Flux-cored wire for electric arc additive, and method of making and using same

Abstract

This invention discloses a flux-cored welding wire for arc additive manufacturing, comprising a flux core and an outer sheath. The flux core is composed of the following components: 0.01-0.05% carbon powder, 11-13% chromium powder, 4.5-6.5% nickel powder, 1.5-3% molybdenum powder, 0.1-0.5% manganese powder, 0.3-0.6% silicon powder, 0.05-0.2% niobium powder, 0.1-0.3% vanadium powder, 1.0-3% copper powder, with the remainder being iron powder, and the sum of the mass percentages of the above components being 100%. The outer sheath is made of 0Cr18Ni9 austenitic stainless steel strip. This invention also discloses the preparation method and application method of the flux-cored welding wire for arc additive manufacturing. This invention solves the problems of existing commercial martensitic stainless steel being sensitive to hydrogen embrittlement, difficulty in balancing high strength and resistance to hydrogen embrittlement, and the lack of dedicated welding wire materials suitable for arc additive manufacturing processes.

Description

Technical Field

[0001] This invention belongs to the field of welding materials technology, specifically relating to flux-cored welding wires for arc additive manufacturing, and also to methods for preparing and applying flux-cored welding wires for arc additive manufacturing. Background Technology

[0002] With dwindling fossil fuel reserves and intensifying global warming, there is an urgent need to find green, efficient, and low-cost renewable energy sources. Hydrogen energy, due to its lack of intermittency, volatility, and randomness, is becoming a bridge between fossil fuels and renewable energy. Because hydrogen atoms readily permeate conventional materials, finding effective and safe hydrogen storage technologies is crucial for developing a "hydrogen economy." Compared to natural gas, hydrogen is more likely to cause material embrittlement and leakage, so the compatibility of container materials with hydrogen must be carefully considered when designing hydrogen storage containers. In hydrogen storage containers, hydrogen enters the container material through adsorption and diffusion processes; some is captured by hydrogen traps, and some diffuses between crystal lattices. The amount of hydrogen entering the container material is a significant factor affecting the container's performance and lifespan.

[0003] When designing hydrogen storage containers, the extremely harsh hydrogen storage environment must be considered. Under high-pressure hydrogen storage conditions, the container material needs to possess high strength, good low-temperature toughness, and excellent resistance to hydrogen embrittlement. Martensitic stainless steel is widely used in aerospace, equipment manufacturing, and petrochemical fields due to its high strength and excellent corrosion resistance. However, common commercial martensitic stainless steels are usually sensitive to hydrogen embrittlement. Only through specific composition design and heat treatment processes can modified martensitic stainless steel combine high strength, lightweight, and resistance to hydrogen embrittlement, making it an ideal material for manufacturing hydrogen storage containers.

[0004] Arc additive manufacturing (AIM) is a digital manufacturing technology that uses a layer-by-layer cladding principle. The welding heat source is an electric arc generated by a gas metal arc welding machine (GMAW). By adding wire and under program control, complex metal parts are gradually formed from lines to surfaces and then to solids based on a 3D model. The core advantages of using AIM to manufacture hydrogen storage containers lie in its high efficiency, low cost, and high design freedom, directly addressing the needs for lightweight, customized structures, and low-cost manufacturing of hydrogen storage containers. Summary of the Invention

[0005] The purpose of this invention is to provide flux-cored welding wire for arc additive manufacturing, which solves the problems of existing commercial martensitic stainless steel being sensitive to hydrogen embrittlement, making it difficult to balance high strength and resistance to hydrogen embrittlement, and lacking dedicated welding wire materials suitable for arc additive manufacturing processes.

[0006] A second objective of this invention is to provide a method for preparing flux-cored welding wire for arc additive manufacturing.

[0007] A third objective of this invention is to provide a method for using flux-cored welding wire for arc additive manufacturing.

[0008] The technical solution adopted in this invention is a flux-cored welding wire for arc additive manufacturing, comprising a flux core and an outer sheath; the flux core is composed of the following components: 0.01-0.05% carbon powder, 11-13% chromium powder, 4.5-6.5% nickel powder, 1.5-3% molybdenum powder, 0.1-0.5% manganese powder, 0.3-0.6% silicon powder, 0.05-0.2% niobium powder, 0.1-0.3% vanadium powder, 1.0-3% copper powder, with the remainder being iron powder, and the sum of the mass percentages of the above components is 100%; the outer sheath is made of 0Cr18Ni9 austenitic stainless steel strip; The invention is further characterized by: The thickness of 0Cr18Ni9 austenitic stainless steel strip is 0.2-0.4mm, and the width is 6-8mm.

[0009] The flux-cored wire has a flux filling amount of 20wt%-25wt%; the diameter of the flux-cored wire is 1.0-1.2mm; and the particle size of each component powder of the flux-cored wire is 100-150 mesh.

[0010] The second technical solution adopted in this invention is a method for preparing flux-cored welding wire for arc additive manufacturing, comprising the following steps: Step 1: Weigh the above powder materials according to the mass percentage; Step 2: Mix the weighed powder evenly in a powder mixer, place it in an inert gas atmosphere and heat and keep it at a warm temperature for drying; clean the stainless steel belt with anhydrous ethanol to remove contaminants; Step 3: Roll the cleaned stainless steel strip into a U-shape, fill the dried raw material powder from Step 2 into the U-shaped groove, and control the filling amount of the core powder so that the steel strip changes from a U-shape to an O-shape overlap to form a closed tubular welding wire. Then roll it to make a welding wire of the preset diameter. Step 4: The welding wire obtained in Step 3 is drawn by gradually reducing its diameter to finally produce a flux-cored welding wire.

[0011] The second technical solution of the present invention is further characterized by: In step 2, a V-shaped powder mixer is used for mixing, and the mixing time is 6-8 hours. In step 2, the heating equipment is a tube furnace, the heating temperature is 200-250℃, and the holding time is 2-3 hours. In step 2, the inert gas is argon with a purity of 99.999%.

[0012] In step 3, the rolling equipment is the strip feeding machine of the flux-cored welding wire forming machine, with a filling amount of 20wt%-25wt%; the equipment that changes the steel strip from U-shaped to O-shaped overlap is the O-shaped forming roller; the step 4 of the progressive diameter reduction drawing is as follows: the surface of the welding wire is wiped periodically with anhydrous ethanol, and multiple drawing passes are used to progressively reduce the diameter, with each reduction amount being 0.1-0.3mm, until the final diameter reaches 1.0-1.2mm.

[0013] The third technical solution adopted in this invention is a method for applying flux-cored welding wire for arc additive manufacturing, comprising the following steps: S1. Assemble the flux-cored welding wire onto the fully automatic welding robot, determine the layer height of each layer to be 2-3mm, write the corresponding program and input it into the welding robot; S2. Run the welding machine command to perform multi-layer single-pass welding under a protective gas atmosphere. Use MIG welding as the heat source for additive manufacturing, cool, and obtain a small hydrogen storage container for filling.

[0014] The third technical solution of this invention is further characterized by: The process parameters for MIG welding in S2 are as follows: welding speed is 0.3-0.4 m / min; the welding torch is raised 2-2.5 mm per layer; the shielding gas is argon with a purity of 99.999%; interpass cooling is used in S2, and the interpass temperature is controlled between 80-150℃.

[0015] The beneficial effects of this invention are: The flux-cored welding wire for arc additive manufacturing, its preparation method, and its application method provided by this invention have the advantages of easier alloy composition adjustment, more stable mechanical properties, shorter preparation cycle, and higher production efficiency. The strengthening effect is achieved by adding multiple precipitating phase elements to the welding wire, using Ni as the main alloying element and adding a certain amount of trace alloying elements such as Mo and Cu, while strictly controlling the proportion of each element, thereby obtaining a high-performance hydrogen-embrittlement-resistant martensitic stainless steel flux-cored welding wire. The method for preparing hydrogen-embrittlement-resistant martensitic stainless steel using MIG welding as the heat source and flux-cored welding wire as the raw material in additive manufacturing technology is also described. The resulting small martensitic stainless steel hydrogen storage container has an aesthetically pleasing shape and excellent mechanical properties. Attached Figure Description

[0016] Figure 1 This is a microstructure diagram of Embodiment 10 of the present invention; Figure 2 This is a stress-strain curve diagram from Embodiment 10 of the present invention. Detailed Implementation

[0017] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0018] The present invention provides a flux-cored welding wire for arc additive manufacturing, comprising a flux core and an outer sheath. The flux core is composed of the following components: 0.01-0.05% carbon powder, 11-13% chromium powder, 4.5-6.5% nickel powder, 1.5-3% molybdenum powder, 0.1-0.5% manganese powder, 0.3-0.6% silicon powder, 0.05-0.2% niobium powder, 0.1-0.3% vanadium powder, 1.0-3% copper powder, and the remainder being iron powder, with the sum of the mass percentages of the above components being 100%. The outer sheath is made of 0Cr18Ni9 austenitic stainless steel strip; the thickness of the 0Cr18Ni9 austenitic stainless steel strip is 0.2-0.4 mm, and the width is 6-8 mm. The flux filling amount of the flux-cored welding wire is 20wt%-25wt%. The diameter of the flux-cored welding wire is 1.0-1.2 mm. The particle size of each component powder of the flux-cored welding wire is 100-150 mesh. The functions and roles of each component in this welding wire are as follows: Nickel (Ni): Ni is the most crucial element for obtaining reverse-transformed austenite; it significantly lowers the temperature (point) of the austenite-to-martensite transformation and accumulates in austenite during tempering / heat treatment, improving its thermodynamic stability and allowing it to be retained at room temperature. A relatively high content is typically required. In hydrogen storage container welding materials, the addition of Ni not only promotes the formation of reverse-transformed austenite (RA) but also significantly improves low-temperature toughness. Manganese (Mn): Mn is an austenite stabilizing element that can expand the austenite phase region. It works synergistically with Ni to reduce Ni usage and lower costs. Mn can also accumulate in reverse-transformed austenite (RA), further stabilizing this phase. Excessive Mn content may lead to segregation and reduce weld toughness; therefore, it needs to be controlled within an appropriate range. Copper (Cu): Cu is also an austenite stabilizing element. It not only contributes to the formation of RA (austenite embrittlement) but also forms copper-rich precipitates during subsequent aging. In Ni-rich steels, Cu precipitates extremely fine nanoscale ε-Cu particles during aging / tempering. These particles not only provide extremely high strength but also exhibit good coherence with the matrix, proving to be effective hydrogen traps and reducing hydrogen embrittlement susceptibility. Combined with Ni, it helps prevent hot brittleness during welding. Vanadium (V) and niobium (Nb): Adding trace amounts of V and Nb forms nanoscale vanadium carbide or niobium carbide. These nanocarbides are considered "deep hydrogen traps," which strongly capture hydrogen atoms, making them difficult to escape at room temperature and causing them to aggregate and form cracks. They pin grain boundaries, refine the original austenite grains, and further improve toughness. The Nb content needs to be strictly controlled; too high a content may form coarse eutectic phases in the weld, which is detrimental. Molybdenum (Mo): Molybdenum can improve the high-temperature strength of weld metal and enhance the corrosion resistance of steel. Its most important role is to improve tempering stability and strengthen the secondary hardening effect. It can form solid solutions with other elements in the weld (such as iron), changing the crystal structure of the metal and enabling the metal to withstand greater stress at high temperatures without deformation. Manganese (Mn) and silicon (Si) elements: The main functions of Mn and Si are deoxidation and desulfurization, reducing the oxygen and sulfur content and preventing defects such as porosity in the weld metal, which would lead to a decrease in forming quality. At the same time, adding Si to flux-cored welding wire can also combine with other elements to form composite carbides, improving the strength and hardness of the formed parts.

[0019] The present invention provides a method for preparing flux-cored welding wire for arc additive manufacturing, comprising the following steps: Step 1: Weigh the above powder materials according to the mass percentage; Step 2: Mix the weighed powder evenly in a powder mixer, place it in an inert gas atmosphere and heat and keep it at a warm temperature for drying; clean the stainless steel strip with anhydrous ethanol; Mixing is performed using a V-shaped powder mixer, with a mixing time of 6-8 hours; heating is achieved using a tube furnace, with a heating temperature of 200-250℃ and a holding time of 2-3 hours; the inert gas is argon with a purity of 99.999%. Step 3: Roll the cleaned stainless steel strip into a U-shape, fill the dried raw material powder from Step 2 into the U-shaped groove, and control the filling amount of the core powder so that the steel strip changes from a U-shape to an O-shape overlap to form a closed tubular welding wire. Then roll it to make a welding wire of the preset diameter. The rolling equipment is the strip feeding machine of the flux-cored welding wire forming machine, with a filling amount of 20wt%-25wt%; the equipment that changes the steel strip from a U-shape to an O-shape overlap is the O-shaped forming roller; Step 4: The welding wire obtained in Step 3 is drawn by gradually reducing its diameter to finally produce a flux-cored welding wire; The step-by-step diameter reduction drawing process involves periodically wiping the surface of the welding wire with anhydrous ethanol, using multiple drawing passes to gradually reduce the diameter, with each reduction being 0.1-0.3 mm, until the final diameter reaches 1.0-1.2 mm.

[0020] The present invention provides a method for applying flux-cored welding wire for arc additive manufacturing, which, based on the above-mentioned flux-cored welding wire for arc additive manufacturing, includes the following steps: S1. Assemble the flux-cored welding wire onto the fully automatic welding robot, determine the layer height of each layer to be 2-3mm, write the corresponding program and input it into the welding robot; S2. Run the welding machine command to perform multi-layer single-pass welding in a protective gas atmosphere. Use MIG welding as the heat source for additive manufacturing, cool, and obtain a small hydrogen storage container for filling. The process parameters for MIG welding are as follows: welding speed is 0.3-0.4 m / min; the welding torch is raised 2-2.5 mm per layer; the shielding gas is argon with a purity of 99.999%; interpass cooling is used for cooling in S2, and the interpass temperature is controlled between 80-150℃.

[0021] Example 1 The flux-cored welding wire for arc additive manufacturing proposed in this embodiment includes a flux core and an outer sheath. The flux core is composed of the following components: 0.01-0.05% carbon powder, 11-13% chromium powder, 4.5-6.5% nickel powder, 1.5-3% molybdenum powder, 0.1-0.5% manganese powder, 0.3-0.6% silicon powder, 0.05-0.2% niobium powder, 0.1-0.3% vanadium powder, 1.0-3% copper powder, and the remainder is iron powder. The sum of the mass percentages of the above components is 100%. The outer sheath is made of 0Cr18Ni9 austenitic stainless steel strip.

[0022] Example 2 The flux-cored welding wire for arc additive manufacturing proposed in this embodiment includes a flux core and an outer sheath. The flux core is composed of the following components: 0.01-0.05% carbon powder, 11-13% chromium powder, 4.5-6.5% nickel powder, 1.5-3% molybdenum powder, 0.1-0.5% manganese powder, 0.3-0.6% silicon powder, 0.05-0.2% niobium powder, 0.1-0.3% vanadium powder, 1.0-3% copper powder, and the remainder is iron powder. The sum of the mass percentages of the above components is 100%. The outer sheath is made of 0Cr18Ni9 austenitic stainless steel strip. The thickness of the 0Cr18Ni9 austenitic stainless steel strip is 0.2-0.4 mm, and the width is 6-8 mm. The flux filling amount of the flux-cored welding wire is 20wt%-25wt%. The diameter of the flux-cored welding wire is 1.0-1.2 mm. The particle size of each component powder of the flux-cored welding wire is 100-150 mesh.

[0023] Example 3 The method for preparing flux-cored welding wire for arc additive manufacturing proposed in this embodiment includes the following steps: Step 1: Weigh the above powder materials according to the mass percentage; Step 2: Mix the weighed powder evenly in a powder mixer, place it in an inert gas atmosphere and heat and keep it at a warm temperature for drying; clean the stainless steel strip with anhydrous ethanol; Step 3: Roll the cleaned stainless steel strip into a U-shape, fill the dried raw material powder from Step 2 into the U-shaped groove, and control the filling amount of the core powder so that the steel strip changes from a U-shape to an O-shape overlap to form a closed tubular welding wire. Then roll it to make a welding wire of the preset diameter. Step 4: The welding wire obtained in Step 3 is drawn by gradually reducing its diameter to finally produce a flux-cored welding wire.

[0024] Example 4 The method for preparing flux-cored welding wire for arc additive manufacturing proposed in this embodiment includes the following steps: Step 1: Weigh the above powder materials according to the mass percentage; Step 2: Mix the weighed powder evenly in a powder mixer, place it in an inert gas atmosphere and heat and keep it at a warm temperature for drying; clean the stainless steel strip with anhydrous ethanol; Mixing is performed using a V-shaped powder mixer, with a mixing time of 6-8 hours; heating is achieved using a tube furnace, with a heating temperature of 200-250℃ and a holding time of 2-3 hours; the inert gas is argon with a purity of 99.999%. Step 3: Roll the cleaned stainless steel strip into a U-shape, fill the dried raw material powder from Step 2 into the U-shaped groove, and control the filling amount of the core powder so that the steel strip changes from a U-shape to an O-shape overlap to form a closed tubular welding wire. Then roll it to make a welding wire of the preset diameter. The rolling equipment is the strip feeding machine of the flux-cored welding wire forming machine, with a filling amount of 20wt%-25wt%; the equipment that changes the steel strip from a U-shape to an O-shape overlap is the O-shaped forming roller; Step 4: The welding wire obtained in Step 3 is drawn by gradually reducing its diameter to finally produce a flux-cored welding wire; The step-by-step diameter reduction drawing process involves periodically wiping the surface of the welding wire with anhydrous ethanol, using multiple drawing passes to gradually reduce the diameter, with each reduction being 0.1-0.3 mm, until the final diameter reaches 1.0-1.2 mm.

[0025] Example 5 The application method of flux-cored welding wire for arc additive manufacturing proposed in this embodiment includes the following steps, based on the above-mentioned flux-cored welding wire for arc additive manufacturing: S1. Assemble the flux-cored welding wire onto the fully automatic welding robot, determine the layer height of each layer to be 2-3mm, write the corresponding program and input it into the welding robot; S2. Run the welding machine command to perform multi-layer single-pass welding under a protective gas atmosphere. Use MIG welding as the heat source for additive manufacturing, cool, and obtain a small hydrogen storage container for filling.

[0026] Example 6 The application method of flux-cored welding wire for arc additive manufacturing proposed in this embodiment includes the following steps, based on the above-mentioned flux-cored welding wire for arc additive manufacturing: S1. Assemble the flux-cored welding wire onto the fully automatic welding robot, determine the layer height of each layer to be 2-3mm, write the corresponding program and input it into the welding robot; S2. Run the welding machine command to perform multi-layer single-pass welding in a protective gas atmosphere. Use MIG welding as the heat source for additive manufacturing, cool, and obtain a small hydrogen storage container for filling. The process parameters for MIG welding are as follows: welding speed is 0.3-0.4 m / min; the welding torch is raised 2-2.5 mm per layer; the shielding gas is argon with a purity of 99.999%; interpass cooling is used for cooling in S2, and the interpass temperature is controlled between 80-150℃.

[0027] Example 7 The present invention provides the preparation and application of flux-cored welding wire for arc additive manufacturing. According to the above-mentioned flux-cored welding wire for arc additive manufacturing, the process includes the following steps: Step 1: Weigh out the following by mass percentage: 0.01% carbon powder, 11% chromium powder, 4.5% nickel powder, 1.5% molybdenum powder, 0.1% manganese powder, 0.3% silicon powder, 0.05% niobium powder, 0.1% vanadium powder, 1% copper powder, and the remainder is iron powder; Step 2: Heat the raw material powder weighed in Step 1 to 200℃ in an argon atmosphere and keep it at that temperature for 2 hours; clean the 0Cr18Ni9 austenitic stainless steel strip with anhydrous ethanol to remove contaminants. Step 3: Place a 7mm wide and 0.3mm thick stainless steel strip on the feeding machine of the flux-cored welding wire forming machine. Roll the steel strip into a U-shape through the pressing groove of the forming machine. Fill the raw material powder obtained in Step 2 evenly with the strip. The powder coating rate of the flux-cored wire is controlled at 20wt%. The U-shaped groove is closed by the O-shaped forming roller to form a closed tube welding wire. After passing through the closed forming roller, the wire is made into a 2mm diameter wire. Wipe it clean with anhydrous ethanol and draw it into a 2mm diameter wire. Then, through the step-by-step reduction, the wire is finally made into a 1.18mm flux-cored welding wire. Finally, the wire is coiled into a disc by the wire drawing machine and sealed and packaged to obtain the hydrogen embrittlement resistant martensitic stainless steel flux-cored welding wire for additive manufacturing. Step 4: Load the prepared hydrogen-embrittlement-resistant martensitic stainless steel flux-cored welding wire for additive manufacturing into a fully automated welding robot, ensuring each layer height is 2.5 mm. Program the welding robot to use MIG welding as the heat source for additive manufacturing to obtain the hydrogen storage container. Specific welding parameters are: welding speed 0.3 m / min; torch height 2.5 mm per layer; shielding gas 99.999% argon. The high-strength martensitic stainless steel parts prepared in this example have a beautiful shape, no obvious spatter, and a tensile strength of up to 784 MPa and an elongation of 16% at room temperature.

[0028] Example 8 The present invention provides the preparation and application of flux-cored welding wire for arc additive manufacturing. According to the above-mentioned flux-cored welding wire for arc additive manufacturing, the process includes the following steps: Step 1: Weigh out the following by mass percentage: 0.02% carbon powder, 12% chromium powder, 5% nickel powder, 2% molybdenum powder, 0.2% manganese powder, 0.4% silicon powder, 0.06% niobium powder, 0.2% vanadium powder, 2% copper powder, and the remainder is iron powder. Step 2: Heat the raw material powder weighed in Step 1 to 200℃ in an argon atmosphere and keep it at that temperature for 2 hours; clean the 0Cr18Ni9 austenitic stainless steel strip with anhydrous ethanol to remove contaminants. Step 3: Place a 7mm wide and 0.3mm thick stainless steel strip on the feeding machine of the flux-cored welding wire forming machine. Roll the steel strip into a U-shape through the pressing groove of the forming machine. Fill the raw material powder obtained in Step 2 evenly with the strip. The powder coating rate of the flux-cored wire is controlled at 20wt%. The U-shaped groove is closed by the O-shaped forming roller to form a closed tube welding wire. After passing through the closed forming roller, the wire is made into a 2mm diameter wire. Wipe it clean with anhydrous ethanol and draw it into a 2mm diameter wire. Then, through the step-by-step reduction, the wire is finally made into a 1.18mm flux-cored welding wire. Finally, the wire is coiled into a disc by the wire drawing machine and sealed and packaged to obtain the hydrogen embrittlement resistant martensitic stainless steel flux-cored welding wire for additive manufacturing. Step 4: Load the prepared hydrogen-embrittlement-resistant martensitic stainless steel flux-cored welding wire for additive manufacturing into a fully automated welding robot, determine the layer height of each layer to be 2.5 mm, write a program into the welding robot, and use MIG welding as the heat source to carry out additive manufacturing to obtain a hydrogen storage container; the specific parameters of the welding process are: welding speed of 0.3 m / min; lifting of the welding torch by 2.5 mm per layer; shielding gas of 99.999% argon.

[0029] The martensitic stainless steel parts prepared in this example have a beautiful shape, no obvious spatter, and a tensile strength of up to 762 MPa and an elongation of 20% at room temperature.

[0030] Example 9 Step 1: Weigh out the following by mass percentage: 0.03% carbon powder, 12% chromium powder, 5.5% nickel powder, 2.5% molybdenum powder, 0.3% manganese powder, 0.5% silicon powder, 0.1% niobium powder, 0.2% vanadium powder, 3% copper powder, and the remainder is iron powder. Step 2: Heat the raw material powder weighed in Step 1 to 250°C in an argon atmosphere and keep it at that temperature for 2 hours; clean the 0Cr18Ni9 austenitic stainless steel strip with anhydrous ethanol to remove contaminants. Step 3: Place a 7mm wide and 0.3mm thick stainless steel strip on the feeding machine of the flux-cored welding wire forming machine. Roll the steel strip into a U-shape through the pressing groove of the forming machine. Fill the raw material powder obtained in Step 2 evenly with the strip. The powder coating rate of the flux-cored wire is controlled at 25wt%. The U-shaped groove is closed by the O-shaped forming roller to form a closed tube welding wire. After passing through the closed forming roller, the wire is made into a 2mm diameter wire. Wipe it clean with anhydrous ethanol and draw it into a 2mm diameter wire. Then, through the step-by-step reduction, the wire is finally made into a 1.18mm flux-cored welding wire. Finally, the wire is coiled into a disc by the wire drawing machine and sealed and packaged to obtain the hydrogen embrittlement resistant martensitic stainless steel flux-cored welding wire for additive manufacturing. Step 4: Load the prepared hydrogen-embrittlement-resistant martensitic stainless steel flux-cored welding wire for additive manufacturing into a fully automated welding robot, ensuring each layer height is 2.5 mm. Program the welding robot to use MIG welding as the heat source for additive manufacturing to obtain the hydrogen storage container. Specific welding parameters are: welding speed 0.4 m / min; torch height 2.5 mm per layer; shielding gas 99.999% argon. The martensitic stainless steel parts prepared in this example have a beautiful shape, no obvious spatter, and a tensile strength of up to 866.4 MPa and an elongation of 18% at room temperature.

[0031] Example 10 The present invention provides the preparation and application of flux-cored welding wire for arc additive manufacturing. According to the above-mentioned flux-cored welding wire for arc additive manufacturing, the process includes the following steps: Step 1: Weigh out the following by mass percentage: 0.05% carbon powder, 13% chromium powder, 6.5% nickel powder, 3% molybdenum powder, 0.5% manganese powder, 0.6% silicon powder, 0.2% niobium powder, 0.3% vanadium powder, 3% copper powder, and the remainder is iron powder. Step 2: Heat the raw material powder weighed in Step 1 to 250℃ in an argon atmosphere and keep it at that temperature for 2 hours; clean the 0Cr18Ni9 austenitic stainless steel strip with anhydrous ethanol to remove contaminants. The chemical composition of the 0Cr18Ni9 austenitic stainless steel strip is shown in Table 1. Table 1 Summary of Chemical Composition (Mass Fraction %) of 0Cr18Ni9 Austenitic Stainless Steel Strip

[0032] Step 3: Place a 7mm wide and 0.3mm thick stainless steel strip on the feeding machine of the flux-cored welding wire forming machine. Roll the steel strip into a U-shape through the pressing groove of the forming machine. Fill the raw material powder obtained in Step 2 evenly with the strip. The powder coating rate of the flux-cored wire is controlled at 25wt%. The U-shaped groove is closed by the O-shaped forming roller to form a closed tube welding wire. After passing through the closed forming roller, the wire is made into a 2mm diameter wire. Wipe it clean with anhydrous ethanol and draw it into a 2mm diameter wire. Then, through the step-by-step reduction, the wire is finally made into a 1.18mm flux-cored welding wire. Finally, the wire is coiled into a disc by the wire drawing machine and sealed and packaged to obtain the hydrogen embrittlement resistant martensitic stainless steel flux-cored welding wire for additive manufacturing. Step 4: Load the prepared hydrogen-embrittlement-resistant martensitic stainless steel flux-cored welding wire for additive manufacturing into a fully automated welding robot, ensuring each layer height is 2.5 mm. Program the welding robot to use MIG welding as the heat source for additive manufacturing to obtain the hydrogen storage container. Specific welding parameters are: welding speed 0.4 m / min; torch height 2.5 mm per layer; shielding gas 99.999% argon. Based on the hydrogen embrittlement resistant martensitic stainless steel flux-cored welding wire and the additive manufacturing method for small hydrogen storage containers of the present invention, the martensitic stainless steel formed parts obtained in this example are aesthetically pleasing, free from defects such as porosity and inclusions, and exhibit obvious layering in their macroscopic morphology, with good bonding between layers; the microstructure is as follows: Figure 1 As shown, the microstructure consists of lath martensite, retained austenite, and ferrite.

[0033] During additive manufacturing, the microstructure changes from δ-ferrite to austenite, and the austenite further transforms into lath martensite. The high dislocation density of lath martensite can pin dislocations, thereby increasing the strength of stainless steel. At the same time, carbon and other elements in the weld migrate to dislocations and defects, hindering dislocation movement and further strengthening the martensite. Furthermore, due to the tempering effect of the previous weld pass on the next weld pass, the sensitivity to hydrogen embrittlement is reduced through various nano-precipitates (mainly copper-rich phases) and reverse-transformed austenite phases.

[0034] The stress-strain curves are shown in the mechanical property test results. Figure 2 As shown, the tensile strength of the molded part in this example can reach 1070 MPa, and the elongation can reach 19%.

Claims

1. A flux-cored welding wire for arc additive manufacturing, characterized in that, It includes a core and an outer sheath; the core is composed of the following components: 0.01-0.05% carbon powder, 11-13% chromium powder, 4.5-6.5% nickel powder, 1.5-3% molybdenum powder, 0.1-0.5% manganese powder, 0.3-0.6% silicon powder, 0.05-0.2% niobium powder, 0.1-0.3% vanadium powder, 1.0-3% copper powder, and the remainder is iron powder, the sum of the above components by mass percentage is 100%; the outer sheath is made of 0Cr18Ni9 austenitic stainless steel strip.

2. The flux-cored welding wire for arc additive manufacturing according to claim 1, characterized in that, The thickness of the 0Cr18Ni9 austenitic stainless steel strip is 0.2-0.4 mm, and the width is 6-8 mm.

3. The flux-cored welding wire for arc additive manufacturing according to claim 2, characterized in that, The flux-cored wire has a flux filling amount of 20wt%-25wt%; the diameter of the flux-cored wire is 1.0-1.2mm; and the particle size of each component powder of the flux-cored wire is 100-150 mesh.

4. A method for preparing flux-cored welding wire for arc additive manufacturing, characterized in that, The flux-cored welding wire for arc additive manufacturing according to claim 3 comprises the following steps: Step 1: Weigh the above powder materials according to the mass percentage; Step 2: Mix the weighed powder evenly in a powder mixer, place it in an inert gas atmosphere and heat and keep it at a warm temperature for drying; clean the stainless steel strip with anhydrous ethanol; Step 3: Roll the cleaned stainless steel strip into a U-shape, fill the dried raw material powder from Step 2 into the U-shaped groove, and control the filling amount of the core powder so that the steel strip changes from a U-shape to an O-shape overlap to form a closed tubular welding wire. Then roll it to make a welding wire of the preset diameter. Step 4: The welding wire obtained in Step 3 is drawn by gradually reducing its diameter to finally produce a flux-cored welding wire.

5. The method for preparing flux-cored welding wire for arc additive manufacturing according to claim 4, characterized in that, The mixing in step 2 is performed using a V-shaped powder mixer, and the mixing time is 6-8 hours; the heating equipment in step 2 is a tube furnace, and the heating temperature is 200-250℃, with a holding time of 2-3 hours; the inert gas in step 2 is argon with a purity of 99.999%.

6. The method for preparing flux-cored welding wire for arc additive manufacturing according to claim 4, characterized in that, The rolling equipment mentioned in step 3 is the strip feeding machine of the flux-cored welding wire forming machine, and the filling amount is 20wt%-25wt%; the equipment for changing the steel strip from U-shaped to O-shaped overlap is the O-shaped forming roller; the step-by-step diameter reduction drawing in step 4 specifically involves: periodically wiping the surface of the welding wire with anhydrous ethanol, using multiple drawing passes, and gradually reducing the diameter, with each reduction amount being 0.1-0.3mm, until the final diameter reaches 1.0-1.2mm.

7. A method for applying flux-cored welding wire for arc additive manufacturing, characterized in that, The flux-cored welding wire for arc additive manufacturing according to claim 3 comprises the following steps: S1. Assemble the flux-cored welding wire onto the fully automatic welding robot, determine the height of each layer to be 2-3mm, write the corresponding program and input it into the welding robot; S2. Run the welding machine command to perform multi-layer single-pass welding under a protective gas atmosphere. Use MIG welding as the heat source for additive manufacturing, cool, and obtain a small hydrogen storage container for filling.

8. The method of applying the flux-cored welding wire for arc additive manufacturing according to claim 7, characterized in that, The process parameters for MIG welding described in S2 are as follows: welding speed is 0.3-0.4 m / min; the welding torch is raised by 2-2.5 mm per layer; the shielding gas is argon with a purity of 99.999%; the cooling described in S2 is interpass cooling, and the interpass temperature is controlled between 80-150℃.

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