JP2709663B2 - Aluminum alloy with excellent wear resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cast aluminum alloy having excellent wear resistance used as a cylinder block or the like.

[0002]

2. Description of the Related Art Casting aluminum alloys represented by A390 have been conventionally used as cylinder blocks for vehicles in order to reduce weight. This aluminum alloy
Utilizing its excellent wear resistance, practical engine,
Widely used as wear-resistant parts.

[0003] Aluminum alloy of A390 series is Si:
16.0 to 18.0% by weight, Cu: 4.0 to 5.0% by weight, Mg: 0.45 to 0.65% by weight, Fe: less than 0.5% by weight, Mn: 0.1% by weight , Ti: less than 0.20% by weight, and a large amount of Si is added to secure the required wear resistance. However, as the Si content increases, the liquidus temperature of the aluminum alloy increases.

[0004] As a result, it is necessary to melt and cast at a temperature much higher than that of ordinary alloys, so that expensive lining refractories are required, as well as a decrease in furnace life, an increase in fuel consumption, and so on. The problem is that the life of the die-casting mold and the like is shortened. In addition, the distribution of the primary crystal Si becomes non-uniform, and casting defects such as sink marks are liable to occur.

In order to solve the disadvantage of the A390-based aluminum alloy, Japanese Patent Laid-Open Publication No.
It is introduced that the i content is set as low as 13.5 to 16.0% by weight to ensure castability, and that the addition of Cu, Mg, Zn or the like improves the altitude and wear resistance.

[0006]

However, the non-uniform distribution of primary crystal Si, which is another disadvantage of the A390-based aluminum alloy, remains unsolved even by the alloy design described in the above-mentioned publication. Therefore, it is still treated as a material in which casting defects and the like easily occur. In addition, non-uniformly distributed primary Si
In particular, the properties of the aluminum alloy casting fluctuate particularly between a portion subjected to the quenching effect and a portion to be gradually cooled, which causes a lack of reliability in the material.

The present invention has been devised to solve such a problem, and has a Si content of 14.0 to 16.0.
Cu, Mg, Mn, C in an alloy system set to
An object of the present invention is to provide an aluminum cast alloy having excellent wear resistance and no casting defects by specifying the mixing ratio of r, Ti, P, Fe, etc., to achieve uniform dispersion of fine primary crystal Si.

[0008]

The aluminum casting alloy of the present invention has an Si content of 14.0 to 14.0 in order to achieve the object.
16.0% by weight, Cu: 2.0 to 5.0% by weight, Mg:
0.1-1.0% by weight, Mn: 0.3-0.8% by weight,
Cr: 0.1 to 0.3% by weight, Ti: 0.05 to 0.2
0% by weight, P: 0.003 to 0.05% by weight, Fe:
1.5% by weight or less, the content of Ca as an impurity is regulated to less than 0.005% by weight, and the average particle diameter is 10%.
It is characterized by having a structure in which primary crystal Si of ｍ50 μm is uniformly dispersed.

The aluminum casting alloy further contains B: 0.0001 to 0.01% by weight and Ni: 0.3 to
It may contain 3.0% by weight of one or two.

[0010]

[Operation] The present inventors have developed Si, Cu, Mg, Mn, and the like for abrasion resistance, mechanical properties, physical properties, machinability, castability, and the like.
The effects of alloying elements such as Cr were examined in detail. As a result, they have found that even if the Si content is reduced to 16% by weight or less, which is the lower limit of the A390 alloy, as long as the primary crystal Si is fine and uniformly dispersed, the wear resistance can be ensured.

That is, in the aluminum casting alloy of the present invention, the Si content is 1 compared with the A390 series alloy.
Since it is set to be as low as 6.0% by weight or less, the solubility and castability are greatly improved, and the operation becomes easy. The problems of the A390 series alloy regarding the machinability, solubility, castability, etc. required for wear-resistant parts such as cylinder blocks are adjusted by adjusting the content of alloy elements such as Si, strengthening the matrix, and the like. This is solved without a decrease in wear resistance.

The addition of Cr is particularly effective for miniaturization and uniform dispersion of primary crystal Si. Cr is an element mixed in primary crystal Si. It is presumed that the mixture of Cr increases the specific gravity of primary crystal Si, and suppresses the floating of Si during casting. At the same time, a fine Al-Cr-based compound is crystallized, which also improves wear resistance. In addition, a certain amount of P is effective for miniaturization of primary crystal Si.

Hereinafter, the contents and functions of each alloy element will be described. Si: an important element for improving wear resistance and elastic modulus. However, when the Si content is 1
If the content exceeds 6.0% by weight, the liquidus temperature of the alloy increases, so that the solubility and castability deteriorate, and the dispersion of primary crystal Si tends to become non-uniform. On the other hand, if the Si content is less than 14.0% by weight, the wear resistance is insufficient. Therefore, in the present invention, the Si content is specified in the range of 14.0 to 16.0% by weight.

When the Si content is less than 16.0% by weight, the machinability of the aluminum alloy is sharply improved.
As a result, the tool life does not decrease due to the wear, and the cutting cost can be significantly reduced.

Cu: has the effect of strengthening the matrix, thereby improving wear resistance. In order to obtain such an effect, it is necessary to contain 2.0% by weight or more of Cu. However, the Cu content is 5.0% by weight.
Above, the occurrence of nests increases.

Mg: An alloy element effective for increasing hardness, wear resistance, mechanical strength, and the like, and these effects can be obtained when the content of Mg is 0.1% by weight or more. However, 1.0
When Mg is contained in excess of the weight percentage, a tendency to decrease toughness is observed.

Mn: an alloying element that strengthens the matrix and improves mechanical properties. Mn content is 0.3% by weight
If it is less than 3, the abrasion resistance tends to decrease. On the other hand, if the Mn content exceeds 0.8% by weight, the castability deteriorates, and conversely, the mechanical properties deteriorate.

Cr: An important alloying element for finely and uniformly dispersing primary crystal Si, it effectively acts to improve hardness and mechanical properties. Cr, together with the action of Ti for refining Al-Si eutectic grains, further improves the structure of the casting. Such an effect of Cr becomes remarkable at a Cr content of 0.1% by weight or more. However, when the Cr content is 0.3
If the content is more than the weight percentage, castability and mechanical properties decrease.
Further, a large amount of Cr content causes coarsening of the Al-Cr-based crystallized product.

Ti: exhibits an effect of improving mechanical properties and is also effective in homogenizing the structure. In order to obtain these effects, it is necessary to contain 0.05% by weight or more of Ti. However, if the Ti content exceeds 0.20% by weight, the mechanical properties deteriorate.

P: It has the function of making the primary crystal Si finer together with Cr and uniformly dispersing it. This effect on the primary crystal Si is ensured with a P content of 0.003% by weight or more. However, if the P content exceeds 0.05% by weight, castability such as hot metal flow deteriorates. Therefore, in the present invention, the 0.1.
The P content was set in the range of 003 to 0.05% by weight.
When the P content is maintained in this range, the flowability of the molten metal is improved due to the decrease in the viscosity of the molten metal, and the castability is improved.

Fe: an impurity taken into the aluminum alloy from a raw material or the like during the melting process. If a large amount of Fe is mixed in, the Al-Fe
-Based compounds, Al-Fe-Mn-Si-based compounds, and the like are generated, and cause microporosity. As a result, the toughness and strength of the obtained aluminum alloy are reduced.
In order to prevent this drawback, in the present invention, the Fe content is regulated to 1.5% by weight or less.

However, when an aluminum alloy is used for die casting, Fe is an effective alloy element in preventing the high-temperature alloy from burning on the inner surface of the mold. Therefore, when used as a die-casting casting, 0.1%
It is preferable to secure an Fe content of 1% by weight or more.

Ca: Like Fe, it is an impurity mixed into the aluminum alloy from the raw material Si during the melting process. If the Ca content exceeds 0.005% by weight, the internal shrinkage increases at the time of casting, which causes a decrease in castability. Also, P
Inhibits the primary crystal Si refining action. Therefore, in the present invention, the Ca content is specified to be 0.005% by weight or less.

B: B added as an optional component is Ti
In addition, it contributes to making the crystal grains fine. This effect is seen at a B content of 0.0001% by weight. But,
Since a large amount of B content causes embrittlement of the aluminum alloy,
The upper limit was set to 0.01% by weight.

Ni: Ni added as an optional component is
It is an effective alloy element for improving high-temperature strength and improving hardness and wear resistance. These effects are caused by the Ni content of 0.3.
It is found at weight percent and above. However, including a large amount of expensive Ni is not preferable because it increases the cost of the aluminum alloy. Also, with the increase in Ni content,
There is also a decrease in corrosion resistance. Therefore, in the present invention,
The upper limit of the Ni content is set to 3.0% by weight, and the action of Ni is replaced or supplemented by Mn.

Particle diameter of primary crystal Si: In order to secure wear resistance, machinability and castability, the average particle diameter of primary crystal Si is 10 to 50.
It is necessary to adjust to the range of μm. When the average grain size of the primary crystal Si is less than 10 μm, the effect of the primary crystal Si for improving the wear resistance is reduced. Conversely, when the average grain size of the primary crystal Si exceeds 50 μm, the presence of large primary crystal Si causes a reduction in galling, mechanical properties, and machinability.

The aluminum casting alloy of the present invention thus designed can be manufactured into a target casting by gravity casting, low pressure casting, sand casting, die casting, molten metal forging, or the like. In addition, heat treatment such as T ₅ and T ₆ can be performed.

[0028]

The present invention will be described below in detail with reference to examples. An aluminum alloy having the components and compositions shown in Table 1 was melted and cast using a boat mold maintained at a temperature of 350 ° C. The obtained casting was cut with a lathe and its cutting property was investigated. Further, wear resistance, solubility, castability, mechanical properties and the like were examined, and these are summarized in Table 2.

[0029]

[Table 1]

[0030]

[Table 2]

Abrasion resistance was measured using a Frictron type friction and wear tester. The friction speed was 0.238 m / sec, the friction distance was 6000 m, the friction load was 160 kg, and the mating material was hard chromium plated SK-4 steel. It was examined under abrasion conditions. ◎, 100 to 30 mg with a wear amount of 0 to 100 mg
0 mg: ○, 300-500 mg: Δ, 5
Those having a value of 00 mg or more were evaluated as x, and the results are shown in Table 2.

As is evident from Table 2, alloys containing Si, Cu, Mn, Cr, etc. within the range specified in the present invention exhibit excellent wear resistance with a wear amount of 100 mg or less. You can see that On the other hand, for example, in the alloys of Test Nos. 11 and 13, since the Si content is as low as 13.0% by weight and 12.0% by weight, respectively, the crystallization amount of primary Si is small and the wear resistance is low. Is getting worse.

In the machinability test, a cemented carbide tool was used, and the cutting speed was set to 200 m / min, 400 m / min and 600 m / min.
Step, feed rate: 0.05 mm / rotation, 0.1 mm / rotation, and 0.2 mm / rotation, 3 steps, cutting depth: 0.5 m
m, 1.0 mm and 2.0 mm. The flank wear width, cutting resistance, and finished surface roughness of the flank of the cutting tool when the cutting length reached 5,000 m were examined, and evaluated in four steps based on the criteria shown in Table 3.

[0034]

[Table 3]

The evaluation points for each test item were summed up, and a total evaluation point of 4 points or less was evaluated as ◎, 5-7 points as ○,
8 to 10 points were evaluated as Δ, and those exceeding 10 points were evaluated as ×.

As is clear from Table 2, Si, Cu, M
When the alloy components such as n and Cr are in the ranges specified in the present invention, good cutting properties are obtained in each case. Generally speaking, the machinability is worse as the Si content is higher.
As the i content decreases, the machinability improves. For example, in the alloy example of test number 13, the Si content is 12.0
Since it is as low as% by weight, extremely excellent machinability is shown.

However, the alloy example of Test No. 13 shows that the primary crystal S
As described above, the crystallization of i was hardly detected and the wear resistance was poor. Furthermore, it can be seen that the harder the crystallization amount of the hard Cu, Mn, Cr-based compound, etc., the better the machinability.

The solubility was evaluated relative to the liquidus temperature of the aluminum alloy, taking into account gas absorption during melting and damage to the lining refractory, etc.
Good was indicated by ，, slightly poor by Δ, and bad by X. Generally, when the Si content increases by 1% by weight, the liquidus temperature of the aluminum alloy increases by about 10 ° C. P is also an element that raises the liquidus temperature,
When the P content exceeds 0.05% by weight, the viscosity of the molten metal increases, and the meltability decreases.

The castability was determined based on the evaluation criteria shown in Table 4 with respect to the casting temperature, the particle size and distribution of primary crystal Si, the run-off property, and the like. In addition, the particle size and distribution of primary crystal Si were determined at a temperature of 200
The test was conducted by observing a cross section at the center of a sample cast using a JIS No. 4 boat type without coating kept at ° C.

The meltability was examined by casting using an uncoated wedge mold maintained at 300 ° C. This wedge mold has a rectangular shape with a flat cross section shown in FIGS.
It had an inclined cavity in the side section. Then, the area ratio of the molten metal spread in the cavity was divided by the rectangular area in FIG. Those with good run-off properties have clear edges and marks on the product.

[0041]

[Table 4]

The evaluation points for each test item were summed up, and 合計 indicates that the total evaluation point was 4 points or less, ○ indicates that the total evaluation point was 5 to 7, and
The castability was relatively evaluated by setting 8 to 10 points to Δ and exceeding 10 points to X.

As shown in Table 2, Si, Fe,
It can be seen that good castability was obtained in alloy examples in which the content of P and the like was within the range specified in the present invention. On the other hand, Test No. 14 having a large Si content of 19.0% by weight
In the case of the alloy No., the castable temperature was as high as 780 ° C., and the castability was poor. And many casting defects were detected.

As is clear from the above description, the aluminum alloy according to the present invention exhibits excellent properties in all of wear resistance, machinability, dissolvability and castability.
Therefore, the obtained aluminum alloy casting is used as a material exhibiting excellent characteristics as a cylinder block, a piston, a compressor component, a transmission component and the like. In addition, since the machinability is good, it is easy to finish the required shape.

[0045]

As described above, according to the present invention, the castability is ensured by reducing the Si content,
By comprehensively controlling alloy components such as Cu, Mg, Mn, Cr, Ti, and P, solubility, castability, machinability, etc. are improved without impairing wear resistance. Therefore, damage to the lining refractory of the melting furnace can be reduced, and the life of the mold is prolonged. Moreover,
When the obtained aluminum alloy casting is machine-cut into a target shape, the life of the cutting tool is prolonged. In this way,
Materials suitable for cylinder blocks, pistons, compressor parts, transmission parts, and the like are provided.

[Brief description of the drawings]

FIG. 1 is a plan view showing a cavity of a boat mold used for judging the meltability in an embodiment of the present invention.

FIG. 2 is a side view of the cavity.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yamaharu Kitaoka 1-34-1 Kambara, Kambara-cho, Anbara-gun, Shizuoka Prefecture Inside Nikkei Giken Co., Ltd. (72) Inventor Yasuhiko Watanabe 3--13 Mita, Minato-ku, Tokyo No. 12 Nippon Light Metal Co., Ltd. (72) Inventor Mamoru Sashishi, Kanagawa Prefecture, Kanagawa Prefecture, 2 Takaracho, Nissan Motor Co., Ltd. Inside (72) Inventor Hiroji Watanabe 2 Nissan Motor Co., Ltd., 2 Takara-cho, Kanagawa-ku, Yokohama-shi, Kanagawa (56) References JP-A-1-298131 (JP, A) JP-A-1-319646 (JP) JP-A-3-170634 (JP, A) JP-A-1-180938 (JP, A) JP-A-2-115338 (JP, A)

Claims (4)

(57) [Claims] 1. Si: 14.0 to 16.0% by weight, C
u: 2.0 to 5.0% by weight, Mg: 0.1 to 1.0% by weight, Mn: 0.3 to 0.8% by weight, Cr: 0.1 to 0.
3% by weight, Ti: 0.05 to 0.20% by weight, P: 0.
003-0.05% by weight, Fe: 1.5% by weight or less, the balance has a composition of Al and unavoidable impurities, the Ca content as impurities is regulated to less than 0.005% by weight, and An aluminum cast alloy having excellent wear resistance, characterized by having a structure in which primary crystal Si having an average particle size of 10 to 50 µm is uniformly dispersed. 2. Si: 14.0 to 16.0% by weight, C
u: 2.0 to 5.0% by weight, Mg: 0.1 to 1.0% by weight, Mn: 0.3 to 0.8% by weight, Cr: 0.1 to 0.
3% by weight, Ti: 0.05 to 0.20% by weight, P: 0.
003 to 0.05% by weight, Fe: 1.5% by weight or less,
B: 0.0001 to 0.01% by weight, the balance being A
l and the composition of unavoidable impurities,
An aluminum cast alloy excellent in wear resistance, characterized in that the content of a is regulated to less than 0.005% by weight and that the primary crystal Si having an average particle size of 10 to 50 µm is uniformly dispersed. 3. Si: 14.0 to 16.0% by weight, C:
u: 2.0 to 5.0% by weight, Mg: 0.1 to 1.0% by weight, Mn: 0.3 to 0.8% by weight, Cr: 0.1 to 0.
3% by weight, Ti: 0.05 to 0.20% by weight, P: 0.
003 to 0.05% by weight, Fe: 1.5% by weight or less, N
i: 0.3 to 3.0% by weight, with the balance being Al and
It has a composition of unavoidable impurities, the content of Ca as impurities is regulated to less than 0.005% by weight, and the average particle diameter is 10%.
An aluminum casting alloy having excellent wear resistance, characterized by having a structure in which primary crystal Si of ５０50 μm is uniformly dispersed. 4. Si: 14.0 to 16.0% by weight, C
u: 2.0 to 5.0% by weight, Mg: 0.1 to 1.0% by weight
%, Mn: 0.3 to 0.8% by weight, Cr: 0.1 to 0.
3% by weight, Ti: 0.05 to 0.20% by weight, P: 0.
003 to 0.05% by weight, Fe: 1.5% by weight or less, N
i: 0.3 to 3.0% by weight, B: 0.0001 to 0.0
1% by weight, with the balance being Al and unavoidable impurities
With a Ca content of 0.005% by weight as an impurity
% And a primary crystal having an average particle size of 10 to 50 μm
Characterized by having a structure in which Si is uniformly dispersed
Aluminum cast alloy with excellent wear resistance.