Alloy powder for laser powder filling welding of Zr-4 alloy, its preparation method and application

Abstract

The present invention discloses an alloy powder for laser powder filling welding of Zr-4 alloy, its preparation method and application. The alloy powder includes Zr-4 alloy powder, and Sn, Fe, Cr, Nb, Cu and Si powders are added to the Zr-4 alloy powder. By weight percentage, the alloy powder includes the following components: Sn 0.3-0.35%, Fe 0.1%, Cr 0.1-0.2%, Nb 0.4-0.5%, Cu 0.1%, Si 0.05%, and the balance is Zr-4 alloy powder. By adding Sn, Fe, Cr, Nb, Cu and Si powders to the Zr-4 alloy powder, the present invention compensates for the evaporation and burning loss of alloy elements in the weld seam in a targeted manner, and forms a new zirconium alloy in the local area of the weld seam, thereby improving the corrosion resistance of the zirconium alloy weld seam. Since the alloy powder is added to the weld seam synchronously during the welding process in the present invention, it can more flexibly compensate for the evaporation and burning loss of alloy elements in the weld seam, form a new zirconium alloy in the local area of the weld seam, and regulate the microstructure and properties of the weld seam without changing the composition of the material to be welded, so as to improve the corrosion resistance of the Zr-4 alloy weld seam.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear reactor material welding, and particularly to an alloy powder for laser powder filling welding of Zr-4 alloy, a preparation method thereof, and an application thereof. Background Art

[0002] Zr-4 alloy has characteristics such as low thermal neutron absorption rate, high mechanical properties, and good high-temperature properties, and is currently the most widely used nuclear reactor fuel cladding material. The fuel cladding is the first safety barrier for the operation of a nuclear reactor, and the assembly welding quality of the Zr-4 alloy fuel cladding is crucial for the operation safety of the nuclear reactor. However, a large number of experimental studies have shown that the corrosion resistance of the weld area significantly decreases after welding of zirconium alloys, becoming a weak area during the service process of nuclear fuel elements. It is found that after melting welding of Zr-4 alloy by vacuum electron beam, TIG, etc., alloying elements such as Sn, Fe, Cr, etc. in the melting zone are volatilized and burned excessively, and the alloy composition and microstructure in the welding area change significantly, which is the main reason for the decrease in the corrosion resistance of the weld. Through the butt welding tests of Zr-Nb, Zr-Sn-Nb, and high-Fe, Cr zirconium alloys with Zr-4 alloy, it is verified that the corrosion resistance of the joint is improved in a high-temperature steam environment of 400 °C, 10.3 MPa, and 160 d. This proves that the "alloying element compensation method" has become an effective solution for improving the corrosion resistance of zirconium alloy welding joints represented by Zr-4 alloy.

[0003] However, usually, the selection of materials on both sides of the weld is comprehensively restricted by many factors such as functional requirements, structural design, and manufacturing cost, and it cannot be easily adjusted. Therefore, the method of changing the alloy composition of the material to be welded often cannot be realized in engineering. How to effectively solve the problem of alloying element compensation in the weld without changing the composition of the material to be welded is an urgent problem in the industry. Summary of the Invention

[0004] The purpose of the present invention is to provide an alloy powder for laser powder filling welding of Zr-4 alloy. Adding this alloy powder to the weld synchronously during the welding process can more flexibly and pertinently compensate for the evaporation and burning loss of alloying elements in the weld, and form a new zirconium alloy in the local area of the weld, thereby improving the corrosion resistance of the zirconium alloy weld.

[0005] In addition, the present invention also provides a preparation method and an application of the above alloy powder.

[0006] The present invention is achieved by the following technical solutions:

[0007] An alloy powder for laser powder filling welding of Zr-4 alloy, the alloy powder includes Zr-4 alloy powder, and Sn, Fe, Cr, Nb, Cu, and Si powders are added to the Zr-4 alloy powder.

[0008] Among them, the purity of Sn, Fe, Cr, Nb, Cu, and Si powders is better than 99.9%, and the composition of the Zr-4 alloy powder meets the relevant requirements of GB / T 26314-2010 "Grades and Chemical Compositions of Zirconium and Zirconium Alloys".

[0009] In the present invention, by adding Sn, Fe, Cr, Nb, Cu, and Si powders to the Zr-4 alloy powder, the evaporation and burning loss of alloy elements in the weld are compensated targeted, and a new zirconium alloy is formed in the local area of the weld, thereby improving the corrosion resistance of the zirconium alloy weld.

[0010] Since the present invention adds alloy powder to the weld synchronously during the welding process, it can more flexibly compensate for the evaporation and burning loss of alloy elements in the weld, form a new zirconium alloy in the local area of the weld, and effectively solve the problem of compensating alloy elements in the weld without changing the composition of the material to be welded.

[0011] Furthermore, by weight percentage, the alloy powder includes the following components:

[0012] Sn 0.3-0.35%, Fe 0.1%, Cr 0.1-0.2%, Nb 0.4-0.5%, Cu 0.1%, Si 0.05%, and the balance is Zr-4 alloy powder.

[0013] Furthermore, the particle size of the Zr-4 alloy powder is 60 μm to 120 μm.

[0014] Furthermore, the particle sizes of Sn, Fe, Cr, Nb, and Cu powders are all 30 μm to 50 μm.

[0015] Furthermore, the particle size of the Si powder is 30 μm to 80 μm.

[0016] Powders with a particle size of 30 μm to 80 μm are easy to mix and suitable for the laser powder filling welding process.

[0017] The preparation method of the alloy powder is to mix the various components of the alloy powder and mix them evenly in a circumferential planetary ball mill to prepare a mixed powder.

[0018] Furthermore, it includes the following steps:

[0019] S1. Prepare each component of the alloy powder separately to make each component spherical;

[0020] S2. Mix each component according to the mass ratio;

[0021] S3. Mix the mixed materials evenly in a circumferential planetary ball mill to prepare a mixed powder.

[0022] Further, the Zr-4 alloy powder, as well as the Sn, Fe, Cr, Nb, and Cu powders, are prepared by the liquid metal atomization method; the Si powder is prepared by the mechanical crushing method.

[0023] Further, the circumferentially full planetary ball mill pot includes rotations in three directions: self-rotation, revolution, and flipping. ZrO2 ceramic balls are placed inside the pot to assist in mixing; the self-rotation speed is 60 r / min to 300 r / min, the revolution speed is 30 r / min to 200 r / min, the flipping speed is 12 r / min to 30 r / min, and the mixing time is > 18 h.

[0024] The above parameter settings can achieve uniform mixing of the powders to ensure uniform weld composition in the subsequent welding process.

[0025] Application of alloy powder in improving the corrosion resistance of the weld area of Zr-4 alloy.

[0026] During welding, by adding to the welding molten pool to compensate for the loss of alloying elements, a new zirconium alloy is formed locally in the weld to regulate the weld microstructure and properties, and improve the corrosion resistance of the Zr-4 alloy weld.

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0028] 1. Based on the "alloying element compensation method", alloying elements are added to the weld in the form of powder. Without changing the composition of the material to be welded, the problem of compensating for alloying elements in the weld is effectively solved. At the same time, the powder as a welding material has outstanding advantages such as flexible composition adjustment, low cost, and high efficiency.

[0029] 2. The alloy powder of the present invention improves the corrosion resistance of the Zr-4 alloy weld. Through verification tests, the weld formation is good, there are no pores or cracks inside, and the welded joint has passed the uniform corrosion tests under two corrosion conditions: 360 °C / 18.7 MPa / water and 400 °C / 10.3 MPa / steam. The corrosion resistance of the weld has been significantly improved compared with autogenous welding, realizing high-quality and high-efficiency laser welding of Zr-4 alloy.

[0030] 3. The preparation process of the alloy powder of the present invention has a simple process flow, low cost, strong operability, and good repeatability, and can be popularized in the nuclear engineering field and other applications of zirconium alloy welding, with good application prospects. Description of the Drawings

[0031] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not limit the embodiments of the present invention. In the drawings:

[0032] Figure 1 It is the surface morphology after corrosion of the weld of the flat plate sample welded with the alloy powder of Example 1.Figure 1 The two pictures in it are parallel samples;

[0033] Figure 2 It is the surface morphology after the weld corrosion of the flat sample welded with the alloy powder of Example 2, Figure 2 The two pictures in it are parallel samples;

[0034] Figure 3 It is the surface morphology after the weld corrosion of the flat sample by laser autogenous welding of Zr-4 alloy;

[0035] Figure 4 It is the surface morphology after the weld corrosion of the pipe sample welded with the alloy powder of the present invention. Specific Embodiments

[0036] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with the embodiments and the drawings. The illustrative embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0037] Example 1:

[0038] The alloy powder for laser powder filling welding of Zr-4 alloy, the alloy powder includes Zr-4 alloy powder, and Sn, Fe, Cr, Nb, Cu and Si powders are added to the Zr-4 alloy powder.

[0039] In this embodiment, by weight percentage, the components of the alloy powder are shown in Table 1:

[0040] Table 1 Composition of alloy powder (wt%)

[0041]

[0042] Among them, the purity of Sn, Fe, Cr, Nb, Cu, and Si powders is better than 99.9%, and the composition of the Zr-4 alloy powder meets the relevant requirements of GB / T26314-2010 "Grades and Chemical Compositions of Zirconium and Zirconium Alloys".

[0043] The alloy powder of this embodiment is prepared by the following steps:

[0044] (1) Raw material control: Zr-4 powder: The chemical composition meets the requirements of GB / T 26314-2010, spherical, particle size range: 60μm - 120μm; Sn, Fe, Cr, Nb, Cu powders: The purity is better than 99.9%, spherical, particle size range 30μm - 50μm; Si powder: The purity is better than 99.9%, granular, particle size range 30μm - 80μm.

[0045] (2) Weighing and proportioning ingredients: Weigh and proportion 500 g according to the ingredient ratio in Table 1 above. Put powders such as Zr-4 alloy powder, Sn powder, Fe powder, Cr powder, Nb powder, Cu powder, and Si powder into the material tank, and place ZrO2 ceramic balls of different sizes in the material tank to assist in mixing, ensuring that the total amount of balls and materials in the material tank reaches 1 / 3 - 2 / 3 of the volume of the material tank.

[0046] (3) Ball milling and mixing: Clamp the material tank symmetrically in the ball mill and lock it firmly. Start the ball mill, and set the self-rotation speed to 160 r / min, the revolution speed to 120 r / min, the flipping speed to 20 r / min, and the mixing time to 20 h.

[0047] (4) Powder storage: After the mixing in step (3) is completed, take out the material tank. Open the material tank in a glove box protected by inert gas and transfer the mixed alloy powder to a sealed material tank for sealed storage for later use.

[0048] Laser welding tests of Zr-4 alloy plates are carried out using the alloy powder prepared by the above steps (1) - (4). Coaxial powder feeding with fiber laser is adopted, and the powder filling welding parameters are set as follows: carrier gas 8 L / min, powder feeding rate 6 g / min, powder spot and light spot difference ≤ ±1 mm, laser power 1200 W, welding speed 1000 mm / min, defocusing amount +2 mm.

[0049] Performance verification of the alloy powder in this embodiment:

[0050] I. Carry out laser autogenous welding comparison tests using Zr-4 alloy plates of the same batch and the same specification with the same welding process parameters (i.e., laser power 1200 W, welding speed 1000 mm / min, defocusing amount +2 mm).

[0051] After welding, samples of the two kinds of welded joints are sampled for corrosion tests according to the requirements of EJ / T 1028 - 2014. The test conditions are 360°C ± 6°C / 18.7 MPa ± 1.4 MPa / water, 400°C ± 3°C / 10.3 MPa ± 0.7 MPa / water vapor.

[0052] As Figure 1 、 Figure 3 shown, after the autoclave corrosion test, the weight gain of the welded specimens using the alloy powder in this embodiment is equivalent to that of the Zr-4 base material of the same batch, and no white corrosion products or other foreign matters are found at the weld position. The surface of the specimen shows a uniform black and bright oxide film color. Obvious white corrosion products appear at the weld position of the laser autogenous welding sample after corrosion. The comparison proves that the corrosion resistance of the Zr-4 alloy weld after welding with the alloy powder described in the present invention is significantly improved.

[0053] Here, Figure 1 are the corrosion test results after welding with the powder of the present invention, Figure 3This is the result of the post-welding corrosion test of the non-invention direct welding. Figure 1 , Figure 3 By comparison, whether white corrosion products are generated on the surface of the weld after corrosion is a general criterion for judging the corrosion performance of zirconium alloy.

[0054] Example 2:

[0055] The alloy powder for laser powder filling welding of Zr-4 alloy, the alloy powder includes Zr-4 alloy powder, and Sn, Fe, Cr, Nb, Cu and Si powders are added to the Zr-4 alloy powder.

[0056] In this example, by weight percentage, the components of the alloy powder are shown in Table 2:

[0057] Table 2 Composition of alloy powder (wt%)

[0058]

[0059] Weigh the ingredients according to the composition of Table 2, and prepare the alloy powder according to the steps (1) to (4) of the alloy powder preparation in Example 1. The laser welding test of Zr-4 alloy plates is carried out using the same welding process as in Example 1.

[0060] After welding, the welded samples are sampled for corrosion test according to the requirements of EJ / T 1028-2014. The test conditions are 360°C ± 6°C / 18.7 MPa ± 1.4 MPa / water. The weight gain of the welded samples using the alloy powder in this example after corrosion is equivalent to that of the Zr-4 base material of the same batch, and no white corrosion products or other foreign matters are found at the weld position. The surface of the specimen shows a uniform black and bright oxide film color.

[0061] Here, Figure 2 This is the result of the post-welding corrosion test using the powder in this example, Figure 3 This is the result of the post-welding corrosion test of the non-invention direct welding. Figure 2 , Figure 3 By comparison, whether white corrosion products are generated on the surface of the weld after corrosion is a general criterion for judging the corrosion performance of zirconium alloy.

[0062] Example 3

[0063] The laser powder filling welding test of Zr-4 alloy pipes is carried out using the alloy powder described in Example 1. The powder filling welding parameters are set as follows: carrier gas 6 L / min, powder feeding rate 5 g / min, powder spot and light spot difference ≤ ±1 mm, laser power 800 W, welding rotation speed 20 r / min, defocus amount +2 mm, rotation angle 380°. As Figure 4As shown, after welding, samples were taken for corrosion test according to the requirements of EJ / T 1028-2014, and the test conditions were 360°C ± 6°C / 18.7 MPa ± 1.4 MPa / water. No white corrosion products or other foreign matters were found at the weld position of the welded sample using the alloy powder of the present invention, and the surface of the weld and its adjacent area showed a uniform black bright oxide film color, proving that the Zr-4 alloy weld after welding with the alloy powder of the present invention has excellent corrosion resistance.

[0064] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. Alloy powder for laser powder filling welding of Zr-4 alloy, characterized in that, The alloy powder includes Zr-4 alloy powder, and Sn, Fe, Cr, Nb, Cu and Si powders are added to the Zr-4 alloy powder; By weight percentage, the alloy powder includes the following components: Sn 0.3-0.35%, Fe 0.1%, Cr 0.1-0.2%, Nb 0.4-0.5%, Cu 0.1%, Si 0.05%, and the balance is Zr-4 alloy powder.

2. The alloy powder for laser powder filling welding of Zr-4 alloy according to claim 1, wherein, The particle size of the Zr-4 alloy powder is 60 μm to 120 μm.

3. The alloy powder for laser powder filling welding of Zr-4 alloy according to claim 1, wherein The particle sizes of the Sn, Fe, Cr, Nb and Cu powders are all 30 μm to 50 μm.

4. The alloy powder for laser powder filling welding of Zr-4 alloy according to claim 1, characterized in that, The particle size of the Si powder is 30 μm to 80 μm.

5. The preparation method of the alloy powder according to any one of claims 1 to 4, characterized in that After mixing the respective components of the alloy powder, they are uniformly mixed in a circumferential planetary ball mill to prepare a mixed powder.

6. The preparation method according to claim 5, characterized in that, It includes the following steps: S1. Respectively prepare the respective components of the alloy powder to make each component spherical; S2. Mix the respective components according to the mass ratio; S3. Uniformly mix the mixed material in a circumferential planetary ball mill to prepare a mixed powder.

7. The preparation method according to claim 6, characterized in that, The Zr-4 alloy powder, as well as the Sn, Fe, Cr, Nb and Cu powders are prepared by a liquid metal atomization method; the Si powder is prepared by a mechanical crushing method.

8. The preparation method according to claim 5 or 6, characterized in that, The circumferential planetary ball mill tank includes rotations in three directions of self-rotation, revolution and flipping. ZrO2 ceramic balls are placed in the tank to assist in mixing; the self-rotation speed is 60 r / min to 300 r / min, the revolution speed is 30 r / min to 200 r / min, the flipping speed is 12 r / min to 30 r / min, and the mixing time > 18 h.

9. The application of the alloy powder according to any one of claims 1 to 4 in improving the corrosion resistance of the weld area of the Zr-4 alloy.

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