JPH11241135A - Aluminum alloy for casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high strength and high toughness aluminum alloy member by providing it with a compsn. consisting of the specified ratio of Si, Mn, Sb and Sr in which the ratio of Sb/Sr also is in a specified range and the balance consists substantially of Al. SOLUTION: This alloy member has a compsn. contg., by weight, 6.5 to 7.5% Si, 0.2 to 0.4% Mg, <=0.024% (including no zero) Sb, 0.003 to 0.03% Sr in which the ratio of Sb/Sr is in the range of 0.1 to 0.8 and the balance consists substantially of Al. As for the balance, besides Al, Cu, Fe, Ni, Zn, Ti, Mn, Sn and Ca may be contained but the contents thereof are made to the following ranges. The content of Cu is made to <=0.2%, that of Fe is made to <=0.2%, that of Ni is made to <=0.05%, that of Zn is made to <=0.10%, that of Ti is made to <=0.20%, that of Mn is made to <=0.10%, that of Sn is made to <=0.05% and that of Ca is made to <=0.01%. In this way, as the high strength and high toughness aluminum alloy member, e.g. an aluminum wheel is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy used for casting automotive parts and other members, and more particularly to an Al-Si-Mg alloy suitable for low-pressure casting, molten forging or semi-solid forming. About.

[0002]

2. Description of the Related Art Al-Si-Mg based alloys are used as casting materials for automobile parts and various mechanical parts because of their good castability and high finishing accuracy after machining.
For example, disc wheels, which are important security parts for automobiles, are required to have an elongation value and impact resistance.
An alloy composed of CH (see JIS H5202) is frequently used. This aluminum alloy disc wheel (hereinafter referred to as an aluminum wheel) has a main body 1 comprising a thin rim portion 2 on which a tire is mounted and a relatively thick disc portion 3 as shown in FIG. The body is in weight% (the same applies hereinafter), Si 6.5 to 7.5%, Mg 0.20
About 0.40%, the balance being an alloy having a composition consisting of Al and unavoidable impurities (low pressure casting is common);
Solution treatment at a temperature of ~ 550 ° C,
It is manufactured by subjecting to aging treatment at a temperature of ° C. (T6 treatment) followed by machining.

The cast structure of this aluminum wheel is mainly composed of aluminum (α) in which Si, Mg, etc. forming a matrix are dissolved, and eutectic Si which cannot be dissolved in aluminum and is crystallized. The eutectic Si changes from acicular to granular by the solution treatment after casting. At this time, it is common to select and add elements such as Sr, Na and Sb to promote the effect. (Improvement processing). However, when this improvement treatment is performed using Sr, the spheroidization of eutectic Si is significantly inhibited by the incorporation of Sb. At present, it is common to use Sr for the improvement process, but Sb is often used until more than ten years ago, and Sb may be used even now.

[0004]

Here, when purchasing scrap aluminum wheels from the market and using them as materials, Sb may be mixed. In particular, when the effect of the improvement treatment is obtained using Sb, the weight ratio of Sr is 20%.
It is required to be about 30 times, and scrap improved by using Sb is likely to have a remarkable effect even if a small amount is mixed. For example, even in the case of an aluminum wheel manufactured by precisely adjusting the content of each element, the mechanical properties vary, and for example, an aluminum wheel having low toughness (in particular, low elongation value) may be generated. When an aluminum wheel purchased from the market is used, the content of Fe tends to increase and the toughness tends to decrease, so that this improvement treatment is even more important.

[0005] Accordingly, an object of the present invention is to provide an aluminum alloy for casting capable of obtaining an aluminum alloy member having high toughness.

[0006]

In order to achieve the above-mentioned object, the present invention provides a method for manufacturing a semiconductor device comprising: 6.5 to 7.5% by weight of Si;
0.2-0.4%, Sb 0.024% or less, Sr 0.0
The technical means of adopting a composition of 0.3 to 0.03%, an Sb / Sr ratio of 0.8 or less, and a balance substantially consisting of Al was employed. In the present invention, the Sb / Sr ratio is preferably in the range of 0.1 to 0.8.

The effects of the components contained in the aluminum alloy of the present invention and the reasons for limiting the contents are as follows. Si
Content is 6.5 to 7.5% (% is% by weight, the same applies hereinafter)
And 5. Si has the effect of improving fluidity, but
If it is less than 5%, the effect is small, and if it exceeds 7.5%, casting defects increase and high toughness cannot be obtained. The content of Mg is set to 0.2 to 0.4%. Mg
Forms Mg ₂ Si with Si. This Mg ₂ Si is uniformly and finely precipitated by heat treatment, and is added to improve tensile strength and proof stress.
If the amount is less than 0.4%, the effect is not obtained. If the amount exceeds 0.4%, no improvement in strength is observed, and only the elongation value is reduced. The content of Sr is set to 0.003 to 0.03%. Sr is used as an improving agent for eutectic Si (refinement and spheroidization of eutectic Si). However, if it is less than 0.003%, it has no effect, and if it exceeds 0.03%, castability decreases. It is. In particular, in the present invention, the ratio of Sb to Sr (Sb
/ Sr ratio) is 0.8 or less. Sb / Sr ratio is 0.8
If it is larger than this, the elongation value decreases and high toughness cannot be obtained. The preferred range of the Sb / Sr ratio is 0.1
~ 0.8. From the Sr content and the Sb / Sr ratio,
The Sb content is set to 0.024% or less.

Further, in the present invention, "the remainder is substantially A
l "means, in addition to Al, Cu, Fe, Ni, Zn, Ti,
Mn, Sn, and Ca may be contained, but the content is in the following range. If the content of Cu is large, the toughness is reduced. Fe content is 0.20
% Or less. Fe is mixed as an impurity into ordinary aluminum ingots.
Al-Fe compound or Al-Si-Fe
This is because the compound is crystallized and the toughness is reduced due to the notch effect of these intermetallic compounds. Ni has a high content of 0.05% or less, because mechanical properties are degraded. Zn, if contained in a large amount, reduces toughness (particularly high-temperature toughness). Ti has an effect of making crystal grains fine, but if it is large, the toughness is reduced. Mn has the effect of suppressing the coarsening of the acicular structure (Al-Fe-Si compound) crystallized in the matrix, but if it is too much, the mechanical properties are reduced, so Mn is made 0.10% or less. If the content of Sn is too large, the toughness is reduced. Ca has an adverse effect on castability, so is made 0.01% or less.

In the case of manufacturing a disk wheel using the aluminum alloy of the present invention, for example, an aluminum base metal is melted so as to have the above-described composition, and then the molten aluminum alloy is poured into a mold, and after completion of solidification, the mold is completed. And T6 treatment, for example, solution treatment ｛(500 to 550)
° C) x (4 to 10 hr)} and aging treatment {(140 to 1)
60 [deg.] C.) * (2-7 hr)} and machined.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Al-7% Si-containing Sb
Ten types of base metal based on 0.3% Mg were prepared, dissolved, degassed and degassed, Sr was added, and then a boat mold (JIS H5) preheated to 150 ° C.
Table 1 shows the alloy composition of the test pieces. Sample No. 1-4 are examples of the present invention.

[0011]

[Table 1]

[0012] Each of the above test pieces was subjected to a solution treatment at 535 ° C for 5 hours, then put into water at 15 ° C for quenching, and then subjected to an aging treatment at 145 ° C for 4 hours. Each test piece was processed into a predetermined shape and then subjected to a tensile test. (3 times for each test piece). The results are shown in FIGS. FIG. 2 shows the relationship between the tensile strength and the Sb / Sr ratio. FIG. 3 shows the relationship between the Charpy impact value, which is one of the factors representing toughness, and the Sb / Sr ratio. 4 is sample 11, FIG. 5 is sample 1, FIG. 6 is sample 3, FIG. 7 is sample 4, FIG. 8 is sample 5, FIG. 9 is sample 6, FIG.
0 shows a photograph of the structure of Sample 8.

As shown in FIG. 2, when the Sb / Sr ratio is in the range of 0.1 to 4.2, a tensile strength of 26 to 29 kgf / mm ² is obtained.
27-29 kg especially when the Sb / Sr ratio is in the range of 0.1-2.
It can be seen that a tensile strength of f / mm ² can be obtained.

FIG. 3 shows that when the Sb / Sr ratio is 0.8 or more,
The Charpy impact value is only about 4 to 5.5 J / cm ^2, but when the Sb / Sr ratio is 0.8 or less, 7 J / cm 2
A Charpy impact value of ² or more was obtained. 4 to 7 from S
When the b / Sr ratio is 0.8 or less, the eutectic Si exhibits a good spherical shape.
It can be seen that spheroidization is inhibited when the ratio exceeds.

[0015]

As described above, according to the present invention, A
Not only each component of the l-Si-Mg alloy, but also Sb / Sr
Is controlled within a specific range, so that an aluminum alloy member having high strength and high toughness, for example, an aluminum wheel can be obtained.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of an aluminum wheel.

FIG. 2 is a diagram showing a relationship between tensile strength and Sb / Sr.

FIG. 3 is a diagram showing a relationship between elongation and Sb / Sr.

FIG. 4 is an optical micrograph showing a metal structure of an aluminum wheel having the composition of Sample 11.

FIG. 5 is an optical micrograph showing a metal structure of an aluminum wheel having the composition of Sample 1.

6 is an optical micrograph showing a metal structure of an aluminum wheel having the composition of Sample 3. FIG.

FIG. 7 is an optical micrograph showing a metal structure of an aluminum wheel having the composition of Sample 4.

8 is an optical micrograph showing a metal structure of an aluminum wheel having the composition of Sample 5. FIG.

9 is an optical micrograph showing a metal structure of an aluminum wheel having the composition of Sample 6. FIG.

FIG. 10 is an optical micrograph showing a metal structure of an aluminum wheel having the composition of Sample 8.

[Explanation of symbols]

 1 body, 2 rims, 3 discs

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[Procedure amendment]

[Submission date] February 2, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006] In order to achieve the above object, the present invention relates to a method for producing Si by 6.5 to 7.5% by weight, Mg by 0.2 to 0.4%,
Sb 0.024% or less (excluding O), Sr 0.00
3 to 0.03%, and the Sb / Sr ratio is 0.1 to 0.8.
The technical means that the balance has a composition substantially consisting of Al was adopted.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

The effects of the components contained in the aluminum alloy of the present invention and the reasons for limiting the contents are as follows. Si
Content is 6.5 to 7.5% (% is% by weight, the same applies hereinafter)
And 5. Si has the effect of improving fluidity, but
If it is less than 5%, the effect is small, and if it exceeds 7.5%, casting defects increase and high toughness cannot be obtained. The content of Mg is set to 0.2 to 0.4%. Mg
Forms Mg ₂ Si with Si. This Mg ₂ Si is uniformly and finely precipitated by heat treatment, and is added to improve tensile strength and proof stress.
If the amount is less than 0.4%, the effect is not obtained. If the amount exceeds 0.4%, no improvement in strength is observed, and only the elongation value is reduced. The content of Sr is set to 0.003 to 0.03%. Sr is used as an improving agent for eutectic Si (refinement and spheroidization of eutectic Si). However, if it is less than 0.003%, it has no effect, and if it exceeds 0.03%, castability decreases. It is. In particular, in the present invention, the ratio of Sb to Sr (Sb
/ Sr ratio) is 0.8 or less. Sb / Sr ratio is 0.8
If it is larger, the Charpy impact value is reduced, and high toughness cannot be obtained. The lower limit of the Sb / Sr ratio is 0.
It is one. Based on the Sr content and the Sb / Sr ratio, the Sb content is set to 0.024% or less (excluding 0).

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

FIG. 2 shows that a tensile strength of 26 to 29 kgf / mm ² can be obtained when the Sb / Sr ratio is in the range of 0.1 to 4.2, but the tensile strength slightly decreases when the Sb / Sr ratio is 2.9 or more. You can see that

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

FIG. 3 shows that when the Sb / Sr ratio exceeds 0.8, the Charpy impact value remains at about 4 to 5.5 J / cm ^2, but when the Sb / Sr ratio is 0.8 or less, the Charpy impact value becomes 7 J / cm.
^It can be seen that a Charpy impact value of ² or more is obtained. 4 to 7, when the Sb / Sr ratio is 0.8 or less, the eutectic Si
Have a good spherical shape, and Sb / S
It can be seen that when the r ratio exceeds 0.8, spheroidization is inhibited.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Sato 5200 Mikajiri, Kumagaya City, Saitama Prefecture Inside the Kumagaya Plant, Hitachi Metals Co., Ltd. 72) Inventor Tsukasa Yokoyama 5200 Sankajiri, Kumagaya City, Saitama Prefecture Inside the Kumagaya Plant of Hitachi Metals Co., Ltd.

Claims (2)

[Claims] 1. 6.5% to 7.5% by weight of Si, Mg
0.2-0.4%, Sb 0.024% or less, Sr 0.0
An aluminum alloy for casting, characterized by having a composition of 0.3 to 0.03%, an Sb / Sr ratio of 0.8 or less, and a balance substantially consisting of Al. 2. The aluminum alloy for casting according to claim 1, wherein the Sb / Sr ratio is in the range of 0.1 to 0.8.