JPH02133362A - Production of ceramics product - Google Patents

Abstract

PURPOSE:To prevent warpage deformation in molding of a sheet-like product and to improve the efficiency of finishing by packing ceramics powder parts into the die in such a manner as to be symmetrical via a conductive powder part, press molding and sintering the powders, then removing the part where the conductive powder part is sintered by electric discharge machining. CONSTITUTION:The following constitution is adopted in the process for producing the ceramics product by compressively molding ceramics powder by the press die and sintering the molding, then machining the molding to the product: The ceramics powders 6, 7 are packed into the die (a lower punch 3, an upper punch 4 and a barrel part 5) so as to be symmetrical via the conductive powder part 8 (e.g.: pure iron) and these materials are press molded and sintered. The part 11 where the conductive powder part 8 is sintered is selectively removed by electric discharge machining (electrodes 12 and 13) to obtain plural sintered bodies 9 and 10. The ceramics sintered bodies 9 and 10 separated in such a manner are subjected to the removal of the separating face where the sintered material 11 of the conductive powder layer 8 remains by mechanical grinding, by which the product is obtd.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method of manufacturing a ceramic product by molding ceramic powder using a mold press and sintering the mold to obtain a ceramic product. The present invention relates to a method for producing ceramic products that exhibits extremely little warpage after sintering even in the case of ceramic products, and can minimize the amount of parts removed by machining.

(Prior Art) Ceramics are used as electrical or mechanical parts by taking advantage of their excellent physical and mechanical properties. Then,
For ceramics, there is a need for technology that can manufacture products with complex shapes and high dimensional accuracy at low cost.

However, ceramics are hard and brittle, making them unsuitable for machining, and electric discharge machining is also difficult because they are difficult to conduct electricity. Therefore, a process is adopted in which ceramic powder is molded into a shape and size close to the final product, sintered, and then mechanically (grinded) processed to produce the product.

FIG. 4 shows the steps of the mold press method, which is a typical ceramic coloring method.

First, a mold having a shape similar to that of the product is filled with ceramic powder and compression molded using a press to obtain a molded body called a green part (FIG. 4(a)). Next, this compact is sintered by holding it in a temperature range above the sintering temperature in a heating furnace for a long time.

Through this sintering process, the powders bond together and the apparent density increases, so the volume of semi-finished products called brown parts after sintering shrinks more than that of green parts (see Figure 4).
b)). Therefore, the dimensions and shape of the mold are designed to be larger than the product in anticipation of shrinkage during the sintering process. After sintering, the brown parts are machined (ground finish)
The product is made into a product (Fig. 4 (C)).

Conventionally, when molding ceramic powder using a mold press in order to obtain a thin slope-shaped product as shown in Figure 5(a), it was molded into a green part with a shape as shown in Figure 5(b). , After sintering this, the part shown in FIG. 5(b) (the part below the broken line) was polished away and made into a product.

When a green part with the shape shown in Fig. 5(a) is sintered, warping occurs due to the asymmetry of the shape, so it is molded into a thick green part as shown in Fig. 5(1)). The resistance to deformation during the sintering process was increased to minimize deformation.

However, since the portion 11 shown in FIG. 5(b) of the cylinder 5 must be removed after sintering, there is a problem of increasing the manufacturing cost. Since the ceramic after sintering is hard and brittle, the unnecessary portion 1 has to be removed by grinding, which is inefficient.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned problems in the prior art when manufacturing thin plate-shaped ceramic products by a mold press method, and provides a process that can be manufactured at low cost. It was done for that purpose.

(Means for Solving the Problems) A feature of the present invention is that in a method for manufacturing a ceramic product in which ceramic powder is compression-molded in a press mold, sintered, and then machined into a product, The ceramic powder part is filled symmetrically through the conductive powder part and press-formed, and after sintering, the sintered part of the conductive powder part is selectively removed by electrical discharge machining. The purpose is to obtain a plurality of sintered bodies.

The present invention will be explained in detail below.

The inventors theoretically investigated the relationship between the density distribution of green parts obtained by molding ceramic powder using a mold press and the deformation of brown parts caused by shrinkage during the sintering process, and determined the mechanism of warp deformation. Based on this, we established a shape and press conditions that prevent warping, as well as a manufacturing process that incorporates these requirements.

Hereinafter, with reference to the drawings showing one embodiment of the present invention,
This will be explained in more detail.

FIG. 1 shows a mold and the filling state of ceramic powder inside the mold.

FIG. 1 is a longitudinal sectional view including the axis of the mold press in the pressing direction. In Fig. 1, 3 is a lower punch, 4 is an upper punch, 5 is a cylindrical part, and is a mold (floating die 2) that can press both sides. 6°7 is a ceramic powder, which is used after sintering This is a part that will become a product. 8 is a conductive material powder layer. Ceramic powder parts 6 and 7 are vertically symmetrical with respect to the conductive material powder layer 8.

The ceramic powder 6.7 and the conductive material powder layer 8 are
It is press-formed by compression caused by the axial displacement of the upper and lower punches. At this time, the axial displacements of the upper and lower punches are controlled to be equal across the conductive material powder layer 8.

Thus i! The green parts are kept in a heating furnace at a temperature of 28 degrees above the sintering temperature for a long time and sintered.

FIG. 2 shows the pattern of the electrical discharge machine used to remove the thus obtained brown part and the portion where the conductive material powder layer 8 was sintered.

FIG. 2(a) is a plan view, and FIG. 2(b) is a longitudinal sectional view.

In FIG. 2, reference numeral 9.10 is a ceramic part that will become a product, and II is a part on which the conductive material powder layer 8 is sintered. 12 is a wire electrode of the electrical discharge machine, and 13 is another electrode of the electrical discharge machine, which is connected to the portion 11 where the conductive material powder layer 8 is sintered.

By applying a voltage between the wire electrode 12 and the other electrode 13 of the electric discharge machine and bringing the wire electrode 12 into contact with the portion 11 where the conductive material powder layer 8 is sintered, an arc discharge is generated between the two. let

In this way, only the portion (2) where the conductive material powder layer 8 is sintered is melted and removed, and in the embodiment shown in FIG. 2, two ceramic semi-finished products 9.10 are obtained. This semi-finished product9,10
The separated surface is subjected to mechanical processing such as grinding to produce a product.

Next, the present invention will be explained in detail.

Figure 3 shows the main reasons why green parts, which were flat at the time, warp during the sintering process.

If the apparent density of the upper surface 15 and lower surface 14 of the green part is different, for example, if the density of the upper surface 15 is smaller than the density of the lower surface 14, and if both reach the theoretical density after sintering, then the upper surface The amount of contraction of No. 15 is greater than that of the lower surface. As a result, the brown part becomes warped as shown by the broken line in FIG.

Conversely, when the density of the lower surface 14 is lower than the density of the upper surface 15, downward warpage occurs.

From this, in order to prevent brown parts from warping,
It is necessary to make the density uniform in the green parts. However, as shown for example by reference numerals 7 and 6 in FIG. 1, it is impossible to make the density of the green part uniform on the upper surface of the green part.

Therefore, the inventors considered making the green part symmetrical with respect to its center in the thickness direction. The density of the green part is determined by the molding conditions using the mold press, mainly the mold shape and loading mode.

Therefore, as shown in Figure 1, by molding multiple green parts into one green part with symmetrical surfaces by combining multiple temperatures so that the green parts are symmetrical with respect to the central plane in the thickness direction, it is possible to The mold shape can now be designed symmetrically.

Regarding the loading pattern by the mold press, in the case of the mode shown in Figure 1, it is possible to achieve overall vertically symmetrical molding conditions by applying a molding machine that can apply vertically symmetrical loads. can.

Since the green parts thus obtained are symmetrical in apparent density with respect to the center in the vertical direction, warpage as shown by the broken line in FIG. 3 does not occur after sintering.

In the present invention, since the brown part obtained after sintering is a combination of multiple cylinder parts, it is necessary to separate them. Ceramics are hard and brittle and are extremely difficult to cut by mechanical means. On the other hand, electrical discharge machining is not possible because it does not conduct electricity.

In the present invention, this separation is taken into consideration in advance, and as shown in FIG. 1, when filling the powder, powder of a material with good conductivity is interposed in a layer at the portion that will become the separation surface. Then, the filled powder is molded with a mold press to form a green part, which is sintered to form a brown part, and then, as shown in Figure 2, the part where the conductive material powder layer is sintered is formed. Electrodes 12 and 13 of an electric discharge machine are connected to 11, an arc is generated between the electrode 12 and the part 11 where the conductive material powder layer is sintered, and the part 11 where the conductive material powder layer is sintered is Melt and remove.

The thus separated brown parts are made into products by mechanically grinding and removing the separated surfaces on which the substance on which the conductive material powder layer is sintered remains.

According to the present invention described above, there is no need for the extra portion that was conventionally added to prevent warping, so the material yield can be increased, and the extra portion can be mechanically removed by grinding. This eliminates the need for this and can significantly increase productivity.

(Example) An example of the present invention will be described using FIG. 1, FIG. 2, and Table 1.

The structure and arrangement of the device used are based on those shown in FIGS. 1 and 2, and the conditions are as shown in Table 1.

Taking into consideration the shrinkage of the powder during surface pressing, the powders were layered in the order of alumina, pure iron, and alumina as shown in Figure 1 so that the mating surfaces were flat. As a result of compression molding this using a 5OLon hydraulic press, green parts as shown in Table 1 were obtained.

Since a vertically symmetrical pushing force was applied by the floating die, cross-sectional observation by cutting the plate revealed that the upper and lower surfaces and the mating surfaces remained substantially flat.

When the green part was sintered in a heating furnace, the dimensions became smaller due to sintering shrinkage and a sintered brown part was obtained.

As a result of cross-sectional observation by cutting the plate, it was found that both the upper and lower surfaces and the mating surfaces were sufficiently flat, and it became clear that a forming method that utilized symmetry was effective in preventing warping of the thin plate.

The pure iron layer of the brown part is conductive, and when it was machined along the pure iron layer on the mating surface using a wire electrical discharge machine as shown in Figure 2, it was able to be completely cut.

However, since there was a pure iron layer on the cut surface, grinding was required to remove it, but the depth of the grinding was sufficient just near the surface.

(Effects of the Invention) By having the structure and operation as described above, the present invention prevents warping and deformation during mold pressing and sintering of ceramic powder into thin plate products, and also prevents finishing process. It has a remarkable effect in making it possible to carry out the process efficiently.

[Brief explanation of drawings]

1 and 2 show embodiments of the present invention.
The figure is an explanatory diagram of the mold and the state of powder filling in the mold, and Figure 2 shows two situations of discharge application of a brown part. (a) is a plan view, (b) is a longitudinal cross-sectional view, and Figure 3 Figures 4 and 5 are explanatory diagrams of the effect of warping of thin plate-like products during the sintering process.
The figure shows the conventional method.
5A and 5B are explanatory diagrams of the molding process of ceramics using a mold press method, and FIGS. 5(a) and 5(b) are explanatory diagrams of the molding process of a thin plate-like product. 1.2... Upper and lower surfaces of thin plate-like brown parts 3... Mold upper punch 4... Mold upper punch 5... Mold cylindrical part 6.7... Ceramic layer (powder) 8. ... Layer of conductive material (powder) 9.10 ... Ceramic layer (solid) 11 ... Layer of conductive material (solid) 12 ... Electrode of wire electrical discharge machine (work side)] 3
...Wire electrical discharge machine electrode (fixed side) 14...
Green part bottom surface 15...Green part top surface

Claims (1)

[Claims] In a method for manufacturing ceramic products in which ceramic powder is compression-molded in a press mold, sintered, and then machined into a product, the ceramic powder part is placed in the mold in a symmetrical shape with the conductive powder part in between. A method for producing a ceramic product, which comprises filling, press-molding, and sintering, and then selectively removing the sintered portion of the conductive powder by electrical discharge machining to obtain a plurality of sintered bodies. .