Abstract
	This article deals with a substitution of classic-type moulding mixtures with a siliceous  opening material by moulding  mixtures  with  a  DUNIT  MAGNOLITHE  -  GS opening material.
	At the beginning of steel production  with increased Mn content  in  plant  in ZTS Dubnica nad Váhom  the classic moulding mixtures with a siliceous opening material were used for  the  manufacture  of  moulding  mixtures. As results of casting surface quality did  not meet requirements when using  of such mixtures, it was  necessary to develop new technology of moulding mixture production. The opening material DUNIT- MAGNOLITHE GS  was  selected   for  its  suitable chemical and physical parameters.
	DUNIT AFS40 and AFS60 materials were subjected to initial chemical and mechano-chemical  testing. Technological  instructions were  proposed  for  the  production of model, VCT and CT mixtures with this opening material. Laboratory tests proved the required parameters of these mixture were achieved. At present castings from 50 tons of liquid metal were  produced according  to this  new technology  of  moulding  mixtures  proving better surface quality.
	Savings when  finishing surface of  castings compensated  costs on purchase of the DUNIT-MAGNOLITHE material.