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FABRICATION AND QUALITY CONTROL OF STRUCTURAL STEEL

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Fabrication definition

Fabrication is the second main process in steel lifecycle after production from mills.

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Difference bet. Q.C & Q.AQuality control: activities used to fulfill

requirements for quality. (ex: calibration)“Quality control is a process for maintaining

standards and not for creating them.”Quality assurance: activities that do not

control quality but establish the extent to which quality will be.(ex: statistical control)

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Main raw materialsStandard sections Plates Fasteners Weld electrodes

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Main procedures• Receiving ,

storage, identification and traceability of raw materials.

• Preparation of material.

• Production.• Surface

preparation & protection.

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1.Receiving , storage, identification and traceability of raw materials

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1.Receiving , storage, identification and traceability of raw materials

Color Coding Printed Heat No.

Hard Stamp

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2.Preparation of materialMaterial is prepared for bolting (in site) or

welding (in next stage) by:Cutting of steel elements.Edge preparation.Holes drilling or punching.Rolling of plates.

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2.Preparation of material

Hole Punching

Hole Drilling

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3.ProductionCold forming: using bend machine

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Welding (main process)Factors affecting quality of weld:

1-Proper electrode2-Welding apparatus3-Welding method4-Welding position5-Edge preparation6-Control of distortion

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Welding (main process)Possible defects in weld:1-Lack or incomplete fusion.2-Inadequate edge preparation.3-Porosity and gas pockets.4-Undercut.5-Slag inclusion.6-Cracks.

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Non-destructive testsRadiography test(RT): used for small thicknesses to show the defects

inside weld .It uses x-rays and gamma rays.

Ultrasonic test (UT): using ultrasonic waves, used for large thicknesses, it’s faster and easier for judgment and need one technician to be carried out but it needs a certified and qualified technician.

Magnetic Test (MT): using magnet to identify subsurface defect up to 6 mm below surface for A.C current or up to 4 mm below surface for D.C current.

It must be used with materials that have magnetic properties.

Dye penetrant test (PT): used for identifying surface defects or subsurface but open to surface.

As red spot gots wider as defect is deeper.

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MT device Plan of weld

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4.Surface preparation & protectionMethods of preparation: -Wire brush (manual or automatic)

-Blasting using : - Sand - Marble Methods of protection:

-Painting: primer layer followed by another epoxy layer

-Galvanization: for higher protection requirements

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Refrences

China code of practice for steel construction and bridges.

AISC structural steel building specifications.