ASTM A307 Hex Bolt Flange Pack | Grade A/B Marine | sinofastener
ASTM A307 Hex Bolt Flange Pack for Marine Piping and Flange Connections
sinofastener supplies ASTM A307 hex bolt flange packs — pre-assembled bolt, nut, and flat washer sets ready for marine pipe flange installation. Available in Grade A (general purpose, hex head) and Grade B (heavy hex head, specifically for cast-iron flanged piping joints per ASTM A307). Sizes 1/4"through 4"diameter, UNC/UNF Class 2A thread per ASME B1.1. Each flange pack ships with matching ASTM A563 nuts and F844 flat washers. All carbon steel hex bolts are supplied with mill test certificates per EN 10204 3.1.
What Is an ASTM A307 Hex Bolt Flange Pack?
AnASTM A307 hex bolt flange pack is a complete bolting set containing one carbon steel hex bolt, one matching nut (ASTM A563), and one flat washer (ASTM F844), bundled for single-point installation on pipe flange joints. The ASTM A307 specification covers carbon steel bolts and studs with a minimum tensile strength of 60,000 psi in sizes 1/4"through 4"diameter. The flange pack eliminates the need to source individual components separately and ensures grade compatibility across all three fastener elements.
Grade B is the primary grade for marine flange bolt applications involving cast-iron flanges. It uses a heavy hex head (per ASME B18.2.1) and caps tensile strength at 100 ksi maximum to prevent cracking brittle cast-iron flanges under over-torquing — a critical safety feature specified in ASTM A307 Section 1.1.
Marine Applications
| Application | Typical Size | Grade | Source |
|---|---|---|---|
| Cast-iron marine pipe flange joints | 1/2"–2" | Grade B (heavy hex) | ASTM A307 Sec. 1.1: Grade B for cast-iron flanges |
| Low-pressure ballast piping | 1/2"–4" | Grade A | ASTM A307 Sec. 1.1: Grade A for general applications |
| Hull non-structural bolted connections | 1/2"–1-1/2" | Grade A | ASME B18.2.1 hex bolt dimensions |
| Engine room pipe hanger clamps | 3/8"–1" | Grade A | ASTM A307 general mechanical assembly |
| HVAC and ventilation duct flanges | 1/4"–3/4" | Grade A | ASTM A307 low-stress mechanical connections |
| Deck equipment base plate bolting | 1/2"–1-1/2" | Grade A (HDG) | ASTM F2329 hot-dip galvanized coating |
Specifications and Materials
Standard References:
- ASTM A307 — Standard specification for carbon steel bolts and studs, 60,000 PSI tensile strength (Grade A and Grade B)
- ASME B18.2.1 — Dimensional standard for hex bolts (body diameter, width across flats, head height)
- ASME B1.1 — UNC and UNF thread form, Class 2A tolerance
- ASTM A563 — Matching nut specification (Grade A hex or heavy hex)
- ASTM F844 — Flat washer specification
- ASTM F2329 — Hot-dip galvanizing for fasteners (optional finish)
- ASTM F1941 — Electroplated zinc coating (optional finish)
Mechanical Properties (per ASTM A307):
| Property | Grade A | Grade B | Test Method |
|---|---|---|---|
| Tensile Strength | 60 ksi min (no max) | 60 ksi min, 100 ksi max | ASTM A307 Table 1 |
| Elongation (2") | 18% min | 18% min | ASTM A307 Sec. 5 |
| Reduction of Area | 35% min | 35% min | ASTM A307 Sec. 5 |
| Hardness (Rockwell B) | 69–100 HRB | 69–100 HRB | ASTM A307 Sec. 5 |
| Yield Strength | Not specified | Not specified | ASTM A307 does not specify yield |
Chemical Composition (Grade A, per ASTM A307 heat analysis):
| Element | Max % | Standard |
|---|---|---|
| Carbon | 0.29% | ASTM A307 Grade A |
| Manganese | 1.20% | ASTM A307 Grade A |
| Phosphorus | 0.04% | ASTM A307 Grade A |
| Sulfur | 0.15% | ASTM A307 Grade A |
Heavy Hex Bolt Dimensions — Grade B (per ASME B18.2.1):
| Nominal Dia. | UNC | Width Across Flats (F) | Head Height (H) Basic | Thread Length ≤6" |
|---|---|---|---|---|
| 1/2" | 13 | 7/8"(0.875") | 11/32"(0.344") | 1.250" |
| 5/8" | 11 | 1-1/16"(1.062") | 27/64"(0.422") | 1.500" |
| 3/4" | 10 | 1-1/4"(1.250") | 1/2"(0.500") | 1.750" |
| 7/8" | 9 | 1-7/16"(1.438") | 37/64"(0.578") | 2.000" |
| 1" | 8 | 1-5/8"(1.625") | 43/64"(0.672") | 2.250" |
| 1-1/8" | 7 | 1-13/16"(1.812") | 3/4"(0.750") | 2.500" |
| 1-1/4" | 7 | 2"(2.000") | 27/32"(0.844") | 2.750" |
| 1-1/2" | 6 | 2-3/8"(2.375") | 1"(1.000") | 3.250" |
Recommended Nut and Washer Pairing (per ASTM A307 Sec. 1.3):
| Bolt Grade | Nut | Washer | Standard Reference |
|---|---|---|---|
| Grade A (1/4"–1-1/2") | ASTM A563 Grade A, Hex | ASTM F844 Plain Flat | ASTM A307 Table, Nut Requirements |
| Grade A (over 1-1/2"–4") | ASTM A563 Grade A, Heavy Hex | ASTM F844 Plain Flat | ASTM A307 Table, Nut Requirements |
| Grade B (1/4"–4") | ASTM A563 Grade A, Heavy Hex | ASTM F844 Plain Flat | ASTM A307 Table, Nut Requirements |
Why Choose sinofastener for ASTM A307 Hex Bolt Flange Packs?
| Complete flange pack sets: Bolt + nut + washer matched by grade, ready for installation |
| Grade A and Grade B available: Grade A for general marine bolting; Grade B heavy hex for cast-iron piping flanges |
| Full size range: 1/4"through 4"diameter, bolt lengths per project requirement |
| Surface treatment: Hot-dip galvanized per ASTM F2329; Zinc plated per ASTM F1941; Plain (as manufactured) |
| Quality documentation: EN 10204 3.1 mill certificates with heat number, chemistry, tensile, and hardness test results |
| Annual capacity: 50,000 tons — supports bulk marine project supply and just-in-time delivery |
Standards Reference
| Standard | Scope |
|---|---|
| ASTM A307 | Carbon steel bolts and studs, 60,000 PSI tensile strength — Grade A (general) and Grade B (cast-iron flanges) |
| ASME B18.2.1 | Dimensional standard for square and hex bolts — body diameter, head height, width across flats |
| ASME B1.1 | Unified inch screw threads — UNC and UNF Class 2A |
| ASTM A563 | Carbon and alloy steel nuts for bolts — Grade A hex and heavy hex |
| ASTM F844 | Plain flat washers for bolted assemblies |
| ASTM F2329 | Hot-dip zinc coating on fasteners |
| ASTM F1941 | Electroplated zinc coating on fasteners |
FAQ
Q1: What is the difference between Grade A and Grade B for marine flange bolting?
Grade A allows any head style (hex or square) and has no tensile strength ceiling — it is the default for general marine bolting. Grade B requires a heavy hex head and caps tensile strength at 100 ksi maximum. This ceiling prevents over-torquing from cracking cast-iron flanges, which is why Grade B is the mandatory grade for cast-iron piping systems per ASTM A307 Section 1.1.
Q2: Why does ASTM A307 not specify a yield strength?
ASTM A307 is a low-carbon, non-heat-treated bolt specification. Unlike structural grades (A325, A490) or high-temperature grades (A193), A307 derives its properties from base composition and cold finishing rather than heat treatment. The standard controls hardness (69–100 HRB), elongation, and tensile strength, but does not define a specific yield point. If yield strength is a design requirement, specify ASTM A449 or higher.
Q3: Can A307 Grade B bolts be used with steel flanges instead of cast iron?
Yes. While ASTM A307 Grade B was designed for cast-iron flanges, the heavy hex head and 100 ksi tensile ceiling also work with steel flanges in low-to-moderate pressure marine piping systems. For high-pressure or high-temperature service, upgrade to ASTM A193 B7.
Q4: What surface treatment should I specify for marine environments?
For marine pipe flange bolting, hot-dip galvanizing per ASTM F2329 provides the most durable corrosion protection for carbon steel A307 bolts. For interior or less aggressive environments, zinc plating per ASTM F1941 is sufficient. For saltwater or ballast systems, consider upgrading the bolt material to stainless steel (ASTM F593) instead of relying on carbon steel coatings.
Contact sinofastener for ASTM A307 Hex Bolt Flange Packs:
Email: sales@sinofastener.com | bobo@sinofastener.com
Tel: 0574-86592068
Website: www.zlfastener.com | www.sinofastener.com (Main)
