Method of manufacturing metal additive manufactured object

Abstract

To provide a method of manufacturing a metal additive manufactured object that is capable of solving the problem of deformation or cracking in additive manufacturing by inhibiting the deformation of a base plate and improving the lay-ability of a metal powder layer, while inhibiting the deformation of a metal additive manufactured object.MEANS FOR SOLVING THE PROBLEM: A method of manufacturing a metal additive manufactured object includes forming a metal additive manufactured object on a base plate arranged on a forming stage according to powder bed fusion, the base plate consisting of a plurality of members ground to a same height and the plurality of members being arranged with their ground surfaces facing upward and aligned in the direction of grinding.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing metal additive products. [Background technology]

[0002] In recent years, additive manufacturing (also called layered manufacturing) has come to be used as a method for manufacturing metal parts. Among additive manufacturing methods, powder bed fusion is a method in which metal powder is spread on a base plate placed on a vertically movable base, and the metal powder is melted and solidified or sintered with an energy source such as a laser or electron beam to obtain a solidified layer, and then metal powder is spread on top of that and the process of obtaining a further solidified layer is repeated to obtain a metal part.

[0003] In such additive manufacturing processes in which a solidified layer is obtained from a metal powder using an energy source, it is known that after the solidified layer is obtained by melting and solidifying the metal powder, the solidified layer gradually shrinks over time. As a result, there is a problem in that the lower solidified layer formed at the beginning of the additive manufacturing process is deformed as if it is pulled upward due to the shrinkage of the solidified layer formed later in the additive manufacturing process.

[0004] In response to such problems, Patent Document 1 discloses an additive manufacturing device including a substrate including a plurality of divided plates that support powder, a powder solidification unit that solidifies the powder on the divided plates, and a guide including a direction regulating unit that regulates the direction of movement and / or deformation of the divided plates. With such a configuration, the direction of movement and / or deformation of the substrate is regulated by the direction regulating unit, and as a result, the substrate can flexibly follow the thermal deformation of the object, and therefore it is believed that it is possible to suppress a decrease in the molding accuracy or quality of the object without causing unintended thermal stress to the thermally deformed object.

[0005] Patent Document 2 also discloses that a base plate for stacking material powder is fixed to a jig plate at one or more locations using a fixing member, and that the fixing locations are located near the center of the jig plate. With this configuration, it is said that deformation of the base plate is permitted, and after the deformation of the sintered body and the base plate has ceased, the residual stresses of the sintered body and the base plate can be balanced, preventing further deformation. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2020-168787 [Patent Document 2] Patent Publication 2019-183219 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the base plate described in Patent Document 1 and Patent Document 2, the rigidity of the base plate may become insufficient toward the latter half of the additive manufacturing process, causing deformation. In addition, the base plate is made of multiple members, and the spread of the metal powder layer may be disturbed due to deformation or surface irregularities of the base plate. As a result, defects such as poor melting may occur in the solidified layer in contact with the base plate, and the solidified layer formed later in the additive manufacturing process may shrink, causing deformation or cracks originating from these defects.

[0008] The present invention has been made in consideration of these circumstances, and provides a method for manufacturing metal additive products that can solve the problems of deformation and cracking in additive manufacturing by suppressing deformation of the metal additive product, suppressing deformation of the base plate, and improving the spreading of the metal powder layer. [Means for solving the problem]

[0009] The manufacturing method of a metal additive product of the present invention includes a first step of forming a metal powder layer on a plurality of divided base plates arranged on a base support installed on a modeling stage, and irradiating a predetermined location of the metal powder layer with a light beam to melt and solidify the metal powder at the predetermined location to form a solidified layer, and a second step of forming a new metal powder layer on an upper surface of the solidified layer, and repeating the process of irradiating a predetermined location of the new metal powder layer with the light beam to form a further solidified layer, and is characterized in that it includes a grinding step of forming a grinding surface having grinding marks on the surface of the plurality of divided base plates on which the metal powder layer is formed, and obtaining the plurality of divided base plates of the same thickness, and the plurality of divided base plates are arranged on the base support with the grinding direction aligned in the same direction.

[0010] In addition, after obtaining the metal additive product, the method includes a process of removing the metal additive product integrated with the divided base plate from the base support together with the divided base plate, and a process of separating the metal additive product from the divided base plate.

[0011] In addition, it is preferable to apply a divided base plate separated from the metal additive product to the grinding process.

[0012] It is also preferable that the grinding process is an intensive grinding process in which each divided base plate is attached to the base base and ground collectively on the base base to form a grinding surface having the same thickness and grinding marks in the same direction.

[0013] It is also preferable that the split base plates are made of a non-magnetic material and the base platform is made of a magnetic material.

[0014] In this case, it is preferable that the split base plates are made of an austenitic stainless steel material.

[0015] It is also preferable that the split base plates are made of a magnetic material, and the base platform is also made of a magnetic material.

[0016] In this case, it is preferable that the split base plates are made of a ferritic or martensitic stainless steel material.

[0017] It is also preferable that the base is a split base divided into a plurality of parts, with each split base plate being attached onto one of the split bases, and another individual split base plate being attached onto the other split base.

[0018] It is also preferable that the divided base plates are preheated before a metal powder layer is formed on the divided base plates. Effect of the Invention

[0019] According to the manufacturing method of the metal additive product of the present disclosure, by fixing each divided base plate to a rigid base, deformation of the metal additive product can be suppressed, and deformation of the base plate can be suppressed, and the spreading property of the metal powder layer can be improved. In addition, by attaching each divided base plate to the base base and having the divided base plates have the same thickness on the base base and the same grinding direction, it is possible to prevent the occurrence of defects such as poor melting in the solidified layer in the part in contact with the base plate, and to prevent deformation and cracking. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic diagram showing an example of an additive manufacturing apparatus for carrying out the method for manufacturing a metal additive product of the present invention. [Diagram 2] FIG. 1 is a schematic diagram showing an example of a method for producing a metal additive product of the present invention. [Diagram 3] FIG. 2 is a schematic diagram showing a method for carrying out the grinding step in the method for manufacturing a metal additive product of the present invention. [Figure 4] FIG. 10 is a schematic diagram showing another example of a grinding step in the manufacturing method of the metal additive product of the present invention. [Diagram 5] FIG. 2 is a schematic diagram showing an example of a divided base plate of the present invention. [Figure 6] FIG. 2 is a schematic diagram showing an example of a base foundation of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment for carrying out the present invention will be described in detail with reference to the attached drawings. First, the configuration of an additive manufacturing apparatus for carrying out the present invention will be described, and then the manufacturing method of a metal additive product of the present invention will be described.

[0022] [Additive manufacturing equipment] FIG. 1 shows a schematic diagram of an additive manufacturing apparatus 1 for carrying out the manufacturing method of the metal additive product of the present invention. The additive manufacturing apparatus 1 has a chamber (not shown) that surrounds the entire apparatus, and a modeling stage 2, a divided base plate 3, a base base 4, a powder stage 5, a powder spreading means 6, a powder collector 7, a heat source 8, and metal powder 9 are provided in the chamber. When manufacturing a metal additive product using the additive manufacturing apparatus 1, the chamber can be in a vacuum, low pressure state, or filled with an inert gas. This can prevent the metal additive product from deteriorating due to oxidation during the additive manufacturing process.

[0023] A base support 4 is installed on the upper surface of the modeling stage 2, and a divided base plate 3 is installed on the upper surface of the base support 4. The modeling stage 2 can move in the vertical direction, and by lowering the modeling stage 2 by the amount of the solidified layer formed on the upper surface of the divided base plate 3 during the additive manufacturing process, the height of the metal powder layer during the additive manufacturing process can be kept constant. In this way, it is not necessary to change the output of the heat source 8 during the additive manufacturing process depending on the height of the metal powder layer.

[0024] The powder stage 5 is filled with metal powder 9 before being spread out. The powder stage 5 can be moved in the vertical direction, and can be raised by the amount of metal powder to be spread out on the divided base plate 3 or the uppermost surface of the solidified layer.

[0025] The metal powder 9 filled in the powder stage 5 is spread on the upper surface of the divided base plate 3 or the solidified layer using a powder spreading means 6. The powder spreading means 6 is not particularly limited, but specifically, a recoater is used to scrape the metal powder 9 on the powder stage 5 onto the uppermost surface of the divided base plate 3 or the solidified layer formed on the divided base plate 3, thereby forming a metal powder layer.

[0026] The powder collector 7 is provided to collect the excess metal powder 9 spread from the powder stage 5 by the powder spreading means 6. The powder collector 7 may be directly connected to a collection container inside or outside the apparatus, for example, but may also be a mechanism that allows it to move up and down as shown in Fig. 1 and move up and down depending on the amount of excess metal powder 9. In this way, it is possible to prevent the metal powder 9 from flying up when the excess metal powder 9 is collected by the powder collector 7.

[0027] The heat source 8 is required to form a solidified layer on the metal powder layer. A light beam is most preferably used as the heat source 8 because it provides high resolution during modeling, but other melting heat sources such as an electron beam or an arc heat source can also be used. This method can also be applied to the binder jet method, which also forms a metal powder layer and models the material. The following embodiment shows an example using the most preferred light beam.

[0028] In the additive manufacturing apparatus 1 as described above, the divided base plate 3 and the base support 4 are configured as follows.

[0029] (Split base plate) The split base plate 3 is placed on the upper surface of the base foundation 4, which will be described later. By dividing the base plate into several parts in this way, rather than as a one-piece unit, it is possible to disperse the thermal stress that occurs with the shrinkage of the solidified layer. Furthermore, since the size of each split base plate 3 can be reduced compared to a one-piece base plate, it is easier to increase the flatness during manufacturing. There is no particular limit to the number of divisions into the split base plate 3. This can be set appropriately depending on the size of the molded product, i.e., the size of the range in which thermal stress occurs.

[0030] In addition, the multiple divided base plates 3 are all aligned to the same thickness, and the upper surface is a ground surface 12 having grinding marks 13. When each divided base plate 3 is installed on the base support 4, the ground surfaces are aligned so that the grinding marks of each divided base plate 3 are in the same direction. By arranging in this manner, the resistance between the metal powder 9 and the divided base plate 3 on the divided base plate 3 becomes uniform, and by aligning the thicknesses of all the multiple divided base plates 3 to the same thickness, the layer thickness of the metal powder 9 formed on the divided base plate 3 becomes uniform. Therefore, the spreading property of the metal powder 9 on the entire base plate is improved. At this time, the accuracy of the uniform thickness of the multiple divided base plates 3 refers to the absolute value of the deviation from the target thickness being less than half the thickness of one metal powder layer. This is because if the divided base plate 3 has a deviation from the target thickness that is greater than half the thickness of one metal powder layer, the individual divided base plates 3 may have a thickness difference that exceeds the thickness of one metal powder layer, and the metal powder layer cannot be spread uniformly. The absolute value of the deviation of each divided base plate 3 from the target thickness is preferably 0.02 mm or less, and more preferably 0.01 mm or less.

[0031] Furthermore, when placing the split base plates 3 on the base support 4, it is preferable to provide a width between adjacent individual base plates 3 in order to distribute thermal stress. Taking into consideration deformation due to thermal expansion of the split base plates, the width between adjacent individual split base plates 3 is preferably 0.1 mm or more so that the metal powder layer formed on the upper surface of the split base plates 3 can maintain a constant layer thickness. On the other hand, if the width is too wide, it becomes necessary to form a metal powder layer not required for molding between the split base plates, so the width is preferably 10 mm or less. More preferably, it is 5 mm or less.

[0032] The material of the split base plate 3 is selected according to the material of the metal powder 9 from alloys that are the same as or compatible with the metal powder 9, such as iron, nickel alloy, aluminum alloy, and titanium alloy. In this case, using a magnetic material for the split base plate 3 makes it possible to fix it using a magnetic chuck, which is preferable because it facilitates processing in the grinding process of the split base plate 3 described later. In consideration of productivity, the divided base plates 3 may be ground together in a set, stored, and then used for molding. In this case, if rust occurs during storage, re-polishing is required, so it is preferable that the divided base plates 3 have corrosion resistance that can withstand storage. Therefore, rusting can be prevented by using stainless steel as the material for the split base plates 3. For this reason, it is more preferable to use an austenitic stainless steel material when the split base plates 3 are made of a non-magnetic material, and a ferritic or martensitic stainless steel material when the split base plates 3 are made of a magnetic material.

[0033] The method of fixing the split base plate 3 is not particularly limited, but examples thereof include fixing with a screw or using a magnetic chuck with the split base plate 3 made of a magnetic material as described above. When fixing with a screw, each split base plate 3 is provided with a screw hole penetrating from the upper surface to the lower surface. In addition, it is preferable that a counterbore is provided on the upper surface side of the screw hole of each split base plate 3. In this way, it is possible to prevent the head of the screw from protruding from the upper surface of the split base plate 3 and to prevent a decrease in the spreading property of the metal powder 9. In addition, when using a magnetic chuck, it is possible to fix the split base plate 3 by providing an electromagnet or a permanent magnet chuck on the upper surface of the grinding machine's base plate or the modeling stage 2.

[0034] (Base foundation) The base support 4 is provided to fix the split base plate 3 to the modeling stage 2. By sandwiching the base support 4 between the split base plate 3 and the modeling stage 2, the split base plate 3 can be fixed to the modeling stage 2 even if the fixing method of the split base plate 3 is different from the fixing method of the base plate to the modeling stage 2. The base support 4 may also be a split base support divided into multiple parts. In this case, the split base plate 3 can be fixed to the modeling stage 2 by attaching each split base plate 3 to the upper surface of each split base support.

[0035] The material of the base foundation 4 is not particularly limited as long as it has the strength to support the divided base plates 3, but in order to efficiently dissipate heat from the divided base plates 3 during the additive manufacturing process, it is preferable that the material of the base foundation 4 has a higher thermal conductivity than the divided base plates 3. In addition, using a magnetic material for the base foundation 4 is preferable because it allows fixation by a magnetic chuck in the grinding process described below. Furthermore, using a material with a harder material than the base foundation 4 is preferable because it is less susceptible to damage during use and storage and can be used repeatedly over a long period of time as a reference surface for the divided base plates 3.

[0036] The method for fixing the base foundation 4 is not particularly limited, but examples include fixing with screws or using a magnetic chuck with the base foundation 4 made of a magnetic material, similar to the divided base plate 3. When fixing with screws, the base foundation 4 is provided with a screw hole penetrating from the top surface to the bottom surface.

[0037] There is no particular limitation on the combination of the material of the split base plate 3 and the material of the base base 4. The split base plate 3 and the base base 4 may both be made of a magnetic material and fixed to the magnetic chuck, or the split base plate 3 and the base base 4 may both be made of a non-magnetic material and fixed with screws. Of course, the split base plate 3 may be made of a magnetic material and the base base 4 may be made of a non-magnetic material, and only the split base plate 3 may be fixed to the magnetic chuck, or the split base plate 3 may be made of a non-magnetic material and the base base 4 may be made of a magnetic material and only the base base 4 may be fixed to the magnetic chuck. Incidentally, even if a magnetic material is used for the split base plates 3 or the base foundation 4, screw fixing may be used instead of magnetic chuck fixing. In cases such as when the metal powder 9 is made of a magnetic material, screw fixing may be more preferable than magnetic chuck fixing, so the fixing method can be appropriately selected regardless of the material of the split base plates 3 or the base foundation 4.

[0038] Furthermore, it is preferable to provide pins, spacers, etc. between split base plates 3 and base support 4 to set the positions of the split base plates.

[0039] [Metal additive manufacturing method] The manufacturing method of a metal additive product of the present invention includes a first step of forming a metal powder layer on a plurality of divided base plates arranged on a base support installed on a modeling stage, and irradiating a predetermined location of the metal powder layer with a light beam to melt and solidify the metal powder at the predetermined location to form a solidified layer, and a second step of forming a new metal powder layer on an upper surface of the solidified layer, and repeating the process of irradiating a predetermined location of the new metal powder layer with the light beam to form a further solidified layer, and is characterized in that the manufacturing method of a metal additive product includes a grinding step of forming a grinding surface having grinding marks on the surface of the plurality of divided base plates on which the metal powder layer is formed, and obtaining the plurality of divided base plates of the same thickness, and the plurality of divided base plates are arranged on the base support with the grinding direction aligned in the same direction. That is, the present invention relates to a method for manufacturing a metal additive product, in which a metal additive product is formed by powder bed fusion on a base plate placed on a modeling stage, the base plate being made of a plurality of components ground to the same height, and the plurality of components being arranged with their ground surfaces facing upward and with the grinding directions aligned.

[0040] Figure 2 shows a flow diagram of an example of a manufacturing method for a metal additive product of the present invention. Below, each step will be explained in the order of (a) to (h) in the flow of Figure 2. In this example, the grinding steps (a) to (b) are performed as separate steps (work at a different place or time), and this is an example of a manufacturing method in which the grinding steps are connected to the additive manufacturing steps (c) to (g).

[0041] (Grinding process: (a)~(b)) First, in the grinding step (a), a plurality of split base plates 3 are fixed to a surface grinding machine 10 and ground by a grinding wheel 11 to form a ground surface 12 having grinding marks 13 in the same direction on the surface on which the metal powder layer is formed, and a plurality of split base plates 3 having the same thickness are obtained. FIG. 3 shows a schematic diagram of an example of the grinding step in which the split base plate 3 is fixed to the base base 4 as an example of the grinding step. At this time, the grinding step may be performed by grinding a single split base plate 3 individually, but it is preferable to perform an intensive grinding step in which a plurality of split base plates 3 are ground collectively. By grinding a plurality of split base plates 3 collectively, it becomes easier to align the grinding surface 12 of each split base plate 3 with the grinding marks 13 aligned in a certain direction, and it becomes easier to align the thickness of each split base plate 3 to a certain value. In the following, the grinding surface 12 of the split base plate 3 is referred to as the upper surface. Although (a) and (b) of FIG. 2 show an example in which a magnetic chuck is used as a method for fixing the split base plate 3 to the surface grinding machine 10, fixing by a fixing screw 14 may also be used.

[0042] Alternatively, multiple split base plates 3 may be fixed to the base base 4, and the base base 4 may be fixed to the surface plate of a grinding machine. In this case, the flow of the part corresponding to (a) to (b) of FIG. 2, (a') to (b'), is shown in FIG. 4. In this way, by performing grinding while the individual split base plates 3 are fixed to the base base 4, the grinding marks 13 of the split base plates 3 are aligned in the same direction, which is preferable since it is not necessary to change the arrangement of the split base plates 3 again. Furthermore, it is not necessary to re-fix the split base plates 3 from the surface plate of the grinding machine to the base base 4 before the additive manufacturing process. Note that the multiple split base plates 3 fixed to the base base 4 can be disassembled once after grinding, and then reassembled after cleaning.

[0043] Although the grinding machine used in the grinding step is not particularly limited, it is preferable to use a surface grinding machine since it can simultaneously grind a plurality of divided base plates 3. In the flow (b) of Fig. 2, a surface grinding machine 10 is shown as an example. As other equipment, a wire saw, an electric discharge machine, a cutting machine, etc. can also be applied.

[0044] (Additive manufacturing process: (c)~(g)) Thereafter, additive manufacturing steps (c) to (g) are performed. First, in flow (c) of FIG. 2, the ground individual divided base plates 3 are fixed to the base support 4 with fixing screws 14 or the like. At this time, the ground surfaces 12 of the divided base plates 3 are aligned in a certain direction. By arranging them in this manner, the spreading of the metal powder layer formed on the upper surfaces of the divided base plates 3 is improved. At this time, the base support 4 may be fixed to the modeling stage 2 before the divided base plates 3 are fixed. In addition, if each divided base plate 3 is fixed to the base base 4 before the base foundation 4 is fixed to the modeling stage 2, the base base 4 to which the divided base plates 3 are fixed is fixed to the modeling stage 2. This procedure is effective, for example, when the grinding process is performed with multiple divided base plates 3 fixed to the base foundation 4 as shown in FIG.

[0045] First, as shown in (d), the base 4 and the divided base plate 3 are installed on the modeling stage 2 with fixing screws 14 or the like. Then, in (e), a metal powder layer 15 is formed on the divided base plate 3, and then, in (f), an energy beam is irradiated to a predetermined portion of the metal powder layer to melt and solidify the metal powder at the predetermined portion to form a solidified layer 16. Here, (e) to (f) are the first process. Then, a new metal powder layer 15 is formed on the modeled solidified layer 16, and a predetermined portion of this new metal powder layer is irradiated with an energy beam to form a further solidified layer 16, which is repeated, and this is the second process. After that, the additive product 17 is modeled in (g). Here, the thickness of the divided base plate 3 is made uniform, and uniform grinding marks 13 are formed on the grinding surface 12, so that the metal powder layer 15 on the divided base plate 3 is uniformly formed. Therefore, in the solidified layer 16 obtained by energy beam irradiation, cracks and deformations originating from partial unmelted parts due to non-uniformity in the thickness of the metal powder layer 15 can be prevented. It is also possible to prevent peeling between the solidified layer 16 and the divided base plate 3. If the direction of the grinding marks 13 is parallel to the formation direction of the metal powder layer 15 on the grinding surface 12, i.e., the movement direction of the powder spreading means 6 in Fig. 1, the powder may slip in the direction of the grinding marks 13 on the divided base plate 3, making it difficult to form the metal powder layer 15. To prevent this phenomenon, it is preferable to set the angle between the grinding marks 13 and the powder spreading means 6 to be 30 degrees or more and 90 degrees or less (i.e., perpendicular).

[0046] Here, it is preferable to preheat the divided base plate 3 when forming the powdered metal layer 15 on the upper surface of the divided base plate 3. In this way, the temperature gradient between the divided base plate 3 and the powdered metal layer 15 becomes gentle when the powdered metal layer 15 is irradiated with an energy beam, and residual compression in the solidified layer can be suppressed.

[0047] (Cutting process:(h)) After the additive manufacturing process is completed, as shown in (h), the additive product 17 integrated with the split base plate 3 is removed from the base base together with the split base plate 3, and the additive product 17 is separated from the split base plate 3. The separation method is not particularly limited, but FIG. 2(h) shows an example in which an electric discharge machine using a processing wire 18 is used.

[0048] It is preferable that the used divided base plate 3 after separation is again subjected to a grinding process to remove the residue of the additive product 17 and the altered parts caused by the separation, and the surface of the divided base plate 3 is again smoothed and used repeatedly. The flow of the grinding process at this time is the same as that of the grinding process described above. A problem with repeatedly using a conventional base plate is that the base plate warps due to the stress generated in the additive manufacturing process, and a thicker layer needs to be ground to obtain a smooth surface in the grinding process. If the warping of the base plate is too large, the thickness required as a base plate after grinding cannot be secured, and it may not be possible to use it for additive manufacturing. As described above, the divided base plate 3 of the present invention suppresses deformation due to thermal stress during the additive manufacturing process, so that it can be reused in the additive manufacturing process with a smaller amount of grinding by returning it to the grinding process (a) to (b), which has the effect of shortening the grinding process and increasing the number of times the base plate can be used.

[0049] Furthermore, as mentioned above, by using stainless steel as the material for the split base plate 3, rust can be prevented, so the split base plate 3 that has been subjected to the grinding process again after the additive manufacturing process can be used as is even if stored in a room temperature environment without the need for grinding before reuse. EXAMPLES

[0050] The present invention will be described in more detail below with reference to examples and comparative examples, although the present invention is not limited to these examples.

[0051] (Configuration of split base plate) The split base plate 3 used in the modeling is shown in FIG. 5, and the base stand 4 is shown in FIG. Split base plate 3 is manufactured by cutting, and has a rectangular shape with an outer shape of 84 mm in width, 84 mm in depth, and 22 mm in thickness. At the four corners of split base plate 3, there are through holes with a diameter of 10 mm for installing fixing screws 14 (M8 bolts) for fixing to base 4, and countersunk holes with a diameter of 14 mm and a depth of 10.5 mm for accommodating the heads of fixing screws 14 at a position lower than ground surface 12 of split base plate 3. The material of split base plate 3 will be described later in the explanation of Examples 1 to 3 and Comparative Examples 1 and 2.

[0052] (Base foundation configuration) The base 4 (prehardened steel, manufactured by Proterial Co., Ltd.) is manufactured by cutting, and has an outer shape of a rectangle with a width of 252 mm, a depth of 252 mm, and a thickness of 14.5 mm. The base 4 has a through hole with a diameter of 8.5 mm, a countersink with a diameter of 14 mm and a depth of 8.5 mm, and a screw hole for arranging a plurality of split base plates 3 and fixing them with fixing screws 14, in order to arrange screws for fixing them to the modeling stage 2 of the additive manufacturing device 1 described later. In this embodiment, the split base plates 3 are designed so that a total of nine plates, three in the width direction and three in the depth direction, can be fixed to the base 4 with fixing screws 14.

[0053] (Split base plate grinding process) Example 1 In Example 1, the material of the divided base plate 3 was carbon steel for mechanical construction (S50C). A total of nine divided base plates 3, three in the width direction and three in the depth direction, were arranged side by side on the magnetic chuck of the surface grinding machine 10, and a grinding surface 12 in a certain direction was formed by an intensive grinding process using a grinding wheel 11 (manufactured by Teiken Co., Ltd.), to obtain individual divided base plates 3 with a thickness of 22 mm ± 0.01 mm. Thereafter, each divided base plate 3 was removed from the surface grinding machine and washed, and fixed to the base base 4 with the same arrangement and orientation as when grinding with a fixing screw 14. At this time, they were arranged so that the direction of the grinding marks 13 was aligned perpendicular to the laying direction when the metal powder 9 was laid using the additive manufacturing device 1 later.

[0054] Example 2 In Example 2, the material of the divided base plate 3 was 13Cr martensitic stainless steel (HPM38: manufactured by Proterial Co., Ltd., HPM38 is a registered trademark of the company). As in Example 1, a total of nine divided base plates 3, three in the width direction and three in the depth direction, were arranged and subjected to an intensive grinding process to form a grinding surface 12 in a certain direction, and individual divided base plates 3 with a thickness of 22 mm ± 0.01 mm were obtained. Thereafter, each divided base plate 3 was removed from the surface grinding machine 10 and washed, and fixed to the base base 4 with the fixing screws 14 in the same arrangement and orientation as when grinding. At this time, they were arranged so that the direction of the grinding marks 13 was aligned perpendicular to the laying direction when the metal powder 9 was laid using the additive manufacturing device 1 later.

[0055] Example 3 In Example 3, the material of the split base plate 3 was austenitic stainless steel (SUS316L). In Example 3, a total of nine split base plates 3, three in the width direction and three in the depth direction, were arranged and fixed with fixing screws 14. Then, the base base 4, which is made of a magnetic material, was fixed on the magnetic chuck of the surface grinding machine 10 and subjected to an intensive grinding process, forming a grinding surface 12 in a certain direction, and individual split base plates 3 with a thickness of 22 mm ± 0.01 mm were obtained. Then, the split base plate 3 and the base base 4 integrated with each other were removed from the magnetic chuck, and the individual split base plates 3 were removed from the base base 4 and washed, and re-fixed to the base base 4 with the washed fixing screws 14 in the same arrangement and orientation as when grinding. At this time, they were arranged so that the direction of the grinding marks 13 was aligned perpendicular to the laying direction when the metal powder 9 was laid using the additive manufacturing device 1 later.

[0056] Example 4 In Example 4, the material of the split base plate 3 was carbon steel for mechanical construction (S50C), and three split base bases (pre-hardened steel, manufactured by Proterial Co., Ltd.) with external dimensions of 252 mm in width, 84 mm in depth, and 14.5 mm in thickness, on which three split base plates 3 can be arranged, were manufactured by cutting. Three split base plates 3 were arranged and fixed in the width direction on each of the three split base bases in advance, and three split base bases were fixed in the depth direction on the base base 4, and then the base base 4 was fixed on the magnetic chuck of the surface grinding machine 10. Then, through an intensive grinding process, a ground surface 12 in a certain direction was formed, and individual split base plates 3 with a thickness of 22 mm ± 0.01 mm were obtained. Thereafter, the divided base plate 3, divided base base, and base base 4, which were integrated together, were removed from the magnetic chuck, and the divided base base and divided base plate 3 were removed from the base base 4 and washed, and then re-fixed to the base base 4 in the same arrangement and orientation as at the time of grinding with the cleaned fixing screws 14. At this time, they were arranged so that the direction of the grinding marks 13 would be aligned perpendicular to the spreading direction when the metal powder 9 was later spread using the additive manufacturing device 1.

[0057] Example 5 In Example 5, the material of the split base plate 3 was carbon steel for mechanical construction (S50C). In this example, the split base plates 3 were fixed one by one on the magnetic chuck of the surface grinding machine 10, and a grinding surface 12 in a fixed direction was formed by the grinding wheel 11. The grinding process was set so that the thickness of all the split base plates 3 was within a deviation of 22 mm ± 0.01 mm. After that, each split base plate 3 was removed from the surface grinding machine and washed, and a total of nine split base plates 3 were arranged on the base base 4, three in the width direction and three in the depth direction, with the grinding marks aligned, and fixed with the fixing screws 14. At this time, they were arranged so that the direction of the grinding marks was aligned perpendicular to the laying direction when the metal powder 9 was laid using the additive manufacturing device 1 later.

[0058] Comparative Example 1 In Comparative Example 1, the material of the split base plate 3 was carbon steel for mechanical construction (S50C). In Comparative Example 1, the split base plates 3 were fixed individually one by one on the magnetic chuck of the surface grinding machine 10, and a grinding surface 12 in a fixed direction was formed by the grinding wheel 11. The thickness specification of the split base plate 3 at this time was relaxed to 22 mm ± 0.03 mm. Thereafter, as in Example 5, each split base plate 3 was removed from the surface grinding machine and washed, and a total of nine split base plates, three in the width direction and three in the depth direction, were arranged on the base base 4 with the grinding marks aligned in the direction, and fixed with the fixing screws 14. At this time, they were arranged so that the direction of the grinding marks 13 was aligned perpendicular to the laying direction when the metal powder 9 was laid using the additive manufacturing device 1 later.

[0059] Comparative Example 2 As Comparative Example 2, the material of the divided base plate 3 was 13Cr martensitic stainless steel (HPM38: manufactured by Proterial Co., Ltd., as above). As in Examples 1 to 3, a total of nine divided base plates 3, three in the width direction and three in the depth direction, were arranged and subjected to an intensive grinding process to form a ground surface 12, and individual divided base plates 3 with a thickness of 22 mm ± 0.01 mm were obtained and washed. At this time, only one divided base plate 4 at the center was intentionally rotated 90 degrees and arranged to form a grinding mark 13 in a different direction from the other eight. Thereafter, the other divided base plates were arranged and oriented in the same manner as when they were ground, except for the one at the center, and fixed to the base base 4 with an M8 bolt. At this time, when the metal powder 9 was laid using the additive manufacturing device 1 later, only the one at the center was arranged so that the direction of the grinding mark 13 was parallel to the laying direction, and the other eight were arranged so that the direction of the grinding mark 13 was aligned perpendicular to the laying direction.

[0060] (Alloy powders for additive manufacturing) The alloy powder used for additive manufacturing was a Ni-Cr-Mo alloy (ADMUSTER C21P (registered trademark), Ni-19Cr-19Mo-1.8Ta, manufactured by Proterial Co., Ltd.). This alloy powder was prepared by preparing the raw materials Ni, Cr, Mo, and Ta to have a predetermined alloy composition, and classifying the powder by a vacuum gas atomization method to adjust the particle size to 10 μm to 53 μm and the average particle size (d50) to about 35 μm.

[0061] (Evaluation of powder spreading ability) Next, the spreading property of the metal powder 9 was evaluated using an additive manufacturing apparatus 1. The base base 4 on which the divided base plate 3 shown in any of the above-mentioned Examples or Comparative Examples was arranged was fixed to the modeling stage 2 of an additive manufacturing apparatus 1 (EOS M290, manufactured by EOS) using the SLM (Selective Laser Melting) method, and the modeling stage 2 was parallelized in the additive manufacturing apparatus 1, and then a test was performed in which the metal powder 9 was spread for one layer (thickness 0.04 mm) in the additive manufacturing process described below. Note that for Example 4 in which the divided base base was used in the grinding process, the divided base base was still used. Here, the evaluation index was the area ratio of the defective spreading part where the powder could not be distributed or was excessively distributed, confirmed by visual evaluation of the total of nine divided base plates 3, and when the modeling stage 2 was parallelized and the area ratio was less than 10% of the total, it was judged as acceptable, and when the area ratio was 10% or more, it was judged as unacceptable.

[0062] Table 1 shows the evaluation results of powder spreading. In Examples 1 to 4, which were subjected to the intensive grinding process, in addition to the thickness of all the divided base plates 3 being uniform, the grinding marks 13 formed by the surface grinder 10 act to make the frictional force between the metal powder 9 and the grinding surface 12 of the divided base plate 3 constant, and the area ratio of the powder spreading defect part after the parallelization of the modeling stage 2 was able to be less than 1%. This action worked appropriately in all of Example 2, in which the divided base plate 3 was made of martensitic stainless steel, Example 3, in which the divided base plate 3 was made of austenitic stainless steel, and Example 4, in which a plurality of divided base bases were arranged on the base base 4 and each divided base plate 3 was attached on one divided base base. In Example 5, in which the divided base plates 3 were ground individually, the thickness of all the divided base plates 3 was ground to an accuracy of 22 mm ± 0.01 mm, and the area ratio of the spreading defect part was able to be less than 1% as in Examples 1 to 4.

[0063] [Table 1]

[0064] On the other hand, in Comparative Example 1, in which the thickness deviation of the divided base plates 3 was relaxed to ±0.03 mm and the divided base plates 3 were individually ground by a surface grinder, two of the nine plates had more defective packing than the other seven plates. This is thought to be due to the occurrence of variation in the thickness of the divided base plates 3 that were individually ground. As shown in Example 5, this type of defective packing can be improved by reducing the thickness deviation. In Comparative Example 2, in which the direction of the grinding marks on only one of the divided base plates 3 at the center was changed, the friction force between the alloy powder and the grinding surface 12 on the one divided base plate 3 at the center changed, and the powder was not distributed well, resulting in a defective packing with less powder than the others. In this way, it was shown that the divided base plate 3 having a grinding surface in a certain direction and the same thickness as shown in the present invention functions effectively in the powder packing required in additive manufacturing.

[0065] (Storage of split base plates) The powder was removed from the divided base plates of Examples 1 to 5 shown above after the powder spreading test, and the divided base plates were stored for one month in a storage environment simulating summer (average room temperature 25°C, humidity 70°C), and then the presence or absence of rust was visually confirmed. The divided base plates 3 made of carbon steel for mechanical construction (S50C) of Examples 1, 4, and 5 showed slight discoloration due to rust on the ground surface 12, but the divided base plates 3 made of martensitic stainless steel (HPM38) of Example 2 and the divided base plates 3 made of austenitic stainless steel (SUS316L) of Example 3 did not show such rust, and it was confirmed that they can be used for molding without re-polishing.

[0066] (Additive manufacturing of alloy components) Next, using the divided base plate 3 of Example 1, an additive product 17 was actually produced by additive manufacturing using alloy powder. Using the additive manufacturing device 1 described above, alloy powder was similarly placed on the divided base plate 3, and additive manufacturing was performed under the following conditions by the SLM method, forming 10 additive products 17 (10 mm x 10 mm x 10 mm) on each of the nine divided base plates 3. The molding conditions were set to a scanning pitch of 0.11 mm, a layer thickness of 0.04 mm, a laser output of 300 W, and a scanning speed of 1000 mm / sec. After molding to a predetermined height, the divided base plate 3 on which the additive products 17 were formed was removed from the base base 4, and it was confirmed that there were no abnormalities such as unmelted parts or cracks at the interface between the total of 90 molded bodies and the divided base plate 3. Furthermore, a total of 90 additive products 17 were cut off from the divided base plate 3 by a wire electric discharge machine, and it was confirmed that no cracks occurred in any of the additive products 17.

[0067] (Reuse of split base plate) For the purpose of reusing the nine divided base plates 3 of Example 1 used in additive manufacturing in the previous section, the nine divided base plates after removal processing by the wire electric discharge machine were arranged in the same arrangement as when they were molded, three in the width direction and three in the depth direction, and fixed to a surface grinder with a magnetic chuck, and the residue of the additive product 17 and the altered parts formed during wire electric discharge machining were removed with a grinding wheel 11, and a divided base plate 3 having a ground surface 12 with grinding marks in a certain direction was obtained. After that, each divided base plate 3 was removed from the surface grinder and washed, and a total of nine divided base plates 3 were arranged on the base base 4, three in the width direction and three in the depth direction, with the grinding marks aligned in the direction, and fixed with cleaned fixing screws 14. Then, a total of 90 additive products 17 were formed in the same manner as in the previous example, and it was confirmed that they could be molded without any abnormalities. [Explanation of symbols]

[0068] 1: Additive manufacturing equipment 2: Modeling stage 3: Split base plate 4: Base foundation 5: Powder stage 6: Powder packing means 7: Powder collector 8:Heat source 9: Metal powder 10: Surface grinding machine 11: Grinding wheel 12: Grinding surface 13: Grinding marks 14: Fixing screw 15: Metal powder layer 16: Solidified layer 17: Additive manufacturing

Claims

1. A first step of forming a metal powder layer on a plurality of divided base plates arranged on a base stand installed on a modeling stage, and irradiating a light beam onto a predetermined portion of the metal powder layer to melt and solidify the metal powder at the predetermined portion to form a solidified layer; 1. A method for manufacturing a metal additive product, comprising: a second step of forming a new powdered metal layer on top of the solidified layer, and repeatedly irradiating a predetermined portion of the new powdered metal layer with the light beam to form a further solidified layer, a grinding step for forming a grinding surface having grinding marks on a surface on which the metal powder layer is formed in the plurality of divided base plates, and obtaining the plurality of divided base plates having the same thickness; The plurality of split base plates are arranged on the base so that the grinding directions are aligned in the same direction. A method for producing a metal additive product, comprising:

2. After obtaining the metal additive product, the metal additive product integrated with the divided base plate is removed from the base base together with the divided base plate; and separating the metal additive product from the segmented base plate. The method of claim 1 , further comprising:

3. The method for manufacturing a metal additive product according to claim 2, characterized in that a divided base plate separated from the metal additive product is applied to the grinding step and applied to the first step and the second step.

4. 3. The method for manufacturing a metal additive manufacturing product according to claim 1 or 2, characterized in that the grinding process is a collective grinding process in which each divided base plate is attached to the base base and ground collectively on the base base to form a grinding surface having the same thickness and grinding marks in the same direction.

5. The method for manufacturing a metal additive manufacturing product according to claim 1 or 2, wherein the divided base plate is made of a non-magnetic material, and the base foundation is made of a magnetic material.

6. The method for manufacturing a metal additive product according to claim 5, wherein the split base plate is made of an austenitic stainless steel material.

7. The method for manufacturing a metal additive manufacturing product according to claim 1 or 2, wherein the divided base plate is made of a magnetic material, and the base foundation is also made of a magnetic material.

8. The method for manufacturing a metal additive product according to claim 7, characterized in that the split base plate is made of a ferritic or martensitic stainless steel material.

9. The method for manufacturing a metal additive manufacturing product according to claim 1 or 2, characterized in that the base base is a split base base divided into a plurality of parts, and each of the split base plates is attached onto one of the split base bases, and another individual split base plate is attached onto the other split base base.

10. 3. The method of claim 1, further comprising preheating the divided base plate and then forming a powdered metal layer on the divided base plate.

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