1.All mother tubes are post-annealed or post-normarized on the electric-resistence welded region and have homogeneous structures on weld joint.

2.SKK use only mother tubes which are eddy current tested or ultrasonically tested.

3.After tubes are cold finished, welded regions and base metals are again checked by eddy current or ultrasonic flaw detection tests.

In paticular our full automatic ultrasonic flaw detector is already provided to detect flaws on entire surface for outside diameters 260mm max,length 9000mm max,both welded regions and base metals, and SKK are given the best rank from the customers on quality guarantee.