In 2011 Almatis introduced a new high alumina sintered aggregate to the market – BSA 96. The idea was to offer a European alternative to other high alumina aggregates – fused, natural or sintered. This paper will present a brief overview of the special characteristics of BSA 96 and describe the experience over the past five years using BSA 96 in various applications such as AMC bricks, high alumina bricks and blast furnace runner castables. Special focus will be on the formation of so-called CAM phases found in sintered castables with BSA 96 as the matrix component together with fine spinel and cement.
The permanent development of steel producing technology is a main driver for the development of new and improved refractories. The paper briefl y discusses the trends in steel secondary metallurgy and how modern engineered refractories provide innovative solutions for challenging conditions in the steel making process. Examples are given how refractories contribute to steel quality and economical improvements in the process.
Abstract: Calcium-mono-aluminate (CA or CaAl2O4) and calcium-di-aluminate (CA2 or CaAl4O7) are the main phases in iron free high alumina cements (CAC) which are used in demanding refractory applications. It is well known that the hydraulic reactivity of calcium aluminate phases increases with the calcium content of the phase, and therefore CA shows higher reactivity than CA2. Some literature even claims that CA2 would be an almost inert Phase with regard to hydraulic reactivity. This study investigates the Hydration of pure CA and blends of CA and CA2 using heat flow calorimetry and quantitative in-situ X-ray diffraction (QXRD) during hydration. Heat flow was calculated by combining the QXRD data obtained during hydration of the mixes together with the standard enthalpies of formation of the participating phases. Comparing the observed heat flow from calorimetry with the heat flow calculated from QXRD data, good conformance could be obtained. The results show a clear pronounced influence of CA2 on hydration of CAC and its heat of hydration during the first 22 hours. After more than 10 hours the hydration of CA2 gives the major contribution to the heat flow. Introduction The hydration of calcium-mono-aluminate (CA) is part of several previous investigations and is well known. In common calcium aluminate cements (CAC) CA is the main hydraulic phase responsible for early strength development. Although recent investigations showed that CA reactivity can be increased by its fineness , it is worth having a closer look at CA2 - the second main phase in most white CACs. CA2 is known to be weakly hydraulic and was not of great interest in past investigations which looked into the hydration of CAC . The hydration of synthesised CA and CA2 in different ratios together with ZrSiO4 as an inert filler, were investigated with isothermal heat flow calorimetry and in-situ X-ray diffraction. Through a combination of both methods the heat flow contributions of CA and CA2 were evaluated.
Alumina, due to its powerful physical, thermal and electrical properties is by far the most used and cost-effective ceramic material in technical applications. As a result of the high mechanical strength, excellent chemical resistance, electrical properties and dimensional stability at high temperatures, alumina ceramics makes an ideal material for many parts in automotive applications. Some of the typical applications include catalytic substrates, electronic substrates, various mechanical wear parts, spark plugs and polishing. Almatis offers the broadest alumina portfolio in the industry with a broad variety of product solutions for the industry.
There are many perceptions in the market about the most appropriate refractory aggregate for a particular application. Opinions about the relative benefits of the fused and sintered versions of synthetic high alumina materials are set and often difficult to discuss and refute. But changes in the refractory raw materials market over the past few years have influenced the properties of the currently available synthetic high alumina materials and triggered the development of new aggregates. The purpose of this paper is to outline the differences between high alumina fused and sintered raw materials. The focus will be on physical properties such as density, porosity and grain shape, but the influence on the final properties of refractory formulations such as bricks, castables or dry vibratable mixes is also discussed (DVMs).
The owners of German speciality alumina producer Almatis and its shareholders have agreed to sell the group to Turkey’s largest pension fund, Oyak.
The use of monolithic refractories has spread throughout various industries over the past few decades. Today it is common practice to install monolithics in heavy wear areas. In the past, only refractory bricks were used. Unlike bricks, unshaped products require sintering during operational use to obtain their final properties. Applications outside the iron and steel industry are often referred to as “industrial applications”. Industrial applications also demand improved castable properties such as better chemical stability, mechanical strength and abrasion resistance in intermediate temperature ranges. The service temperatures in industrial applications are often below 1200 °C, so castables do not attain sufficient energy for strong sintering reactions. Matrix properties are important for refractory castables. They determine not only workability and strength, but also performance within an application. By optimising the overall particle size distribution of fine and superfine materials including the binder, better workability can be achieved. In addition, the physical properties of castables can be improved, especially in intermediate temperature ranges. Calcined and reactive aluminas and dispersing additives can also contribute significantly to the improvement of matrix performance with respect to water demand, setting control and strength development.
Part 2 of this paper compares the performance of traditional and modern additive concepts in silica fume castables with regard to additive dosage, storage stability of the dry mix, fl ow properties, working and setting time and also the strength development during curing.
As the world’s leading speciality alumina producer Almatis’ thoughts on the market are always a good indication on trends looking ahead for the whole industry. The optimism displayed by the company underscored other accounts by refractories and raw materials producers this week in Aachen and Rimini.
Since the use of low cement castable technology became extensive in the early 1990‘s, the application of additives for the effi cient dispersion of fi ne and ultrafine matrix components has become essential. Part 1 of this paper discusses the value of additives in general, and compares the differences in various traditional and modern additive concepts covering fl ow properties, working time, setting behaviour, and their impact on physical properties incl. hot properties in silica fumefree low cement castables. Part 2 will be published in in the next issue rwf 4/2014 and will discuss additives used in castables containing silica fume as fi ne matrix fi ller in the range of 3–5 % additions.