Medium-strength, heat-treated steel — the ASTM grade comparable to SAE Grade 5, across a wider diameter range.
ASTM A449 covers headed bolts, rods, and anchor bolts from 1/4″ through 3″ inclusive. It's a medium-strength fastener made from medium-carbon or alloy steel that develops its mechanical values through heat treatment (quench and temper), intended for general engineering applications.
A449 is virtually identical in chemistry and strength to ASTM A325 and SAE J429 Grade 5 — but it's more flexible, covering a larger diameter range and not being restricted to a specific product configuration. That's why it's the usual call-out when a Grade 5-equivalent is needed above the 1-1/2″ where J429 stops.
A449 heads carry the manufacturer's identification symbol and the marking “A449”. Note that the SAE radial-line system (three lines for Grade 5, six for Grade 8) applies to J429 fasteners — A449 is identified by its stamped designation instead, even though its strength matches Grade 5.
| Type | Material |
|---|---|
| Type 1 | Plain carbon, carbon boron, alloy, or alloy boron steel. |
| Type 2 | Withdrawn in 2003. |
| Type 3 | Weathering steel (atmospheric-corrosion resistant). |
| Size Range | Tensile, min | Yield, min | Elongation, min | Reduction of Area, min |
|---|---|---|---|---|
| 1/4″ thru 1″ | 120,000 psi | 92,000 psi | 14% | 35% |
| Over 1″ thru 1-1/2″ | 105,000 psi | 81,000 psi | 14% | 35% |
| Over 1-1/2″ thru 3″ | 90,000 psi | 58,000 psi | 14% | 35% |
Strength steps down as diameter increases — the reason A449 is banded by size rather than a single figure. The 1/4″–1-1/2″ values match SAE J429 Grade 5 exactly.
| Element | Carbon Steel | Carbon Boron | Alloy Steel | Alloy Boron |
|---|---|---|---|---|
| Carbon | 0.30–0.52% | 0.30–0.52% | 0.30–0.52% | 0.30–0.52% |
| Manganese, min | 0.60% | 0.60% | 0.60% | 0.60% |
| Phosphorus, max | 0.040% | 0.040% | 0.035% | 0.035% |
| Sulfur, max | 0.050% | 0.050% | 0.040% | 0.040% |
| Silicon | 0.15–0.30% | 0.10–0.30% | 0.15–0.35% | 0.15–0.35% |
| Boron | — | 0.0005–0.003% | — | 0.0005–0.003% |
Type 3 (weathering steel) has its own composition defined across six manufacturer-selectable classes (A–F), not shown here.
| Finish | Size | Nut | Washer |
|---|---|---|---|
| Plain | 1/4″ – 1-1/2″ | ASTM A563 Grade B hex | ASTM F436 |
| 1-5/8″ – 3″ | ASTM A563 Grade A heavy hex | ||
| Galvanized | 1/4″ – 3″ | ASTM A563 DH heavy hex |
Nuts of other grades with proof-load stresses greater than the specified grade are also suitable.