JP3044981B2 - Core for cast-in - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core for as-cast
In particular, the present invention relates to a ceramic core for a metal insert, which can prevent defects such as blowholes in a cast portion.

[0002]

2. Description of the Related Art Conventionally, a core made of silicon nitride (Si ₃ N ₄ ) -based ceramics has been used as a core for metal casting. However, when this Si ₃ N ₄ ceramic core is cast with metal, N ₂ gas is generated by silicification of the molten metal by Si ₃ N ₄ or by decomposition of Si ₃ N ₄ , Due to this gas generation, a defect called a blowhole occurs in the metal casting.

[0003] In order to solve this problem,
In ₃ N ₄ based surface a ceramic core, a method of preventing the generation of N ₂ gas ceramic powder spray coating has been proposed (Japanese Patent Laid-Open No. 5-38566).

[0004]

However, even if the above ceramic powder is spray-coated, it may not be possible to prevent the occurrence of blowholes. That is, the coated ceramic powder merely adheres to the surface of the core made of Si ₃ N ₄ ceramics, and may be separated by the flow of the molten metal during handling and casting. Also, the spray coating layer is porous in nature and N ₂ gas flows out through its continuous open pores. For this reason, it is considered that blow holes are generated.

The present invention solves the above-mentioned conventional problems, and solves the above-mentioned problems.
_An object of the present invention is to provide a core for cast-in which prevents generation of defects called blowholes by preventing generation of N ₂ gas due to decomposition of ₃ N ₄ -based ceramics or silicification of molten metal.

[0006]

Casting-core for the present invention SUMMARY OF] is a one obtained by forming an oxide layer on the surface of the core body made of silicon nitride ceramic, of claim 1 IG
The core for run is a core book made of silicon nitride ceramics.
Oxide on the surface by heat treatment of the body in an oxidizing atmosphere
A layer is formed.

[0007]

Further, insert casting core for the second aspect, by spraying the core body made of nitrided silicon-based ceramics, characterized in that the formation of the oxide layer.

Hereinafter, the present invention will be described in detail.

[0010] In the present invention, the oxide constituting the oxide layer formed on the Si ₃ N ₄ based ceramic core body surface, composed mainly of SiO ₂ produced by oxidation the Si ₃ N ₄ ceramics Oxides, furthermore SiO ₂ ,
Al ₂ O ₃ , ZrO ₂ , MgAl ₂ O ₄ , 3Al ₂ O _{3
· 2SiO 2, ZrO 2 · SiO} 2 , etc. one or a mixture comprising two or more thereof. As a method of forming such an oxide layer, a core body made of Si ₃ N ₄ ceramics is heat-treated at about 1000 to 1300 ° C. in an oxidizing atmosphere. Alternatively, the above oxide or a mixture thereof is sprayed on the surface of the core body made of Si ₃ N ₄ ceramics. A method can be used, whereby an oxide layer that is dense and has excellent adhesion to the core body can be formed.

When the oxide layer is formed by thermal spraying, it is also effective to subject the surface of the core body to a metallizing treatment in order to further increase the adhesion to the core body.

The thickness of the oxide layer to be formed is not particularly limited, but is preferably 1 μm or more when heat treatment is performed in an oxidizing atmosphere from the viewpoint of the oxide layer forming step and the effect of preventing the generation of N ₂ gas. In particular, the thickness is preferably about 5 to 10 μm, and more preferably 10 μm or more when spraying.
In particular, the thickness is preferably about 30 to 100 μm.

[0013]

[Function] By forming an oxide layer on the surface of a core body made of Si ₃ N ₄ ceramics, silicification of molten metal and Si
Generation of N ₂ gas due to decomposition of ₃ N ₄ is reliably prevented. Therefore, the occurrence of defects such as blowholes in the metal casting is eliminated.

This oxide layer can be formed into a dense oxide layer having excellent adhesion to the core body by forming the core body by heat treatment in an oxidizing atmosphere or by thermal spraying.

[0015]

The present invention will be described more specifically with reference to the following examples and comparative examples.

Example 1 By performing a heat treatment at 1250 ° C. in an air atmosphere,
Core body made of i ₃ N ₄ ceramics (100 × 20 × 1
0 mm) on a surface of an as-cast core having an 8 μm-thick oxide layer formed thereon, is cast with a silver alloy (Ag-7.5 wt% Cu, so-called sterling silver), and the obtained The body was cut, and the presence or absence of blow holes at the interface between the alloy portion and the ceramic was examined. As a result, it was confirmed that it was a sound cast body without blow holes.

Embodiment 2 A core body made of Si ₃ N ₄ ceramics (100 × 20 ×
10 mm) on a surface of a cast-in core in which a 100-μm-thick alumina layer was formed by spraying white alumina on the surface,
Casting was performed in the same manner as in Example 1, and the presence or absence of blow holes was examined. As a result, it was confirmed that it was a sound cast body without blow holes.

Comparative Example 1 Core body made of Si ₃ N ₄ ceramics (100 × 20 ×
Without forming an oxide layer (10 mm), casting was performed in the same manner as in Example 1, and the presence or absence of blow holes was examined. As a result, it was confirmed that a large number of blowholes were present at the interface between the alloy portion and the ceramics, and particularly, the blowhole occurrence rate at the interface was high.

[0019]

As described in detail above, according to the casting core of the present invention, generation of N ₂ gas due to decomposition of Si ₃ N ₄ or silicification of molten metal is prevented, and blow holes are formed in the metal casting. A good cast body having almost no defects such as defects can be obtained.

Continuing from the front page (72) Inventor Shinichi Yamamoto 1230 Kamijiya, Okegawa-shi, Saitama Mitsubishi Materials Corporation Okegawa Works (56) References JP-A-5-38566 (JP, A) JP-A-5-96357 (JP, A) JP-A-5-96358 (JP, A) JP-A-53-11816 (JP, A) JP-A-51-50811 (JP, A) (58) Fields investigated (Int. Cl. ⁷⁾ B22D 19/00 B22C 3/00 B22C 9/10

Claims (2)

(57) [Claims] 1. A by the core body made of nitrided silicon-based ceramic is heat-treated in an oxidizing atmosphere, the tang body
A core for cast-in, wherein an oxide layer is formed on a surface of the core. Wherein the surface of the core body made of nitrided silicon-based ceramics, spraying the core for insert casting, characterized by comprising forming an oxide layer.