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Certifications: EN 10204 3.1 / 3.2 material test certificates and complete export documentation packages.
ASTM A307
Carbon Steel
Bolts
A world-class technical reference for EPC contractors, structural and piping engineers, procurement heads, and TPI inspection agencies specifying ASTM A307 carbon steel bolts, studs, and anchor bolts — covering the Grade A/B/C distinction (including Grade B’s specific role in flanged joints), why A307 is not a slip-critical structural bolt grade (in direct contrast to ASTM A325/A490, per RR Hydraulic’s dedicated references), and the QC and documentation discipline required for general industrial and low-pressure EPC bolting supply.
Key Properties
& Selection Logic
ASTM A307 is the standard governing general-purpose, low-to- moderate-strength carbon steel bolts, studs, and anchor bolts — a fundamentally different application category from the high- strength structural bolt grades (A325/A490, per RR Hydraulic’s dedicated references) discussed elsewhere in our fastener reference library.
1.1 — What ASTM A307 Governs
ASTM A307 (“Standard Specification for Carbon Steel Bolts, Studs, and Threaded Rod 60,000 PSI Tensile Strength”) governs low-alloy- free carbon steel fasteners with a minimum tensile strength of 60,000 psi (60 ksi / 415 MPa) — roughly comparable in strength role to the metric property class 4.6 tier, and notably lower strength than either ASTM A325 (120 ksi) or ASTM A490 (150 ksi), the high-strength structural bolt grades discussed in RR Hydraulic’s dedicated references. A307 is the standard specification for general-purpose, non-structural-connection bolting — anchor bolts, U-bolts, machinery mounting bolts, and (in its Grade B variant specifically) flanged pipe joint bolting for lower-pressure and cast iron flange applications.
1.2 — Grade Classification: A, B, and C
Grade A — General Purpose
The standard, most commonly specified A307 grade — carbon steel with minimum tensile strength 60 ksi and no specified minimum yield strength, used for general-purpose, non-critical bolted connections including machinery mounting, general structural anchor bolts, U-bolts, and miscellaneous low-load fastening applications where high strength or controlled preload is not a design requirement.
Grade B — Flanged Joint / Pipe Fitting Bolting
A specifically controlled variant of A307 intended for use as bolting material for cast iron flanges and low-pressure steel pipe flanges — Grade B has tighter chemistry and hardness controls than Grade A, specifically to reduce the risk of brittle fracture in the bolt when used with cast iron flanges, whose lower ductility and lower tolerance for point-loading make bolt brittleness a specific historical failure concern. Grade B is explicitly referenced in ASME B16.1 (cast iron flanges) and related lower-pressure flange standards as the appropriate bolting material, distinct from the higher-strength alloy steel bolting (A193 B7, discussed in RR Hydraulic’s Alloy 4140 reference) used with steel ANSI B16.5 flanges.
Grade C — Structural Anchor Applications
A less commonly encountered A307 grade with a specified minimum yield strength (unlike Grade A, which has no minimum yield requirement) — used for structural anchor bolt applications where a minimum yield strength value is required for the anchor bolt design calculation, though many structural anchor bolt applications in current practice have transitioned to ASTM F1554 (a dedicated modern anchor bolt standard with defined grades and yield strength requirements) rather than A307 Grade C.
1.3 — Why A307 Is Not a Slip-Critical Structural Bolt Grade
Mechanical Reference
& Comparison to High-Strength Grades
ASTM A307 is manufactured to specific mechanical property requirements by grade, with a straightforward comparison against the high-strength structural bolt grades clarifying its distinct role in EPC procurement.
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2.1 — Governing Standards
ASTM A307 — Carbon Steel Bolts, Studs, and Threaded Rod
The primary specification governing all three A307 grades — chemical composition, mechanical property requirements, and general dimensional/testing requirements for carbon steel bolting at the 60 ksi minimum tensile strength tier.
ASME B16.1 — Cast Iron Pipe Flanges
References A307 Grade B as the standard bolting material for cast iron flanged joints — the specific dimensional standard where Grade B’s controlled chemistry for brittle fracture resistance (Section 1.2) is a direct, referenced requirement.
ASTM F1554 — Anchor Bolts (Modern Alternative to Grade C)
The current, purpose-built US standard for structural anchor bolts, offering defined Grade 36, 55, and 105 yield strength tiers — increasingly specified in place of A307 Grade C for new structural anchor bolt design, discussed in Section 1.2.
ASTM A563 — Carbon and Alloy Steel Nuts
Governs the mating nuts (typically Grade A or Grade C) for A307 bolts — matched to the bolt grade’s strength level and application.
2.2 — Mechanical Properties by Grade
| Grade | Min. Tensile Strength | Min. Yield Strength | Typical Application |
|---|---|---|---|
| Grade A | 60 ksi (415 MPa) | Not specified | General-purpose bolting, U-bolts, machinery mounting, non-critical anchor bolts |
| Grade B | 60 ksi (415 MPa) | Not specified (tighter chemistry/hardness control) | Cast iron and low-pressure steel flanged joint bolting (per ASME B16.1) |
| Grade C | 58 ksi (400 MPa) | 36 ksi (250 MPa) minimum | Structural anchor bolt applications requiring a defined yield strength (largely superseded by ASTM F1554) |
2.3 — Comparison to High-Strength Structural Bolt Grades
| Property | ASTM A307 | ASTM A325 | ASTM A490 |
|---|---|---|---|
| Min. Tensile Strength | 60 ksi (415 MPa) | 120 ksi (825 MPa) | 150 ksi (1035 MPa) |
| Material | Plain carbon steel | Medium-carbon steel (Type 1) | Alloy steel (Type 1) |
| Controlled installation / RCSC framework | No — snug-tight installation only | Yes — turn-of-nut, calibrated wrench, TC bolts, DTI | Yes — same RCSC framework as A325 |
| Slip-critical connection use | Not applicable | Yes | Yes |
| Hot-dip galvanizing | Permitted — no hydrogen embrittlement concern at this low strength level | Permitted (with nut over-tap) | Prohibited |
| Typical use | Anchor bolts, U-bolts, general/non-structural bolting, cast iron flanges (Grade B) | Default high-strength structural connections | Highest-load/seismic structural connections |
& Fabrication Guidance
ASTM A307’s three grades map to distinct, non-overlapping application categories — correct grade selection depends on matching the specific service application (flanged joint, general fastening, or structural anchor) to the appropriate grade’s controlled properties.
3.1 — Grade B for Flanged Joint Bolting
Grade B’s specific role as cast iron and low-pressure flange bolting material reflects a historical and continuing engineering concern: cast iron flanges (per ASME B16.1) have significantly lower ductility and impact toughness than steel flanges, and are more sensitive to point-loading and stress concentration at the bolt hole/flange interface. A brittle bolt failure at a cast iron flanged joint — historically associated with poorly controlled carbon steel bolt chemistry and heat treatment — poses a disproportionate risk given the flange’s own brittleness. Grade B’s tighter chemistry and hardness controls (compared to the more loosely specified Grade A) specifically address this concern, making Grade B the standard, code-referenced bolting material for cast iron flanged pipe joints and appropriate low-pressure steel flange applications where A307-level strength (rather than the higher-strength A193 B7 alloy steel bolting discussed in RR Hydraulic’s Alloy 4140 and ANSI B16 references) is the specified bolting material.
3.2 — Anchor Bolts and General-Purpose Applications
Structural Anchor Bolts (Grade A, Historically Grade C)
A307 Grade A anchor bolts for general, non-critical structural base plate anchoring where a defined minimum yield strength is not a specific design requirement — for applications requiring a specified minimum yield strength for structural anchor design calculations, ASTM F1554 (Section 2.1) is the current, purpose-built standard, generally preferred over the legacy A307 Grade C in modern structural engineering practice.
U-Bolts and Pipe Clamps
A307 Grade A is the standard material for U-bolts, pipe clamps, and similar low-load mechanical restraint hardware across general industrial, piping support, and mechanical fastening applications — the default, cost-effective carbon steel bolting grade for this broad, high-volume product category.
General Machinery Mounting and Miscellaneous Fastening
A307 Grade A bolts and studs for machinery base plate mounting, equipment skid fastening, and general miscellaneous industrial bolting where high strength and controlled preload are not design requirements — the practical, economical default carbon steel bolting grade across the majority of non-structural, non-pressure-critical EPC bolting scope.
3.3 — Corrosion Protection and Fabrication
As a plain carbon steel without alloy additions, A307 has no inherent corrosion resistance and requires the same surface treatment considerations discussed throughout RR Hydraulic’s surface treatment references (Plain/Self-Colour, Zinc Plated, Hot- Dip Galvanized) — hot-dip galvanizing is a very common and fully permitted finish for A307 bolting given its low strength and correspondingly negligible hydrogen embrittlement risk (Section 2.3), making galvanized A307 the standard choice for outdoor anchor bolts, U-bolts, and general fastening requiring long-term corrosion protection without the embrittlement caution required for higher-strength bolting grades.
Industry Applications
& Documentation
RR Hydraulic maintains full traceability from certified carbon steel heat to finished, tested, and packed ASTM A307 component shipment. Chemical composition and mechanical verification are standard on all project-grade supply.
4.1 — Inspection & QC Protocol
4.2 — EN 10204 / Documentation Requirements
| Certificate | Content | EPC Requirement | When Mandatory |
|---|---|---|---|
| 2.1 / 2.2 | Declaration / non-specific | Acceptable for non-critical, general-purpose applications | Low-consequence general fastening (per project QA/QC procedure) |
| 3.1 (EN 10204) | Heat-traceable chemical + mechanical test report | Mandatory — EPC project supply | Flange bolting (Grade B), structural anchor bolts, and general EPC procurement |
| 3.2 (EN 10204) | 3.1 + TPI countersign | Conditional — owner-specified critical items | Critical flange bolting or structural anchor applications per project requirement |
4.3 — Applications by Industry
Cast Iron and Low-Pressure Flanged Joint Bolting
A307 Grade B studs and bolts for cast iron pipe flanges per ASME B16.1, and for low-pressure steel flange applications where the higher-strength A193 B7 (discussed in RR Hydraulic’s Alloy 4140 and ANSI B16 references) is not required — a specific, code-referenced application where Grade B’s controlled brittle-fracture-resistant chemistry is the correct, standard specification.
Structural Anchor Bolts
A307 Grade A (or historically Grade C) anchor bolts for general structural base plate connections not requiring a defined minimum yield strength design value — increasingly supplemented or replaced by ASTM F1554 for new structural anchor bolt design in current practice.
General Industrial and Mechanical Fastening
A307 Grade A U-bolts, pipe clamps, and general-purpose bolting across the broad range of non-critical, non-structural fastening applications throughout general industrial, piping support, and mechanical equipment installation — the practical, cost-effective default carbon steel bolting grade wherever high strength and controlled preload are not design requirements.
4.4 — Export Packaging Specification
- Bolts, studs, and U-bolts packed in labelled cartons or bulk bins by grade, size, and coating, with clear grade marking to distinguish Grade A, B, and C where multiple grades are supplied on the same project
- Rust-preventive oil or VCI treatment for uncoated carbon steel components; galvanized components packed with adequate separation to prevent coating damage during transit
- Heat/lot number marked or tagged on each bundle/carton for traceability to the accompanying material test certificate
- Documentation in a waterproof pocket: EN 10204 3.1/3.2 (or 2.1/2.2 where acceptable) MTC, chemical composition report, mechanical test report, coating thickness report (where applicable), and packing list with grade/size/coating breakdown per item
- ISPM-15 timber or export cartons for international shipment, with country of origin and HS tariff code documentation matched to the fastener product category
Submit your grade, size, length, and quantity to RR Hydraulic for a complete, certified commercial offer.