ASTM F3125 Grade A325 Bolts
Heavy hex structural bolts per ASTM F3125 Grade A325 — medium carbon steel, quenched and tempered, 120,000 psi minimum tensile (105,000 psi over 1"), proof load 85 ksi, Types 1 and 3. The standard structural steel connection bolt.
Last updated: 2026-11
Specifications
A325 (now standardized under ASTM F3125) is the most widely used structural steel bolt in North America: heavy hex head, controlled thread and shank lengths so threads stay out of the shear plane, and a quenched-and-tempered medium carbon steel body good for 120,000 psi minimum tensile up to 1" diameter. Type 1 is the standard medium carbon steel bolt and may be hot-dip galvanized; Type 3 uses weathering steel for unpainted, atmospheric-corrosion-resistant connections. It installs under torque or tension control with matching heavy hex nuts and hardened washers.
| Standard | ASTM F3125 Grade A325 (supersedes ASTM A325); heavy hex structural bolt |
|---|---|
| Material | Type 1: medium carbon steel, quenched and tempered; Type 3: atmospheric-corrosion-resistant (weathering) steel |
| Tensile strength, min | 120,000 psi (1/2"–1"); 105,000 psi (over 1" to 1-1/2") |
| Proof load, min | 85 ksi (1/2"–1"); 74 ksi (1-1/8"–1-1/2") |
| Hardness | C25–C34 (1/2"–1", Type 1); C19–C30 (over 1") |
| Galvanizing | Type 1 may be hot-dip or mechanically galvanized; Type 3 is supplied bare (weathering steel) |
| Installation | Torque wrench or tension control (TC) pre-tensioning; matched heavy hex nuts (A563) and hardened washers (F436) |
| Typical applications | Steel frameworks, bridge and highway construction, load-bearing structural connections |
Materials
- Medium carbon 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 A325 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
What is the difference between A325 Type 1 and Type 3?
Steel and corrosion strategy. Type 1 is standard medium carbon steel, quenched and tempered — it must be coated (typically hot-dip galvanized) for atmospheric exposure. Type 3 is weathering steel that forms its own protective patina, so it is used bare in unpainted bridges and structures; it cannot be galvanized. Mechanically the two carry the same strength minimums, so the choice is driven by the corrosion protection system the structure specifies.
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