JPS63125304A - Method and device for molding powdered body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Applications> The present invention relates to the molding of highly elastic fine powders (particle size of 107 nm or less) such as ceramics and cemented carbide.

<Prior art and problems to be solved by the invention> Various molding methods have been known as powder molding methods, such as press molding, hot pressing, indie-excillin molding, and slip casting. . Among these, press forming is one of the methods that has great advantages in terms of mass production and forming costs. However, since fine powders such as ceramics and cemented carbide have high elasticity, press forming When this is molded, the friction generated between the mold and the powder makes it impossible to perform sufficient filling and pressurization in areas remote from the pressurizing surface. Therefore, depending on the shape of the molded object, such as a cylindrical shape that is long in the pressurizing direction or a shape that has a step in the middle, a density difference may occur inside the molded object, resulting in cracks after sintering. there were. On the other hand, with the aim of eliminating the drawbacks of such press molding methods, there is the Injiexi Ashin molding method, in which paraffin or the like is mixed into the powder and then pushed into the mold, and the powder is dissolved in a liquid such as water to form a slurry. There is a slip casting method (sedimentation method) in which the material is poured into a Ceracola mold, but methods using such solvents require tens of hours to several days to discharge the paraffin, water, etc. used as the solvent. Because of this, there was a problem with mass production.

Means for Solving the Problems> Therefore, in the present invention, powder mixed with a solvent is flowed into a mold, and then the inside of the mold is pressurized and heated to cause the solvent to be discharged from the mold. The powder was molded. In order to realize such a method, a molding device is equipped with a plunger that pressurizes the inside of the mold, a strainer installed at a location remote from the plunger that allows the solvent to pass through but not the powder, and a heating device that heats the forming mold. It was constructed with a vessel.

Embodiment> An embodiment of the molding method and apparatus according to the present invention will be described below. Figure 1 shows an embodiment of the molding device.
The raw material is ceramic powder, which is used to mold engine valves. Made of this molding! ! ! No. 2 has a mold 6 and a heater 14 in an outer frame 4, and a pressure plate 8 and a nozzle 10 communicating with the mold 6 are provided on the upper part of the frame 4. As described above, the mold 6 has the shape of a valve, and has the side communicating with the nozzle 10 serving as an input port for the raw material, and the other end, that is, the lower end, having a strainer 1. This strainer 12 is made of a porous member through which liquid or gas can pass, such as a metal sintered body, ceramic sintered body, filter paper, etc., and the average diameter of the pores is 5 to 20 times the diameter of the powder. It's about double that. Furthermore, a heater 14 for heating the mold 6 is provided inside the frame 4 so as to surround the forming mold 6, and an exhaust pump (not shown) is provided on the wall of the frame 4.
An exhaust hole 16 is provided which communicates with the other parts. On the other hand, the nozzle 10 is provided with a plunger 18 connected to a pressing device (not shown) for pressurizing the powder, etc. that has flowed into the mold 6, and the plunger 18 slides in the nozzle 10 in the axial direction. It is supposed to move.

The pressure plate 8 on which the nozzle 10 is provided is in contact with the mold 6 through a gasket between the pressure plate 8 and the mold 6, and is provided with a suppressing device (not shown) so as to be able to withstand the reaction force from within the mold 6. ) is pressed toward the frame 4 and mold 6.

Next, the operating procedure and conditions will be described.

Knead the ceramic powder with a solvent in advance. This solvent is a low boiling point material such as water or alcohol, and a predetermined amount of the fluid material kneaded with this solvent is poured into the mold 6 through the nozzle 10 and pressurized with a plunger 18 at a pressure of about 500 kg/cd. Press. Due to this pressurization, excess solvent other than the solvent remaining between the powders is discharged to the outside through the strainer 12. Furthermore, the mold 6 is heated by the heater 14,
The solvent is vaporized and evaporated from the strainer 12, and at the same time its vapor pressure (in the case of methyl alcohol, 203.
At 5° C. and 40 atm), the solvent, including the liquid solvent, is discharged from the strainer 12. The time required for its discharge is several tens of minutes. In case (B), if air is removed from the exhaust hole 16 and the inside of the frame 4 is maintained in a vacuum state, vaporization of the solvent is promoted and the above-mentioned evacuation time can be further shortened. During heating, the plunger 18 continues to apply pressure to maintain contact between the initially solidified powder, but the pressure applied by the plunger 18 is 4 to 5 times the steam pressure, that is, at a mold temperature of 203.5°C. 160 kg weight/-
~200 kgf/d. The reason for this is that the mixed solvent acts as a lubricant for the material when it is supplied, so the coefficient of friction between the powder particles is low, and even when pressurized by the plunger 18, the internal stress of the material does not become uneven. This is because as the powder is discharged, the coefficient of friction between the powders and between the powder and the mold 6 increases, and as a result, excessive pressure causes uneven density of the material. After the solvent has been discharged, the heating by the heater 14 is stopped to lower the temperature of the mold 6,
At the same time, the internal pressure inside the mold 6 is lowered to complete the molding.

By molding the ceramic powder in this way, the solvent can be quickly discharged even in the case of axially long parts such as engine valves, which tend to have non-uniform density due to pressurization. Therefore, the ceramic powder can be molded in a short time.

<Effects of the Invention> As described above, according to the present invention, 97% dissolved in a solvent
The books flow into the mold, are pressurized and heated (heated), and the solvent is discharged to the outside through a strainer, so that the material that has flowed into the mold is not pressurized without causing uneven pressure. Since it is possible to pressurize the mold and to quickly discharge the solvent mixed inside to the outside by heating, a molded product having a uniform density can be molded in a short time. Furthermore, the molding apparatus according to the present invention includes a mold for molding, a plunger that pressurizes the inside of the mold, a strainer provided at a location apart from the plunger, and a heating path that heats the mold. As a result, the solvent can be quickly discharged from the abrasive material under a uniformly pressurized state, so that the molding process of the powder can be performed quickly.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a molding apparatus according to the present invention. In the drawing, 2 is a molding device, 4 is a frame, 6 is a mold, 10 is a nozzle, 12 is a strainer, 14 is a heating word, 16 is an exhaust hole, and 18 is a plunger.

Claims (2)

[Claims] (1) In powder molding, the powder mixed with a solvent is injected into a mold, then pressurized and heated, and the solvent is discharged to form the powder. Method. (2) It comprises a mold for molding, a pressure plunger that pressurizes the powder in the mold, a strainer provided at a location remote from the plunger, and a heater that heats the mold. Characteristic powder molding equipment.