An arc additive forming method for large metal components

Abstract

The application belongs to the technical field of large metal component manufacturing, and particularly relates to an electric arc additive forming method for large metal components. The method combines a submerged arc additive manufacturing method and a cold metal transition manufacturing method, the edge of the metal component is prepared by the cold metal transition method to improve the contour size accuracy and reduce the surface roughness, and the core of the metal component is prepared by the submerged arc additive manufacturing method to improve the forming efficiency of the part. Compared with traditional forging or a single electric arc additive forming mode, the method can realize rapid prototyping of large metal components, accurately control the machining allowance of the formed part contour by using the cold metal transition method, improve the size accuracy, significantly improve the material utilization rate, and reduce the production cost.

Description

Technical Field

[0001] This invention belongs to the field of large metal component manufacturing technology, specifically relating to an electric arc additive manufacturing method for large metal components. Background Technology

[0002] Traditional large-scale, high-performance metal components (such as petrochemical pressure vessels and fracturing pump main casings) are typically manufactured using casting and forging techniques, followed by machining. This approach struggles to meet the requirements of low-cost, high-efficiency manufacturing and integrated structural design. In contrast, additive manufacturing, based on the principle of material accumulation, enables the integrated forming of large metal components without molds. This facilitates innovative structural design and cost control, offering significant advantages and broad application prospects.

[0003] Compared to laser additive manufacturing and electron beam additive manufacturing, arc additive manufacturing uses an electric arc as a heat source, resulting in lower equipment and material costs, higher material utilization, and higher deposition efficiency, making it suitable for the fabrication of large metal components. Cold metal transfer technology, as a novel welding process, offers advantages such as ultra-low heat input and spatter-free droplet transfer, making it highly suitable for additive manufacturing. However, the forming efficiency of cold metal transfer technology is approximately 1–2 kg / h, which is still insufficient for industrial applications of large metal components (weighing over 2 tons). Submerged arc additive manufacturing technology, another arc additive manufacturing technology, boasts the highest forming efficiency (4–8 kg / h) and better forming quality. It has been used in the trial production of large products such as nuclear reactor pressure vessels, refrigerator end caps, and tees, providing a new solution for the rapid prototyping of large metal components.

[0004] However, submerged arc additive manufacturing (SAW) technology still faces numerous technological challenges. Compared to conventional additive manufacturing technologies that employ gas shielded welding processes such as cold metal transfer, SAW requires the application of auxiliary materials during the printing process. Therefore, patent CN 104526114 A employs welding baffles to the workpiece edges to address the flux flow problem at these edges. However, this approach requires repeated welding of the baffles during printing, resulting in cumbersome operations, reduced automation, and increased printing time. Furthermore, due to the high heat input of SAW, significant heat accumulation occurs during printing, leading to prolonged solidification time in the molten pool at the edges of the formed part. This results in edge collapse, making it difficult to control edge shape and dimensions, particularly unsuitable for fabricating large-angle suspended structures. Ultimately, this directly impacts the dimensional accuracy and surface finish of the parts. Summary of the Invention

[0005] This invention proposes an electric arc additive manufacturing method for large metal components to solve the problem in the prior art that large components require fixed baffles to lay flux during submerged arc additive manufacturing, and the large heat input makes it difficult to control the edge dimension accuracy.

[0006] To achieve the above objectives, the present invention proposes the following technical solution:

[0007] An arc additive manufacturing method for large metal components, comprising the following steps:

[0008] Step 1: Design the machining allowance of the part to be formed according to the design drawing; construct the overall three-dimensional model of the blank to be formed using three-dimensional drawing software;

[0009] Step 2: Divide the overall three-dimensional model of the blank to be formed obtained in Step 1 into a shell structure model composed of the edges of the formed part and a core structure model composed of the remaining structure after removing the edges.

[0010] Step 3: Using preset slicing software, slice the shell structure model and the core structure model respectively to obtain multi-layer two-dimensional contour data of the formed part model;

[0011] Step 4: Clean the substrate, fix the substrate on the printing platform, and control the substrate temperature between 150-200℃;

[0012] Step 5: Input the two-dimensional contour data of the shell structure into the motion control system of the cold metal transition welding torch, which includes a gantry or robot motion mechanism;

[0013] The cold metal transition welding torch motion control system controls the cold metal transition welding torch to start printing the shell structure on the substrate according to the set process parameters. Printing stops when the printing height exceeds the core area to be filled by 6-10mm. The cold metal transition welding torch is then moved to a safe position.

[0014] The two-dimensional contour data of the core structure model is input into the motion control system of the submerged arc welding torch, which includes a gantry or robot motion mechanism; the core structure surrounded by the shell structure is then filled using the submerged arc additive manufacturing process.

[0015] After the core structure has been printed in multiple layers, stop printing when the height of the core is 2-4mm lower than the height of the edge shell area, and move the submerged arc welding gun to a safe position.

[0016] Repeat the above operation to stack the obtained components layer by layer to obtain a shaped part;

[0017] Step 6: Remove the formed part from the work platform and send it into the heat treatment furnace for stress relief heat treatment;

[0018] Step 7: Remove the bottom substrate of the formed part by mechanical processing, and process it according to the drawing requirements to obtain a large metal component.

[0019] Preferably, in step 1, the forming part is designed with a machining allowance of 3-6mm on one side.

[0020] Preferably, in step 2, the thickness of the shell structure model is 8-15mm;

[0021] Preferably, in step 2, the single-sided allowance of the core structure model is 5-8mm.

[0022] Preferably, in step 4, the substrate is preheated by resistance contact heating or flame gun baking.

[0023] Preferably, in step 5, the cold metal transfer process uses welding wire with the same composition as that used in submerged arc additive manufacturing.

[0024] Preferably, in step 5, after each layer is printed, the surface oxide film is polished with a grinding wheel to expose the fresh metal surface, while controlling the interlayer temperature to 100-200℃.

[0025] Preferably, in step 5, during the printing of the core structure, the flux and slag on the surface of the weld bead are removed simultaneously, and the interlayer temperature is controlled at 150-250℃.

[0026] Preferably, in step 5, the thickness of a single addition in the submerged arc additive manufacturing process is 2-6 mm.

[0027] The advantages of this invention are:

[0028] By combining submerged arc additive manufacturing with cold metal transfer manufacturing, the edges of metal components are prepared using cold metal transfer to improve dimensional accuracy and reduce surface roughness; the core of the metal components is prepared using submerged arc additive manufacturing to improve part forming efficiency. Compared with traditional forging or single-arc additive manufacturing, this method enables rapid prototyping of large metal components. At the same time, the cold metal transfer method precisely controls the machining allowance of the formed parts, improves dimensional accuracy, significantly improves material utilization, and reduces production costs.

[0029] Introducing submerged arc welding (SAW) into the manufacturing of large metal components avoids the dust hazards associated with fume emissions and manual oxide scale removal inherent in traditional gas-shielded welding (GSW) methods, thus benefiting employee health. Introducing cold metal transfer (CMT) into SAW significantly improves the automation level of the process, reduces manual labor costs associated with welding baffles in traditional SAW methods, and increases production efficiency. The edge regions formed by CMT provide excellent support for the SAW area, enabling the creation of large-angle suspended structures and expanding the applicability of SAW. Furthermore, SAW can partially remelt the edge structures prepared by CMT, significantly reducing defects such as incomplete melting and porosity, ensuring that the performance of large metal components manufactured using SAW is comparable to that of forgings. Attached Figure Description

[0030] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0031] Figure 1 A flowchart of an electric arc additive manufacturing method for large metal components;

[0032] Figure 2 This is a schematic diagram of the process of traditional submerged arc additive manufacturing.

[0033] Figure 3 A schematic diagram of the process for arc additive manufacturing of large metal components;

[0034] Figure 4 A schematic diagram illustrating the electric arc additive manufacturing method for pressure vessels;

[0035] Figure 5 This is a schematic diagram illustrating the arc additive manufacturing method for a conical ring.

[0036] Among them, 1 is the substrate used for printing, 2 is the baffle used to block the flux, 3 is the submerged arc welding gun, 4 is the submerged arc flux, 5 is the submerged arc additive metal deposition layer, 6 is the cold metal transition welding gun, and 7 is the cold metal transition metal deposition layer. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0038] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this invention is for describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0039] Example 1:

[0040] Please see Figure 1 As shown, this invention provides an arc additive manufacturing method for large metal components; specifically, it includes the following steps:

[0041] Step 1: Design the machining allowance according to the design drawing of the forming part, with a machining allowance of 3-6mm on each side; use 3D drawing software to construct the overall 3D model of the blank to be formed.

[0042] Step 2: Divide the overall 3D model of the formed part blank into a shell structure model composed of the edges of the formed part and a core structure model composed of the remaining structure after removing the edges; using the outer wall surface and inner wall surface of the formed part as reference planes, stretch the curved surface along the printing plane inwards to form a hollow 3D model, called the shell structure model; using the outer wall surface and inner wall surface of the formed part as reference planes, thin the 3D model of the formed part along the printing plane inwards to form a solid 3D model, called the core structure 3D model;

[0043] The thickness of the shell structure formed by the edge of the formed part is 8-15mm. When the inclination at the edge is small, the thickness of the shell structure can be reduced. When the inclination at the edge is large, the thickness of the shell structure needs to be increased to enhance the support of the structure for the submerged arc welding pool. When the angle between the plane where the edge of the formed part is located and the deposition direction is less than 30 degrees, it is judged as a large inclination, and the thickness of the shell structure is reduced. Otherwise, it is judged as a small inclination, and the thickness of the shell structure is increased until the thickness of the shell structure is not less than 12mm.

[0044] The dimensions of the core structure model are increased to accommodate the overlapping area between the shell structure and the core structure, with a single-sided allowance of 5-8mm. During the printing process, the submerged arc additive manufacturing process melts the overlapping area and forms a metallurgical bond with the shell structure.

[0045] Step 3: Using preset slicing software, slice the shell structure model and the core structure model respectively to obtain multi-layer two-dimensional contour data of the formed part model.

[0046] Step 4: Based on the two-dimensional contour data of the shell structure and core structure, and the corresponding cold metal transition and submerged arc additive printing processes, a metal layer is deposited on the substrate surface to obtain the large metal component; the specific process includes the following steps:

[0047] Step 41: After degreasing and removing rust from the substrate surface, fix the substrate to the printing platform and preheat the substrate using resistance contact heating or flame gun baking, controlling the substrate temperature to 150-200℃.

[0048] Step 42: Input the two-dimensional contour data of the shell structure into the cold metal transfer welding torch motion control system (including a gantry or robot motion mechanism). The cold metal transfer welding torch motion control system controls the cold metal transfer welding torch to start printing the shell structure on the substrate according to the set process parameters. Printing stops when the printing height exceeds the core area to be filled by 6-10mm, and the cold metal transfer welding torch is moved to a safe position. The cold metal transfer process uses welding wire with the same composition as submerged arc additive manufacturing or with verified performance similar to that used in submerged arc additive manufacturing. During the printing process, after each layer is printed, the surface oxide film must be ground with a grinding wheel in a timely manner to expose the fresh metal surface. At the same time, the interlayer temperature must be monitored in a timely manner during the printing process and controlled at 100-200℃.

[0049] Step 43: Input the two-dimensional contour data of the core structure model into the submerged arc welding torch motion control system (including gantry or robot motion mechanism). Begin filling the core structure surrounded by the shell structure using submerged arc additive manufacturing process. During the printing process, flux and slag on the weld surface must be removed in a timely manner, while controlling the interpass temperature at 150-250℃. Stop printing when the core height is 2-4mm lower than the height of the edge shell area after multiple layers of core structure have been printed, and move the submerged arc welding torch to a safe position;

[0050] The thickness of a single additive manufacturing process using the submerged arc additive method is 2-6 mm.

[0051] Step 44: Repeat the operations of steps 42-43 above, and after stacking them layer by layer, the large metal component is obtained.

[0052] Step 5: Remove the formed part from the work platform and send it into the heat treatment furnace for stress relief heat treatment.

[0053] Step 6: Remove the bottom substrate of the formed part by mechanical processing and process it according to the design requirements according to the drawings to obtain the large metal component.

[0054] Example 2:

[0055] Figure 2 This is a schematic diagram of the process of the conventional submerged arc additive manufacturing method described in the embodiment; the submerged arc welding power source, flux delivery device, motion control mechanism, and other devices are omitted in the figure. Figure 2 As shown, when using the traditional submerged arc welding process for submerged arc additive manufacturing, a baffle 2 needs to be welded onto the substrate 1 before printing. When the flux 4 is delivered to the substrate surface for welding, the baffle on both sides of the flux hinders the flow of flux. After the submerged arc welding gun 3 ignites in the flux 4, it moves along the trajectory to form a submerged arc additive metal deposition layer 5 on the surface of the substrate 1. As the thickness of the submerged arc additive metal deposition layer 5 increases, the height of the baffle 4 needs to be continuously increased. Finally, after the height meets the requirements, the entire formed part is obtained.

[0056] Example 3:

[0057] Figure 3 This is a schematic diagram of the process of electric arc additive manufacturing of large metal components. The submerged arc and cold metal transfer welding power supply devices are omitted in the figure.

[0058] like Figure 3 As shown, when using the arc additive manufacturing method proposed in the embodiment, a cold metal transition metal deposition layer 7 of a certain height is first printed on the substrate using a cold metal transition welding gun. This layer not only serves as an important component of the formed part but also blocks the flow of flux during the submerged arc additive manufacturing process. After the cold metal transition printing is completed, a submerged arc additive manufacturing metal deposition layer 5 is deposited in the core using the submerged arc additive manufacturing method. During the submerged arc additive manufacturing process, the submerged arc molten pool partially remelts the cold metal transition metal layer. As the height of the submerged arc additive manufacturing metal deposition layer 5 increases, the height of the cold metal transition metal deposition layer 7 needs to be continuously increased. Finally, the cold metal transition metal deposition layer 7 and the submerged arc additive manufacturing metal deposition layer 5 together form the entire formed part.

[0059] Compared to traditional submerged arc additive manufacturing methods, the preparation method in this embodiment uses a cold metal transfer method to prepare the edges of the formed part, which can significantly improve the dimensional accuracy of the formed part and reduce surface roughness. The use of submerged arc additive manufacturing to fill the core can improve the forming efficiency of the part, ensure forming quality, and reduce the amount of manual grinding. Simultaneously, the metal layer prepared by the cold metal transfer technology provides a good supporting structure for the submerged arc additive manufacturing process, overcoming the limitation of traditional submerged arc additive manufacturing methods in forming large-angle suspended structures, and significantly expanding the applicability of arc additive technology.

[0060] Example 4:

[0061] Taking a pressure vessel component as an example, the method for arc additive manufacturing of a large metal component is described in detail.

[0062] As attached Figure 4 As shown, this embodiment provides a method for forming a pressure vessel component. In this embodiment, the pressure vessel component is large in size and weight, and contains a hollow structure at its center; the material used is 30CrMoA. This embodiment describes the process of fabricating a pressure vessel using a cold metal transfer method and a submerged arc additive manufacturing method. Figure 4 This is a schematic diagram illustrating the electric arc additive manufacturing method of this embodiment. The selected submerged arc additive manufacturing process parameters are: submerged arc welding wire diameter 4mm, low-carbon low-alloy steel material, and the performance of the formed parts prepared by the welding wire meets the 30CrMoA forging standard; welding current 600A, welding voltage 32V, wire feed speed 131cm / min, and welding torch movement speed 700mm / min. The selected cold metal transfer process parameters are: cold metal transfer welding wire diameter 1.2mm, low-carbon low-alloy steel material, and the performance of the formed parts prepared by the welding wire meets the 30CrMoA forging standard; shielding gas 82%Ar + 18%CO2; welding current 123A, welding voltage 11.4V, wire feed speed 5.3m / min, and welding torch movement speed 1200mm / min.

[0063] The specific implementation steps are as follows:

[0064] (1) Using 3D modeling software, the entire model is divided into a shell structure composed of a cold metal transition metal deposition layer 7 and a core structure composed of a submerged arc welding additive metal deposition layer 5. The shell structure has a printing thickness of 8mm, and the core structure's width needs to be increased by 5mm on each side of the remaining model width to provide allowance for the submerged arc welding torch to remelt the cold metal transition metal layer. For example... Figure 4 As shown, the angle α between the submerged arc additive forming plane and the height direction of the cold metal transition printing area is ≥90°. Therefore, during the submerged arc additive process, the height of the cold metal transition printing area will not interfere with the submerged arc welding gun, and the shell structure is evenly divided along the edge of the formed part.

[0065] (2) Using a preset slicing software, the shell structure model and the core structure model are sliced ​​to obtain the two-dimensional contour data of each layer.

[0066] (3) Import the shell structure slice data into the cold metal transfer welding torch motion control system. Use the cold metal transfer method to print the edge of the formed part layer by layer on the substrate surface. When the height of the edge of the formed part exceeds the submerged arc additive manufacturing plane by 6-8mm, stop printing and return the cold metal transfer welding torch to the safe position. The forming height of a single layer in the cold metal transfer process is 1.6mm.

[0067] (4) Import the core structure slice data into the submerged arc welding torch motion control system, and fill the core structure using the submerged arc additive manufacturing method. After completing the printing of two metal layers, move the submerged arc welding torch to a safe position. The single-layer deposition layer prepared by the submerged arc additive manufacturing method has a forming height of 2 mm.

[0068] (5) Based on the forming height data, repeat the operations of (4) and (5) to obtain the pressure vessel component after stacking layer by layer.

[0069] Example 5:

[0070] Taking a conical metal ring component as an example, the metal component forming method is described in detail.

[0071] As attached Figure 5 As shown, an electric arc additive manufacturing method for a conical ring is provided. In this embodiment, the outer side of the metal conical ring contains a large-angle suspended structure, and the material is ZG35CrMoA. If this component is prepared using a conventional submerged arc additive manufacturing method, edge collapse makes it difficult to guarantee the forming dimensions and quality.

[0072] Figure 5 This is a schematic diagram illustrating the arc additive manufacturing method of this embodiment. The process parameters for the submerged arc additive manufacturing method are as follows: submerged arc welding wire diameter 4mm, low-carbon low-alloy steel material selected, the performance of the formed parts prepared by the welding wire meets the ZG35CrMoA standard after quenching and tempering; welding current 500A, welding voltage 30V, wire feed speed 120cm / min, welding torch movement speed 700mm / min. The process parameters for the cold metal transfer method are as follows: cold metal transfer welding wire diameter 1.2mm, low-carbon low-alloy steel material selected, the performance of the formed parts prepared by the welding wire meets the ZG35CrMoA standard after quenching and tempering; shielding gas 82%Ar + 18%CO2 selected; welding current 100A, welding voltage 10.2V, wire feed speed 4.1m / min, welding torch movement speed 1000mm / min.

[0073] like Figure 5 As shown, since the angle α between the submerged arc additive forming plane and the height direction of the cold metal transition printing area on the inner side of the formed part is less than 90°, the height of the cold metal transition printing area will interfere with the movement path of the submerged arc welding torch. In this embodiment, the area on the inner side of the formed part that causes interference adopts a stepped segmentation strategy. When the submerged arc welding torch moves to the inner side, since the angle between the submerged arc additive forming plane and the height direction of the cold metal transition printing area after segmentation is equal to 90°, the above problem can be effectively solved.

[0074] The specific implementation steps are as follows:

[0075] (1) The entire model was divided into a shell structure composed of a cold metal transition metal deposition layer 7 and a core structure composed of a submerged arc welding additive metal deposition layer 5 using 3D drawing software. A uniform segmentation strategy was adopted on the outer side of the shell structure, with a printing thickness of 8mm for the cold metal transition forming area; a stepped segmentation strategy was adopted on the inner side of the shell structure, with the side of the cold metal transition forming area being a trapezoidal structure with a height of 5mm and a bottom width of 15mm. After removing the shell structure, the remaining model was left with a 5mm margin on each side to form the core structure, providing a margin for the submerged arc welding torch to remelt the cold metal transition metal layer.

[0076] (2) The shell structure model and the core structure model are sliced ​​using slicing software.

[0077] (3) Based on the slice contour data of the shell structure, a metal layer is deposited on the substrate surface using the cold metal transfer method to form the edge of the shaped part; when the forming height reaches 7mm, printing is stopped and the cold metal transfer welding gun is moved to a safe position.

[0078] (4) Fill the edge core area using submerged arc additive manufacturing based on the slice outline data of the core structure; stop printing when the forming height reaches 5mm and move the submerged arc welding gun to a safe position.

[0079] (5) Based on the forming height data, repeat the operations of (4) and (5) to obtain the metal container component by stacking layers.

[0080] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative in all respects and are not the only ones. All modifications within the scope of this invention or its equivalents are included in this invention.

Claims

1. An electric arc additive manufacturing method for large metal components, characterized in that, The specific steps include: Step 1: Design the machining allowance of the part to be formed according to the design drawing; use 3D drawing software to construct the overall 3D model of the blank to be formed; Step 2: Divide the overall three-dimensional model of the blank to be formed obtained in Step 1 into a shell structure model composed of the edges of the formed part and a core structure model composed of the remaining structure after removing the edges. Step 3: Using preset slicing software, slice the shell structure model and the core structure model respectively to obtain multi-layer two-dimensional contour data of the formed part model; Step 4: Clean the substrate, fix the substrate on the printing platform, and control the substrate temperature between 150-200℃; Step 5: Input the two-dimensional contour data of the shell structure into the motion control system of the cold metal transition welding torch, which includes a gantry or robot motion mechanism; The cold metal transition welding torch motion control system controls the cold metal transition welding torch to start printing the shell structure on the substrate according to the set process parameters. Printing stops when the printing height exceeds the core area to be filled by 6-10mm. The cold metal transition welding torch is then moved to a safe position. The two-dimensional contour data of the core structure model is input into the motion control system of the submerged arc welding torch, which includes a gantry or robot motion mechanism; the core structure surrounded by the shell structure is then filled using the submerged arc additive manufacturing process. After the core structure has been printed in multiple layers, stop printing when the height of the core is 2-4mm lower than the height of the edge shell area, and move the submerged arc welding gun to a safe position. Repeat the above operation to stack the obtained components layer by layer to obtain a shaped part; Step 6: Remove the formed part from the work platform and send it into the heat treatment furnace for stress relief heat treatment; Step 7: Remove the bottom substrate of the formed part by mechanical processing, and process it according to the drawing requirements to obtain a large metal component.

2. The method for arc additive manufacturing of large metal components as described in claim 1, characterized in that, In step 1, the forming part is designed with a machining allowance of 3-6mm on one side.

3. The method for arc additive manufacturing of large metal components as described in claim 1, characterized in that, In step 2, the thickness of the shell structure model is 8-15mm.

4. The method for arc additive manufacturing of large metal components as described in claim 1, characterized in that, In step 2, the single-sided allowance of the core structure model is 5-8mm.

5. The method for arc additive manufacturing of large metal components as described in claim 1, characterized in that, In step 4, the substrate is preheated by resistance contact heating or flame gun baking.

6. The method for arc additive manufacturing of large metal components as described in claim 1, characterized in that, In step 5, the cold metal transfer process uses welding wire with the same composition as that used in submerged arc additive manufacturing.

7. The method for arc additive manufacturing of large metal components as described in claim 1, characterized in that, In step 5, during the printing of the shell structure, after each layer is printed, the surface oxide film is polished with a grinding wheel to expose the fresh metal surface, while controlling the interlayer temperature to 100-200℃.

8. The method for arc additive manufacturing of large metal components as described in claim 1, characterized in that, In step 5, during the printing of the core structure, the flux and slag on the surface of the weld bead are removed, and the interlayer temperature is controlled at 150-250℃.

9. The method for arc additive manufacturing of large metal components as described in claim 1, characterized in that, In step 5, in the submerged arc additive manufacturing process, the thickness of a single additive step is 2-6 mm.

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