JPH01234538A - Zinc-based alloy - Google Patents

Abstract

PURPOSE:To improve the mechanical strength, ductility and hardness of the title alloy without impairing its castability and workability by specifying the contents of Al, Cu and Mg in a zinc-based alloy and adding trace amounts of Si and Sr thereto. CONSTITUTION:The compsn. of a Zr-based alloy is formed with, by weight percentage, 6-15% Al, 8-15% Cu, 0.01-1% Si, 0.001-0.1% Sr, 0.01-0.3% Mg and the balance consisting of Zn with inevitable impurities. In the Zn-based alloy, mechanical strength and hardness are improved by the strict regulation of the adding amounts of Al and Cu and by the addition of Si, and the influence of aging (dimentional change and lowering of strength) can furthermore be suppressed. At the time of using the alloy as a mold for the molding of plastics, there is no apprehension of generating cleavage and cracks on the surface and the accuracy of the mold does not decrease even when molding operation is repeated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a high-strength zinc-based alloy suitable for use in molds and the like mainly used for molding plastics.

(Prior Art) In recent years, housings, parts, etc. of various devices such as OA devices have been made of plastic, and model changes have been frequently made to improve the performance of the devices.

Along with this trend, molding cycles for plastic products are being shortened and high-mix low-volume production is being implemented.

For this reason, there is a need for new materials for plastic molds that can be easily cast and processed, and can be manufactured in a short period of time, in place of conventional materials.

Conventionally, metals such as cast iron and cast steel have been used for plastic molding molds, particularly injection molding molds, from the viewpoint of dimensional accuracy and number of molding shots.

Although these metals have excellent mechanical strength, they are difficult to cast and process, and their casting temperatures are high, so large-scale equipment is required for casting.

Further, since casting is performed in a sand mold, the surface of the cast product becomes rough, and therefore a large number of man-hours are required for surface polishing.

Moreover, in order to manufacture a precise mold, a large amount of time is required for machining such as cutting and electrical discharge machining.

Therefore, in terms of delivery time and cost, it has become difficult to meet the demands for high-mix, low-volume production.

Therefore, copper alloys are used instead of cast iron and cast steel, but since copper alloys have a high casting temperature, special equipment and treatments such as oxidation prevention are required for casting. Furthermore, since the casting temperature exceeds 1000° C., gypsum cannot be used for the mold, and a ceramic mold is used, making it difficult and expensive to manufacture the mold.

Moreover, when making molds from copper alloys, as with cast iron and cast steel, long-time electric discharge machining is required, which is no longer meeting the requirements for molds for high-mix, low-volume production.

In order to solve these drawbacks, we have developed a mold material for plastic molding that has a low casting temperature (and is easy to cast and process).
Zinc-based alloys have been proposed.

Many of these zinc-based alloys are zinc alloys for gui casting (Z
DC-1) and contains aluminum, copper, magnesium, etc. in addition to zinc.

For example, Japanese Patent Publication No. 48-209 G7 discloses a wear-resistant zinc-based alloy consisting of υJ, aluminum, copper, magnesium, helium, titanium, and the balance zinc, and Japanese Patent Publication No. 48-20967 discloses aluminum ,
The same discloses a wear-resistant zinc-based alloy consisting of magnesium, helium, titanium, silver and the balance zinc.

However, the above zinc-based alloy has insufficient mechanical strength, and when used as a mold for plastic molding, the precision of the mold decreases as molding operations are repeated, and there is a risk that so-called burrs may occur on the product. .

Furthermore, due to the lack of ductility of the alloy, it has the disadvantage of being prone to cracking and cranking during mold processing and plastic molding, and for this reason, it could only be used for prototype molds.

Therefore, in order to increase the strength of zinc-based alloys, it is possible to increase the amount of aluminum or copper added, but when these elements increase, dimensional changes due to aging become large, making it difficult to manufacture precision molds and complex shapes. There was a problem that it was not suitable for molds.

(Problems to be Solved by the Invention) In view of the above-mentioned drawbacks, the object of the present invention is to provide a zinc-based material with high mechanical strength, excellent ductility, little dimensional change due to aging, and excellent castability and workability. Our goal is to provide alloys.

(Means for Solving the Problems) The present invention was made to solve the above-mentioned conventional problems.
8-15% copper, 0.01-1% silicon, 0 strontium
．． 001-0.1%, magnesium 0.01-0.3%
The above object is achieved by containing zinc and inevitable impurities.

That is, the present invention strictly controls the amounts of aluminum and copper added to the zinc-based alloy, and also improves mechanical strength and hardness by adding silicon, as well as improving the effects of aging (dimensional changes, strength (deterioration) to a minimum.

In the present invention, the amount of aluminum is 6 to 15% by weight in order to fully exhibit the effect of its addition.

If it is too small, it will not be possible to obtain sufficient mechanical strength and hardness, and if it is too large, the solidification starting point will rise, making phase separation more likely to occur, and causing cracks and Js or cavities to occur inside the alloy.

The amounts of copper and silicon added are 8-15% by weight and 0% by weight, respectively.
．． 01-1% by weight.

If it is too small, it will not be possible to obtain sufficient mechanical strength or hardness, and if it is too large, the hardness will increase, but brittleness will increase.
Sufficient mechanical strength cannot be obtained.

In addition, the amount of strontium added is 0.001 to 0.1
Weight%.

If it is too small, it will be impossible to reduce the effects of aging (dimensional changes, strength reduction), and if it is too large, brittleness will increase.
Sufficient mechanical strength cannot be obtained.

Magnesium precipitates at grain boundaries and is known to be particularly effective in preventing intergranular corrosion, and the amount added is 0.
01-''0.3% by weight.

If it is too small, there will be no effect, and if it is too large, the strength of the alloy will decrease and brittleness will increase.

Incidentally, unavoidable impurities here are elements that are unavoidable from being mixed in during the refining process even if the purest zinc ingot, which is normally used as zinc alloy for die casting 1~, is used as a raw material, as well as elements that cannot be avoided during the casting process, etc. Refers to all elements that may be mixed in from the outside, specifically, as specified by JIs-H2SO4, P b O, OO 7 or less, F
e 0.10 or less, cd 0.005 or less, Sn 0.0
Refers to 05 or below.

(Example) The present invention will be explained in detail below.

Examples 1 to 9, Comparative Examples 1 to 5 Predetermined amounts of zinc, aluminum, copper, magnesium, silicon, and strontium were uniformly melted to produce an alloy having the composition shown in Table 1. H53
01 Tensile test piece (1) shown in Reference Figure 8 and Reference Figure B
A hardness test piece (2) shown in (2) was prepared.

The tensile strength of this test piece (1) is JIS-
Measured according to Z2241.

In addition, the Brinell hardness (HB) of the test piece (2) was determined by JIs-Z
Measured according to 2243.

Furthermore, the test piece (2) was aged at 90° C. for 720 hours, and the dimensional change (%) before and after the aging treatment was measured. The above measurement results are shown in Table 2.

Table 1 Table 2 From the above results, the effects of adding silicon and strontium are 0.01 to 1% by weight, o, and ooi to 0.1%, respectively.
It is clearly recognized in the range of % by weight.

(Effects of the Invention) As mentioned above, the zinc-based alloy of the present invention does not impair the castability and workability of the zinc-based alloy by strictly controlling the addition of silicon and strontium and the mixing ratio of aluminum and copper. Therefore, mechanical strength, ductility, and hardness can be improved, and dimensional changes due to aging can be suppressed, and the flaw in zinc-based metals, which is easy to crack, can be improved.

Therefore, when this alloy is used as a mold for plastic molding, there is no risk of cracks or cracks occurring on the surface, and the accuracy of the mold will not deteriorate even after repeated molding operations, so there will be no burrs on plastic products. It is very useful as a mold for plastic molding.

Claims (1)

[Claims] 1. By weight percentage, aluminum 6-15%, copper 8-1
5%, silicon 0.01-1%, strontium 0.001
-0.1%, magnesium 0.01-0.3%, and the balance consists of zinc and unavoidable impurities.