The Effect of Electromagnetic (I.e. Induction) Stirring of the Melt ofConcast Billets on the Reduction of their Surface Defects

摘要

Electromagnetic stirring (EMS) suppresses the growth of columnar crystals of billets andrnreduces the tendency to cracking during casting and at low temperatures. A caster was used for therntesting of two induction stirrers – one on the actual mould and the other beneath the mould – torndetermine the effect of EMS on the formation of the structure of non-alloy steel. As part of theserntests, certain parts of the billets had been cast without the use of stirrers and other parts underwentrnalternate switching on and off of the stirrers for as many as nine combinations of modes. Samplesrnwere taken from the sections of these billets, fine-ground and etched in order to make the dendriticrnstructure visible. The mode with the highest efficiency was when both stirrers ran simultaneously.rnThe growth of the columnar crystals, which pointed inward, was limited to ?-to-u0002 of the length ofrnthe case when there was no stirring. Experimental research was also confronted with resultsrnacquired from the application of the models of the temperature field and chemical heterogeneity andrnthe physical-similarity theory. Statistical monitoring of the quality of concast billets has proven thatrnstirring significantly reduces the occurrence of defects – in this case cracks.