Rigorous, standardized marking is the final link in the mill's quality chain, ensuring the correct material is installed in the correct location. It is governed by ASTM A6. Markings are applied at the mill before shipment and must remain legible through normal handling.
Methods of Marking:
Roller Die Stamping/Indenting: The most common and permanent method. Steel dies are pressed or rolled into the steel surface, creating raised or indented letters/numbers on the web or flange. This is highly durable.
Paint Stenciling: Used in conjunction with or instead of stamping. Large, legible characters are sprayed onto the steel, often with a contrasting color.
Tagging: Metal or durable plastic tags wired to bundles or large single pieces, providing a duplicate of the stamped information.
Required Information (per ASTM A6): The marking will include, at a minimum:
Producer's Name or Logo: (e.g., NUCOR, SDI, ArcelorMittal).
Heat Number or Cast Number: The essential traceability code (e.g., 123456A).
Grade Designation: This clearly states the material standard and grade. For our subject steels, it will read:
A572-50 orA572-60
Size Designation: The shape name (e.g., W24x76).
Length: Often included (e.g., 40'-0").
Location of Marking: Typically applied on the web of the beam, at least one foot from the end. It is placed where it will be visible after erection, often on the outside face.
Color Coding (Optional but Common): Many mills and fabricators use a supplemental color paint stripe system for quick visual identification in the yard or on the erection site. While not universal, a common convention is:
A572 Grade 50: Yellow Stripe
A572 Grade 60: White Stripe (or sometimes two stripes)
A36: No Stripe or Blue
Field Verification: Erection inspectors and field engineers are trained to check these markings. Before a beam is lifted into place, they verify that the stamped grade (A572-50) matches what is called for on the structural drawings and in the erection plans. They also cross-reference the heat number with the stack of Mill Test Certificates to confirm the material properties. This simple visual check is a critical quality control step that prevents installation errors.
This system of physical marking, coupled with paper/electronic certification, creates a robust, verifiable chain of custody from the furnace to the finished structure.