JP7640432B2 - Manufacturing method for metal additive manufacturing products - Google Patents

Description

The present invention relates to a method for manufacturing a metal additive manufacturing product, and in particular, to a method for manufacturing a metal additive manufacturing product having an internal space.

The method for manufacturing a metal additive manufacturing product disclosed in Patent Document 1 uses a three-dimensional additive manufacturing method to manufacture a metal additive manufacturing product having a rod-shaped structure with multiple pipes.

JP 2020-070453 A

The present inventors have discovered the following problems.
When a metal additive manufacturing product having an internal space is manufactured using a three-dimensional additive manufacturing method, a rough surface area may be generated on the upper inner wall surface of the internal space. In such a case, stress may be concentrated in the rough surface area, making the product more susceptible to breakage.

In view of the above-mentioned problems, the present invention aims to provide a method for manufacturing a metal additive manufacturing product that smooths the inner wall surface of the internal space.

A method for producing a metal additive manufacturing product according to one aspect of the present invention includes the steps of:
A method for manufacturing a metal additive manufacturing product having an internal space, comprising the steps of:
a plating process for plating an inner wall surface of the internal space of the metal additive manufacturing product to form a plating film on the inner wall surface;
and a heating step of heating the metal additive manufacturing product to generate a molten material on the inner wall surface.

With this configuration, the molten material is generated on the inner wall surface, and penetrates into the bottom of the roughened area of the inner wall surface. This smoothes the surface of the roughened area, suppresses stress concentration, and prevents breakage.

The method may also be characterized in that in the heating step, the metal additive manufacturing product is heated to melt the plating film, thereby generating the molten body on the inner wall surface.

With this configuration, a molten material derived from the plating film can be generated on the inner wall surface, allowing it to penetrate to the bottom of the roughened area of the inner wall surface. A smooth film can be formed on the surface of the roughened area, making the surface of the roughened area smooth.

The melting point of the plating film may also be lower than the melting point of the metal additive manufacturing product.

With this configuration, the temperature of the metal additive manufacturing product can be set to a temperature lower than the melting point of the metal additive manufacturing product during the heating process. This makes it possible to suppress the thermal effects on the metal additive manufacturing product.

The method further includes a solder paste supplying step of supplying a solder paste onto the plated film after the plating step is performed,
In the heating step, the metal additive manufacturing product may be heated to melt the solder paste, thereby generating the molten body on the inner wall surface.

According to this configuration, a molten body derived from the solder paste can be generated on the inner wall surface, and can penetrate to the bottom of the roughened area of the inner wall surface. A smooth film can be formed on the surface of the roughened area, thereby smoothing the surface of the roughened area. Furthermore, in many cases, the melting point of the solder paste is lower than the melting points of the plating film and the metal additive manufacturing product. Therefore, the temperature of the metal additive manufacturing product during the heating process can be suppressed, and the thermal effects on the metal additive manufacturing product can be suppressed.

The plating film may be a silver plating film.

With this configuration, the silver plating film and the film derived from the solder paste are firmly bonded, so a stable film derived from the solder paste can be formed on the surface of the roughened area.

When a surface roughness region is present on the inner wall surface of the internal space of the metal additive manufacturing product,
The heating step may be characterized in that the metal additive manufacturing product is heated while maintaining an orientation of the metal additive manufacturing product such that the rough surface region is located below the internal space.

With this configuration, during the heating process, the molten material is concentrated in the rough surface area located at the bottom of the internal space. This increases the thickness of the smooth film and smooths the surface of the rough surface area.

The present invention can provide a method for manufacturing a metal additive manufacturing product that smooths the inner wall surface of the internal space.

1 is a flowchart showing a method for manufacturing a metal additive manufacturing product according to the first embodiment. 5A to 5C are schematic diagrams showing some steps of a manufacturing method for a metal additive manufacturing product according to the first embodiment. 5A to 5C are schematic diagrams showing some steps of a manufacturing method for a metal additive manufacturing product according to the first embodiment. 13 is a graph showing temperature versus elapsed time in an example of a heating step ST12 in the manufacturing method for a metal additive manufacturing product according to embodiment 1. 10 is a flowchart showing a method for manufacturing a metal additive manufacturing product according to a second embodiment. 5A to 5C are schematic diagrams showing some steps of a method for manufacturing a metal additive manufacturing product according to embodiment 2. 5A to 5C are schematic diagrams showing some steps of a method for manufacturing a metal additive manufacturing product according to embodiment 2. 1 is a photograph showing the internal space of a metal additive manufacturing product after a plating film has been formed. 1 is a photograph showing the internal space of a metal additive manufacturing product according to one embodiment. FIG. 2 is a schematic diagram showing an observation site of the internal space of the metal additive manufacturing product according to the embodiment. FIG. 2 is a schematic cross-sectional view showing a cross-section of a portion observed in the internal space of a metal additive manufacturing product according to an embodiment. 1 is an example of the results of an EPMA (electron probe microanalyzer) analysis of a cross section of a metal additive manufacturing product after a plating film has been formed. FIG. 1 is an enlarged view of an example of the results of an EPMA analysis of a cross section of a metal additive manufacturing product after a plating film has been formed. 1 is an example of the results of an EPMA analysis of a cross section of a metal additive manufacturing product according to one embodiment. FIG. 2 is an enlarged view of an example of the results of an EPMA analysis of a cross section of a metal additive manufacturing product according to one embodiment.

Specific embodiments to which the present invention is applied will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. In addition, the following descriptions and drawings have been simplified as appropriate for clarity of explanation.

(Embodiment 1)
A first embodiment will be described with reference to Figs. 1 to 4. Fig. 1 is a flowchart showing a method for manufacturing a metal additive manufacturing product according to the first embodiment. Figs. 2 and 3 are schematic diagrams showing some steps of the method for manufacturing a metal additive manufacturing product shown in Fig. 1. Fig. 4 is a graph showing temperature versus elapsed time in an example of the heating step ST12 shown in Fig. 1. It should be noted that the right-handed xyz coordinate system shown in Fig. 2 and other drawings is of course for the convenience of explaining the positional relationship of the components. Usually, the z-axis positive direction is vertically upward, and the xy plane is a horizontal plane, which is common between the drawings.

As shown in Figures 1 and 2, plating is performed on the inner wall surface 10b of the internal space 10a of the metal additive manufacturing product 10 to form a plating film 1 on the inner wall surface 10b of the internal space 10a (plating process ST11).

The metal additive manufacturing product 10 is a product manufactured using a metal additive manufacturing (AM) method. In the metal additive manufacturing method, metal powder is melted and solidified, and then laminated. Powders made of a wide variety of metal materials can be used as the metal powder. The metal material may be any metal material to which the metal additive manufacturing method can be applied, such as maraging steel, die steel, and aluminum alloy. Die steel includes materials equivalent to SKD61 defined in the JIS standard. The metal additive manufacturing product 10 has an internal space 10a. The internal space 10a may have a shape extending on a virtual curve in three-dimensional space, such as a circuit, a passage, a pipe, etc. The virtual curve may have multiple bends. The internal space 10a may allow a cooling medium or oil to pass through. The metal additive manufacturing product 10 can be applied to a wide variety of products, but is suitable for die-casting dies and various engine parts that include cooling circuits or oil passages, for example. When a structure having an internal space 10a that extends along a virtual curve in three-dimensional space is manufactured using metal additive manufacturing, meltdown can occur, causing a rough surface area 10c to appear in the upper part of the internal space 10a.

For example, electroless plating can be used as the plating process. Examples of electroless plating include electroless nickel plating, electroless gold plating, electroless silver plating, electroless copper-nickel plating, and electroless palladium plating. Specifically, the plating liquid GL1 is supplied to the internal space 10a of the metal additive manufacturing product 10, and the plating liquid GL1 is brought into contact with the inner wall surface 10b. The plating liquid GL1 contains metal ions. The metal ions are ionized metal atoms of the same type as the metal that constitutes the plating film 1. The electroless plating may be autocatalytic electroless plating. The metal ions contained in the plating liquid GL1 are reduced, and the plating film 1 is precipitated on the inner wall surface 10b. It is preferable to add a reducing agent to the plating liquid GL1 as appropriate. The addition of this reducing agent allows for thick plating, i.e., an increase in the film thickness of the plating film 1. The plating film 1 covers the inner wall surface 10b of the internal space 10a and also covers the rough surface area 10c.

1 and 3, the metal additive manufacturing product 10 is heated in a vacuum furnace 100 to generate a molten body on the inner wall surface 10b (heating step ST12). Specifically, the metal additive manufacturing product 10 is placed in the vacuum furnace 100 so that the rough surface region 10c is located on the lower side of the internal space 10a (here, in the z-axis negative direction). The metal additive manufacturing product 10 is heated and maintained, and then cooled so as to follow the temperature history curve H1 shown in FIG. 4. More specifically, the metal additive manufacturing product 10 is first heated using the vacuum furnace 100, and the temperature of the metal additive manufacturing product 10 is raised from room temperature T ₀ to a predetermined temperature T _1. In addition, the metal additive manufacturing product 10 is heated and maintained at the predetermined temperature T ₁ until a predetermined time t ₂ -t ₁ has elapsed. After a predetermined time t ₂ -t ₁ has elapsed, the metal additive manufacturing product 10 is cooled until the temperature of the metal additive manufacturing product 10 drops from the predetermined temperature T ₁ to room temperature T ₀ .

The predetermined temperature T ₂ and the predetermined time t ₂ -t ₁ may be set so as to melt the plating film 1 and generate a molten body. Specifically, the predetermined temperature T ₂ may be higher than the melting point of the plating film 1. More specifically, when the plating film 1 is made of nickel, the predetermined temperature T _{2 may be 900°C or higher. When the plating film 1 is made of gold, the predetermined temperature T 2} may be 1064°C or higher. When the plating film 1 is made of silver, the predetermined temperature T ₂ may be 961°C or higher. When the plating film 1 is made of copper, the predetermined temperature T ₂ may be 1084°C or higher. When the plating film 1 is made of palladium, the predetermined temperature T ₂ may be 1552°C or higher. The melting point _of the plating film 1 may be lower than the melting point of the metal additive manufacturing product 10. The predetermined time t ₂ -t ₁ may be determined according to the volume of the plating film 1. The plating film 1 is melted to generate a molten mass. The molten mass solidifies to form the film 2.

Note that the metal additive manufacturing product 10 may be thermally affected by carrying out the heating step ST12. Even in such a case, the metal additive manufacturing product 10 maintains the properties required for a metal additive manufacturing product, such as mechanical strength. This is because the predetermined temperature T ₂ and the predetermined time t ₂ -t ₁ are set so as to be able to melt the plating film 1 and generate a molten body. This is also because the metal additive manufacturing product 10 has a significantly larger volume than the plating film 1.

After carrying out the heating step ST12, the metal additive manufacturing product 10 may be heat-treated as necessary. This heat treatment can appropriately adjust the material of the metal additive manufacturing product 10 and suppress the thermal effects on the metal additive manufacturing product 10 caused by carrying out the heating step ST12. Such heat treatments include, for example, quenching and aging.

As described above, the molten material is generated on the inner wall surface 10b, and penetrates into the bottom of the rough surface region 10c of the inner wall surface 10b. The molten material solidifies, and the film 2 is formed. The surface of the plating film 1 has a shape that follows the surface of the inner wall surface 10b. Meanwhile, the surface of the film 2 changes from the surface of the plating film 1 to a shape that is closer to a flat surface due to the surface tension of the molten material. Therefore, the film 2 is smoother than the plating film 1. The film 2 covers the inner wall surface 10b and also covers the rough surface region 10c. This smooths the surface of the rough surface region 10c and suppresses stress concentration. The occurrence of damage on the inner wall surface 10b of the internal space 10a of the metal additive manufacturing product 10 is suppressed.

In addition, in the heating step ST12 according to the first embodiment, the metal additive manufacturing product 10 is heated to melt the plating film 1, thereby generating a molten material on the inner wall surface 10b. With this configuration, the molten material derived from the plating film 1 is generated on the inner wall surface 10b, and can penetrate to the bottom of the rough surface region 10c of the inner wall surface 10b. A smooth film 2 can be formed on the surface of the rough surface region 10c, thereby smoothing the inner wall surface 10b of the internal space 10a.

In addition, the melting point of the plating film 1 according to this embodiment 1 may be lower than the melting point of the metal additive manufacturing product 10. In such a case, the temperature of the metal additive manufacturing product 10 can be suppressed in the heating process ST12 to suppress the thermal effects on the metal additive manufacturing product 10.

(Embodiment 2)
Next, a second embodiment will be described with reference to Fig. 5 to Fig. 7. Fig. 5 is a flow chart showing a method for manufacturing a metal additive manufacturing product according to the second embodiment. Fig. 6 and Fig. 7 are schematic diagrams showing some steps of the method for manufacturing a metal additive manufacturing product shown in Fig. 5.

As shown in Figures 5 and 6, electroless silver plating is performed on the inner wall surface 10b of the internal space 10a of the metal additive manufacturing product 10 to form a silver plating film 1a on the inner wall surface 10b of the internal space 10a (plating process ST21). The plating process ST21 has the same configuration as the plating process ST11 shown in Figures 1 and 2, except that it is limited to performing electroless silver plating to form the silver plating film 1a.

Next, as shown in Figures 5 and 7, solder paste 2a is supplied onto the silver plating film 1a (solder paste supply step ST22).

The polishing body 3 can be used to supply the solder paste 2a onto the silver plating film 1a. Specifically, as shown in FIG. 7, the solder paste 2a is applied to the polishing body 3. The polishing body 3 is sandwiched between the first clamping portion 24 and the second clamping portion 25. One end of the string 4 is attached to the second clamping portion 25. The first clamping portion 24 is disposed between one end and the other end of the string 4. When the other end of the string 4 is pulled so as to move it away from the polishing body 3, the one end of the string 4 pulls the second clamping portion 25 toward the polishing body 3. This brings the second clamping portion 25 closer to the first clamping portion 24. The string 5 is attached to the first clamping portion 24. The second clamping portion 25 is disposed between one end and the other end of the string 5. When the other end of the string 5 is pulled away from the polishing body 3, one end of the string 4 pulls the first clamping portion 24 toward the polishing body 3. This brings the first clamping portion 24 closer to the second clamping portion 25. The polishing body 3 is clamped by bringing the first clamping portion 24 and the second clamping portion 25 closer to each other. The polishing body 3, the first clamping portion 24, and the second clamping portion 25 each have a hole that runs through them, and the string 4 and the string 5 may pass through these holes. By inserting this clamped polishing body 3 into the internal space 10a of the metal additive manufacturing product 10, the solder paste 2a adheres to the silver plating film 1a. As described above, the solder paste 2a is supplied onto the silver plating film 1a.

Next, as shown in Figures 1 and 3, the metal additive manufacturing product 10 is heated in a vacuum furnace 100 to generate a molten body on the inner wall surface 10b (heating step ST23). Specifically, the metal additive manufacturing product 10 is heated to melt the solder paste 2a, thereby generating a molten body on the inner wall surface 10b. Unlike the heating step ST12 shown in Figure 3, it is not necessary to heat the metal additive manufacturing product 10 to melt the silver plating film 1a.

Specifically, the metal additive manufacturing product 10 is heated and held, and then cooled so as to follow the temperature history curve H1 shown in FIG. 4. The predetermined temperature T ₂ and the predetermined time t ₂ -t ₁ may be set so as to melt the solder paste 2a and generate a molten body. Specifically, the predetermined temperature T ₂ may be higher than the melting point of the solder paste 2a and lower than the melting point of the silver plating film 1a, for example, 300°C. The predetermined time t ₂ -t ₁ may be determined according to the volume of the solder paste 2a. The molten body is generated by melting the solder paste 2a. The molten body solidifies to form a film 2b.

In many cases, the melting point of the solder paste 2a is significantly lower than the melting point of the metal material of the metal additive manufacturing product 10. Therefore, the predetermined temperature _T2 in the heating step ST23 is significantly lower than the melting point of the metal material of the metal additive manufacturing product 10. Therefore, by performing the heating step ST23, the metal additive manufacturing product 10 is hardly affected by heat. Furthermore, after performing the heating step ST23, there is almost no need to perform a heat treatment of the metal additive manufacturing product 10.

As described above, the melt is generated on the inner wall surface 10b, and penetrates into the bottom of the rough surface region 10c of the inner wall surface 10b. The melt solidifies and the film 2b is formed. The surface of the silver plating film 1a and the surface of the solder paste 2a supplied to the silver plating film 1a have a shape that follows the surface of the inner wall surface 10b. On the other hand, the surface of the film 2b changes from the surfaces of the silver plating film 1a and the solder paste 2a to a shape close to a flat surface due to the surface tension of the melt. Therefore, the film 2b is smoother than the silver plating film 1a. The film 2b covers the inner wall surface 10b and also covers the rough surface region 10c. This smoothes the surface of the rough surface region 10c, suppresses stress concentration, and suppresses the occurrence of breakage. Since the predetermined temperature _T2 in the heating process ST23 is low, it is not necessary to melt the silver plating film 1a, and there is almost no thermal effect on the metal additive manufacturing product 10.

In addition, in the heating step ST23 according to the second embodiment, a film 2b derived from the solder paste 2a is formed on the silver plating film 1a. Since the silver plating film 1a and the film 2b derived from the solder paste 2a are firmly bonded to each other, a stable film 2b derived from the solder paste 2a can be formed on the surface of the rough surface region 10c.

In the above-mentioned solder paste supplying step ST22, the solder paste 2a is supplied onto the silver-plated film 1a using the polishing body 3 to which the solder paste 2a is applied, but the present invention is not limited to this, and the solder paste 2a may be supplied onto the silver-plated film 1a using other methods. For example, the solder paste 2a may be supplied onto the silver-plated film 1a by injecting the solder paste 2a into the internal space 10a of the metal additive manufacturing product 10 and then inserting a piston into the internal space 10a. For example, the solder paste 2a may be filled into a capsule, and the capsule may be sandwiched between multiple polishing bodies 3. Next, the multiple polishing bodies 3 and the capsule may be moved into the internal space 10a of the metal additive manufacturing product 10, the capsule may be broken, and the solder paste 2a may be supplied onto the silver-plated film 1a.

In addition, in the heating step ST23 described above, the posture and orientation of the metal additive manufacturing product 10 are not specified, but similar to the heating step ST12 shown in FIG. 3, the metal additive manufacturing product 10 may be placed in the vacuum furnace 100 so that the rough surface region 10c is located below the internal space 10a (here, in the negative z-axis direction).

(Example)
Next, examples will be described with reference to Figs. 8 to 15. Fig. 8 is a photograph showing the internal space of a metal additive manufacturing product after a plating film is generated. Fig. 9 is a photograph showing the internal space of a metal additive manufacturing product according to one example. Fig. 10 is a schematic diagram showing an observation site of the internal space of a metal additive manufacturing product according to an example. Fig. 11 is a schematic cross-sectional view showing a cross-section of the site shown in Fig. 10. Fig. 12 is an example of the result of EPMA analysis of a cross-section of a metal additive manufacturing product after a plating film is generated. Fig. 13 is an enlarged view of an example of the result of EPMA analysis shown in Fig. 12. Fig. 14 is an example of the result of EPMA analysis of a cross-section of a metal additive manufacturing product according to one example. Fig. 15 is an enlarged view of an example of the result of EPMA analysis shown in Fig. 14.

An example of a metal additive manufacturing product 10 was manufactured using the metal additive manufacturing method. The metal material of the example of the metal additive manufacturing product 10 is maraging steel. An example of the metal additive manufacturing product 10 was cut. In the example of the cut metal additive manufacturing product 10, the inner wall surface 10b of the internal space 10a can be visually observed. Furthermore, a plating step ST11 was performed on an example of the metal additive manufacturing product 10 using an example of the manufacturing method for a metal additive manufacturing product according to the first embodiment. Electroless nickel plating was used as the plating process. In the heating step ST12, the predetermined temperature T ₁ was set to 900° C., the predetermined time t ₁ was set to 60 min _, the predetermined time t ₂ was set to 90 min, and the predetermined time t ₃ was set to 150 min.

Figure 8 shows a metal additive manufacturing product 110, which is an example of a metal additive manufacturing product 10 on which a plating film 1 has been formed. Furthermore, a heating process ST12 was performed on the metal additive manufacturing product 110. Figure 9 shows a metal additive manufacturing product 210, which is an example of a metal additive manufacturing product 10 on which a film 2 has been formed.

As shown in Figures 10 and 11, the metal additive manufacturing product 10 has observation areas P1, P2, P3, and P4 in the cross section 10d near the inner wall surface 10b. EPMA analysis was performed on the observation areas P1, P2, P3, and P4 in the cross section 10d of the metal additive manufacturing products 110 and 210. The analysis results for Fe (iron) and Ni (nickel) are shown in Figures 12 and 14, respectively. Additionally, enlarged views of the observation area P3 are shown in Figures 13 and 15, respectively.

As shown in FIG. 8, a rough surface portion has occurred on the inner wall surface 110a of the metal additive manufacturing product 110. On the other hand, as shown in FIG. 9, the inner wall surface 210a of the metal additive manufacturing product 210 is smoother than the inner wall surface 110a of the metal additive manufacturing product 110 shown in FIG. 8. Therefore, it was confirmed that the rough surface portion of the inner wall surface 210a of the metal additive manufacturing product 210 has been smoothed.

As shown in FIG. 12, the Fe analysis results confirmed that rough surfaces occurred in the observation areas P1, P2, P3, and P4 on the cross section 10d of the metal additive manufacturing product 110. The Ni analysis results confirmed that the plating film covered the rough surfaces in the observation areas P1, P2, P3, and P4 on the cross section 10d of the metal additive manufacturing product 110. The surface shape of the plating film tends to roughly follow the surface shape of the rough surfaces. As shown in FIG. 13, valley shapes resulting from the surface shape of the rough surfaces remain on the surface of the plating film.

As shown in FIG. 14, the Fe analysis results confirmed that rough surfaces occurred in the observation areas P1, P2, P3, and P4 in the cross section 10d of the metal additive manufacturing product 210. The Ni analysis results confirmed that the plating film covered the rough surfaces in the observation areas P1, P2, P3, and P4 in the cross section 10d of the metal additive manufacturing product 110. The surface shape of the plating film does not follow the surface shape of the rough surfaces. As shown in FIG. 15, the plating film sufficiently fills the valley-shaped portions in the surface shape of the rough surfaces. Almost no valley-shaped portions resulting from the surface shape of the rough surfaces remain on the surface of the plating film. The surface shape of the plating film is smoother than the surface shape of the rough surfaces.

The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the invention. The present invention may also be implemented by combining the above-described embodiment or examples thereof as appropriate.

1 Plating film 1a Silver plating film 2, 2b Film 2a Solder paste 3 Polished body 4, 5 String 10, 110, 210 Metal additive manufacturing product 10a Internal space 10b, 110b, 210b Inner wall surface 10c Rough surface area 10d Cross section 24 First clamping part 25 Second clamping part 100 Vacuum furnace GL1 Plating liquid H1 Temperature history curve P1, P2, P3, P4 Observation area ST11, ST21 Plating process ST12, ST23 Heating process ST22 Solder paste supply process
T ₀ Room temperature T ₁ , T ₂ Temperature t ₁ , t ₂ , t ₃ hours

Claims (4)

A method for manufacturing a metal additive manufacturing product having an internal space, comprising the steps of:
a plating process for plating an inner wall surface of the internal space of the metal additive manufacturing product to form a plating film on the inner wall surface;
A heating step of heating the metal additive manufacturing product to melt the plating film to generate a molten body on the inner wall surface ,
The melting point of the plating film is lower than the melting point of the metal additive manufacturing product.
A method for manufacturing metal additive manufacturing products. A method for manufacturing a metal additive manufacturing product having an internal space, comprising the steps of:
a plating process for plating an inner wall surface of the internal space of the metal additive manufacturing product to form a plating film on the inner wall surface;
a solder paste supplying step of supplying a solder paste onto the plating film after the plating step is performed;
A heating step of heating the metal additive manufacturing product to melt the solder paste and generate a molten body on the inner wall surface ,
The melting point of the solder paste is lower than the melting point of the metal additive manufacturing product and the melting point of the plating film;
A method for manufacturing metal additive manufacturing products. The plating film is a silver plating film.
The method for producing a metal additive manufacturing product according to claim 1 . When a surface roughness region is present on the inner wall surface of the internal space of the metal additive manufacturing product,
In the heating step, the metal additive manufacturing product is heated while maintaining a posture of the metal additive manufacturing product such that the rough surface region is located below the internal space.
The method for producing a metal additive manufacturing product according to any one of claims 1 to 3 .

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