A method for laser-GMAW cold wire composite additive manufacturing of stainless steel

Abstract

This invention relates to a method for laser-GMAW cold-wire composite additive manufacturing of stainless steel, aiming to solve the problems of high heat input, low forming accuracy, and low deposition rate in traditional laser-GMAW composite heat source additive manufacturing of stainless steel. This invention adds an independently fed, non-electric cold wire feeding device to the standard laser-GMAW composite additive manufacturing system. This feeding device operates independently and synchronously with the main welding wire feeding system. In conventional laser-GMAW composite heat source additive manufacturing, the arc energy input and wire feeding speed are coupled, and the remelting rate increases with the increase of the wire feeding speed. By adding an independently fed cold wire, the wire feeding speed and arc energy input are decoupled, thereby separating and controlling the arc energy input and the amount of material deposited. This allows for the melting of more stainless steel metal with the lowest possible heat input, reducing the heat input and thermal deformation of the formed part, improving the forming accuracy, mechanical properties, and deposition rate of the formed part, and achieving precise control of heat input during additive manufacturing.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing and welding technology for metal materials, and in particular to a method for laser-GMAW cold wire composite additive manufacturing of stainless steel. Background Technology

[0002] The electric arc additive manufacturing (WAAM) process has the advantages of low cost and high efficiency. Among them, gas metal arc welding (GMAW) has immeasurable advantages in manufacturing large components because it uses consumable electrodes and the coaxial assembly of welding wire and welding gun makes it more flexible in path planning and has high energy transfer efficiency.

[0003] Despite this, WAAM still faces challenges such as poor forming accuracy. Laser-GMAW composite heat sources have garnered more attention due to their ability to maintain a balance between deposition efficiency and surface precision. This technology combines the high energy density and precision of lasers with the high cladding efficiency and low equipment cost of GMAW heat sources. The addition of lasers can compress and stabilize the arc, while the laser's stirring effect on the molten pool increases its fluidity and promotes gas escape. Components manufactured using this technology exhibit high forming accuracy and good mechanical properties. However, the high heat input at high deposition rates can easily lead to high remelting on the substrate or pre-deposited layer, thereby reducing process efficiency and deteriorating mechanical properties. This is because the welding current of MIG welders is coupled with the wire feed speed, and the remelting amount increases with the increase of wire feed speed. Therefore, when using LHAM, only a deposition rate of 3 kg / h can be achieved, which to some extent limits the further development and application of this technology.

[0004] 316L stainless steel is widely used in pressure vessels, boilers, and nuclear reactors due to its excellent corrosion resistance and machinability. However, in the additive manufacturing of stainless steel, high heat input and heat accumulation during layer-by-layer deposition can negatively affect forming accuracy and microstructure properties. Therefore, it is necessary to precisely control the welding current and interpass cooling time to melt more metal with the lowest possible heat input, in order to prevent defects such as porosity, lack of fusion, and cracks, and to improve the deposition rate. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a method for laser-GMAW cold filament composite additive manufacturing of stainless steel. By adding an independently fed cold filament, the wire feeding speed and arc energy input can be decoupled, thereby separating and controlling the arc energy input and the amount of material deposited. This allows for the melting of more stainless steel metal with the lowest possible heat input, thereby reducing the heat input and thermal deformation of the formed part, improving the forming accuracy, mechanical properties, and deposition rate of the formed part, and achieving precise control of heat input during the additive manufacturing process.

[0006] The technical solution adopted in this invention is as follows:

[0007] The present invention proposes a method for laser-GMAW cold wire composite additive manufacturing of stainless steel, which adds an independently fed non-electric cold wire to the standard laser-GMAW composite additive manufacturing system, specifically including the following steps: S1. Use a clamp to fix the substrate on the worktable and clean the substrate; S2. Assemble the welding torch, laser head, and cold wire, with the welding torch in the middle and the laser head and the externally fed cold wire distributed on both sides of the welding torch. S3. Send out hot wires through the MIG welding gun, adjust the positions of the two welding wires and the laser on the substrate so that they are on the same plane, and the center of the laser beam coincides with the ends of the two welding wires. Adjust the following positional parameters of the laser-GMAW composite additive manufacturing system: the angle θ1 between the hot wire and the substrate, the angle θ2 between the laser head axis and the hot wire, the angle θ3 between the hot wire and the cold wire, and the hot wire extension L. S4. Set the initial parameters of the laser-GMAW composite additive manufacturing system: laser power P, hot filament feed speed V1, cold filament feed speed V2, use 99.99% argon as the protective gas, gas flow rate Q, and deposition rate V during the additive manufacturing process. t ; S5. Using a low-power pulsed laser and electric arc as a composite heat source, the molten pool is fed in through a stainless steel hot wire and cold wire, spread and solidified on the substrate, and the single-layer deposition process is completed. S6. In the stainless steel additive manufacturing process, each layer needs to be cooled to the preset temperature before depositing the next layer. Adjust the welding torch height and repeat steps S3 to S5 until the additive manufacturing of the entire stainless steel additive part is completed.

[0008] Furthermore, both the hot wire and the cold wire are 316L stainless steel welding wires.

[0009] Furthermore, in step S3, the angle θ1 between the hot wire and the substrate is 60~90°, the angle θ2 between the laser head axis and the hot wire is 30~60°, the angle θ3 between the hot wire and the cold wire is 60~70°, and the hot wire dry extension L is 10~13mm.

[0010] Furthermore, in step S4, the laser power P is 200~500W, the laser defocusing amount is adjustable from 0 to 2mm, the laser is output in pulse mode with a frequency range of 30~50Hz, and the laser pulse width range is 1~3ms.

[0011] Furthermore, in step S4, the hot wire feeding speed V1 is 5~9 m / min, the corresponding welding current I is 144A~243A, the argon shielding gas flow rate Q is 15~20 L / min, and the shielding gas covers the ends of the hot and cold wires to reduce porosity and oxide inclusion defects, thus increasing the deposition rate V during additive manufacturing. t The speed is 8~12 mm / s.

[0012] Furthermore, in step S4, different hot wire feeding speeds V1 are matched with different cold wire feeding speeds V2, and the cold wire feeding speed V2 is 1~3m / min. The cold wire and hot wire feeding speeds are adjusted independently.

[0013] Compared with the prior art, the present invention has the following advantages: 1. The laser-GMAW cold wire composite additive manufacturing method for stainless steel proposed in this invention adds an independently fed non-energized cold wire to the traditional laser-GMAW composite additive manufacturing system, which significantly improves the deposition rate of stainless steel welding wire under the same current, significantly improves the overall deposition efficiency, greatly shortens the manufacturing cycle, reduces industrial production costs, improves the efficiency of stainless steel additive manufacturing under the same welding current, and reduces energy consumption.

[0014] 2. The laser-GMAW cold wire composite additive manufacturing method for stainless steel proposed in this invention can suppress the problem of arc drift by adding cold wire, and further stabilize the arc on the basis of laser compression and attraction of the arc, thereby improving the deposition efficiency.

[0015] 3. The laser-GMAW cold wire composite additive manufacturing method for stainless steel proposed in this invention, compared with the traditional laser-GMAW composite process, achieves separate control of welding current and wire feeding speed by adding independently fed cold wire. By independently controlling laser power, welding current and wire feeding speed, heat input can be precisely controlled, thereby significantly reducing defects such as deformation and flow caused by remelting and reheating.

[0016] 4. The laser-GMAW cold wire composite additive manufacturing method for stainless steel proposed in this invention has a lower specific energy density than the traditional laser-GMAW composite additive manufacturing process. It can effectively reduce the grain size and anisotropy of the deposited layer structure, ensure the uniformity and fineness of the structure, and thus significantly improve the tensile strength, yield strength, plasticity and other mechanical properties of additively manufactured components such as 316L stainless steel. Attached Figure Description

[0017] Figure 1 This is a schematic diagram illustrating the principle of a laser-GMAW cold wire composite additive manufacturing method for stainless steel proposed in this invention. Figure 2This is a schematic diagram of the thin-walled additive part fabricated using low current in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of a multi-layered, multi-channel block component fabricated using high current in Embodiment 2 of the present invention.

[0018] Figure 1 In the middle: 1-MIG welding torch contact tip; 2-hot wire; 3-laser beam; 4-cold wire; 5-substrate; 6-worktable; L-hot wire extension; θ1-angle between hot wire and substrate; θ2-angle between laser head axis and hot wire; θ3-angle between hot wire and cold wire. Detailed Implementation

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] like Figure 1 As shown, the present invention proposes a method for laser-GMAW cold wire composite additive manufacturing of stainless steel. Based on a standard laser-MIG composite additive manufacturing system, an independently fed non-energized cold wire 4 is added. By adjusting parameters such as the arc current, gas flow rate, welding torch height, and the ratio of hot wire feed speed V1 to cold wire feed speed V2 of the MIG power supply, deposition efficiency is improved, achieving high-efficiency additive manufacturing of stainless steel components. The laser-GMAW composite additive manufacturing method includes a hot wire 2 fed through a MIG welding torch, an independently fed cold wire 4, and a laser head. The additive manufacturing method specifically includes the following steps: S1. Use a clamp to fix the substrate 5 on the worktable 6 and clean the substrate 5.

[0021] S2. Assemble the welding torch, laser head, and cold wire 4 together on the industrial robot, with the welding torch in the middle and the laser head and the cold wire 4 fed by the external wire feeder distributed on both sides of the welding torch.

[0022] S3. The hot wire is fed out through the MIG welding gun. The positions of the two welding wires and the laser above the substrate 5 are adjusted so that they are on the same plane and the center of the laser beam 3 coincides with the ends of the two welding wires. The cold wire 4 and the hot wire 2 are both 316 stainless steel welding wires. Set the following positional parameters for the laser-GMAW composite additive manufacturing system: the angle θ1 between the hot filament and the substrate, the angle θ2 between the laser head axis and the hot filament, the angle θ3 between the hot filament and the cold filament, and the hot filament extension L. In this invention, the angle θ1 between the hot wire 2 and the substrate 5 is 60~90°, the angle θ2 between the laser axis and the hot wire 2 is 30~60°, the angle θ3 between the hot wire 2 and the cold wire 4 is 60~70°, and the dry extension L of the hot wire is 10~13mm.

[0023] S4. Set the initial parameters of the laser-GMAW composite additive manufacturing system: laser power P, hot filament feed speed V1 and cold filament feed speed V2, gas flow rate Q of 99.99% argon protective gas, and deposition rate Vt during the additive manufacturing process. The MIG welding machine power supply is a unified mode, and the welding current and wire feed speed are automatically matched; the laser power P is 200~500W, the laser defocus adjustment range is 0~2mm, the laser is output in pulse mode, the frequency range is 30~50Hz, and the laser pulse width range is 1~3ms. The hot wire feed speed V1 is 5~9 m / min, corresponding to a welding current I of 144A~243A. The argon shielding gas flow rate Q is 15~20 L / min. The shielding gas covers the ends of both the hot and cold wires, reducing porosity and oxide inclusion defects. The deposition rate V during additive manufacturing is... t The speed is 8~12 mm / s; Different hot wire feeding speeds V1 are matched with different cold wire feeding speeds V2; among them, the cold wire feeding speed V2 is 1~3m / min, and the feeding speeds of cold wire 4 and hot wire 2 can be adjusted independently.

[0024] S5. Using a low-power pulsed laser and electric arc as a composite heat source, the material is fed into the molten pool through a stainless steel hot wire and a cold wire, spread and solidified on the substrate, and completes the single-layer deposition process.

[0025] S6. In the stainless steel additive manufacturing process, each layer needs to be cooled to the preset temperature before depositing the next layer. Adjust the welding torch height and repeat steps S3 to S5 until the additive manufacturing of the entire stainless steel additive part is completed.

[0026] This invention adds an independent, non-energized cold wire 4 to the laser-MIG composite heat source, which melts more metal under the same arc current while having a lower heat input. It can also decouple the arc current from the metal feed rate, thereby improving the deposition rate and reducing remelting. Based on these characteristics, the laser-GMAW composite additive manufacturing method is very suitable for additive manufacturing of 316L stainless steel.

[0027] The method of the present invention will be further illustrated below through specific embodiments: Example 1 This embodiment provides a method for manufacturing thin-walled stainless steel additive components based on laser-GMAW cold wire composite additive manufacturing, specifically including the following steps: S1. Select 316L stainless steel welding wire with a diameter of 1.2mm, select Q235 plate with a size of 300mm×300mm×15mm as the substrate, use a clamp to fix the substrate 5 on the workbench 6 and use a polishing machine to clean the substrate 5. S2. Assemble the welding torch, laser head, and cold wire 4 together on the industrial robot, with the welding torch in the middle and the laser and the cold wire 4 fed by the external wire feeder distributed on both sides of the welding torch. S3. The hot wire is fed out through the MIG welding gun. The positions of the two welding wires and the laser above the substrate 5 are adjusted so that they are on the same plane and the center of the laser beam 3 coincides with the ends of the two welding wires. The following positional parameters of the laser-GMAW composite additive manufacturing system are set: the angle between the hot wire 2 and the substrate 5 is θ1=90°, the angle between the laser head axis and the hot wire 2 is θ2=45°, the angle between the hot wire 2 and the cold wire 4 is θ3=65°, and the hot wire extension L=13mm. S4. Set the initial parameters of the laser-GMAW composite additive manufacturing system: average laser power P = 400W, laser defocusing distance 0mm, laser output in pulse mode with a frequency of 30Hz, laser pulse width 3ms, hot filament feed speed V1 = 5m / min, cold filament feed speed V2 = 1m / min, 99.99% argon protective gas flow rate Q = 15L / min, deposition rate V during additive manufacturing process. t =8mm / s; S5. Using a low-power pulsed laser and electric arc as a composite heat source, the heat is fed into the molten pool through stainless steel hot wire 2 and cold wire 4, spread and solidified on the substrate 5, and the single-layer deposition process is completed. S6. In the stainless steel additive manufacturing process, each layer needs to be cooled to 200°C before the next layer is deposited. After one layer is deposited, the robot is raised by 2.4 mm. Steps S3 to S5 are repeated until the additive manufacturing of the entire stainless steel thin-walled additive part is completed.

[0028] like Figure 2 As shown, the stainless steel thin-walled additive parts obtained in this embodiment have no obvious collapse at the arc-starting end and arc-extinguishing end, and the forming is excellent. No obvious defects such as sidewall flow, pores and cracks were found. Through performance testing, the 316L stainless steel thin-walled additive parts obtained by this method have smaller and more isotropic grains, thus having better mechanical properties.

[0029] Example 2 This embodiment provides a method for manufacturing multi-layer, multi-pass block additive components of stainless steel based on laser-GMAW cold wire composite additive manufacturing, specifically including the following steps: S1. Select 316L stainless steel welding wire with a diameter of 1.2mm, select Q235 plate with a size of 300mm×300mm×15mm as substrate 5, use a clamp to fix substrate 5 on workbench 6 and clean substrate with a polishing machine. S2, welding torch, laser head and cold wire are assembled together on the industrial robot, with the welding torch in the middle and the laser and cold wire 4 fed by the external wire feeder distributed on both sides of the welding torch. S3. The hot wire is fed out through the MIG welding gun. The positions of the two welding wires and the laser above the substrate 5 are adjusted so that they are on the same plane and the center of the laser beam 3 coincides with the ends of the two welding wires. The following positional parameters of the laser-GMAW composite additive manufacturing system are set: the angle between the hot wire and the substrate θ1=90°, the angle between the laser head axis and the hot wire θ2=45°, the angle between the hot wire and the cold wire θ3=65°, and the hot wire extension L=13mm. S4. Set the initial parameters of the laser-GMAW composite additive manufacturing system: average laser power P = 400W, laser defocusing distance 0mm, laser output in pulse mode with a frequency of 30Hz, laser pulse width 3ms, hot filament feed speed V1 = 9m / min, cold filament feed speed V2 = 3m / min, 99.99% argon protective gas flow rate Q = 20L / min, deposition rate V during additive manufacturing process. t =10mm / s; S5. Using a low-power pulsed laser and electric arc as a composite heat source, the molten pool is fed in through a stainless steel hot wire and cold wire, spread and solidified on the substrate, and the single-layer deposition process is completed. S6. In the stainless steel additive manufacturing process, each deposition layer needs to be cooled to 200°C before the next deposition layer is deposited. After each deposition layer is completed, the robot moves horizontally by 10mm and repeats steps S3 to S5 until the deposition process of one layer is completed. After completing one layer of deposition, the robot is raised by 3mm, and step S6 is repeated until the additive manufacturing of the entire stainless steel multi-layer, multi-stage block additive component is completed.

[0030] like Figure 3 As shown, the stainless steel multilayer multi-pass block additive component obtained in this embodiment has no obvious collapse at the arc-starting end and arc-extinguishing end, excellent forming, high additive efficiency, and no obvious defects such as sidewall flow, pores and cracks were found. Through performance testing, the 316L stainless steel thin-walled additive component obtained by this method has good metallurgical bonding with the substrate 5, and has smaller and more isotropic grains, thus having better mechanical properties.

[0031] All matters not covered in this invention are common knowledge.

[0032] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for laser-GMAW cold wire composite additive manufacturing of stainless steel, characterized in that: The method adds an independently fed, non-electrically powered cold filament to the standard laser-GMAW composite additive manufacturing system, and specifically includes the following steps: S1. Use a clamp to fix the substrate on the worktable and clean the substrate; S2. Assemble the welding torch, laser head, and cold wire, with the welding torch in the middle and the laser head and the externally fed cold wire distributed on both sides of the welding torch. S3. Send out hot wires through the MIG welding gun, adjust the positions of the two welding wires and the laser on the substrate so that they are on the same plane, and the center of the laser beam coincides with the ends of the two welding wires. Adjust the following positional parameters of the laser-GMAW composite additive manufacturing system: the angle θ1 between the hot wire and the substrate, the angle θ2 between the laser head axis and the hot wire, the angle θ3 between the hot wire and the cold wire, and the hot wire extension L. S4. Set the initial parameters of the laser-GMAW composite additive manufacturing system: laser power P, hot filament feed speed V1, cold filament feed speed V2, use 99.99% argon as the protective gas, gas flow rate Q, and deposition rate V during the additive manufacturing process. t ; S5. Using a low-power pulsed laser and electric arc as a composite heat source, the molten pool is fed in through a stainless steel hot wire and cold wire, spread and solidified on the substrate to complete the single-layer deposition process. S6. In the stainless steel additive manufacturing process, each layer needs to be cooled to the preset temperature before depositing the next layer. Adjust the welding torch height and repeat steps S3 to S5 until the additive manufacturing of the entire stainless steel additive part is completed.

2. The method for laser-GMAW cold wire composite additive manufacturing of stainless steel according to claim 1, characterized in that: Both the hot wire and the cold wire are 316L stainless steel welding wire.

3. The method for laser-GMAW cold wire composite additive manufacturing of stainless steel according to claim 1, characterized in that: In step S3, the angle θ1 between the hot wire and the substrate is 60~90°, the angle θ2 between the laser head axis and the hot wire is 30~60°, the angle θ3 between the hot wire and the cold wire is 60~70°, and the hot wire extension L is 10~13mm.

4. The method for laser-GMAW cold wire composite additive manufacturing of stainless steel according to claim 1, characterized in that: In step S4, the laser power P is 200~500W, the laser defocusing amount is adjustable from 0 to 2mm, the laser is output in pulse mode with a frequency range of 30~50Hz, and the laser pulse width range is 1~3ms.

5. The method for laser-GMAW cold wire composite additive manufacturing of stainless steel according to claim 1, characterized in that: In step S4, the hot wire feed speed V1 is 5~9 m / min, the corresponding welding current I is 144A~243A, the argon shielding gas flow rate Q is 15~20 L / min, and the shielding gas covers the ends of the hot and cold wires to reduce porosity and oxide inclusion defects. The deposition rate V during additive manufacturing is... t The speed is 8~12 mm / s.

6. The method for laser-GMAW cold wire composite additive manufacturing of stainless steel according to claim 5, characterized in that: In step S4, different hot wire feeding speeds V1 are matched with different cold wire feeding speeds V2. The cold wire feeding speed V2 is 1~3m / min, and the cold wire and hot wire feeding speeds are adjusted independently.

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