Zirconium alloy plate texture control method for regulating recrystallization based on cold rolling deformation

Abstract

The invention relates to the technical field of metal processing, in particular to a zirconium alloy plate texture control method for regulating recrystallization based on cold rolling deformation. The zirconium alloy hot-rolled plate blank is subjected to annealing treatment, so that an equiaxial grain structure with the proper size is obtained; cold rolling treatment is conducted on the zirconium alloy plate blank obtained after annealing treatment, different rolling deformation accumulation modes are introduced through total deformation design, rolling pass control and pass deformation control, and different dislocation and subgrain distribution states are formed in the zirconium alloy cold-rolled plate; and the zirconium alloy plate strip prepared through cold rolling deformation is subjected to annealing treatment, so that a completely recrystallized plate with refined grains and weakened texture is obtained, and the plasticity and forming performance of the zirconium alloy plate are improved. The technological process is simple, the recrystallized zirconium alloy plate with the basal texture weakened can be obtained only by slightly changing the zirconium alloy plate machining technology, the anisotropy of the zirconium alloy plate can be reduced, and therefore the use performance of the zirconium alloy plate is improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal processing, and in particular to a texture control method for a zirconium alloy plate based on cold rolling deformation and recrystallization regulation. Background Art

[0002] Zirconium alloys are widely used as cladding materials and structural materials for nuclear reactors because of their excellent corrosion resistance, low thermal neutron absorption cross section and good mechanical properties. For example, the positioning grid is punched out of zirconium alloy strips and is a key clamping structure for fixing the lateral and axial positions of the combustion components of nuclear reactors. However, the strong texture formed in the zirconium alloy sheet during processing will cause the positioning grid to crack during the punching process, making it impossible to achieve stable punching. Therefore, the texture control of zirconium alloy sheet and strip, especially the weakening of the strong texture of the base surface, is a bottleneck problem and process difficulty in the preparation and processing of high-performance zirconium alloys.

[0003] The preparation process of zirconium alloy plates and strips mainly includes multiple processes such as hot rolling-cold rolling-annealing, and the texture characteristics of the plates are closely related to the preparation process parameters of each process. For example: the Chinese patent with publication number CN118048590A proposes the control of hot forging, quenching, double hot rolling and recrystallization annealing of zirconium alloy thick plates (>8mm), which improves the transverse and longitudinal mechanical properties of zirconium alloy plates and ensures the uniformity and consistency of the organization and performance of each region of the plate. The Chinese patent with publication number CN117604414A adopts a cross hot rolling-annealing-cold rolling-annealing process to prepare Zr-4 thin strips and imported Zr-4 plates with similar texture strength. The Chinese patent with publication number CN114277327B, after the zirconium alloy plate is kept at liquid nitrogen temperature, a certain amount of twins are introduced by a special rolling path, and the annealing treatment is combined to adjust the basal texture of the zirconium alloy based on twin-induced recrystallization.

[0004] In summary, the texture of zirconium alloy thin plates can be adjusted by controlling the rolling hot rolling deformation temperature and deformation amount (β-α phase transformation and in the α phase region) and annealing process parameters. However, zirconium alloy has a close-packed hexagonal structure, and the texture of thin plates is still mainly determined by cold rolling deformation and annealing process. At the same time, the cross-rolling and special rolling methods and paths currently used require significant adjustments to existing processes and equipment, which are difficult to apply in process production. Therefore, there is still an urgent need to develop a plate cold rolling control method with a simple process flow for zirconium alloy plates and strips, which can be combined with existing processing technology to achieve the weakening of the base surface texture and obtain high punching performance. Summary of the invention

[0005] The purpose of the present invention is to provide a method for controlling the texture of zirconium alloy plates based on cold rolling deformation to regulate recrystallization, so as to solve the problems in the prior art that the texture of zirconium alloy plates is difficult to regulate and the strong texture of the base surface is weakened, thereby combining the existing processing technology to achieve the weakening of the base surface texture and obtain high punching performance.

[0006] The technical solution of the present invention is:

[0007] A method for controlling texture of zirconium alloy plates based on cold rolling deformation and recrystallization regulation comprises the following steps:

[0008] 1) Cutting the zirconium alloy hot-rolled sheet into billets and annealing them in a box-type resistance furnace to obtain an equiaxed grain structure with a suitable size;

[0009] 2) cold rolling the annealed zirconium alloy sheet blank, wherein the process parameters include: total rolling deformation, single-pass rolling deformation or single-pass reduction rate, number of rolling passes, and rolling method. By reasonably designing the total deformation, controlling the rolling passes and the pass deformation, and introducing different rolling deformation accumulation methods, different dislocation and subgrain distribution states are formed inside the zirconium alloy cold-rolled sheet;

[0010] 3) The zirconium alloy sheet and strip prepared by cold rolling deformation is annealed to obtain a fully recrystallized sheet with refined grains and weakened texture, and the organizational characteristics and texture types are characterized in detail through experiments.

[0011] In the method for controlling the texture of zirconium alloy plates by regulating recrystallization through cold rolling deformation, in step 1), the annealing temperature and time are adjusted to obtain an equiaxed grain structure with a size of 5 μm, thereby providing reliable conditions for controlling the deformation structure state in the subsequent cold rolling process.

[0012] In the method for controlling the texture of zirconium alloy plates by regulating recrystallization through cold rolling deformation, in step 2), the total rolling deformation is 30% to 80%, the single-pass rolling deformation is 0.1 mm to 0.5 mm or the single-pass reduction rate is 5% to 25%, the number of rolling passes is 3 to 30 times, and the rolling method is unidirectional rolling or cross rolling.

[0013] In the method for controlling the texture of zirconium alloy plates by regulating recrystallization through cold rolling deformation, in step 2), the plate is subjected to multiple passes of equal reduction, i.e., each pass uses the same small rolling reduction of 0.05 to 0.15; or, the plate is subjected to equal-pass rolling, i.e., a fixed rolling pass is used for any total reduction.

[0014] In the method for controlling texture of zirconium alloy plates based on cold rolling deformation and regulating recrystallization, in step 2), a combination of equal reduction and equal pass deformation is used.

[0015] In the method for controlling texture of zirconium alloy plates based on cold rolling deformation and regulating recrystallization, in step 3), the annealing temperature ranges from 500° C. to 650° C. and the time ranges from 5 min to 240 min.

[0016] The design concept of the present invention is:

[0017] Based on the fact that the non-uniformity of cold rolling deformation promotes the occurrence of discontinuous static recrystallization, the discontinuous static recrystallization fraction is increased by optimizing the rolling passes and deformation of the plate, thereby achieving the weakening of the base surface texture. First, the zirconium alloy hot-rolled annealed plate is prepared, and after the sample surface is cleaned, the plate is cold-rolled and deformed by a specially designed cold rolling process. Process A: the plate is rolled with multiple passes with equal reduction, that is, each pass uses the same small rolling reduction (0.1mm~0.5mm); Process B: the plate is rolled with equal passes, that is, a fixed rolling pass is used for any total reduction; secondly, the rolled zirconium alloy plate is vacuum annealed, and the vacuum annealing temperature is 500℃~650℃, and the annealing time is 5~240min. Therefore, by making a small change in the processing technology of the zirconium alloy plate, a recrystallized zirconium alloy plate with weakened base surface texture is obtained.

[0018] The advantages and beneficial effects of the present invention are:

[0019] 1. The present invention performs rolling processing on zirconium alloy plates, and the process flow is simple and controllable. By adjusting the rolling passes and the deformation amount of each pass and matching the corresponding annealing system, the base surface texture, plasticity and formability of the zirconium alloy plates can be significantly improved.

[0020] 2. The present invention optimizes the existing rolling passes and the deformation amount of each pass, performs cold rolling on the plate, and can introduce different non-uniform deformations between grains and sub-grain structures inside the grains into the zirconium alloy plate.

[0021] 3. The annealing treatment in the present invention is intended to utilize the differences in static recrystallization mechanisms corresponding to the intergranular non-uniform deformation introduced by the cold rolling process and the subgrain structure inside the grains, thereby introducing different recrystallization types, so that fine equiaxed grains can be generated inside the thin plate and their orientation can be controlled at the same time, so as to achieve the purpose of controlling the texture of the zirconium alloy plate.

[0022] 4. The rolling deformation regulation recrystallization texture proposed in the present invention is applicable not only to zirconium alloy plates, but also to zinc (Zn), titanium (Ti), cobalt (Co), magnesium (Mg) and other alloy plates with hexagonal close-packed (HCP) structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The plates are the plates after rolling deformation amounts (15.4%, 29.7%, 51.3%, 70.2%, 78.4%) in the same reduction process as in Example 1;

[0024] Figure 2 The microstructures of the rolled surface (RD-TD) of the plate after different deformation and annealing in Example 1 are as follows: (a) 30%; (b) 30%-650℃ / 2h; (c) 50%; (d) 50%-650℃ / 2h; (e) 80%; (f) 80%-650℃ / 2h;

[0025] Figure 3 The (0001) pole figures of the rolled surface (RD-TD) of the Zr-4 plate with different deformation amounts and the annealed plate in Example 1 are as follows: (a) 30%; (b) 30%-650℃ / 2h; (c) 50%; (d) 50%-650℃ / 2h; (e) 80%; (f) 80%-650℃ / 2h;

[0026] Figure 4 The microstructures of the rolled surface (RD-TD) of Zr-4 plate with different rolling processes of equal reduction and five-pass rolling in Example 2 are shown as follows: (a) equal reduction; (b) five-pass unequal reduction;

[0027] Figure 5 The (0001) PF (pole figure) and Cohen coefficient of the cold-rolled sheet with constant reduction and 5-pass rolling processes in Example 2: (a) constant reduction; (b) 5-pass unequal reduction;

[0028] Figure 6 The microstructures of the plates after annealing under different rolling processes of equal reduction and five-pass rolling in Example 2 are as follows: (a) equal reduction; (b) five-pass unequal reduction;

[0029] Figure 7 The (0001) PF and Cohen coefficient of the cold-rolled plates after annealing with different rolling processes of equal reduction and 5-pass rolling in Example 2: (a) equal reduction; (b) 5-pass unequal reduction. DETAILED DESCRIPTION

[0030] In the specific implementation process, the present invention proposes a method for controlling the texture of a zirconium alloy plate based on cold rolling deformation and regulating recrystallization, comprising the following steps:

[0031] 1) Cutting the zirconium alloy hot-rolled sheet into billets of a certain size and annealing it in a box-type resistance furnace to obtain an equiaxed grain structure with a suitable size;

[0032] 2) The annealed zirconium alloy sheet blank is subjected to cold rolling, and the process parameters include: total rolling deformation, single-pass rolling deformation (single-pass reduction rate), number of rolling passes, rolling method, etc. Through reasonable design of total deformation, control of rolling passes and pass deformation, and introduction of different rolling deformation accumulation methods, different dislocation and subgrain distribution states are formed inside the zirconium alloy cold-rolled sheet;

[0033] 3) The zirconium alloy sheet and strip prepared by cold rolling deformation is annealed to obtain a fully recrystallized sheet with refined grains and weakened texture, and the organizational characteristics and texture types are characterized in detail through experiments.

[0034] Among them, in the step 1), the annealing temperature and time are used to obtain an equiaxed grain structure with appropriate size, providing reliable conditions for controlling the deformation structure state in the subsequent cold rolling process; in the step 2), the total rolling deformation is 30% to 80%, the single-pass rolling deformation is 0.1mm to 0.5mm (reduction rate 5% to 25%), the rolling pass number is 3 to 30 times, and the rolling method is unidirectional rolling; in the step 2), the rolling reduction scheme can be determined according to actual needs, and can be carried out in a combination of equal reduction and equal pass deformation; in the step 3), the annealing treatment is determined according to the deformation, and the annealing temperature range is 500°C to 650°C, and the time is 10min to 120min.

[0035] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments.

[0036] Example 1

[0037] In this embodiment, the thickness of the Zr-4 alloy plate is 3.7 mm. The initial plate used in the experiment is taken from the initial hot-rolled annealed plate. The experimental plate is obtained by wire cutting, and its specific size is 80 mm (RD) × 50 mm (TD) × 3.7 mm (ND).

[0038] In order to obtain an equiaxed, twin-free recrystallized initial structure, the original plate was homogenized and annealed at 650°C for 2 h to obtain a grain structure with a size of 5 μm.

[0039] The initial hot-rolled annealed sheet with a thickness of 3.7 mm was subjected to cold rolling experiments with different processes. The experiments were carried out on a φ200×200mm two-roll experimental cold rolling mill. The roll gap spacing of the rollers was set to 0.1mm per pass. The sheets with different deformation amounts needed to be rolled for 5, 11, 19, 26 and 29 passes respectively. After rolling, the thickness of the sheets was 3.1mm, 2.6mm, 1.9mm, 1.1mm and 0.8mm respectively. Figure 1As shown, the actual deformations measured correspond to 15.4%, 29.7%, 51.3%, 70.2% and 78.4% respectively.

[0040] like Figure 2 and Figure 3 As shown, the rolled surface (RD-TD) microstructure and (0001) pole figure of plates with cold rolling deformation of 30%, 50%, and 80% are annealed and kept at 650°C for 2h.

[0041] By comparing the texture results of annealing at the same temperature and time with different deformation amounts, it can be seen that the deformation texture Fn (Fn refers to the normal Cohen coefficient) of the plate with a deformation amount of 30% is the largest, and the annealing texture Fn after annealing is the smallest, which is significantly reduced to 0.183. The difference in Fn of annealed plates with different cold rolling deformation amounts is due to the difference in rolling deformation, which makes the deformation inside the plate uneven, forming high dislocation density areas and low dislocation density areas, resulting in different mechanisms of nucleation and growth of grains inside the plate during annealing, resulting in differences in annealing textures.

[0042] Example 2

[0043] In this embodiment, the thickness of the Zr-4 alloy plate is 3.7 mm. The initial plate used in the experiment is taken from the initial hot-rolled annealed plate. The experimental plate is obtained by wire cutting, and its specific size is 80 mm (RD) × 50 mm (TD) × 3.7 mm (ND).

[0044] In order to obtain an equiaxed, twin-free recrystallized initial structure, the original plate was homogenized and annealed at 650°C for 2 h to obtain a grain structure with a size of 5 μm.

[0045] The initial hot-rolled annealed plate with a thickness of 3.7 mm was subjected to cold rolling experiments with different processes, including unequal reduction rolling and equal reduction rolling. The experiments were carried out on a φ200×200mm two-roll experimental cold rolling mill, namely: 5 passes of unequal reduction rolling (the reduction of each pass was 0.4mm, 0.5mm, 0.6mm, 0.8mm and 0.6mm respectively) and 29 passes of equal reduction rolling (the reduction of each pass was equal, all 0.1mm). After rolling, the thickness of the plate remained consistent at 0.8mm.

[0046] like Figure 4 As shown in the figure, the microstructures of the plates after rolling by two different rolling processes. The two different rolling processes have different internal structures of the plates after deformation due to the different speeds of the deformation process; Figure 5 As shown in the figure, the (0001) pole figure distribution of cold-rolled plates with different rolling processes shows that the normal Cohen coefficient of the deformation texture of the plate rolled with equal reduction is higher than that of the deformed plate rolled with 5 passes.

[0047] For the cold-rolled plates prepared by two different rolling processes, samples were taken at the uniform rolling position of the plates by wire cutting. The cold-rolled plate samples were vacuum-sealed in a quartz tube and placed in a vacuum environment of a box-type resistance furnace for annealing experiments. The annealing temperature was 650°C and the annealing time was 2h. The plates after annealing were taken for EBSD experimental observation.

[0048] like Figure 6 and Figure 7 The following are the microstructure and texture diagrams of cold-rolled plates with two different rolling processes annealed at 650℃ for 2h. The orientation of some grains after annealing of the plate with 5-pass rolling process is different from the red orientation of the original cold-rolled plate, which indicates that during the 5-pass cold rolling process, some grains are deflected and their C-axis rotates from ND to TD, resulting in a significant weakening of the orientation of the plate after annealing.

[0049] The implementation results show that the process flow of the present invention is simple, and only a small change in the processing technology of the zirconium alloy plate can be made to obtain a recrystallized zirconium alloy plate with weakened base surface texture, which helps to reduce the anisotropy of the zirconium alloy plate, thereby improving its performance.

Claims

1. A method for controlling the texture of a zirconium alloy sheet based on cold rolling deformation and recrystallization, characterized in that: The steps include: 1) Cutting the zirconium alloy hot-rolled sheet into billets and annealing them in a box-type resistance furnace to obtain an equiaxed grain structure with a suitable size; 2) cold rolling the annealed zirconium alloy sheet blank, wherein the process parameters include: total rolling deformation, single-pass rolling deformation or single-pass reduction rate, number of rolling passes, and rolling method. By reasonably designing the total deformation, controlling the rolling passes and the pass deformation, and introducing different rolling deformation accumulation methods, different dislocation and subgrain distribution states are formed inside the zirconium alloy cold-rolled sheet; 3) The zirconium alloy sheet and strip prepared by cold rolling deformation is annealed to obtain a fully recrystallized sheet with refined grains and weakened texture, and the organizational characteristics and texture types are characterized in detail through experiments.

2. The method for controlling texture of zirconium alloy sheet based on cold rolling deformation and recrystallization according to claim 1, characterized in that: In step 1), the annealing temperature and time are adjusted to obtain an equiaxed grain structure with a size of 5 μm, providing reliable conditions for controlling the deformation structure state in the subsequent cold rolling process.

3. The method for controlling texture of zirconium alloy sheet based on cold rolling deformation and recrystallization according to claim 1, characterized in that: In step 2), the total rolling deformation is 30% to 80%, the single-pass rolling deformation is 0.1 mm to 0.5 mm or the single-pass reduction rate is 5% to 25%, the rolling passes are 3 to 30 times, and the rolling method is unidirectional rolling or cross rolling.

4. The method for controlling texture of zirconium alloy sheet based on cold rolling deformation and recrystallization according to claim 1, characterized in that: In step 2), the plate is rolled in multiple passes with equal reduction, i.e., each pass uses the same small rolling reduction of 0.05-0.15; or, the plate is rolled in equal passes, i.e., a fixed rolling pass is used for any total reduction.

5. The method for controlling texture of zirconium alloy sheet based on cold rolling deformation and regulating recrystallization according to claim 3, characterized in that: In step 2), a combination of equal pressure reduction and equal number of deformations is adopted.

6. The method for controlling texture of zirconium alloy sheet based on cold rolling deformation and regulating recrystallization according to claim 1, characterized in that: In step 3), the annealing temperature ranges from 500° C. to 650° C., and the annealing time ranges from 5 min to 240 min.

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