CN112846228B - Selective laser melting forming method for supporting-free local lower tube seat of nuclear fuel assembly - Google Patents

Selective laser melting forming method for supporting-free local lower tube seat of nuclear fuel assembly Download PDF

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Publication number
CN112846228B
CN112846228B CN202011625253.XA CN202011625253A CN112846228B CN 112846228 B CN112846228 B CN 112846228B CN 202011625253 A CN202011625253 A CN 202011625253A CN 112846228 B CN112846228 B CN 112846228B
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fuel assembly
nuclear fuel
tube seat
lower tube
printing
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CN112846228A (en
Inventor
秦国鹏
张丽英
佟鑫
黄玉山
胡正正
尹富斌
陈仲权
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Guangzhou Xinyanjin Additive Technology Co ltd
China Jianzhong Nuclear Fuel Co Ltd
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Guangzhou Xinyanjin Additive Technology Co ltd
China Jianzhong Nuclear Fuel Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/24—After-treatment of workpieces or articles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y10/00—Processes of additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
    • B33Y40/20—Post-treatment, e.g. curing, coating or polishing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y80/00—Products made by additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/24—After-treatment of workpieces or articles
    • B22F2003/245—Making recesses, grooves etc on the surface by removing material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/24—After-treatment of workpieces or articles
    • B22F2003/247—Removing material: carving, cleaning, grinding, hobbing, honing, lapping, polishing, milling, shaving, skiving, turning the surface
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/24—After-treatment of workpieces or articles
    • B22F2003/248—Thermal after-treatment
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/30—Nuclear fission reactors

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Laser Beam Processing (AREA)

Abstract

The invention particularly relates to a selective laser melting forming method for a nuclear fuel assembly local lower tube seat free of supporting, which comprises the following steps: forming auxiliary entities by laser melting in a selected area on the square side surface of a printing model of a local lower tube seat of the nuclear fuel assembly; dividing the nuclear fuel assembly partial lower tube seat printing model into an upper part of the nuclear fuel assembly partial lower tube seat printing model and a lower part of the nuclear fuel assembly partial lower tube seat printing model by using a parting surface; respectively selecting laser melting to form the lower part of the partial lower tube seat printing piece of the nuclear fuel assembly and the upper part of the partial lower tube seat printing piece of the nuclear fuel assembly by taking the parting surface as an initial printing surface; and removing the auxiliary entity of the printed part of the partial lower tube seat of the nuclear fuel assembly to obtain the partial lower tube seat of the nuclear fuel assembly. The method provided by the invention can be used for rapidly preparing the local lower tube seat of the pressurized water reactor nuclear fuel assembly, and realizes the integral molding of the local lower tube seat, wherein the manufacturing period is less than or equal to 70h, and the material utilization rate is more than 99.0%.

Description

Selective laser melting forming method for supporting-free local lower tube seat of nuclear fuel assembly
Technical Field
The invention relates to the technical field of nuclear power fuel element manufacturing, in particular to a selective laser melting forming method of a local lower tube seat of a nuclear fuel assembly.
Background
The existing lower tube seat of the pressurized water reactor nuclear fuel assembly is mainly manufactured by mechanical milling of sectional materials, subsequent welding and finish machining. The CF3 lower tube seat is one of key components of the Hualong No. 1 nuclear fuel assembly, and mainly has the functions of positioning the in-pile position of the fuel assembly, positioning the guide tube and the central tube, supporting the weight of the fuel assembly and filtering foreign matters and scraps in the pile. Referring to fig. 1-3, the cf3 lower tube seat adopts an integrated chip-proof plate design, the filtering flow passage adopts a space curved surface, the structure is precise and complex, and the manufacturing difficulty is high. The number of the CF3 lower tube seat parts is up to 106, and the traditional machining process is adopted, so that the working procedures are more, the production period is long, the product assembling and welding difficulty is high, the rejection rate is high, and the production cost is high.
Referring to fig. 4, the space curved surface chip-preventing plate part of the CF3 lower tube seat is also called as the CF3 local lower tube seat, and is prepared by adopting a selective laser melting forming technology, 105 parts of the original tube seat are integrally formed and printed, so that the problems of complex working procedures and low material utilization rate of the traditional processing technology can be solved, the preparation efficiency is improved, and the raw material utilization rate can reach more than 99%. Referring to fig. 5-6, because the upper end face and the lower end face of the CF3 partial lower tube seat have uneven rib structures which are crisscrossed, if the support is difficult to avoid by adopting the traditional selective laser melting forming technology, the surface quality and the post-treatment of the part are greatly affected.
Disclosure of Invention
Based on the above, it is necessary to provide a selective laser melting forming method of a local lower tube seat of a nuclear fuel assembly, which is necessary to solve the problem that the traditional selective laser melting forming needs to be supported and greatly affects the surface quality and post-treatment of the parts.
In order to achieve the above object, the present invention provides the following technical solutions:
a selective laser melting forming method for a partial lower tube seat of a nuclear fuel assembly without supporting comprises the following steps:
step one, selecting a local lower tube seat printing model of the laser melting forming nuclear fuel assembly, and integrating a selected laser melting forming auxiliary entity on the square side surface of the local lower tube seat printing model of the nuclear fuel assembly;
dividing a nuclear fuel assembly local lower tube seat printing model into an upper part of the nuclear fuel assembly local lower tube seat printing model and a lower part of the nuclear fuel assembly local lower tube seat printing model by using a parting surface, wherein the part of the nuclear fuel assembly local lower tube seat printing model above the parting surface is the upper part of the nuclear fuel assembly local lower tube seat printing model, and the part of the nuclear fuel assembly local lower tube seat printing model below the parting surface is the lower part of the nuclear fuel assembly local lower tube seat printing model;
respectively selecting laser melting to form the lower part of the partial lower tube seat printing piece of the nuclear fuel assembly and the upper part of the partial lower tube seat printing piece of the nuclear fuel assembly by taking the parting surface as an initial printing surface to obtain the partial lower tube seat printing piece of the nuclear fuel assembly;
removing auxiliary entities of the printed part of the partial lower tube seat of the nuclear fuel assembly, and processing square side surfaces of the printed part of the partial lower tube seat of the nuclear fuel assembly to be flat to obtain the partial lower tube seat of the nuclear fuel assembly;
and thirdly, the lower part of the nuclear fuel assembly local lower tube seat printing piece and the upper part of the nuclear fuel assembly local lower tube seat printing piece are formed by taking the upper part of the nuclear fuel assembly local lower tube seat printing model and the lower part of the nuclear fuel assembly local lower tube seat printing model as template selective laser melting.
Further, the third step comprises the following steps:
1. accurately positioning, mounting and rigidly fixing a printing substrate on laser printing equipment;
2. forming the lower part of a local lower tube seat printing piece of the nuclear fuel assembly by selective laser melting on the printing substrate;
3. removing the rigidity limit of the printing substrate, performing vacuum heat treatment and double-sided grinding on the lower part of the printing piece of the local lower tube seat of the nuclear fuel assembly and the printing substrate, respectively processing counter bores and positioning holes on the lower part of the printing piece of the local lower tube seat of the nuclear fuel assembly and the printing substrate, and tapping internal threads in the counter bores;
4. cutting the lower part of a printing piece of a local lower tube seat of the nuclear fuel assembly from a printing substrate, and processing a counter bore on the cutting surface after the cutting surface is ground;
5. accurately positioning, mounting and rigidly fixing the printing substrate on the laser printing equipment; the lower part of the nuclear fuel assembly partial lower tube seat printing piece is arranged on the printing substrate through the cooperation of the screw and the locating pin, and the installation needs to ensure that the cutting surface of the lower part of the nuclear fuel assembly partial lower tube seat printing piece faces upwards;
6. forming the upper part of the partial lower tube seat printing piece of the nuclear fuel assembly by selective laser melting on the cutting surface of the lower part of the partial lower tube seat printing piece of the nuclear fuel assembly to obtain the partial lower tube seat printing piece of the nuclear fuel assembly;
7. performing vacuum heat treatment on the local lower tube seat printing piece of the nuclear fuel assembly and the printing substrate;
8. unloading the positioning pins and the screws which are connected with the partial lower tube seat printing piece of the nuclear fuel assembly and the printing substrate, and taking down the partial lower tube seat printing piece of the nuclear fuel assembly;
9. removing auxiliary entities on the printed part of the partial lower tube seat of the nuclear fuel assembly by using a machining method, and machining four side surfaces of the printed part of the partial lower tube seat of the nuclear fuel assembly to be flat to obtain the partial lower tube seat of the nuclear fuel assembly;
and 4, the cutting surfaces in the step 5 and the step 6 are parting surfaces.
Further, forming a local lower tube seat printing model of the nuclear fuel assembly by selective laser melting, and forming 3 auxiliary entities on each side surface of the local lower tube seat printing model of the nuclear fuel assembly by integral selective laser melting; the maximum outline of the auxiliary entity does not exceed the outline of the printing substrate, and the thickness direction of the auxiliary entity is flush with the entity on the upper part of the nuclear fuel assembly partial lower tube seat printing model or the entity on the lower part of the nuclear fuel assembly partial lower tube seat printing model.
Further, the parting surface is positioned in the middle of the printing model of the partial lower tube seat of the nuclear fuel assembly and is parallel to the bottom surface of the printing model of the partial lower tube seat of the nuclear fuel assembly; the parting surface is a plane with the smallest area and respectively connected with the upper part of the nuclear fuel assembly partial lower tube seat printing model and the lower part of the nuclear fuel assembly partial lower tube seat printing model, and the upper part of the nuclear fuel assembly partial lower tube seat printing part and the lower part of the nuclear fuel assembly partial lower tube seat printing part can be formed by selective laser melting on the parting surface without design support.
Further, the printing substrates in step 1 and step 5 are the same printing substrate, two positioning holes are machined in the printing substrate in advance, and the printing substrate is accurately positioned and mounted on the laser printing device through the cooperation of the positioning holes of the printing substrate and the positioning pins on the laser printing device. The upper part of the nuclear fuel assembly local lower tube seat printing piece and the lower part of the nuclear fuel assembly local lower tube seat printing piece are required to be used by selective laser melting, the printing substrate between the two forming needs to be installed and disassembled, and the position of the printing substrate, which is installed on the laser printing equipment for two times, can be kept unchanged through the positioning holes on the printing substrate.
Further, in the step 2, grinding allowance of 0.5mm is made on the upper surface of the lower part of the nuclear fuel assembly partial lower tube seat printing model, and linear cutting allowance of 0.8mm is made on the lower surface of the lower part of the nuclear fuel assembly partial lower tube seat printing model; and the parting surface is used as an initial printing surface to be formed at the lower part of the local lower tube seat printing piece of the nuclear fuel assembly by selective laser melting on the printing substrate.
Further, in step 3, the vacuum heat treatment process includes the following steps: placing a protective substrate on the upper surface of the lower part of the printing piece of the partial lower tube seat of the nuclear fuel assembly, and clamping and locking the lower part of the printing piece of the partial lower tube seat of the nuclear fuel assembly between the printing substrate and the protective substrate by using a universal clamping device; placing the lower parts of the printing substrate, the protective substrate and the nuclear fuel assembly partial lower tube seat printing piece into a vacuum heat treatment furnace together, wherein the pressure in the furnace is less than 1Pa, heating to 1050 ℃, preserving heat for 40min, cooling to room temperature along with the furnace, and taking out; the lock is released and the protective substrate is removed.
Further, in step 3, the double-sided grinding includes the following steps: the lower part of the printing piece of the local lower tube seat of the nuclear fuel assembly after heat treatment and the printing substrate are sent to a grinding machine for grinding; the lower plane of the printing substrate is firstly ground, then the upper surface of the lower part of the printing part of the local lower tube seat of the nuclear fuel assembly is ground, the grinding amount is not more than 0.1mm, and the planeness after grinding is not more than 0.04mm.
Further, in step 3, the processing of the counter bore and the positioning hole on the lower part of the printing piece of the local lower tube seat of the nuclear fuel assembly and the printing substrate, and the tapping of the internal thread in the counter bore, includes the following steps: machining a counter bore with the diameter of 14mm and the depth of 8mm on a hole position on the upper surface C1 of the lower part of a printing piece of a local lower tube seat of the nuclear fuel assembly, and tapping M8 standard threads on the corresponding position of a printing substrate; machining a counter bore with the diameter of 8mm and the depth of 6mm on a C2 hole on the upper surface of the lower part of a printing piece of a local lower tube seat of the nuclear fuel assembly, and tapping M4 standard threads on the corresponding position of a printing substrate; a positioning hole with the tolerance level of H7 is formed in the position of a D hole on the lower part of a printing piece of the local lower tube seat of the nuclear fuel assembly and the printing substrate, and the surface roughness is better than 1.6um; and the machining positioning precision of the threads and the positioning holes of the tap M4 is not more than 0.02mm.
Further, the step 4 specifically includes the following steps: cutting the lower part of the nuclear fuel assembly partial lower tube seat printing piece from the printing substrate by using linear cutting, and respectively grinding the cutting surfaces of the printing substrate and the lower part of the nuclear fuel assembly partial lower tube seat printing piece by using a grinding machine; the deviation between the height dimension of the lower part of the printed part of the local lower tube seat of the nuclear fuel assembly after grinding and the theoretical dimension is not more than +/-0.05 mm; processing a counter bore with the diameter of 14mm and the depth of 7mm at a C11 counter bore position of a cutting and grinding surface at the lower part of a local lower tube seat printing piece of the nuclear fuel assembly; and processing a counter bore with the diameter of 8mm and the depth of 6mm at a C21 counter bore position of a cutting and grinding surface at the lower part of the local lower tube seat printing piece of the nuclear fuel assembly.
Further, in step 5, the lower part of the partial lower tube seat printing part of the nuclear fuel assembly is mounted on the printing substrate by matching the screw and the positioning pin, and the mounting needs to ensure that the cutting surface of the lower part of the partial lower tube seat printing part of the nuclear fuel assembly faces upwards, which comprises the following steps: and (3) enabling the cutting surface of the lower part of the nuclear fuel assembly local lower tube seat printing piece to face upwards, enabling a positioning pin to pass through a positioning hole on the lower part of the printing piece of the nuclear fuel assembly local lower tube seat and fixedly connect the printing substrate with the lower part of the nuclear fuel assembly local lower tube seat printing piece, sequentially locking a screw by using a torque wrench, enabling the torque to be 21N/m, and firmly locking the lower part of the nuclear fuel assembly local lower tube seat printing piece on the printing substrate.
Further, step 6 includes the steps of: the method comprises the steps of using a cutting grinding surface of the lower part of a nuclear fuel assembly local lower tube seat printing piece as a printing substrate when the upper part of the nuclear fuel assembly local lower tube seat printing piece is formed by laser melting, directly forming the upper part of the nuclear fuel assembly local lower tube seat printing piece by selective laser melting on the cutting grinding surface of the lower part of the nuclear fuel assembly local lower tube seat printing piece, and observing whether the dislocation preventing mark is complete or not and has no dislocation in the selective laser melting forming process.
Further, the dislocation preventing mark is recessed or protruded to be at least more than 0.5mm, is arranged at two positions of the parting surface, and is divided into two parts after the laser melting forming of the whole selected area of the lower part of the nuclear fuel assembly local lower tube seat printing piece and the upper part of the nuclear fuel assembly local lower tube seat printing piece is finished.
Further, in step 7, the vacuum heat treatment process includes the following steps: placing a protective substrate on the upper surface of the upper part of the printing piece of the partial lower tube seat of the nuclear fuel assembly, and clamping and locking the printing piece of the partial lower tube seat of the nuclear fuel assembly between the protective substrate and the printing substrate by using a universal clamping device; placing the protective substrate, the printing substrate and the nuclear fuel assembly partial lower tube seat printing piece into a vacuum heat treatment furnace together, wherein the pressure in the furnace is less than 1Pa, heating to 1050 ℃, preserving heat for 40min, cooling to room temperature along with the furnace, and taking out; the lock is released and the protective substrate is removed.
Compared with the prior art, the invention has the beneficial technical effects that:
the selective laser melting forming method for the partial lower tube seat of the nuclear fuel assembly, which is provided by the invention, can be used for rapidly preparing the partial lower tube seat of the nuclear fuel assembly of the pressurized water reactor, realizing the integral forming of the partial lower tube seat, and has the manufacturing cycle of less than or equal to 70h and the material utilization rate of more than 99.0%.
Drawings
FIG. 1 is a schematic view of the exterior of a CF3 nuclear fuel assembly bottom nozzle;
FIG. 2 is a schematic cross-sectional view of the internal structure of the lower header of the CF3 nuclear fuel assembly;
FIG. 3 is an enlarged view of a portion of the space curvature of the bottom nozzle of the CF3 nuclear fuel assembly;
FIG. 4 is a schematic view of a partial bottom nozzle of a CF3 nuclear fuel assembly;
FIG. 5 is an enlarged view of a portion of the lower end face rib structure of a partial lower header of a CF3 nuclear fuel assembly;
FIG. 6 is a view of the upper end face of a partial lower header of a CF3 nuclear fuel assembly;
FIG. 7 is a schematic perspective view of a partial bottom nozzle print of a nuclear fuel assembly;
FIG. 8 is a schematic diagram of a parting plane position;
FIG. 9 is a schematic perspective view of a nuclear fuel assembly partial bottom header print upper portion and a nuclear fuel assembly partial bottom header print lower portion;
FIG. 10 is a diagram showing the effect of a laser melt-molding of a selected area of a lower portion of a partial bottom nozzle print of a nuclear fuel assembly;
FIG. 11 is a diagram showing the effect of the lower heat treatment clamping of a partial bottom nozzle print of a nuclear fuel assembly;
FIG. 12 is a schematic view of a nuclear fuel assembly partial bottom nozzle print lower portion and a print substrate tooling counterbore, threaded hole and locating hole;
FIG. 13 is a schematic illustration of the location of a lower tooling counterbore of a partial bottom nozzle print of a nuclear fuel assembly after being cut from a print substrate;
FIG. 14 is an assembly view of a nuclear fuel assembly prior to laser melt molding of selected areas of the upper portion of a partial bottom nozzle print;
FIG. 15 is a schematic view showing the effect of laser melting and forming the upper selected area of the partial bottom nozzle print of the nuclear fuel assembly;
FIG. 16 is a graph showing the effect of heat treatment clamping of a partial bottom nozzle print of a nuclear fuel assembly.
In the figure, 1, an anti-dislocation mark; 2. an auxiliary entity; 3. a parting surface; 4. the upper part of the nuclear fuel assembly partial lower tube seat printing piece; 5. the lower part of the nuclear fuel assembly partial lower tube seat printing piece; 6. printing a substrate; 7. a protective substrate; 8. c1 hole location; 9. c2 hole positions; 10. d, hole position; 11. c11 counterbore position; 12. c21 counterbore position; 13. local lower tube seat printing piece of nuclear fuel assembly
Detailed Description
A selective laser melting forming method for a nuclear fuel assembly lower tube seat free of supporting comprises the following steps:
1. the selective laser melting molding nuclear fuel assembly partial lower tube seat printing model, and each side face of the nuclear fuel assembly partial lower tube seat printing model is integrated with the selective laser melting molding 3 auxiliary bodies 2, the maximum outline of the auxiliary bodies 2 does not exceed the outline of the printing substrate 6, and the thickness direction is flush with the entity of the nuclear fuel assembly partial lower tube seat printing part upper part 4 or the nuclear fuel assembly partial lower tube seat printing part lower part 5.
2. Dividing a nuclear fuel assembly partial lower tube seat printing model into a nuclear fuel assembly partial lower tube seat printing model upper part and a nuclear fuel assembly partial lower tube seat printing model lower part by using a parting surface 3, wherein the part of the nuclear fuel assembly partial lower tube seat printing model above the parting surface 3 is the nuclear fuel assembly partial lower tube seat printing model upper part, and the part of the nuclear fuel assembly partial lower tube seat printing model below the parting surface 3 is the nuclear fuel assembly partial lower tube seat printing model lower part; the parting surface 3 is positioned in the middle of the nuclear fuel assembly local lower tube seat printing model and is parallel to the bottom surface of the nuclear fuel assembly local lower tube seat printing model; the parting surface 3 is a plane with the smallest area and respectively connected with the upper part of the nuclear fuel assembly partial lower tube seat printing model and the lower part of the nuclear fuel assembly partial lower tube seat printing model, and the upper part 4 of the nuclear fuel assembly partial lower tube seat printing part and the lower part 5 of the nuclear fuel assembly partial lower tube seat printing part can be formed by selective laser melting on the parting surface 3 without design support.
The nuclear fuel assembly partial lower tube seat printing piece lower part 5 and the nuclear fuel assembly partial lower tube seat printing piece upper part 4 are formed by taking the nuclear fuel assembly partial lower tube seat printing model upper part and the nuclear fuel assembly partial lower tube seat printing model lower part as template selective laser melting.
The auxiliary entity 2 is used for auxiliary installation and fixing of the subsequent nuclear fuel assembly partial lower tube seat printing piece 13.
3. Two positioning holes are processed in advance on the printing substrate 6, and the printing substrate 6 is accurately positioned and installed on the laser printing device through the cooperation between the positioning holes of the printing substrate 6 and positioning pins on the laser printing device; the printing substrate 6 is rigidly fixed to the laser printing apparatus using a common clamping device.
4. The laser melting forming of the lower part 5 of the partial lower header print of the nuclear fuel assembly on the print substrate 6 comprises the following steps: grinding allowance of 0.5mm is made on the upper surface of the lower part of the nuclear fuel assembly partial lower tube seat printing model, and linear cutting allowance of 0.8mm is made on the lower surface of the lower part of the nuclear fuel assembly partial lower tube seat printing model; the parting surface 3 is used as an initial printing surface to select a region on the printing substrate 6 for laser melting and forming at the lower part 5 of the local lower tube seat printing piece of the nuclear fuel assembly.
5. The rigidity limit of the lower part 5 of the nuclear fuel assembly partial lower tube seat printing piece and the printing substrate 6 is released, the lower part 5 of the nuclear fuel assembly partial lower tube seat printing piece and the printing substrate 6 are unloaded from the laser printing equipment, and the lower part 5 of the nuclear fuel assembly partial lower tube seat printing piece and the printing substrate 6 are subjected to vacuum heat treatment, wherein the vacuum heat treatment comprises the following steps: the protective substrate 7 is placed on the upper surface of the lower part 5 of the nuclear fuel assembly partial lower tube seat printing piece, and the lower part 5 of the nuclear fuel assembly partial lower tube seat printing piece is clamped and locked between the printing substrate 6 and the protective substrate 7 by using a universal clamping device; placing the printing substrate 6, the protective substrate 7 and the lower part 5 of the nuclear fuel assembly partial lower tube seat printing piece into a vacuum heat treatment furnace, wherein the pressure in the furnace is less than 1Pa, heating to 1050 ℃, preserving heat for 40min, cooling to room temperature along with the furnace, and taking out; the lock is released and the protective substrate 7 is detached.
6. The nuclear fuel assembly partial lower tube seat printing piece lower part 5 and the printing base plate 6 are subjected to double-sided grinding, and the method comprises the following steps of: the lower part 5 of the printing piece of the local lower tube seat of the nuclear fuel assembly after heat treatment and the printing substrate 6 are sent to a grinding machine for grinding; the lower plane of the printing substrate 6 is firstly ground, then the upper surface of the lower tube seat printing piece lower part 5 of the nuclear fuel assembly is ground, the grinding amount is not more than 0.1mm, and the planeness after grinding is not more than 0.04mm.
7. Processing counter bores and positioning holes on the lower part 5 of the nuclear fuel assembly local lower tube seat printing piece and the printing base plate 6, and tapping internal threads in the counter bores, comprising the following steps: machining a counter bore with the diameter of 14mm and the depth of 8mm at the position 8 of a hole on the upper surface C1 of the lower part 5 of the printing piece of the partial lower tube seat of the nuclear fuel assembly, and tapping M8 standard threads at the corresponding position of the printing substrate 6; machining a counter bore with the diameter of 8mm and the depth of 6mm on a hole position 9 on the upper surface C2 of the lower part 5 of the printing piece of the local lower tube seat of the nuclear fuel assembly, and tapping M4 standard threads on the corresponding position of the printing substrate 6; a positioning hole with the tolerance level of H7 is formed in the position 10 of the D hole on the lower part 5 of the printing piece of the partial lower tube seat of the nuclear fuel assembly and the printing substrate 6, and the surface roughness is better than 1.6um; and the machining positioning precision of the threads and the positioning holes of the tap M4 is not more than 0.02mm.
8. The lower part 5 of the printing piece of the partial lower tube seat of the nuclear fuel assembly is cut from the printing substrate 6, and after the cutting surface is ground flat, the cutting surface faces upwards to machine a counter bore, and the method comprises the following steps: cutting the lower part 5 of the nuclear fuel assembly partial lower tube seat printing piece from the printing substrate 6 by linear cutting, and respectively grinding the cutting surfaces of the printing substrate 6 and the lower part 5 of the nuclear fuel assembly partial lower tube seat printing piece by a grinding machine; the deviation between the height dimension of the lower part 5 of the printed part of the local lower tube seat of the ground nuclear fuel assembly and the theoretical dimension is not more than +/-0.05 mm; machining a counter bore with the diameter of 14mm and the depth of 7mm at a C11 counter bore position 11 of a cutting and grinding surface of the lower part 5 of the nuclear fuel assembly local lower tube seat printing piece; a counterbore 8mm in diameter and 6mm deep is machined in the C21 counterbore location 12 of the cutting and grinding face of the lower portion 5 of the nuclear fuel assembly partial bottom nozzle print.
10. The printing substrate 6 is accurately positioned and installed on the laser printing equipment through the matching between the positioning holes of the printing substrate 6 and the positioning pins on the laser printing equipment; the printing substrate 6 is rigidly fixed to the laser printing apparatus using a common clamping device. The upper part 4 of the nuclear fuel assembly partial lower tube seat printing piece and the lower part 5 of the nuclear fuel assembly partial lower tube seat printing piece are formed by selective laser melting, the same printing substrate 6 is used, the printing substrate 6 needs to be installed and disassembled between the two forming, and the positions of the printing substrate 6 installed on the laser printing equipment for two times can be kept unchanged through the positioning holes on the printing substrate 6.
11. The partial lower tube seat printing part lower part 5 of the nuclear fuel assembly is installed on the printing substrate 6 through the cooperation of the screw and the locating pin, and the installation is required to ensure that the cutting surface of the partial lower tube seat printing part lower part 5 of the nuclear fuel assembly faces upwards, and the method comprises the following steps: the cutting surface of the lower part 5 of the nuclear fuel assembly partial lower tube seat printing piece faces upwards, the printing substrate 6 and the lower part 5 of the nuclear fuel assembly partial lower tube seat printing piece are connected in a positioning way through the positioning pins which penetrate through the printing substrate 6 and the positioning holes of the lower part 5 of the nuclear fuel assembly partial lower tube seat printing piece, then the screws are locked by torque wrenches in sequence, the torque is 21N/m, and the lower part 5 of the nuclear fuel assembly partial lower tube seat printing piece 13 is firmly locked on the printing substrate 6.
12. The method for forming the upper part 4 of the nuclear fuel assembly local lower tube seat printing piece by selective laser melting on the cutting surface of the lower part 5 of the nuclear fuel assembly local lower tube seat printing piece comprises the following steps: the cutting grinding surface of the lower part 5 of the nuclear fuel assembly is used as a printing substrate 6 when the upper part 4 of the nuclear fuel assembly is formed by laser melting, and the upper part 4 of the nuclear fuel assembly is directly formed by selective laser melting on the cutting grinding surface of the lower part 5 of the nuclear fuel assembly, and the mark 1 is observed to be complete or not without dislocation in the selective laser melting forming process.
The dislocation preventing mark 1 consists of letters, numbers, characters or other patterns, and the dislocation preventing mark 1 is recessed or protruded into a local lower tube seat printing model of the nuclear fuel assembly to be at least more than 0.5mm so as to ensure that the mark is clear and distinguishable; the dislocation preventing marks 1 are arranged at two positions of the parting surface 3, and after the laser melting forming of all selected areas of the lower part 5 of the nuclear fuel assembly local lower tube seat printing piece and the upper part 4 of the nuclear fuel assembly local lower tube seat printing piece is finished, the dislocation preventing marks 1 which are divided into two parts are required to form a whole mark without dislocation.
12. The vacuum heat treatment of the nuclear fuel assembly partial lower header print 13 and the print substrate 6 comprises the steps of: placing the protective substrate 7 on the upper surface of the upper part 4 of the nuclear fuel assembly partial lower tube seat printing piece, and clamping and locking the nuclear fuel assembly partial lower tube seat printing piece 13 between the printing substrate 6 and the protective substrate 7 by using a universal clamping device; placing the printing substrate 6, the protective substrate 7 and the nuclear fuel assembly partial lower tube seat printing piece 13 together into a vacuum heat treatment furnace, wherein the pressure in the furnace is less than 1Pa, heating to 1050 ℃, preserving heat for 40min, cooling to room temperature along with the furnace, and taking out; the lock is released and the protective substrate 7 is detached.
13. And unloading the positioning pins and screws of the nuclear fuel assembly partial lower tube seat printing piece 13 and the printing substrate 6, and removing the nuclear fuel assembly partial lower tube seat printing piece 13.
14. And (3) removing the auxiliary entity 2 on the nuclear fuel assembly local lower tube seat printing piece 13 by using machining, and machining square side surfaces of the nuclear fuel assembly local lower tube seat printing piece 13 to be flat to obtain the nuclear fuel assembly local lower tube seat.
The lower part 5 of the nuclear fuel assembly partial lower tube seat printing piece and the upper part 4 of the nuclear fuel assembly partial lower tube seat printing piece are formed by taking the upper part of the nuclear fuel assembly partial lower tube seat printing model and the lower part of the nuclear fuel assembly partial lower tube seat printing model as template selective laser melting.
The foregoing examples illustrate only a few embodiments of the invention and are described in detail herein without thereby limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.

Claims (9)

1. A selective laser melting forming method for a partial lower tube seat of a nuclear fuel assembly without supporting is characterized by comprising the following steps:
step one, selecting a local lower tube seat printing model of the laser melting forming nuclear fuel assembly, and integrating a selected laser melting forming auxiliary entity on the square side surface of the local lower tube seat printing model of the nuclear fuel assembly;
dividing the nuclear fuel assembly partial lower tube seat printing model into an upper part of the nuclear fuel assembly partial lower tube seat printing model and a lower part of the nuclear fuel assembly partial lower tube seat printing model by using a parting surface;
respectively selecting laser melting to form the lower part of the partial lower tube seat printing piece of the nuclear fuel assembly and the upper part of the partial lower tube seat printing piece of the nuclear fuel assembly by taking the parting surface as an initial printing surface to obtain the partial lower tube seat printing piece of the nuclear fuel assembly;
removing auxiliary entities of the printed part of the partial lower tube seat of the nuclear fuel assembly, and processing square side surfaces of the printed part of the partial lower tube seat of the nuclear fuel assembly to be flat to obtain the partial lower tube seat of the nuclear fuel assembly;
the lower part of the nuclear fuel assembly partial lower tube seat printing piece and the upper part of the nuclear fuel assembly partial lower tube seat printing piece are formed by taking the upper part of the nuclear fuel assembly partial lower tube seat printing model and the lower part of the nuclear fuel assembly partial lower tube seat printing model as templates to select areas for laser melting;
the third step comprises the following steps:
(1) Accurately positioning, mounting and rigidly fixing the printing substrate on laser printing equipment;
(2) Forming the lower part of a local lower tube seat printing piece of the nuclear fuel assembly by selective laser melting on the printing substrate;
(3) Removing the rigidity limit of the printing substrate, carrying out vacuum heat treatment and double-sided grinding on the lower part of the printing piece of the nuclear fuel assembly local lower tube seat and the printing substrate, respectively processing counter bores and positioning holes on the lower part of the printing piece of the nuclear fuel assembly local lower tube seat and the printing substrate, and tapping internal threads in the counter bores;
(4) Cutting the lower part of the printing piece of the local lower tube seat of the nuclear fuel assembly from the printing substrate, and processing a counter bore on the cutting surface after the cutting surface is ground;
(5) Accurately positioning, mounting and rigidly fixing the printing substrate on the laser printing equipment again; the lower part of the nuclear fuel assembly partial lower tube seat printing piece is arranged on the printing substrate through the cooperation of the screw and the locating pin, and the installation needs to ensure that the cutting surface of the lower part of the nuclear fuel assembly partial lower tube seat printing piece faces upwards;
(6) Selecting a region on a cutting surface of the lower part of the nuclear fuel assembly local lower tube seat printing piece to melt and form the upper part of the nuclear fuel assembly local lower tube seat printing piece to obtain the nuclear fuel assembly local lower tube seat printing piece;
(7) Performing vacuum heat treatment on the local lower tube seat printing piece of the nuclear fuel assembly and the printing substrate;
(8) Unloading the positioning pins and the screws which are connected with the partial lower tube seat printing piece of the nuclear fuel assembly and the printing substrate, and taking down the partial lower tube seat printing piece of the nuclear fuel assembly;
(9) And removing auxiliary entities on the partial lower tube seat printing piece of the nuclear fuel assembly by using a machining method, and machining four side surfaces of the partial lower tube seat printing piece of the nuclear fuel assembly to be flat to obtain the partial lower tube seat of the nuclear fuel assembly.
2. The method for selective laser melting forming of a partial bottom nozzle of a nuclear fuel assembly free of support of claim 1, wherein the maximum outline of the auxiliary entity does not exceed the outline of the printed substrate, and the thickness direction is flush with the entity above the printing pattern of the partial bottom nozzle of the nuclear fuel assembly or below the printing pattern of the partial bottom nozzle of the nuclear fuel assembly.
3. The selective laser melting forming method of a nuclear fuel assembly local lower tube seat free of support according to claim 1, wherein the parting surface is positioned in the middle of the nuclear fuel assembly local lower tube seat printing model, is parallel to the bottom surface of the nuclear fuel assembly local lower tube seat printing model, and is a plane with the smallest area for respectively connecting the upper part of the nuclear fuel assembly local lower tube seat printing model and the lower part of the nuclear fuel assembly local lower tube seat printing model.
4. The selective laser melting forming method of a partial bottom nozzle of a nuclear fuel assembly without supporting according to claim 1, wherein in step 2, a grinding allowance of 0.5mm is made on the upper surface of the lower part of the printing model of the partial bottom nozzle of the nuclear fuel assembly, and a linear cutting allowance of 0.8mm is made on the lower surface of the lower part of the printing model of the partial bottom nozzle of the nuclear fuel assembly.
5. The method for selective laser melting forming of a partial bottom nozzle of a nuclear fuel assembly free of support of claim 1, wherein in step 3, the double-sided lapping comprises the steps of: the lower part of the printing piece of the local lower tube seat of the nuclear fuel assembly after heat treatment and the printing substrate are sent to a grinding machine for grinding; the lower plane of the printing substrate is firstly ground, then the upper surface of the lower part of the printing part of the local lower tube seat of the nuclear fuel assembly is ground, the grinding amount is not more than 0.1mm, and the planeness after grinding is not more than 0.04mm.
6. The method for forming a local bottom nozzle of a nuclear fuel assembly by selective laser melting free of support according to claim 1, wherein in step 3, the method for forming a counter bore and a positioning hole in the lower part of the printed part of the local bottom nozzle of the nuclear fuel assembly and in the printed substrate, and tapping a female screw in the counter bore comprises the following steps: machining a counter bore with the diameter of 14mm and the depth of 8mm on a hole position on the upper surface C1 of the lower part of a printing piece of a local lower tube seat of the nuclear fuel assembly, and tapping M8 standard threads on the corresponding position of a printing substrate; machining a counter bore with the diameter of 8mm and the depth of 6mm on a C2 hole on the upper surface of the lower part of a printing piece of a local lower tube seat of the nuclear fuel assembly, and tapping M4 standard threads on the corresponding position of a printing substrate; a positioning hole with the tolerance level of H7 is formed in the position of a D hole on the lower part of a printing piece of the local lower tube seat of the nuclear fuel assembly and the printing substrate, and the surface roughness is better than 1.6um; and the machining positioning precision of the threads and the positioning holes of the tap M4 is not more than 0.02mm.
7. The method for selective laser melting forming of a partial bottom nozzle of a nuclear fuel assembly free of support of claim 1, wherein step 4 comprises the steps of: cutting the lower part of the nuclear fuel assembly partial lower tube seat printing piece from the printing substrate by using linear cutting, and respectively grinding the cutting surfaces of the printing substrate and the lower part of the nuclear fuel assembly partial lower tube seat printing piece by using a grinding machine; the deviation between the height dimension of the lower part of the printed part of the local lower tube seat of the nuclear fuel assembly after grinding and the theoretical dimension is not more than +/-0.05 mm; processing a counter bore with the diameter of 14mm and the depth of 7mm at a C11 counter bore position of a cutting and grinding surface at the lower part of a local lower tube seat printing piece of the nuclear fuel assembly; and processing a counter bore with the diameter of 8mm and the depth of 6mm at a C21 counter bore position of a cutting and grinding surface at the lower part of the local lower tube seat printing piece of the nuclear fuel assembly.
8. The method of non-supporting selective laser melting forming a partial bottom bracket of a nuclear fuel assembly of claim 1, wherein step 6 comprises the steps of: the cutting grinding surface of the lower part of the nuclear fuel assembly local lower tube seat printing piece is used as a printing substrate when the upper part of the nuclear fuel assembly local lower tube seat printing piece is formed by laser melting, and the upper part of the nuclear fuel assembly local lower tube seat printing piece is directly formed by selective laser melting on the cutting grinding surface of the lower part of the nuclear fuel assembly local lower tube seat printing piece, so that the integrity of dislocation preventing marks is ensured in the selective laser melting forming process, and dislocation is avoided.
9. The selective laser melting forming method of the nuclear fuel assembly local lower tube seat free of supporting of claim 8, wherein the dislocation preventing mark is recessed or protruded into the nuclear fuel assembly local lower tube seat printing model at least more than 0.5mm, and is arranged at two positions of the parting surface, and after the selective laser melting forming of the lower part of the nuclear fuel assembly local lower tube seat printing part and the upper part of the nuclear fuel assembly local lower tube seat printing part is completed, the dislocation preventing mark divided into two parts should form a whole complete mark without dislocation.
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