Manufacturing method of metal molded object

Abstract

To provide a metal molded article production method capable of reducing a production time by a simple method without requiring the large scale modification of a production apparatus.SOLUTION: A metal molded article production method has a step in which, in the presence of a shield gas to be fed to the circumference of a metal powder on a base plate, heat is fed to the metal powder using an energy line, and metal layers are molded on the base plate to successively laminate the metal layers. When a first metal layer in contact with the base plate is molded, the mass per unit volume at a temperature of 25°C under a pressure of 0.1 MPa of the shield gas is controlled to 1.00×10-4 g / cm3 to 1.3×10-3 g / cm3.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a metal shaped object. [Background technology]

[0002] There is a technology called additive manufacturing, which can produce three-dimensional structures of any shape using any material, and is therefore attracting attention as a promising technology in cutting-edge technology fields such as the aircraft industry and medical care. One example of a device that uses additive manufacturing technology is a metal 3D printer, which can produce metal objects with high precision by stacking metal layers obtained by heating metal powder with energy rays such as a laser (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-170454 Summary of the Invention [Problem to be solved by the invention]

[0004] When using a metal 3D printer to produce large metal objects, it takes a significant amount of time. This is because the metal layer formed by laser irradiation is very thin, at just 10 to 100 μm thick, and large metal objects require a large number of layering operations.

[0005] In metal 3D printers, the laser output is often set relatively low due to concerns that heat accumulation in the metal object during production could reduce its mechanical strength. When there is a certain upper limit on the laser energy, if an attempt is made to shorten the production time by increasing the laser scanning speed, it becomes difficult to maintain the interlayer bonding strength between the metal layers.

[0006] Therefore, Patent Document 1 discloses a laser processing device that aims to improve energy efficiency when processing metal powder. If energy efficiency when processing metal powder is improved, the time required to form one metal layer can be shortened, and the overall time required to manufacture a metal object can be shortened. However, the laser processing device described in Patent Document 1 requires multiple laser light sources. Therefore, installing multiple laser light sources requires extensive modification of the manufacturing device. Furthermore, it is not easy to control multiple laser light sources in a single manufacturing process.

[0007] An object of the present invention is to provide a method for manufacturing a metal shaped product that can shorten the manufacturing time using a simple method without requiring major modifications to the manufacturing equipment. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides the following method for producing a metal shaped article. [1] A method for manufacturing a metal shaped product, in which heat is supplied to a metal powder on a base plate using an energy beam in the presence of a shielding gas supplied around the metal powder, metal layers are formed on the base plate, and the metal layers are sequentially stacked, wherein when forming a first metal layer in contact with the base plate, the mass per unit volume at a shielding gas temperature of 25°C and a pressure of 0.1 MPa is reduced to 1.00 x 10 -4 g / cm 3 ~1.3×10 -3 g / cm 3 A method for manufacturing a metal shaped object. [2] The method for manufacturing a metal molded product according to [1], wherein when forming the first metal layer, the shielding gas contains 20% by volume or more of helium relative to 100% by volume of the shielding gas. [3] A method for manufacturing a metal object according to [1] or [2], wherein, after forming the first metal layer, when sequentially stacking the metal layers from the surface of the first metal layer, the mass per unit volume of the shielding gas at a temperature of 25°C and a pressure of 0.1 MPa is the same as the mass per unit volume of the shielding gas when forming the first metal layer. [4] A method for manufacturing a metal molded product according to [1] or [2], wherein, after the first metal layer is molded, as the metal layers are sequentially stacked from the surface of the first metal layer, the mass per unit volume of the shielding gas at a temperature of 25°C and a pressure of 0.1 MPa is increased stepwise from the mass per unit volume of the shielding gas when the first metal layer is molded. [5] A method for manufacturing a metal molded product according to [1] or [2], wherein, after forming the first metal layer, as the metal layers are sequentially stacked from the surface of the first metal layer, the mass per unit volume of the shielding gas at a temperature of 25°C and a pressure of 0.1 MPa is appropriately changed from the value of the mass per unit volume of the shielding gas when forming the first metal layer. [6] The method for producing a metal shaped article according to any one of [1] to [5], wherein the output value of the energy beam is 100 to 1500 W. [7] The method for producing a metal shaped article according to any one of [1] to [6], wherein the scanning speed of the energy beam is 600 to 3000 mm / s. [8] The method for producing a metal shaped article according to any one of [1] to [7], wherein the scanning width of the energy beam is 0.01 to 0.20 mm. [9] The method for producing a metal shaped product according to any one of [1] to [8], wherein the composition of the shielding gas is selected in accordance with the metal powder. [Effects of the Invention]

[0009] According to the method for manufacturing a metal shaped product of the present invention, it is possible to shorten the manufacturing time in a simple manner without requiring major modifications to the manufacturing equipment. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram illustrating a configuration of a metal object manufacturing apparatus to which a method for manufacturing a metal object according to an embodiment can be applied. [Figure 2] 2 is a schematic diagram illustrating the configuration inside a chamber when the metal structure manufacturing apparatus of FIG. 1 performs an n-th laser irradiation. FIG. [Figure 3]1 is a graph showing a comparison of average penetration depths in Test Example 1, Test Example 6, Test Example 11, Test Example 16, and Test Example 21. [Figure 4] 1 is a graph showing the relationship between the laser scanning speed and the average penetration depth in Test Examples 1 to 5 and Test Examples 6 to 25. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] In this specification, the "mass per unit volume [g / cm 3 ]" of a gas 3 ]" is a value measured using a gas density meter (for example, manufactured by Yokogawa Electric Corporation) under conditions of a temperature of 25°C and a pressure of 0.1 MPa. In this specification, the term "gauge pressure" refers to a value measured at 25°C using a Bourdon tube pressure gauge. In this specification, the use of "to" to indicate a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0012] The method for manufacturing a metal shaped product according to this embodiment will be described in detail below with reference to the drawings. Note that the drawings used in the following description may show characteristic portions enlarged for convenience in order to make the characteristics easier to understand, and the dimensional proportions of the components may not necessarily be the same as those in the actual product.

[0013] 1 is a schematic diagram showing the configuration of a metal object manufacturing apparatus 20 to which the metal object manufacturing method of the present embodiment can be applied. As shown in FIG. 1, the metal object manufacturing apparatus 20 includes a laser oscillator 1, an optical system 2, a chamber 3, a first shielding gas supply source 4, and a second shielding gas supply source 5. The configuration of the metal shaped product manufacturing apparatus 20 will be described below.

[0014] The laser oscillator 1 is not particularly limited as long as it can emit a laser. The laser oscillator 1 emits a laser beam into the chamber 3 via an optical system 2. This allows the metal object manufacturing apparatus 20 to sinter or melt and solidify the metal powder at the position irradiated with the laser. As a result, a layer containing a sintered or melted and solidified metal powder (hereinafter referred to as a "metal layer") is formed in the chamber 3.

[0015] The optical system 2 is not particularly limited as long as it can control the reflection position of the laser irradiated onto the metal powder from the laser oscillator 1 according to pre-entered data. The optical system 2 can be composed of, for example, one or more reflecting mirrors. The metal object manufacturing apparatus 20 can control the laser irradiation position on the metal powder by controlling the optical system 2 according to pre-entered data, which allows the metal object manufacturing apparatus 20 to form a metal layer in any shape.

[0016] Examples of metal powders include powders of various metals such as carbon, boron, magnesium, calcium, chromium, copper, iron, manganese, molybdenum, cobalt, nickel, hafnium, niobium, titanium, and aluminum, as well as alloys thereof. When the metal powder is in particulate form, the particle size of the metal particles of the metal powder is not particularly limited, but can be, for example, about 10 to 200 μm.

[0017] The chamber 3 is a housing in which the operation of irradiating a laser onto metal powder to form a metal layer and laminating the metal layers is repeatedly performed. The chamber 3 is not particularly limited as long as it can be filled with a shielding gas. The upper side of the chamber 3 is connected to a pipeline 8. Shielding gas can be introduced into the chamber 3 via the pipeline 8 from a first shielding gas supply source 4 and a second shielding gas supply source 5. The shielding gas is a gas supplied to the surrounding area of ​​the metal powder in the chamber 3. A control device (not shown) is provided in the pipeline 8. The control device is not particularly limited as long as it can change the composition of the shielding gas supplied into the chamber 3 via the pipeline 8. A specific example of the control device is a flow rate regulator that controls the flow rate of the shielding gas supplied from the first supply source 4 and the flow rate of the shielding gas supplied from the second supply source 5 to desired values.

[0018] The chamber 3 has a manufacturing stage 6. The manufacturing stage 6 is a place where the manufacturing of metal layers and the stacking of the manufactured metal layers are repeated. A base plate 7 is placed on the upper surface of the manufacturing stage 6. The base plate 7 is a plate on which a metal shaped object is placed. Metal powder is spread over the base plate 7. The base plate 7 comes into contact with the metal layer that constitutes the bottom layer of the metal object. The metal layer that constitutes the bottom layer of the metal object is the metal layer that is first shaped by the laser that is irradiated when manufacturing the metal object.

[0019] The method for manufacturing a metal structure according to this embodiment, using the metal structure manufacturing apparatus 20 having the above-described configuration, will be specifically described with reference to FIG. In the method for manufacturing a metal shaped product of this embodiment, heat is supplied to metal powder using energy rays in the presence of a shielding gas, and metal layers are formed on the base plate 7, and the metal layers are stacked.

[0020] First, before the metal layer is formed, a shielding gas G1 is supplied from the first shielding gas supply source 4 into the chamber 3. This allows the chamber 3 to be filled with the shielding gas G1. However, in the method for manufacturing a metal shaped product according to this embodiment, it is preferable to purge oxygen remaining in the chamber 3 from the chamber 3 before supplying the shielding gas G1 into the chamber 3. This improves the mechanical strength of the metal shaped product. When purging oxygen, the shielding gas G1 may be used as the purge gas, and the purging method is not particularly limited. Specifically, purging is preferably performed until the oxygen concentration in the chamber 3 is 5% by volume or less. When the oxygen concentration in the chamber 3 is 5% by volume or less, the metal powder is less likely to oxidize, and the mechanical strength of the metal shaped product is further improved.

[0021] In the method for producing a metal shaped product according to this embodiment, the shielding gas G1 preferably contains at least one gas selected from the group consisting of hydrogen, helium, nitrogen, neon, argon, and xenon, more preferably at least one gas selected from the group consisting of hydrogen, helium, nitrogen, and neon, even more preferably one or both of hydrogen and helium, and particularly preferably helium. The shielding gas G1 may contain one of these gas components alone or two or more of them in combination. However, it is most preferable that the shielding gas G1 contain only helium.

[0022] Next, in the method for manufacturing a metal object according to this embodiment, a laser is irradiated onto the metal powder on the base plate 7 to supply heat. This forms the first metal layer X1, which is a metal layer in contact with the base plate 7. In this manner, the first metal layer X1 is formed by the laser that is first irradiated when manufacturing the metal object. In other words, the first metal layer X1 is the metal layer that constitutes the bottommost layer of the metal object.

[0023] In the method for manufacturing a metal shaped product according to the present embodiment, when the first metal layer X1 is formed, the mass per unit volume of the shielding gas G1 is set to 1.00×10 -4 g / cm 3 ~1.3×10 -3 g / cm 3 The mass per unit volume of shielding gas G1 is 1.00 x 10 -4g / cm 3 By setting the mass per unit volume of the shielding gas G1 to 1.3 × 10 or more, voids and the like are less likely to form in the metal molded product during manufacturing. -3 g / cm 3 By satisfying the above condition, the penetration depth can be increased when forming the first metal layer X1, i.e., the degree of melting of the metal powder can be increased, so that the laser scanning speed can be maintained high and the manufacturing time of the metal object can be shortened. When forming the first metal layer X1, the mass per unit volume of the shielding gas G1 is set to, for example, 1.00 × 10 -4 g / cm 3 It is preferable to maintain it at 1.00 x 10 -4 g / cm 3 ~1.3×10 -3 g / cm 3 may be maintained at a higher value within the range

[0024] In the method for manufacturing a metal shaped product according to this embodiment, the shielding gas G1 preferably contains helium, which makes it easier to control the mass per unit volume of the shielding gas G1 within the above-mentioned range. When the shielding gas G1 contains helium, the helium content of the shielding gas G1 is preferably 20% by volume or more, more preferably 50% by volume or more, and even more preferably 90% by volume or more, relative to 100% by volume of the shielding gas G1. When the shielding gas G1 contains 20% by volume or more of helium relative to 100% by volume of the shielding gas G1, the penetration depth can be increased, i.e., the degree of melting of the metal powder can be increased, thereby further shortening the manufacturing time. There is no particular upper limit for the helium content, but a value of 100% by volume or less is particularly preferred.

[0025] In the method for manufacturing a metal shaped product according to this embodiment, the shielding gas G1 may contain oxygen. However, even if the shielding gas G1 contains oxygen, the oxygen content of the shielding gas G1 is preferably 5% by volume or less, and ideally 0% by volume (i.e., less than the detection limit), relative to 100% by volume of the shielding gas G1. When the oxygen content of the shielding gas G1 is 5% by volume or less, the mechanical strength of the metal shaped product is improved.

[0026] When the shielding gas G1 contains helium and argon, the helium content is preferably 20 to 100% by volume, and the argon content is preferably 0 to 80% by volume. When the shielding gas G1 contains helium and nitrogen, the helium content is preferably 20 to 100% by volume, and the nitrogen content is preferably 0 to 80% by volume.

[0027] Once the formation of the first metal layer X1 is complete, the modeling stage 6 moves downward. Next, additional metal powder is supplied to the upper side of the first metal layer X1. The laser is again irradiated onto the additional metal powder supplied to the upper side of the first metal layer X1, thereby forming a new metal layer in any desired shape, and the new metal layer is stacked on top of the previously formed metal layer. By repeating the laser irradiation, downward movement of the modeling stage 6, supply of new powder, and stacking of metal layers in this order multiple times, metal layers in any desired shape are sequentially stacked, and a metal object can be manufactured as a three-dimensional structure of any desired shape.

[0028] FIG. 2 is a schematic diagram illustrating the configuration inside the chamber when the metal molded product manufacturing apparatus performs the nth laser irradiation, where n is an integer of 2 or more. When the nth laser irradiation is performed, n-1 metal layers are sequentially stacked on top of the first metal layer X1. A shielding gas G is then supplied from the base plate 7 to surround the metal powder above the n-1th metal layer. n is being supplied.

[0029] In a first aspect of the method for manufacturing a metal shaped product of this embodiment, after the first metal layer X1 is formed, when metal layers are sequentially stacked from the surface of the first metal layer X1, a shielding gas G n The mass per unit volume of the shielding gas G1 is set to be the same as the mass per unit volume of the shielding gas G1 when the first metal layer X1 is formed. For example, in the manufacturing process of a metal object, the number of metal layer stacks may be relatively small in the early to middle stages of manufacturing, and the height of the metal object may be small. On the other hand, in the middle to later stages of manufacturing, the number of stacks may be relatively large, and the height of the metal object may be large. Shielding Gas G n The mass per unit volume is small (e.g., 1.00 × 10 -4 g / cm 3 The higher the temperature, the higher the melting point of the metal powder, which further reduces the manufacturing time. n has a large mass per unit volume (e.g., 1.3 × 10 -3 g / cm 3 The more the temperature is increased, the less likely voids and the like will be formed in the metal shaped product during manufacturing. The number of cycles in each of the initial, middle, and final stages of production, as well as the total number of cycles, can be appropriately selected depending on factors such as the size of the metal shaped object and the material of the metal powder, and is not particularly limited.

[0030] In a second aspect of the method for manufacturing a metal shaped product according to the present embodiment, after the first metal layer X1 is formed, a shielding gas G is introduced as the metal layers are sequentially stacked from the surface of the first metal layer X1. n The mass per unit volume of the shielding gas G1 is increased in stages from the mass per unit volume of the shielding gas G2. For example, in the manufacturing process of a metal molded object, the number of metal layer stacks is relatively small from the early to middle stages of manufacturing, and the height of the metal molded object may be small. Also, in the middle to later stages of manufacturing, a certain number of stacks have been performed, and the height of the metal molded object may be relatively large. nIt is preferable to increase the mass per unit volume of the shielding gas G1 stepwise. -4 g / cm 3 Even if the melting point of the metal powder is high, the melting point of the metal powder can be gradually lowered as the number of laminations increases, thereby reducing the penetration depth and shortening the manufacturing time. This reduces the likelihood of voids or other defects forming in the metal molded object during manufacturing, and also enables economical gas utilization. The number of cycles in the initial, middle, and final stages of manufacturing, as well as the total number of cycles, can be selected appropriately depending on factors such as the size of the metal molded object and the material of the metal powder, and is not particularly limited.

[0031] In the second embodiment, the shielding gas G n The mass per unit volume of shielding gas G1 is calculated as 1.3 x 10 -3 g / cm 3 In this case, the shielding gas G n The lower limit of the numerical range of the mass per unit volume is the mass per unit volume of shielding gas G1. The upper limit is 1.3 x 10 -3 g / cm 3 is. In this case, after forming the metal layer X1, the shielding gas G n The mass per unit volume of the metal layer X1 is preferably determined by the following formula (1). This allows for a stepwise appropriate melting degree to be obtained, making it less likely for voids to form in the metal object during production. Furthermore, the laser scanning speed can be maintained high even after the metal layer X1 is formed, shortening the production time. Furthermore, this allows for economical gas usage.

[0032] (Shielding gas G n (mass per unit volume of shielding gas G1) = {1-(n / N)}*(mass per unit volume of shielding gas G1) + (n / N)*(1.3×10 -3 )...Equation (1) In the formula (1), N is an integer and represents the number of laser irradiations when the production of the metal shaped object is completed.

[0033] In a third aspect of the method for manufacturing a metal shaped product according to the present embodiment, after the first metal layer X1 is formed, as metal layers are sequentially stacked from the surface of the first metal layer X1, a shielding gas G n The mass per unit volume of the shielding gas G1 is appropriately changed from the mass per unit volume of the shielding gas G1. For example, in the manufacturing process of a metal molded object, the number of metal layer stacks is relatively small from the early to middle stages of manufacturing, and the height of the metal molded object may be small. Also, in the middle to later stages of manufacturing, a certain number of stacks have been performed, and the height of the metal molded object may be relatively large. n The mass per unit volume may be changed as appropriate. For example, if the mass per unit volume of shielding gas G1 is 1.00 x 10 -4 g / cm 3 Even if the melting degree of the metal powder is high, as the number of layers increases, the melting degree of the metal powder is gradually lowered or increased to obtain the optimum melting degree. n Alternatively, a mass per unit volume of 1000 MPa or less may be selected. This allows for further improvement in the quality of the metal molded product while also taking into consideration shortening the production time and economical gas usage. The number of cycles in the initial, middle, and final stages of production, as well as the total number of cycles, can be appropriately selected depending on factors such as the size of the metal molded product and the material of the metal powder, and is not particularly limited.

[0034] In the third embodiment, the shielding gas G n The mass per unit volume of shielding gas G1 is calculated as 1.3 x 10 -3 g / cm 3 In this case, for example, the temperature and humidity near the molten part of the metal powder irradiated with the laser can be used as a reference. The shielding gas G that can obtain the melting degree (or penetration depth) suitable for the reference can be selected. nIf the correlation between the mass per unit volume of the shielding gas and the shielding gas G is investigated in advance and a reference table is created, the control device can automatically n This allows the melting degree to be selected under appropriate conditions during the lamination process. Therefore, even if an unexpected environmental change occurs during the step-by-step lamination process, voids and the like are less likely to form in the metal object during production. In addition, the laser scanning speed can be maintained high even after the metal layer X1 is formed, shortening the production time and enabling economical use of gas.

[0035] For example, when using temperature as the reference, the temperature near the molten part is measured using an optical sensor, etc., and the shielding gas G is adjusted to obtain a melting degree appropriate for the measured temperature. n The mass per unit volume can be changed as appropriate. Specifically, in the process of sequentially stacking metal layers from the surface of the first metal layer X1, it is expected that the temperature near the fusion zone may become relatively high. In this case, the shielding gas G is adjusted so that the melting degree of the metal powder becomes relatively low (i.e., the penetration depth becomes small). n The mass per unit volume is 1.3 x 10 -3 g / cm 3 In this way, the laser scanning speed can be maintained high, and the manufacturing time can be shortened while achieving economical gas usage. Although the temperature near the molten part and the humidity near the molten part are given as examples of the physical property values ​​to be used as references, the physical property values ​​are not limited to these examples.

[0036] In the method for manufacturing a metal shaped product according to the present embodiment, the shielding gas G is gradually increased as metal layers are sequentially stacked from the surface of the first metal layer X1. n The mass of the shielding gas G is changed by a control device (not shown). n By changing the mixed composition of the shielding gas G or changing the gas type, n The mass per unit volume is controlled to fall within the above-mentioned range.

[0037] In the method for manufacturing a metal molded product according to the present embodiment, a shielding gas G n Preferably, the shielding gas G contains helium. n contains helium, the shielding gas G n This makes it easier to control the mass per unit volume within the above-mentioned range. Shielding Gas G n If the shielding gas G contains helium, n The helium content of shielding gas G n The amount of the shielding gas G is preferably 20% by volume or more, more preferably 50% by volume or more, and even more preferably 90% by volume or more, based on 100% by volume. n However, shielding gas G n When 20% by volume or more of helium is contained relative to 100% by volume, the production time can be further shortened. There is no particular upper limit to the helium content, but a content of 100% by volume or less is particularly preferred.

[0038] In the method for manufacturing a metal molded product according to the present embodiment, a shielding gas G n However, the shielding gas G may contain oxygen. n Even if the shielding gas G contains oxygen, n The oxygen content of shielding gas G n The amount of the shielding gas G is preferably 5% by volume or less, and ideally 0% by volume (i.e., below the detection limit). n When the oxygen content is 5% by volume or less, the mechanical strength of the metal shaped article is improved.

[0039] Shielding Gas G n However, when helium and argon are contained, the helium content is preferably 20 to 100% by volume, more preferably 50 to 100% by volume, and even more preferably 90 to 100% by volume, and the argon content is preferably 0 to 80% by volume, more preferably 0 to 50% by volume, and even more preferably 0 to 10% by volume.

[0040] Shielding Gas G nHowever, when helium and nitrogen are contained, the helium content is preferably 20 to 100% by volume, more preferably 50 to 100% by volume, and even more preferably 90 to 100% by volume, and the nitrogen content is preferably 0 to 80% by volume, more preferably 0 to 50% by volume, and even more preferably 0 to 10% by volume.

[0041] In the method for manufacturing a metal shaped product according to the present embodiment, the shielding gas G1 and the shielding gas G2 are selected according to the type of metal powder. n It is preferable to select a composition of For example, metals with an austenitic structure, such as austenitic stainless steel and nickel alloys, have low susceptibility to hydrogen embrittlement. When the metal powder contains a metal with an austenitic structure, the metal powder is prone to oxidation, which can lead to deterioration in corrosion resistance, etc. Therefore, when the metal powder contains a metal with an austenitic structure, such as austenitic stainless steel and nickel alloys, it is recommended to use a shielding gas G n It is preferable to use a reducing gas such as hydrogen gas as the gas.

[0042] When the metal powder contains an alloy whose main component is iron, shielding gas G1 and shielding gas G2 are used to prevent hydrogen embrittlement. n It is preferable that no hydrogen gas is contained in the metal powder. When the metal powder contains aluminum, titanium, or an alloy containing these as the main component, the shielding gas G1 and the shielding gas G2 should be used in order to prevent the formation of blowholes. n It is preferable that no hydrogen gas is contained therein.

[0043] In the method for producing a metal shaped article according to this embodiment, the laser output power is not particularly limited, but may be, for example, 100 to 1500 W. When the laser output power is 100 W or more, the interlayer bonding strength of the metal layer is further improved. When the laser output power is 1500 W or less, the mechanical strength of the metal shaped article is improved.

[0044] In the method for producing a metal shaped product of this embodiment, the laser scanning speed is preferably 600 to 3,000 mm / s, more preferably 800 to 2,500 mm / s, and even more preferably 1,000 to 2,000 mm / s. In the method for producing a metal shaped product of this embodiment, even when the laser scanning speed is 600 mm / s or higher, the interlayer bonding strength of the metal layers can be maintained and the production time of the metal shaped product can be further reduced. In the method for producing a metal shaped product of this embodiment, when the laser scanning speed is 3,000 mm / s or lower, the interlayer bonding strength of the metal layers is even better.

[0045] In the method for producing a metal shaped product according to this embodiment, the laser scanning width is preferably 0.01 to 0.20 mm, more preferably 0.03 to 0.18 mm, and even more preferably 0.05 to 0.15 mm. When the laser scanning width is 0.01 mm or more, the production time of the metal shaped product can be further reduced. When the laser scanning width is 0.20 mm or less, voids and the like are less likely to be formed in the metal shaped product during production. There are no particular limitations on the gauge pressure inside the chamber 3. The gauge pressure can be set to, for example, 0 to 0.1 MPa.

[0046] (Action and effect) In the method for manufacturing a metal object according to the present embodiment described above, when forming the first metal layer X1 in contact with the base plate 7, the mass per unit volume of the shielding gas G1 is set to 1.00×10 -4 g / cm 3 ~1.3×10 -3 g / cm 3 Therefore, the laser penetrates deeper into the surface of the molten metal powder pool. Therefore, when using a relatively low-energy laser with an output power of approximately 100 to 300 W, the interlayer bonding strength of the metal layers can be maintained even if the laser scanning speed is increased to approximately 600 to 1,600 mm / s. As described above, the method for manufacturing a metal shaped object according to this embodiment can shorten the manufacturing time in a simple manner without requiring major modifications to the manufacturing equipment.

[0047] The reason why the laser penetrates deeper into the surface of the molten pool of metal powder is not entirely clear, but it is thought to be, for example, as follows. In the metal molded product manufacturing apparatus 20, it is believed that the metal powder on the surface of the base plate 7 melts before the base plate 7, and a molten pool of the metal powder is formed on the base plate 7. This is because the metal powder is likely to reach its melting point before the thermal energy transferred to the metal powder diffuses into the base plate 7. The transmitted heat energy is diffused throughout the base plate 7, making it difficult for the temperature to rise and melting of the base plate 7 to occur. Therefore, if a molten pool exists on the surface of the base plate 7, a depression will form in the molten pool, making it easier for the laser light to concentrate. At this time, it is thought that the concentration of the laser light forms a deep melt called a keyhole. In the method for manufacturing a metal shaped product according to the present embodiment, when the first metal layer X1 in contact with the base plate 7 is formed, the mass per unit volume of the shielding gas G1 is set to 1.3 × 10 -3 g / cm 3 It is thought that the cross-sectional area of ​​the keyhole is reduced to maintain the value below 0.01 mm. As a result, the laser beam is more easily concentrated in the keyhole, forming a narrow and deep keyhole, which increases the penetration depth of the laser into the surface of the molten pool.

[0048] As described above, in the method for manufacturing a metal object according to this embodiment, the laser penetrates deeply into the surface of the molten pool. Therefore, when using a relatively low-energy laser with a laser output of approximately 100 to 300 W, the interlayer bonding strength of the metal layers can be maintained even when the laser scanning speed is increased to approximately 600 to 1,600 mm / s. As a result, the method for manufacturing a metal object according to this embodiment allows for a simple reduction in manufacturing time without requiring extensive modifications to the manufacturing equipment.

[0049] In the method for manufacturing a metal object according to this embodiment, the shielding gas G n By changing the composition of the shielding gas Gn Therefore, the method for manufacturing a metal object according to this embodiment can shorten the manufacturing time of the metal object while preventing the formation of voids and the like.

[0050] Although several embodiments of the present invention have been described above, the present invention is not limited to these specific embodiments. Furthermore, the present invention may be modified by adding, omitting, substituting, or otherwise altering components within the scope of the spirit of the present invention as defined in the claims.

[0051] For example, in the embodiment described above, the metal object manufacturing apparatus is configured to irradiate a laser onto metal powder spread over the upper side of a base plate, but in other embodiments, the metal object manufacturing apparatus may be configured to supply metal powder while spraying it onto the laser irradiation position.

[0052] <Example> The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following descriptions.

[0053] (Measurement method) For the "average penetration depth [μm]", a square molten metal piece described below was cut together with the base plate 7 in a direction perpendicular to the base plate 7 without being separated from the base plate 7. The cut molten metal piece was embedded in resin and polished with a grindstone or the like, and then the penetration depth was measured by observing the cross section of the molten metal piece and the base plate 7. The penetration depth was measured three times in this manner, and the average value of the three measurements was taken as the average penetration depth [μm]. "Gauge pressure" was measured at 25°C using a Bourdon tube pressure gauge.

[0054] (Test Example 1) A metal molded product was manufactured using a metal molded product manufacturing apparatus 20. A Red Power manufactured by SPI Lasers was used as the laser oscillator 1. The optical system 2 was configured using a galvanometer mirror. The base plate 7 was made of pure titanium. Titanium alloy Ti6Al4V (manufactured by LPW Technology, Φ10-45 μm) was used as the metal powder. The laser output was 200 W, the laser scanning width was 0.05 mm, and the laser scanning speed was 800 mm / s. A layer of metal powder 30 μm thick was placed on the base plate 7. In Test Example 1, 100% by volume helium gas was supplied into the chamber 3 as a shielding gas at a flow rate of 30 L / min. When forming the first metal layer in contact with the base plate 7, the mass per unit volume of the shielding gas was 1.60 × 10 -4 g / cm 3 maintained at Under the above conditions, a 10 mm × 10 mm square molten metal product was produced. The 10 mm × 10 mm square molten metal product corresponds to a metal shaped object for one layer of the metal layer, i.e., the first metal layer.

[0055] (Test Example 2) In Test Example 2, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 1, except that the laser scanning speed was set to 1,200 mm / s.

[0056] (Test Example 3) In Test Example 3, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 1, except that the laser scanning speed was set to 1,600 mm / s.

[0057] (Test Example 4) In Test Example 4, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 1, except that the laser scanning speed was set to 2,000 mm / s.

[0058] (Test Example 5) In Test Example 5, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 1, except that the laser scanning speed was set to 2,500 mm / s.

[0059] (Test Example 6) In Test Example 6, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 1, except that a mixed gas of 20 volume % argon gas and 80 volume % helium gas was used as the shielding gas. In Test Example 6, when forming the first metal layer in contact with the base plate 7, the mass per unit volume of the shielding gas was set to 4.48 × 10 -4 g / cm 3 maintained at

[0060] (Test Example 7) In Test Example 7, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 6, except that the laser scanning speed was set to 1,200 mm / s.

[0061] (Test Example 8) In Test Example 8, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 6, except that the laser scanning speed was set to 1,600 mm / s.

[0062] (Test Example 9) In Test Example 9, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 6, except that the laser scanning speed was set to 2,000 mm / s.

[0063] (Test Example 10) In Test Example 10, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 6, except that the laser scanning speed was set to 2,500 mm / s.

[0064] (Test Example 11) In Test Example 11, a 10 mm x 10 mm square metal melt was produced in the same manner as in Test Example 1, except that a mixed gas of 50 volume % argon gas and 50 volume % helium gas was used as the shielding gas. In Test Example 11, when forming the first metal layer in contact with the base plate 7, the mass per unit volume of the shielding gas was set to 8.80 × 10 -4 g / cm3 maintained at

[0065] (Test Example 12) In Test Example 12, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 11, except that the laser scanning speed was set to 1,200 mm / s.

[0066] (Test Example 13) In Test Example 13, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 11, except that the laser scanning speed was set to 1,600 mm / s.

[0067] (Test Example 14) In Test Example 14, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 11, except that the laser scanning speed was set to 2,000 mm / s.

[0068] (Test Example 15) In Test Example 15, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 11, except that the laser scanning speed was set to 2,500 mm / s.

[0069] (Test Example 16) In Test Example 16, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 1, except that a mixed gas of 80 volume % argon gas and 20 volume % helium gas was used as the shielding gas. In Test Example 16, when forming the first metal layer in contact with the base plate 7, the mass per unit volume of the shielding gas was set to 1.3 × 10 -4 g / cm 3 maintained at

[0070] (Test Example 17) In Test Example 17, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 16, except that the laser scanning speed was set to 1,200 mm / s.

[0071] (Test Example 18) In Test Example 18, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 16, except that the laser scanning speed was set to 1,600 mm / s.

[0072] (Test Example 19) In Test Example 19, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 16, except that the laser scanning speed was set to 2,000 mm / s.

[0073] (Test Example 20) In Test Example 20, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 16, except that the laser scanning speed was set to 2,500 mm / s.

[0074] (Test Example 21) In Test Example 21, a 10 mm×10 mm square molten metal was produced in the same manner as in Test Example 1, except that 100% by volume of argon gas was used as the shielding gas. In Test Example 21, when forming the first metal layer in contact with the base plate 7, the mass per unit volume of the shielding gas was set to 1.60 × 10 -3 g / cm 3 maintained at

[0075] (Test Example 22) In Test Example 22, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 21, except that the laser scanning speed was set to 1,200 mm / s.

[0076] (Test Example 23) In Test Example 23, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 21, except that the laser scanning speed was set to 1,600 mm / s.

[0077] (Test Example 24) In Test Example 24, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 21, except that the laser scanning speed was set to 2,000 mm / s.

[0078] (Test Example 25) In Test Example 25, a 10 mm x 10 mm square molten metal was produced in the same manner as in Test Example 21, except that the laser scanning speed was set to 2,500 mm / s.

[0079] (Reference example 1) In Reference Example 1, the base plate 7 was irradiated with a laser under the same conditions as in Test Example 1, except that no layer of metal powder was placed on the base plate 7 .

[0080] (Reference example 2) In Reference Example 2, the base plate 7 was irradiated with a laser under the same conditions as in Test Example 6, except that no layer of metal powder was placed on the base plate 7 .

[0081] (Reference example 3) In Reference Example 3, the base plate 7 was irradiated with a laser under the same conditions as in Test Example 11, except that no layer of metal powder was placed on the base plate 7 .

[0082] (Reference example 4) In Reference Example 4, the base plate 7 was irradiated with a laser under the same conditions as in Test Example 16, except that no layer of metal powder was placed on the base plate 7 .

[0083] (Reference example 5) In Reference Example 5, the base plate 7 was irradiated with a laser under the same conditions as in Test Example 21, except that no layer of metal powder was placed on the base plate 7.

[0084] FIG. 3 is a graph showing a comparison of the average penetration depths in Test Examples 1, 6, 11, 16, and 21. From the results shown in Fig. 3, it can be seen that when the laser scanning speed is 800 mm / s, the average penetration depth increases as the mass per unit volume of the shielding gas decreases. Figure 4 is a diagram showing the relationship between the laser scanning speed and the average penetration depth in Test Examples 1 to 5 and Test Examples 6 to 25. In Figure 4, △ indicates the results of Test Examples 1 to 5, ◯ indicates the results of Test Examples 6 to 10, □ indicates the results of Test Examples 11 to 15, × indicates the results of Test Examples 16 to 20, and ◆ indicates the results of Test Examples 21 to 25. From the results shown in Fig. 4, even when the laser scanning speed is 2,500 mm / s, the mass per unit volume of the shielding gas is 1.3 × 10 -3 g / cm 3 In the following Test Examples 5, 10, 15, and 20, the average penetration depth exceeds the average particle diameter of the material metal powder, 27.5 μm, confirming its usefulness as a shielding gas.

[0085] [Table 1]

[0086] Table 1 shows the average penetration depths of Test Example 1, Test Example 6, Test Example 11, Test Example 16, Test Example 21, and Reference Examples 1 to 5. Note that melting of the base plate 7 did not occur in Reference Examples 1 to 5. This is thought to be why deep penetration called a keyhole was not formed. From the results shown in Table 1, it can be confirmed that in Reference Examples 1 to 5, no penetration was formed regardless of the mass per unit volume of the shielding gas. In contrast, in Test Examples 1, 6, 11, 16, and 21, the formation of a molten pool was confirmed, suggesting the formation of a keyhole.

[0087] The reason why the formation of the keyhole differs depending on whether or not there is a layer of metal powder on the base plate 7 is thought to be as follows. If there is no metal powder on the base plate 7, a molten pool of the metal powder is not formed. Therefore, a keyhole is formed on the base plate 7 only when the base plate 7 itself melts due to heat conduction to the base plate 7. However, because there is a concern that heat accumulation in the metal molded object may reduce its mechanical strength, the laser output value was set relatively low at 200 W in Test Examples 1 to 5, Test Examples 6 to 25, and Reference Examples 1 to 5. With a laser output value of 200 W, the laser energy density is low, so the base plate 7 does not melt and it is thought that a keyhole is unlikely to be formed. As described above, in the method for manufacturing a metal shaped object, since there is a restriction on the upper limit of the thermal energy of the energy beam, it is thought that keyholes are unlikely to be formed.

[0088] From the results of the above test examples, when forming the first metal layer in contact with the base plate 7, the mass per unit volume of the shielding gas is set to 1.00 × 10 -4 g / cm 3 ~1.3×10 -3 g / cm 3 It was confirmed that the average penetration depth was increased by doing so. Therefore, it was suggested that when the laser output value is relatively low at 200 W, the interlayer bonding strength of the metal layers can be maintained and the manufacturing time can be shortened even if the laser scanning speed is increased to approximately 800 to 2,500 mm / s.

[0089] Furthermore, the helium gas used in Test Examples 1 to 5, Test Examples 6 to 20, and Reference Examples 1 to 4 is a gas with a relatively high thermal conductivity. Initially, the inventors of the present invention predicted that under the conditions of Test Examples 1 to 5, Test Examples 6 to 20, and Reference Examples 1 to 4, where the thermal conductivity is relatively high, the cooling effect of the molten pool would also be likely to be high, making it difficult for keyholes to be formed. Despite this, when forming the first metal layer in contact with the base plate 7, the mass per unit volume of the shielding gas was set to 1.00 × 10 -4 g / cm 3 ~1.3×10 -3 g / cm 3It is quite surprising that the effect of increasing the average penetration depth can be obtained by doing so. [Explanation of symbols]

[0090] 1...laser oscillator, 2...optical system, 3...chamber, 4...first supply source, 5...second supply source, 6...molding stage, 7...base plate, 8...pipe line, 20...metal molded object manufacturing device, G1...shielding gas for first laser irradiation, G n …shielding gas when irradiating the laser for the nth time, X1…first metal layer

Claims

1. 1. A method for manufacturing a metal shaped product, comprising: supplying heat to a metal powder on a base plate using an energy beam in the presence of a shielding gas supplied around the metal powder; forming metal layers on the base plate; and sequentially stacking the metal layers; When forming the first metal layer in contact with the base plate, the mass per unit volume at a shielding gas temperature of 25 ° C. and a pressure of 0.1 MPa is set to 1.00 × 10 －４ g / cm ３ ~1.3 x 10 －３ g / cm ３ year, After the first metal layer is formed, as the metal layers are sequentially stacked from the surface of the first metal layer, the mass per unit volume of the shielding gas at a temperature of 25°C and a pressure of 0.1 MPa is increased stepwise from the mass per unit volume of the shielding gas when the first metal layer is formed; The method for manufacturing a metal shaped product, wherein the mass per unit volume of the shielding gas is determined by the following formula (1): (Mass per unit volume of shielding gas Gn) = {1 - (n / N)} × (Mass per unit volume of shielding gas G1) + (n / N) × (1.3 × 10 －３ )...Formula (1) In formula (1), n ​​is an integer of 2 or greater, and represents the number of laser irradiations after the metal layer is formed, with each laser irradiation on the same metal layer being counted as one irradiation; N is an integer of 2 or greater, and represents the number of laser irradiations when the production of the metal object is completed, with each laser irradiation on the same metal layer being counted as one irradiation.

2. The method for manufacturing a metal shaped product according to claim 1 , wherein the shielding gas used in forming the first metal layer contains 20% by volume or more of helium relative to 100% by volume of the shielding gas.

3. 3. The method for producing a metal shaped product according to claim 1, wherein the output value of the energy beam is 100 to 1,500 W.

4. 3. The method for producing a metal shaped product according to claim 1, wherein the scanning speed of the energy beam is 600 to 3,000 mm / s.

5. 3. The method for producing a metal shaped product according to claim 1, wherein the scanning width of the energy beam is 0.01 to 0.20 mm.

6. The method for producing a metal shaped product according to claim 1 or 2, wherein a composition of the shielding gas is selected in accordance with the metal powder.

Images