JP6432480B2 - Laser overlaying method - Google Patents

Description

  The present invention relates to a laser overlay method, and more particularly to a laser overlay method for a valve seat.

  The cylinder head of the engine is provided with a combustion chamber and an intake port / exhaust port communicating with the combustion chamber. A valve seat with which the back surface of the valve abuts is provided at the periphery of the opening end of the intake port / exhaust port on the combustion chamber side. When the valve seat and the valve come into contact with each other, the airtightness of the combustion chamber is maintained.

  The valve seat is required to have heat resistance and wear resistance because the valve repeatedly contacts in a high temperature environment. Therefore, the valve seat is formed with an annular counterbore groove by machining at the periphery of the opening end of the intake port / exhaust port of the cylinder head rough material, and a built-up layer made of a copper alloy or the like is formed in the counterbore groove. Can be obtained.

  As a method for overlaying such a valve seat, a laser overlaying method (so-called laser cladding) in which a metallized layer, which is a material for the overlaying layer, is supplied to the counterbored groove and a cladding layer is formed by irradiating a laser beam. Law) is known. Such a laser cladding method is disclosed in Patent Document 1, for example.

  In the laser cladding method disclosed in Patent Document 1, as shown in FIG. 8 of Patent Document 1, the laser machining head is held while holding the cylinder head so that the central axis of the valve seat coincides with the vertical direction. While rotating around the central axis of the valve seat, a metal powder is supplied to the counterbored groove and irradiated with a laser beam to form a built-up layer.

JP 2005-021908 A

  However, in the laser overlaying method disclosed in Patent Document 1, the supply amount of the metal powder is small at the start end (formation starter) where the formation of the overlaying layer is started. As a result, the region directly irradiated with the laser beam is increased on the side wall of the counterbore groove, and the amount of the constituent metal of the cylinder head rough shape material melted by the laser beam is increased. As a result, the build-up layer is diluted with molten metal melted from the side wall of the counterbored groove, so that alloying proceeds and becomes brittle and cracks occur.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a laser cladding method capable of suppressing the occurrence of cracks in the cladding layer for a valve seat.

According to one aspect of the present invention, a laser cladding method includes:
In the cylinder head rough profile, a step of forming an annular counterbore groove at the opening end of the port on the combustion chamber side;
In a state where the central axis of the counterbored groove is aligned with the vertical direction, a metal beam is supplied to the counterbored groove and irradiated with a laser beam to form a built-up layer for a valve seat, and
In the step of forming the counterbored groove,
The counterbore groove is formed so as to have a bottom surface portion, a side wall portion, and a slope portion provided between the bottom surface portion and the side wall portion, and a recess is formed in the side wall portion of the counterbore groove.

  According to the aspect mentioned above, the effect that generation | occurrence | production of the crack of the built-up layer for valve seats can be suppressed is acquired.

It is a perspective view which illustrates typically the outline of the laser cladding method concerning an embodiment. It is sectional drawing which illustrates typically the outline | summary of the laser cladding method concerning embodiment. It is a figure which is a build-up layer formed by the laser build-up method concerning an embodiment, and illustrates the build-up layer seen from the combustion chamber side. It is a cross-sectional view illustrating a counterbored groove according to a comparative example after the metal powder is supplied. FIG. 6 is an enlarged cross-sectional view illustrating a counterbored groove according to a comparative example after the laser beam is irradiated. It is an expanded sectional view which illustrates the counterbore groove concerning an embodiment. FIG. 4 is an enlarged cross-sectional view illustrating a counterbored groove according to an embodiment after the metal powder is supplied. FIG. 3 is an enlarged cross-sectional view illustrating a counterbored groove according to an embodiment after the laser beam has been irradiated. It is an expanded sectional view which illustrates the counterbore groove concerning the modification of an embodiment.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following embodiment. In addition, for clarity of explanation, the following description and drawings are simplified as appropriate.

  First, with reference to FIG.1 and FIG.2, the outline | summary of the laser cladding method concerning this Embodiment is demonstrated. 1 and 2 are diagrams schematically illustrating an outline of the laser cladding method according to the present embodiment, in which FIG. 1 is a perspective view and FIG. 2 is a cross-sectional view. In FIG. 2, an after-mentioned intake port 12 is shown, but an after-mentioned exhaust port 13 may be used.

  First, the configuration of the cylinder head rough profile 10 will be described. The cylinder head rough profile 10 is a casting made of, for example, an aluminum alloy. As shown in FIG. 1, the rough cylinder head member 10 includes a plurality of (four in the example of FIG. 1) combustion chambers 11. Each combustion chamber 11 includes an intake port 12 and an exhaust port 13.

  A rough cylinder head member 10 shown in FIG. 1 is for a four-cylinder 16-valve engine, and is provided with two intake ports 12 and two exhaust ports 13 in each of four combustion chambers 11. As a matter of course, the numbers of the combustion chamber 11, the intake port 12, and the exhaust port 13 are not limited to the example of FIG. 1, but are appropriately determined.

  In such a rough cylinder head member 10, an annular counterbore groove 15 is formed at the end of the opening 14 on the combustion chamber 11 side of the intake port 12 and the exhaust port 13 so as to surround the opening 14. The counterbore groove 15 is formed by machining. As shown in FIG. 2, the counterbore groove 15 is formed to have a bottom surface portion 15a, a side wall portion 15c, and an inclined surface portion 15b provided between the bottom surface portion 15a and the side wall portion 15c. The bottom surface portion 15a, the slope portion 15b, and the side wall portion 15c are also annular. Further, a concave portion 15d is formed in the side wall portion 15c. A detailed description of the recess 15d will be described later.

  As shown in FIGS. 1 and 2, a laser beam 22 (optical axis A <b> 1) is irradiated while supplying metal powder 21 made of a copper-based alloy or the like from the laser processing head 20 to the counterbore groove 15. Inside the counterbore groove 15, the metal powder 21 is melted by the laser beam 22, and a molten pool (not shown) obtained from the molten metal powder 21 is solidified to form a built-up layer 16 for a valve seat. Is done. At this time, the laser processing head 20 is rotated about the central axis A2 of the circular counterbore groove 15. As a result, the metal powder 21 and the laser beam 22 are sequentially supplied from the laser processing head 20 in an annular shape along the counterbored grooves 15. In this way, the built-up layer 16 is formed on the entire circumference of the counterbored groove 15. For the purpose of preventing oxidation of the molten pool, the overlay layer 16 may be formed by spraying a sealing gas from the laser processing head 20 to the molten pool while rotating the laser processing head 20 about the central axis A2. .

  Here, the central axis A2 of the counterbore groove 15 is as follows. The center of the ring formed by the circular counterbore groove 15 is defined as a center O. An axis that is perpendicular to two diameters orthogonal to each other in the ring and passes through the center O is defined as a center axis A2. The center O is substantially the same as the center of the opening 14. When forming the built-up layer 16, the cylinder head rough profile 10 is held so that the center axis A2 coincides with the vertical direction with the combustion chamber 11 side facing upward so that the opening 14 faces upward. The surface of the built-up layer 16 is ground to obtain a product shape.

  Subsequently, the overlaying layer 16 formed by the laser overlaying method according to the present embodiment will be described with reference to FIG. FIG. 3 is a diagram illustrating the build-up layer 16 formed by the laser build-up method according to the present embodiment and viewed from the combustion chamber side. In FIG. 3, the built-up layer 16 of the intake port 12 is shown, but the built-up layer 16 of the exhaust port 13 may be used.

  The cladding layer 16 viewed from the combustion chamber 11 side is formed in an annular shape so as to surround the opening 14 at the periphery of the opening 14 of the intake port 12. The build-up layer 16 is formed inside the counterbore groove 15. The central axis of the counterbore groove 15 is perpendicular to the paper surface. The built-up layer 16 is used as a valve seat of a cylinder head with which the valve repeatedly contacts in a high temperature environment.

  The built-up layer 16 has an overlap portion 17 and a non-overlap portion 18. The location that is the starting point when the overlay layer 16 is formed is defined as 0 °. Here, the direction of rotation of the timepiece around the center O is defined as the cladding direction.

  First, the overlap part 17 will be described. In the annular built-up layer 16, a portion from 0 ° to x ° in the cladding direction is an overlap portion 17. For example, x can be in a range of 0 <x ≦ 45. The overlap portion 17 includes a start end portion 17a and a terminal end portion 17b. As for the overlap part 17, the start part 17a and the termination | terminus part 17b have overlapped. A hatched line 17c in FIG. 3 is shown to indicate that the start end part 17a and the terminal end part 17b overlap, and the hatched line 17c is not actually formed.

  The start end portion 17 a is a portion that is formed first in the formation of the built-up layer 16. Therefore, the supply amount of the metal powder 21 supplied from the laser processing head 20 is reduced at the start end portion 17a. The start end portion 17a is a portion from 0 ° to x ° in the cladding direction in the annular cladding layer 16. The end portion 17 b is a portion that is formed last in the formation of the build-up layer 16. The end portion 17b is formed so as to overlap the start end portion 17a so as to overlap the start end portion 17a in order to compensate for a small supply amount of the metal powder 21 in the start end portion 17a.

  On the other hand, the non-overlap portion 18 is a portion other than the overlap portion 17 in the built-up layer 16. The non-overlap portion 18 is a portion from x ° to 360 ° in the cladding direction in the annular cladding layer 16.

  Next, the recess 15d formed in the side wall 15c of the counterbore groove 15 will be described. In the following description, the counterbore groove 15 in which the recess 15d is formed in the side wall 15c according to the present embodiment, the counterbore groove 15 in which the recess 15d is not formed in the side wall 15c (comparative example. This will be explained in contrast to “)”.

  First, with reference to FIG. 4 and FIG. 5, the counterbore groove 15 'which does not form the recessed part 15d in the side wall part 15c concerning a comparative example is demonstrated. 4 and 5 are enlarged cross-sectional views illustrating the configuration of a counterbore groove 15 'according to a comparative example. 4 shows a state after the metal powder 21 is supplied to the counterbored groove 15 ′, and FIG. 5 shows a state after the laser beam 22 is irradiated to the counterbored groove 15 ′. In FIG. 4, a laser irradiation range R indicates a range irradiated with the laser beam 22 from the laser processing head 20 (the same applies to FIG. 7 below). The laser irradiation range R covers the entire area of the inclined surface portion 15b, a partial region of the bottom surface portion 15a on the inclined surface portion 15b side, and a partial region of the side wall portion 15c on the inclined surface portion 15b side, centering on the inclined surface portion 15b. .

  When the build-up layer 16 is formed, the center axis A2 of the circular counterbore groove 15 'is aligned with the vertical direction, so that the posture of the counterbore groove 15' is as shown in FIG. That is, the side wall portion 15c is standing along substantially the same direction as the vertical direction, and the inclined surface portion 15b is inclined obliquely downward toward the central axis A2 of the annular counterbore groove 15 '. Therefore, when the metal powder 21 is supplied from the laser processing head 20 to the counterbore groove 15 ′, the metal powder 21 supplied to the side wall portion 15 c and the slope portion 15 b falls down due to gravity. Further, when forming the built-up layer 16, the bottom surface portion 15a is in the substantially same direction as the horizontal direction, and the metal powder 21 is easily deposited. Therefore, the metal powder 21 that has fallen down from the side wall portion 15c and the slope portion 15b accumulates on the bottom surface portion 15a.

  If the supply amount of the metal powder 21 supplied from the laser processing head 20 is large, the metal powder 21 gradually accumulates on the bottom surface portion 15a from the state of FIG. Therefore, it is considered that finally the deposited metal powder 21 reaches a region corresponding to the laser irradiation range R in the side wall portion 15c and the deposited metal powder 21 can cover the laser irradiation range R.

  On the other hand, when the supply amount of the metal powder 21 supplied from the laser processing head 20 is small, it is conceivable that the metal powder 21 is not supplied any more in the state shown in FIG. In the state of FIG. 4, since the supply amount of the metal powder 21 is small, the region corresponding to the laser irradiation range R in the side wall portion 15c is not covered with the metal powder 21, and the region is very large.

  When the counterbored groove 15 ′ in the state of FIG. 4 is irradiated with the laser beam 22 from the laser processing head 20, as shown in FIG. 5, the region corresponding to the laser irradiation range R in the side wall portion 15 c is Since it is directly irradiated, the constituent metal of the cylinder head rough shape member 10 (referred to as aluminum, hereinafter the same) is melted from that region. In addition, since the region corresponding to the laser irradiation range R in the side wall portion 15c is very large, the molten amount of molten aluminum becomes very large. Thereby, the molten pool 23 obtained by melting the metal powder 21 is diluted by flowing a large amount of molten aluminum, and alloying proceeds. As a result, the built-up layer 16 obtained by solidifying the molten pool 23 becomes brittle and cracks occur. This phenomenon occurs particularly conspicuously at the start end 17a where the supply amount of the metal powder 21 supplied from the laser processing head 20 is small in the annular built-up layer 16.

  In the state of FIG. 4, a part of the region corresponding to the laser irradiation range R in the inclined surface portion 15 b is not covered with the metal powder 21 and is directly irradiated with the laser beam 22. Aluminum which is a constituent metal of the cylinder head rough profile 10 is dissolved.

  However, since the region directly irradiated with the laser beam 22 on the slope 15b is very small compared to the region directly irradiated with the laser beam 22 on the side wall 15c, the melting amount of molten aluminum from the slope 15b is small. Compared with the melting amount of the molten aluminum from the side wall portion 15c, it is very small. Therefore, even if only the molten aluminum from the slope portion 15b flows into the molten pool 23, the possibility that the build-up layer 16 will crack is very small.

  Therefore, in the present embodiment, in order to reduce the amount of molten aluminum melted from the side wall portion 15c, a concave portion 15d is formed in the side wall portion 15c as will be described in detail below.

  Next, with reference to FIGS. 6 to 8, the counterbored groove 15 according to the present embodiment in which the concave portion 15 d is formed in the side wall portion 15 c will be described. 6 to 8 are enlarged cross-sectional views illustrating the configuration of the counterbore groove 15 according to the present embodiment. 7 shows a state after the metal powder 21 is supplied to the counterbored groove 15, and FIG. 8 shows a state after the laser beam 22 is irradiated to the counterbored groove 15.

  As shown in FIG. 6, in the present embodiment, a recess 15 d is formed in the side wall portion 15 c of the counterbored groove 15 for holding the metal powder 21 supplied from the laser processing head 20. Similarly to the bottom surface portion 15a, the inclined surface portion 15b, and the side wall portion 15c, the concave portion 15d is also annular. Further, the recess 15 d is preferably formed so as to overlap with a region corresponding to the laser irradiation range R in the side wall portion 15 c when viewed from the central axis of the counterbore groove 15. Further, the recess 15d shown in FIG. 6 has a rectangular parallelepiped shape.

  When the build-up layer 16 is formed, the center axis A2 of the annular counterbored groove 15 is made to coincide with the vertical direction, so that the posture of the counterbored groove 15 is as shown in FIG. However, in the present embodiment, unlike the comparative example, a recess 15d is formed in the side wall portion 15c of the counterbore groove 15. Therefore, even if the metal powder 21 is supplied from the laser processing head 20 to the counterbore groove 15 in the state of FIG. 6, the metal powder 21 supplied to the side wall portion 15 c is below as shown in FIG. 7. It does not fall and is held inside the recess 15d formed in the side wall 15c. Thereby, even if there is little supply amount of the metal powder 21, the area | region equivalent to the laser irradiation range R in the side wall part 15c can be covered with the metal powder 21 hold | maintained inside the recessed part 15d. Therefore, the region not covered with the metal powder 21 in the region corresponding to the laser irradiation range R in the side wall portion 15c is eliminated or very small.

  Therefore, even if the counterbored groove 15 in the state of FIG. 7 is irradiated with the laser beam 22 from the laser processing head 20, as shown in FIG. 8, the region corresponding to the laser irradiation range R in the side wall portion 15c is a concave portion. Direct irradiation of the laser beam 22 is prevented by the metal powder 21 held inside 15d. Therefore, the region directly irradiated with the laser beam 22 in the region corresponding to the laser irradiation range R in the side wall portion 15c is eliminated or very small. Further, the metal powder 21 composed of a copper-based alloy or the like has a higher absorption rate of the laser beam 22 than aluminum, which is a constituent metal of the cylinder head rough profile 10. Therefore, the laser energy of the laser beam 22 applied to the side wall portion 15 c can be consumed for increasing the temperature of the metal powder 21. Thereby, the melting amount of aluminum which is a constituent metal of the cylinder head rough profile 10 from the side wall 15c of the counterbore groove 15 can be reduced. As a result, since the amount of molten aluminum flowing into the molten pool 23 obtained by melting the metal powder 21 can be reduced, the build-up layer 16 obtained by solidifying the molten pool 23 is cracked. Can be suppressed.

  Note that the metal powder 21 held inside the recess 15d of the counterbore groove 15 plays a role of preventing the laser beam 22 from the laser processing head 20 from being directly irradiated onto the side wall portion 15c. Therefore, the metal powder 21 held inside the recess 15d does not have to be completely melted by the laser beam 22 to become the molten pool 23, and there may be metal powder 21 remaining as powder. When the metal powder 21 remaining as powder is generated, it may be recovered by an arbitrary recovery means at an arbitrary timing.

  As described above, according to the present embodiment, the counterbored groove 15 has the bottom surface portion 15a, the side wall portion 15c, and the inclined surface portion 15b provided between the bottom surface portion 15a and the side wall portion 15c. The recess 15 d is formed in the side wall 15 c of the counterbore groove 15.

  Therefore, when forming the build-up layer 16, the metal powder 21 supplied to the side wall part 15c of the counterbore groove 15 can be hold | maintained inside the recessed part 15d. Therefore, even if the supply amount of the metal powder 21 is small, it is possible to prevent the laser beam 22 from being directly irradiated onto the side wall 15c by the metal powder 21 held inside the recess 15d, and the side wall 15c. It is possible to reduce the amount of melting of the constituent metal of the cylinder head rough profile 10 that is melted from. As a result, since the amount of molten metal flowing into the molten pool 23 can be reduced, it is possible to suppress the occurrence of cracks in the overlay layer 16.

Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention.
For example, in the above embodiment, the shape of the concave portion 15d formed in the side wall portion 15c of the counterbored groove 15 is a rectangular parallelepiped shape, but is not limited thereto. The shape of the recess 15d may be, for example, a hemispherical shape as shown in FIG. That is, the shape of the recess 15d may be any shape as long as the metal powder 21 can be held inside the recess 15d, and may be a semi-ellipsoidal shape, a cylindrical shape, a conical shape, a cubic shape, or the like.

DESCRIPTION OF SYMBOLS 10 Cylinder head rough shape 11 Combustion chamber 12 Intake port 13 Exhaust port 14 Opening 15 Counterbored groove 15a Bottom face part 15b Slope part 15c Side wall part 15d Concave part 16 Overlay layer 17 Overlap part 17a Start end part 17b End part 17c Oblique 18 Lapping unit 20 Laser processing head 21 Metal powder 22 Laser beam 23 Molten pool A1 Optical axis of laser beam A2 Center axis of counterbored groove R Laser irradiation range

Claims (1)

In the cylinder head rough profile, a step of forming an annular counterbore groove at the opening end of the port on the combustion chamber side;
In a state where the central axis of the counterbored groove is aligned with the vertical direction, a metal beam is supplied to the counterbored groove and irradiated with a laser beam to form a built-up layer for a valve seat, and
In the step of forming the counterbored groove,
Forming the counterbored groove so as to have a bottom surface portion, a side wall portion, and a slope portion provided between the bottom surface portion and the side wall portion, and forming a recess in the side wall portion of the counterbored groove;
Laser overlaying method.

Images