JPH0578770A - Cast aluminum alloy having excellent wear resistance - Google Patents

Abstract

PURPOSE:To obtain a cast Al alloy having excellent meltability, castability and machinability without deteriorating wear resistance by reducing the content of Si and regulating the contents of Cu, Mg, Mn, Cr, Ti, P, Fe, B, etc. CONSTITUTION:This cast Al alloy contains, by weight, 14.0-16.0% Si, 2.0-5.0% Cu, 0.1-1.0% Mg, 0.3-0.8% Mn, 0.1-0.3% Cr, 0.05-0.20% Ti, 0.003-0.05% P, <=1.5% Fe and <0.005% Ca or further contains 0.00010.01% B and/or 0.3-3.0% Ni. The average grain size of proeutectic Si in this alloy has been regulated to 10-50mum. This alloy is used for a cylinder block, a piston, compressor parts, change gear parts, etc.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As a cylinder block for a vehicle, an aluminum alloy for casting represented by A390 has been conventionally used for the purpose of weight reduction. This aluminum alloy is
Taking advantage of its excellent wear resistance, a practical engine,
Widely used as wear resistant parts.

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

As a result, it is necessary to melt and cast at a temperature considerably higher than that of a normal alloy, which requires expensive refractory linings, of course, shortens the life of the furnace, increases fuel consumption, There is a problem of shortening the life of die casting molds. In addition, the distribution of primary crystal Si becomes non-uniform, and casting defects such as sink marks are likely to occur.

In order to solve the drawbacks of the A390 type aluminum alloy, Japanese Patent Laid-Open No. 506464107 discloses S.
It has been introduced that the i content is set to a low value of 13.5-16.0% by weight to secure the castability, and the addition of Cu, Mg, Zn and the like improves the altitude and the wear resistance.

[0006]

However, the non-uniform distribution of primary crystal Si, which is another drawback of the A390 series aluminum alloy, remains unsolved by the alloy design described in the above publication. Therefore, it is still treated as a material that is prone to casting defects and the like. In addition, non-uniformly distributed primary crystal Si
In particular, the properties of the aluminum alloy casting fluctuate between the part that is subjected to the rapid cooling effect and the part that is gradually cooled, and this causes the lack of reliability of 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 the alloy system set to wt%
By specifying the blending ratio of r, Ti, P, Fe, etc., it is an object of the present invention to achieve a uniform dispersion of fine primary crystal Si and to provide an aluminum casting alloy having excellent wear resistance and no casting defects.

[0008]

The aluminum casting alloy of the present invention has a Si: 14.0 to
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:
It is characterized in that it contains 1.5 wt% or less, the Ca content is regulated to less than 0.005 wt%, and the primary crystal Si having an average grain size of 10 to 50 μm is uniformly dispersed.

The cast aluminum 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 inventors of the present invention have found that the wear resistance, mechanical properties, physical properties, machinability, castability, etc. of Si, Cu, Mg, Mn,
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, wear resistance can be ensured as long as the primary crystal Si is finely and uniformly dispersed.

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

The addition of Cr is particularly effective for the refinement and uniform dispersion of the primary crystal Si. Cr is an element mixed in primary crystal Si. It is presumed that the presence 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 compound is crystallized, which also improves the wear resistance. In addition, the inclusion of a predetermined amount of P is also effective for refining the primary crystal Si.

The contents and actions of each alloying element will be described below. Si: An important element for improving wear resistance and elastic modulus. However, the Si content is 1
If it exceeds 6.0% by weight, the liquidus temperature of the alloy increases, the solubility, castability, etc. 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, abrasion resistance is insufficient. Therefore, in the present invention, the Si content is defined in the range of 14.0 to 16.0% by weight.

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

Cu: Exhibits the effect of strengthening the matrix, which improves the 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
Beyond that, the number of shrinkage nests increases.

Mg: An alloying element effective in increasing hardness, wear resistance, mechanical strength and the like, and these effects are obtained when Mg is contained in an amount of 0.1% by weight or more. But 1.0
If Mg is contained in excess of wt%, the toughness tends to be reduced.

Mn: An alloying element that strengthens the matrix and improves mechanical properties. Mn content is 0.3% by weight
If it is less than 1, the wear resistance tends to decrease. On the other hand, if the Mn content exceeds 0.8% by weight, the castability is deteriorated and conversely the mechanical properties are deteriorated.

Cr: An alloying element important for finely and uniformly dispersing primary crystal Si, and effectively acts to improve hardness and mechanical properties. This effect is 0.1% by weight
It becomes remarkable with the above Cr contents. However, if the Cr content exceeds 0.3% by weight, castability and mechanical properties deteriorate. In addition, a large amount of Cr content also causes coarsening of Al—Cr-based crystallized substances.

Ti: It has 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 are deteriorated.

P: With Cr, it has the function of refining and uniformly dispersing the primary crystal Si. The action given to the primary crystal Si is secured by the P content of 0.003% by weight or more. However, if the P content exceeds 0.05% by weight, castability such as molten metal flow deteriorates. Therefore, in the present invention, 0.
The P content was set in the range of 003 to 0.05% by weight.
Further, when the P content is maintained in this range, the melt flowability is improved due to the decrease in the viscosity of the molten metal, and the castability is improved.

Fe: Impurity taken into the aluminum alloy during the melting process. If a large amount of Fe is mixed in, especially in the slow cooling part, the hot spot part, etc., the Al-Fe compound, A
An l-Fe-Mn-Si-based compound or the like is generated, which causes generation of 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 specified to be 1.5% by weight or less.

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

Similar to Ca: Fe, it is an impurity mixed into the aluminum alloy from the raw material Si during the melting process. When the Ca content exceeds 0.005% by weight and increases, the internal sink mark becomes large during casting, resulting in deterioration of castability. Also, P
Inhibits the primary crystal Si refining effect. 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
At the same time, it contributes to the refinement of crystal grains. 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 alloying element for improving high temperature strength, hardness and wear resistance. These actions have a Ni content of 0.3.
It is seen in the weight% and above. However, the inclusion of a large amount of expensive Ni is not preferable because it increases the cost of the aluminum alloy. In addition, as the Ni content increases,
Corrosion resistance is also reduced. Therefore, in the present invention,
The upper limit of the Ni content is specified to be 3.0% by weight, and the action of Ni is replaced or complemented by Mn.

Grain size of primary crystal Si: In order to secure wear resistance, machinability and castability, the average grain size of primary crystal Si is 10 to 50.
It is necessary to adjust to the μm range. 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 becomes small. On the contrary, when the average grain size of the primary crystal Si exceeds 50 μm, a large primary crystal Si is present, so that the galling phenomenon, mechanical properties, machinability and the like are deteriorated.

The aluminum casting alloy of the present invention, which is alloy-designed as described above, can be manufactured into a target casting by die gravity casting, low pressure casting, sand casting, die casting, molten metal forging and the like. It is also possible to perform heat treatment such as T ₅ and T ₆ .

[0028]

EXAMPLES The present invention will be specifically described below with reference to examples. Aluminum alloys having the components and compositions shown in Table 1 were melted and cast using a boat mold held at a temperature of 350 ° C. The obtained casting was cut with a lathe, and its machinability was investigated. Further, wear resistance, solubility, castability, mechanical properties, etc. were examined, and shown in Table 2.

[0029]

[Table 1]

[0030]

[Table 2]

As for the wear resistance, a SK-4 steel was used, in which a friction speed was 0.238 m / sec, a friction distance was 6000 m, a friction load was 160 kg, and a mating material was hard-chrome plated using a frictron type friction wear tester. It was examined under wear conditions. And, wear amount of 0 to 100 mg is ◎, 100 to 30
0 mg is ○, 300-500 mg is △, 5
Those having a dose of 00 mg or more were evaluated relative to each other and shown in Table 2.

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

For the machinability test, a cemented carbide tool was used, and the cutting speed was 200 m / min, 400 m / min and 600 m / min.
3 steps, feed rate 0.05mm / revolution, 0.1mm / revolution and 0.2mm / revolution, depth of cut 0.5m
m, 1.0 mm, and 2.0 mm. Then, the wear width, the cutting resistance, and the finished surface roughness of the flank of the cutting tool when the cutting length reached 5000 m were examined, and evaluated in four levels based on the criteria shown in Table 3.

[0034]

[Table 3]

The evaluation points of the respective test items are added up, and the total evaluation points are 4 or less, ⊚, 5 to 7 points are ∘,
Relative evaluation was made with a score of 8 to 10 as Δ and a score of more than 10 as x.

As is clear from Table 2, Si, Cu, M
When the alloy components such as n and Cr are in the range specified in the present invention, good machinability is obtained in all cases. Generally speaking, the machinability is worse as the Si content is higher, and S
The machinability improves as the i content decreases. For example, in the alloy example of test number 13, the Si content is 12.0.
Since it is as low as wt%, extremely excellent machinability is shown.

However, the alloy example of Test No. 13 has the primary crystal S
As described above, the crystallization of i was hardly detected and the abrasion resistance was poor. Further, it can be seen that the smaller the amount of hard Cu, Mn, Cr-based compound or the like crystallized out, the better the machinability.

The solubility is relatively evaluated by focusing on the liquidus temperature of the aluminum alloy and taking in gas absorption at the time of melting, damage to the lining refractory, and the like.
The good ones are shown as O, the slightly bad ones as Δ, and the bad ones as X. Generally speaking, 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 hot running property deteriorates.

The castability was judged according to the evaluation criteria shown in Table 4 regarding the casting temperature, the grain size and distribution of the primary crystal Si, the hot running property and the like. The grain size and distribution of the primary crystal Si is 200
It was examined by observing the central cross section of the sample cast using an uncoated JIS No. 4 boat type held at 0 ° C.

The hot running property was examined by casting using an uncoated wedge mold held at 300 ° C. This wedge mold has a rectangular cross section with a flat cross section as shown in FIGS.
It had an inclined cavity in the side section. Then, the area of the molten metal spread in the cavity was divided by the rectangular area of FIG. The product having good hot running property has clear edges and markings on the product.

[0041]

[Table 4]

The evaluation points for each test item are added together, and the total evaluation points are 4 or less, ⊚, 5 to 7 points are ∘,
Castability was relatively evaluated by assigning 8 to 10 points as Δ and exceeding 10 points as x.

As shown in Table 2, Si, Fe,
It can be seen that good castability is obtained in the alloy examples in which the content of P and the like is within the range specified in the present invention. On the other hand, Test No. 14 having a high Si content of 19.0% by weight
In the alloy example, 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 characteristics in wear resistance, machinability, solubility and castability.
Therefore, the obtained aluminum alloy casting is used as a material exhibiting excellent characteristics as a cylinder block, a piston, a compressor part, a transmission part, and the like. Further, since the machinability is good, the processing for finishing into a required shape becomes easy.

[0045]

As described above, in the present invention, the Si content is lowered to secure the castability, and
By comprehensively controlling alloying components such as Cu, Mg, Mn, Cr, Ti, P, the 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 extended. Moreover,
When the obtained aluminum alloy casting is mechanically cut into a target shape, the life of the cutting tool is extended. In this way
Materials suitable for cylinder blocks, pistons, compressor parts, transmission parts, etc. are provided.

[Brief description of drawings]

FIG. 1 is a plan view showing a cavity of a boat mold used when determining the hot running property in an example of the present invention.

FIG. 2 is a side view of the cavity.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yamaji Kitaoka 1-34 Kambara, Kambara-cho, Anbara-gun, Shizuoka Prefecture Nichiritsu Giken Co., Ltd. (72) Inventor Yasuhiko Watanabe 3-13 Mita, Minato-ku, Tokyo No. 12 In Japan Light Metals Co., Ltd. (72) Inventor Mamoru Sashishi 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Hiroshi Kobe 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Stock In-house (72) Inventor Hiroko Watanabe 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd.

Claims (3)

[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 to 0.02% by weight, Fe: 1.5% by weight or less, and the Ca content is regulated to less than 0.005% by weight.
An aluminum casting alloy having excellent wear resistance, which has a structure in which primary crystal Si having an average grain 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 wt% is contained, the Ca content is regulated to less than 0.005 wt%, and the average particle size is 1
An aluminum casting alloy having excellent wear resistance, which has a structure in which primary crystal Si of 0 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: 0.3-3.0% by weight, Ca content: 0.
Regulated to less than 005% by weight and having an average particle size of 10 to 50
An aluminum casting alloy with excellent wear resistance, which has a structure in which μm of primary crystal Si is uniformly dispersed.