Titanium alloy suitable for high-temperature nitric acid environment of spent fuel reprocessing and preparation method thereof

Abstract

The application discloses a titanium alloy suitable for a high-temperature nitric acid environment of spent fuel reprocessing and a preparation method thereof, belongs to the field of spent fuel reprocessing materials, and provides a high-temperature nitric acid corrosion-resistant titanium alloy which comprises Pd 0.02-0.08 wt.%, Zr 1-7 wt.% and the balance of titanium and inevitable impurities, and the content is in percentage by mass. The high-temperature nitric acid corrosion-resistant titanium alloy prepared by the application not only has higher hardness, but also has excellent corrosion resistance in a high-temperature nitric acid environment, and has a wide application prospect in the field of spent fuel reprocessing.

Description

Technical Field

[0001] This invention belongs to the field of spent fuel reprocessing materials, specifically relating to a titanium alloy suitable for high-temperature nitric acid environments in spent fuel reprocessing and its preparation method. Background Technology

[0002] Nuclear power, with its advantages of high energy efficiency, low pollution, environmental friendliness, large unit capacity, and stable power generation, will become an important component of future baseload energy. However, with the development of nuclear energy, a large amount of spent fuel is generated, and how to handle this spent fuel is a key issue that urgently needs to be addressed. Commercial spent fuel reprocessing mainly uses nitric acid, a highly oxidizing agent, to dissolve the spent fuel. This process is accompanied by high temperatures and radioactivity, thus requiring materials used in this environment to have high corrosion resistance.

[0003] In the field of spent fuel reprocessing, where the application environment is extremely harsh, titanium alloys, represented by Ti-5Ta and Ti-5Ta-1.8Nb, have demonstrated excellent corrosion resistance and have been widely used in overseas reprocessing plants. However, given the excellent corrosion resistance and good mechanical properties of titanium alloys in the harsh environment of spent fuel reprocessing, developed countries in Europe and America are actively developing high-corrosion-resistant and high-strength titanium alloys.

[0004] Alloying is one of the important methods to improve the corrosion resistance and mechanical properties of titanium alloys. Platinum group metal Pd, as an important corrosion-resistant element, can significantly improve the corrosion resistance of pure titanium or titanium alloys even with small amounts. Zr has high solubility in both α-Ti and β-Ti, which can play a supplementary strengthening role and also significantly improve the heat resistance of titanium alloys. Zr oxide ZrO2 has excellent chemical stability and a low dissolution rate in high-temperature nitric acid. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a titanium alloy suitable for high-temperature nitric acid environment in spent fuel reprocessing and its preparation method, which addresses the above-mentioned shortcomings of the existing technology. The alloy prepared by the present invention not only has high hardness, but also exhibits excellent corrosion resistance in high-temperature nitric acid environment, and can meet the requirements of use.

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

[0007] A titanium alloy suitable for high-temperature nitric acid environments in spent fuel reprocessing, comprising, by mass percentage: 0.02-0.08 wt.% Pd, 1-7 wt.% Zr, with the balance being titanium and unavoidable impurities.

[0008] In one or more embodiments, the titanium alloy comprises, by mass percentage: 0.04-0.06 wt.% Pd, 1-6 wt.% Zr, with the balance being titanium and unavoidable impurities.

[0009] In a preferred embodiment, the titanium alloy comprises, by mass percentage: 0.04 wt.% Pd, 3 wt.% Zr, with the balance being titanium and unavoidable impurities.

[0010] In one or more embodiments, the titanium alloy is required to have the following unavoidable impurity element content: H < 0.0125 wt.%, O < 0.13 wt.%, N < 0.05 wt.%, and C < 0.08 wt.%.

[0011] This invention also proposes a method for preparing a titanium alloy suitable for the high-temperature nitric acid environment of spent fuel reprocessing, comprising the following steps:

[0012] Step 1: Mix the raw materials evenly according to the specified ratio;

[0013] Step 2: The mixture is melted using a vacuum arc remelting method to obtain an ingot;

[0014] Step 3: Press the ingot to obtain the alloy electrode;

[0015] Step 4: Weld the alloy electrodes, and then preheat the welded electrodes.

[0016] Step 5: The preheated welding electrode is melted multiple times using a water-cooled copper crucible.

[0017] Furthermore, the alloy is prepared by vacuum consumable melting as described in step 2, and the weight of the ingot is 50Kg to 3000Kg;

[0018] Furthermore, the ingots obtained in step 2 can be directly processed into corrosion-resistant components, or they can be forged and rolled into bars, wires and plates for use. The forging temperature is 1000℃-1200℃, and the rolling temperature is 850℃-1050℃.

[0019] Furthermore, the alloy electrode described in step 3 is pressed using a 1000Kg to 5000Kg press, and the weight of a single electrode is 5Kg to 30Kg.

[0020] Furthermore, in step 4, the electrode welding is performed in a vacuum glove box, and the welded electrode is preheated at a temperature of 50°C to 150°C.

[0021] Furthermore, in step 5, the welded electrode is melted 2 to 5 times using a water-cooled copper crucible, and the ingot size is 50mm to 1000mm.

[0022] The beneficial effects of this invention are:

[0023] This invention develops a material suitable for spent fuel reprocessing equipment by adding different proportions of Pd and Zr elements to titanium alloys, thereby improving the high-temperature nitric acid corrosion resistance and mechanical properties of the titanium alloys. The titanium alloy formulation of this invention, suitable for the high-temperature nitric acid environment of spent fuel reprocessing, is scientifically sound and reasonable. Its preparation method is simple and easy to implement, and it exhibits good mechanical and corrosion resistance in the high-temperature nitric acid environment. Attached Figure Description

[0024] Figure 1 The titanium alloys prepared in Examples 1-3 of this invention are subjected to a process at 100°C containing V. 5+ Cr 6+ Ce 4+ Potentiodynamic polarization curves of electrochemical corrosion test in concentrated nitric acid solution;

[0025] Figure 2 The image shows the Vickers hardness of the titanium alloys prepared in Examples 1-3 of this invention at room temperature. Detailed Implementation

[0026] The technical solutions in various embodiments of the present invention will now be clearly and thoroughly described in conjunction with the accompanying drawings.

[0027] Example 1

[0028] This embodiment discloses a titanium alloy suitable for high-temperature nitric acid environment in spent fuel reprocessing. The mass percentage of each component is: 0.04 wt.% Pd, 1 wt.% Zr, and the unavoidable impurity element content requirements are: H < 0.0125 wt.%, O < 0.13 wt.%, N < 0.05 wt.%, C < 0.08 wt.%, with the balance being Ti.

[0029] A process for producing titanium alloys suitable for the high-temperature nitric acid environment of spent fuel reprocessing includes the following steps:

[0030] Step 1: Mix the raw materials evenly using a cloth-making machine according to the specified proportions;

[0031] Step 2: Prepare an alloy by vacuum arc remelting of the obtained molten material, with an ingot weight of 50 kg;

[0032] Step 3: Press the ingot obtained in Step 2 using a 1000Kg press to obtain alloy electrodes, with each electrode weighing 5Kg.

[0033] Step 4: Weld the electrodes obtained in Step 3 in a vacuum glove box. After welding, preheat the electrodes to 100°C.

[0034] Step 5: The welded electrode is melted 5 times using a water-cooled copper crucible, and the ingot size is 50mm.

[0035] Depend on Figure 1 The electrodynamic polarization curves of the electrochemical corrosion test show that the titanium alloy suitable for the high-temperature nitric acid environment of spent fuel reprocessing in Example 1 has a significant passivation region, with a passivation current density of 5.638 × 10⁻⁶ at a passivation potential of 1.5 V. -5 A / cm 2 It has low current density and strong resistance to high-temperature nitric acid corrosion. Figure 2 The Vickers hardness results at room temperature show that the titanium alloy in Example 1, suitable for the high-temperature nitric acid environment of spent fuel reprocessing, has a Vickers hardness of 155HV1 and excellent mechanical properties.

[0036] Example 2

[0037] This embodiment discloses a titanium alloy suitable for high-temperature nitric acid environment in spent fuel reprocessing. The mass percentage of each component is: 0.04 wt.% Pd, 3 wt.% Zr, and the unavoidable impurity element content requirements are: H < 0.0125 wt.%, O < 0.13 wt.%, N < 0.05 wt.%, C < 0.08 wt.%, with the balance being Ti.

[0038] A process for producing titanium alloys suitable for the high-temperature nitric acid environment of spent fuel reprocessing includes the following steps:

[0039] Step 1: Mix the raw materials evenly using a cloth-making machine according to the specified proportions;

[0040] Step 2: Prepare an alloy from the molten material obtained in Step 1 using vacuum arc remelting, with an ingot weight of 50 kg.

[0041] Step 3: Press the ingot obtained in Step 2 using a 1000Kg press to obtain alloy electrodes, with each electrode weighing 5Kg.

[0042] Step 4: Weld the electrodes obtained in Step 3 in a vacuum glove box. After welding, preheat the electrodes to 100°C.

[0043] Step 5: The welded electrode is melted 5 times using a water-cooled copper crucible, and the ingot size is 50mm.

[0044] Depend on Figure 1 The electrodynamic polarization curves of the electrochemical corrosion test show that the titanium alloy suitable for the high-temperature nitric acid environment of spent fuel reprocessing in Example 2 has a significant passivation region, with a passivation current density of 4.192 × 10⁻⁶ at a passivation potential of 1.5 V. -5 A / cm 2It has low current density and strong resistance to high-temperature nitric acid corrosion. Figure 2 The Vickers hardness results at room temperature show that the Vickers hardness of the high-temperature nitric acid corrosion resistant titanium alloy in Example 2 is 164HV1, which indicates that it has excellent mechanical properties.

[0045] Example 3

[0046] This embodiment discloses a titanium alloy suitable for high-temperature nitric acid environment in spent fuel reprocessing. The mass percentage of each component is: 0.04 wt.% Pd, 5 wt.% Zr, and the unavoidable impurity element content requirements are: H < 0.0125 wt.%, O < 0.13 wt.%, N < 0.05 wt.%, C < 0.08 wt.%, with the balance being Ti.

[0047] A process for producing titanium alloys suitable for the high-temperature nitric acid environment of spent fuel reprocessing includes the following steps:

[0048] Step 1: Mix the raw materials evenly using a cloth-making machine according to the specified proportions;

[0049] Step 2: Prepare an alloy from the molten material obtained in Step 1 using vacuum arc remelting, with an ingot weight of 50 kg.

[0050] Step 3: Press the ingot obtained in Step 2 using a 1000Kg press to obtain alloy electrodes, with each electrode weighing 5Kg.

[0051] Step 4: Weld the electrodes obtained in Step 3 in a vacuum glove box. After welding, preheat the electrodes to 100°C.

[0052] Step 5: The welded electrode is melted 5 times using a water-cooled copper crucible, and the ingot size is 50mm.

[0053] Depend on Figure 1 The electrodynamic polarization curves of the electrochemical corrosion test show that the high-temperature nitric acid corrosion-resistant titanium alloy in Example 3 has a significant passivation zone, with a passivation current density of 5.158 × 10⁻⁶ at a passivation potential of 1.5 V. -5 A / cm 2 It has low current density and strong resistance to high-temperature nitric acid corrosion. Figure 2 The Vickers hardness results at room temperature show that the Vickers hardness of the high-temperature nitric acid corrosion resistant titanium alloy in Example 3 is 168HV1, which indicates that it has excellent mechanical properties.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. The preferred embodiments of the present invention disclosed above are only for illustrating the invention and do not limit the invention to the specific embodiments described. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope demonstrated by the present invention, based on the technical solutions and inventive concepts of the present invention, should be covered within the technical protection scope of the present invention.

Claims

1. A titanium alloy suitable for use in the high-temperature nitric acid environment of spent fuel reprocessing, characterized in that, The titanium alloy is composed of the following components by mass percentage: Pd 0.04 wt.%, Zr 1-6 wt.%, with the balance being titanium and unavoidable impurities; wherein the content of unavoidable impurity elements meets the following requirements: H<0.0125 wt.%, O<0.13 wt.%, N<0.05 wt.%, C<0.08 wt.%.

2. The titanium alloy suitable for high-temperature nitric acid environment in spent fuel reprocessing according to claim 1, characterized in that, The composition by mass percentage includes: Pd 0.04 wt.%, Zr 3 wt.%, with the balance being titanium and unavoidable impurities.

3. A method for preparing a titanium alloy suitable for high-temperature nitric acid environment in spent fuel reprocessing, as described in any one of claims 1-2, characterized in that, Includes the following steps: Step 1: Mix the raw materials evenly according to the specified ratio; Step 2: The obtained molten material is processed by vacuum arc remelting to obtain an ingot; Step 3: Press the ingot to obtain the alloy electrode; Step 4: Weld the alloy electrode in a vacuum glove box. After welding, preheat the electrode at a temperature of 50℃-150℃. Step 5: Use a water-cooled copper crucible to melt the preheated welding electrode 2 to 5 times, and cast the ingot in size 50 to 1000 mm.

4. The method for preparing a titanium alloy suitable for high-temperature nitric acid environment in spent fuel reprocessing according to claim 3, characterized in that, The weight of the ingot obtained in step 2 is 50Kg-3000Kg.

5. The method for preparing a titanium alloy suitable for high-temperature nitric acid environment in spent fuel reprocessing according to claim 3, characterized in that, The ingots obtained in step 2 can be directly processed into corrosion-resistant components, or forged and rolled into bars, wires and plates for use. The forging temperature is 1000℃-1200℃, and the rolling temperature is 850℃-1050℃.

6. The method for preparing a titanium alloy suitable for high-temperature nitric acid environment in spent fuel reprocessing according to claim 3, characterized in that, In step 3, an alloy electrode is pressed using a 1000Kg-5000Kg press, with each electrode weighing 5Kg-30Kg.

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