Method for improving rolling quality of thin-wall cladding tube

Abstract

The invention discloses a method for improving the rolling quality of a thin-wall cladding tube, which comprises the following steps of: configuring a rolling tool mold and a tube blank; rolling a pipe blank by using the rolling tool mold to obtain a rolled cone in the rolling process; sampling is carried out on different positions of the rolling cone to obtain a plurality of sampling sections, and characteristic parameters of each sampling section are obtained; based on the multiple characteristic parameters, the deformation mechanism of the pipe blank in the rolling process is judged; according to the deformation mechanism, parameters of the rolling tool and mold are adjusted, and a new rolling tool and mold is formed; and the steps are repeated, and parameters of the rolling tool and mold are iteratively optimized. The rolling quality and performance of the zirconium alloy thin-wall cladding tube are improved, and therefore safe and reliable operation of a nuclear reactor is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of cold rolling, and in particular relates to a method for improving the rolling quality of a thin-wall clad tube. Background Art

[0002] Zirconium alloy cladding tubes are an important part of the fuel assembly of nuclear reactors and nuclear power plants. They contain fuel pellets and are the first barrier to ensure the safe and normal operation of nuclear reactors. Pilger cold rolling is widely used in the rolling of zirconium alloy cladding tubes due to its advantages of high dimensional accuracy, high surface quality and high yield rate.

[0003] However, if the rolling die design is unreasonable, the rolling quality will be reduced. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0005] The inventors realized that the ratio of wall thickness to outer diameter of thin-walled zirconium alloy cladding tubes for nuclear reactors is less than 1 / 30, and the tooling design ideas in the related art are mostly used for rolling thick-walled cladding tubes with a ratio of wall thickness to outer diameter of about 1 / 15. If the rolling tools are not optimized, the dimensional accuracy and surface quality of the tubes cannot be improved at the same time.

[0006] The inventors also realized that since Pilger cold rolling is a pressure process, the quality of the cladding tube is closely related to the size and distribution of the pressure during its rolling process. The smaller the wall thickness to outer diameter ratio of the finished tube, the greater the rolling pressure on the tube and the tool (hole type and core head). If the tool curve design is unreasonable, serious collisions and deformations may occur between the tools, resulting in reduced rolling quality, poor coaxiality, poor surface quality and other problems. Among them, coaxiality will affect the assembly of the fuel assembly, and the surface quality will affect the corrosion performance of the cladding tube in the high-temperature steam environment of the nuclear reactor.

[0007] To this end, an embodiment of the present invention provides a method for improving the rolling quality of a thin-walled cladding tube.

[0008] A method for improving the rolling quality of a thin-walled cladding tube according to an embodiment of the present invention comprises:

[0009] Configure rolling dies and tube blanks;

[0010] Rolling the tube blank using the rolling die to obtain a rolling cone during the rolling process;

[0011] Sampling different positions of the rolling cone to obtain a plurality of sampling sections, and obtaining characteristic parameters of each of the sampling sections;

[0012] Based on the plurality of characteristic parameters, determining the deformation mechanism of the tube blank during the rolling process;

[0013] According to the deformation mechanism, adjusting the parameters of the rolling die and forming a new rolling die;

[0014] Repeat the above steps to iteratively optimize the parameters of the rolling tool and die.

[0015] The embodiment of the present invention improves the rolling quality and performance of the zirconium alloy thin-wall cladding tube by redesigning the rolling die, thereby ensuring the safe and reliable operation of the nuclear reactor.

[0016] In some embodiments, sampling different positions of the rolling cone to obtain multiple sampling sections includes:

[0017] The rolling cone is divided into sections along the rolling direction and cut into a plurality of rolling sections;

[0018] Each of the rolling sections is cut to obtain a sampling section.

[0019] In some embodiments, the characteristic parameters include the metallographic structure of the sampling segment, the surface morphology of the sampling segment, and the mechanical properties and corrosion properties of the sampling segment.

[0020] In some embodiments, judging the deformation mechanism of the tube during the rolling process based on the plurality of characteristic parameters includes:

[0021] Based on the metallographic structure and surface morphology of the plurality of sampling sections, the distribution and evolution law of the internal grains of the tube billet during the rolling process are obtained;

[0022] Based on the metallographic structure of each sampling section and the mechanical properties and corrosion properties measured for each sampling section, a corresponding relationship between the metallographic structure and the mechanical properties and corrosion properties is established;

[0023] Establish the metallographic deformation mechanism of the tube billet during rolling, as well as the deformation mechanism of mechanical properties and corrosion properties.

[0024] In some embodiments, the surface topography includes any one or more of outer dimensions, straightness, roundness, and surface defects;

[0025] And / or, the mechanical properties are obtained by any one or more methods including pressure sensor and finite element simulation.

[0026] In some embodiments, adjusting the parameters of the rolling tool and die according to the deformation mechanism and forming a new rolling tool and die comprises:

[0027] Obtaining initial parameters of rolling dies;

[0028] According to the deformation mechanism, some initial parameters of the rolling tool are adjusted;

[0029] Based on the adjusted parameters, other initial parameters are adjusted to optimize the rolling tool curve;

[0030] A new rolling tool is produced based on all adjusted parameters.

[0031] In some embodiments, the parameters of the rolling tool and die include hole parameters and core head parameters;

[0032] The hole parameters and core head parameters of the rolling die satisfy the following formula:

[0033]

[0034]

[0035] SBK=q*d*n m ;

[0036]

[0037] Among them, D x K is the outer diameter of the groove bottom at section X in the rolling direction;

[0038] D F It is the outer diameter of the rolled tube;

[0039] C x is the hole shape factor;

[0040] D L is the outer diameter of the tube;

[0041] Z is the minimum taper of the hole in the diameter direction;

[0042] l i It is the gap between the inner diameter of the tube and the outer diameter of the core head in the diameter direction at the entrance of the hole;

[0043] The section X is of length L. K The moving coordinates on the deformation segment, L K is the length of the deformation section, and the hole outlet Hole entrance

[0044] n X is the clearance correction factor;

[0045] l a It is the gap in the diameter direction between the outer diameter of the tube and the bottom of the hole groove at the entrance of the hole;

[0046] EXP1 is the hole type index;

[0047] β min is the minimum taper of the hole expressed in %;

[0048] EXP2 is the gap index;

[0049] D X D is the core diameter at section X;

[0050] d F is the inner diameter of the finished pipe;

[0051] c x is the core shape factor;

[0052] d L is the inner diameter of the tube;

[0053] z is the minimum taper of the core head in the diameter direction;

[0054] SBK is the elastic rebound of the core head in the diameter direction;

[0055] EXP3 is the core index, which is determined by the characteristics of the billet metal;

[0056] α min is the minimum taper of the core expressed in %;

[0057] q is the core head Unit pressure on the space;

[0058] d is the core head The diameter at

[0059] n m is the first correction factor;

[0060] T X is the groove depth of the hole type;

[0061] Sp is the gap between the upper and lower hole profiles;

[0062] G X The moving coordinates are Section X to the hole outlet The center angle of the arc on the hole pitch circle corresponding to the line segment between them;

[0063] L X The moving coordinates are Section X to the hole outlet The distance between

[0064] D R It is the pitch diameter of the gear on the roll shaft.

[0065] In some embodiments, ExP1 is 2.0 to 3.5;

[0066] EXP2 is 2.0;

[0067] EXP3: 1.7 to 3.5;

[0068] n m 0.4 to 1.0.

[0069] In some embodiments, the step is to adjust some initial parameters of the rolling tool and die according to the deformation mechanism, and the adjusted hole parameters include the length of the deformation section of the hole, the minimum taper of the hole and the gap between the upper and lower hole types, and the adjusted core head parameters include the minimum taper of the core head.

[0070] In some embodiments, the ratio of the length of the deformation section of the hole profile after adjustment to the length of the deformation section of the hole profile before adjustment is 1.2 to 2.5, the ratio of the minimum taper of the hole profile after adjustment to the minimum taper of the hole profile before adjustment is 0.5 to 0.8, the ratio of the gap between the upper and lower hole profiles after adjustment to the gap between the upper and lower hole profiles before adjustment is 0 to 5; the ratio of the minimum taper of the core head after adjustment to the minimum taper of the core head before adjustment is 0.5 to 0.8. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 The present invention is a flowchart of a method for improving the rolling quality of a thin-walled cladding tube according to an embodiment of the present invention.

[0072] Figure 2 2 is a cross-sectional view of a rolling cone in an embodiment of the present invention.

[0073] Figure 3 It is a schematic diagram of the working status of the core head, rollers and tube blank in an embodiment of the present invention.

[0074] Serial number in the picture:

[0075] 1. Tube blank;

[0076] 2. Core head;

[0077] 3. Roller. DETAILED DESCRIPTION

[0078] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0079] In the embodiment of the present invention, a rolling die made according to the existing design concept is selected to roll the tube blank. At this time, the quality of the rolled tube is poor and there are many defects. The size range, straightness, roundness and surface defects are observed macroscopically, and correspond to the surface defects on the corresponding rolling die. The metallographic structure of different transverse / longitudinal sections at different positions is observed microscopically to obtain the deformation mechanism such as the grain orientation information, deformation process and organizational evolution law of the tube during rolling, and then adjust the design parameters of the original rolling die according to the obtained deformation mechanism, and realize the design and optimization of the die curve through multiple iterations.

[0080] like Figure 1 and Figure 2 Specifically, the method for improving the rolling quality of thin-walled cladding tube according to an embodiment of the present invention includes:

[0081] S101. Configure rolling dies and tube blanks.

[0082] S102, rolling the tube blank using a rolling die to obtain a rolling cone during the rolling process.

[0083] S103, sampling different positions of the rolling cone to obtain multiple sampling sections, and obtaining characteristic parameters of each sampling section.

[0084] S104. Determine the deformation mechanism of the tube billet during the rolling process based on multiple characteristic parameters.

[0085] S105. According to the deformation mechanism, the parameters of the rolling die are adjusted and a new rolling die is formed.

[0086] S106, repeat the above steps to iteratively optimize the parameters of the rolling tool and die.

[0087] The rolling die in step S101 is a rolling die made with the design ideas in the relevant technology. When it is used for rolling zirconium alloy thin-walled cladding tubes, the quality and performance of the rolled zirconium alloy thin-walled cladding tubes will be poor, and the quality and performance requirements of zirconium alloy thin-walled cladding tubes of nuclear reactors cannot be met. Therefore, the embodiment of the present invention adopts the rolling die made with the existing design ideas to roll the tube blank, samples the rolling cone section between the tube blank and the finished tube, analyzes the deformation mechanism of the tube blank during the rolling process, and optimizes the rolling die.

[0088] Since the tube billet needs to be deformed by pressure processing during rolling into finished tubes, when the curve design of the rolling tool and die is unreasonable, the rolling quality will be reduced, the force between the tool and die will be unstable, and even collision or deformation will occur. The embodiment of the present invention samples different positions of the rolling cone, analyzes the characteristic parameters of each sampling section, and obtains the deformation mechanism during the process of rolling the tube billet into the finished tube, so as to better find out the factors affecting the quality and performance, and then reasonably optimize the rolling tool and die.

[0089] The embodiment of the present invention uses multiple iterations of optimization until the quality and performance of the zirconium alloy thin-walled cladding tube produced by the optimized rolling die meet the requirements. The embodiment of the present invention provides an optimization design idea for the rolling die. By optimizing and designing the rolling die, a new rolling die is produced to improve the quality and performance of the zirconium alloy thin-walled cladding tube during the rolling process, and to ensure the safe and reliable operation of the nuclear reactor.

[0090] In some embodiments, sampling is performed at different positions of the rolling cone to obtain multiple sampling sections, including: segmenting the rolling cone along the rolling direction and cutting it into multiple rolling sections; cutting each rolling section to obtain sampling sections.

[0091] In the embodiment of the present invention, the rolling cone is divided into sections in the rolling direction, and each rolling section is further divided into multiple sampling sections. The rolling sections are ring-shaped, and each rolling section is divided into multiple sampling sections distributed along its circumference. At this time, the sampling sections at different axial and circumferential positions of the rolling cone can be analyzed to obtain their respective characteristic parameters. Combined with the position of each sampling section, the deformation mechanism in the process of gradually rolling the tube billet into the finished tube can be analyzed and judged, and the rolling tool and die curve of the corresponding section can be optimized in a targeted and reasonable manner, and the length of each section in the deformation section and the urgency of the curve are redistributed to ensure that the deformation amount is evenly distributed during the rolling of the tube billet and improve the stress condition of the rolling tool and die.

[0092] In some embodiments, the characteristic parameters include the metallographic structure of the sampling segment, the surface morphology of the sampling segment, the mechanical properties and the corrosion properties of the sampling segment.

[0093] The metallographic structure can reflect the specific morphology of the metal metallographic structure. By observing the metallographic structure of each sampling section, the grain structure of that position can be obtained, which in turn reflects its physical and chemical properties. By comparing the metallographic structures of multiple sampling sections, the grain orientation information, deformation process and organizational evolution law during the tube billet rolling process can be obtained.

[0094] The surface morphology can reflect the dimensional changes, surface defects, straightness, roundness and other characteristics of the rolling cone. It can also reflect the force stability of the tube billet during the rolling process and determine whether the circumferential extrusion force is balanced, thereby facilitating the adjustment of the design parameters of the rolling tooling.

[0095] Mechanical properties and corrosion properties are the main factors affecting the quality and performance of zirconium alloy thin-walled cladding tubes, and determine whether zirconium alloy thin-walled cladding tubes can ensure the safe and stable operation of nuclear reactors. Therefore, for the determination of mechanical properties and corrosion properties during the rolling process, the loss of mechanical properties and corrosion properties during the rolling process can be reduced by optimizing the rolling tools and dies to ensure product quality.

[0096] In some embodiments, the deformation mechanism of the tube billet during the rolling process is determined based on multiple characteristic parameters, including: obtaining the distribution and evolution law of the internal grains of the tube billet during the rolling process based on the metallographic structure and surface morphology of multiple sampling sections; establishing the corresponding relationship between the metallographic structure and the mechanical properties and corrosion properties based on the metallographic structure of each sampling section and the mechanical properties and corrosion properties measured for each sampling section;

[0097] Establish the metallographic deformation mechanism of the tube billet during rolling, as well as the deformation mechanism of mechanical properties and corrosion properties.

[0098] The embodiment of the present invention observes the metallographic structure of each sampling section and determines the distribution and evolution law of the metallographic structure of the pipe along the rolling direction in combination with the surface morphology quality of each sampling section to infer its deformation mechanism. By measuring the mechanical properties and corrosion properties of the pipe, a corresponding relationship between the metallographic structure and performance of the pipe is established. When adjusting parameters, multiple factors such as metallographic structure, surface morphology, mechanical properties and corrosion properties can be taken into account to improve the optimization effect of rolling tools and dies.

[0099] The embodiment of the present invention measures the mechanical properties and corrosion properties of the pipe for comparison to ensure that there is no loss in performance after the rolling quality is optimized; combines pressure sensors and finite element simulation to comprehensively determine the stress conditions of the rolling tools and dies during the rolling process, and develops a reasonable tool curve to make the force distribution of the tools and dies in the rolling direction more uniform and reduce its fluctuation with the rolling process, thereby improving the rolling quality of zirconium alloy pipes for nuclear reactors.

[0100] Furthermore, the surface morphology includes any one or more of outer dimensions, straightness, roundness, and surface defects.

[0101] The mechanical properties are obtained through room temperature / high temperature tensile tests and other methods.

[0102] In some embodiments, according to the deformation mechanism, adjusting the parameters of the rolling die and forming a new rolling die includes:

[0103] Obtain the initial parameters of the rolling tool and die. Obtain the design parameters of the rolling tool and die based on the original design ideas, so as to continuously optimize the rolling tool and die based on the design parameters and improve the performance and quality of the rolled pipe.

[0104] According to the deformation mechanism, some initial parameters of the rolling die are adjusted.

[0105] Based on the adjusted parameters, other initial parameters are adjusted to optimize the rolling tool and die curve. When optimizing the initial parameters, the embodiment of the present invention first determines multiple parameters that can affect the metallographic structure, surface morphology, mechanical properties and corrosion properties during the tube billet rolling process, first adjusts and optimizes the multiple parameters, and then synchronously optimizes and designs other parameters of the rolling tool and die based on the parameters.

[0106] A new rolling tool is produced based on all adjusted parameters.

[0107] After the initial parameters are adjusted, new rolling dies are made using the new design parameters.

[0108] Furthermore, in order to achieve the ideal requirements, the embodiments of the present invention need to perform multiple iterations of optimization on the parameters of the rolling tool and die to achieve the ultimate goal.

[0109] In the actual application process, the rolling die curve is designed for zirconium alloy thin-walled cladding tubes, the curvature of the curve in each deformation stage is reasonably distributed, and the fluctuation of the rolling force in each stage is reduced by adjusting the deformation amount in each stage.

[0110] By selecting tube blanks with certain size and surface quality, Pilger cold rolling is carried out using rolling dies designed with thick-walled tube ideas to obtain rolling cones and rolled tubes.

[0111] Take cross-section and longitudinal section samples at different positions on the rolling cone to observe the metallographic structure. Observe the metallographic structure and determine the distribution and evolution of the metallographic structure of the pipe along the rolling direction in combination with the surface quality to infer its deformation mechanism, measure the mechanical properties and corrosion properties of the pipe, and establish a corresponding relationship.

[0112] According to the deformation mechanism obtained, the curve of the rolling die (pass and core head) was redesigned, the length of each deformation section of the pass and the distribution of deformation amount were optimized, and the core head curve and taper were optimized to obtain a new rolling die suitable for Pilger cold rolling of thin-walled tubes. Multiple iterations of optimization were performed to obtain the final rolling die.

[0113] The final rolling dies were used for Pilger cold rolling, and the size and surface quality of the rolled pipes were greatly improved. The force on the dies was more uniform, and the bumping phenomenon was reduced.

[0114] In some embodiments, the parameters of the rolling tool and die include hole parameters and core head parameters.

[0115] According to the given coefficient and a certain calculation formula, the hole outer diameter and core head diameter at different positions along the rolling direction are calculated, and then half of the difference between the two values ​​is taken as the wall thickness.

[0116] The hole parameters of the rolling die satisfy the following formula:

[0117]

[0118]

[0119] Among them, D X K is the outer diameter of the groove bottom at section X in the rolling direction;

[0120] D F It is the outer diameter of the rolled tube;

[0121] C X is the hole shape factor;

[0122] D L is the outer diameter of the tube;

[0123] Z is the minimum taper of the hole in the diameter direction;

[0124] l i It is the gap between the inner diameter of the tube and the outer diameter of the core head in the diameter direction at the entrance of the hole. When the thin-walled tube is rolled, l i is a smaller value;

[0125] The section X is of length L. K The moving coordinates on the deformation segment;

[0126] L K is the length of the deformation section, and the hole outlet Hole entrance

[0127] n X is the clearance correction factor;

[0128] l a It is the gap in the diameter direction between the outer diameter of the tube and the bottom of the hole groove at the entrance of the hole;

[0129] EXP1 is the hole index, which is determined by the characteristics of the billet metal;

[0130] β min is the minimum taper of the hole expressed in %;

[0131] EXP2 is the gap index.

[0132] The core head parameters of the rolling die satisfy the following formula:

[0133]

[0134] SBK=q*d*n m ;

[0135] Among them, D X D is the core diameter at section X;

[0136] d F is the inner diameter of the finished pipe;

[0137] C X is the core shape factor;

[0138] d L is the inner diameter of the tube;

[0139] Z is the minimum taper of the core head in the diameter direction;

[0140] SBK is the elastic rebound of the core head in the diameter direction;

[0141] EXP3 is the core index, which is determined by the characteristics of the billet metal;

[0142] α min is the minimum taper of the core expressed in %;

[0143] q is the core head Unit pressure on the space;

[0144] d is the core head The diameter at

[0145] n m is the first correction factor.

[0146] Furthermore, the hole type also satisfies the following formula:

[0147]

[0148] Among them, T X is the groove depth of the pass, i.e. the depth of the roll groove of the roll;

[0149] Sp is the gap between the upper and lower hole profiles;

[0150] G X The moving coordinates are Section X to the hole outlet The center angle of the arc on the hole pitch circle corresponding to the line segment between them;

[0151] L X The moving coordinates are Section X to the hole outlet The distance between

[0152] D R It is the pitch diameter of the gear on the roll shaft.

[0153] In the embodiment of the present invention, the formula β min is the minimum taper of the hole expressed in %, that is, it is obtained by the ratio of the two dimensions, while Z is the taper β expressed in ratio min Multiply The obtained L K is the length of the deformation segment, so L K The unit is the same as that of Z, both can be mm. Z is used to represent the minimum taper of the hole in the diameter direction, which facilitates the calculation of hole parameters.

[0154] Similarly, in the embodiment of the present invention, the formula α in min is the minimum taper of the core expressed in %, that is, obtained by the ratio of the two dimensions, while z is the taper α expressed in ratio min Multiply The obtained L K is the length of the deformation segment, so L K The unit is the same as z, both can be mm. z is used to represent the minimum taper of the core head in the diameter direction, which facilitates the calculation of the core head parameters.

[0155] like Figure 3 As shown, the pilger rolling adopted in the embodiment of the present invention is a round hole type, and its specific working principle is that the core head is sleeved inside the tube blank to control the inner diameter of the formed tube, and the two rollers are distributed up and down, and the tube is formed by reciprocating rolling. At the rear limit position, the hole diameter formed by the grooves of the two rollers is the same as the outer diameter of the tube blank, and at the front limit position, the hole diameter formed by the grooves of the two rollers is the same as the outer diameter of the finished tube. In the front and rear rotating sections, the tube must be rotated by a certain angle to ensure the roundness of the cross-section. The deformation section and the finishing section are the main working sections, which are responsible for size forming and rounding respectively. One reciprocating motion is a cycle, which is divided into a positive stroke (from the rear limit position to the front limit position) and a reverse stroke (from the front limit position to the rear limit position), and it is only fed once in one cycle.

[0156] Figure 3 In the figure, L1 is the front rotation section, L2 is the finishing section, L3 is the rear rotation section, M is the rear limit position, and N is the front limit position.

[0157] Since the hole motion mode is rolling (i.e. roller rolling), the action mark is Section X and hole type outlet The line segment between (length L X ) can correspond to an arc on the hole pitch circle, and the length of the arc is also L X , G X It represents the central angle of the arc.

[0158] The relevant coefficients and exponents in the embodiment of the present invention are used to correct and adjust the formula to more accurately reflect the time situation, eliminate data deviations, and improve the reliability and accuracy of the calculation results.

[0159] Further, EXP1 is 2.0 to 3.5; EXP2 is 2.0; EXP3 is 1.7 to 3.5; n m 0.4 to 1.0.

[0160] For example, EXP1 is 2.0, 2.1, 2.3, 2.75, 2.96, 3.2, or 3.5.

[0161] For example, EXP31.7, 2.21, 2.43, 2.75, 2.96, 3.2 or 3.5.

[0162] For example, n m It is 0.4, 0.47, 0.57, 0.8, 0.92 or 1.0.

[0163] The selection of the above specific parameters is determined according to the selected tube blank material.

[0164] In some embodiments, the step is to adjust some initial parameters of the rolling tool and die according to the deformation mechanism, and the adjusted hole parameters include the length of the deformation section of the hole, the minimum taper of the hole and the gap between the upper and lower hole types, and the adjusted core head parameters include the minimum taper of the core head.

[0165] It should be understood that after determining the deformation mechanism during the tube rolling process, the length of the deformation section of the hole, the minimum taper of the hole, the gap between the upper and lower holes, and the minimum taper of the core head are adjusted, and then the adjusted length of the deformation section of the hole, the minimum taper of the hole, the gap between the upper and lower holes, and the minimum taper of the core head are substituted into the above formula to obtain the hole outer diameter D X K, core diameter D X D. Groove depth T X 、Central angle G X And other parameters, and according to the redistribution of the deformation of the support, a new hole shape and core head are produced.

[0166] Furthermore, the ratio of the length of the deformation section of the hole after adjustment to the length of the deformation section of the hole before adjustment is 1.2 to 2.5, the ratio of the minimum taper of the hole after adjustment to the minimum taper of the hole before adjustment is 0.5 to 0.8, the ratio of the gap between the upper and lower hole profiles after adjustment to the gap between the upper and lower hole profiles before adjustment is 0 to 5; the ratio of the minimum taper of the core head after adjustment to the minimum taper of the core head before adjustment is 0.5 to 0.8. By setting a reasonable adjustment interval, iterative optimization can be more effectively achieved, the effect of iterative optimization can be improved, and the number of iterative optimization can be reduced.

[0167] After the new rolling tool and die are manufactured, the embodiment of the present invention selects a qualified tube blank, uses the newly designed hole type and mandrel to perform rolling, and observes its surface quality and dimensional condition.

[0168] After several iterations of optimization, the design of the hole profile and core head for zirconium alloy cladding tubes (thin-walled tubes) for nuclear reactors was completed. The surface quality and dimensional stability of the zirconium alloy tubes rolled with the new hole profile and core head have been significantly improved.

[0169] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0170] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0171] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0172] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0173] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0174] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for improving the rolling quality of thin-walled cladding tubes, characterized in that: include: Configure rolling dies and tube blanks; Rolling the tube blank using the rolling die to obtain a rolling cone during the rolling process; Sampling different positions of the rolling cone to obtain a plurality of sampling sections, and obtaining characteristic parameters of each of the sampling sections; Based on the plurality of characteristic parameters, determining the deformation mechanism of the tube blank during the rolling process; According to the deformation mechanism, adjusting the parameters of the rolling die and forming a new rolling die; Repeat the above steps to iteratively optimize the parameters of the rolling tool and die.

2. The method for improving the rolling quality of thin-walled cladding tube according to claim 1, characterized in that: The method of sampling different positions of the rolling cone to obtain a plurality of sampling sections comprises: The rolling cone is divided into sections along the rolling direction and cut into a plurality of rolling sections; Each of the rolling sections is cut to obtain a sampling section.

3. The method for improving the rolling quality of thin-walled cladding tube according to claim 1, characterized in that: The characteristic parameters include the metallographic structure of the sampling section, the surface morphology of the sampling section, and the mechanical properties and corrosion properties of the sampling section.

4. The method for improving the rolling quality of thin-walled cladding tube according to claim 3, characterized in that: The step of determining the deformation mechanism of the tube billet during the rolling process based on the plurality of characteristic parameters includes: Based on the metallographic structure and surface morphology of the plurality of sampling sections, the distribution and evolution law of the internal grains of the tube billet during the rolling process are obtained; Based on the metallographic structure of each sampling section and the mechanical properties and corrosion properties measured for each sampling section, obtaining a corresponding relationship between the metallographic structure and the mechanical properties and corrosion properties; Establish the metallographic deformation mechanism of the tube billet during rolling, as well as the deformation mechanism of mechanical properties and corrosion properties.

5. The method for improving the rolling quality of thin-walled cladding tube according to claim 3, characterized in that: The surface morphology includes any one or more of outer dimensions, straightness, roundness, and surface defects; And / or, the mechanical properties are obtained by any one or more methods including pressure sensor and finite element simulation.

6. The method for improving the rolling quality of thin-walled cladding tube according to any one of claims 1 to 5, characterized in that: The step of adjusting the parameters of the rolling die and forming a new rolling die according to the deformation mechanism comprises: Obtaining initial parameters of rolling dies; According to the deformation mechanism, some initial parameters of the rolling tool are adjusted; Based on the adjusted parameters, other initial parameters are adjusted to optimize the rolling tool curve; A new rolling tool is produced based on all adjusted parameters.

7. The method for improving the rolling quality of thin-walled cladding tube according to claim 6, characterized in that: The parameters of the rolling die include hole parameters and core head parameters; The hole parameters and core head parameters of the rolling die satisfy the following formula: <h2 style=";text-align:left;direction:ltr">SBK=q*d*n<h2 style=";text-align:left;direction:ltr"> m <h2 style=";text-align:left;direction:ltr"> ; Among them, D X K is the outer diameter of the groove bottom at section X in the rolling direction; D F It is the outer diameter of the rolled tube; C X is the hole shape factor; D L is the outer diameter of the tube; Z is the minimum taper of the hole in the diameter direction; l i It is the gap between the inner diameter of the tube and the outer diameter of the core head in the diameter direction at the entrance of the hole; is the section X with a length of L K The moving coordinates on the deformation segment, L K is the length of the deformation section, and the hole outlet Hole entrance n X is the clearance correction factor; l a It is the gap in the diameter direction between the outer diameter of the tube and the bottom of the hole groove at the entrance of the hole; EXP1 is the hole type index; β min It is the minimum taper of the hole type expressed in %; EXP2 is the gap index; D X D is the core diameter at section X; d F is the inner diameter of the finished pipe; c X is the core shape factor; d L is the inner diameter of the tube; z is the minimum taper of the core head in the diameter direction; SBK is the elastic rebound of the core head in the diameter direction; EXP3 is the core index; α min is the minimum taper of the core expressed in %; q is the core head Unit pressure on the space; d is the core head The diameter at n m is the first correction factor; T X is the groove depth of the hole type; Sp is the gap between the upper and lower hole profiles; G X The moving coordinates are Section X to the hole outlet The center angle of the arc on the hole pitch circle corresponding to the line segment between them; L X The moving coordinates are Section X to the hole outlet The distance between D R It is the pitch diameter of the gear on the roll shaft.

8. The method for improving the rolling quality of thin-walled cladding tube according to claim 7, characterized in that: EXP1 is 2.0 to 3.5; EXP2 is 2.0; EXP3: 1.7 to 3.5; n m 0.4 to 1.

0.

9. The method for improving the rolling quality of thin-walled cladding tube according to claim 7 or 8, characterized in that: The step is to adjust some initial parameters of the rolling tool and die according to the deformation mechanism, wherein the adjusted hole parameters include the length of the deformation section of the hole, the minimum taper of the hole and the gap between the upper and lower holes, and the adjusted core head parameters include the minimum taper of the core head.

10. The method for improving the rolling quality of thin-walled cladding tube according to claim 9, characterized in that: The ratio of the length of the deformation section of the hole profile after adjustment to the length of the deformation section of the hole profile before adjustment is 1.2 to 2.5, the ratio of the minimum taper of the hole profile after adjustment to the minimum taper of the hole profile before adjustment is 0.5 to 0.8, the ratio of the gap between the upper and lower hole profiles after adjustment to the gap between the upper and lower hole profiles before adjustment is 0 to 5; the ratio of the minimum taper of the core head after adjustment to the minimum taper of the core head before adjustment is 0.5 to 0.8.

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