A nuclear fuel assembly casting type upper nozzle machining clamp and machining method

Abstract

The application relates to the technical field of nuclear fuel assembly manufacturing, and particularly discloses a nuclear fuel assembly casting type upper tube seat machining clamp and a machining method, wherein the tube seat blank is placed on a bottom plate, a positioning top block is pushed, four positioning pins below a positioning push rod are centered with positioning holes of the tube seat blank; then a positioning rod B is screwed to shorten the distance with a positioning rod A; then locking screws and fastening bolts on the edge frame of a positioning frame plate are locked to fix the tube seat blank on the bottom plate, positioning is realized; finally, the positioning rod B is completely screwed out of the positioning rod A, the bottom plate, the positioning frame plate and the tube seat blank are integrally taken out and fixed on a machining equipment. The machining clamp and the machining method satisfy the positioning clamping and machining requirements of the casting type upper tube seat, the upper tube seat after machining completely satisfies the drawing and technical condition requirements, and the machining scheme satisfies the engineering production.

Description

Technical Field

[0001] This invention belongs to the field of nuclear fuel assembly manufacturing technology, specifically relating to a machining fixture and machining method for a casting upper tube seat of a nuclear fuel assembly. Background Technology

[0002] This type of nuclear fuel assembly represents the first time China has imported a third-generation nuclear fuel assembly from abroad. The upper tube seat is a cast type, which is machined after casting. This type of cast tube seat features complex structural characteristics such as irregular grooves and stepped holes, and is a thin-walled, multi-cavity component. Currently, domestic technology has not been used to process this type of tube seat.

[0003] In order to achieve the localization of manufacturing technology, it is urgent to design a casting upper tube seat machining fixture and machining method. Summary of the Invention

[0004] The purpose of this invention is to provide a machining fixture and machining method for the upper tube seat of a nuclear fuel assembly casting, which meets the positioning, clamping and machining requirements of the upper tube seat.

[0005] The technical solution of the present invention is as follows:

[0006] A machining fixture for casting upper tube seat of nuclear fuel assembly includes a fixture connecting plate, stiffening plate, snap plate, camshaft, positioning top block, positioning push rod, upper plate, locking nut, positioning rod A, positioning rod B, locking rod, spring, base plate, and positioning frame plate;

[0007] The clamp connecting plate is the reference plane of the entire clamp, and four mounting holes are machined at its four corners.

[0008] The base plate is a rectangular plate, which is fixed to the clamp connecting plate;

[0009] The positioning frame plate is a rectangular frame and is fixedly installed on the top of the base plate;

[0010] Fastening bolt holes are provided on the four sides of the positioning frame plate;

[0011] There are two positioning rods A, which are respectively inserted into two mounting holes at opposite corners of the clamp connecting plate; positioning rod B is located above positioning rod A, and the two are connected by threads.

[0012] The stiffening plate is in the shape of a long strip, and both ends of the stiffening plate are connected to the top of the positioning rod B.

[0013] A snap plate is provided above the center position of the stiffener plate, and an upper plate is provided above the snap plate;

[0014] The camshaft passes through the locking nut, upper plate, buckle plate and stiffening plate from top to bottom, and is connected to the locking nut and stiffening plate by threads. The upper plate, buckle plate and stiffening plate are pressed and fixed by rotating the locking nut.

[0015] A protruding rod is provided on the inner top wall of the buckle plate near both ends; one end of the locking rod is fixed to the inside of the protruding rod of the buckle plate, and a spring is sleeved on the other end of the locking rod;

[0016] The positioning top block is a rectangular block with a spring groove and a push rod groove machined on its upper surface; there are two positioning top blocks, which are inserted into the two ends of the buckle plate respectively, so that the locking rod extends into the spring groove of the positioning top block, and the other end of the spring abuts against the inner wall of the spring groove of the positioning top block;

[0017] There are two positioning push rods, each of which is engaged in the push rod groove of the positioning top block;

[0018] Positioning pins are provided at the bottom of both ends of the positioning push rod.

[0019] A circular support section is machined at the center of the stiffener.

[0020] The center of the buckle is machined into a circle, and the upper plate is a circular plate.

[0021] Through holes are machined at the center of the clamp connecting plate and the base plate to reduce weight.

[0022] The base plate is fixed to the clamp connecting plate by four pins at the four corners.

[0023] The positioning frame plate is fixedly connected to the base plate by four locking screws on the four side edges.

[0024] The positioning push rod is a C-shaped block.

[0025] A method for machining the upper tube seat of a nuclear fuel assembly casting, using the aforementioned machining fixture, includes the following steps:

[0026] Step 1: Fix the tube seat blank;

[0027] Place the tube seat blank on the base plate, push the positioning block to align the four positioning pins below the positioning push rod with the positioning holes of the tube seat blank; then tighten the positioning rod B to shorten the distance with the positioning rod A, press the tube seat blank firmly, and ensure that the tube seat blank no longer moves up and down; then tighten the locking screws and fastening bolts on the edge of the positioning frame plate to fix the tube seat blank on the base plate and achieve positioning; finally, completely unscrew the positioning rod B out of the positioning rod A, and take out the base plate, positioning frame plate, and tube seat blank as a whole, and place them on the processing equipment for fixing;

[0028] Step 2: Set the tool machining parameters;

[0029] Step 3: Mill the positioning hole and its surrounding surfaces;

[0030] Step 4: Mill the total height;

[0031] Step 5: Machining guide tube holes and instrument tube holes;

[0032] Step 6: Machining the S-hole and spring groove.

[0033] Specifically, the following steps are included:

[0034] Step 1: Fix the tube seat blank

[0035] Place the tube seat blank on the base plate, push the positioning block to align the four positioning pins below the positioning push rod with the positioning holes of the tube seat blank; then tighten the positioning rod B to shorten the distance with the positioning rod A, press the tube seat blank firmly, and ensure that the tube seat blank no longer moves up and down; then tighten the locking screws and fastening bolts on the edge of the positioning frame plate to fix the tube seat blank on the base plate and achieve positioning; finally, completely unscrew the positioning rod B out of the positioning rod A, and take out the base plate, positioning frame plate, and tube seat blank as a whole, and place them on the processing equipment for fixing;

[0036] Step 2: Set tool machining parameters

[0037] Set the cutting speed to 60–80 m / min and the feed rate to 0.1–0.5 mm / r;

[0038] Step 3: Mill the positioning hole and surrounding surfaces

[0039] Using the support plane of the tube seat as the reference, the workpiece thickness is offset and defined as Z0. A disc milling cutter is used to machine the smooth surface, and an end mill is used to mill the four sides. Then the width of the adjacent sides is measured. The X and Y coordinates are corrected according to the data to determine the (X0, Y0) coordinates. The process hole is machined using a drill bit.

[0040] Step 4: Mill the total height

[0041] Mill the four sides of the frame to make the product's length and width conform to the dimensions required by the drawing; then machine the overall height of the product, as well as the markings and pin holes on each side;

[0042] Step 5: Machining guide holes and instrument holes

[0043] Perform machining of guide tube holes and instrument tube holes, and complete the chamfering around the four sides;

[0044] Step 6: Machining the S-hole and spring groove

[0045] Using the bottom surface of the tube base as the reference point, offset Z'0 coordinate in the Z direction to complete the machining of the total height. Then, machine the height of the inner cavity of the base, the four sides and the boss, machine the spring groove and its pin hole for installing the clamping spring, machine the anti-misalignment hole, S1 hole and S2 hole, and finally complete the machining of each chamfer feature.

[0046] In step 2, the cutting depth ap is set to 2-5 mm for roughing and 0.2-0.5 mm for finishing.

[0047] The significant advantages of this invention are:

[0048] (1) The machining fixture and machining method of the present invention meet the positioning, clamping and machining requirements of the cast upper tube seat. The machined upper tube seat fully meets the requirements of the drawings and technical conditions. The machining scheme meets the requirements of engineering production.

[0049] (2) Since the upper tube seat is a cast blank, there is no good flat surface around it for machining and positioning. However, the machining fixture of the present invention can fit the positioning frame plate well with the blank, ensuring machining accuracy.

[0050] (3) The method of the present invention uses multiple forming tools to process irregular holes and other structures, and forms them in one process, which can well ensure the dimensional requirements of irregular structures. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the fixture structure for machining the upper tube seat;

[0052] Figure 2 A sectional view of the fixture for machining the upper tube seat;

[0053] In the diagram: 1. Fixture connecting plate; 2. Rib plate; 3. Buckle plate; 4. Camshaft; 5. Positioning top block; 6. Positioning push rod; 7. Upper plate; 8. Locking nut; 9. Positioning rod A; 10. Positioning rod B; 11. Locking rod; 12. Mounting hole; 13. Spring; 14. Base plate; 15. Positioning frame plate. Detailed Implementation

[0054] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0055] like Figures 1-2 The above describes a machining fixture for a casting upper tube seat of a nuclear fuel assembly, which includes a fixture connecting plate 1, a stiffening plate 2, a buckle plate 3, a camshaft 4, a positioning top block 5, a positioning push rod 6, an upper plate 7, a locking nut 8, a fastening bolt, a positioning rod A9, a positioning rod B10, a locking rod 11, a mounting hole 12, a spring 13, a base plate 14, and a positioning frame plate 15.

[0056] The clamp connecting plate 1 is the reference plane of the entire clamp. Four mounting holes 12 are machined at its four corners, and a through hole is machined at its center to reduce weight.

[0057] The base plate 14 is a rectangular plate with a through hole machined in its center to reduce weight. The base plate 14 is fixed to the clamp connecting plate 1 by four pins at its four corners.

[0058] The positioning frame plate 15 is a rectangular frame, located above the base plate 14, and is fixedly connected to the base plate 14 by four locking screws at the center of its four sides. Fastening bolt holes are provided on the sides of the four sides of the positioning frame plate 15, and the bolts are used to lock and position it against the tube base blank.

[0059] There are two positioning rods A9, which are respectively inserted into the two mounting holes 12 on opposite sides of the clamp connecting plate 1; positioning rod B10 is located above positioning rod A9, and the two are connected by threads to support positioning rib plate 2.

[0060] The stiffening plate 2 is in the shape of a long strip. Both ends of the stiffening plate 2 are fixedly connected to the top of the positioning rod B10 by bolts. A circular support section is machined at the center of the stiffening plate 2.

[0061] A snap plate 3 is provided above the circular support section of the stiffener 2, and an upper plate 7 is provided above the snap plate 3. The center of the snap plate 3 is machined into a circle, and the upper plate 7 is a circular plate.

[0062] The camshaft 4 passes through the locking nut 8, the upper plate 7, the buckle plate 3 and the stiffening plate 2 from top to bottom. The camshaft 4 is connected to the locking nut 8 and the stiffening plate 2 by threads. The upper plate 7, the buckle plate 3 and the stiffening plate 2 are pressed and fixed by rotating the locking nut 8.

[0063] On the inner top wall of the buckle plate 3, near both ends, there are protruding rods. One end of the locking rod 11 is fixed to the inside of the protruding rod of the buckle plate 3, and the spring 13 is sleeved on the other end of the locking rod 11.

[0064] The positioning top block 5 is a rectangular block with a spring groove and a push rod groove machined on its upper surface. There are two positioning top blocks 5, which are inserted into the two ends of the buckle plate 3 respectively, so that the locking rod 11 extends into the spring groove of the positioning top block 5, and the other end of the spring 13 abuts against the inner wall of the spring groove of the positioning top block 5.

[0065] The positioning push rod 6 is a C-shaped block, and there are two of them, which are respectively engaged in the push rod groove of the positioning top block 5. Positioning pins are provided at the lower ends of the positioning push rod 6.

[0066] A method for machining a casting upper tube seat for nuclear fuel assemblies includes the following steps:

[0067] Step 1: Fix the tube seat blank

[0068] Place the tube seat blank on the base plate 14, push the positioning top block 5 to align the four positioning pins below the positioning push rod 6 with the positioning holes of the tube seat blank; then tighten the positioning rod B10 to shorten the distance with the positioning rod A9, press the tube seat blank tightly, and ensure that the tube seat blank no longer moves up and down; then tighten the locking screws and fastening bolts on the frame of the positioning frame plate 15 to fix the tube seat blank on the base plate 14 to achieve positioning; finally, completely unscrew the positioning rod B10 out of the positioning rod A9, and take out the base plate 14, positioning frame plate 15, and tube seat blank as a whole, and place them on the processing equipment for fixing;

[0069] Step 2: Set tool machining parameters

[0070] Set the tool cutting speed to 60-80 m / min, feed rate to 0.1-0.5 mm / r, depth of cut ap = 2-5 mm for roughing, and depth of cut ap = 0.2-0.5 mm for finishing;

[0071] The tool parameters for rough machining of the tube seat are: depth of cut 50mm, width of cut 0.6mm, speed S=1000, F=0.2;

[0072] The tool parameters for finishing are: depth of cut 50mm, width of cut 0.4mm, spindle speed S=1200, F=0.1;

[0073] To ensure reasonable tool durability, the cutting speed should be reduced, generally selected as 40-60% of that for cutting ordinary carbon steel, i.e., 60-80 m / min. For small-diameter tools or special tools, the cutting speed should be reduced even further due to poor tool rigidity, heat dissipation, cooling and lubrication effects, and chip removal.

[0074] To improve the surface quality of the machined surface, a smaller feed rate should be used during finishing, but the feed rate should not be less than 0.1 mm / r. Avoid cutting in the work-hardened zone due to micro-feeding, and be careful not to let the cutting edge stay on the cutting surface.

[0075] When roughing, the allowance is large, so a larger depth of cut should be selected and the number of passes should be reduced. This can also avoid the tool tip from contacting the tube blank and reduce tool wear. However, increasing the depth of cut should avoid vibration caused by excessive cutting force. An ap of 2 to 5 mm can be selected. When finishing, a smaller depth of cut should be selected and the hardened layer should be avoided. Generally, an ap of 0.2 to 0.5 mm is used.

[0076] Step 3: Mill the positioning hole and surrounding surfaces

[0077] Using the support plane of the tube seat as a reference, offset from the workpiece thickness by 18.8 mm in the Z direction, defined as Z0, a smooth surface is machined using a disc milling cutter, and then... The end mill mills the width of the four sides of the frame to 10mm. The width of the four adjacent sides is measured, and the X and Y coordinates are corrected according to the data to determine the (X0, Y0) coordinates. Five process holes are machined using a drill bit, including two Φ10H8 holes as positioning holes and three Φ10.5 holes for fixing.

[0078] Step 4: Mill the total height

[0079] Mill the four sides of the frame to make the product's length and width conform to the dimensions required by the drawing; then machine the overall height of the product, leaving a 0.2mm allowance, machine the markings on each side, and machine the pin holes;

[0080] Step 5: Machining guide holes and instrument holes

[0081] Machining of 24 guide tube holes and 1 instrument tube hole, and completion of chamfering around all four sides;

[0082] Step 6: Machining the S-hole and spring groove

[0083] Using the bottom surface of the tube base as the reference and offset by 110mm as the Z'0 coordinate, the overall height is machined. The height of the inner cavity of the base, the four sides and the four bosses are machined. The spring groove and its pin hole for installing the clamping spring are machined. The anti-misalignment hole, S1 hole and S2 hole are machined. The chamfer features are machined.

[0084] Currently, the fixture and machining method of this invention have been experimentally applied to the machining of casting upper tube seats for a certain type of fuel assembly, which can meet production needs, and six casting upper tube seats have been machined in succession.

[0085] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0086] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A machining fixture for a casting upper tube seat of a nuclear fuel assembly, characterized in that: Includes clamp connecting plate (1), stiffener plate (2), buckle plate (3), camshaft (4), positioning top block (5), positioning push rod (6), upper plate (7), locking nut (8), positioning rod A (9), positioning rod B (10), locking rod (11), spring (13), base plate (14), and positioning frame plate (15); The clamp connecting plate (1) is the reference plane of the entire clamp, and four mounting holes (12) are machined at its four corners respectively; The base plate (14) is a rectangular plate and is fixed on the clamp connecting plate (1); The positioning frame plate (15) is a rectangular frame and is fixedly installed above the base plate (14); Fastening bolt holes are provided on the four sides of the positioning frame plate (15); There are two positioning rods A (9), which are respectively inserted into two mounting holes (12) on opposite sides of the clamp connecting plate (1); positioning rod B (10) is located above positioning rod A (9), and the two are connected by threads; The stiffening plate (2) is in the shape of a long strip, and the two ends of the stiffening plate (2) are respectively connected to the top of the positioning rod B (10); A buckle plate (3) is provided above the center position of the stiffener plate (2), and an upper plate (7) is provided above the buckle plate (3); The camshaft (4) passes through the locking nut (8), upper plate (7), buckle plate (3) and rib plate (2) from top to bottom. The locking nut (8) and rib plate (2) are connected by threads respectively. The upper plate (7), buckle plate (3) and rib plate (2) are pressed and fixed by rotating the locking nut (8). On the inner top wall of the buckle plate (3), near both ends, there are protruding rods respectively; one end of the locking rod (11) is fixed to the inner side of the protruding rod of the buckle plate (3), and the spring (13) is sleeved on the other end of the locking rod (11); The positioning top block (5) is a rectangular block with a spring groove and a push rod groove respectively machined on its upper surface; there are two positioning top blocks (5), which are inserted into the two ends of the buckle plate (3) respectively, so that the locking rod (11) extends into the spring groove of the positioning top block (5), and the other end of the spring (13) abuts against the inner wall of the spring groove of the positioning top block (5); There are two positioning push rods (6), which are respectively locked in the push rod groove of the positioning top block (5); Positioning pins are provided at both ends of the positioning push rod (6).

2. The machining fixture for the upper tube seat of a nuclear fuel assembly casting as described in claim 1, characterized in that: A circular support section is machined at the center of the stiffener (2).

3. The machining fixture for the upper tube seat of a nuclear fuel assembly casting as described in claim 2, characterized in that: The center of the buckle plate (3) is machined into a circle, and the upper plate (7) is a circular plate.

4. The machining fixture for the upper tube seat of a nuclear fuel assembly casting as described in claim 1, characterized in that: Through holes are machined at the center of the clamp connecting plate (1) and the base plate (14) to reduce weight.

5. The machining fixture for the upper tube seat of a nuclear fuel assembly casting as described in claim 1, characterized in that: The base plate (14) is fixed to the clamp connecting plate (1) by four pins at the four corners.

6. The machining fixture for the upper tube seat of a nuclear fuel assembly casting as described in claim 1, characterized in that: The positioning frame plate (15) is fixedly connected to the base plate (14) by four locking screws on the four sides.

7. A machining fixture for the upper tube seat of a nuclear fuel assembly casting as described in claim 1, characterized in that: The positioning push rod (6) is a C-shaped block.

8. A method for machining the upper tube seat of a nuclear fuel assembly casting, using the machining fixture as described in claim 1, characterized in that: Includes the following steps: Step 1: Fix the tube seat blank; Place the tube seat blank on the base plate (14), push the positioning top block (5) so that the four positioning pins below the positioning push rod (6) are aligned with the positioning holes of the tube seat blank; then tighten the positioning rod B (10) to shorten the distance with the positioning rod A (9), press the tube seat blank to ensure that the tube seat blank no longer moves up and down; then tighten the locking screws and fastening bolts on the frame of the positioning frame plate (15) to fix the tube seat blank on the base plate (14) to achieve positioning; finally, completely unscrew the positioning rod B (10) from the positioning rod A (9), and take out the base plate (14), positioning frame plate (15) and tube seat blank as a whole, and place them on the processing equipment for fixing; Step 2: Set the tool machining parameters; Step 3: Mill the positioning hole and its surrounding surfaces; Step 4: Mill the total height; Step 5: Machining guide tube holes and instrument tube holes; Step 6: Machining the S-hole and spring groove.

9. A method for machining the upper tube seat of a nuclear fuel assembly casting as described in claim 8, characterized in that: Specifically, the following steps are included: Step 1: Fix the tube seat blank Place the tube seat blank on the base plate (14), push the positioning top block (5) so that the four positioning pins below the positioning push rod (6) are aligned with the positioning holes of the tube seat blank; then tighten the positioning rod B (10) to shorten the distance with the positioning rod A (9), press the tube seat blank to ensure that the tube seat blank no longer moves up and down; then tighten the locking screws and fastening bolts on the frame of the positioning frame plate (15) to fix the tube seat blank on the base plate (14) to achieve positioning; finally, completely unscrew the positioning rod B (10) from the positioning rod A (9), and take out the base plate (14), positioning frame plate (15) and tube seat blank as a whole, and place them on the processing equipment for fixing; Step 2: Set tool machining parameters Set the cutting speed to 60–80 m / min and the feed rate to 0.1–0.5 mm / r; Step 3: Mill the positioning hole and surrounding surfaces Using the support plane of the tube seat as the reference, the workpiece thickness is offset and defined as Z0. A disc milling cutter is used to machine the smooth surface, and an end mill is used to mill the four sides. Then the width of the adjacent sides is measured. The X and Y coordinates are corrected according to the data to determine the (X0, Y0) coordinates. The process hole is machined using a drill bit. Step 4: Mill the total height Mill the four sides of the frame to make the product's length and width conform to the dimensions required by the drawing; then machine the overall height of the product, as well as the markings and pin holes on each side; Step 5: Machining guide holes and instrument holes Perform machining of guide tube holes and instrument tube holes, and complete the chamfering around the four sides; Step 6: Machining the S-hole and spring groove Using the bottom surface of the tube base as the reference point, offset Z'0 coordinate in the Z direction to complete the machining of the total height. Then, machine the height of the inner cavity of the base, the four sides and the boss, machine the spring groove and its pin hole for installing the clamping spring, machine the anti-misalignment hole, S1 hole and S2 hole, and finally complete the machining of each chamfer feature.

10. A method for machining the upper tube seat of a nuclear fuel assembly casting as described in claim 9, characterized in that: In step 2, the cutting depth ap is set to 2-5 mm for roughing and 0.2-0.5 mm for finishing.

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