JP2017094345A - Powder molding metal mold for stepped sintered part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust molding density of an area for compressing raw material powder by a core rod and an upper punch or a die and the upper punch, in a short time, by dispensing with disassembling and reassembly of a die set, on a powder molding metal mold for molding a step part of a stepped sintered part by the core rod and the die.SOLUTION: A powder molding metal mold is constituted of a body part having a step part molding part for forming a step part in a core rod for molding an inner peripheral surface including the step part of a molding body, and a plurality of tip pieces detachably connected to its body part. The plurality of tip pieces are different in the respective lengths, and any of its plurality of tip pieces is selectively connected to the upper end of the body part, to adjust the length up to the upper end of the tip pieces from the step part molding part.SELECTED DRAWING: Figure 1

Description

  The present invention provides a core rod or die having a stepped surface on which an outer diameter and an inner diameter are changed, on an inner peripheral surface or an outer peripheral surface, and forming a stepped portion and a region sandwiching the stepped portion therebetween. The present invention relates to a powder molding die for molding a stepped sintered part made by:

  An example of a stepped sintered part manufactured by powder metallurgy is shown in FIGS. The stepped sintered component 20 in FIG. 3 has a stepped portion 22 that causes a diameter difference between an upper region and a lower region of a central hole 21 (inner peripheral surface).

  The stepped portion 22 of the illustrated sintered part causes a diameter difference in the entire circumference of the central hole 21, but it is also conceivable that a step difference in the circumferential direction of the central hole 21 occurs.

  On the other hand, the stepped sintered component 30 of FIG. 4 has a stepped portion 32 on the outer periphery that causes a difference in outer diameter between the upper region and the lower region of the outer peripheral surface (which need not be the entire periphery). Yes. The central hole 31 is replaced with a stepped hole or omitted depending on the shape of the part.

  The forming of the step portion in the compacting process of such a sintered part is generally performed by an independent punch. However, the punch portion is formed for reasons such as a small step portion size or a taper step portion. When the strength cannot be ensured, and therefore the use of an independent punch is not allowed, the stepped portion is sandwiched between the stepped portion and the stepped core rod having a stepped molding surface or a stepped die. It is necessary to adopt a method of forming the molds in a lump.

  In the following, a case where the stepped sintered part 20 in FIG. 3 is formed using a powder molding die having a stepped core rod is taken as an example, and the strength variation of each part of the part is reduced in the forming (of the molded body). A method conventionally employed to make the molding density uniform will be described.

  Molding of the stepped sintered component 20 in FIG. 3 in the compacting process is performed using the powder molding die shown in FIG. 7, that is, a die including the die 1, the lower punch 3, the core rod 4, and the upper punch 5. Done.

  FIG. 7 shows the filling state of the powder P into the cavity of the powder molding die. In FIG. 7, the compression ratio of the powder in the region A compressed by the core rod 4 and the upper punch 5 and in the region B compressed by the lower punch 3 and the upper punch 5 is as follows. It is necessary to adjust each to make the density uniform.

  Regarding the adjustment, the compression ratio of the region B can be optimized by changing the standby position of the lower punch 3. On the other hand, the compression ratio in the region A is basically determined by the length L from the stepped portion 4c of the core rod 4 to the tip (upper end).

  In order to make the length L the length corresponding to the target compression ratio of the region A, conventionally, the following method has been adopted.

  The method is to prepare a number of core rods with different lengths L, perform a molding test using one of the core rods, and examine the density difference between the regions A and B of the resulting molded body. Check for excess or deficiency of length L.

  When it is determined that the length L is too long, the core rod is shorter than the core rod used for the molding test, and when the length L is determined to be too short, the core rod is used for the molding test. The molding test is performed again by replacing the core rod with a long length L, and the operation is repeated until the density of the regions A and B of the obtained molded body becomes uniform.

  Patent Document 1 below describes a powder molding method using a stepped core rod. In the stepped core rod of Patent Document 1, the upper part (tip side) and the lower part are divided at the installation point of the step part, and the upper part and the lower part are mechanically fastened or bonded. Yes.

JP 2008-272895 A

  Based on the results of the molding test, the conventional method of replacing the core rod with a spare part with a different length and optimizing the length from the step to the tip of the core rod is a die set for removing and reattaching the core rod. It was necessary to remove all the molding elements (die, punch, core rod) of the assembled powder molding die and reassemble them, and there was a problem that a lot of labor and time were spent on the reassembly work.

  The replacement of the core rod usually takes 2 to 3 hours, and during that time, the molding operation is also stopped, so a solution to the problem is desired.

  Even when the stepped portion of the sintered part having a stepped portion on the outer peripheral surface that causes a diameter difference between the upper region and the lower region is formed by a die having a forming surface with a stepped portion, It is necessary to remove the die once and replace it with a die having a different dimension from the stepped portion to the upper end of the molding surface, and even in this case, it is regarded as a problem that the reworking time becomes long.

  In addition, although the said patent document 1 is equipped with the core rod which is divided | segmented into a longitudinal direction and can remove an upper part, this patent document 1 cannot respond to said problem, and suggests the technical thought of this application mentioned later. I can't even see it.

  The present invention relates to a powder molding die for molding a step portion of a stepped sintered part with a core rod or a die, and adjusts a molding density in a region where the raw material powder is compressed by the core rod and the upper punch or the die and the upper punch. The purpose of this is to eliminate the need for disassembling and reassembling, and to make it possible in a short time.

  A powder molding die according to one embodiment of the present invention provided as a solution to the above problems will be described below.

  The powder molding die of 1) below is for producing a powder compact of a sintered part having a step part whose inner diameter is changed on the inner periphery in the manufacture of a stepped sintered part. In addition, the powder molding die of 2) below is for producing a powder compact of a sintered part having a step portion for changing the outer diameter on the outer periphery. Both molds comprise a die, a lower punch, a core rod and an upper punch.

1) The core rod for forming the inner peripheral surface including the step portion of the molded body has a main body portion provided with a step portion forming portion for forming the step portion, and a plurality of the core rods are detachably connected to the main body portion. The plurality of tip pieces are different in length, and any one of the plurality of tip pieces is selectively connected to the upper end of the main body portion to form the step portion molding portion. Powder molding die whose length to the upper end of the tip piece is adjusted.

2) The die for forming the outer peripheral surface including the step portion of the molded body has a main body portion having a step portion forming portion for forming the step portion, and a plurality of pieces detachably connected to the main body portion. The plurality of divided plates have different thicknesses, and any one of the plurality of divided plates is selectively placed and connected to the upper surface of the main body to form the stepped portion. Powder molding mold in which the length from the upper part to the upper surface of the split plate is adjusted.

  According to the powder molding die of the present invention, the molding density in the region where the raw material powder is pressed by the core rod or the stepped portion molding part of the die can be set to the target value in a short time without disassembling and reassembling the die set. Can be adjusted.

It is sectional drawing which shows an example of the powder shaping die of this invention. It is sectional drawing which shows the other example of the powder shaping die of this invention. It is sectional drawing which shows an example of the stepped sintered component manufactured by shape | molding with the powder mold of this invention. It is sectional drawing which shows the other example of the stepped sintered component manufactured by shape | molding with the powder mold of this invention. It is sectional drawing which shows the powder compact for the stepped sintered component of FIG. It is sectional drawing which shows the powder compact for the stepped sintered component of FIG. It is sectional drawing of the conventional powder molding die which shape | molds the stepped sintered component of FIG. It is sectional drawing which shows the dimension specification of the prototype of a powder molding die.

[Description of Embodiment of the Present Invention]
The powder molding die for stepped sintered parts according to one aspect of the present invention forms a molded body having a stepped portion on the inner periphery. With respect to the powder molding die, the tip end side of the core rod is constituted by a tip piece that is detachable from the main body of the core rod.

  The tip piece includes a plurality of pieces having different lengths, one of which is selected and detachably connected to the upper end of the main body portion of the core rod. And the length from the step part shaping | molding part formed in the said main-body part of the core rod to the upper end of the said tip piece is changed by changing the tip piece from which the length differs.

  In addition, it is good to set the connection point of the main-body part of a core rod, and a tip piece above the lower end (lower end of the upper punch in a bottom dead center) of the upper punch in a compaction completion point.

  For those satisfying the condition, the joint between the main body and the tip piece is not transferred to the molded body, and the quality of molding does not deteriorate.

  In another embodiment of the powder molding die for molding a molded body having a stepped portion on the outer periphery, the die tip is constituted by a split plate that is detachable from the main body.

  A plurality of divided plates having different thicknesses are prepared, and one of them is selected and placed on and connected to the main body of the die. And the length from the step part formation part formed in the said main-body part of die | dye to the upper surface of a division | segmentation plate is changed by replacement | exchange of the division | segmentation plate from which the thickness differs.

  In this mold as well, for the same reason as described above, the connecting point between the die body and the dividing plate is preferably set above the upper end position of the molded body at the point where the compacting by the mold is completed.

[Details of the embodiment of the present invention]
Specific examples of the powder molding die according to one embodiment of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to these illustrations, is shown by the claim, and it is intended that all the changes within the meaning and range equivalent to a claim are included.

  The powder molding die shown in FIG. 1 is for molding a powder compact (20A in FIG. 5) for the stepped sintered component 20 in FIG. 4 provided with a step on the inner periphery.

  This powder molding die includes a die 1 that molds the outer periphery of the molded body 20A, a lower punch 3 that molds one end surface of the molded body 20A, a core rod 4 that molds the inner periphery of the molded body 20A, and a molded body 20A. This is a combination of the upper punch 5 for forming the other end face of the above.

  The core rod 4 has a stepped portion forming portion 4c for forming a stepped portion 22 formed on the inner periphery of the formed body 20A on the outer periphery. The core rod 4 is configured by detachably attaching the divided tip piece 4b to the tip of the main body portion 4a.

  The illustrated core rod 4 has a recess 6 at the tip of the main body 4a. Moreover, it has the convex part 7 which fits and fits with respect to the said recessed part 6 in the abutting surface (bottom surface) with respect to the main-body part 4a of the front-end | tip piece 4b.

  Positioning of the tip piece 4b with respect to the main body portion 4a is performed by the concave portion 6 and the convex portion 7.

  The tip piece 4b is a column that extends upward from the upper end of the main body 4a. The tip piece 4b has a mounting hole 8 with a seat groove at the center. Moreover, it has the outer peripheral surface of the same shape as the outer peripheral surface of the part above the level | step difference shaping | molding part 4 of the main-body part 4a. Thereby, there is no step at the joint position between the tip piece 4b and the main body 4a. The term “cannot be stepped” as used herein does not require that there is no step in a geometrically strict sense. For example, a step that allows a minute step that is less than 10 μm due to a manufacturing intersection is allowed. It is.

  Moreover, the main-body part 4a has the screw hole 9 on the upper surface. The tip piece 4b is connected to the main body 4a using a fastening screw 10 passed through the attachment 8. The fastening screw 10 is screwed into the screw hole 9 with its head depressed in the seat groove of the mounting hole 8.

  According to the powder molding die of FIG. 1, by changing the tip piece 4b of the core rod, the length from the step forming portion 4c provided on the core rod 4 to the upper end of the tip piece 4b is optimized, and the step portion of the core rod It is possible to eliminate or reduce the molding density difference between the region A of the molded body formed by the forming portion 4 c and the upper punch 5 and the region B formed by the lower punch 3 and the upper punch 5.

  If such a mold is used, it is only necessary to replace the tip piece 4b of the core rod 4 with one having a different length, so there is no need to disassemble the die set (and therefore no reassembly is required), and replacement of the tip piece (region) Adjustment of the molding density of A) can be performed in just a few minutes.

  Note that in a mold for forming a molded body having a step portion on the inner periphery, a step portion formed on the inner diameter side of one end surface (the surface to be lowered at the time of molding) of the molded body can also be formed with a core rod.

  As shown by a chain line in FIG. 3, when the stepped portion 23 formed on the inner diameter side of the end surface is a tapered surface intersecting an obtuse angle with respect to the inner peripheral surface or a stepped portion having a small radial dimension, The use of the divided lower punch is not allowed from the viewpoint of securing the strength of the punch. However, in the case of forming with a core rod, the stepped portion of the tapered surface of the end face is also provided with a second stepped portion forming portion on the core rod. It can be done without hindrance.

  In the powder molding die of FIG. 1, the connection point Cp between the main body portion 4a of the core rod 4 and the tip piece 4b is set above the upper end position of the compact at the compacting completion point by the die. Therefore, there is no deterioration in molding quality (transfer of the seam) due to the seam between the main body 4a and the tip piece 4b.

  The powder molding die 1 for the stepped sintered component 30 shown in FIG. 2 is for molding the molded body 30A of FIG. 6 in which the step portion 32 is provided on the outer periphery.

  This powder molding die includes a die 1 for molding the outer periphery including the step portion 32 of the molded body 30A, a lower punch 3 for molding one end face of the molded body 30A, and a core rod 4 for molding the inner circumference of the molded body 30A. And the upper punch 5 which shape | molds the other end surface of the molded object 30A is combined.

  The die 1 has a stepped portion forming portion 1c for forming a stepped portion 32 on the outer periphery of the molded body 30A on the inner periphery. The die 1 is configured by detachably attaching a dividing plate 1b to the tip of a main body 1a.

  A plurality of divided plates 1b having different thicknesses are prepared, and any one of the divided plates is selectively placed and connected to the upper surface of the die body 1a. The length from the step forming portion 1c to the upper surface of the divided plate 1b is adjusted.

  The hole 2a serving as a powder inlet provided in the divided plate 1b is provided in the main body 1a in consideration of the diameter expansion amount (about 2/100 to 5/100 mm on one side) due to the spring back of the molded body at the time of taking out. It is preferable to set the inner diameter to be larger than the large-diameter portion hole diameter of the molding hole 2 to be formed (preferably larger by the amount corresponding to the diameter expansion amount), so that the molded body can be taken out from the mold.

  In the powder mold shown in FIG. 2, the divided plate 1b is connected to the main body 1a using fastening bolts (not shown). Positioning of the divided plate 1b with respect to the main body 1a can be performed using a die assembly hole provided in a die plate (not shown), and positioning unevenness is provided on the main body 1a and the divided plate 1b. You can also.

  Also in this mold, the connection point Cp between the die body 1a and the dividing plate 1b is set above the upper end position of the molded body at the point where the compacting by the mold is completed.

  The powder molding die of FIG. 2 optimizes the length from the step forming portion 1c formed on the die 1 to the upper surface of the die 1 by replacing the die dividing plate 1b with one having a different thickness. A difference in molding density of each part of the molded body can be eliminated or reduced.

  Since this die only needs to replace the divided plate 1b of the die, the replacement operation can be performed in a few minutes.

  It should be noted that the powder molding die of the present invention has a region A in the initial stage of pressurization by the upper punch (the region A in the molding by the die in FIG. 2 is a region where the powder P is pressed by the die 1 and the upper punch 5 ) May be provided with a powder escape portion that allows excess powder to escape outside the cavity.

  With respect to the mold of FIG. 1, when a groove or the like is provided on the outer periphery of the tip piece 4b of the core rod to create a gap between the outer periphery of the tip piece 4b and the inner peripheral surface of the upper punch 5, the gap becomes a powder escape portion. Thus, a part of the powder in the region A can be released into the upper punch 5 at the initial stage of pressurization.

  Further, as shown in FIG. 8, even in a structure in which a groove or a recess that creates a gap between the outer periphery of the upper punch 5 and the die 1 is provided on the inner surface of the upper end portion of the die forming hole 2, the gap is a powder escape. It becomes part 11 and a part of the powder in region A can escape to the outside of the die in the initial stage of pressurization.

  A powder molding die shown in FIG. 8 was prototyped. In this prototype mold, the inner diameter D of the die 1 is 36 mm, the core rod 4 is the outer diameter d1 of the main body portion 4a = 30 mm, the outer diameter of the distal end side small diameter portion of the main body portion 4a and the outer diameter d2 of the tip piece 4b = The distance L from the step forming portion 4c of the core rod to the upper surface of the die 1 (= the tip of the core rod) is 25 mm.

  The tip piece 4b of the core rod 4 was prepared in five types (length l = 23 mm to 27 mm) with different lengths in units of 1 mm.

  At the entrance of the forming hole 2 of the die 1, a powder escape portion 11 is provided to dent a part of the hole surface of the forming hole in the circumferential direction to a position 15 mm below the upper surface of the die 1.

Using this prototype mold, an iron alloy powder compact was formed. The molded product had a target value of the molding density of each part of 6.8 g / cm ³ .

  In this prototype mold, when the tip piece 4b of the core rod 4 is exchanged once, the molding density of the region where the powder is compressed by the core rod and the upper punch (region A in FIG. 1) is set to other regions (FIG. 1). It was possible to approximate the molding density of the region B).

  The time required for the replacement of the tip piece at this time was approximately 1 minute, and the work time that conventionally required 2-3 hours could be greatly shortened.

DESCRIPTION OF SYMBOLS 1 Die 1a Main-body part 1b Dividing plate 1c Step part shaping | molding part 2 Molding hole 2a The hole used as a powder inlet 3 Lower punch 4 Core rod 4a Main body part 4b Tip piece 4c Step part shaping | molding part Cp Connection point of the main-body part and tip piece of a core rod 5 Upper punch 6 Concave part 7 Convex part 8 Mounting hole 9 Screw hole 10 Fastening screw 11 Powder relief part 20, 30 Sintered part 20A, 30A Molded body 21, 31 Center hole 22, 23, 32 Step part P Powder A Area B compressed by core rod and upper punch of powder in cavity C Area L compressed by lower punch and upper punch of powder in cavity Length from stepped portion of core rod to tip

Claims (8)

A mold for forming a powder compact of a sintered part having a step part that changes the inner diameter on the inner periphery, comprising a die, a lower punch, a core rod, and an upper punch,
The core rod for forming the inner peripheral surface including the step portion of the molded body has a main body portion having a step portion forming portion for forming the step portion, and a plurality of tips removably connected to the main body portion. Each of the plurality of tip pieces is different in length, and any one of the plurality of tip pieces is selectively connected to the upper end of the main body portion, so that the tip piece from the step forming portion Powder molding mold whose length to the upper end of the is adjusted.   The powder molding die according to claim 1, wherein a connecting point between the main body portion of the core rod and the tip piece is set above the lower end of the upper punch at the compaction completion point.   The powder molding die according to claim 1 or 2, wherein the core rod includes a second step portion forming portion that further forms a step portion on the inner diameter side of the end surface on the larger inner diameter side of the molded body.   The said core rod is provided with the powder escape part which escapes the excess powder in a cavity to the inside of an upper punch at the initial stage of the pressurization by an upper punch on the outer periphery of the said tip piece. Powder mold. A mold for forming a powder molded body of a sintered part having a step portion that changes the outer diameter on the outer periphery, comprising a die, a lower punch, a core rod, and an upper punch,
The die for forming the outer peripheral surface including the step portion of the molded body has a main body portion provided with a step portion forming portion for forming the step portion, and a plurality of divisions that are detachably connected to the main body portion. Each of the plurality of divided plates has a different thickness, and any one of the plurality of divided plates is selectively placed on and connected to the upper surface of the main body from the step forming portion. Powder molding die whose length to the upper surface of the split plate is adjusted.   The powder molding die according to claim 5, wherein a connecting point between the main body portion of the die and the dividing plate is set above the lower end of the upper punch at the compaction completion point.   The powder molding die according to claim 5 or 6, wherein an inner diameter of a hole serving as a powder inlet into a cavity provided in the divided plate is set larger than an inner diameter of a molding hole provided in a main body portion of the die. .   Either of the Claims 1-7 in which the entrance part of the hole used as the powder injection port to the shaping | molding hole of die | dye is equipped with the powder escape part which escapes the excess powder in a cavity outside a cavity at the initial stage of the pressurization by an upper punch. The powder molding die as described in one.

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