Low-oxygen Zr-Sn alloy plate as well as preparation method and application thereof

Abstract

The invention discloses a low-oxygen Zr-Sn alloy plate as well as a preparation method and application thereof. According to the method, the low-oxygen Zr-Sn alloy cast ingot is cut into the zirconium alloy plate in a saw cutting mode, an existing plate machining mode of forging, hot rolling and cold rolling is replaced, the process flow is short, and the rate of finished products is high. Board surface oxygenation caused by an existing hot working technology is avoided, and low-oxygen board preparation is facilitated; the smelting as-cast structure is reserved to the maximum extent, and the problem that the plate structure is compact and fine due to various plastic processing forming such as forging, hot rolling and cold rolling in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of zirconium and zirconium alloy processing, and in particular to a low-oxygen Zr-Sn alloy plate and a preparation method and application thereof. Background Art

[0002] Reactor fuel elements are the core components of nuclear reactors, and their performance will directly affect the safety, economy and life of nuclear reactors. Zirconium alloys are usually used as reactor cladding materials and core structural materials because of their small thermal neutron absorption cross section, excellent mechanical properties and corrosion resistance under high temperature and high pressure, and good compatibility with nuclear fuel UO2. Zr-2 alloy is usually used as a matrix material for a new generation of fuel elements in the form of powder. The content of impurities such as oxygen in Zr-2 alloy powder will directly affect the performance of the fuel elements. Zr-2 alloy powder is usually made from Zr-2 alloy plates by the hydrogenation and dehydrogenation process.

[0003] At present, in the field of zirconium and zirconium alloy processing, the production process of zirconium alloy powder prepared by hydrogenation and dehydrogenation method will lead to an increase in the oxygen content of zirconium powder relative to zirconium alloy plate, and the elongation of the fuel element core prepared by zirconium powder with high oxygen content does not meet the technical requirements. In order to produce products that meet the technical requirements of zirconium powder, Zr-2 alloy plates with low oxygen content are usually required. However, there is no mature and stable processing method for Zr-2 alloy plates that meet the requirements of oxygen content ≤ 0.080% (mass fraction) and easy hydrogenation and crushing.

[0004] At present, Zr-2 alloy plates are often produced by smelting, free forging, hot rolling and cold rolling, which can obtain plates with oxygen content ≤ 0.16%, but it is difficult to meet the requirements of high-quality Zr-2 alloy for low oxygen, coarse structure and favorable hydrogenation crushing. Therefore, how to reasonably design the processing technology of Zr-2 alloy plates to obtain low-oxygen Zr-2 alloy plates that meet the requirements of high quality, stable quality, mature technology and low cost is the research focus of the preparation of low-oxygen Zr-Sn alloy plates. Summary of the invention

[0005] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0006] To this end, an embodiment of the present invention provides a low-oxygen Zr—Sn alloy plate material and a preparation method and application thereof.

[0007] In the first aspect, the present invention provides a method for preparing a low-oxygen Zr-Sn alloy plate. Figure 1 , including the following steps:

[0008] (a) selecting zirconium sponge so that its oxygen content is at least 0.015wt% lower than that of the low-oxygen Zr-Sn alloy plate;

[0009] (b) vacuum heating and drying the selected zirconium sponge, and then pressing it with a Zr-Sn alloy additive into an electrode block, and welding the electrode block into a consumable electrode under inert gas protection;

[0010] (c) subjecting the consumable electrode to multiple vacuum melting to obtain a low-oxygen Zr-Sn alloy ingot, and subjecting the ingot to machining;

[0011] (d) sawing the low-oxygen Zr-Sn alloy ingot using a high-precision band saw to obtain low-oxygen Zr-Sn alloy plates of different thicknesses.

[0012] In step (a), the sponge zirconium used is 100% selected according to the Zr-Sn alloy ingot formula to avoid the mixing of oxidized, nitrided sponge zirconium and other foreign matter. The sponge zirconium needs to be evaluated for chemical composition, and its oxygen content must be at least 0.015wt% lower than the target Zr-Sn alloy plate.

[0013] The present invention firstly selects low-oxygen sponge zirconium as raw material through a material selection process and removes impurities, so that the oxygen content of the Zr-Sn alloy plate can meet the requirements of high-quality and low-oxygen products.

[0014] Furthermore, the oxygen content of the low-oxygen Zr-Sn alloy plate is below 0.080wt%, and accordingly, the oxygen content of the raw material zirconium sponge is below 0.065wt%. That is, the oxygen content of the target low-oxygen Zr-Sn alloy plate is below 0.080wt%, and the oxygen content of the raw material zirconium sponge is below 0.065wt%.

[0015] Furthermore, the oxygen content of the low-oxygen Zr-Sn alloy plate is below 0.050wt%, and accordingly, the oxygen content of the raw material zirconium sponge is below 0.035wt%. That is, the oxygen content of the target low-oxygen Zr-Sn alloy plate is below 0.050wt%, and the oxygen content of the raw material zirconium sponge is below 0.035wt%.

[0016] Furthermore, in step (b), the temperature of the vacuum heating and drying is 62-150°C, the insulation time is more than 4 hours, and the air leakage rate is below 0.65 Pa / min and the temperature is below 40°C when the product is taken out of the oven.

[0017] In step (b), the selected zirconium sponge is placed in a vacuum annealing furnace, and vacuum is required before heating. The vacuum time is ≥2h. When the vacuum degree in the furnace is less than 3Pa, heating is performed to 62℃~150℃, and the temperature is kept for more than 4h to fully remove the moisture of the sponge, oxygen, nitrogen and other substances on the surface of the zirconium sponge. When the leakage rate of the vacuum annealing furnace tends to be stable and the leakage rate does not exceed 0.65Pa / min, it can be taken out of the furnace, and the temperature of the furnace is not higher than 40℃.

[0018] After vacuum drying is completed, the dried sponge zirconium, required Zr-Sn alloy additives and other raw materials are pressed into electrode blocks, and the electrode blocks are welded into consumable electrodes in a vacuum plasma welding box under inert gas protective atmosphere conditions, and foreign matter such as oxides and weld nodules on the weld surface after welding are cleaned.

[0019] Furthermore, the electrode welding is carried out under vacuum conditions in a vacuum welding box. Before the electrode welding, the vacuum is evacuated to a vacuum degree of ≤0.8Pa, and a vacuum leak test is performed, and the leakage rate is not greater than 0.5Pa / min.

[0020] It is understandable that the type and amount of Zr-Sn alloy additives are determined according to specific circumstances.

[0021] Furthermore, during welding, the flow rate of the inert gas is above 2200 L / h, and the inert gas is argon or helium.

[0022] Electrode welding is carried out under high-flow inert gas protection conditions. The inert gas is argon or helium, and the welding gun gas flow rate is ≥2200L / h to better prevent weld oxidation and reduce the increase in oxygen content.

[0023] Furthermore, during the vacuum melting, vacuum is drawn and the leakage rate is measured. Melting is started after the vacuum degree is below 1Pa and the leakage rate is below 0.5Pa / min. The current of the vacuum melting is 10-30A, and the melting speed is 6-25kg / min. After one melting is completed, the ingot is cooled under argon protection conditions with a pressure value of more than 6000Pa.

[0024] When the welded consumable electrode is vacuum melted in a vacuum consumable arc furnace, first evacuate the vacuum to a vacuum degree of ≤1Pa, then detect the leak, and start melting when the leak rate is no more than 0.5Pa / min to prevent the Zr-Sn alloy ingot from increasing oxygen. The crucible diameter for vacuum consumable melting is Φ360mm~Φ850mm, and the melting adopts a large current of 10kA~30kA, a low melting rate, and a melting rate of 6kg / min~25kg / min. The ingot is cooled under argon protection, and the argon filling pressure is ≥6000Pa. The melting adopts a large current and a low melting rate to increase the activity of the melting pool, fully volatilize the impurities, and minimize the increase of oxygen content during the ingot melting process.

[0025] The number of smelting is 2 to 5 times. Except for the final smelting, after each ingot smelting, the ingot crown and flash are removed by machining, the outer surface is machined to metallic luster, and foreign matter such as surface oxides is removed. After the final smelting is completed, the ingot is machined, and the lathe is used to remove the surface oxides, pores, cold shuts, looseness and other defects of the ingot. The surface of the ingot is a machined surface, and the defects of the riser and bottom pad are removed.

[0026] Furthermore, the cutting speed of the band saw during sawing is 0.5-3 mm / min, and the thickness of the low-oxygen Zr-Sn alloy plate is 3-50 mm.

[0027] The machined ingots are sawn with a high-precision band saw to obtain low-oxygen Zr-Sn alloy plates with thicknesses ranging from δ3mm to δ50mm. During sawing, the blanks are calibrated with a vertical measuring ruler (ruler) before each clamping to ensure the dimensional accuracy of the plate sawing. The band sawing speed is 0.5mm / min to 3mm / min when sawing the plate. The lower speed can ensure that the plate surface is not oxidized and the oxygen content does not increase.

[0028] The present invention adopts a sawing method to cut a low-oxygen Zr-Sn alloy ingot into zirconium alloy plates, replacing the original forging, hot rolling and cold rolling plate processing methods, thereby greatly shortening the process flow and improving the yield rate.

[0029] The sawing process adopted by the present invention can produce plates with various thickness specifications of δ3mm-δ50mm and various shapes, with flexible process, rich products and wide applications.

[0030] Furthermore, the low-oxygen Zr—Sn alloy sheet material is a Zr-2 or Zr-4 sheet material.

[0031] Furthermore, the oxygen content in the Zr-2 alloy and the Zr-4 alloy is ≤0.080wt%.

[0032] Furthermore, the oxygen content in the Zr-2 alloy and the Zr-4 alloy is ≤0.050wt%.

[0033] The oxygen content of the Zr-Sn alloy plate prepared by the present invention is less than 0.080 wt%, and further, the oxygen content can reach an excellent level of less than 0.050 wt%.

[0034] In a second aspect, the present invention proposes a low-oxygen Zr—Sn alloy plate prepared by the method proposed in the first aspect.

[0035] In a third aspect, the present invention proposes the use of the low-oxygen Zr-Sn alloy plate material prepared by the method of the first aspect or the low-oxygen Zr-Sn alloy plate material proposed in the second aspect in nuclear reactor components.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] The present invention can control the increase of oxygen content in the Zr-Sn alloy plate within 0.010wt% during the preparation process through heating and drying, vacuum protective atmosphere welding, high current low melting rate smelting and other processes, reaching the advanced level of oxygen content increase control in vacuum smelting preparation methods.

[0038] The present invention avoids the increase of oxygen on the surface of the plate caused by the existing hot working process, retains the smelting cast structure to the greatest extent, and avoids the problem of dense plate structure caused by plastic working.

[0039] The Zr-Sn alloy plate prepared by the invention has low oxygen content, is easy to hydrogenate, dehydrogenate and crush, and is suitable for preparing high-quality Zr-Sn alloy powder and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0041] Figure 1 The present invention is a flow chart of the preparation method of the low-oxygen Zr-Sn alloy plate. DETAILED DESCRIPTION

[0042] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0043] Example 1

[0044] This embodiment is a method for preparing a Zr-2 alloy plate. The process flow of the preparation method is: material selection → heating and drying → vacuum welding → vacuum melting → ingot casting machine processing → sawing → finished plate, as shown in detail below.

[0045] S1: Material selection: According to the Zr-2 alloy ingot formula and the zirconium sponge chemical composition test report, select zirconium sponge with an oxygen content of ≤0.060wt%, and select 100% of the zirconium sponge used to avoid the mixing of oxidized, nitrided zirconium sponge and other foreign matter.

[0046] S2: Heating and drying: Place the selected zirconium sponge in a vacuum annealing furnace, heat to 80°C, evacuate for 4 hours before heating, heat when the vacuum in the furnace is 2Pa, and heat and dry the zirconium sponge for 4.5 hours. When the leakage rate of the vacuum annealing furnace tends to be stable and the leakage rate is 0.60Pa / min, it can be taken out of the furnace at a temperature of 38°C to fully remove the moisture in the sponge and oxygen and nitrogen on the surface of the zirconium sponge.

[0047] S3: Vacuum welding: The dried zirconium sponge, the required Zr-2 alloy additives and other raw materials are pressed into electrode blocks. Before electrode welding, the vacuum is evacuated to a vacuum degree of 0.75Pa, and the leakage is tested. The leakage rate is 0.45Pa / min. During welding, the argon gas flow rate of the welding gun is 2300L / h to prevent the weld from oxidation. After welding, the oxides, weld nodules and other foreign objects on the weld surface are cleaned to reduce the increase in oxygen content.

[0048] S4: Vacuum melting: Before vacuum melting, first evacuate the vacuum, then perform leak detection. When the vacuum degree is 0.95Pa and the leakage rate is 0.45Pa / min, start melting to prevent the Zr-Sn alloy ingot from increasing oxygen. The welded consumable electrode is melted once in a Φ560mm crucible in a vacuum consumable arc furnace, and then melted twice in a Φ630mm crucible, for a total of 2 melts. The melting current is 16.5-25kA and the melting speed is 10-15kg / min. After the first melting, the ingot is cooled and filled with argon at a pressure of 6000Pa. After the second melting, the ingot is cooled and filled with argon at a pressure of 10000Pa to obtain a low-oxygen Zr-2 alloy ingot. It can be understood that the melting current and melting speed are fluctuating values ​​throughout the melting process, and the range value is used here to indicate its size.

[0049] S5: Ingot machining: Use lathe to remove the surface defects of ingot such as oxide, pores, cold shut, looseness, etc. The surface of ingot is machined, and the defects of riser and bottom pad are removed.

[0050] S6: The machined ingot is sawn by a band saw at a speed of 0.85 mm / min to obtain a low-oxygen Zr-2 alloy plate with a thickness of δ18 mm. The blank needs to be calibrated with a vertical measuring ruler (ruler) before each clamping to ensure the dimensional accuracy of the plate sawing.

[0051] The surface of the low-oxygen Zr-2 alloy plate prepared by the method has a machine-added metallic luster, and the surface is smooth, bright, and non-oxidized. Three plates are randomly selected from each batch of finished plates for oxygen content detection. The third-party testing agency detects that the oxygen content of the chemical composition of all sampling points of the plate is between 0.069wt% and 0.075wt%, respectively, 0.069wt%, 0.075wt%, 0.071wt%, 0.071wt%, 0.070wt%, 0.069wt%, 0.074wt%, 0.073wt%, 0.074wt%, 0.075wt%, and the average value is 0.072wt%, which meets the technical requirements of high-quality low-oxygen products. The results show that the method of the present invention is feasible, and the Zr-2 alloy plate prepared by the present invention is easy to hydrogenate, dehydrogenate, and crush, and can eventually be used to prepare high-quality Zr-2 alloy powder and other purposes.

[0052] Example 2

[0053] This embodiment is a method for preparing a Zr-4 alloy plate. The process flow of the preparation method is: material selection → heating and drying → vacuum welding → vacuum melting → ingot casting machine processing → sawing → finished plate, as shown in detail below.

[0054] S1: Material selection: According to the Zr-4 alloy ingot formula and the zirconium sponge chemical composition test report, select zirconium sponge with an oxygen content of ≤0.034wt%, and select 100% of the zirconium sponge used to avoid the mixing of oxidized, nitrided zirconium sponge and other foreign matter.

[0055] S2: Heating and drying: Heat and dry the selected zirconium sponge to 75°C, evacuate for 5 hours before heating, and heat when the vacuum in the furnace is 1.9Pa. The zirconium sponge is heated and dried for 5 hours. When the leakage rate is 0.55Pa / min, it can be taken out of the furnace. The furnace temperature is 35°C to fully remove the moisture in the sponge and oxygen, nitrogen and other substances on the surface of the zirconium sponge.

[0056] S3: Vacuum welding: The dried zirconium sponge and the required Zr-4 alloy additives are pressed into electrode blocks. Before welding, the electrodes are vacuumed and leak tested. The vacuum degree is 0.6Pa and the leakage rate is 0.40Pa / min. During welding, the argon gas flow rate of the welding gun is 2500L / h to prevent the weld from oxidation. After welding, the oxides, weld bumps and other foreign objects on the weld surface are cleaned to reduce the increase in oxygen content.

[0057] S4: Vacuum melting: Before melting, vacuum is drawn first, and then leak detection is performed. When the vacuum degree is 0.8Pa and the leakage rate is 0.3Pa / min, melting is started again to prevent the Zr-Sn alloy ingot from increasing oxygen. The welded consumable electrode is melted once in a Φ600mm crucible of a vacuum consumable arc furnace, melted twice in a Φ720mm crucible, and melted three times in a Φ820mm crucible, for a total of 3 times. The melting current is 19.5-29kA and the melting speed is 10-20kg / min. After the first melting, the ingot is cooled and filled with argon at a pressure of 6000Pa, and after the second melting, the ingot is cooled and filled with argon at a pressure of 10000Pa. After the third melting, the ingot is cooled and filled with argon at a pressure of 11000Pa to obtain a low-oxygen Zr-4 alloy ingot. It can be understood that the melting current and melting speed are fluctuating values ​​throughout the melting process, and the range value is used here to indicate its size.

[0058] S5: Ingot machining: Use lathe to remove the surface defects of ingot such as oxide, pores, cold shut, looseness, etc. The surface of ingot is machined, and the defects of riser and bottom pad are removed.

[0059] S6: Sawing: The machined ingot is sawn by a band saw at a cutting speed of 1.0 mm / min to obtain a low-oxygen Zr-4 alloy plate with a thickness of δ25 mm.

[0060] The surface of the low-oxygen Zr-4 alloy plate prepared by this method has a machine-added metallic luster, and the surface is smooth, bright and free of oxidation. Three plates are randomly selected from each batch of finished plates for oxygen content detection. The third-party testing agency detects that the oxygen content of the chemical composition of all sampling points of the plate is between 0.045wt% and 0.050wt%, which are 0.045wt%, 0.047wt%, 0.049wt%, 0.05wt%, 0.049wt%, 0.047wt%, 0.05wt%, 0.049wt%, 0.046wt%, and 0.05wt%, respectively, with an average value of 0.048wt%, which meets the technical requirements of high-quality low-oxygen products. The results show that the method of the present invention is feasible, and the Zr-4 alloy plate prepared by the present invention is easy to hydrogenate, dehydrogenate, and crush, and can eventually be used to prepare high-quality Zr-4 alloy powder and other purposes.

[0061] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms may be for different embodiments or examples. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0062] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0063] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for preparing a low-oxygen Zr-Sn alloy sheet. It is characterized in that The following steps are involved: (a) selecting zirconium sponge so that its oxygen content is at least 0.015wt% lower than that of the low-oxygen Zr-Sn alloy plate; (b) vacuum heating and drying the selected zirconium sponge, and then pressing it with a Zr-Sn alloy additive into an electrode block, and welding the electrode block into a consumable electrode under inert gas protection; (c) subjecting the consumable electrode to multiple vacuum melting to obtain a low-oxygen Zr-Sn alloy ingot, and subjecting the ingot to machining; (d) sawing the low-oxygen Zr-Sn alloy ingot using a high-precision band saw to obtain low-oxygen Zr-Sn alloy plates of different thicknesses.

2. The method according to claim 1, It is characterized in that The oxygen content of the low-oxygen Zr-Sn alloy plate is below 0.080wt%, and correspondingly, the oxygen content of the raw material sponge zirconium is below 0.065wt%.

3. The method according to claim 2, It is characterized in that The oxygen content of the low-oxygen Zr-Sn alloy plate is below 0.050wt%, and correspondingly, the oxygen content of the raw material sponge zirconium is below 0.035wt%.

4. The method according to claim 1, It is characterized in that In step (b), the temperature of the vacuum heating and drying is 62-150°C. Before heating, the vacuum is evacuated to a vacuum degree below 3Pa in the furnace and then heating is started. The insulation time is more than 4h. When the furnace is taken out, the leakage rate is below 0.65Pa / min and the leakage rate value is stable, and the temperature is below 40°C.

5. The method according to claim 1, It is characterized in that In step (b), before welding into a consumable electrode, the welding box is evacuated to a vacuum degree below 0.8 Pa and a gas leakage rate below 0.5 Pa / min. During welding, the flow rate of the inert gas is above 2200 L / h, and the inert gas is argon or helium.

6. The method according to claim 1, It is characterized in that In step (c), during the vacuum melting, the vacuum is evacuated to a vacuum degree below 1 Pa, and the gas leakage rate is below 0.5 Pa / min before melting begins. The crucible diameter for vacuum consumable melting is Φ360 mm to Φ850 mm, the current for vacuum melting is 10 to 30 A, and the melting speed is 6 to 25 kg / min. After the first melting is completed, the ingot is cooled under argon protection conditions with a pressure value of more than 6000 Pa.

7. The method according to claim 1, It is characterized in that In step (c), during multiple vacuum smelting processes, except for the final smelting, after each ingot smelting, the ingot crown and burrs are removed by machining, and the outer surface is machined until it has a metallic luster to remove surface oxide foreign matter.

8. The method according to claim 1, It is characterized in that In step (d), when the low-oxygen Zr-Sn alloy ingot is sawed, the blank is calibrated with a vertical detection ruler or a straight ruler before each clamping, the band saw feed speed during the sawing is 0.5-3 mm / min, the thickness of the low-oxygen Zr-Sn alloy plate is 3-50 mm, and the low-oxygen Zr-Sn alloy plate is a Zr-2 or Zr-4 plate.

9. A low-oxygen Zr-Sn alloy sheet, It is characterized in that The method is prepared by any one of claims 1 to 8.

10. Use of the low-oxygen Zr-Sn alloy plate prepared by the method according to any one of claims 1 to 8 or the low-oxygen Zr-Sn alloy plate according to claim 9 in nuclear reactor components.

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