JPH04251653A - Manufacture of intermetallic compound - Google Patents

Abstract

PURPOSE:To manufacture a casting product of an intermetallic compound having no material defect such as void, irregular outer shape caused by shrinkage hole. CONSTITUTION:A Ti-Al base intermetallic compound is melted in a melting furnace in argon atmosphere and the molten metal is poured into a specific heat resistant steel-made mold coated with ceramic and cast while applying pressure of >=50MPa.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing intermetallic compound cast products with few material defects.

0002

[Prior Art] Conventionally, methods for manufacturing products using intermetallic compounds as materials include casting into ordinary sand molds, metal molds, calcia or other ceramic molds under vacuum, reduced pressure, air, or an inert gas atmosphere. (Casting method), the raw material intermetallic compound powder is vacuum sealed in a stainless steel tube or titanium tube and extruded, processed under compressive stress such as swaging or rolling to increase density, and then heated and annealed at high temperature. A method of producing a denser sintered body and then machining it (powder sintering method), mixing the elemental metal powder, vacuum degassing, enclosing it in a tube, and hot pressing or HIP (hot isostatic pressing) ), a method in which a dense sintered body is formed and then machined (element powder method), a method in which an ingot of an intermetallic compound is produced by casting, a dense and uniform structure is made by isothermal forging, etc., and then machined (constant temperature Forging method) etc.

Although each of these methods has excellent characteristics, methods other than constant temperature forging have the disadvantage that shrinkage cavities and other material defects are likely to occur. In particular, in casting methods, even if the latest casting technology using ceramic molds is used, inclusion of impurities and inclusion of structural defects such as voids due to shrinkage cavities are unavoidable, as well as irregularities in external shape and deterioration of mechanical properties. The accompanying drop in product yield was unavoidable.

On the other hand, isothermal forging is an effective means for obtaining products with a uniform structure with few defects, but the processing speed is extremely slow, and in addition, it is difficult to form products with complex shapes, resulting in high manufacturing costs. There are problems that lead to soaring prices. Due to this background, commercialization of products made from intermetallic compounds has not yet reached the practical stage.

[0005]

[Problem to be solved by the invention] As an improved means for manufacturing intermetallic compounds using the casting method, a method of suppressing the contamination of impurities and reaction with the mold by using a special ceramic mold. is being studied. However, the intermetallic compound cast material obtained by this method has mechanical properties, particularly ductility and toughness, which are considerably inferior to those obtained by isothermal forging. The reason for this is
This is because the conditions for introducing defects such as reaction with the mold and voids are complex and cannot be specified, and methods for preventing defects cannot be elucidated.

The present invention was developed as a result of extensive research into commercializing intermetallic compounds that can withstand practical use using casting technology, and its purpose is to effectively reduce structural defects during casting. An object of the present invention is to provide a method for producing an intermetallic compound.

[0007]

[Means for Solving the Problems] A method for producing an intermetallic compound according to the present invention to achieve the above object has a structure in which the intermetallic compound is melted and pressure cast under a pressure of 50 MPa or more. This is a characteristic feature.

[0008] The intermetallic compound used as the casting material of the present invention is not limited in material, composition, etc., but TiAl-based compounds are particularly suitable materials. The intermetallic compound material is melted in an inert atmosphere using a melting furnace such as a plasma beam melting furnace, and the molten metal is poured into a mold and pressure cast. A metal mold or a ceramic-lined mold is used as the mold, and is used in a preheated state.

[0009] It is an important requirement that the pressure during pressure casting be set at 50 MPa or higher. If the pressure is less than 50 MPa, it becomes impossible to prevent shrinkage cavities and irregularities in external shape, and the mechanical strength also decreases, making it impossible to obtain a high-quality cast material.

0010

[Operation] According to the present invention, the generation of shrinkage cavities is effectively suppressed during the process of melting and pressure casting the intermetallic compound that is the raw material, and at the same time, the irregular shape is prevented. Therefore, it is possible to always obtain a high-quality cast product with few structural defects such as voids caused by shrinkage cavities and with good external shape properties.

In addition, the effect of pressure casting makes it possible to mold complex shapes, so it is possible to obtain a shape that approximates the product directly from the raw material, and the dimensional accuracy is extremely high, which greatly reduces the machining required in the post-process. can be reduced to Also,
A fine rapidly solidified structure is obtained, and the mechanical properties are further improved.

0012

[Examples] Examples of the present invention will be explained below in comparison with comparative examples. Examples 1 to 4, Comparative Examples 1 to 2 99.8 mass% purity of Ti and 99.99 mass
Ti-48at synthesized using s% purity Al as raw material
A TiAl-based intermetallic compound having a composition of %Al was melted using a plasma beam melting furnace in an argon atmosphere. Next, about 120 g of the molten metal at about 1700° C. was poured into a special heat-resistant steel mold coated with ceramics (preheated at 500° C.), cast at four pressure levels from 0 to 250 MPa, and then solidified. Table 1 shows the size (mm), amount, surface condition, and casting pressure of the shrinkage cavities present in the final solidified part of the sample (diameter 20 mm, length 100 mm) cast in this way, and the solidification time applied. Indicated.

Table 1

From the results shown in Table 1, the cast products of Comparative Examples 1 and 2 where the casting pressure was less than 50 MPa had shrinkage cavities, structural defects due to voids, and a wavy surface. On the other hand, in the examples that meet the casting requirements of the present invention, no shrinkage cavities are observed and the surface condition is generally good. In addition, all of the cast products according to the present invention showed a yield strength of about 500 MPa or more and a tensile strain at break of about 1.5% in the tensile test, which is almost the same as that obtained in the compression test, but none of the cast products according to the comparative example showed Also, the tensile yield strength was 450 MPa or less, and the tensile strain at break was almost 0.

[0015]

[Effects of the Invention] As described above, according to the present invention, cast products of intermetallic compounds free from material defects such as voids caused by shrinkage cavities and irregularities in appearance can be produced by pressure casting under specific pressure conditions. It becomes possible to manufacture efficiently while maintaining mechanical strength characteristics. Therefore, it is expected to be useful as a means for producing intermetallic compound products as cutting-edge new materials with high practicality.

Claims (1)

[Claims] 1. A method for producing an intermetallic compound, which comprises melting the intermetallic compound and pressure casting it under a pressure of 50 MPa or more.