Heat Numbers and Lot Numbers are essential for quality control and traceability, serving distinct purposes.
Heat Number (or Melt Number): This is a unique alphanumeric code assigned to a single batch of molten steel produced in a furnace. All A36 steel from this specific melt shares the same initial chemical composition. The chemical analysis reported on the certificate is from a sample taken during this heat.
Lot Number (or Batch Number): This identifies a specific quantity of finished product (e.g., a bundle of H-beams) manufactured from a single heat under uniform conditions. A single heat of steel can be used to produce multiple lots. The lot defines the material that underwent the same rolling sequence, thermal history, and finishing process.
For A36 H-beams, mechanical property tests (tensile, elongation) are typically performed on a per-lot basis, as the rolling process can slightly influence final properties. This two-tiered system allows full traceability: from the chemical source (Heat No.) to the specific production run of beams (Lot No.), ensuring any potential issue can be isolated and investigated.