European Certification of Charpy Specimens: Reasoning and Observations

The procedure for the production and certification of BCR (Bureau Communautaire de Reference) Charpy specimens for machine verification according to the European standard EN 10045-2 is described. A master batch is initially certified by interlaboratory comparison and is then used as a reference to certify sub-batches of similar impact toughness by comparative measurements on one dedicated machine. Extensive testing over ten years has shown that, for SAE 4340 steel, a 2 mm striker generally produces higher impact toughness than an 8 mm striker up to 120 J absorbed energy. Another observation is that asymmetric fracture generally occurs in about 50% of all cases, but that small series of tests may produce nearly all symmetric or nearly all asymmetric failures, influencing the mean value of the measured impact toughness.