Forging Samples

Forging samples are reference pieces used in Non-Destructive Testing (NDT) to calibrate equipment and qualify personnel for the inspection of materials that have been strengthened and shaped by the forging process (hammering, pressing, or squeezing).

Forgings are critical components in high-stress applications (like aerospace, power generation, and automotive) due to their superior strength, ductility, and fatigue resistance, which results from the controlled grain flow established during the working process.

 Applications in NDT

Forging samples, like other NDT specimens, are divided into two main categories:

1. Calibration Blocks

These blocks are used to set the sensitivity and ensure the accuracy of the NDT instrument, particularly for Ultrasonic Testing (UT).

• Material Match: Calibration blocks must be made of the same material and have a similar surface finish and geometry (e.g., bar, ring, disc) as the forging being inspected to ensure the correct sound velocity and attenuation are set.

• Reference Reflectors: Forging UT often relies on Flat-Bottom Hole (FBH) blocks conforming to standards like ASTM E127 or ASTM A388/A388M. These blocks feature FBHs of a specific diameter drilled to varying depths to establish a Distance Amplitude Correction (DAC) curve. This compensates for sound loss and ensures that a flaw of a given size produces the same signal amplitude regardless of its depth.

2. Flawed Specimens (Demonstration Blocks)

These are samples of actual forged material that contain purposely induced defects of known size and location.

• Function: Used for procedure qualification and personnel certification to demonstrate the ability to detect and accurately size the flaws unique to forged products (e.g., a forged pipe flange or an eye hook with internal flaws).

• Documentation: Flawed specimens are supplied with certification documents detailing the exact type, size, and location of the internal discontinuities.

Common Flaws in Forging Samples

The flaws found in forgings are generally elongated and planar due to the way they align with the material’s grain flow during the mechanical working process.