ASME Section V T-451 Calibration blocks for coarse grain materials

Ultrasonic examination of coarse grain materials can present additional challenges compared with conventional ferritic weld inspection. 

ASME BPVC Section V, Article 4, Paragraph T-451 – Coarse Grain Materials – addresses these challenges and includes specific provisions for the ultrasonic examination of high-alloy steels, high-nickel-alloy weld deposits, and certain dissimilar-metal welds.

Following revisions to T-451 introduced in the 2023 edition of ASME BPVC Section V, Sonaspection manufactures calibration blocks and representative weld mock-ups to support ultrasonic examination procedures for these requirements, in addition to legacy specifications.

Why are coarse grain materials challenging to inspect?

Coarse grained and directionally oriented material structures can significantly affect the propagation of ultrasonic energy.

As identified in T-451, these structures can result in variations in attenuation, reflection, refraction, and ultrasonic velocity, making reliable examination more challenging.

This is particularly relevant when inspecting:

• High-alloy steels, including stainless steels
• High-nickel-alloy weld deposits
• Dissimilar-metal welds between carbon steel and high-alloy or high-nickel materials

What does ASME Section V T-451 require? 

T-451 provides additional requirements for ultrasonic examination where coarse-grain materials and welds are involved. These include:

• Weld mock-ups containing reference reflectors within the weld deposit
• Single- or dual-element search units producing refracted longitudinal waves

The use of representative weld mock-ups enables the ultrasonic examination technique to be evaluated using materials and weld structures that more closely reproduce the acoustic behaviour of the component being inspected.

This can help inspection teams evaluate sound transmission, attenuation, examination sensitivity, and the detectability of reference reflectors before applying the technique in the field.