Optimering av argonspolning under vakuumtankavgasning för ökad seghet i slitplåt

This work aims to find the optimal argon blowing procedure during vacuum tank degassing in order to achieve optimal toughness and steel cleanliness. During vacuum degassing three different blowing procedures were tested in full scale production of Hardox 450 DQ. Image analysis of the spout eyes during degassing was performed were the spout eyes area was measured every 10’th second and compared to total visible slag surface. Resulting mean values correlated with N and H removal and oxidization of Al, which was found to be an indicator of the degree of stirring. Inclusions in rolled plate, made from charges with variated blowing procedure, were classified according to SS 11 11 16 and it was found that rinse stirring during the latter half of degassing is beneficial for inclusion removal. Results from test charges have been compared to other vacuum degassed charges during 2010 and it was concluded that a high degree of gas stirring is beneficial for H, N and S removal. For the particular steel studied, toughness was not seen to depend on inclusions.Validerat; 20110126 (anonymous