Carbon Steel Stud Bolt — Factory Direct Supplier | Huaxia-Steel
Huaxia-Steel manufactures and exports carbon steel stud bolts from M12 to M72 (1/2″ to 2-1/2″), threaded full-length or double-end in accordance with ASME B18.31.2 and ISO 261, supplied plain, black oxide, or hot-dip galvanized. We supply flange fabricators, valve makers and petrochemical contractors with stud bolts matched to ASME B16.5 flange drilling — factory-direct, with EN 10204 3.1 certificates, hardness and tensile testing per lot, and third-party inspection welcome.
Product Overview
A stud bolt is a headless threaded rod — normally with threads on both ends and a plain shank in between (double-end), or threaded full-length — used with two nuts to clamp flanged joints, valve bodies, heat exchanger closures and equipment nozzles. Stud bolts outperform cap screws in flange service for three reasons: they seat without twisting against the gasket face, they distribute clamping load through two engaged nuts, and they tolerate repeated assembly cycles with less thread wear in the tapped holes.
Our production route: bar stock inspection (heat chemistry per MTC) → cut-to-length → thread rolling (preferred for fatigue performance) or thread cutting → heat treatment where grade requires → surface finish → gauge inspection → packaging. Thread rolling after heat treatment is the quality differentiator: rolled threads in the rolled condition show 20–40% higher fatigue life than cut threads, which matters on cycling pipework. Every production lot is hardness-tested and tensile-tested; results ship on the certificate with the lot number.
Specifications and Tolerances
| Parameter | Range | Standard / tolerance |
|---|---|---|
| Diameter (metric) | M12 – M72 | ISO 261 / 6g thread tolerance |
| Diameter (inch) | 1/2″ – 2-1/2″ (8UN, 8UN-2A UNC on large sizes) | ASME B1.1 Class 2A |
| Length | 50 – 2,000 mm (2″ – 78″) | ±1.0 mm standard; per B16.5 tables for flange sets |
| Thread style | Double-end, full-thread, tap-end | ASME B18.31.2 configurations |
| Grades (carbon steel) | ASTM A307 Gr B; A193 B7/B7M (Cr-Mo); Q235/35#/45# equivalents | See grade table below |
| Nuts | A563 heavy hex; A194 2H/2HM matched | ASME B18.2.2 |
| Finish | Plain, black oxide, HDG (ASTM A153), PTFE-coated | Coating thickness per class |
| Marking | Grade, manufacturer mark, heat number on request | Per ASTM product standard |
Available Grades
| Grade | Base material | Typical strength | Service |
|---|---|---|---|
| ASTM A307 Gr B | Low-carbon steel | Tensile ≥ 415 MPa (60 ksi) | General flanged joints, water, air, low-pressure steam |
| ASTM A193 B7 | 4140 / 42CrMo4 Cr-Mo, Q&T | Yield ≥ 720 MPa (105 ksi) ≤ 2-1/2″ | High-pressure/temperature petrochemical flanges |
| ASTM A193 B7M | 4140/42CrMo4, Q&T, 100% hardness tested | Yield ≥ 620 MPa (90 ksi) | Sour service (NACE MR0175 aligned) pipelines |
| Q235 / 4.8–8.8 class | GB carbon steel equivalents | Property class per ISO 898-1 | Domestic and general engineering |
| 35# / 45# (C35/C45) | Medium-carbon, normalized or Q&T | Per PO specification | Machinery, equipment assembly |
Select the grade from the flange class and service, not from price: A307 Gr B suits ASME B16.5 Class 150–300 water and utility service; A193 B7 with A194 2H nuts is the default for Class 600+ and hydrocarbon service; B7M with 2HM nuts applies where NACE-aligned sour service governs, with its distinctive 100% hardness-test requirement (max 235 HB). We ship grade-marked product with matched nuts, washers and gaskets as complete bolt sets per flange when requested.
Manufacturing Standards
Applications
Quality Assurance
Packaging and Shipping
Standard export packaging: studs in inner cartons of 25/50 kg inside export plywood or steel-strapped wooden cases (ISPM-15 stamped); nuts and washers in separate labeled cartons to prevent thread damage; matched flange-bolt sets bagged per flange on request. Anti-rust oil or VCI paper for plain-finish product; container loading 22–26 t per 20 ft depending on mix. HS Code: 7318.15 (threaded studs and bolts of iron or steel). Packing lists show diameter × length, grade, finish and quantity per case, heat numbers included for certified lots.
Why Source Stud Bolts From Huaxia-Steel
Price Factors and Quotation Checklist
Stud bolt pricing tracks material grade first and size second. A193 B7 carries a significant premium over A307 Gr B because of the Cr-Mo chemistry and the quench-and-temper cycle; B7M adds the 100% hardness testing and documentation overhead. Hot-dip galvanizing adds a coating step (and for galvanized studs, nut oversize tapping). Thread rolling after heat treatment is standard for us but not for all suppliers — it is included in our price, not an add-on. Quantity leverage is strong at full pallet/carton multiples per size.
For an accurate first quotation, tell us: diameter × length per line, thread (metric 6g or UNC 2A), grade (A307 Gr B / B7 / B7M), finish (plain/black oxide/HDG/PTFE), nut grade and washer requirement, whether you need flange-matched sets to B16.5 tables, and packing format. We will quote factory-direct with a certificate pack sample and lead time per line.
What is the difference between A193 B7 and B7M?
Same base chemistry (4140-type Cr-Mo), different acceptance regime. B7M requires 100% hardness testing of every piece (max 235 HB), lower strength minimums, and mandatory marking — it is the sour-service aligned grade for pipeline and facility work per NACE MR0175-aligned specifications. B7 is the standard high-strength grade for normal petrochemical flanges. They are not substitutes for each other; the piping class decides.
Should threads be cut or rolled?
Rolled, where the specification allows. Rolling cold-works the thread profile into the material, leaving compressive residual stress and a smooth root — worth 20–40% in fatigue life versus cut threads, which machine away fibers and notch the root. Rolled threads are standard for our A307 and B7 production above M12; on very large diameters or tap-end studs, cutting may apply by configuration. State your preference on the PO — fatigue-critical joints deserve the rolled route.
Can you supply complete flange bolting sets?
Yes — studs, nuts and washers assembled as sets per ASME B16.5 flange size and class, bagged and labeled per flange (e.g. “8” CL300 — 8× studs 1″ × 4-1/4″ + 8× 2H nuts”). Site crews open the box and install; the per-flange bagging also simplifies progress tracking on large projects. Add the flange schedule to your RFQ and we will generate the full set list for your review.
Common Flange-Set Sizes (ASME B16.5)
| Flange NPS / Class | Stud size | Stud length | Qty per flange |
|---|---|---|---|
| 2″ CL150 | 5/8″ | 3-1/2″ | 4 |
| 4″ CL150 | 5/8″ | 3-3/4″ | 8 |
| 4″ CL300 | 3/4″ | 4-1/2″ | 8 |
| 6″ CL300 | 3/4″ | 4-3/4″ | 12 |
| 8″ CL300 | 3/4″ | 4-3/4″ | 12 |
| 12″ CL600 | 1-1/8″ | 7-1/4″ | 16 |
The full B16.5 table spans every NPS 1/2″–24″ across Class 150–2500 — send your flange list (or the line list from the piping class) and we will generate the complete stud, nut and gasket set list with quantities for your review before production. Set packaging is per-flange bagged and labeled, which site crews consistently report as the fastest-to-install format.
Ordering Process and Lead Time
Standard workflow: send size/grade/finish list → quotation with certificate pack sample within 48 hours → production with per-lot testing (100% hardness on B7M) → pre-shipment inspection → shipment with heat-number traceable documentation. Standard grades and sizes ship in 20–30 days; large-diameter studs above M72 and special coatings are scheduled per campaign. Private-label cartons and per-project lot consolidation available from agreed volumes.
A note on torque and assembly: stud bolt clamping performance depends as much on installation as on manufacture. Lubricated threads, calibrated torque wrenches and a cross-pattern tightening sequence in three passes deliver the gasket stress the flange design assumes; dry, uncalibrated tightening scatters bolt loads by 30–50% regardless of stud grade. We supply torque tables and lubricant recommendations with flange-set orders — ask for them with your quote, and your joint integrity problem shrinks to follow-through at the wrench.
Get a Factory-Direct Quote for Stud Bolts
Send your size, grade and finish schedule — matched nut and washer sets quoted in the same week.
Request a quote: Contact Huaxia-Steel.
