Duplex stainless steel flux-cored wire and preparation method and additive manufacturing method thereof

Abstract

The invention discloses a duplex stainless steel flux-cored wire and a preparation method and an additive manufacturing method thereof, the duplex stainless steel flux-cored wire comprises a flux core and an outer skin, and the flux core is composed of the following raw material components of, by mass, 32%-38% of chromium powder, 1.5%-4% of nickel powder, 11%-14% of molybdenum powder, 0.2%-1% of niobium powder, 3%-6% of manganese powder, 1%-3% of silicon powder, 0.8%-2.2% of titanium nitride and the balance iron powder. The welding wire is subjected to additive manufacturing through MIG welding to obtain a duplex stainless steel structural part, the mechanical property and corrosion resistance of the duplex stainless steel structural part obtained through additive manufacturing are remarkably improved, and the welding wire is short in preparation period, high in production efficiency, attractive in forming, excellent in mechanical property, high in welding efficiency and stable in electric arc in the printing process; and the structural part is attractive in molding, smooth in surface and free of pores and slag inclusion.

Description

Technical Field

[0001] The present invention belongs to the technical field of wire arc additive manufacturing, and relates to a duplex stainless steel flux-cored wire. The present invention also relates to a preparation method and an additive manufacturing method of the above-mentioned duplex stainless steel flux-cored wire. Background Art

[0002] In recent years, with the continuous growth of global energy demand, the development of deep-sea oil and gas resources has become an important development direction in the energy field. As a key infrastructure for the development of deep-sea oil and gas resources, deep-sea oil and gas pipelines undertake the important task of transporting the extracted oil and gas to land. In the deep-sea environment, oil and gas pipelines face extreme conditions such as high pressure, low temperature, high chloride ion corrosion and microbial corrosion. Traditional welding materials are difficult to meet the requirements of corrosion resistance and mechanical properties. Duplex stainless steel (DSS), due to its combination of the toughness of austenitic stainless steel and the corrosion resistance of ferritic stainless steel, is expected to become the core material for deep-sea pipeline construction. Due to the excellent properties of both austenite and ferritic stainless steels, duplex stainless steel has outstanding resistance to pitting corrosion, crevice corrosion and chloride stress corrosion, especially suitable for chloride-containing environments such as the ocean, and has a small tendency to hot cracking. The corrosion resistance of the joint is equivalent to that of the base metal. Therefore, it shows good strength and corrosion resistance in the deep-sea environment and has good welding performance.

[0003] Additive manufacturing (AM), namely 3D printing technology, as a revolutionary manufacturing technology, manufactures three-dimensional entities by layer-by-layer stacking of materials, and has advantages such as high design freedom, high material utilization rate and short production cycle. In the application field of duplex stainless steel, additive manufacturing technology provides a new solution for the rapid manufacturing of complex structural components, effectively overcoming the limitations of traditional manufacturing technologies.

[0004] Because the deep-sea environment is extremely harsh, with characteristics such as high pressure, low temperature, high salinity and complex corrosive media, extremely high requirements are put forward for the material properties of oil and gas pipelines. However, the weld microstructure of duplex stainless steel structural parts in the prior art is prone to failure due to microbial corrosion and pitting during long-term service in the deep sea, and the passivation film stability is poor. Therefore, it is of great practical significance and broad application prospects to develop a high-performance flux-cored wire for duplex stainless steel additive manufacturing applicable to deep-sea oil and gas pipelines and its preparation method. Summary of the Invention

[0005] The first object of the present invention is to provide a duplex stainless steel flux-cored wire, which solves the problems of low strength and poor corrosion resistance of duplex stainless steel structural parts in the prior art.

[0006] The second object of the present invention is to provide a preparation method of the above-mentioned duplex stainless steel flux-cored wire.

[0007] The third object of the present invention is to provide an additive manufacturing method for the above-mentioned duplex stainless steel flux-cored wire.

[0008] The first technical solution adopted by the present invention is that the duplex stainless steel flux-cored wire includes a flux core and an outer skin. The flux core is composed of the following raw material components by mass percentage: chromium powder 32% - 38%, nickel powder 1.5% - 4%, molybdenum powder 11% - 14%, niobium powder 0.2% - 1%, manganese powder 3% - 6%, silicon powder 1% - 3%, titanium nitride 0.8% - 2.2%, and the balance is iron powder; the particle size of the flux core powder is 100 - 150 mesh.

[0009] The characteristics of the first technical solution of the present invention also lie in: The outer skin is a 0Cr18Ni9 austenitic stainless steel strip.

[0010] The filling rate of the flux core powder is 20% - 25%.

[0011] The second technical solution adopted by the present invention is a preparation method for the duplex stainless steel flux-cored wire, which is specifically implemented according to the following steps: Step 1: Weigh the following raw materials respectively according to the mass percentage: Chromium powder 32% - 38%, nickel powder 1.5% - 4%, molybdenum powder 11% - 14%, niobium powder 0.2% - 1%, manganese powder 3% - 6%, silicon powder 1% - 3%, titanium nitride 0.8% - 2.2%, and the balance is iron powder; the particle size of the flux core powder is 100 - 150 mesh; Step 2: First mix the raw material powders weighed in Step 1 evenly, then heat them to 150°C - 200°C in an argon atmosphere with a purity of 99.999% and keep them warm for 2h - 3h to fully dry the flux core powder, and finally cool them to room temperature with the furnace; Step 3: Place the outer skin on the tape feeder of the wire forming machine, and roll the outer skin into a U-shaped groove through the grooving of the forming machine; Step 4: Put the flux core powder processed in Step 2 into the U-shaped groove of the outer skin, close the U-shaped outer skin, and finally make the required diameter of the duplex stainless steel flux-cored wire by the method of gradually reducing the diameter.

[0012] The characteristics of the second technical solution of the present invention also lie in: The outer skin is a 0Cr18Ni9 austenitic stainless steel strip.

[0013] The filling rate of the flux core powder is 20% - 25%.

[0014] The third technical solution adopted by the present invention is an additive manufacturing method for the duplex stainless steel flux-cored wire. Using the duplex stainless steel flux-cored wire for additive manufacturing by MIG welding to obtain a duplex stainless steel structural part, which is specifically implemented according to the following steps: Step 1: Assemble the prepared duplex stainless steel flux-cored wire onto a fully automatic welding robot; Step 2: Design a 3D model and layer it to determine the number of layers and the layer height; Step 3: Program a welding procedure for the welding robot; set the welding parameters for MIG welding in the welding procedure; Step 4: Perform additive manufacturing under a shielding gas.

[0015] The third technical solution of the present invention is further characterized in that: In Step 2, the layer height is 2 mm to 3 mm.

[0016] The welding parameters in Step 3 are as follows: the welding speed is 0.2 m / min to 0.3 m / min; the welding torch is lifted 2 mm to 3 mm for each layer, the welding current is 160 A to 170 A, the welding voltage is 19 V to 22 V, and the weaving amplitude is 6 mm to 8 mm.

[0017] In Step 4, the shielding gas is argon with a purity of 99.999%; the cooling method during the additive manufacturing process is interlayer cooling, and the interlayer temperature is 100 °C to 150 °C.

[0018] The beneficial effects of the present invention are as follows: The duplex stainless steel flux-cored wire designed and manufactured by the present invention significantly improves the mechanical properties and corrosion resistance of the duplex stainless steel structural parts obtained by additive manufacturing by adding trace elements and adjusting the proportion of each component. Its preparation cycle is short, production efficiency is high. At the same time, the production of the flux-cored wire is pollution-free and the cladding efficiency during the welding process is high. The duplex stainless steel structural parts are obtained by programming a fully automatic welding robot for MIG welding, with beautiful forming, excellent mechanical properties, high welding efficiency, stable arc during the printing process, beautiful forming of the structural parts, smooth surface, no pores and no slag inclusions. Description of the Drawings

[0019] Figure 1 It is the metallographic structure diagram of the structural part prepared by the additive manufacturing method using the duplex stainless steel flux-cored wire in Embodiment 1 of the present invention. Detailed Description of the Invention

[0020] The present invention will be described in detail below in conjunction with the drawings and specific embodiments.

[0021] The present invention provides a duplex stainless steel flux-cored wire, which includes a flux core and an outer skin. The flux core is composed of the following components by mass percentage: Chromium powder 32% - 38%, nickel powder 1.5% - 4%, molybdenum powder 11% - 14%, niobium powder 0.2% - 1%, manganese powder 3% - 6%, silicon powder 1% - 3%, titanium nitride 0.8% - 2.2%, and the balance is iron powder; The particle size of the flux core powder is 100 - 150 mesh; The outer skin is a 0Cr18Ni9 austenitic stainless steel strip with a width of 7 mm to 10 mm and a thickness of 0.2 to 0.3 mm; The filling rate of the flux core powder is 20% to 25%.

[0022] The functions of the components in the flux core of the duplex stainless steel flux cored wire of the present invention are as follows: Cr element: As one of the main alloying elements of martensitic / duplex stainless steel, the Cr element also plays an important role in improving the strength and corrosion resistance of the surfacing alloy. The Cr element can be incorporated into carbides in atomic form (such as M 23 C 6 ), and replace Fe atoms to form a composite phase, such as (Fe, Cr) 7 C 3 and (Fe, Cr) 23 C 6 etc. In addition, the Cr element in the surfacing alloy can dissolve in γ-Fe and α-Fe, improving the high-temperature strength and hardness of the alloy and enhancing the corrosion resistance of the material.

[0023] Ni element: The alloying element Ni can significantly inhibit the migration of carbon element, effectively reduce the stability of carbides and the binding ability of carbide-forming elements to carbon, promote the formation of austenite and ferrite duplex structure, inhibit the growth of carbides, and improve the overall mechanical properties.

[0024] Nb element: Nb can dissolve in the iron matrix. Through solid solution strengthening, it can improve the strength and hardness of stainless steel. At the same time, Nb can be used as a grain boundary strengthening element to promote grain refinement, improve the toughness and tensile resistance of the material, and has an impact on the phase transformation behavior of stainless steel, which helps to optimize the organizational structure and performance of duplex stainless steel.

[0025] Mn element and Si element: During the welding process, the main functions of Mn and Si are deoxidation and desulfurization, reducing the oxygen and sulfur content in the surfacing alloy, and preventing defects such as pores from occurring in the surfacing metal, which may lead to a decline in the forming quality.

[0026] TiN element: On the one hand, ceramic particles can serve as a heterogeneous nucleation substrate, reducing the nucleation energy barrier and promoting heterogeneous nucleation in the molten pool. On the other hand, the random orientation of equiaxed grains breaks the directional arrangement of columnar grains, making the microstructure tend to be isotropic. Therefore, introducing a ceramic reinforcement phase into the flux cored wire is one of the solutions. As a strong ferrite nucleation site, adding TiN to stainless steel will promote the nucleation of ferrite, thus promoting the precipitation and refinement of ferrite.

[0027] Its strengthening effect is achieved by adding various precipitation-phase elements to the welding wire. Using Cr and Mo elements as the main alloying components, a certain amount of trace alloying elements such as Ni, Nb, TiN, and Mn are added. At the same time, the ratio of each element is strictly controlled. Through Jmatpro thermodynamics software for metallographic structure prediction, when the ferrite:austenite ratio is 1:1, the duplex stainless steel has the best performance.

[0028] The present invention also provides a method for preparing a duplex stainless steel flux-cored wire, which is specifically implemented according to the following steps: Step 1: Weigh the following raw materials by mass percentage respectively: Chromium powder 32% - 38%, nickel powder 1.5% - 4%, molybdenum powder 11% - 14%, niobium powder 0.2% - 1%, manganese powder 3% - 6%, silicon powder 1% - 3%, titanium nitride 0.8% - 2.2%, and the rest is iron powder; The particle size of the flux powder is 100 - 150 mesh; Step 2: First, mix the raw material powders weighed in Step 1 evenly, then heat and keep warm in an inert gas atmosphere to fully dry the flux powder, and finally cool it to room temperature with the furnace; The specific steps for mixing evenly are: Mix the raw material powders in a V-type powder mixer with a rotation speed of 60 r / min - 70 r / min for 2 - 3 hours; The heating temperature is 150°C - 200°C, the holding time is 2 h - 3 h, and the inert gas is argon with a purity of 99.999%; Step 3: Place the outer skin on the tape feeder of the wire forming machine, and roll the outer skin into a U-shaped groove through the grooving of the forming machine; The outer skin is a 0Cr18Ni9 austenitic stainless steel strip; Step 4: Put the flux powder processed in Step 2 into the U-shaped groove of the outer skin, close the U-shaped outer skin, and finally make the required diameter of the duplex stainless steel flux-cored wire by the method of step-by-step diameter reduction; The filling rate of the flux powder is 20% - 25%; After the outer skin is closed and formed by the rolling mill, a wire with a diameter of 2.10 mm is first made, and finally a wire with a diameter of 1.18 mm is obtained.

[0029] The present invention also provides an additive manufacturing method for a duplex stainless steel flux-cored wire. Using the above duplex stainless steel flux-cored wire for additive manufacturing by MIG welding to obtain a duplex stainless steel structural part, which is implemented according to the following specific steps: Step 1: Assemble the prepared duplex stainless steel flux-cored wire onto a fully automatic welding robot; Step 2: Design a three-dimensional model and layer it to determine the number of layers and the layer height; The number of layers is determined according to actual production needs, and the layer height of each layer is 2 mm - 3 mm; Step 3: Write a welding program for the welding robot; set the welding parameters for MIG welding in the welding program; The welding parameters are as follows: the welding speed is 0.2 m / min to 0.3 m / min; the welding torch is lifted 2 mm to 3 mm for each layer, the welding current is 160 A to 170 A, the welding voltage is 19 V to 22 V, and the weaving amplitude is 6 mm to 8 mm; Step 4: Perform additive manufacturing under a shielding gas; The shielding gas is argon with a purity of 99.999%; the cooling method during additive manufacturing is interlayer cooling, and the interlayer temperature is 100 °C to 150 °C.

[0030] Example 1 In this example, a duplex stainless steel flux-cored wire is prepared, and the specific implementation steps are as follows: Step 1: Weigh the following raw materials by mass percentage respectively: Chromium powder 32%, nickel powder 1.8%, molybdenum powder 12%, niobium powder 0.5%, manganese powder 4.3%, silicon powder 1%, titanium nitride 1.3%, and the rest is iron powder; the particle size of the flux powder is 100 to 150 mesh; Step 2: Mix the raw material powders weighed in Step 1 evenly and place them in a tubular furnace. Under the condition of continuously introducing argon, keep them at 200 °C for 2.5 h to fully dry the flux powder, and finally cool it to room temperature with the furnace; Step 3: Place the outer skin on the tape feeder of the wire forming machine, and roll the outer skin into a U-shaped groove through the grooving of the forming machine; the outer skin is a 0Cr18Ni9 austenitic stainless steel strip with a width of 7 mm and a thickness of 0.3 mm; The chemical composition (mass fraction %) of the 0Cr18Ni9 austenitic stainless steel strip is shown in Table 1 below: Table 1

[0031] Step 4: Put the flux powder processed in Step 2 into the U-shaped groove of the outer skin, close the U-shaped outer skin, wipe it clean with acetone or absolute ethanol, and finally make a metal type flux-cored wire with the required diameter by the method of stepwise reducing the diameter; The filling rate of the flux powder is 25%; After passing through the closing and forming rollers, a wire of 2.10 mm is made, and finally a duplex stainless steel flux-cored wire of 1.18 mm is made by the method of stepwise reducing the diameter. It is straightened by a wire drawing machine, coiled into a disk, and sealed and packaged.

[0032] In this example, the duplex stainless steel structural part is made by additive manufacturing using the above-prepared duplex stainless steel wire through MIG welding, and the specific implementation steps are as follows: Step 1: Assemble the prepared duplex stainless steel flux-cored wire onto a fully automatic welding robot; Step 2: Design a 3D model and layer it to determine the number of layers and layer height; The number of layers is 42, and the layer height is 2 mm to 3 mm for each layer; Step 3: Write a welding program for the welding robot; set the welding parameters for MIG welding in the welding program; The welding speed is 0.27 m / min; the welding torch is lifted by 2 mm to 3 mm for each layer, the welding current is 160 A, the welding voltage is 21 V, and the weaving amplitude is 8 mm; Step 4: Implement additive manufacturing under a shielding gas; The shielding gas is argon with a purity of 99.999%; The cooling method during additive manufacturing is interlayer cooling, and the interlayer temperature is 100 °C to 150 °C.

[0033] As Figure 1 shown, the formed duplex stainless steel component obtained in this example is beautiful in appearance. The macroscopic morphology shows that the stacked parts present obvious stratification phenomena, and there is good metallurgical bonding between layers, without defects such as pores and inclusions. Its microstructure is austenite (A) + ferrite (δ-F). The light-colored part in the figure is austenite tissue, and the dark color is ferrite tissue, and the ratio of austenite to ferrite is close to 1:1, which fully conforms to the microstructure of duplex stainless steel.

[0034] After mechanical property testing, the overall formed duplex stainless steel structural part in this example is beautiful in appearance, there is no obvious spatter on the structural part, the tensile strength reaches 847.8 MPa, and the elongation is 31.5%, having good mechanical property indexes.

[0035] Example 2 This example prepares a duplex stainless steel flux-cored wire, which is specifically implemented according to the following steps: Step 1: Weigh the following raw materials by mass percentage respectively: 32% chromium powder, 1.5% nickel powder, 11% molybdenum powder, 0.5% niobium powder, 3% manganese powder, 1.3% silicon powder, 0.8% titanium nitride, and the rest is iron powder; the particle size of the flux powder is 100 - 150 mesh; Step 2: Mix the raw material powders weighed in Step 1 evenly and place them in a tubular furnace. Under the condition of continuously introducing argon, keep them at 200 °C for 2.5 h to fully dry the flux powder, and finally cool it to room temperature with the furnace; Step 3: Place the outer skin on the tape feeder of the wire forming machine, and roll the outer skin into a U-shaped groove through the grooving of the forming machine; the outer skin is a 0Cr18Ni9 austenitic stainless steel strip with a width of 7 mm and a thickness of 0.3 mm; Step 4: Put the flux powder processed in Step 2 into the U-shaped groove of the outer skin, close the U-shaped outer skin, and finally make the metal type flux-cored wire with the required diameter by the method of gradually reducing the diameter; The filling rate of the flux cored powder is 23%; After passing through the closing and forming rollers, a welding wire with a diameter of 2.10 mm is made, and finally a duplex stainless steel flux cored wire with a diameter of 1.18 mm is made by the method of stepwise reducing the diameter.

[0036] In this embodiment, the duplex stainless steel welding wire prepared above is used for additive manufacturing by MIG welding to obtain a duplex stainless steel structural part, which is specifically implemented according to the following steps: Step 1: Assemble the prepared duplex stainless steel flux cored wire onto a fully automatic welding robot; Step 2: Design a three-dimensional model and layer it to determine the number of layers and the layer height; The number of layers is 45, and the layer height of each layer is 2 mm to 3 mm; Step 3: Program the welding procedure for the welding robot; set the welding parameters of MIG welding in the welding procedure; The welding speed is 0.25 m / min; the welding torch is lifted 2 mm to 3 mm for each layer, the welding current is 160 A, the welding voltage is 19 V, and the swing arc amplitude is 6 mm; Step 4: Implement additive manufacturing under a shielding gas; The shielding gas is argon with a purity of 99.999%; The cooling method during additive manufacturing is interlayer cooling, and the interlayer temperature is 100 °C to 150 °C.

[0037] The duplex stainless steel structural part prepared in this example has a beautiful overall shape, no obvious spatter on the structural part, a tensile strength of 793.6 MPa, and an elongation of 32.5%.

[0038] Example 3 In this embodiment, a duplex stainless steel flux cored wire is prepared, which is specifically implemented according to the following steps: Step 1: Weigh the following raw materials by mass percentage respectively: 35% chromium powder, 13% molybdenum powder, 0.7% niobium powder, 4% manganese powder, 1.4% silicon powder, 1.8% titanium nitride, 1.5% nickel powder, and the rest is iron powder; the particle size of the flux cored powder is 100 - 150 mesh; Step 2: Mix the raw material powders weighed in Step 1 evenly and place them in a tubular furnace. Under the condition of continuously introducing argon, keep them at 200 °C for 2.5 h to fully dry the flux cored powder, and finally cool it to room temperature with the furnace; Step 3: Place the outer skin on the tape feeder of the welding wire forming machine, and roll the outer skin into a U-shaped groove through the groove pressing of the forming machine; the outer skin is a 0Cr18Ni9 austenitic stainless steel strip with a width of 7 mm and a thickness of 0.3 mm; Step 4: Put the flux cored powder processed in Step 2 into the U-shaped groove of the outer skin, close the U-shaped outer skin, and finally make a metal cored wire with the required diameter by the method of gradually reducing the diameter. The filling rate of the flux cored powder is 23%. After passing through the closing and forming rollers, a wire with a diameter of 2.10 mm is made, and finally a duplex stainless steel cored wire with a diameter of 1.18 mm is made by the method of gradually reducing the diameter.

[0039] In this embodiment, the duplex stainless steel wire prepared above is used for additive manufacturing by MIG welding to obtain a duplex stainless steel structural part, which is specifically implemented according to the following steps: Step 1: Assemble the prepared duplex stainless steel cored wire onto a full-automatic welding robot. Step 2: Design a three-dimensional model and layer it to determine the number of layers and the layer height. The number of layers is 50, and the layer height of each layer is 2 mm to 3 mm. Step 3: Program the welding procedure for the welding robot; set the welding parameters of MIG welding in the welding procedure. The welding speed is 0.27 m / min; the welding torch is lifted 2 mm to 3 mm for each layer, the welding current is 165 A, the welding voltage is 21 V, and the swing arc amplitude is 6 mm to 8 mm. Step 4: Implement additive manufacturing under a shielding gas. The shielding gas is argon with a purity of 99.999%. The cooling method during additive manufacturing is interlayer cooling, and the interlayer temperature is 100 °C to 150 °C.

[0040] The overall shape of the duplex stainless steel structural part prepared in this example is beautiful, there is no obvious spatter on the structural part, the tensile strength reaches 815.2 MPa, and the elongation is 27.6%.

[0041] Example 4 In this embodiment, a duplex stainless steel cored wire is prepared, which is specifically implemented according to the following steps: Step 1: Weigh the following raw materials by mass percentage respectively: Chromium powder 35%, molybdenum powder 13%, niobium powder 0.7%, manganese powder 4%, silicon powder 1.4%, titanium nitride 1.8%, nickel powder 1.5%, and the rest is iron powder; the particle size of the flux cored powder is 100 to 150 mesh. Step 2: Mix the raw material powders weighed in Step 1 evenly and place them in a tube furnace. Under the condition of continuously introducing argon, keep them at 200 °C for 2.5 h to fully dry the flux cored powder, and finally cool it to room temperature with the furnace. Step 3: Place the outer skin on the tape feeder of the wire forming machine, and roll the outer skin into a U-shaped groove through the grooving of the forming machine; the outer skin is a 0Cr18Ni9 austenitic stainless steel strip with a width of 7 mm and a thickness of 0.3 mm. Step 4: Put the flux-cored powder processed in Step 2 into the U-shaped groove of the outer skin, close the U-shaped outer skin, and finally make a metal-cored wire with the required diameter by the method of gradually reducing the diameter. The filling rate of the flux-cored powder is 23%. After passing through the closing and forming rollers, a wire with a diameter of 2.10 mm is made, and finally a duplex stainless steel metal-cored wire with a diameter of 1.18 mm is made by the method of gradually reducing the diameter.

[0042] In this embodiment, the duplex stainless steel wire prepared above is used for additive manufacturing by MIG welding to obtain a duplex stainless steel structural part, which is specifically implemented according to the following steps: Step 1: Assemble the prepared duplex stainless steel metal-cored wire onto a fully automatic welding robot. Step 2: Design a three-dimensional model and layer it to determine the number of layers and the layer height. The number of layers is 46, and the layer height of each layer is 2 mm to 3 mm. Step 3: Write a welding program for the welding robot; set the welding parameters of MIG welding in the welding program. The welding speed is 0.3 m / min; the welding torch is lifted 2 mm to 3 mm for each layer, the welding current is 170 A, the welding voltage is 22 V, and the swing arc amplitude is 6 mm. Step 4: Implement additive manufacturing under a shielding gas. The shielding gas is argon with a purity of 99.999%. The cooling method during additive manufacturing is interlayer cooling, and the interlayer temperature is 100 °C to 150 °C.

[0043] The duplex stainless steel structural part prepared in this example has a beautiful overall shape, no obvious spatter on the structural part, a tensile strength of 824.2 MPa, and an elongation of 30.8%.

[0044] Example 5 In this embodiment, a duplex stainless steel metal-cored wire is prepared, which is specifically implemented according to the following steps: Step 1: Weigh the following raw materials by mass percentage respectively: Chromium powder 36%, molybdenum powder 12.5%, niobium powder 0.3%, manganese powder 4.5%, silicon powder 2%, titanium nitride 1.3%, nickel powder 2.5%, and the rest is iron powder; the particle size of the flux-cored powder is 100 to 150 mesh. Step 2: Mix the raw material powders weighed in Step 1 evenly and place them in a tubular furnace. Under the condition of continuously introducing argon, keep them at 200 °C for 3 h to fully dry the flux-cored powder, and finally cool it to room temperature with the furnace. Step 3: Place the outer skin on the tape feeder of the wire forming machine, and roll the outer skin into a U-shaped groove through the grooving of the forming machine; the outer skin is a 0Cr18Ni9 austenitic stainless steel strip with a width of 7 mm and a thickness of 0.3 mm. Step 4: Put the flux-cored powder processed in Step 2 into the U-shaped groove of the outer skin, close the U-shaped outer skin, and finally make a metal-cored wire with the required diameter by the method of gradually reducing the diameter. The filling rate of the flux-cored powder is 25%. After passing through the closing and forming rollers, a wire with a diameter of 2.10 mm is made, and finally a duplex stainless steel metal-cored wire with a diameter of 1.18 mm is made by the method of gradually reducing the diameter.

[0045] In this embodiment, the duplex stainless steel wire prepared above is used for additive manufacturing by MIG welding to obtain a duplex stainless steel structural part, which is specifically implemented according to the following steps: Step 1: Assemble the prepared duplex stainless steel metal-cored wire onto a full-automatic welding robot. Step 2: Design a three-dimensional model and layer it to determine the number of layers and the layer height. The number of layers is 49, and the layer height of each layer is 2 mm to 3 mm. Step 3: Program the welding procedure for the welding robot; set the welding parameters of MIG welding in the welding procedure. The welding speed is 0.27 m / min; the welding torch is lifted 2 mm to 3 mm for each layer, the welding current is 160 A, the welding voltage is 20 V, and the swing arc amplitude is 8 mm. Step 4: Implement additive manufacturing under a shielding gas. The shielding gas is argon with a purity of 99.999%. The cooling method during additive manufacturing is interlayer cooling, and the interlayer temperature is 100°C to 150°C.

[0046] The duplex stainless steel structural part prepared in this example has a beautiful overall shape, no obvious spatter on the structural part, a tensile strength of 855.2 MPa, and an elongation of 32.3%.

[0047] Example 6 In this embodiment, the duplex stainless steel metal-cored wire is prepared, which is specifically implemented according to the following steps: Step 1: Weigh the following raw materials by mass percentage respectively: Chromium powder 37%, molybdenum powder 14%, niobium powder 1%, manganese powder 3%, silicon powder 1.5%, titanium nitride 2%, nickel powder 3%, and the rest is iron powder; the particle size of the flux-cored powder is 100 - 150 mesh. Step 2: Mix the raw material powders weighed in Step 1 evenly and place them in a tubular furnace. Under the condition of continuously introducing argon, keep them at 200 °C for 2 h to fully dry the flux-cored powder, and finally cool them to room temperature with the furnace; Step 3: Place the outer skin on the tape feeder of the wire forming machine, and roll the outer skin into a U-shaped groove through the grooving of the forming machine; the outer skin is a 0Cr18Ni9 austenitic stainless steel strip with a width of 7 mm and a thickness of 0.3 mm; Step 4: Put the flux-cored powder processed in Step 2 into the U-shaped groove of the outer skin, close the U-shaped outer skin, and finally make a metal-cored wire with the required diameter by the method of gradually reducing the diameter; The filling rate of the flux-cored powder is 24%; After passing through the closing and forming rollers, a wire with a diameter of 2.10 mm is made, and finally a duplex stainless steel flux-cored wire with a diameter of 1.18 mm is made by the method of gradually reducing the diameter.

[0048] In this embodiment, the duplex stainless steel wire prepared above is used for additive manufacturing by MIG welding to obtain a duplex stainless steel structural part, which is specifically implemented according to the following steps: Step 1: Assemble the prepared duplex stainless steel flux-cored wire onto a full-automatic welding robot; Step 2: Design a 3D model and layer it to determine the number of layers and the layer height; The number of layers is 44, and the layer height of each layer is 2 mm to 3 mm; Step 3: Program the welding procedure for the welding robot; set the welding parameters of MIG welding in the welding procedure; The welding speed is 0.3 m / min; the welding torch is lifted 2 mm to 3 mm for each layer, the welding current is 165 A, the welding voltage is 19 V, and the weaving amplitude is 6 mm; Step 4: Implement additive manufacturing under a shielding gas; The shielding gas is argon with a purity of 99.999%; The cooling method during additive manufacturing is interlayer cooling, and the interlayer temperature is 100 °C to 150 °C.

[0049] The overall shape of the duplex stainless steel structural part prepared in this example is beautiful, there are no obvious spatter on the structural part, the tensile strength reaches 819.2 MPa, and the elongation is 31.9%.

Claims

1. Duplex stainless steel flux-cored welding wire, characterized in that: It includes a core and a sheath, wherein the core is composed of the following raw material components according to mass percentage: Chromium powder 32%~38%, nickel powder 1.5%~4%, molybdenum powder 11%~14%, niobium powder 0.2%~1%, manganese powder 3%~6%, silicon powder 1%~3%, titanium nitride 0.8%~2.2%, and the rest is iron powder; The particle size of the core powder is 100~150 mesh.

2. The duplex stainless steel flux-cored welding wire according to claim 1, characterized in that: The outer skin is a 0Cr18Ni9 austenitic stainless steel strip.

3. The duplex stainless steel flux-cored welding wire according to claim 1, characterized in that: The filling rate of the medicine core powder is 20% to 25%.

4. A method for preparing a duplex stainless steel flux-cored welding wire, characterized in that: Follow the steps below to implement it: Step 1: Weigh the following raw materials by mass percentage: Chromium powder 32%~38%, nickel powder 1.5%~4%, molybdenum powder 11%~14%, niobium powder 0.2%~1%, manganese powder 3%~6%, silicon powder 1%~3%, titanium nitride 0.8%~2.2%, and the rest is iron powder; the particle size of the core powder is 100~150 mesh; Step 2, the raw material powder weighed in step 1 is first mixed evenly, and then heated to 150°C~200°C in an argon atmosphere with a purity of 99.999% and kept warm for 2h~3h to fully dry the core powder, and finally cooled to room temperature with the furnace; Step 3, placing the outer skin on the unwinding machine of the welding wire forming machine, and rolling the outer skin into a U-shaped groove through the groove pressing of the forming machine; Step 4: Place the flux core powder processed in step 2 into the U-shaped groove of the outer skin, close the U-shaped outer skin, and finally produce a duplex stainless steel flux cored welding wire of the required diameter by a step-by-step diameter reduction method.

5. The method for preparing a duplex stainless steel flux-cored welding wire according to claim 4, characterized in that: In step 3, the outer skin is a 0Cr18Ni9 austenitic stainless steel strip.

6. The method for preparing a duplex stainless steel flux-cored welding wire according to claim 4, characterized in that: The filling rate of the medicine core powder in step 4 is 20% to 25%.

7. An additive manufacturing method for duplex stainless steel flux-cored welding wire, characterized in that: Using the duplex stainless steel flux-cored welding wire according to any one of claims 1 to 3 to perform additive manufacturing by MIG welding to obtain a duplex stainless steel structural part, the method is specifically implemented in the following steps: Step 1, assembling the prepared duplex stainless steel flux-cored welding wire onto a fully automatic welding robot; Step 2: Design the 3D model and divide it into layers, and determine the number of layers and layer height; Step 3, write a welding program for the welding robot; set the welding parameters of MIG welding in the welding program; Step 4: Implement additive manufacturing under a protective gas.

8. The additive manufacturing method of duplex stainless steel flux-cored welding wire according to claim 7, characterized in that: In step 2, the layer height is 2 mm to 3 mm.

9. The additive manufacturing method of duplex stainless steel flux-cored welding wire according to claim 7, characterized in that: The welding parameters in step 3 are: welding speed is 0.2m / min~0.3m / min; welding gun is lifted 2mm~3mm per layer, welding current is 160A~170A, welding voltage is 19V~22V, and arc swing amplitude is 6mm~8mm.

10. The additive manufacturing method of duplex stainless steel flux-cored welding wire according to claim 7, characterized in that: In step 4, the protective gas is argon gas with a purity of 99.999%; the cooling method in the additive manufacturing process is interlayer cooling, and the interlayer temperature is 100° C. to 150° C.

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