JPH10298690A - Sliding member made of aluminum alloy, and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lightweight sliding member made of aluminum alloy, capable of combining excellent strength with excellent wear resistance. SOLUTION: This sliding member is composed of an Al-Si type casting aluminum alloy having a composition consisting of, by weight, 14.0-17.5% Si, 2.0-5.0% Cu, 0.1-1.0% Mg, 0.3-0.8% Mn, 0.05-0.30% Cr, 0.05-0.20% Ti, 0.003-0.050% P, <=1.5% Fe, Ca in an amount limited to <0.005%, and the balance essentially Al. Moreover, the average grain size of primary-crystal Si of the sliding surface is regulated to <=12 μm and also the average grain size of α-phases, excluding eutectic, is regulated to >=10 μm, and further, the grain size of primary-crystal Si of the sliding surface is regulated to <=35 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding member made of an aluminum alloy, which is used as a material for a shift fork or the like and has excellent strength and abrasion resistance, and a method for producing the sliding member.

[0002]

2. Description of the Related Art In recent years, the use of aluminum alloys to reduce the weight of power equipment has been studied in many cases.
For the sliding portion, a hypereutectic Al-Si-based aluminum alloy having excellent wear resistance and seizure resistance has attracted attention.

[0003] This hypereutectic Al-Si-based aluminum alloy has a structure in which primary crystal Si exists, and its hard primary crystal S
i secures excellent wear resistance.

[0004]

In this case, in order to obtain sufficient wear resistance, it is necessary to increase the grain size of primary crystal Si to some extent. However, a sliding member requiring strength, such as a shift fork, has a problem that impact strength and fatigue strength are particularly reduced when the primary crystal Si particle size is larger than necessary. In addition, even if the amount of primary crystal Si is too large, there is a problem that impact strength and fatigue strength are reduced. On the other hand, when the primary crystal Si is fine or small, the impact strength and the fatigue strength are sufficiently good, but there is a problem that the wear resistance is insufficient.

[0005] Therefore, in order to achieve both excellent strength and excellent wear resistance in a part, it is necessary to reduce the stress by changing the shape or to secure the wear resistance by increasing the area of the sliding surface. In some cases, it was necessary to adopt the method described above.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is an object of the present invention to provide a primary crystal Si having an appropriate size.
In the case where wear resistance decreases due to the uniform dispersion of primary crystal Si and the refinement of primary crystal Si, the decrease in wear resistance is compensated for by reducing the α phase, which is particularly poor in wear resistance, to provide excellent strength and resistance. An object of the present invention is to provide a sliding member made of an aluminum alloy, which is excellent in abrasion resistance and is capable of satisfying both abrasion characteristics, and a method for manufacturing the same.

[0007]

According to the present invention, a sliding member made of an aluminum alloy according to the present invention is made of an Al-Si-based aluminum casting alloy and has a primary surface of primary crystal Si on a sliding surface. The average particle size is 12 μm or less, and
The sliding surface is characterized in that the primary crystal Si has a particle size of 35 μm or less.

[0008] Similarly, the sliding member made of an aluminum alloy according to the present invention is an aluminum alloy sliding member.
Primary crystal S on sliding surface made of Si-based aluminum casting alloy
The average particle diameter of i is 12 μm or less, the average particle diameter of the α phase excluding the eutectic is 10 μm or less, and the particle diameter of primary crystal Si on the sliding surface is 35 μm or less. Features.

In the embodiment of the sliding member made of an aluminum alloy according to the present invention, in order to uniformly disperse primary crystal Si of an appropriate size, it is preferable that the sliding member is described in claim 3. The Al-Si based aluminum casting alloy has a weight percentage of Si: 14.0 to 17.5% and Cu:
2.0-5.0%, Mg: 0.1-1.0%, Mn:
0.3-0.8%, Cr: 0.05-0.30%, T
i: 0.05 to 0.20%, P: 0.003 to 0.05
0%, Fe: 1.5% or less, and Ca:
The content can be restricted to less than 0.005%, and the balance can be substantially composed of Al.

Similarly, in the embodiment of the sliding member made of aluminum alloy according to the present invention, in order to secure sufficient wear resistance even with fine primary crystal Si, it is preferable that the sliding member is described in claim 4. Further, at least the surface roughness of the sliding surface may be 1.6 μm or less in arithmetic average roughness (Ra).

In the method for manufacturing an aluminum alloy sliding member according to the present invention, in order to uniformly disperse primary crystal Si of an appropriate size, Melting temperature is 710 ° C or higher, casting temperature is 68
It can be made to be 0 ° C. or higher.

[0012]

Next, the operation of the aluminum alloy sliding member having excellent wear resistance and the method of manufacturing the same according to the present invention will be described in more detail.

First, the reasons for limiting the grain size of the primary crystal Si and the numerical value of the α phase will be described.

Average grain size of primary crystal Si on sliding surface: desirably 4 μm or more and 12 μm or less Primary crystal Si is essential for improving the wear resistance of an Al—Si aluminum alloy. If the average particle size of Si is less than 4 μm, it may not be possible to obtain sufficient wear resistance.
m or more. On the other hand, when the thickness exceeds 12 μm, the impact strength and the fatigue strength decrease, which is not preferable.

Particle size of primary Si on the sliding surface: 35 μm or less If the particle size of primary Si exceeds 35 μm, elongation is insufficient.
In addition, the primary crystal Si is easily cracked or dropped, and destruction starting from this portion is also easily caused. These are not preferred because impact strength and fatigue strength decrease.

Average grain size of primary crystal Si on sliding surface: 12 μm or less Average grain size of α phase excluding eutectic: 10 μm or less If the average grain size of primary crystal Si exceeds 12 μm, impact strength and fatigue strength decrease. Is not preferred. On the other hand, if the average particle size of the α phase exceeds 10 μm, the abrasion resistance decreases, which is not preferable.

Next, the reasons for limiting the alloy composition (% by weight) will be described.

Si: 14.0 to 17.5% Si is an important element for improving the wear resistance of an Al-Si based aluminum alloy. However, if the Si content exceeds 17.5%, the liquidus of the alloy rises, so that the solubility and castability deteriorate, and the dispersion of primary crystal Si tends to be uneven and coarsening occurs. Therefore, the impact value and the fatigue strength decrease. On the other hand, less than 14.0% Si
With the content, the wear resistance is insufficient.

Cu: 2.0-5.0% Cu has the effect of strengthening the matrix of the aluminum alloy, thereby improving the strength and wear resistance.
In order to obtain such an effect, it is necessary to contain 2.0% or more of Cu. However, if the Cu content exceeds 5.0%, the number of shrinkage cavities increases, which is not preferable.

Mg: 0.1-1.0% Mg is an effective element for improving the hardness, wear resistance, mechanical strength, etc. of an aluminum alloy. Can be obtained. However, 1.
When Mg is contained in excess of 0%, a tendency to lower toughness is observed.

Mn: 0.3-0.8% Mn disperses Al-Si-Fe-Mn-Cr intermetallic compound finely and uniformly, improves wear resistance, and strengthens the aluminum alloy matrix. And is an alloying element that improves mechanical properties. When the Mn content is less than 0.3%, the abrasion resistance tends to decrease. On the other hand, if it exceeds 0.8%, the mechanical properties deteriorate.

Cr: 0.05 to 0.30% Cr is an important alloy element for uniformly dispersing primary crystal Si in a matrix of an aluminum alloy, and effectively acts to improve hardness and mechanical properties. I do. Also, Al-Si
It is an important alloying element for uniformly dispersing the -Fe-Mn-Cr-based intermetallic compound as fine crystallized substances and improving wear resistance. And such an effect is 0.05
% Or more becomes significant. However, when the Cr content exceeds 0.30%, castability and mechanical properties are reduced.

Ti: 0.05 to 0.20% Ti has an effect of improving the mechanical properties of an aluminum alloy, and is an effective element for making the structure uniform.
In order to obtain these effects, it is necessary to contain 0.05% or more of Ti. However, 0.2
If the Ti content exceeds 0%, the mechanical properties deteriorate.

P: 0.003 to 0.050% P has an effect of making primary crystal Si finer together with Cr and uniformly dispersing it. The effect on the primary crystal Si is as follows:
It is ensured at a content of 0.003% or more. However, if the P content exceeds 0.050%, castability such as molten metal flow deteriorates.

Fe: 1.5% or less Fe is an Al—Si—Fe intermetallic compound and Al—S
The i-Fe-Mn-Cr intermetallic compound is finely crystallized to improve wear resistance. However, when a large amount of Fe is mixed in the aluminum alloy, Al- A coarse Fe-based compound is generated, which causes microporosity. As a result, the toughness and strength of the obtained aluminum alloy are reduced. Therefore, in the present invention, the Fe content is regulated to 1.5% or less.

Ca: less than 0.005% When the Ca content is 0.005% or more, internal shrinkage becomes large at the time of casting, resulting in a decrease in castability. In addition, it inhibits the action of P to refine the primary crystal Si.

Next, the reason for limiting the surface roughness will be described.

At least the surface roughness of the sliding surface: 1.6 μm or less in arithmetic average roughness (Ra) If at least the surface roughness of the sliding surface exceeds 1.6 μm in arithmetic average roughness (Ra), sliding Since there is a portion where a sufficient oil film thickness cannot be obtained at the initial stage, the true contact area decreases, and the surface pressure on the contact surface increases, so that the amount of wear increases.

Finally, the reasons for limiting the casting conditions will be described.

Melting temperature: 710 ° C. or higher Casting temperature: 680 ° C. or higher If the melting temperature is lower than 710 ° C. or the casting temperature is lower than 680 ° C., it is not preferable because coarse primary Si particles are unevenly distributed.

[0031]

The sliding member made of an aluminum alloy according to the present invention is made of an Al-Si based aluminum casting alloy as described in claim 1, and the average grain size of primary crystal Si on the sliding surface is 12 μm. The present invention provides a lightweight aluminum alloy sliding member that achieves both excellent strength and excellent wear resistance because the primary crystal Si of the sliding surface is 35 μm or less and the sliding surface is 35 μm or less. A significant effect of being able to do so.

Similarly, the sliding member made of an aluminum alloy according to the present invention has the following features.
Primary crystal Si of sliding surface made of i-type aluminum cast alloy
Has an average particle size of 12 μm or less, and the average particle size of the α phase excluding the eutectic is 10 μm or less.
Since the particle size of i is 35 μm or less, a remarkable effect that it is possible to provide a lightweight aluminum alloy sliding member having both excellent strength and excellent wear resistance can be provided. Brought.

And, as described in claim 3,
Al-Si based aluminum casting alloy is expressed in weight%
i: 14.0 to 17.5%, Cu: 2.0 to 5.0%,
Mg: 0.1-1.0%, Mn: 0.3-0.8%, C
r: 0.05 to 0.30%, Ti: 0.05 to 0.20
%, P: 0.003 to 0.050%, Fe: 1.5% or less, and Ca: less than 0.005%, with the balance being substantially Al-Si-based aluminum The use of a cast alloy has a remarkable effect that it is possible to provide a lightweight aluminum alloy sliding member having both excellent strength and excellent wear resistance.

Further, as described in claim 4, the surface roughness of at least the sliding surface is not more than 1.6 μm in arithmetic average roughness (Ra), so that it is sufficient in the initial stage of sliding. The present invention provides a lightweight aluminum alloy sliding member excellent in wear resistance by obtaining a large oil film thickness, increasing the true contact area and reducing the surface pressure at the contact surface. The great effect that it is possible is brought about.

Further, as described in claim 5, in the production, by setting the melting temperature at 710 ° C. or higher and the casting temperature at 680 ° C. or higher, coarse primary crystal Si grains are unevenly distributed. , And a remarkable effect that a lightweight aluminum alloy sliding member excellent in both strength and abrasion resistance can be manufactured can be obtained.

[0036]

EXAMPLES Examples of the present invention will be specifically described below along with comparative examples.

In this example and comparative example, Table 1
Four types of Al-Si-based aluminum alloys having the chemical composition shown in Table 1 were used.

[0038]

[Table 1]

(Melting Casting Method) In Examples 1 and 2 and Comparative Examples 1 to 6, a die casting machine having a melting temperature, casting temperature and casting pressure shown in Table 2 and a capacity of 350 tons was used for ingots of the alloys shown in Table 1. By using and die-casting, a plate material (die-cast material) having a thickness of 15 mm was obtained.

In Comparative Example 7, an ingot of the alloy shown in Table 1 was die-cast under the conditions of melting temperature, casting temperature and die temperature of 280 to 300 ° C. shown in Table 2 to obtain a thickness of 2 mm.
A 6 mm plate material (mold casting material) was obtained.

(Average particle diameter of primary crystal Si, maximum particle diameter of primary crystal Si, average particle diameter of α excluding eutectic) Similarly, Table 2 shows the cutting positions in Table 2 for each die casting material and die casting material. The average grain size and the maximum grain size of the primary crystal Si and the average grain size of α excluding the eutectic on the surface shown in the section are shown. Here, the measurement of the particle size was performed at a magnification of 1000.
The measurement was performed by an image analyzer using an optical microscope photograph observed at a magnification of × 2.

[0042]

[Table 2]

(Method of abrasion test) Examples 1 and 2 shown in Table 2
Abrasion tests were performed on the die-cast material of Comparative Example 2 and Comparative Examples 1 to 6 and the die-cast material of Comparative Example 7 using a ring-on-plate type friction and wear tester.

At this time, a ring 1 made of chrome steel having the shape shown in FIG. 1 was used as the ring. That is, the ring 1, the outer shape _{D O} as shown in Table 3, the inner diameter _{D I,} which has dimensions of length L, a and slightly larger notches 1a depth _{C L} with a width _{W L,} the depth in the width _{W S} slightly smaller cutout 1 of the _{C S}
b is formed.

[0045]

[Table 3]

As the plate, a plate 2 having a shape shown in FIG. 2 cut out from a die casting material and a die casting material shown in Table 2 was used. That is, this plate 2
Is the length L _{A of} one side and the length L _{B of the} other side as shown in Table 4.
And has a thickness T and a diameter D at the center.
In which a round hole 2a is formed.

[0047]

[Table 4]

The sliding surface B of FIG.
It was cut out to the position shown in the section of the cut-out position in the middle, and processed so as to have the surface roughness shown in the section of the surface roughness in Table 2. The wear test conditions were a surface pressure of 10 MPa, a slip speed of 0.25 m / s, and an oil temperature of 80 ° C. The test time was a maximum of 10 hours, and the test was stopped when the amount of wear exceeded 50 μm.

After completion of the wear test, the roughness of the sliding surface of the plate test piece was measured, and the wear depth was measured.

(Fatigue Test Method) Examples 1 and 2 shown in Table 2
Fatigue test pieces having the shape shown in FIG. 3 were cut out from the die-cast material of Comparative Example 2 and Comparative Examples 1 to 6 and the die-cast material of Comparative Example 7. The fatigue test piece 3 shown in FIG. 3 has the dimensions shown in Table 5, and each of the test pieces has the surface C shown in FIG.
It was cut out to the position shown in the section of the cut-out position in the middle, and processed so as to have the surface roughness shown in the section of the surface roughness in Table 2. Then, using this test piece, by Schenk bending fatigue tester, to measure the 10 ⁷ fatigue strength at room temperature.

[0051]

[Table 5]

(Results of Wear Test) Table 6 shows the wear depth (amount of wear) of each test piece. Of these, in Example 2, as is clear from Table 2, although no primary crystal Si was observed in an optical microscope photograph at a magnification of 1000, sufficient abrasion resistance was obtained due to the fine α phase.

On the other hand, in Comparative Example 2, as is clear from Table 1, the amount of abrasion was larger than that of the Example because the content of Si was small. Further, in Comparative Example 4, the surface roughness was large, so that the primary crystal could not be used, and the amount of wear was larger than that of the example.

Furthermore, in Comparative Example 5, since the casting temperature was too low, large primary crystal Si was unevenly distributed, resulting in a larger wear amount than that of the example. Furthermore, in Comparative Example 6, since the melting temperature was too low, a large primary crystal S
i was unevenly distributed, resulting in a larger wear amount than that of the example.

[0055]

[Table 6]

(Results of Fatigue Test) Similarly, Table 6 shows the results of the fatigue test. As is clear from Table 6, Examples 1 and 2 were found to have high fatigue strength due to the fine structure. On the other hand, Comparative Example 1 showed a lower fatigue strength than that of the Example because the average grain size of primary crystal Si was large and large. In Comparative Example 3, the average grain size of primary crystal Si and the average grain size of α excluding eutectic were both large, and coarse primary crystal Si was unevenly distributed on the surface. The strength was indicated. Furthermore, Comparative Examples 5 and 6
Shows that the primary crystal Si has a large average grain size and coarse primary crystal Si is unevenly distributed, and thus has a lower fatigue strength than that of the example. Furthermore, Comparative Example 7 showed a lower fatigue strength than that of the Example because both the average grain size of the primary crystal Si and the average grain size of α excluding the eutectic were large.

[Brief description of the drawings]

FIG. 1 is a cross-sectional explanatory view ((A) of FIG. 1) and a side explanatory view ((B) of FIG. 1) of a ring-shaped test piece used in Examples and Comparative Examples of the present invention.

FIG. 2 is an explanatory front view (FIG. 2A) and an explanatory sectional view (FIG. 2B) of a plate-shaped test piece used in Examples and Comparative Examples of the present invention.

3 is a side view (FIG. 3A) and a plan view (FIG. 3B) of a fatigue test piece used in Examples and Comparative Examples of the present invention.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takaaki Inogari 1-34-1 Kambara, Kambara-cho, Anbara-gun, Shizuoka Prefecture Inside Nippon Light Metal Co., Ltd. Group Technology Center (72) Inventor Masahiko Shioda Yokohama-shi, Kanagawa 2 Takaracho, Kanagawa-ku Nissan Motor Co., Ltd. (72) Inventor Tomohiro Aoki 2nd Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Nissan Motor Co., Ltd. (72) Takao Hayashi 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa 2nd Nissan Motor Co., Ltd. (72) Inventor Hidetoshi Shiga 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa

Claims (5)

[Claims] 1. An aluminum-alloy cast aluminum alloy having an average grain size of primary Si on a sliding surface of 12 μm or less and a grain size of primary Si on a sliding surface of 35 μm or less. A sliding member made of an aluminum alloy having excellent wear resistance. 2. An aluminum-alloy cast aluminum alloy, wherein the average grain size of primary crystal Si on the sliding surface is 12 μm or less, and the average grain size of α phase excluding eutectic is 10 μm or less. A sliding member made of an aluminum alloy excellent in wear resistance, characterized in that the primary surface Si of the sliding surface has a particle diameter of 35 μm or less. 3. An Al-Si based aluminum casting alloy,
% By weight, Si: 14.0 to 17.5%, Cu: 2.0
-5.0%, Mg: 0.1-1.0%, Mn: 0.3-
0.8%, Cr: 0.05 to 0.30%, Ti: 0.0
5 to 0.20%, P: 0.003 to 0.050%, F
e: 1.5% or less, and Ca: 0.005
%. The sliding member made of an aluminum alloy having excellent wear resistance according to claim 1, wherein the sliding member is regulated to less than% and the balance substantially consists of Al. 4. The wear resistance according to claim 1, wherein at least the surface roughness of the sliding surface is 1.6 μm or less in arithmetic average roughness (Ra). Aluminum alloy sliding member. 5. A melting temperature of 710 ° C. or higher and a casting temperature of 6
The method for producing a sliding member made of an aluminum alloy having excellent wear resistance according to any one of claims 1 to 4, wherein the temperature is 80 ° C or higher.