Ultrasonic testing can help evaluate the internal soundness of a steel forging, but the phrase “UT required” does not create a complete inspection requirement. The order must connect the examination method to a stated quality level, acceptance rule and report.
What ASTM A388/A388M covers
ASTM A388/A388M describes contact, pulse-echo ultrasonic examination of steel forgings using straight-beam and angle-beam techniques. The standard is used when an inquiry, contract, order or specification requires examination to that practice. ASTM also states that the ultrasonic quality level should be clearly stated in the order requirements.
The practice explains how the examination is performed. Acceptance still depends on the applicable product specification, drawing or purchase requirement. That distinction is essential: a test method tells the inspector how to look; the acceptance criteria tell the inspector what the buyer will accept.
Source: ASTM A388/A388M-26, Standard Practice for Ultrasonic Examination of Steel Forgings ↗
Identify the forging geometry and examination stage
Provide the forging drawing, nominal and supplied dimensions, material grade and delivery condition. State whether the part is a solid round, rectangular block, disc, ring, hollow forging or a machined component. Geometry controls the available scan surfaces and the directions from which discontinuities can be detected.
ASTM’s description notes that cylindrical surfaces are prepared for radial examination of round forgings, ends are machined perpendicular to the axis for axial examination, and faces of discs and rectangular forgings are machined flat and parallel. If the order requires testing before final machining, confirm that the available surfaces and allowances support the required scan.
Define coverage and technique
The RFQ should identify the volume that must be examined, any excluded zones and any critical region requiring additional coverage. State whether straight-beam examination is sufficient or whether angle-beam examination is required for the geometry and risk being evaluated. Rings, hollow forgings and complex shapes may need a technique that differs from a simple solid block.
Do not specify a technique based only on habit. Discuss the likely orientation of relevant discontinuities, access from each surface, surface finish and the thickness range with the qualified inspection provider. If a reference-block technique, DGS method or customer-specific calibration is required, state that in the order.
Put the acceptance criteria in writing
A complete purchase requirement identifies how indications are evaluated. Depending on the governing specification, this may involve amplitude, equivalent reflector size, length, number, spacing, location, loss of back reflection or a combination of these factors. Critical zones may have different limits from noncritical stock that will be removed during machining.
The order should also say what happens when an indication exceeds a recording threshold: whether it is mapped, investigated from another direction, removed by additional machining, submitted for engineering review or rejected. Suppliers should not have to infer an acceptance class after testing is complete.
Require traceable reporting
- Purchase order, drawing and revision
- Forging identification, heat number and quantity
- Material grade and condition at examination
- Applicable standard and acceptance level
- Instrument, probe, frequency and calibration method
- Scan surfaces, directions and examination coverage
- Recording and rejection thresholds
- Location and evaluation of reportable indications
- Examination date, operator identity and qualification basis
- Final disposition and authorized approval
Sample RFQ wording
“Ultrasonic examination is required in accordance with the edition of ASTM A388/A388M stated on this purchase order. Examine the full accessible volume after preliminary machining and heat treatment, from the scan surfaces identified on drawing SB-UT-01. Acceptance criteria, recording thresholds and critical zones shall be as stated on the drawing. Submit the signed UT report and indication map for review before shipment.”
This sample is a structure, not a finished specification. The buyer must insert the correct standard edition, scan plan and acceptance rules for the application. When those details are agreed before forging and machining, the supplier can preserve the necessary test surfaces and plan inspection at the correct production stage.