JP2019214770A - Surface hardening treatment method for metal work - Google Patents

Abstract

To provide a surface hardening treatment method for a metal work by a laser, for obtaining a sufficient depth of a hardened layer and a flat surface shape after the hardening treatment.SOLUTION: The surface hardening treatment method of a metal work applies laser light 3 from a laser irradiation source 2 which moves relative to a surface to be hardened (a treatment region to be hardened) 10 on a surface of a work 1 at a prescribed speed with respect to the treatment region to be hardened 10, thereby heating and melting the treatment region to be hardened 10. By way of self-cooling, a hardened layer 12 is formed in the treatment region to be hardened 10. A plurality of grooves 11 extending along the relative movement direction A of the laser irradiation source 2 are formed in advance so as to be adjacent to each other in parallel in the treatment region to be hardened 10.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for surface hardening a metal work using a laser.

  For example, in the case of a shaft work made of steel, such as a camshaft of an automobile part, a ball screw of a machine tool, or a main shaft, a surface hardening treatment is generally performed on a portion requiring mechanical strength and wear resistance. It is being done.

One of such surface hardening treatments is quenching by laser. Laser quenching is performed by irradiating a laser beam to a region to be hardened on the surface of a work made of steel or the like for a short time, heating the irradiated portion to a temperature equal to or higher than the transformation point to austenite, and then self-cooling, that is, The surface layer of the work is quenched (martensite structure) by rapid cooling by heat diffusion into the inside of the work (for example, see Patent Document 1 below).
This surface hardening treatment by laser quenching can generally be performed in the atmosphere, and does not require a cooling device or a cooling material.Furthermore, it can be applied to parts having complicated shapes, and can be applied to extremely small parts, deep grooves, hole side surfaces, This is advantageous in that processing on the bottom of the hole is possible.
However, in the case of general laser quenching, there is a problem in that a sufficient hardened layer depth cannot be obtained as compared with induction hardening or other heat hardening treatments, and the load that can be applied even when the hardening treatment is performed is limited. Was.

Therefore, as a curing treatment method capable of obtaining a sufficient cured layer depth, a re-melt curing treatment of forming a cured layer by partially melting the surface of a metal work is known. For example, Patent Literature 2 below discloses a re-melt hardening method using a laser.
The method will be described with reference to FIGS. 9 to 11. First, as shown in FIG. 9, a region (101) to be hardened on the surface of the metal work (100) is A laser beam (3) is emitted from a laser oscillator (not shown) that relatively moves in a predetermined direction at a predetermined speed.
In the area (101), the portion irradiated with the laser beam is heated to a temperature equal to or higher than the transformation point, the surface of the work (100) is melted, and the laser oscillator passes and the laser beam irradiation is completed. It is quenched by self-cooling, thereby forming a hardened layer (102) composed of a molten re-solidified layer (102a) and a quenched hardened layer (102b) below it, as shown in FIG. In the molten re-solidified layer (102a), the grain size of the metal structure becomes smaller in the process of re-solidification after melting, thereby increasing the hardness.
Here, the molten re-solidified layer (102a) on the surface side of the work (100) has a central portion protruding in a chevron shape, and both sides thereof are concavely underfilled. This is due to the fact that the molten metal is greatly deformed due to expansion due to surface tension or the like, and is rapidly cooled and solidified again as it is.
Therefore, as a finishing step, a region (101) on the surface of the hardened work (100) is subjected to grinding to make the surface of the work (100) flat as shown in FIG. The amount to be finished (ground) is relatively large, as indicated by reference numeral (103) in FIG. The hardened layer (102) thus obtained has a greater depth than that obtained by general laser hardening.

JP-A-4-99217 JP-A-6-246428

  However, in the case of the above-described remelting and hardening treatment by laser, deformation such as expansion due to the surface tension of the molten metal increases, so that the amount of finish processing of the work surface after the hardening treatment increases, which is disadvantageous in processing time. . Further, when the deformation due to melting is too large, there is a problem that the adjustment work in the finishing processing increases and the number of defective products also increases.

  The present invention has been made in view of the above problems, and provides a sufficient hardened layer depth and a flat surface shape after the hardening process as a surface hardening method of a metal work using a laser. It is intended to provide a way.

  The present invention has the following aspects to attain the object mentioned above.

1) irradiating a laser beam from a laser light irradiation source relatively moving at a predetermined speed to the predetermined region on the surface of the metal workpiece to be subjected to the hardening treatment, and heating and melting the predetermined region; By self-cooling, a method of surface hardening treatment of a metal work that forms a hardened layer in the predetermined area,
A surface hardening process for a metal work, which includes forming in advance in the predetermined area one or more grooves extending in parallel with each other in the direction of relative movement of the laser light irradiation source. Method.

2) The method of 1) above, wherein the groove is a groove having a substantially V-shaped cross section.

3) The metal work of the above 2), wherein the groove having the substantially V-shaped cross section has a groove angle of 90 ° or less and an angle of each of the two groove side surfaces with respect to the laser irradiation direction is 45 ° or less. Surface hardening treatment method.

4) The method of 1) above, wherein the groove is a groove having a substantially circular cross section.

5) The surface hardening method for a metal work according to any one of 1) to 4) above, wherein the groove has a groove depth of 0.5 to 1.5 mm.

6) The groove is formed in advance only in a predetermined part of the predetermined area where the degree of melting by the laser beam irradiation is relatively large as compared with other parts. A surface hardening method for any one of the metal workpieces.

In the method for surface hardening of a metal work of the above 1), when a predetermined area on the surface of the metal work to be hardened is irradiated with a laser beam and a sufficient amount of heat is applied, a portion close to the surface, That is, when one groove is formed in advance, a portion close to the opening edge of the groove, and when a plurality of grooves are formed in advance, a mountain-shaped portion between adjacent grooves is melted first, and the same portion is melted. Molten metal flows into the bottom of the groove with directivity. Therefore, after the laser irradiation source passes, in a state where the melted portion is re-solidified by self-cooling, the above-mentioned region does not show a large deformation unlike the prior art shown in FIG. 10 and has a substantially flat surface shape. .
Therefore, according to the above method 1), the finishing work after the surface hardening treatment of the metal work becomes easy, the number of steps can be reduced, and the depth of the obtained hardened layer is sufficient and more uniform from the surface. Therefore, a product excellent in performance can be obtained.

  According to the surface hardening method of the metal work of the above 2), the groove formed in a predetermined region of the work surface is a groove having a substantially V-shaped cross section, so that the surface shape of the hardened work is flat. Easy to become things.

  According to the surface hardening method of the metal work of the above 3), the groove having a substantially V-shaped cross section formed in a predetermined region of the work surface is formed at a groove angle of 90 ° or less and each of the two groove side surfaces. Since the angle with respect to the laser irradiation direction is 45 ° or less, the reflected light of the laser light applied to one side of the groove is easily irradiated to the other side of the groove, and therefore, the loss due to reflection is reduced. As a result, the amount of heat input to the work increases, and processing with a lower laser output becomes possible.

  According to the surface hardening method of the metal work of the above 4), the groove formed in advance in the predetermined region of the work surface is a substantially arc-shaped groove in cross section, so that the surface shape of the hardened work is flat. It is easy to become something.

  According to the method of 5) for hardening the surface of the metal work, the depth of the groove formed in advance in the predetermined area of the work surface is set to 0.5 mm or more, so that the area is melted by laser light irradiation. The time required for the surface to be flattened is sufficiently secured. Therefore, a sufficient quenching depth is obtained, and the groove depth is set to 1.5 mm or less. The amount of heat required for melting and flattening does not become too large.

  According to the surface hardening method of the metal work of the above 6), only a predetermined part of the predetermined area of the surface of the metal work, the degree of melting due to the irradiation of the laser beam, is relatively larger than other parts. In addition, by forming the grooves in advance, the predetermined area after the re-solidification of the molten portion by self-cooling has a flatter surface shape, and the above-mentioned effect described in the above method 1) is more remarkably exhibited. Is done.

It is a perspective view showing one process of the surface hardening treatment method of the metal work concerning a 1st embodiment of this invention. FIG. 2A is a cross-sectional view illustrating a state where a hardened processing area on a work surface is irradiated with a laser beam in the above process, and FIG. 2B is a cross-sectional view illustrating a part of FIG. It is. It is sectional drawing which shows the state after the hardening process of the said hardening process area. It is sectional drawing which shows the state after the finishing processing of the said hardening process area | region. It is sectional drawing which shows the modification of the groove | channel formed in the said hardening process area | region. FIG. 9 is a cross-sectional view showing one step of a method for hardening a surface of a metal work according to a second embodiment of the present invention, and showing a state where a hardened region of the work surface is irradiated with laser light. is there. It is sectional drawing which shows the state after the hardening process of the said hardening process area. It is sectional drawing which shows the state after the finishing processing of the said hardening process area | region. FIG. 4 is a cross-sectional view showing a state where a region to be cured on the surface of a work is irradiated with a laser beam in a conventional method of hardening a metal work. It is sectional drawing which shows the state after the hardening process of the hardening process area | region in the conventional method. It is sectional drawing which shows the state after finish processing of the hardening process area | region in the conventional method.

  An embodiment of the present invention will be described below with reference to FIGS.

[First Embodiment]
1 to 5 show a first embodiment of the present invention.
As shown in FIG. 1, in this embodiment, a hardened layer is formed on a predetermined surface (10) of a steel work (1) by a hardening treatment method according to the present invention.
Above a surface (a region to be cured) (10) of the work (1) to be subjected to a curing process, a laser oscillator (laser irradiation source) (2) is arranged in an opposed manner. The laser oscillator (2) is relatively moved at a predetermined speed in a predetermined direction (A) along the length direction of the hardened surface (10) of the work (1) by a feeding device (not shown). As the laser oscillator (2), one having a rectangular energy distribution is used.

A plurality of grooves (11) extending in the longitudinal direction are formed in advance on the surface (10) of the work (1) to be hardened so as to be adjacent to and parallel to each other. The means for forming these grooves (11) is not particularly limited.For example, if the work (1) is of an axial type, the work (1) is formed by cutting the surface of the work (1) using a parting tool of a lathe or the like. can do.
The plurality of grooves (11) formed on the surface (10) of the workpiece (1) to be cured are formed of V-shaped cross sections as shown in detail in FIG. Each groove (11) has a groove angle (B) of 90 ° or less, and the angles (B1) and (B2) of the two groove side surfaces (11a) and (11b) with respect to the irradiation direction of the laser light (3) are 45 °. It is as follows. The groove depth (C) of each groove (11) is set to 0.5 to 1.5 mm.
Although not shown, the number of grooves to be formed is appropriately set depending on the size of the hardened region of the work, and may be one in some cases.

Then, while relatively moving the laser oscillator (2) at a predetermined speed in the direction indicated by the symbol (A) in FIG. 1, the laser oscillator (2) moves the laser beam from the laser oscillator (2) to the hardened surface (10) of the work (1). Light (3) is irradiated at an angle of 90 °. At this time, the moving speed of the laser oscillator (2), the output of the laser beam (3) to be irradiated, and the like are appropriately set so as to obtain a desired cured layer.
When the laser beam (3) is irradiated, the surface (10) to be cured of the work (1) is heated to a temperature equal to or higher than the transformation point by the energy of the laser beam (3). In particular, in this embodiment, as shown in FIG. 2, the laser light (3) applied to one groove side surface (11a) of each groove (11) formed on the surface to be cured (10) is reflected. Then, the other groove side surface (11b) is irradiated, so that the heating by the irradiation of the laser beam (3) is efficiently performed.

When heated by the irradiation of the laser beam (3), the surface (10) of the workpiece (1) to be hardened is closer to the surface, that is, from the mountain-like portion between the adjacent grooves (11). It melts. The molten metal (steel) in the same portion flows with directivity toward the bottom of each groove (11).
Then, when the laser oscillator (2) passes and the irradiation of the laser beam (3) is completed, the irradiated portion (10a) of the surface to be cured (10) is self-cooled, that is, heat applied to the inside of the work (1). Quenched by diffusion. As a result, as shown in FIG. 3, a hardened layer (12) composed of a molten re-solidified layer (121) and a quenched hardened layer (122) below the hardened layer (121) is formed on the hardened surface (10) of the work (1). Is formed. The molten re-solidified layer (121) has slightly raised both end portions, but the other portions have a substantially flat surface shape.

Finally, as a finishing step, the hardened region (10) on the surface of the hardened workpiece (1) is subjected to grinding to make the surface of the workpiece (1) flat as shown in FIG. The amount of finishing (grinding) to be performed is as shown by reference numeral (4) in FIG. 3, and is greatly reduced as compared with the amount of finishing (103) in the case of the conventional technique shown in FIG.
The hardened layer (12) obtained in this way has a more sufficient depth than the hardened layer (102) obtained by the method of the prior art shown in FIG. 11, and has a substantially uniform depth from the surface. It will be.
Therefore, according to the surface hardening treatment method of this embodiment, it is possible to impart desired mechanical strength, abrasion resistance, and the like to the hardened surface (10) of the work, and the product has excellent performance. Is obtained.

FIG. 5 shows a modified example of a groove formed in advance on the surface to be hardened (10) of the work. The groove (11X) shown in the figure is a groove having a circular cross section. The groove depth (C) of the groove (11X) is the same as that of the V-shaped groove (11) shown in FIG.
And, even when a plurality of grooves (11X) having a circular cross section as described above are previously formed on the hardened surface (10) of the work (1), the grooves (11) having a V-shaped cross section are formed. The same operation and effect as in the above-described case are exerted.

[Second Embodiment]
6 to 8 show a second embodiment of the present invention.
In the method for hardening a metal work according to this embodiment, as shown in FIG. 6, a predetermined region (a region to be hardened) (10) to be hardened on the surface of a metal work (1) made of steel or the like. The groove (11) is formed in advance only in a part, that is, only in a part (10X) where the degree of melting by the irradiation of the laser beam (3) is relatively large as compared with other parts. The shape and size of the groove (11) are the same as those of the first embodiment.
The hardened region (10) has a length along the relative movement direction of the laser oscillator (2) (see FIG. 1) and a width (W1) along a direction orthogonal to the relative movement direction. are doing.
The portion (10X) where the groove (11) is formed in advance is a part of the width (W1) of the region to be cured (10), specifically, an intermediate portion excluding both ends of the width (W1). . Preferably, the portion (10X) in which the groove (11) is formed in advance has a width (W2) of about 50% of the width (W1) of the region to be cured (10). The range from the center position of the width (W1) of the region (10) to a position equidistant toward both ends is set.

Then, when a laser beam (3) is irradiated from a laser oscillator (not shown) to the hardened area (10) of the work (1), the hardened area (10) melts first from a portion close to the surface. To go. In particular, in the middle width portion (10X) where the groove (11) is formed in advance in the hardened region (10), the energy distribution of the laser light (3) emitted from the laser oscillator and the like make it possible to compare with the both end portions. As a result, the degree of melting increases, and the molten metal (steel) in the mountain-like portion between the adjacent grooves (11) flows with directivity toward the bottom side of each groove (11).
When the irradiation of the laser beam (3) is completed after passing through the laser oscillator, the irradiated portion of the hardened region (10) is rapidly cooled by self-cooling. As a result, as shown in FIG. 7, a hardened layer (12) composed of a molten re-solidified layer (121) and a quenched hardened layer (122) below the hardened layer (121) is formed in the hardened area (10) of the work (1). Is formed. In this embodiment, as described above, the portion (10X) in which the groove (11) is preformed is only a predetermined part of the hardened region (10), and therefore, compared to the first embodiment. On the other hand, the degree of protrusion at both ends of the molten re-solidified layer (121) is smaller, and the proportion of the portion having a substantially flat surface shape is larger.

  Thereafter, as a finishing step, the hardened region (10) on the surface of the hardened work (1) is subjected to grinding to make the surface of the work (1) flat as shown in FIG. The finishing amount is as indicated by reference numeral (4X) in FIG. 7, and is greatly reduced as compared with the finishing amount (103) in the case of the prior art shown in FIG. 10, and the first processing amount shown in FIG. In this embodiment, the finishing amount (4) is even smaller.

  INDUSTRIAL APPLICABILITY The present invention is suitably used as a means for surface hardening a metal work such as a camshaft of an automobile part, a ball screw of a machine tool, and a main shaft.

(1): Work
(10): Hardened surface, hardened area, hardened area
(10X): a part of the hardened area where a groove is to be formed
(11) (11X): Groove
(11a) (11b): Groove side
(12): Hardened layer
(121): Melt re-solidified layer
(122): Hardened hardened layer
(2): Laser oscillator (laser irradiation source)
(3): Laser light
(4) (4X): Grinding amount
(A): Relative movement direction of laser oscillator
(B): Groove angle
(B1): Angle of one groove side surface to laser light
(B2): Angle of the other groove side surface with respect to laser light
(C): Groove depth

Claims (6)

A predetermined area on the surface of the metal work to be hardened is irradiated with a laser beam from a laser light irradiation source relatively moving at a predetermined speed with respect to the predetermined area, and the predetermined area is heated and melted. By performing the method, a surface hardening treatment method of a metal work for forming a hardened layer in the predetermined region,
A surface hardening process for a metal work, which includes forming in advance in the predetermined area one or more grooves extending in parallel with each other in the direction of relative movement of the laser light irradiation source. Method.   The method according to claim 1, wherein the groove has a substantially V-shaped cross section.   The metal work according to claim 2, wherein the groove having the substantially V-shaped cross section has a groove angle of 90 ° or less and an angle of each of the two groove side surfaces with respect to the laser irradiation direction is 45 ° or less. 4. Surface hardening treatment method.   The method according to claim 1, wherein the groove is a groove having a substantially circular cross section.   The method according to any one of claims 1 to 4, wherein the groove has a groove depth of 0.5 to 1.5 mm. 6. The groove according to claim 1, wherein the groove is formed in advance only in a predetermined part of the predetermined area, the degree of melting due to the irradiation of the laser beam being relatively larger than other parts. 7. The surface hardening method for a metal work according to any one of the first to third aspects.

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