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ASTM A307 is a standard specification for carbon steel bolts, studs, and threaded rods, typically offering a minimum tensile strength of 60,000 PSI. It is widely considered the "everyday" fastener specification for general-purpose, non-critical applications. Key Fastener Grades The specification is divided into three primary grades, each suited for different functional roles:

ASTM A307: Standard Specification for Carbon Steel Bolts, Studs, and Threaded Rods (60,000 PSI Tensile Strength) 1. Overview ASTM A307 is a standard specification issued by ASTM International for carbon steel bolts, studs, and threaded rods with a minimum tensile strength of 60,000 psi (415 MPa). It is one of the most common, general-purpose fastener standards used in non-critical, low-stress applications, particularly in construction, plumbing, and machinery assembly. Unlike higher-strength bolts (e.g., ASTM A325 or A490), A307 bolts are not intended for structural connections subject to heavy dynamic or fatigue loading. Instead, they are ideal for light-duty fastening, flanged joints, cast iron connections, and general maintenance. 2. Grades of ASTM A307 The specification includes two primary grades, plus a third less common grade: | Grade | Description | Typical Use | |-------|-------------|--------------| | Grade A | Low carbon steel (no heat treat required). Soft, ductile, and easily bendable. | General purpose fasteners, pipe flanges, electrical conduits, anchor bolts. | | Grade B | Low carbon steel (may be heat treated). Slightly higher strength and hardness. | Flanged joints in piping systems (especially cast iron flanges), mild machinery assembly. | | Grade C | (Rarely used/obsolete) | Replaced by F1554 for anchor bolts. | Key distinction: Grade A is fully threaded and more ductile; Grade B is often partially threaded and has tighter hardness restrictions. 3. Mechanical Properties (Grade A & B) | Property | Grade A | Grade B | |----------|---------|---------| | Tensile Strength | 60,000 psi (min) | 60,000–100,000 psi | | Yield Strength (approx.) | 36,000 psi (min) | No explicit requirement, but typically 36,000–55,000 psi | | Hardness (Rockwell) | B69–B100 | B69–B95 | | Elongation | 18% min (in 8 in.) | 18% min (in 8 in.) |

Note: Grade B must pass a hardness test , while Grade A is usually accepted based on tensile and bend tests.

4. Chemical Composition (max values) | Element | Grade A & B | |---------|-------------| | Carbon (C) | 0.29% | | Manganese (Mn) | 1.20% | | Phosphorus (P) | 0.04% | | Sulfur (S) | 0.05% | No alloying elements are required; the steel is plain carbon, often AISI 1006–1022 grade. 5. Common Forms and Finishes astm 307

Hex bolts (most common) Studs (double-ended or continuous thread) Threaded rods Finishes: Plain (uncoated, oiled), hot-dip galvanized, zinc plated (for mild corrosion resistance).

Caution: Galvanized A307 bolts are common, but the specification does not explicitly cover galvanizing — that is usually referenced under ASTM F2329 (for coating).

6. Applications Typical Uses

Plumbing & Piping: Flange bolting for cast iron, ductile iron, or carbon steel flanges (Class 125 or 250). Construction: Anchor bolts for light structural supports, secondary members, or equipment. Electrical: Conduit hangers, strut channel fittings. General Maintenance: Machinery guards, handrails, tank supports.

Where NOT to use A307

Do not use for structural steel connections requiring high-strength bolts (A325, A490, A449). Do not use in severe cyclic or fatigue loading. Do not use at elevated temperatures >400°F (204°C) without checking creep/relaxation. ASTM A307 is a standard specification for carbon

7. Comparison with Other Standards | Standard | Tensile Strength | Typical Application | |----------|----------------|----------------------| | ASTM A307 Gr. A | 60 ksi min | General utility, flanges | | ASTM F1554 Gr. 36 | 58–80 ksi | Anchor bolts (better for seismic) | | SAE J429 Gr. 2 | 60 ksi min | Automotive/machinery bolts (similar but not interchangeable for spec compliance) | | ASTM A449 | 90–120 ksi | Higher strength general use | | ISO 898-1 Class 4.6 | 58–71 ksi | Metric equivalent to A307 Gr. A | 8. Marking and Identification

Grade A: Usually marked with three radial lines or "A307" (some manufacturers use no mark for Grade A). Grade B: Marked with three circumferential dashes or "A307B". Higher-strength bolts (e.g., A325) have completely different marking patterns to avoid confusion.