JP3346380B2 - Method for removing fine voids on casting surface and stirring tool used for the method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing minute voids on a surface of, for example, an aluminum alloy casting and a stirring tool used for the method. In this specification,
Unless otherwise specified, the surface refers to the surface and the surface layer of the casting, and the fine void refers to either or both of fine irregularities on the surface and fine voids in the surface layer.

[0002]

2. Description of the Related Art In the vicinity of a surface layer of a casting or a die-cast product made of aluminum or an alloy thereof (hereinafter, simply referred to as aluminum), hydrogen gas dissolved in a molten metal or about 0.1 to 0 due to metal shrinkage. Fine voids of 0.5 mm are likely to occur. Also, fine irregularities may occur on the casting surface of the casting surface made of aluminum, other metals, and alloys. If these minute voids and irregularities are present on the surface layer or surface, the mechanical properties and surface treatment characteristics of a cast product such as aluminum are significantly reduced.

[0003] For this reason, for example, in order to remove fine irregularities on the surface of an aluminum casting, a method for modifying the surface of an aluminum casting has been proposed (Japanese Patent Laid-Open No. 10-183316). This method is a surface modification method for removing fine irregularities by subjecting a surface of an aluminum casting to a probe that rotates at high speed and performing friction stir welding to soften the frictional heat (see the above publication). However, in the above-mentioned reforming method, no study has been made on fine voids in the vicinity of the surface layer where the influence of strength reduction is greater than that of surface irregularities in castings such as aluminum.

In order to efficiently remove fine irregularities and voids by modifying the surface and surface layer over a wide area of the casting, it is conceivable to use the probe with a large diameter. However, the use of a tool having a large-diameter probe to expand the reforming treatment area is naturally limited in terms of the strength of the probe itself and equipment including the tool having the probe. For this reason, it is necessary to repeat the operation of bringing the normal-sized probe in the stirring tool into contact with and moving along the surface of a wide range of castings a plurality of times. However, there is a problem that a dent having a shape following the probe is formed at the trace where the probe is pulled out from the casting surface in each operation, and the strength of the casting is rather lowered. Moreover, if the recess is filled with metal of the same material, there is a problem that the number of steps is further increased and the cost is increased.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, and enables fine voids and irregularities on the casting surface and surface layer to be reliably and efficiently removed. It is an object to propose a removing method and a stirring tool used for the removing method.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention reduces the number of insertion and withdrawal operations in the operation of a stirring tool including a main body and a probe rotating while moving with respect to a casting surface. The present invention has been made with the idea of suppressing the metal material fluidized in the casting from scattering to the outside and eliminating the supply shortage of the metal material in the stirring section formed on the movement trajectory of the stirring tool. That is, the method for removing fine voids on the casting surface of the present invention,
A stirring tool including a main body that moves while rotating along the surface of the casting and a probe protruding from the center of the bottom surface, the probe is positioned near the surface of the casting while the bottom surface abuts or substantially abuts the surface of the casting. When removing the minute gap by inserting, the stirring tool is continuously moved so that the movement trajectories are adjacent to each other while including a U-turn or a right or arbitrary angle turn with respect to the surface of the casting in plan view. , Characterized in that.

According to this, near the surface of the casting where the probe and the bottom of the main body of the stirring tool have moved while rotating, the metal material of the casting material is stirred in a solid state, and the dense structure which is fluidized and solidified is stirred. A part is formed along the movement locus of the tool. In addition, such a movement locus refers to a locus where the probe of the stirring tool and the bottom surface of the main body have moved along the surface of the casting. Further, after the stirring tool is linearly moved along the casting surface, it is U-turned to continuously form the stirring portion adjacent to the original movement trajectory, or the linear movement and the U-turn are repeated several times. By moving the casting surface in a wide range, it is possible to remove fine voids and surface irregularities on the surface layer of the casting. Alternatively, after the stirring tool is moved linearly along the casting surface, a right-angled L-turn is made to move adjacent to the original movement trajectory, and the L-turn and the linear movement are alternately repeated or approximated to a concentric circle. By moving between the center and the periphery of the casting surface while adjoining the moving trajectories in a spiral shape, it is possible to remove fine voids and surface irregularities in the casting surface layer over a wide range. In addition, since the movement of the stirring tool is performed continuously, the dent remaining in the trace of the last extraction of the probe of the tool can be limited to only one place,
It is also possible to suppress a decrease in strength near the casting surface. Alternatively, even when the moving operation is performed a plurality of times depending on the shape of the casting surface, the dent of the trace from which the probe is extracted can be minimized.

The bottom surface (shoulder) of the main body of the stirring tool contacts (abuts or substantially abuts on) the casting surface while pressing it against the casting surface, and flows in the solid state of the casting material by the probe of the tool. This suppresses scattering of the converted metal material to the outside. As the stirring tool, a metal or an alloy having a higher melting point and a harder metal than the metal material of the casting, for example, a tool formed from high-speed tool steel is used. The stirring tool is not particularly limited as long as it has the same form as a welding tool including a cylindrical main body used for so-called friction stir welding and a probe protruding from the center of the bottom surface thereof. In particular, those having a ridge that spirally protrudes from the peripheral edge toward the base end of the probe on the bottom surface of the probe are particularly preferably used.

[0009] The present invention also includes a method for removing minute voids on the surface of a casting, in which adjacent stirring portions near the surface of the casting stirred by the probe of the stirring tool include portions overlapping each other. According to this, the stirrer of the dense structure in which the metal material of the casting material is stirred and fluidized in the solid state has an overlapping portion along the stirrer formed adjacent to the former. It is formed. Therefore, the fine irregularities on the surface of the casting can be surely removed from the base, and the minute voids near the surface layer can be reliably removed. be able to.

Further, when the stirring tool is moved to an adjacent movement trajectory on the surface of the casting, the pressing amount of the bottom of the tool main body in the first stirring is smaller than the bottom of the tool main body in the second stirring adjacent thereto. The method also includes a method of removing fine voids on the surface of the casting, in which the indentation of the casting is increased by 0.1 mm or more in the depth direction of the casting. According to this, the surface of the first stirring portion formed on the movement locus of the stirring tool closer to the beginning is slightly pressed by the bottom surface of the tool main body, but the adjacent movement locus formed continuously. The surface of the second agitating section formed at the bottom is further depressed. For this reason, the supply amount of the fluidized metal material to be supplied to the second and subsequent stirring units can be optimized, and internal defects that form voids in the stirring unit due to insufficient supply can be reliably prevented. The first stirring and the second stirring relatively indicate the stirring positions near the beginning and the end point when the stirring tool is moved.
Further, if the increasing amount of indentation is less than 0.1 mm, a surface defect may occur, and this is excluded.
Further, the upper limit of the amount of indentation to be increased is not particularly defined, but if it exceeds 0.5 mm, for example, burrs of the metal material extruded along both sides of the surface of the agitating portion become remarkable. A more desirable increased indentation is in the range of 0.15 to 0.25 mm.

In addition, when the stirring tool is moved while rotating along the surface of the casting, the axes of the main body and the probe of the stirring tool are maintained in a vertical position with respect to the casting surface, and a minute gap in the casting surface is provided. Removal methods are also included. According to this, when the stirring tool is made to make a U-turn or an L-turn, the moving operation can be continuously performed in the same posture, and the stirring part of the linear moving part and the stirring part of the bent part such as the U-turn can be used. Can be formed as a uniform structure. Further, the function of adjusting the inclination angle of the stirring tool becomes unnecessary, and the arrangement of the main body and the probe in the stirring tool and the driving source for rotating these components, and the power transmission mechanism between the driving source, the main body and the probe can be easily and easily performed. It can also be simplified.

On the other hand, the stirring tool of the present invention, which is particularly preferably used in the method for removing fine voids, is a tool inserted near the surface of a casting to remove fine voids, while rotating along the surface of the casting. A moving cylindrical main body, a probe protruding from the center of the bottom surface of the main body, and a ridge provided on the bottom surface of the main body so as to spirally protrude from the periphery of the bottom surface toward the base end of the probe. And including
It is characterized. According to this, the metal material plasticized and fluidized by the probe inserted near the casting surface,
A spiral ridge provided on the bottom surface of the main body that comes into contact with the casting surface while being pressed against the casting surface is guided to flow toward the probe. As a result, a stirrer with a dense and uniform metal structure by reliably preventing the occurrence of surface defects whose surface is dented due to lack of material in the stirrer and internal defects due to void formation, over a wide range near the casting surface. It can be formed continuously.

[0013] The present invention also includes an agitation tool in which the spirally projecting ridges have three-quarters or more turns on the bottom surface of the main body. According to this, in the vicinity of the bottom surface of the tool body, it is possible to prevent the metal material of the plastic material that has been plasticized and fluidized from scattering and overflowing to the outside, and it is possible to more reliably prevent surface defects in the stirring section. In addition, if the above-mentioned ridge is less than three-quarters of a turn, the above-mentioned effect becomes insufficient, so that this is excluded.

[0014] Further, a stirring tool, wherein a ratio D / d of a diameter (D) of the main body including the bottom surface to a diameter (d) of the probe is 1.8 or more, is also included. According to this, since the main body and the bottom surface of the probe have a large diameter with respect to the probe, the metal material of the casting material plasticized and fluidized by the probe is retained in the stirring section by the spiral ridge provided on the bottom surface, A sound stirring part without surface defects can be formed. The above ratio D / d
However, when the diameter is less than 1.8, the diameter of the bottom surface of the main body approaches the probe, and the fluidized metal material cannot be stored near the bottom surface, but may be scattered outside to cause surface defects. The castings to which the method for removing fine voids and the stirring tool of the present invention are applied include not only aluminum castings but also iron castings, steel castings, castings of titanium and its alloys, and the like.

[0015]

Preferred embodiments of the present invention will be described below with reference to the drawings. FIGS. 1A and 1B show an outline of a method for removing fine voids on a casting surface according to the present invention, and a use state of a stirring tool 10 used for the method. As shown, along the surface 2 of the aluminum casting 1, a cylindrical body 12 is provided.
A stirring tool 10 including a probe 14 projecting coaxially from the center of the bottom surface (shoulder) 13 is rotated and moved rightward in FIG. 1A. The stirring tool 10
The probe 14 is inserted toward the surface layer of the casting 1 while rotating at a rotation speed of 500 to 15000 rpm and applying a pushing force of 1 to 30 kN along its axis toward the surface 2 of the casting 1. 1 (A) 50mm to the right
It is sent at a moving speed of 2 meters / min. As shown in FIG. 1B, a screw (thread and thread valley) 16 is formed on the peripheral surface of the probe 14.

As shown in FIGS. 1A and 1B, at the mark where the stirring tool 10 has passed, the aluminum of the casting 1 plasticized and fluidized in the solid state by the probe 14 is stirred. The agitation section 4 having a solidified and dense structure is formed. Further, the surface 6 of the stirring unit 4 is provided with a stirring tool 10.
As a result of being pressed against the bottom surface 13 of the main body 12 at
Is slightly depressed by about 0.2 mm from the surface 2 of FIG.
The stirring section 4 and its surface 6 as described above are continuously formed along the movement locus of the stirring tool 10. That is,
The surface 6 of the stirring section 4 is common to the movement locus of the stirring tool 10. The screw 16 on the peripheral surface of the probe 14 has a function of increasing the contact area with aluminum and promoting the above-mentioned fluidization and stirring action.

The stirring tool 10 is formed of, for example, a high-speed tool steel having a melting point higher than that of the aluminum casting 1 and hard, and as shown in FIGS. 2A to 2C, a bottom surface 13 of a cylindrical main body 12. In addition, from the periphery of the bottom surface 13 toward the base end of the probe 14, there is integrally formed a spiral ridge 17 that protrudes in a spiral shape about two rounds when viewed from the bottom in FIG. As shown by the arrow in FIG. 2 (B), when the stirring tool 10 rotates, the plasticized aluminum is forced to flow toward the base end of the probe 14 when the stirring tool 10 rotates. It is set in advance so that Symbols 18 and 19 in FIGS. 2B and 2A are:
The both ends of the spiral ridge 17 are shown. The protruding ridges 17 project at least three-quarters or more rounds on the bottom surface 13 so that the aluminum fluidized by the probe 14 gathers near the center of the surface 6 of the stirring section 4 and scatters to the outside. Can prevent surface defects. Incidentally, the bottom surface 1 of the stirring tool 10
The diameter D of the main body 12 including 3 is 15 mm and the length is about 6 mm.
The diameter d of the probe 14 is 6 mm in the thread root diameter of the screw 16.
And the ratio D / d between the diameters D and d is 2.5. Since the ratio D / d is 1.8 or more, leakage of the fluidized aluminum due to scattering to the outside can be prevented. The screw 16 has, for example, a thread outer diameter of about M7 × 1 and a pitch.

FIG. 3 relates to one embodiment of the method for removing minute voids in a casting surface according to the present invention. As shown in FIG.
On the rectangular surface 2 of the aluminum casting 1, the rotating stirring tool 10 is arranged near the upper left corner, and the probe 14 is inserted vertically into the surface layer of the casting 1 while pressing the bottom surface 13 of the main body 12 against the surface 2. The contact (contact) is performed, and the start S is first performed. At this time, as shown in FIG. 3B, the surface of the casting 1 near the probe 14 is
Is formed. Next, as shown by the arrow in FIG. 3 (A), the stirring tool 10 is moved while rotating clockwise from the start S position, and then the U-turn 7 is performed. At this time, the axis of the main body 12 of the stirring tool 10 and the axis of the probe 14 are
The U-turn 7 can be performed smoothly because it is moving while rotating in a vertical (perpendicular) posture with respect to the surface 2 of the camera.

Subsequently, the stirring tool 10 is alternately and linearly moved in the left / right direction and the U-turn 7 therebetween is alternately repeated. In addition, the moving paths of the tool 10 are set in advance so that the stirring units 4 and 4 formed on the adjacent movement trajectories through which the stirring tool 10 has passed overlap each other. As a result, FIG.
As shown in FIG. 3 (C), in a state where a plurality of adjacent stirring portions 4 are overlapped with each other, as shown in FIG. 3 (A), the stirring portions 4 extend over almost the entire surface 2 of the aluminum casting 1. 4 are formed in a zigzag shape. The symbol E in FIGS. 3A and 3C indicates the end point position of the stirring tool 10, and a recess 9 is formed in the center of the stirring tool 10 after the probe 14 has been pulled out.

When the stirring tool 10 in FIG. 3 is moved, as shown in FIGS. 4A and 4B, the surface 6a of the initial (first) stirring section 4a of the adjacent stirring sections 4a and 4b.
In comparison with the depression amount n1 with respect to the surface 2 of the casting 1 in
The stirring tool 1 is so set that the recess amount n2 in the surface 6b of the second stirring section 4b formed thereafter is slightly increased.
The first and second pushing amounts at 0 are adjusted. Thereby, the supply amount of the fluidized aluminum to be supplied to the stirring unit 4b can be optimized, and the stirring unit 4b
It is possible to prevent internal defects that cause voids inside. The pushing amount increased in the stirring tool 10 is 0.1 m
m or more, and preferably 0.15 mm or more.
If the pushing amount to be increased is increased too much, burrs generated along both sides of the surface 6 of the stirring section 4 due to scattering of aluminum increase, so the pushing amount to be increased is 0.5.
mm or less, desirably 0.25 mm or less. As a result, the fluidized aluminum does not overflow from the stirring sections 4a and 4b to the outside, and there is no shortage of supply.
In a and 4b, internal defects due to insufficient aluminum can be reliably prevented.

FIG. 4 (C) shows a different movement pattern of the stirring tool 10, which is a square aluminum casting 1 in plan view.
On the surface 2 of the surface 2, the tool 10 is started S from the position of the lower left corner, and after linearly moving along each side of the surface 2 and repeating the L-turn 8 that bends at a right angle, the tool 10 is alternately repeated. The tool 10 is omitted as the end point E. Therefore, the stirring section 4 adjacent to the surface 2 of the casting 1
The inner and outer triple surfaces 6a, 6b, 6c are formed in a substantially rectangular shape,
In almost all areas except the central part of the surface 2, fine voids near the surface layer and fine irregularities on the surface 2 can be removed. FIG. 4 (D) shows the stirring tool 10 from the lower left position on the surface 2.
And then alternately repeats the linear movement and the L-turn 8 that bends at a right angle, and moves along the U-turn 7 on the way to form the surfaces 6a and 6b of the inner and outer double stirring sections 4, and then starts. The tool 10 is pulled out at the end point E at a position diagonally outside of S.

Further, FIG. 4E shows that the stirring tool 10 is started S from the position of the lower left corner of the surface 2 and alternately repeats the linear movement and the L-turn 8 which is bent at a right angle.
The tool 10 is removed as the end point E at a position adjacent to the start S after the surfaces 6a and 6b of the inner and outer double agitating sections 4 are formed by moving including the turn 7. Also,
FIG. 4 (F) shows the stirring tool 1 from the center of the left side of the surface 2.
0, the surface is curved in a clockwise direction toward the center of the surface 2 and is spirally moved to form the surfaces 6a, 6b, 6c by the spiral agitating portion 4 which approximates concentric circles. Tool 1 as end point E near the center of 2
It is the number that is out of zero. In FIG. 4F, a movement pattern in which the positions of the start S and the end point E of the stirring tool 10 may be reversed. In this case, probe 1
The recess 9 from which the hole 4 has come out can be formed at a position near the periphery of the surface 2.

As described above, the stirring tool 1 shown in FIG.
1, 3, and 4 by using the probe 1 of the stirring tool 10.
In the vicinity of the surface 2 of the aluminum casting 1 to which the aluminum alloy 4 has moved while rotating, the agitation unit 4 having a dense structure in which aluminum is agitated and fluidized in a solid state and solidified is formed along the movement locus of the tool 10. You. In addition, the stirring tool 10 is
After linearly moving along the surface 2 of the above, the U-turn 7 is performed to continuously form the agitating portion 4 adjacent to the original movement trajectory, or the linear movement and the U-turn 7 are repeated a plurality of times and widened. By moving the surface 2 of the casting 1 within the range, fine voids in the surface layer of the casting 1 and fine irregularities on the surface 2 can be removed. Further, after the stirring tool 10 is linearly moved along the surface 2 of the aluminum casting 1, a right angle L-turn 8 is made to move adjacent to the original movement trajectory, and the L-turn 8 is further moved.
And the linear movement are alternately repeated, or moved between the center and the periphery of the surface 2 of the casting 1 while adjoining the movement trajectory in a spiral shape, so that the fine gaps and It is also possible to remove the two fine irregularities.

In addition, since the stirring tool 10 is moved continuously, the number of recesses 9 remaining at the end point E where the probe 14 of the tool 10 was lastly drawn can be reduced to only one or a minimum. A decrease in strength near 2 can also be suppressed. In addition, on the surface 2 of the casting 1, there is an overlapping portion between the agitating sections 4 and 4 formed by the probe 14 and adjacent to each other. Can be modified into tissue. Further, the pushing amount of the bottom surface 13 of the main body 12 in the stirring tool 10 in the adjacent stirring units 4a and 4b is
Since the diameter is sequentially increased in the range of 0.1 to 0.5 mm, it is possible to prevent internal defects that may cause voids in the subsequently formed stirring section 4b.

In addition, in order to move the stirring tool 10 while rotating the axis of the main body 12 and the probe 14 with respect to the surface 2 of the casting 1 in a vertical posture, the U-turn 7 and the L-turn 8 Movement becomes easy and the tool 10
The operation itself is also easy. On the other hand, the stirring tool 10 has at least four spiral ridges 17 on the bottom surface of its main body 12.
The probe 14
This makes it possible to prevent the fluidized aluminum from collecting near the center of the surface 6 of the stirring section 4 and overflowing to the outside. Moreover, the ratio D / d of the diameter D of the main body 12 (bottom surface 13) to the diameter d of the probe 14 is 1.8.
As described above, the fluidized aluminum is deposited on the bottom surface 13.
The inside of the agitating portion 4 is fixed by the spiral ridge 17 provided on the agitating portion 4, and a sound agitating portion 4 free from surface defects can be reliably formed. Note that the method for removing microvoids according to the present invention employs the method of
Not only the stirring tool 10 having
This can be realized even by using the stirring tool 10a without the above.

[0026]

Embodiments 1 and 2 Here, specific embodiments of the present invention will be described together with comparative examples. FIG. 5 (A) shows a state in which the stirring tool 10 is moved while rotating the surface of the aluminum casting 1 near the surface 2 to form the stirring section 4 and the surface 6 thereof. In this case, the bottom surface 13 of the stirring tool 10
And only the spiral ridge 17 is inserted into the surface layer of the casting 1. In such a tool 10, the diameter D of the main body 12 including the bottom surface 13 is 15 mm,
The diameter d of the probe 14 having a length of 6 mm is 6 mm in terms of the thread root diameter of the screw 16, and the ratio D / d between the diameters D and d is 2.5. The cross-sectional dimension of the ridge 17 is 0.5 mm in width and 1 mm in height.

FIGS. 5B and 5C show different types of stirring tools 10a and their use. The stirring tool 10a
It is the same as the welding tool used for the so-called friction stir welding, and has a body 12 having the same diameter (D) of 15 mm as the stirring tool 10 and a 6 mm projecting from the slightly recessed center portion of the bottom surface 13 a of the same as the stirring tool 10. And has a diameter (d) of 6 mm and the same screw 16 on its peripheral surface. The rake angle θ1 at the periphery of the bottom surface 13a of the main body 12 is 10 °. As shown in FIG. 5 (C), the stirring tool 10a is
In contrast, in a state where the axes of the main body 12 and the probe 14 are inclined several degrees (advance angle θ2) to the opposite side to the forward direction,
It is used while rotating and moving. In this case, the pushing amount (ap) of the stirring tool 10a against the surface 2 is as shown in FIG.
As shown in the figure, the vertical distance between the surface 2 of the casting 1 and the axis of the bottom surface 13a is shown.

Here, a thickness of 20 mm, 100 mm × 2
Aluminum casting having a surface 2 of 00 mm (JIS:
5 sets of AC4C) 1 were prepared. Further, three sets of stirring tools 10 and two sets of stirring tools 10a were separately prepared. Of the three sets of agitating tools 10, one having a spiral ridge 17 projecting from the bottom surface 13 of the main body 12 in a spiral form is used in the first and third quarters (3/4). Example 2, half circumference
A (1/2) -wound coil was used as Comparative Example 1. Two sets of stirring tools 10a were used as Comparative Examples 2 and 3. As shown in Table 1,
The stirring tools 10 and 10a of each example are divided according to the presence or absence of the pushing amount (ap) and the presence or absence of the inclination (advance angle θ2) with respect to the surface 2,
And with the same rotation speed of 890 rpm and travel speed of 500 mm / min, the surface 2 of each set of aluminum castings 1
The probe 14 was moved in a straight line having a length of 180 mm along the line. The stirring portions 4 of the casting 1 formed by the tools 10 and 10a of each example were individually cut and visually inspected for internal defects and surface defects. These results are also shown in Table 1 as Examples 1 and 2 and Comparative Examples 1 to 3 corresponding to the tools 10 and 10a of each example.

[0029]

[Table 1]

According to Table 1, there was no defect in Examples 1 and 2, whereas in Comparative Example 1 using the stirring tool 10 having a spiral ridge 17 of a half circumference, the surface of the stirring section 4 was A concave surface defect had occurred. In Comparative Example 1, since the ridge 17 had only a half circumference, the aluminum which was fluidized by the probe was scattered to the outside from the agitating section 4 to cause a surface defect. In Comparative Example 2 in which the stirring tool 10a was used in a vertical posture, an internal defect occurred in the stirring section 4. This is because the agitating tool 10a without the ridge 17 was used in a vertical position, and the indentation (ap) was added at 0.2 mm, so that the fluidized aluminum was insufficient in the agitating section 4, resulting in internal defects. Things. In Comparative Example 3,
Although the same indentation amount (ap) as in Comparative Example 2 was added, as a result of tilting the stirring tool 10a by 3 °, the fluidized aluminum remained in the stirring section 4, so that no internal defect or surface defect occurred. However, as in Comparative Example 3, the tool 10
It is not practical to incline a by 3 ° because the U-turn 7 and the like are difficult when continuously moving the wide surface 2 of the casting 1. From the above results, the superiority of the microvoid removing method of the present invention and the stirring tool 10 used for the method can be understood.

[0031]

Embodiments 3 and 4 100 mm x 200 mm with a thickness of 20 mm
aluminum casting (JIS: AC
4C) Three sets of 1 were prepared, and three sets of stirring tools 10 were also prepared. As shown in Table 2, the bottom surface 1 of the tool 10 of each example
3, the diameter D of the probe 14 is set to 15 mm in common, and the diameter d of the probe 14 (the thread root diameter of the screw 16) is changed so that the ratio D /
d was changed in three ways. Further, the number of turns of the spiral ridge 17 was changed as shown in Table 2 to obtain Examples 3 and 4 and Comparative Example 4. These were individually moved along the surface 2 of each set of aluminum castings 1 in a linear fashion with a length of 180 mm, with the same rotation speed of 890 rpm and the same moving speed of 500 mm / min. Tool 10 for each example
The stirrer 4 of the casting 1 formed by the above was cut individually and visually inspected for internal defects and surface defects. These results are also obtained in Example 3 corresponding to the tool 10 of each example.
4 and Comparative Example 4 are shown in Table 2.

[0032]

[Table 2]

According to Table 2, no defects occurred in Examples 3 and 4 in which the ratio D / d was 1.8 or more and the ridge 17 was wound three-quarters or more. On the other hand, in Comparative Example 4, since the ratio D / d was less than 1.8 despite the fact that the ridges 17 were wound three-quarters, surface defects occurred in the agitating part 4. Was. That is, the ratio D / d is less than 1.8, and the bottom surface 1 is smaller than the diameter d of the probe 14.
Since the diameter D of the sample 3 becomes relatively small, the aluminum fluidized by the probe 14 overflows from the stirring unit 4,
This is because it scattered from the periphery of the tool 10 to the outside. From these results, the ratio D / d was set to 1.8 or more and the ridge 1
The stirring tool 10 of the present invention in which 7 is 3/4 or more windings
The advantage of is easily understood.

[0034]

Embodiments 5 and 6 An aluminum mold for injection-molding a resin is generally made of a rolled material obtained by rolling an aluminum alloy for spreading, and the surface of the cavity is made of, for example, F
e plating is coated for heat and wear resistance. However, since such a mold is expensive, application of an aluminum casting is being studied. However, there is a problem that a cavity with good surface accuracy is difficult to be formed due to the presence of a cavity in an aluminum casting. For this reason, it has not been put to practical use until now. Here, an example in which the method for removing fine voids of the present invention was applied to an injection molding die made of an aluminum casting was performed, and the above-described problems could be solved. First, as shown in FIG.
Three sets of aluminum (JIS: A5083) castings 20 having a surface 22 of 100 mm x 200 mm in mm were prepared. These castings 20 are simulated test pieces for producing an injection mold.

Further, a stirring tool 10 similar to the above was prepared. The tool 10 has a main body 12 including a bottom surface 13 having a diameter D of 15 mm and a diameter d of a probe 14 having a length of 6 mm.
Is a thread root diameter of the screw 16 of 7 mm, and a ratio D / d between the diameters D and d is about 2.1. As shown in FIG. 6 (B), each set of aluminum castings 2 is
On the surface 22 of the zero, a reforming unit 24 composed of two agitating units 4 having a U-shape in plan view including one U-turn 7 at the left position and having overlapping passages is formed individually. . Also, three U-turns 7 are located on the right side of the surface 22.
Are formed in a zigzag shape in a plan view including alternately and the passing trajectories overlap each other.
It was formed individually on each set of castings 20. At this time, the stirring tool 10 was kept vertical to the surface 22 of the casting 20, and moved while rotating at the same rotation speed of 890 rpm and the same movement speed of 500 mm / min.

Then, one set of the aluminum casting 20 is
On the surface 22, the amount of pushing of the bottom surface 13 of the main body 12 in the tool 10 is increased by 0.2 mm with respect to the initial or immediately preceding moving linear portion in both the modified portions 24 and 26. Thus, a casting 20 having the obtained modified portions 24 and 26 was used as Example 5. In addition, the casting 20 of another set, in which the pushing amount was increased by 0.5 mm, was set as Example 6. Further, in another casting 20, the one in which the amount of indentation was kept constant at the initial value of 0.2 mm was used as Comparative Example 5.

Reforming part 2 of aluminum casting 20 of each example
4, 26 were cut and visually inspected for internal defects and surface defects. As a result, no defect occurred in any of Examples 5 and 6. On the other hand, in Comparative Example 5, fine internal defects were confirmed. From these results, it is understood that the superiority of the fine void removing method of the present invention in which the tool 10 is sequentially pushed deeper by 0.1 mm or more for each adjacent stirring unit 4. In Example 6, since the pushing amount was large, burrs were notably formed along both sides of the stirring section 4. For this reason, it can be said that the increasing pushing amount is preferably smaller than 0.5 mm.

[0038]

Embodiment 7 Two separate sets of the aluminum casting 20 shown in FIG. 6A were prepared. In one set, after the modified portions 24 and 26 shown in FIG. 6B are formed in the same manner as described above, as shown in FIG. 6C, the modified portions 24 and 26 are formed along the longitudinal direction of the modified portions 24 and 26. Groove 2
After forming modified portions 24a and 26a having a thickness of about 2 mm and a substantially concave cross section, a simulated injection molding die 28 having a surface coated with Fe plating was manufactured. This was designated as Example 7. The modified portions 24a and 26a correspond to cavities in the injection mold 28. The above F
e-plating is performed on the surface 22 of the aluminum casting 20 by Ni.
After coating the Cr plating layer, by applying an electric current in an iron plating bath in which ferrous sulfide, sodium fluoride, and pyrogal is mixed, Fe
It further covers the plating layer. On the other hand, another set of FIG.
The casting 20 shown in (A) was directly coated with the same Fe plating as described above under the same conditions, and the obtained simulated injection mold was used as Comparative Example 6. Modification units 24a and 26a of Embodiment 7
As a result of observing the state of Fe plating, a dense and uniform plated surface was obtained. On the other hand, in Comparative Example 6, holes and irregularities due to the porosity near the surface layer were confirmed. Therefore,
It has been confirmed that the method for removing fine voids according to the present invention can be effectively applied to an aluminum injection mold.

The present invention is not limited to the embodiments and embodiments described above. For example, the surface 6 of the stirring unit 4 may be used as it is, or a finishing process for cutting the vicinity of the surface 6 may be performed so that most of the stirring unit 4 remains. Further, when the stirring tool 10 is moved, an acute angle or an obtuse angle turn may be included between the linearly moving parts. Further, the tip surface of the probe 14 in the stirring tool 10 may be provided with a large number of lattice-like or scattered projections, or the circumferential surface of the probe 14 may be replaced with the screw 16 and its axis centered. May be provided. The surface 2 of the casting 1 is not limited to the flat surface, but includes a curved surface that protrudes or is depressed by a gentle curve. Various movement patterns accompanying the rotation of the stirring tools 10 and 10a are stored in advance in, for example, a RAM of a personal computer for controlling the tools, and the length of the linear moving portion and the diameter of the U-turn can be input at any time. As an alternative, it is possible to automate the method for removing fine voids of the present invention.

[0040]

According to the method for removing fine voids on the casting surface of the present invention described above, the metal material of the casting is stirred in a solid state near the casting surface where the probe of the stirring tool has been rotated and moved. A fluidized, dense tissue agitator is formed along the movement trajectory of the tool. Also,
After linearly moving the stirring tool along the casting surface, it is U-turned to continuously form a stirring part adjacent to the original movement trajectory, or such linear movement and U-turn are repeated several times to cover a wide range. The surface of the casting can be moved to remove fine voids and irregularities on the surface of the casting. Alternatively, after the stirring tool is moved linearly along the casting surface, the L tool is moved adjacent to the original movement trajectory by making a right angle L turn, and
Turns and linear movements are alternately repeated, or moving between the center and the periphery of the casting surface while adjoining the movement trajectory in a spiral shape, to remove minute voids and surface irregularities on the casting surface layer over a wide range You can also. Moreover, since the tool is continuously moved, the number of dents left in the trace of the last extraction of the probe of the tool can be reduced to one or a minimum, and a reduction in strength near the casting surface can be suppressed.

According to the minute void removing method of the present invention, the stirrer of the dense structure in which the metal material of the casting is stirred and fluidized in the solid state is replaced with the stirrer formed adjacently. Along with each other. Therefore, fine voids near the surface layer can be reliably removed from the base of the fine irregularities on the casting surface, so that the casting surface area has a dense structure to increase the strength of the casting product and exhibit the required characteristics. I can make it. Furthermore, according to the method for removing fine voids of the third aspect, the surface of the first stirring portion formed on the movement locus of the stirring tool is slightly pressed by the bottom surface of the tool body, but is continuously formed. The surface of the second stirrer formed on the adjacent moving trajectory is further depressed. As a result, the fluidized metal material of the casting material is appropriately supplied to the stirring section,
Internal defects due to a shortage of material can be reliably prevented in the stirring section.

On the other hand, according to the stirring tool of the present invention, the metal material plasticized and fluidized by the probe inserted in the vicinity of the casting surface is formed into a spiral convex provided on the bottom surface of the main body which comes into contact with the casting surface while pressing the same. The streak induces flow toward the probe. Therefore, it is necessary to reliably prevent the occurrence of surface defects or internal defects whose surface is depressed due to lack of material in the stirrer, and to form a stirrer with a dense and uniform metal structure continuously over a wide range near the casting surface. Can be.
According to the stirring tool of claim 7, since the main body and the bottom face have a large diameter with respect to the probe, the metal material of the casting plasticized and fluidized by the probe is stirred by the spiral ridge provided on the bottom face. It is possible to form a sound stirring section free from surface defects by being fixed in the section.

[Brief description of the drawings]

FIG. 1A is a perspective view schematically showing a method for removing fine voids according to the present invention, and FIG. 1B is a cross-sectional view taken along a line BB in FIG.

FIGS. 2A and 2B are side and bottom views showing the stirring tool of the present invention, and FIG. 2C is a sectional view taken along a line CC in FIG.

3A is a plan view showing one embodiment of a method for removing microvoids according to the present invention, and FIGS. 3B and 3C are cross sections at different points in time along a line BB in FIG. FIG.

4 (A) and 4 (B) are schematic diagrams showing a pressing mode of a stirring tool in the method for removing microvoids of the present invention, and FIGS. 4 (C) to 4 (F).
FIG. 4 is a plan view showing a method for removing fine voids in a different form.

5A is a schematic view showing a use state of the stirring tool of the present invention, FIG. 5B is a cross-sectional view of a stirring tool of a different form which can be used in the method for removing microvoids of the present invention, and FIG. The schematic diagram which shows a state.

6 (A) to 6 (C) are schematic views showing a process for producing a test piece of an injection mold using the method for removing fine voids according to the present invention.

[Explanation of symbols]

 1, 20 ... aluminum casting (casting) 2, 22 ... surface 4 ... stirrer 6 ... stirrer part surface (movement trajectory) 7 ... U Turn 8 L turn (right-angle turn) 10, 10a Stirring tool 12 Main body 13, 13a Bottom surface 14 Probe 17 Protrusion n1, n2 ... Indent amount

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP 2001-246458 (JP, A) JP 2000-15426 (JP, A) JP 2001-181809 (JP, A) JP 2001-32058 (JP, A A) JP-A-2000-336465 (JP, A) JP-A-2001-347360 (JP, A) JP-A-2001-347359 (JP, A) JP-A-10-183316 (JP, A) JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B22D 29/00 B23K 20/12 310 B23K 103: 10

Claims (8)

(57) [Claims] An agitating tool including a main body rotating and moving along a surface of a casting and a probe protruding from a center portion of a bottom surface of the main body, the probe being moved while the bottom surface abuts or substantially abuts the surface of the casting. When removing the minute voids by inserting near the surface of the casting, the stirring tool with respect to the surface of the casting in plan view,
A method for removing fine voids on a casting surface, wherein the method includes a U-turn or a turn at a right angle or an arbitrary angle and continuously moving so that the movement trajectories are adjacent to each other. 2. The method according to claim 1, wherein adjacent stirring portions near the surface of the casting stirred by the probe of the stirring tool include portions overlapping each other. 3. When the stirring tool is moved to an adjacent movement trajectory on the surface of the casting, the amount of depression of the bottom of the tool body in the first stirring is smaller than the bottom of the tool body in the second stirring adjacent to the tool. 3. The method for removing fine voids on a casting surface according to claim 1 or 2, wherein the amount of indentation is increased by 0.1 mm or more in the depth direction of the casting. 4. When the stirring tool is moved while rotating along the surface of the casting, the axes of the main body and the probe of the stirring tool are maintained in a vertical position with respect to the surface of the casting.
The method for removing fine voids on a casting surface according to any one of claims 1 to 3, wherein: 5. A tool inserted near the surface of a casting to remove minute voids, comprising: a cylindrical main body rotating and moving along the surface of the casting; and a probe protruding from a center of a bottom surface of the main body. And a ridge provided on the bottom surface of the main body so as to spirally protrude from a periphery of the bottom surface toward the base end of the probe. 6. The stirring tool according to claim 5, wherein the spirally projecting ridge is three-quarters or more turns on the bottom surface of the main body. 7. The stirring according to claim 5, wherein a ratio D / d of a diameter (D) of the main body including the bottom surface to a diameter (d) of the probe is 1.8 or more. tool. 8. The method for removing fine voids in a casting surface according to claim 1, wherein the joining tool according to any one of claims 5 to 7 is used.