JPH0625791A - High-strength magnesium alloy - Google Patents

Abstract

PURPOSE: To provide a heat resistant lightweight magnesium alloy for general purpose which is excellent in strength both at a room temperature and at a high temperature and suitable for the engine parts of an automobile in which the light weight and heat resistance are requested.

CONSTITUTION: This magnesium alloy excellent in strength both at a room temperature and at a high temperature, contains, by weight, 3-8% zinc, 0.8-5% calcium and 0-10% copper and also contains, as necessary, each ≤2% manganese, zirconium, silicon and at least one element selected from a group comprising ≤4% rare earth metal element and the balance magnesium with inevitable impurities.

COPYRIGHT: (C)1994,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnesium alloy having excellent strength at room temperature and high temperature, and more particularly to a magnesium alloy having sufficient strength even at high temperatures up to about 473K which is required for weight reduction of automobile engine parts. .

[0002]

2. Description of the Related Art Due to the increasing awareness of global environmental protection in recent years,
With the increasing demand for improved fuel efficiency of automobiles, the development of lightweight materials for automobiles has been strongly demanded.

Magnesium alloy has the lowest density among the metallic materials currently put into practical use, and is strongly expected as a lightweight material for automobiles in the future. Currently, the most commonly used magnesium alloy is Mg-Al-Zn-Mn.
System alloy (for example, AZ91 alloy = Mg-9Al-1Zn)
-0.5 Mn), peripheral technologies such as casting technology of this alloy are in the completion stage, and this alloy is first studied for weight reduction of automobiles. Further, as a heat-resistant magnesium alloy, an alloy in which a rare earth element (RE) is added to magnesium, such as an Mg-RE-Zr alloy, has been developed.

[0004]

However, the above-mentioned Mg-Al-Zn-Mn-based alloy has a reduced strength at 393 K or higher and is not suitable for use in automobile engine parts where heat resistance is required. In addition, the above heat-resistant Mg-RE-
In a Zr-based alloy, since RE is a heavy element, RE tends to be biased downward in the molten metal, and addition of Zr, which is used as an essential component, is unstable, resulting in high cost.

It is desired to develop a lightweight material having high temperature strength equivalent to A390 (Al-18% Si alloy) which is currently used as a piston material for automobile engines.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a novel material suitable for a material for automobile engine parts which requires both heat resistance and room temperature strength. Another object is to provide a heat-resistant high-strength magnesium alloy.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted various studies to solve the above-mentioned problems, and as a result, by adding an appropriate amount of zinc and an appropriate amount of calcium to magnesium, and optionally an appropriate amount of copper, It was found that the strength at room temperature and high temperature was improved.

It is already known that the strength at room temperature and high temperature is improved by adding calcium to the AZ alloy and the like. However, the amount of calcium added in these cases is generally 0.15% by weight or less, and it is merely used to complement the strength of the AZ alloy.
On the other hand, by adding calcium in an amount of 0.8 to 5% by weight, adding zinc in an amount of 3 to 8% by weight, and further adding copper in an amount of 10% by weight or less, strength at room temperature and high temperature can be improved. The present invention has been achieved by finding that the value is significantly improved.

That is, the magnesium alloy excellent in room temperature and high temperature strength of the present invention is characterized by containing 3 to 8% by weight of zinc and 0.8 to 5% by weight of calcium, and the balance being magnesium and unavoidable impurities. To do.

The magnesium alloy of the present invention which is excellent in room temperature and high temperature strength has zinc content of 3 to 8% by weight and calcium content of 0.
It is characterized by containing 8 to 5% by weight and 10% by weight or less of copper, and the balance consisting of magnesium and inevitable impurities. If desired, the magnesium alloy excellent in room temperature and high temperature strength of the present invention further comprises 2% by weight or less of manganese, zirconium and silicon, and 4% by weight or less of rare earth elements (eg, yttrium, neodymium, lanthanum,
At least one element selected from the group consisting of cerium and misch metal) can be contained.

In the magnesium alloy of the present invention excellent in strength at room temperature and high temperature, calcium is an element effective for improving high temperature strength. However, the amount of calcium added is 0.8
If it is less than wt%, the high temperature strength of the alloy is insufficient. Further, the high temperature strength is improved as the amount of calcium added increases, but the effect of addition reaches saturation when the amount of calcium added is 5% by weight. Considering the cost, there is no merit in adding calcium in excess of 5% by weight. Therefore, in the magnesium alloy of the present invention excellent in room temperature and high temperature strength, the amount of calcium added is 0.8 to 5% by weight, preferably 1 to 5% by weight.

In the magnesium alloy of the present invention excellent in room temperature and high temperature strength, zinc is an element effective for improving room temperature strength. However, when the amount of zinc added is less than 3% by weight, the room temperature strength of the alloy is insufficient as compared with the strength of the Mg-Al based alloy and is insufficient. Further, the room temperature strength improves with an increase in the amount of zinc added, but the effect of addition reaches saturation when the amount of zinc added is 8% by weight, and the ductility of the alloy decreases when the amount of zinc added exceeds 8% by weight. Therefore, in the magnesium alloy of the present invention excellent in strength at room temperature and high temperature, the amount of zinc added is 3 to 8% by weight, preferably 4 to 7% by weight.

In the magnesium alloy excellent in room temperature and high temperature strength of the present invention, copper is an element effective for improving both room temperature strength and high temperature strength, and the strength thereof improves as the amount of copper added increases. However, if the addition amount exceeds 10% by weight, gravity segregation occurs in the casting, and it becomes impossible to manufacture a uniform casting. Therefore, in the magnesium alloy of the present invention excellent in room temperature and high temperature strength, when copper is added, its addition amount is 10% by weight or less, preferably 2 to 10% by weight.
And

In addition, in the magnesium alloy of the present invention excellent in strength at room temperature and high temperature, the compound as in the case of the composite addition of aluminum and calcium can be obtained by the composite addition of calcium and zinc or calcium, zinc and copper. No instability at high temperature due to the formation of was observed. That is,
Since an Al-Ca compound is formed in the Mg-Al-Ca-based alloy, this compound must be stabilized by processing, heat treatment, etc., but the Mg-Zn-Ca-based alloy and the Mg-Zn-Cu-Ca-based alloy are required. In the case of an alloy, since there is no precipitation of such a heat-labile compound, the cast material can be used in a high temperature state as it is.

Zirconium and manganese, which are generally added to the Mg alloy in an amount of 2% by weight or less, are also effective in the magnesium alloy of the present invention, and have the effect of making the structure fine and improving the strength.

In the magnesium alloy of the present invention excellent in strength at room temperature and high temperature, the combination of silicon and calcium is extremely effective and has the effect of improving high temperature strength. However, if the amount of silicon added exceeds 2% by weight, the primary crystal Mg ₂ Si will become coarse and the mechanical strength will decrease, such being undesirable.

It is known that rare earth elements (eg, yttrium, neodymium, lanthanum, cerium, misch metal) improve the high temperature strength of magnesium alloys,
Recently, neodymium and yttrium have been used especially in heat-resistant magnesium alloys. It was found that this effect is further improved by the combined use with calcium. The improvement of the effect by this combined use is saturated when the amount of the rare earth element added is 4% by weight.
Considering the cost, there is no merit in adding rare earth elements in excess of 4% by weight.

[0018]

【Example】

Examples 1 to 12 and Comparative Examples 1 to 2 Raw materials were charged and melted in a vacuum melting furnace in an argon atmosphere so as to be an alloy having the composition shown in Table 1. SUS304 material was used as the crucible, and no flux or the like was used. The molten metal was cast into a mold of 25 mm × 50 mm × 300 mm to prepare a test casting. A JIS No. 4 test piece was prepared from the test casting thus obtained. The heat treatment is 500K for 10 hours. The following tests were carried out using these test pieces: Tensile test: Crosshead speed 10 mm / min, measuring temperature 298K and 473K, measuring unit of tensile strength = MPa, elongation at break =% by Instron tensile tester Measurement. The measurement results were as shown in Table 1 (% in the table is elongation at break).

[0019]

[Table 1]

Examples 13 to 26 and Comparative Examples 3 to 4 Raw materials were charged into a vacuum melting furnace in an argon atmosphere so that alloys having the compositions shown in Table 2 were melted. SUS304 material was used as the crucible, and no flux or the like was used. The molten metal was cast into a mold of 25 mm × 50 mm × 300 mm to prepare a test casting. A JIS No. 4 test piece was prepared from the test casting thus obtained. The heat treatment is 500K for 10 hours. The following tests were carried out using these test pieces: Tensile test: crosshead speed 10 mm / min, measuring temperature 298K and 523K by Instron tensile tester, measuring unit of tensile strength = MPa, elongation at break =% Measurement. The measurement results were as shown in Table 2 (% in the table is elongation at break).

[0021]

[Table 2]

[0022]

INDUSTRIAL APPLICABILITY The magnesium alloy of the present invention is superior in room-temperature and high-temperature strength to the conventionally used general-purpose Mg-Al-Zn-Mn alloys, and is lightweight and heat-resistant automobile engine parts. It is a general-purpose heat-resistant lightweight magnesium alloy suitable for.

[Procedure amendment]

[Submission date] May 22, 1992

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[0018]

A vacuum melting furnace of EXAMPLE 1 to 11 and Comparative Examples 1 and 2 an argon atmosphere, the way raw wood charge the alloys having compositions shown in Table 1 and charging and dissolved. SUS304 material was used as the crucible, and no flux or the like was used. The molten metal was cast into a mold of 25 mm × 50 mm × 300 mm to prepare a test casting. A JIS No. 4 test piece was prepared from the test casting thus obtained. The heat treatment is 500K for 10 hours. The following tests were carried out using these test pieces: Tensile test: Crosshead speed 10 mm / min, measuring temperature 298K and 473K, measuring unit of tensile strength = MPa, elongation at break =% by Instron tensile tester Measurement. The measurement results were as shown in Table 1 (% in the table is elongation at break).

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[0019]

[Table 1]

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Examples 12 to 25 and Comparative Examples 3 to 4 Raw materials were charged and melted in an argon atmosphere vacuum melting furnace so that alloys having the compositions shown in Table 2 were obtained. SUS304 material was used as the crucible, and no flux or the like was used. The molten metal was cast into a mold of 25 mm × 50 mm × 300 mm to prepare a test casting. A JIS No. 4 test piece was prepared from the test casting thus obtained. The heat treatment is 500K for 10 hours. The following tests were carried out using these test pieces: Tensile test: crosshead speed 10 mm / min, measuring temperature 298K and 523K by Instron tensile tester, measuring unit of tensile strength = MPa, elongation at break =% Measurement. The measurement results were as shown in Table 2 (% in the table is elongation at break).

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[0021]

[Table 2]

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Ryuji Ninomiya 1333-2 Hara-shi, Ageo-shi, Saitama Mitsui Mining & Smelting Co., Ltd. (72) Kohei Kubota 1333-2 Hara-shi, Ageo-shi, Saitama Mitsui Mining & Smelting Co., Ltd. Research Institute (72) Inventor Günter Naite Germany Federal Republic of Germany D-6350 Bad Nauheim Mainus Strasse 9 (72) Inventor Eberhard Eschmidt Federal Republic of Germany D-8755 Arsenau Eye Unter Frankfurt Iglauer Strasse 2E

Claims (4)

[Claims] 1. 3-8% by weight zinc and 0.8 calcium
A magnesium alloy excellent in room temperature and high temperature strength, characterized in that the content is up to 5 wt% and the balance is magnesium and inevitable impurities. 2. 3-8% by weight zinc and 0.8 calcium
To 5% by weight, each further containing at least 2% by weight or less of manganese, zirconium and silicon, and 4% by weight or less of a rare earth element, and the balance being magnesium and unavoidable. A magnesium alloy excellent in room temperature and high temperature strength, which is characterized by comprising impurities of 3. Zinc 3-8% by weight, calcium 0.8-
A magnesium alloy excellent in room temperature and high temperature strength, characterized by containing 5% by weight and 10% by weight or less of copper, and the balance being magnesium and unavoidable impurities. 4. Zinc 3-8% by weight, calcium 0.8-
5% by weight and 10% by weight or less of copper, further containing 2% by weight or less of each manganese, zirconium and silicon, and at least one element selected from the group consisting of 4% by weight or less of a rare earth element, A magnesium alloy excellent in room temperature and high temperature strength, characterized in that the balance comprises magnesium and inevitable impurities.