Formation of Titanium Compounds,so-called Titanium Bear,in the Blast Furnace Hearth 原文手打版

Formation of Titanium Compounds,so-called Titanium Bear,in the Blast Furnace Hearth 原文手打版
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Formation of Titanium Compounds,so-called Titanium Bear,

in the Blast Furnace Hearth

Abstract

Titanium compounds,so-called titanium bear,are generally formed in the blast furnace hearth,because iron are contains more or less titanium oxide. Physico-chemical examinations were carried out on the titanium compounds picked up from the blown-out blast furnace hearth.

It was found that the titanium compounds are TiC-TiN solid solution and a cross sectional surface of the crystal seems to be an annual ring consisting of many layers,of which color changes corresponding to the carbon nitrogen concentration ratio. This annual ring would be related to the condition of its formation,such as the temperature,partial pressure of nitrogen,and motion of molten iron,where the crystal grew. Therefore,the titanium compounds,which had grown over long period,reflect the cyclic changes of operational condition of the blast furnace. Introduction

Recent marked increase in steel production demands a large quantity of iron ores. Then,from a viewpoint of resources in future,an utilization of lean ores,which contain much alumina,magnesia or titania,should be seriously considered. For this purpose,it is necessary to clarify the influence of use of these ores on various phenomena in a blast furnace,and to establish a proper way to use them and optimum operational technique. According to the previous publication,it is well known that a heavy charge of titania brings about some troubles in operation,such as a breakage of the tuyere,heaving phenomenon of the hearth,metal flowing from the cinder notch,and difficulty in tapping. It is also confirmed,however,that it is effective in protecting against a local erosion of brick of the hearth. Generally in normal operation,maximum quantity of titania in burdens is limited to about 10kg/t·pig from experiences. But even if the ore containing high titania is not used,titania compounds,so-called titanium bear,are formed at the hearth,because the iron ore contains more or less titania. Although titanium bears were often found in many blast furnaces and investigated,the conditions and mechanism of formation are not yet sufficiently clarified.

In this paper,the physico-chemical examinations have been made on the titanium compounds picked up from the blown-out furnace. The formation mechanism is also discussed in relation to their behaviors in blast furnaces.

Experimental method

As the samples for examination,titanium compounds,pig iron and chamotte bricks have been taken from the hearths of Kobe No.3 blast furnace(1850m3 in volume,blown-out in September,1973 after 7 years of operation)and Kakogawa No.1 blast furnace(2843m,September,1974 after 4 years and 1 month),Kobe Steel,Ltd.

The crystal structure and lattice parameter of titanium compounds were determined by X-ray diffraction method using Nelson-Riley function. Because TiC and TiN are completely miscible mutually,the lattice parameter of solid solution follows approximately Vegard’s law. Thus,the composition of Ti(C,N)can be estimated from a lattice parameter. Furthermore,in order to investigate the local composition changes in the Ti(C,N)crystal,carbon and nitrogen were 3

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