JP2017087226A - Manufacturing method of ceramic casting mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a ceramic casting mold capable of imparting high mechanical strength over the whole casting mold.SOLUTION: A manufacturing method of a ceramic casting mold sinters this by molding a shape by adding a resin binder to an aggregate ceramic particle 10. The manufacturing method of the ceramic casing mold 1 sinters after impregnating ceramic slurry of including a sintering ceramic particle 12 of a size impregnable between the aggregate ceramic particles 10 after molding. In the manufacturing method of the ceramic casting mold 1, the average particle diameter ratio of the sintering ceramic particle 12 to the aggregate ceramic particle 10 is smaller than 1/100, and an average particle diameter of the aggregate ceramic particle 10 is 100 μm or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a mold made of ceramics, and more particularly to a method for producing a ceramic mold obtained by adding a resin binder to aggregate ceramic particles to form a mold and firing the mold.

  A method for producing a cast metal product by pouring molten metal (molten metal) into a mold (sand mold) made of sand is known. In such a sand mold, a wooden mold corresponding to the product shape is arranged in a frame, and sand mixed with a binder is poured into this, and further, a hardener is given to solidify the sand and then the wooden mold is pulled out. Can be manufactured. In such a manufacturing method, when the molten metal is poured into the sand mold, if the binder is decomposed by heat, gas may be generated, which may cause gas defects in the cast product. In addition, in the case of a metal having a high melting point, the binder may be decomposed before solidification and the sand shape cannot be maintained, and casting itself may not be performed.

  On the other hand, a casting method using a fired mold is also known. Generally, since the mold is chemically stabilized at the firing temperature, stable casting is possible up to the vicinity of the firing temperature. Referred to as Typical examples include a shell mold method and a lost wax method.

  For example, Patent Document 1 discloses a method of manufacturing a firing mold by blowing resin-coated sand into a mold heated to a firing temperature in a shell mold method. Since the binder contained in the resin-coated sand is desorbed during firing, gas defects during casting due to this can be prevented. On the other hand, since the firing temperature depends on the heating temperature of the mold, in the case of a mold made of ordinary steel, the heating temperature cannot be set to a very high temperature, and depending on the binder, it may not be possible to sufficiently desorb. is there.

  Patent Document 2 discloses a method for producing a mold by a lost wax method in which a mold is fired while removing a “wax mold” made of a wax modeled on a product. Here, a slurry made of aggregate and binder is applied to a wax mold and dried, and the periphery is placed in an external box, and the slurry is injected into the external box and solidified, and then heat-treated. Yes. For example, when zirconia is used for the first slurry and delta alumina is used for the second slurry, it can be fired by heat treatment at about 1000 ° C.

  By the way, in the mold obtained through the firing process as described above, cracks are likely to occur when the slurry is dried and / or fired, making it unsuitable for a mold for a large casting product. In addition, for example, in a ceramic mold in which ceramic powder is sintered, if the sintered body has insufficient mechanical strength, cracks and the like are likely to occur when molten metal is poured, resulting in a defective casting surface. And casting may not be possible.

  For example, Patent Document 3 discloses a method for producing a ceramic porous body having high mechanical strength while being coarse ceramic particles having a particle diameter of 10 μm or more, which is difficult to sinter. The mechanical strength can be improved by dispersing fine particles or an inorganic polymer precursor between coarse particles and then firing to form a thicker neck portion. By applying this to the above-described method for producing a fired mold, high mechanical strength can be imparted over the entire mold.

JP 2011-41968 A JP 2014-79766 A JP 2008-156170 A

  In a ceramic porous body in which fine particles are dispersed between coarse particles disclosed in Patent Document 3 and fired to form a thick neck portion, a high mechanical strength can be obtained while having a macroporous structure. On the other hand, it is necessary to devise the application to the mold such as how to perform molding while maintaining such high mechanical strength.

  The present invention has been made in view of the situation as described above. The object of the present invention is to provide a ceramic mold obtained by adding a resin binder to aggregate ceramic particles, shaping a mold, and firing the mold. In the manufacturing method, the present invention is to provide a method for manufacturing a ceramic mold capable of imparting high mechanical strength over the entire mold.

  A method for manufacturing a ceramic mold according to the present invention is a method for manufacturing a ceramic mold in which a resin binder is added to aggregate ceramic particles to form a mold and then sintered. The ceramic mold is impregnated between the aggregate ceramic particles after molding. It is characterized by impregnating a ceramic slurry containing ceramic particles for sintering of a size that can be sintered and then sintering.

  According to this invention, it is possible to provide a ceramic mold that can reliably sinter the aggregate ceramic particles and impart high mechanical strength over the entire mold, thereby giving a sound casting product.

  In the above-described invention, an average particle diameter ratio of the ceramic particles for sintering to the aggregate ceramic particles may be smaller than 1/100. According to this invention, the ceramic particles for sintering can be reliably disposed between the aggregate ceramic particles, and the sintering can be ensured and higher mechanical strength can be imparted over the entire mold.

  In the above-mentioned invention, the average particle diameter of the aggregate ceramic particles may be 100 microns or more. According to this invention, a ceramic mold that gives a good casting surface can be provided.

It is an expanded sectional view which shows the joining state of the aggregate ceramic particle of the ceramic casting_mold | template by this invention. It is process drawing of the manufacturing method of the ceramics mold by this invention. It is sectional drawing which shows typically the sintered part of the ceramic casting_mold | template by this invention. 2 is a scanning electron micrograph of a fracture surface of a ceramic mold according to the present invention. 2 is a scanning electron micrograph of a fracture surface of a ceramic mold according to the present invention. 2 is a scanning electron micrograph of a fracture surface of a ceramic mold according to the present invention. It is a graph of the bending strength in the ceramic mold by this invention. 2 is a scanning electron micrograph of a fracture surface of a ceramic mold according to the present invention.

  Below, the detail is demonstrated about one Example of the manufacturing method of the ceramics mold by this invention.

  As shown in FIG. 1, the cross-sectional structure of the obtained mold 1 is a porous structure in which an aggregate ceramic 10 is bonded with a sintering ceramic 12, and compared with a case where the aggregate ceramic 10 is simply sintered. Thus, the neck portion A can be made thicker. As a result, high mechanical strength can be obtained.

  A typical manufacturing method of such a mold 1 will be described with reference to FIG. In the following, only the molding method using the sand mold will be described, but the present invention is not limited to this, and it goes without saying that the gas curing method, the 3D molding method, and the like are also possible.

  First, a binder (binder) 14 is kneaded with the aggregate ceramic 10 (FIG. 2, S1). As will be described later, when the binder 14 imparts the bonding force between the particles of the aggregate ceramic 10 with the curing agent, the curing agent is also kneaded together.

The aggregate ceramic 10 is a main body of the ceramic mold. As such an aggregate ceramic, refractory materials such as alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), zircon (ZrO ₂ · SiO ₂ ), mullite (3Al ₂ O ₃ · 2SiO ₂ ) are selected. obtain.

  The particle size of the aggregate ceramic 10 is not particularly limited as long as it provides a good casting skin of the product obtained as the mold 1. However, according to the method of the present invention, even a particle having a larger particle size can be used, and from the viewpoint of reliably disposing the sintering ceramic particles 12 described later, the particle size must be larger. Is preferred. In other words, the average particle size is preferably 50 to 200 μm, particularly 100 μm or more.

  The binder 14 is not particularly limited. For example, the binder 14 is a phenol resin binder, which is made of a water-soluble alkaline phenol resin, and is an acid generated by hydrolysis by giving an ester as a curing agent. The polymer is made into a polymer to provide a bonding force between the particles of the aggregate ceramic 10.

  Next, a wooden mold or the like is placed in a wooden frame, and the aggregate ceramics 10 and the binder 14 (including a hardener) are poured into the wooden frame to mold (FIG. 2, S2), and the wooden mold is extracted. To obtain a sand mold (FIG. 2, S3).

  Next, the sand mold is impregnated with a ceramic slurry containing particles of the ceramic 12 for sintering (FIG. 2, S4) and dried (FIG. 2, S5). In the ceramic slurry, particles of the ceramic 12 for sintering having a predetermined particle diameter may be given to water, and a dispersant for the ceramic particles may be mixed as necessary. Further, the stirring may be performed while ultrasonic bubbles or degassing in vacuum. Further, the impregnation may be performed in a vacuum with a stirred ceramic slurry.

The sintering ceramic 12 is not particularly limited as long as it is provided as a powder and can provide connection between particles of the aggregate ceramic 10. A ceramic having a melting point lower than that of the aggregate ceramic 10 is preferred. For example, alumina (Al ₂ O ₃ ), silica (SiO ₂ ), zirconia (ZrO ₂ ), zircon (ZrO ₂ · SiO ₂ ), mullite (3Al ₂ O ₃ · 2SiO ₂ ) and the like.

  By the way, as shown in FIG. 3, the ceramic slurry permeates between the particles of the sand-type aggregate ceramic 10 given the shape by the binder 14 to dispose the ceramic particles 12 for sintering. Therefore, the particle size of the sintering ceramic particles 12 depends on the particle size of the aggregate ceramic 10 and is preferably 1/100 or less. On the other hand, if the particle size is too fine, the particles are easily aggregated even if a dispersant is applied. Therefore, for example, it is 2 μm or less, preferably 0.5 μm or more.

  Next, the sintering ceramic particles 12 are fired at a temperature that gives a neck between the particles of the aggregate ceramic 10 (FIG. 2, S6). Such a temperature is generally sufficient to remove the binder 14.

  The mold 1 is provided by the process as described above. Such a mold 1 can reliably sinter the particles of the aggregate ceramic 10 and can impart high mechanical strength over the entire mold 1 to give a sound casting product.

[Example]
Next, examples will be described.

  For the aggregate ceramics 10, melted mullite particles having a substantially spherical shape with an average particle size of 110 μm were used (trade name: Lunamos MS, manufactured by Kao Quaker Corporation). A commercially available phenol resin binder and a curing agent were used for the binder (binder) 14. A 2.3 weight ratio binder 14 was kneaded into the aggregate ceramic 10 and put into a wooden mold to form a sand mold.

  The ceramic slurry was prepared by mixing alumina powder having a particle diameter of 0.15 mm as the sintering ceramic 12 and water in a ratio of 3: 2, and further dispersing as a dispersant for ceramic particles (manufactured by San Nopco, trade name: NOPCOSPERS). 5600) was added at a weight ratio of 1.5 and stirred.

  A ceramic slurry in which the sand mold which had been allowed to stand for one day and hardened was sufficiently stirred was immersed, and the sand slurry was impregnated with the ceramic slurry. Then, this was dried and fired at a predetermined temperature in an atmospheric furnace for 3 hours to produce a ceramic mold 1. In such a ceramic mold 1, 20 to 25 weight ratio of sintering ceramics could be introduced with respect to the aggregate ceramic weight.

  FIG. 4 shows a scanning electron micrograph of the fracture surface of the ceramic mold 1 fired at 500 ° C., which is a relatively low firing temperature, for 3 hours. The sintered ceramics 12 aggregated in the neck portion A (see FIG. 1) of the aggregate ceramics 10 can be confirmed. This is because the fine ceramic 12 for sintering in the ceramic slurry aggregates in the neck portion A of the aggregate ceramic 10 by using the surface tension as a driving force by viscous flow in the drying step (FIG. 1, S5).

  Further, FIG. 5 shows the gap B after the binder is decomposed in the fracture surface of the neck portion A (see FIG. 1). In the impregnation step (FIG. 2, S4), the binder 14 is present in the neck portion A of the aggregate ceramic 10, but as described with reference to FIG. Ceramics 12 agglomerates. Then, in the firing step (FIG. 2, S6), the binder 14 is decomposed and becomes a gas and is discharged from the gap between the ceramics 12 for sintering. A gap B is formed.

  Next, the results of a bending test (bending strength test) will be described.

  In FIG. 6, the ceramic mold 1 was produced from a wood mold of 10 × 16 × 50 mm, and the bending strength result by a bending test using such a test piece was shown. The sintering temperature in the firing step (FIG. 2, S6) was changed by 100 ° C. in the range of 1300 to 1600 ° C., the test pieces at each temperature were measured five times, and the average strength is shown in the figure.

  Moreover, in FIG. 7, the scanning electron micrograph of the fracture | rupture part of a bending test piece was shown. An arrow indicates a portion broken inside the aggregate ceramic 10.

  The bending strength increased with increasing sintering temperature. Further, when the sintering temperature rises, the fracture occurs not in the neck portion between the aggregate ceramics 10 but in the aggregate ceramics 10, and the internal void introduced at the time of manufacturing the aggregate ceramics 10 is the starting point. It is thought that it is broken.

  In FIG. 8, the scanning electron micrograph in the part which the three aggregate ceramics 10 adjoin is shown. The firing temperatures are (a) 1300 ° C, (b) 1400 ° C, (c) 1500 ° C, and (d) 1600 ° C. As in (a) and (b), at a low firing (sintering) temperature, densification of the ceramic 12 for sintering does not proceed and many cracks can be confirmed in the neck portion (see arrows). On the other hand, as shown in (c) and (d), as the sintering temperature rises, densification of the ceramic 12 for sintering proceeds. In particular, in (d), a “scale” shape is formed at the neck portion. From the fact that the “structure” can be confirmed, it is suggested that the neck portion of the sintering ceramic 12 made of alumina is made mullite by diffusion from the aggregate ceramic 10. The bending strength is increased by strengthening the neck portion.

  As mentioned above, although the Example by this invention and the modification based on this were demonstrated, this invention is not necessarily limited to this, A person skilled in the art will deviate from the main point of this invention, or the attached claim. Various alternative embodiments and modifications could be found without doing so.

1 Mold 10 Aggregate Ceramics 12 Sintering Ceramics 14 Binder

Claims (3)

  A method for producing a ceramic mold in which a resin binder is added to an aggregate ceramic particle to form a mold and then sintered. The ceramic mold for sintering has a size that can be impregnated between the aggregate ceramic particles after molding. A method for producing a ceramic mold, comprising impregnating a ceramic slurry containing the ceramic slurry and then sintering the ceramic slurry.   The method for producing a ceramic mold according to claim 1, wherein an average particle diameter ratio of the ceramic particles for sintering to the aggregate ceramic particles is smaller than 1/100. The method for producing a ceramic mold according to claim 2, wherein the average particle diameter of the aggregate ceramic particles is 100 microns or more.

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