Welding processes and consumables

Welding in PEB fabrication

Every primary member of a pre-engineered building is a welded product. Long web-to-flange fillet welds of tapered built-up members are made by automatic machines; end plates, stiffeners, clips and base plates are welded manually or semi-automatically. Weld quality therefore controls structural reliability. The choice of process, consumable classification matched to the base metal, and qualified procedures and welders are the three pillars that codes such as AWS D1.1, AS/NZS 1554.1 and EN 1090-2 with EN ISO 3834 regulate.

Welding processes used

Consumable classifications

Consumables are classified by standards that define strength, toughness and chemistry of the deposited weld metal. Matching consumables for 345–355 MPa steels typically have about 490 MPa (70 ksi) minimum tensile strength.

In Canada, consumables are certified to CSA W48 and welding companies are certified to CSA W47.1; in Australia, AS/NZS 1554.1 references the AS/NZS ISO consumable standards. Low-hydrogen consumables (H8 or better) are recommended for thicker plates, restrained joints and higher-strength steels. Consumables must be stored and, where required, baked per manufacturer guidance.

Shielding gases, fluxes, hydrogen control and preheat

A matching wire or electrode is only part of the consumable system. Gas, flux and storage conditions change weld metal properties as much as the filler itself.

For seismic force-resisting systems designed to AISC 341-22, demand-critical welds require filler metals with specified notch toughness and testing per AWS D1.8; in PEB this mainly affects end-plate and base connections of moment frames in high-seismic regions. In thin PEB plates (webs of about 4–8 mm), preheat is rarely required for 350 MPa steel, but thick base plates, crane girder flanges and cold conditions can trigger it.

Procedures, welders and inspection

• Procedures: AWS D1.1 allows prequalified WPSs within defined limits; others are qualified by PQR testing. AS/NZS 1554.1 has prequalified procedures; EN 1090-2 requires WPS qualified to EN ISO 15614-1 or equivalent routes depending on execution class.
• Welders and operators: qualified to AWS D1.1 Clause 6, AS/NZS 2980 / ISO 9606-1, or ISO 14732 for operators of mechanised equipment.
• Quality management: EN ISO 3834-2 (comprehensive quality requirements) is required for EXC3 work in Europe.
• Inspection: visual inspection of all welds; ultrasonic (UT) or magnetic particle (MT) testing at frequencies set by the code, execution class or category (e.g. SP or GP in AS/NZS 1554.1).
• Distortion control: sequencing and fixturing on automatic lines keep tapered members straight within tolerance.

Welding at WSC

World Steel welds built-up members on automatic SAW lines and uses FCAW and GMAW for fittings, under procedures and welder qualifications to the welding code specified for each project, within an ISO 3834-2 certified welding quality system and EN 1090-2 EXC3 and AS/NZS 5131 CC3 certifications. Consumables are sourced from established international and regional producers and matched to the steel grade of each project. See automatic welding of built-up members, quality control and inspection, and WSC's manufacturing capability.