Guía de pernos estructurales de alta resistencia: pernos...
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Guía de pernos estructurales de alta resistencia: pernos...

2026-06-02· ~12 min read

Guía completa de pernos estructurales de alta resistencia que cubre ASTM A325, A490 e ISO Grado 10.9.

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What Are High-Tensile Structural Bolts?

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ASTM Standards: A325 vs A490

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StandardMaterialTensile StrengthYield StrengthGalvanizing
ASTM A325Medium carbon steel825 MPa635 MPaAllowed (mechanical or hot-dip)
ASTM A490Alloy steel1035 MPa895 MPaNot allowed
ISO 4014 Grade 10.9Alloy steel1000 MPa900 MPaAllowed
ISO 4014 Grade 8.8Medium carbon steel800 MPa640 MPaAllowed

Proper Installation: Turn-of-Nut & DTI Methods

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MethodEquipment NeededAccuracyBest For
Turn-of-NutSpud wrench, marking penGoodField installation
DTI WashersDTI washers, standard wrenchVery goodCritical connections
Torque WrenchCalibrated torque wrenchModerateIndoor/factory work
TC BoltsTwist-off bolts, special wrenchExcellentHigh-volume production

Applications in African Construction

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Procurement Checklist for African Projects

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Frequently Asked Questions

See frequently asked questions below.

What's the difference between A325 and Grade 10.9 bolts?

A325 and Grade 10.9 are roughly equivalent in strength. A325 has a minimum tensile of 825 MPa while Grade 10.9 is 1000 MPa. However, A325 is specifically designed for structural applications with controlled installation requirements, while 10.9 is a general mechanical property class. For structural steel work, either is acceptable if specified by the engineer.

Can A490 bolts be hot-dip galvanized?

No, ASTM A490 prohibits hot-dip galvanizing due to risk of hydrogen embrittlement. For corrosion resistance, A490 bolts must use alternative coatings such as zinc-flake (Geomet, Magni) or mechanically deposited zinc. This significantly increases cost compared to A325.

What happens if structural bolts are under-tightened?

Under-tightened structural bolts act as ordinary bearing-type connections rather than friction-type connections. This reduces the load-carrying capacity of the joint and can lead to joint slippage, which may cause structural failure under dynamic or cyclic loading. Always follow the specified tightening procedure.

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