Flare workability method of evaluation of forge welding tube

摘要

PROBLEM TO BE SOLVED: To provide a forge welded tube superior in workability, and hardly generating cracks in a connection part even in high deformation such as flaring.SOLUTION: There is provided the forge welded tube manufactured by heating the whole width in a heating furnace, increasing the temperature of the edge part of a steel band by spraying oxygen or air and using oxidation heat, or by performing edge abutting and forge welding after high frequency heating, wherein the forge welded tube superior in workability allows the size A (%) of an eddy current denoting the eddy current detected with eddy current inspection of the connection part of the forge welded tube in a percentage for the eddy current detecting a drill hole of 3.2 mm of a diameter penetrating through thickness as a calibration flaw to be A1 or less of a critical value denoted by formula 1 using the ratio (R1) of the thickness direction length of the connection part to the pipe thickness. The formula is expressed by A≤A1=12.5×R1+7.5.