JPH04224066A - Sleeve for die-casting machine - Google Patents

Abstract

PURPOSE:To improve the wear resistance of the inner surface of sleeve against the sliding movement of the piston by fitting the inner cylinder formed of the prescribed composite material in the outer cylinder made of the steel, and providing the titanium nitride layer on the inner surface of the inner cylinder. CONSTITUTION:The inner tube to fit in the outer tube of steel is formed of the composite material of titanium of titanium alloy and ceramics having excellent erosion resistance, impact resistance and heat insulating property against the molten non-ferrous metal. The titanium nitride layer is formed on the inner surface of this inner tube. This titanium nitride layer can be formed firmly on the inner surface of the inner tube by nitriding the titanium included in the composite material, and the wear resistance against the sliding movement of the piston to be inserted in the sleeve can be improved remarkably with this titanium nitride layer.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sleeve for a die-casting machine suitable for casting nonferrous metals (including alloys thereof) such as aluminum, zinc, tin, and lead.

0002

[Prior Art] In recent years, die-casting technology that allows non-ferrous metals such as aluminum to be cast with high precision and high speed has become popular in automobiles,
It is an important casting method for various parts in the fields of industrial machinery and home appliances.

[0003] Conventionally, sleeves for die casting machines (hereinafter referred to as sleeves) were JIS SKD11 or S.
Cold or hot die steel such as KD61 is used. However, since non-ferrous metals generally tend to react easily with iron, erosion and wear occur on the inner surface of the sleeve, expanding its inner diameter, and significant erosion occurs particularly at the bottom of the pouring spout. Therefore, the sleeve must be replaced frequently and has a short lifespan. Further, since the sleeve made of steel has high thermal conductivity, the temperature of the molten metal injected into the sleeve tends to drop, which significantly reduces the manufacturing yield of the cast product.

[0004] Therefore, in order to extend the life of the sleeve, cope with the larger and more complex casting products, and improve the heat retention of the molten metal to improve the manufacturing yield of the casting products, we are using non-ferrous metals. A sleeve in which a ceramic member is cast or shrink-fitted to the contacting portion is also used. However, in this case, although the sleeve has excellent corrosion resistance, an extremely large impact is applied to the sleeve at the moment the molten metal is injected, so that the ceramic portion, which is inherently brittle, may be destroyed. In this case, it is necessary to interrupt the work, resulting in poor work efficiency.

[0005] Therefore, in recent years, sleeves in which an inner cylinder formed of a composite material made of titanium or a titanium alloy and ceramics is cast or shrink-fitted have been used. This composite material has excellent erosion resistance, impact resistance, and molten metal heat retention.

[0006]

[Problems to be Solved by the Invention] However, although the above-mentioned conventional sleeves made of composite materials cast or shrink-fitted have excellent erosion resistance, impact resistance, and molten metal heat retention, the hardness of the composite material is Since its hardness is lower than that of steel or ceramics, it has a problem of poor wear resistance. For this reason, the inner diameter of the sleeve expands due to wear caused by sliding of the piston, increasing the clearance between the sleeve and the piston, and there is a risk that molten metal may leak from between the sleeve and the piston during casting, resulting in so-called flashback. be. When such flashback occurs, the life of the sleeve is shortened and workability is reduced.

The present invention has been made in view of these problems, and has excellent corrosion resistance, impact resistance, and heat retention against molten nonferrous metals, as well as excellent wear resistance against piston sliding. The purpose of the present invention is to provide a sleeve for a die-casting machine that has a long life and excellent workability.

[0008]

[Means for Solving the Problems] A sleeve for a die-casting machine according to the present invention includes an outer cylinder made of steel, an inner cylinder molded from a composite material made of titanium or a titanium alloy, and ceramics and fitted into the outer cylinder. , and a titanium nitride layer formed on the inner surface of the inner cylinder.

[0009]

[Operation] In the present invention, the inner cylinder fitted into the steel outer cylinder is made of a composite material of titanium or titanium alloy and ceramics, which has excellent corrosion resistance against molten nonferrous metals, impact resistance, and heat retention. A titanium nitride layer (TiN, Ti2N, etc.) is formed on the inner surface of the inner cylinder. This titanium nitride layer can be strongly formed on the inner surface of the inner cylinder by nitriding the titanium contained in the composite material, and this titanium nitride layer provides wear resistance against sliding of the piston inserted into the sleeve. can significantly improve performance. In this way, the titanium nitride layer is less likely to be worn away by the sliding movement of the piston, so that it is possible to prevent the inner diameter of the sleeve from expanding. Therefore, the sleeve for a die-casting machine according to the present invention has a long life and can improve workability during casting.

[0010] The above-mentioned sleeve for a die-casting machine can be manufactured as follows. That is, after fitting the inner cylinder formed from a composite material into the outer cylinder, it is heated to a predetermined temperature in an atmosphere of nitrogen gas or decomposed ammonia gas using a vacuum furnace or hot isostatic press equipment. By performing nitriding treatment, a titanium nitride layer is formed on the inner surface of the inner cylinder. In this case, if the heating temperature in the nitriding treatment is less than 400°C, the formation of the titanium nitride layer will be insufficient. On the other hand, when the heating temperature exceeds 1200° C., although a titanium nitride layer is sufficiently formed, the crystal grains of titanium or titanium alloy contained in the composite material become coarse. If this happens, the inner cylinder itself becomes brittle and cracks are likely to occur. Therefore, the heating temperature in nitriding treatment is 400 to 1
Preferably, the temperature is 200°C.

[0011]

EXAMPLE Next, the results of actually manufacturing a sleeve for a die-casting machine according to an example of the present invention and comparing its performance with that of a comparative example will be described.

First, titanium (Ti) with an average particle size of 20 μm
) powder is about 80% by weight, silicon carbide (SiC) powder with an average particle size of 5 μm is about 18% by weight, and the average particle size is 10% by weight.
Approximately 2% by weight of μm cobalt (Co) powder was mixed uniformly to form a raw material for a composite material.

[0013] This raw material is sealed in a rubber mold, and the pressing force is 1
Cold isostatic pressing (CIP) was performed under the condition of ton/cm2. Thereby, a cylindrical green compact was obtained. next,
This green compact is placed at a vacuum level of 10-5 Torr and a temperature of 135 Torr.
After sintering in a vacuum furnace at 0° C., the sintered body was lathe-processed to obtain an inner sleeve made of a composite material having the above-mentioned composition. Next, using a vacuum furnace, this sleeve inner cylinder was heated to 1000°C in nitrogen gas at 1 atm to undergo a nitriding treatment, thereby adding Ti2 to the inner surface of the sleeve inner cylinder.
A titanium nitride layer made of N and TiN was formed. The JIS standard has an inner diameter that is approximately the same as the outer diameter of the sleeve inner cylinder.
The sleeve according to this example was manufactured by shrink-fitting an inner sleeve tube provided with a titanium nitride layer to an outer sleeve tube made of S45C steel.

[0014] Furthermore, conventionally used die steel (
Comparative Example 1 was a sleeve made of SKD61), and Comparative Example 2 was a sleeve in which an inner cylinder made of ceramics (silicon nitride) was shrink-fitted to an outer cylinder made of steel. Furthermore, Comparative Example 3 was a sleeve in which an inner cylinder made of a composite material having the same composition as in the above-mentioned example was shrink-fitted to a steel outer cylinder without providing a titanium nitride layer.

The following tests were conducted on the sleeves of the above-mentioned Examples and Comparative Examples to examine their characteristics. ■
Hardness Test The micro Vickers hardness of the inner surface of the sleeve was measured. ■Tensile test The elongation of the inner surface of the sleeve was measured. ■Practical test A sleeve was attached to a cold chamber die-casting machine (capacity 250 tons), and an automobile engine cover was actually cast from molten aluminum alloy (ADC 12). After 10,000 shots, the sleeve was removed and the state of wear and tear was examined.

The results of these tests are shown in Table 1 below. In addition, in Table 1, regarding the corrosion damage condition, cases where the maximum amount of corrosion damage on the inner surface of the sleeve relative to the dimensions before use is 0.1 mm or less are indicated by ◎, and cases where it is more than 0.1 mm and 0.3 mm or less are indicated by ○. It is shown by △ if it exceeds 0.3 mm.

[0017]

[Table 1] As is clear from Table 1, the sleeve according to this example has an elongation of 1.0% and has excellent impact resistance, and the inner surface has a hardness of 1200 and has excellent wear resistance. was. Furthermore, even after being shot 10,000 times, this sleeve was hardly eroded and no cracks occurred.

On the other hand, although the die steel sleeve according to Comparative Example 1 has excellent impact resistance, the inner hardness is 60.
The wear resistance was as low as 0, and the wear resistance was poor, and the amount of erosion on the inner surface was extremely large. In addition, although the sleeve according to Comparative Example 2, in which a ceramic inner cylinder was shrink-fitted, had excellent wear resistance, its elongation was only 0.1%, and its impact resistance was poor.
Cracks occurred in the ceramic part after 200 shots. Furthermore, although the sleeve according to Comparative Example 3, in which the inner cylinder made of a composite material was shrink-fitted, has relatively excellent impact resistance and erosion resistance, the inner hardness is low at 450 because the titanium nitride layer is not provided. Abrasion resistance was poor.

Note that the ceramics that can be used in the present invention are not limited to the above-mentioned silicon carbide (SiC), but also include Cr2O3, TiO2, ZrO2, Mg
Oxide ceramics such as O and Y2 O3, Si3
Various materials can be used, such as nitride ceramics such as N4, TiN, BN and AlN, carbide ceramics such as TiC, B4C and CrC2, boride ceramics such as ZrB2 and TiB2, and sialon. Moreover, two or more types of these ceramics can be mixed and used.

[0020]

As explained above, according to the present invention, an inner cylinder formed of a predetermined composite material is fitted into an outer cylinder made of steel, and a titanium nitride layer is provided on the inner surface of the inner cylinder. The wear resistance of the inner surface of the sleeve against sliding of the piston can be significantly improved. Therefore, the sleeve for a die-casting machine according to the present invention has excellent corrosion resistance, impact resistance, and heat retention against molten nonferrous metals, has excellent wear resistance against piston sliding, and has a long life. Excellent workability.

Claims (1)

[Claims] 1. An outer cylinder made of steel, an inner cylinder molded from a composite material made of titanium or a titanium alloy, and ceramics and fitted into the outer cylinder, and a titanium nitride layer formed on the inner surface of the inner cylinder. A sleeve for a die-casting machine, comprising: