Preparation method of medium-strength and high-plasticity Zr-4M zirconium alloy for nuclear use

Abstract

The present invention discloses a preparation method of medium-strength and high-plasticity Zr-4M zirconium alloy for nuclear use, which comprises the following steps: First, mix and press sponge zirconium with an alloy package to obtain an electrode block, and then perform vacuum consumable arc melting to obtain an alloy ingot; Second, turn the surface of the alloy ingot smooth, and then perform multi-pass forging and remove the surface oxide scale to obtain an alloy forging; Third, perform multi-pass hot rolling on the alloy forging, then perform heat treatment, and then cool and remove the surface oxide scale to obtain an alloy billet; Fourth, perform multi-pass cold rolling on the alloy billet, and perform vacuum heat treatment after each pass. After cooling, a medium-strength and high-plasticity Zr-4M zirconium alloy is obtained. The present invention successively adopts vacuum consumable arc melting, multi-pass forging, multi-pass hot rolling, heat treatment, multi-pass cold rolling, inter-pass heat treatment and finished product heat treatment to prepare the Zr-4M zirconium alloy, realizing the synchronous improvement of strength and plasticity, and solving the problem that the strength and elongation of the existing zirconium alloy cannot be improved synchronously.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of rare metal materials for nuclear use, and particularly relates to a preparation method of a medium-strength and high-plasticity Zr-4M zirconium alloy for nuclear use. Background Art

[0002] The cladding material of nuclear reactor components is the heart of in-core components, playing key roles such as encapsulating nuclear fuel, maintaining the structural stability of the reactor, heat transfer, and isolating fuel from the coolant. Currently, for the only nuclear reactors that have achieved large-scale commercial applications, their cladding materials are all zirconium alloys, and among them, Zr-4 alloy is the most widely used.

[0003] Zr-4M alloy is a new type of zirconium alloy improved on the basis of Zr-4 alloy, which has higher strength and plasticity compared to Zr-4 alloy. The standard composition of Zr-4 alloy is: Zr-98.2%, Sn-1.5%, Fe-0.2%, Cr-0.1%. The main alloying element of this alloy is the Sn element, which is a typical low-melting-point metal with a melting point of only 232°C, while the melting point of the zirconium matrix is 1852°C. During the melting process of Zr-4 alloy, due to the large difference in melting points between the two, element segregation is extremely likely to occur, resulting in uneven composition distribution of the zirconium alloy finished product, and greatly reducing the corrosion resistance and mechanical properties of the zirconium alloy, posing a hidden danger to the safe service of nuclear reactors. Therefore, how to prepare a Zr-4M alloy ingot with uniform composition is the key problem that must be solved first in alloy preparation.

[0004] In addition, the plastic deformation process of Zr-4M alloy directly affects the mechanical properties of the finished product. Since the composition of this alloy has been improved, its plastic processing process must be specifically designed to ensure the manifestation of its excellent strength and plasticity. Currently, there is no public report on the plastic processing process of Zr-4M alloy. If prepared according to the traditional preparation method of zirconium alloy, on the one hand, it may lead to failure in material preparation, such as cracking, bending, fracture, etc., and on the other hand, it is difficult to ensure that the prepared Zr-4M alloy meets its designed mechanical properties.

[0005] People urgently hope to obtain a preparation method of a medium-strength and high-plasticity Zr-4M alloy for nuclear use. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a preparation method of a medium-strength and high-plasticity Zr-4M zirconium alloy for nuclear use in view of the deficiencies of the above-mentioned prior art. This method successively adopts vacuum consumable arc melting, multi-pass forging, multi-pass hot rolling, heat treatment, multi-pass cold rolling, inter-pass heat treatment, and finished product heat treatment to prepare the Zr-4M zirconium alloy, realizing the synchronous improvement of strength and plasticity, and solving the problem that the strength and elongation of existing zirconium alloys cannot be improved synchronously.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A preparation method of medium-strength and high-plasticity Zr-4M zirconium alloy for nuclear use, characterized in that the method comprises the following steps:

[0008] Step 1: Mix sponge zirconium with an alloy cladding, then press to obtain an electrode block, and then subject the electrode block to vacuum consumable arc melting to obtain an alloy ingot;

[0009] Step 2: Turn the surface of the alloy ingot obtained in Step 1, and then perform multi-pass forging and remove the surface oxide scale to obtain an alloy forging;

[0010] Step 3: Subject the alloy forging obtained in Step 2 to multi-pass hot rolling, then perform heat treatment, then cool and remove the surface oxide scale to obtain an alloy billet;

[0011] Step 4: Subject the alloy billet obtained in Step 3 to multi-pass cold rolling, and perform vacuum heat treatment after each pass. After cooling, a medium-strength and high-plasticity Zr-4M zirconium alloy is obtained.

[0012] The present invention successively adopts vacuum consumable arc melting, multi-pass forging, multi-pass hot rolling, heat treatment, multi-pass cold rolling, inter-pass vacuum annealing and finished product annealing to prepare a finished zirconium alloy product. Secondly, by using the alloy cladding method, the burning loss of raw materials is reduced, ensuring the uniform controllability of alloy components, and obtaining a Zr-4M zirconium alloy ingot with uniform composition distribution. To make the alloying elements completely dissolve into the matrix, the peeled ingot is subjected to multi-pass forging to ensure the workability and composition uniformity during the subsequent deformation process of the material, and a fine-grained structure with uniform element distribution and dispersed second-phase particles is obtained. In order to further refine the lamellar structure obtained by forging and reduce the formation of deformation texture, the forged alloy is subjected to multi-pass hot rolling treatment to ensure the full fragmentation of the lamellar structure and obtain a hot-rolled alloy. Finally, the peeled hot-rolled alloy is subjected to multi-pass cold rolling and vacuum annealing to further refine the grains and synchronously improve the strength and plasticity, obtaining a medium-strength and high-plasticity Zr-4M zirconium alloy. The tensile strength of the prepared medium-strength and high-plasticity Zr-4M zirconium alloy is greater than 551 MPa, the yield strength is greater than 493 MPa, and the elongation after fracture is less than 29.5%. The medium-strength and high-plasticity Zr-4M zirconium alloy prepared by the present invention has excellent mechanical properties.

[0013] The preparation method of the above medium-strength and high-plasticity Zr-4M zirconium alloy for nuclear use is characterized in that the method for making the alloy package in step one is: using iron foil to wrap tin grains, chromium grains, iron grains and zirconium dioxide powder into an alloy package, the mass purity of the iron foil, tin grains, chromium grains and iron grains is not less than 99.99%, the purity of the zirconium dioxide powder is not less than analytical pure, the sponge zirconium is of atomic energy level, with the brand number HZr-01, the thickness of the iron foil is not more than 0.1 mm, and the electrode block contains not less than 3 alloy packages. The present invention uses high-purity iron foil to wrap high-purity tin, zirconium dioxide powder, high-purity chromium grains and high-purity iron grains, and the components in the alloy package are added according to the proportion of the designed components of the Zr-4M alloy. Since the melting point of iron is relatively high and the melting points of zirconium and tin differ by more than 1600 °C, serious burning loss of tin is likely to occur during the alloy melting process. In order to avoid the segregation and burning loss of tin, the alloy element iron is cleverly utilized, and high-purity tin is wrapped with high-purity iron foil, which can avoid the premature melting and overflow of tin during the heating process of zirconium alloy melting, avoid the segregation of the ingot composition or the loss of tin content, obtain a Zr-4M zirconium alloy ingot with uniform composition distribution, and also avoid the cumbersome process of first preparing intermediate alloy and then melting in the traditional method, greatly reducing the production cycle and cost.

[0014] The preparation method of the above-mentioned medium-strength and high-plasticity Zr-4M zirconium alloy for nuclear use is characterized in that the number of multi-pass forging in step two is more than 2 times, and the forging is pressed downward in 9 directions, and the 9 directions are respectively: up-down, left-right, front-back, upper front-lower back, upper back-lower front, upper left-lower right, upper right-lower left, left front-right back, left back-right front. The amount of each downward press shall not be less than 40%; in the multi-pass forging, the temperature of the first forging is 200°C to 400°C above the β phase transformation point temperature of the alloy ingot, and the cooling method is water quenching. The temperature of the second forging is 10°C to 200°C below the β phase transformation point temperature of the alloy ingot, and the cooling method is air cooling. The forging parameters of the third and subsequent forgings are the same as those of the second forging.In the forging of the present invention, the alloy ingot is pressed downward in 9 directions. The alloy ingot has six directions: up, down, left, right, front, and back. Up-down, left-right, and front-back respectively represent pressing downward from the up-down direction of the alloy ingot, pressing downward from the left-right direction of the alloy ingot, and pressing downward from the front-back direction of the alloy ingot. In the up-front - down-back direction, up-front refers to the intersection of the upper and front sides, and down-back refers to the intersection of the lower and back sides, that is, pressing downward from the diagonal direction of up-front - down-back. The same applies to up-back - down-front, up-left - down-right, up-right - down-left, left-front - right-back, and left-back - right-front. The alloy ingot is pressed downward in all 9 directions. The purpose of pressing downward in 9 directions is, on the one hand, to avoid the generation of processing flow lines. Processing flow lines are deformation bands formed by the fragmentation of the microstructure along the direction of the maximum shear force during the hot plastic deformation of zirconium alloy. β-Zr and second-phase particles distributed in bands will be formed inside them. These microstructures will be inherited into the zirconium alloy in subsequent hot rolling, cold rolling, and heat treatment states, resulting in a decrease in the microstructural uniformity of the material. By performing downward deformation in 9 directions, the processing flow lines can be completely eliminated. On the other hand, in this unidirectional compression process of forging, the zirconium alloy bears the maximum shear force at about 45° in the compression direction and deforms most severely, while the relative deformation amount in other regions is smaller, that is, the "dead deformation zone". The grains in this area are not sufficiently fragmented, so the microstructural uniformity inside the zirconium alloy after forging is poor. By performing downward deformation in 9 directions, the "dead deformation zone" can be completely eliminated. When the downward pressure per time is less than 40%, the degree of grain fragmentation is insufficient, and it is difficult to ensure the strength and plasticity of the prepared Zr-4M alloy. In order to completely dissolve the alloying elements into the matrix, the peeled ingot is forged in one heat at a temperature 200°C to 400°C above the β phase transformation point and water quenched to ensure that all alloying elements of the Zr-4M alloy are completely dissolved into the zirconium matrix. Through forging deformation in the β phase region, grain fragmentation and uniform distribution of alloying elements are achieved. Then, with the subsequent water quenching, the uniformly distributed alloying elements will not precipitate, thereby ensuring the workability and compositional uniformity of the material in subsequent deformation. To ensure the workability and compositional uniformity of the material in subsequent deformation, in order to fully fragment and refine the lamellar α-Zr and residual β phase obtained by one heat forging, multi-pass forging is then carried out at a temperature 10°C to 200°C below the β phase transformation point to fully fragment the lamellar α-Zr formed by cooling in the β phase region and the residual β phase solid-solved with alloying elements, further refine the grains, and ensure the uniform distribution of alloying elements, avoid the precipitation and growth of large-sized second phases, and avoid the inheritance of the residual β phase into a banded second phase, obtaining a fine-grained structure with uniform element distribution and dispersed second-phase particles.

[0015] The above-mentioned method for preparing a medium-strength, high-plasticity Zr-4M zirconium alloy for nuclear use is characterized in that the temperature of the multiple hot rolling passes in step 3 is 100°C to 400°C below the β phase transformation point, the cumulative deformation is 50% to 90%, and the temperature of the heat treatment is 400°C to 700°C. The present invention ensures sufficient fragmentation of the lamellar structure by controlling the parameters of the multiple hot rolling passes, avoids the formation of strong anisotropy of α-Zr, and facilitates subsequent cold working. By rationally designing the hot rolling temperature, cross-phase deformation caused by the temperature rise of hot rolling deformation is avoided, preventing the destruction of the ideal microstructure of the previous process. By rationally designing the deformation amount, a dynamic balance is achieved between grain fragmentation and grain recovery and recrystallization during the hot rolling process, avoiding coarse grains.

[0016] The above-mentioned method for preparing a medium-strength and high-plasticity Zr-4M zirconium alloy for nuclear use is characterized in that the cumulative deformation of the multiple cold rolling passes in step 4 is 20% to 80%, and the vacuum degree of the vacuum heat treatment is not higher than 4×10 -3 Pa, and the temperature is 400°C to 700°C. The present invention ensures maximum grain refinement by controlling the parameters of multiple cold rolling passes, achieving a synergistic improvement in strength and plasticity. Through the design of the preceding process, the Zr-4M alloy can achieve a high degree of cold working deformation without cracking, thereby achieving maximum grain refinement.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. The present invention adopts an alloy package addition method to ensure the uniformity and controllability of the alloy composition. It cleverly utilizes iron as an alloy element and uses high-purity iron foil to wrap high-purity tin. Due to the high melting point of iron, it can prevent the premature melting and overflow of tin during the heating process of zirconium alloy smelting, thereby avoiding the segregation of ingot composition or loss of tin content. This method also avoids the cumbersome process of preparing the intermediate alloy and then smelting it in the traditional method, greatly reducing the production cycle and cost.

[0019] 2. The design of the forging process of the present invention ensures the uniform distribution of alloying elements and the uniform dispersion distribution of nano-second phase particles. Through multiple forging processes, in which the first fire forging temperature is the β phase region, it can ensure that all alloying elements of the Zr-4M alloy are completely dissolved in the zirconium matrix. Through forging deformation in the β phase region, grain crushing and uniform distribution of alloying elements are achieved. With the help of subsequent water quenching, the uniformly distributed alloying elements will not precipitate, thereby ensuring the machinability and composition uniformity of the material in subsequent deformation. The deformation of the second and subsequent fires is below the β phase transformation temperature. The main purpose is to fully crush the lamellar α-Zr formed by cooling the β phase region and the residual β phase with dissolved alloying elements, further refine the grains, and ensure the uniform distribution of alloying elements, avoid the precipitation and growth of large-sized second phases, and avoid the residual β phase from becoming a banded distributed second phase.

[0020] 3. The design of the hot rolling process of the present invention ensures the full fragmentation of the lamellar structure, avoids the formation of strong anisotropy of α-Zr, is beneficial to the subsequent cold working process. By reasonably designing the hot rolling temperature, it is avoided that during the hot rolling deformation and temperature rise process of the Zr-4M alloy, cross-phase region deformation is caused due to the deformation and temperature rise, thereby causing the destruction of the ideal microstructure retained by the previous process. In addition, by reasonably designing the deformation amount, a dynamic balance is achieved between grain fragmentation and grain recovery and recrystallization during the hot rolling process, avoiding coarse grains.

[0021] 4. The design of the cold deformation process of the present invention ensures the maximum degree of fine grain strengthening and realizes the coordinated improvement of strength and plasticity. Through the design of the previous process, the Zr-4M alloy can achieve a high degree of cold working deformation without cracking, and then achieve the maximum degree of grain refinement.

[0022] The technical solution of the present invention will be further described in detail below through examples. Specific embodiments

[0023] Example 1

[0024] This example includes the following steps:

[0025] Step 1: Use 0.05 mm thick iron foil with a mass purity of not less than 99.99% to wrap tin grains, chromium grains, iron grains and zirconia powder with a mass purity of not less than 99.99% into alloy packages, and then mix and press them with atomic level sponge zirconium to obtain electrode blocks. Each electrode block contains 4 alloy packages, which are evenly distributed in the length direction of the electrode. Then, the electrode blocks are subjected to 6 times of vacuum consumable arc melting to obtain alloy ingots;

[0026] Step 2: Turn the surface of the alloy ingot obtained in Step 1, and then perform 3 forging passes and remove the surface oxide scale. Among them, the first forging is carried out at 400 °C above the β phase transformation point temperature, and the forging directions are up-down, left-right, front-back, upper front-lower back, upper back-lower front, upper left-lower right, upper right-lower left, left front-right back, left back-right front. The reduction per pass is 45%. After forging, water quenching is carried out. The second and third forging passes are carried out at 10 °C below the β phase transformation point temperature, and the forging directions are up-down, left-right, front-back, upper front-lower back, upper back-lower front, upper left-lower right, upper right-lower left, left front-right back, left back-right front. The reduction per pass is 45%. After forging, air cooling is carried out to obtain a square alloy forging;

[0027] Step 3: Subject the alloy forging obtained in Step 2 to multi-pass hot rolling at 100 °C below the β phase transformation point temperature, with a cumulative deformation amount of 90%. The hot-rolled alloy forging is subjected to annealing heat treatment at 700 °C. After air cooling, the surface oxide scale is removed to obtain alloy blanks;

[0028] Step 4. Subject the alloy billet obtained in Step 3 to multi-pass cold rolling with a cumulative deformation of 80%. After each pass, perform vacuum annealing at a vacuum degree not higher than 4×10 -3 Pa and a temperature of 700 °C, and then obtain medium-strength and high-ductility Zr-4M zirconium alloy after cooling.

[0029] After testing, the tensile strength of the medium-strength and high-ductility Zr-4M zirconium alloy prepared in this example is 551 MPa, the yield strength is 493 MPa, and the elongation after fracture is 29.5%.

[0030] Comparative Example 1

[0031] This comparative example includes the following steps:

[0032] Step 1. Directly mix and press iron blocks, tin grains, chromium grains, iron grains, and zirconium dioxide powder with atomic-level sponge zirconium to obtain an electrode block, and then subject the electrode block to 2 times of vacuum consumable arc melting to obtain an alloy ingot;

[0033] Step 2. Turn the surface of the alloy ingot obtained in Step 1, and then perform 2 forging passes and remove the surface oxide scale. Among them, the first forging is carried out at 100 °C above the β phase transformation point temperature, and the forging directions are up and down, left and right, front and back, with a single reduction of 30%. After forging, water quenching is carried out. The second forging is carried out at 250 °C below the β phase transformation point temperature, and the forging directions are up and down, left and right, front and back, with a single reduction of 30%. After forging, air cooling is carried out to obtain a square alloy forging;

[0034] Step 3. Subject the alloy forging obtained in Step 2 to multi-pass hot rolling at 450 °C below the β phase transformation point temperature with a cumulative deformation of 40%. The alloy after hot rolling is subjected to annealing treatment at 400 °C, and after air cooling, the surface oxide scale is removed to obtain an alloy billet;

[0035] Step 4. Subject the alloy billet obtained in Step 3 to multi-pass cold rolling with a cumulative deformation of 90%. After each pass, perform vacuum annealing at a vacuum degree not higher than 1 Pa and a temperature of 400 °C, and then obtain Zr-4 zirconium alloy after cooling;

[0036] After testing, the tensile strength of the Zr-4 zirconium alloy prepared in this example is 450 MPa, the yield strength is 390 MPa, and the elongation after fracture is 15%.

[0037] It can be seen from the comparison between Example 1 and Comparative Example 1 that Comparative Example 1 is the preparation method of traditional Zr-4 zirconium alloy. The present application improves the manufacturing process, i.e., the preparation parameters, to realize the preparation of medium-strength and high-ductility Zr-4M zirconium alloy. Compared with the traditional Zr-4 zirconium alloy, the prepared medium-strength and high-ductility Zr-4M zirconium alloy has improved tensile strength, yield strength and elongation after fracture, realizing the simultaneous improvement of strength and plasticity, and solving the problem that the strength and elongation of existing zirconium alloys cannot be improved simultaneously.

[0038] Example 2

[0039] This example includes the following steps:

[0040] Step 1: Use 0.1mm thick iron foil with a mass purity of not less than 99.99% to wrap tin grains, chromium grains, iron grains and zirconium dioxide powder with a mass purity of not less than 99.99% into an alloy package, and then mix and press it with atomic-level sponge zirconium to obtain an electrode block. Each electrode block contains 3 alloy packages, which are evenly distributed in the length direction of the electrode. Then, the electrode block is subjected to 3 times of vacuum consumable arc melting to obtain an alloy ingot;

[0041] Step 2: Turn the surface of the alloy ingot obtained in Step 1, and then perform 3 forging passes and remove the surface oxide scale. Among them, the first forging is carried out at 200°C above the β phase transformation point temperature, and the forging directions are up-down, left-right, front-back, up-front-down-back, up-back-down-front, up-left-down-right, up-right-down-left, left-front-right-back, left-back-right-front. The reduction per pass is 40%. After forging, water quenching is carried out. The second and third forging passes are carried out at 200°C below the β phase transformation point temperature, and the forging directions are up-down, left-right, front-back, up-front-down-back, up-back-down-front, up-left-down-right, up-right-down-left, left-front-right-back, left-back-right-front. The reduction per pass is 40%. After forging, air cooling is carried out to obtain a square alloy forging;

[0042] Step 3: Perform multi-pass hot rolling on the alloy forging obtained in Step 2 at 400°C below the β phase transformation point temperature. The cumulative hot rolling deformation is 50%. The hot-rolled alloy is subjected to annealing treatment at 400°C. After air cooling, the surface oxide scale is removed to obtain an alloy blank;

[0043] Step 4: Perform multi-pass cold rolling on the alloy blank obtained in Step 3. The cumulative deformation is 20%. After each pass, vacuum annealing treatment is carried out at a vacuum degree not higher than 4×10 -3 Pa and a temperature of 400°C. After cooling, a medium-strength and high-ductility Zr-4M zirconium alloy is obtained.

[0044] After testing, the tensile strength of the medium-strength and high-ductility Zr-4M zirconium alloy prepared in this example is 590 MPa, the yield strength is 517 MPa, and the elongation after fracture is 25.5%.

[0045] Example 3

[0046] This example includes the following steps:

[0047] Step 1: Use 0.05 mm thick iron foil with a mass purity of not less than 99.99% to wrap tin grains, chromium grains, iron grains, and zirconium dioxide powder with a mass purity of not less than 99.99% into an alloy package, and then mix and press it with atomic-level sponge zirconium to obtain electrode blocks. Each electrode block contains 5 alloy packages, which are evenly distributed in the electrode length direction. Then, the electrode blocks are subjected to 5 times of vacuum consumable arc melting to obtain alloy ingots;

[0048] Step 2: Turn the surface of the alloy ingot obtained in Step 1 smooth, and then perform forging 3 times and remove the surface oxide scale. Among them, the first forging is carried out at 300 °C above the β phase transformation point temperature, and the forging directions are up-down, left-right, front-back, upper front-lower back, upper back-lower front, upper left-lower right, upper right-lower left, left front-right back, left back-right front. The reduction per pass is 50%. After forging, water quenching is carried out. The second and third forging are carried out at 50 °C below the β phase transformation point temperature, and the forging directions are up-down, left-right, front-back, upper front-lower back, upper back-lower front, upper left-lower right, upper right-lower left, left front-right back, left back-right front. The reduction per pass is 50%. After forging, air cooling is carried out to obtain a square alloy forging;

[0049] Step 3: Perform multi-pass hot rolling on the alloy forging obtained in Step 2 at 200 °C below the β phase transformation point temperature. The cumulative hot rolling deformation is 60%. The alloy after hot rolling is subjected to annealing treatment at 600 °C. After air cooling, the surface oxide scale is removed to obtain an alloy blank;

[0050] Step 4: Perform multi-pass cold rolling on the alloy blank obtained in Step 3. The cumulative deformation is 60%. After each pass, vacuum annealing treatment is carried out at a vacuum degree not higher than 4×10 -3 Pa and a temperature of 600 °C. After cooling, a medium-strength and high-ductility Zr-4M zirconium alloy is obtained.

[0051] After testing, the tensile strength of the medium-strength and high-ductility Zr-4M zirconium alloy prepared in this example is 578 MPa, the yield strength is 507 MPa, and the elongation after fracture is 28%.

[0052] The above is only a preferred embodiment of the present invention and does not impose any limitation on the present invention. Any simple modification, change, and equivalent change made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A preparation method of medium-strength and high-plasticity Zr-4M zirconium alloy for nuclear use, characterized in that, The method includes the following steps: Step 1: Mix sponge zirconium with alloy packages, then press to obtain electrode blocks, and then subject the electrode blocks to vacuum consumable arc melting to obtain alloy ingots; the method for making the alloy packages is as follows: use iron foil to wrap tin grains, chromium grains, iron grains and zirconium dioxide powder into alloy packages, the mass purity of the iron foil, tin grains, chromium grains and iron grains is not less than 99.99%, the purity of the zirconium dioxide powder is not less than analytical pure, the sponge zirconium is of atomic energy level, the grade is HZr-01, the thickness of the iron foil is not more than 0.1 mm, and the electrode blocks contain not less than 3 alloy packages; Step 2: Turn the surface of the alloy ingot obtained in Step 1, and then perform multi-pass forging and remove the surface oxide scale to obtain alloy forgings; the number of multi-pass forging is more than 2 times, and the forging is pressed down in 9 directions, and the 9 directions are respectively: up-down, left-right, front-back, upper front-lower back, upper back-lower front, upper left-lower right, upper right-lower left, left front-right back, left back-right front, and the amount of each press-down shall not be less than 40%; in the multi-pass forging, the temperature of the first forging is 200°C to 400°C above the β phase transition point temperature of the alloy ingot, and the cooling method is water quenching, the temperature of the second forging is 10°C to 200°C below the β phase transition point temperature of the alloy ingot, and the cooling method is air cooling, and the forging parameters of the third and subsequent forgings are the same as those of the second forging; Step 3: Subject the alloy forgings obtained in Step 2 to multi-pass hot rolling, then perform heat treatment, then cool and remove the surface oxide scale to obtain alloy blanks; the temperature of the multi-pass hot rolling is 100°C to 400°C below the β phase transition point temperature, and the cumulative deformation amount is 50% to 90%, and the temperature of the heat treatment is 400°C to 700°C; Step 4. Subject the alloy blank obtained in Step 3 to multi-pass cold rolling, and perform vacuum heat treatment after each pass. After cooling, a medium-strength and high-ductility Zr-4M zirconium alloy is obtained; the cumulative deformation of the multi-pass cold rolling is 20% to 80%, and the vacuum degree of the vacuum heat treatment is not higher than 4×10 -3 Pa, and the temperature is 400°C to 700°C.