Abstract

 Recently, the demand against high purity steel becomes higher and the secondary refining rate for molten steel becomes larger. Keeping the working ratio of RH-degasser has become one of the most important tasks for steel production lines.

 One of the shortest refractories life part in RH-degasser is a snorkel. Especially, sudden damage of an upleg snorkel requires unscheduled replacement of it that harms stable steel production.

 In most cases of the sudden damaged snorkels, the deformation of steel shell of snorkel are observed. Therefore, the risk of sudden damage of the snorkels might be reduced by prevention of the shell deformation.

 It is well-known strength of steel decreases along with temperature increase, and this degradation has negative influence to the shell deformation.

In this study we tried to cool the steel shell by using gas flow pipes, used for lifting molten steel.

 Two types of test snorkels were prepared for the actual equipment experiment, and the steel shell’s temperature were measured continuously. Type1 had gas pipes placed on almost all area of steel shell, and type2 had that intensively placed near the lower area of steel shell.

 Both type of test snorkel were kept lower temperature than conventional one. Especially, the test snorkel type2 showed the drastic effect for cooling, and deformation occurred in very limited area near the lower edge. It suggests that the cooling effect is increased by concentrating cooling near the lower edge of steel shell.

 The deformation rate of the steel shell were decreased, and their lifetime were prolonged. Their lifetime was 140% in type1 and 160% in type2 compared with the average life of conventional snorkels, respectively.

The relationship between the temperature and deformation of steel shell of RH-snorkels is strongly indicated and possibility of sudden damages will be reduced under 1230 K.