EVALUATION OF ALLOY CLEANNESS USING COLD CRUCIBLE MELTING

Cold crucible levitation has been applied to the assessment of alloy c leanness. Trials were performed using pure nickel doped with a known n umber of Al2O3 particles of uniform size. Evaluation of the buttons sh owed that the inclusions collected in the 'veins' facing the slits in the crucible and on the surface around the centre of the button. From examination of the button using scanning electron microscopy, it was s hown that 85% of the inclusions collected on the surface of the button , which is comparable to that obtained in electron beam button melting (EBBM). The method appears to have considerable potential, since (i) it is relatively inexpensive compared with EBBM and, consequently, can be applied to routine monitoring of product quality, (ii) it can be a pplied to steels, for which EBBM is unsuitable, and (iii) sample weigh ts (approximately 80 g) are sufficiently large to give statistically s ignificant values for alloy cleanness. The hierarchy of cleanness deri ved for four steel casts was identical to that obtained using conventi onal metallographic methods. IS/1060