A method for preparing a nuclear-grade zirconium-niobium intermediate alloy wire

Abstract

The application discloses a preparation method of a nuclear-grade zirconium-niobium intermediate alloy wire, which is composed of the following components in mass percentage: 15-75% of Nb, and the balance of Zr and inevitable impurities; the method comprises the following steps: step one, vacuum self-consumption arc smelting and forging are performed on sponge zirconium and niobium blocks to obtain a rod blank; step two, the rod blank is rolled at 850-950 DEG C by using a rolling mill, is peeled after annealing in an argon atmosphere, and is cold-rolled to obtain a wire blank; and step three, the wire blank is peeled, is subjected to intermediate vacuum annealing and polishing in multiple cold-drawing passes to obtain the zirconium-niobium intermediate alloy wire. The method can realize the synchronization and uniformity of alloy flow on the surface and in the core of the wire by controlling the Nb content of the zirconium-niobium intermediate alloy and the rolling temperature of the rolling mill, adopting the process of cold rolling and multiple cold-drawing passes, and obtaining the zirconium-niobium intermediate alloy wire with good quality, and is suitable for the technical field of metal material processing.

Description

Technical Field

[0001] This invention belongs to the field of metal material processing technology, and in particular relates to a method for preparing nuclear-grade zirconium-niobium master alloy wire. Background Technology

[0002] Because niobium has a melting point as high as 2477℃, which is 600℃ higher than that of zirconium, the traditional process of directly introducing elemental niobium into the ingot during the preparation of zirconium-niobium alloy materials is prone to introducing high-melting-point niobium infusible blocks into the ingot and causing metallurgical defects such as elemental segregation; in addition, there are problems such as complex processes and difficulty in controlling impurity elements.

[0003] By preparing zirconium-niobium master alloys to reduce the melting point difference with the matrix zirconium, problems such as inclusions and segregation that easily occur in the preparation of existing zirconium-niobium alloy materials can be effectively solved; at the same time, it can simplify the production process and reduce manufacturing costs. Zirconium-niobium master alloys are crucial for improving the quality of zirconium alloy products and are gradually becoming an essential raw material for preparing high-quality, high-performance zirconium-niobium alloys. Commonly used granular zirconium-niobium master alloy products are usually made by cutting wire. To obtain granular zirconium-niobium master alloy products with qualified chemical composition, appearance, and dimensions, high-quality zirconium-niobium master alloy wires need to be prepared.

[0004] In existing technologies, zirconium-niobium master alloys are prone to defects such as tailing, porosity, and delamination during drawing; furthermore, traditional acid pickling for surface treatment results in poor wire surface quality. Therefore, how to produce high-quality zirconium-niobium master alloy wire has become an urgent problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing nuclear-grade zirconium-niobium master alloy wire. This method achieves synchronous and uniform alloy flow between the wire surface and the core by controlling the Nb content in the zirconium-niobium master alloy wire, controlling the rolling temperature of the rolling mill, and employing a combination of cold rolling and multi-pass cold drawing processes. This results in high-quality zirconium-niobium master alloy wire and solves the problems of tail shrinkage, porosity, and delamination that occur in existing zirconium-niobium master alloys during drawing.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing nuclear-grade zirconium-niobium master alloy wire, characterized in that the zirconium-niobium master alloy wire is composed of the following mass fractions: Nb 15%–75%, with the balance being Zr and unavoidable impurities; the preparation method includes the following steps:

[0007] Step 1: Using sponge zirconium and niobium blocks as raw materials, zirconium-niobium master alloy ingots are obtained by vacuum consumable arc melting, and then forged into billets;

[0008] Step 2: The bar billet obtained in Step 1 is rolled into a strip by a rolling mill at 850℃~950℃, annealed under argon atmosphere, peeled off, and then cold rolled to obtain a wire blank.

[0009] Step 3: After peeling the wire blank obtained in Step 2, perform multiple cold drawing passes, and conduct intermediate vacuum annealing and polishing during the multiple cold drawing passes to obtain zirconium-niobium master alloy wire.

[0010] This invention controls the temperature of the rolling mill to 850℃~950℃. Under this temperature condition, the zirconium-niobium master alloy billet has good machinability, which can reduce the rolling difficulty, reduce the probability of defects such as porosity in the rolled strip, and thus reduce the internal defects of the zirconium-niobium master alloy wire.

[0011] The above-mentioned method for preparing nuclear-grade zirconium-niobium master alloy wire is characterized in that the annealing temperature in step two is 700℃~800℃, and the annealing holding time is 0.5h~2h.

[0012] This invention improves the phase structure and uniformity of the internal structure of the strip by controlling the annealing temperature at 700℃~800℃ and the holding time at 0.5h~2h, thereby reducing the internal stress generated after rolling and enabling the strip to be cold rolled smoothly.

[0013] The above-mentioned method for preparing nuclear-grade zirconium-niobium master alloy wire is characterized in that the multi-pass cold drawing in step three adopts a roller die drawing process, and ultrasonic damage removal is performed before the multi-pass cold drawing.

[0014] This invention reduces the probability of defects in the wire material during the drawing process by using a roller drawing process for cold drawing and by using ultrasonic screening to remove defects from the wire blank.

[0015] The above-mentioned method for preparing nuclear-grade zirconium-niobium intermediate alloy wire is characterized in that the intermediate vacuum annealing process in step three is as follows: heating to 600℃~750℃ and holding for 0.5h~1h, then cooling to below 150℃ and removing from the furnace.

[0016] This invention reduces the internal stress generated after the first multi-pass cold drawing by performing vacuum annealing between two multi-pass cold drawing processes and controlling the temperature of the vacuum annealing. This allows the second multi-pass cold drawing to proceed smoothly, further reducing the probability of defects and resulting in zirconium-niobium master alloy wire with good surface and internal quality.

[0017] This invention comprehensively designs the heat treatment temperature in each process based on the elemental composition, diameter, and deformation amount of the zirconium-niobium master alloy.

[0018] The above-mentioned method for preparing nuclear-grade zirconium-niobium master alloy wire is characterized in that, after multiple cold drawing processes in step three, ultrasonic cleaning, drying, and polishing are performed sequentially.

[0019] The method for preparing nuclear-grade zirconium-niobium master alloy wire described above is characterized in that the zirconium-niobium master alloy wire in step three is a straight wire or a coiled wire, and the diameter of the zirconium-niobium master alloy wire is 1.0 mm to 5.0 mm.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. This invention continuously reduces the diameter of the zirconium-niobium master alloy by sequentially performing hot rolling and cold rolling, distributing the deformation amount to each step and reducing the deformation amount in the final cold drawing process, thus making the wire preparation easier. By controlling the Nb element content in the zirconium-niobium master alloy wire, controlling the rolling temperature of the rolling mill, and adopting a process combining cold rolling and multi-pass cold drawing, the synchronous and uniform flow of alloy on the wire surface and in the core is achieved. In addition, the deformation amount in each stage of the process is relatively small, which helps to reduce defects generated during the preparation process, and finally obtains zirconium-niobium master alloy wire without defects such as tail shrinkage, porosity, and delamination.

[0022] 2. By controlling the annealing process to argon or vacuum conditions and by peeling the material at each stage, this invention can reduce the oxidation degree of zirconium-niobium master alloy wire and avoid using traditional acid washing for surface treatment to obtain zirconium-niobium master alloy wire with excellent surface quality.

[0023] 3. This invention reduces internal stress by annealing the zirconium-niobium master alloy during the preparation process, which further reduces the difficulty of forming zirconium-niobium master alloy wire, thereby reducing the probability of defects in the zirconium-niobium master alloy wire and improving the yield.

[0024] 4. The zirconium-niobium master alloy wire prepared by this invention has a smooth surface, qualified low-magnification structure, and controllable diameter, and has a wide range of applications and good practical performance.

[0025] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0026] Figure 1 This is a physical image of the ZrNb45 intermediate alloy wire used in Embodiment 1 of the present invention.

[0027] Figure 2 This is a low-magnification microstructure of the ZrNb45 intermediate alloy wire in Example 1 of the present invention.

[0028] Figure 3 This is a physical image of the ZrNb15 intermediate alloy wire used in Embodiment 2 of the present invention.

[0029] Figure 4 This is a physical image of the ZrNb75 intermediate alloy wire used in Embodiment 3 of the present invention. Detailed Implementation

[0030] Example 1

[0031] The zirconium-niobium master alloy wire of this embodiment is composed of the following components by mass: Nb 45%, Hf 0.008%, O 0.14%, Ta 0.1%, Fe 0.15%, Si 0.01%, with the balance being Zr and unavoidable impurities;

[0032] The preparation method of this embodiment includes the following steps:

[0033] Step 1: Using sponge zirconium and niobium blocks with a purity of over 99.9% as raw materials, zirconium-niobium master alloy ingots are obtained through vacuum consumable arc melting, and then forged into billets.

[0034] Step 2: The bar blank obtained in Step 1 is rolled into a strip at 900℃ using a rolling mill. Then, it is annealed at 750℃ for 1 hour under argon atmosphere. After peeling, it is cold rolled to obtain a wire blank.

[0035] Step 3: Peel and ultrasonically remove defects from the wire blank obtained in Step 2. Perform three cold drawing passes using a roller drawing process, followed by vacuum annealing and polishing. Then perform three more cold drawing passes, and finally perform ultrasonic cleaning, drying, and polishing with a scouring pad to obtain a ZrNb45 master alloy wire with a diameter of 3mm. The vacuum annealing process is as follows: heat to 700℃ and hold for 1 hour, then cool to 150℃ and remove from the furnace. The ZrNb45 master alloy wire is a straight wire.

[0036] The ZrNb45 master alloy wire prepared in this embodiment is as follows: Figure 1 As shown, the appearance quality is good; low-magnification microstructure analysis of this ZrNb45 master alloy wire reveals... Figure 2 As shown, the low-magnification microstructure contains no shrinkage tails, cracks, pores, delamination, or Nb infusible matter, fully meeting the usage requirements.

[0037] Example 2

[0038] The zirconium-niobium master alloy wire of this embodiment is composed of the following components by mass: Nb 15%, Hf 0.01%, O 0.12%, Ta 0.1%, Fe 0.1%, Si 0.006%, with the balance being Zr and unavoidable impurities;

[0039] The preparation method of this embodiment includes the following steps:

[0040] Step 1: Using sponge zirconium and niobium blocks with a purity of over 99.9% as raw materials, zirconium-niobium master alloy ingots are obtained through vacuum consumable arc melting, and then forged into billets.

[0041] Step 2: The bar blank obtained in Step 1 is rolled into a strip at 850℃ using a rolling mill. Then, it is annealed at 700℃ for 2 hours under argon atmosphere. After peeling, it is cold rolled to obtain a wire blank.

[0042] Step 3: Peel and ultrasonically remove defects from the wire blank obtained in Step 2. Perform four cold drawing passes using a roller drawing process, followed by vacuum annealing and polishing. Then, perform three more cold drawing passes. Finally, perform ultrasonic cleaning, drying, and polishing with a scouring pad to obtain a ZrNb15 master alloy wire with a diameter of 1 mm. The vacuum annealing process is as follows: heat to 600℃ and hold for 1 hour, then cool to 150℃ and remove from the furnace. The ZrNb15 master alloy wire is a coiled wire.

[0043] The ZrNb15 master alloy wire prepared in this embodiment is as follows: Figure 3 As shown, the appearance quality is good; after testing, the low magnification structure showed no shrinkage tails, cracks, pores, delamination, or Nb infusible matter, fully meeting the usage requirements.

[0044] Example 3

[0045] The zirconium-niobium master alloy wire of this embodiment is composed of the following components by mass: Nb 75%, Hf 0.007%, O 0.13%, Ta 0.08%, Fe 0.13%, Si 0.008%, with the balance being Zr and unavoidable impurities;

[0046] The preparation method of this embodiment includes the following steps:

[0047] Step 1: Using sponge zirconium and niobium blocks with a purity of over 99.9% as raw materials, zirconium-niobium master alloy ingots are obtained through vacuum consumable arc melting, and then forged into billets.

[0048] Step 2: The bar blank obtained in Step 1 is rolled into a strip at 950℃ using a rolling mill. Then, it is annealed at 800℃ for 0.5h under argon atmosphere. After peeling, it is cold rolled to obtain a wire blank.

[0049] Step 3: The wire blank obtained in Step 2 is peeled, ultrasonically de-damaged, and then cold-drawn in three passes using a roller drawing process. It is then vacuum annealed and polished, followed by two more cold draws. Finally, it undergoes ultrasonic cleaning, drying, and polishing with a scouring pad to obtain a ZrNb75 master alloy wire with a diameter of 5mm. The vacuum annealing process involves heating to 750℃ and holding for 0.5 hours, then cooling to 150℃ before removing it from the furnace. The ZrNb75 master alloy wire is a straight wire.

[0050] The ZrNb75 master alloy wire prepared in this embodiment is as follows: Figure 4 As shown, the appearance quality is good; after testing, the low magnification structure showed no shrinkage tails, cracks, pores, delamination, or Nb infusible matter, fully meeting the usage requirements.

[0051] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing nuclear-grade zirconium-niobium master alloy wire, characterized in that, The zirconium-niobium master alloy wire is composed of the following components by mass fraction. Composition: Nb 15%~75%, balance Zr and unavoidable impurities; the preparation method includes the following steps: Step 1: Using sponge zirconium and niobium blocks as raw materials, zirconium-niobium master alloy ingots are obtained by vacuum consumable arc melting, and then forged into billets; Step 2: The bar billet obtained in Step 1 is rolled into a strip by a rolling mill at 850℃~950℃, annealed under argon atmosphere, peeled off, and then cold rolled to obtain a wire blank; the annealing temperature is 700℃~800℃. Step 3: After peeling the wire blank obtained in Step 2, perform multiple cold drawing passes, and conduct intermediate vacuum annealing and polishing during the multiple cold drawing passes to obtain zirconium-niobium master alloy wire.

2. The method for preparing nuclear-grade zirconium-niobium master alloy wire according to claim 1, characterized in that, The annealing holding time in step two is 0.5h to 2h.

3. The method for preparing nuclear-grade zirconium-niobium master alloy wire according to claim 1, characterized in that, The multi-pass cold drawing in step three adopts a roller die drawing process, and ultrasonic damage removal is performed before the multi-pass cold drawing.

4. The method for preparing nuclear-grade zirconium-niobium master alloy wire according to claim 1, characterized in that, The intermediate vacuum annealing process described in step three is as follows: heat to 600℃~750℃ and hold for 0.5h~1h, then cool down to below 150℃ and remove from the furnace.

5. The method for preparing nuclear-grade zirconium-niobium master alloy wire according to claim 1, characterized in that, After multiple cold drawing processes as described in step three, ultrasonic cleaning, drying, and polishing are performed sequentially.

6. The method for preparing nuclear-grade zirconium-niobium master alloy wire according to claim 1, characterized in that, The zirconium-niobium master alloy wire mentioned in step three is a straight wire or a coiled wire, and the diameter of the zirconium-niobium master alloy wire is 1.0 mm to 5.0 mm.

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