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Technical guides

Choosing tube, without the guesswork

Short, practical notes from our quotation desk: which grade, which wall, which standard, and what actually goes wrong on a first container.

Q355B vs Q235B Difference between Q235B and Q355B square tube: yield strength, weldability, price impact and how to choose for structures, trailers and machinery. How to choose wall thickness for square tube Practical guide to picking wall thickness for square and rectangular hollow sections: load cases, deflection, welding, galvanising and cost trade-offs. EN 10219 vs ASTM A500 vs GB/T 6728 How the three hollow section standards differ on tolerance, testing and marking, and how to map an EN or ASTM requirement onto a Chinese mill certificate. SPA-H weathering steel SPA-H (corten-type) weathering steel square tube: chemistry, corrosion behaviour, welding rules, and where it beats galvanised steel on lifetime cost. Square tube weight Exact formula for square and rectangular hollow section weight per metre, worked examples, and a table for 30×30 to 400×400. Importing steel tube from China Practical checklist for first-time buyers: MOQ per size, container loading, mill certificates, third-party inspection timing and payment terms. Hot-dip galvanised vs painted steel tube When to specify hot-dip galvanising to EN ISO 1461 and when a paint system is the better buy: cost per m², service life, maintenance cycles and detailing rules. Square tube vs angle iron Comparing square hollow sections and equal angle for frames, purlins and bracing: torsion, weight, connection cost and when each one actually wins. How to read a mill certificate Field-by-field guide to a steel tube mill certificate: heat number, chemistry, tensile results, impact test, dimensional checks, and what to verify before accepting a shipment. How much steel tube fits in a container Container capacity for square and rectangular tube: tonnes per 20GP and 40HQ, loading patterns, bundle weights and how to plan a mixed order. RHS vs SHS When a rectangular hollow section beats a square one: bending efficiency, connection geometry, headroom and availability of sizes.