JPH03111525A - Refractory metal matrix composite and its manufacture - Google Patents

Abstract

PURPOSE:To easily and efficiently manufacture the refractory metal matrix composite having high strength in an axial direction by adding short fibers and a bond to refractory metallic powder, kneading the above, extruding the obtd. extruding stock from a nozzle of an extruding machine and executing sintering. CONSTITUTION:Extruding stock 3 prepd. by adding reinforcing short fibers 2, a bond, a solvent or the like to refractory metallic powder and kneading the above is housed in the body 1a of an extruding machine 1. As the above refractory metals, W, Mo, Ta, Nb or their alloys are used, and the above short fibers are also formed from the above metals, alloys or the like. Furthermore, as the above bond, methyl cellulose or the like are used in the addition amt. of about 1 to 6% together with a solvent such as water. The above extruding stock 3 is pressurized to about 20 to 200kg/cm<2> by a pressurizer 5 and is extruded from an injection hole 6 of a nozzle 4 to mold a molded product 7. After that, the molded body 7 is sintered after the removal of the bond or the like therefrom by volatilization. In this way, the refractory metal matrix composite constituted of a sintered body in which short fibers are fibrously arranged in an axial direction and are dispersed into a metallic matrix can be obtd.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Field of Application) The present invention relates to a high melting point metal matrix composite material used for electronic equipment materials, heat-resistant structural parts, etc., and a method for producing the same. The present invention relates to a high melting point metal matrix composite material that has high strength in the axial direction, is easy to mold, and can be molded efficiently, and a method for manufacturing the same.

(Conventional technology) Tungsten (W), molybdenum (Mo), tantalum (
High-melting point metal matrix composite materials, which have a matrix of Ta), niobium (Nb), etc. and high-strength short fibers dispersed in the matrix, are generally made by laminating or molding metal powder or its alloy powder and short fibers into a predetermined shape. It is manufactured using a powder metallurgy method in which it is then sintered. In this case, raw materials such as metal powder are molded by mechanical press (hydraulic press) in which high-melting point metal powder is filled into a mold and pressurized in a uniaxial direction, or by using a rubber mold and filling the powder into the mold. This is done using the rubber press method, which applies hydrostatic pressure uniformly to the raw material.

(Problems to be Solved by the Invention) However, in molded bodies formed by conventional mechanical press methods and rubber press methods, the arrangement direction of the dispersed reinforcing short fibers is mutually random, so the molding There was a problem in that the axial strength of the product and the product obtained by sintering it were low.

Furthermore, among the conventional manufacturing methods mentioned above, the mechanical press method is relatively excellent as a method for forming a flat plate-shaped molded product, but
For products with other complicated shapes, it is necessary to devise a method of laminating raw materials and a mold, and there are restrictions on the shape and dimensions of the molded product. In particular, there was a drawback that it was difficult to obtain round rod-shaped or cylindrical shaped bodies and long shaped bodies.

On the other hand, with the rubber press method, it is possible to easily obtain a round bar-shaped compact, but the filling operation of the raw material powder and the pressing operation are batch-type, which requires a considerable amount of labor and has low work efficiency. It has the disadvantage that the yield and dimensional accuracy of the product tend to decrease, and in any case, it has the disadvantage that it requires a lot of labor and processing time, so it tends not to be suitable for mass production.

The present invention has been made to solve the above problems, and provides a high melting point metal matrix composite material that has particularly high strength in the axial direction of the product, is easy to mold, and can be molded efficiently. The purpose is to provide a method for producing the same. , [Structure of the Invention] (Means and Effects for Solving the Problems) The inventors of the present application have discovered that a product with greater axial strength can be obtained compared to products manufactured by conventional mechanical press methods or rubber press methods. As a result of examining various manufacturing methods that would increase manufacturing efficiency, they prepared an extruded base by adding and kneading short fibers and a binder to high-melting point metal powder, and extruded the extruded base through the nozzle of an extrusion molding machine to form a predetermined shape. When a shaped article is formed and then sintered, short fibers are arranged in the axial direction in the high melting point metal or its alloy matrix, resulting in higher axial strength than conventional methods. Furthermore, the present invention was completed based on the knowledge that manufacturing efficiency could be dramatically improved.

That is, the high melting point metal matrix composite material according to the present invention consists of a sintered body of a mixture of a high melting point metal or its alloy and short fibers, and the short fibers dispersed in the metal matrix of the sintered body are It is arranged in a fibrous shape in the axial direction.

Powders used in the high melting point metal matrix composite material that is the object of the present invention include tungsten (W) and molybdenum (Mo).
, tantalum (Ta), niobium (Nb), or an alloy powder containing these metals.

In addition, short fibers include tungsten (W), molybdenum (MO), which have excellent high-temperature strength like matrix metals,
Fibers made of one or more metals selected from tantalum (Ta) and of (Nb) or alloys thereof are used.

As a binder to be added to the metal powder, organic binders such as methyl cellulose and PVP (polyvinylpyrrolidone) can be used alone or in combination, and the amount added can be 1 to 6% of the powder weight. desirable. This binder is generally diluted in a solvent such as water and added to the metal powder. The amount of binder added has a large effect on the bonding strength between metal powders and the finished shape of the molded product, and the amount added is 1
If it is less than %, sufficient bonding strength will not be obtained, the shape retention of the molded product will be poor, and there is a high possibility that cracks will occur in the extruded product or cracks will occur during drying.

On the other hand, if the amount added exceeds 6%, deformation tends to occur after extrusion molding, making it difficult to obtain the desired shape accuracy, and also making it difficult to increase the specific gravity of the sintered body, making it difficult to obtain the desired strength in many cases.

Further, the solvent is added to improve the dispersion of the organic binder, and for example, water, lower alcohol, etc. are used. For the same reason as the organic binder, the amount of the solvent added is preferably 3% or more and less than 7% of the weight of the metal powder.

The obtained metal powder mixture (extrusion base) is extruded using a known extrusion molding machine. By this extrusion molding operation, the short fibers dispersed in the extruded base are aligned in the extrusion direction, intertwined with each other, and arranged in the form of fibers.

In this case, the extrusion pressure during molding is 20 to 200 kg
/c is desirable; if it is less than 20 kg/c, sufficient green density cannot be obtained. On the other hand, 200k
If it exceeds g/cJl, the frictional resistance within the extrusion molding machine will increase, causing a local temperature rise, and as a result, the organic binder may partially change in quality and a good molded product may not be obtained. be.

The shape of the molded product obtained by the method of the present invention is wide-ranging, such as a round bar, a square bar, a plate shape, and a long material having a polygonal cross section.

The molded product molded into a predetermined shape is kept at room temperature to 1-00°C.
After being held at a certain temperature for a certain period of time to gradually evaporate the contained solvent and dry it, it is further heat-removed in a reducing atmosphere to volatilize and remove the organic binder and solvent, and then it is subjected to preliminary sintering. . The pre-sintered compact is subjected to main sintering at a predetermined high temperature to produce a high melting point metal matrix composite material.

According to the method of the present invention, it is possible to continuously and efficiently mold long molded products using an extrusion molding machine, and the addition of reinforcing short fibers and a binder provides excellent shape retention.
It is possible to efficiently produce products with superior axial strength compared to molded products and sintered bodies thereof obtained by conventional mechanical pressing methods or rubber pressing methods.

In particular, according to the method of the present invention, the orientation of the reinforcing short fibers randomly dispersed in the extruded base material is aligned in the axial direction during extrusion molding, so that the molded product obtained and the product obtained by firing the same are The tensile strength, compressive strength, buckling strength in the axial direction, and shear strength in the direction perpendicular to the short fibers of the sintered body become extremely large.

(Example) An example of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a partial sectional view showing the configuration of an extrusion molding machine for carrying out the method of the present invention. This extrusion molding machine
The molding machine itself has a form and structure well known in the field of molding technology, and includes a molding machine main body 1a that houses an extrusion base material 3 prepared by adding and kneading reinforcing short fibers 2, a binder and a solvent to metal powder, and It consists of a nozzle 4 attached to the lower part of the machine body 1a, and a screw-shaped pressurizer 5 that applies pressure to extrude the extruded base material 3 from the nozzle 4.

The extruded base material 3 prepared to have a predetermined composition is extruded by a pressurizer 5 through an injection hole 6 formed at the center of the bottom of the nozzle 4 to form a columnar molded product 7. The molded product 7 is cut into required dimensions, and then sent to drying, preliminary sintering, and main sintering steps.
It becomes a high melting point metal matrix composite material.

Next, the effects of producing a high melting point metal matrix composite material using the above extrusion molding machine will be explained in more detail.

Examples 2 and Comparative Examples 1 and 2 As Examples 1 and 2, tungsten powder with an average particle size of 2.1 μm and molybdenum powder with an average particle size of 2.5 μm were prepared, and the weight of each powder was adjusted as a binder. Add 3% methylcellulose and 6% water as a solvent, and
Two types of extruded bases were prepared by adding 5% by weight of tungsten wire with a length of 3 μm and 1200 μm and thoroughly kneading, and each extruded base was filled into an extrusion molding machine to produce 80 kg/c.
While applying a molding pressure of ar, length 'J, mm, width 60+n
It was extruded from the nozzle of an extruder having +++ injection holes.

After each extruded molded product is cut into 120mm sections,
The material was left standing in a drying chamber at a temperature of 100° C. for 5 hours, and then the temperature was gradually raised in a hydrogen atmosphere, and preliminary sintering was performed at a maximum temperature of 1600° C. for 2 hours. After preliminary sintering, main sintering was further performed at 1850'C for 2 hours in a hydrogen atmosphere. Then, the bow tensile strength and three-point bending strength of the obtained sintered body were measured.
The time required to produce 0 molded objects was measured, and the average manufacturing time per molded object was calculated.

On the other hand, as Comparative Examples 1 and 2, raw materials having the same shape, size, and composition as the matrix metal powder and reinforcing short fibers in Examples 1 and 2 were used, and 100 pieces were manufactured using the rubber press method under the same molding pressure. The obtained molded product was dried, pre-sintered, and main sintered under the same conditions as in Examples 1 and 2. The average production time was measured, and the results shown in Table 1 below were obtained.

Table 1 As is clear from the results in Table 1, according to this example, the strength characteristics after sintering were significantly improved compared to the conventional rubber press method, and the efficiency was extremely high. Molding operations are possible, and the manufacturing efficiency of high-melting point metal matrix composite materials can be dramatically increased.

〔Effect of the invention〕

As explained above, according to the high melting point metal matrix composite material and the manufacturing method thereof according to the present invention, it is possible to continuously, efficiently and easily mold a long molded product using an extrusion molding machine, In addition, the addition of reinforcing short fibers and a binder provides excellent shape retention, allowing us to efficiently produce products with superior strength compared to molded products and sintered bodies obtained by conventional mechanical press methods or rubber press methods. It becomes possible to do so.

In particular, according to the method of the present invention, the orientation of reinforcing short fibers that were randomly dispersed in the extruded base material is aligned in the axial direction in a fibrous manner during extrusion molding. The axial strength characteristic value of the sintered body becomes extremely high, and a high-strength, high-melting-point metal matrix composite material can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial sectional view showing an embodiment of an extrusion molding machine for carrying out the method of the present invention. 1... Extrusion molding machine, 1a... Molding machine main body, 2...
Reinforcing short fiber, 3... Extruded base material, 4... Nozzle, 5
... Pressure machine, 6 ... Injection hole, 7 ... Molded product.

Claims (1)

[Claims] 1. Consisting of a sintered body of a mixture of a high-melting point metal or its alloy and short fibers, the short fibers dispersed in the metal matrix of the sintered body are arranged in the axial direction of the sintered body in the form of fibers. A high melting point metal matrix composite material characterized by being arranged in the following manner. 2. Add and knead short fibers and a binder to high-melting point metal powder to prepare an extrusion base, extrude the extrusion base from the nozzle of an extrusion molding machine to form a molded product of a predetermined shape, and then mold the molded product. A method for producing a high melting point metal matrix composite material, the method comprising: sintering a high melting point metal matrix composite material.