JP2923578B2 - Wear resistant aluminum alloy - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a wear-resistant aluminum alloy suitable for use in a vehicle part such as an engine, and particularly to a wear-resistant aluminum alloy for casting suitable for the above-mentioned use.

[Related Art] In recent years, in various vehicles such as automobiles, the demand for lighter weight has been further increased in terms of improving fuel efficiency, and as a result, aluminum parts of engine parts, undercarriage, drive trains and other vehicle parts have been developed. I have.

Of the above vehicle parts, the use of aluminum for engine parts such as cylinder blocks and pistons contributes most to the weight reduction of vehicles, but these sliding members have high temperature strength, wear resistance, low coefficient of thermal expansion, heat fatigue, etc. Since excellent properties at high temperatures are required, the alloys that have been practically used have many problems and cannot satisfy the required properties sufficiently. Therefore, aluminum is completely aluminized except for some vehicles. It is not at present.

Recently, the use environment of vehicle parts, especially engine-related parts, has become more severe due to the increase in the output of engines and the spread of turbo vehicles, and the characteristics required for sliding members have become more severe accordingly. .

Conventionally, sliding members for engines include hypereutectic Al-Si alloy, ASTM-390 alloy, or eutectic Al-Si alloy JIS-AC8A
(JIS aluminum alloy casting) and the like have been used.

Among these, hypereutectic Al-Si alloy is, for example, Si12 ~ 20wt
%, Cu4 ~ 5wt%, balance Al, used in the manufacture of cylinders, etc., JIS-AC of eutectic Al-Si alloy
8A alloy is, for example, Si11-13wt%, Cu0.8-1.3wt%, Ni0.
8 to 1.5 wt%, Mg 0.7 to 1.3 wt%, Zn 0.15 wt% or less, and the rest of the composition is Al, and because of its excellent wear resistance, it is widely used with the above hypereutectic Al-Si alloy. Have been.

In addition, ASTM-390 alloy has excellent wear resistance due to the dispersion of primary crystal Si, and also has a characteristic of a low coefficient of thermal expansion, and thus has been used as a linerless cylinder block material. However, since this alloy contains a lot of brittle and high-hardness Si, it has difficulties in machinability and attack properties (abrasion of the counterpart material), and because the α phase is coarse, there is also a problem in scuffing properties (seizure). There is.

In the casting operation, it is necessary to increase the casting temperature in order to make the primary crystal Si fine, and there is a problem that the life of the mold or the crucible is shortened by the high casting temperature. Furthermore, in casting under a high pressure such as die casting, segregation of primary crystal Si is likely to occur, so that Si may be unevenly distributed on the sliding surface, and there is still a problem in uniformity.

[Problems to be solved by the invention]

As described above, conventional wear-resistant alloys have the disadvantage that any of wear resistance or castability, attackability, and machinability is inferior. Therefore, when used for sliding members such as cylinder blocks and pistons. Has a problem that its use is restricted.

SUMMARY OF THE INVENTION An object of the present invention is to provide a wear-resistant aluminum alloy having sufficient wear resistance and attack property and excellent machinability.

Further, the present invention, without adding Si up to the hypereutectic region,
An object of the present invention is to obtain a wear-resistant aluminum alloy having excellent machinability by reducing the amount of addition.

An object of the present invention is to provide an aluminum alloy for casting having sufficient wear resistance that can be used for sliding members such as pistons and cylinder liners.

[Means for solving the problem]

The present invention has achieved the above object by the following constitutions.

(1) Mg 5.0-8.0 wt%, Ni 3.5-6.0 wt%, Si 3.0-5.0 wt%
%, Cu 1.0 ~ 4.0wt%, Mn0.5 ~ 2.5wt%, and Fe0.5 ~ 2.0w
t <%, Sn <0.5wt%, Zn <0.5wt
%, With the balance being Al.

(2) As a contained element, Ti-0.01 to 0.3 wt%, B0.001
2. A wear-resistant aluminum alloy according to claim 1, which contains at least one of 0.1% by weight.

The present invention relates to Mg 5.0 to 8.0 wt%, Ni 3.5 to 6.0 wt%, Si 3.0
By adding about 5.0 wt% to aluminum to crystallize fine Al ₃ Ni and Mg ₂ Si on one surface, sufficient wear resistance and attack properties can be obtained.
It is no longer necessary to increase the amount of Si used in conventional alloys to the hypereutectic region.

Next, the reasons for limiting the composition of each component in the alloy of the present invention will be described.

The addition of Mg has the effect of strengthening the matrix by solid solution, increasing the hardness and tensile strength, and increasing the attack and wear resistance by forming Si and fine Mg ₂ Si.
If the content of Mg is less than 5.0 wt%, the above effect is insufficient, and if it exceeds 8.0 wt%, ductility, toughness, and castability are reduced. Therefore, the content of Mg should be in the range of 5.0 to 8.0 wt%. If the content exceeds 6.0 wt%, the α phase becomes finer, so that the content is preferably in the range of 6.0 to 8.0 wt%.

Addition of Ni has the effect of forming fine Al ₃ Ni with Al and forming an Al-Ni-Cu-based compound with Cu to enhance tensile strength, hardness, attack and wear resistance. is there. If the content of Ni is less than 3.5 wt%, the effect is insufficient, and 6.0 wt%.
When it exceeds, a coarse needle compound of Al-Fe-Ni system is formed,
In addition, Al ₃ Ni is coarsened, and toughness and ductility are significantly reduced. In addition, it is necessary to add Ni in the range of 3.5 to 6.0 wt% because the wear resistance is lowered due to the decrease in the attack property and the liquidus temperature rises and the castability is lowered. .

Addition of Si tends to improve castability and lower the coefficient of thermal expansion. In addition, it forms Mg and fine Mg ₂ Si,
Improves attack and wear resistance. Further, there is an effect of making Al ₃ Ni finer.

If the content is less than 3.5 wt%, the above effect is insufficient. If the content exceeds 5.0 wt%, the hardness, wear resistance, and tensile strength will be reduced. Therefore, Si should be added in the range of 3.0 to 5.0 wt%. is necessary.

Addition of Cu improves the hardness and abrasion resistance by dissolving in the matrix similarly to Mg. Further, an Al-Ni-Cu-based compound and an Al-Ni-Si-Mn-Fe-based compound are formed, which has the effect of improving wear resistance. If it is less than 1.0 wt%, the effect is insufficient, and if it exceeds 4.0 wt%, the α phase and Al-Ni-S
Cu must be added in the range of 1.0 to 4.0 wt-% because the i-Mn-Fe-based compound becomes coarse and the wear resistance and tensile strength decrease.

The addition of Mn strengthens the matrix by solid solution like Mg and Cu, forms Fe and Al-Fe-Mn-based compounds,
It has the effect of increasing hardness, tensile strength and wear resistance. 0.5wt
If it is less than 2.5% by weight, the effect is insufficient. If it exceeds 2.5% by weight, the Al—Fe—Mn-based compound becomes coarse and the attack property is lowered, so that the wear resistance is lowered. Mn for these reasons
Must be added in the range of 0.5 to 2.5% by weight.

Addition of Fe forms Mn and an Al-Fe-Mn-based compound, and has the effects of improving hardness and wear resistance and preventing seizure. 0.5w
If the content is less than t%, the above effect is insufficient. If the content exceeds 2.0% by weight, the Al—Fe—Mn-based compound becomes coarse, resulting in a decrease in tensile strength and a decrease in attack, resulting in a decrease in wear resistance. I do. For these reasons, Fe is added in the range of 0.5 to 2.0 wt%.

The properties of the alloy of the present invention can be improved by adding Ti, B and Be in addition to the above-described elements.

The addition of Ti and B significantly promotes grain refinement. Ti
If the content is less than 0.01% by weight and B is less than 0.001% by weight, the above effect is insufficient. If the content exceeds 0.3% by weight and 0.1% by weight of B, a harmful compound is formed and the toughness is reduced.

Be is known as an element that suppresses the oxidative consumption of Mg,
It is desirable to add in the range of 0.001 to 0.005 wt%.

These additions of Ti and B may be Ti or B alone,
A combination of Ti and B may be used. Therefore, Ti0.01 ~ 0.3wt
%, B0.001 ~ 0.1wt%, or Ti0.01 ~ 0.3wt% and B0.0
It can contain from 01 to 0.1 wt%.

When adding Be as described above, Ti 0.01 to 0.3 wt
% And Be0.001 ~ 0.005wt%, B0.001 ~ 0.1wt% and Be0.001 ~
0.005wt% or Ti0.01 ~ 0.3wt% and B0.001 ~ 0.1wt% and B
e 0.001 to 0.005 wt%.

〔Example〕

Hereinafter, the present invention will be described specifically with reference to examples. However, the present invention is not limited to only these examples.

Example A molten alloy having a composition shown in Table 1 was cast using a 90-ton die casting machine at a casting temperature of 680 to 700 ° C, a mold temperature of 110 to 114 ° C,
Under the conditions of an injection speed of 1.8 to 1.9 m / sec, a casting pressure of 760 kg / cm ² , and a curing time of 5 to 6 seconds, a test piece having a shape shown in FIGS. 4a and 4b was cast. did. other
Cast using ASTM-390 alloy (casting temperature 700-720 ° C) (hereinafter referred to as “390 alloy”) under the same conditions as above and sample
No. 17 was used as a sample of Reference Example. FIG. 4a is a plan view of the tensile test piece A, and FIG. 4b is a plan view of the wear test piece B. Tensile test piece A has a of 120 mm and b has 6
The wear test piece B has a length (d) of 145 mm, a width (e) of 20 mm, and a thickness of 10 mm.
It has a rectangular shape of the size of

The following tests were performed using the above sample Nos. 1 to 17. The test results are shown in Tables 2 and 3, and in FIGS.
Shown in the figure.

(1) Tensile test Using samples No. 1 to 17 in the form of a tensile test piece shown in FIG.
A tensile test was performed at room temperature in an as-cast state.

(2) Hardness Test A hardness test was performed on an as-cast Rockwell B scale using samples No. 1 to 17 in the form of abrasion test pieces shown in FIG. 4b.

(3) Abrasion test An abrasion test was performed using an Ogoshi type abrasion tester using the sample Nos. 1 to 17 in the form of abrasion test pieces shown in FIG. 4b. The test conditions were a final load of 2.1 kg, a wear distance of 100 m, and a mating material FC25.

(4) Observation of Metal Structure The metal structures of the alloys of samples No. 1 and No. 17 which were die-cast in the shape of the tensile test piece shown in FIG. 4a were observed. A 0.5 wt% hydrofluoric acid aqueous solution was used for the corrosion treatment.

FIG. 1 shows No. 1 and No. 4 of two examples of the alloy of the present invention and FIG.
9 is a diagram illustrating the relationship between the specific wear amount and the friction speed of No. 17 of the 390 alloy. FIG. 2 shows a sample N of the alloy of the present invention.
o.1 is a micrograph (× 1000) of the metal structure, and FIG. 3 is a micrograph (× 1000) of the metal structure of the ASTM-390 alloy (sample No. 17).

As shown in Table 2, the alloy of the present invention has a tensile strength of 23.0 to 2
6.9 (kgf / mm ² ), 0.2% proof stress 21.8 to 26.0 (kgf / mm ² ), hardness 72.4 to 80.9 (HRB). Tensile strength is equal to or higher than that of 390 alloy in Reference Example. Yes, the 0.2% proof stress and hardness are clearly superior. As for the wear resistance, as is apparent from the specific wear amounts shown in Table 3 and FIG. 1, excellent results were obtained for the 390 alloy or more of Reference Example.

The metal structure of the alloy of the present invention is composed of fine Al ₃ Ni, Mg ₂ Si, an Al—Fe—Mn compound, a small amount of a complex compound, and an α phase as shown in the photograph of FIG. Al ₃ Ni is strongly corroded by hydrofluoric acid and has a black color, and its shape is a strip. Mg ₂ Si
Also, it is corroded by hydrofluoric acid and has a gray color, and the shape is linear and clinging. The Al-Fe-Mn-based compound is also strongly corroded by hydrofluoric acid and has a black color, and has a polygonal shape.

These compounds improve hardness and tensile strength. Further, since it is formed finely, it is excellent in attack property as compared with primary crystal Si in a hypereutectic Al-Si alloy.

〔The invention's effect〕

The aluminum alloy of the present invention is superior in wear resistance, 0.2% proof stress and hardness to conventional 390 alloy, has a tensile strength equal to or higher than that of ASTM-390 alloy, and has a high elastic modulus. For this reason, the aluminum alloy of the present invention has excellent attack properties. Further, since this alloy does not require refinement of primary crystal Si unlike the 390 alloy, it is not necessary to increase the casting temperature. Furthermore, since this alloy has good castability and has the above-mentioned excellent hardness and wear resistance in an as-cast state,
Shows high performance when used for sliding parts such as cylinder liners. For this reason, this alloy can be used for various applications.

[Brief description of the drawings]

FIG. 1 is a graph showing the results of a wear test of the alloy of the present invention, FIG. 2 is a micrograph of the metal structure of the alloy of the present invention, and FIG. 3 is a micrograph of the metal structure of the ASTM-390 alloy. FIG. 4a is a plan view of the tensile test piece A, and FIG.
FIG. 4b is a plan view of the wear test piece B. Explanation of symbols A: tensile test specimen B: wear test specimen

Claims (2)

(57) [Claims] (1) Mg: 5.0 to 8.0 wt%, Ni: 3.5 to 6.0 wt%, Si3.0
~ 5.0wt%, Cu1.0 ~ 4.0wt%, Mn0.5 ~ 2.5wt%, and Fe
0.5 ~ 2.0wt%, Sn <0.5wt%, Z
A wear-resistant aluminum alloy containing n <0.5 wt% and the balance being Al. 2. The composition further comprises Ti 0.01 to 0.3 wt%, B
2. A wear-resistant aluminum alloy according to claim 1, which contains at least one of 0.001 to 0.1 wt%.