Discussion on Seamless Steel Pipe Defects of Separation Layer and Lamination

The discussion involves the expressions and descriptions of separation layer and lamination as defects of the seamless steel tube in relevant standards and literature.It is identified that for the seamless steel tube,separation layer and lamination are two different defects,instead of one.Therefore,the co-authors suggest that it be expressively specified in applicable national standard for seamless steel tubes and pipes that “No defects of separation layer and lamination shall be permitted for the steel pipe”,while a supplementary requirement be made to National Standard YB/T 4149—2006 for CC rounds for tube-making,saying that “No melting process-caused lamination defect of the pipe as rolled with the CC round shall be permitted.And any lamination of the ma-terial can be detected with the ultrasounic thickness gauge.”