JP3171321B2 - Powder molding 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 powder molding method, and more particularly to a powder capable of reducing a density difference between an upper convex portion and a pedestal portion of a green compact and improving partial strength. It relates to a molding method.

[0002]

SUMMARY OF THE INVENTION In powder metallurgy,
2. Description of the Related Art A green compact is formed by molding a raw material powder containing a metal as a main component by a powder compacting apparatus, and the green compact is heated and sintered in a sintering furnace. Here, an example of a conventional powder molding method will be described with reference to FIG. A mold 1 of a powder molding apparatus used in this powder molding method includes a die 3 fixed to a die plate 2, a core rod 4, a lower punch 5, and an upper punch 7 held by an upper punch holder 6. The core rod 4 is located in the die 3. The lower punch 5 has a cylindrical shape and is fitted between the die 3 and the core rod 4 from below. The upper punch 7 has a cylindrical shape and is fitted between the die 3 and the core rod 4 from above. Thus, a cavity 8 is formed between the die 3, the core rod 4, and the upper punch 7 and the lower punch 5. In the drawing, 9 is a flange protruding below the lower punch, 10 is a die fixing frame provided between the die 3 and the die plate 2, and 11 is a fixing frame provided between the die fixing frame 10 and the die plate 2. is there.

On the other hand, a feeder 12 has an opening 13A on the lower surface.
A hopper 14 is connected to a feeder box 13 having a flexible feed pipe 15. The feeder box 13 has an opening 13A on the lower surface.
13A is larger than the outer periphery of each of the punches 5 and 7. A feeder lever 16 is connected to a rear portion of the feeder box 13, and a drive mechanism (not shown) is connected to the feeder lever 16. The feeder box 13 is driven by the die plate 2 by the drive mechanism. And move back and forth on the die 3. In addition,
The supply pipe 15 is connected to a supply pipe connection opening 17 provided on the upper rear center of the feeder box 13.

When powder is formed, the feeder box 13 is raised above the lower punch 5 with the upper punch 7 raised and separated from the die 3 as shown in the figure.
To move forward. Further, the raw material powder P is supplied into the feeder box 13 via the supply pipe 15 from the hopper 14 storing the raw material powder. Along with this, feeder box 13
Reciprocates once or several times before and after the cavity 8 formed between the die 3, the core rod 4 and the lower punch 5, and the raw powder P is supplied from the feeder box 13 into the cavity 8. Is done. When the filling of the raw material powder P into the cavity 8 is completed, the feeder box 13 retreats and comes off the position above the cavity 8. Then, the upper punch 7 is lowered to be fitted between the die 3 and the core rod 4, and the die 3 is lowered and the raw powder P is formed between the die 3 and the core rod 4 by the lower punch 5 and the upper punch 7. Is compressed and hardened to form a cylindrical green compact. Thereafter, the upper punch 7 is raised, and the die 3 is further lowered, and the green compact is extracted from the die 3 by the lower punch 5. Further, as described above, as the feeder box 13 advances to fill the raw material powder P into the cavity 8, the green compact is discharged by the feeder box 13.
Such a molding cycle is repeated.

In the conventional powder molding method described above,
The raw material powder P filled in the cavity 8 is difficult to move in the horizontal direction because the operation direction of the upper punch 7 is vertical, and there is a problem that a difference in density occurs at the boundary between the upper convex portion and the pedestal portion. Depending on the use of the molded body, there is a case where it is desired to partially improve the strength such as a convex portion or a projection. However, in the conventional powder molding as described above, it is difficult to partially improve the strength by filling the same raw material powder. Have difficulty.

[0006] An object of the present invention is to solve the above problems and to provide a powder molding method capable of reducing the density difference between the upper convex portion of the green compact and the pedestal portion. . Another object of the present invention is to provide a powder molding method capable of partially improving the strength of a sintered body.

[0007]

According to a first aspect of the present invention, there is provided a powder molding method comprising: filling a raw material powder in a cavity of a mold member; and compressing the raw material powder by the mold member to form a green compact. In the powder molding method described above, the heated raw material powder is filled in a cavity portion forming a portion where the density or strength of the obtained green compact is to be improved. By adopting such a configuration, the heated raw material powder is filled into a portion of the cavity of the mold member which forms a portion where the density or strength of the green compact is to be improved, and the other portions are not filled with the heated raw material powder. When the raw material powder at a low temperature is filled and the raw material powder is compressed by the mold member, the density of the portion filled with the heated raw material powder can be improved. Along with this, the strength of the portion filled with the heated raw material powder can be improved.

According to a second aspect of the present invention, there is provided a powder molding method, wherein the upper convex portion of the cavity is filled with heated powder. By employing such a configuration, it is possible to reduce the difference in density between the upper convex portion of the green compact and the pedestal portion.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the first method of the powder molding method of the present invention will be described.
An embodiment will be described with reference to FIGS. In addition, the mold 1 of the powder molding apparatus used in this embodiment
Has the same configuration as that shown in FIG. 9 described above, and includes a die 3 fixed to a die plate 2, a core rod 4, a lower punch 5, and an upper punch 7 held by an upper punch holder 6. 3, core rod 4,
And a cavity 8 is formed between the upper punch 7 and the lower punch 5.

On the other hand, a feeder 21 for filling the cavity 8 with raw material powder is provided with a feeder box 22 having an open lower surface as shown in FIGS. The first powder chamber 24 and the second powder chamber 25 are defined side by side on the left and right. The lower opening of each of the powder chambers 24 and 25 is larger than the upper opening of the cavity 8. In addition, each powder chamber 24, 25
Hose connection portions 26 and 27 are provided on the upper surface portion of the feeder box 22. First and second hoses 28, 29 are connected to these hose connection portions 26, 27, respectively.
The other end of each of the first and second hoses 28 and 29 is connected to a separate hopper (not shown). In particular, the second hose 29 is
The raw material powder P2 is connected to a hopper provided with a heating means such as an oil heater, and is heated in the second powder chamber 25.
Is configured to be supplied. The heating temperature of the raw material powder P2 in the hopper provided with this heating means is about 135 ° C., although it depends on the type of the raw material powder used. In the present embodiment, a heater and a temperature sensor (not shown) are provided on the second powder chamber 25 side, and the heated raw material powder P2 supplied to the second powder chamber 25 is kept warm by the control means. It may be configured as follows.

The feeder box 22 slides on the die plate 2 and the die 3.
The position of the first powder chamber 24 overlaps the upper surface of the cavity 8 and the position of the second powder chamber 25 overlaps the upper surface of the cavity 8 by the driving of the left and right movement mechanism 32. It is possible to move left and right between and.

Here, the longitudinal movement mechanism and the lateral movement mechanism
The configuration of 32 will be described with reference to FIG. 33 is a frame,
The frame 33 has a pair of left and right arms 34 in parallel. The two arms 34 are guided by a pair of parallel left and right rails 35 fixed on the die plate 2, and the frame 33 is movable only in the front-back direction. A drive lever 37 is connected to a rear portion of the frame 33 via a joint 36. This drive lever 37
The power from a motor (not shown) provided in the powder molding press is transmitted to the frame 33,
33 is driven in the front-rear direction. The feeder box is provided between the left and right arms 34 of the frame 33.
22 is supported via a support rod 41 so as to be movable only in the left-right direction within a predetermined range. The support rods 41 are fixed to the left and right sides of the feeder box 22 in a front-rear pair, and slidably penetrate and support the arm portion. Then, the both arm portions 34 determine the leftmost position and the rightmost position of the feeder box 22. Air cylinders 42 are fixed to the rear portions of both arms 34 of the frame 33, respectively. A protruding piece 44 provided at the center of the rear surface of the feeder box 22 is connected to the piston rod 43 that moves to the left and right of the air cylinder 42. That is, both air cylinders 42 are driving sources for moving the feeder box 22 right and left.

The operation of the above configuration will be described. Raw material powder P1 at room temperature is supplied from a hopper into the first powder chamber 24 on the right side (lower side in FIG. 1) of the feeder box 22, and the second powder chamber 25 on the left side (upper side in FIG. 1). Is supplied with heated raw material powder P2 from a hopper provided with a heating means such as an oil heater. In powder molding, the upper punch 7 is lifted and separated from the die 3, and then the feeder box 22 is
Is in the leftmost position, the feeder box 22 advances with the frame 33 as shown by the arrow A in FIGS. 1A and 2A, and the first powder chamber 24 is positioned on the cavity 8. I do. In this state, when the die 3 is raised, the lower punch 5 is lowered relatively to the die 3, and as shown in FIG. 2 (a), the lower punch 5 is moved from the first powder chamber 24 into the cavity 8. The raw material powder P1 at normal temperature is filled. Then
As shown by an arrow B in FIGS. 1B and 2B, the feeder box 22 is moved rightward (downward in the figure) by driving the air cylinder 42, and the second powder chamber 25 is placed on the cavity 8. To position. In this state, when the die 3 is further raised, the lower punch 5 is further lowered relative to the die 3 as shown in FIG. 2 (b), whereby the volume of the cavity 8 is increased, and The heated raw material powder P2 from the second powder chamber 25 is filled on the raw material powder P1 filled in the first raw material. In this way, the cavity 8 is filled with the low-temperature normal-temperature raw material powder P1 on the lower side and the high-temperature raw material powder P2 on the upper side. Thereafter, as shown by an arrow C in FIGS. 1 (b) and 2 (b), the feeder box 22 moves back together with the frame 33 and separates from the die 3. Thereafter, the feeder box 22 is moved to the position indicated by the arrow D in FIG.
As shown by, the air cylinder 42 moves leftward (upward in the figure) by driving.

After the feeder box 22 retreats in this manner, the upper punch 7 descends and the die 3
And the core rod 4, the die 3 is lowered, and the raw powders P1 and P2 in the cavity 8 are compressed and hardened by the lower punch 5 and the upper punch 7 between the die 3 and the core rod 4. As a result, a cylindrical green compact is formed. Thereafter, the upper punch 7 is raised, and the die 3 is further lowered, and the green compact is extracted from the die 3 by the lower punch 5. Further, as described above, as the feeder box 13 advances to fill the raw material powder P into the cavity 8, the green compact is discharged by the feeder box 13. Such a molding cycle is repeated.

According to the above embodiment, the feeder box
The first powder chamber 24 and the second powder chamber 25 are formed side by side in the compartment 22 and the feeder box 22 can be moved not only in the front-back direction but also in the left-right direction, so that the raw material powder is filled. At the time, feeder box 22
Is moved to the left (lower side in the figure) to move the raw material powder P1 at room temperature to the lower side of the cavity 8 and the heated raw material powder P2 at a higher temperature to the upper side of the cavity 8. Can be filled. In addition, this raw material powder
At the time of filling P1 and P2, the raw material powders P1 and P2
The feeder box 22 may be finely vibrated back and forth and left and right in order to uniformly fill the box.

The raw material powder thus heated to the upper side
After filling the P2, the raw powder is compressed between the die 3 and the core rod 4 by the lower punch 5 and the upper punch 7, and the raw powder normally filled in the cavity 8 is
Since the operation direction of the upper punch 7 is vertical, the upper punch 7 is difficult to move in the horizontal direction and tends to have a density difference at the boundary between the upper convex portion and the pedestal portion. However, the upper punch 7 is heated above the cavity 8 as in the present embodiment. By filling the raw material powder P2 thus heated, the heated raw material powder P2 tends to be densified by its aggregation effect, so that the density difference in the vertical direction of the obtained green compact can be reduced.

Next, a second embodiment of the powder molding method of the present invention will be described with reference to FIGS. The green compact 51 manufactured in the present embodiment has a shape having a convex portion 53 at the center of one end face (the upper surface in the drawing) 52 as shown in FIG.
The projection 53 is located away from the peripheral edge of the upper surface 52. The green compact 51 has no holes. In such a green compact 51 having the convex portions 53 on the upper surface 52, for example, there is a case where it is desired to improve only the strength of the convex portions 53.

The case where the strength is desired to be partially improved will be described by taking the case of the green compact 51 as an example. FIG.
Is an example of a powder molding die apparatus for the green compact 51, in which 61 is a die, 62 is a lower punch, 63 is an upper punch, and the die 61 constitutes a side surface of the green compact 51. Is what you do. The lower punch 62 is for molding the lower surface of the green compact 51, and is fitted into the die 61 so as to be vertically slidable from below. On the other hand, the upper punch 63 is
The upper surface of the die 51 has a concave portion 63A corresponding to the convex portion 53, and is slidably and removably fitted into the die 61 from above. Thus die 61, lower punch 62
A cavity 64 is formed by the upper punch 63. This upper punch 63 has a rod 65 for air release.
Is provided, and the insertion hole of this air vent rod 65 is provided.
66 communicates with a lateral hole 67 formed in the upper punch 63. In FIG. 5, reference numeral 68 denotes a die holder for fixing the die 61 to a die plate (not shown); 69, a pressing plate fixed to the upper punch 63 by bolts 70;
Is an upper punch presser, and 72 is an upper punch receiving plate, which fixes the upper punch 63 to an upper punch plate (not shown).

When the method of the present invention is applied to the apparatus as described above, the same feeder 21 as in the first embodiment (not shown) is used, and as shown in FIG. The lower punch 62 is lowered relative to the die 61 by raising the die 61 in a state where the raw material powder P1 is separated from the die 61, and the room temperature raw material powder P1 is filled in the cavity 64 formed in the die 61. Then, FIG.
As shown in FIG. 7, the die 61 is slightly raised from the state shown in FIG.
Is relatively slightly lowered, and the cavity 64
A space is further formed above the raw material powder P1, and the raw material powder P1 is filled with the raw material powder P2. In this way, the cavity 64 is thinly filled with the raw material powder P2 having a higher temperature than the raw material powder P1 having a lower temperature and the normal temperature.

Thereafter, the feeder box (not shown) is retracted, and when it is separated from the die 61, the upper punch 63 is lowered to be fitted between the dies 61 as shown in FIG. The raw powders P1 and P2 in the cavity 64 are compressed by the lower punch 62 and the upper punch 63 in 61. At this time, the raw material powder P2 mainly concentrates in the concave portion 63A due to the compression by the upper punch 63. Thus, a green compact 51 as shown in FIG. 5 is formed. afterwards,
As the upper punch 63 rises, the die 61 further descends, and the green compact 51 is extracted from the die 61 by the lower punch 62.

According to the above-described embodiment, the heated raw material powder P2 is heated above the cavity 64 so that the heated raw material powder P2 is concentrated on the concave portion 63A of the upper punch 63 forming the convex portion 53 whose strength is to be improved in the green compact 51. By filling the obtained raw material powder P2, the heated raw material powder P2 tends to be densified due to its aggregation effect, so that in the obtained green compact 51, the strength of the convex portion 53 can be particularly improved. At the same time, the other parts can be formed with the powder P1 at room temperature with high dimensional accuracy.

Although the powder molding method of the present invention has been described with reference to the accompanying drawings, the present invention is not limited to the above embodiment, and various modifications can be made.
For example, the shape of the green compact to be molded can be appropriately changed, and the corresponding portion of the cavity forming the portion where the strength in the shape of the green compact is to be improved may be filled with the heated raw material powder P2. . Further, in the first and second embodiments, one feeder 21 in which the first powder chamber 24 and the second powder chamber 25 are formed side by side is used. A feeder for supplying P1 and a feeder for supplying heated raw material powder P2 may be used. In the first and second embodiments, the heated raw material powder P2 is filled so as to be on the upper side. However, the heated raw material powder P2 may be formed on the lower side in some cases. Further, in each member of the mold 1, a heater, a temperature sensor, and the like are provided only at locations where the heated raw material powder P2 is filled, and the mold 1 is controlled by control means.
May be able to control the temperature at a predetermined location.

[0023]

According to a first aspect of the present invention, there is provided a powder molding method for filling a raw material powder into a cavity of a mold member and then compressing the raw material powder by the mold member to form a green compact. In this method, the heated raw material powder is filled into a cavity portion forming a portion where the density or strength of the obtained green compact is to be improved, so that the density or strength of the green compact obtained in the cavity of the mold member is increased. By filling the heated raw material powder into a portion where a portion to be improved is to be formed, filling the other portions with a raw material powder at a lower temperature than this, and compressing the raw material powder by the mold member, the heating is performed. The density of the portion filled with the raw material powder thus obtained can be improved. Along with this, the strength of the portion filled with the heated raw material powder can be improved.

According to a second aspect of the present invention, there is provided a powder molding method, wherein the upper convex portion of the cavity is filled with heated powder. By employing such a configuration, it is possible to reduce the difference in density between the upper convex portion of the green compact and the pedestal portion.

[Brief description of the drawings]

FIG. 1 is a schematic horizontal sectional view showing an operation of a feeder of a powder molding apparatus to which a powder molding method according to a first embodiment of the present invention can be applied.

FIG. 2 is a vertical sectional view taken along line EE and line FF of FIG. 1 showing an operation of a feeder at the time of powder filling in the powder molding apparatus.

FIG. 3 is a plan view showing a feeder of the powder molding apparatus.

FIG. 4 is a perspective view illustrating a green compact formed by a powder forming method according to a second embodiment of the present invention.

FIG. 5 is an overall sectional view showing a powder molding apparatus for molding the green compact.

FIG. 6 is a cross-sectional view of the powder molding apparatus at the time of filling a raw material powder at a normal temperature.

FIG. 7 is a cross-sectional view showing a state in which the raw material powder heated by the powder molding apparatus is filled.

FIG. 8 is an overall sectional view showing the powder molding apparatus of the second embodiment at the time of pressing.

FIG. 9 is an overall sectional view showing a conventional powder molding apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Die of powder molding apparatus 2 Die plate (die member) 3 Die (die member) 4 Core rod (die member) 5 Lower punch (die member) 6 Upper punch holder (die member) 7 Upper punch (die) (Mold member) 8 cavity P2 Heated raw material powder

Claims (2)

(57) [Claims] In a powder molding method of filling a raw material powder into a cavity of a mold member and compressing the raw material powder with the mold member to form a green compact, the density or strength of the obtained green compact is reduced. A powder molding method, characterized in that a heated raw material powder is filled in a cavity portion forming a portion to be improved. 2. The powder molding method according to claim 1, wherein a heated powder is filled in an upper convex portion of the cavity.