Steel Structure

Stainless structural work has to satisfy load and corrosion at the same time: sensitisation in the heat-affected zone, deflection over long spans, and welding conditions on site decide the grade and the delivery condition.

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Typical parts and material selection

Part	Grade	Surface / size	Watch out for
Space-frame member / bolt ball	304 / 316L	HR plate 6–40 mm, cut to size	Yield strength, dimensional accuracy
Column / beam	304L / 316L	Plate 10–60 mm	WPS/PQR, lamellar tearing
Gusset / node plate	304L	6–20 mm	Intergranular corrosion (low carbon)
High-chloride structure	2205	Plate 8–50 mm	PREN, duplex weld microstructure
Cable / anchorage fitting	316L	Forged bar	Stress corrosion cracking

These are the usual configurations. Actual selection depends on medium, temperature and welding method — the same part may move from 304 to 316L or 2205. Describing the service conditions is more useful than naming a grade.

Three real constraints in this industry

Welding turns 304 into "stainless that rusts"

Between 450–850 °C chromium carbides precipitate and the zone around the weld is chromium-depleted. Load-bearing welded structures should use 304L (C ≤ 0.03%) or stabilised 321, pickled and passivated after welding.

Site welding is worse than the workshop

Wind and humidity on site disperse shielding gas. We supply different delivery conditions (solution annealed / pickled / passivated) depending on how much welding happens on site, and hand over the parameters.

Check deflection before choosing the grade

Stainless modulus is roughly 0.7× that of carbon steel, so the same section deflects more. Bring this into the structural calculation at concept stage — otherwise the grade is right and the structure still sags.