Metal laminate structure manufacturing equipment

Abstract

The method for manufacturing a metal laminate structure is a method for manufacturing a metal additive manufacturing body by depositing metal on a workpiece, and includes the steps of: supplying a laser beam (3) and a center shield gas (6) from a processing head (13); spraying an outer shield gas (10) containing a gas species with a molecular weight smaller than that of the center shield gas (6) from an outer shield gas nozzle (11) provided around the processing head (13) while the laser beam (3) and the center shield gas (6) are being supplied; and supplying a wire (1) from the wire supply mechanism (16) to a processing point (5) while operating the wire supply mechanism (16) while the laser beam (3) and the center shield gas (6) are being supplied.

Description

[Technical Field]

[0001] The present disclosure relates to a method and an apparatus for manufacturing a metal laminate structure. [Background technology]

[0002] Conventionally, a manufacturing device for metal additive manufacturing (AM) that uses a technology called additive manufacturing (AM) has been known as a technology for creating three-dimensional objects. AM is a technology that layers metal objects on a base by repeatedly melting and solidifying metal raw materials.

[0003] When melting raw metal materials, the raw metal materials reach high temperatures. To prevent oxidation, an inert gas called a shielding gas is sprayed near the processing point. The shielding gas is integrated with the processing nozzle and blocks oxygen near the processing point. As the manufacturing process continues, the heat input exceeds the heat output, causing heat to accumulate in the underlying metal. When the raw metal materials are additively molded onto a heated object, the resulting object becomes even hotter. The temperature rises above the oxidation temperature of the raw metal materials not only near the processing point but also throughout the entire object. Under these conditions, oxidation of the object cannot be prevented. As a result, when using titanium alloys, which are prone to oxidation, for example, oxidation significantly reduces ductility, preventing the desired properties from being achieved. Therefore, efforts are being made to expand the range of the shielding gas by using double or triple shielding gas nozzles.

[0004] Patent Document 1 is a document related to a double nozzle used in gas-shielded arc welding, and discloses a basic double nozzle configuration in which gas nozzles are arranged around an arc welding heat source at the center. Patent Document 2 is a document related to a triple nozzle, and discloses a configuration and flow rate of an intermediate shielding gas to prevent the inner and outer shielding gases from mixing. Patent Document 3 discloses a configuration in which nitrogen gas and argon gas are used in combination to suppress defects in laser welding. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2023-23971 [Patent Document 2] International Publication No. 2022 / 163820 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-39749 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventional technology faces two major challenges. The first challenge is caused by the double nozzle, which widens the oxygen shielding range of the shielding gas. The wider the oxygen shielding range, the less likely the object is to oxidize. Therefore, in principle, it is sufficient to use as large a double nozzle as possible. In recent years, AM manufacturing has required high-precision manufacturing using feedback control based on height and temperature measurements, which requires the installation of various sensors such as height sensors, temperature sensors, and vision sensors near the processing point. This places a limit on how large the double nozzle can be. Furthermore, 5-axis machining is essential for high-precision machining, but if the shielding gas nozzle near the processing point is large, the stage and the shielding gas nozzle will interfere with each other when the stage is tilted.

[0007] The technologies disclosed in Patent Documents 1 and 2 employ techniques to make the gas flow spiral or triple-layered in order to straighten the gas flow, which tends to result in a larger nozzle overall. Furthermore, while they disclose that the flow velocity should be set to a specified value or higher, simply increasing the flow velocity is not necessarily good because increasing the flow velocity can cause turbulence.

[0008] Another issue arises from the differences between laser welding and AM. Patent Document 3 uses a double nozzle to prevent blowholes from occurring during laser welding, but laser welding aims to connect two parts, and the number of heat inputs is less than that of AM. The purpose of the technology disclosed in Patent Document 3 is to shield oxygen from the vicinity of the processing point during processing, not to widen the range of the shielding gas to prevent oxidation during heat accumulation. Therefore, unlike laser welding technology, the challenge is to prevent oxidation of metal AM objects that have accumulated heat.

[0009] The present disclosure has been made in view of the above, and aims to provide a method for manufacturing a metal laminate structure that can appropriately expand the range of shielding gases that suppress oxidation. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems and achieve the object, the present disclosure provides a method for manufacturing a metal laminate structure. Device teeth, The machining head includes a raw material supply mechanism for supplying a metal raw material, a center shield gas nozzle for spraying a center shield gas, and a part of a heating mechanism, an outer shield gas spraying mechanism for spraying outer shield gas supplied from an outer shield gas pipe from an outer shield gas nozzle provided outside the center shield gas nozzle and having a blocking structure provided between the nozzle and the center shield gas nozzle, and a movement mechanism for moving a stage on which is placed a molded object formed from the metal raw material supplied from the raw material supply mechanism. The outer shield gas nozzle is a ring-shaped nozzle disposed around the center shield gas nozzle. The blocking structure is provided on the center shield gas nozzle side of the outlet of the outer shield gas sprayed from the outer shield gas nozzle, covering part of the outlet. [Effects of the Invention]

[0011] The method for manufacturing a metal laminate structure according to the present disclosure has the effect of being able to appropriately expand the range of shielding gases that suppress oxidation. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view of a portion of a manufacturing apparatus for a metal additive manufacturing object according to an embodiment; [Figure 2] 1 is a cross-sectional view of an entire manufacturing apparatus for a metal additive manufacturing object according to an embodiment; [Figure 3] FIG. 1 is a block diagram showing the hardware configuration of a control device included in a metal additive manufacturing apparatus according to an embodiment. [Figure 4] FIG. 1 is a diagram showing a processing circuit in a case where the function of a control device included in a manufacturing apparatus for a metal additive manufacturing object according to an embodiment is realized by the processing circuit; [Figure 5]Figure 1 shows the oxidation and nitriding temperatures estimated from the results of TG (Thermogravimetry)-DTA (Differential Thermal Analysis) measurements of pure titanium. [Figure 6] Figure 2 shows the oxidation and nitriding temperatures estimated from the TG-DTA measurement results of pure titanium. [Figure 7] FIG. 1 is a schematic cross-sectional view of an outer shield gas nozzle according to Example 1. [Figure 8] FIG. 2 is a schematic cross-sectional view of an outer shield gas nozzle according to the first embodiment. [Figure 9] FIG. 3 is a schematic cross-sectional view of an outer shield gas nozzle according to the first embodiment. [Figure 10] FIG. 4 is a schematic cross-sectional view of an outer shield gas nozzle according to the first embodiment. [Figure 11] FIG. 1 is a schematic plan view of an outer shield gas nozzle according to a first embodiment; [Figure 12] FIG. 1 shows conditions and measurement results of oxygen amount according to Example 1. [Figure 13] FIG. 1 shows a setting according to Example 1. [Figure 14] 1 shows conditions and results according to Example 2. [Figure 15] FIG. 10 is a schematic cross-sectional view of a connection portion between an outer shielding gas nozzle and an outer shielding gas pipe according to a third embodiment. [Figure 16] 10 shows conditions and results according to Example 3. [Figure 17] 10A and 10B are schematic cross-sectional and plan views of an outer shield gas nozzle according to a fourth embodiment of the present invention; [Figure 18] FIG. 1 shows conditions and results according to Example 4. [Figure 19] FIG. 10 is a diagram showing the performance results based on the oxygen amount and nitrogen amount under each condition according to Example 5. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a metal laminate structure and an apparatus for manufacturing a metal laminate structure according to an embodiment will be described in detail below with reference to the drawings.

[0014] Embodiment The embodiment relates to a method for manufacturing a metal additive manufacturing object and a metal additive manufacturing apparatus 100. First, a description will be given of the metal additive manufacturing apparatus 100 used in the method for manufacturing a metal additive manufacturing object.

[0015] The configuration of a metal additive manufacturing apparatus 100 according to an embodiment will be described. FIG. 1 is a cross-sectional view of a portion of the metal additive manufacturing apparatus 100 according to an embodiment. FIG. 1 schematically illustrates a cross-section of a portion of the metal additive manufacturing apparatus 100. FIG. 1 includes the letters "X," "Y," and "Z." "X" refers to the X-axis, which is an axis in a horizontal plane, and "Y" refers to the Y-axis, which is an axis in a horizontal plane and is perpendicular to the X-axis. "Z" refers to the Z-axis, which indicates the vertical direction. FIG. 2 is a cross-sectional view of the entire metal additive manufacturing apparatus 100 according to an embodiment. FIG. 2 is a schematic diagram illustrating the entire cross-section of the metal additive manufacturing apparatus 100. Like FIG. 1, FIG. 2 also includes the letters "X," "Y," and "Z." Hereinafter, the "metal additive manufacturing apparatus 100" may be referred to as the "manufacturing apparatus 100."

[0016] 1, the manufacturing apparatus 100 includes a wire nozzle 2 that supplies wire 1, which is a metal raw material, a beam nozzle 4 that emits a laser beam 3, which is a heat source, to heat the wire 1, and a center shield gas nozzle 7 that sprays center shield gas 6 toward a processing point 5. The manufacturing apparatus 100 further includes an outer shield gas nozzle 11 that sprays outer shield gas 10 from around the center shield gas nozzle 7 onto a base material 8 and a molded object 9, and a stage 12 on which the base material 8 and the molded object 9 are placed. The molded object 9 is a layered structure of beads formed by the laser beam 3 emitted from the beam nozzle 4 melting the wire 1, and is the entire object formed on the base material 8.

[0017] In this embodiment, the beam nozzle 4 and the center shielding gas nozzle 7 are integrated. The beam nozzle 4 and the center shielding gas nozzle 7 may be separate entities as long as the center shielding gas nozzle 7 can supply the center shielding gas 6 to the processing point 5. The wire nozzle 2 is a raw material supply unit, the beam nozzle 4 is a heating unit, and the center shielding gas nozzle 7 and the outer shielding gas nozzle 11 are shielding gas spraying units.

[0018] (Definition of processing point 5) The processing point 5 is a position where the wire 1 is heated when the beam nozzle 4 emits the laser beam 3 onto the object 9 or the base material 8. The wire 1 melted by the beam nozzle 4 emitting the laser beam 3 is deposited on the object 9 and shaped into a desired shape, so the processing point 5 is also the position where the object 9 is shaped.

[0019] (Overall configuration of the processing head 13) 1 , the manufacturing apparatus 100 has a processing head 13. In this embodiment, a beam nozzle 4, a center shield gas nozzle 7, and an outer shield gas nozzle 11 are fixed to the processing head 13. The processing head 13 moves relative to a stage 12 on which a molded object 9 is placed. In other words, the processing head 13 moves relative to the stage 12, so that the beam nozzle 4, the center shield gas nozzle 7, and the outer shield gas nozzle 11 can move relative to the stage 12.

[0020] (Wire Nozzle 2 explanation) A wire nozzle 2, which is a raw material supply unit, supplies wire 1, which is a metal raw material. The wire nozzle 2 advances the wire 1 toward the position where the laser beam 3 emitted by the beam nozzle 4 reaches, i.e., toward the processing point 5. The area that fully encompasses the area where the wire 1 melts and spreads due to the laser beam 3 is defined as the processing area. The processing point 5 is included in the processing area. As shown in FIG. 1 , the wire nozzle 2 is positioned at a different position from the beam nozzle 4, and advances the wire 1 in a direction oblique to the direction in which the beam nozzle 4 emits the laser beam 3. Depending on the shape of the object 9, one or both of the relative positions and directions of the wire nozzle 2 and the beam nozzle 4 may be changed.

[0021] As shown in FIG. 2, the supply of wire 1 is controlled by a wire supply mechanism 16 including a spool 14, a rotary motor 15, and a wire nozzle 2. The wire supply mechanism 16 is a raw material supply mechanism. The spool 14 is a supply source of metal raw material around which wire 1 is wound. The spool 14 is attached to the rotary motor 15, which is a servo motor. When the rotary motor 15 is driven, the spool 14 rotates, causing the wire 1 to be unwound from the spool 14. The wire 1 unwound from the spool 14 is supplied to the processing point 5 through the wire nozzle 2. When the rotary motor 15 is rotated in the direction opposite to the direction in which the wire 1 is unwound from the spool 14, the wire 1 supplied to the processing point 5 can be pulled out. In this case, the unwound wire 1 is wound up by the reverse rotation of the rotary motor 15 and stored on the spool 14. The wire 1 may be supplied by a method other than the above-described method.

[0022] The wire 1 is a metal raw material for manufacturing a metal additive manufacturing object. For example, the material of the wire 1 may be a Ni-based alloy, an Fe-based alloy, an Al-based alloy, a Ti-based alloy, or other metals. The wire 1 may be replaced with a powder material.

[0023] (Explanation of Beam Nozzle 4) The beam nozzle 4, which is a heating unit, emits a laser beam 3, which is a heat source, toward a printing position of the object 9, and the wire 1 supplied from the wire nozzle 2 is heated and melted by the laser beam 3. As described above, the printing position of the object 9 is the processing point 5. A heating mechanism 19 that emits the laser beam 3 is configured by a laser oscillator 17, a fiber cable 18, and the beam nozzle 4. As shown in FIG. 2, the beam nozzle 4 is connected to the laser oscillator 17 that emits the laser beam 3 by the fiber cable 18. The laser beam 3 is emitted from the laser oscillator 17 via the fiber cable 18 and through the beam nozzle 4. The heat source is not limited to the laser beam 3. For example, an arc may be used as the heat source.

[0024] (Shielding gas nozzle explanation) The center shield gas nozzle 7 and the outer shield gas nozzle 11 are shield gas spraying units that spray gas toward the molded object 9 or the periphery of the molded object 9 to suppress oxidation of the molded object 9. The center shield gas nozzle 7 sprays the center shield gas 6 toward the processing point 5 along the emission direction of the laser beam 3 emitted from the beam nozzle 4.

[0025] The center shield gas spray mechanism 20 includes a center shield gas supply device 22, a center shield gas pipe 23, and a center shield gas nozzle 7. The outer shield gas spray mechanism 21 includes an outer shield gas supply device 24, an outer shield gas pipe 25, and an outer shield gas nozzle 11.

[0026] Center shield gas 6 is supplied to processing point 5 from center shield gas supply device 22 via center shield gas piping 23 and center shield gas nozzle 7. Because processing point 5 is a laser welding part, the temperature at processing point 5 is extremely high, and if relatively inexpensive nitrogen gas is used as center shield gas 6, nitriding will occur depending on the material type. Therefore, argon gas, among inert gases, is used as center shield gas 6.

[0027] The outer shielding gas 10 is supplied from an outer shielding gas supply device 24 to the periphery of the base material 8 and the molded object 9 via an outer shielding gas pipe 25 and an outer shielding gas nozzle 11. Argon gas may be used as the outer shielding gas 10, but nitrogen gas may also be used. When nitrogen gas is used as the outer shielding gas 10, a wider shielding range can be obtained compared to when argon gas is used.

[0028] The outer shield gas nozzle 11 is a ring-shaped nozzle arranged around the center shield gas nozzle 7. Inside the outer shield gas nozzle 11, a mechanism is provided for dispersing the outer shield gas 10 supplied from an outer shield gas supply device 24 and an outer shield gas pipe 25. The outer shield gas nozzle 11 disperses the outer shield gas 10 and sprays it around the base material 8 and the molded object 9 as a laminar flow.

[0029] (Stage 12 explanation) The processing head 13, to which the beam nozzle 4, center shield gas nozzle 7, and outer shield gas nozzle 11 are fixed, moves relative to the stage 12. The processing head 13 moves by being driven by a head drive device 26. The stage 12 rotates or moves by a rotation device 27. The processing head 13, head drive device 26, stage 12, and rotation device 27 constitute a movement mechanism 28 that moves the processing head 13 and stage 12 relative to each other, and the movement mechanism 28 has five processing axes. The above-mentioned configuration is one example of the configuration of the movement mechanism 28, and the configuration of the movement mechanism 28 is not limited to the above-mentioned configuration.

[0030] 2, the stage 12 is located on and connected to a rotation device 27, a base material 8 is placed on the stage 12, and deposits are deposited on the base material 8. The rotation device 27 rotates and / or moves the stage 12, thereby changing the posture or position of the object 9. In other words, by moving the stage 12, the object 9 can be moved relative to the processing head 13. The manufacturing apparatus 100 has the rotation device 27, and therefore can also manufacture objects 9 with complex shapes.

[0031] (Control mechanism of control device 29) 2, the manufacturing apparatus 100 further includes a control device 29 that controls the operation of the manufacturing apparatus 100 according to an NC (Numerical Control) program. The control device 29 controls the wire supply mechanism 16, the heating mechanism 19, the center shielding gas spraying mechanism 20, the outer shielding gas spraying mechanism 21, and the movement mechanism 28. For example, a numerical control device is used as the control device 29. The control device 29 controls the operation of the manufacturing apparatus 100 by outputting various commands.

[0032] Regarding the control of the wire supply mechanism 16, the control device 29 controls the drive of the rotary motor 15 by outputting to the rotary motor 15 a command corresponding to the conditions of the supply amount of metal raw material. The control device 29 adjusts the speed at which the wire 1 is supplied from the spool 14 to the processing point 5 by controlling the drive of the rotary motor 15. Regarding the control of the heating mechanism 19, the control device 29 controls the laser oscillation by the laser oscillator 17 by outputting to the laser oscillator 17 a command corresponding to the conditions of the output of the laser beam 3, and causes the laser beam 3 to be emitted from the beam nozzle 4.

[0033] Regarding control of the shielding gas spraying mechanism, the control device 29 outputs a command corresponding to the conditions for the supply amount of the center shielding gas 6 to the center shielding gas supply device 22 and outputs a command corresponding to the conditions for the supply amount of the outer shielding gas 10 to the outer shielding gas supply device 24, thereby controlling the supply amounts of the center shielding gas 6 and the outer shielding gas 10. Regarding control of the machining head 13 constituting the movement mechanism 28, the control device 29 outputs a movement command to the head drive device 26, thereby controlling the drive of the head drive device 26 and moving the machining head 13.

[0034] Regarding the control of the stage 12 constituting the moving mechanism 28, the control device 29 outputs a rotation command to the rotation device 27 to control the driving of the rotation device 27 and cause the stage 12 to move and / or rotate. To form an object 9 having a desired shape, the control device 29 controls the moving mechanism 28 to move the machining head 13 and the stage 12 relative to each other. As described above, the control device 29 controls the wire supply mechanism 16, the heating mechanism 19, the center shield gas spraying mechanism 20, the outer shield gas spraying mechanism 21, and the moving mechanism 28, so that the manufacturing apparatus 100 can manufacture an object 9 having a desired shape.

[0035] (Regarding the hardware of the control device 29) A description will be given of the hardware configuration of the control device 29. The control performed by the control device 29 shown in Fig. 2 is realized by the hardware executing a control program, which is a program for executing control of the manufacturing apparatus 100.

[0036] 3 is a block diagram showing the hardware configuration of a control device 29 included in a metal additive manufacturing apparatus 100 according to an embodiment. The control device 29 includes a CPU (Central Processing Unit) 30 that executes various processes, a RAM (Random Access Memory) 31 that includes a data storage area, a ROM (Read Only Memory) 32 that is a nonvolatile memory, an external storage device 33, and an input / output interface 34 for inputting information to the control device 29 and outputting information from the control device 29. Each component shown in FIG. 3 is connected to all the other components via a bus 35.

[0037] The CPU 30 executes programs stored in the ROM 32 and the external storage device 33. The overall control of the manufacturing apparatus 100 performed by the control device 29 is realized by the CPU 30 executing the above programs.

[0038] The external storage device 33 is a hard disk drive (HDD) or a solid state drive (SSD). The external storage device 33 stores a control program and various data. The ROM 32 stores a boot loader such as a basic input / output system (BIOS) or a unified extensible firmware interface (UEFI), which is a control program, and software or a program that controls the hardware. The control program may be stored in the ROM 32.

[0039] The programs stored in the ROM 32 and the external storage device 33 are loaded into the RAM 31. The CPU 30 loads the control program into the RAM 31, executes the control program, and thereby performs various processes. The input / output interface 34 is an interface that connects the control device 29 with devices external to the control device 29. A machining program is input to the input / output interface 34. The input / output interface 34 outputs various commands. The control device 29 may have input devices such as a keyboard and a pointing device, and an output device such as a display.

[0040] The control program may be stored in a computer-readable storage medium. The control device 29 may store the control program stored in the storage medium in the external storage device 33. The storage medium may be a portable storage medium such as a flexible disk, or a flash memory such as a semiconductor memory. The control program may be installed in the control device 29 from a computer or server device external to the control device 29 via a communication network. As described above, the functions of the control device 29 are realized by a computer or a controller.

[0041] The functions of the control device 29 may be realized by a processing circuit, which is dedicated hardware for controlling the manufacturing apparatus 100. FIG. 4 is a diagram showing a processing circuit 99 when the functions of the control device 29 included in the manufacturing apparatus 100 for a metal additive manufacturing object according to an embodiment are realized by the processing circuit 99. FIG. 4 is a block diagram of the processing circuit 99. That is, the functions of the control device 29 may be realized by the processing circuit 99. The processing circuit 99 is a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof. Some of the functions of the control device 29 may be realized by dedicated hardware, and the remaining functions may be realized by software or firmware.

[0042] (Description of manufacturing method and usage) Next, the operation of the manufacturing apparatus 100 according to the embodiment and a method for manufacturing a metal additive manufacturing object using the manufacturing apparatus 100 will be described.

[0043] A beam nozzle 4, which moves relative to a stage 12 on which a base material 8 and a model 9 are placed, emits a laser beam 3, and the wire 1 supplied by a wire nozzle 2 is heated by the laser beam 3, thereby adding the model 9 to the base material 8. The manufacturing apparatus 100 manufactures the desired metal additive manufacturing object by stacking a model 9 on the added model 9 in a process similar to the process described above.

[0044] The manufacturing conditions for the metal additive manufacturing body are determined by the laser output conditions selected based on the material of the wire 1, the supply amount of the wire 1, the axial movement speed of the beam nozzle 4 fixed to the processing head 13, the type and flow rate of the center shield gas 6, and the type and flow rate of the outer shield gas 10.

[0045] (Explanation of Center Shield Gas 6) The center shield gas 6 is sprayed toward the processing point 5. The purpose of the center shield gas 6 is to prevent oxygen and nitrogen from the atmosphere from being drawn into the processing point 5 and to prevent changes such as oxidation of the wire 1. The changes such as oxidation can be either oxidation or nitriding, or both. The wire 1 may be replaced with a powdered metal raw material. Because the laser beam 3, a heat source, is irradiated, the temperature of the processing point 5 reaches a temperature higher than the melting point of the metal raw material. Therefore, it is necessary to prevent changes such as oxidation or nitriding from occurring at the high temperature at which the metal raw material melts. Among inert gases, argon gas and helium gas are candidates for the center shield gas 6, and argon gas is used as the center shield gas 6 from an economical standpoint. The heat source is not limited to the laser beam 3.

[0046] (Explanation of Outer Shield Gas 10) The outer shielding gas 10 is sprayed around the work point 5 from an outer shielding gas nozzle 11 located outside the center shielding gas nozzle 7 that sprays the center shielding gas 6. The area where the center shielding gas 6 provides an oxygen shielding effect is approximately 5 to 10 mm wide in the planar direction. If the size of the workpiece 9 exceeds 10 mm, the center shielding gas 6 will not provide an oxygen shielding effect for a portion of the workpiece 9. The purpose of the outer shielding gas 10 is to prevent a portion of the workpiece 9 that has accumulated heat during continuous fabrication from coming into contact with the atmosphere and oxidizing if that portion moves outside the area where the center shielding gas 6 provides an oxygen shielding effect. As described above, the center shielding gas 6 is sprayed toward the work point 5 to suppress oxidation and nitridation of the molten metal, and the temperature range targeted by the center shielding gas 6 is very high. On the other hand, the temperature range targeted by the outer shielding gas 10 is the same as that of heat accumulation, lower than the temperature of the workpoint 5. In this manner, the present invention has focused on the fact that the center shield gas 6 and the outer shield gas 10 have different target temperature ranges.

[0047] (Explanation of the difference between oxidation temperature and nitriding temperature) This section explains the oxidation and nitridation of metal raw materials due to temperature differences. Figure 5 shows the oxidation and nitridation temperatures estimated from TG-DTA measurements of pure titanium (Fig. 1). Figure 6 shows the oxidation and nitridation temperatures estimated from TG-DTA measurements of pure titanium (Fig. 2). When titanium powder was heated at a constant temperature in an air atmosphere, the oxidation behavior was estimated from the mass increment due to oxidation. It was found that oxidation was gradual up to approximately 400°C, accelerated around 500°C, and rapidly increased above 600°C. Similarly, when titanium powder was heated at a constant temperature in a nitrogen atmosphere, no nitridation occurred up to 400°C, gradually increased above 400°C, and progressed above approximately 700°C. The mass increment was also smaller than that of oxidation, suggesting that nitridation is less sensitive than oxidation. In other words, titanium rapidly oxidizes when exposed to air while stored at, for example, 600°C, but is unlikely to be nitrided in a nitrogen atmosphere. This makes it possible to use appropriate gas types depending on the temperature range during modeling.

[0048] (Effects of different gas types) The effect of using different gas types will be explained below. By using argon gas, which has a relatively large molecular weight, for the center shielding gas 6 and nitrogen gas, which has a relatively small molecular weight, for the outer shielding gas 10 that surrounds the center shielding gas 6, the effect of reducing pressure loss can be achieved. The outer shielding gas 10 must be discharged from the outer shielding gas nozzle 11 in a laminar flow to prevent the surrounding atmosphere from being drawn in. The outer shielding gas 10 that flows in from the outer shielding gas piping 25 becomes turbulent because a large flow rate of gas is discharged from the piping, so it is necessary to uniformly disperse the outer shielding gas 10 inside the outer shielding gas nozzle 11 to form a laminar flow before discharging it.

[0049] The outer shielding gas 10 is supplied from the outer shielding gas nozzle 11 via the outer shielding gas supply device 24 and the outer shielding gas piping 25. Because the diameter of the outer shielding gas nozzle 11 is larger than that of a typical piping, the inflow velocity of the outer shielding gas 10 into the outer shielding gas nozzle 11 is greater than the outflow velocity, resulting in pressure loss due to the difference between the inflow and outflow velocities. The pressure loss of a gas flowing through a circular pipe can be calculated using the Darcy-Weisbach equation, which indicates that pressure loss is proportional to the fluid density. Therefore, nitrogen gas, which has a smaller molecular weight and lower density, can reduce pressure loss more than argon gas. As a result, using nitrogen gas instead of argon gas as the outer shielding gas 10 allows the outer shielding gas 10 discharged from the outer shielding gas nozzle 11 to be dispersed over a wider area, resulting in wider shielding than when argon gas is used as the outer shielding gas 10.

[0050] Nitrogen gas is cheaper than argon gas, and its superior economical efficiency is another benefit of using nitrogen gas instead of argon gas as outer shielding gas 10. As described above, when attention is paid to the difference between the nitriding temperature and the oxidation temperature of the metal raw material, it is not necessary to use argon gas as outer shielding gas 10, and nitrogen gas, which has a relatively small molecular weight and good dispersibility, can be used as outer shielding gas 10. In other words, when nitrogen gas is used as outer shielding gas 10, it is possible to obtain a wide range of oxygen shielding effects that have not been achieved in the past.

[0051] (Explanation of gas flow rate, etc.) There are several points to note when using the outer shielding gas 10. The common purpose of the center shielding gas 6 and the outer shielding gas 10 is to prevent atmospheric oxygen and nitrogen from being drawn into the processing point 5, thereby preventing changes such as oxidation and nitridation of the raw metal material. Therefore, it is important to spray the center shielding gas 6 and the outer shielding gas 10 onto or around the processing point 5, base material 8, and workpiece 9 without drawing in surrounding gases. For this reason, it is desirable for the center shielding gas 6 and the outer shielding gas 10 to be laminar flows rather than turbulent flows.

[0052] Whether a flow is laminar or turbulent is determined by the Reynolds number, and it is generally known that turbulent flow occurs when the Reynolds number exceeds 2300. Since the Reynolds number is determined by the kinematic viscosity coefficient, characteristic length, and flow velocity, the smaller the nozzle diameter and the higher the flow velocity, the more turbulent the flow. Therefore, it is necessary to control the flow velocity of the gas used for shielding gas and the flow rate that determines the flow velocity.

[0053] Next, we will explain the precautions to take when using nitrogen gas as the outer shielding gas 10. As mentioned above, the machining point 5 becomes very hot, so if nitrogen gas flows in, nitriding may occur. Therefore, it is necessary to prevent the outer shielding gas 10 from flowing into the machining point 5. To do this, the flow velocity of the center shielding gas 6 must be made greater than the flow velocity of the outer shielding gas 10.

[0054] The desired characteristics can be obtained by making the center shield gas 6 and the outer shield gas 10 laminar flows and making the flow velocity of the center shield gas 6 greater than the flow velocity of the outer shield gas 10.

[0055] As described above, the metal additive manufacturing apparatus 100 according to the embodiment includes a wire supply mechanism 16 that supplies the wire 1, a processing head 13 that includes a center shield gas nozzle 7 that sprays the center shield gas 6, and a part of a heating mechanism 19. The manufacturing apparatus 100 further includes an outer shield gas spraying mechanism 21 that sprays the outer shield gas 10 supplied from the outer shield gas nozzle 11 provided outside the center shield gas nozzle 7 through an outer shield gas piping 25 connected to the side of the outer shield gas nozzle 11, and a movement mechanism 28 that moves the stage 12 on which the object 9 to be formed using the wire 1 supplied from the wire supply mechanism 16 is placed.

[0056] In the method for manufacturing a metal additive manufacturing product by depositing metal on a workpiece according to the embodiment, the steps are: supplying a laser beam 3 and a center shield gas 6 from a processing head 13; ejecting an outer shield gas 10 containing a gas species with a molecular weight smaller than that of the center shield gas 6 from an outer shield gas nozzle 11 provided around the processing head 13 while the laser beam 3 and the center shield gas 6 are being supplied; and supplying a wire 1 from the wire supply mechanism 16 to a processing point 5 while operating the wire supply mechanism 16 while the laser beam 3 and the center shield gas 6 are being supplied. More specifically, the laser beam 3 and the center shield gas 6 are supplied to the processing point 5, and the outer shield gas 10 is supplied toward the periphery of the processing point 5.

[0057] Since the outer shielding gas 10 contains gas species with a molecular weight smaller than that of the center shielding gas 6, the method for manufacturing a metal laminate structure according to the embodiment can appropriately expand the range of shielding gases that suppress oxidation. Furthermore, since the outer shielding gas 10 contains gas species with a molecular weight smaller than that of the center shielding gas 6, the range of shielding gases that suppress oxidation can be appropriately expanded without increasing the sizes of the center shielding gas nozzle 7 and the outer shielding gas nozzle 11. For example, argon gas is used as the center shielding gas 6, and nitrogen gas is used as the outer shielding gas 10.

[0058] Specific examples will be described below. In Examples 1 to 3, oxygen concentration measurements were carried out without evaluating the shape of the object in order to quantify the effect of blocking oxygen.

[0059] (Example 1) (Difference between argon gas and nitrogen gas) In Example 1, the difference between the case where argon gas is used as the outer shield gas 10 and the case where nitrogen gas is used will be described based on the results of measuring the oxygen concentration.

[0060] 7 is a first diagram schematically showing a cross section of the outer shielding gas nozzle 11 according to Example 1. The outer shielding gas pipe 25 is provided on the opposite side of the discharge port of the outer shielding gas 10. A structure for dispersing and discharging the gas uniformly is formed inside the outer shielding gas nozzle 11. The diameter of the discharge port of the center shielding gas nozzle 7 is 10 mm, the outer diameter of the discharge port of the outer shielding gas nozzle 11 is 70 mm, the inner diameter of the discharge port of the outer shielding gas nozzle 11 is 15 mm, and the shape of the discharge port of the outer shielding gas nozzle 11 is ring-shaped. The center shielding gas nozzle 7 and the outer shielding gas nozzle 11 are connected by being positioned in the inner hole of the outer shielding gas nozzle 11.

[0061] The outer shielding gas nozzle 11 has a lattice structure and a partition structure for dispersing and uniformly discharging the gas. The lattice structure can be fabricated using a three-dimensional printer by setting a fine mesh size based on CAD (Computer-Aided Design) data. The partition structure is provided for the purpose of dispersing the outer shielding gas 10 flowing from the inlet through the outer shielding gas pipe 25 using the lattice structure and then rectifying the flow. For example, the discharge port is provided with a partition structure that divides the space into an annular shape at 5 mm intervals in the radial direction. The lattice structure is just one example, and a member made of wool, which is a typical gas dispersing mechanism, may be filled inside the outer shielding gas nozzle 11. The partition structure may be provided with a partition plate or may be molded integrally with the outer shielding gas nozzle 11. FIG. 11 is a schematic plan view of the outer shielding gas nozzle 11 according to Example 1. As shown in FIG. 11, the outer shielding gas nozzle 11 according to Example 1 has a plurality of partition structures 36 provided therein. The specific shape of each of the plurality of partition structures 36 is cylindrical. One partition structure 36 may be provided inside the outer shield gas nozzle 11.

[0062] The outlet of the outer shielding gas nozzle 11 is tapered at 45° relative to the outlet of the center shielding gas nozzle 6. This is to prevent interference between the outer shielding gas nozzle 10 and the stage 12 when the stage 12 is tilted during five-axis machining. The outlet of the outer shielding gas nozzle 11 does not necessarily have to be tapered at 45°. As shown in FIGS. 8 to 10 , the outlet of the center shielding gas nozzle 7 and the outlet of the outer shielding gas nozzle 11 may be aligned, the distance between the outlet and the base material may be uniform, or a portion of the wire 1 supplied from the wire nozzle 2 may be enclosed within the outer shielding gas nozzle 11. FIG. 8 is a second diagram schematically illustrating a cross section of the outer shielding gas nozzle 11 according to Example 1. FIG. 9 is a third diagram schematically illustrating a cross section of the outer shielding gas nozzle 11 according to Example 1. FIG. 10 is a fourth diagram schematically illustrating a cross section of the outer shielding gas nozzle 11 according to Example 1.

[0063] In Example 1, the oxygen content was measured under each of Conditions A to C shown on the left side of FIG. 12 as an example of gas flow rates for the purpose of comparing argon gas and nitrogen gas. FIG. 12 illustrates the conditions and oxygen content measurement results for Example 1. FIG. 13 illustrates the setup for Example 1. An oxygen concentration meter 37 was placed on the base material 8. Argon gas was used as the center shielding gas 6, and the center shielding gas 6 was flowed at 10 L / min. Comparisons were made under three conditions: Condition A, in which no outer shielding gas 10 was used; Condition B, in which nitrogen gas was used as the outer shielding gas 10; and Condition C, in which argon gas was used as the outer shielding gas 10. FIG. 12 shows the flow rate for reference. While it is difficult to determine the exact flow rate, the reference flow rate at the discharge port can be easily calculated by dividing the flow rate by the cross-sectional area. The processing point 5 was set as the 0 mm point, and the oxygen concentration was measured under each of Conditions A to C by setting the oxygen concentration meter 37 at a position spaced apart from the processing point 5 in the fabrication direction.

[0064] Figure 12 shows the results of oxygen concentration measurements under each condition. It can be seen that the oxygen concentration is higher under condition A, where the outer shielding gas 10 is not used. This is because the center shielding gas 6 alone is not enough to shield from the atmosphere. Next, we compare conditions B and C, where the outer shielding gas 10 is used. Under condition B, the oxygen concentration is 300 ppm at the 8 mm point, while under condition C, the oxygen concentration is 300 ppm at the 16 mm point. Thus, using nitrogen gas as the outer shielding gas 10 doubles the shielding performance under the same flow rate conditions, and it was found that the shielding range is broader depending on the gas type, even when shielding is performed using the same nozzle under the same conditions.

[0065] (Example 2) (Study of flow rate conditions) In Example 2, the flow rate conditions will be explained. In Example 2, to determine whether or not there is an oxygen shielding effect, the results of Example 1 using argon gas were referenced, and it was determined that oxygen shielding performance was obtained if the concentration was below 1000 ppm at the 12 mm point. Fig. 14 is a diagram showing the conditions and results of Example 2.

[0066] (Conditions D~G) In order to confirm the shielding performance when the flow rate of the center shielding gas 6 was set to the lower limit, the flow rate of the center shielding gas 6 was set to a small value of 5 L / min, and the flow rate of the outer shielding gas 10 was adjusted. Under condition D, the flow rate of the outer shielding gas 10 was 30 L / min, and it was found that sufficient shielding performance could not be obtained. This can be determined to be because the flow rate per unit area was low compared to the discharge area of ​​the outer shielding gas nozzle 11, and a flow rate of 30 L / min was not sufficient to ensure appropriate shielding performance. It was found that appropriate shielding performance was obtained under conditions E and F, but a tendency for the oxygen concentration to be high was observed under condition G, where the flow rate was 150 L / min.

[0067] When gas visualization was performed using schlieren, it was confirmed that the outer shielding gas 10 being discharged from the outer shielding gas nozzle 11 was turbulent. This is thought to be because the flow rate became too high, causing the flow velocity of the outer shielding gas 10 flowing from the outer shielding gas piping 25 to the outer shielding gas nozzle 11 to become extremely high, and the outer shielding gas 10 was unable to disperse properly inside the outer shielding gas nozzle 11, causing it to be discharged from the outer shielding gas nozzle 11. This result showed that increasing the flow rate of the outer shielding gas 10 in order to ensure appropriate shielding performance could result in turbulence.

[0068] (Conditions H~I) In order to understand the tendency of the oxygen shielding effect by changing the flow rate of the center shielding gas 6, the flow rate of the center shielding gas 6 was set to 10 L / min and the flow rate of the outer shielding gas 10 was adjusted, and it was confirmed that turbulence occurred under condition I, just as in condition G.

[0069] (conditions J~M) The behavior of the center shielding gas 6 was confirmed when the flow rate was increased to 20 L / min. At flow rates above 20 L / min, the center shielding gas 6 becomes turbulent, so 20 L / min is the upper limit for the flow rate of the center shielding gas 6. It was found that in condition J, the flow rate of the outer shielding gas 10 was insufficient, and sufficient shielding performance could not be obtained. At a flow rate of 50 L / min, it was confirmed that the oxygen concentration was below the desired level, and in condition M, the flow rate of the outer shielding gas 10 was 150 L / min, so turbulence occurred, just as in conditions G and J.

[0070] From the above verification results, it was found that in order for the outer shield gas 10 to exhibit sufficient performance, it is necessary to flow nitrogen gas at a flow rate of 50 L / min or more and less than 150 L / min.

[0071] (Example 3) (Improvement of dispersion of outer shield gas nozzle 11) Under conditions G, I, and M of Example 2, the outer shielding gas 10 from the outer shielding gas nozzle 11 became turbulent at a flow rate of 150 L / min, and the desired results could not be obtained. Therefore, in order to improve the dispersion of the outer shielding gas 10, the installation method of the outer shielding gas pipe 25 that supplies the outer shielding gas 10 to the outer shielding gas nozzle 11 was changed.

[0072] 15 is a diagram schematically showing a cross section of the connection between the outer shielding gas nozzle 11 and the outer shielding gas pipe 25 according to Example 3. The outer shielding gas pipe 25 is provided in a direction perpendicular to the outlet of the outer shielding gas 10, and a structure is formed inside the outer shielding gas nozzle 11 that disperses and uniformly discharges the outer shielding gas 10. Connecting the outer shielding gas pipe 25 perpendicularly to the outlet of the outer shielding gas 10 serves to prevent the outer shielding gas 10 from being discharged from the outer shielding gas nozzle 11 without being dispersed.

[0073] FIG. 16 is a diagram showing conditions and results according to the third embodiment.

[0074] (Conditions N~S) Under condition N, the outer shielding gas 10 was sprayed at a flow rate of 150 L / min. Under condition G, turbulence occurred. However, under condition N, the outer shielding gas 10 was sprayed from the side, dispersing the outer shielding gas 10 inside the outer shielding gas nozzle 11 and creating a laminar flow. This resulted in the desired oxygen shielding effect. Under conditions O to Q, the flow rates of the outer shielding gas 10 were set to 180, 200, and 250 L / min. Consequently, the oxygen concentration varied greatly under conditions P and Q. This is thought to be due to the relatively low flow rate of the center shielding gas 6 and the relatively high flow rate of the outer shielding gas 10, resulting in the center shielding gas 6 and the outer shielding gas 10 mixing together. Under these conditions, the nitrogen gas used as the outer shielding gas 10 may flow into the machining point 5, causing nitriding.

[0075] Under conditions R and S, the flow rate of the outer shielding gas 10 was 250 L / min, and the flow rate of the center shielding gas 6 was 10 or 20 L / min. Under these conditions, the oxygen concentration was stable and the desired oxygen shielding effect was obtained. In other words, by adjusting the flow rates of the center shielding gas 6 and the outer shielding gas 10 and preventing the center shielding gas 6 and the outer shielding gas 10 from mixing, the oxygen shielding effect can be obtained.

[0076] (Example 4) (Prevention of Mixing of Center Shield Gas 6 and Outer Shield Gas 10) Under conditions P and Q in Example 3, the flow velocity of the center shield gas 6 was relatively small and the flow velocity of the outer shield gas 10 was relatively large, resulting in the problem of mixing of the center shield gas 6 and the outer shield gas 10. In Example 4, a method for preventing the mixing of gases will be described.

[0077] FIG. 17 is a schematic diagram showing a cross section and a plan view of an outer shielding gas nozzle 11 according to Example 4. The upper side of FIG. 17 shows a cross section of the outer shielding gas nozzle 11, and the lower side of FIG. 17 shows a plan view of the outer shielding gas nozzle 11. In Example 4, a blocking structure 38 is used to block a portion of the outlet of the outer shielding gas nozzle 11 near the center shielding gas nozzle 7. For example, for a ring-shaped outer shielding gas nozzle 11 having an outlet with an outer diameter of 70 mm and an inner diameter of 15 mm, a blocking structure 38 capable of blocking an inner diameter of 25 mm is used. The blocking structure 38 is a ring-shaped component having an outer diameter of 25 mm and an inner diameter of 15 mm. The blocking structure 38 covers a portion of the outlet of the outer shielding gas nozzle 11. This prevents nitrogen gas from flowing out from the 25 mm diameter area, thereby preventing interference between the outer shielding gas 10 and the center shielding gas 6. The ratio of the inner diameter to the outer diameter is not limited to the above example, but it is important to ensure a sufficient distance between the outer shielding gas 10 and the center shielding gas 6. Fig. 18 is a diagram showing the conditions and results of Example 4.

[0078] (Conditions T~U) The outer shield gas nozzle 11 of Example 4 was used for re-evaluation under condition P, in which the center shield gas 6 and the outer shield gas 10 were mixed in Example 3. As a result, the desired oxygen shielding effect was obtained under condition T, in which the gas flow rate was 200 L / min. On the other hand, under condition U, in which the gas flow rate was 250 L / min, the desired oxygen shielding effect could not be obtained, possibly because the two types of gases were still mixed.

[0079] From the above, it was found that the likelihood of use increases by providing the blocking structure 38 on a part of the outer shield gas nozzle 11.

[0080] (Summary) From the above, it was found that in Examples 1 and 2, in which the dispersibility of the outer shield gas nozzle 11 was not taken into consideration, a sufficient oxygen shielding effect could not be obtained at a flow rate of less than 50 L / min, and turbulence occurred at a flow rate of 150 L / min.

[0081] By improving the dispersion of the outer shielding gas nozzle 11, the flow rate of the outer shielding gas 10 can be increased to 250 L / min. However, because there is a risk of the center shielding gas 6 and the outer shielding gas 10 mixing due to differences in flow rate, it is necessary to consider the flow rate ratio taking into account the flow rate ratio and the discharge area. It was found that providing a blocking structure 38 in part of the outer shielding gas nozzle 11 is effective in improving this likelihood.

[0082] In the examples, the ranges of the flow rate ratio and flow velocity ratio that can obtain the oxygen shielding effect are as follows, based on the results of conditions K and T. That is, the range of the flow rate ratio needs to be 2.5 to 40, and the range of the flow velocity ratio needs to be 0.05 to 0.83. That is, it is preferable that the flow rate of the outer shielding gas 10 is 2.5 to 40 times the flow rate of the center shielding gas 6, and the flow velocity of the outer shielding gas 10 is 0.05 to 0.83 times the flow velocity of the center shielding gas 6.

[0083] (Example 5) Verification of the usefulness of the outer shield gas nozzle 11 A molding experiment was conducted using the outer shield gas nozzle 11, the oxygen shielding effect of which was verified based on oxygen concentration measurements in Examples 1 to 4. In the experiments, a titanium alloy, which is easily oxidized, was used as the metal raw material. A titanium alloy (Ti-6Al-4V) wire 1 with a diameter of 1.2 mm was prepared, and molding was performed using the manufacturing apparatus 100 shown in Figures 1 and 2. The manufactured object was a wall-like object created by producing a single 50 mm long bead and continuing to layer on top of it, and was molded to a height of 50 mm. The molding was performed at an output of 1500 W and an axial speed of 400 mm / min. The above-mentioned molding conditions and shapes are described as an example of the conditions for verification, but the conditions and shapes are not limited to these.

[0084] In order to check whether nitriding occurs in the area where the outer shield gas 10 is sprayed, it is effective to confirm that the molding is being performed at a temperature below the nitriding temperature using a radiation thermometer or thermoviewer.

[0085] The ductility of titanium alloys decreases depending on the amount of oxygen, and the JIS standard stipulates that the amount must be 0.2% or less. Therefore, in order to verify whether or not titanium oxidizes, the oxygen content of the molded object was measured to verify whether or not oxidation occurs. Since nitrogen gas is used, nitrogen was also measured, and the standard set at 0.05% according to the JIS standard. The purpose of the double shielding gas nozzle is to suppress oxidation of the alloy. Therefore, the standard for whether or not oxidation is suppressed was whether or not the titanium alloy molded object satisfied the JIS standard for titanium alloys.

[0086] FIG. 19 is a diagram showing the performance evaluation based on the oxygen and nitrogen amounts under each condition in Example 5. Here, condition B using argon gas was used as the standard to verify the usefulness of using nitrogen gas. Condition A failed because it did not use the outer shield gas nozzle 11, resulting in extremely significant oxidation. Conditions B and later used the outer shield gas nozzle 11, which suppressed oxidation more effectively than condition A. As a result, it was confirmed that nitrogen gas enabled sound molding with a smaller amount of oxygen, verifying the usefulness of using a gas with a relatively small molecular weight as the outer shield gas 10.

[0087] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, and parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0088] 1 wire, 2 wire nozzle, 3 laser beam, 4 beam nozzle, 5 processing point, 6 center shield gas, 7 center shield gas nozzle, 8 base material, 9 molded object, 10 outer shield gas, 11 outer shield gas nozzle, 12 stage, 13 processing head, 14 spool, 15 rotation motor, 16 wire supply mechanism, 17 laser oscillator, 18 fiber cable, 19 heating mechanism, 20 center shield gas spray mechanism, 21 outer shield gas spray mechanism, 22 center shield gas supply device, 23 center shield gas piping, 24 outer shield gas supply device, 25 outer shield gas piping, 26 head drive device, 27 rotation device, 28 movement mechanism, 29 control device, 30 CPU, 31 RAM, 32 ROM, 33 external storage device, 34 input / output interface, 35 bus, 36 partition structure, 37 oxygen concentration meter, 38 blocking structure, 99 processing circuit, 100 Metal additive manufacturing equipment.

Claims

1. A method for manufacturing a metal additive manufacturing body, which involves depositing metal onto a workpiece and repeatedly performing a molding process on the deposited portion, The steps include supplying a heat source and a center shielding gas from the processing head, The steps include: when the heat source and the center shield gas are supplied, an outer shield gas containing a gas species with a molecular weight smaller than that of the center shield gas is ejected from an outer shield gas nozzle provided around the processing head; The steps include supplying metal raw materials from the raw material supply mechanism to the processing point while operating the raw material supply mechanism when the heat source and the center shield gas are supplied, and Includes, Nitrogen gas is used as the outer shielding gas. A method for manufacturing a metal laminated structure, characterized by the above.

2. Argon gas is used as the center shielding gas. A method for manufacturing a metal laminated structure according to claim 1.

3. The flow rate of the center shield gas is less than the flow rate of the outer shield gas. The flow velocity of the center shield gas, calculated by dividing the flow rate of the center shield gas by the cross-sectional area of ​​the outlet of the center shield gas nozzle that discharges the center shield gas, is greater than the flow velocity of the outer shield gas, calculated by dividing the flow rate of the outer shield gas by the cross-sectional area of ​​the outlet of the outer shield gas nozzle. A method for manufacturing a metal laminated structure according to claim 1 or 2.

4. The flow rate of the outer shield gas is 2.5 times or more and 40 times or less than the flow rate of the center shield gas. The flow velocity of the outer shield gas is 0.05 times or more and 0.83 times or less the flow velocity of the center shield gas. A method for manufacturing a metal laminated structure according to claim 3.

5. A raw material supply mechanism that supplies metal raw materials, A machining head having a center shield gas nozzle for blowing center shield gas and part of a heating mechanism, An outer shield gas blowing mechanism is provided on the outside of the center shield gas nozzle and has a structure that seals between it and the center shield gas nozzle, and blows outer shield gas supplied from the outer shield gas piping from the outer shield gas nozzle. A moving mechanism for moving a stage on which a molded object, formed from the metal raw material supplied from the raw material supply mechanism, is placed. A manufacturing apparatus for a metal laminated structure, characterized by comprising the following features.

6. A partition structure is provided inside the outer shield gas nozzle. The apparatus for manufacturing a metal laminated structure according to feature 5.

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