TECHNICAL FIELD

The invention relates to a method of making the wax casting mold sand, which is used as a precision casting in the industry, completes its life and becomes a solid waste and has no mold properties, available in the production of opaque glaze, a kind of ceramic coating material, and opaque frit production that is used in the production of this glaze.

PRIOR ART

It is seen that there is no studies have been carried out scientifically and technologically about the transformation of the precision casting mold material into waste, and the availability of the precision cast sand material which has been turned into waste, yet.

BRIEF DESCRIPTION OF THE INVENTION

The invention is about to research the use of wax casting mold sand, which is used as a precision casting in the industry, completes its life after a certain use and becomes a solid waste and has no mold properties, in the production of opaque frit, which is a kind of ceramic coating material, and in the production of opaque frit production that is used in the production of this glaze; to regain a waste material whose amount is increasing day by day to a different production sector, ensure economic gain, contribute to natiire and and also to reduce the cost of raw materials by supplying zircon material, which is a major component for opaque glaze material, from waste material.

LIST OF FIGURES

Figure 1. XRD analysis result of casting sand waste (Wax casting mold waste)

Figure 2a. Schematic representation of zirconia cubic polymorph

Figure 2b. Schematic representation of the zirconia tetragonal polymorph Figure 2c. Schematic representation of monoclinic polymorph of zirconia Figure 3. Opaque frit production techniques

Figure 4. Opaque glaze production and application techniques

DETAILED DESCRIPTION OF THE INVENTION

With the invention of our patent application, the precision casting sand material, which is converted into waste, can be used for making opaque glaze and opaque frit so that both the waste material will be recovered and the economic gain will be obtained.

When the results of chemical analysis and phase analysis (made at Dumlupinar University ILTEM) of the waste casting sand to be used in our invention were examined, it was found that 5.43% zircon mineral was found in the waste (Table 1 ).

Tablel. XRF analysis of casting sand waste (Wax casting mold waste)

Since the zircon material is difficult to melt and has a high tendency to crystallize, it is an important material for the opaque glaze layer used as a coating material in ceramic materials. The presence of Zircon (ZrSi04) in the waste sand to be used in our invention makes possible the method subject to our invention.

Mixtures that are obtained from ground ceramic raw materials of suitable composition, can form a structure similar to a glass structure as a result of firing on a ceramic body and this layer is called as glaze. Oxides with a high melting temperature increase the opacity of the glaze and make it opaque, because they are placed as crystals in the glaze composition. It is a kind of glaze which is used in cases where ceramic structure is to be completely covered. Zircon material, which melts during firing and crystallizes during cooling, is an important opacifying material. Significantly frit is used in the glazes of ceramic products that are fired under temperatures as low as 1200 °C. Frit is a glass structure intermediate product which is formed as a result of melting of ground and powdered ceramic raw materials after weighing according to a recipe and mixing, then rapidly cooling of the melt. Glazes could be obtained with or without frit.

Zircon is a chemical compound having the chemical formula Zr02.Si02 and having the theoretical (by weight) of 67.23% Zr02 and 32.77% Si02. It has tetrahedral crystal structure and a= 6.60 A°, c = 5.88 A° unit cell parameters. Its average density is 4.6 g/cm ³ Zirconium or zirconium silicate mineral, which is shown as ZrSi04 or Zr02.Si02, has been used for many years as refractory and as an opacifier in the traditional ceramics industry due to its high purity and high quality, chemical and physical properties and technological developments resulting from researches. It is the main source of Zr02 used in the production of zirconate products.

Zirconia is a refractory material with high temperature resistance and excellent insulation. Especially it has high corrosion resistance to basic slag in continuous casting. Sintered zirconia has high stability against temperature and chemical effects. Ladles and firing boats made of sintered compact Zr02 and can be used up to 2500 °C. Depending on the type of stabilizing component, the melting temperature of the stabilized Zr02 is lower than pure Zr02. There are 3 known polymorphs of zirconia (Figure 2).

The conversion of zirconia from tetragonal to monoclinic is a common phenomenon in which the strength and toughness of ceramic materials is increased. Although zirconia toughening was applied to many ceramics, the most studied system is zirconia toughened alumina. The addition of sintered alumina zirconia as the second component causes the final particle size of the alumina to be small. In addition, the second phase in the grain boundaries prevents simultaneous grain growth during high temperature plastic deformation.

Casting is the process by filling the liquid metal into the molds with cavity having the shape of the part to be produced. The dimensions of the mold cavity are made slightly larger than the part to be obtained. Thus, the size reduction resulting from cooling will be balanced. Metal casting is very important for many modern machine parts and elements. For example, more than 50% of the weight of a tractor is cast. This exceeds 90% for the automobile engine. The turbine and jet engine propeller are cast parts that require high precision. On average, one tenth of the iron and steel produced in the last 20 years was used as casting. 75% of all metal casting is gray (Camel Graphite) cast iron. Steel, malleable iron, copper alloys, Al, Zn alloys, Mg-Ni-based alloys, Pb and Ti cast follow it. According to the historical information available, copper alloys have been poured for at least 6000 years and gray iron has been poured for 4000 years. Aluminum has been casted since 1900, nickel-based alloys are casted since 1940 and titanium have been casted since 1950.

The precision casting technology is the process of transferring molten metal to the ceramic mold cavity which is emptied by firing the ceramic and melting of the wax inside the ceramic after the around of melting wax parts at the appropriate temperature are covered with ceramic. The other name is "Wax Molding". First, the model made of wax or plastic is covered with room temperature curing refractory mud. When heated, the wax melts away. Wax and plastic-like models are used in this method where the number of model is required as much as produced parts. Models are produced by injection of wax or plastic into a metal mold and a large number of models are connected to a common path and arranged as bunch. Even models of the most complex parts can be produced very quickly by using these methods. Generally, mixed-shaped parts which are difficult to manufacture in machines are produced by this method. After casting almost it can be used without additional processing. It provides high dimensional accuracy and smoother surface according to other casting methods. METHOD

The sample opaque frit recipe to be used in the processes is given below.

A part of the Zircon input seen in the sample opaque frit recipe is provided at least 1 % by using the above-mentioned precision casting sand waste. Aluminum oxide, dolomite, marble, quartz, zircon (at least 1 % will be obtained from precision casting sand waste) that are used for producing of opaque frit will be ground. It is homogenously blended in a suitable mixer. The raw material mixture is filled into the furnace. At least one of the box, rotary, continuous oven is used as furnace. The melted mixture is cooled rapidly in water or with water-cooled rolls.

The sample opaque glaze recipe to be used in the processes is given below.

A part of the Zircon input seen in the sample opaque glaze recipe, at least 1 %, above, is provided by the use of the precision cast sand waste that is mentioned above in the our invention. Thus zircon raw material cost is reduced in production.

Glaze preparation begins with the weighing of contents such as: kaolin (AI2O3.2SiO2.2H2O), zircon (ZrSi04) and frit for opaque glaze with frit; kaolin (AI2O3.2SiO2.2H2O), zircon (ZrSi04), dolomite (CaMg(C03)2), marble (CaCOs), Na- feldspar (Na20.Al203.6Si02) and K-feldspar (K2O.AI2O3.6S1O2) quartz (S1O2), Zinc Oxide (ZnO), Boric acid (H3BO3), Alumina (AI2O3) components for frit-free opaque glaze. The weighed raw materials are ground with precision casting sand waste at least 1 % with water and auxiliary additives are milled in ball mill. Fritted or non- fritted glazes could be prepared depending on the firing temperature. The sieve residue, liter weight, viscosity and thixotropy values of the prepared opaque glaze suspension are measured. If it is in accordance with the standard values, it is applied by dipping, spraying and pouring on the ceramic body. An opaque glaze layer that is transformed to a glassy layer by heat treatment (sintering) and completely covers the ceramic body is obtained.