Related Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
ASTM A193 Grade B16 Stud Bolts
Cr-Mo-V Alloy Steel Stud Bolts for High-Temperature Pressure-Vessel and Flange Service
ASTM A193 Grade B16 stud bolts (also written A193 B16 studs, ASTM A193 Gr B16 stud bolts, SA-193 B16 stud bolts, UNS K14072 stud bolts) are chromium-molybdenum-vanadium quenched-and-tempered alloy-steel fasteners manufactured to ASTM A193 / A193M Table 2 mechanical limits and used as the standard high-temperature flange-bolting solution above the B7 service envelope. TorqBolt produces the full B16 stud-bolt family from its Rajkot plant with imperial diameters from 1/4 in to 4 in and metric diameters from M6 to M100, both fine and coarse threads, in stock and on indent.
Stud bolt configurations
B16 studs are supplied in four standard configurations per ASME B18.31.2 (inch) and B18.31.1M (metric):
- Continuous-thread stud bolts (most common for flange service) - thread full length, used with two A194 Grade 7 nuts. ASME B18.31.2 / B18.31.1M dimensions.
- Tap-end stud bolts - one end machined with a coarser tap-end thread for permanent installation into a tapped hole, other end with finer nut-end thread for the nut.
- Double-end stud bolts - both ends threaded with a centre body left unthreaded, used in flange joints where preload uniformity matters.
- Single-end stud bolts - one threaded end + one plain end, used as anchor studs in concrete or as suspension studs.
Diameter and length range
| Series | Stock diameter range | Indent diameter range | Length range (stock) | Length range (indent) |
|---|---|---|---|---|
| Inch (B18.31.2) | 1/2 in to 2-1/2 in | 1/4 in to 4 in | up to 24 in | up to 60 in |
| Metric (B18.31.1M) | M12 to M64 | M6 to M100 | up to 600 mm | up to 1500 mm |
| Heavy diameter (large flange) | 2-1/2 in to 3 in | up to 4 in / M150 | up to 36 in | up to 80 in |
B16 stud bolt material
B16 stud bolts are forged from AISI 4140 / 4142 chromium-molybdenum-vanadium alloy steel, conforming to the ASTM A193 Table 1 chemistry envelope. Vanadium addition of 0.25 to 0.35 % is the key differentiator from the B7 grade and is responsible for the creep and stress-relaxation resistance that justifies the B16 premium at elevated service temperatures.
| Element | Cr-Mo-V (% by mass) | Product analysis variation |
|---|---|---|
| C | 0.36 - 0.47 | 0.02 |
| Mn | 0.45 - 0.70 | 0.03 |
| P (max) | 0.035 | 0.005 |
| S (max) | 0.040 | 0.005 |
| Si | 0.15 - 0.35 | 0.02 |
| Cr | 0.80 - 1.15 | 0.05 |
| Mo | 0.50 - 0.65 | 0.03 |
| V | 0.25 - 0.35 | 0.03 |
B16 stud bolt mechanical properties
| Diameter, in. | 2-1/2 and under | over 2-1/2 to 4 | over 4 to 8 |
|---|---|---|---|
| Min. tempering temperature, °F | 1200 | 1200 | 1200 |
| Tensile strength, min, ksi | 125 | 110 | 100 |
| Yield strength, min, 0.2 % offset, ksi | 105 | 95 | 85 |
| Elongation in 4D, min, % | 18 | 17 | 16 |
| Reduction of area, min, % | 50 | 45 | 45 |
| Hardness, max | 321 HBW / 35 HRC | 321 HBW / 35 HRC | 321 HBW / 35 HRC |
Heat treatment
B16 stud bolts are supplied in the quenched-and-tempered (Q&T) condition. The standard heat-treatment route is: austenitise at 1650 to 1700 °F (900 to 925 °C), oil quench to develop a fully martensitic structure, then temper at 1200 °F (650 °C) minimum for time sufficient to meet the ASTM A193 Table 2 mechanical limits. Each heat-treat lot is tested per A193 sect 7. When Supplement S12 is invoked, stress-rupture testing at 1100 °F / 20 ksi is performed (suffix B16R). When Supplement S4 is invoked, hardness is verified on each stud bolt.
Companion nut grade for B16 stud bolts
The canonical companion nut for B16 stud bolts is ASTM A194 Grade 7. Do not pair B16 studs with A194 Grade 2H nuts for sustained service above 750 °F - the Grade 2H carbon-steel nut creeps while the B16 stud retains tension, producing thread-jacking and loss of clamp force. Do not pair B16 studs with A194 Grade 8 or 8M austenitic stainless nuts at elevated temperature due to coefficient-of-thermal-expansion mismatch.
Coatings and surface finish
B16 stud bolts are supplied in the following finish options:
- Plain (uncoated, as-machined) - default; protective oiling prevents shipping corrosion
- Black oxide - light protective finish for low-corrosion environments
- Hot-dip galvanised (HDG) per ASTM A153 - thick zinc coating for atmospheric service; baking required to prevent hydrogen embrittlement
- Zinc plating per ASTM B633 - thinner electroplated coating
- Cadmium plating per ASTM B766 / AMS-QQ-P-416 - aerospace and chemical-service applications
- Xylan 1424 / 1070 fluoropolymer - subsea and offshore high-temperature service
- PTFE coating (Teflon-based) - chemical-process flange bolting
- Geomet 500B / 720 - chromium-free corrosion protection for offshore
- Magni 565 / 575 - zinc-aluminium flake coating
- Phosphate and oil - shipping protection
Quality certification regime
TorqBolt supplies B16 stud bolts with the following certification options:
- EN 10204 Type 3.1 - default mill test certificate covering heat analysis, product analysis, mechanical-properties test, and heat traceability
- EN 10204 Type 3.2 - third-party-witnessed certificate (DNV, Lloyd’s Register, TÜV, Bureau Veritas) for offshore and pressure-vessel projects
- NORSOK M-650 qualified test record (QTR) - five-year validity, essential-variable changes trigger re-qualification
- NACE MR0175 / ISO 15156-2 sour-service certificate - project waiver required (B16 is not a default sour-service grade; B7M is)
- PED 2014/68/EC certificate - European Pressure Equipment Directive compliance for vessel-attached bolting
- API 6A / 17D PSL-3 - subsea and surface wellhead high-temperature applications
- Charpy V-notch impact test (Supplement S6) - on request, for piping below -20 °F
- Magnetic-particle examination (Supplement S7) - for refinery and offshore wellhead service
- ISO 17782 manufacturer-of-standard-fasteners certification - subsea SUBSEA+ pressure-traceability tier (offshore project requirement)
Lead time and procurement
Stock diameters (1/2 in to 2-1/2 in / M12 to M64) ship within 3 to 5 business days of order confirmation. Indent diameters (1/4 to 2-1/2 in / M6 to M48 with custom length, or 3 to 4 in / M64 to M100) carry a 4 to 8 week lead time depending on heat-treatment lot consolidation and certification level (3.1 vs 3.2 vs NORSOK QTR). For NORSOK M-650 QTR-required studs, expect 8 to 12 weeks for first-time grade qualification or 4 to 6 weeks for repeat orders under valid QTR. MOQ on stock is 5 pieces; on indent is 25 pieces per diameter / length combination.
Frequently asked questions
What is the maximum service temperature for A193 B16 stud bolts?
840 °F (450 °C) for continuous service per ASME B31.1 / B31.3 / B16.5 flange-bolting tables. 1100 °F (595 °C) for stress-rupture-qualified service with Supplement S12 (suffix B16R, 25 h rupture life at 20 ksi). Some industry sources cite 1000 °F as a conservative peak.
Are B16 stud bolts NACE-compliant for sour service?
B16 is not a default NACE MR0175 / ISO 15156-2 sour-service grade. For combined high-temperature and sour service, B16 requires a project-specific NACE waiver supported by stress-rupture and sulphide-stress-cracking testing. The default NACE sour-service A193 grade is B7M (impact-tested, hardness-controlled). For high-temperature sour service, an A193 B7M / B16 split assessment is often required.
Can B16 stud bolts be used at cryogenic temperature?
No. B16 has no Charpy V-notch requirement below -20 °F (-29 °C). For cryogenic service, use ASTM A320 Grade L7 (UNS G41400) which is the low-temperature counterpart of B16 with mandatory Charpy testing to -150 °F (-101 °C).
What is the minimum order quantity (MOQ)?
5 pieces on stock diameters / lengths. 25 pieces on indent diameters / custom lengths. Smaller MOQ available on a project-by-project basis at premium pricing.
Related TorqBolt resources
- ASTM A193 Grade B16 bolting specification overview
- A193 B16 vs A193 B7 - full side-by-side comparison
- B16 hex bolts
- B16 heavy hex bolts
- B16 threaded rods
- B16 round bar (mill source)
- ASME SA-193 Grade B16 bolting specification
- B16 anchor bolts (high-temp foundation anchoring)
Satisfaction Survey
