Contribution to Melt Refinement of Special Steels with Calcium Aluminate in Open Induction Furnaces

Dipl.-Ing. Johannes Schadock1, Dr.rer.nat. Johannes Södje2, Dr.-Ing. Peter Bartha3, Horst Diesing4, Dr.-Ing. Manfred Markworth5

1 Refratechnik Casting GmbH
2 head of Mineralogy in the R&D department, of Refratechnik Cement GmbH, Göttingen, since 1993
3 Consultant at Refratechnik Holding, München
4 founded his own company, HDW Diesing Walzwerktechnik, in 1982
5 has led his own engineering consultancy since 1981

Revision

Volume 2, Issue 1, Pages 72 - 81

Abstract

A special investigation of cast ingots was carried out at temperatures of up to 1630 °C to monitor and especially to minimize nonmetallic inclusions including carbide formers in the structure of highalloy special steel castings of the type S 11-2-6-4. The purpose of the trials is to develop a melt-refining treatment in which scrap metal with largely divergent target compositions has to be used as basis, resulting in difficult furnace operations due to a lack of homogenous lumpiness. By using calcium aluminate, without high contents of oxidation susceptible elements, it is possible to beneficially influence the size and distribution of non-metallic inclusions in the steel structure, and also to decrease the number of defects. The quantitative metallographic evaluations of samples taken from four heats verify these facts. On the refractory side, unshaped and shaped refractory materials can be used for lining induction furnaces. Currently, corundum-spinel provides optimum durability and lifetime; the basis is  resynthesized and/or in-situ spinel. An alumina-rich spinel is formed by the addition of MgO and Al2O3 in an Al2O3-enriched environment. This spinel type reveals a disordered crystal lattice with free atom sites, and thus can incorporate elements with adequate ionic radius. As in the case of calcium aluminate, the incorporation of undesirable components in the refractory corundum-spinel lining could be also verified. Additional works will deal with further developments of novel refractory materials.

Keywords

melt refinement, special steels, calcium aluminate, open induction furnaces, minimizing non-metallic inclusions in high-alloy steel castings, corundum-spinel furnace linings, use of scrap metal

References

Copyright

© 2010 Göller Verlag