JPH02284754A - Metallic mold for casting light alloy - Google Patents

Abstract

PURPOSE:To reduce the lowering of molten metal temp. and to prevent the generation of solidified piece by using titanium alloy for forming titanium nitride layer on a surface at the prescribed position in one side of metallic mold having a sprue in the dividable metallic molds. CONSTITUTION:In the metallic mold for casting light alloy composed of one pair of the dividable metallic molds, the titanium alloy for forming the titanium nitride layer on the surface is used at the prescribed position in at least one side of the metallic mold having the sprue in the dividable metallic molds. Heat conductivity of this titanium alloy is as low as that of ceramic, and this has excellent toughness and further, lower cost than that of the ceramic. Further, since the high hardness titanium nitride is formed on the surface of this titanium alloy, this titanium alloy has excellent high temp. stability and also does not react with the light alloy of aluminum, magnesium alloy, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a mold for casting light alloys, particularly used for casting light alloys such as aluminum alloys and magnesium alloys.

[Conventional technology]

Die-casting aluminum alloy, magnesium alloy, etc.
Molds are used to perform high-pressure casting, etc., and when pouring the molten light alloys mentioned above, the molds are designed to prevent the temperature of the molten light alloys from dropping. For example, there are those in which ceramics such as sialon are applied to the tip of the sleeve or chimp.

[Problem to be solved by the invention]

The molds used when casting light alloys such as aluminum and magnesium alloys by die casting or high pressure casting have large heat containers and are made of materials with good thermal conductivity. The molten metal of these light alloys passes through the sprues, sleeves, runners, etc. provided in the mold and is filled into the cavity of the mold, so heat is removed over time and the temperature drops, causing the molten metal to cool down. A coagulated layer is formed in a part of the area. Therefore, during subsequent pouring of molten metal, this solidified layer becomes solidified pieces due to breakage caused by injection by the chip and is filled into the cavity together with the molten metal. However, as is well known, a thin oxide film is usually formed on the surface of the solidified piece, resulting in poor adhesion and, as a result, contributing to a decrease in the strength of the cast product.

In order to avoid such problems, ceramics are used to prevent the temperature of the molten metal from decreasing, but as is well known, ceramics are expensive and have the drawbacks of poor toughness and breakage.

Furthermore, when this is used for the cast-out bottle part, the injection sleeve, the tip part for local pressurization, the sleeve part, etc., the mold release material is used in the current products such as 5KD61 (J I SG4404). If it is insufficient, it will seize with the alloy, causing problems during sliding during mold release or injection, resulting in dimensional defects in the cast product, and cavities due to poor pressurization. A problem has arisen.

Accordingly, an object of the present invention is to provide a mold for casting a light alloy, which is capable of casting inexpensive and highly reliable light alloy casting products.

[! l! Means for Solving Problem 3] The present invention has been made to solve the above-mentioned problems, and therefore, the structure of the light alloy casting mold according to the present invention consists of a pair of splittable molds. This light alloy casting mold is characterized in that a titanium alloy having a titanium nitride layer formed on its surface is used at a predetermined position of at least one of the molds on the side having a sprue.

[Effect]

According to the present invention, a titanium alloy is used in which a titanium nitride layer is formed in a predetermined position of one of the light alloy casting molds.

The thermal conductivity of this titanium alloy is as low as that of ceramics, and in addition to its excellent toughness, it is also lower in cost than ceramics, and moreover, a highly hard titanium nitride layer is formed on the surface of this titanium alloy. Therefore, this titanium alloy has excellent high temperature stability and does not react with light alloys such as aluminum and magnesium alloys.

〔Example〕

Examples of the present invention will be described below.

■Futamafuta This first embodiment uses Ti-6A/! as a titanium alloy for the ejection sleeve and tip of the lower mold. -4V using AC
It is made by high pressure casting of 8C (JISH5202) aluminum alloy.

More specifically, after polishing the inner diameter of a sleeve with an inner diameter of 50 mm, the finished surface was subjected to gas nitriding treatment.
/l 171 thick TiNJi is formed, and
The surface of the chip was also treated in the same way as the inner surface of the sleeve, and these were attached to the lower mold G, and a disc-shaped product with a diameter of 180 mm was made into
Built.

The thickness of this TiNji is related to durability, but for practical purposes it is 1
A thickness of 0 μm was sufficient.

On the other hand, castings made of the same material and having the same dimensions as those described above were cast using a mold equipped with a conventional 5KD611!4' sleeve and a thousand knobs, and mechanical strength tests were conducted on both products, as shown in Table 1. I got the exact result.

It can be seen from Table 1 (Table 1, 9: Mechanical Strength Comparison Table) that the molds of this example are superior to conventional molds.

This is because sleeves and tips made of titanium alloys have superior thermal conductivity and heat capacity 1 properties as shown in Table 2, compared to conventional ones.

Table 2: Comparison of properties with titanium alloys However, the unit of thermal conductivity is cal/cm·sec°C1, and the unit of thermal shock is cat/cm1.

By the way, as is well known, titanium alloys are sensitive to oxygen atmosphere at high temperatures.

However, since a TiN layer is formed on the surface of this titanium alloy, it is stable even at high temperatures, and therefore does not cause any particular problems in use.
Moreover, as shown in Table 2 above, titanium alloys have excellent properties, so it is possible to cast products with high mechanical strength without the generation of a solid pieces.

Furthermore, during mold release work during casting work, there was no seizure of the cast pin, and there was no occurrence of cracking as in the case of ceramics.

[JJL[fl This embodiment differs from the first embodiment in the inner diameter of the sleeve. In other words, the inner diameter is 70mm and the 250T
The piston for the compressor was cast using ON's horizontal die-casting machine.

In this embodiment, the AC8 inside this sleeve is
Measure the cooling rate and solidification time between the liquid phase of the molten metal C,
Similar measurements were made for a sleeve made of 5KD61 material.

According to those results, the cooling rate between the liquid phases of the former is 30% slower than that of the latter, and the solidification time of the molten metal is 20% slower than that of the latter.
．． Since it has tripled, the titanium alloy used in this example is
This means that the heat retention of the molten metal is greatly improved.

Therefore, when a sleeve made of Ti alloy was used, there was no occurrence of problems such as hot water leakage or loose rotation, and no occurrence of bottle edges.

In addition,? The details of the measurement results of the cooling rate and solidification time between the liquid phases of the 8 hot water are shown in Table 3.

Table 3: Comparison table of cooling time and solidification time In this example, a titanium alloy was used for the sprue of the mold, and the aluminum alloy was low-pressure casted using this mold.

After pouring the molten metal, the drop in temperature at the sprue is reduced, and as a result of the low pressurizing force, the pouring effect is improved, which reduces the fine cavities, or microporosity, that occur inside the cast product. was able to reduce it significantly.

In this example, a magnesium alloy S artificial product was cast by die-casting using the above titanium alloy for the nozzle part of the mold.

As a result, in conventional molds that do not use titanium alloy in the nozzle part, sprue clogging occurred, but in this embodiment, the sprue clogging could be eliminated.

Incidentally, the titanium alloy used in each of the above-described embodiments is cheaper than the ceramic SiAlON, making it extremely advantageous economically.

Furthermore, the above embodiments are merely specific examples of the present invention, and therefore the scope of the technical idea of the present invention is not limited by these embodiments.

〔Effect of the invention〕

According to the present invention, titanium alloy has a thermal conductivity as low as that of ceramics, has excellent toughness, and is lower in cost than ceramics, and the surface of this titanium alloy is treated with a nitride coating. This titanium alloy has excellent high-temperature stability and does not react with aluminum, magfusium alloys, etc., which reduces the temperature drop of the molten metal and does not generate solid pieces. Tips made of titanium alloy eliminate seizure and darkening during mold release, and it is also possible to prevent cavities from forming due to dimensional defects and poor pressurization in light alloy casting products. Since a cast product can be obtained, it can greatly contribute to improving the quality of the product.

In addition, this titanium alloy is cheaper than ceramics, and is also strong and does not crack and has excellent durability, making it extremely advantageous economically.

Patent applicant: Kobe Steel, Ltd.

Claims (1)

[Claims] (1) In a light alloy casting mold consisting of a pair of splittable molds, a titanium nitride layer is formed on the surface of at least a titanium nitride layer at a predetermined position of one of the molds on the side having a sprue. A light alloy casting mold characterized by using an alloy.