A method for processing a nozzle hole of a basket cylinder

Abstract

The application discloses a kind of processing methods of basket cylinder nozzle hole, comprising: processing down knife hole and lifting hole on basket cylinder;Rough machining is carried out using cutting tool with internal cooling channel, and inverse milling layered cutting mode is used to transport cutting fluid and remove chips through internal cooling channel;Lifting connection structure is set on the excess material, and cutting material is taken after pre-tightening tension is applied, and the lower region is cut first and then the upper region is cut;Finish machining is carried out using boring tool with main offset angle less than 90°, and non-equal cutting amount intermittent cutting mode is used.The application improves processing stability and material taking safety through the synergistic cooperation of inverse milling layered cutting, internal cooling and chip removal, pre-tightening material taking and non-equal cutting amount intermittent cutting, prolongs tool life, and ensures the processing quality of nozzle hole.

Description

Technical Field

[0001] This invention relates to the field of machining technology for nozzle holes in suspended basket cylinders, and particularly to a method for machining nozzle holes in suspended basket cylinders. Background Technology

[0002] In the manufacturing process of civilian nuclear power reactor internals, the cradle shell, as a key component of the reactor internals, directly affects the operational safety and reliability of the reactor due to the machining quality of its nozzle holes. The cradle shell is typically a large, hollow cylindrical structure with a flange at one end. It is large in overall size and thick in wall, and is often made of difficult-to-machine materials such as austenitic stainless steel. Strict requirements are placed on the positional accuracy, dimensional tolerances, form and position tolerances, and surface quality of the nozzle holes. Machining the nozzle holes in this type of cradle shell presents technical challenges, including poor drilling stability, easy vibration during cutting, low safety in removing excess material, rapid tool wear, and low machining efficiency.

[0003] In existing technologies, the nozzle holes of the hoisting basket cylinder are typically machined using a floor-type boring and milling machine. This method involves mounting the hoisting basket cylinder on the worktable of the floor-type boring and milling machine, and using multi-axis linkage of the spindle, along with positioning by the rotary worktable and radial and axial feed of the cutting tool, to complete drilling, milling, and boring operations. The specific machining process typically includes: drilling the material lifting hole and the starting hole, rough milling the annular groove, material removal, and finish boring.

[0004] The drilling process relies mainly on the operator's experience to adjust the drilling parameters; the rough milling process uses a D100R8 round nose cutter for rapid material removal; the material removal process uses a screw to fix the excess material, and with the help of a crane and sling, the fitter performs symmetrical ring cutting from top to bottom; the finishing process uses a flat rotary boring tool to complete the final dimensions and surface quality assurance.

[0005] When using the above method to process the nozzle hole of the suspended platform cylinder, although the hole-opening operation can be completed, there are still many shortcomings. In the drilling stage, if a regular twist drill is used, the processing efficiency is low; if a replaceable head carbide internal coolant drill is used, the workpiece clamping rigidity is unstable, and the tool is prone to vibration during drilling. It is necessary for the operator to adjust the parameters on-site according to the situation, resulting in technical problems of poor drilling stability and insufficient processing consistency.

[0006] During the material handling stage, the overhead crane is directly connected to the scrap material via slings, screws, and lifting rings. This makes precise control of the pulling force difficult, increasing the risk of screw breakage and impact damage. Furthermore, the fitter's top-down, symmetrical circular cutting method is flawed, and the scrap material's tilting direction is uncontrollable upon completion of the cut, posing safety risks and increasing the risk of injury and damage to machined surfaces. In the roughing and finishing stages, high cutting resistance easily causes workpiece vibration, affecting the accuracy of the equipment and the product.

[0007] During fine boring, the nozzle hole area has a saddle-shaped surface structure, resulting in intermittent cutting. Furthermore, the high toughness, low thermal conductivity, and work-hardening tendency of austenitic stainless steel lead to uneven heating and accelerated wear of the boring bar inserts, posing risks of tool breakage and low machining stability. In addition, the round nose cutter used for rough milling has an excessively long axial toolpath due to its shape, resulting in large cutting volumes and rapid insert wear requiring frequent machine stops for replacement, leading to low machining efficiency and long auxiliary time. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a method for machining the nozzle hole of a suspended basket cylinder. To achieve the aforementioned objective, this invention employs the following technical solution: A method for machining the nozzle hole of a suspended basket cylinder includes the following steps. Step 1: Install the basket body onto the worktable of the floor-type boring and milling machine, and machine the cutting hole and lifting hole at the position of the nozzle hole to be machined; Step 2: Use a cutting tool with an internal cooling channel to rough machine the nozzle hole to be machined. During the rough machining process, use reverse milling to remove material in layers, and deliver cutting fluid to the cutting area through the internal cooling channel for chip removal. Step 3: Set up a lifting connection structure on the scrap material formed after rough processing. After applying pre-tight tension to the scrap material through the lifting mechanism, cut and remove the material. During the cutting process, cut the lower part of the scrap material first, and then cut the upper part of the scrap material to separate the scrap material from the basket body. Step 4: Use a boring tool with a principal cutting edge angle of less than 90° to finish the nozzle hole. During the finishing process, use an intermittent cutting method with non-uniform cutting amount for boring. In this process, the reverse milling and internal cooling chip removal in step two, the pre-tightening and material handling in step three, and the intermittent cutting with unequal cutting amount in step four work together to complete the machining of the nozzle hole of the basket cylinder.

[0009] Furthermore, in step one, a U-shaped drill with an anti-vibration structure is used to machine the cutting hole and the lifting hole.

[0010] Furthermore, the reverse milling layer cutting in step two is staggered layer cutting, where adjacent cutting layers are machined using different cutting depths.

[0011] Furthermore, the cutting depth of different cutting layers varies layer by layer along the machining direction to make the cutting load tend to be balanced.

[0012] Furthermore, in step two, a rapid feed milling cutter with an internal cooling channel is used for roughing, and the cutting fluid is delivered to the cutting contact area between the cutter and the workpiece through the internal channel of the cutter.

[0013] Furthermore, the lifting mechanism in step three includes a crane and a hand chain hoist, with the hand chain hoist positioned between the scrap material and the crane.

[0014] Furthermore, in step three, before cutting the scrap material, a pre-tightening force is applied to the scrap material using a hand-operated hoist to reduce the impact load generated during the separation of the scrap material.

[0015] Furthermore, in step three, the lower semicircular area of ​​the remaining material is first cut to form a release space, and then the upper semicircular area of ​​the remaining material is cut to complete the separation of the remaining material.

[0016] Furthermore, in step four, a 45° principal cutting edge angle cutting tool is used for boring.

[0017] Furthermore, the non-equal cutting amount intermittent cutting method in step four involves using at least one of different cutting depths, different feed rates, and different spindle speeds for adjacent cutting strokes.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. In this invention, a U-shaped drill with an anti-vibration structure is used in the drilling preparation stage to drill the entry hole and lifting hole. The U-shaped drill has high rigidity and good chip breaking performance, which can effectively suppress vibration during the drilling process. At the same time, cutting fluid is delivered to the drilling area through the internal cooling channel set inside the U-shaped drill to reduce the drilling temperature and improve the chip removal effect. Through the above methods, the problem of tool vibration caused by unstable clamping rigidity when using a replaceable head carbide internal cooling drill in the prior art is effectively solved, reducing the dependence on on-site parameter adjustment by the operator during the machining process and improving the consistency and controllability of drilling.

[0019] 2. In this invention, during the scrap material cutting and unloading stage, a screw is connected to the scrap material through a lifting hole, and a hand-operated hoist is used to connect the scrap material to the overhead crane. Before cutting, an adjustable pre-tension force is applied to the scrap material using the hand-operated hoist, keeping the scrap material under controlled stress and preventing large displacement of the scrap material at the moment of cutting completion. Simultaneously, the lower semicircular area of ​​the scrap material is cut first, followed by the upper semicircular area. As the lower area is removed, the center of gravity of the scrap material gradually shifts outward, and finally, under the controlled pre-tension force, separation is completed and the scrap material is lifted away by the overhead crane. This method effectively solves the problems of direct connection of the overhead crane via a sling, inaccurate control of the tension, and uncertain tilting direction of the scrap material in existing technologies. It avoids the risks of screw breakage, damage to the processed surface, and personnel injury, significantly improving the safety of the unloading process.

[0020] 3. In this invention, a rapid-feed milling cutter with an internal cooling channel is used in the roughing hole-opening stage, and a reverse milling layered cutting method is employed to remove material. Specifically, a staggered cutting method is used, that is, adjacent cutting layers are machined with different cutting depths, so that the cutting load of each layer tends to be balanced, avoiding tool vibration and workpiece deformation caused by excessive cutting load in a single layer. At the same time, the internal cooling system continuously delivers cutting fluid into the tool, and the cutting fluid directly reaches the cutting contact area through the tool's internal channels, forming a continuous chip removal flow, which promptly removes chips from the machining area, avoiding chip accumulation that affects machining quality. Through the above methods, the problems of excessively long axial toolpath, large cutting volume, and easy vibration when using a D100R8 round nose cutter for rough milling in the prior art are effectively solved, improving roughing efficiency and workpiece accuracy.

[0021] 4. In this invention, a 45° principal cutting edge angle turning tool with wear-resistant coated inserts is used in the finishing stage. Boring is performed using intermittent cutting with non-uniform cutting amounts. Adjacent cutting strokes are adjusted using at least one parameter among different cutting depths, feed rates, and spindle speeds to prevent the tool from being under constant heating for extended periods, thus reducing thermal shock. This effectively solves the problem of uneven insert heating and accelerated wear caused by the high toughness, low thermal conductivity, and work hardening tendency of austenitic stainless steel when using a flatbed precision boring tool for continuous cutting with uniform cutting amounts in existing technologies. It reduces the risk of tool breakage, extends tool life, reduces downtime for insert replacement, and ensures the dimensional accuracy, form and position tolerances, and surface quality of the nozzle hole.

[0022] 5. In this invention, through the coordinated operation of reverse milling layered cutting and internal cooling chip removal processes, pre-tightening controlled material removal processes, and non-equal cutting amount intermittent boring processes, the entire process from drilling, roughing, material removal to finishing is achieved, realizing high-stability machining of the nozzle hole of the hoisting basket cylinder. This comprehensively solves the technical problems of poor drilling stability, low safety of residual material removal, poor cutting stability, fast tool wear, and low machining efficiency in the prior art, and meets the requirements of high precision, high quality, high stability, and high efficiency for the machining of nozzle holes in nuclear power reactor internal components. Attached Figure Description

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of the overall structure of the suspended basket cylinder and the remaining material of the present invention. Figure 2 This is a schematic diagram of the overall structure of the present invention, showing the separation of the basket body and the waste material. Figure 3 This is a schematic diagram of the overall structure of the residual material under stress according to the present invention.

[0024] In the attached drawings: 10, 101, 102, 20, 1, 1, 2. Detailed Implementation

[0025] To better understand the purpose, structure, and function of this invention, the following detailed description of a method for processing nozzle holes in a suspended basket cylinder is provided in conjunction with the accompanying drawings.

[0026] For ease of description, the direction in which the axis of the suspended platform extends is referred to as "axial" or similar term; the direction perpendicular to the axis is referred to as "radial" or similar term; the direction near the outside of the suspended platform is referred to as "outer" or similar term; the direction near the inside of the suspended platform is referred to as "inner" or similar term; and the direction of tool feed during machining is referred to as "feed direction" or similar term.

[0027] It should be noted that the above directional description is only for the purpose of facilitating understanding of the technical solution of the present invention and is not intended to limit the scope of protection of the present invention.

[0028] like Figure 1 , 2 As shown, the present invention provides a method for machining nozzle holes in a suspended basket cylinder, for forming nozzle holes 2 that meet design requirements on the suspended basket cylinder 10. The suspended basket cylinder 10 is mounted on the worktable of a floor-type boring and milling machine and is positioned and fixed by tooling fixtures to ensure stability during the machining process.

[0029] The main processing objects involved in this embodiment include the basket body 10, the nozzle hole 2, and the scrap material 20 formed during the rough processing. The scrap material 20 is located inside the nozzle hole 2 to be processed and remains connected to the basket body 10 before the nozzle hole 2 is processed.

[0030] In this embodiment, as Figure 1 , 2 As shown, the suspended basket body 10 includes a body 101, which is configured as a hollow circular cylindrical structure. It also includes a flange 102 disposed at one end of the body 101 and fixed to the body 101.

[0031] The machining system used in this invention includes a floor-type boring and milling machine, drilling tools, roughing tools, finishing tools, a lifting mechanism, and an internal cooling system. The internal cooling system is connected to an internal cooling channel inside the roughing tool, used to deliver cutting fluid to the cutting area for cooling and chip removal. The lifting mechanism includes a traveling crane and a hand-operated hoist, the hand-operated hoist being positioned between the scrap material 20 and the traveling crane to apply an adjustable preload to the scrap material 20.

[0032] In this embodiment, as Figure 1 , 2As shown, the processing method of the present invention includes the following steps: Step 1: Drilling preparation.

[0033] First, the basket body 10 is installed on the worktable of a floor-type boring and milling machine, and positioned and fixed using tooling fixtures. Then, the cutting hole and lifting hole 1 are machined at the location of the nozzle hole 2 to be machined. In this embodiment, a U-shaped drill with an anti-vibration structure is preferably used for drilling.

[0034] Because of its high rigidity and excellent chip-breaking performance, the U-shaped drill can effectively suppress vibrations during drilling and improve the stability of the drilling process. Simultaneously, during drilling, cutting fluid can be delivered to the drilling area through the internal cooling channels within the U-shaped drill, thereby reducing drilling temperature and improving chip removal.

[0035] Step 2: Rough machining to create holes.

[0036] After machining the lower cutting hole and lifting hole 1, the nozzle hole 2 is rough-machined using a roughing tool. In this embodiment, a rapid feed milling cutter with an internal cooling channel is preferably used for roughing. It should be noted that material is removed during the machining process using a reverse milling layer-by-layer cutting method. Specifically, the reverse milling layer-by-layer cutting is preferably a staggered cutting method, that is, adjacent cutting layers are machined with different cutting depths.

[0037] For example, the first layer uses a larger depth of cut, the second layer uses a smaller depth of cut, and the third layer adjusts the depth of cut again to balance the cutting load across all layers. This method avoids tool vibration and workpiece deformation caused by excessive cutting load in a single layer. Simultaneously, the internal cooling system continuously supplies cutting fluid to the tool.

[0038] The cutting fluid reaches the cutting contact area between the tool and the workpiece directly through the internal channels of the tool, forming a continuous chip removal flow in the cutting area. This promptly removes the chips generated during the cutting process from the machining area, preventing chip accumulation and affecting machining quality. After rough machining, a 20mm residue is formed inside the area to be machined.

[0039] Step 3: Cutting and removing leftover materials.

[0040] like Figure 1 As shown, after the scrap material 20 is formed, it is connected to the scrap material 20 by a screw passing through the lifting hole 1. Then, a hand-operated hoist is used to connect the scrap material to the overhead crane. Before cutting, a pre-tension force is applied to the scrap material by the hand-operated hoist. In this way, the scrap material 20 is kept in a controlled stress state, avoiding large displacement of the scrap material 20 at the moment of completion of cutting.

[0041] Then, the remaining material 20 is cut. In this embodiment, it is preferable to cut the lower semicircular area of ​​the remaining material 20 first, and then cut the upper semicircular area of ​​the remaining material 20. Specifically, the lower part of the remaining material 20 is cut off first, so that a release space is formed below the remaining material 20.

[0042] As the lower region is removed, such as Figure 3 As shown, the center of gravity of the scrap material 20 gradually shifts outward. Then, cutting continues on the upper part of the scrap material 20 until it is completely separated from the basket body 10. Because the scrap material 20 is constantly subjected to the pre-tension force applied by the hand-operated hoist, it can be separated under controlled conditions and finally lifted away from the processing area by the overhead crane. Specifically, in Figure 3 In the figure, F is the pre-tension force, G is the weight of the remaining material 20, and d is the direction of movement of the remaining material 20.

[0043] Step 4: Finishing.

[0044] like Figure 2 As shown, after the excess material 20 is removed, the nozzle hole 2 is finished using a finishing tool. In this embodiment, a 45° principal cutting edge turning tool is preferably used for finishing. Simultaneously, a wear-resistant coated insert for machining austenitic stainless steel is mounted on the turning tool. Boring is performed using an intermittent cutting method with non-uniform cutting amounts during the finishing process.

[0045] Specifically, adjacent cutting strokes are adjusted using at least one of the following parameters: different depths of cut, different feed rates, and different spindle speeds. For example, the first cut uses a larger depth of cut, the second cut uses a smaller depth of cut, and the third cut further reduces the depth of cut. Alternatively, the feed rate and spindle speed can be varied while keeping the depth of cut constant.

[0046] This intermittent cutting method with non-uniform cutting amounts avoids the tool being under constant heating for extended periods, thus reducing thermal shock and improving the stability of the machining process. After finishing, a nozzle hole 2 that meets the requirements for dimensional accuracy, geometric tolerances, and surface quality is obtained.

[0047] In summary, this invention achieves highly stable machining of the nozzle hole in the basket cylinder by combining reverse milling layered cutting and internal cooling chip removal processes, pre-tightened controlled material removal processes, and non-equal cutting amount intermittent boring processes. This effectively reduces the risk of machining vibration and chip blockage, improves the safety of the residual material removal process, and ensures the machining quality of the nozzle hole.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method of processing a basket cylinder nozzle hole, characterized by, Includes the following steps, Step 1: Install the basket body (10) on the worktable of the floor boring and milling machine, and machine the cutting hole and lifting hole (1) at the position of the nozzle hole to be machined. Step 2: Use a cutting tool with an internal cooling channel to rough machine the nozzle hole to be machined. During the rough machining process, use reverse milling to remove material in layers, and deliver cutting fluid to the cutting area through the internal cooling channel for chip removal. Step 3: Set up a lifting connection structure on the scrap (20) formed after rough processing. After applying a pre-tightening force to the scrap (20) through the lifting mechanism, cut and remove the material. During the cutting process, first cut the lower area of ​​the scrap (20) and then cut the upper area of ​​the scrap (20) to separate the scrap (20) from the basket cylinder (10). Step 4: Use a boring tool with a principal cutting edge angle of less than 90° to finish the nozzle hole (2). During the finishing process, use an intermittent cutting method with non-equal cutting amount for boring. In this process, the reverse milling layer cutting and internal cooling chip removal in step two, the pre-tightening material removal in step three, and the intermittent cutting with non-equal cutting amount in step four work together to complete the machining of the nozzle hole (2) of the basket cylinder (10).

2. The method of claim 1, wherein, In step one, a U-shaped drill with an anti-vibration structure is used to machine the cutter hole and lifting hole (1).

3. The method of claim 1, wherein, The reverse milling layer cutting in step two is staggered layer cutting, where adjacent cutting layers are machined using different cutting depths.

4. The method for processing the nozzle hole of the suspended basket cylinder according to claim 3, characterized in that, The cutting depth of different cutting layers varies layer by layer along the machining direction to make the cutting load tend to be balanced.

5. The method for processing the nozzle hole of the suspended basket cylinder according to claim 1, characterized in that, In step two, a rapid feed milling cutter with an internal cooling channel is used for roughing. The cutting fluid is delivered to the cutting contact area between the cutter and the workpiece through the internal channel of the cutter.

6. The method for machining the nozzle hole of the suspended basket cylinder according to claim 1, characterized in that, The lifting mechanism in step three includes a crane and a hand hoist, with the hand hoist positioned between the scrap material (20) and the crane.

7. The method for processing the nozzle hole of the suspended basket cylinder according to claim 6, characterized in that, In step three, before cutting the scrap (20), a pre-tightening force is applied to the scrap (20) by a hand chain hoist to reduce the impact load generated when the scrap (20) is separated.

8. The method for machining the nozzle hole of the suspended basket cylinder according to claim 1, characterized in that, In step three, the lower semicircular area of ​​the remaining material (20) is first cut to form a release space, and then the upper semicircular area of ​​the remaining material is cut to complete the separation of the remaining material.

9. The method for machining the nozzle hole of the suspended basket cylinder according to claim 1, characterized in that, In step four, a 45° principal cutting edge angle cutting tool is used for boring.

10. The method for processing the nozzle hole of the suspended basket cylinder according to claim 1, characterized in that, The non-equal cutting amount intermittent cutting method in step four involves using at least one of different cutting depths, different feed rates, and different spindle speeds for adjacent cutting strokes.

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