Method for identifying weld seam of individual longitudinally seam-welded tubes

摘要: The present invention relates to a method for identifying the weld seam (14) of individual longitudinally seam-welded tubes (1) made ferritic or austenitic material, wherein during which tube is placed in direct current magnetic field and rotated around longitudinal axis thereof. differences structure and/or permeability resulting between parent material are determined as differentiation criterion by am eddy probe (8) proximity tube. According invention, introduces with frequency ranging from about 100 kHz 1 MHz into can be distinguished an input voltage that differentiated reference (24) tangential force on at least 500 Oerstedt.