JP2725112B2 - High strength magnesium alloy - Google Patents

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 a high temperature up to about 473 K required for weight reduction of automobile engine parts and the like. .

[0002]

2. Description of the Related Art In recent years, awareness of global environmental conservation has increased,
The demand for improving the fuel efficiency of automobiles has increased, and the development of lightweight materials for automobiles has been strongly demanded.

[0003] Magnesium alloys have the lowest density among metallic materials currently in practical use, and are expected to be used as lightweight materials for automobiles in the future. At present, the most commonly used magnesium alloy is Mg-Al-Zn-Mn.
System alloy (for example, AZ91 alloy = Mg-9Al-1Zn
-0.5 Mn), and peripheral technologies such as the casting technology of this alloy are in the stage of completion, and this alloy is first studied for weight reduction of automobiles. Further, as a heat-resistant magnesium alloy, an alloy obtained by adding a rare earth element (RE) to magnesium, for example, an Mg-RE-Zr-based alloy has been developed.

[0004]

However, the above-mentioned Mg-Al-Zn-Mn-based alloy has a reduced strength at 393K or more, and is not suitable for applications requiring heat resistance among automobile engine parts. In addition, the heat-resistant Mg-RE-
In a Zr-based alloy, RE is a heavy element, so that RE tends to be biased downward in the molten metal, and addition of Zr used as an essential component is unstable, resulting in an increase in cost.

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

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a novel material suitable for a material for an automobile engine part which requires both heat resistance and room temperature strength. An object of the present invention is to provide a high heat resistant high strength magnesium alloy.

[0007]

The present inventors have made various studies to solve the above-mentioned problems. As a result, the present inventors have found that by adding an appropriate amount of zinc and an appropriate amount of calcium to magnesium and, if desired, an appropriate amount of copper. It has been found that the strength at room temperature and high temperature is improved.

It is already known that the strength at room temperature and high temperature is improved by adding calcium to the AZ alloy or the like. However, the amount of calcium added in these cases is generally 0.15% by weight or less, and is merely used to complement the strength of the AZ alloy.
On the other hand, strength at room temperature and high temperature can be obtained by adding calcium in an amount of 0.8 to 5% by weight, zinc in an amount of 3 to 8% by weight, and further adding copper in an amount of 10% by weight or less as required. Was found to be significantly improved, and the present invention was reached.

That is, the magnesium alloy of the present invention having excellent strength at room temperature and high temperature contains 3 to 8% by weight of zinc and 0.8 to 5% by weight of calcium, with the balance being magnesium and unavoidable impurities. I do.

The magnesium alloy of the present invention having excellent strength at room temperature and high temperature has a zinc content of 3 to 8% by weight and a calcium content of 1.0% .
It contains 5 to 5% by weight and 10% by weight or less of copper, with the balance being magnesium and unavoidable impurities. The magnesium alloy having excellent room temperature and high temperature strength of the present invention may further contain, if desired, 2% by weight or less of manganese, zirconium and silicon, and 4% by weight or less of a rare earth element (for example, yttrium, neodymium, lanthanum,
At least one element selected from the group consisting of cerium and misch metal).

In the magnesium alloy excellent in room temperature and high temperature strength of the present invention, calcium is an element effective for improving high temperature strength. However, if the amount of calcium added is 0.8
When the amount is less than the weight%, the high-temperature strength of the alloy is insufficient. Although the high-temperature strength increases with an increase in the amount of calcium added, the effect of the addition reaches saturation when the amount of calcium added is 5% by weight. Considering cost, there is no merit even if calcium is added in excess of 5% by weight. Therefore, in the magnesium alloy of the present invention having excellent strength at room temperature and high temperature, the amount of added calcium is set to 0.8 to 5% by weight, preferably 1 to 5% by weight.

In the magnesium alloy of the present invention having excellent strength at room temperature and high temperature, zinc is an element effective for improving the strength at room temperature. However, when the addition amount of zinc is less than 3% by weight, the strength of the alloy at room temperature is insufficient to be less than the strength of the Mg-Al alloy. Although the room temperature strength is improved with an increase in the amount of zinc added, the effect of the addition reaches saturation when the amount of zinc added is 8% by weight, and when added in excess of 8% by weight, the ductility of the alloy decreases. Therefore, in the magnesium alloy of the present invention having excellent strength at room temperature and high temperature, the amount of zinc to be 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 according to the present invention, copper is an element effective for improving both room temperature strength and high temperature strength, and their strength increases with an increase in the amount of copper added. However, when the addition amount exceeds 10% by weight, gravity segregation occurs in the casting, so that a uniform casting cannot be produced. Therefore, in the magnesium alloy having excellent strength at room temperature and high temperature according to the present invention, when copper is added, the addition amount is 10% by weight or less, preferably 2 to 10% by weight.
And

In the magnesium alloy of the present invention having excellent strength at room temperature and high temperature, the compound addition of calcium and zinc, or of calcium, zinc and copper, as in the case of compound addition of aluminum and calcium, No high temperature instability due to the formation of was found. That is,
Since an Al-Ca compound is formed in the Mg-Al-Ca-based alloy, the compound must be stabilized by processing, heat treatment, or the like. However, 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 compound unstable to heat, it is possible to use the cast material as it is at a high temperature.

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 finer and improving the strength.

In the magnesium alloy excellent in room temperature and high temperature strength of the present invention, the combination of silicon and calcium is extremely effective and has an effect of improving high temperature strength. However, if the addition amount of silicon exceeds 2% by weight, the primary crystal Mg ₂ Si becomes coarse, and the mechanical strength decreases, which is not preferable.

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

[0018]

EXAMPLES Examples 1 to 9 and Comparative Examples 1 and 2 Raw materials were charged and melted in a vacuum melting furnace in an argon atmosphere so as to obtain 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 25 mm × 50 mm × 300 mm mold to prepare a test casting. A JIS No. 4 test piece was prepared from the test casting thus obtained. The heat treatment is performed at 500 K for 10 hours. The following tests were carried out using these test pieces: Tensile test: Crosshead speed 10 mm / min using an Instron tensile tester, measuring temperatures 298 K and 473 K, measuring unit of tensile strength = MPa, elongation at break =% Measurement. The measurement results were as shown in Table 1 (% in the table is elongation at break).

[0019]

[Table 1] Alloy composition 298K 473K Example No. Zn Ca Mg Other tensile strength % Tensile strength % Example 1 5.0 3.0 Remain 280 3 195 8 Example 2 3.2 3.0 Remain 275 4 190 9 Example 3 5.0 3.0 Remain Mn: 1.8 285 3 2007 Example 4 5.0 3.0 Remaining Zr: 1.8 285 3 2007 Example 5 5.0 3.0 Remaining Si: 1.8 285 3 2007 Example 6 5.0 3.0 Remaining Mm: 3.5 290 3 205 7 Example 7 5.0 3.0 Remaining Nd: 3.5 290 3 205 7 Example 8 5.0 3.0 Remaining Y: 3.5 290 3 205 7 Comparative Example 1 5.0 0.5 Remaining 260 3 130 7 Comparative Example 2 2.5 3.0 Remaining 230 5 150 9

[0020]

[0021]

[0022]

The magnesium alloy of the present invention is superior in room temperature and high-temperature strength to conventional general-purpose Mg-Al-Zn-Mn alloys, and is required to be lightweight and heat-resistant. General-purpose heat-resistant lightweight magnesium alloy suitable for

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ryuji Ninomiya 1333-2, Hara-shi, Ageo-shi, Saitama Prefecture Mitsui Kinzoku Mining Co., Ltd. (72) Inventor Kohei Kubota 1333-2, Hara-shi, Ageo-shi, Saitama Mitsui Mining Inside the Research Institute, Inc. (72) Inventor Gunter Naite D-6350 Bad Nauheim Meinusstrasse 9 (72) Inventor Eberhard E. Schmidt D-8755 Arzena U I Unter Frankfurt i Grauer Strasse 2E (56) References JP-A-52-92811 (JP, A) JP-A-50-62112 (JP, A) JP-A-3-47941 (JP, A) JP-B-43-20893 (JP, B1) JP-B-54 -11765 (JP, B2)

Claims (3)

(57) [Claims] 1. A zinc 3-6 wt% and calcium 1.5
A magnesium alloy having excellent room-temperature and high-temperature strength, characterized in that it contains about 4 % by weight and the balance consists of magnesium and inevitable impurities. 2. 3-6% by weight of zinc and 1.5% of calcium
Manganese and up to 2% by weight.
Containing any one of the fine zirconium, the balance being made of magnesium and unavoidable impurities at room temperature and high temperature strength superior magnesium alloy. 3. 3-6% by weight of zinc and 1.5% of calcium
-4% by weight, and further contains 2% by weight or less of silicon
And, or 4 selected from among the weight percent of rare earth elements
A magnesium alloy excellent in room-temperature and high-temperature strength, comprising at least one kind and a balance of magnesium and unavoidable impurities.