A novel laboratory technique for introducing inclusion to liquid steel
Previous studies in steel cleanness have been hampered by limited control of inclusions’ phase and composition. This limited control is often a result of studying inclusion formation and development using industrial steel melts and the inclusions therein as starting material. This is an extremely complex situation and not always readily amenable to analysis. A new experimental laboratory technique has been developed that allows addition of inclusions of known, size, phase and composition to be added to liquid steel. These inclusions can then be tracked and changes in morphology with time can be assessed for different melt conditions. The technique involves the formation of a steel-oxide compact, where high-purity inclusions are sandwiched in steel foil at high pressure. This compact is added to a steel melt of controlled and known composition. The use of this sandwiching technique overcomes problems of passing small particles (inclusions <50 μm) through the gas-melt interface and inclusion agglomeration. Details of the technique are presented and discussed and results applying this new technique in a reactivity study using cerium oxide as a synthetic inclusion in steel are given.
The Effective Modification of Spinel Inclusions by Ca Treatment in LCAK Steel
This paper postulates the mechanisms of spinel formation in LCAK steel produced via the EAF route. The effective modification of solid spinel inclusions into liquid inclusions by Ca treatment is also demonstrated.
Microstructure of the solder-casting zone in bridges of dental gold alloys.
The composition and structure were studied in the cast and in the solder of bridges which had failed clinically. Both materials were gold alloys but with different contents of Pt, Ag and Zn. The metallographic investigation revealed defects mostly in the solder, situated in the subsurface layer. SEM studied of the fracture surface revealed large porosites and a structure of dense parallel lines--striations--, indicating that the material had failed from fatigue. The materials in the fractured bridges were identified by micro-probe measurements. It was stated that cast material and solder material used together, were of different composition.