Ultrasonic Testing Sound Velocity by Material

How to use this reference

The table keeps longitudinal and shear velocities separate because these are different wave modes. Use a value only with the probe, mode and measurement method that match it. Water is listed as a longitudinal reference at 20 °C; no shear value is supplied.

For pulse-echo thickness measurement with a longitudinal wave, d = v × t / 2, where t is round-trip transit time. Do not use a shear velocity in that longitudinal setup or omit the factor of two.

Calibrate on representative material

Evident labels these values as references. Actual grade, composition, heat treatment, grain size, casting structure, temperature and anisotropy can change the measured value. A generic steel figure may not represent a particular plate, casting, weld or alloy condition.

For reliable thickness work, calibrate on a known-thickness sample with representative material condition. Confirm sound path, probe, couplant, zero offset and instrument mode before recording measurements.

Interpret material names

Rows name specific materials where the maker provides them, including Steel 1020, Steel 302 and Steel 4340. Those labels are not interchangeable across every steel product, heat treatment or direction. Cast iron is split into slow and fast reference categories.

Where the actual material is not an exact match, follow the written procedure or measure velocity on a representative sample. Do not choose a nearby row just because its name looks similar.

Keep wave modes distinct

Longitudinal waves generally travel faster than shear waves in a solid, and the difference appears in the paired values. Straight-beam thickness checks commonly use longitudinal waves, while angle-beam examinations often use shear waves. The procedure determines the mode.

For shear-wave examination, use the corresponding shear velocity and procedure geometry. The simple pulse-echo thickness formula does not replace angle-beam geometry or weld examination rules.

Account for conditions

Only the water row explicitly states 20 °C; many solid rows are reference values without detailed specimen conditions. Temperature, texture and direction can matter, especially in anisotropic or coarse-grained material. Treat the list as a starting point rather than a guaranteed property.

For a measurement near a tolerance boundary, use verified velocity for the material and temperature and account for instrument uncertainty. Follow the applicable NDT standard and written practice for calibration and acceptance.

Stay inside the NDT procedure

A velocity table does not determine flaw acceptance, sensitivity, scan plan, probe frequency or inspection qualification. Those depend on the governing code, procedure, component geometry and examination purpose. Use qualified personnel and applicable procedures for production inspection.

The values are selected from Evident’s technical note for setup orientation. The written examination procedure and calibration block remain the controlling references.

Read the source scope

Each row preserves the source designation, units and conditions available for this reference. A value is useful only when the specification basis matches the part, process, instrument or machine under review. If a source does not state a condition, do not assume one that could change the result.

Keep the table and metadata together when saved or shared. If a current controlled supplier document conflicts with this snapshot, check the revision and use the latest applicable specification. This table is a comparison aid, not a substitute for supplier approval.

Verify the application

The table narrows a lookup but does not decide whether a component or process is acceptable. Confirm the drawing, equipment-maker instructions, safety rules, environment and complete operating duty before making a design, inspection or purchase decision.

For critical applications, have the responsible engineer review the selected value and supporting calculation. Record assumptions, material identity, measurement conditions and approvals that govern the final choice.

Keep units and terminology clear

Read column headings before comparing entries. A number can be a limit, reference value, conversion or one condition from a manufacturer catalogue. Do not mix units, standards, grades or measurement modes simply because the values appear comparable.

When converting units, document the factor and rounding. Retain unrounded values during calculations and round only to the precision required by the governing drawing or specification.

Check current documentation

Technical catalogues and standards can be revised. Check the current source before procurement, production release or inspection. Confirm that the cited edition applies to the customer contract and jurisdiction.

This article explains the table structure and key checks. It does not establish compliance or replace a qualified procedure. When information is incomplete, contact the manufacturer or standards body for the controlling document.

Source and scope

Sources: Evident ultrasonic transducers technical notes. Use the source editions and conditions recorded with the table.