JP5577557B2 - Die for molding - Google Patents

Description

  The present invention relates to a metal mold for molding metallurgical powder, and more particularly to a molding die for manufacturing a sintered part having a large step on the upper surface.

  Sintered parts are manufactured through a molding process and a sintering process. In the molding process, the green compact is manufactured by compressing the metallurgical powder using a molding press. The green compact is conveyed to a sintering furnace and sintered to produce a sintered body. The molding press is provided with a molding die including a molding die, an upper punch, and a lower punch, and metallurgical powder is supplied to a molding hole formed in the molding die.

In general, the pressure during molding of the green compact is about 6 to 10 t / cm ² , and very large stress is applied to the mold. Therefore, the mold for molding is required to have wear resistance, pressure resistance, fatigue strength, toughness and the like. Patent Document 1 listed below discloses a die constituted by an inner ring and an outer ring. This die satisfies the requirements for pressure resistance and wear resistance by an outer ring having pressure resistance and an inner ring having wear resistance.

  When molding a product having a groove on the upper surface of the sintered part, molding is performed using an upper punch provided with a protrusion corresponding to the groove. When the groove of the sintered part is large, the protrusion of the upper punch becomes large, and the density of the portion compressed by the protrusion becomes larger than the other part. Therefore, in order to obtain a green compact with a uniform density, the following document 2 discloses a technique using a powder oyster provided with a groove in a molding die and attached to a feeder box. By molding after removing unnecessary metallurgical powder in the groove portion by powder oyster, it is possible to produce a sintered part having a uniform density in the part.

JP 58-116999 A JP-A-6-15492

  However, when the forming die having a groove on the upper surface disclosed in Patent Document 2 is constituted by the inner ring and the outer ring disclosed in Patent Document 1, the stress of shrink fitting is concentrated on the groove of the die, The mold could be damaged.

  Therefore, the present invention prevents damage caused by the fitting stress of the mold in the molding die having a groove on the upper surface, and manufactures a sintered part having a uniform density by powder molding using the molding die. The challenge is to do.

In order to solve the above problem, in the present invention,
A molding die that is used in a mold for powder molding and has a groove on its upper surface,
The molding die is composed of an upper die and a lower die that contacts the upper die,
The groove bottom of the groove is provided on the lower die,
The groove side surface of the groove is composed of an upper groove side surface provided on the upper die and a lower groove side surface provided on the lower die so as to follow the upper groove side surface.
The lower die was a molding die having a first lower die having a molding hole and a second lower die fitted into the outside of the first lower die by shrink fitting.

  The molding die according to the present invention includes an upper die and a lower die that contacts the upper die, a groove bottom portion of the groove is provided on the lower die, and a groove side surface of the groove is an upper portion provided on the upper die. It is composed of a groove side surface and a lower groove side surface provided in the lower die so as to follow it, and the lower die is fitted into the first lower die having a molding hole and the outside of the first lower die by shrink fitting. And a lower die. With this configuration, the size of the groove of the lower die to be shrink-fitted can be reduced. When the lower die is manufactured by shrink fitting, it is possible to prevent the mold from being damaged due to stress on the mold that is greater than the strength of the groove.

  A molding die having a step on the side surface of the molding hole of the first lower die is preferable.

  The position of the lower surface of the upper punch at the position where the compression ends is taken as the compression position of the upper punch. When the forming hole has a step, the compression position of the upper punch is determined by the position of the step from the die upper surface, and the degree of freedom in setting the compression position of the upper punch is small. If the mating surface of the upper die and the lower die is below the mold position from the compression position of the upper punch, streaks of the mating surface may be formed in the resulting green compact, or the mold may be deformed by stress during compression. There is a risk of damage. If a step is formed on the side of the molding hole of the lower die and the lower groove side of the groove is also formed on the lower die, the mating surface between the upper die and the lower die even if the degree of freedom in setting the compression position of the upper punch is small A sufficient distance from the compression position of the upper punch can be taken.

  A molding die having a distance from the groove bottom to the upper surface of the lower die is preferably 10 mm or less.

  If the distance between the bottom of the side surface of the lower groove of the groove and the upper surface of the lower die is 10 mm or less, when the lower die is manufactured by shrink fitting, the mold may be damaged due to stress on the mold that exceeds the strength of the groove. Can be prevented.

  The molding die of the present invention is a molding die having a groove on the upper surface, and has an upper die having an upper groove side surface of the groove and a lower die in contact with the upper die and having a lower groove side surface of the groove. Therefore, it is possible to prevent damage caused by the fitting stress of the mold, and to manufacture a sintered part having a uniform density by compacting using the molding die.

It is a metal mold sectional view of one embodiment of this invention. It is a metal mold sectional view from the side of the embodiment. It is an enlarged view of the upper die and lower die of the embodiment. It is a top view of the upper die of the same embodiment. It is a metal mold sectional view from the side at the time of powder supply of the embodiment. It is a metal mold sectional view from the side at the time of the end of compression of the embodiment. It is a perspective view of the sintered component manufactured by the same embodiment. It is metal mold | die sectional drawing of other embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings.
The molding die of the present invention is used for a sintered part having a dent, and is used for producing a green compact by compressing metallurgical powder filled in a molding hole. The green compact is then sintered and sized and machined according to product specifications. The target sintered parts are automotive parts. Hereinafter, the structure of the mold and the molding process will be described.
[Mold structure]

  The embodiment of the present invention shown in FIG. 1 is a molding die for producing the sintered part A shown in FIG. FIG. 1 is a sectional view of a mold during molding. The mold of this embodiment includes an upper punch 2, an upper die 3, a lower die 4, and a lower punch 5. The lower die 4 includes a first lower die 4a and a second lower die 4b from the inside. The first lower die 4a is fitted into the second lower die 4b by shrink fitting. The outer periphery of the first lower die 4a and the inner periphery of the second lower die 4b are cylindrical.

  The upper punch 2 is attached to an upper punch plate (not shown) driven by an upper ram of a molding press. The lower punch 5 is attached to a base plate (not shown). The upper die 3 and the lower die 4 are attached to a die plate 6.

The sintered part A in FIG. 7 has a semicircular recess 1 on the top surface and a protrusion 7 on the side surface. FIG. 3 is an enlarged view of the upper die 3 and the lower die 4. An upper molding hole 8 is formed in the upper die 3, and a lower molding hole 9 is formed in the first lower die 4a. The upper molding hole 8 and the lower molding hole 9 are set so as not to be stepped on the upper surface of the first lower die 4a, or the upper molding hole 8 is set to have a larger cross section than the lower molding hole 9. The On the side surface of the lower molding hole 9 , there is a step 10 for forming the projection 7 of the sintered part A.

  In the upper die 3, the first lower die 4a, and the second lower die 4b, a groove portion 11 is formed in a portion corresponding to the recessed portion 1 of the sintered part A. The side surface of the groove 11 includes an upper groove side surface 12 formed on the upper die 3 and a lower groove side surface 13 formed on the first lower die 4a and the second lower die 4b so as to follow the upper groove side surface 12. The mating part of the upper groove side surface 12 and the lower groove side surface 13 may be smoothly connected, or the lower groove side surface 13 has a step which is located inside the groove rather than the upper groove side surface 12. It may be formed. A groove bottom 14 which is the lowest part of the groove 11 is formed in the first lower die 4a and the second lower die 4b. A distance D from the groove bottom portion 14 to the upper surface of the first lower die 4a is set to 10 mm or less. When the distance D is 10 mm or less, it is possible to prevent the lower die 4 from being damaged from the lower groove side surface 13 even if the first lower die 4a is engaged with the second lower die 4b by shrink fitting. it can. The size of the groove 11 is determined by the size of the recess 1 of the sintered part A. When the required size of the groove portion 11 is very large, if the groove portion is formed only on the upper die 3, the thickness of the upper die 3 is increased. In this case, the mating surface of the upper die 3 and the lower die 4 comes below the compression position of the upper punch, causing problems such as streaking in the molded body. Therefore, in the present embodiment, the groove portion is constituted by the upper groove side surface 12 and the lower groove side surface 13 so that the mating surface of the upper die 3 and the lower die 4 is set above the compression position of the upper punch. It is possible to do.

FIG. 2 is a sectional view of the mold from the side of the mold. A feeder box 15 for supplying metallurgical powder is in contact with the upper surfaces of the upper die 3 and the die plate 6 in a state where it can slide back and forth. A powder oyster 16 is provided on the front surface of the feeder box 15. As shown in FIG. 1, wherein the powder oyster 1 6 protrusions 17 conforming to the configuration of the groove 11 is formed. As the feeder box 15 moves back and forth, the protrusion 17 of the powder oyster 16 removes unnecessary metallurgy powder from the metallurgy powder supplied to the upper molding hole 8 and the lower molding hole 9. .

  As shown in FIG. 3, the upper groove side surface 12 has an inclination θ of 60 degrees or less with respect to the upper surface of the upper die 3. By setting the inclination θ to 60 degrees or less, the shape of the metallurgical powder left in the upper molding hole 8 and the lower molding hole 9 after being removed by the projections 17 of the powder oyster 16 is easy. Can be held in.

FIG. 4 is a top view of the upper die 3. The groove 11 is formed linearly from the upper molding hole 8 and the lower molding hole 9 in the outer peripheral direction of the upper die 3. The groove 11 may be cut through to the outer periphery of the upper die 3 or may be stopped in the middle of the upper die 3. When the groove 11 is cut through to the outer periphery of the upper die 3, the upper die 3 is constituted by two members on the left and right with the groove 11 as a boundary. In that case, there are advantages such that the location for securing the metallurgical powder removed by the powder oyster 16 can be set in advance, and the upper die 3 can be easily manufactured.
[Molding process]

  In the forming step, as shown in FIG. 5, first, metallurgy powder 18 is filled from a feeder box 15 into a cavity formed by the upper forming hole 8, the lower forming hole 9 and the lower punch 5. Generally, the metallurgical powder 18 filled in the cavity is leveled by the lower surface of the feeder box 15. If the lower surface shape of the feeder box 15 is flat, the density of the portion compressed by the protrusion of the upper punch 2 will be higher than the other portions. For this reason, in the present embodiment, it is possible to remove the excess metallurgical powder in the recess 1 by the protrusion 17 of the powder oyster 16 and obtain a uniform density.

  Thereafter, the upper punch 2 is lowered. As shown in FIG. 6, the metallurgical powder is compressed by the cooperation of the lower die 4, the upper punch 2 and the lower punch 5 to form a green compact 19. The position of the lower surface of the upper punch 2 at the end of compression is set below the lower surface of the upper die 3.

  FIG. 8 shows another embodiment of the present invention. When the removal amount of the powder is insufficient, the lower punch 5 may be divided into a first lower punch 5a and a second lower punch 5b. In that case, the first lower punch 5a corresponding to the portion to be removed when the metallurgical powder is filled in the molding hole is installed upward to adjust the filling amount of the metallurgical powder. Further, the upper punch 2 may be divided into a first upper punch 2a and a second upper punch 2b. By performing powder movement with the first lower punch 5a and the first upper punch 2a, the shape of the groove 11 can be maintained and a sintered part with a uniform density can be manufactured.

A sintered part A illustrated in FIG. 7 was molded using the mold shown in FIG. The dimensions of the sintered part A are as follows.
Width W: 100mm
Thickness T1: 20mm
Recess radius: 25mm
Total length H: 45mm
The length L of the protrusion 7: 12 mm
The dimensions of the mold are as follows.
Upper die 3 thickness T2: 15 mm
Distance D between groove bottom 14 and upper surface of lower die: 8 mm
Angle θ between upper groove side surface 16 and upper die 3 upper surface: 60 degrees Material of first lower die 4a: alloy steel Material of second lower die 4b: cemented carbide

It was confirmed that the density difference between the lower part B of the cylindrical part and the other part C was 0.1 g / cm ³ by compacting using this mold.

  In addition, this invention is not necessarily limited to the Example mentioned above, In the range which does not deviate from the summary of this invention, it can change suitably.

    The powder molding die of the present invention is suitable for obtaining sintered parts for automobiles.

DESCRIPTION OF SYMBOLS 1 Recessed part 2 Upper punch 2a 1st upper punch 2b 2nd upper punch 3 Upper die 4 Lower die 4a 1st lower die 4b 2nd lower die 5 Lower punch 5a Lower punch 5b 2nd lower punch 6 Die plate 7 Protrusion 8 Upper part Molding hole 9 Lower molding hole 10 Step 11 Groove portion 12 Upper groove side surface 13 Lower groove side surface 14 Groove bottom portion 15 Feeder box 16 Oyster 17 Powder oyster projection 18 Metallurgical powder 19 Compact A Sintered part θ Upper groove side surface Angle between upper die upper surfaces

Claims (3)

A molding die that is used in a mold for powder molding and has a groove on its upper surface,
The molding die is composed of an upper die and a lower die that contacts the upper die,
The groove bottom of the groove is provided on the lower die,
The groove side surface of the groove is composed of an upper groove side surface provided on the upper die and a lower groove side surface provided on the lower die so as to follow the upper groove side surface.
The lower die is a molding die having a first lower die having a molding hole and a second lower die to be fitted on the outside of the first lower die by shrink fitting.   The molding die according to claim 1, wherein a step is formed on a side surface of the molding hole of the first lower die.   The molding die according to claim 1 or 2, wherein a distance from a groove bottom of the groove to an upper surface of the lower die is 10 mm or less.

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