ASTM F3125 Grade A490 Bolts
Heavy hex structural bolts per ASTM F3125 Grade A490 — alloy steel, quenched and tempered, 150,000 psi minimum tensile, Types 1 and 3, never galvanized. The high-strength structural bolt for the heaviest connections.
Last updated: 2026-11
Specifications
A490 (standardized under ASTM F3125) is the high-strength counterpart to A325: quenched-and-tempered alloy steel at 150,000 psi minimum tensile, used where the heaviest or most critically loaded structural connections need more clamp force than A325 provides in the same footprint. Its strength comes with handling rules: A490 must never be hot-dip or mechanically galvanized (hydrogen embrittlement risk), it is more susceptible to stress corrosion and hydrogen cracking in service, and it is supplied with weathering-steel Type 3 option for bare atmospheric exposure. Where a job does not require the extra strength, A325 remains the more forgiving specification.
| Standard | ASTM F3125 Grade A490 (supersedes ASTM A490); heavy hex structural bolt |
|---|---|
| Material | Type 1: alloy steel, quenched and tempered; Type 3: weathering steel |
| Tensile strength, min | 150,000 psi minimum; vendor grade charts list 150/130 ksi across size groups |
| Galvanizing | Not permitted — hydrogen embrittlement risk from hot-dip or mechanical galvanizing; protect by painting or Type 3 weathering steel |
| Service caution | Higher susceptibility to stress corrosion cracking and hydrogen cracking than A325 |
| Installation | Pre-tensioned installation per structural bolting practice; matched heavy hex nuts and hardened washers |
| Typical applications | Very heavy and critical structural connections where A325 strength is insufficient |
Where this grade fits
A490 is the strongest structural grade and the most constrained: galvanizing is not permitted — the hydrogen embrittlement risk from hot-dip or mechanical galvanizing is why protection is by paint systems or by specifying Type 3 weathering steel. It also carries higher susceptibility to stress-corrosion and hydrogen cracking than A325, so inspection discipline matters more, not less, at this strength.
Deep read: Hydrogen Embrittlement in High-Strength Bolts: Which Grades Need Controls, Which Coatings and Baking Schedules Are Acceptable, and What to Require Before the RFQ · Fastener Failure Modes: Which Fatigue, Creep and SCC Controls the Evidence Supports
Materials
- Alloy steel, quenched and tempered (Type 1)
- Weathering steel (Type 3)
Ordering & documentation
Documents
Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.
Quotation
- The fastener family (ASTM F3125 Grade A490 Bolts) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
- Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
- Quantity per size and your target delivery date.
- Destination country, and any required documents (for example a mill test certificate) so the quote includes them.
Sample & supply
Minimum order quantity is 1,000–10,000 pieces depending on size. Stock items run 3–7 days. High-strength and custom parts run 15–25 days. Quantities or variants outside the standard range are confirmed at quotation.
Storage & shipping
Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.
Frequently asked questions
Why can A490 bolts not be galvanized when A325 can?
Hydrogen embrittlement. At A490's strength level, hydrogen introduced by the acid pickling and zinc bath of the galvanizing process can crack the bolt under load, and the standard prohibits hot-dip and mechanical galvanizing for that reason. A325 Type 1, at its lower hardness, tolerates galvanizing within the standard. For corrosive service, A490 is protected by paint systems over primer, or specified as Type 3 weathering steel for bare exposure.
What is the MOQ and lead time for this bolt grade?
The minimum order quantity is 1,000–10,000 pieces depending on size. Stock items ship in 3–7 days; high-strength and custom parts in 15–25 days. Common diameters in this grade are widely stocked; confirm the exact schedule against quantity and size mix at quotation.
What should an RFQ for this bolt grade state?
State the standard and grade (for example ISO 4017 Class 8.8 or ASTM F3125 Grade A325 Type 1), diameter and length, thread type (metric coarse or UNC/UNF), finish (plain, zinc, or hot-dip galvanized where the grade permits), required certificates such as a mill test report per EN 10204 3.1, and quantity per size — plus destination country.
Related knowledge
- What Bolt Property Classes 8.8, 10.9 and 12.9 Encode — and When High Strength Stops Being the Right Choice
- Bolt Grade Selection: ISO 898-1 8.8/10.9/12.9 vs ASTM A307 and A325
- 8.8 vs 10.9 vs 12.9 Bolts: Strength, Hardness and Cost — What the Evidence Settles
- Calculating Bolt Preload and Clamp Force: Torque, Friction and Tightening Method
- How to Determine Tightening Torque and Choose a Tightening Method for a Bolted Joint
- Fastener Failure Modes: Which Fatigue, Creep and SCC Controls the Evidence Supports
- Hydrogen Embrittlement in High-Strength Bolts: Which Grades Need Controls, Which Coatings and Baking Schedules Are Acceptable, and What to Require Before the RFQ
Request a Quote
Get factory-direct pricing from the manufacturer.
What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support