JPS61269991A - Production of build-up valve for internal-combustion engine - Google Patents

Abstract

PURPOSE:To make uniform the material quality of a laser build-up part over the entire part of a valve face part by irradiating laser light on said part and spraying a cooling medium to the rear side of the irradiated part during the time when the laser light returns again to the initially irradiated part. CONSTITUTION:Laser build-up is executed by rotating gradually an exhaust valve 1 while supplying build-up alloy powder 3 from a build-up alloy powder supplying device 4 to the valve face part 2 of the valve 1, supplying at the same time a shielding gas thereto from a shielding gas supplying device and irradiating the laser light 5 on said part. A cooler 6 installed apart at a prescribed distance from a head bevel 12 is operated upon starting of the irradiation of the light 5 to spray the cooling water 11 to the head 12. The generated steam is sucked and discharged to the outside through a conduit 9 by a suction pump. The irradiated part is thus cooled during the time when the laser light 5 returns again to the part irradiated first with the laser light and therefore the heating up to the high temp. at which dilution arises is obviated and the material quality uniform over the entire build-up layer is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing an overlay valve for an internal combustion engine such as an automobile, and particularly for an internal combustion engine suitable for overlaying using a laser as a high-density energy source. The present invention relates to a method of manufacturing a weld overlay valve.

[Conventional technology]

Intake valves used in automobile engines,
An engine valve such as an exhaust valve is a valve that controls intake or exhaust air in a combustion chamber, and consists of a bulk part and a shaft part. The bulk of this engine valve is installed inside the combustion chamber, and repeatedly comes into contact with and separates from the valve seat press-fitted into the cylinder head on the valve face surface. In particular, the valve face portion of the exhaust valve is exposed to high temperatures of 700° C. to 800° C. in the combustion chamber and repeatedly collides with the valve seat, so it is required to have heat resistance, corrosion resistance, and wear resistance.

Conventionally, one way to provide the valve face of an engine valve with the above-mentioned properties such as heat resistance is to use a material with excellent heat resistance, corrosion resistance, and wear resistance, such as a cobalt-based superalloy or a nickel-based material, on the valve face surface. A method of overlaying superalloy etc. is adopted.

Gas overlay using acetylene gas is currently the mainstream for overlaying the valve face.

There are other methods that use a TIG welding power source and a method that uses a plasma power source. And such acetylene gas and T
In overlaying using a heat source such as IG, the base material to be overlaid is first preheated and then the overlay alloy is welded, so that the base material is partially melted.

However, the melting of the iron contained in this base metal mixes with the overlay alloy and deteriorates the overlay alloy material. For this reason, in build-up using acetylene gas or TIC, the build-up alloy is diluted by iron and the material quality deteriorates, so it has been necessary to thicken the build-up layer to obtain a healthy build-up part.

Therefore, recently, for reasons such as eliminating preheating that causes dilution, it has been considered to perform overlay using a laser, which is a high-density energy source.

[Problems to be Solved by the Invention] Since overlaying using such a laser does not require preheating, a built-up layer without dilution from the base material is formed in the early and middle stages of overlaying.

However, when overlaying annularly, such as overlaying the valve face of an engine valve, the area near the end of the overlay is preheated by the heat of the first overlay, so It was found that dilution from the material occurred. That is,
Near the interface between the first part irradiated with the laser beam and the last part where the laser beam returns, dilution progresses due to the introduction of iron from the base material, and deterioration becomes severe in some parts.

Therefore, in laser overlaying, it has been desired to completely eliminate dilution from the base material and make the overlay material uniform throughout.

[Means for solving problems]

The above problem is solved by the method for manufacturing a built-up valve for an internal combustion engine according to the present invention, which will be described below.

That is, the method for manufacturing an overlay valve for an internal combustion engine of the present invention involves overlaying an overlay valve for an internal combustion engine by using a laser to overlay an alloy with excellent heat resistance and wear resistance on the valve face of the engine valve. The method comprises: supplying an alloy powder with excellent heat resistance and wear resistance to the valve face portion of the engine valve; and, while sealing the irradiation portion with a shielding gas, at least one of the engine valve or the laser beam is directed relative to the valve face portion of the engine valve; The first irradiation section is cooled by spraying a cooling medium onto the back side of the irradiation section while the laser beam returns to the first irradiation section.

In the present invention, a cobalt-based superalloy, a nickel-based superalloy, or the like can be used as the overlay material. This cobalt-based superalloy is a well-known alloy developed based on stellite, and mainly contains molybdenum (Mo) and tungsten (
It relies on solid solution strengthening by the addition of W) and dispersion strengthening of chromium (Cr) carbide. Examples of cobalt-based superalloys include (a) C: 2.5%, Si: 1.1%, Ni: 1.
5%, Cr: 30.0%, Mo: Q, 5%, W: 4-1
2.0%, Fe < 1.5% and balance Co, (b
) C: 0.25%, Si: 1.1%, Ni: 22.
0%, Cr: 26, 0%, B: 0.2%, Fe
<1.5% and the balance CO, etc. can be used.

In addition, nickel-based superalloys contain around 20% chromium (Cr).
In addition, in terms of high temperature strength, aluminum (,l),
It is a precipitation-strengthened alloy to which titanium (Ti) and niobium (Nb) are added. Examples of nickel-based superalloys include (
a) In weight% (hereinafter all units are weight%), Co < 1.5%, Cr: 14-23%, Mo:
5-16%, W<4.0%, l”e<5.Q%, Si
<0.8%, Mn<1.0%, C: 0.05-0.1%
, Ca: 0.1-2.0% and the balance N i , (b
) Co < 5.0%, Cr: 18-22%, Mo
:3-6%, Fe<4.0%, St<1.0%,
Mn<1.0%, C: 0.05-0.1%, Ca: 0.
1 to 2.0%, A J < 1.0% and the balance Ni, etc. can be used.

In the present invention, cooling is performed by spraying a cooling medium onto the front side of the umbrella portion (hereinafter referred to as the “bulk surface”), that is, the side opposite to the valve face portion. At this time, the entire umbrella surface may be cooled, or only a portion of the umbrella surface (mainly the first irradiation part) may be cooled. Further, cooling may be performed from beginning to end during the laser build-up operation, or may be performed only for a period of time. In short, it is only necessary that the vicinity of the part irradiated with the first laser beam be relatively cooled to a predetermined temperature or lower when the laser beam returns. As the cooling medium, in addition to liquids such as water, gases such as nitrogen gas can be used.

[Effect]

According to the manufacturing method of an overlay valve for an internal combustion engine of the present invention, the vicinity of the first irradiated part heated to about 400°C (hereinafter, temperature refers to the temperature of the bulk surface of the engine valve) by laser light irradiation is , the laser beam is relatively cooled by the time it returns to the first irradiation part. Therefore, even at the final end of laser beam irradiation, the temperature is only heated to around 400° C. and does not rise any higher. For this reason, the temperature near the built-up part does not rise to 500°C to 600°C, where dilution by iron begins, so dilution by iron does not occur, and the built-up part becomes a sound and uniform material over the entire valve face. .

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

(First Example) As a first example, an example will be shown in which only a part of the engine valve surface is cooled.

Here, FIG. 1 is a schematic configuration diagram showing one step of a method for manufacturing an overlay valve for an internal combustion engine according to a first embodiment of the present invention, and FIG.
The figure is a graph showing the temperature change of the back part of the cap corresponding to the first irradiation part of the laser beam.

Total length 94mm, bulk diameter 28in, shaft diameter 6 days heat resistance a
An exhaust valve 1 made of (SUH3B) was prepared. This exhaust valve 1 consists of a shaft' portion 1a and an umbrella portion 1b, and a recessed portion is formed in the valve face portion 2 of the umbrella portion 1b for overlaying. This exhaust valve 1 is tilted until the upper valve face portion 2 becomes horizontal, and the tip of the shaft portion 1a is held rotatably around the shaft. Then, an overlay alloy supply device 4 for supplying overlay alloy powder 3 is installed directly above the upper valve face portion 2.
do. Further, although not shown, shielding gas is supplied toward the upper valve face portion 2 from a shielding gas supply device. Further, the upper valve face portion 2 is irradiated with laser light 5 from a laser device (not shown).

A cooling device 6 is provided below the bulkhead 12 of the exhaust valve 1, that is, 180 degrees opposite the portion to which the laser beam 5 is irradiated. This cooling device 6 has a cylindrical cooling device main body 8 in which a cooling medium jetting nozzle 7 is incorporated, and one end of this cooling device main body 8 is open, and a part of the cooling device main body 8 is a pressure reducing means through a conduit 9. It is connected to a vacuum pump (not shown). In addition, the cooling medium jet nozzle 7
is connected to a cooling medium supply source (not shown) via a conduit 10.

Overlay alloy powder 3 contains C: 1.0%, Si: 1.2%, N
i<3. Q%, Cr: 28.0%, W: 4. Q
%, Fe<3. A stellite column 6 consisting of Q% and the balance Co was used.

Next, the manufacturing method will be explained.

The exhaust valve 1 was gradually rotated while supplying the overlay alloy powder 3 from the overlay alloy supply device 4 to the recessed portion of the valve face portion 2 . At the same time, nitrogen gas was supplied as a shielding gas from a shielding gas supply device (not shown), and laser light 5 was irradiated. At this time, the laser build-up conditions were: laser irradiation output power: 2.5KW, beam scanning speed: 2.00
Tsuru/min, beam diameter: φ5 Tsuru. And laser beam 5
At the start of the irradiation, the cooling device 6, which was installed 2 fl away from the umbrella surface 12, was activated. That is, water 11 at 5°C is supplied as a cooling medium from the cooling medium supply source at a rate of 2 kg/11 until the completion of welding.
At the same time, the suction pump (vacuum cleaner) was operated. At this time, the cooling medium and droplets that collided with the umbrella table 12 and took away heat and became water vapor,
It is sucked in by a suction pump and discharged to the outside through a conduit 9.

During the above-mentioned laser build-up, the temperature change of the surface portion of the umbrella corresponding to the first irradiation portion of the laser beam 5 was examined. .

The results are shown in FIG. In addition, in the same manner, the temperature change on the surface of the cap was investigated when nitrogen gas was sprayed as a cooling medium instead of water at a gas pressure of 4 kg/cd and a gas flow rate of 301/min, and when no cooling was performed. . The results are also shown in FIG.

As is clear from Figure 2, the temperature at the top of the umbrella was initially 40°C.
Although the temperature is around 0°C, the temperature drops to around 100°C by spraying a cooling medium such as water or nitrogen gas.

Then, in the final process, it receives heat from the laser beam again, but
The temperature did not rise above 0°C. On the other hand, if cooling was not performed, the temperature of the first irradiated part rose to about 700°C in the final stage. In fact, when we investigated the build-up material, we found that the build-up valves that were cooled had uniform quality throughout, whereas the build-up valves that were not cooled had iron in the first irradiated area. It was observed that dilution had occurred.

As described above, according to this embodiment, a healthy overlay valve with stable quality and no dilution can be obtained. In addition, since cooling was performed partially and on the opposite side from the laser beam irradiation, even if some water vapor is generated, it may disturb the shielding gas, absorb the laser beam, or generate plasma. Never.

(Second example) As a second embodiment, an example will be shown in which the entire back of the umbrella is cooled.

Here, FIG. 3 is a schematic configuration diagram showing one step of a method for manufacturing a built-up valve for an internal combustion engine according to a second embodiment of the present invention.

The second embodiment differs from the first embodiment in that the diameter of the cooling device main body 8 is approximately the same as the valve diameter, and cooling is performed centering on the center of the J-shape surface, and that the cooling medium such as water vapor is used. The second embodiment is substantially the same as the first embodiment except that a conduit 9 for suction is provided above.

In the second example, the same effects as in the first example were obtained. Note that, unlike the first embodiment, since the entire back of the cap was cooled, the leaked water vapor sometimes disturbed the shielding gas to some extent.

Although specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, but includes various embodiments within the scope of the claims.

) For example, although the embodiment shows an example in which cooling is performed from the beginning to the end of laser beam irradiation, this cooling may be performed only immediately before the final stage.

〔Effect of the invention〕

As described above, according to the manufacturing method of an overlay valve for an internal combustion engine of the present invention, the vicinity of the first irradiated part, which is preheated and reaches a high temperature by laser beam irradiation, is cooled down until the laser beam returns again. Because of this, it does not reach high enough temperatures to cause dilution.

Therefore, the material of the build-up layer is uniform over the entire valve face portion, and the build-up quality is greatly improved.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing one step of the manufacturing method of a built-up valve for an internal combustion engine according to the first embodiment of the present invention, and Fig. 2 shows the temperature of the back part of the cap corresponding to the first irradiation part of the laser beam. Graph showing changes FIG. 3 is a schematic configuration diagram showing one step of a method for manufacturing a built-up valve for an internal combustion engine according to a second embodiment of the present invention. 1-- Exhaust valve (engine valve) 1
a--Shaft portion 1b--Umbrella portion 2-----Valve face total---- Overlay alloy powder 4---- Overlay alloy Supply device 5--Laser beam 6--Cooling device 7--1111-Cooling medium jetting nozzle 8--
・Cooling device body 9--・--・Conduit 1 (L--------・-・Conduit 11, ---------・Water (cooling medium) 12...-・
-・Shape Applicant Toyota Motor Corporation Figure 1 ω Inui Kakuhi Figure 3

Claims (1)

[Claims] (1) A method for manufacturing an overlay valve for an internal combustion engine, which uses a laser to overlay an alloy with excellent heat resistance and wear resistance on the valve face portion of an engine valve, the method comprising: We supply alloy powder with excellent heat resistance and wear resistance, and while sealing the irradiation area with shielding gas,
At least one of the engine valve or the laser beam is moved relatively to irradiate the laser beam, and while the laser beam returns to the first irradiation part, a cooling medium is sprayed on the back side of the irradiation part. A method for manufacturing an overlay valve for an internal combustion engine, characterized by cooling an irradiation part.