JPH0248833B2 - RUTSUBOOYOBISONOSEIZOHOHO - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crucible and a method for manufacturing the same, and more particularly to a crucible for metal melting and a method for manufacturing the same.

Conventionally, as crucibles using refractory materials, alumina crucibles, calcia crucibles, magnesia crucibles, zirconia crucibles, silica crucibles, etc. have been widely put into practical use, and crucibles using silicon titanide or boron titanide and several types of refractory materials mixed together have been widely used. Dripping crucibles have recently been developed. These crucibles were usually made by mixing fine powders of refractory material and caking material and sintering them using powder metallurgy. However, such a crucible has the disadvantage that it is susceptible to heat shock because the entire crucible is homogeneously integrated. That is,
Individual elements such as Al ₂ O ₃ , MgO, and CaO have high refractory properties, but as the crucible becomes larger, cracks occur in the crucible because there is a temperature difference between the inside and outside of the crucible when the temperature rises or falls. For example, as shown in Figure 1, when a Pd metal 2 is placed in a zirconia crucible 1 with a thickness of 10 mm and the temperature is raised, a crack 3 occurs at about 700°C to 1200°C and gradually spreads. This kind of thing was also observed in silicone titanium crucibles and alumina crucibles. For this reason, attempts were made to reduce the temperature change by slowing down the heating rate or surrounding the crucible with heat insulating material, but cracks still occurred when the molten metal 2 was removed from the crucible 1. Therefore, in order to slowly take out the molten metal 2 from the crucible 1, a hole with a diameter of 3 mm was made at the bottom of the crucible 1, but due to the high temperature and the weight of the molten metal being added to the bottom of the crucible 1, a crack appeared from the hole. . Therefore, it could not be used not only for high melting point metals such as Pd and Pt, but also for low melting point metals such as Ag.

The present invention has been made in view of the above-mentioned drawbacks, and it is an object of the present invention to provide a crucible that does not cause cracks and is resistant to heat shock, and a method for manufacturing the same.

The crucible of the present invention is a crucible made of a binder and a refractory material, and is characterized in that the refractory material in the form of grains or short fibers is laminated in layers.

Further, the method for producing a crucible of the present invention is a method for producing a crucible made of a caking material and a refractory material. This method of manufacturing a crucible is characterized by repeating the process of sprinkling with refractory material to stack refractory materials in the form of particles or short fibers in layers.

In the crucible of the present invention, the refractory material in the form of particles or short fibers is laminated in layers to reduce heat shock as much as possible by dispersing the refractory material in the form of relatively large particles or short fibers in the crucible. This is to prevent cracks from occurring due to the formation of layers, and to prevent cracks generated by layering from developing into large cracks. In this way, it is possible to provide a crucible that is resistant to heat shock, can melt high-melting point metals even at high temperatures of 1900°C or higher, and even if cracks occur, they will not propagate to the next layer.

Furthermore, in the crucible manufacturing method of the present invention, the crucible base is immersed in the slurry in order to form a uniform slurry thin layer on the crucible base. Slurry is made by dispersing refractory material of several microns in colloidal form in water, and adding the necessary binder. When a crucible base material such as a wooden mold or plastic coated with rubber is dipped into this slurry and pulled up, a uniform thin layer of slurry is formed. This uniform thin layer of slurry is coated with a layer of refractory material in the form of grains or short fibers. Part of the granular or short fiber refractory material sinks into the thin slurry layer, and a portion of the refractory material absorbs the slurry layer by capillary action, making the thin slurry layer thick and uniform as a whole. Therefore,
By repeating this process, the crucible base bodies are laminated in layers. It is preferable to use the same material as the refractory material in the slurry of the present invention and the refractory material in the form of particles or short fibers in order to avoid heat shock as much as possible. However, different materials can also be used to increase crucible strength at elevated temperatures.

Examples and conventional examples will be described below.

Example 1 As shown in FIG. 2, a plastic crucible base (diameter 30mm, height 50mm) 4 was immersed in a slurry 5 made of alumina, a binder, and water.
A uniform thin film of slurry was applied to the plate. Next, particles of silica refractory agent (approximately 0.1 mm in diameter) are placed on this crucible matrix 4.
6 was sprinkled to form a layer. This process was repeated 8 times to form layers up to a thickness of 3 mm as shown in Figure 4. Thereafter, this base body 4 was dried and calcined (1400° C.) by a conventionally known method to burn and decompose the base body 4 to obtain a laminated crucible 7 as shown in FIG. This is designated as implementation product 1.

Example 2 In the same manner as in Example 1, a rubber-lined wooden crucible base 4' (diameter 70φmm, height
200mm, bottom protrusion diameter 8φmm, height 25mm) was immersed in a slurry consisting of zirconia, a binder, and water, and then sprinkled with zirconia staple fibers (diameter approx. 0.01mm, length approx. 0.5mm). This process was repeated 35 times until the layers were stacked to a thickness of 14 mm. Then this mother body 4'
was decomposed by firing in a gently heated state, and a hole was made in the protrusion to obtain a perforated laminated crucible 7'. This is designated as implementation product 2.

Conventional Example 1 A crucible having the same shape and the same material as in Example 1 was manufactured by high-pressure molding. This is referred to as conventional product 1.

Conventional Example 2 A crucible having the same shape and the same material as Example 2 was kneaded and molded and then fired. This is called conventional product 2.

Example 3 300g of Pd was added to Example 1 and heated to 1600°C (heating rate 60
°C/min) and then cooled in air. After repeating this process 10 times, no cracks appeared in the crucible.

Example 4 Attach a stopper to Example 2 and close the hole.
Pt10Kg was added and the temperature reached 1850℃ (heating rate 62℃) using a light thermometer.
C/min), the stopper was removed, the molten platinum was allowed to flow out of the hole, and when it was cooled, cracks were found on the inner surface of the crucible, but did not propagate to the outside.

Conventional Example 3 When 300g of Pd was added to Conventional Product 1 and heated at a heating rate of 60°C/min, a crackling sound was heard at 1555°C, so the product was cooled. Upon inspection, there was one large crack around the crucible.

Conventional Example 4 A stopper was attached to Conventional Product 2, and 300 kg of Pt was inserted into the hole to cover the hole. When the stopper was removed after heating to 1850°C at a heating rate of 62°C/min, a cracking sound was heard. Upon inspection after cooling, large cracks were found in and around the hole, from which Pt was seeping out.

As is clear from the above explanation, according to the crucible and its manufacturing method of the present invention, since particles of refractory material or short fiber refractories are layered, cracks are less likely to occur in the crucible, and cracks do not occur easily. Even if it does, it does not spread throughout the crucible, so it has a strong effect on heat shock. It is therefore particularly suitable for molten metals. Furthermore, according to the manufacturing method of the present invention, it is possible to stack many layers of refractory particles or short fibers, so that a crucible that is extremely resistant to heat shock can be easily obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional perspective view of a conventional crucible when a crack occurs, and FIGS. 2 to 7 are cross-sectional views showing the manufacturing process of the present invention.
The figure shows the dusting process, FIG. 4 shows the laminating process, FIGS. 5 and 7 show the laminated crucible, and FIG. 6 shows the matrix. 4, 4'...Main body, 5...Slurry, 6...Grains or short fibers of refractory material, 7,7'...Laminated crucible.

Claims (1)

[Claims] 1. In a crucible made of a binder and a refractory material,
A crucible characterized in that granular or short fibrous refractory materials are laminated in layers. 2. In a method for manufacturing a crucible made of a binder and a refractory material, the crucible matrix is immersed in a liquid slurry made of a binder and a refractory material, and then the process of sprinkling the refractory material in the form of grains or short fibers is repeated. A method for producing a crucible, characterized by laminating short fibrous refractory material in layers.