high-temperature molten salt energy storage. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing heat-resistant alloy thin sheets for high-temperature molten salt energy storage, which provides a novel alloy thin sheet that is cheaper than nickel-based alloys, has excellent mechanical properties, and outstanding corrosion resistance.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention discloses a method for preparing heat-resistant alloy thin plates for high-temperature molten salt energy storage. The heat-resistant alloy is smelted with aluminum, and after smelting, it is hot-rolled at 1200℃ and rolled with a deformation of 60% to obtain hot-rolled plates. After solution treatment, the hot-rolled plates are water-quenched, ground, and rolled to obtain high-alumina heat-resistant alloy plates.

[0007] Preferably, the high-alumina heat-resistant alloy sheet is annealed to obtain a high-alumina heat-resistant alloy thin sheet.

[0008] Preferably, the hot rolling process is as follows: the temperature is raised to 1200℃ at a rate of 10℃ / min and held for 20min, and then rolled with a deformation of 60%, with a deformation of 1-3% per pass and a heat treatment of 5min after each pass.

[0009] Preferably, the amount of aluminum added is 3 to 7 wt.%.

[0010] Preferably, the heat-resistant alloy has the following composition: Cr 2.5-24 wt.%, Ni 30-32 wt.%, Ti 0.1-0.4 wt.%, C 0.02-0.08 wt.%, Al 3-4 wt.%, with the balance being Fe.

[0011] Preferably, the solution treatment temperature is 1150℃, the heating rate is 10℃ / min, and the holding time is 40min.

[0012] Preferably, after grinding, the deformation amount of a single rolling pass is 0.2 mm, the final deformation amount is 90%, the rolling speed is 0.4 m / min, and the roll speed is 15 r / min.

[0013] Preferably, the annealing process involves heating to 800°C at a heating rate of 10°C / min, holding at that temperature for 60 minutes, and then removing and water quenching.

[0014] The present invention has the following beneficial effects:

[0015] 1. This invention improves the corrosion resistance of materials by adding Al to meet the requirements of next-generation CSP systems. Corrosion tests on this material at 700℃ in ternary carbonates of 34.5 wt.% K₂CO₃-33.4 wt.% Na₂CO₃-32.1 wt.% Li₂CO₃ have also verified that the corrosion rate is significantly lower than that of commercially available 800H plates.

[0016] 2. The heat-resistant alloy disclosed in this invention exhibits excellent machinability, with a cold rolling deformation rate exceeding 90%. Furthermore, the thin sheet obtained through cold rolling contains a large number of dislocations, which can provide nucleation sites for the NiAl phase. The NiAl phase, in turn, provides a large amount of Al elements to the material surface for the formation of a protective oxide film, significantly improving corrosion resistance.

[0017] 3. Through a 500-hour static corrosion test, this invention found that the sample annealed at 800℃ for 60 hours had the best corrosion resistance. Therefore, the annealing temperature (800℃) and annealing time (60 min) were determined to be the optimal heat treatment regime. Attached Figure Description

[0018] Figure 1 A photograph of the high-alumina 800H plate prepared in Example 1;

[0019] Figure 2 Corrosion rate curves for unrolled raw sheet and cold-rolled ultrathin sheet with 90% deformation;

[0020] Figure 3 TEM image (ad) of the material with 90% deformation and annealing temperature of 900℃;

[0021] Figure 4 The TEM morphology and diffraction pattern of the material with a deformation of 90% and an annealing temperature of 900℃ are shown in the left figure. The selected area electron diffraction pattern of the particle positions (labeled positions) is shown in the right figure. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Unless otherwise specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.

[0024] Aluminum-containing austenitic stainless steel is typically a single-phase γ-fcc, but Al is a strong ferrite (α-Fe) forming element, and its ability to stabilize ferrite is 2.55 to 5.5 times that of Cr. Adding excessive Al significantly reduces the microstructure stability of austenite, causing the matrix to become a γ(fcc) + α(bcc) dual-phase structure, thus drastically reducing its creep resistance. To mitigate the adverse effects of BCC, the Ni content can be increased to stabilize austenite. However, increasing the Ni content increases the cost of the alloy. Therefore, matching the Ni and Al contents through alloy design to generate a uniform and stable austenitic matrix under appropriate processing conditions is the primary task in the compositional design of aluminum-containing austenitic stainless steel.

[0025] This invention discloses a method for preparing heat-resistant alloy thin plates for high-temperature molten salt energy storage, the steps of which are as follows:

[0026] (1) Melting the heat-resistant alloy with aluminum, specifically: evacuating to 10... -2 Pa, enter the alloy melting system interface, start the power, adjust the power knob to heat the alloy until the alloy bar is completely melted and no bubbles are generated on the surface of the molten steel.

[0027] (2) After melting, the surface layer of the ingot obtained by induction melting is removed, and a 6mm thick sheet is cut by wire cutting and then hot rolled at 1200℃. The rolling mill used is a two-roll cold and hot rolling mill (main motor power 160kW, maximum rolling force 220kN).

[0028] The specific process for hot-rolled billet preparation is as follows: A 6mm thick as-cast sample is placed in a resistance heating furnace, heated to 1200℃ at a rate of 10℃ / min and held for 20min. Then, it is rolled with a deformation of 60%, with a deformation of 1-3% per pass, and the sample is returned to the furnace for 5min after each pass. The rolling speed is 0.4m / min and the roll speed is 15r / min. After rolling, the sample is air-cooled to obtain hot-rolled sheet.

[0029] (3) After solution treatment, hot-rolled sheet is water-quenched, ground and rolled to obtain high-alumina heat-resistant alloy sheet. After annealing, high-alumina heat-resistant alloy sheet is obtained.

[0030] Furthermore, the amount of aluminum added is 3-7 wt.%, and the composition of the heat-resistant alloy is: Cr 2.5-24 wt.%, Ni 30-32 wt.%, Ti 0.1-0.4 wt.%, C 0.02-0.08 wt.%, Al 3-4 wt.%, with the balance being Fe.

[0031] Furthermore, the solution treatment temperature is 1150℃, the heating rate is 10℃ / min, and the holding time is 40min. After grinding, the deformation per rolling pass is 0.2mm, the final deformation is 90%, the rolling speed is 0.4m / min, and the roll speed is 15r / min. The annealing treatment involves heating to 800℃ at a heating rate of 10℃ / min, holding for 60min, and then water quenching.

[0032] The present invention will be further described below with reference to specific embodiments.

[0033] Example 1

[0034] The preparation process of heat-resistant alloy thin plates for high-temperature molten salt energy storage is as follows:

[0035] 1. Select austenitic single-phase 800H heat-resistant alloy with the alloy composition shown in Table 1 for melting, and then roll at 1200℃ with a deformation of 60% to obtain 4mm thick high-alumina Incoloy 800H hot-rolled plate.

[0036] Table 1 Chemical composition (wt.%) of high-alumina 800H heat-resistant steel

[0037] Al Cr Ni Ti C Fe 3.33 12.49 31.41 0.10 0.028 margin

[0038] 2. Select a solution treatment temperature of 1150℃, place the experimental plate in a box-type resistance furnace and heat it to 1150℃ at a rate of 10℃ / min. After holding at this temperature for 40 minutes, remove the plate and quench it in water.

[0039] 3. Cut 30mm×60mm×4mm samples from the solution-treated sheet and polish them sequentially with 120#, 240#, and 500# sandpaper. Roll the polished samples using a two-roll cold and hot rolling mill (main motor power 160kW, maximum rolling force 220kN). The deformation per pass is 0.2mm, the rolling speed is 0.4m / min, the roll speed is 15r / min, and the final sample thickness is 0.4mm. A picture of the resulting high-alumina 800H sheet is shown below. Figure 1 As shown.

[0040] 4. Anneal the rolled sample. Heat the sample in a resistance heating furnace from room temperature to 800℃ at a heating rate of 10℃ / min and hold for 60 minutes. Then remove the sample and quench it in water to obtain the heat-resistant alloy sheet.

[0041] Example 2

[0042] The thin sheet prepared in Example 1 was subjected to relevant tests.

[0043] A corrosion test was conducted at 700℃ in a ternary molten salt (Li₂CO₃-Na₂CO₃-K₂CO₃ (43.5:31.5:25.0 mol%)) for a total duration of 500 hours, with the unrolled original sheet material as a comparison. The results are shown in [Figure number missing]. Figure 2 As shown in the figure. The results showed that the corrosion rate of cold rolling with large deformation (90%) in ternary carbonate was significantly reduced.

[0044] TEM analysis revealed that the large amount of cold rolling deformation introduced numerous dislocations into the material, which in turn provided nucleation sites for the NiAl phase precipitation. The NiAl phase, acting as a "reservoir" for storing Al within the material matrix, continuously provides Al to the material surface, thus forming an Al2O3 protective film. The TEM morphology of the sample with 90% deformation and annealed at 800℃ for 60 hours is shown below. Figure 3 As shown. The TEM macroscopic morphology and diffraction pattern of the sample are as follows. Figure 4 As shown.

[0045] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a heat-resistant alloy thin sheet for high-temperature molten salt energy storage, characterized in that: The heat-resistant alloy is smelted with aluminum, and then hot-rolled at 1200℃ to obtain a hot-rolled plate with a deformation of 60%. The hot-rolled plate is then solution-treated, water-quenched, ground, and rolled to obtain a high-alumina heat-resistant alloy plate.

2. The method for preparing a heat-resistant alloy thin sheet for high-temperature molten salt energy storage according to claim 1, characterized in that: Annealing high-alumina heat-resistant alloy sheets yields high-alumina heat-resistant alloy thin sheets.

3. The method for preparing a heat-resistant alloy thin sheet for high-temperature molten salt energy storage according to claim 1, characterized in that: The hot rolling process is as follows: the temperature is raised to 1200℃ at a rate of 10℃ / min and held for 20min, and then rolled with a deformation of 60%. The deformation of each rolling pass is 1-3%, and after each rolling pass, the roll is returned to the furnace for 5min of heat preservation.

4. The method for preparing a heat-resistant alloy sheet for high-temperature molten salt energy storage according to claim 1, characterized in that: The amount of aluminum added is 3-7 wt.%.

5. The method for preparing a heat-resistant alloy sheet for high-temperature molten salt energy storage according to claim 1 or 4, characterized in that: The composition of the heat-resistant alloy is: Cr 2.5-24 wt.%, Ni 30-32 wt.%, Ti 0.1-0.4 wt.%, C 0.02-0.08 wt.%, Al 3-4 wt.%, with the balance being Fe.

6. The method for preparing a heat-resistant alloy sheet for high-temperature molten salt energy storage according to claim 1, characterized in that: The solution treatment temperature is 1150℃, the heating rate is 10℃ / min, and the holding time is 40min.

7. The method for preparing a heat-resistant alloy sheet for high-temperature molten salt energy storage according to claim 1, characterized in that: After grinding, the deformation in a single rolling pass is 0.2 mm, the final deformation is 90%, the rolling speed is 0.4 m / min, and the roll speed is 15 r / min.

8. The method for preparing a heat-resistant alloy thin sheet for high-temperature molten salt energy storage according to claim 2, characterized in that: The annealing process involves heating to 800°C at a heating rate of 10°C / min, holding at that temperature for 60 minutes, and then removing and water quenching.

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