WO2020005178A2

WO2020005178A2 - A production method of clay based ceramic materials opaque glazes and opaque frits using precision casting waste sand

Info

Publication number: WO2020005178A2
Application number: PCT/TR2019/050086
Authority: WO
Inventors: Tuba Bahtli
Original assignee: Tuba Bahtli
Priority date: 2018-06-27
Filing date: 2019-02-11
Publication date: 2020-01-02
Also published as: WO2020005178A3; TR201809079A2

Abstract

The invention relates to a method of manufacturing clay based ceramic materials with wax casting mold sand that is used for casting Cobalt, 4140 steel and stainless steel as precision casting in industry, become solid waste after completing its lifetime as a result of particular use and has no mold feature. The aim of the invention is to regain a waste material whose amount is increasing day by day to a different production sector, ensure economic gain, contribute to nature and also to produce approximately the same or improved physical, chemical, thermal and mechanical properties as existing products produced in the industry by using this waste in productions of clay-based ceramics. Furthermore, the construction of opaque glazes which are the coating material of ceramics, the production of opaque frit which is an important component of opaque glazes will be achieved by using zircon mineral in the waste without adding an external zircon raw material.

Description

A PRODUCTION METHOD OF CLAY BASED CERAMIC MATERIALS OPAQUE GLAZES AND OPAQUE FRITS USING PRECISION CASTING WASTE SAND

TECHNICAL FIELD

PRIOR ART

Its amount is increasing day by day in casting companies after precision casting mold material become waste and end of its usability as wax casting sand. It is seen that there has been no scientific and technological study in order to investigate the usability of the precision cast sand material which is transformed into waste, yet. In addition, recycling and regaining of waste could be used as inputs in different sectors is important for both in terms of environment and economy of our country.

BRIEF DESCRIPTION OF THE INVENTION

With this patent subject to our invention, either waste material will be recovered or economic gain will be obtained. It is considered to be a study to be applied to industrial application of original scientific studies which may contribute to international science.

As a result of chemical analysis and phase analysis of this waste cast sand that were done at Dumlupinar University ILTEM, in addition to Silica and Alumina, zircon was also found.

Table 1. XRF analysis of casting sand waste (Wax casting mold waste)

Zircon dissolves at high temperatures to form S1O2 and Zr02 and Zr02 increases toughness.

By using at least 1 % of this waste instead of at least clay and kaolin that are used in the production of clay based ceramic products, the amount of raw materials will be reduced and the production cost will be reduced since some of the silica (S1O2) and alumina (AI2O3) ratios will be obtained from this waste.

And also; by using zircon in the waste without the use of extra zircon raw material, the higher physical, chemical, mechanical and thermal properties and thus longer service life of clay based ceramic materials will be produced. In addition, precision casting sand waste material will be used in the production of the opaque type of glaze belong to glaze layer which is the coating material of the ceramic structures, in the production of opaque frit used for glazes under 1200 °C. Zircon mineral in the waste is an important component used in the productions of opaque glaze and opaque frit. The glass-shaped product, which is produced by melting of milled and powdered ceramic raw materials after that are weighed according to a recipe and mixed, and by the rapid cooling of the melt is called frit.

Opaque glaze will be made by adding this waste to the glaze and frit recipe at least by 1 %, and by using zircon raw material in the waste will be added without using zircon raw material. The S1O2 in the waste is glass-forming oxide, while AI2O3 will provide scratch resistance. LIST OF FIGURES

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

Figure 2. Production Methods and Research Techniques of Clay Based Ceramics

DETAILED DESCRIPTION OF THE INVENTION

The ceramic can be defined as the products obtained by utilizing the heat energy of the appropriate mixtures of the elements in the form of compounds in nature. Another general definition is that inorganic compounds made of metal or semi-metals with non- metallic elements are called ceramics. Clays are fine-grained sediments less than 0.02 millimeters in size; earthy, minerals with high alumina and silica content, whose plasticity are increased by adding certain amount of water.

Clays are generally formed under certain conditions by the decomposition of feldspar or by the dissolution, changing of volcanic rocks. Along with aluminum silicates in clay which has never been found in pure form; minerals such as iron, magnesium, potash, calcium, sodium and quartz form "non-clay material", ie impurities. Many clay minerals can also contain organic materials and water-soluble salts.

Clay (kaolin: AI2O3.2SiO2.2H2O) is always moist since it has a moisture absorption property; hardens if the moisture in the structure is removed. Using this feature, clay is used as building material. The iron oxide in the clay gives a red color to the fired material. Lime, magnesium, iron oxide and alkali oxides act as fluxes that reduce the fusion point of clay. Silica increases the porosity and refractory nature, but also reduces shrinkage.

Silicate based (clay based) ceramics: They are ceramics with S1O2 in their structure and they are cheaper. Most of the traditional ceramics are in this group; building materials (Brick, Tile, Cement), wall and floor covering panels (Tile), vitrified ceramics (sanitary ware, porcelain), pottery etc.

Generally, floor and wall coverings are obtained by methods such as grinding, sieving, mixing and drying methods of mixtures of inorganic raw materials such as clay, feldspar, quartz used; being pressed and shaped into thin plates, glazing one side at high temperatures.

Vitrified ceramics are generally made of a mixture of clay minerals (plastic materials) produced in alumina-rich form, quartz and feldspar. Feldspars are natural fluidizing agents and increase the amount of viscous liquid phase that plays a role in joining ceramic structures. Vitrified ceramic products are widely used as tableware and sanitary ware due to their low water absorption and good mechanical resistances. The technological properties of these products are affected by the chemical, mineralogical composition and sintering states (heating temperature, waiting time, atmosphere and heating rate) of the raw materials.

Porcelain is divided into hard and soft porcelain according to the ratio of the raw materials and temperature. The most important characteristic of hard porcelain is the high ratio of kaolin and feldspar glaze which is formed at a high temperature such as 1400 °C. This creates surface hardness and durability at glaze. The kaolin ratio of the soft porcelain is low and the glaze formation temperature is lower. Therefore, it has less mechanical hardness and impact resistance than hard porcelain.

Cement is an inorganic binder. Inorganic binders are materials used to make solid particles defined as sand, gravel and aggregate in the building industry as stable solid products that maintain a tight and long-lasting structure. The natural starting materials used for the production of cement are CaO, S1O2, AI2O3 and Fe203 minerals which contain the main components of the cement. It is a simple mixture obtained by firing gypsum and clay at high temperatures such as 1350- 1450 °C (1400-1600 °C in some references).

Brick and tile is the result of the process of making the clay and fine shaft used as raw material in the quarries and making them ready for use in the factory. At the end of this process, the materials used in the construction industry and whose properties were given below are produced. Land suitable for brick-tile production can be called sandy clay. These soils are also known as clay, barren, miles, silt, loam and slime. These lands contain minerals such as quartz, montmorillonite, kaolinite, calcite, limonite, hydromica, sericite, illite and chlorite. Some of the soil is made up of amorphous clays. Limestone parts, gypsum, organic matter and coarse rock residues are the elements that disrupt the quality. Brick has gained importance as a substitute material in aluvial plains without building blocks in the prehistoric times such as Mesopotamia and Nile Valley. Soil suitable for brick making may not be suitable for tile production. In this case, sandy soils may be necessary to mix with more plastic fine grain clays. In some cases, it may be necessary to mix the highly oily soils that are sensitive to drying with less plastic soil. The fact that the soil can be used as both brick and tile soil and also does not require any other process is one of the features that are required in it.

Zircon is a chemical compound having the chemical formula Zr02.Si02 and having the theoretical (by weight) of 67.23% Zr02 and 32.77% S1O2. It has tetrahedral crystal structure and a= 6.60 A°, c = 5.88 A° unit cell parameters. Its average density is 4.6 g/cm³ 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.

A similar occurrence of martensitic transformation occurs in zirconia also. When monoclinic zirconia crystals are heated to the conversion temperature, tetragonal phase domains begin to form in the monoclinic matrix. During the conversion a significant amount of stress energy is generated. Because the domain boundaries are adherent to each other and there is a significant volume difference between these two phases. The transformation of the monoclinic zirconia proceeds with small movements (less than the interatomic distance) of the oxygen atom in the (100) plane. The tetragonal phase above the critical crystal size of about 300 A° is unstable. If the monoclinic and tetragonal phases are present at a critical crystal size of 300 A°, their free energies must also be equal.

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. Precision Casting (Wax Molding): 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.

Description of Production Method

Clay based ceramics are building materials (Brick, Tile, Cement), wall and floor covering panels (Tile, porcelain tile), vitrified ceramics (sanitary ware, porcelain), pottery etc. The production process of each ceramic material is different. However, the most common characteristics are that they contain at least one of clay and kaolin (AI2O3.2SiO2.2H2O) raw materials. Opaque glaze and opaque frit is the covering layer for the purpose of providing hygiene in ceramic structures. The main oxide for this layer production is S1O2 and opaque glaze and opaque frit can be produced with either clay or without clay.

In the method according to our invention, for the transformation of clay based ceramic product to clay-based opaque glaze and opaque frit due to the presence of S1O2 and AI2O3 in the content of precision casting waste sand; By using precision casting sand at least 1 % kaolin instead of at least one of the clay or kaolin, production will be realized in the same production process in the sector with existing infrastructures for each products. When it is desired to produce a clay-free production, instead of clay, similarly in the production of opaque glaze and frit, a part of the S1O2 source will be provided from waste sand by using at least 1 % of the precision casting sand waste into the glaze and frit recipes, opaque glaze and opaque frit will be produced with AI2O3, which is more scratch resistant and also provides opacification with Zircon content.

Although the shaping and heat treatment processes vary, the overall production method for all products will be defined by weighing, mixing and grinding raw materials together with waste precision casting sand, shaped or formless production, and finally drying and heat treatment processes.

For example, the waste sand for the production of coating materials (such as tile, porcelain tiles), which are clay-based ceramics, if necessary, some of the raw materials of clay, kaolin and feldspar will be wet milled together with the defloculant and then will be granulated by the spray-dryer, shaped by pressing.

The wall tiles will be fired in a temperature range of at least 1100 °C and the floor tiles will be cooked in 30-45 minutes at higher temperatures such as at least 1150 °C. Porcelain tiles will have less than 0.5% water absorption and will be produced at higher temperatures (minimum 1200 °C) and longer periods (50-60 minutes) due to their high vitrified structure. Floor and wall tiles will be mixed for at least 15 minutes and porcelain tile will be mixed for at least 30 minutes.

In vitrified products (sanitary ware, porcelain), which are clay based ceramics, water slurry will be made with waste sand, clay, kaolin, feldspar, Na-silicate defloculant and will be plaster casting will be made or forming will be done by pressure casting for porcelain. For the production of sanitary ware and porcelain; the raw materials will be milled for at least 1 hour and then poured into the plaster mold. The heat treatment will be at most 1300 °C for sanitary ware. The production temperature for porcelain will be at least 1300 °C.

Similarly, in the production of building materials such as bricks and tiles, which are clay based ceramics, the waste material and/or clay mixture will be shaped by plastic forming method such as press or extrusion.

The cement material will be produced without forming. Clay, limestone and iron ore materials will be ground into a fine powder.

In the production of opaque frit, the materials which are melted at a temperature of at least 500 °C will be shocked in water and an amorphous structure will be obtained.

In the production of opaque glaze, while the precision casting sand mixed at least 1 % instead of clay used in recipe and/or without clay content glaze recipe will be wet milled at least 30 minutes, it will be applied by dipping, spraying, pouring methods on ceramic structures. When it will be dry milled, it will be applied by electrostatic method.

Claims

1 . A method of production of clay based ceramic materials, opaque glazes and opaque frits using precision casting waste sand, characterized in that comprising the steps below;

- to be used instead of at least one of clay or kaolin and to provide a part of the S1O2 source, to provide more scratch resistant with AI2O3 and opacification with the Zircon content, and the addition of at least 1 % precision casting waste sand to improve mechanical, chemical, physical and thermal properties,

- Converting into granule by spray dryer and forming by pressing

- Casting with plaster mold as sluryy

- Extrusion forming,

- Production without shaping after heat treatment,

- Firing at least 1 100 °C for 30-60 minutes,

- It is characterized by mixing stages for at least 15 min.