JPS60162703A - Production of metallic powder - Google Patents

Abstract

PURPOSE:To eliminate thoroughly intrusion of a ceramic component into a molten metal and to obtain metallic powder having high quality with a process for producing the metallic powder by dropping the metallic powder onto a rotating body by melting the bottom end of a metallic bar material to form the molten metal. CONSTITUTION:A metallic bar material 2 is liftably held vertically long in a vessel 1. A preheater 4 provided with a heating element 5, a heater 6 and a discoid rotating body 7 are disposed as shown in the figure. After the inside of the vessel 1 is substd. with a non-oxidative atmosphere, for example, gaseous He, the material 2 is preheated by the heater 4 up to the temp. approximate to the melting temp. and heat energy is concentrically applied to the bottom end part of the material 2. The body 7 is rotated at high speed during this time and the molten metal 7 melting and dropping successively from the bottom end of the material 2 is received by the body 7 and is scattered horizontally by the centrifugal force thereof, by which the molten metal is solidified to metallic powder 10. The intrusion of a ceramic component from a crucible for melting, tundish, nozzle, etc. into the molten metal is thoroughly eliminated and the metallic powder having high quality is obtd. according to the above-mentioned method.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing metal powder suitable for producing metal powder used as a raw material powder in powder metallurgy for producing sintered parts, for example. It is.

(End of technology) In recent years, the application of powder metallurgy has become widespread, in which metal powder is used as a raw material and the metal powder is molded into a predetermined shape, and then the molded body is fired to obtain a sintered part with a desired shape.

As a method for obtaining metal powder used in such powder metallurgy, there is, for example, a disk rotating centrifugal atomization method. In this disk-rotating centrifugal atomization method, molten metal is dropped onto a circular flat disk that rotates around a vertical axis, and the molten metal is pulverized by the centrifugal force received from this disk, producing metal powder. It is one of the most effective methods of manufacturing. Unlike the water atomization method, which is generally used for mass production of metal powders, this disk-rotating centrifugal atomization method is capable of producing powder in a non-oxidizing atmosphere, and also has gas atomization properties. Since rapid solidification is possible, it has the advantage that high quality and fine powder can be achieved. Therefore, this disk rotating centrifugal atomization method is suitable for the production of powder of active metals or alloys containing active metals, which are expensive and have strict quality requirements.For example, in the powder metallurgy of Ni-based heat-resistant superalloys,
In order to improve the heat cycle fatigue properties of sintered crystals,
It is required to eliminate impurity components such as ceramic components in the powder as much as possible.

However, in the conventional method for producing metal powder, the base metal is melted in a high-frequency induction furnace, then transferred into a tundish, and the molten metal is dropped onto a rotating disk through a nozzle provided at the bottom of the tundish.
Refractories constituting the melting crucible, tundish, nozzle, etc. of a high-frequency induction furnace were eroded and mixed into the molten metal, and ceramic particles were sometimes mixed in the resulting metal powder. Therefore, it is then necessary to perform an inspection to remove the ceramic particles in the metal powder and select metal powders whose ceramic particles are below the allowable limit, and this process requires an extremely large amount of time and cost.

(Objective of the Invention) This invention was made to solve the above-mentioned problems of the conventional art. It is an object of the present invention to provide a method for producing metal powder, which allows obtaining metal powder.

(Structure of the Invention) A method for producing metal powder according to the present invention involves preheating a vertically held metal bar to near its melting point, and further applying thermal energy intensively to the lower end portion of the metal bar. The metal powder is manufactured by sequentially melting the molten metal starting from its lower end and letting it fall as droplets or liquid streams, and then receiving the fallen molten metal on a rotating body and cooling and solidifying it to produce metal powder. .

FIG. 1 is a principle explanatory diagram for explaining this invention, and 1
2 is a container, 2 is a metal rod held vertically by a holder 3 that can be raised and lowered, 4 is a preheating device equipped with a heating element 5, 6
7 is a heating device that intensively applies thermal energy to the lower end portion of the metal bar 2; 7 is a disk-shaped rotating body; and 8 is a rotating shaft of the disk-shaped rotating body 7.

In producing the metal powder, the inside of the container 1 is made into, for example, a non-oxidizing atmosphere, and specifically, after the inside of the container 1 is replaced with, for example, helium gas, the metal bar 2 is preheated to near the melting temperature by the preheating device 4. , the metal bar 2 is heated by a heating device 6, and thermal energy is intensively applied to the lower end portion of the metal bar 2 by this heating. During this time, the disk-shaped rotating body 7 is rotated at high speed via the rotating shaft 8, and the metal bar 2 is melted from its lower end by the heat energy, and the molten metal 2 falling is received on the rotating body Z. do. The molten metal 2 that has fallen onto the corotating body Z is blown away in the horizontal direction by the centrifugal force. At this time, if the rotation center of the rotating body 7 and the axis of the metal bar 2 almost coincide, the molten metal 2 falls onto the rotating body 7 and after the rapid cooling starts, fine powder is formed. The particles become granular and fly in the centrifugal direction, and solidify during the scattering after the start of the rapid cooling. Here, molten metal 2
If the droplets are large and these large droplets fall intermittently onto the rotating body Z, there is a risk that centrifugal spraying will not be stable. It is more preferable to allow it to fall.

In such a method for producing metal powder, it is difficult to obtain a desired cooling rate when the atmosphere is vacuum, so it is more desirable to use a non-oxidizing atmosphere 1, for example, an inert gas atmosphere.

In addition, in order to continuously melt the metal bar 2 and drop it onto the rotating body 7L, a means for lowering the metal bar 2 sequentially according to the amount of melted and fallen metal bar 2, a preheating device 4 and a heating device are required. A means for raising the device 6 according to the melting and falling amount of the metal bar 2 may be used, but the metal bar should be adjusted so that the drop of the molten metal 2 that melts and falls is always approximately constant. It is more desirable to lower the material 2 one after another, and the structure is also simpler.

As mentioned above, in order to stably perform centrifugal spraying, it is more desirable to cause small droplets of molten metal 2 to fall continuously. It is also desirable that the molten metal on the lower end surface of the metal bar 2 resists the surface tension and easily falls.

In addition, as another means to make it easier to fall, there is a metal bar 2
It is also conceivable to taper the lower end of the .

In this case, in order to maintain the tapered shape during melting, for example, if the heating device uses plasma arc heating, there is a method of tilting the direction of a plurality of plasma arcs toward one specific point, In the case of induction heating, it is possible to take a method such as making the diameter of the lower coil smaller, and by adding vibration to the tapered shape of the metal bar 2, small droplets of molten metal 2 are caused to fall continuously. be able to.

Further, the cross-sectional shape of the metal bar 2 can be any suitable shape, such as a cross, a modified cross, a temple, a star, etc., as illustrated in FIG. In this way, the holding area of the molten metal 2 becomes smaller, so that it becomes easier to continuously drop the molten metal 2 in small droplets. For example, in the case of the star shape shown in FIG. 2(d), the outer part tends to melt first, so the lower end part of the metal bar 2 becomes tapered, so that a continuous droplet can be obtained. Cheap.

Furthermore, the heating device 6 that intensively applies thermal energy to the lower end portion of the metal bar 2 may include plasma arc heating,
High frequency induction heating, laser heating, thermal beam heating, radiation heating, etc. can be employed.

Note that since electron beam heating results in a vacuum atmosphere, it is difficult to provide a sufficient cooling rate to the molten metal 2.

Further, in some cases, it may be desirable to preheat the metal bar 2 using the preheating device 4 before intensively applying thermal energy to the lower end portion of the metal bar 2.

(Example 1) A device having the same principle and configuration as shown in Fig. 1 was used, and the metal bar 2 was made of a nickel-based heat-resistant alloy (INloo (product name)) with a layer diameter of 50 m and a length of 500 mm. , the lowermost end was not tapered and was hung by a holder 3.

On the other hand, high frequency induction heating is used as the heating device 6,
The lower end portion of the metal bar 2 was heated intensively by inputting kW. Then, the droplet-shaped molten metal formed by this heating was continuously dropped onto the rotation center of a disk-shaped rotating body 7 having a diameter of 90 mm and rotating at a high speed of 15,000 Ppm. At this time, the molten metal 2 fell in the form of continuous droplets, but centrifugal spraying was performed well, and the metal powder 10 was obtained by being scattered by the centrifugal force of the rotating body 7.

In the metal powder 10 subjected to the tll treatment, although there was some coarse powder mixed in, no ceramic particles were found to be mixed in at all. By appropriately pulverizing and classifying the coarse powder, it was possible to obtain a metal powder with extremely excellent properties as powder metallurgy Kawahara #1 powder.

In this example, the weight of the liquid molten metal 2 falling at one time was 200 to 500 g, and the dissolution rate of the metal rod 2 was about 300 g/min.

(Example 2) Using an apparatus having the same principle and configuration as shown in FIG. 1, a metal bar 2 of =-/Kel-based heat-resistant alloy (INloo (product name)) with a diameter of 50 mm and a length of 500 mm was used. It was suspended from a holder 3 using a tapered bottom end.

On the other hand, high frequency induction heating is used as the heating device 6,
The lower end tapered portion of the metal bar 2 was intensively heated with an input of kW, and at the same time, impactful vibrations were applied to the metal bar 2 at a frequency of approximately once per second. Due to this vibration, about 20 to 30 g of molten metal droplets fell down at a rate of about once every 5 seconds. Then, this molten metal 2 was continuously dropped onto the center of rotation of a disk-shaped rotating body 7 having a diameter of 90+s+s and rotating at a high speed of 1500 Orpm. The centrifugal force of the rotating body 7 caused good centrifugal spraying, and the centrifugal force of the rotating body 7 caused the metal powder 10 to be scattered and formed.

The obtained metal powder 10 had some coarse powder mixed in, but no ceramic particles were found mixed in at all. By appropriately pulverizing and classifying the coarse powder, it was possible to obtain a metal powder with extremely excellent properties as a raw material powder for powder metallurgy.

(Example 3) In Example 2, the metal bar 2 is preheated to about 1200°C by the preheating device 4, and the lowest end is heated by high frequency induction by the heating device 6, and the metal bar 2 is subjected to impact heating at a frequency of about 1 meter per second. gave a vibration. As a result, about 20 to 30 g of droplet-shaped molten metal 2 can be dropped onto the rotating body 7 that rotates at a high speed of about 1500 Orpm per second, and the centrifugal I! It was possible to form the metal powder 10 by +1 mist well, and the centrifugal spraying could be completed in a short time.

(Example 4) In Example 2, the horizontal cross-sectional shape of the metal bar 2 was changed to the modified cross shape shown in FIG. 4(b), and other aspects were the same. As a result, the droplet falling interval 1711 was shortened to 2 to 3 seconds, making it possible to obtain finer and more uniform metal powder 10. This was thought to be due to the fact that the holding area of the metal droplets became smaller at the lower end portion of the metal bar 2, making it easier for the metal droplets to fall.

(Effects of the Invention) As explained above, the method for producing metal powder according to the present invention concentrates thermal energy on the lower end portion of a metal rod held vertically, and moves the metal rod from the lower end portion. Metal powder is manufactured by sequentially melting and dropping the metal, and the fallen molten metal is received on a rotating body and cooled and solidified, so it is possible to produce high-quality metal powder with significantly less contamination. By performing powder metallurgy using this metal powder, mechanical properties,
This can bring about a significant effect in that it is possible to obtain sintered crystals with extremely excellent thermal properties, chemical properties, etc.

[Brief explanation of the drawing]

FIG. 1 is an explanatory view of a metal powder manufacturing apparatus showing the basic configuration of the present invention, and FIGS. 2(a) to 2(d) are explanatory views showing examples of shapes of metal bars. 2... Metal bar material, 6... Heating device, 7... Rotating body, 2... Molten metal, 10... Metal powder. Figure 1 Figure 2 (a) (C)

Claims (1)

[Claims] (1) Heat energy is intensively applied to the lower end of a metal bar held vertically, the metal bar is sequentially melted and dropped from the lower end, and the fallen molten metal is received on a rotating body. A method for producing metal powder, which comprises producing metal powder by cooling and solidifying it.