JPH055593B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of overlaying the surface of a metal member using a laser beam.

The method of the present invention prevents material deterioration of the metal in the build-up area and facilitates laser beam alignment.

[Prior Art] Conventionally, so-called overlaying, in which dissimilar metals are welded to the surfaces of metal members such as engine valves, has been carried out for the purpose of improving heat transfer properties, wear resistance, or for the purpose of overlaying.

This is a method in which dissimilar metals are supplied as overlay material to the part to be overlaid (the part to be overlaid) on the surface of the metal component and welded by heating. Consideration is being given to using a laser beam with good quality.

However, the above method has the following drawbacks.

First, the quality of the base metal near the part to be overlaid tends to deteriorate. As the laser beam deviates from the area to be overlaid and often irradiates the surrounding area, the overlay area is diluted due to melting of the base metal in the irradiated peripheral area, or pinholes are generated. It is. This drawback is particularly noticeable when the peripheral area is oxidized scale.

Second, mass production is difficult. There are slight variations in the individual shapes and sizes of the large number of metal parts to be overlaid, so the metal parts are set on the work table of a laser processing machine (generally, a predetermined part of the metal part is placed on a predetermined position on the work table). This is because the position of the part to be overlaid relative to the work table shifts slightly for each metal member, requiring precise position adjustment of the laser beam for each metal member. On the other hand, if the position adjustment is not performed precisely, the first drawback described above will inevitably occur.

[Problems to be Solved by the Invention] The present invention has been devised in view of the above-mentioned circumstances, and it is relatively easy to adjust the position of the laser beam, and the present invention can be applied to the base material near the area to be overlaid. This provides a method of overlaying that does not deteriorate metal.

[Means and effects for solving the problem] The present invention solves the above problems by processing the surface of the metal member near the area to be overlaid in advance into a metallic glossy surface with high reflectance to the laser beam. It overcomes shortcomings.

That is, the present invention provides the following steps: supplying a build-up material to a site to be built-up on the surface of a metal member;
In a build-up method using a laser beam, which irradiates the area to be built-up with a laser beam to weld the build-up material to the area to be built-up, prior to the laser beam irradiation, the area around the area to be built-up is This is a build-up method using a laser beam, which is characterized by processing a metallic glossy surface with high reflectance to the laser beam.

Metal parts are overlaid on at least part of their surface for the purpose of improving heat resistance, wear resistance, or overlay (welding of dissimilar metals to the overlay area).
The present invention can be applied to any member that requires this, such as engine valves, valve seats, rocker arms, etc.

The part to be overlaid is the part on the surface of the metal member where the overlay is to be applied, and its shape is circular,
It can be any shape such as rectangle, band shape, ring shape, etc. for example,
This corresponds to the groove (ring band shape) on the valve face of an engine valve.

The build-up material is a metal material that is welded to the build-up site, and is generally a different type of metal from the base metal. The overlay material can be used in powder form or
It is supplied in the form of a rod to the part to be overlaid. When it is in powder form, an appropriate amount can be supplied with good productivity.

Irradiation of the laser beam to the entire area to be overlaid is as follows:
This can be carried out using any known method using a known laser processing machine, such as beam scanning, laser head movement, work table movement, and combinations thereof. Further, the laser amplification medium is determined in consideration of the material of the metal member, the shape and size of the part to be overlaid, the type and material of the overlay material, and the required heating temperature. Usually CO ₂ or YAG is used.

In the present invention, prior to irradiation with the laser beam, a predetermined portion around the part to be overlaid is processed into a metallic glossy surface with high reflectance to the laser beam to be used. The area and shape of the predetermined portion are determined in consideration of the shape and size of the metal member, the shape and size of the part to be overlaid, and the like. Further, for processing, known methods such as electropolishing method and machining method can be used. Note that the degree of finishing of the glossy surface may be such that it can efficiently reflect the laser beam used.

The beam diameter of the laser beam is set to a size that does not extend beyond the metallic luster surface when the beam center (point on the beam center axis) is located at the center of the part to be overlaid. On the other hand, the size of the portion to be subjected to the metallic luster treatment is determined by taking into consideration the beam diameter. The beam diameter is preferably the short axis of the part to be overlaid (the minimum distance between opposing sides on each side defining the outer periphery of the part to be overlay; for example, if the part to be overlay is rectangular, (distance between long sides). For example, if the part to be overlaid is band-shaped and the beam center of the laser beam moves on the center line in the longitudinal direction of the part to be overlaid in the form of a belt,
The beam diameter is larger than the band width (the short axis), and
The size is such that the glossy surfaces formed along the band on both sides of the band do not protrude.

According to the method of the present invention, since the area around the part to be overlaid is protected from the laser beam by the metallic shiny surface, it is possible to irradiate only the part to be overlaid with the laser beam. Deterioration of metal members around the fleshy parts can be suppressed.
Furthermore, the positioning of the laser beam does not have to be performed very precisely, making it suitable for mass production.

[Examples] The present invention will be described below based on specific examples.

FIG. 1 is a perspective view of an engine valve 7, which is a metal member to which the embodiment method of the present invention is applied, and FIG. 2 is an explanatory diagram of the principle of determining the beam diameter of the laser beam 1 used in this embodiment. It is.

In this embodiment, the groove portion 6 of the valve face of the automobile engine valve 7 is used as the part to be overlaid.
This is a case where a powdered cobalt (Co)-based overlay material (trade name: Stellite No. 6) is used as the overlay material 5.

First, as shown in Fig. 1, the engine valve 7
Groove portion 6 of the valve face (cap portion 8 of the valve face)
A belt-like metallic shiny surface 3 was formed along the groove 6 on both sides of the ring belt-like surface (which was formed in a ring belt-shape) by lathe processing. The finish level of the shiny surface is the finish symbol ▽▽, and the width C of the metallic shiny surface 3 is
It was set to 1.0mm.

Next, the beam diameter D of the laser beam was set to D=4.8 mm from B+Ccos45°+Ccos15°≧D D≧B+A/√2 (see Figure 2). Here, B is the width of the groove 6, and A is the variation in the diameters of the multiple bulbs to be overlaid (the difference between the maximum and minimum values of the diameters (φ28) of the multiple bulbs), which is approximately 0.85. mm.

Next, set the above valve on the work table of the laser processing machine and use Stellite No. 6 as the overlay material.
(1.2g/piece ~ 3.0g/piece) while supplying laser beam (output 1.0~5.0kw; irradiation speed 100~2000)
mm/min; beam diameter: 4.8 mm) to weld the overlay material to the groove portion 6.

FIG. 3 is a cross-sectional photograph of a valve overlaid by the method of this embodiment, and FIG. 4 is a cross-sectional photograph of a valve overlaid by a conventional method.

As shown in FIG. 3, according to the method of this embodiment, the curve of the bottom surface of the groove portion 6 (the boundary line between the overlay material 5 and the groove portion 6) forms a beautiful lens-shaped curve. In contrast, in FIG. 4, the peripheral portion of the groove 6 (the end of the lenticular curve in the figure) is irregularly distorted as shown by the white arrow in the figure. This is because even though the peripheral area is also irradiated with the laser beam, a shiny metallic surface is not formed in the area, so the base metal in the area is heated and diluted.
This is because pinholes occur and cause deterioration.

[Effects] In summary, the present invention provides a method for overlaying by irradiating a laser beam while supplying overlay material to the area to be overlaid on the surface of a metal member. The process involves processing the metal into a shiny metallic surface that has a high reflectance to laser beams.

As is clear from the examples described,
According to the method of the present invention, a shiny metallic surface is formed around the part to be overlaid and reflects the laser beam, so precise positioning is not required and mass production is relatively easy.

Further, it is possible to suppress dilution of the built-up portion due to the base metal in the peripheral portion and the generation of pinholes. Therefore, deterioration of the material is also suppressed.

It is clear that the principle of the invention described above can be applied not only to overlaying on the surface of a metal member but also to various laser processing such as hardening.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an engine valve to which an embodiment method of the present invention is applied. FIG. 2 is a diagram explaining the principle of beam diameter determination. FIGS. 3 and 4 are photographs of the metal structure showing the cross section of the valve after overlaying,
FIG. 3 shows the case according to this embodiment, and FIG. 4 shows the case according to the conventional method. 1...Laser beam, 3...Metallic glossy surface, 4
... Black skin part, 5 ... Overlay material, 6 ... Groove part, 7 ...
valve.

Claims (1)

[Claims] 1. A laser beam for supplying a build-up material to a part to be built-up on the surface of a metal member, and irradiating the part to be built-up with a laser beam to weld the build-up material to the part to be built-up. A build-up method using a laser beam, characterized in that, prior to the laser beam irradiation, the periphery of the build-up area is processed into a metallic glossy surface with high reflectance to the laser beam. . 2. The part to be overlaid has a band shape, the beam center of the laser beam moves on the center line of the band part, the beam diameter of the laser beam is greater than or equal to the width of the band part, and the beam diameter of the laser beam is greater than or equal to the width of the band part, and A method of overlaying using a laser beam according to claim 1, which has a size that does not protrude. 3. The overlay method using a laser beam according to claim 1, wherein the metal member is an automobile engine valve. 4. The overlay method using a laser beam according to claim 1, wherein the overlay material is a metal powder.