DETERMINATION OF THE DEGREE OF MACROSCOPI C CLEANLINESS OF CONTINUOUS-CAST SLABS BY AN OFF-LINE ULTRASONIC INSPECTION

Increasingly exacting quality requirements on flat steel products (DWI , ULC, IF and HIC) make it necessary to develop new approaches in meta llurgy and casting technology. The Midas method (Mannesmann Inclusion Detection by Analysing Surfboards) is the first statistically signific ant, highly sensitive testing technique for the selective and timely q uantitative assessment of measures in the steelworks. Strand specimens , which represent in a characteristic manner the casting cross section , are flat rolled vertically to the strand shell in two directions. Wi th the controlled cooled ''ReinHus'' specimen (ultrasonic cleanliness detection at Hoesch) this subtle rolling method has been extended to c over also Ti-stabilized IF steels. All types of inclusions and cluster s can be subsequently detected ultrasonically in flat-rolled condition . The test result includes the number of indications, the correspondin g position coordinates, the amplitude of the ultrasonic echo, the indi vidual flaw area as well as the specific ratio of indications per flaw . The comparison the QTM methods reveals the statistical inadequacy of the latter.