Application of Semi-rebonded Magnesite-Chrome Bricks of LRCO at RH Lower Vessel of NKK Keihin Works

摘要

The application results of semi-rebonded mag-nesite-chrome bricks at RH lower vessel of the NKK Corporation Keihin Works have been analysed. The results indicate that the main reasons that cause the damage of the refractory bricks include chemical attack of slag to the semi-rebonded magnesite-chrome bricks; penetration of molten steel and slag into the bricks; and thermal spatting due to temperature fluctuation during steel making operation. The results of multiple effection of these factors lead to alternative action of erosion (chemical attack and penetration) and spatting (thermal spatting and structure peeling) resulting in the damage of the brick. In order to improve the performance of the bricks, it is necessary to promote the resistance to erosion and thermal shock resistance as well as to keep the accurate dimensions of the brick. The measures to improve the resistance to erosion of magnesite-chrome bricks taken by the researchers mainly include: lowering the contents of impurities in the bricks (mainly including SiO_2, CaO, and next Fe_2O_3 and Al_2O_3); promoting the extent of direct bond of the brick; forming a large amount of magnesia-chrome composite spinel well-distributed in the bricks through adding a large amount of synthesized materials; enhancing the resistance to erosion by adding a little amount of high-effective additives. Improvement of thermal shock resistance of the bricks is mainly through introducing some additive to make a certain amount of micro-cracks occur-ing in the brick so as to obtain the effect of increase toughness or through formation of second high tem-perture solid phase in the brick by adopting additive. In addition, it is needed to improve the quality of the brick appearance and ensure accurate dimensions of the brick. The purpose of this paper is to describe the further improvement of the service life of refractory bricks by the measures taken on the basis of the analysis results to the used bricks.