JP2013202733A - Chip for cutting and friction work - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chip for cutting and friction work, capable of reducing the generation amount of a cavity right below the surface of a workpiece and preventing generation of an annular metal piece in a burr state generated at an end point of friction work on the surface of the workpiece.SOLUTION: A side cutting blade is formed at the part on a chip feed side of a chip distal end part, so that a raised part on the surface of a workpiece is excised together with cracks by the side cutting blade, when a chip is moved in a feed direction accompanying friction work. Thus, the generation of a cavity right below the surface of the workpiece can be reduced. Also, the raised part is pertinent to a small burr part, so that an annular metal piece in a burr state that appears at the end part of the friction work on the surface accompanying the friction work is not generated, by successively excising the raised part by the side cutting blade immediately after being generated.

Description

  The present invention relates to a cutting friction processing chip, and more particularly to a cutting friction processing chip capable of forming a fine crystal grain layer in a shallow region from the surface of a workpiece.

In recent years, it has been discovered that when a metal material is machined, the surface layer is processed extremely strongly, and a fine crystal structure is generated in a shallow region having a thickness of several microns to several tens of microns from the surface of the metal material. The fine crystal grain layer has higher hardness and higher compressive residual stress than the base material, and has characteristics suitable for machine parts.
As one of the methods for producing a fine crystal grain layer, friction processing disclosed in Patent Document 1 is known. This is because, for example, by pressing a tip for frictional machining (round surface) with a gently curved surface (round surface) on the outer peripheral surface of the workpiece (metal material) rotating by a lathe, the workpiece is processed. The surface layer of the material is finely crystallized.

JP 2011-105991 A

However, in the friction processing chip used in Patent Document 1, the friction processing surface that comes into contact with the surface (processing surface) of the workpiece is simply a round surface with no corners. there were. Therefore, at the time of friction processing, due to the pressing pressure at the tip of the tip, a part of the surface in the tip feed direction rises with (internal) cracks from the tip pressing portion, and immediately after that, the tip moving in the feed direction rises up. By crushing the part, cavities as defects were generated in the part directly under the surface after the surface modification. In addition, the metal piece (attachment) that swelled from the surface and peeled off in this way was approached to the end point portion of the friction processing and attached in a ring shape in the sacrificial state.
In addition, deep flaws (dents) different from tool marks (friction processing marks) locally occurred on the surface of the workpiece after friction processing. This is because the surface is roughened by friction processing, and the raised portion (convex portion) is peeled off and attached as a metal piece to the tip of the tip for friction processing, and then the metal peeled off from the tip of the tip It is inferred that the piece was sandwiched between the workpiece being frictionally processed and the frictional working surface at the tip of the tip, thereby damaging the surface of the workpiece. This local deep scratch leads to deterioration of the surface condition (surface roughness) of the workpiece, which is not preferable.

Therefore, as a result of earnest research, the inventor has formed a side cutting edge at the tip feed side portion of the tip end portion, and when the tip for cutting friction machining is moved in the feed direction along with the friction machining, The present invention has been completed by discovering that it is possible to excise a bulge portion on the surface in the tip feed direction from the tip pressing portion with a crack (part or all of the crack) using a cutting edge. In other words, if the portion raised by the side cutting edge is cut in advance, then the tip end portion crushes the raised portion, thereby reducing the occurrence of cavities due to cracks directly under the surface of the workpiece. At the same time, it is possible to sequentially remove the small sacrificial portions while performing the friction processing so that the ring-shaped metal piece in the state of the brush generation generated in the end portion of the surface friction processing due to the friction processing does not occur.
In addition, as a result of earnest research, the inventor forms an upper cutting edge in the upper center portion of the tip, and the metal piece generated during the friction processing adheres to the workpiece, and as the workpiece rotates, It has been found that it can be prevented from being sandwiched (from above) between the workpiece during friction processing and the friction processing surface of the tip of the tip. In other words, in the friction processing using the conventional tip, the metal piece generated by the friction processing adheres to the tip end portion of the tip for friction processing, and then the metal piece peeled off from the tip end portion of the tip becomes the workpiece and the tip being friction processed. As a result, a deep flaw different from the tool mark is locally generated on the surface of the work material. Generation of deep scratches can be prevented.

The present invention can reduce the generation of cavities directly under the surface of the workpiece, and can prevent the generation of a ring-shaped metal piece in a crumpled state that occurs at the end point of friction processing on the surface of the workpiece. It aims at providing the chip | tip for cutting friction processing which can be performed.
In addition to the above-described effects, the present invention also provides a cutting friction cutting tip that can prevent the occurrence of local deep scratches on the surface of a workpiece caused by a metal piece peeled off from the tip end portion. It is an object.

  According to the first aspect of the present invention, the tip of the workpiece is pressed against the surface of the workpiece made of a metal having a friction working surface at the tip and rotating around the axis, and the axis of the workpiece is In the tip for cutting friction processing that performs friction processing as super-strong processing in the shallow region of the surface of the workpiece by being fed in the tip feed direction parallel to the tip feed portion, Cutting friction in which a side cutting edge is formed in the surface of the workpiece to cut away a portion of the surface raised from the pressing position of the tip portion in the tip feed direction along with the friction processing. Chip for processing.

  According to the first aspect of the present invention, when the cutting friction processing chip is sent along with the friction processing, the raised portion on the surface of the workpiece is cut by the side cutting edge. Thus, conventionally, the tip of the tip for friction processing that is moving in the feed direction (friction processing direction) is then crushed at the portion that has risen from the surface of the workpiece with a crack, so that the workpiece There was a cavity directly under the surface. However, in the present invention, since this raised portion is excised together with a crack (a part or all of the crack) by the side cutting edge before the cutting friction processing tip is passed upward, the generation of a cavity can be reduced (prevented). . In addition, this bulging portion becomes a small crumpled portion on the surface of the workpiece, if viewed differently. Therefore, this raised part is cut off with the side cutting blades immediately after the occurrence, and in the case of friction processing with the conventional product, the brushed state that appeared at the end point of the friction processing on the surface with friction processing The generation of the annular metal piece can be prevented.

  The friction processing here refers to the number of thicknesses from the surface of the workpiece by pressing the gently curved friction processing surface of the tip of the cutting friction processing tip against the surface of the workpiece made of metal. The surface layer (shallow region) of micron to several tens of microns is generated by a fine grain layer with surface modification to a fine crystal structure and plastic deformation by friction processing without surface modification to the fine crystal structure. Among the work-hardened layers to be performed, at least a work-hardened layer is generated. In the friction processing in which both the fine crystal grain layer and the work hardened layer are generated on the surface layer of the work material, the fine crystal grain layer and the work hardened layer are continuous from the surface of the work material to the inside thereof. Generated. When performing friction processing, for example, using a lathe for metal grinding processing, adopting a cutting friction processing tip instead of a grinding tip (blade) fixed to a cutting tool, the friction processing action of the tip of the tip The surface is pressed against the surface of the workpiece, and the surface layer of the workpiece is finely crystallized. Specifically, there is a case where friction processing is performed by a cutting friction processing tip in which an outer peripheral surface (surface) of a workpiece is fixed to a right single-blade tool.

The term “fine crystal grain layer” as used herein refers to a region whose surface has been modified to a fine crystal structure by friction processing. As the thickness of the fine crystal grain layer is thicker, better results are obtained.
In addition to generating a fine grain structure (fine crystal grain layer) by friction processing, the hardness of the surface layer of the workpiece can be increased by utilizing work hardening generated by plastic deformation by friction processing. This region (hereinafter referred to as work hardened layer) is located between the outermost surface where the fine crystal grain layer is obtained and the internal structure that is not affected by processing. Play an important role. Friction processing may occur in some cases where a fine grain structure cannot be obtained depending on the processing conditions, but the work hardened layer can sufficiently increase the fatigue strength.
In the case of friction machining of the outer peripheral surface of the workpiece, the “region of the workpiece surface in the tip feed direction from the pressing position of the tip of the tip” refers to, for example, a cutting friction machining tip When moving from one end of the outer peripheral surface toward the other end, it refers to a region (part) on the other end side of the workpiece from the pressing position of the tip end portion of the chip.

Tungsten carbide, cermet, or the like can be used as the material for the cutting friction processing tip.
Cutting friction machining inserts do not turn the surface of the workpiece with a turning tip with a sharp tip, but the friction working surface at the tip of the tip does not have a corner in order to perform friction machining. It has a round surface. As the external shape of the cutting friction processing chip, for example, a triangular plate shape, a square plate shape, or the like can be adopted.
The thickness of the tip portion of the cutting friction processing tip is 1.0 mm or more and 20 mm or less. If it is less than 1.0 mm, the thickness of the friction processed pressing portion becomes insufficient, and the workpiece is protruded. On the other hand, if it exceeds 20 mm, the tip end of the tip becomes too thick, and the portion not related to friction processing increases more than necessary, which is not economical.

The radius of curvature of the friction working surface in plan view is 0.1 to 15.0 mm. If it is less than 0.1 mm, the surface pressure that acts on the outer peripheral surface of the workpiece from the tip end during friction processing becomes too high, and the tip end is deeply embedded in the workpiece. Moreover, if it exceeds 15.0 mm, the surface pressure at the time of friction processing will become low too much, and the required plastic work degree with respect to the surface layer of a workpiece will not be obtained. Thereby, the hardness increase of the processed surface of the workpiece after friction processing is not sufficient. A preferable radius of curvature when the friction working surface is viewed in plan is 0.2 to 15.0 mm. If it is this range, moderate pressing pressure (surface pressure) will be obtained and the smooth processed surface of a workpiece will be obtained.
The shape of the friction working surface of the cutting friction processing chip as viewed from the side (longitudinal section) may be flat (planar) or circular.

The pressing load on the surface of the cutting friction machining tip needs to be changed to an optimum size according to the shape of the cutting friction machining tip and the material of the workpiece. In the case of a hard work material and when the radius of curvature of the cutting friction cutting insert in plan view is large, the pushing load is increased. On the contrary, in the case of a soft material or when the insert curvature radius is small, the pushing load is increased. Let be smaller. However, it is generally 20-2000N. If it is less than 20N, sufficient plastic working cannot be obtained, and the hardness of the processed surface will not be sufficiently increased. On the other hand, if it exceeds 2000 N, the roughness of the processed surface will not be good, and the deflection of the workpiece will also increase.
The feed speed of the cutting friction cutting insert is selected to be an optimum value according to the material and the radius of curvature of the insert. The smaller the tip nose radius is, the smaller the feed needs to be, but it is generally 0.01 to 2.0 mm / rev. If it is less than 0.01 mm / rev, the efficiency of friction processing is reduced and seizure is likely to occur. On the other hand, if it exceeds 2.0 mm / rev, the surface layer of the work material is not subjected to plastic working, and the hardness of the work surface of the work material is not sufficiently increased.
Although it is desirable that the relative speed between the workpiece and the friction processing chip is high, a good processed layer can be obtained even at a low speed depending on conditions.

The shape of the side cutting edge is arbitrary. The side cutting edge may be formed integrally with the cutting friction machining tip or may be separate from the tip. The formation position of the side cutting edge is a portion on the tip feed side of the tip end portion and needs to be disposed at a position farther from the workpiece than at least the tip end that performs the friction processing. If the cutting edge is positioned at the tip, cutting will be prioritized and the effect of surface modification by friction processing will be diminished. Further, the side cutting edge needs to be disposed at a position below the upper surface of the cutting friction processing tip. In this way, since the friction processing is performed at a position lower than the upper surface of the cutting friction processing tip, when the cutting friction processing tip is sent along with the friction processing, the raised portion of the surface of the workpiece is cut by the side cutting edge. The effect of excision is born.
One or two or more side cutting edges may be formed. Further, if the side cutting edges are formed on both side portions of the tip end portion, the tip feed direction can be reversed left and right.

The shortest distance between the tip edge and the side cutting edge in plan view is 0.1 to 1.5 mm. If it is less than 0.1 mm, cutting is preferential, and if it exceeds 1.5 mm, a partial rise in the workpiece cannot be effectively removed.
`` Part of the surface that swelled with friction processing '' means that the surface layer of the work material undergoes compositional deformation due to the large pressing pressure of the cutting friction processing tip moving in the feed direction during friction processing, This refers to the raised portion of the surface that occurs in the tip feed side region of the tip end of the friction working surface.

As the material of the workpiece, almost all metals such as various steels such as S45C and various titanium alloys such as Ti-6Al-4V alloy can be targeted. As the shape of the workpiece, for example, a round bar, a cylinder, or the like can be adopted. The frictional working surface of the cutting frictional cutting tip refers to a region of a round surface that is pressed against the surface of the workpiece and has no corners in the tip portion of the tip.
For example, a cemented carbide can be used as the material for the cutting friction processing chip.
The tip portion of the cutting friction processing tip refers to a portion on the tip end side that corresponds to the blade portion of the grinding tip and that is equal to or less than one third of the total length of the tip. Here, “the shallow region of the surface of the workpiece” refers to the surface of the workpiece that is subjected to friction processing, and a shallow region with a depth (thickness) of several microns to several tens of microns from the surface. A surface layer consisting of

The “tip feed side portion of the tip portion” means that the tip for cutting friction processing is performed during friction processing when the tip tip portion is equally divided into a left portion, a center portion (intermediate portion), and a right portion in the tip width direction. This is the end part of the moving direction (feeding direction). For example, when the tip for cutting friction processing is sent from the tip (right end) of the workpiece to the base end (left end), it means the left portion of the tip end portion.
The “sacrifice state” here refers to a state in which the surface (worked surface) of the workpiece is finely torn or turned. The size of each small crepe portion is a raised height of 0.1 to 2.0 mm and a length of 1.0 to 2.0 mm. A large number of small brush portions are continuously generated in the circumferential direction of the work piece, so that the end portion of the friction processing on the surface of the work piece has a large “roll shape in a state of 0.1 to 0.5 mm”. Metal piece ".

  In particular, in the invention according to claim 2, the portion formed on the upper end of the center portion in the chip width direction among the formation portions of the friction working surface of the tip portion is generated by friction processing and adheres to the workpiece. An upper cutting edge for cutting off a portion of the surface of the workpiece was formed immediately before the metal piece was sandwiched from above between the workpiece rotating around the axis and the friction working surface. It is a chip | tip for cutting friction processing of Claim 1.

  According to the second aspect of the present invention, when the pressure is high by pressing the tip portion of the cutting friction processing tip against the surface of the workpiece along with the friction processing, the surface of the workpiece has a fine uneven shape. Roughly, some become metal pieces and adhere to the workpiece. Thereafter, as the workpiece rotates, the metal piece adhering to the workpiece immediately before the metal piece is sandwiched from above between the workpiece being friction processed and the friction working surface of the tip of the tip. The piece can be excised with an upper cutting edge. That is, in the conventional friction processing by the tip, the metal piece is peeled off and attached to the tip of the tip for friction processing, and then the metal piece peeled off from the tip end of the tip is the workpiece and the tip end of the tip during friction processing. As a result, a deep flaw different from the tool mark locally occurred on the surface of the work material. In the present invention, this local deep flaw is Occurrence can be prevented.

“Among the part of the tip of the friction working surface at the tip, the upper part of the center in the chip width direction” means that the part of the friction working surface of the tip of the cutting friction working tip is used for friction machining. The upper portion of the intermediate region in the feed direction length of the cutting friction machining tip (the upper portion of the intermediate region in the width direction of the tip end portion or the tip feed side portion of the tip tip portion and this portion Means the upper part of the central part between the opposite part). In a lathe in which the cutting friction machining tip is used instead of the turning tip, the rotation direction of the workpiece with respect to the cutting friction machining tip is generally set so as to be directed downward from above. Therefore, the upper cutting edge is formed in the upper part of the center of the friction processing surface of the tip end of the tip so that the metal piece on the surface of the workpiece rough and raised by friction processing can be cut smoothly. Yes.
The shape and size of the upper cutting edge are arbitrary. For example, an arc shape or the like can be adopted as the shape.

  According to a third aspect of the present invention, in the cutting according to the first or second aspect, the friction working surface of the tip portion is curved in an arc shape in which an intermediate portion in the chip thickness direction is recessed inwardly. This is a tip for friction processing.

  According to the third aspect of the present invention, at the time of friction processing, the friction processing surface of the tip end portion of the tip is not flat (flat) when viewed from the side, but the arc in which the middle portion in the chip thickness direction is recessed inward The curved surface was shaped (drum shape). As a result, when the tip of the cutting friction machining tip is pressed against the surface of the workpiece (columnar or cylindrical), the friction working surface is simply a plan view of the cutting friction machining tip. This can be reduced compared to the case of only the curvature. As a result, for example, when friction processing is performed on a workpiece having low hardness, it is possible to suppress the occurrence of crust and roughness on the processed surface of the workpiece.

The “arc shape in which the intermediate portion in the chip thickness direction is recessed inwardly” here is the shape of the friction working surface when the friction processing chip is viewed from the side (longitudinal section).
The radius of curvature of the friction working surface as viewed from the side needs to be at least larger than the radius of the workpiece. When the radius of curvature of the friction processing surface as viewed from the side is smaller than the radius of the workpiece, there are two contact portions between the cutting friction processing tip and the workpiece, which is not preferable. However, the closer the radius of the workpiece and the radius of curvature of the friction processed surface viewed from the side, the greater the effect of reducing the contact surface pressure.

  According to the first aspect of the present invention, since the side cutting edge is formed at the tip feed side portion of the tip end portion, when the tip for cutting friction machining is moved in the feed direction along with the friction machining, A raised portion including a crack is cut out from the surface of the workpiece with a cutting edge. Thereby, the front-end | tip part of the chip | tip for cutting friction processing currently moving to a feed direction crushes this bulging part, and generation | occurrence | production of the cavity produced directly under the surface of a workpiece can be reduced. In addition, this bulging portion becomes a small crumpled portion on the surface of the workpiece, if viewed differently. Therefore, this raised part is cut off with the side cutting blades immediately after the occurrence, and in the case of friction processing with the conventional product, the brushed state that appeared at the end point of the friction processing on the surface with friction processing The generation of the annular metal piece can be prevented.

  In particular, according to the invention described in claim 2, with the friction processing, the tip of the cutting friction processing tip is pressed against the surface of the workpiece, and the surface is roughened into a fine uneven shape, and a part thereof is a metal piece. And adheres to the workpiece. The metal piece adhering to the workpiece is rotated by the upper cutting edge immediately before being sandwiched from above between the workpiece during friction processing and the friction processing surface of the tip of the tip as the workpiece rotates. Excised. Therefore, it is possible to prevent the occurrence of local deep scratches generated on the surface of the workpiece due to the metal piece peeled off from the tip end portion of the chip.

  According to the third aspect of the present invention, at the time of friction processing, the friction working surface of the tip end portion is an arc-shaped curved surface in which the middle portion in the tip thickness direction is recessed inward, so that the tip end portion is The surface pressure when pressed against the surface of the workpiece can be reduced as compared with the case where the frictional working surface is simply curved when the cutting frictional machining tip is viewed in plan view. Accordingly, for example, when friction processing is performed on a workpiece having low hardness, it is possible to suppress occurrence of crust and roughness on the surface of the workpiece.

It is a perspective view which shows the use condition of the chip | tip for cutting friction processing which concerns on Example 1 of this invention. It is a principal part enlarged plan view containing the partial cross section figure which shows the use condition of the chip | tip for cutting friction processing which concerns on Example 1 of this invention. It is a principal part expanded vertical sectional view which shows the use condition of the chip | tip for cutting friction processing which concerns on Example 1 of this invention. It is a comparison figure with the external appearance of the workpiece which performed the friction processing using the chip | tip for cutting friction processing based on Example 1 of this invention, and the conventional chip | tip, and the processing conditions. It is a graph of the SN curve at the time of conducting a fatigue test on the workpiece of the S45C tempered material friction processed using the cutting friction processing tip according to Example 1 of the present invention and the conventional tip. It is a front view which shows the size of the test piece used at the time of the friction processing of FIG. SN curve when a fatigue test was performed on a workpiece of Ti-6Al-4V alloy that was friction processed using the cutting friction cutting tip according to Example 1 of the present invention and a comparative material simply manufactured by turning It is a graph of. It is a front view which shows the size of the test piece used at the time of the friction processing of FIG.

  Examples of the present invention will be specifically described below.

  1 and 2, reference numeral 10 denotes a cutting friction machining tip according to Embodiment 1 of the present invention, which is used by being fixed to a cutting tool instead of a turning tip of a lathe and frictionally machining the surface of a workpiece 11. Chip. The cutting friction machining tip 10 has a tip tip portion 10b on which a friction working surface 10a is formed, and a tip tip portion on the surface (outer peripheral surface) 11a of a workpiece 11 made of metal rotating around an axis. 10b is pressed, and in this state, the cutting friction machining tip 10 is moved in a feed direction parallel to the axial direction of the workpiece 11, thereby the fine crystal grain layer 11b and the work hardened layer 11e are formed in a shallow region of the surface 11a. Are continuously generated from the surface of the workpiece 11 toward the inside thereof. The lathe becomes a friction processing device by mounting the cutting friction processing tip 10 on a cutting tool. The workpiece 11 is a test piece shown in FIG. 6 made of an S45C tempered material.

  The cutting friction processing chip 10 is made of a superalloy and is a diamond-shaped plate piece in plan view with a thickness of 3.0 mm. Both ends of the cutting friction machining tip 10 are arranged vertically, and are stopped at the tip of the lathe tool by the same method as a normal turning tool through a stop hole 10c at the center of the chip. The tip end portion 10b refers to a corner portion on one end side of the diagonal line on the long side among the diagonal lines having different lengths of the cutting friction processing tip 10. The upper part of the peripheral side surface of the tip end portion 10b is the friction working surface 10a having an arc shape (curvature radius of 0.8 mm) in plan view. Thus, the reason why only the upper part of the peripheral side surface of the tip end portion 10b is the friction working surface 10a is to make the upper cutting edge 13 act effectively. The friction working surface 10a is an arc-shaped curved surface in which an intermediate portion in the chip thickness direction is recessed inward. Thereby, the surface pressure when the tip end portion 10b is pressed against the surface of the columnar workpiece 11 can be reduced as compared with the case where the friction processing surface 10a is flat (the friction processing surface 10a is (Even on a flat surface). As a result, for example, when friction processing is performed on the workpiece 11 having low hardness, it is possible to suppress the occurrence of roughing and roughening on the processed surface of the workpiece 11. In the friction machining, the cutting friction machining tip 10 is not an abutting tip of the turning tip which is brought into contact with the outer peripheral surface of the turning material as in lathe machining, but is an intermediate portion in the thickness direction of the tip tip portion 10b. The nearby friction working surface 10a is pressed against the surface 11a of the workpiece 11 and used.

A portion on the tip feed side of the upper end portion of the tip tip portion 10b is a part of the surface 11a of the workpiece 11 in the tip feed direction from the pressing position of the tip tip portion 10b in the surface 11a of the workpiece 11 due to friction processing. However, only one side cutting edge 12 that cuts the raised portion 11c raised with a crack is formed (FIGS. 1 and 2). The side cutting edge 12 has a substantially rhombus shape in plan view, and has an end portion on the tip feed side of the tip end portion 10b that is recessed in parallel with the top surface of the tip.
Further, the center upper portion of the tip end portion 10b (the portion of the tip end portion 10b on which the friction working surface 10a is formed, the upper portion in the chip thickness direction) has a rough surface that has been raised by friction processing. Only one horizontally long upper cutting edge 13 that cuts off the metal piece 11d peeled off from the surface 11a of the workpiece 11 is formed (FIGS. 1 and 2). The upper cutting edge 13 is obtained by cutting the upper portion of the tip end portion 10b with a constant width over the entire length thereof into a circular arc shape (substantially drum shape) to form the friction working surface 10a. Thereby, the angle of the cutting edge of the upper cutting edge 13 can be set to an acute angle (75 ° to 89 °) as compared with the case where the cross-sectional arc shape is not formed, and the metal piece 11d can be easily cut.

Next, with reference to FIGS. 1-4, the friction processing method of the workpiece 11 by the chip | tip 10 for cutting friction processing which concerns on Example 1 of this invention is demonstrated.
First, the work material 11 is fixed to a chuck of a lathe, and the work material 11 is rotated together with the chuck so that the friction processing speed becomes 44.0 m / min, with the axis of the work material 11 as the center. During this rotation, the portion of the tip end portion 10b of the friction working surface 10a is pressed against the surface 11a of the workpiece 11 with a load 315N, and this state is maintained and the cutting friction processing tip 10 is 0.05 mm / rev. To move in the feed direction (axial direction of the workpiece 11). As a result, the surface layer of the work material 11 is surface-modified to a fine crystal structure (fine crystal grain layer 11b) in a shallow region having a depth of 5 μm from the surface 11a of the work material 11, and the surface of the work material 11 is 5 An increase in hardness due to plastic deformation (work hardening layer 11e) was observed between ˜40 μm (surface layer). As described above, the surface layer of the workpiece 11 is altered not only by the fine crystal grain layer 11b but also by the fine crystal grain layer 11b and the work hardened layer 11e. As a result, a thicker hardened phase can be obtained. .

When the cutting friction processing chip 10 is fed along with the friction processing, a part of the surface 11a in the chip feeding direction rises with a crack from the chip pressing portion due to the pressing pressure of the tip end portion 10b (FIG. 2). At this time, the shortest distance d between the tip of the chip and the side cutting edge 12 in plan view is 0.5 mm. Immediately after the occurrence, the raised portion 11c is cut off by the side cutting edge 12 that has moved in the tip feed direction. As a result, conventionally, the bulging portion 11c including the crack of the workpiece 11 is crushed by the tip end portion of the tip for friction processing that is moving in the feed direction, so that a cavity is formed immediately below the surface of the workpiece 11. However, here, before the cutting friction machining tip 10 passes above the raised portion 11c, the side cutting edge 12 cuts out the raised portion 11c together with some or all cracks. The generation of cavities can be prevented.
In addition, while the friction processing is performed, the raised portion 11c corresponding to the small crumpled portion is sequentially cut out immediately after the occurrence using the side cutting edge 12 (FIG. 4B). As a result, in the case of the conventional product, the ring-shaped metal piece 11f (FIG. 4 (a)) in the crumpled state that is generated at the end point of the friction processing on the surface 11a of the workpiece 11 is not generated.

  Furthermore, with the friction processing, by pressing the tip end portion 10b of the cutting friction processing tip 10 against the surface 11a of the workpiece 11, in the case of the conventional product, the surface 11a is roughened into a fine concavo-convex shape, and a part thereof It becomes the metal piece 11c and adheres to the workpiece 11 (FIG. 4A). However, here, the metal piece (fine raised portion) 11d of the rough surface is cut by the upper cutting edge 13 as the workpiece 11 rotates (FIGS. 1 and 3), and therefore the tip end portion 10b. The local deep scratch 11g of the surface 11a due to the metal piece 11d peeled off is less likely to occur (FIG. 4B). That is, when the surface 11a of the workpiece 11 is rough, conventionally, the finely raised portion of the rough surface is peeled off from the outer peripheral surface and adheres to the tip of the chip as a metal piece 11d, and then the metal piece 11d is chipped. Although it peeled off from the front-end | tip part 10b and was pinched | interposed into the friction processing surface 10a of the to-be-processed material 11 and the chip | tip front-end | tip part 10b, the outer peripheral surface of the to-be-processed material 11 was damaged (FIG. 4 (a)), but here Since the upper cutting edge 13 removes the causal portion, the generation of the local deep scratch 11g can be prevented. In addition, Y described in the column of the processing conditions of FIG. 4 represents the deviation | shift between the upper surface of the cutting friction processing chip | tip 10, and the axis line of the workpiece 11. FIG. HV is the Vickers hardness of the workpiece 11, Ra is the arithmetic average roughness of the surface 11 a of the workpiece 11, and Rz is the ten-point average roughness of the surface 11 a of the workpiece 11.

Here, referring to the SN curve graph of FIG. 5, the cutting friction machining tip 10 of Example 1 was used, and the outer peripheral surface of the S45C tempered material (work material) was rubbed to the size shown in FIG. We report the results of a fatigue test conducted on test pieces obtained by processing in accordance with JIS Z2273 (a fatigue test method for metal materials).
As is clear from the graph of FIG. 5, the test piece made of the S45C tempered material had a fatigue limit of 870 MPa, which is the limit of the stress amplitude. Thereby, the test piece of the stable intensity | strength which does not fracture | rupture with the repeated stress of 870 Mpa or less was obtained. Although this test piece has the same strength against fatigue as compared with the conventional friction processed material, the variation in life was greatly suppressed. Variations in life are due to internal destruction, which is due to internal defects. Therefore, it is presumed that the occurrence of internal defects was suppressed by adopting the cutting friction machining tip 10 of Example 1.

Next, with reference to the SN curve graph of FIG. 7, the surface 11 a of the workpiece 11 made of the Ti-6Al-4V alloy of Example 1 is used using the cutting friction machining tip 10 of Example 1. Fatigue tests were conducted in accordance with JIS Z2273 for test pieces obtained by friction processing (shape and dimensions are shown in FIG. 8) and comparative test pieces of the same size that are not subjected to friction processing (hereinafter referred to as comparison pieces). Report the results.
As is clear from the graph of FIG. 7, the fatigue limit of the comparative specimen was 480 MPa, the fatigue strength of the test specimen was 490 MPa, and there was almost no difference in the fatigue strength based on 10 ⁷ times. However, the fatigue life in the finite life region was significantly longer for the test piece than for the comparative piece. From this point, it can be evaluated that the fatigue strength of the test piece is higher than that of the comparative piece.

  Moreover, as a result of the fracture surface observation, fish eyes of internal fracture were observed from most of the test pieces that had a long life and fractured. The starting point of the fish eye is a crack of α grains existing in a deeper position than the surface layer (fine crystal grain layer) reinforced by friction processing. The nominal stress in the region where fracture occurred was 460 to 560 MPa, and this numerical range was near or higher than the fatigue limit of the comparative specimen. That is, the destruction starting from the region not strengthened by the friction processing was dominant. In addition, as described above, although the test piece has a variation in fatigue life, the cause of the variation is internal destruction, which causes a problem during friction processing with a conventional friction processing tip in which the side cutting edge 12 is not mounted. It is not a rupture starting from a surface defect (local deep flaw 11 g). As a result, the effect of the upper cutting edge 13 formed on the tip end portion 10b was verified from the result of the fatigue test shown in the graph of FIG. That is, it is considered that at least the surface of the workpiece 11 is sufficiently strengthened by the friction processing.

  The present invention is useful as a tip for friction processing that increases the surface hardness of a metal part manufactured by a lathe and improves the wear resistance and fatigue resistance characteristics of a product.

10 Cutting friction processing tips,
10a Friction working surface,
10b Tip end (tip),
11 Work material
11a outer peripheral surface (surface),
11b Fine grain layer,
11c Swelling part,
11d metal piece,
12 side cutting edge,
13 Upper cutting edge.

Claims (3)

The tip is pressed against the surface of the workpiece made of metal that has a friction working surface at the tip and is rotating around the axis, and is fed in a chip feed direction parallel to the axis of the workpiece. Thus, in a cutting friction processing chip for performing friction processing as super-strong processing in a shallow region of the surface of the workpiece,
The portion on the tip feed side of the tip portion is a portion of the surface of the workpiece that is part of the surface raised in accordance with friction processing in a region in the tip feed direction from the pressing position of the tip portion. Cutting friction cutting tip with side cutting edges to be cut.   Of the formation part of the frictional working surface of the tip part, a metal piece generated by frictional processing and attached to the workpiece is rotating around the axis in the upper part of the center part in the chip width direction. 2. The cutting friction machining tip according to claim 1, wherein an upper cutting edge for cutting off a portion of the surface of the workpiece is formed immediately before being sandwiched from above between the workpiece and the friction working surface. .   The tip for frictional friction processing according to claim 1 or 2, wherein the frictional working surface of the tip portion is curved in an arc shape in which an intermediate portion in the tip thickness direction is recessed inwardly.

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