JP2019070194A - Sintered component - Google Patents

Abstract

To provide a method for manufacturing a sintered component capable of suppressing occurrences of edge fracture upon forming an open hole in a powdery compact and excellent in productivity.SOLUTION: A method for manufacturing a sintered component comprises a forming step that makes a powdery compact by press-forming a base powder containing a metal powder, a hole opening step that forms a hole in the powdery compact by a drill, and a sintering step that performs sintering for the powdery compact after the hole opening step. The drill used in the hole opening step has an arcuate cutting edge at a tip.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method of manufacturing a sintered part, a sintered part, and a drill for drilling a green compact. In particular, the present invention relates to a method of manufacturing a sintered part which can suppress generation of edge chipping when forming a through hole in a green compact and has excellent productivity.

  BACKGROUND ART A sintered body (sintered alloy) obtained by sintering a compact of metal powder such as iron powder is used for automobile parts, machine parts and the like. Examples of such sintered alloy parts (hereinafter simply referred to as "sintered parts") include sprockets, rotors, gears, rings, flanges, pulleys, vanes, bearings and the like. In general, sintered parts are manufactured by press-forming a raw material powder containing metal powder to prepare a green compact (green compact) and sintering it, and after sintering, it is necessary. Accordingly, machining is performed as finishing.

  By the way, there are some sintered parts in which holes such as through holes (through holes) passing through and blind holes not passing through are formed. For example, there is a component in which a through hole (for example, an oil hole) which passes from an outer peripheral surface to an end surface or an inner peripheral surface is formed. With regard to such parts, since a through hole can not be formed integrally with the green compact at the time of molding, drilling is performed with a drill after sintering (see Patent Document 1).

  As a drill to be used for drilling, one having a V-shaped cutting edge at its tip is typical. In the case of a cemented carbide drill, the tip angle of the cutting edge is often set to about 130 ° to 140 °.

Unexamined-Japanese-Patent No. 2006-336078

  When a sintered part is drilled by drilling, it is difficult to make a hole after sintering, and there is a problem that productivity is low.

  A sintered part is hard because particles of metal powder are diffusively bonded and alloyed and firmly bonded by sintering. Therefore, if drilling is performed on a sintered part with a drill, cutting resistance is high and the drill is difficult to enter, so cutting is difficult, machining takes time, and the tool life is shortened. In addition, since the resistance at the time of biting the drill is high, it is difficult to obtain a stable drilled hole accuracy, for example, the drill is likely to run out of axis. Furthermore, since the cutting resistance is high and the thrust load is high, when forming the through hole, burrs are likely to be generated along the opening edge on the outlet side from which the drill is removed. Since the thickness of the bottom of the through hole is reduced when the drill penetrates, the burr is deformed so that the bottom can not be cut if the strength of the bottom can not be maintained against the thrust load, and the burr is pushed out to the outlet side Is generated by The generated burrs need to be removed in a later step, which requires time and effort. It may be difficult or impossible to remove depending on the location of the burr. Therefore, in the production of sintered parts, improvement of productivity is desired from the viewpoint of reducing the production cost.

  It is conceivable that the green compact before sintering is drilled with a drill to form through holes in the green compact in advance. The powder compact is only a compact of the raw material powder by compacting, and the particles of the metal powder are in a state in which the particles of the metal powder are in close mechanical contact, so they are not firmly bonded as after sintering. Therefore, when drilling is performed on the green compact before sintering, the bonding between the metal powder particles is weak and cutting is easy as compared to the case of drilling after sintering, and the cutting resistance (thrust load) Is greatly reduced. When the green compact is drilled, the metal powder particles are cut with a drill and cut to form through holes. However, when the green compact is drilled with a drill, when the through hole is formed, a so-called edge chipping, in which the opening edge on the outlet side from which the drill is removed is chipped, is likely to occur.

  Therefore, one of the objects of the present invention is to provide a method of manufacturing a sintered part which can suppress the occurrence of chipping when forming a through hole in a green compact and at the same time, has excellent productivity. Another object of the present invention is to provide a sintered part excellent in productivity. Yet another object of the present invention is to provide a drill capable of suppressing the occurrence of chipping when forming a through hole in a green compact.

  The method of manufacturing a sintered part according to an aspect of the present invention includes a forming step, a drilling step, and a sintering step. In the forming step, the raw material powder containing the metal powder is press-formed to produce a green compact. In the drilling process, a hole is formed in the green compact by a drill. The sintering step sinters the green compact after the hole drilling process. The drill used for the drilling has an arc-shaped cutting edge at its tip.

  The sintered component according to an aspect of the present invention is a sintered component in which a hole is formed. In the sintered component, the inner circumferential surface of the hole is textured.

  The drill according to one aspect of the present invention is a drill that performs drilling on a workpiece. The said to-be-cut object is a compacting body which press-formed the raw material powder containing metal powder. The drill has an arc-shaped cutting edge at its tip.

  The manufacturing method of the said sintered component can be excellent in productivity while being able to suppress generation | occurrence | production of edge chipping when forming a through-hole in a compacting body. The said sintered component is excellent in productivity. The said drill can suppress generation | occurrence | production of an edge chipping when forming a through-hole in a compacting body.

It is a comparative explanatory view of a case where it is drilled with a drill having an arc-shaped cutting edge and a case where it is drilled with a drill having a V-shaped cutting edge. It is process explanatory drawing explaining the manufacturing method of the sintered component which concerns on embodiment. It is a schematic diagram explaining an example of the drill concerning an embodiment. It is a microscope picture which shows the exit of the through hole at the time of forming a through hole using R drill in Experiment 1. FIG. It is a microscope picture which shows the exit of the through hole at the time of forming a through hole using V drill in Experiment 1. FIG. It is a graph which shows the relationship between the rake angle at the time of forming a through-hole using R drill in Experiment 2, a thrust load, and torque. It is a microscope picture which shows the internal peripheral surface of the through-hole of the compacting body produced by Experiment 3. FIG.

Description of the embodiment of the present invention
The inventors of the present invention have intensively studied the technology for improving the productivity of sintered parts, and as a result, the productivity can be achieved by drilling holes in the powder compact before sintering, not after sintering. I found that I could improve. This is because when the powder compact is drilled, the bonding of the metal powder particles is weak, cutting is easy, and cutting resistance (thrust load) is significantly reduced. And compared with the drilling which has conventionally been performed after sintering, the machining time can be shortened, the machining hole accuracy can be improved, and the tool life can be significantly improved. In addition, when the powder compact is drilled with a drill, burrs are less likely to occur. Even if burrs are generated, deburring can be easily performed by air blowing or the like, and the time and labor required for the deburring operation can be reduced.

  Furthermore, as a result of researches by the present inventors, as a result of devising the shape of the drill used for the drilling of the green compact, in particular, the shape of the cutting edge of the tip, an edge chip in forming the through hole We found that we could suppress the occurrence of Specifically, it was found that the generation of the edge chipping can be suppressed by setting the shape of the cutting edge to an arc shape (R shape).

  The generation mechanism of edge chipping is considered as follows. In the case of a green compact, it is brittle because the bonding of metal powder particles is weak. Therefore, when the strength of the bottom can not be maintained against the thrust load because the thickness of the bottom of the through hole becomes thin when the drill penetrates, the bottom can not be cut before the drill can penetrate. It falls off to the outlet side (pushed out). When the bottom of the through hole falls without being cut off, the vicinity of the bottom also collapses together, causing a chip at the opening edge on the outlet side from which the drill is removed.

  The reason why the occurrence of edge chipping can be suppressed by using a drill having an arc-shaped cutting edge (hereinafter sometimes referred to as “R drill”) is considered as follows. The left view of FIG. 1 shows a drill (R drill) 10 whose cutting edge has an arc shape and a work (powder compact) G which has been drilled by the R drill 10. The R drill 10 illustrated in FIG. 1 is illustrated in a simplified manner with grooves and the like omitted for easy understanding of the description. Further, as shown in the upper view on the left side of FIG. 1, in the R drill 10, the shape of the cutting edge 110 is semicircular, and the central angle α of the arc forming the cutting edge 110 is 180 °, and the arc The radius R of is equal to the radius of the diameter d of the drill. In the R drill 10, the length h of the tip 100 along the axial direction of the drill is equal to the radius R of the arc. The tip portion is a portion from the tip (apex) of the cutting edge 110 to the outer peripheral corner 120.

  As shown in the lower two figures on the left side of FIG. 1, when the green compact G is drilled by using the R drill 10 (white arrows in the figure indicate the feed direction of the drill), the shape of the cutting edge 110 is After being transferred to the green compact G, a hole with a bottom surface shaped like an arc (semicircle) in cross section, that is, a hemispherical shape, is formed in the green compact G. In the R drill 10, since the shape of the cutting edge 110 is a circular arc (semi circular arc), thrust loads are dispersed radially and act as indicated by solid arrows in the figure. On the other hand, in the green compact G, the bottom surface of the hemispherical hole is supported by the side of the arc (hemispherical surface) against the thrust load of the drill as shown by the solid arrow in the figure. high. That is, in the case of drilling the green compact G with the R drill 10, the thrust load itself is low and the thrust load acting on the bottom is dispersed, so that the stress concentration is also small and the strength of the bottom is maintained. In addition, the maximum thickness Ht of the bottom of the hole is equal to the length h of the tip 100, and becomes larger as the length h of the tip 100 is larger. In the case of the R drill 10, the maximum thickness Ht of the bottom of the hole can be made large, so the strength of the bottom becomes high by that thickness. Therefore, when drilling is performed on the green compact G with the R drill 10, the lower thrust load is combined with the lower bottom against the thrust load even if the thickness of the bottom of the through hole is reduced when the drill penetrates. Strength is easily maintained, and it is possible to cut just before the drill penetrates. Therefore, since it can suppress that a bottom part can not be cut without being able to be cut before a drill penetrates, generation | occurrence | production of an edge chip can be suppressed. This indicates that even if it is not a through hole, a blind hole in front of it is effective. Specifically, even in the case of a blind hole in which the thickness of the bottom of the hole (minimum thickness from the bottom of the hole to the opposite surface) is a thin hole, the bottom of the hole is formed in a hemispherical shape with an R drill, Bottom strength increases. That is, even if the thickness of the bottom of the hole is reduced, it is possible to suppress the bottom from being broken, and therefore, it is possible to form a blind hole with a thin bottom. For example, it is possible to process until the thickness of the bottom portion becomes 1/2 or 1/4 of the drill diameter (hole diameter).

  On the other hand, when a drill having a V-shaped cutting edge (hereinafter sometimes referred to as "V drill") which is widely used conventionally is used, it is difficult to suppress the occurrence of edge chipping. The right view of FIG. 1 shows a drill (V drill) 11 having a V-shaped cutting edge and a workpiece (powder compact) G which has been drilled by the V drill 11. Like the R drill 10, the V drill 11 illustrated in FIG. Moreover, in this example, the tip angle β of the cutting edge 110 of the V drill 11 is about 130 ° to 140 °, and the drill diameter d is equivalent to that of the R drill 10.

  As shown in the lower two figures on the right side of FIG. 1, when drilling into the green compact G with the V drill 11, the shape of the cutting edge 110 is transferred to the green compact G, and the bottom surface is triangular in cross section A conical hole will be formed in the green compact G. In the V drill 11, since the shape of the cutting edge 110 is V-shaped (triangular), the thrust load acts in the direction orthogonal to the side (conical surface) of the triangular as indicated by the solid arrow in the figure. On the other hand, in the green compact G, since the bottom of the conical hole is supported by the side of the triangle (conical surface) against the thrust load of the drill as shown by the solid arrow in the figure, the bottom of the hemispherical hole In comparison with, stress is concentrated and strength is also low. That is, when the green compact G is drilled with the V-drill 11, the thrust load acting on the bottom can not be dispersed as compared with the R-drill 10, and the strength of the bottom is difficult to maintain. In addition, in the case of the V drill 11, since the maximum thickness Ht of the bottom of the hole is small, the strength of the bottom is reduced by that thickness. Therefore, when the green compact G is drilled with the V-drill 11, the thickness of the bottom of the through hole is reduced when the drill penetrates, so that the bottom can not be cut before the drill penetrates. It is easy to collapse. Therefore, it is difficult to suppress the occurrence of chipping.

  The inventors obtained the above findings and completed the present invention. First, the embodiments of the present invention will be listed and described.

  (1) A method of manufacturing a sintered part according to an aspect of the present invention includes a forming step, a drilling step, and a sintering step. In the forming step, the raw material powder containing the metal powder is press-formed to produce a green compact. In the drilling process, holes are formed in the green compact by a drill. A sintering process sinters a compacting body after drilling processing. The drill used for drilling has an arc-shaped cutting edge at the tip.

  According to the above-described method of manufacturing a sintered part, drilling is performed on the green compact before sintering with a drill, so cutting is easy and cutting resistance (thrust load) is significantly reduced. Therefore, compared with the conventional manufacturing method which performs a drilling process with a drill after sintering, machining time can be shortened, machining hole accuracy can be improved, and tool life can be significantly improved. In addition, when the powder compact is drilled with a drill, burrs are less likely to occur. Even if burrs are generated, it is possible to easily remove the burrs by, for example, air blow, and it is possible to reduce the time and labor required for the deburring operation. The above-mentioned "hole" includes a through hole (through hole) passing through and a blind hole not passing through.

  Furthermore, according to the manufacturing method of the said sintered component, when forming a through-hole in a compacting body by using the drill which has a circular-arc-shaped cutting blade in a front-end | tip part, generation | occurrence | production of an edge chip can be suppressed. Therefore, the manufacturing method of the said sintered component can be excellent in productivity while it can suppress generation | occurrence | production of a chipping. The “shape of the cutting edge” referred to here means the cutting when the cutting edge is parallel to the plane parallel to the axis passing through the central axis of the drill and projected from the direction orthogonal to the parallel plane It is the projection shape of the blade. And "an arc-shaped cutting edge" points out the cutting edge whose projection shape is an arc shape (refer the upper left figure of FIG. 3). When the shape of the cutting edge is arc-shaped, when the drill is rotated and the cutting edge is viewed from the direction orthogonal to the rotation axis of the drill, the rotation trajectory of the cutting edge looks like an arc. Here, the drill is disposed so that the cutting edge is parallel to the horizontal plane, and the plane viewed from the direction orthogonal to the horizontal plane is called a plane.

  (2) As one mode of the manufacturing method of the above-mentioned sintered part, it is mentioned that the above-mentioned drill has a rake angle of the above-mentioned cutting edge of more than 0 degree and 10 degrees or less.

  From the viewpoint of suppressing the occurrence of edge chipping, it is considered that smaller cutting force (thrust load) is advantageous. Since the thrust load can be reduced by the rake angle of the cutting edge being more than 0 ° and 10 ° or less, the occurrence of edge chipping can be suppressed more effectively. When the rake angle is more than 0 °, the cutting edge becomes sharp and the thrust load is reduced. On the other hand, when the rake angle is increased, the cutting edge strength is lowered because the cutting edge becomes sharp. However, since the material to be cut is a powder compact, chipping due to the reduction in cutting edge strength hardly occurs. However, if the rake angle is more than 10 °, the rake angle is preferably 10 ° or less because the thrust load increases. The rake angle is more preferably, for example, 5 ° or more and 8 ° or less from the viewpoint of reducing the thrust load. Here, "rake angle" is the angle between the parallel plane and the rake plane when the cutting edge is parallel to the plane parallel to the central axis of the drill (see the lower right diagram in FIG. 3). See). Here, the drill is disposed so that the cutting edge is parallel to the horizontal plane, and the plane when viewed from a direction perpendicular to the central axis of the drill and parallel to the horizontal plane is called a side plane.

  (3) As one mode of the manufacturing method of the above-mentioned sintered part, it is mentioned that the central angle of the circle which forms the above-mentioned cutting edge of the above-mentioned drill is 135 degrees or more and 180 degrees or less.

  When the central angle of the arc forming the cutting edge is 135 ° or more and 180 ° or less, the occurrence of edge chipping can be sufficiently suppressed. If the central angle of the arc-shaped cutting edge is 135 ° or more, the shape of the cutting edge approaches a semicircular shape, and the thrust load is dispersed radially, so the effect of reducing the thrust load is high, and the thrust load at the time of drilling Can be distributed. In addition, since the shape of the bottom of the hole approaches a hemispherical shape, the strength against a thrust load can be increased, and in addition, the strength is improved as the maximum thickness Ht of the bottom of the hole (see left figure in FIG. 1) increases. Therefore, the strength of the bottom can be sufficiently maintained. The central angle of the arc is, for example, more preferably 150 ° or more, and particularly preferably 180 ° so as to form a semicircular cutting edge.

  On the other hand, the radius of the arc forming the cutting edge is preferably substantially equal to the radius of the drill diameter, and for example, it is preferably 0.4 times to 0.6 times the drill diameter. In particular, the shape of the cutting edge is preferably semicircular, the central angle of the arc is 180 °, and the radius of the arc is preferably 0.5 times the drill diameter, ie equal to the radius of the drill diameter d . The "drill diameter (drill diameter)" as used herein refers to the outer diameter of the portion (so-called, blade portion) where the cutting edge is formed.

  (4) The sintered component according to an aspect of the present invention is a sintered component in which a hole is formed. And, the inner circumferential surface of the hole is like a satin.

  As described above, when the powder compact before sintering is drilled by drilling, since the bonding between the metal powder particles is weak, the metal powder particles are cut while being cut off by a drill to form holes. Go. For this reason, the inner circumferential surface of the hole formed in the green compact has a rough texture due to the formation of irregularities by the particles. Since the surface properties of the inner peripheral surface of the hole are substantially maintained even after sintering, the inner peripheral surface of the hole has a satin-like shape even in a sintered part obtained by sintering a green compact having a hole formed therein. . That is, the fact that the inner circumferential surface of the hole formed in the sintered part is in the form of a satin indicates that the green compact before sintering is drilled with a drill. Therefore, the said sintered component is excellent in productivity compared with the conventional sintered component which formed the hole after sintering.

  On the other hand, in the case of drilling with a drill after sintering, the particles of the metal powder are firmly bonded by sintering, so the particles of the metal powder are cut while cutting with a drill to form a hole Go. Therefore, the inner peripheral surface of the hole formed by drilling with respect to the sintered part with a drill becomes a smooth surface with little unevenness as a whole and has a gloss.

  (5) As one form of the above-mentioned sintered part, it is mentioned that the ten-point average roughness Rz of the inner skin of the above-mentioned hole is 20 micrometers or more.

  When a hole is formed by a drill in a green compact before sintering and sintered, the ten-point average roughness Rz of the inner peripheral surface of the hole formed in the sintered part is the shape and size of the metal powder particles Depending on the kind, for example, it may be 20 μm or more. The upper limit of the ten-point average roughness Rz of the inner circumferential surface of the hole is, for example, 150 μm or less. On the other hand, when forming a hole with a drill after sintering, the ten-point average roughness Rz of the inner peripheral surface of the hole formed in the sintered part is usually less than 20 μm, and further 15 μm or less.

  (6) The drill which concerns on one form of this invention is a drill which performs a drilling process to a to-be-cut object. The workpiece is a green compact obtained by press-forming a raw material powder containing a metal powder. The drill has an arc-shaped cutting edge at its tip.

  According to the above-described drill, the formation of the edge chip can be suppressed when forming the through hole in the powder compact by having the arc-shaped cutting edge at the tip end.

Details of the Embodiment of the Present Invention
Hereinafter, specific examples of a method of manufacturing a sintered part, a sintered part, and a drill according to an embodiment of the present invention will be described with reference to the drawings. The present invention is not limited to these exemplifications, but is shown by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

<Method of manufacturing sintered parts>
In the method of manufacturing a sintered part according to an embodiment of the present invention, a compacting process for producing a green compact, a drilling process for forming a hole with a drill in the green compact, and a compact after compacting And sintering the material. One of the features of the method for manufacturing a sintered part is to use a drill having an arc-shaped cutting edge at its tip in the drilling process. Hereinafter, each step of the manufacturing method will be described in detail with reference mainly to FIG.

(Molding process)
In the forming step, the raw material powder containing the metal powder is press-formed to produce a green compact G (see the upper view of FIG. 2). The green compact G is a raw material of a sintered part, and is formed into a shape corresponding to the sintered part S to be manufactured (see the lower diagram in FIG. 2). Here, as the green compact G (sintered part S), a cylindrical one in which a circular axial hole 30 is formed at the center is taken as an example.

Raw material powder
The raw material powder mainly contains metal powder. The material of the metal powder can be appropriately selected according to the material of the sintered part to be manufactured, and typically, an iron-based material can be mentioned. The "iron-based material" is iron or an iron alloy containing iron as a main component. Examples of iron alloys include those containing one or more additive elements selected from Ni, Cu, Cr, Mo, Mn, C, Si, Al, P, B, N and Co. Specific iron alloys include stainless steel, Fe-C alloy, Fe-Cu-Ni-Mo alloy, Fe-Ni-Mo-Mn alloy, Fe-P alloy, Fe-Cu alloy, Fe -Cu-C-based alloy, Fe-Cu-Mo-based alloy, Fe-Ni-Mo-Cu-C-based alloy, Fe-Ni-Cu-based alloy, Fe-Ni-Mo-C-based alloy, Fe-Ni-Cr Alloy, Fe-Ni-Mo-Cr alloy, Fe-Cr alloy, Fe-Mo-Cr alloy, Fe-Cr-C alloy, Fe-Ni-C alloy, Fe-Mo-Mn-Cr And -C-based alloys and the like. By mainly using a powder of iron-based material, an iron-based sintered component can be obtained. When the powder of the iron-based material is mainly used, the content thereof is, for example, 90% by mass or more, and further 95% by mass or more when the raw material powder is 100% by mass.

  When the powder of the iron-based material, particularly iron powder, is mainly used, metal powder such as Cu, Ni, Mo may be added as an alloy component. Cu, Ni, and Mo are elements for improving the hardenability, and the addition amount thereof is, for example, more than 0% by mass and 5% by mass or less and 0.1% by mass or more and 2% by mass, when the raw material powder is 100% by mass. % Or less. In addition, non-metallic inorganic materials such as carbon (graphite) powder may be added. C is an element that improves the strength of a sintered body or its heat-treated body, and the content thereof is, for example, more than 0% by mass and 2% by mass or less, and further 0.1% by mass, when the raw material powder is 100% by mass. The above content is 1% by mass or less.

  The raw material powder preferably contains a lubricant. When the raw material powder contains a lubricant, the lubricity at the time of molding is enhanced when the green body G is produced by press-molding the raw material powder, and the moldability is improved. Therefore, even if the pressure for press molding is lowered, it is easy to obtain a compact green compact G, and by increasing the density of the green compact G, it is easy to obtain a high-density sintered component S. Furthermore, if a lubricant is mixed with the raw material powder, the lubricant will be dispersed in the green compact G. Therefore, the green compact G is drilled with a drill 10 in a later step (see the middle view of FIG. 2). Also functions as a lubricant for drills. Therefore, cutting resistance (thrust load) can be reduced and tool life can be improved. Examples of the lubricant include metal soaps such as zinc stearate and lithium stearate, fatty acid amides such as stearic acid amide, and higher fatty acid amides such as ethylenebisstearic acid amide. The lubricant may be in any form such as solid, powder or liquid. The content of the lubricant is, for example, 2% by mass or less, and further 1% by mass or less when the raw material powder is 100% by mass. If the content of the lubricant is 2% by mass or less, the proportion of the metal powder contained in the green compact G can be increased. Therefore, even when the pressure for press molding is lowered, a compact green compact G can be easily obtained. Furthermore, when the green compact G is sintered in a later step, volume shrinkage due to disappearance of the lubricant can be suppressed, and dimensional accuracy is high, and a sintered component S with high density can be easily obtained. The content of the lubricant is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more from the viewpoint of obtaining the effect of improving the lubricity.

  The raw material powder does not contain an organic binder. Since the ratio of the metal powder contained in the green compact G can be increased by not containing the organic binder in the raw material powder, a compact green compact G can be easily obtained even if the pressure of press molding is lowered. Furthermore, it is not necessary to degrease the green compact G in a later step.

  The raw material powder is mainly composed of the above-mentioned metal powder, and allows inclusion of unavoidable impurities.

  As the metal powder described above, water atomized powder, reduced powder, gas atomized powder and the like can be used, and among them, water atomized powder or reduced powder is preferable. Since the water atomized powder and the reduced powder have many irregularities formed on the particle surface, the irregularities of the particles are engaged at the time of molding, and the shape retention ability of the green compact G can be enhanced. In general, in the gas atomized powder, particles with less unevenness are easily obtained on the surface, while in the water atomized powder or reduced powder, particles with more unevenness are easily obtained. Moreover, it is mentioned that the average particle diameter of a metal powder shall be 20 micrometers or more and 50 micrometers or more and 150 micrometers or less, for example. The "average particle diameter of metal powder" is a particle diameter (D50) at which the cumulative volume in the volume particle size distribution measured by the laser diffraction type particle size distribution measuring device is 50%. If the average particle size of the metal powder is within the above range, it is easy to handle and press-form.

<Press molding>
In press molding, a molding apparatus (molding die) capable of molding into a shape corresponding to a sintered part as a final product is used. In the cylindrical green compact G illustrated in FIG. 2, the axial hole 30 is integrally formed at the time of molding. The green compact G is, for example, inserted into the upper and lower punches having an annular press surface forming both end surfaces of the green compact G, and the upper and lower punches, and the inner circumference of the green compact G is obtained. It can form using the cylindrical inner die which forms a surface, and the outer die in which the circular insertion hole which surrounded the outer periphery of an upper and lower punch and formed the outer peripheral surface of the compacting body G was formed. Both axial end surfaces of the green compact G are press surfaces pressed by the upper and lower punches, and the inner and outer peripheral surfaces are sliding contact surfaces with the inner and outer dies, and the axial hole 30 is integrally formed at the time of molding Be done. The pressure of press molding is, for example, 250 MPa or more and 800 MPa or less.

(Drilling process)
In the drilling process, a hole 50 is formed in the green compact G with a drill 10 (see the middle view in FIG. 2). The holes 50 are through holes or blind holes. Here, through holes are formed by the drill 10 so as to pass from the outer peripheral surface of the green compact G to the inner peripheral surface. That is, the axial hole (forming hole) 30 formed in the powder compacting body G and the through hole (drilling hole) 50 formed by the drill 10 are connected, and the opening on the outlet side of the through hole 50 is a powder compacting body It is provided on the inner peripheral surface of G (the inner peripheral surface of the shaft hole 30). In this example, the through hole 50 is formed at a location where the distance (thickness) between the inner circumferential surface of the through hole 50 and the outer surface (end face) of the powder compact G is equal to or greater than the diameter of the through hole 50 There is. With reference to FIG. 3, the drill 10 used for the drilling process of the compacting body G is demonstrated.

<drill>
The upper left of FIG. 3 is a schematic plan view of the drill, the lower left of FIG. 3 is a schematic front view of the drill viewed from the tip side, and the lower right of FIG. 3 is a schematic side view partially showing the tip of the drill FIG. The drill 10 is for drilling a hole in a workpiece, and the workpiece is a green compact G (see the middle view in FIG. 2) obtained by press-forming a raw material powder containing a metal powder. The drill 10 is according to an embodiment of the present invention.

  The drill 10 illustrated in FIG. 3 is a so-called R drill having an arc-shaped cutting edge 110 at the tip end portion 100. The tip portion 100 is a portion from the tip (apex) of the cutting edge 110 to the outer peripheral corner 120.

<Shape of cutting edge>
When the drill 10 has the cutting edge 110 parallel to the plane parallel to the central axis of the drill 10 as shown in the upper left view of FIG. The projected shape of the cutting edge 110 is arc-shaped. The central angle α of the arc forming the cutting edge 110 is, for example, 130 ° or more, preferably 135 ° or more and 180 ° or less, more preferably 150 ° or more. In this example, the central angle α of the arc is 180 °. On the other hand, the radius R of the arc forming the cutting edge is, for example, not less than 0.4 times and not more than 0.6 times the diameter d of the drill, preferably 0.5 times the diameter d of the drill, It is equivalent to d / 2). In this example, the shape of the cutting edge is semicircular, the central angle α of the arc is 180 °, and the radius R of the arc is equal to the radius of the drill diameter d. Although the diameter d of the drill 10 is not specifically limited, For example, they are 1.0 mm or more and 20.0 mm or less.

<Rake angle of cutting edge>
The rake angle of the cutting edge 110 is, for example, 0 ° or more, preferably more than 0 ° and 10 ° or less, and more preferably 5 ° or more and 8 ° or less. The rake angle of the cutting edge 110 is perpendicular to the central axis of the drill 10 with the cutting edge 110 parallel to the plane parallel to the central axis of the drill 10, as shown in the lower right view of FIG. When viewed from the side parallel to the direction, the angle γ between the plane P parallel to the axis and the rake face 111 constituting the cutting edge 110. In this example, the rake angle of the cutting edge 110 is 7 °.

<Cutting conditions>
The cutting conditions such as the rotation speed and feed rate (feed amount) of the drill 10 may be appropriately set according to the material of the powder compact G (metal powder), the depth of the through hole 50 to be formed, the diameter of the drill 10, etc. (See also Figure 2). For example, the rotational speed is 1000 rpm or more, further 2000 rpm or more, the feed rate is 100 mm / min or more, further 200 mm / min or more, and the feed amount is 0.01 mm / rev. The above, further 0.1 mm / rev. Above, it can be mentioned. Through experiments, it has been found that processing at a compacted body enables processing at a higher speed than processing a sintered body.

  The inner peripheral surface of the hole (through hole) 50 formed in the green compact G with the drill 10 is in a satin shape. In the green compact G, since the bonding between the metal powder particles is weak, when drilling is performed with a drill, the metal powder particles are cut off with a drill and cut to form the through holes 50. For this reason, the inner circumferential surface of the through hole 50 formed in the green compact G has a concavo-convex shape in which unevenness due to particles is entirely formed.

(Sintering process)
In the sintering step, the green compact G is sintered after drilling. For sintering, a suitable sintering furnace (not shown) capable of temperature atmosphere control is used. As the sintering conditions, conditions necessary for sintering may be appropriately set according to the material of the green compact G (metal powder) and the like. The sintering temperature may be, for example, 1000 ° C. or more, and further, 1100 ° C. or more, 1200 ° C. or more, and may be equal to or less than the melting point of the main metal powder (eg, 1400 ° C. or less). The sintering time is, for example, 15 minutes or more and 150 minutes or less, and further 20 minutes or more and 60 minutes or less. By sintering, a sintered component S in which the holes (through holes) 50S are formed is obtained (see the lower view of FIG. 2). The sintered part S relates to an embodiment of the present invention.

<Sintered parts>
In the sintered component S, a hole (through hole) 50S is formed. The through holes 50S are through holes 50 formed by the drill 10 in the green compact G by drilling before sintering (see the middle view in FIG. 2). As described above, the inner circumferential surface of the through hole 50 formed in the green compact G with the drill 10 is in a satin-like shape. Since the surface properties of the inner peripheral surface of the through hole 50 are substantially maintained even after sintering, the inner peripheral surface of the through hole 50S of the sintered component S obtained by sintering the green compact G is also textured. It becomes. In other words, the fact that the inner peripheral surface of the through hole 50S formed in the sintered component S is in the shape of a satin indicates that the powder compact G before sintering is drilled by the drill 10 There is. In the sintered component S, the ten-point average roughness Rz of the inner peripheral surface of the through hole 50S may be, for example, 20 μm or more and 150 μm or less.

  In this example, the through hole 50S is formed at a location where the distance (thickness) between the inner peripheral surface of the through hole 50S and the outer surface (end face) of the sintered component S is equal to or larger than the diameter of the through hole 50S There is.

<Function effect>
In the method of manufacturing a sintered component according to the above-described embodiment, since the drilling process is performed on the green compact before sintering with a drill, cutting is easy and cutting resistance (thrust load) is significantly reduced. Ru. Therefore, compared with the conventional manufacturing method which performs a drilling process with a drill after sintering, machining time can be shortened, machining hole accuracy can be improved, and tool life can be significantly improved. Furthermore, in the method of manufacturing a sintered component according to the above-described embodiment, since the drilling is performed using a drill having an arc-shaped cutting edge at the tip end, an edge chip is formed when forming a through hole in the powder compact. Can be suppressed. Therefore, the manufacturing method of the said sintered component can be excellent in productivity while it can suppress generation | occurrence | production of a chipping.

  In the sintered component according to the above embodiment, a hole (through hole) is formed, and the inner peripheral surface of the hole is in a satin-like shape, so drilling is performed on the green compact before sintering using a drill. Good productivity.

  The drill according to the above-described embodiment has the arc-shaped cutting edge at the tip end, so that the occurrence of edge chipping can be suppressed when forming the through hole in the powder compact.

  Although the case where a through-hole is formed with a drill in a compacting body was mentioned as the example and demonstrated in the said embodiment, the hole to form may be a blind hole. In the case of a blind hole, the thickness of the bottom of the hole can be reduced. For example, it is suitable when forming the blind hole whose thickness of the bottom is twice or less of the drill diameter (hole diameter). The lower limit of the thickness of the bottom portion may be about 1⁄4 to 1⁄2 or more of the drill diameter (hole diameter).

[Test Example 1]
A raw material powder containing a metal powder was press-formed to prepare a green compact, and a drilling test was performed on the green compact using a drill having a different shape of the cutting edge.

(Compacted compact)
Water atomized iron powder (average particle diameter (D50) 100 μm), water atomized copper powder (average particle diameter (D50) 30 μm), carbon (graphite) powder (average particle diameter (D50) 20 μm), ethylene as a lubricant The bis-stearic-acid amide was prepared, these were mixed and the raw material powder was prepared.

The prepared raw material powder was filled in a predetermined molding die and press molded at a pressure of 600 MPa to produce a plate-like compact of 50 mm long × 20 mm wide × 10 mm thickness. The density of this green compact was 6.9 g / cm ³ . This density is an apparent density calculated from the volume and the mass of the green compact.

  Next, drilling processing was performed to the produced compacting body with a drill, and a through hole was formed in the thickness direction of the compacting body. And the opening part by the side of the exit of a penetration hole was observed, and the generating situation of edge chipping was investigated.

  For the drill, an R drill having a semicircular shape as shown in FIG. 3 was prepared. The prepared R drill has a drill diameter d of 8.0 mm, a central angle α of the arc forming the cutting edge is 180 °, and a radius R of the arc of 4.0 mm (0.5 times the drill diameter d ). Also, the rake angle of the cutting edge is 0 °. The R drill was manufactured by polishing the cutting edge at the tip of a drill (model number: MDW0800GS4, material: cemented carbide) manufactured by Sumitomo Electric Hard Metal Co., Ltd.

  Furthermore, the shape of a cutting blade prepared V-shaped V drill. The prepared V drill is a drill manufactured by Hitachi Tool Co., Ltd. (model number: 05WHNSB0400-TH, material: cemented carbide). The V-drill has a drill diameter d of 4.0 mm and a tip angle of 140 °.

  The green compact was drilled using the above-mentioned R drill and V drill to form a through hole. The cutting conditions in the case of using the R drill were a rotational speed of 4000 rpm and a feed rate of 1600 mm / min. When using a V-drill, the cutting conditions are: rotation speed 4000rpm, feedrate 800mm / min from the inlet side to reach a hole depth of 5mm, feedrate 1600mm / min from a hole depth of 5mm to penetration And

  About the compacting body which formed the through-hole by each drill after drilling processing, the opening part at the exit side of the through-hole was observed with the optical microscope. The results are shown in FIG. 4 and FIG. FIG. 4 shows the case where an R drill is used, and FIG. 5 shows the case where a V drill is used. In the photomicrographs of FIGS. 4 and 5, the central circular portion is a through hole. In FIG. 4, a black annular portion with a certain width that encloses the periphery of the central circular portion (through hole) is a portion where the inner peripheral surface of the through hole is visible. In FIG. 5, the gray portion extending around the through hole is a chipped edge. As shown in FIG. 4, when the through hole is formed by the R drill, the edge chipping is very small at the opening on the outlet side of the through hole, and in this example, the edge chipping could not be confirmed. On the other hand, when the through hole is formed by the V drill, as shown in FIG. 5, it can be seen that a large edge chipping occurs at the opening on the outlet side of the through hole. Moreover, it was 1.55 mm when the amount of edge chippings at the time of forming a through-hole with V drill was measured. The edge chipping amount is obtained by measuring the distance from the center of the through hole to the point farthest from the center of the through hole from the photomicrograph of FIG. It calculated | required by calculating the difference. From this result, it is understood that the occurrence of edge chipping can be suppressed by using an R drill having an arc-shaped cutting edge.

[Test Example 2]
Drilling was performed on the green compact using an R drill with different rake angles of the cutting edge, and the thrust loads at the time of forming the through holes were compared.

  The same compacting body as that of Test Example 1 was used as a green compact for processing.

  The R drill used has a semicircular shape as in Test Example 1, and has a cutting edge at the tip of a drill (model number: MDW0800GS4, material: cemented carbide) manufactured by Sumitomo Electric Hard Metal Co., Ltd. It was polished and produced. In this R drill, the drill diameter d is 8.0 mm, the central angle α of the arc forming the cutting edge is 180 °, and the radius R of the arc is 4.0 mm (0.5 times the drill diameter d). Then, three types of R drills with rake angles of 0 °, 7 ° and 10 ° are prepared, R drills with a rake angle of 0 ° are R0, R drills with a rake angle of 7 ° are R7, and rake angles of 10 ° The R drill is called R10.

  The green compact was drilled three times with each of the three types of drills (R0, R7, R10) to form three through holes in the thickness direction of the green compact. The cutting conditions were a rotational speed of 2000 rpm and a feed rate of 200 mm / min (feed amount: 0.1 mm / rev.). And thrust load and torque at the time of forming a penetration hole were measured in each drilling processing from the 1st to the 3rd. The thrust load and torque were measured from the start of drilling until the formation of a through hole using a cutting dynamometer (manufactured by Japan Kistler Co., Ltd., Model No. 9272), and the maximum value was determined. Moreover, the average value was also calculated from each thrust load and torque in each drilling process.

  The thrust load and the torque in the case of drilling using the drill of R0, R7 and R10 are shown in Tables 1 to 3, respectively. For example, in Table 1, "R0-1" indicates that it is the first drilling process using the drill of R0, the first half of the symbol is the drill used, and the second half is the number of processes. (See also Table 2 and Table 3). Furthermore, based on the average value of thrust load and torque in each drill, the relationship between the rake angle and the thrust load and torque is shown in FIG. In the graph of FIG. 6, the abscissa represents the rake angle (°), the left ordinate represents the thrust load (N), the right ordinate represents the torque (N · m), and ■ represents the thrust load Is the torque.

  From the results of Tables 1 to 3 and FIG. 6, it can be seen that the R drill having a rake angle of 7 ° has a smaller thrust load as compared to the R drill having a rake angle of 0 ° or 10 °. If the rake angle is in the range of more than 0 ° and 10 ° or less, it is considered that the thrust load can be reduced as compared with the case where the rake angle is 0 °. Therefore, it is considered that the occurrence of edge chipping can be more effectively suppressed by using an R drill having a rake angle of more than 0 ° and 10 ° or less. On the other hand, it can be seen that the torque tends to decrease as the rake angle increases.

[Test Example 3]
After drilling into a green compact using an R drill, the green compact having through holes formed by the R drill is sintered to produce a sintered part.

  The same compacting body as that of Test Example 1 was used as a green compact for processing.

  Here, an R drill having a semicircular shape and a drill diameter d of 3.5 mm was used. The R drill was manufactured by polishing the cutting edge at the tip of a drill (model number: MDW 0350 GS4, material: cemented carbide) manufactured by Sumitomo Electric Hard Metal Co., Ltd. In this R drill, the central angle α of the arc forming the cutting edge is 180 °, the radius R of the arc is 1.75 mm (0.5 times the drill diameter d), and the rake angle is 0 °.

  The green compact was drilled using the above-mentioned R drill to form a through hole in the thickness direction of the green compact. The cutting conditions were a rotational speed of 2000 rpm and a feed rate of 200 mm / min (feed amount: 0.1 mm / rev.). After drilling, the green compact having the through holes was sintered at 1130 ° C. for 20 minutes to produce a sintered part.

  Similarly, a green compact having a through hole formed therein was cut in the thickness direction so as to pass through the central axis of the through hole, and the inner peripheral surface of the through hole was observed with an optical microscope. The cross-sectional photograph is shown in FIG. In FIG. 7, a band portion extending in the left and right direction at the center is the inner peripheral surface of the through hole. As shown in FIG. 7, the inner circumferential surface of the through hole was in a textured form. Moreover, when the ten-point average roughness Rz of the inner peripheral surface of this through-hole was measured, it was 40 micrometers. Furthermore, when the sintered component produced above was cut in the thickness direction so as to pass through the central axis of the through hole, and the inner peripheral surface of the through hole was observed with an optical microscope, The surface texture was the same as that of the peripheral surface, and the ten-point average roughness Rz of the inner peripheral surface was also equivalent. The ten-point average roughness Rz is a value measured in accordance with "Geometrical Product Specification (GPS)-Surface Properties: Contour Curve Method-Terms, Definitions, and Surface Properties Parameters JIS B 0601: 2013".

  As a result of forming a through hole with a drill on a sintered part after sintering and observing the inner peripheral surface of the through hole in the same manner, the illustration is omitted, but the inner peripheral surface of the through hole is smooth with few irregularities. It had a surface and had a gloss. Moreover, when the ten-point average roughness Rz of the inner peripheral surface of this through-hole was measured, it was 11 micrometers. The drill used for drilling sintered parts is MDW0350GS4 manufactured by Sumitomo Electric Hard Metal Co., Ltd., with a V-shaped cutting edge, drill diameter d of 3.5 mm, and cutting edge angle of 135 ° It is.

  The method of manufacturing a sintered part according to an aspect of the present invention is used to manufacture various sintered parts such as automobile parts and machine parts (eg, sprockets, rotors, gears, rings, flanges, pulleys, vanes, bearings, etc.) It is possible. The sintered parts according to an aspect of the present invention can be used for various sintered parts such as automobile parts and machine parts. The drill according to one aspect of the present invention can be used for drilling of a green compact.

10 drill (R drill) 11 drill (V drill)
100 tip 110 cutting edge 111 rake face 120 peripheral corner 30 axial hole 50 hole (through hole)
50S hole (through hole)
G Powder compact (cut)
S sintered parts

Claims (6)

A forming step of press-forming a raw material powder containing a metal powder to produce a green compact;
A drilling process step of forming a hole in the powder compact by a drill;
And Sintering the sintered compact after sintering.
The said drill used for the said drilling process is a manufacturing method of the sintered components which have an arc-shaped cutting blade in a front-end | tip part.   The method according to claim 1, wherein a rake angle of the cutting edge of the drill is more than 0 ° and 10 ° or less.   The method for manufacturing a sintered part according to claim 1, wherein a central angle of an arc forming the cutting edge of the drill is 135 ° or more and 180 ° or less. A sintered part having a hole formed therein,
The sintered component whose inner peripheral surface of the said hole is in the shape of a satin.   The sintered part according to claim 4, wherein a ten-point average roughness Rz of the inner peripheral surface of the hole is 20 μm or more. A drill that drills a workpiece,
The said to-be-cut object is a compacting body which press-formed the raw material powder containing metal powder,
A drill with an arc-shaped cutting edge at the tip.