A rolling method and tooling for improving the core quality of zirconium alloy bars
By optimizing the die profile and deformation distribution of zirconium alloy bars, the white core problem during Pilger rolling was solved, the corrosion resistance of the bars was improved, and the safety of nuclear reactors was enhanced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- STATE NUCLEAR BAOTI ZIRCONIUM IND CO
- Filing Date
- 2023-10-27
- Publication Date
- 2026-07-21
AI Technical Summary
The white core phenomenon that occurs in existing zirconium alloy bars during the Pilger rolling process affects their corrosion resistance and the safety and reliability of nuclear reactors.
By analyzing the initial design of the die profile and deformation distribution, the rolling process of the zirconium alloy bar was adjusted to optimize the die profile and deformation distribution, reduce the difference in metal flow velocity between the edge and core of the bar cross section, reduce the difference in microstructure and texture, and improve the core quality of the bar.
It effectively reduces the white core phenomenon in the core of the rods, improves the corrosion resistance of zirconium alloy rods, and enhances the safety of nuclear reactors.
Smart Images
Figure CN117583379B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for rolling metals, and more particularly to a method for rolling a zirconium alloy bar core to improve its quality. Background Technology
[0002] Zirconium alloy rods are an important component of nuclear reactor internals, and their material properties directly affect reactor safety.
[0003] In addition to the conventional room temperature and high temperature mechanical property requirements, there are also strict requirements for the low magnification structure of the bar stock, because in the nuclear reaction, under the dual effects of pressure and water-side corrosion, defects in the low magnification structure will become weak points in the material.
[0004] The Pilger cold rolling process for nuclear fuel rods has been widely used due to its high dimensional accuracy, surface quality, and high yield, making it an important method for processing nuclear fuel rods. However, traditional rolling processes, such as pass design and deformation distribution, still refer to the Pilger tube rolling concept, using methods such as the classic design method represented by Shevakin, the Grenlon design method represented by Professor Anston of Grenlon GmbH in Sweden, and the Demark design method established by Nessmann Demark GmbH in Germany to design the pass and deformation distribution.
[0005] In bar rolling production, if the die designed using the Pilger tube rolling concept is used for bar rolling, after the microstructure test sample has undergone acid corrosion treatment, a "white core" phenomenon appears where the core color differs from the edge color. This low-magnification microstructure anomaly is not a reflection of cracks, folds, porosity, segregation, shrinkage, looseness, metallic or non-metallic inclusions, or other visually visible metallurgical defects. Instead, it is a macroscopic color difference phenomenon caused by applying the Pilger tube rolling concept to bars. This manifests as dense corrosion pits in the white area when observed under a microscope.
[0006] As corrosion resistance is an important indicator for evaluating materials used in nuclear reactors, the low-magnification white core poses a challenge to the safety and reliability of nuclear reactors. This problem is also faced in scenarios such as using Pilger rolling to process reactor fuel assemblies, including end plug rods, upper and lower connecting rods, and combustible poison rods. Therefore, how to reduce the white core of processed rods when using the Pilger rolling method is a technical problem that needs to be solved. Summary of the Invention
[0007] The purpose of this invention is to provide a rolling method for improving the core quality of zirconium alloy bars, in order to solve the technical problem of white cores appearing when bars are rolled using Pilger rolling in the prior art.
[0008] To solve the above-mentioned technical problems, according to some embodiments, in a first aspect, the present invention provides a method for rolling a zirconium alloy rod core to improve its quality, characterized in that it includes: Using the initially designed die profile and deformation distribution, the zirconium alloy rod billet was subjected to Pilger rolling to obtain the rolled deformed cone and rod. The deformed cone and the rod were dissected longitudinally and laterally according to a certain pattern to obtain samples of metal structure deformation and change at different spatial locations; Determine whether the white core range of the material texture surface of the entire spatial range of the sample meets the optimization conditions. The optimization conditions specifically include: along the direction from the billet to the rolled rod of the zirconium alloy rod, the surface texture is distributed within a circumference from the center to 60°, and the difference in diffraction intensity between the core and the edge is within 8%-30%. The length of the deformation section during the rolling of the zirconium alloy rod billet is adjusted and optimized, including: determining the secondary design of the die profile curve and deformation distribution based on the initial design die profile curve and deformation distribution; Using the die profile curve and deformation distribution of the secondary design, the zirconium alloy rod billet is subjected to Pilger rolling to obtain the improved zirconium alloy rod.
[0009] In some embodiments, determining the secondary design's hole profile curve and deformation distribution based on the initial design's hole profile curve and deformation distribution specifically includes: Based on the initially designed die profile curve and deformation distribution, the processing area L of the rolled deformed cone and bar is determined. k ; Adjust the processing area EL of the secondary design k For the initial processing area L k 1 / 3 to 4 / 5 of the length; Along the direction from coarse to fine in the processing area, at (2 / 3) L k The initial processing area L within and above k Within, adjust the minimum taper EZ of the secondary hole shape to 1-3 times the minimum taper Z of the initial hole shape, within (2 / 3) L k The initial processing area L outside k Inside, adjust the minimum taper EZ of the secondary hole shape to 1 / 4 to 3 / 4 of the minimum taper Z of the initial hole shape.
[0010] In some embodiments, it also includes: According to the adjusted secondary processing area EL k The value of the minimum taper EZ of the secondary hole is used to redetermine the top diameter D of the hole at the x-position of the cross section. X K, groove depth TX, and angle position GX information parameters; Based on the newly determined parameters, the hole pattern was remade and the deformation amount of each section was allocated.
[0011] In some embodiments, the initial design of the aperture curve and deformation distribution specifically includes: The diameter D of the top of the aperture is calculated using the following formula. XK : D XK =D F +C X (D L -D F -Z)+ (Z)+ n X (l a ); Among them, L k C is the length of the initially designed processing area. X The shape factor of the aperture is L. k Calculated Let x be the moving coordinate of the cross section relative to point 0, and D be the moving coordinate of the cross section. L D is the outer diameter of the billet of the zirconium alloy rod. F To determine the outer diameter of the rolled bar, Z is the minimum taper of the die required in the diameter direction, expressed in mm, based on L. k Calculations show that la is the outer diameter D of the zirconium alloy rod billet. L With the groove The gap in the diametrical direction between the top diameters at point =1, n X This is the gap correction coefficient for la.
[0012] In some embodiments, the C X The shape factor of the aperture is L. k The calculation is obtained using the following formula: C X =( ) EXP1； EXP1 is the characteristic index of the top curve variation of the roll pass (referred to as the roll pass index), which is determined based on the characteristics of the metal of the rolled material.
[0013] In some embodiments, the value of EXP1 ranges from 2.0 to 3.5.
[0014] In some embodiments, Z is the minimum taper of the hole shape required in the diametrical direction, expressed in mm, according to L. k The calculation is obtained using the following formula: Z=β min * ; Where: β minIt is the minimum taper coefficient of the hole type, expressed as a percentage.
[0015] In some embodiments, n X The calculation method is as follows: n X = ; EXP2 is the index of the effect of the sum of the two gaps on the hole profile curve (referred to as the gap index).
[0016] In some embodiments, the value of EXP2 is 2.0.
[0017] In some embodiments, the initial design of the aperture curve and deformation distribution further includes: The formula for calculating the groove depth TX of the rolling pass is as follows: TX= ; Sp represents the gap between the upper and lower holes.
[0018] In some embodiments, the initial design of the aperture curve and deformation distribution further includes: The moving coordinates are The angle position GX is calculated using the following formula: GX= *360°; Among them, L X X is the distance from position 0 to the calculated position x, in mm; DR is the pitch circle diameter of the pinion on the roll shaft; and GX is the angle of the calculated section position.
[0019] Secondly, embodiments of the present invention also provide a rolling fixture for improving the core quality of zirconium alloy bars, wherein the fixture is a fixture determined according to any one of the methods of the first aspect.
[0020] The above-mentioned technical solution of the present invention has at least the following beneficial technical effects: The technical solution of the present invention analyzes the initial design of the die profile curve and deformation distribution after rolling to find the pattern of white core. After determining that white core is generated, a secondary design is carried out based on the initial design of the die profile curve and deformation distribution. The deformation cone and the deformation section (processing section) in the bar after initial rolling are redesigned to transfer the force generated during Pilger rolling to the center of the bar, so that the difference in metal flow velocity between the edge and the core of the bar cross-section becomes smaller, and the corresponding difference in microstructure texture is also smaller. That is, the content of surface texture formed by the rotation of metal grains on the cross-section is reduced, and it is less white, thereby improving the macroscopic core quality problem of the bar. Attached Figure Description
[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or in the conventional art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0022] Figure 1 This is a schematic diagram of a rolling process for improving the core quality of zirconium alloy rods according to an embodiment of the present invention; Figure 2 This is an embodiment L of the present invention. k Schematic diagram of length adjustment and optimization of the deformable section; Figure 3 This is a top curve diagram of a deformed cone and hole type according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the bar billet before rolling according to an embodiment of the present invention; Figure 5 This is an embodiment of the deformed cone and rod of the present invention; Figure 6 This is a schematic diagram illustrating the deformation and changes in metal microstructure at different spatial locations according to an embodiment of the present invention; Figure 7 This is a schematic diagram illustrating the determination of material microstructure evolution according to an embodiment of the present invention; Figure 8 This is a diagram showing the shape of a hole according to an embodiment of the present invention. Detailed Implementation
[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0024] If the embodiments of this application involve descriptions such as "first" or "second," such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include at least one of those features; the technical solutions of various embodiments can be combined with each other, based on what those skilled in the art can implement.
[0025] In the embodiments of this application, when A and / or B are mentioned, it means three cases: A and B, and A and B.
[0026] It should be noted that the sequence number mentioned in this application does not necessarily mean that the execution must be strictly in the correct order in the actual implementation process. It is just to distinguish each step and prevent confusion.
[0027] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0028] Currently, when using the Pilger rolling process to roll bar stock, a white core phenomenon occurs after processing. Corrosion resistance is an important indicator for evaluating materials used in nuclear reactors, and this low-magnification white core poses a challenge to the safety and reliability of nuclear reactors. Therefore, how to reduce the white core of processed bar stock during the Pilger rolling process is a technical problem that needs to be solved.
[0029] Experimental analysis revealed that Pilger rolling in bar billet production leads to a significant difference in metal flow rate between the inner and outer layers of the bar, resulting in differences in the microstructure of the metal. Ultimately, after acid etching treatment, the samples tested for microstructure exhibited a "white core" phenomenon where the core color differed from the edge color.
[0030] In bar rolling production, significant differences in metal flow rates between the inner and outer layers of the bar can lead to variations in the microstructure of the metal. Ultimately, after acid etching, samples undergoing microstructure testing exhibit a "white core" phenomenon, where the core color differs from the edges. This low-magnification microstructure anomaly is not a reflection of cracks, folds, porosity, segregation, shrinkage, looseness, metallic or non-metallic inclusions, or other visually visible metallurgical defects. Instead, it is a macroscopic color difference caused by poorly designed die curves and deformation distribution in the Pilger tube rolling process. This results in numerous surface textures formed by grain rotation in the metal core, manifesting as dense corrosion pits in the white area under a microscope.
[0031] Therefore, by conducting X-ray diffraction texture determination, hardness testing, and corrosion testing on the cross-sectional area of the rolled bar under the designed bar die profile curve and deformation distribution, the material microstructure texture planes and white core range of the longitudinal and transverse cross-section crystal planes of the bar are determined, and information on grain orientation, metal deformation mechanism, and microstructure evolution is obtained. Based on this, the bar die profile curve is further optimized, and an appropriate amount of rolling outer diameter deformation is allocated. Pilger rolling is then performed accordingly, which reduces the difference in metal flow velocity between the edge and core of the cross-section, and the corresponding difference in microstructure texture is also reduced. That is, the content of surface texture formed by the rotation of metal grains on the cross-section is reduced, and the whitening is reduced, thereby improving the macroscopic core quality problem of the bar.
[0032] Based on the above-mentioned inventive concept, an embodiment of the present invention provides a rolling method for improving the core quality of zirconium alloy rods, comprising: Using the initially designed die profile and deformation distribution, the zirconium alloy rod billet was subjected to Pilger rolling to obtain the rolled deformed cone and rod. The deformed cones and bars were dissected longitudinally and laterally according to a set pattern to obtain samples of metal microstructure deformation and changes at different spatial locations. Determine whether the white core range of the material texture surface of the entire spatial range of the sample meets the optimization conditions. The optimization conditions specifically include: along the direction from the billet to the rolled rod of the zirconium alloy rod, the surface texture is distributed within a circumference from the center to 60°, and the difference in diffraction intensity between the core and the edge is within 8%-30%. The length of the deformation section during the rolling of zirconium alloy rod billets is adjusted and optimized, including: determining the secondary design of the die profile and deformation distribution based on the initial design die profile and deformation distribution; By employing a secondary design of the die profile curve and deformation distribution, the billet of zirconium alloy rods is subjected to Pilger rolling to obtain improved zirconium alloy rods.
[0033] The following is an illustration through specific examples, such as Figure 1 As shown.
[0034] S101: Using the initially designed die profile curve and deformation distribution, the zirconium alloy rod billet is subjected to Pilger rolling to obtain the rolled deformed cone and rod.
[0035] In Pilger rolling, the rolling of bars differs from that of tubes. The initial design of the pass profile and deformation distribution can be simply understood as applying the rolling method used for tubes to the rolling state of bars based on the initial design of the pass profile and deformation distribution in Pilger rolling.
[0036] During billet preparation, a zirconium alloy rod of a certain length is selected as the billet, and its dimensions are determined by the rolling process. The billet is Pilger rolled using the initially designed pass profile to obtain the rolled deformed cone and rod.
[0037] S102: The deformed cone and rod are dissected longitudinally and laterally according to a certain pattern to obtain samples of metal structure deformation and changes in different spatial positions.
[0038] like Figure 2 As shown, the deformed cone and rod were dissected longitudinally and laterally according to a certain pattern to obtain samples of metal structure deformation and changes at different spatial locations.
[0039] S103: Determine whether the white core range of the material texture surface of the entire spatial range of the sample meets the optimization conditions. The optimization conditions specifically include: along the direction from the billet to the rolled rod of the zirconium alloy rod, the surface texture is distributed within a circumference from the center to 60°, and the difference in diffraction intensity between the core and the edge is within 8%-30%.
[0040] Through the above steps, after obtaining samples of metal microstructure deformation and changes in different spatial locations, X-ray diffraction texture determination, hardness testing, corrosion testing, etc. can be performed on the samples in longitudinal and transverse sections to obtain samples of metal microstructure deformation and changes in different spatial locations. This allows for the determination of the material microstructure texture surface and white core range throughout the entire spatial range during the deformation process of the billet being rolled into a bar, thereby obtaining information on grain orientation, metal deformation mechanism, and microstructure evolution.
[0041] For example, if it is a Zr-4 alloy rod, the {100}{110} surface texture can be distributed in a circumference from the center to about 60°. The difference in diffraction intensity between the core and the edge is within 8%-30%, which is the range of white core of the sample structure as defined in this application. For other materials, the appropriate surface can be determined by X-ray diffraction texture measurement, hardness test, corrosion test, etc.
[0042] S104: Adjust and optimize the length of the deformation section during the rolling of zirconium alloy rod billets, including: determining the secondary design of the die profile curve and deformation distribution based on the initial design die profile curve and deformation distribution.
[0043] The hole profile curve and deformation distribution determined in the initial design have resulted in white cores. Therefore, the initial design can no longer meet the requirements and a second design of the hole profile curve and deformation distribution is required.
[0044] When designing the die profile curve and deformation distribution in the secondary design, based on the initial design, the length of the deformation section of the rolled bar is shortened and the minimum taper Z of the deformation section is increased for the deformation cone and the deformation section (processing section) in the bar after initial rolling. This transfers the force to the center of the bar, making the difference in metal flow velocity between the edge and core of the bar's cross-section smaller. Consequently, the difference in the microstructure texture is also smaller. That is, the content of the {100}{110} surface texture formed by the rotation of metal grains on the cross-section is reduced, and the bar is less white, thereby improving the macroscopic core quality problem of the bar.
[0045] S105: Using a secondary-designed die profile curve and deformation distribution, the zirconium alloy rod billet is subjected to Pilger rolling to obtain an improved zirconium alloy rod.
[0046] Based on the adjusted die profile and the parameters determined by the deformation distribution, the tooling is remade, and the zirconium alloy rod billet is subjected to Pilger rolling. After the rolled rod undergoes conventional processing such as degreasing and annealing, the white core of the low magnification structure will be greatly improved, resulting in an improved zirconium alloy rod.
[0047] The technical solution of this invention analyzes the initial design of the roll pass curve and the deformation distribution after rolling to find the pattern of white core. After determining that white core is generated, a secondary design is carried out based on the initial design of the roll pass curve and the deformation distribution. The deformation cone and the deformation section (processing section) in the bar after initial rolling are redesigned to transfer the force generated during Pilger rolling to the center of the bar, so that the difference in metal flow velocity between the edge and the core of the bar cross-section is reduced, and the corresponding difference in microstructure is also reduced. That is, the content of surface texture formed by the rotation of metal grains on the cross-section is reduced, and it is less white, thereby improving the macroscopic core quality problem of the bar.
[0048] Optionally, as one embodiment, the hole profile curve and deformation distribution of the secondary design are determined based on the initial design hole profile curve and deformation distribution, specifically including: Based on the initial design of the die profile and deformation distribution, the processing area L of the rolled deformed cone and bar is determined. k ; Adjusting the processing area EL in the secondary design k For the initial processing area L k 1 / 3 to 4 / 5 of the length; Along the direction from coarse to fine in the processing area, at (2 / 3) L k The initial processing area L within and above k Within, adjust the minimum taper EZ of the secondary hole shape to 1-3 times the minimum taper Z of the initial hole shape, within (2 / 3) L k The initial processing area L outside k Inside, adjust the minimum taper EZ of the secondary hole shape to 1 / 4 to 3 / 4 of the minimum taper Z of the initial hole shape.
[0049] That is, EL k The range is (1 / 3)L k - (4 / 5)L k Between, the secondary design of the processing area EL k The range is adjusted to the initial processing area L k Between 1 / 3 and 4 / 5 of the length.
[0050] like Figure 3 As shown, the direction along which the processing area transitions from coarse to fine refers to the direction from... Figure 3 From the top to the bottom, in (2 / 3) L k The initial processing area L within and abovek Within the range, the minimum taper EZ of the secondary hole is between 1 and 3 times the minimum taper Z of the initial hole, that is, the range of the minimum taper EZ of the secondary hole is between the minimum taper Z and 3Z of the initial hole.
[0051] In (2 / 3) L k The initial processing area L outside k "Inner" can be simply understood as the remaining (1 / 3) L k Within the range, adjust the minimum taper EZ of the secondary hole to 1 / 4-3 / 4 of the minimum taper Z of the initial hole. That is, the range of the minimum taper EZ of the secondary hole is (1 / 4)Z – (3 / 4)Z of the minimum taper Z of the initial hole.
[0052] That is, in (2 / 3) L k Within the range, increase the minimum taper of the hole type, in the later section at (1 / 3) L k Within the range, reduce the minimum taper of the hole.
[0053] For specific parameter adjustments, please refer to [link / reference]. Figure 2 As shown.
[0054] The adjustment of the hole profile curve and deformation distribution in the secondary design is based on shortening the initial machining area L. k Increasing the length and the minimum taper of the hole in the first two-thirds of the section allows the force to be transferred to the center of the bar during Pilger rolling, reducing the difference in metal flow velocity between the edge and core of the cross-section. Consequently, the difference in microstructure and texture is also reduced, meaning the content of the {100}{110} surface texture formed by the rotation of metal grains on the cross-section is reduced, resulting in less whitening and thus improving the macroscopic quality of the bar core.
[0055] Optionally, based on the adjusted secondary processing area EL k The value of the minimum taper EZ of the secondary hole is used to redetermine the top diameter D of the hole at the x-position of the cross section. X K, groove depth TX, and angle position GX information parameters; Based on the newly determined parameters, the hole pattern was remade and the deformation amount of each section was allocated.
[0056] Optionally, as one embodiment, the initial design of the aperture curve and deformation distribution specifically includes: The diameter D of the top of the aperture is calculated using the following formula. XK : D XK =D F +C X (D L -D F -Z)+ (Z)+n X(l a (1) like Figure 3 As shown, Figure 3 This is a top curve diagram of the deformed cone and hole type of this application. The parameters circled in the figure are the parameters of key interest in this application.
[0057] Among them, L k C is the length of the initially designed processing area. X The shape factor of the aperture is L. k Calculated Let x be the moving coordinate of the cross section relative to point 0, and D be the moving coordinate of the cross section. L D is the outer diameter of the billet of the zirconium alloy rod. F To determine the outer diameter of the rolled bar, Z is the minimum taper of the die required in the diameter direction, expressed in mm, based on L. k Calculations show that la is the outer diameter D of the zirconium alloy rod billet. L With the groove The gap in the diametrical direction between the top diameters at point =1, n X This is the gap correction coefficient for la.
[0058] The C X The shape factor of the aperture is L. k The calculation is obtained using the following formula: C X =( ) EXP1 ; EXP1 is the characteristic index of the top curve variation of the roll pass (referred to as the roll pass index), which is determined based on the characteristics of the metal of the rolled material.
[0059] The value of EXP1 can be between 2.0 and 3.5.
[0060] Optionally, Z is the minimum taper of the hole required in the diametrical direction, expressed in mm, according to L. k The calculation is obtained using the following formula: Z=β min * ; Where: β min It is the minimum taper coefficient of the hole type expressed as a percentage. This value is an empirical coefficient related to the properties of the material to be processed (such as zirconium alloy rods), the size of the outer circle of the tooling hole, and the tooling material itself.
[0061] Optionally, the value of EXP2 is 2.0.
[0062] Optionally, the initial design of the aperture profile curve and deformation distribution further includes: The formula for calculating the groove depth TX of the rolling pass is as follows: TX= (2) Sp represents the gap between the upper and lower holes.
[0063] Optionally, as one embodiment, the initially designed aperture curve and deformation distribution further include: The moving coordinates are The angle position GX is calculated using the following formula: GX= *360° (3) Among them, L X X is the distance from position 0 to the calculated position x, in mm; DR is the pitch circle diameter of the pinion on the roll shaft; and GX is the angle of the calculated section position.
[0064] The following is an explanation through specific examples.
[0065] like Figure 3 As shown, Figure 3 This is a curve diagram of the deformed cone and the top of the die after rolling.
[0066] The pass profile and deformation distribution in this application are specifically designed for Pilger rolling of bars. A key feature is that when calculating the outer diameter (pass profile top diameter), the inner diameter and wall thickness are not considered; only the following coefficients are given, and the pass profile top diameter D is calculated according to the formula in this application. XK .
[0067] Then, the top diameter D of the hole is calculated according to the above formula (1). XK Then, the groove depth TX is calculated based on formula (2).
[0068] Then, according to formula (3), the moving coordinate in the hole design is... Calculation of the angle position GX.
[0069] For the top diameter D of the hole XK The depth TX of the roll pass and the angular position GX are calculated as follows: The calculation formula is as follows: D X K=D F +C X (D L -D F -Z)+ (Z)+n X (l a ); In the formula: D X K — The diameter of the top of the hole at position x in the calculation section.
[0070] C X — Shape factor of the aperture, C X =( ) EXP1 .
[0071] — Calculate the dynamic coordinates of section x relative to point 0.
[0072] L k —The length of the deformed section needs to be adjusted based on subsequent sample testing information.
[0073] EXP1—the characteristic index of the top curve variation of the roll pass (hereinafter referred to as the roll pass index) is determined by the characteristics of the rolled metal. The value of EXP1 is between 2.0 and 3.5.
[0074] D L —Outer diameter of the inlet billet.
[0075] D F —Outer diameter of the exported bar stock (rolled bar stock).
[0076] Z—The minimum taper of the hole required in the diametrical direction, expressed in mm, Z=β min * .
[0077] Where: β min — The minimum taper coefficient of the hole shape, expressed as a percentage. This value is an empirical coefficient related to the properties of the material to be processed (such as zirconium alloy rods), the size of the outer circle of the tooling hole, and the tooling material itself.
[0078] la——Inlet bar outer diameter and slot The gap in the diametrical direction between the top diameters at point =1 (see details). Figure 3 (Illustration in the image).
[0079] nX—la gap correction coefficient, nX= .
[0080] EXP2—an index reflecting the effect of the sum of the two gaps on the die profile (referred to as the gap index) is generally set to 2.0.
[0081] Based on the above calculation of the hole top diameter D XK The groove depth TX can then be calculated using the following formula: TX= ; In the formula, Sp represents the gap between modules (upper and lower hole types), such as... Figure 8 As shown.
[0082] For hole design, the moving coordinate is The angle position GX is calculated using the following formula: GX= *360°; In the formula: L X —that is, X from The distance (mm) between the position =0 and the calculated position; DR—Pitch circle diameter of the pinion on the roll shaft; GX — Angle for calculating the position of the cross section; To more clearly illustrate the specific process of the embodiments of the present invention, the embodiments of the present invention will be described in full.
[0083] For billet preparation, zirconium alloy rods of a certain length are selected as billets, and their dimensions are determined by the rolling process, such as... Figure 4 As shown, the diameter of the zirconium alloy rod used as the billet is D. L .
[0084] The billet is Pilger rolled using the designed die profile to obtain deformed cones and bars after rolling, such as... Figure 5 As shown.
[0085] The rolled deformed cone and its connected bars were dissected longitudinally and laterally to prepare samples of metal microstructure deformation and changes at different spatial locations, such as... Figure 6 As shown.
[0086] X-ray diffraction texture determination, hardness testing, and corrosion testing were performed on the longitudinal and transverse sections of the samples to determine the material microstructure texture plane and white core range throughout the entire spatial range during the deformation process of the billet into a bar. This allowed for the acquisition of information on grain orientation, metal deformation mechanism, and microstructure evolution. Figure 7 As shown.
[0087] As can be seen from the figure, the {100}{110} texture is distributed in a circumference from the center to about 60°. The white core of the tissue is defined as the difference in diffraction intensity between the core and the edge within 8%-30%.
[0088] Based on the evolution of the sample material's microstructure and the extent of the white core, L... k The length of the deformed section was adjusted and optimized; see [link to adjustment method] for details. Figure 2 As shown.
[0089] Through the optimized L k The length of the deformed section and the minimum taper Z of the hole are substituted back into formula (1) to calculate the top diameter D of the hole. XK Complete the design of the special die for bar stock and the distribution of deformation.
[0090] The groove depth TX is further calculated using formula (2), and the angular position GX is calculated using formula (3).
[0091] According to the adjusted and optimized D X Information such as K, groove depth TX, and angle position GX is used to create the die and allocate the deformation amount of each section. The billet is then rolled using Pilger rolling. After conventional processing such as degreasing and annealing, the white core of the low-magnification structure will be greatly improved.
[0092] This invention also provides a rolling fixture for improving the core quality of zirconium alloy bars, wherein the fixture is determined according to any of the methods described in the above embodiments.
[0093] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0094] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.
Claims
1. A rolling method for improving the core quality of zirconium alloy bars, characterized in that, include: Using the initially designed die profile and deformation distribution, the zirconium alloy rod billet was subjected to Pilger rolling to obtain the rolled deformed cone and rod. The deformed cone and the rod were dissected longitudinally and laterally according to a certain pattern to obtain samples of metal structure deformation and change at different spatial locations; Determine whether the white core range of the material texture surface of the entire spatial range of the sample meets the optimization conditions. The optimization conditions specifically include: along the direction from the billet to the rolled rod of the zirconium alloy rod, the surface texture is distributed within a circumference from the center to 60°, and the difference in diffraction intensity between the core and the edge is within 8%-30%. The length of the deformation section during the rolling of the zirconium alloy rod billet is adjusted and optimized, including: determining the secondary design of the die profile curve and deformation distribution based on the initially designed die profile curve and deformation distribution; specifically, determining the processing area L of the rolled deformation cone and rod based on the initially designed die profile curve and deformation distribution. k Adjust the processing area EL of the secondary design. k For the initial processing area L k 1 / 3 to 4 / 5 of the length; along the direction from coarse to thin in the processing area, at (2 / 3) L k The initial processing area L within and above k Within, adjust the minimum taper EZ of the secondary hole shape to 1-3 times the minimum taper Z of the initial hole shape, within (2 / 3) L k The initial processing area L outside k Internally, adjust the minimum taper EZ of the secondary hole shape to 1 / 4-3 / 4 of the minimum taper Z of the initial hole shape; Using the die profile curve and deformation distribution of the secondary design, the zirconium alloy rod billet is subjected to Pilger rolling to obtain the improved zirconium alloy rod.
2. The method according to claim 1, characterized in that, Also includes: According to the adjusted secondary design, the processing area EL k The value of the minimum taper EZ of the secondary hole is used to redetermine the top diameter D of the hole at the x-position of the cross section. X K, groove depth TX, and angle position GX information parameters; Based on the newly determined parameters, the hole pattern was remade and the deformation amount of each section was allocated.
3. The method according to claim 1, characterized in that, The initial design of the aperture curve and deformation distribution specifically includes: The diameter D of the top of the aperture is calculated using the following formula. XK : D XK =D F +C X (D L -D F -Z)+ (Z)+ n X (l a ); Among them, L k C is the length of the initially designed processing area. X The shape factor of the aperture is L. k Calculated Let x be the moving coordinate of the cross section relative to point 0, and D be the moving coordinate of the cross section. L D is the outer diameter of the billet of the zirconium alloy rod. F To determine the outer diameter of the rolled bar, Z is the minimum taper of the die required in the diameter direction, expressed in mm, based on L. k Calculations show that la is the outer diameter D of the zirconium alloy rod billet. L With the groove The gap in the diametrical direction between the top diameters at point =1, n X This is the gap correction coefficient for la.
4. The method according to claim 3, characterized in that, The C X The shape factor of the aperture is L. k The calculation is obtained using the following formula: C X =( ) EXP1； EXP1 is the characteristic index of the top curve variation of the roll pass (referred to as the roll pass index), which is determined based on the characteristics of the metal of the rolled material.
5. The method according to claim 4, characterized in that, The value of EXP1 ranges from 2.0 to 3.
5.
6. The method according to claim 3, characterized in that, Z is the minimum taper of the hole required in the diametrical direction, expressed in mm, according to L. k The calculation is obtained using the following formula: Z=β min* ； Where: β min It is the minimum taper coefficient of the hole type, expressed as a percentage.
7. The method according to claim 3, characterized in that, n X The calculation method is as follows: n X = ； EXP2 is the index of the effect of the sum of the two gaps on the hole profile curve (referred to as the gap index).
8. The method according to claim 7, characterized in that, The value of EXP2 is 2.
0.
9. The method according to claim 3, characterized in that, The initial design of the aperture curve and deformation distribution also includes: The formula for calculating the groove depth TX of the rolling pass is as follows: TX= ; Sp represents the gap between the upper and lower holes.
10. The method according to claim 3, characterized in that, The initial design of the aperture curve and deformation distribution also includes: The moving coordinates are The angle position GX is calculated using the following formula: GX= *360°; Among them, L X X is the distance from position 0 to the calculated position x, in mm; DR is the pitch circle diameter of the pinion on the roll shaft; and GX is the angle of the calculated section position.
11. A rolling tooling for improving the core quality of zirconium alloy bars, characterized in that, The tooling is the tooling determined by any one of claims 1-10.