JP2006336078A - Sintered part, method for producing the part, and sizing die - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a sintered part whose machining workability after sizing can be improved. <P>SOLUTION: A sintered part is subjected to sizing using a sizing die having both of a straightening face of straightening the dimensions of a sintered part and a non-straightening face which lies at a position confronted with the outer face of the sintered part and is not brought into contact with the sintered part, and thereafter, the region which has not been sized and in which a sintered skin is left is subjected to machining. For example, regarding a sintered part 1 in figure, the outer circumferential face 2 is provided with a recessed part 5 separating from the molding hole of a die, and the recessed part 5 which is not subjected to sizing, and in which a sintered skin is left is provided with a small hole 6 obtained by drilling after the sizing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sintered part that is finished by machining a part of the region after sizing, a method for manufacturing a sintered part that improves the machinability of the part, and a sizing die used in the method.

  Sintered parts made by sintering a raw material powder after molding are subject to a decrease in dimensional accuracy due to thermal strain. Therefore, after sintering, sizing for dimensional correction is performed before shipment. For sizing, a die having a combination of a punch and a die and, if necessary, a core is further used. A sintered part to be processed is pressed with a punch and press-fitted into a die forming hole. At that time, the part is compressed and the dimensions of the part are corrected.

  By the way, among sintered parts used as power system parts for vehicles, there is a sintered part that is subjected to sizing after sintering and further machined partially. For example, there is a part with an oil hole that goes out from the outer peripheral surface to the end face or inner diameter surface, and for that part, the oil hole cannot be molded using a mold, so drill the necessary part with a drill after sizing Yes.

  However, when sizing sintered parts, the outer peripheral surface is rubbed against the inner surface of the die forming hole, the inner peripheral surface is rubbed against the outer peripheral surface of the core, and the top and bottom surfaces are pressed by upper and lower punches. Therefore, the entire surface is hardened, and the surface is smoothed and slippery, making it difficult to machine. The drilling by the drill D as shown in FIG. 10 is performed, and in particular, when the drilling is performed on the curved surface or the slope of the sintered part 1, the biting of the drill D with respect to the sintered part 1 becomes unstable. The drill D is likely to swing, and burrs due to processing are likely to occur.

  If the shaft swings when the drill D bites the sintered part 1, the blade is damaged and the tool life is shortened, and the drill may break depending on the state of shaft swing. In addition, when a burr having a size that cannot be ignored occurs, it is necessary to remove the burr. Even when the tool to be machined is a cutting tool other than a drill, a grinding tool, a polishing tool, or the like, the same problem occurs when the surface of a component is sized and hardened.

  The sintered parts that are finished by machining after sizing are accompanied by the above-mentioned problems, but there are no methods for manufacturing sintered parts that can solve the problems, nor prior literatures that disclose such methods.

  An object of the present invention is to provide a sintered part that can improve the machinability after sizing, a method for manufacturing the sintered part, and a sizing mold used in the method.

  In order to solve the above problems, in the present invention, a correction surface that corrects the dimensions of the sintered part, and a non-correction surface that is in a position facing the outer surface of the sintered part and does not contact the sintered part, A sintered part characterized in that a sintered part is sized using a sizing die having both, and thereafter, machining is performed on a portion where the sintered skin is left without sizing the sintered part. A manufacturing method is provided.

The non-correcting surface of the sizing mold by this method can be generated by the following methods (1) and (2), for example.
(1) A concave portion having a dent larger than the sizing allowance of the sintered part is provided on a part of the correction surface of the sizing mold to generate the non-correction surface.
(2) A concave portion having a dent larger than the sizing allowance of the sintered part is provided on the outer peripheral surface or end face of the sintered part to generate the uncorrected surface.

  In the case of adopting the method (1), it has a punch for pressing the sintered part in the axial direction and a die for press-fitting the sintered part into the forming hole, and at least one of the punch and die has a sintered part. A sizing mold is used in which a recess having a larger amount of recess than the sizing allowance is provided, and the recess is in a position facing the outer surface of the sintered part. In the present invention, the sizing mold and a sintered part manufactured by the method of the present invention are also provided.

  The sintered part of the present invention has a sized skin surface that is sized and a non-sized sintered skin surface, and is machined to a portion having the sintered skin surface. The machining is notably limited to drilling, although the effects of the present invention are particularly remarkable when drilling. Even in cutting, grinding, and polishing with other tools, it can be expected to improve workability and improve tool life.

  In the method of the present invention, an unsized region is formed in the sintered part. Sintered skin is left in the non-sized region, and the surface is not hardened or smoothed by sizing. Since machining is performed there, the biting of the blade is improved and the life of the blade is improved. In addition, the stable run-off suppresses tool runout, and the non-sizing area maintains free-cutting performance unlike the sized area, which reduces the burrs generated by machining. It is also possible to simplify or omit the burr removal work.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, a recess 5 extending in the axial direction is provided on the outer periphery of a rectangular parallelepiped sintered part 1, the sintered part 1 is sized with a sizing die 10 shown in FIG. 2, and then a small hole 6 communicating with the central hole 4. Are processed by drilling. In the recess 5, the amount of recess from the outer peripheral surface 2 of the component is larger than the sizing allowance (for the radius) in the radial direction.

  An exemplary sizing die 10 includes a die 11, an upper punch 12, a lower punch 13 that faces the upper punch 12, and a core 14 that corrects the center hole 4. The die 11 has a forming hole 15 having a cross-sectional shape in which the hole size is reduced by an amount corresponding to the sizing allowance compared to the outer shape of the sintered part before sizing. The lower punch 13 and the core 14 are inserted into the molding hole 15. In this state, the sintered part 1 is pressed with the upper punch 12 and pressed into the molding hole 15, and the outer periphery of the sintered part 1 is applied to the inner wall of the molding hole 15. The inner periphery of the same part is rubbed against the outer periphery of the core 14, respectively. Further, the upper punch 12 is lowered to the bottom dead center, and the sintered parts 1 are compressed in the axial direction by the upper and lower punches 12 and 13.

  With the above operation, the outer dimension and the axial dimension of the sintered part 1 are corrected. At this time, the inner wall surface of the portion facing the recess 5 of the molding hole 15 is separated from the component 1 and does not work as a correction surface. Accordingly, the concave portion 5 is not sized and the surface of the sintered skin remains. The surface of the sintered skin is not hardened by sizing and is rough compared to the surface of the smoothed sizing skin. The point deviation is suppressed, and the shaft runout during machining is reduced. Although the recessed part 5 provided in the sintered component 1 is a through groove extending from one end to the other end in FIG. 1, it may be a stop groove as shown in FIG.

  Moreover, as shown in FIG. 4, the recessed part 5 is provided in the end surface 3 of the sintered component 1, and the recessed amount of the recessed part 5 is made larger than the axial sizing allowance of the end surface 3, and sintering skin remains without sizing. The recess 5 may be machined after sizing to provide a small hole 6 or the like. The recess 5 provided in the end surface 3 may be in a region deviated from the center of the component end surface, for example, in a position biased toward the outer periphery. Further, since it is not preferable that the side surface and the end surface of the recess 5 provided in the sintered part 1 have an acute edge on the surface of the part, as shown in FIG. 5, an obtuse angle (α = 90) with respect to the outer surface of the part 1. It is better to have a slope that meets

  Forming the non-sized region in the sintered part 1 can also be performed by other methods. As shown in FIG. 6 or FIG. 7, a non-sizing region is formed on the outer periphery of the sintered part 1 by a method in which a recess 16 is provided on the inner periphery of the die 11 and sizing is performed using the die 11 having the recess 16. 7 can be formed. FIG. 8 shows the sintered part 1 sized using the die 11 of FIG. 6 and the groove 8 processed by an end mill. The groove 8 is processed in the non-sizing region 7 where the sintered skin remains. ing.

In addition, since the dimensional correction effect by sizing cannot be obtained in the area that is not sized,
Choose a location that does not require high dimensional accuracy. Or when it becomes a field which faces other parts, it is good to form a crevice in other parts or sintered parts beforehand so that other parts of the other party and the area where a sintered part is not sized may not contact. Further, when there is no degree of freedom in selecting a place and it is necessary to set a region where dimensional accuracy is required, the area of the region that is not sized should be minimized.

  An example of the surface properties before and after sizing the outer peripheral surface of the sintered part is shown in FIG. FIG. 9A shows the surface roughness of the surface (sintered surface) of the part before sizing, and FIG. 9B shows the surface roughness of the surface after sizing (sizing surface). Table 1 shows the maximum value, median value, and average value of the roughness of these surfaces.

  As can be seen from FIG. 9 and Table 1, when sizing is applied, the tip of the pointed crest is crushed and the surface of the sintered part is smoothed. To rise. For this reason, in drilling, the drill becomes slippery and the biting property is deteriorated, the biting point is shifted, the deflection of the drill during processing is increased, and burrs are easily generated. In addition, the blade is easily damaged by cutting processing other than drilling, for example, processing by an end mill, and the tool life is shortened.

  On the other hand, in the present invention, sizing is performed so that the sizing mold does not come into contact with a part of the sintered part, and machining is performed on the area where the surface of the sintered skin is left without sizing. The bite of the blade is improved, the wear and loss of the blade is suppressed, and the life of the blade is improved. In addition, the surface of the machined part of the part is not hardened, and the shaft runout of the blade during processing is also suppressed, making it difficult for burrs to come out, and it is possible to simplify or omit burrs removal. .

  In addition, the sintered part manufactured by the method of the present invention may have a structure without a center hole, and the sizing of the part is performed with a mold not including a core. Further, after sizing, heat treatment such as quenching and tempering may be performed at a necessary portion.

The perspective view which shows an example of the sintered component manufactured by the method of this invention Sectional view showing the sizing state of the sintered part of FIG. The perspective view which shows the other example of the sintered component manufactured by the method of this invention The perspective view which shows the further another example of the sintered component manufactured by the method of this invention The figure which shows an example of the preferable shape of a recessed part (A) A plan view showing an example of a die provided with a recessed groove recess in a forming hole, (b) a sectional view of the same die. (A) A plan view showing an example of performing sizing by providing a through-groove recess in the die forming hole, (b) a cross-sectional view showing an example of a die having a through-groove recess in the forming hole The perspective view which shows an example of the sintered component manufactured by processing a groove | channel after performing sizing using the die | dye of FIG. (A) Enlarged view showing surface properties of sintered parts before sizing, (b) Enlarged view showing surface properties of parts after sizing Diagram showing an example of drilling holes for sintered parts

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sintered part 2 Outer peripheral surface 3 End surface 4 Center hole 5 Recess 6 Small hole 7 Non-sizing area 8 Groove 10 Sizing die 11 Die 12 Upper punch 13 Lower punch 14 Core 15 Molding hole 16 Recess D Drill

Claims (6)

  A sintered part that has been sized and has a sizing skin surface that has been sized and a non-sized sintered skin surface, and a part that has a sintered skin surface is machined. Bonding parts.   The sintered part according to claim 1, wherein a hole processed by a drill is provided as the machining.   Sizing of sintered parts using a sizing mold that has both a correction surface that corrects the dimensions of the sintered part and a non-correcting surface that faces the outer surface of the sintered part and does not contact the sintered part And thereafter, machining is performed on a portion where the sintered skin is left without sizing the sintered component.   4. The method for manufacturing a sintered part according to claim 3, wherein the non-correcting surface is generated by providing a recess having a dent amount larger than a sizing allowance of the sintered part on a part of the correcting surface of the sizing mold.   4. The method for manufacturing a sintered part according to claim 3, wherein the non-correcting surface is generated by providing a recess having a dent amount larger than a sizing allowance of the sintered part on an outer peripheral surface or an end surface of the sintered part.   It has a punch that presses the sintered part in the axial direction and a die that press-fits the sintered part into the forming hole, and at least one of the punch and the die is provided with a recess having a dent amount larger than the sizing cost of the sintered part. And a sizing die for a sintered part, the recess of which is in a position facing the outer surface of the sintered part.

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