A325 Structural Bolts:
The ASTM A325 specification addressed high-strength heavy hex structural bolts with diameters ranging from 1/2′′ to 1-1/2′′ before it was phased out in 2016 and replaced with spec ASTM F3125. Because these bolts are meant for structural connections, their thread lengths are shorter than normal hex bolts. Only heavy hex structural bolts are covered by this specification. For bolts with similar mechanical qualities but different configurations and thread lengths.
Specification A449. Bolts for common applications, including anchor bolts, are included. For quenched and tempered steel bolts and studs with diameters bigger than 1-1/2′′ but identical mechanical characteristics.
A490 Structural Bolts:
A490 bolts are comparable to A325 heavy hex structural bolts in terms of application and dimensions, however they are composed of alloy steel rather than medium carbon steel, resulting in a stronger fastener. Only heavy hex structural bolts are covered under the A490 specification. Bolts with thread lengths differing from those stipulated for structural bolts but similar mechanical qualities.
Prior to its discontinuation in 2016 and replaced with the new spec of F3125, the ASTM A490 specification covers quenched and tempered alloy steel heavy hex structural bolts with a minimum tensile strength of 150 ksi. Because these bolts are meant for structural connections, their thread lengths are shorter than normal hex bolts. Due to the risk of hydrogen embrittlement, ASTM A490 bolts must not be coated by hot-dip galvanizing, mechanical deposition, or zinc electroplating. As per ASTM F1136 Grade 3, commercially known as Geomet, coating A490 bolts with Zinc/Aluminum Corrosion Protective Coatings has been certified. The A490 specification requires further testing in the form of Magnetic Particle Inspection for Longitudinal Discontinuities and Transverse Cracks.
Your engineers will ultimately determine the grade of structural bolts you’ll need, but it’s crucial to understand the differences between grades A325 and A490. Although Grade A490 is stronger than Grade A325, strength isn’t the sole consideration when choosing bolts. Bolts made of A490 cannot be hot-dip galvanized or mechanically galvanized. Although Grade A325 is not as strong as Grade A327, it is a less expensive bolt that can be galvanized to prevent corrosion.