JPH0720615B2 - Molded article and its molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a molded article which is molded by filling a molding material in a split mold and a molding method thereof.

(Prior Art) For example, many ceramic products are cast or press-molded by filling a mold with a molding material. Also, as a mold, a split mold is used to reduce the number of mold assembling steps and releasing steps. Is common. As a product of this type, for example, there is a pipe for forging or holding a molten metal, which is made of silicon carbide particles or the like as an aggregate, and these are mutually bonded by an inorganic binder to form a porous material. The manufacturing method was obtained by filling a predetermined molding material between the outer molds 1a, 1b and the inner mold 2 of a wooden cylindrical molding die as shown in FIG. The molded product 3 was dried and then fired at a high temperature.

(Problems to be Solved by the Invention) In the above manufacturing process, when the molded product 3 is released from the mold, the outer molds 1a and 1b need to be pulled in the tangential direction indicated by the arrow A to release the mold. Substantially, this is extremely difficult. For example, when the mold piece 1a is pulled in the direction shown by the arrow B in FIG. 7, the mold pieces 1a and 1b are simultaneously molded over the entire inner peripheral surface at the time of mold release. Instead of being peeled off from the outer surface of the mold 3, as shown by the white arrow in the figure, the mold piece 1a moves so as to be twisted, and the sharp edge portion 4 of each of the molded products 3 is formed. It becomes easy to apply a large pressure near the mold-matching portion of the mold piece 1a. However, since the molded product 3 is in a considerably brittle state at this stage where it has not been fired, minute cracks are generated by the sharp edge portion 4. These cracks grow further during the firing process, making the fired product unusable as a pipe. To avoid this, one method is to divide the molding die into as many pieces as possible in the circumferential direction, but this is not a good idea because it complicates the production and handling of the mold. This is a method that is difficult to use in press molding in which the material is filled and pressed between the upper mold and the mold.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a molded product and a molding method thereof, which can prevent cracks from occurring as much as possible in the process of removing from a mold after molding.

[Structure of the Invention] (Means for Solving the Problems) In the first invention, a ridge is formed on the surface of the molded product at a position corresponding to the mating portion between the mold pieces of the split mold. The molding method according to the second aspect of the present invention is characterized in that the split mold is used to form a concave groove in the mating portion of each mold piece of the split mold.

(Operation) In the first aspect of the invention, since the protrusions are formed on the molding surface of the molded product at the positions corresponding to the mating portions of the pieces, it is easy to release the mold, and the molded meat is locally formed. Since the thickness is increased, even if the molded product is locally compressed near the mating portion of each mold piece when taking out the molded product, cracking is suppressed by the reinforcing effect due to the above-mentioned thickened portion. .

Further, in the second invention, the corners where the mating portions of the mold pieces forming the split mold intersect are sharp as compared with the conventional one, but in the present invention, the ends of the mold pieces are chamfered. And
By using a split mold in which a groove is formed when the mold pieces are assembled, even if each mold piece moves when it is taken out, the surface of the molded product Generation of cracks can be suppressed without causing large concentrated stress.

(Example) A first example in which the present invention is applied to a pipe for forging or holding a molten metal will be described below with reference to FIGS. 1 to 4.

First, as shown in FIG. 4, the molded product 5 as a porous pipe has a cylindrical shape as a whole, and its outer peripheral surface projects along the axial bisecting line of the cylindrical body. Article 6 is integrally formed. In this case, the ridge 6 has an apex angle of about 90.
It has a chevron cross section. The height of the ridges 6 is the minimum required to facilitate mold release and prevent cracks when the molded product is taken out, depending on the thickness of the cylindrical molded product 5 and the composition of the molding raw material. The vertical angle is preferably 90 ° to 150 °, and the height is preferably 1 to 5 mm. In this example, it was confirmed that if the thickness of the molded product 5 is 20 mm, the height of the protrusion 6 is 10 to 20% of the thickness.

Next, in FIGS. 1 to 3 showing the split mold 7 for molding the molded product 5, the split mold 7 is composed of an outer mold composed of a combination of two arc-shaped mold pieces 8 and a substantially circular shape. It is composed of a columnar inner mold 9 and a bottom mold 11 that closes the bottom end of a vertical cylindrical molding cavity 10, and each of these mold pieces is made of wood. Each of the two arc-shaped mold pieces 8 has a shape corresponding to a cylindrical body bisected along the axial direction, and each of the mold pieces 8 has a mating portion (face) 8a between the molds. Molding cavity 10
The chamfered portion 12 is provided by chamfering the edge portion where the molding surface 8b as the portion located on the side intersects. Therefore, when the two mold pieces 8 are assembled into a cylindrical body by using the fastening band 13 as shown in FIG. 2, the adjacent mold pieces are formed on the outer peripheral surface of the molding cavity 10 as shown in FIG. A V-shaped recessed groove 14 is formed along the mating portion 8a of No. 8 toward the molding cavity 10 side. The cylindrical inner mold 9 has a bottom mold 11 having a bottom end portion.
It is coaxially fixed in the outer mold by being fitted in the circular recess 11a provided on the upper surface of the.

Next, a method of molding the above-mentioned molded product 5 will be described. First, the split mold 7 is assembled in the state shown in FIG. On the other hand, fine granular silicon carbide is used as a main aggregate, and an appropriate amount of an inorganic binder is added to the aggregate, and then water is included to prepare a molding material. This molding material is a rammer as a tamping tool as shown in FIG.
While using 15, tightly fill the molding cavity 10.

When the filling of the molding material into the split mold 7 is completed, next, the fastening band 13
After removing the mold pieces 8, each mold piece 8 is peeled off from the surface of the molded product 5 and removed. At this time, when the mold piece 8 is peeled from the molded product 5 as already described with reference to FIG. , One of the side edges may act as a fulcrum and the other may act as a force point, and in such a case, the edge portion of each mold piece 8 on the side of the molding cavity 10 may be twisted. Unlike the above, it is not sharp, and because it is in a chamfered state,
The pressure exerted on the molding surface of the molded product 5 is remarkably weakened, and the generation of cracks is suppressed.

In this way, the molded product 5 taken out from the split mold 7 without causing cracks does not crack even in the process of performing high temperature firing in a firing furnace after being dried to remove the water content, A good finished product as a quality pipe is obtained.

FIG. 5 shows a second embodiment of the present invention. An outer mold (not shown) for molding this molded product 16 uses a mold similar to the molding split mold 7 of the first embodiment, but the dividing method is not divided into two in the circumferential direction. It is divided into three. The outer die has a structure corresponding to three axially connected ones, and the entire die is composed of a total of nine arc-shaped die pieces. Then, chamfered portions are provided at the mating portions of the respective mold pieces. Therefore, three protrusions 6 are formed at equal intervals over the entire length of the cylinder on the outer peripheral surface of the molded product 16 made by using such a mold, and the two protrusions 6 in the cylinder axial direction are formed. An annular protrusion 17 is provided along each of the mating portions.

The ridges 6 and 17 of each of the above-mentioned examples not only serve to prevent the occurrence of cracks, but also contribute to the improvement of the strength of the molded product. Furthermore, regarding the ridges 6 of the first embodiment, It also helps prevent rolling when storing or handling a cylindrical molded product. However, if these ridges are unnecessary, the ridges may be deleted prior to firing.

Further, the above-mentioned examples are described only in the case of producing a porous pipe as a refractory material by the Rammer molding method,
Of course, the shape of the molded product is not limited to the cylindrical shape, the shape and structure of the split mold may be appropriately selected, and the molding method may be a flow molding method or a press molding method. The effects of the present invention can be obtained as long as the molded product is likely to be cracked when the mold is removed after molding.

[Effects of the Invention] As is clear from the above description, according to the die-molded product of the first invention, the ridges are provided at the positions corresponding to the mating portions of the die pieces constituting the split die. Release is easy because of this, and the wall thickness at this position is locally increased,
Even if the mold piece is peeled off from the molded product so as to be twisted, the reinforcing effect of the ridges can suppress the occurrence of cracks. Further, according to the second invention, since a split mold is used in which a groove is formed in the mating portion of each mold piece, it is possible to prevent a local pressure from being applied to the molded product when the mold is removed. In addition to suppressing the occurrence of cracks,
It is also useful for improving the strength and preventing rolling of molded products.

[Brief description of drawings]

1 to 4 show a first embodiment of the present invention,
FIG. 1 is an exploded perspective view of a split mold for molding a molded product, and FIGS. 2 and 3 are vertical cross-sectional views showing a state in which a molding cavity is filled with a molding material, and III of FIG. Fig. 4 is a cross-sectional view taken along line -III, and Fig. 4 is a perspective view of the molded product. FIG. 5 is a perspective view of a molded product according to the second embodiment of the present invention,
FIG. 6 is a cross-sectional view showing a conventional split mold molding cavity filled with a molding material. FIG. 7 is a cross-sectional view showing a state in which the edge portion of the mold piece presses the surface of the molded product when the molded product is removed from the conventional split mold. In the figure, 5 is a molded product, 6 is a protruding portion, 7 is a split mold, 8 is a mold piece, 8a is a mating portion, 9 is an inner mold, 10 is a molding cavity, 12
Is a chamfered portion, 14 is a concave groove, and 16 is a molded product.

Claims (2)

[Claims] 1. A mold which is formed by a split mold composed of a plurality of mold pieces, and has a ridge on the surface at a position corresponding to a mating portion of the mold pieces of the split mold. Molded product that does. 2. A mold for filling a split mold composed of a plurality of mold pieces with a molding material and then dividing the split mold to take out a molded product, wherein a concave portion is formed at a mating portion of each mold piece of the split mold. A method for molding a molded product, which comprises using a split mold for forming a groove.