JP2023174403A - Metal additive manufacturing method and apparatus thereof - Google Patents

Abstract

To provide a metal additive manufacturing method due to additive manufacturing capable of performing an adjustment process in series with the additive process with good controllability and accuracy.SOLUTION: The present invention relates to a metal additive manufacturing apparatus and method for modeling a metal additive manufacturing object by supplying a metal material onto a modeling stage and moving a localized melted part by an irradiated heat source. The device includes a movement control unit that positions a tip of a pressing tool at the rear in a moving direction of the local melting part, and freely maintains and controls a separation distance of the tip from the modeling stage, and it is characterized in that it slides following the movement of the local melting part while pressing the tip against the metal material. The method involves sliding the tip following the movement of the local melting part while pressing the tip against the metal material, in the movement control unit that positions the tip of the pressing tool at the rear in the moving direction of the local melting part, and freely maintains and controls the separation distance of the tip from the modeling stage.SELECTED DRAWING: Figure 1

Description

The present invention relates to a metal additive manufacturing method and apparatus using additive manufacturing.

While moving a heat source such as an arc discharge or a laser, the supplied metal material is locally melted and solidified to form tracks, which are stacked horizontally and/or vertically to form a three-dimensional structure. Metal additive manufacturing methods are known. Here, if pores are formed inside during the melting and solidification process, the mechanical properties of the structure will deteriorate. Therefore, a method has been proposed in which tracks are formed while applying plastic deformation during the melting and solidification process to collapse the pores.

For example, in Non-Patent Document 1, in additive manufacturing by arc discharge (AAM), molten metal flows due to large energy input, generates shrinkage pores and cracks, and also causes residual stress and deformation. After discussing the ``bottleneck problem,'' he proposed that a hot rolling process be applied to solve this problem. A plurality of cylindrical rollers apply plastic deformation to the back of the torch to which the metal wire is supplied, in order to restore mechanical strength.

In addition, in Patent Document 1, similar to Non-Patent Document 1, a large energy source such as a plasma fusion deposition gun using arc discharge or a gas shield laser gun is used to move the micro roller in synchronization with this movement. This disclosure discloses a method of plastically deforming the surface of the region immediately after solidification behind the molten pool on the spot, controlling rolling and cooling, and performing deformation correction, removal processing, and/or finishing processing.

JP2020-108960A

"Improvement in Geometrical Accuracy and Mechanical Property for Arc-Based Additive Manufacturing Using Metamorphic Rolling Mechanism"; Yang Xie, Haiou Zhang, and Fei Zhou; Journal of Manufacturing Science and Engineering, NOVEMBER 2016, Vol. 138.

In metal additive manufacturing using additive manufacturing, it is difficult to control the initial pores formed during modeling, and it is desirable to provide an adjustment (plastic working) process that is a series of the additive process as described above. In particular, in metal additive manufacturing that requires high shape accuracy and mechanical properties, it is also required to be able to accurately perform adjustment steps in each lamination process with good controllability.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a metal additive manufacturing method using additive manufacturing in which an additive process and a series of adjustment processes can be performed accurately with good controllability. and to provide its equipment.

The apparatus according to the present invention is a metal additive manufacturing apparatus that supplies a metal material onto a modeling stage and moves a locally melted part by an irradiated heat source to create a metal additively manufactured object, and the apparatus is a metal additive manufacturing apparatus that supplies a metal material onto a modeling stage and moves a locally melted part by an irradiated heat source to create a metal additively manufactured object. a movement control section that is disposed at the rear in the moving direction of the melting section and that freely maintains and controls the separation distance of the tip from the modeling stage, and presses the tip against the metal material while controlling the local melting section. It is characterized by sliding following the movement of.

According to this feature, it is possible to easily and accurately apply plastic deformation that can greatly contribute to improving mechanical properties by so-called "iron processing" in which the tip of the pressing tool is slid as a series of additional steps.

In the above invention, the tip portion may be made of a metal with a high melting point of 2000° C. or higher. Furthermore, the high melting point metal may be one selected from niobium, tantalum, molybdenum, and tungsten, or an alloy based thereon. Further, in the above-described invention, the pressing tool may be characterized in that the tip portion is a part of the rod-shaped body made of the high-melting point metal. Furthermore, the tip may have a partially spherical three-dimensional curved surface. According to these features, sufficient hot plastic deformation behind the locally fused portion can be provided to greatly contribute to improving mechanical properties, and reduction in tool life can be suppressed, resulting in stable sliding at the tip. You can also get movement.

In the above-described invention, the movement control section holds the pressing tool using either or both of fixed control that keeps the separation distance constant and constant pressure control that presses the tip part against the metal material with a predetermined pressure. It may be characterized by controlling the state. According to these features, fixed control can easily control while giving sufficient plastic deformation, while constant pressure control can easily control hot plastic deformation at a softening position at a predetermined temperature or higher behind the local melting zone. .

Furthermore, the method according to the present invention is a metal additive manufacturing method in which a metal material is supplied onto a modeling stage and a locally melted part is moved by an irradiated heat source to create a metal additively manufactured object, and the method comprises: A movement control unit disposed behind the local melting portion in the moving direction and freely maintaining and controlling the separation distance of the tip from the modeling stage presses the tip against the metal material while controlling the local melting. It is characterized by sliding following the movement of the molten part.

According to this feature, it is possible to easily and accurately apply plastic deformation that can greatly contribute to improving mechanical properties by so-called "iron processing" in which the tip of the pressing tool is slid as a series of additional steps.

In the above invention, the tip portion may be made of a high melting point metal having a melting point higher than the melting point of the metal material by 1000° C. or more. According to this feature, hot plastic deformation behind the locally fused portion can be sufficiently provided to greatly contribute to improving mechanical properties, and a decrease in tool life can be suppressed.

In the above invention, the holding state of the pressing tool may be controlled by either or both of fixed control in which the separation distance is constant, and constant pressure control in which the tip portion is pressed against the metal material with a predetermined pressure. It may also be a feature. According to these features, fixed control can easily control while giving sufficient plastic deformation, while constant pressure control can easily control hot plastic deformation at a softening position at a predetermined temperature or higher behind the local melting zone. .

In the above-described invention, the constant pressure control may include a step of providing a tapered shape to a pressing start position of the pressing tool. According to this feature, hot plastic deformation behind the local melting part under constant pressure control can be easily controlled.

FIG. 1 is a block diagram showing an example of a metal additive manufacturing apparatus according to the present invention. It is (a) a top view and (b) a side view which show lamination pattern A of a manufacturing test. It is (a) a top view and (b) a side view which show laminated pattern B of a manufacturing test. FIG. 2 is a photograph of an external appearance of a metal laminate-molded product formed by laminating a molded object and metals, and a diagram showing the cutout position of a micro-tensile test piece. It is (a) a top view and (b) an external appearance photograph which shows the test piece shape of a micro tensile test piece. It is a table of manufacturing conditions and test results of a metal laminate-molded article in a manufacturing test.

A metal additive manufacturing apparatus and a metal additive manufacturing method as one embodiment of the present invention will be described using FIG. 1.

As shown in FIG. 1, the metal additive manufacturing apparatus 10 includes a feed table 1 that fixes the object to be manufactured 5 and enables horizontal movement, an irradiation section 2 that irradiates a laser beam L, a pressing tool 3, and a press tool 3. The controller includes a controller 14 that controls the operation of the controller. The object to be modeled 5 is used as a model stage for melting and stacking the metal material 9 on its upper surface, and is fixed to the feed table 1 so that the upper surface is substantially horizontal. The laser beam L irradiated from the irradiation unit 2 is a heat source for melting the metal material 9 supplied onto the object to be modeled 5, and can form a local melting part 8 in which the metal material 9 is melted. can.

The local melting part 8 is a part where the metal material 9 is locally melted or semi-molten by heating with the laser beam L, and is generally about three times the irradiation spot diameter from the center where the laser beam L is irradiated. It is defined as a range within a circle with a diameter. Actually, since the laser beam L is moved relative to the metal material 9, the local melted portion 8 is considered to be formed in a range of shape extending from a circle to the rear depending on the movement speed. Here, the semi-molten state refers to a state in which the metal material 9 has a temperature equal to or higher than the solidus temperature and solid-liquid coexist.

In addition, as the heat source, an electron beam, arc discharge, etc. can be used. In addition, the pressing tool 3 slides while pressing its tip 3a against the track of the metal material 9 that remains softened after melting, and by applying so-called "iron processing", the metal material 9 is subjected to hot plastic deformation. In this way, initial pores and the like formed during modeling can be reduced.

Specifically, the feed table 1 is connected to the feed mechanism 11a so that the object 5 can be fed in one direction at least in a horizontal plane. As the feeding mechanism 11a, for example, a mechanism including a ball screw can be used. Further, the feed mechanism 11a is connected to the feed control section 11 included in the control section 14, and includes a driver that receives a signal regarding movement of the feed table 1 from the feed control section 11 and operates the feed table 1.

By such an operation of the feeding mechanism 11a, the object 5 to be formed is moved horizontally so that the object 5 is fed with respect to the irradiation section 2, and the locally melted portion 8 of the metal material 9 is relatively transferred to the object 5 to be formed. It can be moved against. That is, while moving the local melted portion 8 obtained by melting the metal material 9 supplied in the form of powder or the like on the object 5, the metal material 9 is sequentially solidified to form a track. By stacking them horizontally and/or vertically to perform layered manufacturing, it is possible to form a three-dimensional metal layered structure. It is also preferable that the metal additive manufacturing apparatus 10 further includes a height adjustment mechanism that moves the feed table 1 in the vertical direction and a mechanism that adjusts the position in a horizontal plane in a direction perpendicular to the feed direction.

The irradiation unit 2 is connected to the laser control unit 12 and can adjust the output of the laser light L and switch it ON and OFF. As a result, the above-mentioned locally melted portion 8 can be obtained. Laser control section 12 is also included in control section 14 . Note that it is also preferable that an angle adjustment mechanism (not shown) is provided so that the irradiation angle of the laser beam L can be adjusted.

On the other hand, the pressing tool 3 is connected to a movement control section 13 that controls the movement of the pressing tool 3 via a moving mechanism 13a that moves the pressing tool 3. The movement control section 13 is also included in the control section 14 . The distal end portion 3a of the pressing tool 3 is made variable by freely maintaining the separation distance from the surface of the object to be modeled 5, which is a modeling stage, by the movement control unit 13. In other words, the pressing tool 3 is suspended with the tip 3a facing downward, and is held movable up and down by the moving mechanism 13a, and can be held fixed at a position where the above-mentioned separation distance is a given value. . For example, the movement mechanism 13a and the movement control section 13 can be configured by a known servo mechanism. Note that this separation distance is appropriately determined depending on the thickness of the supplied metal material 9 and the amount of deformation to be applied by the pressing tool 3.

Here, the movement control unit 13 performs fixed control to keep the distance between the tip 3a and the surface of the object 5 constant, and constant pressure control to press the tip 3a against the track formed by the metal material 9 with a predetermined pressure. It is preferable that the holding state of the pressing tool 3 can be controlled by one or both of them. According to the fixed control, the height of the track formed by the metal material 9 after plastic deformation can be kept constant, and the adjustment process by plastic deformation can be performed more accurately. Moreover, according to constant pressure control, the amount of plastic deformation of the metal material 9 after plastic deformation can be made constant. Note that although constant pressure control is used, the load applied to the pressing tool 3 is kept constant, and the pressure on the metal material 9 of the tip portion 3a is not concerned.

The pressing tool 3 is also made to be able to follow the movement of the local melting part 8, but it is preferable to set it apart from the local melting part 8 by a predetermined distance, for example, because control becomes easier. Therefore, it is preferable to provide a mechanism for adjusting the position of the pressing tool 3 in the horizontal direction (feeding direction) with respect to the irradiation section 2. This predetermined distance is within a predetermined range in order to apply "iron processing" to sufficiently process the track formed by the metal material 9 after passing through the local melting zone 8, thereby reducing pores and improving mechanical properties. The temperature is determined so that the tip 3a can be pressed against a portion of the track that has reached a temperature of . Therefore, this predetermined distance is determined by various conditions such as the type of metal material 9, feeding speed, and heat removal from the local melting portion 8, including the temperature within the predetermined range. Therefore, such a predetermined distance can be determined experimentally, for example.

For example, if the metal material 9 maintains a semi-molten state at the tip 3a of the pressing tool 3 that is a predetermined distance away from the locally molten part 8, the pores are easily crushed by ironing and the porosity is reduced. It is preferable from the viewpoint of reduction. On the other hand, if the metal material 9 is in a softened state after solidification at the same position, plastic working can be imparted by ironing, which is preferable from the viewpoint of improving the mechanical properties of the base material.

As described above, the object to be printed 5 is fed by the feed table 1. On the other hand, the pressing tool 3 is disposed at the rear in the moving direction of the local melting section 8 and follows the movement of the local melting section 8. Therefore, the pressing tool 3 is positioned in the feeding direction of the object 5 with respect to the local melting portion 8 . That is, as shown in the figure, when the feed direction of the feed table 1 is to the left, the pressing tool 3 is located on the left side of the local melting part 8. Note that a structure may be adopted in which the object to be modeled 5 is fixed and both the local melting portion 8 and the pressing tool 3 are fed.

Further, the tip 3a of the pressing tool 3 is pressed against the melted high-temperature metal material 9 as described above. Therefore, the tip portion 3a is preferably made of a high melting point metal having a melting point of 2000° C. or higher. Further, it is also preferable that the tip portion 3a is made of a high melting point metal having a melting point higher than the melting point of the metal material 9 by 1000° C. or more. Examples of such high melting point metals include niobium, tantalum, molybdenum, and tungsten, and one selected from these or an alloy based on these may be used. By using such a high melting point metal, it is possible to suppress a decrease in the life of the pressing tool 3, and furthermore, it is possible to obtain stable sliding of the tip portion 3a and stabilize plastic working.

Incidentally, since such a high melting point metal is relatively expensive, it is also preferable that a part of the rod-shaped body is made of a high melting point metal to form the tip portion 3a. Further, the shape of the tip portion 3a is not particularly limited as long as it can slide stably during ironing. For example, in addition to a shape having a partially spherical three-dimensional curved surface such as a part of a hemisphere or an ellipsoid, it may also be a cut surface of a rod-shaped body such as a rectangular parallelepiped.

In the metal additive manufacturing apparatus 10, in order to melt and solidify the metal material 9, a feed table 1, an irradiation unit 2, and a pressing tool 3 are installed in a chamber where an inert gas atmosphere can be obtained so as to suppress oxidation of the metal material 9. It is preferable to let The chamber also includes a source of inert gas as well as a vacuum pump for evacuating air from the interior space to facilitate purging of the inert gas. For example, argon gas can be used as the inert gas.

The metal additive manufacturing method using the metal additive manufacturing apparatus 10 is as follows.

First, the object 5 to be formed is fixed on the feed table 1, the atmosphere inside the chamber is made into an inert gas atmosphere, and then, for example, metal powder is spread as the metal material 9 on the object 5 to be formed. The thickness of the metal material 9 spread on the object 5 is constant, for example, 0.1 mm. Note that it is also preferable to provide a tapered shape in the object 5 at the position where pressing by the pressing tool 3 is started, and may include a step of forming the tapered shape in advance.

Next, the movement control unit 13 adjusts the position in the vertical direction so that the distance of the distal end portion 3a from the surface of the object to be modeled 5, which serves as a modeling stage, is a predetermined distance. Note that the horizontal position of the tip 3a of the pressing tool 3 with respect to the locally melted portion 8 is adjusted in advance.

The laser control section 12 causes the irradiation section 2 to irradiate the laser beam L, and at the same time, the feed control section 11 feeds the feed base 1 via the feed mechanism 11a. Thereby, while forming local melted portions 8 in the metal material 9, plastic deformation can be applied by "ironing" by pressing and sliding the tip 3a of the pressing tool 3 on the track formed by the melted metal material 9. During this time, the movement control unit 13 performs the above-described fixing control and/or constant pressure control to control the separation distance of the tip portion 3a from the object 5 and/or the pressing force against the track.

After the laser control unit 12 stops irradiating the laser beam L, the laser beam L is fed by a predetermined distance, and then the feed control unit 11 stops the feeding, thereby completing the formation of one track. Laminate manufacturing can be performed by repeating the formation of tracks and stacking them horizontally and/or vertically as needed, thereby producing a three-dimensional metal layered product.

Here, in the "ironing process" in which the tip portion 3a is slid on the softened track, the state of stress applied to the softened metal material 9 is considered to be different from that in pressing process using a roller, for example. In pressing processing using rollers, only a pressing force is applied in the direction perpendicular to the surface of the track, whereas in "ironing processing", in addition to such pressing force, the friction force generated by sliding is applied to the track. A horizontal force is applied near the surface. Although the mechanism caused by such a stress state is currently unknown, it is known that at least it reduces the porosity of metal additive-produced products obtained by laminating tracks and greatly contributes to improving the mechanical properties. This will be discussed later. Note that it is preferable that the porosity in the cross section of the metal layered product is reduced to 10% or less.

As described above, according to the metal additive manufacturing apparatus 10, there is an additional process of forming a localized melted part 8 in the metal material 9 and moving it to obtain a track, and a series of adjustment processes using "iron processing". can be carried out accurately and with good controllability.

[Manufacturing test]
Next, a manufacturing test in which tracks were actually formed and laminated using the metal additive manufacturing apparatus 10 to obtain a metal additive-molded product by metal lamination will be described using FIGS. 2 to 6.

As shown in FIGS. 2 and 3, a shaped object 5 having a tapered shape 5a at one end and circular in top view (see FIG. 4) was prepared, and a path for forming a track on its surface was determined. Note that the x and y directions in the figure are directions within the horizontal plane, and the z direction is the vertical direction. The x direction is the direction in which the local melting portion 8 and the pressing tool 3 are moved relative to the object 5 (the direction in which the laser beam L is scanned), and is the opposite direction to the feeding direction. The tapered shape 5a is formed at the pressing start position of the pressing tool 3. When such a tapered shape is given, by controlling the movement control unit 13 at a constant pressure, the tip 3a of the pressing tool 3 moves along the tapered surface of the object 5, and The separation distance from the surface of the shaped body 5 can be automatically obtained. In other words, the position control of the pressing tool 3 can be facilitated. Note that the slope of the tapered shape 5a was set to 1/10. The lamination pattern will be described later.

The tracks were formed with a thickness of 0.1 mm in the longitudinal direction (x direction) of the laminated pattern, and a plurality of tracks were formed parallel to each other at a pitch of 0.15 mm in the y direction so that the overall width was 3.6 mm. did. Further, a plurality of layers each having a width of 3.6 mm were formed so that the overall thickness was 1 mm in laminated pattern A (see FIG. 2) and 1.5 mm in laminated pattern B (see FIG. 3). Here, in the laminated pattern A, the positions of paths for forming tracks in adjacent layers in the y direction were aligned. On the other hand, in stacked pattern B, the positions of the paths in the y direction were shifted by half a pitch in adjacent layers.

In addition, if the end of each lamination pattern on the start side of track formation is tapered so as to extend and maintain the tapered shape 5a of the object 5, the tip 3a of the pressing tool 3 is tapered. It is preferable that it can be moved along the shape. Therefore, in order to maintain the tapered shape not only in the object to be printed but also in the laminated parts, the starting position of track formation for each layer is machined, and the starting position of track formation is shifted backward each time the layers are laminated. Good too. With such a lamination pattern, a structure 6 (see FIG. 4) made of a metal layered product was obtained.

Maraging steel powder was used as the metal material 9, the output of the laser beam L was 126 W, the spot diameter was 0.2 mm, the feed rate was 15 mm/s, and the horizontal distance between the local melting part 8 and the tip 3a was 1.0 mm. was formed. Note that the layered manufacturing was performed in an argon gas atmosphere.

As shown in FIGS. 4 and 5, a micro tensile test piece 7 was cut out avoiding the tapered portion 5a of the obtained structure 6. The micro tensile test piece 7 is a tensile test piece having a total length of 15.4 mm, a cross section of a parallel portion having a width of 1.0 mm, and a thickness of 0.4 mm. Further, the cross section (yz plane) of each structure 6 was observed to determine the porosity. The porosity was calculated from the area ratio of the portion corresponding to the pores by taking a cross-sectional photograph and then binarizing the image of the photograph.

As shown in FIG. 6, under conditions 1 and 3, "iron processing" with the press tool 3 is not performed, that is, no adjustment by plastic working to reduce voids is performed, and under conditions 2 and 4, "iron processing" is not performed. I did it.

As a result of a tensile test using a micro tensile test piece, very high tensile strength was obtained under conditions 2 and 4 compared to conditions 1 and 3. In other words, the tensile strength was able to be improved when the ironing process was performed compared to the case where the ironing process was not performed.

Further, in the case of laminated pattern A, the porosity was 20.6% in condition 1, whereas it was very small at 6.9% in condition 2. Similarly, in laminated pattern B, the ratio was 16.0% under condition 3, whereas it was very small at 2.9% under condition 4. In other words, more pores could be crushed when ironing was performed than when ironing was not performed. It can also be seen that these results correspond well to the results of the tensile test.

As described above, in manufacturing tests, it was found that a structure made of a metal laminate-molded product obtained by laminating ironed tracks can suppress porosity to a low level and obtain high tensile strength.

Regarding the laminated pattern, it was confirmed that the tensile strength was increased and the porosity was decreased in laminated pattern B in which the positions of the paths in adjacent layers were shifted by half a pitch.

Although typical embodiments of the present invention have been described above, the present invention is not necessarily limited thereto, and those skilled in the art will understand without departing from the spirit of the present invention or the scope of the appended claims. , various alternative embodiments and modifications may be found.

1 Feeding stand 2 Irradiation section 3 Pressing tool 9 Metal material 10 Metal additive manufacturing device 14 Control section

Claims (10)

A metal additive manufacturing apparatus that supplies a metal material onto a modeling stage and moves a localized melted part by an irradiated heat source to create a metal additively manufactured object,
The tip of the pressing tool is disposed at the rear in the moving direction of the local melting part, and includes a movement control unit that freely maintains and controls the separation distance of the tip with respect to the modeling stage, and A metal additive manufacturing apparatus characterized in that the metal additive manufacturing apparatus slides while following the movement of the local melting part while being pressed by. 2. The metal additive manufacturing apparatus according to claim 1, wherein the tip portion is made of a metal with a high melting point of 2000° C. or higher. 3. The metal additive manufacturing apparatus according to claim 2, wherein the high melting point metal is one selected from niobium, tantalum, molybdenum, and tungsten, or an alloy based thereon. 4. The metal additive manufacturing apparatus according to claim 3, wherein the pressing tool has a part of the rod-shaped body made of the high melting point metal as the tip end. 5. The metal additive manufacturing apparatus according to claim 4, wherein the tip portion has a partially spherical three-dimensional curved surface. The movement control unit controls the holding state of the pressing tool by either or both of fixed control in which the separation distance is constant, and constant pressure control in which the tip is pressed against the metal material with a predetermined pressure. 6. A metal additive manufacturing apparatus according to claim 5, characterized in that: A metal additive manufacturing method for manufacturing a metal additive manufacturing object by supplying a metal material onto a modeling stage and moving a localized melted part by an irradiated heat source, the method comprising:
The tip of the pressing tool is placed behind the local melting portion in the moving direction, and a movement control unit that freely maintains and controls the separation distance of the tip with respect to the modeling stage moves the tip of the pressing tool to the metal material. A metal additive manufacturing method characterized by sliding the local melted portion while following the movement of the local melted portion. 8. The metal additive manufacturing method according to claim 7, wherein the tip portion is made of a high melting point metal having a melting point higher than the melting point of the metal material by 1000° C. or more. Claim characterized in that the holding state of the pressing tool is controlled by either or both of fixed control in which the separation distance is constant, and constant pressure control in which the tip is pressed against the metal material with a predetermined pressure. 8. The metal additive manufacturing method according to 7 or 8. 10. The metal additive manufacturing method according to claim 9, wherein the constant pressure control includes a step of giving a tapered shape to a pressing start position of the pressing tool.

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