Centre Segregation, Soft Reduction and Oxide Cleanness for Large Diameter Line Pipe with Highest Demands on HIC

Starting material to meet maximum demands requires low centre segregation and excellent oxide cleanness. Comparative tests were performed for this purpose on an oval-bow caster with a 5 m radius and a vertical bending machine with a 3 m vertical section and a 9 m radius. Both types of machine are capable of producing an excellent strand-centre quality provided strand support system settings are well monitored. Oxide cleanness is superior in slabs cast on the vertical bending machine; the inclusion band is further from the surface than on the bow caster. Sulphur prints are not suitable for inspection purposes, whereas MIDAS (Mannesmann Inclusion Detection by Analysing Surfboards) is able to detect macroscopic inclusions with certainty.