Lamination

A discontinuity in rolled or forged material consisting of the separation of internal layers parallel to the surface. Laminations are typically caused by entrapment of non-metallic oxides or voids during rolling. They weaken material through-thickness strength and can trigger cracking under stress. Ultrasonic testing with proper technique is effective for detecting laminations, particularly in high-strength steel plates and forgings used in pressure vessels.

Detection and Assessment

Lamination must be detected early and accurately characterized to determine safety implications. Multiple NDT methods may be required for comprehensive evaluation.

Acceptance Criteria

Industry standards such as ASME Section V, AWS D1.1, and API standards provide specific acceptance limits. Whether a detected lamination is acceptable depends on material, component function, and applicable code.

Best Practices

• Always follow applicable NDT standards and procedures
• Use properly calibrated and maintained equipment
• Ensure personnel are properly trained and certified
• Document inspection procedures and results completely
• Keep current with industry standards and best practices