JPH01252749A - Zinc-based alloy - Google Patents

Abstract

PURPOSE:To improve the mechanical strength and tensile elongation rupture of the title alloy and to provide it with excellent mechanical workability by adding trace amounts of Mg and Ti to a Zn-based alloy contg. specific amounts of Al and Cu. CONSTITUTION:The compsn. of a Zn-based alloy is constituted of, by weight, 10-15% Al, >10-15% Cu, 0.01-<0.05% Mg, 0.01-3% Ti and the balance consisting of Zn with inevitable impurities. A trace amount of Ti to be added forms a stable compound with Cu to deposit into grain boundaries, by which the grain boundaries of the alloy are fined and its mechanical strength and surface hardness are improved. It furthermore forms a slip plane at the time of applying stress to provide the alloy with ductility. Mg deposits into the crystal boundaries to show the effect of preventing intergranular corrosion. At the time of using the alloy as a mold for the molding of plastics, there is no apprehension of generating cracks on the surface and the precision of the mold is not reduced even if 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 for molding plastics.

(Prior Art) In recent years, various types of equipment such as office automation equipment (OA equipment) have been made of plastic for their parts and parts, and model changes have been made frequently to improve the performance of the equipment.

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

For this reason, new materials are required 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 and special injection molding molds in terms of dimensional accuracy and number of molding seats.

Although these metals have excellent 1a mechanical strength, they cannot be cast or
It is difficult to process and requires large-scale equipment for casting because the casting temperature is high.

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 copper alloys have a high casting temperature.

#-shaping requires equipment and treatment to prevent oxidation, and the casting temperature exceeds 1000°C, so plaster cannot be used for the #-type, and ceramic molds are used.

Ceramic molds are expensive and difficult to manufacture.

Moreover, like cast iron and cast steel, copper alloys require long electrical discharge machining, so they are not meeting the requirements for molds for high-mix, low-volume production.

In order to solve these drawbacks, we 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), for example, the special public
20% No. 7 discloses a pressure-resistant zinc-based alloy consisting of aluminum% JR% magnesium, berylicum, titanium, and the balance zinc, and Japanese Patent Publication No. 51-5342 discloses a pressure-resistant zinc-based alloy consisting of aluminum, copper, magnesium, perilicum, and titanium. , silver and a balance zinc-based alloy are disclosed, respectively.

(Problems to be Solved by the Invention) However, although the surface hardness of all of the above zinc-based alloys improves by adding perilicum, they develop brittleness and become brittle, and furthermore, perilicum worsens the working environment. There were problems such as.

In addition, since the zinc-based alloy described 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 in the molded product. However, it has drawbacks such as lack of ductility and easy cracking during processing and molding, and therefore can only be used for prototype molds.

Points (Means for solving the problem) - The present invention was made to solve the above-mentioned conventional MA problem, and it involves adding trace amounts of magnesium and titanium to a zinc-based alloy containing aluminum and copper. The purpose of this invention is to improve mechanical strength and tensile elongation at break, and to provide an alloy for molds with excellent machinability.

The zinc-based alloy of the present invention has an aluminum content of 10 to 15% by weight.
, over 10% copper, 151! % or less, magnesium α
01% by weight or more and less than 05% by weight, titanium (Lo
The above object is achieved by containing zinc or zinc and unavoidable impurities.

The small amount of titanium added in the present invention forms a stable compound with copper and precipitates at the grain boundaries, making the crystal grain size of the alloy finer, improving mechanical strength and surface hardness, and improving stress resistance. O can form a slip surface during loading and impart ductility.The amount of O added is limited to (LOI ~ 3% by weight, but too little will have no effect, and too much will increase surface hardness but cause brittleness. increases, mechanical strength and elongation decrease.

Magnesium is known to be effective in preventing grain boundary precipitation, especially intergranular corrosion, and its addition is essential for suppressing intergranular corrosion. Added less than

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.

The amount of aluminum added is 10 to 15% by weight. If it is too small, the mechanical strength and hardness will be insufficient, and if it is too large, the solidification starting point will rise and phase separation will occur easily (causing shrinkage cavities).

The amount of copper added is more than 10% and less than 15% by weight.

If it is too small, the mechanical strength and surface hardness will be insufficient, and if it is too large, the hardness will increase, but brittleness will develop, making it difficult to impart ductility.

Incidentally, unavoidable impurities here refer to unavoidable impurities, even if the purest zinc ingot, which is normally used as a zinc alloy for Gui casting, is used as a raw material.
It refers to elements that must be avoided during the refining process and all elements that may be mixed in from the outside during the casting process, etc. Specifically, as specified in JIS-H2BO3 type, weight percentage Pb11007 or less, Feα10
Hereinafter, Cdα005 or less and Snα005 or less are referred to.

(Example) Examples of the present invention will be described below.

Examples 1 to 9, Comparative Example 1 to σ.

Predetermined amounts of each component of zinc, aluminum, copper, magnesium, and chikunicum were sufficiently dissolved to obtain a uniform composition, thereby producing an alloy having the composition shown in Table 1.

From this alloy, a tensile test piece (1) shown in JIS-H5301 reference diagram A and a hardness test piece (2) shown in reference diagram B
)It was created.

The tensile strength (Kit/j) and tensile elongation at break (%) of this test piece (1) immediately after casting (within 30 hours after casting) were determined by J
Measured according to IS-Z2241.

In addition, the Grinnell hardness (HB) of the test piece (2) was determined by JIS-
Measured according to Z2243.

The above measurement results are shown in Table 2r.

Table 1 (Unit: Weight %) Table 2 □ = Te From the above results, AI-Cu with the above specific composition
-M g -Z In the n-based zinc-based alloy, the effect of adding titanium is obvious in the range of 0.01 to 3% by weight.

(Effect of the invention) The zinc-based alloy of the present invention has the above structure.

By strictly controlling the addition of Titaecum and the mixing ratio of aluminum, copper, and MagneRecum, it is possible to achieve excellent mechanical strength and surface hardness, and to improve the ease of cracking, which is a drawback of zinc-based alloys.

Furthermore, this zinc-based alloy has a low casting temperature and is easy to cast and process.

Therefore, when this alloy is used as a plastic mold, there is no risk of cracks occurring on the surface, and the precision of the mold will not deteriorate even after repeated molding operations.
It is very useful as a material for molds for BLASTIC 9It type.

Claims (1)

[Claims] 1. Weight percentage: 10-15% aluminum, 10% copper
% to 15%, magnesium 0.01% to less than 0.05%, titanium 0.01 to 3%,
A zinc-based alloy characterized in that the remainder consists of zinc or zinc and inevitable impurities.