JP2010253597A - Face milling method and material to be face-milled - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a face milling method preventing burrs from occurring, and a material to be cut. <P>SOLUTION: The method of face milling a material to be cut made of iron-based metal includes a step of hardening the vicinity of a line to be cut off on a cutter outlet surface of the material beforehand by heat treatment. Preferably, a hard region with hardness (Hv) of 600 or more is formed by the heat treatment. The heat treatment is preferably laser irradiation treatment. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a face milling method and a work material for face milling that can suppress generation of burrs.

  The burr generated during the cutting process not only degrades the product quality but also hinders the subsequent process, and increases the production cost by adding a deburring operation. Therefore, it is very important to suppress burrs generated in finish cutting in consideration of surface quality and processing efficiency. As a countermeasure, it is ideal to find cutting conditions that do not generate burrs at all. However, it is not easy to find such a condition. Therefore, at present, a technique is taken to reduce the burden on deburring work performed after cutting by making the burrs generated as small as possible. From this point of view, analysis of burr generation mechanism using computer simulation (Non-patent Document 1) and experimental investigation of the relationship between cutting conditions and burr generation (Non-Patent Documents 2-6, 9) There has been research. However, even if the burrs can be kept small, if any burrs are generated, it is necessary to perform a deburring operation, which does not necessarily lead to an improvement in processing efficiency. There is also research on a method for removing burrs using a laser (Non-Patent Document 7). This method is a method using laser cutting. Since an air jet is used in combination, a plurality of devices are required, and debris scattering is also a problem.

  As described above, researches on how to reduce the burrs generated by cutting and how to remove the generated burrs have been conducted so far. No effective method has been found yet.

Masayuki Hashimura, Kanji Ueda, Junji Manabe, David A. Dornfeld, "Analysis of beam generation mechanism in two-dimensional cutting", Journal of Japan Society for Precision Engineering, Japan Society for Precision Engineering, February 2000, No. 1 66, 218-223 Gwo-Lianq Chern, "Experimental observation and analysis of burr formation mechanism in face milling of aluminum alloy", Journal of the Japan Society of Mechanical Engineers, Japan Society of Mechanical Engineers, 2006, Vol. 46, p.1517 -1525 O. O. Olverai, G. G. Barrow, “An Experimental Study of Burr Formation in Square Shoulder Face Milling”, International Journal of Machine Tools and Manufacture), 1996, Vol. 36, No. 9, pp. 1005-1020 Gwo-Lianq Chern, “Study on mechanisms of burr formation and edge breakout near the exit of orthogonal cutting”, Journal of Materials Processing of Technology (Journal of Materials Processing Technology), 2006, Vol. 176, p.152-157 Teruaki Miyake, Akihiro Yamamoto, Kazuichiro Kishimoto, Keiichi Yamanaka, Kyosuke Takano, "Study on Burr Formation in Face Milling (1st Report)-About Burr Formation Conditions and Formation Mechanism", Journal of Precision Engineering, Precision Engineering Society, 1998, Vol. 53, No. 1, p. 98-104 Seoung Hwan Lee, David A. Dornfeld, “Precision Laser Deburring”, Journal of Manufacturing Science and Engineering, 2001, 123, p.601-608 Yujiro Yajima et al., “Machine and metal materials for young engineers”, 2nd edition, Maruzen, 2004, p. 148 Ryutaro Tanaka, Yongchuan LIN, Kazuma Tanabe, Takashi Ueda, Satoshi Hosokawa, “Basic research on improvement of chip disposal by laser heat treatment”, Journal of Japan Society for Precision Engineering, Japan Society for Precision Engineering, 2007, No. 1 Volume 73, Number 9, p.1025 "Burr generated by face milling and its processing", Japan Institute of Mechanical Engineering, Research Institute, March 1990, Machining technology data file, 1990 case supplement, cutting work, case number 1420

  The present invention has been made in view of the above circumstances, and a problem to be solved is to provide a cutting method and a cutting work material capable of suppressing the generation of burrs.

  As a result of diligent research to solve the above-mentioned problems, the inventors of the present invention have made the processing near the cutting line of the surface to be the cutter exit surface of the work material in front milling by heat treatment in advance. Finding that burrs will no longer occur at the edge of the finished surface of the workpiece afterwards (the edge of the boundary between the finished surface and the cutter exit surface), and further research based on this knowledge completes the present invention. It came to do.

That is, the present invention
(1) A face milling method for a work material made of an iron-based metal, characterized in that the vicinity of a cut line on the cutter exit surface of the work material is previously hardened by heat treatment. Method,
(2) The method according to (1) above, wherein a hardened region having a hardness (Hv) of 600 or more is formed by heat treatment,
(3) The method according to (1) or (2) above, wherein the heat treatment is a laser irradiation treatment,
(4) The method according to any one of (1) to (3) above, wherein the iron-based metal is carbon steel,
(5) A work material for face milling, which is a work material made of an iron-based metal, and is hardened by heat treatment in the vicinity of a planned cut line of a surface to be a cutter exit surface in face milling, and (6 ) It relates to the work material for face milling according to the above (5), wherein a hardened region having a hardness (Hv) of 600 or more is formed by heat treatment.

  According to the face milling method of the present invention, cutting can be performed without generating burrs. Accordingly, it is possible to eliminate the deburring work after the cutting process and to improve the processing efficiency.

  Also, even if the work material is cut multiple times, if the heat treatment is performed near the planned cutting line in the final cutting at the cutter exit surface of the work material, burrs will occur in the previous cutting. However, since the generation of burrs can be suppressed in the final cutting, it is possible to reliably obtain a product without burrs even when processing with a large total amount of cutting (total cutting depth is large). it can.

  Further, since the surface roughness of the finished surface after cutting is hardly affected by the heat treatment, a product having a finished surface having a desired surface roughness and having no burrs can be manufactured.

  Further, the face milling method of the present invention only needs to be hardened in advance by heat treatment such as laser irradiation in the vicinity of the cut line of the surface to be the cutter exit surface of the work material. Easy.

  In addition, since the work material for face milling according to the present invention is hardened by heat treatment in the vicinity of the planned cutting line of the surface that becomes the cutter exit surface in face milling, the face milling that causes the cutter to exit the hardened area. By performing the above, it is possible to reliably obtain a product without burrs.

FIG. 1 is a perspective view schematically showing the face milling method of the present invention. FIG. 2 is a cross-sectional photograph of a hardened region as an example of a work material (carbon steel S45C) in which a hardened region is formed by laser heat treatment in the face milling method of the present invention. FIG. 3 is a cross-sectional photograph of the work material (carbon steel S45C) in FIG. 2 after being cut in the hardened region by face milling. FIG. 4 is a diagram showing an example of a cutting method in the face milling method of the present invention. FIG. 5A shows an SEM image (comparative example) of the end of the work material after face milling on the work material (carbon steel S45C) not subjected to laser heat treatment, and FIG. 5B shows high energy. It is a SEM image (Example 1) of the edge part of a workpiece after carrying out face milling to the workpiece (carbon steel S45C) which performed the laser heat processing of density (526 W / mm < ² >). Fig. 6 shows the cross-sectional shape of the work piece end measured with a laser displacement meter, the cut end of the work material (carbon steel S45C) not subjected to laser heat treatment (carbon steel S45C), high energy density An end portion (Example 1) after cutting of a work material (carbon steel S45C) subjected to laser heat treatment of (526 W / mm ² ) and a work subjected to laser heat treatment of low energy density (57 W / mm ² ) It is a figure which shows the edge part (Example 2) after cutting of material (carbon steel S45C). Fig. 7 shows the height distribution in the length direction of burrs at the cutter exit surface of the work material, and the burr height distribution in the work material (carbon steel S45C) not subjected to laser heat treatment (comparative example) ), the laser heat treatment of high energy density (526W / mm ²⁾ workpiece to the laser heat treatment was carried out for (height distribution of the burrs in the carbon steel S45C) (example 1) and a low energy density (57 W / mm ²⁾ It is a figure which shows the height distribution (Example 2) in the performed cut material (carbon steel S45C). FIG. 8 shows a structural photograph of the cross-section of the workpiece after cutting, and FIG. 8A shows a cross-sectional photograph of the end of the workpiece (carbon steel S45C) that has not been subjected to laser heat treatment (comparative example). , 8 (b) is an end cross-sectional photograph (example 2) low energy density (57 W / mm ²⁾ workpiece to the laser heat treatment was carried out in the (carbon steel S45C), and FIG. 8 (c) high energy It is an edge part cross-section photograph (Example 1) of the cut material (carbon steel S45C) which performed the laser heat processing of density (526 W / mm < ² >). FIG. 9 is a diagram showing a change in the height of burrs generated on the cutter exit surface according to the cutting distance when cutting is performed while changing the depth of cut. FIG. 10 is a diagram showing the transition of the burr height as the number of cutting passes increases for the work material (carbon steel S45C) subjected to laser heat treatment with high energy density (526 W / mm ² ) along the final cut line. is there. FIG. 11 shows the cutting resistance in the tangential direction at the time of cutting in a work material not subjected to laser heat treatment (carbon steel S45C) and a work material subjected to laser heat treatment of high energy density (526 W / mm ² ) (carbon steel S45C). FIG. FIG. 12 (a) is a diagram showing the shape and hardness of a chip of a workpiece (carbon steel S45C) that has not been subjected to laser heat treatment, and FIG. 12 (b) is a laser heat treatment with a high energy density (526 W / mm ² ). It is a figure which shows the shape and hardness of the chip of the performed cut material (carbon steel S45C). FIG. 13 is a diagram showing the influence of laser heat treatment on the finished surface roughness. The work material (carbon steel S45C) subjected to laser heat treatment at a high energy density (526 W / mm ² ) and the workpiece not subjected to laser heat treatment. It is a figure which shows the relationship between the cut about a cutting material (carbon steel S45C), and finished surface roughness (Rz, Ra).

  In the face milling method of the present invention, the vicinity of the cut line on the cutter exit surface of the work material is hardened beforehand by heat treatment, and the cutter is cut out from the hardened region to cut.

  Further, the work material for face milling according to the present invention is a work material made of iron-based metal, and is formed by heat-treating the vicinity of the planned cut line of the surface to be a cutter exit surface in face milling. It is.

  In the present invention, the “work material” is not particularly limited as long as it is hardened by heat treatment, that is, can be hardened, but the degree of hardening (curing progress) is controlled by heat treatment conditions. From the standpoint of easy handling, iron-based metals such as steel (carbon steel, alloy steel) and cast iron are suitable. Specifically, carbon steel for mechanical structure, bearing steel, ferritic stainless steel, heat resistant steel, Tool steel, chromium / molybdenum steel, nickel / chromium steel, and the like.

FIG. 1 is a perspective view schematically showing the face milling method of the present invention.
As shown in FIG. 1, a milling cutter (not shown) rotates in the direction of arrow A with respect to the work material 1, and cutting is performed along a path indicated by a dotted line B. In the present invention, the vicinity of the planned cut line 2 on the cutter exit surface 1A of the work material 1 is hardened by, for example, heat treatment such as laser irradiation, and the milling cutter is extended from the hardened region (heat treatment region) 3.

  FIG. 2 shows a laser power (Q): 500 W, a spot diameter (D): 1.1 mm, a scanning speed (S): 12.5 mm / sec. 1 is a cross-sectional photograph of an example of a cutting material (a cross-sectional photograph cut in a direction perpendicular to the cutter exit surface 1A), and the hardened region 3 is a cutter formed in the depth direction from the cutter exit surface 1A of the work material 1; A substantially semicircular martensite region 3A (maximum depth: about 0.15 mm) having a width of about 0.6 mm on the exit surface 1A, and an unmartensite region 3B (width) formed around the martensite region 3A About 0.2 mm). The width of the non-martensite region 3B here is a dimension in a direction orthogonal to the outline of the outer periphery of the martensite region 3A on the cross-sectional photograph. In addition, the code | symbol 4 in FIG. 2 is the resin material used in order to embed the cutting material 1 in the case of cross-section formation (cutting) of the cutting material 1. FIG.

  In this way, when the vicinity of the planned cut line 2 of the cutter exit surface 1A of the work material 1 is previously cured by heat treatment and the cutter is brought out from the hardened region 3, the work material 1 is obtained as shown in FIG. The work material 1 is finished without generating burrs at the end portion 12 (the edge portion at the boundary between the finish surface 11 and the cutter exit surface 1A) 12. 3 shows the work material 1 shown in FIG. 2 in which the cutting speed (V): 100 m / min, the cutting depth (a): 0.4 mm, and the feed speed (f) of the work material: 0.1 mm / tooth. It is the processed product obtained by cutting with.

  In the present invention, the formation of the hardened region by heat treatment is generally performed by laser irradiation (laser heat treatment) from the viewpoints of workability, efficiency, easy hardness control, and the like. As long as selective heat treatment in the vicinity of the line is possible, a method other than laser irradiation, such as electron beam irradiation, may be used.

  One of the factors that determine the shape of the end of the workpiece after cutting in cutting is the mechanical properties of the workpiece (see Non-Patent Document 7). In general, when a work material having low hardness and high ductility is cut, when the cutter approaches the exit surface, large plastic deformation occurs at the end portion, and burrs are generated. As the hardness increases, the ductility decreases and the burrs become smaller because the region where plastic deformation occurs becomes smaller. Further, when the hardness of the work material increases and becomes brittle, the chipping occurs due to brittle fracture. In the method of the present invention, the generation of burrs can be suppressed because the vicinity of the cut line 2 of the cutter exit surface 1A of the work material 1 is hardened by heat treatment, and the milling cutter passes through the hardening region 3. This is considered to be because the ductility at the time of cutting out from the cutter exit surface of the work material decreases, and the area where plastic deformation occurs is reduced.

  The degree of hardening of the hardened region 3 in the vicinity of the planned cutting line 2 in the work material 1 varies depending on the type of the work material 1 and the material of the milling cutter (particularly, the tip tool (hard tip)), but in general, The hardness of the cured region 3 is preferably Hv600 or higher. More specifically, when the work material is carbon steel or alloy steel, the hardness of the hardened region 3 is preferably Hv 600 or more, more preferably Hv 650 or more, and particularly preferably Hv 680 or more. In addition, although the upper limit of the hardness of the hardening area | region 3 is not restrict | limited in particular, Hv700 or less is preferable from a viewpoint of suppressing that an edge crack becomes excessive.

  In addition, Hv (Vickers hardness) as used in this specification is the value measured on conditions with a load of 300 g and holding time of 5 seconds.

  Moreover, it is preferable that the hardening area | region 3 is hardened | cured in the state which the structure transformation to a martensite or a bainite produces at least one part.

  In the present invention, the hardened region 3 by heat treatment is formed so as not to generate burrs at the end of the finished surface of the work material, and when it becomes larger than necessary, the processed product obtained by cutting the work material Therefore, a large amount of originally hardened portion remains. Therefore, it is preferable that the hardened region 3 is formed as small as possible within a range in which the ductility when the cutter comes out from the cutter exit surface of the work material is sufficiently reduced and the region where plastic deformation occurs is sufficiently small. Is a strip having a width of about 0.5 to 1.5 mm with the planned cutting line 2 as an axis on the cutter exit surface 1A of the work material 1, and the depth from the cutter exit surface 1A is 0.1 mm or more, It is preferable to form it within a range of 0.5 mm or less. In the band-like region having a width of about 0.5 to 1.5 mm on the cutter exit surface 1A, the central region having a width of about 0.5 to 1.0 mm including the planned cut line 2 is at least a martensite region. More preferably, the entire belt-like region is preferably a martensite region.

In the present invention, when the heat treatment of the work material 1 is performed by laser irradiation, the laser oscillator is not particularly limited, and a carbon dioxide laser, an argon laser, an excimer laser, a YAG laser, a helium neon laser, a ruby laser, and the like can be used. However, a carbon dioxide laser and a YAG laser are preferable because large heat energy necessary for processing can be easily obtained (high output can be easily obtained). The laser irradiation conditions (laser output, spot diameter, scanning speed, etc.) are appropriately set according to the type of workpiece 1, desired hardness, etc. For example, the workpiece is carbon steel or alloy steel. The laser power is 300 to 1000 W, the spot diameter is 1.0 to 1.5 mm, the scanning speed is selected within the range of 10 to 50 mm / second, and the energy density is 10 ² to 10 ³ W / mm ² . It is preferable to irradiate the laser so that the processing time is 10 ⁻³ to 10 ⁻² s.

  Before performing laser irradiation, a laser absorbent such as a carbon-based absorbent may be applied to increase the laser absorption rate on the surface of the work material. A commercial item can be used for a laser absorber.

  In the present invention, a milling cutter in front face milling, a tool (hard tip) attached to the tip of the milling cutter, etc. are not particularly limited, and a general-purpose tool can be used without limitation. A hard alloy or the like is preferable.

  As is clear from the experimental examples described later, the method of the present invention enables cutting without generating burrs. Edge breakage may occur, but the edge breakage is minute and does not hinder the product obtained by processing. Further, the method of the present invention can make the burrs extremely minute depending on the degree of hardening by heat treatment (quenching hardening) even when burrs cannot be completely eliminated. That is, it is possible to control the shape of the end portion (edge portion) of the product obtained by processing the work material.

  Hereinafter, the present invention will be described more specifically with reference to experimental examples including examples and comparative examples. However, the following examples are merely examples, and the present invention is not limited to the following examples.

[Experiment 1]
(Experimental conditions)
Table 1 below shows the chemical composition and hardness of the work material (carbon steel JIS S45C) used in the experiment. After hot forging, the work material was kept at 850 ° C. for 5 hours, and then kept cold and normalized. The hardness (hardness) was Hv240.

Table 2 below shows laser irradiation conditions. In addition, before performing laser irradiation, in order to increase the laser absorption rate on the surface of the work material, a carbon-based absorbent (Ishihara Pharmaceutical Co., Ltd., UNiCON laser non-loss 371) was applied. Using a carbon dioxide laser processing machine, irradiation was performed under two conditions of output 100 W, spot diameter 1.5 mm (energy density: 57 W / mm ² ) and output 500 W, spot diameter 1.1 mm (energy density: 526 W / mm ² ). . The laser scanning speed (S) was constant at 12.5 mm / s.

As shown in FIG. 1, the laser heat treatment was performed by continuous oscillation on the planned cut line 2 along the end of the cutter exit surface 1 </ b> A of the work material 1. An arrow C in FIG. 1 indicates a cutting distance, and a dimension a indicates a cut.
Table 3 shows the cutting conditions.

  TiN coated cemented carbide tool M20 (tool shape TEEN1603PETR1) is attached to a 50 mm diameter cutter (SE300R503S32 manufactured by Mitsubishi Materials Corporation), cutting speed V is set to 100 m / min, feed speed f is set to 0.1 mm / tooth, and cutting a Was changed between 0.2 mm and 1.0 mm, and face milling was performed in a dry manner. The dimensions of the work material are 20 mm wide and 50 mm long.

  FIG. 4 shows the cutting method. 4, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts, and the arrow D indicates the feed direction of the work material 1. Front milling was performed in a state where the rotation center 5 of a milling cutter (not shown) was moved 9.2 mm from the center line 6 of the work material 1 to the cutting edge inlet side and the outlet angle 7 was 140 °. The work material laser-heat treated along the planned cutting line 2 was face milled, and the effect on the generated burr was examined as compared with the case where the work material not laser-heat treated was cut. Observation of the end shape after cutting was performed by measuring with a laser displacement meter (LK-080, manufactured by KEYENCE (Keyence Japan)) and after polishing the cross section with a thermosetting resin (KEYENCE (Keyence Japan). ) VH-5910) made by observation.

  In addition, in order to investigate the influence of laser heat treatment on the work material on the cutting state, chip observation, finish surface roughness measurement and cutting resistance measurement were also performed. Cutting resistance was measured using a piezoelectric sensor type three-component tool dynamometer (Type 9257A manufactured by KISTLER (Japan Kistler Co., Ltd.)).

(Results and discussion)
(1) Heat treatment characteristics of carbon steel by laser FIG. 2 is a cross-sectional photograph of carbon steel S45C after laser heat treatment. The photograph shows a plane perpendicular to the laser scanning direction and is after corrosion by a night solution. From the figure, a semicircular region discolored by laser irradiation can be confirmed in the structure of the pro-eutectoid ferrite + pearlite which is the base material. This discolored semicircular region is divided into two regions: a region that is completely martensified near the surface and a region that is discolored due to thermal influence but has not yet been martensitized. The hardness of the two discolored regions was higher than the hardness (Hv: about 240) of the base material (carbon steel S45), and the maximum hardness was about Hv700 in the martensitic structure region close to the surface. This confirmed that the work material can be partially heat-treated by laser irradiation and can be cured.

(2) Effect of laser heat treatment on generation of burrs FIG. 5 shows an SEM image of the end of carbon steel S45C after face milling. As shown in FIG. 5 (a), it was confirmed that burrs were generated at the ends when the work material not subjected to laser heat treatment was cut (Comparative Example 1). On the other hand, when a workpiece subjected to laser heat treatment (energy density q: 526 W / mm ² ) is cut at a cutting depth of 0.5 mm, almost no burrs are seen at the end as shown in FIG. A small chipping of a size of about 0.2 mm and a height of about 0.1 mm occurred (Example 1).

FIG. 6 shows an example of the cross-sectional shape of the workpiece end portion measured using a laser displacement meter. When a work material not subjected to laser heat treatment is cut, a burr having a height of approximately 0.6 mm is generated at the end. On the other hand, when a work material subjected to laser heat treatment with a high energy density (energy density q: 526 W / mm ² ) is cut, there is no burr and chipping occurs (Example 1). Further, it can be seen that burrs are generated when a workpiece subjected to laser heat treatment at a low energy density (energy density q: 57 W / mm ² ) is cut. However, the size is considerably smaller than that in the case where laser heat treatment is not performed (Example 2).

FIG. 7 shows the distribution of the height of the burr generated on the cutter exit surface in the length direction of the work material. The cross-sectional shape was measured with a laser displacement meter at an arbitrary cutting distance, and the distribution of the height of burrs generated on the cutter exit surface was examined. When edge breakage occurred, the height was evaluated as a negative value. In the case of a work material not subjected to laser heat treatment, a burr having a height of about 0.7 mm at maximum was generated (Comparative Example 1). In contrast, when the energy density of the laser is low (energy density q: 57 W / mm ^2), burr height becomes 0.1mm approximately at a maximum (Example 2), as compared with the case not subjected to laser heat treatment significantly The burr height decreased. When the work material heat-treated with a laser having a high energy density (energy density q: 526 W / mm ² ) was cut, no burrs were generated, and minute edge chipping of about 0.1 mm occurred (Example 1). As described above, it has been found that the shape of the end portion of the work material after cutting is greatly affected by the laser irradiation to the work material performed before cutting, and burr can be suppressed.

FIG. 8 shows a structural photograph of the cross-section of the workpiece end after cutting. The photo shows the surface perpendicular to the feed direction of the tool, and is after corrosion by the nital solution. In the work material not subjected to the laser heat treatment, a large burr was generated at the end (FIG. 8A, Comparative Example 1). When cutting a laser-irradiated work material having a high energy density (energy density q: 526 W / mm ² ), edge cracks occurred in the martensite structure in the region affected by heat (FIG. 8C). Example 1). On the other hand, when the energy density was low (energy density q: 57 W / mm ² ), it was found that minute burrs were generated at the end after cutting, and there was almost no martensite structure around the burrs ( FIG. 8B), Example 2). Therefore, it was found that in order to eliminate the generation of burrs, it is preferable to perform heat treatment so that at least a martensite structure is formed on the surface layer of the hardened region.

FIG. 9 shows changes in the height of burrs generated on the cutter exit surface according to the cutting distance when cutting is performed while changing the depth of cut a in the range of 0.2 mm to 1.0 mm. The laser heat treatment is performed at an energy density q: 526 W / mm ² , so that the center of the laser heat treatment is the finished surface (that is, the planned cut line 2 that is the axis of the band-shaped cured region 3 formed by the heat treatment shown in FIG. Was subjected to laser heat treatment (so that it was included in the finished surface). When a work material that has not been subjected to laser heat treatment is cut, the size of the burrs generated differs depending on the difference of the depth of cut a. Further, as the cut a increases, the size of the burr increases. However, when the cut a exceeds 0.6 mm, the burr height decreases. This is considered to be due to a secondary burr formed by separating the burr tips (see Non-Patent Documents 2, 3, and 5). On the other hand, when the work material subjected to laser heat treatment (energy density q: 526 W / mm ² ) is cut, the end of the work material after cutting does not generate burrs regardless of the size of the cut, and the work material is minute. It turned out to be a chipped edge.

FIG. 10 shows the transition of the burr height as the number of cutting passes increases. The workpiece was subjected to laser heat treatment along the final cut line (scheduled line in the sixth cutting) before cutting. The laser heat treatment was performed at an energy density q: 526 W / mm ² . There were no burrs before the start of cutting. As the cutting started, burrs were generated, and the burrs showed an almost constant height even when the number of cutting passes increased. Burr was not generated at the end of the work material after the sixth cutting, which was the last cutting, and a minute edge chipped. For this reason, even if burrs are generated in the work material before cutting, laser heat treatment is performed only on the final cut line to be applied to the finished surface of the product on the surface that is the cutter exit surface of the work material. It has been found that if a hardened region is formed, the generation of burrs can be suppressed.

(3) Influence of Laser Heat Treatment on Cutting Resistance and Finished Surface Roughness FIG. 11 shows tangential cutting resistance during cutting. When the laser-heat-treated work material was cut, there was a portion where the cutting resistance increased in a pulse shape at the end of cutting. This is thought to be due to the presence of a high hardness portion in front of the tool edge, which affected the deformation of the work material and increased the cutting resistance instantaneously.

  FIG. 12 shows the chip shape and hardness. FIG. 12A is a photograph of chips obtained by cutting a workpiece without laser heat treatment, and FIG. 12B is a photograph of chips obtained by cutting a workpiece subjected to laser heat treatment. When the laser heat-treated workpiece was cut, a portion subjected to the laser heat treatment was observed at the end of the chip (FIG. 12B). Chips were work hardened by plastic deformation received during cutting and showed higher hardness than the work material. The hardness of the work material before cutting was Hv240, and the hardness of the chip was about HV300. When the hardness of the edge part of a chip was measured and it was about Hv650, it turned out that the part which became the edge chip was separated from a work material with a chip.

  FIG. 13 shows the effect of laser heat treatment on the finished surface roughness. The figure shows the arithmetic average roughness Ra and the maximum height roughness Rz. In each case, 10 points were measured and the average value was shown. As for Rz, when the workpiece subjected to the laser heat treatment is cut, the roughness may be reduced compared to the case where the laser heat treatment is not performed, but the roughness is almost the same regardless of the presence or absence of the laser heat treatment. I understood it. In turning of carbon steel S45C, it is recognized that the surface roughness tends to be small although the laser processing is performed on the work material (Non-patent Document 8). However, this trend did not appear in this face milling because the cutting method is intermittent cutting, the width of the work material is as small as 20 mm, and one cutting is completed in a relatively short time. It is considered that there was little adhesion of the work material.

1 Work Material 1A Cutter Exit Surface 2 Cut Line 3 Curing Area (Heat Treatment Area)
3A Martensite region 3B Non-martensite region a Cutting

Claims (6)

  A face milling method for a work material made of a ferrous metal, characterized in that a vicinity of a cut line on a cutter exit surface of the work material is previously hardened by heat treatment.   The method according to claim 1, wherein a hardened region having a hardness (Hv) of 600 or more is formed by heat treatment.   The method according to claim 1 or 2, wherein the heat treatment is a laser irradiation treatment.   The method according to any one of claims 1 to 3, wherein the ferrous metal is carbon steel.   A work material for face milling, which is a work material made of an iron-based metal, and which is hardened by heat treatment in the vicinity of a planned cut line of a surface to be a cutter exit surface in face milling.   The work material for face milling according to claim 5, wherein a hardened region having a hardness (Hv) of 600 or more is formed by heat treatment.