How your steel structure is fabricated in the World Steel factory

Fabrication starts only when the shop drawings are approved and released. Production planning issues the material requisition, and the cutting plan nests every web, flange, plate and stiffener on stock sizes to keep off-cuts and scrap to a minimum. The project Inspection and Test Plan (ITP) is fixed at the same time.

Hot-rolled plates and sections, sourced from mills in Europe, Japan, Korea and Taiwan, arrive with their mill certificates. QC checks grade, thickness, size and surface against the certificate and the order, and the heat number or ID code is recorded so that the material stays traceable. Non-conforming material is tagged on hold and kept apart.

Operators mark cutting lines, gauge lines and drilling points from the cutting plan. Webs and flanges for built-up members are cut in one operation on the CNC multi-torch plasma and gas cutting machine, fine parts on the Bodor fibre-laser cutter, and thinner plates up to 12 mm on the hydraulic shear. Each part gets its piece mark and ID code straight after cutting.

Bolt holes are drilled on the CNC drilling machine or punched on the CNC punching machine, after the hole diameter and count have been checked against the latest shop drawing; portable magnetic drills handle special cases. Rolled H, I, channel and angle sections are cut to length on the band saw. This is where bolts that line up on your Thai site are decided.

Flange and web plates are spliced to length with full-penetration butt welds, cleaned of loose mill scale, then tack-welded together on the H-beam assembly line with the web exactly on the flange centre line. Tapered PEB rafters and columns are built the same way, so steel goes only where the forces are.

Web-to-flange fillet welds run on the automated beam welding line and gantry beam welding machines using submerged-arc welding (SAW), with single or twin wires under granular flux for deep, even, low-spatter welds. The beam then goes through the beam straightening machine to correct flange distortion before fit-up.

Fitters read the shop drawing, mark centre lines and working points, then fit end plates, base plates, stiffeners, gussets and cleats with tack welds placed where the full weld will cover them. Full-penetration joints are prepared to the WPS, with a maximum root gap of 3 mm.

Qualified welders, tested to AWS D1.1, complete all shop welds to the written welding procedure specification (WPS), with members positioned flat or horizontal wherever possible. Base metal over 38 mm thick, or where the WPS requires it, is preheated. Run-on tabs are used at weld ends and removed by grinding, and each welder checks and cleans his own work.

QC inspects every weld visually and checks the finished member against the drawing. Non-destructive testing, ultrasonic (UT) and magnetic particle (MT), is carried out to the scope set in the project ITP or specification. Defects are marked, repaired by the repair team and re-inspected before the member can move on.

Weld spatter, sharp edges, oil and grease are removed first. Members then pass through the shot blasting machine indoors, with dry, clean abrasive selected for the steel and the surface profile required. The cleanliness and profile are checked by visual comparison and with a profile comparator gauge, typically to Sa 2½ (ISO 8501-1) or the grade in your paint specification.

Blasted surfaces are blown dust-free and painted with the paint system chosen for your site, by airless spray with each pass overlapping the last by 50%. No paint is applied when the steel is less than 3 °C above the dew point. Dry film thickness (DFT) is measured on every coat; fire-protection (intumescent) coatings are applied in the same controlled bays.

Each member keeps its piece mark from the shop drawing, so your erection team can find it on the erection drawing and in the packing list. When every signature on the process control tag is complete and the final inspection is accepted, QC attaches the green Pass sticker and releases the member for packing.

The packing plan is issued 10 days ahead so that timber, straps and frames are ready. Members are grouped by shape, size and erection sequence; small parts and bolts go into bundles, pallets or sealed crates with their packing list; long items are bundled on timber with steel straps, and wrapped in PE film when required. Straps never touch the paint directly: foam or hard carton sits underneath.

Bundles are loaded in layers on a support frame for 20 ft or 40 ft containers, with foam or fabric at every contact point, then pushed into the container. Lifting points are protected and items over 5 m are lifted with a spreader bar. QC checks the load and signs before it leaves; the delivery note goes on the container, the seal is photographed, and the final packing list goes to our export team for CIF shipping to Thailand.