KR100257959B1 - A mold for precision casting having advanced destructiveness - Google Patents

Abstract

PURPOSE: A precision casting mold having superior collapsibility is provided to reduce manpower and time required in the shake-out process of a mold thereby to obtain effects such as cost reduction of precision casting articles by adding fused silica to constituents consisting back-up slurry. CONSTITUTION: In a precision casting mold manufactured by the manufacturing method comprising the processes of manufacturing a model of a product which is to be manufactured using wax or plastics; coating once or twice the surface of the wax or plastics using sand and a slurry consisting of colloidal silica and zirconium powder; coating a back-up slurry consisting of colloidal silica and alumina silicate together with powder phase sand 3 to 10 times on the once or twice coated surface of the wax or plastics; and dewaxing and firing the back-up slurry coated surface, thereby removing the wax or the plastics, the precision casting mold having superior collapsibility is characterized in that the alumina silica in the back-up slurry is replaced with fused silica having a particle size equivalent to a sieve size of 100 mesh or more.

Description

Precision casting mold with excellent collapsible

The present invention relates to a ceramic mold required during the process of making a precision casting by the lost wax method (or an investment method), which is one of the precision casting methods. More specifically, Fused Silica is added to one of the layers of the mold. By improving the disintegration of the mold.

Looking at the general process of the lost wax method, which is a precision casting method, first, a model of a product to be manufactured using wax or plastic is formed, and the models are clustered so that the molten metal can be injected into the product through a tap and a ball. Assemble in clusters or trees.

Thereafter, the slurry in the slurry state and the powdered sand are repeatedly coated on the wax surface of the wax state in seven to ten times according to the shape and size of the final metal product. In the coating process, the refractory sand is applied to the surface of the cluster before the refractory is dried, and then the refractory sand is dried and then dried.

After the firing process, the wax or plastic inside is removed, the metal in the molten state is injected, solidified and cooled, and the outer mold is removed to leave only the metal in the cluster state, and then the metal is cut and polished. How to produce a product.

Here, the slurry used as a material in the mold manufacturing process through the coating process is used by mixing a fine powder with a colloidal silica (Colloidal Silica) or ethyl silicate (Ethyle Silicate) as a binder, Depending on the characteristics, there is a difference in the degree of fire resistance and disintegration of the mold, and the breathability of the mold depends on the Stucco material in which sand is usually used.

In addition, the colloidal silica as described above is a liquid in which colloidal silica particles of negatively charged Si—O—Si structure are dispersed and suspended in water, and the silica particles are usually 6 × 10 ^−3. Ultra-fine particles of 탆 to 100 × 10 ⁻³ 탆.

Meanwhile, as the primary slurry commonly used in the precision casting method, colloidal silica, zircon powder, an antifoaming agent, a surfactant, and the like are mixed and used, and their properties and components are shown in Table 1 below.

Table 1.

Colloidal silica SiO content 30 wt% Particle size 8 × 10 ^-3 μm to 13 × 10 ^-3 μm pH (room temperature) 10.5 Zircon powder Particle size 200-325 mesh Chemical composition ZrSiO ₄ 97.7% min. free SiO ₂ 0.2% max. TiO ₂ 035% max. Fe ₂ O ₃ 0.05% max. Al ₃ O ₃ 2.0% max. Viscosity of blended slurry 38 to 47 seconds with Zahn Cup # 4

In addition, as the sand used for the primary coating, zircon sand having a particle size of 80 to 120 mesh and having the same chemical composition as that of the zircon powder used in the primary slurry is used.

As the secondary slurry, colloidal silica, zircon powder, antifoaming agent, surfactant, and the like are mixed and used, and their properties and components are shown in Table 2 below.

Table 2.

Colloidal silica SiO content 30 wt% Particle size 8 × 10 ^-3 μm to 13 × 10 ^-3 μm pH (room temperature) 10.5 Zircon powder Particle size 100 to 200 mesh Chemical composition ZrSiO ₄ 97.7% min. free SiO ₂ 0.2% max. TiO ₂ 035% max. Fe ₂ O ₃ 0.05% max. Al ₃ O ₃ 2.0% max. Viscosity of blended slurry 18 to 27 seconds with Zahn Cup # 4

As the sand used for the secondary coating, zircon sand having the same chemical composition as the zircon powder used in the primary slurry but having a particle size of 0.25 to 0.5 mm is used.

Back-Up slurry is a slurry that is commonly used from the third coating to the final coating, and is prepared by mixing colloidal silica, alumina silicate, and an antifoaming agent. Is shown in Table 3 below.

Table 3.

Colloidal silica SiO content 30 wt% Particle size 8 × 10 ^-3 μm to 13 × 10 ^-3 μm pH (room temperature) 10.5 Alumina Silicate Powder Particle size 100 to 200 mesh Chemical composition Al ₃ O ₃ 50.0% SiO ₂ 45.9% TiO ₂ 2.61% Fe ₂ O ₃ 1.33% CaO 0.06% MgO 0.04% Na ₂ O 0.03% K ₂ O 0.03% Viscosity of blended slurry 10 to 17 seconds with Zahn Cup # 4

The sand used for the backup coating differs only in the particle size of the sand according to the number of coating layers, and the chemical composition generally uses the same alumina silicate sand as the alumina silicate powder used in the backup slurry.

Depending on the shape and size of the product, the back-up coating is repeatedly applied in the 7th to 10th order, and then only the backup slurry is applied to dry to prevent the sand particles from falling off from the surface. Coating).

On the other hand, after the coating of each layer in a constant temperature and humidity room maintained at a temperature of 23 ± 1 ℃, relative humidity 50 ~ 60% for 5 hours or more, the next order of coating must be carried out, which is the drying of the coating layer This is because it can be prevented from cracking the mold only if it is made sufficiently.

After the coating up to the desired number of layers by the above process and after the Manurie coating, it is dried in the drying chamber under the above conditions for 12 hours or more.

However, since the sintering of the mold prepared by the above process is performed when zircon or alumina silicate is injected when the molten metal of about 1400-1600 ° C. is injected, a lot of time, manpower, and equipment are put into the demolition of the mold after solidification of the molten metal. have.

In order to solve the problems described above, the present invention adds molten silica to the components of the backing slurry so as to reduce the manpower and time required for the process of removing the mold, thereby reducing the cost of precision casting. It is an object of the present invention to provide an excellent precision casting mold.

In order to achieve the above object, the present invention is to make a model of the product to be produced using wax or plastic, etc., using the slurry and sand consisting of colloidal silica and zircon powder on the surface of the wax or plastic 1, 2 In the mold for precision casting, after the primary coating, the back-up slurry composed of colloidal silica and alumina silicate is coated with powdered sand three to ten times, and then dewaxed and calcined to remove wax or plastic. In addition, the present invention provides an accurate casting mold for the collapse, characterized in that the alumina silicate in the back-up slurry is used by replacing the molten silica having a particle size of 100mesh or more.

The reason for limiting the particle size of the molten silica to 100 mesh or more is that the bonding strength with colloidal silica acting as a binder is less than 100 mesh.

Hereinafter, an Example is given and this invention is demonstrated in detail.

<Example>

In the present invention, in the coating of the surface of wax or plastic, the refractory, sand and mixing conditions of the slurry required for the primary and secondary coating processes are the same as in the conventional method, but the components of the backing slurry to be coated thereafter are The molten silica powder was used instead of the alumina silicate used conventionally, and the sand added together was the same as the conventional one.

Table 4 shows the composition of the backup slurry used in the present invention.

Table 4.

Colloidal silica SiO content 30 wt% Particle size 8 × 10 ^-3 μm to 13 × 10 ^-3 μm pH (room temperature) 10.5 Fused Silica Powder Particle size 100 mesh or more Chemical composition SiO ₂ 99.8% Al ₃ O ₃ 0.1% max. TiO ₂ 0.025% max. Fe ₂ O ₃ 0.035% max. CaO 0.010% max. MgO 0.010% max. Na ₂ O 0.005% max. K ₂ O 0.010% max. Viscosity of blended slurry 17 to 20 seconds with Zahn Cup # 5

In the present invention, in order to determine the collapsibility of the mold thus prepared, the present invention manufactured the collapsible test specimen under the mold manufacturing conditions, and then measured the change in strength when the same thermal history as the casting condition was applied to the test specimen and when it was not applied. It was.

In addition, the specimens were prepared using the standard mold manufacturing method, and the specimens were also compared for the specimens with the same thermal history as the casting conditions.

Table 5 and Table 6 show the results of the collapsible test of the mold production material and the mold produced by the conventional method and the present invention.

Table 5. Conventional Method

Number of coating layers Types and particle sizes of refractory materials Type of sand material and particle size Primary Zorcon (325 mesh) Zorcon (120 mesh) Secondary Zorcon (200 mesh) Zorcon (0.25 mm) Tea Alumina Silicate (200 mesh) Alumina Silicate (0.5 mm) 4th Alumina Silicate (200 mesh) Alumina Silicate (0.5 mm) 5th Alumina Silicate (200 mesh) Alumina Silicate (1.0 mm) 6th Alumina Silicate (200 mesh) Alumina Silicate (1.0 mm) 7 tea Alumina Silicate (200 mesh) Alumina Silicate (1.0 mm) Finish coating Alumina Silicate (200 mesh) - Strength 0.6 kg / mm ² Plastic strength after firing at 1400 ℃ for 30 minutes 1.2 kg / mm ²

Table 6. The present invention

Number of coating layers Types and particle sizes of refractory materials Type of sand material and particle size Primary Zorcon (325 mesh) Zorcon (120 mesh) Secondary Zorcon (200 mesh) Zorcon (0.25 mm) Tea Fused Silica (-100 mesh) Alumina Silicate (0.5 mm) 4th Fused Silica (-100 mesh) Alumina Silicate (0.5 mm) 5th Fused Silica (-100 mesh) Alumina Silicate (1.0 mm) 6th Fused Silica (-100 mesh) Alumina Silicate (1.0 mm) 7 tea Fused Silica (-100 mesh) Alumina Silicate (1.0 mm) Finish coating Fused Silica (-100 mesh) - Strength 0.4 kg / mm ² Plastic strength after firing at 1400 ℃ for 30 minutes 0.3 kg / mm ²

In the case of the cast material specimen prepared by the conventional method as shown in the above table, the strength after firing at 1400 ° C. for 30 minutes increased about twice as much as the strength of the non-calcined mold, which made it difficult to remove the mold.

However, in the case of the mold specimen according to the present invention, the strength after the firing at 1400 ° C. for 30 minutes shows a phenomenon that the strength of the mold is lowered than that of the non-calcined mold.

By applying molten silica instead of the refractory material added to the backup slurry by the present invention as described above, the mold strength after molten metal injection is lowered, thereby reducing the manpower and time required in the desalting process after precision casting, thereby reducing the cost of the product. Can be written.

Claims (1)

A model of the product to be manufactured using wax or plastic is made, and the surface of the wax or plastic is subjected to primary and secondary coatings using slurry and sand made of colloidal silica and zircon powder, and then colloidal silica and In the mold for precision casting, the back-up slurry made of alumina silicate is coated with powdered sand three to ten times, and then dewaxed and fired to remove wax or plastic. Mold for excellent casting, characterized in that the alumina silicate in the back-up slurry is replaced by molten silica having a particle size of 100 mesh or more.