JP2001123239A - High strength aluminum alloy for casting and aluminum alloy casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a high toughness aluminum alloy casting capable of substituting for AC4CH, satisfying cost effectiveness as well as castability and moreover having tensile strength of >=380 Mpa, elongation of >=9%, 0.2% proof stress of 200 Mpa and impact value of >=90 kJ/m2. SOLUTION: This alloy casting has a composition containing 3.5 to 4.3% Cu, 5.0 to 7.5% Si, 0.10 to 0.25% Mg, <=0.2% Fe and <=0.0003% P, and the balance Al with inevitable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to tensile strength and elongation.
The present invention relates to a high-strength aluminum alloy for casting which has an excellent impact value, and further to a high-strength aluminum alloy for casting which has a beautiful surface treatment finish and a high-strength aluminum alloy casting using the alloy.

[0002]

2. Description of the Related Art Aluminum alloys are widely used as constituent materials in automobiles, industrial machines, aircraft, home appliances and various other fields. One of them is the field of aluminum casting alloys, and a typical example thereof is an aluminum casting alloy represented by AC4CH. This Al
BACKGROUND ART Cast alloys are used in applications such as automobile vehicles, overhead wire fittings, hydraulic components, and other important security components requiring mechanical properties.

[0003] However, the T6 treated material of this alloy casting has a drawback of high elongation but low tensile strength, 0.2% proof stress and impact value. Table 1 below shows general mechanical properties of the AC4CH-T6 treated material, and Table 2 shows components of AC4CH.

[0004]

[Table 1]

[0005]

[Table 2]

[0006]

SUMMARY OF THE INVENTION
1, castability be those obtained instead AC4CH also satisfied than the original economy, moreover tensile strength of more than 380 MPa, elongation of 9% or more, 0.2% proof stress is 200 MPa, impact value 90 kJ / m ² or more A second object is to develop a high-toughness aluminum alloy casting, and secondly to develop a high-strength aluminum alloy for casting that satisfies the above-mentioned conditions and is also excellent in appearance when subjected to surface treatment.

[0007]

The high-strength casting aluminum alloy for castings according to claim 1 (first embodiment) has a Cu: 3.5
~ 4.3%, Si: 5.0 ~ 7.5%, Mg: 0.10 ~ 0.25%, Fe≤0.2%,
P ≦ 0.0003%, and the balance consists of Al and unavoidable impurities. ”

[0008] Since the P of this alloy is very low, that is, 0.0003% or less, the metal structure of the T6 treated material of the cast material is usually P-containing material (P:
0.0004% to 0.0030% Eutectic Si is finer than that of Fig. 1-No.59 Normal P content). As a result, it is more satisfactory in terms of castability and economy than conventional AC4CH materials, and satisfies competitiveness. While the tensile strength is more than 380MPa, elongation is more than 9%, 0.2%
Excellent mechanical conditions with a proof stress of 200 MPa and an impact value of 90 kJ / m ² or more could be satisfied. (See FIG. 1-No. 47, low P) The content ranges of basic components such as Cu, Si, Mg, and Fe will be described later based on experimental data of Examples and Comparative Examples.

The high-strength aluminum alloy for casting according to the second aspect of the present invention (second embodiment) is as follows: "Cu: 3.5 to 4.3%, Si: 5.0%".
~ 7.5%, Mg: 0.10 ~ 0.25%, Fe≤0.2%, P: 0.0004 ~ 0.0
030%, Sb: 0.05-0.2%, with the balance being Al and unavoidable impurities. "

This alloy is usually a P-containing material (P: 0.0004 to 0.003)
0% Sb: 0.05-0.2%
The metal structure of the T6 treated material of the cast material despite the fact that it is usually a P-containing material due to the presence of a small amount of Sb
(Refer to Fig. 1-No.62 Normal P content) can make eutectic Si finer than the normal P-containing material to which Sb is not added. 38 tensile strength while satisfying competitiveness in terms of castability and economy
Excellent mechanical conditions of 0 MPa or more, elongation of 9% or more, 0.2% proof stress of 200 MPa, and impact value of 90 kJ / m ² or more could be satisfied.

The high-strength casting aluminum alloy for casting according to claim 3 (third embodiment) has a composition of “Cu: 3.5-4.3%, Si: 5.0-
7.5%, Mg: 0.10 to 0.25%, Fe ≦ 0.2%, P: 0.0004 to 0.003
0%, Sr: 0.005 to 0.030%, and the balance consists of Al and unavoidable impurities. "

This alloy is usually a P-containing material (P: 0.0004 to 0.003)
0% Sr: 0.005 to 0.03
0%, usually P due to the presence of slight Sr
Despite the inclusion, the metal structure of the cast T6 treated material (see Fig. 1-No.60 Sr) makes the eutectic Si finer than the normal P-containing material without Sr added. As a result, the tensile strength is more than 380MPa, the elongation is more than 9%, the 0.2% proof stress is 200MPa, and the impact is higher than the conventional AC4CH material while satisfying the competitiveness with sufficient castability and economy. Value is 90k
Excellent mechanical conditions of J / m ² or more could be satisfied.

[0013] Claim 4 is a high-strength aluminum alloy for casting according to any one of claims 1 to 3, to which Ti is added, wherein "the amount of Ti added is 0.05 to 0.35%". And "Claim 5" is obtained by adding Ti and B to the aluminum alloy for high-strength casting according to any one of claims 1 to 3, wherein "the addition amount of Ti is 0.05 to 0.35% and the addition amount of B is 0.003
% Or less ".

According to this, by adding a small amount of Ti, Ti and B, it is possible to achieve a finer crystal grain, although the improvement of the impact resistance is not expected, and the finish of the surface treatment is improved. In this case, it is possible to further refine the crystal grains by adding B to Ti rather than adding only Ti. (Figure 1
4 is a photograph of the metallographic structure used as a drawing. ) In addition, tensile strength and 0.2% proof stress improve with refinement of crystal grains.

[0015] Claim 6 relates to the heat treatment of the alloy according to claims 1 to 5, characterized in that "the alloy according to claims 1 to 5 is cast and then subjected to T6 treatment".

In the alloy of the present invention, the tensile strength and elongation in the as-cast state are not much different from those of the conventional AC4CH material, but the tensile strength is improved by making eutectic Si finer and granulated by performing T6 treatment. 380MPa or more, elongation 9% or more, 0.2% proof stress 200
MPa and impact value of 90 kJ / m ² or more.

[0017]

Embodiments of the present invention will be described below with reference to Examples (Sample No. 4).
7,53,63,51,54,55,60,62,57,58) and Comparative Example (Sample Nos. 49,4
6, 48, 44, 43, 50, 52, 56, 59). Table 3 shows a component table and mechanical properties of Examples of the present invention and Comparative Examples thereof.

[0018]

[Table 3]

Example 1 of a high-strength casting aluminum alloy to which the present invention is applied (Sample Nos. 47, 53, 63, 51, 54, 55)
The micrograph (see FIG. 1 No. 47 low P) has the following composition:

Cu: 3.5 to 4.3%, Si: 5.0 to 7.5%, Mg: 0.10 to
0.25%, Fe ≦ 0.2%, P ≦ 0.0003%, balance: Al and unavoidable impurities The characteristic feature here is that the P content is less than 0.0003% and smaller than the usual P content (0.0004 to 0.0030%). is there. When the P content is high, the eutectic Si after T6 treatment is elongated and large, which causes a notch effect, which causes the mechanical properties, particularly the impact resistance, to decrease. By reducing the content of P to 0.0003% or less, which is lower than the usual content of P, eutectic Si after T6 treatment can be made fine and spherical, and the mechanical properties, especially the impact resistance, can be improved. done.

The second embodiment of the high-strength casting aluminum alloy of the present invention (see FIG. 1, sample No. 62Sb) has the following composition.

Cu: 3.5-4.3%, Si: 5.0-7.5%, Mg: 0.10-
0.25%, Fe ≦ 0.2%, P: 0.0004 ~ 0.0030%, Sb: 0.05 ~
0.2% balance: Al and unavoidable impurities The characteristic feature here is that the content of P is 0.0004 to 0.0030%, which is the content of ordinary materials,
Is that a small amount of 0.05 to 0.2% is added. The metal structure of the T6 treated material of the ordinary P-containing cast material with Sb added is Sb
Eutectic Si could be made finer than in the case where no was added.

The third embodiment of the high-strength casting aluminum alloy of the present invention (see FIG. 1, sample No. 60Sr) has the following composition.

Cu: 3.5 to 4.3%, Si: 5.0 to 7.5%, Mg: 0.10 to
0.25%, Fe ≦ 0.2%, P: 0.0004-0.0030%, Sr: 0.005
-0.030% Remainder: Al and unavoidable impurities The characteristic feature is that the P content is 0.0004-0.0030% as in the case of the ordinary material, as in the second embodiment, but the Sr content is as small as 0.005-0.030%. That is the point. The metal structure of the T6 treated material of the ordinary P-containing cast material to which Sb was added was able to make eutectic Si finer than in the case where Sb was not added.

The fourth embodiment (sample No. 57) of the present invention is obtained by adding 0.05 to 0.35% of Ti to the alloys shown in the first to third embodiments. No. 58) was obtained by adding 0.05 to 0.35% of Ti:
0.003% or less is added. Although the addition of a small amount of Ti, Ti and B does not contribute to the improvement of the impact resistance value,
The crystal grains of the treatment material can be made finer, which contributes to the improvement of the surface treatment finish.

The alloys shown in the first to fifth embodiments have a tensile strength and an elongation that are substantially the same as those of the conventional AC4CH material in an as-cast state, and are usually subjected to a heat treatment called T6 treatment. The processing conditions of T6 treatment are as follows: solution temperature is 500-520 ° C, solution time is 4-12 hours, aging temperature is 140-180 ° C,
The aging time is 2 to 7 hours. The alloy of the present invention achieved a tensile strength of 380 MPa or more, an elongation of 9% or more, a 0.2% proof stress of 200 MPa, and an impact value of 90 kJ / m ² or more by performing T6 treatment.

Next, the alloy of the present invention and a comparative example will be described. Example 1 (Sample No. 47, 53, 63, 51, 54, 55) and Comparative Example (Sample No.
o. 49, 46, 48, 44, 43, 50, 52, 56), all had low P of 0.0003%, and the effects were examined by changing the contents of Cu, Si, Mg, and Fe. In the comparative example (sample number No. 59), the contents of Cu, Si, Mg, and Fe were set in the specified ranges, and P was increased to 0.0007%, and the influence of P was examined. In the examples (Sample Nos. 60 and 62), the amount of P was
0.0019% and 0.0010%, to which Sr and Sb are added
The effects of r and Sb were investigated. In the example (sample No. 57), the content was within the specified range including the amount of P, and Ti was added thereto.
(Sample No. 58) was within the specified range including the amount of P, and Ti and B were added thereto, and the effects of Ti and B were examined. All the alloys in Table 1 were T6 treated and the treatment conditions were 520 ° C.
For 12 hours, water-cooling, aging treatment at 160 ° C. for 5 hours, and then air-cooled.

After the solution treatment, the addition of Cu precipitates a copper-aluminum intermetallic compound (eg, CuAl ₂ compound) by aging treatment, thereby strengthening α-Al and improving the tensile strength of the T6 treated material. It is intended. When the Cu content of other components is as low as 3.24% within the specified range (Comparative Example = Sample No. 4
In 9), when the tensile strength is as low as 364 MPa and the Cu content is as high as 4.51% (Comparative Example = Sample No. 46), the elongation is 5.2% and the impact value is as low as 66 kJ / m ² . (Comparative Example = Sample No. 48) shows the same tendency. On the other hand, when the Cu content is 4.03% (Example =
Sample No. 47) has a tensile strength of 395 MPa, an elongation of 10.4%,
0.2% proof stress is 229MPa, impact value was achieved the target value indicates a value of 109kJ / m ^2. FIG. 2 shows a change in copper content and a change in mechanical properties. Al-X% Cu-7% Si-0.2% Mg-0.1% Fe-
Copper content in low P alloy T6 treated material is around 4% (ie,
(3.5 to 4.3%) is within the range satisfying the target mechanical properties.

The addition of Si is intended to secure the fluidity of the molten metal and improve the castability. Other ingredients within the specified range
When the amount of Si is as high as 9% or more (Comparative example = sample numbers 44 and 43)
The elongation 3-4%, the impact value is low and 45~47kJ / m ^2. Si
When the amount is 5% or less, the fluidity is low and it cannot be used as a casting material. On the other hand, when the Si content is 5 to 7% (Examples: sample numbers 46 and 48), the tensile strength is 390 MPa or more, the elongation is 10.4%, the 0.2% proof stress is 229 MPa, and the impact value is 109 kJ / m ^2. And achieved the target value. FIG. 3 shows a change in Si content and a change in mechanical properties. Al-4% Cu-X% Si-0.2% M
It can be seen that the content of Si in the T6 treated material of g-0.1% Fe-low P alloy is around 7% (that is, 5.0-7.5%), which is a range satisfying the target mechanical properties.

In the case of adding Mg, a solution treatment is performed, followed by an aging treatment, whereby a magnesium-silicon intermetallic compound (for example, Mg ₂ Si or an Al—Cu—Mg compound) precipitates like α, and α Strengthen the Al phase; Other components, within the specified range Mg
When the amount is as low as 0.01% (Comparative Example = Sample No. 50), the tensile strength is 380 MPa, the elongation is as low as 8.9%, and the Mg amount is 0.30.
% (Comparative Example = Sample No. 52), the elongation is 5.4%,
Impact value as low as 75 kJ / m ^2. When the Mg content is 0.10 to 0.20% (Examples: sample numbers 44 and 43), the tensile strength is 386 MPa or more, the elongation is 10.4% or more, the 0.2% proof stress is 219 MPa or more, and the impact value is 109
The value of kJ / m ² was achieved, achieving the target value. FIG. 4 shows changes in the content of Mg and changes in mechanical properties. Al-4% Cu-
7% Si-X% Mg-0.1% Fe-Low P alloy T6 treated material with Mg content around 0.15% (that is, 0.10-0.25%) is a range that satisfies the target mechanical properties I understand.

Since Fe addition is an element which lowers the mechanical strength, the lower it is, the more preferable it is.
When the Fe content is as high as 0.29% (Comparative Example = Sample No. 56), the tensile strength is 377 MPa, the elongation is 8.5%, and the impact value is as low as 88 kJ / m ² . On the other hand, when the Fe content is as low as 0.20% or less (Example = Sample No. 55), the tensile strength is 383 MPa or more and the elongation is
9.9% or more, 0.2% proof stress is 223MPa or more, impact value is 98kJ / m ²
And achieved the target value. FIG. 5 shows a change in Fe content and a change in mechanical properties. Al-4% Cu-7% Si-
Fe content in T6 treated material of 0.15% Mg-X% Fe-low P alloy is 0.2
% Or less is a range that satisfies the target mechanical properties.

Incidentally, (Comparative Example = Sample No. 59) is a high-P material, showing a low elongation of 7.6% and a low impact value of 70 kJ / m ² . This is because the eutectic Si of the T6 treated material is elongated and large as shown in the macrostructure photograph of sample No. 59 in FIG. 1. By measuring the fineness and grain size of Si, not only the tensile strength and 0.2% proof stress, but also the target elongation and impact value can be achieved.

Next, (Example = sample numbers 60 and 62) will be described. In this case, when Sb and Sr were added, the content of P was larger than the specified amount, and the elongation and impact value were low.
b, Addition of Sr to refine and granulate eutectic Si,
This is an improvement in elongation and impact value. (Example =
In the case of sample No. 60), P: 0.0019% and Sr 0.0088%
%, The target mechanical properties can be achieved. In the case of (Example = sample No. 62), the target mechanical properties can be achieved by adding 0.158% of Sb to P: 0.0010%. Was achieved.

Next, FIGS. 6 to 10 show the relationship between the mechanical properties and the modifier. The alloy used here is Al-4
% P-7% Si-0.15% Mg-0.1% Fe-alloy high P material (comparative example = sample No.59), low P material (P ≦ 0.0003%), Tb treated material with Sb additive material and Sr additive material It is. FIG. 6 relates to the relationship between the tensile strength and the modifier, and all the average values exceed the target values. However, in the case of the Sr-added material, the dispersion tends to be large.

FIG. 7 shows the relationship between the 0.2% proof stress and the modifier, and all the average values exceed the target values. The Sb additive has little variation, but the other three variations are large.

FIG. 8 relates to the relationship between the elongation and the improver. The average value of the high P material is 7.4%, which is far below the target of 9%. The other three show more than 10%, exceeding the target.

FIG. 9 relates to the relationship between the impact value and the modifier, and the average value of the high P material is 70 kJ / m ^2, which is much lower than the target value of 90 kJ / m ² . The other three showed 100 kJ / m ² or more, exceeding the target value.

FIGS. 10 to 13 show changes in mechanical properties when Ti or Ti + B was added to the low P material.
u-7% Si-0.15% Mg-0.1% Fe-low P alloy is a comparative example.
Ti or Ti + B is added. The macro structure photograph is shown in FIG. It can be seen that the crystal grains are finer in the low-P material with the Ti-added material and in the low-P material with the Ti + B-added material than in the low-P material with no added Ti or Ti + B. Both are T6 treated materials.

In FIG. 10, Ti or Ti + is added to the low P material and the low P material.
The change in tensile strength when the B additive was used was examined. The average value was equal to a certain value, and the tensile strength tended to increase as the particles became finer. That is, the Ti-added low-P material has a higher Ti content than the low-P material.
+ P added low P material is higher.

In FIG. 11, Ti or Ti + is added to the low P material and the low P material.
The change in 0.2% proof stress when B was added was examined. In this case also, the average value was equal to a percentage.
The low P material showed the highest value, and the low P material added the next Ti + B showed the lowest value.

In FIG. 12, Ti or Ti + is added to the low P material and the low P material.
Investigation of the change in elongation when B additive is used.
The Ti + B-added low-P material and the low-P material showed the same elongation, but the elongation of the Ti-added low-P material was lower than the former two, and was slightly higher than the target value of elongation.

In FIG. 13, Ti or Ti + is added to the low P material and the low P material.
The change in impact value when B-added material was examined. The impact value of Ti + B-added low-P material and Ti-added low-P material was significantly lower than that of low-P material, and slightly exceeded the target value of the impact value. Met.

[0043]

As described above, the first aspect of the alloy of the present invention is that P ≦
By using a low P material as low as 0.0003%, the second and third P: 0.00
Even if the P material is as high as 04-0.0030%, by adding Sb and Sr, the eutectic Si can be refined and granulated, and the castability satisfies the economic efficiency as well as the T6 treatment. The material has tensile strength of 380MPa or more, elongation of 9% or more, 0.2% proof stress of 200MPa,
The impact value exceeded the target value of 90 kJ / m ² or more.

Further, by adding Ti or Ti and B to the low-P material of the alloy of the present invention, the crystal grains can be refined without impairing the mechanical properties, and thereby the aesthetic appearance when the surface treatment is performed. Was able to be improved.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a micrograph of a high-P material as a comparative example of the present invention, a low-P material, an Sr-added material, and an Sb-added material according to the alloy of the present invention.

FIG. 2 is a graph showing the relationship between Cu content and mechanical properties.

FIG. 3 is a graph showing the relationship between Si content and mechanical properties.

FIG. 4 is a graph showing the relationship between Mg content and mechanical properties.

FIG. 5 is a graph showing the relationship between Fe content and mechanical properties.

FIG. 6 is a graph showing the relationship between mechanical properties and high P and modifier.

FIG. 7 is a graph showing the relationship between 0.2% proof stress, high P and modifier.

FIG. 8 is a graph showing the relationship between elongation, high P, and modifier.

FIG. 9 is a graph showing the relationship between impact value and high P and modifier.

FIG. 10 is a graph showing the relationship between the tensile strength of a low P material, a Ti-added low P material, and a Ti + B added low P material.

FIG. 11 is a graph showing the relationship between 0.2% proof stress of a low P material, a Ti-added low P material, and a Ti + B added low P material.

FIG. 12 is a graph showing the relationship between the elongation of a low P material, a Ti-added low P material, and a Ti + B added low P material.

FIG. 13 is a graph showing a relationship between impact values of a low P material, a Ti-added low P material, and a Ti + B added low P material.

FIG. 14 is a photograph showing a macrostructure of a low-P material serving as a reference example and a Ti-added low-P material and a Ti + B-added low-P material for the low-P material serving as reference examples in the present embodiment.

Claims (6)

[Claims] 1. Cu: 3.5-4.3%, Si: 5.0-7.5%, M
g: A high-strength casting aluminum alloy containing 0.10 to 0.25%, Fe ≦ 0.2%, and P ≦ 0.0003%, with the balance being Al and unavoidable impurities. 2. Cu: 3.5-4.3%, Si: 5.0-7.5%, M
g: 0.10 to 0.25%, Fe ≤ 0.2%, P: 0.0004 to 0.0030%, S
b: A high-strength casting aluminum alloy containing 0.05 to 0.2%, with the balance being Al and unavoidable impurities. 3. Cu: 3.5-4.3%, Si: 5.0-7.5%, M
g: 0.10 to 0.25%, Fe ≤ 0.2%, P: 0.0004 to 0.0030%, S
r: A high-strength casting aluminum alloy containing 0.005 to 0.030%, with the balance being Al and unavoidable impurities. 4. The aluminum alloy for high-strength casting according to claim 1, wherein Ti: 0.05 to 0.35.
% High-strength aluminum alloy for casting. 5. The aluminum alloy for high-strength casting according to claim 1, wherein Ti: 0.05 to 0.35.
%, B ≦ 0.003%. High strength aluminum alloy for casting. 6. An aluminum alloy casting for high-strength casting, wherein the alloy according to claim 1 is cast and then subjected to T6 treatment.