JPH05140679A - Zinc base alloy for mold free from generation of inverse shrinkage at the time of gravity casting - Google Patents

Abstract

(57) [Summary] [Structure] (1) At least 1 selected from the group consisting of 12 to 30% by weight of aluminum and titanium, zirconium, hafnium, yttrium and lanthanide series elements.
Whether the content of the seed element is 0.03 to 0.5% by weight and the balance is zinc and inevitable impurities, or (2) the component (1) further contains not more than 5.5% by weight of copper. Or (3) a zinc-based alloy containing 1 to 4% by weight of magnesium in the component (1) or (2). [Effect] Since the high aluminum zinc-based alloy of the present invention does not cause reverse drawing during gravity casting, it is possible to manufacture a high-strength and sound zinc-based alloy mold by gravity casting, which has been strongly demanded in recent years. It is suitable for small-volume production molds.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a zinc-based alloy for molds. More specifically, the present invention relates to a zinc-based alloy for a mold that does not cause reverse shrinkage during gravity casting.

[0002]

2. Description of the Related Art In recent years, there has been a trend toward high-mix low-volume production throughout the industry, and even with regard to dies, conventional steel dies with long delivery times and high unit prices cannot respond to agile model changes. There is a need for a low-volume production mold that is easy and inexpensive to manufacture. To meet this demand, for example, aluminum alloy mold blocks and ZA
There are dies manufactured using zinc-based alloys such as -8, ZA-12, and ZA-27. Aluminum alloy is the cutting performance,
Since it is excellent in EDM performance, it is easier to process in the case of aluminum alloy mold blocks than in the case of steel molds, thus reducing the delivery time and processing cost, and the zinc-based alloy. In this case, since the mold can be manufactured by the casting method, the number of steps is small, and therefore the delivery time and the processing cost can be reduced.

[0003]

Conventionally, many zinc-based alloys have been cast by gravity casting. However, among the zinc-based alloys, as a casting characteristic of high aluminum zinc-based alloys such as ZA-12 and ZA-27, since a light aluminum phase floats during solidification, segregation occurs and solidification occurs from the upper part where the solidification temperature is high. Beginning, and finally there will be a final solidification part at the bottom. Such a phenomenon is called reverse shrinkage. When casting high aluminum zinc-based alloys by gravity casting, small castings can be produced without problems, but large castings cause reverse shrinkage due to the high aluminum content, which results in lower surface of the cast product. In some cases, solidification shrinkage occurs and a sound casting cannot be manufactured. For this reason, these high aluminum zinc base alloys are used as die casting alloys in Europe and the United States, but are not used for gravity casting.

An object of the present invention is to provide a high aluminum zinc base alloy which does not cause reverse shrinkage even when it is carried out by a gravity casting method.

[0005]

The present inventors have added at least one element selected from the group consisting of titanium, zirconium, hafnium, yttrium and lanthanide series elements to a high aluminum zinc based alloy. Makes the aluminum phase crystallized in the solidification stage very fine, and as a result, the aluminum phase is prevented from floating,
The present invention has been completed by finding that reverse drawing does not occur during gravity casting.

That is, the zinc-based alloy for molds which does not cause reverse shrinkage during gravity casting of the present invention is (1) aluminum 12 to 3
0% by weight and 0.03 to 0.5% by weight of at least one element selected from the group consisting of titanium, zirconium, hafnium, yttrium and lanthanide series elements, the balance being zinc and inevitable impurities Or (2)
The above component (1) further contains not more than 5.5% by weight of copper, or (3) the above component (1) or (2) further contains 0.01 to 0.2% by weight of magnesium. It is a base alloy.

Aluminum has a function of increasing mechanical strength such as tensile strength and hardness of a zinc alloy, and 3% by weight is required to exert its addition effect and achieve the object of the present invention.
It is necessary to include the above. However, the reverse shrinkage during gravity casting, which is the subject of the present invention, has an aluminum content of 1
Since it does not occur below 2% by weight, the aluminum content is 12
Less than wt% is outside the scope of this invention. On the other hand, if the aluminum content exceeds 30% by weight, the solidification start temperature becomes high and the alloy cannot be used as a casting alloy. Therefore, in the present invention, a high aluminum zinc base alloy having an aluminum content of 12 to 30% by weight is targeted.

In the zinc base alloy for molds of the present invention, at least one element selected from the group consisting of titanium, zirconium, hafnium, yttrium and lanthanide series elements is added to the high aluminum zinc base alloy. As a result, at the solidification stage during casting, these elements act as nuclei for aluminum phase crystallization to form a fine aluminum phase, and as a result, prevent the aluminum phase from floating,
It seems that reverse pulling does not occur even during gravity casting. The reason why these elements become nuclei for aluminum phase crystallization is considered to be that these elements have extremely high melting points. When the aluminum phase formed by these elements as a core has a needle-like shape, the mechanical properties of the alloy tend to deteriorate, so that the shape of the aluminum phase is preferably close to a sphere. When these elements are added in an amount of 0.03% by weight or more, they bring about a significant effect of preventing reverse shrinkage. The anti-shrink effect is lost.

In the present invention, copper can be added in order to further increase the mechanical strength such as tensile strength and hardness of the high aluminum zinc base alloy. The effect of addition increases with the amount added, but if the amount added exceeds 5.5% by weight, a zinc phase containing a large amount of copper crystallizes before the aluminum phase crystallizes, and this copper is added in large amounts. Since the contained zinc phase is heavier than the specific gravity of the molten metal, it precipitates in the lower part, and solidification proceeds from the lower part, so that the above-mentioned reverse shrinkage does not occur, so it is not the subject of the present invention.

Magnesium can be added to the zinc-based alloy of the invention to suppress intergranular corrosion. Magnesium brings about a significant effect when added in an amount of 0.01% by weight or more, but it is not preferable if it exceeds 0.2% by weight because mechanical properties are deteriorated.

Examples 1 to 15 and Comparative Examples 1 to 3 Alloys containing the alloy components shown in Table 1 in the amounts (% by weight) shown in Table 1 and the balance being zinc and inevitable impurities were prepared. The blocks were cast by gravity casting using the alloys and sand molds that could cast 15 cm square blocks. When the cast product was inspected for reverse shrinkage, it was as shown in Table 1. In Table 1, “None” in the column of presence or absence of reverse shrinkage means that there is no shrinkage cavity from the middle part to the lower part of the cast product and it is in a healthy state, and “Yes” is the lower end of the cast product. It means that the shrinkage cavities occur within 1/3 of.

[0012]

[Table 1] Example No. Al Cu Mg Others With or without reverse shrinkage 1 27 3.5 0.05 Ti 0.1 None 2 27 3.5 0.05 Zr 0.1 None 3 27 3.5 0.05 Hf 0.1 None 4 27 3.5 0.05 Y 0.1 None 5 27 3.5 0.05 La 0.1 None 6 27 3.5 0.05 Ce 0.1 No 7 27 3.5 0.05 Mm 0.1 No 8 27 3.5 0.05 La 0.1 Ce 0.1 No 9 12 3.5 0.05 Ti 0.1 No 10 20 3.5 0.05 Ti 0.1 No 11 20 0 0.05 Ti 0.1 No 12 20 5 0.05 Ti 0.1 No 13 20 3.5 0 Ti 0.1 No 14 20 3.5 0.01 Ti 0.1 No 15 20 3.5 0.2 Ti 0.1 No Comparative Example No. 1 12 3.5 0.05 Yes 2 20 3.5 0.05 Yes 3 27 3.5 0.05 Yes

[0013]

Since the high aluminum zinc-based alloy of the present invention does not cause reverse drawing during gravity casting, it is possible to produce a high-strength and sound zinc-based alloy mold by gravity casting, which has been strongly demanded in recent years. Suitable for small-volume production molds.

Claims (4)

[Claims] 1. At least 1 selected from the group consisting of 12 to 30% by weight of aluminum and titanium, zirconium, hafnium, yttrium and lanthanide series elements.
A zinc-based alloy for a die, which contains 0.03 to 0.5% by weight of a seed element, the balance being zinc and inevitable impurities, and which does not cause reverse shrinkage during gravity casting. 2. At least one element selected from the group consisting of 12 to 30% by weight of aluminum, 0.01 to 0.2% by weight of magnesium and titanium, zirconium, hafnium, yttrium and lanthanide series elements, and 0.0.
A zinc-based alloy for molds containing 3 to 0.5% by weight, the balance consisting of zinc and inevitable impurities, and preventing reverse shrinkage during gravity casting. 3. Aluminum 12 to 30% by weight, copper 5.
5% by weight or less and titanium, zirconium, hafnium,
At least one element selected from the group consisting of yttrium and lanthanide series elements 0.03 to 0.5% by weight
Zinc-based alloy for molds, which contains zinc and the balance consists of zinc and unavoidable impurities and does not cause reverse shrinkage during gravity casting. 4. Aluminum 12 to 30% by weight, copper 5.
5% by weight or less, 0.01 to 0.2% by weight of magnesium, and 0.03 to 0.5% by weight of at least one element selected from the group consisting of titanium, zirconium, hafnium, yttrium and lanthanide series elements. A zinc-based alloy for molds that contains zinc and the balance is zinc and unavoidable impurities, and does not cause reverse shrinkage during gravity casting.