Porous structure of graphitic crucibles

Abstract

In recent years graphite-containing refractories have been used, together with other types: they are superior to many refractories in terms of thermal-shock resistance, thermal conductivity, slag-and metal-resistance [i, 2].Of the range of graphitic products the most widespread are crucibles used for melting and casting nonferrous metals [3,4]. They are used when a high-quality metal is required in small amounts, and so the condition of the crucibles, their composition and the resistance to a large degree, influence the economics of the process, the quality of the final metal or alloy, and the safety of the melting procedures.The resistance of such crucibles is determined by many factors, among which the most crucial is the resistance of the graphite to oxidation. The reliability of the crucibles' operation depends on the extent to which it is possible to reduce the rate of this process. For example, Soviet-made crucibles obtained by dry pressing have better physicoceramic and thermal-strength properties than those made by Morgan Crucibles (England); nevertheless, their resistance (life) during the melting of nonferrous metals is sometimes only a half or even less.The question has been dealt with in many articles, in particular those dealing with the influence of the body composition [5][6][7][8][9], or defects in the crystal structure of the carbon [i0, ii] on the reaction capacity of the graphite component. Z2,gO 1,8; 0,,;8 0,~ J~50 Z,93 I,l; 0,/6 0,02 :00~ 7oo Table i.East Institute of Refractories.