JPH08224681A - Built-up welding method for valve seat of cylinder head - Google Patents

Abstract

PURPOSE: To stabilize powder feeding density and to eliminate deviation between a powder feeding position and an irradiation position of a laser beam on the surface of a seat. CONSTITUTION: The seat surface 2a of a valve seat 2 is irradiated with a laser beam 3 while a powder 5 is supplied from a powder feeding nozzle 4 to the surface. The valve seat 2 is rotatably moved in the circumferential direction against the laser beam 3 to form a build-up layer 6 on the entire circumference of the seat surface 2a of the valve seat 2. The angle formed by the normal line (a) of a cross-sectionally circular-arc seat surface 2a with the powder feeding nozzle 4 is set to 0-20 deg., and the angle formed by the powder feeding nozzle 4 with the laser beam 3 is set to 5-20 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for depositing a valve seat in an aluminum alloy cylinder head of an internal combustion engine, and more specifically, for improving the heat resistance and wear resistance of the seat surface of the valve seat, copper is used. The present invention relates to a method for forming a built-up layer such as a system alloy.

[0002]

2. Description of the Related Art A technique called a laser cladding method for improving the physical and mechanical properties of a base material such as a steel pipe is disclosed in, for example, Japanese Patent Laid-Open No. 62-183989. Basically, a cladding layer is formed by irradiating a laser beam while supplying a powder of a material according to required characteristics to the surface of a base material, melting and solidifying the powder once, and overlaying the powder to form a cladding layer.

On the other hand, by applying this laser cladding method, a built-up layer of a copper alloy or the like is formed on a valve seat of a cylinder head made of an aluminum alloy. As shown in FIGS. 7 and 8, in this valve seat build-up method, the seat surface 2a of the valve seat 2 of the cylinder head 1 to be processed is formed in advance into a groove shape having a predetermined curvature and an arcuate cross section. At the same time, the entire cylinder head 1 is tilted by 45 degrees so that the normal line a to the curvature of the groove shape is oriented in the vertical direction, and the powder 5 such as a copper alloy is continuously supplied from the powder supply nozzle 4 to the seat surface 2a. The laser beam 3 is irradiated, and the cylinder head 1 and the laser beam 3 are relatively rotated about the axis b of the valve seat 2 along the circumferential direction of the valve seat 2 to form the buildup layer 6. I am trying to do it.

Here, as shown in FIG. 8, the inclination angle θ of the powder supply nozzle 4 with respect to the normal line a is set to 45 °, and the axis c of the powder supply nozzle 4 is on the seat surface 2a. It is set so as to direct the laser beam irradiation position.

[0005]

In the conventional padding method as described above, as shown in FIG. 8, since the powder 5 is charged onto the seat surface 2a from the direction inclined by 45 °, the seat surface 2
A large amount of the powder 5 that has fallen onto the sheet a is scattered and spills from the sheet surface 2a, so that the supply yield of the powder 5 is poor, and the spread of the powder 5 on the sheet surface 2a is caused by the sheet. Since it becomes large in the longitudinal direction of the surface 2a, the powder 5 at the actual laser beam irradiation position becomes insufficient, and the powder supply density at the laser beam irradiation position decreases. As a result, the amount of heat dosed by the laser beam 3 becomes too large for the powder supply density, and a processing defect called base material dilution occurs. That is, powder 5
In some cases, the base material of the cylinder head 1 itself is melted and diluted in the build-up layer 6 formed by once melting and solidifying, whereby the original performance of the build-up layer 6 may not be exhibited. .

Further, in the conventional method, the processing position is easily influenced by the variation in the vertical direction, and in particular, the position of the sheet surface 2a at the laser beam irradiation position is shown in FIGS.
Of the powder supply nozzle 4 with respect to the laser beam irradiation position is largely deviated in the relative rotation direction between the laser beam 3 and the valve seat 2, and this causes the powder 5 to move in the same manner as described above. It is not preferable because it leads to a decrease in supply yield and processing defects such as dilution of the base material.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a valve seat padding method which is particularly aimed at improving the powder supply yield and the processing quality. To do.

[0008]

According to a first aspect of the present invention, powder of a build-up material is continuously supplied from a powder supply nozzle to a seat surface of a valve seat of a cylinder head, and a laser beam is irradiated from above the powder. The cylinder head and the laser beam are relatively rotated in the circumferential direction of the valve seat to form a build-up layer on the entire circumference of the seat surface. The angle between the line perpendicular to the powder supply nozzle and the powder supply nozzle is set to 0 to 20 °, and the angle between the powder supply nozzle and the optical axis of the laser beam is set to 5 to 20.
The feature is that it is set to °.

Here, the angle formed by the line perpendicular to the sheet surface and the powder supply nozzle is 0 to 20 °, and the angle formed by the powder supply nozzle and the laser beam is 5 to 20 °.
The reason is that if the angle exceeds 20 °, the powder dropped from the powder supply nozzle onto the sheet surface spreads too much and scatters, resulting in a large amount of powder spilling from the sheet surface, leading to a decrease in the powder supply yield and the laser beam. This is because the powder supply density at the irradiation position decreases.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the offset amount between the optical axis of the laser beam and the axis of the powder supply nozzle on the sheet surface is the same as that of the cylinder head. It is characterized in that the relative rotation direction of the laser beam is set within ± 2 mm.

When the offset amount exceeds ± 2 mm, the powder is not stably supplied to the laser beam irradiation position, resulting in processing defects such as dilution of the base material.

According to a third aspect of the invention, in addition to the configuration of the first or second aspect, the distance between the irradiation position of the laser beam on the sheet surface and the tip of the powder supply nozzle is 5 to 5. It is characterized by being set to 50 mm.

The distance between the laser beam irradiation position on the sheet surface and the tip of the powder supply nozzle is 5 to 50 m.
The range of m is less than 5 mm because the powder supply nozzle may be melted or damaged due to reflected light and heat generated from the processed portion, or spatter adhesion may occur. This is because the supply density cannot be obtained and the frequency of defects such as dilution of the base material and cracks increases.

In addition to the structure according to any one of claims 1 to 3, the invention according to claim 4 is characterized in that the inner diameter of the powder supply nozzle is set to 1 to 5 mm.

The inner diameter of the powder supply nozzle is also determined by the inclination angle of the nozzle itself, but if the inner diameter is less than 1 mm, the powder may become clogged and the continuous supply of the powder cannot be performed stably, and the inner diameter of the powder supply nozzle may be too small. If it exceeds 5 mm, the powder supply amount becomes too large and the powder supply yield decreases.

In addition to the structure according to any one of claims 1 to 4, the invention according to claim 5 is characterized in that the seat surface is previously formed in a groove shape having a concave cross section.

[0017]

According to the first aspect of the invention, the powder is supplied from the powder supply nozzle in a direction substantially perpendicular to the sheet surface, so that the powder spreads or falls on the sheet surface. The powder supply amount is reduced and the powder supply yield is improved, and the deviation amount between the laser beam irradiation position and the powder is reduced.

According to the second aspect of the present invention, the laser beam irradiation position is controlled by controlling the offset amount between the laser beam on the sheet surface and the axis of the powder supply nozzle to fall within a predetermined range. On the contrary, powder supply is accurate,
And it becomes stable.

According to the third aspect of the present invention, the distance from the laser beam irradiation position to the tip of the powder supply nozzle is set to a predetermined dimension, so that the melting damage of the nozzle when the powder supply nozzle is brought too close It is possible to prevent adhesion of dust and spatter, and yet to prevent processing defects such as dilution of the base material while securing an optimum powder supply density at the laser beam irradiation position.

According to the fourth aspect of the present invention, by setting the inner diameter of the powder supply nozzle to a specific dimension, clogging of the nozzle can be prevented and the powder can be stably supplied.

According to the invention described in claim 5, since the sheet surface is previously formed in the shape of a groove having a concave cross section, the powder holding capacity is large and stable, and the build-up processing is stabilized. Besides, the yield of powder is improved.

[0022]

1 and 2 are views showing an embodiment of the present invention. FIG. 1 corresponds to a cross section taken along the line AA of FIG.
7 is an enlarged view of a main part of FIG. 7, and parts common to FIGS. 7 and 8 are given the same reference numerals.

As shown in FIGS. 1 and 2, the cylinder head 1
Is formed of an aluminum alloy corresponding to JIS AC2A material as in the conventional case, and the seat surface 2a of the valve seat 2 to be processed, that is, the valve seat 2 previously formed in a groove shape having an arcuate cross section is formed. The cylinder head 1 is entirely positioned and clamped by a jig (not shown) in a tilted posture so that the normal a of the sectional curvature of the seat surface 2a is in a vertical posture. Then, during the overlay processing, the entire cylinder head 1 is rotationally driven at a predetermined speed with the axis b (see FIG. 7) of the valve seat 2 to be processed as the center of rotation.

The seat surface 2a of the valve seat 2
Is irradiated with the laser beam 3 from the direction of its normal line a, and a powder supply nozzle 4 is provided at a position inclined by a predetermined angle to the rear side in the rotational direction of the valve seat 2 from the optical axis of the laser beam 3. The powder 5 of the copper-based alloy material is continuously supplied from the supply nozzle 4 to the laser beam irradiation portion by a predetermined amount. The copper alloy powder used here is, for example, Cu-15.5%, Ni-14.1%, Co-0.9.
1%, Al-1.58%, V-1.84%, Nb-2.
The composition is 78% and Si-balance.

In this embodiment, the cylinder head 1 shown in FIGS. 1 and 2 is provided with a rotary feed of 0.8 m / min about the axis b of the valve seat 2 shown in FIG. After making the normal line a of the surface 2a and the irradiation direction (optical axis) of the laser beam 3 coincide with each other, 45 g / min from the powder supply nozzle 4 having an inclination angle of 20 ° with respect to the irradiation direction of the laser beam. While continuously supplying the powder 5 of the copper-based alloy material to the seat surface 2a of the valve seat,
A laser beam 3 having a laser output of 4.0 kW and an output mode of a ring mode is linearly formed, and the laser beam 3 is formed.
The sheet surface 2a was subjected to the overlay processing while irradiating the width direction of the sheet with the processing feed direction to form the overlay layer 6.

The distance (standoff) f from the laser beam irradiation unit in FIG. 1 to the tip of the powder supply nozzle 4 is set to 1
0 mm, the inner diameter D of the powder supply nozzle 4 is 3.4 mm,
Further, the offset amount in the working feed direction between the optical axis (normal line a) of the laser beam 3 and the axis c of the powder supply nozzle 4 on the sheet surface 2a shown in FIG. 1 was regulated within ± 2 mm.

As a result, it has been confirmed that the valve seat 2 can be formed with a good build-up layer 6 which is free from so-called base material dilution and cracks caused by the melted base material on the build-up layer 6 side.

The valve seat 2 of the cylinder head 1 on which the build-up layer 6 is formed is subjected to a cutting process in a post process so as to partially cut off the build-up layer 6 as shown in FIG. Finally, a predetermined sheet surface shape 2b required for product function is finished.

FIG. 3 shows JIS A under the same conditions as above.
Aluminum alloy sample (square) corresponding to C2A material 1
1 is a photomicrograph of a cross section when the build-up layer 6 is formed, and FIG. 4 is a schematic view of the cross section of FIG. Recognize.

As a comparative example, as shown in FIG. 8, the powder of the copper-based alloy material is supplied from the powder supply nozzle 4 inclined by 45 ° with respect to the normal line a (the optical axis of the laser beam 3) perpendicular to the surface where the buildup layer is formed. 5 and 6 are cross-sectional micrographs and schematic diagrams in the case where 5 is continuously supplied and the other conditions are set in exactly the same manner as above to form the built-up layer 6 on the sample 11.

In the case of this comparative example, as is clear from FIGS. 5 and 6, an altered layer 12 due to the melting of the base material is generated at both widthwise ends of the overlay layer 6, and one of the altered layers is still present. A crack 13 occurs around 12.

[0032]

According to the invention described in claim 1, the angle formed by the line perpendicular to the seat surface of the valve seat and the powder supply nozzle is set to 0 to 20 °, and the powder supply nozzle and the laser are set. By setting the angle formed by the beam to 5 to 20 °, the unnecessary spread of the powder falling from the powder supply nozzle to the sheet surface is reduced, and the powder spilled from the sheet surface is reduced, so that the powder supply yield is improved. In addition to the improvement, the offset amount between the laser beam irradiation position and the powder supply position is reduced, and the optimum powder supply density can be obtained at the laser beam irradiation position. The occurrence of defects such as melting and cracks in the material is eliminated and the quality of the overlay processing is greatly improved.

Particularly, as in the second aspect of the invention, the laser beam irradiation position is controlled by controlling the offset amount between the laser beam on the sheet surface and the axis of the powder supply nozzle to be within ± 2 mm. As a result, the powder can be accurately and stably supplied to, and the processing quality can be further improved.

According to the third aspect of the invention, the distance from the laser beam irradiation position to the tip of the powder supply nozzle is 5 to 5.
By setting to 50mm, in addition to the above effects,
It is possible to prevent meltdown of the nozzle and adhesion of spatter when the powder supply nozzle is brought close to the processing part, and to prevent the powder from spreading undesirably on the sheet surface and scattering, and the optimum powder supply density can be obtained. This is also obtained, and this also has an advantage that processing defects such as dilution of the base material can be prevented and the processing quality can be greatly improved.

According to the invention described in claim 4, by setting the inner diameter of the powder supply nozzle to 1 to 5 mm, in addition to the above effects, the clogging of the nozzle is prevented and the powder supply is further improved. Can be stabilized.

According to the invention described in claim 5, since the sheet surface is previously formed in a groove shape having a concave cross section, in addition to the above effects, the powder holding capacity is large and stable. As a result, it is possible to further improve the powder supply yield and the quality of the overlay processing.

[Brief description of drawings]

FIG. 1 is a view showing an embodiment of the present invention and is a sectional explanatory view corresponding to a section taken along the line AA of FIG. 7.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a micrograph showing a metal structure of a cross section of a built-up layer formed by the method of the present invention.

FIG. 4 is a schematic view of the cross section of FIG.

FIG. 5 is a micrograph showing a metal structure of a cross section of a built-up layer formed by a conventional method.

FIG. 6 is a schematic view of the cross section of FIG.

FIG. 7 is an explanatory cross-sectional view showing a method of overlaying a valve seat in a conventional cylinder head.

FIG. 8 is an explanatory cross-sectional view taken along the line AA of FIG.

[Explanation of Codes] 1 ... Cylinder head 2 ... Valve seat 2a ... Seat surface 3 ... Laser beam 4 ... Powder supply nozzle 5 ... Copper-based alloy material powder 6 ... Build-up layer

Claims (5)

[Claims] 1. A powder of a build-up material is continuously supplied to a seat surface of a valve seat of a cylinder head from a powder supply nozzle, and a laser beam is irradiated from above the powder, so that the cylinder head and the laser beam are circled on the valve seat. In a method for depositing a valve seat in a cylinder head, which is configured to form a buildup layer on the entire circumference of a seat surface by relatively rotating in the circumferential direction, a line perpendicular to the seat surface and a powder supply nozzle A method for depositing a valve seat in a cylinder head, wherein the angle formed is set to 0 to 20 °, and the angle formed between the powder supply nozzle and the optical axis of the laser beam is set to 5 to 20 °. 2. The offset amount between the optical axis of the laser beam and the axis of the powder supply nozzle on the sheet surface is set within ± 2 mm in the relative rotation direction of the cylinder head and the laser beam. The method for building up a valve seat in a cylinder head according to claim 1. 3. The distance between the irradiation position of the laser beam on the sheet surface and the tip of the powder supply nozzle is 5 to 50.
3. The valve seat build-up method for a cylinder head according to claim 1, wherein the valve seat is set to mm. 4. The inner diameter of the powder supply nozzle is 1 to 5 mm
4. The method for building up a valve seat in a cylinder head according to claim 1, wherein: 5. The method of overlaying a valve seat in a cylinder head according to claim 1, wherein the seat surface is previously formed in a groove shape having a concave cross section.