Method for oxidizing metal powder

Abstract

Provided is a method for oxidizing metal powder that easily controls oxidation of the metal powder. A method for oxidizing metal powder (M) housed in a container (3), wherein: the container (3) is placed in an atmosphere of an inactive gas at a first pressure higher than atmospheric pressure; and a mixed gas containing an inactive gas and oxygen is introduced into the container (3) in such a manner that the oxygen concentration in the container (3) is lower than the limit oxygen concentration of the metal powder (M), and the pressure in the container (3) is raised to a second pressure higher than the first pressure.

Description

Technical Field

[0001] This invention relates to a method for oxidizing metal powders. Background Technology

[0002] Patent Document 1 discloses a metal stabilization system. The metal stabilization system comprises: a mounting platform housed within a sealed container; an active metal disposed on the mounting platform; and a leakage valve disposed on a connecting pipe that connects the sealed container to the atmosphere. According to Patent Document 1, the metal is placed inside the sealed container, which is then sealed and evacuated. After a prescribed treatment is performed on the metal inside the sealed container, air from the atmosphere is intermittently introduced into the sealed container by intermittently opening the leakage valve. When air is introduced into the sealed container, the metal powder generated by the prescribed treatment oxidizes upon contact with the air.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 1-257105 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] When a sealed container has an accidental leak, atmospheric air can enter the vacuum-sealed container through this leak. In this case, the metal powder comes into contact with the invading air and oxidizes. Because it is difficult to control the flow rate of air entering through the accidental leak, there are cases where the metal powder oxidizes rapidly. Therefore, the metal stabilization system described in Patent Document 1 sometimes fails to control the oxidation of the metal powder.

[0008] The purpose of this invention is to provide a method for oxidizing metal powder, which allows for easy control of the oxidation of the metal powder.

[0009] Problem-solving methods

[0010] This invention provides a method for oxidizing metal powder, specifically a method for oxidizing metal powder contained in a container, comprising:

[0011] The step of placing the container in an inactive gas atmosphere at a first pressure higher than atmospheric pressure;

[0012] The step of introducing a mixed gas containing inactive gas and oxygen into the container in such a way that the oxygen concentration in the container is lower than the limiting oxygen concentration of the metal powder, and raising the pressure in the container to a second pressure higher than the first pressure.

[0013] According to the method for oxidizing metal powder of the present invention, because the container is under a first pressure higher than atmospheric pressure and an inert gas atmosphere, atmospheric air is difficult to penetrate into the container. Therefore, the oxidation of the metal powder is easily controlled. Furthermore, because a mixed gas is introduced into the container in a manner that keeps the oxygen concentration below the limiting oxygen concentration, the metal powder can be oxidized relatively slowly. In other words, rapid oxidation of the metal powder is suppressed. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the metal powder manufacturing system of this embodiment.

[0015] Figure 2 This is a flowchart illustrating the process of oxidizing metal powder.

[0016] Figure 3 This shows the state of introducing a mixed gas into a metal powder manufacturing system.

[0017] Figure 4 This illustrates the state of gas flow within a metal powder manufacturing system.

[0018] Figure 5 This shows the state of the gas being discharged from the metal powder manufacturing system.

[0019] Figure 6 This is a diagram that roughly illustrates an example of changes in oxygen concentration and pressure within a container. Detailed Implementation

[0020] Hereinafter, a method for oxidizing metal powder according to one embodiment of the present invention will be described with reference to the accompanying drawings.

[0021] Figure 1 This is a schematic diagram of the metal powder manufacturing system 100 according to this embodiment. The metal powder manufacturing system 100 is a closed system that manufactures metal powder M from molten metal. The metal powder manufacturing system 100 includes: a metal powder generating furnace 1, a pipe 2, a container 3, a blower 4, an inlet port 5, an outlet port 6, a concentration meter 7, and a pressure gauge 8.

[0022] In the metal powder generating furnace 1, metal powder M is generated from molten metal. An inert gas is injected into the molten metal in the metal powder generating furnace 1. Through the injection of the inert gas, the molten metal is decomposed and cooled, becoming metal powder M. The metal powder generating furnace 1 may include, for example, a gas atomizing device. The generated metal powder M is separately recovered. A portion of the metal powder M may not be recovered and may remain within the metal powder manufacturing system 100. The metal powder oxidation method of the present invention is used to oxidize the metal powder M remaining within the metal powder manufacturing system 100.

[0023] The metal powder M includes powders of active metals such as aluminum, titanium, lead, sodium, magnesium, lithium, zinc, and iron. The metal powder M produced in this embodiment is titanium powder. The oxidation method of the metal powder M of the present invention is suitable for oxidizing titanium powder. The particle size of the metal powder M is 5 μm or less. The particle size of the metal powder M includes the average particle size.

[0024] The inert gas used in this embodiment is argon. The inert gas can also be a rare gas such as helium, or other inert gases such as nitrogen or carbon dioxide. Argon is cheaper than other rare gases and reacts more slowly than nitrogen or carbon dioxide, thus making it suitable for the oxidation method of the metal powder M applicable to this invention.

[0025] Pipe 2 connects the metal powder generating furnace 1 and the container 3. In pipe 2, inert gas, oxygen (which oxidizes the metal powder M), and the metal powder M flow. Through pipe 2's connection to the metal powder generating furnace 1 and the container 3, the inert gas, oxygen, and metal powder M can circulate within the metal powder manufacturing system 100.

[0026] Container 3 contains residual metal powder M. Container 3 traps the residual metal powder M. Container 3 contains a bag filter. Metal powder M flowing through pipe 2, if it reaches container 3, is trapped by the filter located within container 3.

[0027] Blower 4 creates the flow within the metal powder manufacturing system 100. Blower 4 is located in pipe 2. Through the operation of blower 4, inert gas, oxygen, and metal powder M can circulate within the metal powder manufacturing system 100. Blower 4 includes a Roots blower. The blower can also be a centrifugal blower.

[0028] An inert gas, or a mixture of an inert gas and oxygen, is introduced into the metal powder manufacturing system 100 through inlet port 5. Inlet port 5 is located in pipe 2. Inlet port 5 contains a valve.

[0029] Gas within the metal powder manufacturing system 100 is discharged through exhaust port 6. Exhaust port 6 is located in pipe 2. Exhaust port 6 contains a valve.

[0030] Concentration meter 7 measures the oxygen concentration within the metal powder manufacturing system 100. Concentration meter 7 is located on pipe 2. Because pipe 2 is connected to container 3, the oxygen concentration measured by concentration meter 7 is equivalent to the oxygen concentration within container 3.

[0031] Pressure gauge 8 measures the pressure within the metal powder manufacturing system 100. Pressure gauge 8 is located on pipe 2. Because pipe 2 is connected to container 3, the pressure measured by pressure gauge 8 is equivalent to the pressure inside container 3.

[0032] In the manufacturing of metal powder M, the inactive gas injected from the metal powder generating furnace 1 flows through pipe 2 to container 3 along with the residual metal powder M. Because the metal powder M is captured in container 3, the inactive gas passing through container 3 separates from the metal powder M and flows back to the metal powder generating furnace 1 through pipe 2. The inactive gas flowing from container 3 to the metal powder generating furnace 1 is then injected again into the molten metal.

[0033] During the manufacturing of metal powder M, residual metal powder M is repeatedly captured by container 3, which can lead to filter clogging in container 3. To clear the filter clogging, the metal powder M captured in container 3 can be recovered. Before being recovered, the captured metal powder M is pre-oxidized to prevent rapid oxidation caused by contact with air. In other words, the captured metal powder M is recovered in an oxidized state.

[0034] Figure 2 This is a flowchart illustrating the oxidation treatment process of metal powder M. (Refer to...) Figure 2 The oxidation method for metal powder M is described. The oxidation of metal powder M takes place within container 3. During the oxidation process of metal powder M, the generation of metal powder M in metal powder generating furnace 1 is interrupted.

[0035] First, in step S1, the pressure inside container 3 is adjusted so that container 3 is in an inert gas atmosphere with a first pressure higher than atmospheric pressure. The first pressure is, for example, 0.01 MPaG or higher and 0.02 MPaG or lower. When the pressure inside container 3 during the manufacture of metal powder M is lower than the first pressure, the pressure inside container 3 is adjusted to the first pressure by introducing inert gas from inlet port 5. When the pressure inside container 3 during the manufacture of metal powder M is higher than the first pressure, the pressure inside container 3 is adjusted to the first pressure by discharging inert gas from outlet port 6. In the manufacture of metal powder M, if container 3 is in an inert gas atmosphere with the first pressure, pressure adjustment inside container 3 may not be necessary. At the time of step S1, oxygen is absent in container 3, or a trace amount of oxygen is present to a degree that will not intentionally oxidize the metal powder M.

[0036] The pressure inside container 3 is measured by pressure gauge 8 located in pipe 2. The pressure inside container 3 is adjusted based on the pressure value obtained from pressure gauge 8.

[0037] Because the pressure inside container 3 is at the first level, atmospheric air has difficulty penetrating into it, thus suppressing the oxidation of the metal powder M by oxygen in the air. In other words, it can suppress unintended oxidation of the metal powder M. Therefore, the oxidation of the metal powder M is easily controlled.

[0038] Secondly, in step S2, a mixture of inactive gas and oxygen is introduced into container 3. Figure 3 This shows the state of introducing a mixed gas into the metal powder manufacturing system 100. Figure 3 In the diagram, the flow of the mixed gas is indicated by arrows. A gas cylinder 9, sealed with an inert gas and oxygen, is connected to the inlet port 5. By opening the valve at the inlet port 5, the mixed gas is introduced into pipe 2. The mixed gas introduced into pipe 2 flows to container 3, which is connected to pipe 2. Thus, the mixed gas is introduced into container 3. The introduction of the mixed gas causes the pressure inside container 3 to rise to a second pressure, which is higher than the first pressure. The second pressure is, for example, above 0.02 MPaG and below 0.03 MPaG.

[0039] The mixed gas is introduced into container 3 such that the oxygen concentration inside container 3 is lower than the limiting oxygen concentration of metal powder M. The oxygen concentration of the mixed gas is set within a range above the oxygen concentration at which metal powder M is intentionally oxidized and below the limiting oxygen concentration of metal powder M. For example, the oxygen concentration of the mixed gas is the limiting oxygen concentration of metal powder M. In this embodiment, the oxygen concentration of the mixed gas refers to the oxygen concentration inside gas cylinder 9. Before the mixed gas is introduced, because container 3 is in an inert gas atmosphere, the oxygen concentration inside container 3 after the mixed gas is introduced is lower than the oxygen concentration of the mixed gas. In other words, the oxygen concentration is diluted due to the introduction into container 3. That is, by keeping the oxygen concentration of the mixed gas below the limiting oxygen concentration, it is easy to maintain the oxygen concentration inside container 3 below the limiting oxygen concentration.

[0040] The oxygen concentration in container 3 is measured by a concentration meter 7 installed in pipe 2. The oxygen concentration in container 3 can be measured continuously or intermittently through the oxidation treatment of metal powder M. The amount of mixed gas introduced can be adjusted based on the oxygen concentration obtained from the concentration meter 7.

[0041] By introducing a mixed gas, the metal powder M inside container 3 comes into contact with the oxygen contained in the mixed gas and is oxidized. Because the oxygen concentration inside container 3 is below the limiting oxygen concentration, the metal powder M can be oxidized relatively slowly. In other words, by maintaining the oxygen concentration inside container 3 below the limiting oxygen concentration, the rapid oxidation of the metal powder M can be suppressed.

[0042] The limiting oxygen concentration is the minimum oxygen concentration required for the metal powder M to undergo a rapid oxidation reaction. The limiting oxygen concentration can be appropriately set according to the environment in which the metal powder M oxidizes. For example, the limiting oxygen concentration can be set based on parameters such as the type of metal powder M, the particle size of the metal powder M, the dust concentration of the metal powder M in container 3, the pressure in container 3, and the temperature in container 3. The limiting oxygen concentration can also be set based on past empirical rules or experimentally. In this embodiment, the limiting oxygen concentration of the metal powder M is 4%. The oxygen concentration at which the metal powder M is intentionally oxidized can also be set based on past empirical rules or experimentally. In this embodiment, the oxygen concentration at which the metal powder M is intentionally oxidized is 0.5%. Therefore, the oxygen concentration of the mixed gas is set in the range of 0.5% to 4%.

[0043] Next, in step S3, the gas is circulated within the metal powder manufacturing system 100. Figure 4 This shows the state of gas flow in the metal powder manufacturing system 100. Figure 4 In the diagram, the gas flow caused by the operation of blower 4 is indicated by arrows. The gas flowing in the metal powder manufacturing system 100 contains inert gases and oxygen. The gas circulates within the metal powder manufacturing system 100 due to the operation of blower 4. This gas circulation creates gas flow within container 3. As the gas flows within container 3, the metal powder M readily oxidizes with the oxygen contained in the circulating gas. That is, by creating gas flow, the oxidation of metal powder M is promoted even below the limiting oxygen concentration, thus the oxidation of metal powder M is easily and rapidly completed. Gas circulation can be implemented continuously or intermittently through the oxidation process of metal powder M.

[0044] Next, in step S4, after a first predetermined time, in step S5, it is determined whether the time change of the oxygen concentration in container 3 is constant. In step S5, it is determined whether the metal powder M was intentionally oxidized after the mixed gas was introduced. If the mixed gas was introduced in step S2, the oxygen concentration in container 3 increases and then decreases due to the subsequent oxidation of the metal powder M. The time change of oxygen concentration in step S5 includes the value obtained by subtracting the oxygen concentration after the first predetermined time from the oxygen concentration immediately after the mixed gas was introduced. A constant time change of oxygen concentration includes a substantially constant time change of oxygen concentration. A constant time change of oxygen concentration, for example, includes a time change of oxygen concentration within ±0.05 pt.

[0045] The first specified time is, for example, set between tens of seconds and several minutes. The starting point of the first specified time can be the moment the mixed gas is introduced or the moment the blower starts operating.

[0046] In step S5, if the change in oxygen concentration over time is determined to be uncertain, then in step S6, a second predetermined time is elapsed. During this second predetermined time, the metal powder M is further oxidized. The second predetermined time is generally longer than the first predetermined time. The second predetermined time can be constant. The second predetermined time can also be changed based on the change in oxygen concentration over time. That is, the second predetermined time can end when the oxygen concentration reaches 0%, or when the decrease in oxygen concentration over time falls below a predetermined value. The decrease in oxygen concentration includes the change in oxygen concentration per unit time.

[0047] Next, in step S7, the gas inside container 3 is discharged to the outside. Specifically, in step S7, the gas inside container 3 is discharged until the pressure inside container 3 drops to the first pressure. Figure 5 This shows the state of gas being discharged from the metal powder manufacturing system 100. Figure 5 The diagram shows the flow of gas being discharged from container 3. In step S7, by opening the valve at discharge port 6, the gas in container 3 is discharged from discharge port 6 through pipe 2.

[0048] After step S7, steps S2-S5 are performed again. That is, steps S2-S7 are performed repeatedly until the change in oxygen concentration over time after the first specified time is constant.

[0049] Therefore, according to the oxidation method of metal powder M in this embodiment, the mixed gas is repeatedly replaced until the oxygen concentration changes over time after the mixed gas is introduced into container 3, whichever is constant. The replacement of the mixed gas includes venting the gas from container 3 to the outside until the pressure inside container 3 decreases to a first pressure. After the gas is vented, the mixed gas is reintroduced into container 3 so that the oxygen concentration inside container 3 is below a limiting oxygen concentration, thereby increasing the pressure inside container 3 to a second pressure. When the mixed gas is introduced, the metal powder M that failed to oxidize during oxidation can be oxidized by contacting the oxygen contained in the replaced mixed gas. Thus, the metal powder M stored in container 3 can be oxidized more reliably.

[0050] In step S5, if the change in oxygen concentration over time is determined to be constant, then in step S8, a third predetermined time is elapsed. This third predetermined time is longer than the first predetermined time. The third predetermined time can be constant. For example, the third predetermined time is 1 hour.

[0051] Next, in step S9, it is determined whether the time-varying change of oxygen concentration in container 3 is constant. The time-varying change of oxygen concentration in step S9 is the value obtained by subtracting the oxygen concentration after a third predetermined time from the oxygen concentration immediately after the mixed gas is introduced. Alternatively, the time-varying change of oxygen concentration in step S9 can also be the value obtained by subtracting the oxygen concentration after a third predetermined time from the oxygen concentration at the beginning of the third predetermined time.

[0052] In step S9, if the change in oxygen concentration over time in container 3 is determined to be non-constant, then in step S7, the gas in container 3 is discharged to the outside, and steps S2-S9 are repeated. That is, steps S2-S9 are repeated until the change in oxygen concentration over time becomes constant after a third predetermined time.

[0053] In step S9, if the change in oxygen concentration within container 3 over time is determined to be constant, the oxidation process of metal powder M is complete. Therefore, the oxidation of metal powder M is finished. The oxidized metal powder M can be recovered by operators by disassembling container 3.

[0054] Therefore, according to the oxidation method of metal powder M in this embodiment, by repeatedly replacing the mixed gas, when the oxygen concentration in container 3 changes over a certain time after the mixed gas is introduced into container 3, the oxidation treatment of metal powder M ends after a predetermined time. This predetermined time includes the third predetermined time mentioned above. Steps S8 and S9 are steps to ensure the completion of oxidation of metal powder M. That is, the completion of oxidation of metal powder M is confirmed in step S5, and the completion of oxidation of metal powder M is confirmed again in step S9. Through the processing of steps S8 and S9, the possibility of metal powder M being oxidized by oxygen contained in the air can be further reduced during the subsequent recovery of metal powder M.

[0055] Figure 6 This is a diagram that schematically illustrates an example of the changes in oxygen concentration and pressure within container 3 during the oxidation treatment of metal powder M. Figure 6 In the diagram, the horizontal axis represents time, the left vertical axis represents oxygen concentration, and the right vertical axis represents pressure. The thick solid line represents the oxygen concentration value, and the thick dashed line represents the pressure value.

[0056] exist Figure 6 In this context, interval A is the interval where the pressure inside container 3 is adjusted to the first pressure. Figure 6 In the example, the pressure inside container 3 rises to the first pressure in interval A. Figure 6 In this example, the first pressure is 0.01 MPaG. Section B is the section where the mixed gas is introduced. Through the introduction of the mixed gas, the pressure inside container 3 rises to the second pressure. Figure 6 In the example, the second pressure is 0.04 MPaG. Figure 6 In the example, the oxygen concentration of the mixed gas is 4%. By introducing a mixed gas with an oxygen concentration of 4% into interval B, the oxygen concentration in container 3 increases within a range not exceeding 4%.

[0057] Interval C corresponds to the first specified time. Interval D corresponds to the second specified time. In intervals C and D, the oxygen concentration decreases because the oxygen in container 3 is consumed for the oxidation of metal powder M. The decrease in oxygen concentration leads to a decrease in the partial pressure of oxygen, and therefore the pressure inside container 3 also decreases. The oxygen concentration in intervals C and D decreases slowly over time. The percentage decrease in oxygen concentration in intervals C and D decreases over time. The second specified time ends when the percentage decrease in oxygen concentration falls below a specified value. Ending the second specified time based on the percentage decrease in oxygen concentration is more effective for oxidizing metal powder M compared to ending the second specified time when the oxygen concentration reaches 0%.

[0058] Zone E is the zone where gas is discharged from container 3. Due to the discharge of gas, some inactive gases and oxygen are discharged, resulting in a decrease in oxygen concentration.

[0059] After the gas in zone E is discharged, oxygen is present in container 3 at a specified oxygen concentration. Therefore, if the treatment from zone B to zone E is repeated, the oxygen concentration after the mixed gas is introduced will increase and approach 4%.

[0060] Because the oxygen concentration in the mixed gas is 4%, the oxygen concentration inside container 3 is difficult to reach 4%. Interval F corresponds to the third specified time. Before the oxygen concentration inside container 3 reaches 4%, the time variation of the oxygen concentration is constant. Therefore, during a series of oxidation processes, the oxygen concentration inside container 3 is easily maintained below 4%, thus suppressing the rapid oxidation of the metal powder M.

[0061] The oxidation method of metal powder M according to this embodiment can achieve the following effects.

[0062] (1) A method for oxidizing metal powder M stored in container 3, comprising:

[0063] The container 3 is placed in an inactive gas atmosphere with a pressure higher than atmospheric pressure.

[0064] A mixture of inactive gas and oxygen is introduced into container 3 such that the oxygen concentration inside container 3 is lower than the limiting oxygen concentration of metal powder M, until the pressure inside container 3 rises to a second pressure higher than the first pressure.

[0065] Because container 3 is at pressure level 1, atmospheric air has difficulty penetrating it, thus suppressing the oxidation of metal powder M by oxygen in the air. Therefore, the oxidation of metal powder M is easily controlled. The mixed gas is introduced with an oxygen concentration in container 3 below the limiting oxygen concentration, allowing metal powder M to oxidize relatively slowly. Therefore, rapid oxidation of metal powder M can be suppressed.

[0066] (2) The oxygen concentration of the mixed gas is below the limiting oxygen concentration.

[0067] By keeping the oxygen concentration in the mixed gas below the limiting oxygen concentration, it is easy to maintain the oxygen concentration in container 3 below the limiting oxygen concentration. Therefore, the rapid oxidation of the metal powder M can be further suppressed.

[0068] (3) It also includes repeated gas replacement until the oxygen concentration in container 3 changes over time after the mixed gas is introduced into container 3, and the gas replacement includes:

[0069] Discharge the gas from container 3 to the outside until the pressure inside container 3 drops to the first pressure;

[0070] After the gas is discharged, the mixed gas is introduced into container 3 in such a way that the oxygen concentration in container 3 is lower than the limiting oxygen concentration of metal powder M, so that the pressure in container 3 rises to the second pressure.

[0071] By repeatedly replacing the mixed gas, the metal powder M can be oxidized more reliably.

[0072] (4) It also includes repeatedly replacing the mixed gas, and when the oxygen concentration in container 3 changes over a certain time after the mixed gas is introduced into container 3, the oxidation treatment of metal powder M ends after a specified time.

[0073] When the oxygen concentration in container 3 changes over a constant period of time, ending the oxidation process after a predetermined time further ensures the complete oxidation of metal powder M. Therefore, during subsequent recovery of metal powder M, the possibility of oxidation by oxygen in the air can be further reduced.

[0074] (5) Including the flow of gas produced within container 3.

[0075] The oxidation of metal powder M can be promoted by creating a gas flow within container 3.

[0076] (6) Including the oxygen concentration in the measuring container 3.

[0077] Based on the measured oxygen concentration, the amount of mixed gas introduced can be controlled. Based on the measured oxygen concentration, the second or third predetermined time can be terminated. Therefore, the metal powder M can be effectively oxidized.

[0078] (7) Container 3 contains a bag filter.

[0079] By applying the oxidation method of the metal powder M of this embodiment to a bag filter, the metal powder M captured by the bag filter can be recovered in an oxidized state.

[0080] (8) Metal powder M contains titanium powder.

[0081] The oxidation method for metal powder M in this embodiment is suitable for use in the case of oxidizing titanium powder.

[0082] (9) The inert gas in the gas mixture contains argon.

[0083] The oxygen concentration of the mixed gas is above 0.5% and below 4%.

[0084] Argon gas is suitable for use in the oxidation method of metal powder M according to this embodiment. By making the oxygen concentration in the mixed gas 0.5% or more and 4% or less, the metal powder M can be oxidized effectively while suppressing rapid oxidation.

[0085] Furthermore, the oxidation method of the metal powder of the present invention is not limited to the configuration of the above embodiments, but can be modified in various ways.

[0086] The metal powder oxidation method of the present invention can be carried out in any container holding the metal powder M. For example, the metal powder oxidation method of the present invention can be used in additive manufacturing or powder metallurgy using metal powder to oxidize recycled metal powder. The metal powder oxidation method of the present invention is not limited to a closed system and can also be used in an open system.

[0087] The means of creating gas flow within container 3 is not limited to blower 4. For example, by introducing a mixed gas from inlet port 5 and discharging gas from outlet port 6, a unidirectional flow from inlet port 5 through container 3 toward outlet port 6 can be formed. For example, after creating this unidirectional flow, by introducing a mixed gas from outlet port 6 and discharging gas from inlet port 5, a flow in the opposite direction can be formed.

[0088] The oxygen concentration in the mixed gas can also be higher than the limiting oxygen concentration. In this case, the oxygen concentration in container 3 can be continuously measured while the amount of mixed gas introduced is controlled, ensuring that the oxygen concentration in container 3 does not exceed 4%.

[0089] The mixed gas can be directly introduced into container 3.

[0090] The inactive gas pre-stored in container 3 and the inactive gas contained in the mixed gas can be the same or different.

[0091] Pressure and oxygen concentration can be measured inside container 3. Either pressure or oxygen concentration can be measured only inside container 3.

[0092] The first and second pressures can be fixed or variable through a series of oxidation processes. For example, the first and second pressures can be variable according to the oxygen concentration in container 3.

[0093] The oxidation process of metal powder M can be performed manually or automatically. When the oxidation process of metal powder M is performed automatically, a fluid supply device is provided to automatically introduce the mixed gas into container 3 at a specified flow rate, and a control device electrically connected to the fluid supply device, pressure gauge, and concentration meter. Based on data obtained from the pressure gauge and concentration meter, the control device can send an operation command to the fluid supply device to introduce the mixed gas into container 3 at a specified flow rate.

[0094] [appendix]

[0095] The method for oxidizing metal powder according to the present invention provides the following approach.

[0096] [Method 1]

[0097] A method for oxidizing metal powder, wherein the metal powder is present in a container, comprising:

[0098] The container is placed in an inactive gas atmosphere with a pressure higher than atmospheric pressure (first pressure).

[0099] A mixture of inactive gas and oxygen is introduced into the container such that the oxygen concentration inside the container is lower than the limiting oxygen concentration of the metal powder, and the pressure inside the container is increased to a second pressure higher than the first pressure.

[0100] [Method 2]

[0101] The oxidation method of metal powder according to Method 1, wherein the oxygen concentration of the mixed gas is below the limiting oxygen concentration.

[0102] [Method 3]

[0103] According to the oxidation method of metal powder described in method 1 or 2, wherein,

[0104] It also includes repeatedly replacing the mixed gas until the oxygen concentration in the container changes over time after the mixed gas is introduced into the container to a certain extent, wherein the replacement of the mixed gas includes:

[0105] The gas inside the container is discharged to the outside until the pressure inside the container drops to the first pressure;

[0106] After the gas is discharged, the mixed gas is introduced into the container in such a way that the oxygen concentration in the container is lower than the limiting oxygen concentration, and the pressure in the container is increased to the second pressure.

[0107] [Method 4]

[0108] The metal powder oxidation method according to Method 3 further includes, by repeatedly performing the displacement of the mixed gas, when the oxygen concentration in the container changes over a certain time after the mixed gas is introduced into the container, ending the metal powder oxidation treatment after a predetermined time.

[0109] [Method 5]

[0110] The oxidation method of metal powder according to any one of methods 1 to 4 includes generating a gas flow within the container.

[0111] [Method 6]

[0112] The oxidation method of metal powder according to any one of methods 1 to 5 includes measuring the oxygen concentration in the container.

[0113] [Method 7]

[0114] The oxidation method of metal powder according to any one of methods 1 to 6, wherein the container contains a bag filter.

[0115] [Method 8]

[0116] The oxidation method of metal powder according to any one of methods 1 to 7, wherein the metal powder contains titanium powder.

[0117] [Method 9]

[0118] The oxidation method of metal powder according to any one of methods 1 to 8, wherein,

[0119] The inactive gas in the mixed gas includes argon.

[0120] The oxygen concentration of the mixed gas is above 0.5% and below 4%.

[0121] Explanation of reference numerals in the attached figures

[0122] 1: Metal Powder Generation Furnace

[0123] 2: Pipeline

[0124] 3: Container

[0125] 4: Blower

[0126] 5: Import Port

[0127] 6: Discharge port

[0128] 7: Concentration meter

[0129] 8: Pressure gauge

[0130] 9: Gas cylinder

[0131] 100: Metal Powder Manufacturing System

[0132] M: Metal powder

Claims

1. A method for oxidizing metal powder, wherein the metal powder exists in a container, include: The step of placing the container in an inactive gas atmosphere at a first pressure higher than atmospheric pressure; The step of introducing a mixed gas containing inactive gas and oxygen into the container in such a way that the oxygen concentration in the container is lower than the limiting oxygen concentration of the metal powder, and raising the pressure in the container to a second pressure higher than the first pressure.

2. The method for oxidizing metal powder according to claim 1, wherein, The oxygen concentration of the mixed gas is below the limiting oxygen concentration.

3. The method for oxidizing metal powder according to claim 1, wherein, It also includes the step of repeatedly replacing the mixed gas until the oxygen concentration in the container changes over time after the mixed gas is introduced into the container to a certain extent. The displacement of the mixed gas includes: The step of discharging gas from the container to the outside until the pressure inside the container drops to the first pressure; After the gas is discharged, the mixed gas is introduced into the container in such a way that the oxygen concentration in the container is lower than the limiting oxygen concentration, so that the pressure in the container rises to the second pressure.

4. The method for oxidizing metal powder according to claim 3, wherein, It also includes the step of repeatedly performing the displacement of the mixed gas, and when the oxygen concentration in the container changes over a certain period of time after the mixed gas is introduced into the container, ending the oxidation treatment of the metal powder after a predetermined time.

5. The method for oxidizing metal powder according to any one of claims 1 to 4, wherein, This includes the step of creating a gas flow within the container.

6. The method for oxidizing metal powder according to any one of claims 1 to 4, wherein, This includes the step of measuring the oxygen concentration inside the container.

7. The oxidation method of metal powder according to any one of claims 1 to 4, wherein, The container contains a bag filter.

8. The method for oxidizing metal powder according to any one of claims 1 to 4, wherein, The metal powder contains titanium powder.

9. The method for oxidizing metal powder according to any one of claims 1 to 4, wherein, The inactive gas in the mixed gas includes argon. The oxygen concentration of the mixed gas is above 0.5% and below 4%.

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