Patent Publication Number: US-2021178488-A1

Title: Gas supply device for manufacturing device, atomizing device, 3d additive manufacturing device, additive manufacturing system, and shaped object and gas supply method for manufacturing device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to Japanese Patent Application Number 2019225669 filed on Dec. 13, 2019. The entire contents of the above-identified application are hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a gas supply device for a manufacturing device, an atomizing device, a 3D additive manufacturing device, an additive manufacturing system, and a shaped object and a gas supply method for a manufacturing device. 
     RELATED ART 
     The use of a 3D additive manufacturing method to manufacture a component has been increasing in recent years. In particular, as an example of an additive manufacturing method using metal powder, a method called a powder bed method is widely used. In this method, metal powder is spread on a bed, and a shaping target portion is irradiated with a laser or an electron beam functioning as a heat source, to melt and solidify the metal powder. A shaped object can be obtained by repeating this process. 
     The metal powder as described above has large surface area. Thus, an oxide layer is likely to be formed in the surface, and oxygen content of a final shaped object tends to become large. In addition, since melting and solidifying is repeated in a high-temperature environment due to a laser or an electron beam, oxygen in a workspace atmosphere tends to be incorporated into a shaped object. In the case of large oxygen content as described above, in a shaped object including, for example, a nickel alloy as a base material, creep strength decreases. Moreover, in a shaped object including a copper alloy as a base material, hydrogen embrittlement is likely to occur. Thus, as described in JP 2011-178627 A, it is conceivable to use a deoxidization pump to make oxygen partial pressure of a workspace atmosphere extremely smaller. 
     SUMMARY 
     However, even when oxygen partial pressure is lowered as described above, nitrogen in an atmosphere tends to be incorporated into a shaped object. In this case, as with the case of large oxygen content, quality of a product decreases due to nitridation. 
     The present disclosure is made to solve the problems described above, and an object of the present disclosure is to provide a gas supply device for a manufacturing device, an atomizing device, a 3D additive manufacturing device, an additive manufacturing system, and a shaped object and a gas supply method for a manufacturing device capable of realizing higher quality. 
     SOLUTION TO PROBLEM 
     To solve the problems described above, a gas supply device for a manufacturing device according to the present disclosure includes an inert gas supply source that supplies inert gas, a supply line connected to the inert gas supply source, a nitrogen removal portion that is provided on the supply line and that removes at least a portion of nitrogen in the inert gas, and an oxygen removal portion that is provided on the supply line and that removes at least a portion of oxygen in the inert gas. 
     According to a gas supply device for a manufacturing device, an atomizing device, a 3D additive manufacturing device, an additive manufacturing system, and a shaped object and a gas supply method for a manufacturing device of the present disclosure, higher quality can be realized. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The disclosure will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a system diagram illustrating a configuration of an additive manufacturing system according to an embodiment of the present disclosure. 
         FIG. 2  is a system diagram illustrating a configuration of an atomizing device according to an embodiment of the present disclosure. 
         FIG. 3  is a system diagram illustrating a configuration of a 3D additive manufacturing device according to an embodiment of the present disclosure. 
         FIG. 4  is a hardware configuration diagram of a first control device according to an embodiment of the present disclosure. 
         FIG. 5  is a function block diagram of a first control device according to an embodiment of the present disclosure. 
         FIG. 6  is a flowchart illustrating a processing flow of a first control device according to an embodiment of the present disclosure. 
         FIG. 7  is a hardware configuration diagram of a second control device according to an embodiment of the present disclosure. 
         FIG. 8  is a function block diagram of a second control device according to an embodiment of the present disclosure. 
         FIG. 9  is a flowchart illustrating a processing flow of a second control device according to an embodiment of the present disclosure. 
         FIG. 10  is an Ellinghum diagram illustrating relationship between oxygen partial pressure and a redox equilibrium state of a metal. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Configuration of Additive Manufacturing System 
     Hereinafter, an additive manufacturing system  100  according to an embodiment of the present disclosure will be described with reference to  FIGS. 1 to 7 . The additive manufacturing system  100  according to the present embodiment is a device for manufacturing a three-dimensional shaped object, for example, by melting and layering metal powder. As illustrated in  FIG. 1 , the additive manufacturing system  100  includes an atomizing device  1  and a 3D additive manufacturing device  2 . 
     The atomizing device  1  is used to generate fine metal powder by solidifying a molten metal into a particulate form. A configuration of the atomizing device  1  will be described in detail below. The 3D additive manufacturing device  2  irradiates metal powder generated by the atomizing device  1  with, for example, a laser beam, to melt and solidify the metal powder on the laser beam. A three-dimensional shaped object is manufactured by repeating this processing and stacking a plurality of layers. A configuration of the 3D additive manufacturing device  2  will be described in detail below. An inert gas supply source G that is a portion of a gas supply device for a manufacturing device SG described below is connected to the atomizing device  1  and the 3D additive manufacturing device  2 . The inert gas supply source G is a vessel that stores and supplies inert gas including, for example, argon as a main component. In general, commercially available inert gas include oxygen and nitrogen by small quantity. That is, in the inert gas supply source G described above, the inert gas is stored in a state where oxygen, nitrogen, or other chemical species are mixed, in addition to argon as a main component. 
     Configuration of Atomizing Device 
     Next, the configuration of the atomizing device  1  will be described with reference to  FIG. 2 . As illustrated in  FIG. 2 , the atomizing device  1  includes the gas supply device for a manufacturing device SG and an atomizer  13 . 
     The gas supply device for a manufacturing device SG is a device for removing at least a portion of oxygen and nitrogen in the inert gas supply source G described above and supplying the atomizer  13  that follows. Specifically, the gas supply device for a manufacturing device SG includes the inert gas supply source G described above, a supply line L 11  connected to the inert gas supply source G, a nitrogen removal portion  11 , an oxygen removal portion  12 , a detection portion D 1 , a circulation line L 12 , a circulation compressor P 1 , a first valve device V 11 , a second valve device V 12 , a tank  14 , and a first control device  90 A. 
     The nitrogen removal portion  11  generates intermediate gas by removing at least a portion of a nitrogen component in the inert gas. As an example of the nitrogen removal portion  11 , a known nitrogen removal filter is suitably used. The filter includes a filter member made of titanium, and a heater (heating portion H 1 ) that heats the filter member to approximately 1000° C. The nitrogen component is absorbed by the filter member by causing the inert gas flowing on the supply line L 11  to pass through the filter member heated. 
     The oxygen removal portion  12  is disposed on the supply line L 11  in series in the downstream side of the nitrogen removal portion  11 . The oxygen removal portion  12  removes at least a portion of an oxygen component from the intermediate gas discharged from the nitrogen removal portion  11 . As an example of the oxygen removal portion  12 , a device using a known oxygen pump is suitably used. Although not illustrated in detail, in this type of device, a voltage is applied to a pipe line in a state where target gas flows through the pipe line formed of a solid electrolyte such as yttria-stabilized zirconia. Then, oxygen ions in the gas are ionized, pass through a wall of the pipe line, and are removed to the outside. Accordingly, the oxygen component in the gas can be removed. In addition, as with the nitrogen removal portion  11  described above, the oxygen removal portion  12  also includes a heater (heating portion H 2 ) that heats the inert gas. The inert gas is heated by this heater to approximately 600° C., for example. The intermediate gas having passed through the oxygen removal portion  12  includes no oxygen or a very small amount of oxygen (as treated gas) and is fed to the atomizer  13  in the downstream side. Note that temperature of the inert gas fed to the atomizer  13  is lower than temperature of the inert gas heated by the heating portions H 1  and H 2  (room temperature, for example). 
     Here, in the present embodiment, appropriate oxygen partial pressure is determined for each metal species on the basis of an Ellinghum diagram schematically illustrated in  FIG. 10 . The Ellinghum diagram is a diagram indicating whether oxidation reaction or reduction reaction proceeds when each metal species is held at a certain temperature and oxygen partial pressure. In the Ellinghum drawing, iron (Fe) is used as an example of the metal species for the determination of appropriate oxygen partial pressure. First, a straight line L passing from an origin (0 point) on the upper left in the drawing to a melting point M is drawn, and an intersection Pg of the straight line L and a graph right vertical axis (oxygen partial pressure) is determined. A value less than or equal to the intersection Pg is target oxygen partial pressure. At the melting point, when the oxygen partial pressure is Pg, an equilibrium state where neither oxidation nor reduction reaction occurs is reached, but when the oxygen partial pressure is less than Pg, reduction reaction proceeds and oxygen concentration in the metal decreases. Note that the nitrogen removal portion  11  described above also determines optimal nitrogen partial pressure on the basis of on the same Ellinghum diagram. 
     The atomizer  13  is connected to an end portion in the downstream side of the supply line L 11 . The atomizer  13  forms metal powder by spraying the treated gas described above supplied from the supply line L 11  on a molten metal. 
     The detection portion D 1  is provided in the downstream side of the oxygen removal portion  12  in the supply line L 11 . The detection portion D 1  detects oxygen partial pressure and nitrogen partial pressure of the treated gas flowing through the supply line L 11  and transmits the oxygen partial pressure and the nitrogen partial pressure to the first control device  90 A described below, as an electrical signal. 
     One end of the circulation line L 12  is connected to a portion between the detection portion D 1  and the atomizer  13  on the supply line L 11 . The circulation line L 12  extends from the one end to a portion between the inert gas supply source G and the nitrogen removal portion  11 . That is, the circulation line L 12  can circulate the treated gas having passed through the detection portion D 1  to the upstream side of the nitrogen removal portion  11  in the supply line L 11 . 
     A valve device is provided on each of the supply line L 11  and the circulation line L 12 . Specifically, the first valve device V 11  is provided between the inert gas supply source G and the nitrogen removal portion  11  on the supply line L 11 . Further, the second valve device V 12  is provided between the detection portion D 1  and the atomizer  13  on the supply line L 11 . The first valve device V 11  and the second valve device V 12  are each a solenoid valve having an opening amount and an open/closed state that can be changed by an electrical signal input from the outside. The first valve device V 11  and the second valve device V 12  are electrically connected to the first control device  90 A described below by a signal line not illustrated. 
     The tank  14  and the circulation compressor P 1  are provided in this order from the upstream side (the one end side) to the downstream side on the circulation line L 12 . The tank  14  is a vessel for storing a portion of gas flowing on the circulation line L 12 . When the circulation line L 12  is in an open state, the circulation compressor P 1  pumps gas on the circulation line L 12 . 
     An operation of the atomizing device  1  (that is, an open/closed state of each of the first valve device V 11  and the second valve device V 12 ) is controlled by the first control device  90 A. As illustrated in  FIG. 4 , the first control device  90 A is a computer including a central processing unit (CPU)  91 A, a read only memory (ROM)  92 A, a random access memory (RAM)  93 A, a hard disk drive (HDD)  94 A, and a signal reception module  95 A (input/output or I/O). The signal reception module  95 A receives a signal from the detection portion D 1  and transmits a drive electrical signal to the first valve device V 11  and the second valve device V 12 . The signal reception module  95 A may receive a signal amplified via, for example, a charge amplifier or the like. 
     As illustrated in  FIG. 5 , the CPU  91 A of the first control device  90 A includes a control unit  81 A, a storage unit  82 A, a determination unit  83 A, and a valve drive unit  84 A realized by executing a program stored in the CPU  91 A in advance. The control unit  81 A controls other functional units provided in the first control device  90 A. The storage unit  82 A stores in advance a target value (threshold value) of each of oxygen partial pressure and nitrogen partial pressure of the treated gas determined by the method described above. This target value is determined by using the Ellinghum diagram as described above. The determination unit  83 A compares an actual measured value of each of oxygen partial pressure and nitrogen partial pressure of the treated gas received from the detection portion D 1  and the threshold value and determines magnitude relationship. The valve drive unit  84 A adjusts the open/closed state (or the opening amount) of each of the first valve device V 11  and the second valve device V 12  described above on the basis of a determination result in the determination unit  83 A. 
     Specifically, as illustrated in  FIG. 6 , a processing flow by the first control device  90 A includes a detection step S 11 , a determination step S 12 , a first operation step S 13 , a second operation step S 14 , and an atomizing step S 15 . At the detection step S 11 , the above-described detection portion D 1  detects oxygen partial pressure and nitrogen partial pressure of the treated gas. At the determination step S 12 , the detection result and the threshold value (described above) are compared. In a case where it is determined at the determination step S 12  that the detection result is larger than the threshold value, the first operation step S 13  is executed. At the first operation step S 13 , the first valve device V 11  is opened and the second valve device V 12  is closed. Accordingly, the treated gas circulates through the circulation line L 12  described above to the upstream side of the nitrogen removal portion  11 . Such circulation continues, and thus the treated gas passes through the nitrogen removal portion  11  and the oxygen removal portion  12  a plurality of times. In a case where the oxygen partial pressure and the nitrogen partial pressure decreases through this circulation and it is determined at the determination step S 12  that the detection result is less than or equal to the threshold value, the second operation step S 14  is executed. At the second operation step S 14 , the first valve device V 11  is closed and the second valve device V 12  is opened. Accordingly, the treated gas is supplied from the supply line L 11  to the atomizer  13 . The atomizer  13  uses the treated gas to generate metal powder (atomizing step S 15 ). 
     Then, the configuration of the 3D additive manufacturing device  2  will be described with reference to  FIG. 3 . As illustrated in  FIG. 3 , the 3D additive manufacturing device  2  includes the above-described gas supply device for a manufacturing device SG and a shaping device main body  23 . 
     As described above, the gas supply device for a manufacturing device SG is a device for removing at least a portion of oxygen and nitrogen in the inert gas supply source G and supplying the shaping device main body  23  that follows. The gas supply device for a manufacturing device SG used in the 3D additive manufacturing device  2  includes the inert gas supply source G described above, the supply line L 11  connected to the inert gas supply source G, the nitrogen removal portion  11 , the oxygen removal portion  12 , a detection portion D 2 , a circulation line L 22 , a circulation compressor P 2 , the first valve device V 11 , a tank  24 , and a second control device  90 B. One end of the circulation line L 22  is connected to an end portion in the downstream side of the supply line L 11 . The other end of the circulation line L 22  is connected to a portion between the inert gas supply source G and the nitrogen removal portion  11  in the supply line L 11 . 
     The shaping device main body  23 , the tank  24 , and the circulation compressor P 2  are disposed in this order from the one end side to the other end side on the circulation line L 22 . The shaping device main body  23  forms a target shaped object by melting and layering metal powder in an atmosphere of the treated gas supplied from the circulation line L 22 . The tank  24  is a vessel for storing a portion of gas flowing on the circulation line L 22 . When the circulation line L 22  is in an open state, the circulation compressor P 2  pumps gas on the circulation line L 22 . 
     The detection portion D 2  is provided in the downstream side of the oxygen removal portion  12  in the supply line L 11 . The detection portion D 2  detects oxygen partial pressure and nitrogen partial pressure of the treated gas flowing through the supply line L 11  and transmits the oxygen partial pressure and the nitrogen partial pressure to the second control device  90 B described below, as an electrical signal. 
     The first valve device V 11  is provided between the inert gas supply source G and the nitrogen removal portion  11  on the supply line L 11 . The first valve device V 11  is a solenoid valve having an opening amount and an open/closed state that can be changed by an electrical signal input from the outside. The first valve device V 11  is electrically connected to the second control device  90 B by a signal line not illustrated. 
     An operation of the 3D additive manufacturing device  2  (that is, an open/closed state of the first valve device V 11 ) is controlled by the second control device  90 B. As illustrated in  FIG. 7 , the second control device  90 B is a computer including a central processing unit (CPU)  91 B, a read only memory (ROM)  92 B, a random access memory (RAM)  93 B, a hard disk drive (HDD)  94 B, and a signal reception module  95 B (input/output or I/O). The signal reception module  95 B receives a signal from the detection portion D 2  and transmits a drive electrical signal to the first valve device V 11 . The signal reception module  95 B may receive a signal amplified via, for example, a charge amplifier or the like. 
     As illustrated in  FIG. 8 , the CPU  91 B of the second control device  90 B includes a control unit  81 B, a storage unit  82 B, a determination unit  83 B, and a valve drive unit  84 B realized by executing a program stored in the CPU  91 B in advance. The control unit  81 B controls other functional units provided in the second control device  90 B. The storage unit  82 B stores in advance a target value (threshold value) of each of oxygen partial pressure and nitrogen partial pressure of the treated gas determined by the method described above. This target value is determined by using the Ellinghum diagram as described above. The determination unit  83 B compares an actual measured value of each of oxygen partial pressure and nitrogen partial pressure of the treated gas received from the detection portion D 2  and the threshold value and determines magnitude relationship. The valve drive unit  84 B adjusts the open/closed state (or the opening amount) of the first valve device V 11  described above on the basis of a determination result in the determination unit  83 B. 
     Specifically, as illustrated in  FIG. 9 , a processing flow by the second control device  90 B includes a detection step S 21 , a determination step S 22 , a first operation step S 23 , a second operation step S 24 , and a shaping step S 25 . At the detection step S 21 , the above-described detection portion D 2  detects oxygen partial pressure and nitrogen partial pressure of the treated gas. At the determination step S 22 , the detection result and the threshold value (described above) are compared. In a case where it is determined at the determination step S 22  that the detection result is larger than the threshold value, the first operation step S 23  is executed. At the first operation step S 23 , the first valve device V 11  is opened. Accordingly, the treated gas circulates through the circulation line L 22  described above to the upstream side of the nitrogen removal portion  11 . Such circulation continues, and thus the treated gas passes through the nitrogen removal portion  11  and the oxygen removal portion  12  a plurality of times. In a case where the oxygen partial pressure and the nitrogen partial pressure decreases through this circulation and it is determined at the determination step S 22  that the detection result is less than or equal to the threshold value, the second operation step S 24  is executed. At the second operation step S 24 , the first valve device V 11  is closed. Accordingly, the treated gas is supplied from the supply line L 11  to the shaping device main body  23 . The shaping device main body  23  manufactures a shaped object by using the treated gas (shaping step S 25 ). 
     Operational Effects 
     As described above, the atomizing device  1  generates fine metal powder by spraying gas on a molten metal and solidifying the metal into a particulate form. At this time, when oxygen partial pressure and nitrogen partial pressure of the sprayed gas are too high, oxygen content and nitrogen content of the generated metal powder become large. As a result, it is highly likely that a decrease in quality including creep damage and hydrogen embrittlement occurs in a shaped object manufactured by the 3D additive manufacturing device  2  that follows. 
     Thus, the atomizing device  1  according to the present embodiment includes the gas supply device for a manufacturing device SG described above. According to this configuration, nitrogen and oxygen in the inert gas can be removed by the nitrogen removal portion  11  and the oxygen removal portion  12 , respectively. Accordingly, for example, in a case where the treated gas is used in the atomizing device  1  or the 3D additive manufacturing device  2 , a decrease in quality of a product that occurs in the case of large oxygen content or large nitrogen content can be suppressed. 
     In addition, according to the configuration described above, the circulation line L 12  connected to the supply line L 11  is provided in addition to the supply line L 11 . Thus, oxygen partial pressure and nitrogen partial pressure can further be lowered while the inert gas circulates. Accordingly, purity of the inert gas can further be increased. 
     Further, according to the configuration described above, the inert gas having increased purity (that is, reduced nitrogen partial pressure and reduced oxygen partial pressure) is temporarily stored in the tank  14 . The inert gas is appropriately taken out of the tank  14 , and thus the inert gas can be used immediately in the atomizing device  1  or the 3D additive manufacturing device  2 , for example. 
     Additionally, according to the configuration described above, oxygen partial pressure and nitrogen partial pressure of the treated gas are detected by the detection portion D 1 . The first control device  90 A opens and closes the first valve device V 11  and the second valve device V 12  on the basis of the detection result. Specifically, when each of nitrogen partial pressure and oxygen partial pressure of the treated gas is higher than a predetermined threshold value, the first valve device V 11  is opened and the second valve device V 12  is closed. Accordingly, the treated gas circulates through the supply line L 11  and the circulation line L 12 , and the treated gas can sequentially repeatedly pass through the oxygen removal portion  12  and the nitrogen removal portion  11 . Accordingly, oxygen partial pressure and nitrogen partial pressure of the treated gas become small. In a case where the detection portion D 1  detects that each of the oxygen partial pressure and the nitrogen partial pressure is less than or equal to the threshold value, the first control device  90 A closes the first valve device V 11  and opens the second valve device V 12 . Accordingly, the treated gas is guided from the downstream side of the supply line L 11  to the atomizer  13 . 
     That is, after it is confirmed that each of the oxygen partial pressure and the nitrogen partial pressure is smaller than the threshold value, the treated gas can be used in the atomizer  13 . Since the treated gas sprayed on a molten metal in the atomizer  13  has extremely small oxygen partial pressure and nitrogen partial pressure, oxygen content and nitrogen content of metal powder formed by the atomizer  13  can be made even smaller. 
     On the other hand, the 3D additive manufacturing device  2  irradiates the metal powder generated by the atomizing device  1  with, for example, a laser beam, and melts and solidifies the metal powder on the laser beam. A three-dimensional shaped object is manufactured by repeating this processing and layering a plurality of layers. At this time, when oxygen partial pressure and nitrogen partial pressure of gas used in an atmosphere where processing is performed are too high, oxygen content and nitrogen content of a generated shaped object become large. As a result, it is highly likely that a decrease in quality including creep damage and hydrogen embrittlement occurs in a shaped object. 
     Thus, the 3D additive manufacturing device  2  according to the present embodiment includes the gas supply device for a manufacturing device SG described above. According to this configuration, nitrogen and oxygen in the inert gas can be removed by the nitrogen removal portion  11  and the oxygen removal portion  12 , respectively. Accordingly, in a case where the treated gas is used in the 3D additive manufacturing device  2 , a decrease in quality of a product that occurs in the case of large oxygen content or large nitrogen content can be suppressed. 
     Further, according to the configuration described above, oxygen partial pressure and nitrogen partial pressure of the treated gas is detected by the detection portion Dl. The second control device  90 B opens and closes the first valve device V 11  on the basis of the detection result. Specifically, when each of nitrogen partial pressure and oxygen partial pressure of the treated gas is higher than a predetermined threshold value, the first valve device V 11  is opened. Accordingly, the treated gas circulates through the supply line L 11  and the circulation line L 22 , and can sequentially repeatedly pass through the oxygen removal portion  12  and the nitrogen removal portion  11 . Accordingly, oxygen partial pressure and nitrogen partial pressure of the treated gas become small. In a case where the detection portion D 2  detects that each of the oxygen partial pressure and the nitrogen partial pressure is less than or equal to the threshold value, the second control device  90 B closes the first valve device V 11 . Accordingly, the treated gas is guided through the circulation line L 22  to the shaping device main body  23 . That is, after it is confirmed that each of the oxygen partial pressure and the nitrogen partial pressure is smaller than the threshold value, the treated gas can be used in the shaping device main body  23 . Since the treated gas used in melting metal powder has extremely small oxygen partial pressure and nitrogen partial pressure, oxygen content and nitrogen content of a shaped object can be made even smaller when shaping by the shaping device main body  23  is performed. 
     In addition, according to the configuration described above, the inert gas is heated by the heating portions H 1  and H 2  prior to being supplied to the nitrogen removal portion  11  and the oxygen removal portion  12 . Specifically, prior to being supplied to the nitrogen removal portion  11 , the inert gas is heated by the heating portion H 1  to approximately 1000° C. In addition, the inert gas is heated by the heating portion H 2  to approximately 600° C. Then, nitrogen partial pressure or oxygen partial pressure of the inert gas becomes lower in association with a temperature decrease that occurs when the inert gas is sent to the atomizer  13  and the shaping device main body  23 . More specifically, reaction between hydrogen in an atmosphere of these devices and oxygen in the inert gas is promoted in association with a temperature decrease to precipitate as water in an atmosphere. Accordingly, the inert gas is heated prior to being supplied to use environment and subsequently cooled for use. Thus, oxygen partial pressure of the inert gas can be made lower. 
     Further, according to the method described above, a target value of nitrogen partial pressure can be easily determined for each metal species on the basis of the Ellinghum diagram. In addition, nitridation does not occur in an environment having nitrogen partial pressure less than or equal to the nitrogen partial pressure determined as described above. Accordingly, for example, atomizing and 3D additive manufacturing can proceed in an environment where nitridation of a metal species does not proceed. 
     Similarly, according to the method described above, a target value of oxygen partial pressure can be easily determined for each metal species on the basis of the Ellinghum diagram. In addition, in an environment of the oxygen partial pressure determined as described above, reduction reaction proceeds and oxygen concentration in a metal decreases. Accordingly, for example, atomizing and 3D additive manufacturing can proceed, in an environment where reduction of a metal species proceeds. 
     Other Embodiments 
     The embodiment of the present disclosure is described above in detail with reference to the drawings. However, a specific configuration is not limited to this embodiment, and also includes design change or the like without departing from the gist of the present disclosure. For example, in the embodiment described above, the method for determining oxygen partial pressure based on the Ellinghum diagram is described by using iron as an example. However, a metal species used in the atomizing device  1  and the 3D additive manufacturing device  2  is not limited to iron, and the determination method can suitably be used for other metal species. 
     Further, in the embodiment described above, the example in which the oxygen removal portion  12  is provided in the downstream side of the nitrogen removal portion  11  on the supply line L 11  is described. However, in contrast, the oxygen removal portion  12  can be provided in the upstream side and the nitrogen removal portion  11  can be provided in the downstream side of the oxygen removal portion  12 . 
     Additionally, unlike the embodiment described above, a configuration in which each of the circulation lines L 12  and L 22  is provided for each of the nitrogen removal portion  11  and the oxygen removal portion  12  can also be employed. According to this configuration, nitrogen partial pressure and oxygen partial pressure can be adjusted independently precisely. 
     Notes 
     The gas supply device for a manufacturing device SG, the atomizer  1 , the 3D additive manufacturing device  2 , the additive manufacturing system  100 , the shaped object, and the gas supply method for a manufacturing device according to each of the embodiments described above are understood as follows, for example. 
     (1) A gas supply device for a manufacturing device SG according to a first aspect includes an inert gas supply source G that supplies inert gas, a supply line L 11  connected to the inert gas supply source G, a nitrogen removal portion  11  that is provided on the supply line L 11  and that removes at least a portion of nitrogen in the inert gas, and an oxygen removal portion  12  that is provided on the supply line L 11  and that removes at least a portion of oxygen in the inert gas. 
     According to this configuration, nitrogen and oxygen in the inert gas can be removed by the nitrogen removal portion  11  and the oxygen removal portion  12 , respectively. Accordingly, in a case where, for example, the treated gas is used in the atomizing device  1  or the 3D additive manufacturing device  2 , a decrease in quality of a product that occurs in the case of large oxygen content or large nitrogen content can be suppressed. 
     (2) The gas supply device for a manufacturing device SG according to a second aspect further includes a circulation line L 12  that connects an end portion in a downstream side of the supply line L 11  and a position in a downstream side of the inert gas supply source G and in an upstream side of the nitrogen removal portion  11  and the oxygen removal portion  12 , and a circulation compressor P 1  provided on the circulation line L 12 . 
     According to the configuration described above, the circulation line L 12  connected to the supply line L 11  is provided in addition to the supply line L 11 . Thus, oxygen partial pressure and nitrogen partial pressure can further be lowered while the inert gas circulates. Accordingly, purity of the inert gas can further be increased. 
     (3) The gas supply device for a manufacturing device SG according to a third aspect further includes a tank  14  that is provided on the circulation line L 12  and that stores the inert gas. 
     According to the configuration described above, the inert gas having increased purity (that is, reduced nitrogen partial pressure and reduced oxygen partial pressure) is temporarily stored in the tank  14 . The inert gas is appropriately taken out of the tank  14 , and thus the inert gas can be used immediately in the atomizing device  1  or the 3D additive manufacturing device  2 , for example. 
     (4) The gas supply device for a manufacturing device SG according to a fourth aspect further includes a detection portion D 1  that is provided on the supply line L 11  and that detects oxygen partial pressure and nitrogen partial pressure of the inert gas having passed through the nitrogen removal portion  11  and the oxygen removal portion  12 , a first valve device V 11  provided in a side of the inert gas supply source G of a connection portion with the circulation line L 12  on the supply line L 11 , a second valve device V 12  provided in a downstream side of the connection portion with the circulation line L 12  on the supply line L 11 , and a control device (first control device  90 A) that opens and closes the first valve device V 11  and the second valve device V 12  on the basis of a detection result of the detection portion D 1 , wherein the control device is configured to open the first valve device V 11  and close the second valve device V 12  in a state where nitrogen partial pressure and oxygen partial pressure of the inert gas detected by the detection portion D 1  are higher than predetermined threshold values, and, the control device is configured to close the first valve device V 11  and open the second valve device V 12  in a state where the nitrogen partial pressure and the oxygen partial pressure are less than or equal to the threshold values. 
     In the configuration described above, oxygen partial pressure and nitrogen partial pressure of the treated gas are detected by the detection portion Dl. The control device opens and closes the first valve device V 11  and the second valve device V 12  on the basis of the detection result. Specifically, in a state where nitrogen partial pressure and oxygen partial pressure of the treated gas are higher than predetermined threshold values, the first valve device V 11  is opened and the second valve device V 12  is closed. Accordingly, the treated gas circulates through the supply line L 11  and the circulation line L 12 , and can sequentially repeatedly pass through the oxygen removal portion  12  and the nitrogen removal portion  11 . Accordingly, oxygen partial pressure and nitrogen partial pressure of the treated gas become small. In a case where the detection portion D 1  detects that the oxygen partial pressure and the nitrogen partial pressure are less than or equal to the threshold values, the control device closes the first valve device V 11  and opens the second valve device V 12 . Accordingly, the treated gas is guided from the downstream side of the supply line L 11  to, for example, the atomizer  13 . That is, after it is confirmed that the oxygen partial pressure and the nitrogen partial pressure are smaller than the threshold values, the inert gas can be used in the atomizer  13 . Since the treated gas sprayed on a molten metal in the atomizer  13  has extremely small oxygen partial pressure and nitrogen partial pressure, oxygen content and nitrogen content of metal powder formed by the atomizer  13  can be made even smaller. 
     (5) In the gas supply device for a manufacturing device SG according to a fifth aspect, the control device (second control device  90 B) is configured to open the first valve device V 11  in a state where the nitrogen partial pressure and the oxygen partial pressure of the inert gas detected by the detection portion D 2  are higher than predetermined threshold values, and the control device is configured to close the first valve device V 11  in a state where the nitrogen partial pressure and the oxygen partial pressure are less than or equal to the threshold values. 
     In the configuration described above, oxygen partial pressure and nitrogen partial pressure of the treated gas are detected by the detection portion D 2 . The control device opens and closes the first valve device V 11  on the basis of the detection result. Specifically, when the nitrogen partial pressure and the oxygen partial pressure of the treated gas are higher than predetermined threshold values, the first valve device V 11  is opened. Accordingly, the treated gas circulates through the supply line L 11  and the circulation line L 22 , and can sequentially repeatedly pass through the oxygen removal portion  12  and the nitrogen removal portion  11 . Accordingly, the oxygen partial pressure and the nitrogen partial pressure of the treated gas become small. In a case where the detection portion D 2  detects that the oxygen partial pressure and the nitrogen partial pressure are less than or equal to the threshold values, the control device closes the first valve device V 11 . Accordingly, the treated gas is guided through the circulation line to the shaping device main body  23  that performs 3D additive manufacturing. That is, after it is confirmed that the oxygen partial pressure and the nitrogen partial pressure are smaller than the threshold values, the treated gas can be used in the shaping device main body  23 . Since the treated gas used in melting metal powder has extremely small oxygen partial pressure and nitrogen partial pressure, oxygen content and nitrogen content of a shaped object can be made even smaller when shaping by the shaping device main body  23  is performed. 
     (6) The gas supply device for a manufacturing device SG according to a sixth aspect further includes 
     a heating portion H 1 , H 2  that is provided between the nitrogen removal portion  11  and the oxygen removal portion  12 , and the inert gas supply source G, and that heats the inert gas supplied from the inert gas supply source G to the supply line L 11 . 
     According to the configuration described above, the inert gas is heated by the heating portion H 1 , H 2  prior to being supplied to the nitrogen removal portion  11  and the oxygen removal portion  12 . Specifically, the heating portion H 1 , H 2  heats the inert gas to approximately 600° C. Then, nitrogen partial pressure or oxygen partial pressure of the inert gas becomes lower in association with a temperature decrease that occurs when the inert gas is sent to an atomizer and a shaping device. More specifically, reaction between hydrogen in an atmosphere of these devices and oxygen in the inert gas is promoted in association with a temperature decrease to precipitate as water in an atmosphere. Accordingly, the inert gas is heated prior to being supplied to a use environment and subsequently cooled for use. Thus, oxygen partial pressure of the inert gas can be made lower. 
     (7) In the gas supply device for a manufacturing device SG according to a seventh aspect, 
     in the oxygen removal portion  12 , a straight line L that passes through a inciting point of a preselected metal species on an Ellinghum diagram with standard reaction Gibbs energy on a left vertical axis and oxygen partial pressure on a right vertical axis and that passes through an origin on the left vertical axis of the Ellinghum diagram is defined, and a value less than or equal to a value on the right vertical axis through which the straight line L passes is defined as a target value Pg of oxygen partial pressure of the inert gas. 
     According to the configuration described above, a target value of oxygen partial pressure can be determined easily for each metal species on the basis of the Ellinghum diagram. In addition, reduction reaction of the metal occurs in an environment having oxygen partial pressure less than or equal to the oxygen partial pressure determined as described above. Accordingly, for example, atomizing and 3D additive manufacturing can proceed in a reducing atmosphere environment where oxygen concentration in a metal decreases. 
     (8) In the gas supply device for a manufacturing device SG according to an eighth aspect, 
     in the nitrogen removal portion  11 , a straight line L that passes through a melting point of a preselected metal species on an Ellinghum diagram with standard reaction Gibbs energy on a left vertical axis and nitrogen partial pressure on a right vertical axis and that passes through an origin on the left vertical axis of the Ellinghum diagram is defined, and a value less than or equal to a value on the right vertical axis through which the straight line L passes is defined as a target value of nitrogen partial pressure of the inert gas. 
     According to the configuration described above, a target value of nitrogen partial pressure can be determined easily for each metal species on the basis of the Ellinghum diagram. In addition, nitridation of the metal species does not occur in an environment having nitrogen partial pressure less than or equal to the nitrogen partial pressure determined as described above. Accordingly, for example, atomizing and 3D additive manufacturing can proceed in an environment where nitridation of a metal species does not proceed. 
     (9) An atomizing device  1  according to a ninth aspect includes the gas supply device for a manufacturing device SG according to any one of the aspects described above, and an atomizer  13  that forms metal powder by spraying the inert gas supplied from the gas supply device for a manufacturing device SG on a molten metal. 
     According to the configuration described above, oxygen content and nitrogen content of the metal powder formed by the atomizing device  1  can be made small. 
     (10) A 3D additive manufacturing device  2  according to a tenth aspect includes the gas supply device for a manufacturing device SG according to any one of the aspects described above, and a shaping device main body  23  that performs shaping by melting and layering metal powder in an atmosphere of the inert gas supplied from the gas supply device for a manufacturing device SG. 
     According to the configuration described above, an amount of oxygen and nitrogen in an atmosphere during shaping by the 3D additive manufacturing device  2  can be made small. As a result, oxygen content and nitrogen content of a shaped object can be made even smaller. 
     (11) An additive manufacturing system  100  according to an eleventh aspect includes the atomizing device  1  according to the ninth aspect, and the 3D additive manufacturing device  2  according to the tenth aspect. 
     According to the configuration described above, oxygen content and nitrogen content of metal powder formed by the atomizing device  1  can be made small, and in addition, an amount of oxygen and nitrogen in an atmosphere during shaping by the 3D additive manufacturing device  2  can also be made small. As a result, oxygen content and nitrogen content of a shaped object can be made even smaller. 
     (12) A shaped object according to a twelfth aspect is manufactured by the additive manufacturing system according to the eleventh aspect. 
     According to the configuration described above, a shaped object having even smaller oxygen content and nitrogen content can be provided. 
     (13) A gas supply method for a manufacturing device according to a thirteenth aspect includes a nitrogen removal step of removing at least a portion of nitrogen in inert gas, and an oxygen removal step of removing at least a portion of oxygen in the inert gas. 
     According to this method, nitrogen and oxygen in the inert gas can be removed at the nitrogen removal step and the oxygen removal step, respectively. Accordingly, in a case where, for example, the treated gas is used in the atomizing device  1  or the 3D additive manufacturing device  2 , a decrease in quality of a product that occurs in the case of large oxygen content or large nitrogen content can be suppressed. 
     (14) The gas supply method for a manufacturing device according to a fourteenth aspect further includes 
     a circulation step of repeating the nitrogen removal step and the oxygen removal step after the nitrogen removal step and the oxygen removal step. 
     According to the method described above, the inert gas is again subjected to the nitrogen removal step and the oxygen removal step at the circulation step. Accordingly, oxygen partial pressure and nitrogen partial pressure can further be lowered while the inert gas circulates. That is, purity of the inert gas can further be increased. 
     (15) In the gas supply method for a manufacturing device according to a fifteenth aspect, at the oxygen removal step, a straight line that passes through a melting point of a preselected metal species on an Ellinghum diagram with standard reaction Gibbs energy on a left vertical axis and oxygen partial pressure on a right vertical axis and that passes through an origin on the left vertical axis of the Ellinghum diagram is defined, and a value less than or equal to a value on the right vertical axis through which the straight line passes is defined as a target value of oxygen partial pressure of the inert gas. 
     According to the method described above, a target value of nitrogen partial pressure can be determined easily for each metal species on the basis of the Ellinghum diagram. In addition, a state where nitridation of the metal species does not occur can be maintained in an environment having nitrogen partial pressure less than or equal to the nitrogen partial pressure determined as described above. Accordingly, for example, atomizing and 3D additive manufacturing can proceed in an environment where nitridation of a metal species does not occur. 
     (16) In the gas supply method for a manufacturing device according to a sixteenth aspect, at the nitrogen removal step, a straight line that passes through a melting point of a preselected metal species on an Ellinghum diagram with standard reaction Gibbs energy on a left vertical axis and nitrogen partial pressure on a right vertical axis and that passes through an origin on the left vertical axis of the Ellinghum diagram is defined, and a value less than or equal to a value on the right vertical axis through which the straight line passes is defined as a target value of nitrogen partial pressure of the inert gas. 
     According to the method described above, a target value of oxygen partial pressure can be determined easily for each metal species on the basis of the Ellinghum diagram. In addition, reduction reaction of the metal occurs in an environment having oxygen partial pressure less than or equal to the oxygen partial pressure determined as described above. Accordingly, for example, atomizing and 3D additive manufacturing can proceed in a reducing atmosphere where oxygen concentration in a metal decreases. 
     While preferred embodiments of the invention have been described as above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirits of the invention. The scope of the invention, therefore, is to be determined solely by the following claims.