JP2003328010A - Sintered alloy and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sintered alloy superior in corrosion resistance by sealing porous parts with a plated tin layer. <P>SOLUTION: The subject manufacturing method comprises forming an alloy body of the sintered alloy by compacting a base powder containing copper and sintering (S2) it, plating (S4) the alloy body of the sintered alloy with tin, and sealing the plated tin layer by shot peeling (S5). Then, the plated tin layer is compressed during the shot peening and is made to have approximately uniform thickness, and at the same time, the pores of the alloy body of the sintered alloy opening to the outside are closed with plated tin by compression onto the plated tin layer due to the shot peening. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a sintered alloy and a method for producing the same.

[0002]

Conventionally, it is known that a motor type fuel pump for a gasoline engine has a structure illustrated in FIG. 6 in a schematic sectional view. That is, as shown in the figure, the fuel pump 1
A rotating shaft 4 fixed to both ends of the motor 3 is supported by a bearing 5, an impeller 6 is inserted into one end of the rotating shaft 4, and the impeller 6, the outer peripheral surface of the motor 3 (armature), and It has a structure in which a gasoline flow passage 7 having a narrow gap is formed along a gap (not shown) between the bearing 5 and the rotary shaft 4, and the impeller 6 rotates by the rotation of the motor 3.
The gasoline is taken into the casing 2 by the rotation of the impeller 6, and the taken gasoline is formed along the impeller 6, the outer peripheral surface of the motor 3, and a gap (not shown) between the bearing and the rotating shaft. It is sent out through the road 7 and is operated so as to be sent to a separately installed gasoline engine. In FIG. 6, a small amount of fuel passes through the outer peripheral portions of the bearings 5 and 5, and the gasoline whose pressure is increased by the impeller 6 reaches the outer peripheral surface of the motor 3 through the gasoline passage 7 of the casing 1.

Bearing 5 which is a structural member of the above fuel pump
A copper-based sintered alloy is used for this, and in the production of this sintered alloy, a raw material powder containing copper is compressed to form a green compact, and the green compact is sintered and fire-bonded. Forming the gold body,
This sintered alloy body is subjected to sizing, which is recompression, to finish it to a predetermined size.

Since the bearing 5 is used in an environment exposed to fuel, a copper-based sintered alloy using a raw material powder containing copper is used in consideration of corrosion resistance to fuel. Has been. However, even with such a copper-based sintered alloy, if a fuel mixed with sulfur or its compound or a fuel mixed with an organic acid such as formic acid or acetic acid is used, there is a problem that the life is shortened due to corrosion.

Therefore, in the copper-lead alloy bearing disclosed in JP-A-5-202938, in order to improve the corrosion resistance of the bearing, the inner and outer surfaces of the copper-lead alloy bearing are plated with tin, lead or an alloy thereof. It is effective to apply (Patent Publication No. 0005)
Dan).

However, if there are pores on the surface of the sintered alloy,
Since the plating flows into the pores, there is a problem that the plating layer becomes non-uniform at that portion and the coverage of the sintered alloy surface by the plating is reduced.

The present invention is intended to solve such problems, and an object thereof is to provide a sintered alloy having excellent corrosion resistance by sealing the pores with a tin-plated layer and a method for producing the same. .

[0008]

A sintered alloy according to claim 1 is
In order to achieve the above object, a tin-plated layer is provided on a sintered alloy body obtained by molding and sintering raw material powder, and the tin-plated layer is sealed by shot peening.

The tin-plated layer having corrosion resistance makes it possible to obtain a sintered alloy having high corrosion resistance. Further, since the tin-plated layer is sealed by shot peening, the tin-plated layer is compressed, the tin-plated layer is formed with a substantially uniform thickness, and the adhesion of the tin-plated layer to the sintered alloy is improved, At the same time, the compressed tin plating layer seals the pores on the outer surface of the sintered alloy body, and the tin plating layer has excellent coverage.

According to the invention of claim 2, in the sintered alloy of claim 1, the raw material powder contains copper.

By covering the copper-based sintered alloy body with a corrosion-resistant tin-plated layer, a sintered alloy having high corrosion resistance can be obtained. In particular, by combining a copper-based sintered alloy with tin plating, a sintered alloy having both corrosion resistance to sulfur and its compounds and corrosion resistance to organic acids such as formic acid and acetic acid can be obtained.

In order to achieve the above object, the method for producing a sintered alloy according to claim 3 forms a sintered alloy body by forming and sintering raw material powder, and tin-plating the sintered alloy body. After the application, the tin plating layer is sealed by shot peening.

By using this method, the tin-plated layer is compressed by shot peening, the tin-plated layer is formed to have a substantially uniform thickness, and the adhesion of the tin-plated layer to the sintered alloy is improved. At the same time, since the tin plating is compressed to close the pores open to the outer surface of the sintered alloy body by the tin plating, the compressed tin plating layer seals the pores on the outer surface of the sintered alloy body, and the tin plating layer is used. Coverability is improved.

A fourth aspect of the present invention is the method for producing a sintered alloy according to the third aspect, wherein the raw material powder contains copper.

By combining a copper-based sintered alloy with tin plating, a sintered alloy having both corrosion resistance to sulfur and its compounds and corrosion resistance to organic acids such as formic acid and acetic acid can be obtained.

A fifth aspect of the present invention is the method for producing a sintered alloy according to the third aspect, wherein the size of the hard sphere used for the shot peening is 0.05 to 5 mm.

By making the size of the hard spheres 0.05 to 5 mm, the sealing effect becomes excellent. Preferably, by setting the size of the hard sphere to 0.1 to 1 mm, the sealing effect is further improved.

According to a sixth aspect of the present invention, in the method for producing a sintered alloy according to the third aspect, the rate at which the hard balls hit the tin-plated layer is 1 to 100 m / s.

If the speed is less than 1 m / s, the sealing effect by the hard balls is small, and if the speed exceeds 100 m / s,
The shot that has contributed to the densification and adhesion has the effect of peeling the tin-plated layer on the contrary, so the shot is preferably performed within the above range.

[0020]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 5 show an embodiment of the present invention, in which Cu-Ni-Zn- is used as a raw material for the sintered alloy body.
C-based or Cu-Sn-C-based materials can be used. The bearing 5 will be described below as an example of a sintered alloy. As shown in FIGS. 2 and 3, the bearing 5 is composed of a substantially cylindrical sintered alloy body 51, and a cylindrical sliding surface 52 on which the rotary shaft 4 is rotationally slid is formed in the center thereof. Further, a tin-plated layer 53 covering all exposed outer surfaces of the sintered alloy body 51.
Equipped with. In the present invention, tin plating includes plating of tin or tin alloy.

As an example, the sintered alloy body 51 of the bearing 5 has a mass% of Zn: 10 to 25% and Ni: 10 to 2
5%, P: 0.1 to 0.9%, C: 1 to 8%, with the balance being Cu and inevitable impurities, and 5
A graphite-dispersed Cu-based sintered alloy having a porosity of ˜25% can be used, and a graphite-dispersed Cu-based sintered alloy having another composition can also be used.

The manufacturing method will be described with reference to FIG. 1. For example, as the raw material powder used for the sintered alloy main body 51, all are formed by the water atomizing method and 45
Five kinds of Cu-Ni-Zn alloy powders having an average particle diameter of μm, that is, Cu-15.8% Ni-18.3% Zn
Alloy powder, Cu-16.9% Ni-18.0% Zn alloy powder, Cu-18.8% Ni-18.4% Zn alloy powder, Cu-17.4% Ni-16.4% Zn alloy powder ,
And Cu-17.3% Ni-19.9% Zn alloy powder (above 5 types), water atomized Cu-P alloy (containing P: 33%) powder having an average particle diameter of 45 μm, and further 75
After preparing a graphite powder having an average particle size of μm, blending these raw material powders into a predetermined blending composition, and performing mixing for 40 minutes with a V-type mixer (S1: step 1),
A green compact having a predetermined shape is formed (S2) by a press at a predetermined pressure within a range of 150 to 300 MPa, and the green compact is heated to a predetermined temperature within a range of 750 to 900 ° C. in an ammonia decomposing gas atmosphere. By sintering (S3) under the condition of holding for a minute, a bearing 5 made of a graphite-dispersed Cu-based sintered alloy was manufactured. When the bearings 5 obtained as a result were observed using an optical microscope (200 ×), they were all Cu-
The structure was such that the Cu-P alloy and graphite were finely distributed and distributed in the base material composed of the solid solution phase of the Ni-Zn alloy, and pores were also present. The thus-obtained graphite-dispersed Cu-based sintered alloy bearing 5 is made of Cu-Ni- which forms the base material.
Combined with the excellent strength and corrosion resistance of Zn alloys,
It has excellent wear resistance under the environment exposed to high pressure and high speed flow of gasoline.
A motor-type fuel pump using a base sintered alloy bearing has an excellent life even for a fuel containing sulfur or its compound as an impurity.

In the present invention, in order to further improve the corrosion resistance, the sintered alloy body 51 is plated (S) after the sintering (S3) process.
4) Perform processing. In this plating (S4) process, a tin plating layer 53 containing tin (Sn) having a thickness of about 2 to 25 μm is formed on the outer surface of the sintered alloy body 51 by an electroplating method or the like.

After plating, shot peening (S5)
The tin plating layer 53 is sealed with the above. Incidentally, the shot peening (S5) in this case means that a hard ball such as a small steel ball is blown onto the surface of the tin-plated layer 53 by compressed air or centrifugal force and hit.

As shown in FIG. 4, in the shot peening (S5), a steel ball 61 which is a hard ball is blown and hit against the tin plating layer 53. For example, the size of the steel ball 61 is 0.05.
It is about 5 mm, preferably about 0.1-1 mm.
The speed at which the steel ball 61 hits the tin-plated layer 53 is 1-100.
It is about m / s, preferably about 10 to 50 m / s.

Here, the tin-plated layer before shot peening
In order to confirm the state of 53 and the tin-plated layer 53 after shot peening, a plurality of sintered alloy main bodies 51 were manufactured and an enlarged photograph of the structure was taken. Actually, 24 sintered alloy bodies 51
Was formed under the same conditions until the plating treatment, and half the twelve sintered body bodies 51 were shot peened.

Then, the twelve sintered alloy bodies 51 were cut as shown in FIG. 3, and an enlarged photograph of the structure of the sliding surface 52 was taken. It was confirmed that when the shot peening was performed, the thickness of the tin-plated layer 53 became thin and densified, and the tin-plated layer 53 closed the openings 54A of the pores 54.

In the sintered alloy body 51 which has not been shot peened, as shown in FIG.
There is a pore 54 with A, which is a poorly sealed area by plating. Further, irregularities are seen on the outer surface of the tin-plated layer 53, and these irregularities are formed by the variation in the thickness of the tin-plated layer 53.

On the other hand, in the shot-peened sintered alloy body 51, as shown in FIG. 5, the openings 54A of the pores 54 opening in the sliding surface 52 are closed by the tin plating layer 53, At the same time, the outer surface of the tin-plated layer 53 also had less unevenness.

By performing shot peening (S5) after plating in this way, the tin-plated layer 53 is densified, and the tin-plated 53 is moved by the shot and the pores 54 opened on the outer surface of the sintered alloy body 51. Are covered, and the coverage with the tin-plated layer 53 is improved. Also, shot peening (S
By 5), the outer surface of the tin-plated layer 53 is formed flat, and
The tin plating layer 53 can be finished to have a substantially uniform thickness, the tin plating layer 53 is compressed, and the adhesion of the tin plating layer 53 to the outer surface of the sintered alloy is improved.

As described above, in this embodiment, according to claim 1, the tin-plated layer 53 is provided on the sintered alloy body 51 formed by molding and sintering the raw material powder mainly containing metal. Since the tin-plated layer 53 is sealed by shot peening, it is possible to obtain the bearing 5 which is a sintered alloy having high corrosion resistance due to the tin-plated layer 53 having corrosion resistance.
Since the tin-plated layer 53 is sealed by shot peening,
The tin-plated layer 53 is compressed, the tin-plated layer 53 is formed to have a substantially uniform thickness, the adhesion of the tin-plated layer 53 to the sintered alloy is improved, and at the same time, the compressed tin-plated layer 53 is baked. The pores 54 on the outer surface of the bonded gold body 51 are sealed, and the tin plating layer 53 has excellent coverage.

As described above, in this embodiment, since the raw material powder contains copper, the copper-based sintered alloy body 51 is formed by the corrosion-resistant tin-plated layer 53. By covering, it is possible to obtain the bearing 5, which is a sintered alloy, which has high corrosion resistance. In particular, by combining a copper-based sintered alloy with tin plating, a sintered alloy having both corrosion resistance to sulfur and its compounds and corrosion resistance to organic acids such as formic acid and acetic acid can be obtained.

As described above, in this embodiment, according to claim 3, the raw material powder is molded and sintered to form the sintered alloy main body 51, and the sintered alloy main body 51 is plated with tin. After that, since it is a method of sealing the tin-plated layer 53 by shot peening, the tin-plated layer 53 is compressed by shot peening, and the tin-plated layer 53 is formed to have a substantially uniform thickness, and with respect to the sintered alloy. The adhesion of the tin plating layer 53 is improved, and at the same time, the tin plating is compressed to close the pores 54 opening to the outer surface of the sintered alloy body by the tin plating. 51 The pores 54 on the outer surface are sealed, and the coverage with the tin-plated layer 53 is improved.

As described above, in this embodiment, the raw material powder contains copper in accordance with the fourth aspect. Therefore, by combining a copper-based sintered alloy and tin plating, sulfur It is possible to obtain the bearing 5, which is a sintered alloy, having both corrosion resistance with respect to or its compound and corrosion resistance against organic acids such as formic acid and acetic acid.

As described above, in this embodiment, the steel ball 61 used for the shot peening corresponds to claim 5.
Since the size of the steel balls 61 is 0.05 to 5 mm, setting the size of the steel balls 61 to 0.05 to 5 mm provides an excellent sealing effect.

As described above, in this embodiment, the speed at which the steel ball 61 hits the tin-plated layer 53 ranges from 1 to
When the speed is less than 1 m / s, the sealing effect by the steel balls is small and the speed is 100 m / s.
If it exceeds s, the shot that has contributed to the densification and adhesion will have the effect of peeling the tin-plated layer 53 on the contrary. be able to. Therefore, the performance suitable for the bearing 5 as the sliding member having the sliding surface 52 can be obtained.

The present invention is not limited to the above embodiment, and various modifications can be made. For example, the present invention can be applied to various materials, as long as the raw material powder preferably contains copper or a copper alloy. Also,
The present invention is applicable to various kinds of sintered alloys, not limited to bearings. Further, the bearing is not limited to that of the embodiment, and various shapes can be applied. Further, the sliding member is not limited to the bearing, and can be applied to various sliding members as long as it has a sliding portion.

[0038]

In order to achieve the above object, the sintered alloy according to the present invention is provided with a tin-plated layer on a sintered alloy body formed by molding raw material powder and sintering the powder. Sealing is performed by shot peening. By sealing the hole portion with a tin plating layer, a sintered alloy having excellent corrosion resistance can be provided.

In addition to the effect of claim 1, since the raw material powder contains copper, the invention of claim 2 has corrosion resistance to sulfur and its compounds and corrosion resistance to organic acids such as formic acid and acetic acid. A sintered alloy having both of the above can be obtained.

According to a third aspect of the present invention, in a method for producing a sintered alloy, a raw material powder is molded and sintered to form a sintered alloy main body, the sintered alloy main body is plated with tin, and then shot peening is performed to form tin. This is a method of sealing the plating layer, and by sealing the hole portion with the tin plating layer, a sintered alloy having excellent corrosion resistance can be manufactured.

Further, in addition to the effect of claim 3, the invention of claim 4 is a method in which the raw material powder contains copper, which has corrosion resistance to sulfur and its compounds and corrosion resistance to organic acids such as formic acid and acetic acid. A sintered alloy having both can be manufactured.

In addition to the effect of claim 3, the invention of claim 5 is a method in which the size of the hard spheres used for the shot peening is 0.05 to 5 mm, which is excellent in the sealing effect. Becomes

In addition to the effect of claim 3, the invention of claim 6 sets the speed at which the hard balls hit the tin-plated layer to 1
It is a method of 100 to 100 m / s, and the sealing effect is excellent and the adhesion of the tin-plated layer is good.

[Brief description of drawings]

FIG. 1 is a flowchart illustrating a manufacturing method according to an embodiment of the present invention.

FIG. 2 is a perspective view of the sintered alloy body.

FIG. 3 is a cross-sectional view of a partially expanded sintered alloy.

FIG. 4 is a cross-sectional view for explaining shot peening in the same as above, in which pores are in a state before shot peening.

FIG. 5 is an enlarged cross-sectional view of the tin-plated layer after shot peening as above.

FIG. 6 is a schematic sectional view of a motor type fuel pump for a gasoline engine.

[Explanation of symbols]

1 Bearing (sintered alloy) 51 Sintered alloy body 53 Tin plating layer 61 steel ball (hard ball)

Front page continuation (51) Int.Cl. ⁷ identification code FI theme code (reference) C25D 7/00 C25D 7/00 R 7/10 7/10 F02M 37/08 F02M 37/08 Z F term (reference) 4K018 AA04 BA02 BB04 BC12 CA02 CA11 DA11 DA21 DA33 FA05 FA23 HA01 HA03 KA03 4K024 AA07 AB01 BA09 BB05 BC07 DB07 GA04

Claims (6)

[Claims] 1. A sintered alloy comprising: a sintered alloy body formed by molding a raw material powder and sintering the same; and providing a tin-plated layer, the tin-plated layer being sealed by shot peening. 2. The sintered alloy according to claim 1, wherein the raw material powder contains copper. 3. A raw material powder is molded and sintered to form a sintered alloy body, the sintered alloy body is tin-plated, and then the tin-plated layer is sealed by shot peening. A method for producing a sintered alloy. 4. The method for producing a sintered alloy according to claim 3, wherein the raw material powder contains copper. 5. The method for producing a sintered alloy according to claim 3, wherein the hard spheres used for the shot peening have a size of 0.05 to 5 mm. 6. The method for producing a sintered alloy according to claim 5, wherein the rate at which the hard balls hit the tin-plated layer is 1 to 100 m / s.