JP2859967B2 - Sleeve for die casting machine - Google Patents

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 non-ferrous metals (including alloys thereof) such as aluminum, zinc, tin and lead.

[0002]

2. Description of the Related Art In recent years, die casting technology capable of casting non-ferrous metals such as aluminum, zinc, tin and lead at a high precision and at a high speed has become an important means of producing various parts in the fields of automobiles, industrial machines and home appliances. It has become.

Conventionally, die steel such as JIS SKD61 alloy is mainly used for a sleeve for a die casting machine (hereinafter, referred to as a sleeve). In addition, in order to extend the service life of the sleeve and improve the production yield, and to cope with the increase in the size of the cast product, an inner cylinder made of ceramic or a composite of titanium or a titanium alloy and ceramic is placed inside an outer cylinder made of steel. In some cases, a sleeve is used in which an inner cylinder made of a material is provided by shrink-fitting or casting.

[0004]

However, the above-mentioned conventional sleeve has the following problems. JIS
In a sleeve made of die steel such as SKD61 alloy, the non-ferrous metal alloy generally has a property of easily reacting with iron, so that the bottom of the pouring port of the sleeve is significantly melted and the inner wall of the sleeve is also melted and worn. And will decrease. Therefore, the sleeve needs to be replaced relatively frequently, and the life of the sleeve is short. Also, steel has good thermal conductivity, so when molten metal is injected into the sleeve,
The temperature of the molten metal drops significantly. The decrease in the temperature of the molten metal at this time causes a decrease in the production yield of the cast product.

On the other hand, a sleeve in which a ceramic inner cylinder is shrink-fitted to a steel outer cylinder has excellent erosion resistance, but an extremely large impact is applied to the sleeve at the moment when a die casting machine injects molten metal. As a result, the inner cylinder made of ceramics, which originally has brittle properties, may be broken. In this case, the work must be interrupted, resulting in poor workability. In addition, a sleeve in which an inner cylinder made of a composite material of titanium or a titanium alloy and ceramics is shrink-fitted to a steel outer cylinder has excellent erosion resistance, impact resistance, and heat retention for molten metal. Since the surface hardness is lower than steel or ceramics, the wear resistance of the sleeve is inferior,
The inner diameter expands during use. Then, the clearance between the sleeve and the piston increases, and flashback occurs during casting. This shortens the life of the sleeve.

[0006] The present invention has been made in view of the above problems, and is excellent in erosion resistance, impact resistance, and heat retention of a non-ferrous metal in a molten metal, and also has excellent wear resistance to a piston. Another object of the present invention is to provide a sleeve for a die casting machine having good workability.

[0007]

A sleeve for a die-casting machine according to the present invention comprises a steel outer cylinder, an inner cylinder fitted in the outer cylinder and made of a composite material of titanium or a titanium alloy and ceramics. And a titanium boride layer provided on the inner surface of the inner cylinder.

[0008]

In the present invention, an inner cylinder made of a composite material of titanium or a titanium alloy and ceramics is fitted into a steel outer cylinder. A titanium boride layer is provided on the inner surface of the inner cylinder.

The composite material of titanium or a titanium alloy and ceramics has excellent erosion resistance, impact resistance, and heat retention for a non-ferrous metal melt. Further, the titanium boride layer provided on the inner surface side of the inner cylinder which is in direct contact with the molten metal has excellent wear resistance. Therefore, the sleeve for a die-casting machine according to the present invention has excellent erosion resistance, abrasion resistance, and heat retention of molten metal, and also has excellent impact resistance. Further, the frequency of replacing the sleeve can be reduced as compared with the conventional case, and workability is improved.

[0010]

EXAMPLES Next, examples of the present invention will be described in comparison with comparative examples outside the scope of the claims.

First, a titanium powder having an average particle size of 20 μm,
A silicon carbide (SiC) powder having an average particle diameter of 5 μm and a nickel powder having an average particle diameter of 15 μm were each 80% by weight,
The mixture was uniformly mixed at a ratio of 8% by weight and 2% by weight. Then, the mixture is sealed in a rubber mold, and the pressure is 1 ton / c.
Cold isostatic pressing (CIP) was performed under the conditions of m ² to obtain a cylindrical green compact.

Next, this green compact is vacuumed at 10 ^-5 Torr.
r, sintering in a vacuum furnace at a temperature of 1350 ° C. Next, this sintered body was subjected to lathe processing to obtain a sleeve inner cylinder made of a composite material having the above composition.

Next, this sleeve inner cylinder is used as a cathode,
Using the graphite crucible (electrolysis tank) as the anode, the inner cylinder of the sleeve was subjected to electrolytic boring treatment to form a titanium boride layer on the inner surface of the inner cylinder. In this case, the treatment conditions were as follows: molten anhydrous borax (Na ₂ B ₄ O ₇ ) was used as the molten salt bath electrolyte, the treatment temperature was 1200 K, the treatment time was 50 ks, and the current density was 5
00 A / m ² .

Next, the inner cylinder provided with the titanium boride layer on the inner surface was shrink-fitted to a steel outer cylinder. Thus, a sleeve according to the example of the present invention was obtained.

On the other hand, as a comparative example 1 and a comparative example 2, a sleeve made of a conventional die steel (JIS SKD61 alloy) sleeve and a sleeve made by shrinking an inner cylinder made of ceramics (silicon nitride) into a steel outer cylinder were prepared. did. Comparative Example 3
A sleeve was also prepared in which an inner cylinder made of the same composite material as in the example except that the titanium boride layer was not provided was fitted to an outer cylinder made of steel.

The following tests were performed on the sleeves of these examples and comparative examples. Hardness test The micro Vickers hardness of the inner surface of the sleeve was measured.

Tensile test The elongation of the inner cylinder of the sleeve was measured.

Practical test A sleeve was attached to a die casting machine for cold chamber (capacity: 250 tons), and an aluminum alloy (JIS
An automobile engine cover was cast from the molten metal (ADC12 alloy). Then, the state of erosion wear of the sleeve after 10,000 shots was examined.

The results of these tests are summarized in Table 1 below. However, the erosion condition is indicated by ◎ when the maximum erosion amount is 0.1 mm or less, ○ when the maximum erosion amount is 0.3 mm or less, and △ when the maximum erosion amount exceeds 0.3 mm.

[0020]

[Table 1]

As apparent from Table 1, the sleeve according to the embodiment of the present invention has high hardness and 10,000
The amount of erosion after the shot is extremely small at 0.1 mm or less,
Excellent characteristics as a sleeve for die casting machine. On the other hand, Comparative Example 1 made of die steel had a large amount of erosion,
Cracks occurred in the sleeve of Comparative Example 2 having the ceramic inner cylinder. Further, the sleeve of Comparative Example 3 including the inner cylinder of the composite material without the titanium boride layer had low hardness and a large amount of erosion although not as large as that of Comparative Example 1.

The ceramics usable in the present invention are not limited to the above-mentioned SiC, but may be Cr.
Oxide ceramics such as ₂ O ₃ , TiO ₂ , ZrO ₂ , MgO and Y ₂ O ₃ , nitride ceramics such as Si ₃ N ₄ , TiN, BN and AlN, TiC, B ₄ C and CrC ₂ Carbide ceramics, ZrB ₂ and Ti
Boride-based ceramics and sialon such as B _2,
Various things can be used. Also, two or more of these ceramics can be used in combination. Further, in the above embodiment, the titanium boride layer is formed by the molten salt bath electrolysis method. However, the inner cylinder may be formed by a method such as a CVD (chemical vapor deposition) method, a powder pack method, and a molten salt immersion method. A titanium boride layer can be formed on the inner surface.

[0023]

As described above, the sleeve for a die-casting machine according to the present invention is constituted by an outer cylinder made of steel and an inner cylinder fitted in the outer cylinder and made of a composite material of titanium or a titanium alloy and ceramics. Since the inner cylinder is provided with a titanium boride layer on its inner surface, the erosion resistance, the friction resistance and the heat retention of the molten metal are excellent,
A sleeve having excellent impact resistance and good workability can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) B22D 17/20 B22F 5/12 B22F 7/00 C22C 14/00

Claims (1)

(57) [Claims] 1. An outer cylinder made of steel, an inner cylinder fitted in the outer cylinder and made of a composite material of titanium or a titanium alloy and ceramics, and a titanium boride layer provided on an inner surface of the inner cylinder. A sleeve for a die casting machine, comprising: