SRM Story: SRM 1224 Carbon Steel, AISI 1078 (disk form)

Do you ever think about how steel can be used for surgical instruments, reinforced concrete, cookware, ball bearings, railroad tracks, generating electricity... How can “steel” do all these things? The secret is in the recipe – what types and how much of various elements are added to the base metal (iron), and how that mixture is heat treated. Steels and related alloys have many indispensable uses in our modern world, and their key features such as strength, durability, hardness, and temperature resistance are impacted by their chemical composition. NIST maintains a portfolio of over 80 steel Standard Reference Materials (SRMs) to assist steel producers when testing the composition of their products. These SRMs also help meet critical needs for many other steel standards by supporting the production of additional reference materials (RMs), such as type specific steel RMs, produced by commercial suppliers.

SRM 1224 Carbon Steel, AISI 1078 (disk form) is one such product that has helped ensure strength of structures such as buildings and bridges since its release in 1981. Re-released in June 2025, critical element mass fractions have been updated with new data acquired using instrumental techniques such as X-ray fluorescence (XRF), prompt gamma activation analysis (PGAA), spark source optical emission spectroscopy (SS-OES), combustion, and inert gas fusion (IGF). The updates to this SRM and its accompanying Certificate of Analysis (COA) are essential to ensure industry users can appropriately calibrate and validate their testing methods and ensure accuracy of manufactured steel composition.

As the US National Metrology Institute (NMI), NIST provides materials like SRM 1224 to enable users to establish metrological traceability to the International System of Units (SI). The international network of NMIs, including NIST, maintain measurement equivalence through SI traceability that ensures for decades to come, in laboratories around the world, measurement of steel composition will be accurate and comparable. Steel isn't just metal – imagine it's the backbone of a bridge. If the composition is off, that bridge might not stand up to the forces of nature or time. Stress, corrosion, and heavy loads could cause weak spots, leading to cracks... and eventually, collapse… like the Silver Bridge over the Ohio River in 1967. Science rules, but only if we get it right!