What ASTM E23 Requires for Charpy Testing Records

When a weld or pressure-vessel dossier is challenged, the practical question is what does ASTM E23 require for Charpy testing? ASTM E23 Sections 5 through 9, together with its verification annexes, impose method requirements on the laboratory and test operator when the standard is invoked. ASTM itself does not create a universal legal duty or acceptance value; that obligation comes from the purchase order, material specification, construction code or regulator-approved procedure that calls up E23.

What E23 Governs

ASTM E23 is a test method for notched-bar impact testing of metallic materials. It covers Charpy and Izod arrangements, the machine, specimen preparation, test conditions and reporting. It is not, by itself, a weld acceptance standard.

That distinction matters on pressure-vessel and piping work. ASME BPVC, an ASTM material specification, a project specification or a jurisdictional requirement may require impact testing and may specify a minimum absorbed energy, test temperature, specimen orientation and retest rule. E23 controls how the result is produced. The invoking document controls whether the result passes.

For anyone asking what does ASTM E23 require for Charpy testing, the answer starts with the edition named in the contract. Use that edition, including its figures, tables, annexes and referenced standards. Later editions can change details such as verification provisions or reporting language.

Specimen Geometry and Identity

The standard Charpy V-notch specimen is 10 mm x 10 mm x 55 mm. ASTM E23 Section 6 and the associated specimen figure define a 2 mm-deep V-notch with a 45-degree included angle and a 0.25 mm root radius. The notch must be machined and positioned within the dimensional tolerances in the applicable table; a visually similar notch is not sufficient evidence of compliance.

E23 permits subsize specimens where the product or weld section cannot produce a full-size specimen. Common reduced dimensions are 7.5 mm, 5.0 mm and 2.5 mm in the reduced cross-section dimension, with the remaining geometry governed by the standard. A subsize result must not be treated as equivalent to a full-size acceptance result unless the governing material or construction specification permits that comparison.

Which specimens does ASTM E23 require? The method requires the specimen type, size and notch orientation specified by the invoking document. For weld testing, the record should identify whether the notch is in weld metal, the heat-affected zone or parent metal, as well as the transverse or longitudinal orientation and the exact distance from the fusion line where applicable.

Specimen identity should remain linked to the heat or lot number, weld number, WPS or PQR reference, plate or forging location and machining record. This is particularly important when several weld zones produce similar-looking broken specimens.

Temperature and Timing

ASTM E23 does not prescribe one Charpy temperature for every material. What temperature applies to ASTM E23 impact tests? The required value normally comes from the material specification, purchase order, design code or approved test procedure. E23 Section 7 then controls how closely the specimen must be brought to that value.

The test specimen temperature must be controlled to within +/- 1 deg C, or +/- 2 deg F, of the specified test temperature. For conditioning away from room temperature, E23 requires a minimum holding time of 5 minutes in a liquid medium or 30 minutes in a gaseous medium. The transfer from the conditioning medium to the machine and the start of impact must occur within 5 seconds.

The temperature record should show the target temperature, actual measured temperature, conditioning medium, start and finish times, and transfer time. For low-temperature testing, a generic statement such as tested cold is not adequate traceability. The laboratory must be able to demonstrate that the specimen, not only the chamber display, met the specified condition.

Machine Verification and Test Control

Section 5 requires a suitable impact machine, supports, anvil arrangement and striking edge. The standard Charpy support span is 40 mm, and the machine geometry must conform to the applicable E23 figures and tolerances. Machine capacity, alignment, friction and energy measurement are not matters for operator judgement; they are part of the method control.

The impact machine must be verified in accordance with the E23 verification provisions, including the applicable annexes. Verification is performed at least annually and after relocation, major repair or other work that could affect machine performance. Indirect verification with certified reference specimens provides evidence that the complete machine produces acceptable results; an encoder calibration certificate alone does not establish E23 compliance.

The laboratory file should retain the machine identification, verification date, verification range, reference specimen certificate and any out-of-tolerance investigation. If the machine failed verification, results produced since the last satisfactory verification need a documented technical assessment. That assessment may require retesting, customer notification or rejection of affected results, depending on the governing quality system.

The same control applies to specimen supports and the striker. Worn anvils, a damaged striking edge or incorrect specimen seating can change absorbed energy without leaving an obvious defect on the broken specimen.

Reporting and Acceptance Evidence

How should ASTM E23 results be reported? Section 8 requires a report that identifies the material and specimen, specimen type and dimensions, test temperature and absorbed impact energy. The report should also identify the machine and include the additional measurements required by the invoking specification, such as lateral expansion, shear fracture percentage or fracture appearance.

For weld and pressure-vessel records, a defensible report normally includes:

• material heat or lot, component and weld identification;
• specimen location, notch position, orientation and size;
• specified and actual test temperature;
• absorbed energy for each specimen, in J or the contractually required unit;
• lateral expansion, percent shear fracture and fracture description where required;
• machine number, E23 verification status and test date; and
• deviations, damaged specimens, invalid results and retest authority.

E23 does not set a universal minimum absorbed energy. A result is accepted or rejected against the value and averaging rule in the applicable material specification, code or purchase order. The report should therefore show individual results, not only an average or a pass statement. Where a code permits retesting, the original results and the reason for the retest must remain in the record.

This is why what does ASTM E23 require for Charpy testing is also a traceability question. A technically correct impact value can still be unusable if the laboratory cannot connect it to the correct heat, weld zone, test temperature and verified machine.

Closing Takeaway

ASTM E23 requires controlled specimen geometry, defined temperature and transfer limits, verified impact equipment and a report containing the essential test data. The governing material or construction document adds the acceptance threshold and any special weld, vessel or retest provisions. On scrutinised projects, retain the complete evidence chain from specimen machining and identification through machine verification and the individual reported results.