JPS6234690A - Engine valve for automobile and its production - Google Patents

Abstract

PURPOSE:To prevent the generation of the defect of the dilution, defective deposition and melt-down flaw, etc. of a build-up material by reflecting the energy distribution of a laser beam in the build-up thickness. CONSTITUTION:The energy distributing condition in the cross direction of the groove part for build-up by laser beam is studied in advance. A groove part shape is worked on that part becoming into the value face of the valve main body so as to corresponding to said energy distribution. The laser beam is irradiated on the surface of the power layer of build-up material with feeding the build-up material powder of a stellite powder, etc. The build-up material powder inside the groove part is formed in a build-up part with its melting and resolidification in order with relatively moving the laser beam along the groove part to form the engine valve for automobile. the melt of the base metal is thus caused due to the excess energy and the generation of the dilution and melt-down flaw of the build-up material is prevented. The generation of the defective deposition of the build-up material and under-fill due to the energy shortage is prevented as well.

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a valve used as an exhaust valve for an automobile engine, and in particular, the valve face that contacts the valve seat has excellent wear resistance and heat resistance. The present invention relates to a valve in which dissimilar metals such as stellite are deposited using a laser, and a method for manufacturing the same.

Conventional Technology As is well known, engine valves are required to have excellent heat resistance, and especially the valve face that contacts the valve seat is required to have high wear resistance.In addition, high temperature corrosion resistance and high temperature oxidation resistance are also required. required. In particular, among engine valves, valves used as exhaust valves are exposed to extremely high temperatures, and therefore are required to have excellent wear resistance and heat resistance under cooling conditions.

Conventionally, exhaust valves have been made of ordinary heat-resistant metal materials such as austenitic heat-resistant steel for the main body, and metals with particularly excellent heat resistance and wear resistance, such as Stellite (C), for the valve face.

-Cr-W alloy) has been applied.

As a heat source for this build-up, it has recently been considered to use laser light, which is known as a high-density heating energy source, as shown in, for example, Japanese Patent Laid-Open No. 50-121131. In this case, for example, as shown in FIG. 5, a groove 4 having a concave curved cross section is formed in advance in the portion of the umbrella portion 2 of the valve body 1 where the valve face surface 3 is to be formed, and the groove 4 is While supplying metal powder such as stellite to be overlaid, a laser beam 5 is applied to the metal powder.
The overlaid portion 6 is formed by irradiating and heating and melting the material.

Problems to be Solved by the Invention The valve face build-up by laser beam irradiation proposed in the above-mentioned Japanese Patent Application Laid-Open No. 50-121132 and others is different from the conventional build-up using a gas heat source or build-up by TIG arc. This was merely an extension of the above, in other words, it simply replaced the heat source with laser light, and did not fully consider the properties of laser light as a heat source. Therefore, it has been found through experiments by the present inventors that when overlaying by laser beam irradiation is actually carried out according to the above proposal, the following problem occurs.

In other words, when building up the valve face by actual laser beam irradiation, there are likely to be areas where the laser beam energy is too high or areas where the laser beam energy is insufficient, and in areas where the laser beam energy is too high, only the metal powder used for overlaying will occur. Instead, it melts down to the base material, and as a result, the base material components diffuse into the overlay material for a long time, and the overlay material is diluted by the base material components.As a result, the overlay material has the required wear resistance, etc. The original properties cannot be obtained sufficiently, and conversely, in areas where energy is insufficient, welding failure occurs in which the overlay metal is not sufficiently welded to the base material, resulting in a decrease in the bonding strength of the overlay metal to the base material, and At the edges, there may be areas that are not covered with the sensuous material (missing thickness).

This invention was made against the background of the above-mentioned circumstances. When overlaying a valve face by laser beam irradiation, dilution or melting of the overlay metal by base material components may occur due to excessive laser beam energy. On the contrary, the basic purpose is to prevent defective welding or lack of thickness due to insufficient laser beam energy.

Means for Solving the Problems In order to achieve the above-mentioned object, the inventor of the present invention has carried out extensive experimental studies, and has found that the reason why the above-mentioned irradiation energy tends to be excessive or insufficient is due to the energy distribution of the laser beam. We found that this is due to variations depending on the laser beam oscillation method and model. That is, when building up the valve face by laser beam irradiation, irradiate the valve face so that the width (target width) at the laser beam irradiation position matches or is slightly larger than the width of the building up groove. Overlay is performed by moving the laser beam relatively along the groove (that is, in the circumferential direction of the bulb body), but at this time, the laser beam is moved in the width direction of the groove (therefore, in the transverse direction of the groove or in the radial direction of the bulb). In other words, the energy distribution in this direction is usually not uniform, and the shape of the energy distribution in that direction varies greatly depending on the oscillation method, model, etc. -5 The energy required at each position in the width direction of the groove mainly depends on the thickness of the overlay material to be formed at that position, that is, the thickness of the supplied overlay material powder. A small amount of energy is enough. However, if welding is carried out without particularly considering the laser beam energy distribution in the above direction, there may be insufficient energy for the thickness to be overlaid at a certain position in the width direction of the 1l11 section, resulting in poor welding. However, at other locations, energy is often too high for the thickness to be overlaid, resulting in dilution of the fleshy metal due to melting of the base material.

For example, if the energy is insufficient for the thickness of the cladding material to be formed at the center in the width direction of the groove portion 4, and the energy is excessive for the thickness of the overlay material 7 at the end portions, as shown in FIG. 6(A). As shown, a welding defect 8 of the overlay material 7 occurs at the center, and conversely, a weld 10 occurs due to the melting of the base material 9 at the ends. On the other hand, if the energy is too large for the thickness of the overlay material 7 to be formed at the center in the width direction of the groove aII4, and insufficient at the ends, the energy will be too large at the center as shown in FIG. 6(B). in"+i of the base material 9 occurs, and there is a lack of thickness 1 in the overlay material at the end.
2 will occur.

Therefore, the present inventors looked at the relationship between the energy distribution of the laser beam and the distribution of the build-up thickness, and solved the above-mentioned problem by reflecting the energy distribution of the laser beam in the build-up thickness. They found that it could be obtained and came up with this invention.

Specifically, the first invention provides an automobile engine valve in which a material other than the valve body material is deposited on the valve face using a laser beam, and the distribution of the thickness of the deposited portion in the valve radial direction is as follows: It is characterized in that it is determined to correspond to the energy distribution shape in the direction of the laser beam for overlaying.゛Also, the second invention forms a build-up groove in the portion of the valve body that is to become the valve face, supplies powder of a build-up material different from the valve body material to the build-up groove, and applies the powder to the build-up groove. 7 of an automobile engine valve in which the valve face is built up by melting and re-solidifying the build-up material powder by moving the laser light relatively along the groove while irradiating the layer surface with the laser light. In the J construction method, prior to forming the overlay groove, the overlay groove is adjusted such that the energy distribution shape of the laser beam to be irradiated in the direction of the groove is reflected in the distribution in the transverse direction. It is characterized by processing.

A typical energy distribution shape of the working laser beam is, for example, a trapezoidal mode as shown in FIG.
There is a mode that continues in IT11P, and a typical energy distribution shape different from this is, for example, the 1st!
There is a defocused Gaussian mode as shown in 1(B). The energy distribution is significantly different between the former mode and the latter mode, and therefore, if build-up is performed by irradiating laser light without giving special consideration to the energy distribution, the above-mentioned problem will occur.

Therefore, in the present invention, before machining the fleshy groove of the valve face, the energy distribution of the laser beam to be irradiated for overlaying is investigated in advance.

Specifically, it may be cleaned using, for example, a laser beam analyzer or a burn pattern of acrylic resin. Note that this energy distribution is basically based on the It! of the overlay groove. It is sufficient to examine the distribution in the l'i direction (fit direction), that is, the distribution in the radial direction of the valve body.

Next, when processing the overlay groove, the groove shape is processed so that the thickness distribution of the overlay material to be finally obtained corresponds to the energy distribution of the irradiated laser beam. That is,
In the case of the trapezoidal mode shown in FIG. 1(A), the groove portion is processed so that the thickness distribution of the sensitive material in the radial direction of the bulb body corresponds to the energy distribution of the trapezoidal mode. Further, in the case of the Gaussian mode as shown in FIG. 1(B), the groove portion is processed so that the thickness distribution of the overlay material in the above direction corresponds to the energy distribution of the Gaussian mode.

Here, processing the groove so that the thickness distribution of the overlay material becomes the required distribution actually means processing the groove so that the depth distribution becomes the required depth distribution. The radial cross-sectional shape of the bulb body on the surface of the overlay material obtained by laser beam irradiation is usually not a straight line but a convex curved shape with a predetermined curvature. It is necessary to define

After processing the overlay groove as described above, while supplying overlay material powder such as Stellite powder to the groove, a laser beam is irradiated onto the surface of the overlay material powder layer, and the laser beam is applied along the groove. The overlay material powder in the groove is sequentially melted and re-solidified to form a built-up part while relatively moving the overlay.Here, the amount of the overlay material powder supplied to the groove at each position depends on the depth of the groove. Accordingly, it is sufficient to determine the final build-up thickness to be the required thickness.

If build-up is performed by laser irradiation in this way, the energy distribution of the laser beam will correspond to the build-up thickness distribution, so
It is possible to effectively prevent the occurrence of areas with excessive energy or areas with insufficient energy relative to the build-up thickness. Therefore, it is possible to prevent the base material from melting due to excessive energy and cause dilution or melting of the overlay material due to base material components, and to prevent poor welding or insufficient thickness of the overlay material due to insufficient energy. is effectively prevented.

Examples [Example 1 Covalve body material is austenitic heat-resistant steel 2
l-4Nl (Fe-21%Cr-4%Ni-9%Mn
-0.5%C) was used as the overlay material.
o) Using a powder with a particle size distribution of -100 mesh to +350 mesh, the valve cap diameter is 3 Qim, and the overlay groove width is 4.2 ■.
11 An automobile engine valve having a radius of curvature R1-5,521 of the convex curved surface of the built-up part surface (valve face surface) (see FIG. 2, I!) was manufactured as follows. The laser beam irradiated during overlay has an output of 2.2 kW, a beam target shape of a rectangle of 4.811 x 3.211 (however, the side corresponding to the groove width direction is 4.8 a + m), and a scanning speed (in the bulb circumferential direction). relative movement speed) to 6 mm,'
It was set as E. Also, the radius of curvature of the surface R1-5, 5111ff
The amount of stellite powder supplied to form a built-up portion of 2.5 g per bulb was 2.5 g. Also, what about as a shielding gas during laser beam irradiation? JEI110f/- argon gas was used, and the shield gas nozzle diameter was set to i2m+n.

When the output distribution of the laser beam was examined in advance using a laser beam analyzer, a trapezoidal mode distribution allophore as shown in FIG. 3(A) was obtained. Therefore, the shape and dimensions of the overlay groove 4 on the valve face were determined and processed so that <tA-tβ-tc-0,8 as shown in FIG. 3(B). That is 4.21! ! from the center of the groove with a width of 9
Processing was performed so that the build-up thickness was constant within a range of 1.4 mm. After processing the overlay groove 4 by reflecting its shape in the trapezoidal mode laser beam distribution profile, stellite is overlaid under the above conditions using the trapezoidal mode laser beam shown in FIG. 3(A). did.

When we investigated the resulting build-up area, we found that the dilution of the build-up material by base material components due to melting of the base metal was less than 5%, and defects due to lack of energy such as poor welding did not occur. It turns out there isn't.

[Example 2] In manufacturing an automobile engine valve of the same shape using the same material as in Example VA1, overlay was performed using a laser beam with a different energy distribution from that in Example 1.

That is, when the laser beam energy distribution in this case was investigated in advance using a laser beam analyzer, the fourth
It turned out to be a defocused Gaussian mode distribution profile as shown in Figure (A). Therefore,
The shape and dimensions of the overlay groove 4 on the valve face are shown in Figure 4 (
As shown in B) [＾: t9: tCtan At A2
: BI B2 : Processed to become CI C2. In this case as well, the radius of curvature of the surface of the built-up part R1-5, 5111
It is.

After processing as described above, while supplying the stellite powder to the sensual groove 4, the laser tip output was 2.5 kW and the scanning speed was 1!
[611! /See, a laser beam having the energy distribution shown in FIG. 4(A) was irradiated to perform overlay.

In FIG. 4(A), the energy outside iiE and D was cut by an aperture and irradiated.

In this case, as in the case of Example N1, the dilution of the overlay material by the base material components was less than 5%, and it was confirmed that defects due to lack of energy such as poor welding did not occur.

Effects of the Invention As is clear from the above explanation, according to the present invention, the overlay material is diluted by base material components due to base material melting, and the original wear resistance etc. of the overlay material is no longer maintained. It is also possible to effectively prevent the occurrence of defects such as poor welding of the overlay material, lack of thickness, and melting.

Furthermore, among the defects mentioned above, poor welding of the overlay material is detected through non-destructive testing, but being able to prevent the occurrence of such defects greatly improves the reliability of the valve compared to conventional methods. It is effective to increase the

[Brief explanation of the drawing]

Figures 1 (A) and (B) are miniatures showing an example of the energy distribution of laser light used for overlaying automobile engine valves, and Figure 2 shows half the curvature of the overlay surface! 3(A) and 3(B) are diagrams for explaining the first embodiment of the present invention, and FIG. 3(A) is a pictorial diagram showing the energy distribution of laser light. B) is a cross-sectional view showing the cross-sectional shape of the overlay groove, and FIGS.
) is a diagram showing the energy distribution of laser light, and (B) is a cross-sectional view showing the cross-sectional shape of the overlay groove. Fig. 5 is a schematic front view showing the state of overlaying of an automobile engine valve by laser beam irradiation, and Figs. 6 (A) and (B) are cross-sectional views showing the occurrence of defects in fleshy parts by conventional methods, respectively. It is. 1... Valve body 2, 3... Valve face surface,
4...Groove portion, 5...Laser beam, 6...Build-up portion. Applicant Toyota Motor Corporation Aisan Industries Co., Ltd.

Claims (2)

[Claims] (1) In an automobile engine valve in which a material different from the valve body material is deposited on the valve face using a laser beam, the distribution of the thickness of the deposited portion in the valve radial direction is An engine valve for an automobile, characterized in that the valve is determined to correspond to an energy distribution shape in the above direction. (2) Form a groove for build-up on the part of the valve body that should become the valve face, supply powder of a build-up material different from the valve body material to the build-up groove, and apply a laser beam to the surface of the powder layer. A method for manufacturing an automobile engine valve in which a valve face is built up by melting and resolidifying a building material powder by relatively moving a laser beam along a groove while irradiating light, the building method comprising: Before forming the groove for overlay, the energy distribution shape of the laser beam to be irradiated in the cross direction of the groove is investigated, and the shape of the energy distribution is reflected in the distribution of the overlay thickness in the cross direction of the groove. A method for manufacturing an automobile engine valve, which comprises processing a groove.