Highly Concentrated Ceramic Binding Suspensions Research Articles

Engineering, Manufacturing, and Servicing of Shaped and Unshaped Refractories Based on Highly Concentrated Ceramic Binding Suspensions

An analysis is made of the many years of experience in designing and improving industrial technologies which use quartz-glass HCBSs (highly concentrated ceramic binding suspensions) and high-alumina composite HCBSs to make shaped and unshaped refractories that are effective products for customers and sources of profit for manufacturers. Long before the current boom in nanomaterials, HCBS-based technologies employed elements that are part of nanotechnologies now in widespread use and are responsible for the high technical-economic efficiency of these materials. The volume of commercial production (CP) of the refractories at the OAO “Dinur” jumped 55% from 2013 to 2014. CP volume in the first quarter of 2015 increased by factors of 2.7 and 2.0 compared to the same periods in 2013 and 2014. Over three decades of use of the above technologies, Dinur has produced roughly 180,000 tons of highly profitable refractories that in current prices are worth about 12 billion rubles.

Pressure-molded high-alumina ceramic castables. 3. Effect of processing additives on pressure-induced compaction and properties of bauxite-quartz glass matrix systems

The effect of lignosulfonate (LST) and surface-active substances (SAS) on compaction and properties of bauxite-quartz glass matrix systems is studied. LST added at an optimum concentration to bauxite-based highly concentrated ceramic binding suspensions (HCBS) causes a 2–3% decrease in preform porosity. In materials sintered at high temperature the effect of decreased porosity is more pronounced. In preforms molded at 500–700 MPa no defect due to overpress is observed. The SAS, judged from their efficiency for decreasing porosity, are arranged in ascending order: sodium silicate water glass, sodium tripolyphosphate, complex organomineral thinner, and FS-20 castament.

Press-Molding of High-Alumina Ceramic Castables. 1. Compaction and Properties of Matrix Systems Based on Mixed HCBS of Composition: Bauxite, Quartz Glass, and Commercial Alumina

Preparation of powders based on bauxite HCBS (Highly Concentrated Ceramic Binding Suspensions) containing high-disperse quartz glass and plasticized with refractory clay is described. The powders, molded at moderate pressure (50 – 100 MPa), give a high-density material with an initial porosity of 20 – 25%. Mixes containing 10 to 43% commercial alumina are tested. The materials can be used as matrices for press-molded high-alumina ceramic castables which, when sintered, show a high mechanical strength and volume constancy.

Structure-Mechanical Properties of Plasticized Mixes Based on Highly Concentrated Ceramic Binding Suspensions (HCBS) of High-Alumina Chamotte

Plastic mixes based on high-alumina chamotte HCBS and a multifractional refractory filler are prepared; the mixes molded at low pressures (30 MPa) make it possible to obtain materials with an initial porosity of 14 – 15%. This effect is attained by adding a composite plasticizer (a refractory clay and a complex organomineral thinner) to the mix.

Thinning and Plasticization of HCBS (Highly Concentrated Ceramic Binding Suspension) Based on High-Alumina Chamotte

HCBS (highly concentrated ceramic binding suspensions) based on a high-alumina chamotte (75.5% Al2O3) with a volume concentration CV = 0.73 is prepared by the wet grinding technique. The effect of a complex organomineral thinner on the rheological properties of HCBS (with and without refractory clay added) has been studied. Adding a 0.02% thinning agent composed of 75% sodium tripolyphosphate and 25% SB-5-grade superplasticizer results in a substantial decrease in viscosity of the systems studied.

A Technology for Preparing Sintered Ceramics Based on Bauxite HCBS

A technology for preparing high-density (with zero open porosity) ceramics molded by casting from bauxite highly concentrated ceramic binding suspensions (HCBS) has been developed (90% Al2O3). The precursor HCBS feature a high dispersity (percentage of particles < 2 μm across in excess of 40%; median particle diameter, < 5 μm; dmax = 10 – 20 μm), a high solid-phase concentration (CV ≥ 0.65), and a high fluidity. A material with zero open porosity is obtained by sintering at 1400 – 1450°C and its potential use for making grinding bodies is considered.

Effect of Thinning Agents on Properties of High-Alumina Ceramic Castables

The effect of thinning agents on molding mixtures for the production of high-alumina ceramic castables composed of bauxite HCBS (highly concentrated ceramic binding suspensions) and a refractory filler based on fused corundum and SiC is studied. The thinners used were sodium tripolyphosphate (STPP), SB-5-grade organic plasticizer, mixtures thereof, and liquid glass. The maximum thinning effect is observed for complex organomineral additives (10 – 33% SB-5 + 67 – 90% STPP). The optimum thinner concentration is 0.08 – 0.1 wt.%. The use of thinners makes it possible to reduce significantly the water demand of concrete mixes and leads to a decrease in porosity and an increase in strength of ceramic castables. The composition and concentration of alkali-containing thinners produce little (if any) effect on the deformation behavior of ceramic castables at high temperatures.

HIGHLY CONCENTRATED CERAMIC BINDING SUSPENSIONS (HCBS) AND CERAMIC CASTABLES. STAGES IN RESEARCH AND DEVELOPMENT

Precisely 25 years ago, in the journal Ogneupory (February, 1978), our paper “Fundamentals of ceramic castable technology” was published [1]. Earlier, the principles outlined in that paper were reported and discussed at All-Union conferences held in 1976 in Sverdlovsk and Leningrad. Dating back to 1968, the first data on highly concentrated binding suspensions based on quartz glass were reported in [2, 3]. The technology of ceramic castables is precisely based on the use of ceramic binding suspensions. In 1969 [4], a method for preparation of refractory castables of granular structure using ceramic binding suspensions was reported. A survey of world trends in the development, production, and application of new refractory materials [5 – 8] shows that, viewed in this light, the papers [1 – 4] were pioneering in the field. In particular, these papers provided data, previously unreported, on the preparation of ultra-low-cement and zero-cement refractory castables, that is, refractory materials that at present have a potential for wide applications [6, 7]. In this paper, we discuss, in a historical aspect, priorities and achievements in the field of materials based on highly concentrated ceramic binding suspensions (HCBS).

Refractory Plastic Masses Based on Highly Concentrated Ceramic Binding Suspensions (HCBS). III. Structural-Mechanical Properties of Plasticized Masses Based on Bauxite HCBS and Characterization of Materials Derived from Them

Rheological properties of bauxite HCBS plasticized with refractory clay are studied in the yield state and the solid state. Specimens are prepared from the plasticized suspension with an optimum clay addition (5%), with a open porosity of 24.5% and a bending strength of 65 MPa (after heat treatment at 1300°C). A relation is revealed between the rheological properties and physicomechanical characteristics of plastic masses. The plastic masses studied can be used as matrices for fabrication of unmolded refractory materials.

Refractory Plastic Masses Based on Highly Concentrated Ceramic Binding Suspensions (HCBS). II. Structural and Mechanical Properties of Plasticized HCBS in the System SiO2 – Clay

Rheological properties of individual suspensions of quartz sand, quartz glass, and Nizhne-Uvel'skoe (NU) clay and compound suspensions of these components containing 20 – 80% NU clay are studied. The effect of NU content on rheological properties of the compound suspensions is considered. Structural and mechanical properties of plastic masses (with a moisture content of 10 – 20%) based on compound suspensions using a Tolstoi plastometer are studied. The data obtained are used to determine the main elastoplastoviscous and structural-mechanical properties of the plastic masses. The effect of the added HCBS on the rheological characteristics is considered.

Refractory plastic mixtures based on highly concentrated ceramic binding suspensions (HCBS). 1. Structural and mechanical properties of suspensions (Pastes) of refractory clays

In contrast to the known refractory plastic mixtures that possess certain drawbacks the authors pose the problem of preparing similar mixtures with HCBS under the assumption that by using HCBS of an acid or acid-amphoteric composition plasticized by a refractory clay it is possible to improve the characteristics of this group of unshaped refractories (to reduce the shrinkage due to drying and heat treatment and the porosity and increase the strength). The properties of mixtures based on Nizhne-Uvelskoe clay as a plasticizer of plastic refractory mixtures arc described.

Materials based on highly concentrated ceramic binding suspensions (HCBS). Corundum and corundum-mullite ceramic castables based on plasticized hcbs of bauxite

HCBS of roasted Chinese bauxite, plasticized with additives of refractory clay, and corundum or bauxite filler are used for the production of pressed ceramic castables of corundum and mullite-corundum compositions with 93–95% and 80–85% A12,O3, respectively. The optimum clay additive does not exceed 1–2%. The ceramic castables have a porosity of 15–18% and an ultimate compressive strength of 100–200 MPa after treatment at 1200–1300°C. As compared to traditional corundum refractories they are characterized by a finer capillary structure and a higher mechanical strength attained at a diminished (by a factor of 2–3) pressing pressure and a lower (by 400- 500°C) firing temperature.

Materials based on highly concentrated ceramic binding suspensions (HCBS). Molding processes and strength of silica mixtures based on plasticized hcbs of quartz sand

A composition of a ramming silica mixture based on quartzite filler and HCBS of quartz sand plasticized by an additive of refractory clay and having a total clay content of at most 2% is presented. Three methods of molding (compaction) are considered, namely, pneumo(vibro)ramming, vibropressing, and static pressing. The first is shown to give maximum compaction. The effects of some process factors on the properties of the new refractory material are described. The suggested mixture promises to serve well in rammed monolithic linings of heating units

Materials based on highly concentrated ceramic binding suspensions (HCBS). On preparation and some properties of silica refractory mixtures based on quartzite HCBS

Quartzite-based HCBS plasticized with additives of refractory clay are described. These HCBS and quartzite are used to produce refractory ramming mixtures. As compared with the known quartzite-clay ramming mixture on orthophosphoric acid, the obtained siliceous mixture has a much lower porosity and higher mechanical strength

Materials based on highly concentrated ceramic binding suspensions (HCBS). Fabrication and properties of fine-grain foam concretes based on hcbs of quartz sand

Compositions and methods for fabricating highly porous siliceous (SiO2 > 90%) foam concretes based on HCBS of quartz sand and additives of liquid glass and slags of ferrochrome production are described. Molding systems in the form of mineralized foams are self-solidifying and have a relatively low moisture content. In the process of molding and drying the material does not practically shrink. Foam concretes with a porosity of 65–75% are characterized by an ultimate compressive strength of 0.8–1.2 MPa which attains 5–15 MPa after the heat treatment. The maximum service temperature of such concretes is 1200–1300°C.

Materials based on highly concentrated ceramic binding suspensions (HCBS). The effect of heat treatment temperature on the strength properties of siliceous ceramic castables

Mechanical properties of siliceous ceramic castables shaped by vibration and static pressing with binders of quartz sand HCBS (pure and with a 5% additive of refractory clay) are studied. Other conditions being equal the porosity and the strength of the materials is affected by the content of the binder (varied from 10 to 33%). Ceramic castables heat treated at 1200 — 300°C exhibit a compressive strength of 50 –60 MPa at a porosity of 12–16%. The effect of the porosity on the strength of the materials is analyzed.

New refractory concretes and binding systems: Basic trends of development, production, and use of refractories in the XXIst century. Part I. Trends of development, binding systems

General trends in the development, production, and service of refractories are considered. The share of refractories used in ferrous metallurgy amounts to 60–70%, which means that the predominant trend is determined by the requirements imposed on the refractories used in the steel industry. The proportion of unshaped refractories in the total production will inevitably grow. The basic problem in this field is the improvement of their matrix (disperse) phase, i.e., the binding system. The main types of refractory binders, of which highly concentrated ceramic binding suspensions (HCBS) are the most interesting, are considered. In contrast to natural ceramic binders (clays) HCBS are artificial systems that can be obtained on the basis of many refractory materials. The priority aspect in the creation of new refractory concretes (castables) and binders is described. The first artificial ceramic binders and cement-free refractory concretes based on them were created and installed by the author at the end of the 60s, and in the 70s he suggested many types of ceramic castables, including superlow-cement ones.

Materials based on highly concentrated ceramic binding suspensions (HCBS). Study and comparative evaluation of methods for molding silica ceramic concretes

The processes of molding via vibrocompression (p=0.3 MPa) and static compression (p up to 500 MPa) are studied as applied to the technology of silica ceramic concretes based on a quartz HCBS and a mixture with a 5% addition of clay. The minimum values of the semifinished-product porosity for the aforementioned methods of molding are 11.5–12 and 15–16%, respectively. In static compression, for comparable compositions and moisture content the same porosity values are attained for mixtures with a clay addition at pressures 3–4-fold lower than those required for mixtures without clay.

Materials based on highly concentrated ceramic binding suspensions (HCBS). Comparative evaluation of the properties and in-service durability of pocket blocks of intermediate ladles

The Pervouralsk Dinas Plant has developed a technology for and started industrial production of pocket blocks based on bauxite ceramoconcrete for intermediate ladles. The structure and service properties of the blocks are compared with corresponding imported parts. The structure of the imported blocks is characterized by the presence of large (process) pores and the material is impregnated in service, whereas the developed blocks possess a homogeneous fine-capillary structure and are not impregnated in service.

Materials based on highly concentrated ceramic binding suspensions (HCBS). 3. Properties of mixed binders in the system of quartz sand HCBS and refractory clay

Mixed systems based on an initial HCBS of quartz sand and a suspension of refractory clay are described. It is established that the introduction of a small amount (2–5%) of clay has a substantial positive effect on the properties of quartz sand HCBS and materials based on them. The sedimentation stability, density, casting (binder) strength, and mechanical strength of the material a heat treatment at 800–1400°C are shown to increase. The content of the colloidal component (particles less than 0.1 μm in diameter) in the molded system is shown to depend on the porosity, strength, and drying shrinkage of the binder.