JPH0324245A - Zinc-base alloy for cast mold and cast mold - Google Patents

Abstract

PURPOSE:To obtain a zinc-base alloy for cast metal mold having high mechani cal strength, excellent in castability, and practically free from the occurrence of casting detects in a specific surface layer by specifying a composition consisting of Al, Cu, Mb, and Zn. CONSTITUTION:This alloy is a zinc-base alloy for cast metal mold which has a composition consisting of, by weight, 9.6.-10.5% Al, 9.0-10.5% Cu, 0.01-0.20% Mg, and the balance Zn besides inevitable impurities and in which Rogonne flow length at 430 deg.C and solidification range are regulated to >=230mm and >=13 deg.C, respectively, and also defects of >=50mum within 3mm of the surface of a casting are regulated to <=1 piece/100cm<2>. By using this alloy, a mold excellent in mechanical strength, such as tensile strength and hardness, and having superior casting surface can be easily cast. It is desirable that, at the time of the casting, a top heating method is adopted in the solidification of the molten metal to apply heating to the top and also cooling to the bottom in order to avoid the segregation of Al.

Description

[Detailed Description of the Invention] [Industrial Application Field J] The present invention has high mechanical strength, excellent castability, and can obtain a sound tin product with almost no defects in tin manufacturing, and therefore is suitable for plastic injection molding. It also relates to a zinc base metal for a cast mold suitable for use as a cast mold used in press working, and a mold formed by casting the same. [Prior Art] Conventionally, Al. 1% by weight, Cu3.0% by weight, Mg0.
A zinc alloy ZAS (trade name) containing 0.5% by weight is widely used.This alloy can be cast at a temperature of 410 to 450℃, has good pattern reproducibility and casting surface, and is widely used.
Casting is extremely easy as no special molten metal treatment is required.

In addition, a tensile strength of 22 to 27 kgf/mm can be obtained by sand casting. However, in recent years, with the trend toward high-mix, low-volume production, studies are being conducted to upgrade zinc molds for low-volume production, that is, to improve their strength. For this reason, as a zinc-based alloy related to this, for example, JP-A-51-79633
In the publication, AQ8-11% by weight, Cu8-It% by weight
．． Ni8 to 11% by weight, Mgo. A high-strength, wear-resistant zinc alloy containing 0.3 to 0.06% by weight of Zn and the balance consisting of Zn is disclosed. Furthermore, Japanese Patent Publication No. 51-5342 discloses AJ of 2 to 12% by weight and Cu of 1 to 10% by weight. M
g0.01-0.5% by weight, EeO. OZ~0.15% by weight, TiO. Of-1.5% by weight, AgO. 01-3
．． A wear-resistant zinc-based alloy containing 0% by weight of zinc with the balance being zinc is disclosed. Furthermore, JP-A-63-385
No. 48 discloses AMl - 10% by weight, Cul - 15% by weight, Mg 0.01 - 0.5% by weight, YO. 02～
Zinc-based alloy containing 1.0% by weight and the balance consisting of Zn,
Or, in Japanese Patent Application Laid-Open No. 63-65043, Cu5~1
5% by weight. Mg 0.2% by weight or less, lanthanide 0.0
Contains 5 to 3% by weight and AQ in an amount satisfying a specific formula,
A zinc-based alloy is disclosed in which the remainder is Zn. [Problems to be solved by the invention] However, the invention described in JP-A-51-79633 is based on AQ containing a large amount of N1 as well as AQ and Cu content.
It is a -Cu-Nu-Mg-Zn alloy, and by containing a large amount of N1, the melt flowability becomes poor and t4 manufacturing defects are likely to occur. In addition, the invention described in Japanese Patent Publication No. 51-5342 discloses the addition of trace amounts of Be, Ti, etc. Ag was easily oxidized in the molten metal, and dross was entrained, causing casting defects, which could reduce the manufacturing yield of plastic molded products. Furthermore, the invention described in JP-A-63-38548 and the invention described in JP-A-63-65'J43 are each Y
Since the steel contains lanthanide and lanthanide, these elements are likely to be oxidized and casting defects such as dross entrainment are likely to occur, resulting in the same problems as mentioned above. In view of the above circumstances, the present invention is for a mold made by casting which has high mechanical strength, excellent castability, and almost no casting defects! I! The purpose is to provide lead-based alloys and molds made by casting them. [Means for Solving the Problems] In order to achieve the above-mentioned problems, the present inventors, in the course of intensive research, carried out the machining process described in Japanese Patent Application No. 1-5993 filed by the present applicant. We focused on the zinc-based alloy, which was made of 6 to 12 wt% AQ-5.5 to 12 wt% Cu-Mg-Zn, and which required machining due to its poor castability, and determined the composition range of this alloy. As a result of various studies with different AQ and Cu compositions, we surprisingly found that castability was extremely good and there were almost no casting defects. The present invention was made based on such knowledge, and A Q 9.6 to 10.5% by weight+Cu9. O~1
0.5% by weight. Consisting of 0.01 to 0.20% by weight of Mg, the balance being Zn apart from unavoidable impurities, the Ragonne flow length at 430°C is 230cm or more, and the solidification temperature range is 13
℃ or higher, and there is no more than one defect of 50 μm or more per 100 cm within 3 inches of the surface of the cast product, and a mold made from the same. In the present invention, the Ragonne flow length is defined as a process in which a predetermined molten metal is sufficiently stirred at 430°C, and one end of a glass tube with an outer diameter of 6 mm and an inner diameter of 4 mm is inserted into the molten metal. This is the value obtained by applying a negative pressure of 240a+a+Hg from the other end and measuring the length of the metal that flows into the glass tube and solidifies.In the present invention, in order to ensure good castability, this Lagon Nut at 430℃ The flow length must be 230 mm or more. If the Ragonne flow length is less than 230 mm,
The flowability of the hot metal deteriorates, making it difficult for the hot metal to reach every corner of molds of various shapes. Similarly, in order to obtain good castability, the solidification temperature range width must be 13°C or more. If the solidification temperature range is narrower than 13°C, casting defects are likely to occur inside the cast product. The reason for this is not clear, but it is thought to be because the difference in cooling temperature between the surface and the inside of the casting becomes smaller, making it difficult for bubbles to escape. Furthermore, in the present invention, in order to obtain a sound cast product, defects weighing 50μ or more are present within 3 mm of the cast product surface at a rate of 1/100.
It must be within cm2. Here, the reason for limiting the scope of the precepts of the present invention will be explained once again. Afl: When L exceeds 0.5% by weight, the solidification temperature range becomes narrow and casting defects increase. On the other hand, if the content does not reach 9.6% by weight, the fluidity decreases and the flow of the molten metal becomes poor, and casting defects also increase.

Cu: If it exceeds 10.5% by weight, the fluidity decreases and the flow of the metal becomes poor, and casting defects increase. On the other hand, if it does not reach 9.0% by weight, the solidification temperature range will be narrow and casting defects will increase. Mg: Mg is 0.01 to 0.0 to prevent intergranular corrosion.
2% by weight is required. If it exceeds 0.2% by weight, the alloy becomes brittle. The method for casting such an alloy of the present invention may be the same as that for ZAS alloy, and in order to avoid segregation of aluminum during solidification, it is preferable to use a top heat method in which the top part is heated and the bottom part is cooled. [Function] As described above, in the present invention, A Q - Cu - Mg -
Since it is made of Zn and no other additive elements are added, there is no casting defect caused by the generation of dross and its entrainment.Moreover, the Ragonne flow length is greater than the specified length and the solidification temperature range width is Because it exceeds the specified value, it has excellent castability and mechanical strength of 36 kg/am.
That's all. Examples of the present invention will be described below. Example A zinc-based alloy shown in Table 1 was prepared by melting it in a graphite crucible. Next, these alloys were melted again and cast into test molds at a casting temperature of 430°C, and during solidification, top heating was performed by heating the upper part of the mold with a burner. The number of casting defects, tensile strength, and Brinell hardness of the thus obtained castings were evaluated. In addition, the Ragonne flow length and solidification temperature range width at 430°C of these zinc-based alloys were measured, and these are also shown in Table 1. The test methods for each of these evaluations are as follows.

(Test conditions) (1.) Number of tin defects: Defects were detected by deep penetrating scratches on the 10 cm square surface of the lower part of the #4 product, and the number of defects of 50 μm or more was measured. For the 8 constant surface, measurements were taken on three surfaces: the casting surface, a surface ground by 1.5 mm at the same location, and a surface ground further by 1.5 mm (3 m from the surface + depth), and the average value was taken as the measured value.

(2) Tensile strength: Measured using an Instron tensile tester at a tensile rate of lc-/min and a temperature of 25°C.

The test piece was a JIS No. 4 test piece.

(3) Brinell hardness: Measured using a Brinell hardness tester at a load of 1000 kg, held for 30 seconds, and held at a holding temperature of 25°C. (Left below) The following can be seen from the construction table. (1) If the Al content is lower or the Cu content is higher than the alloy of the present invention, the fluidity expressed by the Ragonne flow length deteriorates. (2) If the AQ is higher or the Cu is lower than the alloy of the present invention, the solidification temperature range becomes narrower. (3) When an attempt was made to improve the strength by adding a small amount of misch metal or Be to the alloy of the present invention, many casting defects occurred. (4) Similarly, when Ni is added to the alloy of the present invention,
As the flowability deteriorated, the number of casting defects increased. All of the alloys of the present invention have a mechanical strength of 36 kgf/mm or more, and therefore, under average conditions, they are molded by injection molding of polyacetal resin of 5 (+000 - 100,000 shots) and then subjected to SPCI in a press.
．． It withstood 2a+■toooo times.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, it has good formability similar to ZAS alloy, the casting method for ZAS alloy can be used as is, and
It is possible to obtain a zinc-based alloy for molds, which has significantly improved mechanical strength compared to S alloy, and which hardly causes casting defects, and a mold made by casting the same.

Claims (1)

[Claims] 1. 9.6 to 10.5% by weight of aluminum, 9.0 to 10.5% by weight of copper
10.5% by weight, 0.01 to 0.20% by weight of magnesium, the balance consisting of zinc apart from unavoidable impurities, 43
The Ragonne flow length at 0°C is 230 mm or more, the solidification temperature range is 13°C or more, and the surface of the cast product is 5 mm or more.
A cast zinc-based alloy for molds that has less than 1 defect of 0 μm or larger per 100 cm^2. 2. Aluminum 9.6~10.5% by weight, copper 9.0~
10.5% by weight, 0.01 to 0.20% by weight of magnesium, the balance consisting of zinc apart from unavoidable impurities, 43
A casting mold having a Ragonne flow length of 230 mm or more at 0°C, a solidification temperature range of 13°C or more, and a defect of 50 μm or more within 3 mm of the surface within 1/100 cm^2.