HALFA Hossam Central Metallurgical R&D Ins

In the last decades, maraging steels were produced via different production routes. Electroslag refining (ESR) technique has been used by Steel Technology Department in Central Metallurgical Research & Development Institute, CMRDI, Egypt, to produce a new maraging steel for tooling applications. In this production route, raw material and different contents of maraging steels were melted in open air induction melting, (IF) followed by ESR process but melting of steel containing Ti, Mo and Cr is a problem. The high affinity of titanium and aluminum for oxygen and nitrogen causes a significant increase in the inclusion level and an unsatisfactory electrode surface when these alloys are cast in air. On the other hand, in the remelting of steels containing nitride – forming elements, such as titanium or chromium, nitrogen is hardly removed from the metal and in some cases its concentration can even increase to some extent. In this work consumable electrode produced (IF) from different contents of new maraging steel were refining under calcium fluoride based slag with different TiO2/Al2O3 contents. Identification of various phases present in the non-metallic inclusions, (NMI) from consumable electrode, as well as ingots from ESR has been carried out by X-Ray diffraction technique. Nitrogen in isolated non-metallic inclusion and metal ingots were determined using Kjeldahl method. Size distribution of non-metallic inclusion was determined using a semi automatic Carl Zeiss particle size analyzer in conjunction with optical micrographs taken on polished specimen. This work aims to study the effect of reactive calcium fluoride based slag containing different content of TiO2 on the non-metallic removal and dissolution of nitrogen rich inclusion during refining process. The results of experimental work show that, the remarkable capability of ESR process on the removing of precipitated nitride. These results also show that, chemical and physical properties (viscosity, surface tension,...etc.) of slag have a great effect on the removing of different kinds of inclusions especially nitride inclusions.

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