JPS6360250A - Zinc-base alloy - Google Patents

Abstract

PURPOSE:To obtain a zinc-base alloy having high surface hardness, excellent in mechanical strength, free from brittleness, and easy of casting and working, by specifying a composition consisting of Al, Cu, Mg, and Zn. CONSTITUTION:The zinc-base alloy has a composition which consists of, by weight, 11-20% Al, 8-15% Cu, 0.03-0.2% Mg, and the balance Zn with inevitable impurities and in which relationship between Al and Cu contents satisfies an inequality 0<Al-0.85Cu<=10 and is applicale to metal mold for plastic molding. The above alloy is improved in surface hardness due to precipitation of CuAl2 in the surface layer part and also is improved in plastic deformability and reduced in brittleness in the inside and, moreover, it has high mechanical strength and low casting temp. As a result, when used for the above metal mold, the above alloy is free from cracks on the surface, also free from deterioration in metal mold accuracy even after subjected to repeated molding operations, and easy to be cast and worked.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a zinc-based alloy that has excellent mechanical strength and is easy to cast and process, and thus can be used for molds for molding plastics and the like.

(Prior Art) In recent years, plastic parts have been used for various damping devices such as OA equipment, and model changes have been made frequently in order to improve the performance of the equipment. Along with this, plastic molding cycles have become shorter, and high-mix, low-volume production is being implemented. For this reason, plastic molds are required to be made of materials that are easy to cast and process.

Plastic molds, especially injection molds,
Metals such as cast iron, cast steel, and copper alloys are used. However, although these metals have excellent mechanical strength, #
Difficult to manufacture and process. Because cast iron and #steel have high casting temperatures, large-scale equipment is required for casting. 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 precise molds, it is necessary to perform electric discharge machining for a long time. Copper alloys also require high casting temperatures, so casting requires equipment and treatments to prevent oxidation. Since the casting temperature exceeds 1000°C, gypsum cannot be used for the casting mold, so a ceramic mold is used. Ceramic molds are expensive and difficult to manufacture. Moreover, copper alloys similarly require long electrical discharge machining.

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. This zinc-based alloy is based on the zinc alloy for gui casting (2DC-1), and contains aluminum, copper, magnesium, etc. in addition to zinc. For example, in Japanese Patent Application Laid-open No. 51-79633, aluminum is 8 to 11 inches, copper is 8 to 10 inches by weight percentage,
11 inches, nickel 8-11 inches, magnesium 0.03-
A high-strength, wear-resistant zinc-based alloy is disclosed containing 0.06% of zinc, with the remainder consisting of zinc and unavoidable impurities. However, these zinc-based alloys have insufficient mechanical strength;
When used as a mold for plastic molding, surface cracks may occur. Furthermore, as molding operations are repeated using this mold, the precision of the mold decreases and cracks occur in the molded product.

(Problems to be Solved by the Invention) The present invention solves the above conventional problems, and its purpose is to provide a zinc-based alloy that has excellent mechanical strength and is easy to cast and process. There is a particular thing.

(Means for solving the problem) The gist of the present invention is that aluminum 1
1-20%, copper 8-15% and magnesium 0.03-
Contains 0.2 h, and the aluminum content is ++ compared to copper.
It is a zinc-based alloy that satisfies formula 11, with the remainder consisting of zinc and inevitable impurities.

0<[AI(%)]-0,85[Cu(%)]≦10・
・・・・・・・・・・・・・・・(1) That is, the present invention:
Weight fraction: 11-20% aluminum, 8-15% copper
and 0.03 to 0.2% of magnesium, the balance being zinc and unavoidable impurities, and the ratio of aluminum to copper is 0.85 times that of copper, that is, more than the amount that satisfies the chemical equivalent of CuAl2+11 It is an essential requirement that the relationship in the formula be satisfied.

In fact, Cζ of this alloy is Cu A in Table 111 of the alloy.
12 precipitates, the surface hardness increases, and the interior consists of a superplastic alloy of zinc and aluminum and the ε phase of zinc-copper, so when the growth of crystal grains is suppressed, the eutectic ζ and plastic deformability increase, It is characterized by the absence of the brittleness that is common with these high-hardness alloys.

In this alloy, the addition of magnesium is essential to suppress intergranular corrosion. If the amount added is too large, the brittleness of the alloy increases and strength decreases. If the aluminum content is too low, the hardness will be insufficient and the strength will also be insufficient; if the aluminum content is too high, the hardness will increase, but it will become brittle and the strength will decrease.

This tendency is more pronounced with copper, and in particular, if the amount added is too large, the fluidity of the alloy is significantly inhibited, so the component ratio must be controlled even more than with aluminum.

(Example) The present invention will be described below with reference to examples.

Example 1 After uniformly melting aluminum 11.0% by weight, copper 8.0% by weight, magnesium 0.05% by weight and residual zinc, a tensile test piece shown in JIS H5301 reference diagram A was created. . The tensile strength of this test piece (kV/d
') was determined according to JIS Z 2241. Furthermore, the Brinell hardness (I(B)) of the test piece was determined by JIS
Measured according to Z 2243. As a result, the tensile strength was 4s, 5 (kg/-), and the Brinell hardness was 16.
It was 0 (HB). These results are shown in Table 1.

Example 2 A tensile test piece was prepared in the same manner as in Example 1, except that the aluminum content was 15.0% by weight. When the tensile strength and Brinell hardness of this test piece were measured, the tensile strength was 45.6 (ki/d) and the Brinell hardness was 210 (HB). These results are shown in Table 1.

Example 3 A tensile test piece was prepared in the same manner as in Example 1 except that the weight of copper was increased by 11.0%. When the tensile strength and Brinell hardness of this test piece were measured, the tensile strength was 45.3 (kq/-) and the Brinell hardness was 175 (
HB).

These results are shown in Table 1.

Example 4 A tensile test piece was prepared in the same manner as in Example 1, except that the aluminum content was 18.07 tjl and the copper content was 11.0% by weight. When the tensile strength and Brinell hardness of this test piece were measured, the tensile strength was 49.2 (#/aJ) and the Brinell hardness was 215 (HB). These results are shown in Table 1.

Example 5 13.0% aluminum and 15.0% M
A tensile test piece was prepared in the same manner as in Example 1, except for the following. When the tensile strength and Brinell hardness of this test piece were measured, the tensile strength was 47.8 (kq/-) and the Brinell hardness was 205 (HB). These results are shown in Table 1.

Example 6 20.0% by weight of aluminum, 15.0% by weight of copper
A tensile test piece was prepared in the same manner as in Example 1, except for the following. When the tensile strength and Brinell hardness of this test piece were measured, the tensile strength was 45.1 (kg/lj) and the Brinell hardness was 250 (HB). These results are shown in Table 1.

(Left below) Comparative Example 1 Aluminum 10.61! fl chi, copper 10.2ii
The amount of magnesium is 0.041fi<, and Iζ
A tensile test piece was prepared in the same manner as in Example 1, except that 9.9% by weight of nickel was added. When the tensile strength and Brinell hardness of this test piece were measured, the Brinell hardness was 200 (HB), but the tensile strength was 35.0 (kg
/lj), and was very brittle and broke during processing. These results are shown in Table 2.

Comparative Example 2 A tensile test piece was prepared in the same manner as in Example 1, except that the aluminum content was 4.0% by weight, the copper content was 3.0% by weight, and the magnesium content was 0.04M#. When the tensile strength and Brinell hardness of this test piece were measured, the tensile strength was 2.
5.6 (~/-), and the Brinell hardness is 110 (HB
)Met.

These results are shown in Table 2.

Comparative Example 3 A tensile test piece was prepared in the same manner as in Example 1, except that the aluminum content was 3.5% by weight, the copper content was 3.5% by weight, and the magnesium content was 0.04% by weight. When the tensile strength and Brinell hardness of this test piece were measured, the tensile strength was 2.
7.6 (kg/lj), Brinell hardness is 115 (HB)
Met. These results are shown in Table 2.

Comparative Example 4 Except that aluminum was 20.0311J3t%,
A tensile test piece was prepared in the same manner as in Example 1. When the tensile strength and Brinell hardness of this test piece were measured, the tensile strength was 25.3 (#/d) and the Brinell hardness was 2.
It was 25 (HB).

These results are shown in Table 2.

Comparative Example 5 A tensile test piece was prepared in the same manner as in Example 1, except that the aluminum content was 20.0% by weight and the copper content was 11.0% by weight. When the tensile strength and Brinell hardness of this test piece were measured, the tensile sag was 39.2 ckg/d') and the Brinell hardness was 235 (FIB). These results are shown in Table 2.

Comparative Example 6 A tensile test piece was prepared in the same manner as in Example 1, except that the copper was 15.0 weight f1 thick. When the tensile strength and Brinell hardness of this test piece were measured, the tensile strength was 37.8.
(kg/-), and the Brinell hardness was 245 (HB). These results are shown in Table 2.

Comparative Example 7 Aluminum 20.0I! ffi%, copper 15.0w1%, magnesium 0.35! ! A tensile test piece was prepared in the same manner as in Example 1, except that m % was used.

When the tensile strength and Brinell hardness of this test piece were measured, the tensile strength was 35.1 (kg/i), and the Brinell hardness was 250 (I(B)).

These results are shown in Table 2.

(The following is a blank space) (Effects of the Invention) Since the zinc-based alloy of the present invention has the above-described structure, it has high surface hardness, excellent mechanical strength, and is not brittle. Therefore, when this alloy is used as a plastic mold, there is no risk of cracks occurring on the surface. Even after repeated molding operations using this alloy, the accuracy of the mold does not deteriorate. This alloy has a low casting temperature and is easy to cast and process. As a result, the zinc-based alloy of the present invention is useful as a material for plastic molds.

Claims (1)

[Claims] 1. Aluminum 11-20%, copper 8-1% by weight
5% and magnesium 0.03 to 0.2%, the aluminum content satisfies formula (1) with respect to copper, and the balance is zinc and inevitable impurities. 0<[Al(%)]-0.85[Cu(%)]≦10・
・・・・・・・・・・・・・・・(1)