A welded carbon steel I-section beam is a structural steel member shaped like the letter “I” in cross-section, fabricated by welding together steel plates rather than rolling from a single billet. It’s a versatile and high-strength element used in buildings, bridges, and industrial structures.
Structure & Composition
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Flanges – The wide horizontal plates at the top and bottom, resist bending stresses.
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Web – The vertical plate between the flanges, resists shear forces.
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Welds – Typically continuous submerged arc welds (SAW) joining web to flanges.
Material
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Carbon steel grades:
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China: Q235B, Q355B, Q390B
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International: ASTM A36, ASTM A572 Gr.50, EN S355JR
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Carbon steel is chosen for high strength, good weldability, and cost-effectiveness.
Manufacturing Process
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Plate cutting – Flange and web plates cut to size by CNC plasma or flame cutting.
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Assembly & tack welding – Align and temporarily weld.
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Full welding – Continuous SAW along both sides of web-flange joint.
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Straightening – Remove distortion caused by welding heat.
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Drilling & machining – Holes for bolts, end plates, or stiffeners.
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Surface treatment – Shot blasting, painting, or galvanizing.
Advantages
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Custom dimensions possible (unlike hot-rolled beams limited by mill sizes).
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High load capacity due to thicker flanges or web if needed.
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Efficient use of steel for specific load conditions.
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Good weldability with structural carbon steel.
Applications
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Building frames (girders, floor beams)
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Bridge beams
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Industrial plant structures
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Crane runway girders
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Marine and offshore structures
Cross-section Example
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Flange thickness: 10–40 mm
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Web thickness: 6–20 mm
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Depth: 200–1,200 mm (or more for special cases)
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Width: 150–500 mm
