WO2003091465A1

WO2003091465A1 - Magnesium alloy for diecasting

Info

Publication number: WO2003091465A1
Application number: PCT/JP2002/004017
Authority: WO
Inventors: Taketoshi Ishida; Shigeharu Kamado; Suguru Takeda
Original assignee: Ahresty Corporation
Priority date: 2002-04-23
Filing date: 2002-04-23
Publication date: 2003-11-06
Also published as: AU2002249626A1

Abstract

A magnesium alloy for a diecasting, which comprises, in wt %, 0.5 to 4 % of zinc, 4 to 10 % of aluminum, 1 to 3 % of calcium, 3 % or less of a rare earth element and the balanced amount of magnesium and inevitable impurities. The magnesium alloy for a diecasting is advantageous in that it combines excellent casting property (flowability of a melt), less susceptibility to hot cracking and excellent resistance to high temperature creeping.

Description

U letter

Technical field of magnesium alloy for die casting

The present invention relates to a magnesium alloy for die-casting, and more particularly, to molding a product which is required to be exposed to high temperatures and at the same time is required to have high-temperature creep resistance, such as parts for automobiles, particularly parts around an engine. It relates to the magnesium alloy for die casting used. Background art

Products made of magnesium alloys are lighter than products made of aluminum alloys as well as iron-based alloys, and can be die-cast as materials for forming products that require strength and weight reduction. Magnesium alloys are attracting attention.

As magnesium alloys that can be die cast, JIS standards include Mg-A1_Zn_Mn-based alloy (AZ91D alloy) and Mg-A1-Mn-based alloy (AM60B alloy). Magnesium alloys lose strength at high temperatures of around 120 ° C, so they cannot be used for products that require heat-resistant strength, such as parts around automobile engines.

Therefore, in order to improve the heat resistance of magnesium alloys, an alloy such as Mg—A 1 -RE (Rare Earth), in which a rare earth element (RE) is added, has been proposed by Dow Chemical Co., Ltd. of the United States, and others. However, for example, the AE42 standard magnesium alloy proposed by Dow Chemical in the United States does not have sufficient high-temperature creep strength, so it is subjected to high temperatures of about 150 ° C under pressure, such as when bolted. It cannot be used for products that require particularly high heat resistance, such as exposed parts. No examples have been used.

In addition, any of the known magnesium alloys has fluidity during die casting (so-called molten metal flowability, the same applies hereinafter) and hot cracking (high heat cracking that occurs immediately after casting). (4) There was a problem with the formability, and it was not suitable for use in mass-produced products.

—Generally, when zinc is added to a magnesium alloy, it is thought that the formability (fluidity) during die-casting is improved, but the high-temperature creep resistance is reduced with an increase in zinc. However, the present inventors have found that it is possible to improve high-temperature creep resistance by simultaneously adding the required amounts of aluminum, calcium, and a rare earth element.

The present invention has been made on the basis of such knowledge, and is excellent in moldability (fluidity) and hardly causes hot cracking in die-casting. Therefore, the present invention is suitable for mass-produced products, An object of the present invention is to provide a magnesium alloy for die casting that has excellent high-temperature creep resistance and can be used for products such as parts around an engine of an automobile that requires heat resistance in a pressurized state.

Disclosure of the invention

In order to achieve the above object, the magnesium alloy for die casting according to the present invention comprises, by weight, 0.5 to 8% of zinc, 1 to 10% of aluminum, 1 to 3% of calcium, and 3% of rare earth element. % Or less, with the balance being magnesium and unavoidable impurities.

At this time, the dumbbell component is set to 0.5 to 4% by weight in order to further improve the formability (that is, the flowability of the molten metal), prevent the occurrence of hot cracking, and improve the high-temperature creep resistance. Aluminum component is 4 to 10% by weight, rare earth element component is 1 to 10% by weight. Preferably it is 3 ° / o.

In order to further improve the high-temperature creep resistance, manganese is contained in the magnesium alloy for die casting in a weight ratio of 0.1 to 2.0%, more preferably 0.15 to 1.5%. It is good to add.

Examples of the rare earth elements include scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, euphyllium, gadolinium, tenorebium, dysprosium, homium, je / rebium, thulium, ytterbium, ruthenium, ruthenium, ruthenium, ruthenium, ruthenium, ruthenium, ruthenium, ruthenium, ruthenium, ruthenium, ruthenium, ruthenium, ruthenium power One or more selected from these can be used, but these rare earth elements are very expensive if separated as a simple substance. It is preferable to use misch metal, which is a cerium-group rare earth natural alloy containing praseodymium, neodymium, samarium, and the like. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a graph showing the influence on the flow length (fluidity) as the Ζη component increases in the embodiment of the magnesium alloy according to the present invention.

FIG. 2 is also a graph showing the effect on creep strain as the Ζη component increases in the example of the present invention.

FIG. 3 is a graph showing the effect of increasing the に η component on hot tearing in the example of the present invention.

FIG. 4 is a graph showing the effect on creep strain when the A1 component is added to the Mg—Zn alloy in the example of the present invention.

FIG. 5 is a graph showing the effect on hot cracking when the A1 component is added to the Mg—Zn alloy in the example of the present invention. FIG. 6 is a graph showing the effect on creep strain when the Ca component is added to the Mg—Zn—4A1 alloy in the example of the present invention.

FIG. 7 is a graph showing the effect on hot cracking when a Ca component is added to the Mg—Zn-4A1 alloy in the example of the present invention.

FIG. 8 is a graph showing the effect of the addition of the Ca component to the Mg_Zn-4A1 alloy in the embodiment of the present invention on the occurrence of a hot junction failure.

FIG. 9 is a graph showing the effect of the RE component added to the Mg—Zn—4A 1-1 Ca alloy on the tarry strain in the example of the present invention.

FIG. 10 is a graph showing the effect on hot cracking when an RE component is added to the Mg_Zn-4A1-1Ca alloy in the example of the present invention.

FIG. 11 is a graph showing the effect on creep strain when the Mn component is added to the Mg—Zn—A 1 —Ca_RE alloy in the example of the present invention.

FIG. 12 is a graph showing the effect on hot cracking when the Mn component is added to the Mg—Zn—A1-Ca—RE alloy in the example of the present invention.

FIG. 13 is a graph showing high-temperature crepe resistance in Examples of the present invention and Comparative Examples.

FIG. 14 is a graph showing the flow length (fluidity) in Examples of the present invention and Comparative Examples.

FIG. 15 is a graph showing hot cracking properties in Examples of the present invention and Comparative Examples.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode of the present invention will be specifically described.

In the magnesium alloy for die casting according to the present invention, zinc (Zn) is contained in a weight ratio of 0. 5 to 8%, and anoremium (A1) 1 to 1: LO%, calcium (Ca) 1 to 3%, and rare earth element (RE) 3% or less, the balance being magnesium and unavoidable It consists of impurities and those containing 0.10 to 2.0% of manganese (Mn) in the above components.

As shown in the graph of Fig. 1, the Zn (zinc) component added as a component of the present magnesium alloy has the function of expanding the solidification range of the magnesium alloy and improving the fluidity during die casting. As shown in the graph of FIG. 2, there is a tendency that as the Zn component increases, the thermally unstable Mg—Zn compound increases and the high-temperature creep resistance tends to decrease. In addition, when a large amount of the Mg_Zn compound is present, as shown in the graph of FIG. 3, there is a tendency that hot cracking tends to occur. In combination with the simultaneously added A 1 (aluminum) component, a thermally stable Mg ₃₂ (Al, Zn) ₄₉ compound precipitates to improve high-temperature creep resistance, — There was also a tendency to suppress the generation of Zn compounds and hot cracking.

Therefore, in the magnesium alloy according to the present invention, the Zn component is added at a maximum weight ratio of 0.5 to 8%, preferably 0.5 to 4%, and more preferably 2 to 4%. Add within the range. That is, as shown in FIG. 1, if the amount of the 11 components is less than 0.5% by weight, the effect of improving the fluidity (fluidity) at the time of die casting cannot be exerted, so 0.5% by weight or more is added. There is a need. However, as shown in FIG. 2, the high-temperature creep resistance tended to decrease as the Zn content increased, and as shown in FIG. 3, the Zn content was 4 wt. If it exceeds ₀ , hot cracking is likely to occur, and if it exceeds 8% by weight, hot cracking is extremely likely to occur. Therefore, the addition amount of the Zn component is set to be in a range of 0.5% to 8 ° / ₀ at maximum by weight, and preferably in a range of 0.5% to 4%. Also, A l (aluminum) component, thermally stable _{M g 3 2 (A l,} Z n) by adding the M g _ Z n alloy was _{4 9} compound precipitation, shown in Figure 4 As shown in Fig. 5, it has the effect of suppressing hot cracking as well as improving the high-temperature creep resistance, but the amount of intermetallic compound also increases with the increase of the A1 component, and grain boundary precipitation occurs. Since the brittleness is reduced due to excessive amount, in the magnesium alloy of the present invention, the A1 component is added in a weight ratio of 1% to 10%, preferably in a range of 4% to 10%.

That is, as shown in FIG. 4, when the A1 component is less than 1% by weight, the effect of improving the high-temperature anti-tarnish property is hardly exhibited, and preferably 4% by weight or more is required. As shown in the figure, when the A1 component is less than 4% by weight, the function of suppressing hot cracking can hardly be exhibited, and when it exceeds 10% by weight, hot cracking becomes extremely large. Therefore, in the magnesium alloy according to the present invention, A

The amount of one component added is in the range of 1% to 10% by weight, preferably in the range of 4% to 10%.

In addition, the Ca (calcium) component becomes a Mg—Zn—Ca compound by combining with the thermally unstable Mg—Zn alloy, and as shown in FIG. While it has the effect of improving the heat resistance, as shown in Fig. 7, the amount of intermetallic compound increases with the increase in the amount of addition, and there is a tendency for hot cracking to occur easily. As shown in the figure, there is also a tendency for the apparent viscosity of the molten metal to increase and for the product to have poor hot junctions and to become chewy.

Therefore, in the magnesium alloy of the present invention, the Ca component is added in a range of 1% to 3% by weight. If the content of Ca is less than 1% by weight, the effect of improving the high-temperature creep resistance can hardly be expected as shown in FIG. 6, while if the content of Ca exceeds 3% by weight, it can be seen in FIG. And as shown in Fig. 8 The incidence of poor hot water borders becomes extremely high.

Further, in the magnesium alloy of the present invention, by adding the Ca component in the above range, an A1-Ca-based compound which is an intermetallic compound is generated, and this compound covers the entire surface of dendrites or crystal grain boundaries. By covering, the weakening of the artificial metal structure is suppressed.

The RE (rare earth element) component forms an Mg_RE compound and combines with the A1 component added at the same time to form an A1-RE compound, resulting in high temperature creep resistance as shown in Fig. 9. There is a function to improve. In other words, in combination with the dendrites or the A1-Ca-based compound covering the grain boundaries, the resulting alloy has a high deformation resistance in a high-temperature region and improves the high-temperature creep resistance. You. However, as shown in FIG. 10, an increase in the RE component increases the cost of the magnesium alloy, and at the same time, increases the amount of the intermetallic compound to easily cause hot cracking. The RE component is added in a weight ratio of 3% or less, preferably in the range of 1% to 3%. If the amount of the RE component is less than 1% by weight, the effect of improving the high-temperature creep resistance can hardly be expected. If the amount of the RE component exceeds 3% by weight, hot cracking increases as shown in FIG. Further, the Mn (manganese) component is added to the magnesium alloy containing Zn—A 1—Ca—RE to form a solid solution with the Mg component to improve the resistance to solid solution and to improve the power resistance. As shown in Fig. 11, it has the function of improving the creep resistance at high temperatures.

Therefore, in the magnesium alloy of the present invention, the Mn component is added in a weight ratio of 0.10 to 2.0%, preferably in a range of 0.15% to 1.50%. If the Mn content is less than 0.10% by weight, the effect of improving high temperature creep resistance can hardly be expected as shown in FIG. If it exceeds 10% by weight, as shown in Fig. 12, the incidence of hot cracking becomes extremely high.

Table 1 below summarizes data on the alloy composition, creep strain, and formability of Examples and Comparative Examples of the present invention. .

As the RE (rare earth element) in the alloy composition, cerium 50 weight ^_0/0, lanthanum 25% by weight, praseodymium 4 wt%, neodymium 20 wt%, samarium 1 wt%, was used mischmetal containing.

In this example, the die casting was performed at a mold temperature of 200 ° C, a forming temperature of 700 ° C, and a forming pressure of 6 OMPa, and a creep test was performed at a temperature of 175 ° C at a temperature of 5 OMpa. This was done with great effort. table 1

Remarks

(1) Comparative Example 1 is JIS standard AZ91 D material.

② Comparative Example 2 is AE42 material from Dow Chemical Company, USA.

③ Comparative Example 3 is an example material disclosed in JP-A-7-331375. As is clear from Table 1 above, a die-cast structure using the magnesium alloy according to the present invention is a comparative example (AZ91D material which is a JIS standard product of magnesium alloy, Dow Chemical Co., USA) Creep strain (%) is in the range of 0.3% to 0.6%, and the flow length during manufacturing is sufficient, from 19 mm to 22 mm. It is understood that the steel is excellent in formability, with a hot cracking rate of about 0% to 3%. Industrial applicability

ADVANTAGE OF THE INVENTION According to the magnesium alloy for die-casting which concerns on this invention, it is excellent in the formability (hot-water flow property) and hard to generate | occur | produce a hot crack at the time of die-casting. It has excellent high-temperature creep resistance and can be used for products such as parts around engines that require heat-resistant strength under pressurized conditions.

Claims

The scope of the claims

1. Contains 0.5 to 8% by weight of zinc, 1 to 10% of aluminum, 1 to 3% of calcium, and 3% or less of rare earth elements. The balance consists of magnesium and inevitable impurities. Magnesium alloy for die casting characterized by the following:

2. Contains 0.5 to 4% by weight of zinc, 4 to 10% of aluminum, 1 to 3% of canoleum, and 1 to 3% of rare earth elements, with the balance being magnesium and unavoidable impurities. Magnesium alloy for die casting.

3. The magnesium alloy for die casting according to claim 1, wherein the magnesium alloy contains 0.10 to 2.0% of manganese by weight.

4. The magnesium alloy for die casting according to claim 1 or 2, which contains 15 to 1.50% of manganese by weight.