JPH10141026A - Valve seat, padding work method therefor, padding work device, and cylinder head for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a padding valve sheet for an engine to provide excellent wear resistance for only the necessary portion of the valve seat part of a cylinder head, improve durability of the valve seat part, and perform lowering of the temperature of a mating valve. SOLUTION: When padding work of the valve seat part 2 of a cylinder head 1 is effected, a high hardness padding layer 6H is formed as a padding layer 6 in a way that padding is effected on an arcuate part in a peripheral angle of 30-90 deg. arc centering around a peripheral part nearmost to an ignition plug 8 by using padding powder to disperse a rigid deposit substance having room temperature rigidity of Hv 250 or more and a hard phase deposit amount of 20% or more in an area percentage. Padding is applied on a remaining part except the arcuate part by using padding powder not to deposit a hard phase having thermal conductivity of 0.4J/cm deg.Cs or more and room temperature hardness of Hv 250 or more, and this way forms a low hardness padding layer 6L as a padding layer 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve seat suitable for use as a valve seat of an engine valve, a method for overlaying the same, an overlay apparatus, and a cylinder head for an engine.

[0002]

SUMMARY OF THE INVENTION Laser overlaying is
As shown in FIG. 5, an overlaid portion 5 on the surface of the metal member 51 is provided.
2, a metal powder overlay material 54 from the powder supply pipe 53;
Is irradiated with the processing laser beam 55 while supplying the material, the cladding portion 52 and the cladding material 54 are simultaneously melted to form the cladding layer 56, and the surface or the entire surface of the metal member 51 is formed with the metal member 51. This is a process of giving different properties by the overlay layer 56.

[0003] This kind of overlaying is performed, for example, in order to improve the heat resistance, abrasion resistance, corrosion resistance and the like of a valve seat portion in the production of an aluminum alloy cylinder head for an automobile engine.

Conventionally, a valve seat having such a build-up is disclosed in Japanese Patent Application No. Hei 6-1682 in which a copper alloy powder is build-up on a valve seat portion of an aluminum alloy cylinder head.
There are examples described in the specification and drawings of Japanese Patent No. 97 and drawings and JP-A No. 62-150014.

[0005] As a valve seat widely used industrially, there is a press-fit valve seat made of an iron-based sintered alloy.

In these conventional valve seats, the sectional structure of the material along the circumferential direction of the seat is uniform, and the heat resistance, abrasion resistance, corrosion resistance, etc. are the same at any part in the circumferential direction. there were.

Therefore, in a wear evaluation test of a valve face and a valve seat using an actual engine, an area near the hottest engine spark plug on the circumference of the seat tends to wear more than other parts. It was observed.

[0008] In particular, in a valve seat which is laser-built with the same alloy powder, when a hard phase is precipitated for the purpose of improving wear resistance, the build-up layer becomes brittle,
There has been a technical problem of how to balance the opposite characteristics with the improvement of wear resistance in a portion near the spark plug in order to easily cause a material defect.

Further, when such a valve seat is used in a high-output engine, it is necessary to further enhance the cooling performance of the valve. Since the thermal conductivity is lower than that of the alloy, how to improve the thermal conductivity has been a technical problem.

[0010] Furthermore, the copper alloy powder from which the hard phase is precipitated is industrially expensive, and it has been a technical problem to reduce the cost while maintaining the performance.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide excellent wear resistance only at necessary portions of a valve seat portion of a cylinder head, thereby improving the durability of the valve seat and improving the valve seat. An object of the present invention is to provide an engine build-up valve seat that can improve thermal conductivity, lower the temperature of a bubble head, and is excellent in productivity.

[0012]

Accordingly, a series of experiments for overlaying at least two types of copper alloy powder on an aluminum alloy cylinder head, an engine actual machine wear evaluation test, and a valve temperature measurement test are performed to obtain a valve seat. As a result, an alloy powder cladding valve seat having the required wear resistance and excellent heat conductivity, hardly causing material defects, and having high productivity has been found.

That is, the valve seat according to the present invention has a structure in which the build-up layers having different characteristics in the circumferential direction are formed in the build-up valve seat. It is characterized by:

Further, in the embodiment of the valve seat according to the present invention, as described in claim 2, a high hardness buildup in which hard precipitates are dispersed only in a portion near the ignition plug in the circumferential direction. A layer may be formed, in which case, as described in claim 3, a circumferential angle of 30% around the circumference closest to the spark plug.
A high hardness build-up layer in which hard precipitates having a room temperature hardness of Hv 250 or more and a hard phase precipitation amount of 20% or more are dispersed in an arc portion of not less than 90 ° and not more than 90 ° can be formed. In addition, as described in claim 4, the circumferential angle of the circumferential portion closest to the spark plug is 30 degrees.
The thermal conductivity is 0.4 J / cm ° C. or more and the room temperature hardness is Hv 250
The low-hardness build-up layer in which the hard phase is not precipitated can be formed.

Further, in the method for building up a valve seat according to the present invention, as set forth in claim 5, the buildup is performed in the circumferential direction by using buildup powder having different characteristics. It is characterized by:

[0016] In the embodiment of the method for overlaying a valve seat according to the present invention, as described in claim 6, hard precipitates are dispersed only in a portion close to the spark plug in the circumferential direction. In this case, as described in claim 7, the circumferential angle of the circumferential portion closest to the spark plug is 30 degrees or more and 90 degrees or more. Room temperature hardness Hv2
It can be made to build up by using a build-up powder that disperses hard precipitates having a hard phase precipitation of 50% or more and an area ratio of 20% or more. As noted, by weight, cobalt: 10-15.
%, Aluminum: 1.0 to 5.0%, iron: 4 to 8%,
Nickel: 10 to 15%, one or more of vanadium, niobium, and tantalum of Group Va elements in the periodic table of elements: 0.1 to 5.0%, silicon: 1.0 to 5.0%,
The remaining portion is made of a copper alloy build-up powder substantially composed of copper as a basic composition, and is used only in an arc portion having a circumferential angle of 30 ° or more and 90 ° or less around the circumferential portion closest to the spark plug. Can be made.

Similarly, in the embodiment of the method for overlaying a valve seat according to the present invention, as set forth in claim 9, a circumferential angle of 30 degrees around a circumferential portion closest to the spark plug is provided. In the remaining portion other than the arc portion of 90 ° or less, a buildup powder is used which does not precipitate a hard phase having a thermal conductivity of 0.4 J / cm ° C. or more and a room temperature hardness Hv of 250 or more. More specifically, as described in claim 10, aluminum: 5.0 to 10.0%, nickel: 1.0 to 100% by weight.
5.0%, iron: 1.0 to 4.0%, the balance being a copper alloy cladding powder substantially composed of copper as a basic composition, with a circumferential angle of 30 degrees centering on the circumferential portion closest to the spark plug. It can be used only for the remaining portion other than the arc portion of 90 degrees or less to build up.

Further, in an embodiment of the method for overlaying a valve seat according to the present invention, an overlaying powder is overlaid by using a laser beam at the time of overlaying. And so on.

According to a twelfth aspect of the present invention, a valve seat overlay processing apparatus according to the present invention is provided.
A powder switching device for supplying a build-up powder having different characteristics described in 8 and 9 and 10 to a build-up processing point of a valve seat portion, and a powder supply for controlling a supply amount of the build-up powder in multiple stages, respectively. It is characterized by having a configuration provided with a quantity control device.

In the embodiment of the valve seat overlay processing apparatus according to the present invention, as described in claim 13, the overlay powder having different characteristics is deposited on the valve seat portion along the same path. A configuration having a powder supply pipe for supplying to a processing point can be employed.

According to a fourteenth aspect of the present invention, there is provided an engine cylinder head having a structure in which a cylinder head body made of an aluminum alloy is provided with the valve seat according to any one of the first to fourth aspects. It is characterized by doing.

[0022]

In the valve seat according to the present invention, the overlaid valve seat is formed with the build-up layer having different characteristics in the circumferential direction, so that the valve seat has different characteristics in the circumferential direction. It is possible to respond effectively when it is desirable, and it is possible to set characteristics such as abrasion resistance, thermal conductivity and corrosion resistance of the valve seat for each required part, greatly increasing the durability of the valve seat. Significantly improved effect.

And, as described in claim 2,
By forming a high-hardness build-up layer in which hard precipitates are dispersed only in the portion close to the spark plug in the circumferential direction, the wear resistance of the portion close to the spark plug with a larger heat load is improved. A remarkably excellent effect that further improvement can be achieved is brought about.

In addition, as described in claim 3, an arc portion having a circumferential angle of 30 ° to 90 ° around the circumferential portion closest to the spark plug has a room temperature hardness Hv of 250 or more and a hard phase. Abrasion resistance of a valve seat portion close to a spark plug is stably improved by forming a high hardness build-up layer in which hard precipitates having an area ratio of 20% or more are dispersed. Is significantly improved.

Further, as set forth in claim 4, a circumferential angle of 30% around the circumferential portion closest to the spark plug.
The thermal conductivity is 0.4 J / cm ° C. or more and the room temperature hardness is Hv 250
By forming the low-hardness build-up layer in which the above-mentioned hard phase is not precipitated, it is possible to improve the cooling performance of the valve, and it is possible to cope with a high-output engine. A remarkably excellent effect that it can be achieved.

In the method for building the valve seat according to the present invention, since the build-up powder having different characteristics is used to build up in the circumferential direction, the build-up layer having different characteristics in the circumferential direction is used. It is possible to manufacture a valve seat formed with a valve seat, and it is possible to provide a valve seat that can effectively cope with a case where it is desirable to have different characteristics in the circumferential direction. Is brought.

And, as described in claim 6,
By forming a high hardness build-up layer in which hard precipitates are dispersed only in the part close to the spark plug in the circumferential direction, the wear resistance of the part close to the spark plug with a larger heat load is further improved. A remarkably excellent effect is obtained that the valve seat can be made to have a reduced shape.

Further, as described in claim 7, an arc portion having a circumferential angle of 30 ° to 90 ° around the circumferential portion closest to the spark plug has a room temperature hardness Hv of 250 or more and a hard phase. By using a build-up powder that disperses hard precipitates having an area ratio of 20% or more in the amount of the build-up, the wear resistance of the valve seat portion close to the ignition plug is more stably improved. A remarkably excellent effect is obtained that the valve seat can be made to have a reduced shape.

Further, as described in claim 8, cobalt: 10 to 15%, aluminum: 1.0 to 5.0%, iron: 4 to 8%, nickel: 10% by weight.
1 to 15%, one or more of vanadium, niobium, and tantalum of group Va elements in the periodic table of the elements: 0.1 to 5.
0%, silicon: 1.0 to 5.0%, the balance being a copper alloy build-up powder substantially composed of copper as the basic composition. It is said that by using only the arc portion of less than or equal to the degree to build up, it is possible to form a build-up layer excellent in wear resistance in which hard precipitates are dispersed only in the portion near the ignition plug. Significant effects are achieved.

Further, as set forth in claim 9, the heat conductivity of the remaining portion other than the arc portion having a circumferential angle of 30 ° to 90 ° around the circumferential portion closest to the spark plug is set. It is possible to obtain a valve seat with improved valve cooling performance by using a build-up powder that does not precipitate a hard phase having a hardness of 0.4 J / cm ° C. or more and a room temperature hardness of Hv 250 or more. Is obtained.

Further, as described in claim 10, aluminum: 5.0 to 10.0% by weight,
Nickel: 1.0 to 5.0%, iron: 1.0 to 4.0%,
The remainder is made of copper alloy build-up powder substantially composed of copper as the basic composition, and is used only for the remaining portion except for the arc portion having a circumferential angle of 30 to 90 degrees around the circumferential portion closest to the spark plug. By increasing the thickness of the valve seat, the heat conductivity of the portion other than the portion close to the ignition plug is increased, and it is possible to obtain a valve seat with further improved valve cooling performance. The effect is brought.

Further, as described in claim 11,
By using a laser beam to build up the build-up powder at the time of build-up, local melting becomes possible, and the heat-affected zone can be made small to perform laser build-up on the valve seat. Is obtained.

In the valve seat overlay processing apparatus according to the present invention, powder for supplying overlay powder having different characteristics to the overlay processing point of the valve seat portion according to the seventh, eighth, ninth, and tenth aspects. Since a switching device is provided and a powder supply amount control device that controls the supply amount of the build-up powder in multiple stages is provided, for example, the wear resistance of the valve seat portion that is closer to the ignition plug in the circumferential direction is reduced. Along with being able to be formed in a further improved wear-resistant overlay,
A remarkably excellent effect is obtained that the valve seat portion other than the portion close to the spark plug can be formed in the good heat conductive overlaying portion in which the heat conductivity is further improved.

According to a thirteenth aspect of the present invention, there is provided a powder supply pipe for supplying build-up powder having different characteristics to the build-up processing point of the valve seat portion through the same path. A remarkably excellent effect is achieved in that the overlay powder having different characteristics can be more accurately supplied to the overlay processing point without complicating the device configuration near the overlay processing point.

Further, the cylinder head for an engine according to the present invention comprises a cylinder head body made of an aluminum alloy and a valve seat according to any one of the first to fourth aspects. The wear resistance of the valve seat portion is good, the durability of the valve seat is further improved, and the heat conductivity of the valve seat portion other than the portion close to the spark plug is good. By improving the cooling performance for the valve, a remarkably excellent effect that it is possible to cope with a high-power engine is provided.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

First, as shown in FIG. 1, when the valve seat portion 2 of the cylinder head 1 made of an aluminum alloy for an engine is to be overlaid, the valve seat portion 2
From the powder supply pipe 3 to the build-up powder 4 made of copper alloy powder (the build-up powder 4 for the high hardness build-up layer).
H or the build-up powder 4L for the low-hardness build-up layer, while irradiating the processing laser beam 5 with the valve seat portion 2.
And the overlay powder 4 are simultaneously melted to form an overlay layer 6 (high hardness overlay layer 6H or low hardness overlay layer 6L).

[0038] In this embodiment, as the processing laser beam 5, using CO ₂ laser with a maximum output of 5 kW, the actual aluminum alloy cylinder head for an engine shown in FIG. 1 made of cast aluminum alloy (AC2A material) The alloy was overlaid on the valve seat portion 2 of No. 1.

As the build-up alloy, a build-up powder 4 made of copper alloy powder having the following component composition (build-up powder 4H for a high-hardness build-up layer) and aluminum bronze (AlBCIn3) specified in JIS H 2206 And two kinds of alloy powders, i.e., a build-up powder 4 made of a copper alloy powder (4 L of a low-hardness build-up layer).

銅 Copper alloy overlay powder (wt%) for high hardness overlay layer: Cu-12.5% Co-6.4% Fe-1
2.7% Ni-1.9% V-2.2% Nb-3.0% S
i-1.0% Al ◎ Copper alloy overlay powder (wt%) for low hardness overlay layer: C
u-10% Al-5% Ni-4% Fe Here, of the valve seat overlay processing apparatus according to the present invention, a powder supply apparatus used to supply the overlay powder 4 (4H, 4L) is shown in FIG. Shown in

The powder supply device 10 includes pots 11 and 12 for separately storing two types of overlay powder 4 (4H and 4L), respectively.
The two types of overlay powder 4
Pot 1 to control the supply amount of (4H, 4L) separately
The reduced weight of the build-up powder 4 (4H, 4L) contained in the samples 1 and 12 can be measured, and the amount of powder supplied is 0.5 g / m.
The apparatus provided with the powder supply amount control devices 13 and 14 capable of controlling and supplying the powder in in was used. The powder supply control devices 13 and 14 are operated by a controller 18.

Branch pipes 15 and 16 are connected to the powder outlets of the pots 11 and 12, respectively.
The lower end of 16 is connected to a powder switching device 17, and in this powder switching device 17, the build-up powder 4 (4H,
4L) can be switched and supplied to the build-up processing point 2A of the valve seat portion 2 via the powder supply pipe 3.

When building up the valve seat portion 2, as shown in FIG. 3, the buildup is started from the buildup start end position SE. Then, at the start, 4 L of a low-hardness overlay layer powder as the overlay powder 4 is supplied to the overlay processing point 2 A via the powder supply pipe 3, and the processing direction D shown in FIG.
, A low hardness buildup layer 6L is formed as a buildup layer 6 on the valve seat portion 2.

Next, when the build-up processing point 2A shown in FIG. 1 is shifted to the switching position B from the low hardness build-up layer to the high hardness build-up layer shown in FIG. 3, that is, in this embodiment, FIG. As shown in the figure, a portion having a circumferential angle of 40 degrees on the front side in the machining direction D with respect to the circumferential portion closest to the spark plug 8 of the engine (the center C of the high hardness buildup layer 6H) according to the pattern also shown in FIG. The copper alloy overlay powder 4L for the low hardness overlay is switched to the copper alloy overlay powder 4H for the high hardness overlay.

Subsequently, when the build-up processing point 2A shown in FIG. 1 moves to the switching position A from the high hardness build-up layer to the low hardness build-up layer shown in FIG. 3, that is, in this embodiment, FIG. As shown in FIG. 4, a pattern having a circumferential angle of 40 degrees on the rear side in the machining direction D with respect to the circumferential portion closest to the spark plug 8 of the engine (the center C of the high-hardness overlay 6H) is also shown in FIG. Is switched from the copper alloy overlay powder 4H for the high hardness overlay to the copper alloy overlay powder 4L for the low hardness overlay.

As described above, the copper alloy overlay powder 4H for a high-hardness overlay layer, which precipitates a hard phase at a circumferential angle of 80 degrees around the circumferential portion closest to the engine spark plug 8, is used. In the other portions, 4 L of a copper alloy build-up powder for a low hardness build-up layer made of aluminum bronze was used.

Thus, two kinds of copper alloy overlay powder 4
The switching of (4H, 4L) was performed twice during one processing, and was controlled to be performed within about 0.3 sec. Then, at the time of switching, the powder supply amount control devices 13 and 14 are adjusted so that the total powder supply amount of the two types of powder 4 (4H, 4L) becomes a predetermined amount.
And the controller 18 were set. In this example, the powder supply amount was set so that 50 g / min could be supplied to the build-up processing point 2A.

Table 1 shows the overlay processing conditions employed in this embodiment.

[0049]

[Table 1]

The build-up process was performed on three cylinders (intake side, exhaust side: a total of 48 valves) for the aluminum alloy cylinder head of the in-line DOHC four-cylinder engine under the conditions shown in Table 1. Processing was performed.

Next, the cylinder head blank thus obtained is machined to a predetermined size and surface roughness, and then each valve seat portion is machined to check the productivity of laser overlaying. By color checking the surface, the presence or absence of material defects in the build-up layer, such as shrinkage cavities, pores, and microcracks, was examined. The defective engine cylinder head is treated as a defective product. The results are shown in the column of "Defect occurrence rate" in Table 3.

As is clear from Table 3, the defect occurrence rate ([number of defective valve seats / total number of valve seats] × 1)
00) is 2 to 2 for hard phase precipitation type overlay powder (4H).
7%, whereas the hard phase precipitation type alloy powder (4
In the combination of H) and an alloy powder (4 L) that did not precipitate a hard phase, the defect occurrence rate was 0%.

Next, a part of the valve seat portion subjected to the build-up processing was cut out, and the heat transfer coefficient was measured by a laser flash method. The result of calculating the heat conductivity from the heat transfer coefficient is shown in the column of “heat conductivity” in Table 3. Table 3
As is clearer, in the example of the present invention, the value was higher than that of the comparative example in which only the hard phase precipitation type alloy powder (4H) was entirely built up.

Next, the engine cylinder heads (one in each embodiment) in which no defect occurred were subjected to the actual machine wear test and the temperature measurement test of the valve head surface under the same conditions as shown in Table 2 below.

[0055]

[Table 2]

The measurement results of the temperature of the valve head surface are shown in the column of "Temperature of valve head surface" in Table 3. As is clear from Table 3, the temperature of the valve head surface during the engine test was measured. In the embodiment of the present invention, although the temperature was higher than that of the alloy powder (4L) on which the hard phase was not precipitated, the hard phase precipitated alloy powder (4H) was overlaid on the entire circumference of the valve seat. Lower temperature.

Next, in the valve seat portion after the engine test, the wear depth of the plug closest portion and the portion on the opposite side were measured. Note that no significant difference in appearance was observed in the wear of the mating valve face portion, so the measurement of the wear amount was omitted.

The results are shown in the column of "depth of wear of valve seat portion" in Table 3. As is clear from Table 3, in the embodiment of the present invention, the amount of wear in the vicinity of the ignition plug is suppressed to a low level. In addition, the amount of wear on the opposite side of the plug was not enough to adversely affect the performance of the engine.

As described above, according to the present invention, the amount of wear in the vicinity of the spark plug can be suppressed low, and the temperature of the front surface of the valve head can be lowered, so that the engine performance can be further improved. Admitted.

[0060]

[Table 3]

[Brief description of the drawings]

FIG. 1 is an explanatory view of a slope showing an embodiment of a method for overlaying a valve seat according to the present invention.

FIG. 2 is an explanatory view of a slope of a powder supply device used in one embodiment of a method for overlaying a valve seat according to the present invention.

FIG. 3 is an explanatory plan view showing one embodiment of a method for processing the build-up of a valve seat according to the present invention.

FIG. 4 is an explanatory diagram of a build-up powder switching pattern employed in an embodiment of the method for processing the build-up of a valve seat according to the present invention.

FIG. 5 is an explanatory sectional view showing a general laser overlaying process.

[Explanation of symbols]

Reference Signs List 1 Cylinder head made of aluminum alloy for engine 2 Valve seat portion 2A Overlay processing point of valve seat portion 3 Powder supply pipe 4 Overlay powder 4H Overlay powder for high hardness overlay layer 4L Overlay powder for low hardness overlay layer 5 Processing laser beam 6 Overlay layer 6H High hardness overlay layer 6L Low hardness overlay layer 8 Spark plug 10 Powder supply device 13,14 Powder supply amount control device 17 Powder switching device A From high hardness overlay to low hardness overlay Switching position to layer B Switching position from low hardness overlay to high hardness overlay C Center of high hardness overlay (position closest to spark plug) D Processing direction SE Overlay start and end

Claims (14)

[Claims] 1. A valve seat characterized in that a build-up layer having different characteristics is formed in a circumferential direction in the build-up valve seat. 2. The valve seat according to claim 1, wherein a high-hardness build-up layer in which hard precipitates are dispersed is formed only in a portion close to the ignition plug in a circumferential direction. 3. A room temperature hardness Hv is formed in an arc portion having a circumferential angle of 30 ° or more and 90 ° or less around a circumferential portion closest to the spark plug.
The valve seat according to claim 2, wherein a high-hardness build-up layer in which hard precipitates having a hard phase precipitation of 250% or more and an area ratio of 20% or more are dispersed is formed. 4. A thermal conductivity of at least 0.4 J / cm ° C.s and room temperature at a remaining portion other than an arc portion having a circumferential angle of 30 ° to 90 ° around a circumferential portion closest to the spark plug. The valve seat according to claim 2, wherein a low-hardness build-up layer in which a hard phase having a hardness of Hv250 or more is not deposited is formed. 5. A method for processing the build-up of a valve seat, wherein the build-up is performed in the circumferential direction by using build-up powders having different characteristics. 6. The method according to claim 5, wherein a hard layer is formed in which hard precipitates are dispersed only in a portion close to the ignition plug in the circumferential direction. 7. A room temperature hardness Hv is formed in an arc portion having a circumferential angle of 30 ° or more and 90 ° or less around a circumferential portion closest to the spark plug.
7. The method according to claim 6, wherein the build-up powder is used to disperse hard precipitates having an area ratio of 250% or more and a hard phase precipitation of 20% or more. 8. Cobalt: 10 to 15%, aluminum: 1.0 to 5.0%, iron: 4 to 8%, nickel: 10 to 15% by weight, vanadium as a Va element in the Periodic Table of the Elements. , Niobium, tantalum, one or more of them:
1 to 5.0%, silicon: 1.0 to 5.0%, the balance being a copper alloy cladding powder having a substantially copper-based basic composition at a circumferential angle centered on the circumferential portion closest to the spark plug. 8. The method for overlaying a valve seat according to claim 7, wherein the overlaying is performed by using only an arc portion of 30 degrees or more and 90 degrees or less. 9. A thermal conductivity of at least 0.4 J / cm ° C.s and room temperature at a remaining portion other than an arc portion having a circumferential angle of 30 ° to 90 ° around a circumferential portion closest to the spark plug. The method according to claim 6, wherein the buildup is performed using a buildup powder that does not precipitate a hard phase having a hardness of Hv250 or more. 10. Aluminum in weight%: 5.0-1.
0.0%, nickel: 1.0 to 5.0%, iron: 1.0 to
4.0%, the balance being a copper alloy overlay powder substantially composed of copper as a basic composition. The remaining portion other than the arc portion having a circumferential angle of 30 ° to 90 ° around the circumferential portion closest to the spark plug is centered. The method according to claim 9, wherein only the portion is used to build up. 11. The method according to claim 5, wherein the cladding powder is clad with a laser beam at the time of cladding. 12. A powder switching device for supplying the build-up powder having different characteristics according to claim 7, 8, 9 and 10 to a build-up processing point of a valve seat portion, and supplying the build-up powder respectively. A build-up apparatus for a valve seat, comprising a powder supply amount control device for controlling the amount in multiple stages. 13. The valve seat build-up apparatus according to claim 12, further comprising a powder supply pipe for supplying build-up powders having different characteristics to the build-up processing point of the valve seat portion along the same path. 14. A cylinder head for an engine, comprising a cylinder head body made of an aluminum alloy and the valve seat according to claim 1.