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General Index for China's Refractories Volume 14,2005

Vol. 14. No.3, 2005

Some Aspects in the Development of High Performance Refractories for Iron and Steel Making in China

Xiangchong Zhong, Fangbao Ye (3) 3
Abstract
In the past 25 years in China, to meet with the rapid increase in steel production accompanied by adoption of advanced metallurgical technologies, there has been fast development of China¡¯s refractories industry in production capacity, in quality improvement and in development of new products. Sophisticated high performance refractory materials mainly based on our rich reserves of magnesite, bauxite and flake graphite have been developed, such as carbon-bonded products, high purity oxide products, bauxite-based low creep and high strength high alumina bricks and LC, ULC and ZC castables. They have been used in blast furnaces, BOFs, EAFs, secondary refining and continuous casting with considerable improvement in service performance.
 

Environmental Problems Related to Refractories
--Some Discussions Based on Historical Surveys mainly in Japan

Kiyoshi Sugita (3) 10
Abstract
Major environmental problems related to refractories are discussed based on their historical studies mostly in Japan. Those issues have been experienced in a wide range of industrial scenes, from processing raw materials, making refractories to relining furnaces, handling after-use refractories.
The key substances dealt with in this paper include, for example, suspended particulate, SOx and other exhaust gaseous emissions, hexa-valent chromium, and dioxin. The measures so far taken to avoid or reduce their influences upon environments are described with some future problems to be tackled.

Thermodynamic Properties of Non-Oxide Composite Refractories

HONG Yanruo, WU Hongpeng and SUN Jialin (3) 17
Abstract
For initiative application of non-oxides in refractories, it is essential to study thermodynamic properties of non-oxides. The stability and stable order of non-oxides under oxidized atmosphere are analyzed firstly and then a new process, ¡°„converse reaction sintering¡°ņ, is proposed. The results of study on oxidation mechanism of silicon and aluminum nitrides indicate that the gaseous suboxides can be produced observably when the oxygen partial pressure is lower than ¡°„conversion oxygen partial pressure¡°ņ. The suboxides can be deposited near the surface of composite to become a compact layer. This causes the material possessing a performance of ¡°„self-impedient oxidation¡°ņ. Metal Si and Al are the better additives for increasing the density and width of compact layer and increasing the ability of anti-oxidation and anti-corrosion. The study on Si3N4-Al2O3, Si3N4-MgO, Si3N4-SiC systems is also enumerated as examples in the paper. The experimental results show that the converse reaction sintering is able to make high performance composites and metal Si and Al not only can promote the sintering but also increase the density and width of compact layer. 
 

Study and Application of Sealing Material for Coke Oven Chamber

GAN Feifang and TAI Li (3) 25
Abstract
A kind of dry refractory sealing material has been developed to repair the fine cracks in coke oven chamber. With silica sand as the main raw material, the sealing material can be blew into coke oven chamber by compressed air when it is applied, and bond to brick surface or fill in fine cracks of chamber under right pressure. The physical properties of the material are very similar to those of silica brick during its application. So it can adapt to conditions of coke oven and has good service life. The study and application results of the sealing material are described in this paper.
 

The hydration and carbonation of tricalcium aluminate (C3A) in the presence of heavy metals

Quanyuan Chen, C. D. Hills, M. Tyrer and I. Slipper (3) 27
Abstract
The hydration of tricalcium aluminate (C3A) has a significant effect on the effectiveness of cement-based systems. In addition, the carbonation of hydration products of C3A is particularly important in respect of durability performance. The present work investigates the hydration and carbonation reactions of C3A and the changes induced by the presence of the heavy metal ions such as Zn2+, Pb2+, Cu2+ and Cr3+ by X-ray diffractometry (XRD). During hydration of C3A, gehlenite hydrate, hydrogarnet, calcium monoaluminate (C4AHx) and calcium carboaluminate were detected in C3A pastes except the Zn2+doped paste, where hydrogarnet did not form. The examinations revealed that heavy metals coexisted with gehlenite hydrate, calcium monoaluminate (C4AHx) and calcium carboaluminate, inhibiting the formation of hydrogarnet. Hydrating C3A was liable to be carbonated on exposure to air and carbon dioxide, especially in the presence of heavy metals, resulting in the formation of carboaluminate and/or calcium carbonate. The presence of heavy metals influenced the polymorphism of calcium carbonate, indicating that heavy metals could co-precipitate with calcium to form a carbonate solid solution. 
 

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