JP6767699B2 - Method for manufacturing a structure containing a β-type titanium alloy - Google Patents

Description

The present invention relates to a method for producing a structure, and more particularly to a method for producing a structure containing a β-type titanium alloy.

Metallic materials have long-term constant mechanical properties and are highly reliable. Therefore, metal materials are used for medical and dental implant applications such as orthopedics. In particular, since titanium has high biocompatibility, titanium alloys containing titanium are widely used as medical and dental implants for artificial joints, bone plates and the like.

However, the elastic modulus of a solid implant made of a metallic material is greater than the elastic modulus of a living bone. Therefore, when the implant is placed in the living bone, the living bone is destroyed at the interface between the living bone and the implant due to the difference in elastic modulus, and the normal stress is not applied to the living bone, so-called stress blocking. Occurs. Therefore, it is required to reduce the elastic modulus of metal implants.

The present inventors have proposed a structure capable of realizing a low elastic modulus in JP-A-2011-136803 (Patent Document 1) and JP-A-2013-94390 (Patent Document 2).

The structures disclosed in Patent Document 1 and Patent Document 2 include a solidified portion formed by dissolving inorganic powder particles and a sintered portion formed by sintering inorganic powder particles and bonded to the solidified portion. To be equipped. Since the sintered portion has a gap inside, the density of the sintered portion is lower than that of the solid material. Therefore, the structure disclosed in Patent Document 1 can have a lower elastic modulus than a solid metal structure. Such a structure can be formed by, for example, a layered manufacturing method of the additive manufacturing technology AM (Adaptive Manufacturing).

Japanese Unexamined Patent Publication No. 2011-136083 Japanese Unexamined Patent Publication No. 2013-94390

In the above Patent Documents 1 and 2, a low elastic modulus is realized by making the structure porous. However, it is more preferable if a low elastic modulus can be realized by other methods.

An object of the present invention is to provide a method for producing a structure containing a β-type titanium alloy, which can realize a low elastic modulus.

As a method for producing a structure containing a β-type titanium alloy according to the present embodiment, a layered manufacturing method is used. In this manufacturing method, a bed forming step and a melting step are alternately repeated to form a structure in which a plurality of solidified layers are laminated. In the bed forming step, powder particles serving as a starting material for the structure are supplied onto the base to form a powder bed. The melting step scans a high energy heat source to melt the powder bed to form a solidified layer containing a β-titanium alloy.

Here, β-type titanium means a titanium alloy having a body-centered cubic lattice structure (bcc). Structures containing β-type titanium include, for example, not only β-type titanium alloys, but also structures containing (α (hcp) + β (bcc)) type titanium, carbides of titanium, and ω having different crystal structures. A structure or the like in which a second phase such as a phase is precipitated.

The production method according to the present embodiment can produce a structure containing a β-type titanium alloy that can realize a low elastic modulus.

Preferably, in the melting step, the energy output E (W) of the high-energy heat source, the scanning speed S (mm / s), the scanning interval P (mm), and the effective molten pool width M (mm) are expressed by the formulas (1) to (1). (4) is satisfied.
E> 200 (1)
S> 600 (2)
E / (S × P) ≧ 2.5 (3)
0.45 ≤ P / M ≤ 0.60 (4)
Here, the effective molten pool width M is a parabolic-shaped bottom of the solidified portion formed by one scan using a high-energy heat source in the melting process and having a parabolic shape whose vertical cross section is convex downward. It means the width (mm) of the portion.

The mechanical properties of metallic materials generally differ greatly depending on the crystal orientation (crystal anisotropy). In the case of β-type titanium alloy, its elastic modulus is the lowest in the crystal orientation <100> and approaches the elastic modulus of living bone. Therefore, if the crystal orientation can be controlled to produce a structure in which the orientation of <100> is enhanced, the elastic modulus can be reduced.

This manufacturing method can manufacture a structure in which the crystal orientation is controlled. Specifically, if the melting steps satisfying the above formulas (1) to (4) are carried out, the orientation of <100> becomes high. Therefore, the elastic modulus of the structure can be lowered to approach the elastic modulus of the living bone.

In the above manufacturing method, the crystal orientation of the structure may be controlled by adjusting the scanning direction in each melting step.

In this case, the crystal orientation (organization) of the structure containing the β-type titanium alloy can be adjusted.

In the above production method, the material of the structure containing the β-type titanium alloy is, for example, Ti-6Al-4V ELI (Extra Low Interstitials) alloy defined in ASTM F136-13 (2013), ISO 5832-11 (2014). Ti-6Al-7Nb alloy specified in ISO 5832-14 (2007), Ti-15Mo-5Zr-3Al alloy specified in JIS T7041-4 (2009), Ti-15Zr-4Nb-4Ta alloy specified in JIS T7041-4 (2009). One or more selected from the group consisting of, and the β-type titanium alloy is, for example, the Ti-15Mo-5Zr-3Al alloy specified in ISO 5832-14 (2007).

In the present manufacturing method, the above-mentioned laminating molding method is, for example, a laser laminating molding method.

FIG. 1 is a block diagram of a laminated modeling apparatus used in the manufacturing method of the present embodiment. FIG. 2 is a diagram showing the relationship between the crystal orientation and the elastic modulus measured using the Ti-15Mo-5Zr-3Al alloy specified in ISO 5832-14 (2007). FIG. 3 shows the output E (W) and scanning speed S (mm / sec) of the high-energy heat source obtained by the laminated molding method, and the lotgering factor (Lotting Factor) = L of the crystal plane (100) in the measurement direction. The relationship with the value of (100) is shown. FIG. 4 shows the output E (W) and scanning speed S (mm / sec) of the high-energy heat source, the value of the energy density D, and the lot-gering factor (100) in the measurement direction obtained by the laminated molding method. It is a figure which shows the relationship with Rotgering Factor) = L (100). FIG. 5A is a schematic view of a cross section (vertical cross section) perpendicular to the scanning direction of the solidified portion formed by one scanning of a high energy heat source in the melting step. FIG. 5B shows the vicinity of the uppermost surface when a structure of Ti-15Mo-5Zr-3Al alloy is manufactured by a laminated molding method with an output E = 300 W, a scanning speed S = 1000 mm / sec, and a scanning interval P = 0.12 mm. It is a vertical cross-sectional photographic image. FIG. 6 shows the ratio (= P / M) of the scanning interval P to the effective molten pool width M obtained by the additive manufacturing method and the lotgering factor (Rotting Factor) = L (100) in the measurement direction. Shows the relationship with. FIG. 7 is a flow chart showing details of a method for manufacturing a structure containing a titanium alloy of the present embodiment. FIG. 8 is a flow chart showing details of the modeling process in FIG. 7. FIG. 9 is a schematic view showing the bed forming step in FIG. FIG. 10 is a schematic view showing one step following FIG. FIG. 11 is a schematic view showing one step following FIG. FIG. 12 is a schematic view showing one step following FIG. FIG. 13 is a schematic view showing one step following FIG. FIG. 14 is a schematic view showing one step following FIG. FIG. 15A is a photographic image of the structure of the Ti-15Mo-5Zr-3Al alloy produced by the production method of this embodiment. FIG. 15B is a photographic image of another structure of the Ti-15Mo-5Zr-3Al alloy, which is different from FIG. 15A. FIG. 16 is a schematic diagram for explaining the scanning direction of the high energy heat source in the additive manufacturing method of the present embodiment. 17 (A) is a pole figure of the structure manufactured by scanning in FIG. 16 (A), and FIG. 17 (B) is a pole figure of the structure manufactured by scanning in FIG. 16 (B). It is a figure.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

In the method for producing a structure containing a β-type titanium alloy according to the present embodiment, for example, the laminated modeling apparatus shown in FIG. 1 is used.

[Structure of laminated modeling equipment]
With reference to FIG. 1, the laminated modeling apparatus 100 is a laser laminated modeling apparatus. The laminated modeling device 100 includes a control device 10, a laser device 14, a lens system 15, a mirror (galvano mirror) 16, and a chamber 20.

The laser device 14 is a high-energy heat source and emits laser light. The laser device 14 is, for example, a solid-state laser such as a fiber laser or a YAG laser, a CO ₂ laser, or the like. The lens system 15 receives the laser light from the laser device 14 and converges the laser light to form the laser 30. The mirror 16 performs an irradiation operation of the laser 30. That is, the mirror 16 adjusts the position where the laser 30 is irradiated.

The chamber 20 includes a bed forming chamber 201, a powder supply chamber 202, a modeling table 203, and a recorder 205.

The bed forming chamber 201 is tubular and has an opening at the upper end. The modeling table 203 is housed in the bed forming chamber 201 and is supported so as to be able to move up and down in the vertical direction. The modeling table 203 is moved up and down by a motor (not shown). A base 208 is arranged on the modeling table 203. The base 208 is made of, for example, a metal such as titanium. The base 208 may be a metal other than titanium. The structure containing the β-type titanium alloy is formed on the base 208.

The powder supply chamber 202 is arranged next to the bed forming chamber 201. The powder supply chamber 202 has a tubular shape and includes a piston 204 that can move up and down in the vertical direction. Powder particles 40, which are starting materials for titanium alloy structures, are laminated on the piston 204. As the piston 204 rises, the powder particles 40 are discharged from the upper opening of the powder supply chamber 202 and are supplied to the bed forming chamber 201.

The recorder 205 is arranged near the upper opening of the powder supply chamber 202. The recorder 205 is moved in a specific direction (horizontal direction) by a motor (not shown), and reciprocates between the powder supply chamber 202 and the bed forming chamber 201. In FIG. 1, the recorder 205 reciprocates in the X direction.

By moving in the X direction, the recorder 205 moves the powder particles 40 discharged from the powder supply chamber 202 in the horizontal direction and supplies the powder particles 40 to the bed forming chamber 201. The powder bed (powder bed) 206 is formed by the powder particles 40 deposited on the base 208 of the modeling table 203 in the bed forming chamber 201. When the recorder 205 moves in the X direction, the powder particles 40 move in the horizontal direction, and the surface of the powder bed 206 is flattened.

A roller may be used instead of the recorder 205. When a roller is used, the powder bed 206 can be formed while arbitrarily pressurizing the powder particles 40 with the roller.

The control device 10 includes a central processing unit (CPU) (not shown), a memory, and a hard disk drive (hereinafter referred to as HDD). A well-known CAD (Computer Aided Design) application and a CAM (Computer Aided Manufacturing) application are stored in the HDD. The control device 10 uses a CAD application to create three-dimensional shape data of a structure to be manufactured.

The control device 10 further uses the CAM application to create machining condition data based on the three-dimensional data. In the additive manufacturing method, a plurality of solidified layers formed by the laser 30 are laminated to form a structure containing a β-type titanium alloy. The processing condition data includes the processing conditions when each solidified layer is formed. That is, the processing condition data is created for each solidified layer (each powder bed 206). The control device 10 controls the laser device 14, the lens system 15, and the mirror 16 based on the processing condition data, and conditions that define the energy density of the laser 30 (output E, scanning speed S, scanning interval P, and irradiation position). To adjust.

[Outline of manufacturing method]
In this embodiment, a structure containing a β-type titanium alloy is manufactured by using a layered manufacturing method. Specifically, in this manufacturing method, the bed forming step and the melting step are alternately repeated to form the structure in which a plurality of solidified layers are laminated. In the bed forming step, powder particles serving as a starting material for the structure are supplied onto the base to form a powder bed. The melting step scans a high energy heat source to melt the powder bed to form a solidified layer containing a β-titanium alloy.

Preferably, in the present production method, the elastic modulus of the structure is lowered by controlling the crystal orientation of the material containing the β-type titanium alloy. This point will be described in detail below.

FIG. 2 is a diagram showing the relationship between the crystal orientation and the elastic modulus measured using a single crystal of the β-type Ti-15Mo-5Zr-3Al alloy defined in ISO 5832-14 (2007). With reference to FIG. 2, in the Ti-15Mo-5Zr-3Al alloy, the elastic modulus differs depending on the crystal orientation. Specifically, the elastic modulus in the crystal orientation <100> is the lowest, 44.4 GPa, and the elastic modulus increases from <100> to <111>, and increases to about 120 GPa in <111>. Then, the elastic modulus gradually decreases from <111> to <011>, and becomes about 80 GPa in <011>.

As described above, the Ti-15Mo-5Zr-3Al alloy has the lowest elastic modulus in the <100> orientation, and its value is close to the elastic modulus of living bone (10 to 40 GPa). Similarly, other β-type titanium alloys have a low elastic modulus of <100>. Therefore, when a structure containing a β-titanium alloy is used as an implant in a living bone, it is preferable to manufacture the structure so that the direction in which the main stress is applied is <100> in order to suppress stress shielding. ..

Therefore, in the present embodiment, a structure containing a β-type titanium alloy is manufactured while controlling the crystal orientation by using a layered manufacturing method, which is a kind of additional manufacturing technology (3D printer). In the additive manufacturing method, the bed forming step and the melting step are alternately repeated to produce a structure in which a plurality of solidified layers are laminated. In the bed forming step, powder particles used as a starting material for the structure are supplied onto the base to form a powder bed. In the melting step, a high-energy heat source is scanned to melt the powder bed to form a solidified layer containing a β-titanium alloy.

In each melting step, in order to control the crystal orientation, the energy output E (W) of the high energy heat source, the scanning speed S (mm / s), the scanning interval P (mm), and the effective molten pool width M (mm) are expressed. The high energy heat source is controlled to melt the powder bed so as to satisfy the equations (1) to (4).
E> 200 (1)
S> 600 (2)
E / (S × P) ≧ 2.5 (3)
0.45 ≤ P / M ≤ 0.60 (4)
Here, the effective molten pool width M is a parabolic-shaped bottom of the solidified portion formed by one scan using a high-energy heat source in the melting process and having a parabolic shape whose vertical cross section is convex downward. It means the width (mm) of the portion. The effective molten pool width M will be described later.

[About equations (1) to (3)]
The orientation of the crystal orientation depends on the output E, the scanning speed S, and the scanning interval P in the melting process. FIG. 3 shows the output E (W) and scanning speed S (mm / sec) of the high energy heat source obtained by the laminated molding method described later, and the lotgering factor (Lotting Factor) = L in the measurement direction. The relationship with the value of (100) is shown. FIG. 4 shows the output E (W) and scanning speed S (mm / sec) of the high energy heat source, the value of the energy density D, and the lot gering of (100) in the measurement direction obtained by the laminated molding method described later. It is a figure which shows the relationship with the factor (Rotting Factor) = L (001). The larger the lot-gering factor L (100) (the maximum value is 1), the higher the orientation of (100).

In FIGS. 3 and 4, Ti-15Mo-5Zr-3Al alloy was produced by additive manufacturing method. The scanning directions of the high-energy-heat sources in each melting step at this time were orthogonal to each other (see FIG. 16 (A)). Further, in FIGS. 3 and 4, the scanning interval P was 0.1 mm. In the measurement of the lotgering factor, the DE direction of FIG. 16 was set as the measurement direction.

The “◯” mark in FIGS. 3 and 4 indicates that the lot gelling factor L (100) of the obtained titanium alloy is 0.5 or more. A “◇” mark indicates that the lot gelling factor L (100) of the obtained titanium alloy is less than 0.5. The numerical value near the mark in the graph in FIG. 3 is the value of the lot gering factor L (100), and the numerical value near the mark in the graph in FIG. 4 is the value of the energy density D. Here, the energy density D is defined by the following equation.
D = E / (S × P)

When the output E (W), the scanning speed S (mm / s), and the scanning interval P (mm) of the high-energy heat source satisfy the equations (1) to (3), respectively, with reference to FIGS. 3 and 4. , The lot-gering factor L (100) becomes 0.5 or more, and the orientation of the (100) orientation is enhanced.

[About equation (4)]
In this production method, the formula (4) is further satisfied in the melting step.
0.45 ≤ P / M ≤ 0.60 (4)

Here, the effective molten pool width M (mm) is defined as follows. FIG. 5A is a schematic cross-sectional view of a solidified portion formed in one scan of a high energy heat source in the melting step. For simplicity, a cross section (vertical cross section) perpendicular to the scanning direction is shown when the scanning directions of the high-energy heat sources in each melting step are parallel to each other (see FIG. 16B). During scanning, the intensity of the high-energy heat source is higher toward the center. Therefore, with reference to FIG. 5A, the longitudinal shape of the solidified portion 300 to be formed has a downwardly convex parabolic shape, and the central portion is the deepest. More specifically, since the central portion is melted deeper than the other portions, a portion (inflection point) X0 whose curvature changes is formed on the parabola. Of the inflection points on the parabola, the distance in the width direction between the inflection points X0 closest to the bottom 300B is defined as the effective molten pool width M.

FIG. 5B shows the most structure when a Ti-15Mo-5Zr-3Al alloy structure is manufactured by a laminated molding method with an output E = 300 W, a scanning speed S = 1000 mm / sec, and a scanning interval P = 0.12 mm. It is a vertical cross-sectional photographic image near the upper surface. With reference to FIG. 5B, “M / 2” in the figure indicates a width (M / 2) of 1/2 of the effective molten pool width M of each solidified portion formed by one scan.

In the present embodiment, the effective molten pool width M is obtained as follows. A vertical cross-sectional photographic image as shown in FIG. 5B is created. In the created photographic image, the effective molten pool width (mm) of the 20 solidified portions 300 of the uppermost solidified layer is measured. The average of the measured values is defined as the effective molten pool width M (mm) in the manufacturing method.

FIG. 6 shows the ratio (= P / M) of the scanning interval P to the effective molten pool width M obtained by the additive manufacturing method described later, and the lotgering factor (Rotting Factor) = L (100) in the measurement direction. ) Is shown. With reference to FIG. 6, the lot-gering factor L (100) increases as the P / M increases. Then, when the P / M becomes 0.45 or more, the lot gering factor L (100) becomes 0.5 or more. Then, the lot-gering factor L (100) peaks when the P / M is around 0.53, and when the P / M exceeds 0.53, the lot-gering factor L (100) increases as the P / M increases. When it decreases and the P / M exceeds 0.6, the lot gering factor L (100) becomes less than 0.5.

In short, the lotgering factor L (100) with respect to P / M becomes an upwardly convex curve. As shown in the formula (4), when 0.45 ≦ P / M ≦ 0.60, the lot gering factor L (100) becomes 0.5 or more, and the orientation toward the (100) orientation is enhanced. The preferable lower limit of P / M is 0.50. The preferred upper limit of P / M is 0.55.

The reason why it is necessary to consider the effective molten pool width M is considered as follows. In the melting step at the counter K, the powder bed is melted while sequentially shifting the scanning at the scanning interval P in the horizontal direction (width direction) of the powder bed. At this time, if the overlapping range between the solidified portion formed in the previous scan and the solidified portion formed in the next scan with the scanning interval P shifted is narrow (that is, when the P / M is too large), the next stage The solidified portion formed in the previous scanning is difficult to melt during the scanning. Therefore, the crystal structure of the solidified portion formed in the previous scan is unlikely to be inherited by the solidified portion formed in the next scan. On the other hand, when the overlapping range between the solidified portion by the previous scan and the solidified portion by the next scan is too wide (that is, when the P / M is too small), the solidified portion in the previous scan is excessively melted. In this case, the crystal structure of the solidified portion of the previous scan disappears when the next scan is melted, and is not inherited by the solidified portion of the next scan.

When the P / M is 0.45 to 0.60, the crystal structure of the solidified portion obtained by the first-stage scanning is likely to be inherited by the crystal structure of the solidified portion obtained by the next-stage scanning. (100) tends to be large, and the orientation toward (100) is increased.

This manufacturing method has been completed based on the above findings. Hereinafter, the present manufacturing method will be described in detail.

[Details of manufacturing method]
FIG. 7 is a flow chart showing details of a method for manufacturing a structure containing the β-type titanium alloy of the present embodiment. Hereinafter, a specific example of the β-type titanium alloy will be a Ti-15Mo-5Zr-3Al alloy, and a specific example of the structure will be described as an implant for living bone. However, this production method can also be applied to other structures containing β-type titanium alloys and other structures.

The control device 10 first creates three-dimensional data of the structure using a CAD application (S1). The created three-dimensional data is stored in the memory in the control device 10. Subsequently, the control device 10 creates machining condition data based on the three-dimensional data using the CAM application (S2).

Processing condition data is created for each solidified layer. First, it is assumed that the structure (implant in this example) is sliced with a preset number of solidified layers SOk (k is a natural number and the maximum number is kmax). At this time, the shapes of the plurality of solidified layers SOk formed by slicing the structure may be different. Therefore, the processing condition data is produced for each solidified layer Sok. As a result, a structure having a desired three-dimensional shape is produced.

The processing condition data of the solidified layer SOk of the kth layer (k = 1 to kmax) is created by the following method. Here, the first layer is the lowest layer, and the first kmax layer is the uppermost layer.

First, the control device 10 creates cross-sectional shape data of the solidified layer SOk in the k-th layer based on the three-dimensional data. Subsequently, the control device 10 creates machining condition data based on the cross-sectional shape data. The processing condition data includes region conditions and laser conditions. The control device 10 determines a region to be irradiated with the laser 30 based on the cross-sectional shape data, and defines it as a region condition. Subsequently, the laser conditions (power E of the laser 30, scanning speed S, scanning interval P) are determined according to the energy density (J / mm ² ) required to form the solidified layer. Information on the laser conditions is stored in advance in the HDD in the control device 10 according to the composition of the powder particles 40. By the above steps, processing condition data for each layer (solidified layer SOk) is created. The created plurality of processing condition data are stored in the memory in the control device 10.

Subsequently, the chamber 20 is evacuated using a vacuum pump (S3). After the inside of the chamber 20 is evacuated, a modeling process is performed to form a structure (S4: modeling process).

[Modeling process (S4)]
FIG. 8 is a flow chart showing details of the mixed layer forming step (S4) in FIG. 7. With reference to FIG. 8, the control device 10 first sets the counter k to “1” (S41), and starts producing the solidified layer SO1 of the first layer to be the lowest layer.

An inert gas (argon, nitrogen, helium, etc.) is supplied into the chamber 20 to preheat the base 208 arranged on the modeling table 203. At the time of preheating, the base 208 may be preheated without supplying an inert gas after being evacuated. Further, the base 208 may be preheated after supplying the inert gas without creating a vacuum. It is not necessary to preheat the base 208.

Subsequently, the control device 10 forms the powder bed 206 (S42: bed forming step). The control device 10 is instructed to raise the piston 204 of the powder supply chamber 202 to discharge the powder particles 40 which are the starting materials of the structure containing the titanium alloy. The powder supply chamber 202 discharges the powder particles 40 in response to an instruction from the control device 10. At this time, as shown in FIG. 9, the recorder 205 moves in the X direction. As a result, the discharged powder particles 40 move in the X direction and are supplied to the bed forming chamber 201. The powder particles are deposited on the base 208 and the modeling table 203 to form the powder bed 206.

The recorder 205 further moves horizontally (in the X direction) on the surface of the powder bed 206 on the base 208. At this time, the powder particles 40 move in the horizontal direction. The thickness of the powder bed 206 of the lowermost layer is, for example, about 5 to 1000 μm.

Next, the control device 10 preheats the powder bed 206 (S43). It can be preheated in various ways. For example, the powder bed 206 may be preheated by irradiating the powder bed 206 with the laser 30, or the powder bed 206 may be preheated by raising the temperature of the modeling table 203. The powder bed 206 may be preheated by heating the powder particles 40 in the bed forming chamber 201 with a heater.

Next, the powder bed 206 is scanned by the laser 30 to melt the powder bed 206 to form the solidified layer SO1 of the first layer (S44: melting step). The control device 10 reads the processing condition data of the solidification layer SO1 of the first layer from the memory among the plurality of processing condition data created in step S2. The control device 10 controls the laser 30 based on the read processing condition data.

Specifically, the control device 10 irradiates the predetermined region of the powder bed 206 with the laser 30 based on the region conditions in the processing condition data. The control device 10 further adjusts the output E (W), the scanning speed S (mm / sec), and the scanning interval P (mm) of the laser 30 based on the laser conditions in the processing condition data. At this time, the output E, the scanning speed S, the scanning interval P, and the effective molten pool width M (mm) satisfy the equations (1) to (4).

In the melting step (S44), not only the powder bed 206 but also the surface layer portion of the base 208 may be melted. The laser 30 is scanned in one direction (X direction) under the above laser conditions to melt the powder bed 206 to form the solidified layer SO1 as shown in FIG. At this time, the powder particles 40 arranged in the region other than the solidified layer SO1 in the powder bed 206 are neither melted nor sintered.

After the solidified layer SO1 of the first layer is formed, the control device 10 determines whether or not the counter k is kmax (S45). Here, since the counter k = 1 (NO in S45), the control device 10 increments the counter k to set k + 1 = 2 (S46). Then, the control device 10 prepares for the production of the solidified layer SO2 of the second layer.

The control device 10 lowers the modeling table 203 by the stacking pitch Δh (S47). As a result, as shown in FIG. 11, the surface of the powder bed 206 is lowered by Δh as compared with FIG.

After step S47 is completed, the process returns to step S42. At this time, the control device 10 forms a new powder bed 206 on the powder bed 206 on which the solidified layer SO1 is formed (S42: bed forming step). Specifically, according to the instruction of the control device 10, the piston 204 in the powder supply chamber 202 rises, and the powder particles 40 are discharged again. At this time, as shown in FIG. 12, the recorder 205 moves in the X direction. Therefore, the powder particles 40 move in the X direction to form a new powder bed 206 having a thickness Δh. The surface of the new powder bed 206 is leveled by the recoater 205.

Subsequently, the control device 10 preheats the powder bed 206 (S43) to form the solidified layer SO2 of the second layer (S44: melting step). At this time, the control device 10 irradiates the powder bed 206 with the laser 30 under the conditions satisfying the equations (1) to (4) based on the processing condition data of the kth layer (here, k = 2). As a result, as shown in FIG. 13, the powder bed 206 in the region irradiated with the laser 30 melts and solidifies, and the solidified layer SO2 is formed. By the above steps, the solidified layer SO2 is laminated on the solidified layer SO1.

Subsequently, the process proceeds to step S45, and the control device 10 repeats the operations from step S42 to step S47 until k = kmax, that is, until the uppermost solidified layer SOkmax is formed. That is, the control device 10 repeats the bed forming step (S42) and the melting step (S44) until the structure IC having a desired shape is completed as shown in FIG. The shape of the solidified layer SOk is not restricted by the shape of the lower solidified layer SOk-1, and can be made larger or smaller than the solidified layer SOk-1. Further, one or more holes can be formed in the shape of the solidified layer SOk. In this case, the structure can have a shape that cannot be obtained by ordinary cutting, such as having a closed space or having a complicated hole shape.

As described above, in the additive manufacturing method, the shape of each solidified layer SOk constituting the structure can be freely formed. Therefore, the structure IC can have a porous structure while increasing the degree of orientation of a specific crystal plane. Therefore, the elastic modulus of the structure IC containing the β-type titanium alloy can be lowered in terms of both the degree of orientation of the crystal plane and the porosity of the structure.

Further, in the present embodiment, the laser 30 which is a high energy heat source in the melting step satisfies the formulas (1) to (4). Therefore, in the manufactured structure IC containing the β-type titanium alloy, the orientation toward (100) is enhanced. Therefore, the elastic modulus of the structure IC can be further lowered, and the elastic modulus of the living bone can be approached.

Through the above manufacturing process, a structural IC containing a β-type titanium alloy is completed. The completed structure is removed from the chamber 20 and cut from the base (S5).
FIG. 15A is a photographic image of the structure of the Ti-15Mo-5Zr-3Al alloy produced by the production method of the present embodiment, and FIG. 15B shows another Ti-15Mo-5Zr-3Al alloy different from FIG. 15A. It is a photographic image of the structure of. In this manufacturing method, a plurality of through holes can be formed in the manufactured structure as shown in FIG. 15A, and a lattice-shaped structure can be manufactured as shown in FIG. 15B. Further, when the structure IC is an implant, a net-shaped product can be provided by creating a CAD model adapted to the patient's skeleton.

[Scanning direction of high energy source in each melting process]
As shown in FIG. 16, in the melting step (S44) of each solidified layer SOk, the scanning direction SDk of the laser 30 which is a high energy source is abbreviated as the scanning direction SDk-1 when forming the lower solidified layer SOk-1. They may intersect at right angles (FIG. 16 (A)) or may intersect in parallel (FIG. 16 (B)). Here, parallel means parallel in geometry and a range within ± 10 ° from parallel. In short, the scanning direction is not particularly limited.

However, the crystal orientation (organization) of the solidified layer can be controlled by adjusting the scanning direction of the laser 30. Therefore, by adjusting the scanning direction of the laser 30, for example, a combination of elastic moduli of a structure used as an implant depending on the orientation (low elastic modulus in only one direction, low elastic modulus in two directions, etc.) can be adjusted. Parts having various elastic moduli can be arranged in a mosaic pattern in the structure, and the elastic modulus of the entire structure can be adjusted.

An example of adjusting the scanning direction of the laser 30 is as follows. For example, as shown in FIG. 16A, the scanning direction SDk of the laser 30 in the solidified layer SOk may be orthogonal to each other with respect to the scanning direction SDk-1 in the lower solidified layer SOk-1, or in FIG. 16B. ), They are parallel to each other. In this case, the degree of orientation of a specific crystal plane with respect to the scanning direction can be increased, and the elastic modulus of the structure can be adjusted.

17 (A) and 17 (B) show (100) as seen from the DE direction of FIG. 16 when the Ti-15Mo-5Zr-3Al alloy was produced in the scanning directions of FIGS. 16 (A) and 16 (B). It is a pole figure of (011). In FIG. 17, a Ti-15Mo-5Zr-3Al alloy was manufactured with a laser output of 300 W during the structure manufacturing step (melting step), a scanning interval of 0.1 mm, and a scanning speed of 1000 mm / s. 17 (A) is the result when the scanning direction is FIG. 16 (A), and FIG. 17 (B) is the result when the scanning direction is FIG. 16 (B).

With reference to FIG. 17 (A), when the scanning direction SDk of the laser 30 in the solidified layer SOk is orthogonal to the scanning direction SDk-1 in the lower solidified layer SOk-1 (FIG. 16 (A)). ), The crystal plane (100) is preferentially oriented in both the two scanning directions and the modeling direction (the height direction of the modeled object in FIG. 16). On the other hand, referring to FIG. 17B, when the scanning direction SDk of the laser 30 in the solidified layer SOk is parallel to the scanning direction SDk-1 in the lower solidified layer SOk-1 (FIG. 16 (FIG. 16). B)), the crystal plane (100) is preferentially oriented in the scanning direction, and (011) is preferentially oriented in the modeling direction.

As described above, by adjusting the scanning direction, various crystal orientations can be given to the structure containing the β-type titanium alloy. The crystal orientation (organization) is not limited to FIGS. 17A and 17B. By appropriately adjusting the scanning direction, a plurality of two or more types of textures shown in FIGS. 17A and 17B can be formed.

[Other Embodiments]
The above-mentioned manufacturing method can be widely applied not only to Ti-15Mo-5Zr-3Al alloys but also to other titanium alloy structures. Other titanium alloys include, for example, Ti-6Al-4V ELI (Extra Low Interstitials) alloys specified in ASTM F136-13 (2013), Ti-6Al-7Nb alloys specified in ISO 5832-11 (2014), JIS. One or more selected from the group consisting of Ti-15Zr-4Nb-4Ta alloys specified in T7041-4 (2009).

Further, the structure manufactured by the above-mentioned manufacturing method does not have to be made of a β-type titanium alloy, and may contain a β-type titanium alloy. If the structure contains a β-type titanium alloy to some extent, the effect of the above manufacturing method will be more effectively exhibited. The above effect is particularly effective when the structure contains a titanium alloy of 30% or more by volume. Preferably, the content of the titanium alloy in the structure is 50% or more in volume%, more preferably 60% or more, still more preferably 70% or more. The content of the β-type titanium alloy in the structure may be substantially 100%.

In the above-mentioned production method, a single crystal containing a β-type titanium alloy can be produced, a columnar crystal material can be produced, or an equiaxed crystal material can be produced.

In the manufacturing method described above, preheating is performed in step S43 (see FIG. 8). However, preheating does not have to be performed.

In the above-mentioned manufacturing method, as an example, among the powder bed melt bonding methods belonging to the layered manufacturing method, the laser layered manufacturing method using a laser as a heat source is used. However, as the above-mentioned manufacturing method, an electron beam additive manufacturing method using an electron beam as a heat source may be used.

The structure manufactured by the above manufacturing method can be widely used as an implant for a living body. The structure manufactured by the manufacturing method of the present embodiment can be applied to, for example, implants for living bones, artificial joints, and the like.

The embodiments of the present invention have been described above. However, the embodiments described above are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and the above-described embodiment can be appropriately modified and implemented without departing from the spirit of the present invention.

40 Powder particles 206 Powder bed 208 Base IC structure SOk solidification layer

Claims (3)

A method for manufacturing a structure containing a β-type titanium alloy using a layered manufacturing method.
A bed forming step of supplying powder particles as a starting material of the structure onto a base to form a powder bed, and
The structure in which the plurality of the solidified layers are laminated is formed by alternately repeating the melting step of scanning the laser to melt the powder bed and forming the solidified layer containing the β-type titanium alloy. ,
In each of the melting steps, the scanning direction of the laser when forming the solidified layer of the kth layer (k is a natural number) is set to the solidified layer of the k-1th layer below the solidified layer of the kth layer. adjust the orthogonal or parallel to the laser scanning direction when forming the,
In each of the melting steps,
The energy output E (W), scanning speed S (mm / s), scanning interval P (mm), and effective molten pool width M (mm) of the high-energy heat source satisfy equations (1) to (4), β. A method for manufacturing a structure containing a type titanium alloy.
E> 200 (1)
S> 600 (2)
E / (S × P) ≧ 2.5 (3)
0.45 ≤ P / M ≤ 0.60 (4)
Here, the effective molten pool width M is the parabolic shape of the solidified portion formed in one scan using the high energy heat source in the melting step and having a parabolic shape whose vertical cross section is convex downward. It means the width (mm) of the bottom portion of the shape. The method for producing a structure containing a β-type titanium alloy according to claim 1.
The material of the structure containing the β-type titanium alloy is Ti-6Al-4V ELI (Extra Low Interstitials) alloy specified in ASTM F136-13 (2013) and Ti specified in ISO 5832-11 (2014). Select from the group consisting of -6Al-7Nb alloy, Ti-15Mo-5Zr-3Al alloy specified in ISO 5832-14 (2007), and Ti-15Zr-4Nb-4Ta alloy specified in JIS T7041-4 (2009). A method for producing a structure containing a β-type titanium alloy, which is one or more of the above. The method for producing a structure containing the β-type titanium alloy according to claim 1 or 2.
The laminating method is a laser laminating method for producing a structure containing a β-type titanium alloy.