Nuclear power valve rocker arm additive manufacturing method

Abstract

The invention relates to a nuclear power valve rocker arm additive manufacturing method. Comprising the following steps that additive manufacturing process parameters are determined, and the additive manufacturing process parameters comprise a layer layout diagram and a welding bead distribution diagram; and the valve rocker arm three-dimensional model is imported into additive manufacturing path planning software, and the melting deposition track path of the electric arc wire of each welding layer is generated according to the layer layout diagram and the welding bead distribution diagram. And based on additive manufacturing process parameters, the wire feeding mechanism feeds wires into the welding gun, and the welding gun is controlled by the robot system to deposit the wires melted through the electric arc on the base material according to the track path and stack the wires layer by layer to form the target forge piece. And post-processing the target forge piece to obtain the valve rocker arm. According to the method, in-plant rapid manufacturing of rocker arm parts can be achieved, various performance requirements of the rocker arm parts are met, the problem that the percentage elongation after fracture of an original wire is insufficient is solved, the percentage elongation after fracture is increased, and the risk that the tail portion is lost after the rocker arm is fractured can be greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and particularly to an additive manufacturing method for a nuclear power valve rocker arm. Background Art

[0002] For check valves on different systems of some nuclear power plants, operating events of rocker arm fracture have occurred. When the rocker arm part fractures, parts of the fractured part will follow the medium to random parts of the system, leading to accidents. It will also cause part of the valve flap assembly to fall off and get stuck at the valve outlet pipe, resulting in blockage of the medium at this place, and thus causing insufficient auxiliary feed water flow of the steam generator in this loop system. For example, in a nuclear power plant unit No. 4, a rocker arm fracture with the tail missing occurred. Finally, the tail of the fractured rocker arm was found and removed in the inverted J-shaped pipeline of the No. 1 steam generator, posing a potential hidden danger to the normal operation of the nuclear power plant.

[0003] However, the process of using traditional manufacturing methods for valve rocker arm parts is long. Under normal circumstances, it takes several months to complete the manufacturing. The procurement process in a nuclear power plant from the demand submission to the part warehousing will experience an even longer cycle. In case of emergency, the nuclear power plant needs to produce rocker arms in the plant. Although the nuclear power plant is equipped with machining capabilities, traditional manufacturing methods still cannot meet this demand. Once a rocker arm fracture event occurs and there is a shortage of spare parts, it is easy to affect the normal operation of the nuclear power plant unit.

[0004] The wire arc additive manufacturing (WAAM) method is a type of additive manufacturing technology suitable for rapid manufacturing. It only needs to configure a robotic system (plus optional external axes), a deposition power supply system, wire materials and other consumables, and cooperate with a dedicated additive manufacturing program and process to achieve the rapid manufacturing of rocker arm parts. Among them, the wire material is the raw material for additive manufacturing of the rocker arm. According to the material classification, the wire material grade matching the rocker arm raw material (RCC-M M3402Z3CN20-09M) is (RCC-M S2910 ER308L).

[0005] However, the elongation after fracture (A%) of the wire material of the model RCC-M S2910 ER308L is ≥30. This is not only less than the requirement of the elongation after fracture of the rocker arm material, but also far lower than that of the target forging. According to the mechanical properties of Z3CN20-09M (rocker arm raw material) in the RCC-M standard M3402, its elongation after fracture (A%) is ≥35. In order to reduce the risk of the tail missing after the rocker arm fractures and ensure the integrity of the rocker arm after fracture, it is necessary to increase the elongation after fracture of the rocker arm material to the forging level. The elongation after fracture (A%) of similar forging materials (such as Z2CN19-10 nitrogen-controlled in the RCC-M standard M3301) is ≥45, and the current traditional manufacturing methods still cannot meet this demand. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an additive manufacturing method for a nuclear power valve rocker arm in view of the defects that the manufacturing time of the rocker arm is too long and the elongation after fracture of the wire material that can be used for wire additive manufacturing does not meet the performance requirements of the valve rocker arm.

[0007] The technical solution adopted by the present invention to solve its technical problems is: an additive manufacturing method for a nuclear power valve rocker arm, comprising the following steps:

[0008] Determine the additive manufacturing process parameters, where the additive manufacturing process parameters include a layer layout diagram and a bead distribution diagram;

[0009] Import the three-dimensional model of the valve rocker arm into the additive manufacturing path planning software, and generate the trajectory path of the melting and deposition of the arc wire material for each welding layer according to the layer layout diagram and the bead distribution diagram;

[0010] Based on the additive manufacturing process parameters, the wire feeding mechanism feeds the wire material into the welding torch, and the welding torch deposits the arc-melted wire material on the base material along the trajectory path under the control of the robot system, and stacks layer by layer to form the target forging;

[0011] Perform post-treatment on the target forging to obtain the valve rocker arm part.

[0012] Furthermore, in the additive manufacturing method for a nuclear power valve rocker arm of the present invention, the additive manufacturing parameters include the total number of welding layers, wire feeding speed, arc welding reference current and voltage, welding torch moving speed, arc length correction value, pulse correction value, arc extinguishing current / time, interlayer temperature, maximum interlayer temperature, base material thickness, deposition thickness, stacking form, composition of the shielding gas, front gas flow rate, current mode and polarity, filling spacing between the wire material melting and deposition in the beads, interlayer angle, and height of each welding layer.

[0013] Furthermore, in the additive manufacturing method for a nuclear power valve rocker arm of the present invention, the total number of welding layers is 27 layers, and the wire feeding speed, arc welding power supply current and voltage for the 1st to 14th layers are 5.9 m / min, 164 ± 5 A, and 20.1 V respectively, and the wire feeding speed, arc welding reference current and voltage for the 15th to 27th layers are 6.2 m / min, 170 ± 5 A, and 20.5 V respectively.

[0014] Furthermore, in the additive manufacturing method for a nuclear power valve rocker arm of the present invention, the welding torch moving speed is 9 mm / s, the arc length correction value is -5, and the pulse correction value is 2.0.

[0015] Furthermore, in the additive manufacturing method for a nuclear power valve rocker arm of the present invention, the arc extinguishing current / time is 50% / 1.3 s of the arc welding reference current, and the interlayer temperature is less than 180°C.

[0016] Further, in the additive manufacturing method of the nuclear power valve rocker arm of the present invention, the maximum interlayer temperature does not exceed 180°C, the substrate thickness is 25 mm, the cladding thickness is 200*135*75 mm, and the stacking form is a rectangular stacking form.

[0017] Further, in the additive manufacturing method of the nuclear power valve rocker arm of the present invention, the composition of the protective gas is 97.5% Ar + 2.5% CO2, the front gas flow rate is 20 L / min, and the current mode and polarity are CMT+P and positive electrode respectively.

[0018] Further, in the additive manufacturing method of the nuclear power valve rocker arm of the present invention, the filling spacing between the wire melting depositions in the weld beads is 3.9 mm, the interlayer angle is 90°, and the height of each weld layer is 3.8 mm.

[0019] Further, in the additive manufacturing method of the nuclear power valve rocker arm of the present invention, in the step of post-treating the target forging to obtain the valve rocker arm, it includes:

[0020] Shot peening, cutting, grinding, heat treatment, and pickling treatment are sequentially performed on the target forging to obtain the valve rocker arm parts.

[0021] Further, in the additive manufacturing method of the nuclear power valve rocker arm of the present invention, the elongation after fracture of the valve rocker arm is greater than or equal to 45.

[0022] Implementing the additive manufacturing method of the nuclear power valve rocker arm of the present invention has the following beneficial effects: The present invention can realize rapid in-factory manufacturing of rocker arm parts based on the arc wire additive manufacturing method, avoiding the long process of the traditional casting method; using a special process ensures the overall stacked forming of the rocker arm parts, can meet the performance requirements of the rocker arm parts, and overcomes the problem of insufficient elongation after fracture of the original wire, increasing the elongation after fracture, and can greatly reduce the risk of tail loss after the rocker arm breaks. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below in conjunction with the drawings and embodiments. In the drawings:

[0024] Figure 1 is a schematic flow chart of the additive manufacturing method of the nuclear power valve rocker arm provided by the embodiment of the present invention;

[0025] Figure 2 is a traditional production and manufacturing flow chart of the rocker arm casting. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] For a clearer understanding of the technical features, objectives, and effects of the present invention, the specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the following description, it should be noted that unless otherwise clearly specified and defined, terms such as "installation", "connection", "attachment", "fixation", "setting", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components. When an element is referred to as being "on" or "under" another element, the element can be "directly" or "indirectly" located above the other element, or there may also be one or more intermediate elements. Terms such as "first", "second", "third", etc. are only for the convenience of describing the present technical solution and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features.

[0027] In the following description, specific details such as specific system structures and technologies are presented for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present invention. However, those skilled in the art should clearly understand that the present invention can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present invention.

[0028] As Figure 1 shown, in one of the embodiments, the additive manufacturing method for the nuclear power valve rocker arm of this embodiment includes the following steps:

[0029] S1. Determine the additive manufacturing process parameters. The additive manufacturing process parameters include the layer layout diagram and the bead distribution diagram. It can be understood that the layer layout diagram is a schematic diagram of the deposition of molten metal by the arc wire in the vertical direction, and the bead distribution diagram refers to the schematic diagram of the deposition of molten metal by the arc wire in the planar direction. They are in the relationship of the vertical section view and the horizontal section view of the same additive manufacturing part.

[0030] Specifically, the additive manufacturing parameters also include the total number of weld layers, wire feeding speed, arc welding reference current and voltage, welding torch moving speed, arc length correction value, pulse correction value, arc extinguishing current / time, interlayer temperature, maximum interlayer temperature, substrate thickness, deposition thickness, stacking form, composition of the shielding gas, front gas flow rate, current mode and polarity, filling spacing between the wire melting depositions in the beads, interlayer angle, and height of each weld layer.

[0031] S2. Import the three-dimensional model of the valve rocker arm into the additive manufacturing path planning software, and generate the trajectory path of the melting deposition of the arc wire for each weld layer according to the layer layout diagram and the bead distribution diagram.

[0032] S3. Based on the additive manufacturing process parameters, the wire feeding mechanism feeds the wire into the welding torch. Under the control of the robot system, the welding torch deposits the wire melted by the arc on the base material along the trajectory path and stacks layer by layer to form the target forging.

[0033] S4. Perform post-processing on the target forging to obtain the valve rocker arm part. Specifically, by performing shot peening, cutting, grinding, heat treatment, and pickling on the target forging in sequence, the finished valve rocker arm is obtained. Figure 2 The traditional production and manufacturing flow chart of the rocker arm casting is shown. The material grade of the rocker arm part is Z3CN20-09M, which belongs to the pressure-bearing castings in Class 1, 2, and 3 equipment made of austenitic-ferritic stainless steel M3402 in the RCC-M standard. The chemical composition requirements are shown in Table 1, and the mechanical property requirements are shown in Table 2. The valve rocker arm part is processed from the casting blank. The traditional production and manufacturing method usually takes several months to complete under normal circumstances.

[0034] Compared with the long process of the traditional production and manufacturing process of valve rocker arm parts, the preparation of rocker arm parts based on the arc wire additive manufacturing method in this embodiment can achieve rapid in-factory manufacturing, avoiding the long process of the traditional casting method; using a special process ensures the overall stacked forming of the rocker arm parts, can meet the performance requirements of the rocker arm parts, and overcomes the problem of insufficient elongation after fracture of the original wire, increasing the elongation after fracture, and can greatly reduce the risk of tail loss after the rocker arm breaks.

[0035] Table 1 Chemical composition requirements of Z3CN20-09M in M3402

[0036]

[0037] Table 2 Mechanical property requirements of Z3CN20-09M in M3402

[0038]

[0039] According to the mechanical properties of Z3CN20-09M in the RCC-M standard M3402, its elongation after fracture (A%) ≥ 35. In order to reduce the risk of tail loss after the rocker arm breaks and ensure the integrity of the rocker arm after fracture, it is necessary to increase the elongation after fracture of the rocker arm material to the forging level. The elongation after fracture (A%) of similar forging materials (such as Z2CN19-10 nitrogen control in the RCC-M standard M3301) ≥ 45. The chemical composition requirements of this material are shown in Table 3, and the mechanical property requirements are shown in Table 4.

[0040] Table 3 Chemical composition requirements of Z2CN19-10 nitrogen control in M3301

[0041] Element (%) Z2CN19-10 (Nitrogen control) C ≤0.035 Si ≤1.00 Mn ≤2.00 Cr 18.50-20.00 Ni 9.00-10.00 Cu ≤1.00 N ≤0.080 S ≤0.015 P ≤0.030

[0042] Mechanical Property Requirements for Nitrogen Control of Z2CN19-10 in Table 4 M3301

[0043] Mechanical properties Z2CN19-10 (Nitrogen control) Rp0.2 (MPa) ≥210 Rm (MPa) ≥520 A％ ≥45 KV (J) ≥100 Rp0.2 (MPa) at 350 °C ≥125 Rm (MPa) at 350 °C ≥394

[0044] In a preferred embodiment, the total number of welding layers is 27. The wire feeding speed, arc welding power source current, and voltage for the 1st to 14th layers are 5.9 m / min, 164 ± 5 A, and 20.1 V respectively. The wire feeding speed, arc welding reference current, and voltage for the 15th to 27th layers are 6.2 m / min, 170 ± 5 A, and 20.5 V respectively. The welding torch moving speed is 9 mm / s, the arc length correction value is -5, and the pulse correction value is 2.0. The post-welding current / time is 50% / 1.3 s of the arc welding reference current, and the interlayer temperature is less than 180°C. The maximum interlayer temperature does not exceed 180°C, the substrate thickness is 25 mm, the deposited thickness is 200*135*75 mm, and the stacking form is a rectangular stacking form. The composition of the shielding gas is 97.5% Ar + 2.5% CO2, the front gas flow rate is 20 L / min, the current mode and polarity are CMT+P and positive respectively. The filling spacing for the wire melted and deposited between the weld beads is 3.9 mm, the interlayer angle is 90°, and the height of each welding layer is 3.8 mm. It can be understood that in order to verify these process parameters, by dissecting the printed rocker arm, tensile, bending, impact, metallographic and other metal material tests are carried out to confirm that the performance indicators meet the requirements of the raw material standard for the valve rocker arm, so as to obtain the determined additive manufacturing process parameters. It should be noted that the shielding gas is used to protect the welding area to prevent oxidation and contamination.

[0045] It can be understood that due to the low elongation after fracture of the ER30L wire, without developing new wire materials, only from the process perspective can we consider increasing the elongation after fracture of the rocker arm parts after additive manufacturing. The embodiment of the present invention has achieved a breakthrough in the elongation after fracture (A%) ≥ 45 of the ER308L material by arc wire additive manufacturing by controlling the electrical parameters and temperature curve in the additive manufacturing process, while ensuring that other mechanical properties of the material are not lower than the requirements of the Z2CN19-10 nitrogen-controlled material in the RCC-M standard M3301.

[0046] Specifically, this embodiment is an additive manufacturing method based on arc welding technology, which realizes the forming of a three-dimensional object by layer-by-layer stacking of molten metal wire. It has high production efficiency. The 6-axis robot system plus an external axis, with the end effector connected to the arc welding power source and wire feeding mechanism, and then combined with additive manufacturing layer slicing and path planning software, the manufacturing efficiency can reach 50-200 cm3 / h, and it can achieve the rapid manufacturing of the rocker arm part blank in the nuclear power plant in about 3 to 4 days. That is to say, in this embodiment, the industrial robot system used has 6 rotating axes. The external axis refers to the positioner that holds the workpiece, which has 2 axes of rotation and flipping and can be linked with the robot. The end effector refers to the arc wire welding torch loaded at the end of the robot. Because the wire needs to be melted and deposited during the robot's movement, it is necessary to connect the arc welding power source and the wire feeding mechanism. The additive manufacturing path planning software generates the trajectory path of the melting and deposition of the arc wire for each layer according to the imported 3D model of the rocker arm. The stacked molten metal forms the body of the rocker arm part. The generated trajectory path is imported into the robot system, and the end of the robot can walk along the generated path with the actuator. At the same time, the power source and the wire feeding mechanism send current and welding wire to the actuator to realize the melting and deposition of a layer of welding wire metal on the planned path. Each layer is reciprocated, and the arc wire continuously melts and deposits in volume to realize the additive manufacturing of the rocker arm.

[0047] The specific numerical values of the additive manufacturing process parameters in this embodiment are shown in Table 5.

[0048] Table 5

[0049]

[0050] It should be noted that the preheating temperature range is no preheating or room temperature. The current mode CMT+P is a welding technology that combines two welding modes: Cold Metal Transfer (CMT) and Pulse Arc. This mode alternately uses short-circuit transfer and spray transfer during welding to improve welding efficiency and forming quality while maintaining the advantages of CMT, such as welding stability and spatter-free characteristics. In the CMT mode, a short circuit is formed when the tip of the welding wire touches the workpiece, the current drops rapidly, and the voltage rises until the molten droplet detaches from the welding wire. This mode has a low heat input and is suitable for welding heat-sensitive materials such as aluminum alloys and titanium alloys. The P mode is a type of Pulse MIG welding, which is characterized by controlling the droplet transfer through pulsed current. In the P mode, the welding machine outputs a periodic pulsed current to melt the welding wire and form molten droplets, and then the molten droplets detach from the welding wire.

[0051] Based on the wire arc additive manufacturing method and the determined specific process parameters, this embodiment can enable the elongation after fracture of the quickly manufactured valve rocker arm to be greater than or equal to 45%. While meeting the performance requirements of the rocker arm parts, it not only avoids the long process of the traditional casting method, but also overcomes the problem of insufficient elongation after fracture of the original wire, increases the elongation after fracture, and can greatly reduce the risk of the tail loss after the rocker arm breaks. The present invention can be applied to the operation and maintenance industry of nuclear power plants, and can also be applied to the operation and maintenance industries of conventional thermal power, refining, steel manufacturing and other industries.

[0052] Those skilled in the art can further realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described according to functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0053] The steps of the method or algorithm described in combination with the embodiments disclosed herein can be directly implemented by hardware, a software module executed by a processor, or a combination of the two. The software module can be placed in a random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, register, hard disk, removable disk, CD-ROM, or any other form of storage medium well-known in the technical field.

[0054] It can be understood that the above embodiments only represent the preferred embodiments of the present invention, and the description is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent of the present invention; it should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can also be made, which all belong to the protection scope of the present invention; therefore, all equivalent transformations and modifications made to the scope of the claims of the present invention shall fall within the scope covered by the claims of the present invention.

Claims

1. An additive manufacturing method for a nuclear power valve rocker arm, characterized in that, Including the following steps: Determine the additive manufacturing process parameters, which include the layer layout diagram and the bead distribution diagram; Import the three-dimensional model of the valve rocker arm into the additive manufacturing path planning software, and generate the trajectory path of the melting and deposition of the arc wire for each welding layer according to the layer layout diagram and the bead distribution diagram; Based on the additive manufacturing process parameters, the wire feeding mechanism feeds the wire into the welding torch. Under the control of the robot system, the welding torch deposits the wire melted by the arc on the substrate according to the trajectory path, and stacks layer by layer to form the target forging; Perform post-treatment on the target forging to obtain the valve rocker arm part.

2. The additive manufacturing method of the nuclear power valve rocker arm according to claim 1, characterized in that The additive manufacturing parameters include the total number of welding layers, wire feeding speed, arc welding reference current and voltage, welding torch moving speed, arc length correction value, pulse correction value, current / time at the end of welding, interlayer temperature, maximum interlayer temperature, substrate thickness, deposition thickness, stacking form, composition of the shielding gas, front gas flow rate, current mode and polarity, filling spacing between the weld beads where the wire melts and deposits, interlayer angle, height of each welding layer.

3. The additive manufacturing method of the nuclear power valve rocker arm according to claim 2, characterized in that, The total number of welding layers is 27. The wire feeding speeds, arc welding power source currents and voltages for the 1st to 14th layers are 5.9 m / min, 164 ± 5 A, and 20.1 V respectively. The wire feeding speeds, arc welding reference currents and voltages for the 15th to 27th layers are 6.2 m / min, 170 ± 5 A, and 20.5 V respectively.

4. The additive manufacturing method of the nuclear power valve rocker arm according to claim 2, characterized in that, The welding torch moving speed is 9 mm / s, the arc length correction value is -5, and the pulse correction value is 2.

0.

5. The additive manufacturing method of the nuclear power valve rocker arm according to claim 2, characterized in that The current / time at the end of welding is 50% of the arc welding reference current / 1.3 s, and the interlayer temperature is less than 180°C.

6. The additive manufacturing method of the nuclear power valve rocker arm according to claim 2, characterized in that, The maximum interlayer temperature does not exceed 180°C, the substrate thickness is 25 mm, the deposition thickness is 200*135*75 mm, and the stacking form is a rectangular stacking form.

7. The additive manufacturing method for the rocker arm of a nuclear power valve according to claim 2, characterized in that The composition of the shielding gas is 97.5% Ar + 2.5% CO2, the front gas flow rate is 20 L / min, and the current mode and polarity are CMT+P and positive respectively.

8. The additive manufacturing method of the nuclear power valve rocker arm according to claim 2, wherein The filling spacing between the weld beads where the wire melts and deposits is 3.9 mm, the interlayer angle is 90°, and the height of each welding layer is 3.8 mm.

9. The additive manufacturing method of the nuclear power valve rocker arm according to claim 1, characterized in that In the step of performing post-treatment on the target forging to obtain the valve rocker arm, it includes: Performing shot peening, cutting, grinding, heat treatment, and pickling treatment on the target forging in sequence to obtain the valve rocker arm part.

10. The additive manufacturing method of the nuclear power valve rocker arm according to claim 1, characterized in that The elongation after fracture of the valve rocker arm is greater than or equal to 45.

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