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Overview

Heavy Forging Inspection

Forging is a process used to manufacture metal components requiring high strength, such as turbine generator shafts and large disks. In this process, metals are most commonly heated and shaped using compressive forces. Forging has the advantage of producing stronger parts than casting or machining.

The forging process is associated with the emergence of natural volumetric defects such as inclusions and porosities. These defects can be located anywhere in the part volume and must be reliably identified and characterized in order to ensure high quality parts.

Natural Defects

Inclusions and voids can be located anywhere in the metal volume, from the subsurface region to the core. These defects must be correctly located and sized regardless of their location inside the part.

Illustration of beam propagation and corresponding DGS curve diagram.

Calibration Reference

Forged part inspection systems are usually calibrated using back wall reflection. A distance gain size (DGS) curve is generated based on the expected equivalent reflector size (ERS). This DGS curve can be converted to a time-corrected gain (TCG) curve to simplify defect identification and improve operator efficiency.

Inspection Technique

Volumetric Inspection

Volumetric inspection is performed using a phased array probe that generates longitudinal waves at various angles. Conventional ultrasonic (UT) probes are added to generate high-angle shear waves.

Subsurface Inspection

Subsurface inspection is conducted using a pitch-catch conventional UT probe, which minimizes the near-surface dead zone.