ASTM A193 B7 Stud Bolt for Marine Pipe Flanges
ASTM A193 B7 Stud Bolt | Marine Pipe Flange | sinofastener
AnASTM A193 B7 stud bolt is a fully threaded, quenched and tempered chromium-molybdenum alloy steel fastener designed for high-temperature and high-pressure flange connections. sinofastener supplies A193 B7 stud bolts paired with ASTM A194 Grade 2H heavy hex nuts for marine pipe flanges per ASME B16.5, covering sizes from M12 to M100 (1/2"to 4"). Material base is AISI 4140/4142 alloy steel, heat treated to 321 HBW maximum. All A193 B7 stud bolts are inspected per ASTM A193 and shipped with mill certificates per EN 10204 2.1/3.1. Third-party inspection (BV, DNV, SGS, LR, ABS) available at client's cost.
What Is an ASTM A193 B7 Stud Bolt?
AnASTM A193 B7 stud bolt is a threaded fastener with threads on both ends and no head. It is installed through a flange connection, secured with a hex nut on each end. The A193 B7 stud bolt is manufactured from AISI 4140 chromium-molybdenum alloy steel, quenched and tempered at a minimum tempering temperature of 593 °C (1100 °F), achieving high tensile strength while maintaining toughness and ductility.
In marine piping systems, A193 B7 stud bolts are the standard fastener choice for ASME B16.5 flange joints on ships and offshore platforms, where pressures and temperatures exceed the limits of carbon steel fasteners such as ASTM A307. The Cr-Mo alloy composition (0.75–1.20% Cr, 0.15–0.25% Mo per ASTM A193 Table 1) gives A193 B7 its creep resistance at elevated temperatures up to approximately 540 °C (1000 °F).
Marine Applications
On board ships and offshore installations, A193 B7 stud bolts are used for flange connections where pressure and temperature demand alloy steel fasteners.
| Location | Pipe System | Typical Flange Class |
|---|---|---|
| Engine room — main steam | Steam piping, exhaust lines | ASME B16.5 Class 300–900 |
| Engine room — high-pressure fuel | Heavy fuel oil supply, boiler feed | ASME B16.5 Class 300–600 |
| Boiler system | Boiler outlet, superheater connections | ASME B16.5 Class 600–1500 |
| Cargo handling | Liquefied gas lines, cargo pump discharge | ASME B16.5 Class 300–900 |
| Ballast & fire main | High-pressure fire main connections | ASME B16.5 Class 150–300 |
Sources: ASTM A193 (high-temperature bolting specification); ASME B16.5 (pipe flanges and flanged fittings).
Specifications and Materials
Standard References for ASTM A193 B7 Stud Bolt:
- ASTM A193 / A193M — Standard specification for alloy steel and stainless steel bolting for high temperature or high pressure service
- ASTM A194 / A194M — Standard specification for carbon and alloy steel nuts for high temperature or high pressure service (Grade 2H matching nut)
- ASME B18.31.2 — Dimensional standard for stud bolts (continuous thread, flange studs)
- ASME B16.5 — Pipe flanges and flanged fittings (NPS 1/2 to NPS 24, Class 150–2500)
- ASME B1.1 — Unified screw threads, UNC and UNF Class 2A
- ASTM F2329 / ISO 1461 — Hot-dip galvanized coating requirements
- ISO 4042 — Electro zinc plating requirements
Chemical Composition — ASTM A193 Grade B7 (AISI 4140):
| Element | Content (%) | Source |
|---|---|---|
| Carbon (C) | 0.37–0.49 | ASTM A193 Table 1 |
| Manganese (Mn) | 0.65–1.10 | ASTM A193 Table 1 |
| Silicon (Si) | 0.15–0.35 | ASTM A193 Table 1 |
| Phosphorus (P), max | 0.035 | ASTM A193 Table 1 |
| Sulfur (S), max | 0.040 | ASTM A193 Table 1 |
| Chromium (Cr) | 0.75–1.20 | ASTM A193 Table 1 |
| Molybdenum (Mo) | 0.15–0.25 | ASTM A193 Table 1 |
Mechanical Properties — ASTM A193 Grade B7:
| Diameter Range | Tensile Strength (min) | Yield Strength (min) | Elongation (min, 4D) | Reduction of Area (min) | Hardness (max) |
|---|---|---|---|---|---|
| ≤ M64 (≤ 2-1/2") | 860 MPa (125 ksi) | 725 MPa (105 ksi) | 16% | 50% | 321 HBW / 35 HRC |
| > M64 to M100 (> 2-1/2"to 4") | 795 MPa (115 ksi) | 655 MPa (95 ksi) | 16% | 50% | 321 HBW / 35 HRC |
Source: ASTM A193 Table 2 (inch-pound) and Table 2M (metric). Tempering temperature minimum 593 °C (1100 °F) per ASTM A193 Section 6.1.
Stud Bolt Dimensions — ASME B18.31.2 (Selected Sizes):
| Nominal Size | Threads per Inch (UNC) | Major Diameter D (mm) | Thread Length (full thread, both ends) |
|---|---|---|---|
| 1/2" | 13 | 12.7 | Per order length |
| 5/8" | 11 | 15.9 | Per order length |
| 3/4" | 10 | 19.1 | Per order length |
| 7/8" | 9 | 22.2 | Per order length |
| 1" | 8 | 25.4 | Per order length |
| 1-1/8" | 7 | 28.6 | Per order length |
| 1-1/4" | 7 | 31.8 | Per order length |
| 1-1/2" | 6 | 38.1 | Per order length |
| 2" | 4.5 | 50.8 | Per order length |
| 2-1/2" | 4 | 63.5 | Per order length |
| 3" | 4 | 76.2 | Per order length |
| 4" | 4 | 101.6 | Per order length |
Source: ASME B18.31.2. Full-threaded stud bolt — entire body is threaded. Length per project specification.
A193 B7 Stud Bolt Length for ASME B16.5 Flanges (Raised Face, RF):
| Flange Size | Class 150 | Class 300 | Class 600 | Class 900 |
|---|---|---|---|---|
| 1/2" | 75 mm | 80 mm | 90 mm | 100 mm |
| 3/4" | 80 mm | 85 mm | 95 mm | 105 mm |
| 1" | 90 mm | 95 mm | 105 mm | 115 mm |
| 1-1/2" | 105 mm | 110 mm | 120 mm | 135 mm |
| 2" | 110 mm | 120 mm | 130 mm | 145 mm |
| 3" | 125 mm | 135 mm | 150 mm | 170 mm |
| 4" | 135 mm | 145 mm | 165 mm | 190 mm |
| 6" | 160 mm | 175 mm | 195 mm | 225 mm |
| 8" | 185 mm | 200 mm | 225 mm | 260 mm |
| 10" | 210 mm | 225 mm | 255 mm | 295 mm |
| 12" | 235 mm | 250 mm | 280 mm | 325 mm |
Note: Lengths are approximate for RF flanges with 2 nuts and 2 washers. Ring Type Joint (RTJ) flanges require longer studs. Confirm final length per project drawing and ASME B16.5 Table B-1.
Matching Nut — ASTM A194 Grade 2H:
| Property | Value | Source |
|---|---|---|
| Type | Carbon or alloy steel, quenched & tempered | ASTM A194 Table 1 |
| Proof load | 150 ksi (1035 MPa) | ASTM A194 Table 2 |
| Hardness (HRC) | 22–32 | ASTM A194 Table 3 |
| Thread | UNC Class 2B | ASME B1.1 |
| Style | Heavy hex | ASME B18.2.2 |
Surface Treatment Options:
| Treatment | Coating Thickness | Source |
|---|---|---|
| Black (plain, oiled) | — | As heat treated per ASTM A193 |
| Hot-dip galvanized (HDG) | ≥ 45 µm (local) / ≥ 55 µm (average) | ASTM F2329 / ISO 1461 |
| Electro zinc plated | ≥ 5 µm | ISO 4042 |
Why Choose sinofastener for A193 B7 Stud Bolt?
sinofastener has been manufacturing alloy steel fasteners for decades. Our ASTM A193 B7 stud bolts are produced under strict quality control:
- Material traceability — Mill certificates per EN 10204 2.1/3.1, with heat number marking on each stud
- Full heat treatment — Quenched and tempered at minimum 593 °C per ASTM A193 Section 6.1
- Mechanical testing — Tensile, yield, elongation, hardness tested per ASTM A193 Section 8
- Thread inspection — Go/No-Go gauge check per ASME B1.1 Class 2A
- Third-party inspection — BV, DNV, SGS, LR, ABS — at client's cost
- Complete supply — Stud bolt + A194 2H nuts + washers as one assembly package
- Annual capacity — 50,000 tons of fastener production
Standards Reference
| Standard | Scope |
|---|---|
| ASTM A193 / A193M | Alloy steel bolting for high temperature or high pressure service |
| ASTM A194 / A194M | Carbon and alloy steel nuts for bolts for high temperature or high pressure service |
| ASME B18.31.2 | Dimensional standard for stud bolts (continuous thread) |
| ASME B16.5 | Pipe flanges and flanged fittings (NPS 1/2–24, Class 150–2500) |
| ASME B1.1 | Unified screw threads (UNC / UNF / 8UN, Class 2A/2B) |
| ASTM F2329 / ISO 1461 | Hot-dip galvanized coating |
| ISO 4042 | Electro zinc plating |
FAQ
Q1: What is the difference between ASTM A193 B7 and ASTM A307 Grade B stud bolts?
A193 B7 is a Cr-Mo alloy steel, quenched and tempered, with minimum tensile strength of 860 MPa. A307 Grade B is carbon steel with minimum tensile strength of only 415 MPa (60 ksi). A193 B7 is used for high-pressure and high-temperature flanges; A307 is for low-pressure, general-purpose connections.
Q2: What nut grade is used with A193 B7 stud bolts?
ASTM A194 Grade 2H heavy hex nut is the standard matching nut for A193 B7. Grade 2H has a proof load of 150 ksi (1035 MPa), designed to match the strength of B7 stud bolts. Per ASME B16.5 flange bolting requirements.
Q3: How do I determine the correct stud bolt length for a flange connection?
Stud bolt length = flange thickness (both flanges) + gasket thickness + protrusion beyond each nut (typically 1–3 threads) + thickness of nuts and washers. ASME B16.5 Appendix B provides reference lengths. For precise calculation, refer to the specific flange class and size in ASME B16.5 Table B-1.
Q4: Can A193 B7 stud bolts be used in seawater service?
A193 B7 (Cr-Mo alloy steel) is not corrosion resistant in seawater. For direct seawater exposure, use ASTM A193 Grade B8M (AISI 316 stainless steel) or duplex stainless steel bolting. A193 B7 is suitable for marine internal piping systems (engine room, boiler) where the fastener is protected from direct saltwater contact.
Need ASTM A193 B7 stud bolts for your marine flange project?
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