Preparation method of zirconium alloy welding wire for obtaining high-strength corrosion-resistant welding joint

Abstract

The invention discloses a preparation method of a zirconium alloy welding wire for obtaining a high-strength corrosion-resistant welding joint, which comprises the following steps of: 1, preparing a zirconium alloy cast ingot, forging to obtain a forging stock, and carrying out multi-pass hot rolling to obtain a wire blank; 2, coating the surface of the wire blank with a lubricant; and thirdly, the wire blank coated with the lubricant is subjected to multi-pass hot drawing and then sequentially straightened and polished, and the zirconium alloy welding wire is obtained. Multi-pass hot drawing is adopted, the forming temperature is high, the plastic deformation capacity is improved, the annealing frequency can be reduced, cracks are not likely to be generated in the drawing process, and therefore the production efficiency is greatly improved, in addition, a lubricating agent is used in cooperation in the drawing process, the flow shear stress is reduced, the surface smoothness and precision of the zirconium alloy welding wire are improved, and the production cost is reduced. The prepared welding wire has the advantages of being compact in microstructure, fine in grain, smooth and tidy in surface and high in size precision, and the corrosion resistance and the mechanical property of a zirconium alloy welding joint are remarkably improved through the prepared welding wire.

Description

Technical Field

[0001] The invention belongs to the technical field of zirconium alloy welding wires, and in particular relates to a method for preparing a zirconium alloy welding wire for obtaining a high-strength corrosion-resistant welding joint. Background Art

[0002] At present, zirconium alloy is one of the important materials used in post-processing equipment. It has strong corrosion resistance to most organic acids, inorganic acids, strong alkalis and certain molten salts. Among them, the room temperature yield strength of commercial Zr702 is only 205MPa, and the tensile strength is only 380MPa, which cannot meet the high strength requirements of key equipment for spent fuel post-processing. Especially at the zirconium alloy welded joints, the presence of welding residual stress leads to poor mechanical properties and corrosion resistance of the welded joints. Therefore, it is urgent to develop a new type of high-strength, corrosion-resistant zirconium alloy welding wire so that the welded joints prepared by it have excellent mechanical properties and corrosion resistance, thereby ensuring the reliability of post-processing related equipment.

[0003] The present invention adopts a hot drawing process to prepare a high-strength, corrosion-resistant zirconium alloy welding wire. When the welding wire is prepared by the traditional extrusion method, the grain refinement and dynamic recrystallization are not sufficient, and the internal grains grow abnormally, which leads to uneven grain size; and the extrusion ratio is very large, the zirconium alloy is difficult to flow, and the mold bears a large extrusion force, so it is difficult to ensure the dimensional accuracy of the zirconium alloy welding wire. Compared with the extrusion process, when the zirconium alloy welding wire is prepared by the hot drawing process, while the dimensional accuracy is greatly improved, the cumulative deformation amount increases, the deformation degree increases, the grains are significantly refined, and the organization is strengthened, so that a zirconium alloy welding wire with fine grains and excellent mechanical properties can be obtained. In the zirconium alloy wire drawing process, the deformation resistance increases with the increase of the drawing deformation amount. An effective lubricant and lubrication method should be selected to reduce adhesion and uneven thickness, reduce the damage to the zirconium wire surface caused by poor lubrication, and improve the surface finish and accuracy of the processed zirconium wire. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing zirconium alloy welding wire for obtaining high-strength corrosion-resistant welded joints in view of the deficiencies of the above-mentioned prior art. The method adopts vacuum consumable arc melting to prepare zirconium alloy ingots, reduces impurity elements, and has a significant improvement effect on macroscopic and microscopic segregation. The forging blank is reduced in diameter by forging and multiple hot rolling to make it suitable for hot drawing, and the alloy structure is refined to improve the mechanical properties. The participating stress is removed by heat treatment to promote the formation of recrystallized grains. The wire blank is further reduced in diameter by multiple hot drawing, and the alloy structure is refined to improve the mechanical properties to obtain a zirconium alloy welding wire, so that the welded joint obtained after the zirconium alloy welding wire is welded has the characteristics of high strength and corrosion resistance.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a zirconium alloy welding wire for obtaining a high-strength corrosion-resistant welded joint, characterized in that the method comprises the following steps:

[0006] Step 1: prepare a zirconium alloy ingot by vacuum consumable arc melting, then cut a riser and peel the ingot, then apply an antioxidant for forging to obtain a forging blank, then perform multiple hot rolling on the forging blank, and perform heat treatment to obtain a wire blank;

[0007] Step 2: Apply a drawing lubricant to the surface of the wire blank obtained in step 1;

[0008] Step 3: subjecting the wire blank coated with the drawing lubricant in step 2 to multiple hot drawing passes, and then straightening and polishing in sequence to obtain a zirconium alloy welding wire.

[0009] The invention adopts vacuum consumable arc melting to prepare zirconium alloy ingots, removes impurity elements such as hydrogen, sulfur, nitrogen, etc., reduces the trace impurity elements under the whole melting atmosphere condition, obtains nearly directional solidification columnar crystals from bottom to top, has obvious improvement effect on macroscopic and microscopic segregation, ensures the performance of zirconium alloy welding wire, reduces the diameter of forging blanks through forging and multiple hot rolling, makes them suitable for hot drawing, refines the alloy structure, improves the mechanical properties, removes participating stress through heat treatment, promotes the formation of recrystallized grains, further reduces the diameter of wire blanks through multiple hot drawing, refines the alloy structure, improves the mechanical properties, and obtains zirconium alloy welding wire. The prepared welding wire has the advantages of dense microstructure, fine grains, smooth and neat surface and high dimensional accuracy, and the welded joint obtained after welding the zirconium alloy welding wire has the characteristics of high strength and corrosion resistance.

[0010] The above-mentioned method for preparing a zirconium alloy welding wire for obtaining a high-strength corrosion-resistant welded joint is characterized in that the temperature of the multiple hot rolling in step one is 650°C to 800°C, the deformation of each pass is 4% to 7%, and the total deformation is 60% to 85%; the temperature of the heat treatment is 550°C to 650°C, and the time is 2h to 4h. The present invention reduces the diameter of the forging billet one by one by controlling the parameters of the multiple hot rolling, thereby preventing the zirconium alloy forging billet with poor plasticity from cracking, and at the same time improving its strength, completing the diameter reduction and refining the alloy structure, and improving the mechanical properties. By controlling the parameters of the heat treatment, the participating stress is fully removed, the formation of recrystallized grains is promoted, and a lower temperature and a shorter time are used to prevent the zirconium alloy from oxidizing.

[0011] The above-mentioned method for preparing a zirconium alloy welding wire for obtaining a high-strength corrosion-resistant welded joint is characterized in that the drawing lubricant in step 2 is composed of 85% to 95% by mass of graphite slurry and the balance of isopropyl alcohol. The present invention reduces the flow shear stress of the wire blank during multiple hot drawing passes by controlling the composition of the drawing lubricant, improves the microstructure of the zirconium alloy welding wire, and improves the surface finish and precision of the zirconium alloy welding wire.

[0012] The above-mentioned method for preparing a zirconium alloy welding wire for obtaining a high-strength corrosion-resistant welded joint is characterized in that the multi-pass hot drawing in step 3 adopts a roller die wire drawing method, and the temperature of the multi-pass hot drawing is 500°C to 600°C. The present invention uses roller die wire drawing to make the microstructure of the zirconium alloy welding wire dense, with good comprehensive mechanical properties and corrosion resistance. In addition, by controlling the temperature after drawing, its forming temperature is higher, so that the plastic deformation capacity is increased, the number of annealing times can be reduced, and cracks are not easy to occur during the drawing process, thereby greatly improving production efficiency.

[0013] The above-mentioned method for preparing a zirconium alloy welding wire for obtaining a high-strength corrosion-resistant welded joint is characterized in that the zirconium alloy welding wire in step 3 is a straight wire or a coiled wire with a diameter of 2.0 mm to 3.0 mm. The zirconium alloy welding wire of the present invention is used for welding high-strength corrosion-resistant zirconium alloys.

[0014] The above-mentioned method for preparing a zirconium alloy welding wire for obtaining a high-strength corrosion-resistant welded joint is characterized in that the corrosion rate of the zirconium alloy welded joint obtained by using the zirconium alloy welding wire in step 3 is lower than 0.04 mm / a in a boiling 8 mol / L nitric acid solution containing ruthenium ions, cerium ions, vanadium ions, and chromium ions, and the tensile strength of the zirconium alloy welded joint at room temperature is greater than 707 MPa, and the yield strength is greater than 629 MPa. The zirconium alloy welded joint obtained by welding the zirconium alloy welding wire prepared by the present invention has both excellent corrosion resistance and excellent mechanical strength.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. The present invention adopts vacuum consumable arc melting to prepare zirconium alloy ingots, removes impurity elements such as hydrogen, sulfur, and nitrogen, reduces the trace impurity elements under the whole melting atmosphere conditions, obtains nearly directional solidification columnar crystals from bottom to top, has a significant improvement effect on macro and micro segregation, ensures the performance of zirconium alloy welding wire, reduces the diameter of the forging blank through forging and multiple hot rolling, refines the alloy structure, improves the mechanical properties, removes participating stress through heat treatment, promotes the formation of recrystallized grains, further reduces the diameter of the wire blank through multiple hot drawing, further refines the alloy structure, improves the mechanical properties, and obtains zirconium alloy welding wire, so that the welded joint obtained after welding the zirconium alloy welding wire has the characteristics of high strength and corrosion resistance.

[0017] 2. The present invention adopts roller die drawing to perform multi-pass hot drawing. The forming temperature is relatively high, which increases the plastic deformation capacity, reduces the number of annealing times, and is not prone to cracks during the drawing process, thereby greatly improving production efficiency. The prepared zirconium alloy welding wire has the advantages of dense microstructure and fine grains. In addition, by using lubricants in multi-pass hot drawing, the flow shear stress is reduced, the surface finish and precision of the zirconium alloy welding wire are improved, and the surface is smooth and neat and the dimensional accuracy is high.

[0018] 3. The zirconium alloy welding wire prepared by the present invention has obvious grain refinement and uniform structure. The zirconium alloy welding wire can be specially used for welding high-strength corrosion-resistant zirconium alloys. The corrosion rate of the obtained welded joint in a boiling 8 mol / L nitric acid solution containing ruthenium ions, cerium ions, vanadium ions, and chromium ions is lower than 0.04 mm / a. The tensile strength of the zirconium alloy welded joint at room temperature is greater than 707 MPa, and the yield strength is greater than 629 MPa, which means that it has both excellent corrosion resistance and excellent mechanical strength.

[0019] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a low-magnification microstructure image of the zirconium alloy welding wire prepared in Example 1 of the present invention.

[0021] Figure 2 This is a high-magnification microstructure image of the zirconium alloy welding wire prepared in Example 1 of the present invention.

[0022] Figure 3 This is a comparison chart of the corrosion rates of the welded joint obtained by welding the zirconium alloy welding wire prepared in Example 1 of the present invention and the welded joint obtained by welding the zirconium alloy welding wire prepared in Comparative Example 1.

[0023] Figure 4 This is a comparison chart of the room temperature mechanical properties of a weld joint obtained by welding with the zirconium alloy welding wire prepared in Example 1 of the present invention and a weld joint obtained by welding with the zirconium alloy welding wire prepared in Comparative Example 1.

[0024] Figure 5 This is a comparison chart of the corrosion rates of the welded joint obtained by welding the zirconium alloy welding wire prepared in Example 1 of the present invention and the welded joint obtained by welding the zirconium alloy welding wire prepared in Comparative Example 2.

[0025] Figure 6 This is a comparison chart of the room temperature mechanical properties of a weld joint obtained by welding with the zirconium alloy welding wire prepared in Example 1 of the present invention and a weld joint obtained by welding with the zirconium alloy welding wire prepared in Comparative Example 2. DETAILED DESCRIPTION

[0026] Example 1

[0027] This embodiment includes the following steps:

[0028] Step 1: prepare an ingot by vacuum consumable arc melting, then cut a riser and peel the ingot, then brush an antioxidant and forge it to obtain a forged billet, then hot-roll the forged billet at 650°C with a deformation amount of 4% per pass and a total deformation amount of 60%, and then heat treat it at 550°C for 2h to obtain a wire billet;

[0029] Step 2: Apply a drawing lubricant to the surface of the wire blank obtained in step 1, wherein the lubricant consists of 95% by mass of graphite slurry and 5% by mass of isopropanol;

[0030] Step 3: The wire blank coated with the drawing lubricant in step 2 is subjected to multiple hot drawing at 500° C. using a roller die drawing method, and then straightened and polished in sequence to obtain a zirconium alloy welding wire with a diameter of 2 mm.

[0031] Figure 1 This is a low-magnification microstructure image of the zirconium alloy welding wire prepared in this embodiment. Figure 2 This is a high-magnification microstructure diagram of the zirconium alloy welding wire prepared in this embodiment. Figure 1 and Figure 2 It can be seen that the zirconium alloy welding wire prepared in this embodiment presents an equiaxed structure, with fine and uniform grains and a grain size of about 11 μm.

[0032] Comparative Example 1

[0033] This comparative example comprises the following steps:

[0034] Step 1: preparing an ingot by vacuum consumable arc melting, then cutting a riser and peeling the ingot, and then brushing an antioxidant and forging to obtain a forging blank;

[0035] Step 2: Apply a drawing lubricant to the surface of the forging blank obtained in step 1, wherein the lubricant consists of 95% by mass of graphite slurry and 5% by mass of isopropanol;

[0036] Step 3: subject the forging blank coated with the drawing lubricant in step 2 to multiple hot drawing at 500° C., and then straighten and polish in sequence to obtain a zirconium alloy welding wire with a diameter of 2 mm.

[0037] The welded joint obtained by welding the zirconium alloy welding wire prepared in Example 1 and the welded joint obtained by welding the zirconium alloy welding wire prepared in Comparative Example 1 were placed in a boiling 8 mol / L nitric acid solution containing ruthenium ions, cerium ions, vanadium ions, and chromium ions for uniform corrosion test. The results are as follows: Figure 3As shown, the corrosion rate of the weld joint obtained in Example 1 is lower than the corrosion rate of the weld joint obtained in Comparative Example 1, indicating that the weld joint obtained in Example 1 has more excellent corrosion resistance.

[0038] The welded joint obtained by welding the zirconium alloy welding wire prepared in Example 1 and the welded joint obtained by welding the zirconium alloy welding wire prepared in Comparative Example 1 were subjected to room temperature tensile tests. The results are as follows: Figure 4 As shown, the tensile strength and yield strength of the welded joint obtained in Comparative Example 1 are only 550 MPa and 478 MPa, while the tensile strength and yield strength of the welded joint obtained in Example 1 are 707 MPa and 629 MPa, and the strength is significantly improved.

[0039] By comparing Example 1 and Comparative Example 1, it can be seen that in Comparative Example 1, the forging blank is not further subjected to multiple hot rolling and heat treatment, but is directly subjected to multiple hot drawing, and the weld joint prepared by the obtained zirconium alloy welding wire has low strength and low corrosion resistance.

[0040] Comparative Example 2

[0041] This comparative example comprises the following steps:

[0042] Step 1: prepare an ingot by vacuum consumable arc melting, then cut a riser and peel the ingot, then brush an antioxidant and forge it to obtain a forged billet, then hot-roll the forged billet at 650°C with a deformation amount of 4% per pass and a total deformation amount of 60%, and then heat treat it at 550°C for 2h to obtain a wire billet;

[0043] Step 2: The wire blank obtained in step 1 is subjected to multiple hot drawing at 500° C., and then straightened and polished in sequence to obtain a zirconium alloy welding wire with a diameter of 2 mm.

[0044] The welded joint obtained by welding the zirconium alloy welding wire prepared in Example 1 and the welded joint obtained by welding the zirconium alloy welding wire prepared in Comparative Example 2 were placed in a boiling 8 mol / L nitric acid solution containing ruthenium ions, cerium ions, vanadium ions, and chromium ions for uniform corrosion test. The results are as follows: Figure 3 As shown, the corrosion rate of the weld joint obtained in Example 1 is lower than the corrosion rate of the weld joint obtained in Comparative Example 2, indicating that the weld joint obtained in Example 1 has more excellent corrosion resistance.

[0045] The welded joint obtained by welding the zirconium alloy welding wire prepared in Example 1 and the welded joint obtained by welding the zirconium alloy welding wire prepared in Comparative Example 2 were subjected to room temperature tensile tests. The results are as follows: Figure 4As shown, the tensile strength and yield strength of the welded joint obtained in Comparative Example 2 are only 640 MPa and 518 MPa, while the tensile strength and yield strength of the welded joint obtained in Example 1 are 707 MPa and 629 MPa, and the strength is significantly improved.

[0046] By comparing Example 1 and Comparative Example 2, it can be seen that Comparative Example 2 does not apply a drawing lubricant, but directly performs multiple hot drawing passes, and the resulting zirconium alloy welding wire has a low strength weld joint and low corrosion resistance.

[0047] Example 2

[0048] This embodiment includes the following steps:

[0049] Step 1: prepare an ingot by vacuum consumable arc melting, then cut a riser and peel the ingot, then brush an antioxidant and forge it to obtain a forged billet, then hot-roll the forged billet at 750°C with a deformation of 6% per pass and a total deformation of 75%, and then heat treat it at 600°C for 3 hours to obtain a wire billet;

[0050] Step 2: Apply a drawing lubricant to the surface of the wire blank obtained in step 1, wherein the lubricant consists of 90% by mass of graphite slurry and 10% by mass of isopropanol;

[0051] Step 3: The wire blank coated with the drawing lubricant in step 2 is subjected to multiple hot drawing at 550° C. using a roller die drawing method, and then straightened and polished in sequence to obtain a zirconium alloy welding wire with a diameter of 2.5 mm.

[0052] After testing, it was found that the welded joint prepared by the zirconium alloy welding wire of this embodiment has excellent corrosion resistance, tensile strength and yield strength.

[0053] Example 3

[0054] This embodiment includes the following steps:

[0055] Step 1: prepare an ingot by vacuum consumable arc melting, then cut a riser and peel the ingot, then brush an antioxidant and forge it to obtain a forged billet, then hot-roll the forged billet at 800°C with a deformation amount of 7% per pass and a total deformation amount of 85%, and then heat treat it at 650°C for 4 hours to obtain a wire billet;

[0056] Step 2: Apply a drawing lubricant to the surface of the wire blank obtained in step 1, wherein the lubricant consists of 85% by mass of graphite slurry and 15% by mass of isopropanol;

[0057] Step 3: The wire blank coated with the drawing lubricant in step 2 is subjected to multiple hot drawing at 600° C. using a roller die drawing method, and then straightened and polished in sequence to obtain a zirconium alloy welding wire with a diameter of 2.5 mm.

[0058] After testing, it was found that the welded joint prepared by the zirconium alloy welding wire of this embodiment has excellent corrosion resistance, tensile strength and yield strength.

[0059] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a zirconium alloy welding wire for obtaining a high-strength corrosion-resistant welded joint, characterized in that: The method comprises the following steps: Step 1: prepare a zirconium alloy ingot by vacuum consumable arc melting, then cut a riser and peel the ingot, then apply an antioxidant for forging to obtain a forging blank, then perform multiple hot rolling on the forging blank, and perform heat treatment to obtain a wire blank; Step 2: Apply a drawing lubricant to the surface of the wire blank obtained in step 1; Step 3: subjecting the wire blank coated with the drawing lubricant in step 2 to multiple hot drawing passes, and then straightening and polishing in sequence to obtain a zirconium alloy welding wire.

2. The method for preparing a zirconium alloy welding wire for obtaining a high-strength corrosion-resistant welded joint according to claim 1, characterized in that: The temperature of the multiple hot rolling in step 1 is 650°C to 800°C, the deformation of each pass is 4% to 7%, and the total deformation is 60% to 85%; the temperature of the heat treatment is 550°C to 650°C, and the time is 2h to 4h.

3. The method for preparing a zirconium alloy welding wire for obtaining a high-strength corrosion-resistant welded joint according to claim 1, characterized in that: The drawing lubricant in step 2 is composed of 85% to 95% by mass of graphite slurry and the remainder of isopropanol.

4. The method for preparing a zirconium alloy welding wire for obtaining a high-strength corrosion-resistant welded joint according to claim 1, characterized in that: The multi-pass hot drawing in step 3 adopts roller die wire drawing, and the temperature of the multi-pass hot drawing is 500°C to 600°C.

5. The method for preparing a zirconium alloy welding wire for obtaining a high-strength corrosion-resistant welded joint according to claim 1, characterized in that: The zirconium alloy welding wire described in step 3 is a straight wire or a coiled wire with a diameter of 2.0 mm to 3.0 mm.

6. The method for preparing a zirconium alloy welding wire for obtaining a high-strength corrosion-resistant welded joint according to claim 1, characterized in that: The zirconium alloy welded joint obtained by using the zirconium alloy welding wire described in step three has a corrosion rate lower than 0.04 mm / a in a boiling 8 mol / L nitric acid solution containing ruthenium ions, cerium ions, vanadium ions and chromium ions, and the tensile strength of the zirconium alloy welded joint at room temperature is greater than 707 MPa, and the yield strength is greater than 629 MPa.

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