Understanding ASTM Specifications
ASTM Fastener Specifications Explained
Understanding A307, A325, A490, A193, F593, and other ASTM standards for fastener materials and mechanical properties.
ASTM International sets the benchmark for fastener material specifications in North America. Unlike dimensional standards (ASME), ASTM tells you what the fastener is made of and how strong it is — critical for specifying the right fastener for your application.
What ASTM Specifications Define
🧪 Chemical Composition
What elements and in what percentages — carbon, manganese, chromium, etc.
💪 Mechanical Properties
Tensile strength, yield strength, elongation, hardness, proof load.
🔬 Testing Requirements
How to verify compliance — test methods, frequency, acceptance criteria.
🏷️ Marking Requirements
How fasteners must be identified — head markings, manufacturer ID.
ASTM A307 — Low-Carbon Steel Bolts
General-purpose, non-critical fasteners for everyday applications
| Property | Value |
|---|---|
| Tensile Strength | 60,000 PSI minimum |
| Material | Low-carbon steel |
| Sizes | 1/4" through 4" diameter |
| Grades | A (general), B (pipe flanges), C (anchor bolts) |
Head Marking: None or "A307" — no radial lines
Common Applications
- General construction
- Non-structural connections
- Light machinery mounting
- Wood-to-metal connections
- Agricultural equipment
ASTM A325 — Structural Steel Bolts
Heat-treated heavy hex bolts for structural steel connections
| Property | Value |
|---|---|
| Tensile Strength | 120,000 PSI minimum |
| Proof Load | 85,000 PSI |
| Material | Medium-carbon steel, quenched & tempered |
| Types | Type 1 (standard), Type 3 (weathering steel) |
Head Marking: "A325" + manufacturer symbol + Type indicator
Common Applications
- Steel building frames
- Bridges
- Industrial structures
- Heavy equipment
- Structural connections
ASTM A490 — High-Strength Structural Bolts
Maximum strength for demanding structural applications
| Property | Value |
|---|---|
| Tensile Strength | 150,000–170,000 PSI |
| Proof Load | 120,000 PSI |
| Material | Alloy steel, quenched & tempered |
| Warning | Cannot be galvanized (hydrogen embrittlement risk) |
Head Marking: "A490" + manufacturer symbol — never galvanize these!
ASTM A193 / A194 — High-Temperature Fasteners
Alloy and stainless steel for pressure vessels and high-temp service
| Grade | Material | Temp Range | Use |
|---|---|---|---|
| B7 | Chrome-moly alloy | -50°F to 1100°F | Pressure vessels, valves |
| B8 | 304 Stainless (Class 1) | Cryogenic to 800°F | Chemical processing |
| B8M | 316 Stainless (Class 1) | Cryogenic to 800°F | Marine, chloride exposure |
💡 A194 = Nuts for A193 Bolts
ASTM A194 covers the nuts designed to work with A193 studs. Grade 2H for B7 studs, Grade 8 for stainless grades.
ASTM F593 / F594 — Stainless Steel Bolts & Nuts
Corrosion-resistant fasteners for general and marine applications
| Alloy Group | Types | Condition | Tensile Strength |
|---|---|---|---|
| Group 1 | 304, 305, 384 | CW1/CW2 | 65,000–100,000 PSI |
| Group 2 | 316, 316L | CW1/CW2 | 70,000–100,000 PSI |
| Group 3 | 410, 416, 431 | Hardened | 110,000+ PSI |
Head Marking: "F593" + alloy group (1, 2, or 3) + condition code
Quick Comparison Chart
| Specification | Tensile (PSI) | Material | Primary Use |
|---|---|---|---|
| A307 | 60,000 | Low-carbon steel | General purpose |
| A325 | 120,000 | Medium-carbon, Q&T | Structural steel |
| A490 | 150,000+ | Alloy steel, Q&T | High-strength structural |
| A193 B7 | 125,000 | Chrome-moly alloy | Pressure/high-temp |
| F593 Gr 1 | 65,000–100,000 | 304 Stainless | Corrosion resistance |
| F593 Gr 2 | 70,000–100,000 | 316 Stainless | Marine/chemical |
Shop by ASTM Specification
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