JP2010275591A - Method for feeding powder for molded body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for feeding powder for a molded body, with which when a molded body is formed by powder, variation in the amount of the powder to be charged into a die can be reduced. <P>SOLUTION: In the feeding method, powder P to be formed into the raw material of a molded body is fed from a hopper 10 to a chute box 11 through a hose 12. A plurality of nozzles 13a, 13b, 13c, 13d, 13e are fixed to the hose 12, and while feeding compressed air from a cylinder part 14 storing compressed air into the hose 12 via each nozzle, the powder P is fed to the chute box 11. By feeding the compressed air, clogging or the like of the powder in the vicinity of a connected part with the chute box 11 in the hose 12 is reduced, and a prescribed amount of powder P can be fed to the chute box 11. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method of supplying powder for a molded body used when filling a metal mold for forming a molded body of metal powder with a chute box. In particular, the present invention relates to a method for supplying powder for a molded body that can reduce variation in the amount of powder filled in a mold.

  Conventionally, various sintered materials manufactured by powder metallurgy are used for automobile parts, general machine parts, and the like. In the powder metallurgy method, generally, metal powder as a raw material is filled in a molding die and molded, and the obtained molded body is sintered to produce a sintered material. When filling the metal mold as a raw material into the mold, a powder feeder as described in Patent Document 1 is used. This powder feeding apparatus is installed above the mold and has a hopper storing powder, a chute box for filling the mold with the powder in the hopper, and a hose connecting the hopper and the chute box. With. The chute box can move on the surface of the mold. When powder is supplied from the hopper through the hose, the chute box moves from a predetermined position on the mold to the mold cavity and allows the powder to fall freely by its own weight. To fill the cavity. The powder in the hose is transferred by its own weight.

Japanese Unexamined Patent Publication No. 07-164193

  Conventionally, it has been desired to reduce variations in the weight and dimensional accuracy of sintered materials.

  Patent Document 1 proposes applying vibration to the chute box in order to make the packing density of the powder filled in the cavity of the mold uniform. However, as a result of investigations by the present inventors, it has been found that the amount of powder supplied to the chute box itself varies in the conventional supply method. As a result, the instability of the supply amount to the chute box resulted in variations in the filling amount into the mold cavity, which in turn caused variations in the weight and dimensional accuracy of the molded body and sintered material. Conceivable.

  Accordingly, an object of the present invention is to provide a method for supplying powder for a molded body that can reduce variations in the amount of powder supplied to a mold.

  This invention achieves the said objective by setting it as the structure which improves the fluidity | liquidity of the powder in the hose which transfers powder to a chute box.

  Specifically, the present invention relates to a method for supplying a powder for a molded body for supplying the powder for a molded body from a hopper to a chute box through a hose. In particular, in the supply method of the present invention, the powder is supplied to the chute box while feeding gas into the hose.

  When the powder is transferred to the chute box only by its own weight as in the prior art, in particular, the powder on the lower side of the hose is pressed against the powder on the upper side of the hose, so that the lower region of the hose close to the chute box The powder is easy to stay. On the other hand, according to the said structure, powder can be pumped to the chute box side with the gas forced into the hose. That is, the powder in the hose easily flows due to the forced inflow of the gas, so that the powder in the hose can be efficiently supplied to the chute box. In particular, in the case of producing a metal powder compact, the raw material powder often contains a lubricant in addition to the metal powder. With this lubricant, the metal powders are solidified to form a bridge, or the metal powder adheres to the inner wall of the hose, so that the powder remains in the hose or does not easily fall into the chute box. On the other hand, by sending gas into the hose as described above, it is possible to substantially prevent the powder transferred from the hopper to the hose by suppressing adhesion between powders, adhesion to the inner wall of the hose, and staying. The whole quantity can be transferred to the chute box. When the predetermined amount of powder is sufficiently supplied to the chute box, the predetermined amount of powder can be filled from the chute box into the cavity of the mold. Therefore, according to the supply method of the present invention, it is possible to reduce the variation in the weight and the size of the compact and the sintered material, and contribute to the mass production of the sintered material with a uniform weight and high dimensional accuracy. It is expected that

  The gas delivery location in the hose can be selected as appropriate. In particular, it is preferable that the gas is fed from the vicinity of the connection point of the hose with the chute box. When the powder is moved in the hose by its own weight as described above, the powder tends to stay in the vicinity of the connection portion with the chute box located on the lower side of the hose. Therefore, powder can be efficiently supplied to the chute box by sending the gas at least in the vicinity of the connection portion of the hose with the chute box. In addition, the vicinity of the connection part with a chute box means the area | region from the said connection part to 1/3 of the length of a hose.

  According to the method for supplying powder for a molded body of the present invention, the amount of powder supplied to the chute box can be made uniform, and in turn, variation in the amount of powder charged into the mold can be reduced.

FIG. 1 is a schematic configuration diagram illustrating a powder feeding apparatus used in the supply method of the present invention. FIG. 2 is a schematic explanatory view showing, in an enlarged manner, a nozzle portion attached to a hose in the powder feeding device used in the supply method of the present invention. FIG. 3 is a graph showing the relationship between the weight of the powder in the chute box and the weight of the compact, and the number of times of powder supply / number of compacts. FIG. 3 (I) shows the gas fed into the hose. However, when the supply method I for transferring the powder is used, FIG. 3 (II) shows the case of using the supply method II for transferring the powder only by its own weight. FIG. 4 is a graph showing the standard deviation of the weight of the powder in the chute box and the standard deviation of the weight of the molded body when the supply methods I and II are used.

  Using two different supply methods I and II, which will be described later, after supplying metal powder to the chute box, filling the molding die from the chute box to produce a plurality of molded bodies, the weight of the obtained molded body And the weight of the powder supplied into the chute box.

  Here, as metal powder, Fe-based alloy powder (Distaloy-AB manufactured by Höganäs AB) having a composition of Fe-1.75% Ni-0.5% Mo + 1.5% Cu (unit: mass%) is added with 0.2 mass% Gr (graphite). ) And a mixed powder in which 0.6% by mass of a lubricant (ethylenebisstearic acid amide) was mixed was used.

  In both supply methods I and II, the powder feeder shown in FIG. 1 was used. The powder feeding device 1 is a device for filling the powder P, which is a raw material of the molded body, into the cavity 21 of the mold 20, and the hopper 10 in which the powder P is stored, and the powder P in the hopper 10 into the cavity 21 A shoot box 11 for filling the hopper 10 and a hose 12 for connecting the hopper 10 and the shoot box 11 to each other. The basic structure of the powder feeder 1 is the same as that of the conventional powder feeder. The hopper 10 is disposed above the mold 20, and the chute box 11 is disposed below the hopper 10, and is moved back and forth in the direction indicated by the white arrow on the plate 22 on the surface of the mold 20 by a moving mechanism (not shown). It is movable. When a predetermined amount of powder P is supplied from the hopper 10 to the chute box 11, the chute box 11 is moved from a predetermined position on the mold 20 to the cavity 21 side, and the powder P in the chute box 11 can be freely moved by its own weight. Drop and fill cavity 21. Although omitted in FIG. 1, the mold 20 is a general assembly including a die holder, upper and lower punches, a core rod, and the like.

  In particular, the powder feeding apparatus 1 shown in FIG. 1 is configured to be able to force gas into the hose 12. Specifically, in the powder supply apparatus 1, a plurality of nozzles 13 (13a, 13b, 13c, 13d, 13e) that are inserted and fixed spaced apart in the longitudinal direction of the hose 12, and a cylinder part 14 that stores compressed air With The cylinder part 14 and each nozzle 13 are connected by a connecting pipe 15. Although not shown in FIG. 1, all the nozzles 13 are connected to the cylinder part 14. Then, the compressed air in the cylinder part 14 is sent to each nozzle 13 via the connecting pipe 15 and sent into the hose 12 via each nozzle 13. Here, as shown in FIG. 2, the end face of each nozzle 13 has an inclined shape that is cut by a plane that intersects the axial direction of the nozzle 13, and each nozzle 13 has its opening 13o facing the lower chute box side. 13 is fixed to the hose 12. By arranging each nozzle 13 with the opening 13o as an inclined surface and with the inclined surface facing downward, the opening becomes a surface orthogonal to the axial direction of the nozzle, and this orthogonal surface is orthogonal to the vertical direction. Compared with the case where it arrange | positions in this way, it is easy to transfer the powder P to the lower chute box side. Further, when the inflow of compressed air is stopped, the powder P does not flow backward from the opening 13o to the cylinder part. In FIG. 2, the powder P is highlighted.

  The material, diameter, number of nozzles, and the like of each nozzle 13 can be selected as appropriate. Further, a position where each nozzle 13 is fixed to the hose 12, an interval between adjacent nozzles, and the like can be appropriately selected. Here, as shown in FIG. 1, at least one hose 12 is located in the vicinity of the connection location with the chute box 11, specifically, at a location within 1/3 of the hose length from the connection location in the hose 12. Two nozzles 13 are attached to allow compressed air to flow in the vicinity of the connection portion of the hose 12. More specifically, here, each nozzle 13 is made of material: SUS steel, outer diameter: φ5 mm, inner diameter: φ3 mm, and five nozzles 13 are installed at a position 1 m above the chute box 11 at intervals of 50 cm.

  Here, compressed air is used, but various gases can be used as long as no trouble such as reaction with the powder P occurs. For example, an inert gas such as nitrogen or argon can be used. In addition, here, the cylinder 14 storing compressed gas (air) is provided, and the inflow amount and the inflow pressure of the gas are adjusted by opening and closing the valve. Alternatively, the ambient air may be compressed by a compressor, and the compressed air may be forcibly flowed into the hose 12 via each nozzle 13. In this case, it is possible to adjust the inflow amount and the inflow pressure of air by controlling the compressor.

  Then, in the supply method I, a predetermined amount of powder P is introduced into the hose 12 from the hopper 10 in a state where the compressed air is forcibly flowed into the hose 12 using the powder feeding device 1 including the plurality of nozzles 13. . After a predetermined time elapsed from the introduction to the hose, the flow of compressed air was stopped, the hose 12 was removed from the chute box 11, and the weight of the powder P in the chute box 11 was measured. The result is shown in FIG. Here, compressed air was introduced from five nozzles. In both supply methods I and II, the amount of powder supplied from the hopper to the chute box at one time was set to a weight necessary for a predetermined molded body (a ring-shaped body described later).

  On the other hand, in the supply method II, a predetermined amount of powder P was introduced into the hose 12 from the hopper 10 without flowing in the compressed air. After a predetermined time elapsed from the introduction to the hose, the hose 12 was removed from the chute box 11, and the weight of the powder P in the chute box 11 was measured. The result is shown in FIG. 3 (II).

  The powder P in the chute box 11 whose weight has been measured is filled into the cavity 21 of the mold 20, and the powder P is cold compression molded (molding pressure: 500MPa), outer diameter: φ80mm, inner diameter: φ50mm, thickness A ring-shaped molded body of 30 mm was produced. And the weight of each obtained molded object was measured. The results are shown in FIGS. 3 (I) and (II). FIG. 4 shows the standard deviation of the weight of the powder in the chute box and the standard deviation of the weight of the compact.

  As shown in Fig. 3, when using the supply method I that supplies powder to the chute box while feeding gas into the hose, the number of times of powder feeding is increased compared to the supply method II that does not send gas. However, it can be seen that the amount of powder supplied into the chute box is uniform and stable. Moreover, it turns out that the fluctuation | variation of the weight of a molded object is also small. These facts are supported by the fact that the standard deviation is smaller in the supply method I as shown in FIG. The reason for this is considered to be that the powder hardly stays in the hose due to the gas feeding.

  From the above test results, when the powder is transferred from the hopper to the chute box via the hose, the amount of powder supplied into the chute box can be made uniform by flowing gas into the hose. It can be seen that the weight of can be made uniform. And since the weight of a molded object is uniform, it is anticipated that the weight of a sintered material can also be made uniform. Moreover, since the amount of powder supplied into the chute box is uniform, a desired molded body can be accurately molded. Therefore, according to the supply method of the present invention, it can be suitably used for mass production of a sintered material having excellent dimensional accuracy.

  The above-described embodiment can be appropriately changed without departing from the gist of the present invention, and is not limited to the above-described configuration. For example, the hole diameter and number of nozzles, the arrangement position with respect to the hose, and the like can be changed as appropriate.

  The method for supplying a powder for a molded body of the present invention can be suitably used for supplying powder to a mold for forming a powder molded body in producing various sintered materials by powder metallurgy.

1 Powder feeder 10 Hopper 11 Chute box 12 Hose
13,13a, 13b, 13c, 13d, 13e Nozzle 13o Opening 14 Cylinder 15 Connecting pipe
20 Mold 21 Cavity 22 Plate
P powder

Claims (2)

A method for supplying powder for a molded body for supplying powder for a molded body from a hopper to a chute box through a hose,
A powder supply method for a compact, wherein the powder is supplied to the chute box while gas is fed into the hose.   2. The method for supplying powder for a molded body according to claim 1, wherein the gas is fed from the vicinity of a connection portion of the hose with the chute box.

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