JPH05295408A - Production of rapidly cooled and solidified powder using inclined function material - Google Patents

Abstract

PURPOSE:To improve the yield of powder by using an inclined function material as a rotary disk at the time of producing the rapidly cooled and solidified powder by a centrifugal spraying method. CONSTITUTION:The inclined function material with which the chemical compsn. changes inclinatorily from ceramics to metal is used as the rotary disk in the centrifugal spraying method, by which the heat resistance, thermal impact resistance, etc., of the disk are improved and the yield is improved in the production of the rapidly cooled and solidified powder, particularly, the rapidly cooled and solidified powder of a high m.p.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the yield of powder by using a functionally graded material as a material of a rotating disk when producing rapidly solidified powder by a centrifugal spraying method.

[0002]

2. Description of the Related Art In recent years, as the importance of developing new materials has been emphasized, powder molding (powder metallurgy) has been attracting attention as a powerful development means, and among them, "quenched solidified powder" has attracted attention. Here, the rapidly solidified powder is one in which the cooling (solidification) rate at the time of producing the powder from the molten metal is made faster than in the case of the conventional general powder production method, for example, the atomization method. .. The powder produced by this method is
It has a fine and homogeneous metallographic structure with little segregation and may have a supersaturated solid solution with alloying elements. The rapidly solidified powder having such characteristics has excellent mechanical properties such as strength, toughness, heat resistance and wear resistance, and also exhibits functionality such as superplasticity and shape memory depending on the alloy composition.

There are various methods for producing the rapidly solidified powder, one of which is the centrifugal spraying method shown in FIG. In the case of this method, if the problems described below are overcome, powder may be mass-produced.
There is a possibility that it will be developed as an effective means for producing rapidly solidified powder. Note that this method is sometimes called a centrifugal spraying method or a rotating disk spraying method.

The manufacturing process of powder by this method will be described with reference to the apparatus shown in FIG. First, the chamber and the melting crucible in FIG. 1 are placed in a vacuum or protective gas atmosphere, and then the melting raw material is melted in a high frequency furnace. Next, this molten metal is jetted onto a disc that is rotating at high speed (up to 22,000 rpm). The injected molten metal is atomized by the centrifugal force of the rotating disk, and by spraying a gas such as helium, argon, or nitrogen for cooling during the scattering,
It becomes a rapidly solidified powder.

In producing the rapidly solidified powder in the centrifugal atomization method, the yield when powdered from the raw metal,
That is, the ratio of the weight of the manufactured powder to the weight of the raw metal (= the weight of the manufactured powder / the weight of the raw metal) is significantly affected by the behavior of the molten raw metal on the rotating disk, that is, the behavior of the molten metal. [Where powder is 850 μm (micron)
The following is defined as powder. According to JIS Z2500, powder is defined as an aggregate of particles having a maximum size of 1 mm or less]. Therefore, compatibility between the molten metal and the rotating disk becomes a problem. However, a suitable rotating disk has not been found yet. Therefore, there is a demand for a method of finding a material suitable for a rotating disk and improving the yield of powder.

[0006]

SUMMARY OF THE INVENTION In the case of producing rapidly solidified powder by centrifugal spraying method, the present inventors have conducted extensive studies in order to improve the yield of powder, and as a result, a functionally graded material as a rotating disk. By using
It proposes a method for improving the yield.

[0007]

The method of the present invention for achieving the above object is characterized by using a functionally graded material as a rotating disk when producing a rapidly solidified powder in a centrifugal atomization method. It is a manufacturing method.

More specifically, the important points in powder production by the centrifugal atomization method are the material, shape, and shape of the rotating disk.
The number of revolutions, the type and injection amount of the cooling gas for rapid solidification, the temperature and ejection amount of the molten metal, and the like, the material and shape of the rotating disk are particularly important.

The material that the rotating disk must have is mechanical strength capable of withstanding centrifugal force, heat resistance and thermal shock resistance sufficient to withstand the temperature of the molten metal, non-reactivity with the molten metal, and the molten metal It has a suitable wettability with the molten metal in order to sufficiently receive the centrifugal force, and is lightweight because it rotates at a high speed. In addition, in a system in which the rotating disk is not preheated or cooled like the device used by the inventors, a rotating disk having a small thermal conductivity and a small heat capacity is used to reduce the viscosity of the molten metal without removing the heat of the molten metal as much as possible. It is important to suppress

Based on such knowledge, various materials have been used as rotating discs so far. That is, when the Zn-22Al superplastic alloy powder having a relatively low melt temperature of about 600 ° C. is manufactured by the centrifugal atomization method, S4 as a rotating disk is used.
5C carbon steel and graphite were used. Al-based Al (99.999%) whose melt temperature is about 1000 ° C, Al-33Cu, Al-8
Graphite was used in the production of the rapidly solidified powder of F, Al-10Mn, Al-5Cr, and Al-25Si. On the other hand, the molten metal temperature is about 1300 ℃
For Cu-based Cu-4Al rapidly solidified powder, graphite, Cu-21Zn-6Al
ZrO ₂ coated disk (base material S45C), Cu-1 for rapidly solidified powder
4Al-3Ni-0.55Zr Sialon ceramics for rapidly solidified powder, ZrO ₂ -8% Y ₂ O ₃ for rapidly solidified Cu-25Sn powder,
Cr ₂ O ₃ , Al ₂ O ₃ -40% TiO ₂ , and Al ₂ O ₃ thermal spray coating (base material S45C) were used. Furthermore, a ZrO ₂ film is used for the Fe-17Cr-13Ni-3Mo rapidly solidified powder of stainless steel whose melt temperature is about 1500 ° C or higher, and SS41, S45 for the rapidly solidified powder of Fe-24Cr-5Ni-1Mo.
C, tungsten, ZrO ₂ · Al ₂ O ₃ · SiO ₂ -Al ₂ O ₃ spray coating
An experiment was performed using (base material S45C), SiO ₂ —Al ₂ O ₃ porous body, and sialon-based ceramics.

As a result, in the case of Zn-based or Al-based rapidly solidified powder having a low melt temperature, the selection of the disc material is relatively gradual, and it is possible to achieve a certain yield by using the graphite rotating disc. did it. For Cu-based rapidly solidified powder, the yield was able to be improved to some extent by using a sprayed coating rotating disk and sialon-based ceramics with improved thermal shock resistance.

However, we have experienced that powder production becomes exponentially stricter as the temperature of the molten metal increases, as in the case of stainless steel materials. That is, specifically, the melting temperature is 1300
When the temperature is higher than 0 ° C, powder production becomes extremely difficult. Even when a rotary coating disk made of a sprayed coating was used in the production of the stainless steel powder, the sprayed coating was often peeled off, and the intended effect on the powder yield was not exhibited. Therefore, it is extremely important to select an appropriate disc material in the case of a high melting temperature such as steel-based rapidly solidified powder.

In view of the present situation in the production of high melting point rapidly solidified powder, as a result of repeated studies to improve it, it has been devised to use a functionally graded material as a rotating disk. That is, in the case of a disk made of a sprayed coating, since the coating thickness is thin, the disk may not function sufficiently for thermal properties such as thermal conductivity and heat capacity, and the base material may be affected. Therefore, it is conceivable to increase the thickness of the ceramics layer, but since the coefficient of thermal expansion of ceramics and the metal material are significantly different, there is a high possibility that they will be separated by heating if they are laminated in a bimetal form.

Therefore, by considering this point, it was devised to introduce a functionally graded material. Here, as is well known, the functionally gradient material is a different layer material type composite material in which the chemical composition is gradually changed from ceramics to metal. This is a novel composite material whose purpose is to supplement the defects of ceramics with poor thermal shock resistance and toughness with a metal material and to supplement the heat resistance with ceramics.

Although this material still has many problems to be solved in the processing process, etc., the rotating disk in the centrifugal atomization method is considered to be an appropriate application field as the application field of this material. In use, in principle, the ceramic part is arranged in the molten metal dropping part, but in view of wettability, a metal may be arranged in the molten metal dropping part in reverse order. We believe that the use of a rotating disk made of functionally graded materials will improve the yield of rapidly solidified powder by centrifugal spraying, especially rapidly solidified powder with high melting point. Therefore, this is a patent application.

[0016]

As described above, according to the method of the present invention, when the rapidly solidified powder is manufactured from the high melting point material, the yield of the powder can be manufactured well.

[Brief description of drawings]

 FIG. 1 shows an outline of the centrifugal spray method.

Claims (1)

[Claims] 1. A method for producing a powder, which comprises using a functionally gradient material as a rotating disk when producing a rapidly solidified powder by a centrifugal atomization method.