JPH01230742A - Zinc-based alloy - Google Patents

Abstract

PURPOSE:To improve the mechanical strength of the title alloy, to reduce its dimentional change caused by aging and to facilitate its casting and working by adding trace amounts of Si and Cr to an Zn-based alloy contg. specific amounts of Al, Cu and Mg. CONSTITUTION:The compsn. of an alloy is formed with, by weight, 6-15% Al, 8-15% Cu, 0.01-1% Si, 0.03-3% Cr, 0.01-0.3% Mg and the balance consisting of Zn with inevitable impurities. Trace amounts of Si to be added to the alloy improves the mechanical strength and hardness. The effect of aging (dimentional change and lowering of strength) can furthermore be suppressed to a minimum by the addition of Cr. At the time of using the Zn-based alloy as a mold for the molding of plastics, there is no apprehension of generating cracks onto the surface. The accuracy of a mold does not decrease as well even when molding operation is repeated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a zinc-based alloy that is suitably used as a mold 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 high casting temperatures, 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, which poses the problem that the mold is expensive and difficult to manufacture.

Moreover, the production of molds for copper alloys requires long electrical discharge machining, just like for cast iron and cast steel, so it no longer meets 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 die casting (Z
DC-1) is used as a heath, for example,
Japanese Patent Publication No. 20967 discloses a wear-resistant zinc-based alloy consisting of aluminum, copper, magnesium, beryllium, titanium, and the balance zinc; , silver and balance zinc are disclosed, respectively.

However, although the hardness of the above two types of zinc-based alloys is improved by adding beryllium,
There were problems such as the development of brittleness and the deterioration of the working environment.

In addition, since the zinc-based alloy mentioned above has insufficient mechanical strength, as molding operations are repeated using this mold, the accuracy of the mold decreases, and there is a risk that so-called burrs may occur on the plastic product. Moreover, since the ductility of the zinc-based alloy is insufficient, there are drawbacks such as the tendency to crack or break during mold processing or plastic molding.

Therefore, this zinc-based alloy could only be used for prototype molds.

(Problems to be Solved by the Invention) In view of the above-mentioned drawbacks, an object of the present invention is to provide a zinc-based alloy that has high mechanical strength and hardness, little dimensional deformation due to aging, and excellent castability and workability. It is in.

(Means for Solving the Problems) The zinc-based alloy of the present invention was made to solve the above conventional problems, and contains 6 to 15% by weight of aluminum.
, 8 to 15% by weight of copper, 0.01 to 1% by weight of silicon, 0.03 to 3% by weight of chromium, and 0.01 to 0.3% by weight of magnesium, with the remainder consisting of zinc and unavoidable impurities. This achieves the above objective.

That is, the present invention adds silicon and chromium in the amount of 100% to a zinc-based alloy containing aluminum, copper, and magnesium, thereby improving mechanical strength, reducing dimensional changes due to aging, and making casting and processing easier. It is easy to manufacture molds in a short time.

The trace amount of silicon added in the present invention improves mechanical strength and
In addition to improving hardness, the addition of chromium can minimize the effects of aging (dimensional changes, strength reduction).

In the present invention, in order to fully exhibit the effect of adding aluminum, the amount added must be 6 to 15% by weight.

If the amount is too low, the mechanical strength and hardness will not be sufficiently exhibited, and if the amount is too high, the solidification start point will rise, making phase separation more likely to occur, making it easier for sink marks and cavities to occur.

The amounts of copper and silicon added are 8 to 15% by weight and 0.5% by weight, respectively.
01-1% by weight.

If it is too small, the mechanical strength and hardness will be insufficient, and if it is too large, the hardness will increase, but brittleness will develop and sufficient mechanical strength will not be obtained.

Further, the amount of chromium added is 0.03 to 3% by weight.

If it is too small, the effects of aging (dimensional changes, strength reduction) cannot be reduced, and if it is too large, (:, r A 1
By producing hard spots such as q, brittleness increases, sufficient mechanical strength cannot be obtained, and dimensional shrinkage occurs.

Magnesium is known to precipitate at grain boundaries and is particularly effective in preventing intergranular corrosion. Its addition is essential for suppressing intergranular corrosion, and addition of 0.01 to 0.3% by weight is essential. be done.

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 refer to unavoidable impurities, even if the purest zinc ingot, which is normally used as zinc alloy for die-casting, is used as a raw material.
In addition, it refers to all elements that are unavoidable to be mixed in during the refining process and all elements that may be mixed in from the outside during the casting process, etc. Specifically, as specified in JTS-H5301 type, weight percentage P b 0.007 or less, F e
O, 10 or less, CdO, OO5 or less, Sn 0.005 or less.

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

Examples 1 to 9, Comparative Examples 1 to 6 Predetermined amounts of each component of zinc, aluminum, copper, magnesium, silicon, and chromium were sufficiently dissolved to obtain a uniform composition, and an alloy having the composition shown in Table 1 was prepared. Created.

From this alloy, JIS-) (5301 tensile test piece (1) shown in reference drawing A and hardness test piece (1) shown in reference drawing B)
2) was created.

The tensile strength (kg/mm2) of this test piece (1) is JIs
- Measured according to Z2241.

In addition, the Brinell hardness (HB) of the test piece (2) was determined according to JIS-
22243. Furthermore, test piece (2) was
Aging treatment was performed at 5° 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.

(Margins below) Table 1 Table 2 From the above results, Al-Cu-
In the Mg-Zn zinc-based alloy, the effect of adding silicon and chromium is 0.01 to 1.0% by weight, respectively.
．． It is clearly recognized in the range of 0.03 to 3.0% by weight.

(Effect of the invention) Since the zinc-based alloy of the present invention has the above structure,
It is possible to improve the mechanical strength and hardness of zinc-based alloys without impairing their castability and workability, and it is also possible to suppress dimensional changes due to aging. can be improved.

Therefore, when this zinc-based alloy is used as a mold for molding plastics, there is no risk of 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 extremely useful as a material for plastic molds.

Claims (1)

[Claims] 1. By weight percentage, aluminum 6-15%, copper 8-1
5% silicon, 0.01-1% silicon, 0.03-3% chromium, and 0.01-0.3% magnesium, with the remainder consisting of zinc and inevitable impurities.